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llvm-project/llvm/lib/CodeGen/CodeGenPrepare.cpp

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//===- CodeGenPrepare.cpp - Prepare a function for code generation --------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This pass munges the code in the input function to better prepare it for
// SelectionDAG-based code generation. This works around limitations in it's
// basic-block-at-a-time approach. It should eventually be removed.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/BasicBlockSectionsProfileReader.h"
#include "llvm/CodeGen/ISDOpcodes.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/IntrinsicsAArch64.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Statepoint.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/IR/ValueMap.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/BlockFrequency.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MachineValueType.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/BypassSlowDivision.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SimplifyLibCalls.h"
#include "llvm/Transforms/Utils/SizeOpts.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <iterator>
#include <limits>
#include <memory>
#include <utility>
#include <vector>
using namespace llvm;
using namespace llvm::PatternMatch;
#define DEBUG_TYPE "codegenprepare"
STATISTIC(NumBlocksElim, "Number of blocks eliminated");
STATISTIC(NumPHIsElim, "Number of trivial PHIs eliminated");
STATISTIC(NumGEPsElim, "Number of GEPs converted to casts");
STATISTIC(NumCmpUses, "Number of uses of Cmp expressions replaced with uses of "
"sunken Cmps");
STATISTIC(NumCastUses, "Number of uses of Cast expressions replaced with uses "
"of sunken Casts");
STATISTIC(NumMemoryInsts, "Number of memory instructions whose address "
"computations were sunk");
STATISTIC(NumMemoryInstsPhiCreated,
"Number of phis created when address "
"computations were sunk to memory instructions");
STATISTIC(NumMemoryInstsSelectCreated,
"Number of select created when address "
"computations were sunk to memory instructions");
STATISTIC(NumExtsMoved, "Number of [s|z]ext instructions combined with loads");
STATISTIC(NumExtUses, "Number of uses of [s|z]ext instructions optimized");
STATISTIC(NumAndsAdded,
"Number of and mask instructions added to form ext loads");
STATISTIC(NumAndUses, "Number of uses of and mask instructions optimized");
STATISTIC(NumRetsDup, "Number of return instructions duplicated");
STATISTIC(NumDbgValueMoved, "Number of debug value instructions moved");
STATISTIC(NumSelectsExpanded, "Number of selects turned into branches");
STATISTIC(NumStoreExtractExposed, "Number of store(extractelement) exposed");
static cl::opt<bool> DisableBranchOpts(
"disable-cgp-branch-opts", cl::Hidden, cl::init(false),
cl::desc("Disable branch optimizations in CodeGenPrepare"));
static cl::opt<bool>
DisableGCOpts("disable-cgp-gc-opts", cl::Hidden, cl::init(false),
cl::desc("Disable GC optimizations in CodeGenPrepare"));
static cl::opt<bool> DisableSelectToBranch(
"disable-cgp-select2branch", cl::Hidden, cl::init(false),
cl::desc("Disable select to branch conversion."));
static cl::opt<bool> AddrSinkUsingGEPs(
"addr-sink-using-gep", cl::Hidden, cl::init(true),
cl::desc("Address sinking in CGP using GEPs."));
static cl::opt<bool> EnableAndCmpSinking(
"enable-andcmp-sinking", cl::Hidden, cl::init(true),
cl::desc("Enable sinkinig and/cmp into branches."));
static cl::opt<bool> DisableStoreExtract(
"disable-cgp-store-extract", cl::Hidden, cl::init(false),
cl::desc("Disable store(extract) optimizations in CodeGenPrepare"));
static cl::opt<bool> StressStoreExtract(
"stress-cgp-store-extract", cl::Hidden, cl::init(false),
cl::desc("Stress test store(extract) optimizations in CodeGenPrepare"));
static cl::opt<bool> DisableExtLdPromotion(
"disable-cgp-ext-ld-promotion", cl::Hidden, cl::init(false),
cl::desc("Disable ext(promotable(ld)) -> promoted(ext(ld)) optimization in "
"CodeGenPrepare"));
static cl::opt<bool> StressExtLdPromotion(
"stress-cgp-ext-ld-promotion", cl::Hidden, cl::init(false),
cl::desc("Stress test ext(promotable(ld)) -> promoted(ext(ld)) "
"optimization in CodeGenPrepare"));
static cl::opt<bool> DisablePreheaderProtect(
"disable-preheader-prot", cl::Hidden, cl::init(false),
cl::desc("Disable protection against removing loop preheaders"));
static cl::opt<bool> ProfileGuidedSectionPrefix(
"profile-guided-section-prefix", cl::Hidden, cl::init(true), cl::ZeroOrMore,
cl::desc("Use profile info to add section prefix for hot/cold functions"));
static cl::opt<bool> ProfileUnknownInSpecialSection(
"profile-unknown-in-special-section", cl::Hidden, cl::init(false),
cl::ZeroOrMore,
cl::desc("In profiling mode like sampleFDO, if a function doesn't have "
"profile, we cannot tell the function is cold for sure because "
"it may be a function newly added without ever being sampled. "
"With the flag enabled, compiler can put such profile unknown "
"functions into a special section, so runtime system can choose "
"to handle it in a different way than .text section, to save "
"RAM for example. "));
static cl::opt<bool> BBSectionsGuidedSectionPrefix(
"bbsections-guided-section-prefix", cl::Hidden, cl::init(true),
cl::desc("Use the basic-block-sections profile to determine the text "
"section prefix for hot functions. Functions with "
"basic-block-sections profile will be placed in `.text.hot` "
"regardless of their FDO profile info. Other functions won't be "
"impacted, i.e., their prefixes will be decided by FDO/sampleFDO "
"profiles."));
static cl::opt<unsigned> FreqRatioToSkipMerge(
"cgp-freq-ratio-to-skip-merge", cl::Hidden, cl::init(2),
cl::desc("Skip merging empty blocks if (frequency of empty block) / "
"(frequency of destination block) is greater than this ratio"));
static cl::opt<bool> ForceSplitStore(
"force-split-store", cl::Hidden, cl::init(false),
cl::desc("Force store splitting no matter what the target query says."));
static cl::opt<bool>
EnableTypePromotionMerge("cgp-type-promotion-merge", cl::Hidden,
cl::desc("Enable merging of redundant sexts when one is dominating"
" the other."), cl::init(true));
static cl::opt<bool> DisableComplexAddrModes(
"disable-complex-addr-modes", cl::Hidden, cl::init(false),
cl::desc("Disables combining addressing modes with different parts "
"in optimizeMemoryInst."));
static cl::opt<bool>
AddrSinkNewPhis("addr-sink-new-phis", cl::Hidden, cl::init(false),
cl::desc("Allow creation of Phis in Address sinking."));
static cl::opt<bool>
AddrSinkNewSelects("addr-sink-new-select", cl::Hidden, cl::init(true),
cl::desc("Allow creation of selects in Address sinking."));
static cl::opt<bool> AddrSinkCombineBaseReg(
"addr-sink-combine-base-reg", cl::Hidden, cl::init(true),
cl::desc("Allow combining of BaseReg field in Address sinking."));
static cl::opt<bool> AddrSinkCombineBaseGV(
"addr-sink-combine-base-gv", cl::Hidden, cl::init(true),
cl::desc("Allow combining of BaseGV field in Address sinking."));
static cl::opt<bool> AddrSinkCombineBaseOffs(
"addr-sink-combine-base-offs", cl::Hidden, cl::init(true),
cl::desc("Allow combining of BaseOffs field in Address sinking."));
static cl::opt<bool> AddrSinkCombineScaledReg(
"addr-sink-combine-scaled-reg", cl::Hidden, cl::init(true),
cl::desc("Allow combining of ScaledReg field in Address sinking."));
static cl::opt<bool>
EnableGEPOffsetSplit("cgp-split-large-offset-gep", cl::Hidden,
cl::init(true),
cl::desc("Enable splitting large offset of GEP."));
static cl::opt<bool> EnableICMP_EQToICMP_ST(
"cgp-icmp-eq2icmp-st", cl::Hidden, cl::init(false),
cl::desc("Enable ICMP_EQ to ICMP_S(L|G)T conversion."));
static cl::opt<bool>
VerifyBFIUpdates("cgp-verify-bfi-updates", cl::Hidden, cl::init(false),
cl::desc("Enable BFI update verification for "
"CodeGenPrepare."));
static cl::opt<bool> OptimizePhiTypes(
"cgp-optimize-phi-types", cl::Hidden, cl::init(false),
cl::desc("Enable converting phi types in CodeGenPrepare"));
namespace {
enum ExtType {
ZeroExtension, // Zero extension has been seen.
SignExtension, // Sign extension has been seen.
BothExtension // This extension type is used if we saw sext after
// ZeroExtension had been set, or if we saw zext after
// SignExtension had been set. It makes the type
// information of a promoted instruction invalid.
};
using SetOfInstrs = SmallPtrSet<Instruction *, 16>;
using TypeIsSExt = PointerIntPair<Type *, 2, ExtType>;
using InstrToOrigTy = DenseMap<Instruction *, TypeIsSExt>;
using SExts = SmallVector<Instruction *, 16>;
using ValueToSExts = DenseMap<Value *, SExts>;
class TypePromotionTransaction;
class CodeGenPrepare : public FunctionPass {
const TargetMachine *TM = nullptr;
const TargetSubtargetInfo *SubtargetInfo;
const TargetLowering *TLI = nullptr;
const TargetRegisterInfo *TRI;
const TargetTransformInfo *TTI = nullptr;
const BasicBlockSectionsProfileReader *BBSectionsProfileReader = nullptr;
const TargetLibraryInfo *TLInfo;
const LoopInfo *LI;
std::unique_ptr<BlockFrequencyInfo> BFI;
std::unique_ptr<BranchProbabilityInfo> BPI;
ProfileSummaryInfo *PSI;
/// As we scan instructions optimizing them, this is the next instruction
/// to optimize. Transforms that can invalidate this should update it.
BasicBlock::iterator CurInstIterator;
/// Keeps track of non-local addresses that have been sunk into a block.
/// This allows us to avoid inserting duplicate code for blocks with
/// multiple load/stores of the same address. The usage of WeakTrackingVH
/// enables SunkAddrs to be treated as a cache whose entries can be
/// invalidated if a sunken address computation has been erased.
ValueMap<Value*, WeakTrackingVH> SunkAddrs;
/// Keeps track of all instructions inserted for the current function.
SetOfInstrs InsertedInsts;
/// Keeps track of the type of the related instruction before their
/// promotion for the current function.
InstrToOrigTy PromotedInsts;
/// Keep track of instructions removed during promotion.
SetOfInstrs RemovedInsts;
/// Keep track of sext chains based on their initial value.
DenseMap<Value *, Instruction *> SeenChainsForSExt;
/// Keep track of GEPs accessing the same data structures such as structs or
/// arrays that are candidates to be split later because of their large
/// size.
MapVector<
AssertingVH<Value>,
SmallVector<std::pair<AssertingVH<GetElementPtrInst>, int64_t>, 32>>
LargeOffsetGEPMap;
/// Keep track of new GEP base after splitting the GEPs having large offset.
SmallSet<AssertingVH<Value>, 2> NewGEPBases;
/// Map serial numbers to Large offset GEPs.
DenseMap<AssertingVH<GetElementPtrInst>, int> LargeOffsetGEPID;
/// Keep track of SExt promoted.
ValueToSExts ValToSExtendedUses;
/// True if the function has the OptSize attribute.
bool OptSize;
/// DataLayout for the Function being processed.
const DataLayout *DL = nullptr;
/// Building the dominator tree can be expensive, so we only build it
/// lazily and update it when required.
std::unique_ptr<DominatorTree> DT;
public:
static char ID; // Pass identification, replacement for typeid
CodeGenPrepare() : FunctionPass(ID) {
initializeCodeGenPreparePass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &F) override;
StringRef getPassName() const override { return "CodeGen Prepare"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
// FIXME: When we can selectively preserve passes, preserve the domtree.
AU.addRequired<ProfileSummaryInfoWrapperPass>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
AU.addRequired<TargetPassConfig>();
AU.addRequired<TargetTransformInfoWrapperPass>();
AU.addRequired<LoopInfoWrapperPass>();
AU.addUsedIfAvailable<BasicBlockSectionsProfileReader>();
}
private:
template <typename F>
void resetIteratorIfInvalidatedWhileCalling(BasicBlock *BB, F f) {
// Substituting can cause recursive simplifications, which can invalidate
// our iterator. Use a WeakTrackingVH to hold onto it in case this
// happens.
Value *CurValue = &*CurInstIterator;
WeakTrackingVH IterHandle(CurValue);
f();
// If the iterator instruction was recursively deleted, start over at the
// start of the block.
if (IterHandle != CurValue) {
CurInstIterator = BB->begin();
SunkAddrs.clear();
}
}
// Get the DominatorTree, building if necessary.
DominatorTree &getDT(Function &F) {
if (!DT)
DT = std::make_unique<DominatorTree>(F);
return *DT;
}
void removeAllAssertingVHReferences(Value *V);
bool eliminateAssumptions(Function &F);
bool eliminateFallThrough(Function &F);
bool eliminateMostlyEmptyBlocks(Function &F);
BasicBlock *findDestBlockOfMergeableEmptyBlock(BasicBlock *BB);
bool canMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const;
void eliminateMostlyEmptyBlock(BasicBlock *BB);
bool isMergingEmptyBlockProfitable(BasicBlock *BB, BasicBlock *DestBB,
bool isPreheader);
bool makeBitReverse(Instruction &I);
bool optimizeBlock(BasicBlock &BB, bool &ModifiedDT);
bool optimizeInst(Instruction *I, bool &ModifiedDT);
bool optimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
Type *AccessTy, unsigned AddrSpace);
bool optimizeGatherScatterInst(Instruction *MemoryInst, Value *Ptr);
bool optimizeInlineAsmInst(CallInst *CS);
bool optimizeCallInst(CallInst *CI, bool &ModifiedDT);
bool optimizeExt(Instruction *&I);
bool optimizeExtUses(Instruction *I);
bool optimizeLoadExt(LoadInst *Load);
bool optimizeShiftInst(BinaryOperator *BO);
bool optimizeFunnelShift(IntrinsicInst *Fsh);
bool optimizeSelectInst(SelectInst *SI);
bool optimizeShuffleVectorInst(ShuffleVectorInst *SVI);
bool optimizeSwitchType(SwitchInst *SI);
bool optimizeSwitchPhiConstants(SwitchInst *SI);
bool optimizeSwitchInst(SwitchInst *SI);
bool optimizeExtractElementInst(Instruction *Inst);
bool dupRetToEnableTailCallOpts(BasicBlock *BB, bool &ModifiedDT);
bool fixupDbgValue(Instruction *I);
bool placeDbgValues(Function &F);
bool placePseudoProbes(Function &F);
bool canFormExtLd(const SmallVectorImpl<Instruction *> &MovedExts,
LoadInst *&LI, Instruction *&Inst, bool HasPromoted);
bool tryToPromoteExts(TypePromotionTransaction &TPT,
const SmallVectorImpl<Instruction *> &Exts,
SmallVectorImpl<Instruction *> &ProfitablyMovedExts,
unsigned CreatedInstsCost = 0);
bool mergeSExts(Function &F);
bool splitLargeGEPOffsets();
bool optimizePhiType(PHINode *Inst, SmallPtrSetImpl<PHINode *> &Visited,
SmallPtrSetImpl<Instruction *> &DeletedInstrs);
bool optimizePhiTypes(Function &F);
bool performAddressTypePromotion(
Instruction *&Inst,
bool AllowPromotionWithoutCommonHeader,
bool HasPromoted, TypePromotionTransaction &TPT,
SmallVectorImpl<Instruction *> &SpeculativelyMovedExts);
bool splitBranchCondition(Function &F, bool &ModifiedDT);
bool simplifyOffsetableRelocate(GCStatepointInst &I);
bool tryToSinkFreeOperands(Instruction *I);
bool replaceMathCmpWithIntrinsic(BinaryOperator *BO, Value *Arg0,
Value *Arg1, CmpInst *Cmp,
Intrinsic::ID IID);
bool optimizeCmp(CmpInst *Cmp, bool &ModifiedDT);
bool combineToUSubWithOverflow(CmpInst *Cmp, bool &ModifiedDT);
bool combineToUAddWithOverflow(CmpInst *Cmp, bool &ModifiedDT);
void verifyBFIUpdates(Function &F);
};
} // end anonymous namespace
char CodeGenPrepare::ID = 0;
INITIALIZE_PASS_BEGIN(CodeGenPrepare, DEBUG_TYPE,
"Optimize for code generation", false, false)
INITIALIZE_PASS_DEPENDENCY(BasicBlockSectionsProfileReader)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)
INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
INITIALIZE_PASS_END(CodeGenPrepare, DEBUG_TYPE,
"Optimize for code generation", false, false)
FunctionPass *llvm::createCodeGenPreparePass() { return new CodeGenPrepare(); }
bool CodeGenPrepare::runOnFunction(Function &F) {
if (skipFunction(F))
return false;
DL = &F.getParent()->getDataLayout();
bool EverMadeChange = false;
// Clear per function information.
InsertedInsts.clear();
PromotedInsts.clear();
TM = &getAnalysis<TargetPassConfig>().getTM<TargetMachine>();
SubtargetInfo = TM->getSubtargetImpl(F);
TLI = SubtargetInfo->getTargetLowering();
TRI = SubtargetInfo->getRegisterInfo();
TLInfo = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
BPI.reset(new BranchProbabilityInfo(F, *LI));
BFI.reset(new BlockFrequencyInfo(F, *BPI, *LI));
PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
BBSectionsProfileReader =
getAnalysisIfAvailable<BasicBlockSectionsProfileReader>();
OptSize = F.hasOptSize();
// Use the basic-block-sections profile to promote hot functions to .text.hot if requested.
if (BBSectionsGuidedSectionPrefix && BBSectionsProfileReader &&
BBSectionsProfileReader->isFunctionHot(F.getName())) {
F.setSectionPrefix("hot");
} else if (ProfileGuidedSectionPrefix) {
// The hot attribute overwrites profile count based hotness while profile
// counts based hotness overwrite the cold attribute.
// This is a conservative behabvior.
if (F.hasFnAttribute(Attribute::Hot) ||
PSI->isFunctionHotInCallGraph(&F, *BFI))
F.setSectionPrefix("hot");
// If PSI shows this function is not hot, we will placed the function
// into unlikely section if (1) PSI shows this is a cold function, or
// (2) the function has a attribute of cold.
else if (PSI->isFunctionColdInCallGraph(&F, *BFI) ||
F.hasFnAttribute(Attribute::Cold))
F.setSectionPrefix("unlikely");
else if (ProfileUnknownInSpecialSection && PSI->hasPartialSampleProfile() &&
PSI->isFunctionHotnessUnknown(F))
F.setSectionPrefix("unknown");
}
/// This optimization identifies DIV instructions that can be
/// profitably bypassed and carried out with a shorter, faster divide.
if (!OptSize && !PSI->hasHugeWorkingSetSize() && TLI->isSlowDivBypassed()) {
const DenseMap<unsigned int, unsigned int> &BypassWidths =
TLI->getBypassSlowDivWidths();
BasicBlock* BB = &*F.begin();
while (BB != nullptr) {
// bypassSlowDivision may create new BBs, but we don't want to reapply the
// optimization to those blocks.
BasicBlock* Next = BB->getNextNode();
// F.hasOptSize is already checked in the outer if statement.
if (!llvm::shouldOptimizeForSize(BB, PSI, BFI.get()))
EverMadeChange |= bypassSlowDivision(BB, BypassWidths);
BB = Next;
}
}
// Get rid of @llvm.assume builtins before attempting to eliminate empty
// blocks, since there might be blocks that only contain @llvm.assume calls
// (plus arguments that we can get rid of).
EverMadeChange |= eliminateAssumptions(F);
// Eliminate blocks that contain only PHI nodes and an
// unconditional branch.
EverMadeChange |= eliminateMostlyEmptyBlocks(F);
bool ModifiedDT = false;
if (!DisableBranchOpts)
EverMadeChange |= splitBranchCondition(F, ModifiedDT);
// Split some critical edges where one of the sources is an indirect branch,
// to help generate sane code for PHIs involving such edges.
EverMadeChange |=
SplitIndirectBrCriticalEdges(F, /*IgnoreBlocksWithoutPHI=*/true);
bool MadeChange = true;
while (MadeChange) {
MadeChange = false;
DT.reset();
for (BasicBlock &BB : llvm::make_early_inc_range(F)) {
bool ModifiedDTOnIteration = false;
MadeChange |= optimizeBlock(BB, ModifiedDTOnIteration);
// Restart BB iteration if the dominator tree of the Function was changed
if (ModifiedDTOnIteration)
break;
}
if (EnableTypePromotionMerge && !ValToSExtendedUses.empty())
MadeChange |= mergeSExts(F);
if (!LargeOffsetGEPMap.empty())
MadeChange |= splitLargeGEPOffsets();
MadeChange |= optimizePhiTypes(F);
if (MadeChange)
eliminateFallThrough(F);
// Really free removed instructions during promotion.
for (Instruction *I : RemovedInsts)
I->deleteValue();
EverMadeChange |= MadeChange;
SeenChainsForSExt.clear();
ValToSExtendedUses.clear();
RemovedInsts.clear();
LargeOffsetGEPMap.clear();
LargeOffsetGEPID.clear();
}
NewGEPBases.clear();
SunkAddrs.clear();
if (!DisableBranchOpts) {
MadeChange = false;
// Use a set vector to get deterministic iteration order. The order the
// blocks are removed may affect whether or not PHI nodes in successors
// are removed.
SmallSetVector<BasicBlock*, 8> WorkList;
for (BasicBlock &BB : F) {
SmallVector<BasicBlock *, 2> Successors(successors(&BB));
MadeChange |= ConstantFoldTerminator(&BB, true);
if (!MadeChange) continue;
for (BasicBlock *Succ : Successors)
if (pred_empty(Succ))
WorkList.insert(Succ);
}
// Delete the dead blocks and any of their dead successors.
MadeChange |= !WorkList.empty();
while (!WorkList.empty()) {
BasicBlock *BB = WorkList.pop_back_val();
SmallVector<BasicBlock*, 2> Successors(successors(BB));
DeleteDeadBlock(BB);
for (BasicBlock *Succ : Successors)
if (pred_empty(Succ))
WorkList.insert(Succ);
}
// Merge pairs of basic blocks with unconditional branches, connected by
// a single edge.
if (EverMadeChange || MadeChange)
MadeChange |= eliminateFallThrough(F);
EverMadeChange |= MadeChange;
}
if (!DisableGCOpts) {
SmallVector<GCStatepointInst *, 2> Statepoints;
for (BasicBlock &BB : F)
for (Instruction &I : BB)
if (auto *SP = dyn_cast<GCStatepointInst>(&I))
Statepoints.push_back(SP);
for (auto &I : Statepoints)
EverMadeChange |= simplifyOffsetableRelocate(*I);
}
// Do this last to clean up use-before-def scenarios introduced by other
// preparatory transforms.
EverMadeChange |= placeDbgValues(F);
EverMadeChange |= placePseudoProbes(F);
#ifndef NDEBUG
if (VerifyBFIUpdates)
verifyBFIUpdates(F);
#endif
return EverMadeChange;
}
bool CodeGenPrepare::eliminateAssumptions(Function &F) {
bool MadeChange = false;
for (BasicBlock &BB : F) {
CurInstIterator = BB.begin();
while (CurInstIterator != BB.end()) {
Instruction *I = &*(CurInstIterator++);
if (auto *Assume = dyn_cast<AssumeInst>(I)) {
MadeChange = true;
Value *Operand = Assume->getOperand(0);
Assume->eraseFromParent();
resetIteratorIfInvalidatedWhileCalling(&BB, [&]() {
RecursivelyDeleteTriviallyDeadInstructions(Operand, TLInfo, nullptr);
});
}
}
}
return MadeChange;
}
/// An instruction is about to be deleted, so remove all references to it in our
/// GEP-tracking data strcutures.
void CodeGenPrepare::removeAllAssertingVHReferences(Value *V) {
LargeOffsetGEPMap.erase(V);
NewGEPBases.erase(V);
auto GEP = dyn_cast<GetElementPtrInst>(V);
if (!GEP)
return;
LargeOffsetGEPID.erase(GEP);
auto VecI = LargeOffsetGEPMap.find(GEP->getPointerOperand());
if (VecI == LargeOffsetGEPMap.end())
return;
auto &GEPVector = VecI->second;
llvm::erase_if(GEPVector, [=](auto &Elt) { return Elt.first == GEP; });
if (GEPVector.empty())
LargeOffsetGEPMap.erase(VecI);
}
// Verify BFI has been updated correctly by recomputing BFI and comparing them.
void LLVM_ATTRIBUTE_UNUSED CodeGenPrepare::verifyBFIUpdates(Function &F) {
DominatorTree NewDT(F);
LoopInfo NewLI(NewDT);
BranchProbabilityInfo NewBPI(F, NewLI, TLInfo);
BlockFrequencyInfo NewBFI(F, NewBPI, NewLI);
NewBFI.verifyMatch(*BFI);
}
/// Merge basic blocks which are connected by a single edge, where one of the
/// basic blocks has a single successor pointing to the other basic block,
/// which has a single predecessor.
bool CodeGenPrepare::eliminateFallThrough(Function &F) {
bool Changed = false;
// Scan all of the blocks in the function, except for the entry block.
// Use a temporary array to avoid iterator being invalidated when
// deleting blocks.
SmallVector<WeakTrackingVH, 16> Blocks;
for (auto &Block : llvm::drop_begin(F))
Blocks.push_back(&Block);
SmallSet<WeakTrackingVH, 16> Preds;
for (auto &Block : Blocks) {
auto *BB = cast_or_null<BasicBlock>(Block);
if (!BB)
continue;
// If the destination block has a single pred, then this is a trivial
// edge, just collapse it.
BasicBlock *SinglePred = BB->getSinglePredecessor();
// Don't merge if BB's address is taken.
if (!SinglePred || SinglePred == BB || BB->hasAddressTaken()) continue;
BranchInst *Term = dyn_cast<BranchInst>(SinglePred->getTerminator());
if (Term && !Term->isConditional()) {
Changed = true;
LLVM_DEBUG(dbgs() << "To merge:\n" << *BB << "\n\n\n");
// Merge BB into SinglePred and delete it.
MergeBlockIntoPredecessor(BB);
Preds.insert(SinglePred);
}
}
// (Repeatedly) merging blocks into their predecessors can create redundant
// debug intrinsics.
for (auto &Pred : Preds)
if (auto *BB = cast_or_null<BasicBlock>(Pred))
RemoveRedundantDbgInstrs(BB);
return Changed;
}
/// Find a destination block from BB if BB is mergeable empty block.
BasicBlock *CodeGenPrepare::findDestBlockOfMergeableEmptyBlock(BasicBlock *BB) {
// If this block doesn't end with an uncond branch, ignore it.
BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
if (!BI || !BI->isUnconditional())
return nullptr;
// If the instruction before the branch (skipping debug info) isn't a phi
// node, then other stuff is happening here.
BasicBlock::iterator BBI = BI->getIterator();
if (BBI != BB->begin()) {
--BBI;
while (isa<DbgInfoIntrinsic>(BBI)) {
if (BBI == BB->begin())
break;
--BBI;
}
if (!isa<DbgInfoIntrinsic>(BBI) && !isa<PHINode>(BBI))
return nullptr;
}
// Do not break infinite loops.
BasicBlock *DestBB = BI->getSuccessor(0);
if (DestBB == BB)
return nullptr;
if (!canMergeBlocks(BB, DestBB))
DestBB = nullptr;
return DestBB;
}
/// Eliminate blocks that contain only PHI nodes, debug info directives, and an
/// unconditional branch. Passes before isel (e.g. LSR/loopsimplify) often split
/// edges in ways that are non-optimal for isel. Start by eliminating these
/// blocks so we can split them the way we want them.
bool CodeGenPrepare::eliminateMostlyEmptyBlocks(Function &F) {
SmallPtrSet<BasicBlock *, 16> Preheaders;
SmallVector<Loop *, 16> LoopList(LI->begin(), LI->end());
while (!LoopList.empty()) {
Loop *L = LoopList.pop_back_val();
llvm::append_range(LoopList, *L);
if (BasicBlock *Preheader = L->getLoopPreheader())
Preheaders.insert(Preheader);
}
bool MadeChange = false;
// Copy blocks into a temporary array to avoid iterator invalidation issues
// as we remove them.
// Note that this intentionally skips the entry block.
SmallVector<WeakTrackingVH, 16> Blocks;
for (auto &Block : llvm::drop_begin(F))
Blocks.push_back(&Block);
for (auto &Block : Blocks) {
BasicBlock *BB = cast_or_null<BasicBlock>(Block);
if (!BB)
continue;
BasicBlock *DestBB = findDestBlockOfMergeableEmptyBlock(BB);
if (!DestBB ||
!isMergingEmptyBlockProfitable(BB, DestBB, Preheaders.count(BB)))
continue;
eliminateMostlyEmptyBlock(BB);
MadeChange = true;
}
return MadeChange;
}
bool CodeGenPrepare::isMergingEmptyBlockProfitable(BasicBlock *BB,
BasicBlock *DestBB,
bool isPreheader) {
// Do not delete loop preheaders if doing so would create a critical edge.
// Loop preheaders can be good locations to spill registers. If the
// preheader is deleted and we create a critical edge, registers may be
// spilled in the loop body instead.
if (!DisablePreheaderProtect && isPreheader &&
!(BB->getSinglePredecessor() &&
BB->getSinglePredecessor()->getSingleSuccessor()))
return false;
// Skip merging if the block's successor is also a successor to any callbr
// that leads to this block.
// FIXME: Is this really needed? Is this a correctness issue?
for (BasicBlock *Pred : predecessors(BB)) {
if (auto *CBI = dyn_cast<CallBrInst>((Pred)->getTerminator()))
for (unsigned i = 0, e = CBI->getNumSuccessors(); i != e; ++i)
if (DestBB == CBI->getSuccessor(i))
return false;
}
// Try to skip merging if the unique predecessor of BB is terminated by a
// switch or indirect branch instruction, and BB is used as an incoming block
// of PHIs in DestBB. In such case, merging BB and DestBB would cause ISel to
// add COPY instructions in the predecessor of BB instead of BB (if it is not
// merged). Note that the critical edge created by merging such blocks wont be
// split in MachineSink because the jump table is not analyzable. By keeping
// such empty block (BB), ISel will place COPY instructions in BB, not in the
// predecessor of BB.
BasicBlock *Pred = BB->getUniquePredecessor();
if (!Pred ||
!(isa<SwitchInst>(Pred->getTerminator()) ||
isa<IndirectBrInst>(Pred->getTerminator())))
return true;
if (BB->getTerminator() != BB->getFirstNonPHIOrDbg())
return true;
// We use a simple cost heuristic which determine skipping merging is
// profitable if the cost of skipping merging is less than the cost of
// merging : Cost(skipping merging) < Cost(merging BB), where the
// Cost(skipping merging) is Freq(BB) * (Cost(Copy) + Cost(Branch)), and
// the Cost(merging BB) is Freq(Pred) * Cost(Copy).
// Assuming Cost(Copy) == Cost(Branch), we could simplify it to :
// Freq(Pred) / Freq(BB) > 2.
// Note that if there are multiple empty blocks sharing the same incoming
// value for the PHIs in the DestBB, we consider them together. In such
// case, Cost(merging BB) will be the sum of their frequencies.
if (!isa<PHINode>(DestBB->begin()))
return true;
SmallPtrSet<BasicBlock *, 16> SameIncomingValueBBs;
// Find all other incoming blocks from which incoming values of all PHIs in
// DestBB are the same as the ones from BB.
for (BasicBlock *DestBBPred : predecessors(DestBB)) {
if (DestBBPred == BB)
continue;
if (llvm::all_of(DestBB->phis(), [&](const PHINode &DestPN) {
return DestPN.getIncomingValueForBlock(BB) ==
DestPN.getIncomingValueForBlock(DestBBPred);
}))
SameIncomingValueBBs.insert(DestBBPred);
}
// See if all BB's incoming values are same as the value from Pred. In this
// case, no reason to skip merging because COPYs are expected to be place in
// Pred already.
if (SameIncomingValueBBs.count(Pred))
return true;
BlockFrequency PredFreq = BFI->getBlockFreq(Pred);
BlockFrequency BBFreq = BFI->getBlockFreq(BB);
for (auto *SameValueBB : SameIncomingValueBBs)
if (SameValueBB->getUniquePredecessor() == Pred &&
DestBB == findDestBlockOfMergeableEmptyBlock(SameValueBB))
BBFreq += BFI->getBlockFreq(SameValueBB);
return PredFreq.getFrequency() <=
BBFreq.getFrequency() * FreqRatioToSkipMerge;
}
/// Return true if we can merge BB into DestBB if there is a single
/// unconditional branch between them, and BB contains no other non-phi
/// instructions.
bool CodeGenPrepare::canMergeBlocks(const BasicBlock *BB,
const BasicBlock *DestBB) const {
// We only want to eliminate blocks whose phi nodes are used by phi nodes in
// the successor. If there are more complex condition (e.g. preheaders),
// don't mess around with them.
for (const PHINode &PN : BB->phis()) {
for (const User *U : PN.users()) {
const Instruction *UI = cast<Instruction>(U);
if (UI->getParent() != DestBB || !isa<PHINode>(UI))
return false;
// If User is inside DestBB block and it is a PHINode then check
// incoming value. If incoming value is not from BB then this is
// a complex condition (e.g. preheaders) we want to avoid here.
if (UI->getParent() == DestBB) {
if (const PHINode *UPN = dyn_cast<PHINode>(UI))
for (unsigned I = 0, E = UPN->getNumIncomingValues(); I != E; ++I) {
Instruction *Insn = dyn_cast<Instruction>(UPN->getIncomingValue(I));
if (Insn && Insn->getParent() == BB &&
Insn->getParent() != UPN->getIncomingBlock(I))
return false;
}
}
}
}
// If BB and DestBB contain any common predecessors, then the phi nodes in BB
// and DestBB may have conflicting incoming values for the block. If so, we
// can't merge the block.
const PHINode *DestBBPN = dyn_cast<PHINode>(DestBB->begin());
if (!DestBBPN) return true; // no conflict.
// Collect the preds of BB.
SmallPtrSet<const BasicBlock*, 16> BBPreds;
if (const PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
// It is faster to get preds from a PHI than with pred_iterator.
for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
BBPreds.insert(BBPN->getIncomingBlock(i));
} else {
BBPreds.insert(pred_begin(BB), pred_end(BB));
}
// Walk the preds of DestBB.
for (unsigned i = 0, e = DestBBPN->getNumIncomingValues(); i != e; ++i) {
BasicBlock *Pred = DestBBPN->getIncomingBlock(i);
if (BBPreds.count(Pred)) { // Common predecessor?
for (const PHINode &PN : DestBB->phis()) {
const Value *V1 = PN.getIncomingValueForBlock(Pred);
const Value *V2 = PN.getIncomingValueForBlock(BB);
// If V2 is a phi node in BB, look up what the mapped value will be.
if (const PHINode *V2PN = dyn_cast<PHINode>(V2))
if (V2PN->getParent() == BB)
V2 = V2PN->getIncomingValueForBlock(Pred);
// If there is a conflict, bail out.
if (V1 != V2) return false;
}
}
}
return true;
}
/// Eliminate a basic block that has only phi's and an unconditional branch in
/// it.
void CodeGenPrepare::eliminateMostlyEmptyBlock(BasicBlock *BB) {
BranchInst *BI = cast<BranchInst>(BB->getTerminator());
BasicBlock *DestBB = BI->getSuccessor(0);
LLVM_DEBUG(dbgs() << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n"
<< *BB << *DestBB);
// If the destination block has a single pred, then this is a trivial edge,
// just collapse it.
if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) {
if (SinglePred != DestBB) {
assert(SinglePred == BB &&
"Single predecessor not the same as predecessor");
// Merge DestBB into SinglePred/BB and delete it.
MergeBlockIntoPredecessor(DestBB);
// Note: BB(=SinglePred) will not be deleted on this path.
// DestBB(=its single successor) is the one that was deleted.
LLVM_DEBUG(dbgs() << "AFTER:\n" << *SinglePred << "\n\n\n");
return;
}
}
// Otherwise, we have multiple predecessors of BB. Update the PHIs in DestBB
// to handle the new incoming edges it is about to have.
for (PHINode &PN : DestBB->phis()) {
// Remove the incoming value for BB, and remember it.
Value *InVal = PN.removeIncomingValue(BB, false);
// Two options: either the InVal is a phi node defined in BB or it is some
// value that dominates BB.
PHINode *InValPhi = dyn_cast<PHINode>(InVal);
if (InValPhi && InValPhi->getParent() == BB) {
// Add all of the input values of the input PHI as inputs of this phi.
for (unsigned i = 0, e = InValPhi->getNumIncomingValues(); i != e; ++i)
PN.addIncoming(InValPhi->getIncomingValue(i),
InValPhi->getIncomingBlock(i));
} else {
// Otherwise, add one instance of the dominating value for each edge that
// we will be adding.
if (PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
PN.addIncoming(InVal, BBPN->getIncomingBlock(i));
} else {
for (BasicBlock *Pred : predecessors(BB))
PN.addIncoming(InVal, Pred);
}
}
}
// The PHIs are now updated, change everything that refers to BB to use
// DestBB and remove BB.
BB->replaceAllUsesWith(DestBB);
BB->eraseFromParent();
++NumBlocksElim;
LLVM_DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
}
// Computes a map of base pointer relocation instructions to corresponding
// derived pointer relocation instructions given a vector of all relocate calls
static void computeBaseDerivedRelocateMap(
const SmallVectorImpl<GCRelocateInst *> &AllRelocateCalls,
DenseMap<GCRelocateInst *, SmallVector<GCRelocateInst *, 2>>
&RelocateInstMap) {
// Collect information in two maps: one primarily for locating the base object
// while filling the second map; the second map is the final structure holding
// a mapping between Base and corresponding Derived relocate calls
DenseMap<std::pair<unsigned, unsigned>, GCRelocateInst *> RelocateIdxMap;
for (auto *ThisRelocate : AllRelocateCalls) {
auto K = std::make_pair(ThisRelocate->getBasePtrIndex(),
ThisRelocate->getDerivedPtrIndex());
RelocateIdxMap.insert(std::make_pair(K, ThisRelocate));
}
for (auto &Item : RelocateIdxMap) {
std::pair<unsigned, unsigned> Key = Item.first;
if (Key.first == Key.second)
// Base relocation: nothing to insert
continue;
GCRelocateInst *I = Item.second;
auto BaseKey = std::make_pair(Key.first, Key.first);
// We're iterating over RelocateIdxMap so we cannot modify it.
auto MaybeBase = RelocateIdxMap.find(BaseKey);
if (MaybeBase == RelocateIdxMap.end())
// TODO: We might want to insert a new base object relocate and gep off
// that, if there are enough derived object relocates.
continue;
RelocateInstMap[MaybeBase->second].push_back(I);
}
}
// Accepts a GEP and extracts the operands into a vector provided they're all
// small integer constants
static bool getGEPSmallConstantIntOffsetV(GetElementPtrInst *GEP,
SmallVectorImpl<Value *> &OffsetV) {
for (unsigned i = 1; i < GEP->getNumOperands(); i++) {
// Only accept small constant integer operands
auto *Op = dyn_cast<ConstantInt>(GEP->getOperand(i));
if (!Op || Op->getZExtValue() > 20)
return false;
}
for (unsigned i = 1; i < GEP->getNumOperands(); i++)
OffsetV.push_back(GEP->getOperand(i));
return true;
}
// Takes a RelocatedBase (base pointer relocation instruction) and Targets to
// replace, computes a replacement, and affects it.
static bool
simplifyRelocatesOffABase(GCRelocateInst *RelocatedBase,
const SmallVectorImpl<GCRelocateInst *> &Targets) {
bool MadeChange = false;
// We must ensure the relocation of derived pointer is defined after
// relocation of base pointer. If we find a relocation corresponding to base
// defined earlier than relocation of base then we move relocation of base
// right before found relocation. We consider only relocation in the same
// basic block as relocation of base. Relocations from other basic block will
// be skipped by optimization and we do not care about them.
for (auto R = RelocatedBase->getParent()->getFirstInsertionPt();
&*R != RelocatedBase; ++R)
if (auto *RI = dyn_cast<GCRelocateInst>(R))
if (RI->getStatepoint() == RelocatedBase->getStatepoint())
if (RI->getBasePtrIndex() == RelocatedBase->getBasePtrIndex()) {
RelocatedBase->moveBefore(RI);
break;
}
for (GCRelocateInst *ToReplace : Targets) {
assert(ToReplace->getBasePtrIndex() == RelocatedBase->getBasePtrIndex() &&
"Not relocating a derived object of the original base object");
if (ToReplace->getBasePtrIndex() == ToReplace->getDerivedPtrIndex()) {
// A duplicate relocate call. TODO: coalesce duplicates.
continue;
}
if (RelocatedBase->getParent() != ToReplace->getParent()) {
// Base and derived relocates are in different basic blocks.
// In this case transform is only valid when base dominates derived
// relocate. However it would be too expensive to check dominance
// for each such relocate, so we skip the whole transformation.
continue;
}
Value *Base = ToReplace->getBasePtr();
auto *Derived = dyn_cast<GetElementPtrInst>(ToReplace->getDerivedPtr());
if (!Derived || Derived->getPointerOperand() != Base)
continue;
SmallVector<Value *, 2> OffsetV;
if (!getGEPSmallConstantIntOffsetV(Derived, OffsetV))
continue;
// Create a Builder and replace the target callsite with a gep
assert(RelocatedBase->getNextNode() &&
"Should always have one since it's not a terminator");
// Insert after RelocatedBase
IRBuilder<> Builder(RelocatedBase->getNextNode());
Builder.SetCurrentDebugLocation(ToReplace->getDebugLoc());
// If gc_relocate does not match the actual type, cast it to the right type.
// In theory, there must be a bitcast after gc_relocate if the type does not
// match, and we should reuse it to get the derived pointer. But it could be
// cases like this:
// bb1:
// ...
// %g1 = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(...)
// br label %merge
//
// bb2:
// ...
// %g2 = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(...)
// br label %merge
//
// merge:
// %p1 = phi i8 addrspace(1)* [ %g1, %bb1 ], [ %g2, %bb2 ]
// %cast = bitcast i8 addrspace(1)* %p1 in to i32 addrspace(1)*
//
// In this case, we can not find the bitcast any more. So we insert a new bitcast
// no matter there is already one or not. In this way, we can handle all cases, and
// the extra bitcast should be optimized away in later passes.
Value *ActualRelocatedBase = RelocatedBase;
if (RelocatedBase->getType() != Base->getType()) {
ActualRelocatedBase =
Builder.CreateBitCast(RelocatedBase, Base->getType());
}
Value *Replacement = Builder.CreateGEP(
Derived->getSourceElementType(), ActualRelocatedBase, makeArrayRef(OffsetV));
Replacement->takeName(ToReplace);
// If the newly generated derived pointer's type does not match the original derived
// pointer's type, cast the new derived pointer to match it. Same reasoning as above.
Value *ActualReplacement = Replacement;
if (Replacement->getType() != ToReplace->getType()) {
ActualReplacement =
Builder.CreateBitCast(Replacement, ToReplace->getType());
}
ToReplace->replaceAllUsesWith(ActualReplacement);
ToReplace->eraseFromParent();
MadeChange = true;
}
return MadeChange;
}
// Turns this:
//
// %base = ...
// %ptr = gep %base + 15
// %tok = statepoint (%fun, i32 0, i32 0, i32 0, %base, %ptr)
// %base' = relocate(%tok, i32 4, i32 4)
// %ptr' = relocate(%tok, i32 4, i32 5)
// %val = load %ptr'
//
// into this:
//
// %base = ...
// %ptr = gep %base + 15
// %tok = statepoint (%fun, i32 0, i32 0, i32 0, %base, %ptr)
// %base' = gc.relocate(%tok, i32 4, i32 4)
// %ptr' = gep %base' + 15
// %val = load %ptr'
bool CodeGenPrepare::simplifyOffsetableRelocate(GCStatepointInst &I) {
bool MadeChange = false;
SmallVector<GCRelocateInst *, 2> AllRelocateCalls;
for (auto *U : I.users())
if (GCRelocateInst *Relocate = dyn_cast<GCRelocateInst>(U))
// Collect all the relocate calls associated with a statepoint
AllRelocateCalls.push_back(Relocate);
// We need at least one base pointer relocation + one derived pointer
// relocation to mangle
if (AllRelocateCalls.size() < 2)
return false;
// RelocateInstMap is a mapping from the base relocate instruction to the
// corresponding derived relocate instructions
DenseMap<GCRelocateInst *, SmallVector<GCRelocateInst *, 2>> RelocateInstMap;
computeBaseDerivedRelocateMap(AllRelocateCalls, RelocateInstMap);
if (RelocateInstMap.empty())
return false;
for (auto &Item : RelocateInstMap)
// Item.first is the RelocatedBase to offset against
// Item.second is the vector of Targets to replace
MadeChange = simplifyRelocatesOffABase(Item.first, Item.second);
return MadeChange;
}
/// Sink the specified cast instruction into its user blocks.
static bool SinkCast(CastInst *CI) {
BasicBlock *DefBB = CI->getParent();
/// InsertedCasts - Only insert a cast in each block once.
DenseMap<BasicBlock*, CastInst*> InsertedCasts;
bool MadeChange = false;
for (Value::user_iterator UI = CI->user_begin(), E = CI->user_end();
UI != E; ) {
Use &TheUse = UI.getUse();
Instruction *User = cast<Instruction>(*UI);
// Figure out which BB this cast is used in. For PHI's this is the
// appropriate predecessor block.
BasicBlock *UserBB = User->getParent();
if (PHINode *PN = dyn_cast<PHINode>(User)) {
UserBB = PN->getIncomingBlock(TheUse);
}
// Preincrement use iterator so we don't invalidate it.
++UI;
// The first insertion point of a block containing an EH pad is after the
// pad. If the pad is the user, we cannot sink the cast past the pad.
if (User->isEHPad())
continue;
// If the block selected to receive the cast is an EH pad that does not
// allow non-PHI instructions before the terminator, we can't sink the
// cast.
if (UserBB->getTerminator()->isEHPad())
continue;
// If this user is in the same block as the cast, don't change the cast.
if (UserBB == DefBB) continue;
// If we have already inserted a cast into this block, use it.
CastInst *&InsertedCast = InsertedCasts[UserBB];
if (!InsertedCast) {
BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
assert(InsertPt != UserBB->end());
InsertedCast = CastInst::Create(CI->getOpcode(), CI->getOperand(0),
CI->getType(), "", &*InsertPt);
InsertedCast->setDebugLoc(CI->getDebugLoc());
}
// Replace a use of the cast with a use of the new cast.
TheUse = InsertedCast;
MadeChange = true;
++NumCastUses;
}
// If we removed all uses, nuke the cast.
if (CI->use_empty()) {
salvageDebugInfo(*CI);
CI->eraseFromParent();
MadeChange = true;
}
return MadeChange;
}
/// If the specified cast instruction is a noop copy (e.g. it's casting from
/// one pointer type to another, i32->i8 on PPC), sink it into user blocks to
/// reduce the number of virtual registers that must be created and coalesced.
///
/// Return true if any changes are made.
static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI,
const DataLayout &DL) {
// Sink only "cheap" (or nop) address-space casts. This is a weaker condition
// than sinking only nop casts, but is helpful on some platforms.
if (auto *ASC = dyn_cast<AddrSpaceCastInst>(CI)) {
if (!TLI.isFreeAddrSpaceCast(ASC->getSrcAddressSpace(),
ASC->getDestAddressSpace()))
return false;
}
// If this is a noop copy,
EVT SrcVT = TLI.getValueType(DL, CI->getOperand(0)->getType());
EVT DstVT = TLI.getValueType(DL, CI->getType());
// This is an fp<->int conversion?
if (SrcVT.isInteger() != DstVT.isInteger())
return false;
// If this is an extension, it will be a zero or sign extension, which
// isn't a noop.
if (SrcVT.bitsLT(DstVT)) return false;
// If these values will be promoted, find out what they will be promoted
// to. This helps us consider truncates on PPC as noop copies when they
// are.
if (TLI.getTypeAction(CI->getContext(), SrcVT) ==
TargetLowering::TypePromoteInteger)
SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT);
if (TLI.getTypeAction(CI->getContext(), DstVT) ==
TargetLowering::TypePromoteInteger)
DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT);
// If, after promotion, these are the same types, this is a noop copy.
if (SrcVT != DstVT)
return false;
return SinkCast(CI);
}
// Match a simple increment by constant operation. Note that if a sub is
// matched, the step is negated (as if the step had been canonicalized to
// an add, even though we leave the instruction alone.)
bool matchIncrement(const Instruction* IVInc, Instruction *&LHS,
Constant *&Step) {
if (match(IVInc, m_Add(m_Instruction(LHS), m_Constant(Step))) ||
match(IVInc, m_ExtractValue<0>(m_Intrinsic<Intrinsic::uadd_with_overflow>(
m_Instruction(LHS), m_Constant(Step)))))
return true;
if (match(IVInc, m_Sub(m_Instruction(LHS), m_Constant(Step))) ||
match(IVInc, m_ExtractValue<0>(m_Intrinsic<Intrinsic::usub_with_overflow>(
m_Instruction(LHS), m_Constant(Step))))) {
Step = ConstantExpr::getNeg(Step);
return true;
}
return false;
}
/// If given \p PN is an inductive variable with value IVInc coming from the
/// backedge, and on each iteration it gets increased by Step, return pair
/// <IVInc, Step>. Otherwise, return None.
static Optional<std::pair<Instruction *, Constant *> >
getIVIncrement(const PHINode *PN, const LoopInfo *LI) {
const Loop *L = LI->getLoopFor(PN->getParent());
if (!L || L->getHeader() != PN->getParent() || !L->getLoopLatch())
return None;
auto *IVInc =
dyn_cast<Instruction>(PN->getIncomingValueForBlock(L->getLoopLatch()));
if (!IVInc || LI->getLoopFor(IVInc->getParent()) != L)
return None;
Instruction *LHS = nullptr;
Constant *Step = nullptr;
if (matchIncrement(IVInc, LHS, Step) && LHS == PN)
return std::make_pair(IVInc, Step);
return None;
}
static bool isIVIncrement(const Value *V, const LoopInfo *LI) {
auto *I = dyn_cast<Instruction>(V);
if (!I)
return false;
Instruction *LHS = nullptr;
Constant *Step = nullptr;
if (!matchIncrement(I, LHS, Step))
return false;
if (auto *PN = dyn_cast<PHINode>(LHS))
if (auto IVInc = getIVIncrement(PN, LI))
return IVInc->first == I;
return false;
}
bool CodeGenPrepare::replaceMathCmpWithIntrinsic(BinaryOperator *BO,
Value *Arg0, Value *Arg1,
CmpInst *Cmp,
Intrinsic::ID IID) {
auto IsReplacableIVIncrement = [this, &Cmp](BinaryOperator *BO) {
if (!isIVIncrement(BO, LI))
return false;
const Loop *L = LI->getLoopFor(BO->getParent());
assert(L && "L should not be null after isIVIncrement()");
// Do not risk on moving increment into a child loop.
if (LI->getLoopFor(Cmp->getParent()) != L)
return false;
// Finally, we need to ensure that the insert point will dominate all
// existing uses of the increment.
auto &DT = getDT(*BO->getParent()->getParent());
if (DT.dominates(Cmp->getParent(), BO->getParent()))
// If we're moving up the dom tree, all uses are trivially dominated.
// (This is the common case for code produced by LSR.)
return true;
// Otherwise, special case the single use in the phi recurrence.
return BO->hasOneUse() && DT.dominates(Cmp->getParent(), L->getLoopLatch());
};
if (BO->getParent() != Cmp->getParent() && !IsReplacableIVIncrement(BO)) {
// We used to use a dominator tree here to allow multi-block optimization.
// But that was problematic because:
// 1. It could cause a perf regression by hoisting the math op into the
// critical path.
// 2. It could cause a perf regression by creating a value that was live
// across multiple blocks and increasing register pressure.
// 3. Use of a dominator tree could cause large compile-time regression.
// This is because we recompute the DT on every change in the main CGP
// run-loop. The recomputing is probably unnecessary in many cases, so if
// that was fixed, using a DT here would be ok.
//
// There is one important particular case we still want to handle: if BO is
// the IV increment. Important properties that make it profitable:
// - We can speculate IV increment anywhere in the loop (as long as the
// indvar Phi is its only user);
// - Upon computing Cmp, we effectively compute something equivalent to the
// IV increment (despite it loops differently in the IR). So moving it up
// to the cmp point does not really increase register pressure.
return false;
}
// We allow matching the canonical IR (add X, C) back to (usubo X, -C).
if (BO->getOpcode() == Instruction::Add &&
IID == Intrinsic::usub_with_overflow) {
assert(isa<Constant>(Arg1) && "Unexpected input for usubo");
Arg1 = ConstantExpr::getNeg(cast<Constant>(Arg1));
}
// Insert at the first instruction of the pair.
Instruction *InsertPt = nullptr;
for (Instruction &Iter : *Cmp->getParent()) {
// If BO is an XOR, it is not guaranteed that it comes after both inputs to
// the overflow intrinsic are defined.
if ((BO->getOpcode() != Instruction::Xor && &Iter == BO) || &Iter == Cmp) {
InsertPt = &Iter;
break;
}
}
assert(InsertPt != nullptr && "Parent block did not contain cmp or binop");
IRBuilder<> Builder(InsertPt);
Value *MathOV = Builder.CreateBinaryIntrinsic(IID, Arg0, Arg1);
if (BO->getOpcode() != Instruction::Xor) {
Value *Math = Builder.CreateExtractValue(MathOV, 0, "math");
BO->replaceAllUsesWith(Math);
} else
assert(BO->hasOneUse() &&
"Patterns with XOr should use the BO only in the compare");
Value *OV = Builder.CreateExtractValue(MathOV, 1, "ov");
Cmp->replaceAllUsesWith(OV);
Cmp->eraseFromParent();
BO->eraseFromParent();
return true;
}
/// Match special-case patterns that check for unsigned add overflow.
static bool matchUAddWithOverflowConstantEdgeCases(CmpInst *Cmp,
BinaryOperator *&Add) {
// Add = add A, 1; Cmp = icmp eq A,-1 (overflow if A is max val)
// Add = add A,-1; Cmp = icmp ne A, 0 (overflow if A is non-zero)
Value *A = Cmp->getOperand(0), *B = Cmp->getOperand(1);
// We are not expecting non-canonical/degenerate code. Just bail out.
if (isa<Constant>(A))
return false;
ICmpInst::Predicate Pred = Cmp->getPredicate();
if (Pred == ICmpInst::ICMP_EQ && match(B, m_AllOnes()))
B = ConstantInt::get(B->getType(), 1);
else if (Pred == ICmpInst::ICMP_NE && match(B, m_ZeroInt()))
B = ConstantInt::get(B->getType(), -1);
else
return false;
// Check the users of the variable operand of the compare looking for an add
// with the adjusted constant.
for (User *U : A->users()) {
if (match(U, m_Add(m_Specific(A), m_Specific(B)))) {
Add = cast<BinaryOperator>(U);
return true;
}
}
return false;
}
/// Try to combine the compare into a call to the llvm.uadd.with.overflow
/// intrinsic. Return true if any changes were made.
bool CodeGenPrepare::combineToUAddWithOverflow(CmpInst *Cmp,
bool &ModifiedDT) {
Value *A, *B;
BinaryOperator *Add;
if (!match(Cmp, m_UAddWithOverflow(m_Value(A), m_Value(B), m_BinOp(Add)))) {
if (!matchUAddWithOverflowConstantEdgeCases(Cmp, Add))
return false;
// Set A and B in case we match matchUAddWithOverflowConstantEdgeCases.
A = Add->getOperand(0);
B = Add->getOperand(1);
}
if (!TLI->shouldFormOverflowOp(ISD::UADDO,
TLI->getValueType(*DL, Add->getType()),
Add->hasNUsesOrMore(2)))
return false;
// We don't want to move around uses of condition values this late, so we
// check if it is legal to create the call to the intrinsic in the basic
// block containing the icmp.
if (Add->getParent() != Cmp->getParent() && !Add->hasOneUse())
return false;
if (!replaceMathCmpWithIntrinsic(Add, A, B, Cmp,
Intrinsic::uadd_with_overflow))
return false;
// Reset callers - do not crash by iterating over a dead instruction.
ModifiedDT = true;
return true;
}
bool CodeGenPrepare::combineToUSubWithOverflow(CmpInst *Cmp,
bool &ModifiedDT) {
// We are not expecting non-canonical/degenerate code. Just bail out.
Value *A = Cmp->getOperand(0), *B = Cmp->getOperand(1);
if (isa<Constant>(A) && isa<Constant>(B))
return false;
// Convert (A u> B) to (A u< B) to simplify pattern matching.
ICmpInst::Predicate Pred = Cmp->getPredicate();
if (Pred == ICmpInst::ICMP_UGT) {
std::swap(A, B);
Pred = ICmpInst::ICMP_ULT;
}
// Convert special-case: (A == 0) is the same as (A u< 1).
if (Pred == ICmpInst::ICMP_EQ && match(B, m_ZeroInt())) {
B = ConstantInt::get(B->getType(), 1);
Pred = ICmpInst::ICMP_ULT;
}
// Convert special-case: (A != 0) is the same as (0 u< A).
if (Pred == ICmpInst::ICMP_NE && match(B, m_ZeroInt())) {
std::swap(A, B);
Pred = ICmpInst::ICMP_ULT;
}
if (Pred != ICmpInst::ICMP_ULT)
return false;
// Walk the users of a variable operand of a compare looking for a subtract or
// add with that same operand. Also match the 2nd operand of the compare to
// the add/sub, but that may be a negated constant operand of an add.
Value *CmpVariableOperand = isa<Constant>(A) ? B : A;
BinaryOperator *Sub = nullptr;
for (User *U : CmpVariableOperand->users()) {
// A - B, A u< B --> usubo(A, B)
if (match(U, m_Sub(m_Specific(A), m_Specific(B)))) {
Sub = cast<BinaryOperator>(U);
break;
}
// A + (-C), A u< C (canonicalized form of (sub A, C))
const APInt *CmpC, *AddC;
if (match(U, m_Add(m_Specific(A), m_APInt(AddC))) &&
match(B, m_APInt(CmpC)) && *AddC == -(*CmpC)) {
Sub = cast<BinaryOperator>(U);
break;
}
}
if (!Sub)
return false;
if (!TLI->shouldFormOverflowOp(ISD::USUBO,
TLI->getValueType(*DL, Sub->getType()),
Sub->hasNUsesOrMore(2)))
return false;
if (!replaceMathCmpWithIntrinsic(Sub, Sub->getOperand(0), Sub->getOperand(1),
Cmp, Intrinsic::usub_with_overflow))
return false;
// Reset callers - do not crash by iterating over a dead instruction.
ModifiedDT = true;
return true;
}
/// Sink the given CmpInst into user blocks to reduce the number of virtual
/// registers that must be created and coalesced. This is a clear win except on
/// targets with multiple condition code registers (PowerPC), where it might
/// lose; some adjustment may be wanted there.
///
/// Return true if any changes are made.
static bool sinkCmpExpression(CmpInst *Cmp, const TargetLowering &TLI) {
if (TLI.hasMultipleConditionRegisters())
return false;
// Avoid sinking soft-FP comparisons, since this can move them into a loop.
if (TLI.useSoftFloat() && isa<FCmpInst>(Cmp))
return false;
// Only insert a cmp in each block once.
DenseMap<BasicBlock*, CmpInst*> InsertedCmps;
bool MadeChange = false;
for (Value::user_iterator UI = Cmp->user_begin(), E = Cmp->user_end();
UI != E; ) {
Use &TheUse = UI.getUse();
Instruction *User = cast<Instruction>(*UI);
// Preincrement use iterator so we don't invalidate it.
++UI;
// Don't bother for PHI nodes.
if (isa<PHINode>(User))
continue;
// Figure out which BB this cmp is used in.
BasicBlock *UserBB = User->getParent();
BasicBlock *DefBB = Cmp->getParent();
// If this user is in the same block as the cmp, don't change the cmp.
if (UserBB == DefBB) continue;
// If we have already inserted a cmp into this block, use it.
CmpInst *&InsertedCmp = InsertedCmps[UserBB];
if (!InsertedCmp) {
BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
assert(InsertPt != UserBB->end());
InsertedCmp =
CmpInst::Create(Cmp->getOpcode(), Cmp->getPredicate(),
Cmp->getOperand(0), Cmp->getOperand(1), "",
&*InsertPt);
// Propagate the debug info.
InsertedCmp->setDebugLoc(Cmp->getDebugLoc());
}
// Replace a use of the cmp with a use of the new cmp.
TheUse = InsertedCmp;
MadeChange = true;
++NumCmpUses;
}
// If we removed all uses, nuke the cmp.
if (Cmp->use_empty()) {
Cmp->eraseFromParent();
MadeChange = true;
}
return MadeChange;
}
/// For pattern like:
///
/// DomCond = icmp sgt/slt CmpOp0, CmpOp1 (might not be in DomBB)
/// ...
/// DomBB:
/// ...
/// br DomCond, TrueBB, CmpBB
/// CmpBB: (with DomBB being the single predecessor)
/// ...
/// Cmp = icmp eq CmpOp0, CmpOp1
/// ...
///
/// It would use two comparison on targets that lowering of icmp sgt/slt is
/// different from lowering of icmp eq (PowerPC). This function try to convert
/// 'Cmp = icmp eq CmpOp0, CmpOp1' to ' Cmp = icmp slt/sgt CmpOp0, CmpOp1'.
/// After that, DomCond and Cmp can use the same comparison so reduce one
/// comparison.
///
/// Return true if any changes are made.
static bool foldICmpWithDominatingICmp(CmpInst *Cmp,
const TargetLowering &TLI) {
if (!EnableICMP_EQToICMP_ST && TLI.isEqualityCmpFoldedWithSignedCmp())
return false;
ICmpInst::Predicate Pred = Cmp->getPredicate();
if (Pred != ICmpInst::ICMP_EQ)
return false;
// If icmp eq has users other than BranchInst and SelectInst, converting it to
// icmp slt/sgt would introduce more redundant LLVM IR.
for (User *U : Cmp->users()) {
if (isa<BranchInst>(U))
continue;
if (isa<SelectInst>(U) && cast<SelectInst>(U)->getCondition() == Cmp)
continue;
return false;
}
// This is a cheap/incomplete check for dominance - just match a single
// predecessor with a conditional branch.
BasicBlock *CmpBB = Cmp->getParent();
BasicBlock *DomBB = CmpBB->getSinglePredecessor();
if (!DomBB)
return false;
// We want to ensure that the only way control gets to the comparison of
// interest is that a less/greater than comparison on the same operands is
// false.
Value *DomCond;
BasicBlock *TrueBB, *FalseBB;
if (!match(DomBB->getTerminator(), m_Br(m_Value(DomCond), TrueBB, FalseBB)))
return false;
if (CmpBB != FalseBB)
return false;
Value *CmpOp0 = Cmp->getOperand(0), *CmpOp1 = Cmp->getOperand(1);
ICmpInst::Predicate DomPred;
if (!match(DomCond, m_ICmp(DomPred, m_Specific(CmpOp0), m_Specific(CmpOp1))))
return false;
if (DomPred != ICmpInst::ICMP_SGT && DomPred != ICmpInst::ICMP_SLT)
return false;
// Convert the equality comparison to the opposite of the dominating
// comparison and swap the direction for all branch/select users.
// We have conceptually converted:
// Res = (a < b) ? <LT_RES> : (a == b) ? <EQ_RES> : <GT_RES>;
// to
// Res = (a < b) ? <LT_RES> : (a > b) ? <GT_RES> : <EQ_RES>;
// And similarly for branches.
for (User *U : Cmp->users()) {
if (auto *BI = dyn_cast<BranchInst>(U)) {
assert(BI->isConditional() && "Must be conditional");
BI->swapSuccessors();
continue;
}
if (auto *SI = dyn_cast<SelectInst>(U)) {
// Swap operands
SI->swapValues();
SI->swapProfMetadata();
continue;
}
llvm_unreachable("Must be a branch or a select");
}
Cmp->setPredicate(CmpInst::getSwappedPredicate(DomPred));
return true;
}
bool CodeGenPrepare::optimizeCmp(CmpInst *Cmp, bool &ModifiedDT) {
if (sinkCmpExpression(Cmp, *TLI))
return true;
if (combineToUAddWithOverflow(Cmp, ModifiedDT))
return true;
if (combineToUSubWithOverflow(Cmp, ModifiedDT))
return true;
if (foldICmpWithDominatingICmp(Cmp, *TLI))
return true;
return false;
}
/// Duplicate and sink the given 'and' instruction into user blocks where it is
/// used in a compare to allow isel to generate better code for targets where
/// this operation can be combined.
///
/// Return true if any changes are made.
static bool sinkAndCmp0Expression(Instruction *AndI,
const TargetLowering &TLI,
SetOfInstrs &InsertedInsts) {
// Double-check that we're not trying to optimize an instruction that was
// already optimized by some other part of this pass.
assert(!InsertedInsts.count(AndI) &&
"Attempting to optimize already optimized and instruction");
(void) InsertedInsts;
// Nothing to do for single use in same basic block.
if (AndI->hasOneUse() &&
AndI->getParent() == cast<Instruction>(*AndI->user_begin())->getParent())
return false;
// Try to avoid cases where sinking/duplicating is likely to increase register
// pressure.
if (!isa<ConstantInt>(AndI->getOperand(0)) &&
!isa<ConstantInt>(AndI->getOperand(1)) &&
AndI->getOperand(0)->hasOneUse() && AndI->getOperand(1)->hasOneUse())
return false;
for (auto *U : AndI->users()) {
Instruction *User = cast<Instruction>(U);
// Only sink 'and' feeding icmp with 0.
if (!isa<ICmpInst>(User))
return false;
auto *CmpC = dyn_cast<ConstantInt>(User->getOperand(1));
if (!CmpC || !CmpC->isZero())
return false;
}
if (!TLI.isMaskAndCmp0FoldingBeneficial(*AndI))
return false;
LLVM_DEBUG(dbgs() << "found 'and' feeding only icmp 0;\n");
LLVM_DEBUG(AndI->getParent()->dump());
// Push the 'and' into the same block as the icmp 0. There should only be
// one (icmp (and, 0)) in each block, since CSE/GVN should have removed any
// others, so we don't need to keep track of which BBs we insert into.
for (Value::user_iterator UI = AndI->user_begin(), E = AndI->user_end();
UI != E; ) {
Use &TheUse = UI.getUse();
Instruction *User = cast<Instruction>(*UI);
// Preincrement use iterator so we don't invalidate it.
++UI;
LLVM_DEBUG(dbgs() << "sinking 'and' use: " << *User << "\n");
// Keep the 'and' in the same place if the use is already in the same block.
Instruction *InsertPt =
User->getParent() == AndI->getParent() ? AndI : User;
Instruction *InsertedAnd =
BinaryOperator::Create(Instruction::And, AndI->getOperand(0),
AndI->getOperand(1), "", InsertPt);
// Propagate the debug info.
InsertedAnd->setDebugLoc(AndI->getDebugLoc());
// Replace a use of the 'and' with a use of the new 'and'.
TheUse = InsertedAnd;
++NumAndUses;
LLVM_DEBUG(User->getParent()->dump());
}
// We removed all uses, nuke the and.
AndI->eraseFromParent();
return true;
}
/// Check if the candidates could be combined with a shift instruction, which
/// includes:
/// 1. Truncate instruction
/// 2. And instruction and the imm is a mask of the low bits:
/// imm & (imm+1) == 0
static bool isExtractBitsCandidateUse(Instruction *User) {
if (!isa<TruncInst>(User)) {
if (User->getOpcode() != Instruction::And ||
!isa<ConstantInt>(User->getOperand(1)))
return false;
const APInt &Cimm = cast<ConstantInt>(User->getOperand(1))->getValue();
if ((Cimm & (Cimm + 1)).getBoolValue())
return false;
}
return true;
}
/// Sink both shift and truncate instruction to the use of truncate's BB.
static bool
SinkShiftAndTruncate(BinaryOperator *ShiftI, Instruction *User, ConstantInt *CI,
DenseMap<BasicBlock *, BinaryOperator *> &InsertedShifts,
const TargetLowering &TLI, const DataLayout &DL) {
BasicBlock *UserBB = User->getParent();
DenseMap<BasicBlock *, CastInst *> InsertedTruncs;
auto *TruncI = cast<TruncInst>(User);
bool MadeChange = false;
for (Value::user_iterator TruncUI = TruncI->user_begin(),
TruncE = TruncI->user_end();
TruncUI != TruncE;) {
Use &TruncTheUse = TruncUI.getUse();
Instruction *TruncUser = cast<Instruction>(*TruncUI);
// Preincrement use iterator so we don't invalidate it.
++TruncUI;
int ISDOpcode = TLI.InstructionOpcodeToISD(TruncUser->getOpcode());
if (!ISDOpcode)
continue;
// If the use is actually a legal node, there will not be an
// implicit truncate.
// FIXME: always querying the result type is just an
// approximation; some nodes' legality is determined by the
// operand or other means. There's no good way to find out though.
if (TLI.isOperationLegalOrCustom(
ISDOpcode, TLI.getValueType(DL, TruncUser->getType(), true)))
continue;
// Don't bother for PHI nodes.
if (isa<PHINode>(TruncUser))
continue;
BasicBlock *TruncUserBB = TruncUser->getParent();
if (UserBB == TruncUserBB)
continue;
BinaryOperator *&InsertedShift = InsertedShifts[TruncUserBB];
CastInst *&InsertedTrunc = InsertedTruncs[TruncUserBB];
if (!InsertedShift && !InsertedTrunc) {
BasicBlock::iterator InsertPt = TruncUserBB->getFirstInsertionPt();
assert(InsertPt != TruncUserBB->end());
// Sink the shift
if (ShiftI->getOpcode() == Instruction::AShr)
InsertedShift = BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI,
"", &*InsertPt);
else
InsertedShift = BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI,
"", &*InsertPt);
InsertedShift->setDebugLoc(ShiftI->getDebugLoc());
// Sink the trunc
BasicBlock::iterator TruncInsertPt = TruncUserBB->getFirstInsertionPt();
TruncInsertPt++;
assert(TruncInsertPt != TruncUserBB->end());
InsertedTrunc = CastInst::Create(TruncI->getOpcode(), InsertedShift,
TruncI->getType(), "", &*TruncInsertPt);
InsertedTrunc->setDebugLoc(TruncI->getDebugLoc());
MadeChange = true;
TruncTheUse = InsertedTrunc;
}
}
return MadeChange;
}
/// Sink the shift *right* instruction into user blocks if the uses could
/// potentially be combined with this shift instruction and generate BitExtract
/// instruction. It will only be applied if the architecture supports BitExtract
/// instruction. Here is an example:
/// BB1:
/// %x.extract.shift = lshr i64 %arg1, 32
/// BB2:
/// %x.extract.trunc = trunc i64 %x.extract.shift to i16
/// ==>
///
/// BB2:
/// %x.extract.shift.1 = lshr i64 %arg1, 32
/// %x.extract.trunc = trunc i64 %x.extract.shift.1 to i16
///
/// CodeGen will recognize the pattern in BB2 and generate BitExtract
/// instruction.
/// Return true if any changes are made.
static bool OptimizeExtractBits(BinaryOperator *ShiftI, ConstantInt *CI,
const TargetLowering &TLI,
const DataLayout &DL) {
BasicBlock *DefBB = ShiftI->getParent();
/// Only insert instructions in each block once.
DenseMap<BasicBlock *, BinaryOperator *> InsertedShifts;
bool shiftIsLegal = TLI.isTypeLegal(TLI.getValueType(DL, ShiftI->getType()));
bool MadeChange = false;
for (Value::user_iterator UI = ShiftI->user_begin(), E = ShiftI->user_end();
UI != E;) {
Use &TheUse = UI.getUse();
Instruction *User = cast<Instruction>(*UI);
// Preincrement use iterator so we don't invalidate it.
++UI;
// Don't bother for PHI nodes.
if (isa<PHINode>(User))
continue;
if (!isExtractBitsCandidateUse(User))
continue;
BasicBlock *UserBB = User->getParent();
if (UserBB == DefBB) {
// If the shift and truncate instruction are in the same BB. The use of
// the truncate(TruncUse) may still introduce another truncate if not
// legal. In this case, we would like to sink both shift and truncate
// instruction to the BB of TruncUse.
// for example:
// BB1:
// i64 shift.result = lshr i64 opnd, imm
// trunc.result = trunc shift.result to i16
//
// BB2:
// ----> We will have an implicit truncate here if the architecture does
// not have i16 compare.
// cmp i16 trunc.result, opnd2
//
if (isa<TruncInst>(User) && shiftIsLegal
// If the type of the truncate is legal, no truncate will be
// introduced in other basic blocks.
&&
(!TLI.isTypeLegal(TLI.getValueType(DL, User->getType()))))
MadeChange =
SinkShiftAndTruncate(ShiftI, User, CI, InsertedShifts, TLI, DL);
continue;
}
// If we have already inserted a shift into this block, use it.
BinaryOperator *&InsertedShift = InsertedShifts[UserBB];
if (!InsertedShift) {
BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
assert(InsertPt != UserBB->end());
if (ShiftI->getOpcode() == Instruction::AShr)
InsertedShift = BinaryOperator::CreateAShr(ShiftI->getOperand(0), CI,
"", &*InsertPt);
else
InsertedShift = BinaryOperator::CreateLShr(ShiftI->getOperand(0), CI,
"", &*InsertPt);
InsertedShift->setDebugLoc(ShiftI->getDebugLoc());
MadeChange = true;
}
// Replace a use of the shift with a use of the new shift.
TheUse = InsertedShift;
}
// If we removed all uses, or there are none, nuke the shift.
if (ShiftI->use_empty()) {
salvageDebugInfo(*ShiftI);
ShiftI->eraseFromParent();
MadeChange = true;
}
return MadeChange;
}
/// If counting leading or trailing zeros is an expensive operation and a zero
/// input is defined, add a check for zero to avoid calling the intrinsic.
///
/// We want to transform:
/// %z = call i64 @llvm.cttz.i64(i64 %A, i1 false)
///
/// into:
/// entry:
/// %cmpz = icmp eq i64 %A, 0
/// br i1 %cmpz, label %cond.end, label %cond.false
/// cond.false:
/// %z = call i64 @llvm.cttz.i64(i64 %A, i1 true)
/// br label %cond.end
/// cond.end:
/// %ctz = phi i64 [ 64, %entry ], [ %z, %cond.false ]
///
/// If the transform is performed, return true and set ModifiedDT to true.
static bool despeculateCountZeros(IntrinsicInst *CountZeros,
const TargetLowering *TLI,
const DataLayout *DL,
bool &ModifiedDT) {
// If a zero input is undefined, it doesn't make sense to despeculate that.
if (match(CountZeros->getOperand(1), m_One()))
return false;
// If it's cheap to speculate, there's nothing to do.
auto IntrinsicID = CountZeros->getIntrinsicID();
if ((IntrinsicID == Intrinsic::cttz && TLI->isCheapToSpeculateCttz()) ||
(IntrinsicID == Intrinsic::ctlz && TLI->isCheapToSpeculateCtlz()))
return false;
// Only handle legal scalar cases. Anything else requires too much work.
Type *Ty = CountZeros->getType();
unsigned SizeInBits = Ty->getScalarSizeInBits();
if (Ty->isVectorTy() || SizeInBits > DL->getLargestLegalIntTypeSizeInBits())
return false;
// Bail if the value is never zero.
Value *Op = CountZeros->getOperand(0);
if (isKnownNonZero(Op, *DL))
return false;
// The intrinsic will be sunk behind a compare against zero and branch.
BasicBlock *StartBlock = CountZeros->getParent();
BasicBlock *CallBlock = StartBlock->splitBasicBlock(CountZeros, "cond.false");
// Create another block after the count zero intrinsic. A PHI will be added
// in this block to select the result of the intrinsic or the bit-width
// constant if the input to the intrinsic is zero.
BasicBlock::iterator SplitPt = ++(BasicBlock::iterator(CountZeros));
BasicBlock *EndBlock = CallBlock->splitBasicBlock(SplitPt, "cond.end");
// Set up a builder to create a compare, conditional branch, and PHI.
IRBuilder<> Builder(CountZeros->getContext());
Builder.SetInsertPoint(StartBlock->getTerminator());
Builder.SetCurrentDebugLocation(CountZeros->getDebugLoc());
// Replace the unconditional branch that was created by the first split with
// a compare against zero and a conditional branch.
Value *Zero = Constant::getNullValue(Ty);
// Avoid introducing branch on poison.
if (!isGuaranteedNotToBeUndefOrPoison(Op))
Op = Builder.CreateFreeze(Op, Op->getName() + ".fr");
Value *Cmp = Builder.CreateICmpEQ(Op, Zero, "cmpz");
Builder.CreateCondBr(Cmp, EndBlock, CallBlock);
StartBlock->getTerminator()->eraseFromParent();
// Create a PHI in the end block to select either the output of the intrinsic
// or the bit width of the operand.
Builder.SetInsertPoint(&EndBlock->front());
PHINode *PN = Builder.CreatePHI(Ty, 2, "ctz");
CountZeros->replaceAllUsesWith(PN);
Value *BitWidth = Builder.getInt(APInt(SizeInBits, SizeInBits));
PN->addIncoming(BitWidth, StartBlock);
PN->addIncoming(CountZeros, CallBlock);
// We are explicitly handling the zero case, so we can set the intrinsic's
// undefined zero argument to 'true'. This will also prevent reprocessing the
// intrinsic; we only despeculate when a zero input is defined.
CountZeros->setArgOperand(1, Builder.getTrue());
ModifiedDT = true;
return true;
}
bool CodeGenPrepare::optimizeCallInst(CallInst *CI, bool &ModifiedDT) {
BasicBlock *BB = CI->getParent();
// Lower inline assembly if we can.
// If we found an inline asm expession, and if the target knows how to
// lower it to normal LLVM code, do so now.
if (CI->isInlineAsm()) {
if (TLI->ExpandInlineAsm(CI)) {
// Avoid invalidating the iterator.
CurInstIterator = BB->begin();
// Avoid processing instructions out of order, which could cause
// reuse before a value is defined.
SunkAddrs.clear();
return true;
}
// Sink address computing for memory operands into the block.
if (optimizeInlineAsmInst(CI))
return true;
}
// Align the pointer arguments to this call if the target thinks it's a good
// idea
unsigned MinSize, PrefAlign;
if (TLI->shouldAlignPointerArgs(CI, MinSize, PrefAlign)) {
for (auto &Arg : CI->args()) {
// We want to align both objects whose address is used directly and
// objects whose address is used in casts and GEPs, though it only makes
// sense for GEPs if the offset is a multiple of the desired alignment and
// if size - offset meets the size threshold.
if (!Arg->getType()->isPointerTy())
continue;
APInt Offset(DL->getIndexSizeInBits(
cast<PointerType>(Arg->getType())->getAddressSpace()),
0);
Value *Val = Arg->stripAndAccumulateInBoundsConstantOffsets(*DL, Offset);
uint64_t Offset2 = Offset.getLimitedValue();
if ((Offset2 & (PrefAlign-1)) != 0)
continue;
AllocaInst *AI;
if ((AI = dyn_cast<AllocaInst>(Val)) && AI->getAlignment() < PrefAlign &&
DL->getTypeAllocSize(AI->getAllocatedType()) >= MinSize + Offset2)
AI->setAlignment(Align(PrefAlign));
// Global variables can only be aligned if they are defined in this
// object (i.e. they are uniquely initialized in this object), and
// over-aligning global variables that have an explicit section is
// forbidden.
GlobalVariable *GV;
if ((GV = dyn_cast<GlobalVariable>(Val)) && GV->canIncreaseAlignment() &&
GV->getPointerAlignment(*DL) < PrefAlign &&
DL->getTypeAllocSize(GV->getValueType()) >=
MinSize + Offset2)
GV->setAlignment(MaybeAlign(PrefAlign));
}
// If this is a memcpy (or similar) then we may be able to improve the
// alignment
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(CI)) {
Align DestAlign = getKnownAlignment(MI->getDest(), *DL);
MaybeAlign MIDestAlign = MI->getDestAlign();
if (!MIDestAlign || DestAlign > *MIDestAlign)
MI->setDestAlignment(DestAlign);
if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) {
MaybeAlign MTISrcAlign = MTI->getSourceAlign();
Align SrcAlign = getKnownAlignment(MTI->getSource(), *DL);
if (!MTISrcAlign || SrcAlign > *MTISrcAlign)
MTI->setSourceAlignment(SrcAlign);
}
}
}
// If we have a cold call site, try to sink addressing computation into the
// cold block. This interacts with our handling for loads and stores to
// ensure that we can fold all uses of a potential addressing computation
// into their uses. TODO: generalize this to work over profiling data
if (CI->hasFnAttr(Attribute::Cold) &&
!OptSize && !llvm::shouldOptimizeForSize(BB, PSI, BFI.get()))
for (auto &Arg : CI->args()) {
if (!Arg->getType()->isPointerTy())
continue;
unsigned AS = Arg->getType()->getPointerAddressSpace();
return optimizeMemoryInst(CI, Arg, Arg->getType(), AS);
}
IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI);
if (II) {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::assume:
llvm_unreachable("llvm.assume should have been removed already");
case Intrinsic::experimental_widenable_condition: {
// Give up on future widening oppurtunties so that we can fold away dead
// paths and merge blocks before going into block-local instruction
// selection.
if (II->use_empty()) {
II->eraseFromParent();
return true;
}
Constant *RetVal = ConstantInt::getTrue(II->getContext());
resetIteratorIfInvalidatedWhileCalling(BB, [&]() {
replaceAndRecursivelySimplify(CI, RetVal, TLInfo, nullptr);
});
return true;
}
case Intrinsic::objectsize:
llvm_unreachable("llvm.objectsize.* should have been lowered already");
case Intrinsic::is_constant:
llvm_unreachable("llvm.is.constant.* should have been lowered already");
case Intrinsic::aarch64_stlxr:
case Intrinsic::aarch64_stxr: {
ZExtInst *ExtVal = dyn_cast<ZExtInst>(CI->getArgOperand(0));
if (!ExtVal || !ExtVal->hasOneUse() ||
ExtVal->getParent() == CI->getParent())
return false;
// Sink a zext feeding stlxr/stxr before it, so it can be folded into it.
ExtVal->moveBefore(CI);
// Mark this instruction as "inserted by CGP", so that other
// optimizations don't touch it.
InsertedInsts.insert(ExtVal);
return true;
}
case Intrinsic::launder_invariant_group:
case Intrinsic::strip_invariant_group: {
Value *ArgVal = II->getArgOperand(0);
auto it = LargeOffsetGEPMap.find(II);
if (it != LargeOffsetGEPMap.end()) {
// Merge entries in LargeOffsetGEPMap to reflect the RAUW.
// Make sure not to have to deal with iterator invalidation
// after possibly adding ArgVal to LargeOffsetGEPMap.
auto GEPs = std::move(it->second);
LargeOffsetGEPMap[ArgVal].append(GEPs.begin(), GEPs.end());
LargeOffsetGEPMap.erase(II);
}
II->replaceAllUsesWith(ArgVal);
II->eraseFromParent();
return true;
}
case Intrinsic::cttz:
case Intrinsic::ctlz:
// If counting zeros is expensive, try to avoid it.
return despeculateCountZeros(II, TLI, DL, ModifiedDT);
case Intrinsic::fshl:
case Intrinsic::fshr:
return optimizeFunnelShift(II);
case Intrinsic::dbg_value:
return fixupDbgValue(II);
case Intrinsic::vscale: {
// If datalayout has no special restrictions on vector data layout,
// replace `llvm.vscale` by an equivalent constant expression
// to benefit from cheap constant propagation.
Type *ScalableVectorTy =
VectorType::get(Type::getInt8Ty(II->getContext()), 1, true);
if (DL->getTypeAllocSize(ScalableVectorTy).getKnownMinSize() == 8) {
auto *Null = Constant::getNullValue(ScalableVectorTy->getPointerTo());
auto *One = ConstantInt::getSigned(II->getType(), 1);
auto *CGep =
ConstantExpr::getGetElementPtr(ScalableVectorTy, Null, One);
II->replaceAllUsesWith(ConstantExpr::getPtrToInt(CGep, II->getType()));
II->eraseFromParent();
return true;
}
break;
}
case Intrinsic::masked_gather:
return optimizeGatherScatterInst(II, II->getArgOperand(0));
case Intrinsic::masked_scatter:
return optimizeGatherScatterInst(II, II->getArgOperand(1));
}
SmallVector<Value *, 2> PtrOps;
Type *AccessTy;
if (TLI->getAddrModeArguments(II, PtrOps, AccessTy))
while (!PtrOps.empty()) {
Value *PtrVal = PtrOps.pop_back_val();
unsigned AS = PtrVal->getType()->getPointerAddressSpace();
if (optimizeMemoryInst(II, PtrVal, AccessTy, AS))
return true;
}
}
// From here on out we're working with named functions.
if (!CI->getCalledFunction()) return false;
// Lower all default uses of _chk calls. This is very similar
// to what InstCombineCalls does, but here we are only lowering calls
// to fortified library functions (e.g. __memcpy_chk) that have the default
// "don't know" as the objectsize. Anything else should be left alone.
FortifiedLibCallSimplifier Simplifier(TLInfo, true);
IRBuilder<> Builder(CI);
if (Value *V = Simplifier.optimizeCall(CI, Builder)) {
CI->replaceAllUsesWith(V);
CI->eraseFromParent();
return true;
}
return false;
}
/// Look for opportunities to duplicate return instructions to the predecessor
/// to enable tail call optimizations. The case it is currently looking for is:
/// @code
/// bb0:
/// %tmp0 = tail call i32 @f0()
/// br label %return
/// bb1:
/// %tmp1 = tail call i32 @f1()
/// br label %return
/// bb2:
/// %tmp2 = tail call i32 @f2()
/// br label %return
/// return:
/// %retval = phi i32 [ %tmp0, %bb0 ], [ %tmp1, %bb1 ], [ %tmp2, %bb2 ]
/// ret i32 %retval
/// @endcode
///
/// =>
///
/// @code
/// bb0:
/// %tmp0 = tail call i32 @f0()
/// ret i32 %tmp0
/// bb1:
/// %tmp1 = tail call i32 @f1()
/// ret i32 %tmp1
/// bb2:
/// %tmp2 = tail call i32 @f2()
/// ret i32 %tmp2
/// @endcode
bool CodeGenPrepare::dupRetToEnableTailCallOpts(BasicBlock *BB, bool &ModifiedDT) {
ReturnInst *RetI = dyn_cast<ReturnInst>(BB->getTerminator());
if (!RetI)
return false;
PHINode *PN = nullptr;
ExtractValueInst *EVI = nullptr;
BitCastInst *BCI = nullptr;
Value *V = RetI->getReturnValue();
if (V) {
BCI = dyn_cast<BitCastInst>(V);
if (BCI)
V = BCI->getOperand(0);
EVI = dyn_cast<ExtractValueInst>(V);
if (EVI) {
V = EVI->getOperand(0);
if (!llvm::all_of(EVI->indices(), [](unsigned idx) { return idx == 0; }))
return false;
}
PN = dyn_cast<PHINode>(V);
if (!PN)
return false;
}
if (PN && PN->getParent() != BB)
return false;
auto isLifetimeEndOrBitCastFor = [](const Instruction *Inst) {
const BitCastInst *BC = dyn_cast<BitCastInst>(Inst);
if (BC && BC->hasOneUse())
Inst = BC->user_back();
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst))
return II->getIntrinsicID() == Intrinsic::lifetime_end;
return false;
};
// Make sure there are no instructions between the first instruction
// and return.
const Instruction *BI = BB->getFirstNonPHI();
// Skip over debug and the bitcast.
while (isa<DbgInfoIntrinsic>(BI) || BI == BCI || BI == EVI ||
isa<PseudoProbeInst>(BI) || isLifetimeEndOrBitCastFor(BI))
BI = BI->getNextNode();
if (BI != RetI)
return false;
/// Only dup the ReturnInst if the CallInst is likely to be emitted as a tail
/// call.
const Function *F = BB->getParent();
SmallVector<BasicBlock*, 4> TailCallBBs;
if (PN) {
for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) {
// Look through bitcasts.
Value *IncomingVal = PN->getIncomingValue(I)->stripPointerCasts();
CallInst *CI = dyn_cast<CallInst>(IncomingVal);
BasicBlock *PredBB = PN->getIncomingBlock(I);
// Make sure the phi value is indeed produced by the tail call.
if (CI && CI->hasOneUse() && CI->getParent() == PredBB &&
TLI->mayBeEmittedAsTailCall(CI) &&
attributesPermitTailCall(F, CI, RetI, *TLI))
TailCallBBs.push_back(PredBB);
}
} else {
SmallPtrSet<BasicBlock*, 4> VisitedBBs;
for (BasicBlock *Pred : predecessors(BB)) {
if (!VisitedBBs.insert(Pred).second)
continue;
if (Instruction *I = Pred->rbegin()->getPrevNonDebugInstruction(true)) {
CallInst *CI = dyn_cast<CallInst>(I);
if (CI && CI->use_empty() && TLI->mayBeEmittedAsTailCall(CI) &&
attributesPermitTailCall(F, CI, RetI, *TLI))
TailCallBBs.push_back(Pred);
}
}
}
bool Changed = false;
for (auto const &TailCallBB : TailCallBBs) {
// Make sure the call instruction is followed by an unconditional branch to
// the return block.
BranchInst *BI = dyn_cast<BranchInst>(TailCallBB->getTerminator());
if (!BI || !BI->isUnconditional() || BI->getSuccessor(0) != BB)
continue;
// Duplicate the return into TailCallBB.
(void)FoldReturnIntoUncondBranch(RetI, BB, TailCallBB);
assert(!VerifyBFIUpdates ||
BFI->getBlockFreq(BB) >= BFI->getBlockFreq(TailCallBB));
BFI->setBlockFreq(
BB,
(BFI->getBlockFreq(BB) - BFI->getBlockFreq(TailCallBB)).getFrequency());
ModifiedDT = Changed = true;
++NumRetsDup;
}
// If we eliminated all predecessors of the block, delete the block now.
if (Changed && !BB->hasAddressTaken() && pred_empty(BB))
BB->eraseFromParent();
return Changed;
}
//===----------------------------------------------------------------------===//
// Memory Optimization
//===----------------------------------------------------------------------===//
namespace {
/// This is an extended version of TargetLowering::AddrMode
/// which holds actual Value*'s for register values.
struct ExtAddrMode : public TargetLowering::AddrMode {
Value *BaseReg = nullptr;
Value *ScaledReg = nullptr;
Value *OriginalValue = nullptr;
bool InBounds = true;
enum FieldName {
NoField = 0x00,
BaseRegField = 0x01,
BaseGVField = 0x02,
BaseOffsField = 0x04,
ScaledRegField = 0x08,
ScaleField = 0x10,
MultipleFields = 0xff
};
ExtAddrMode() = default;
void print(raw_ostream &OS) const;
void dump() const;
FieldName compare(const ExtAddrMode &other) {
// First check that the types are the same on each field, as differing types
// is something we can't cope with later on.
if (BaseReg && other.BaseReg &&
BaseReg->getType() != other.BaseReg->getType())
return MultipleFields;
if (BaseGV && other.BaseGV &&
BaseGV->getType() != other.BaseGV->getType())
return MultipleFields;
if (ScaledReg && other.ScaledReg &&
ScaledReg->getType() != other.ScaledReg->getType())
return MultipleFields;
// Conservatively reject 'inbounds' mismatches.
if (InBounds != other.InBounds)
return MultipleFields;
// Check each field to see if it differs.
unsigned Result = NoField;
if (BaseReg != other.BaseReg)
Result |= BaseRegField;
if (BaseGV != other.BaseGV)
Result |= BaseGVField;
if (BaseOffs != other.BaseOffs)
Result |= BaseOffsField;
if (ScaledReg != other.ScaledReg)
Result |= ScaledRegField;
// Don't count 0 as being a different scale, because that actually means
// unscaled (which will already be counted by having no ScaledReg).
if (Scale && other.Scale && Scale != other.Scale)
Result |= ScaleField;
if (countPopulation(Result) > 1)
return MultipleFields;
else
return static_cast<FieldName>(Result);
}
// An AddrMode is trivial if it involves no calculation i.e. it is just a base
// with no offset.
bool isTrivial() {
// An AddrMode is (BaseGV + BaseReg + BaseOffs + ScaleReg * Scale) so it is
// trivial if at most one of these terms is nonzero, except that BaseGV and
// BaseReg both being zero actually means a null pointer value, which we
// consider to be 'non-zero' here.
return !BaseOffs && !Scale && !(BaseGV && BaseReg);
}
Value *GetFieldAsValue(FieldName Field, Type *IntPtrTy) {
switch (Field) {
default:
return nullptr;
case BaseRegField:
return BaseReg;
case BaseGVField:
return BaseGV;
case ScaledRegField:
return ScaledReg;
case BaseOffsField:
return ConstantInt::get(IntPtrTy, BaseOffs);
}
}
void SetCombinedField(FieldName Field, Value *V,
const SmallVectorImpl<ExtAddrMode> &AddrModes) {
switch (Field) {
default:
llvm_unreachable("Unhandled fields are expected to be rejected earlier");
break;
case ExtAddrMode::BaseRegField:
BaseReg = V;
break;
case ExtAddrMode::BaseGVField:
// A combined BaseGV is an Instruction, not a GlobalValue, so it goes
// in the BaseReg field.
assert(BaseReg == nullptr);
BaseReg = V;
BaseGV = nullptr;
break;
case ExtAddrMode::ScaledRegField:
ScaledReg = V;
// If we have a mix of scaled and unscaled addrmodes then we want scale
// to be the scale and not zero.
if (!Scale)
for (const ExtAddrMode &AM : AddrModes)
if (AM.Scale) {
Scale = AM.Scale;
break;
}
break;
case ExtAddrMode::BaseOffsField:
// The offset is no longer a constant, so it goes in ScaledReg with a
// scale of 1.
assert(ScaledReg == nullptr);
ScaledReg = V;
Scale = 1;
BaseOffs = 0;
break;
}
}
};
} // end anonymous namespace
#ifndef NDEBUG
static inline raw_ostream &operator<<(raw_ostream &OS, const ExtAddrMode &AM) {
AM.print(OS);
return OS;
}
#endif
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void ExtAddrMode::print(raw_ostream &OS) const {
bool NeedPlus = false;
OS << "[";
if (InBounds)
OS << "inbounds ";
if (BaseGV) {
OS << (NeedPlus ? " + " : "")
<< "GV:";
BaseGV->printAsOperand(OS, /*PrintType=*/false);
NeedPlus = true;
}
if (BaseOffs) {
OS << (NeedPlus ? " + " : "")
<< BaseOffs;
NeedPlus = true;
}
if (BaseReg) {
OS << (NeedPlus ? " + " : "")
<< "Base:";
BaseReg->printAsOperand(OS, /*PrintType=*/false);
NeedPlus = true;
}
if (Scale) {
OS << (NeedPlus ? " + " : "")
<< Scale << "*";
ScaledReg->printAsOperand(OS, /*PrintType=*/false);
}
OS << ']';
}
LLVM_DUMP_METHOD void ExtAddrMode::dump() const {
print(dbgs());
dbgs() << '\n';
}
#endif
namespace {
/// This class provides transaction based operation on the IR.
/// Every change made through this class is recorded in the internal state and
/// can be undone (rollback) until commit is called.
/// CGP does not check if instructions could be speculatively executed when
/// moved. Preserving the original location would pessimize the debugging
/// experience, as well as negatively impact the quality of sample PGO.
class TypePromotionTransaction {
/// This represents the common interface of the individual transaction.
/// Each class implements the logic for doing one specific modification on
/// the IR via the TypePromotionTransaction.
class TypePromotionAction {
protected:
/// The Instruction modified.
Instruction *Inst;
public:
/// Constructor of the action.
/// The constructor performs the related action on the IR.
TypePromotionAction(Instruction *Inst) : Inst(Inst) {}
virtual ~TypePromotionAction() = default;
/// Undo the modification done by this action.
/// When this method is called, the IR must be in the same state as it was
/// before this action was applied.
/// \pre Undoing the action works if and only if the IR is in the exact same
/// state as it was directly after this action was applied.
virtual void undo() = 0;
/// Advocate every change made by this action.
/// When the results on the IR of the action are to be kept, it is important
/// to call this function, otherwise hidden information may be kept forever.
virtual void commit() {
// Nothing to be done, this action is not doing anything.
}
};
/// Utility to remember the position of an instruction.
class InsertionHandler {
/// Position of an instruction.
/// Either an instruction:
/// - Is the first in a basic block: BB is used.
/// - Has a previous instruction: PrevInst is used.
union {
Instruction *PrevInst;
BasicBlock *BB;
} Point;
/// Remember whether or not the instruction had a previous instruction.
bool HasPrevInstruction;
public:
/// Record the position of \p Inst.
InsertionHandler(Instruction *Inst) {
BasicBlock::iterator It = Inst->getIterator();
HasPrevInstruction = (It != (Inst->getParent()->begin()));
if (HasPrevInstruction)
Point.PrevInst = &*--It;
else
Point.BB = Inst->getParent();
}
/// Insert \p Inst at the recorded position.
void insert(Instruction *Inst) {
if (HasPrevInstruction) {
if (Inst->getParent())
Inst->removeFromParent();
Inst->insertAfter(Point.PrevInst);
} else {
Instruction *Position = &*Point.BB->getFirstInsertionPt();
if (Inst->getParent())
Inst->moveBefore(Position);
else
Inst->insertBefore(Position);
}
}
};
/// Move an instruction before another.
class InstructionMoveBefore : public TypePromotionAction {
/// Original position of the instruction.
InsertionHandler Position;
public:
/// Move \p Inst before \p Before.
InstructionMoveBefore(Instruction *Inst, Instruction *Before)
: TypePromotionAction(Inst), Position(Inst) {
LLVM_DEBUG(dbgs() << "Do: move: " << *Inst << "\nbefore: " << *Before
<< "\n");
Inst->moveBefore(Before);
}
/// Move the instruction back to its original position.
void undo() override {
LLVM_DEBUG(dbgs() << "Undo: moveBefore: " << *Inst << "\n");
Position.insert(Inst);
}
};
/// Set the operand of an instruction with a new value.
class OperandSetter : public TypePromotionAction {
/// Original operand of the instruction.
Value *Origin;
/// Index of the modified instruction.
unsigned Idx;
public:
/// Set \p Idx operand of \p Inst with \p NewVal.
OperandSetter(Instruction *Inst, unsigned Idx, Value *NewVal)
: TypePromotionAction(Inst), Idx(Idx) {
LLVM_DEBUG(dbgs() << "Do: setOperand: " << Idx << "\n"
<< "for:" << *Inst << "\n"
<< "with:" << *NewVal << "\n");
Origin = Inst->getOperand(Idx);
Inst->setOperand(Idx, NewVal);
}
/// Restore the original value of the instruction.
void undo() override {
LLVM_DEBUG(dbgs() << "Undo: setOperand:" << Idx << "\n"
<< "for: " << *Inst << "\n"
<< "with: " << *Origin << "\n");
Inst->setOperand(Idx, Origin);
}
};
/// Hide the operands of an instruction.
/// Do as if this instruction was not using any of its operands.
class OperandsHider : public TypePromotionAction {
/// The list of original operands.
SmallVector<Value *, 4> OriginalValues;
public:
/// Remove \p Inst from the uses of the operands of \p Inst.
OperandsHider(Instruction *Inst) : TypePromotionAction(Inst) {
LLVM_DEBUG(dbgs() << "Do: OperandsHider: " << *Inst << "\n");
unsigned NumOpnds = Inst->getNumOperands();
OriginalValues.reserve(NumOpnds);
for (unsigned It = 0; It < NumOpnds; ++It) {
// Save the current operand.
Value *Val = Inst->getOperand(It);
OriginalValues.push_back(Val);
// Set a dummy one.
// We could use OperandSetter here, but that would imply an overhead
// that we are not willing to pay.
Inst->setOperand(It, UndefValue::get(Val->getType()));
}
}
/// Restore the original list of uses.
void undo() override {
LLVM_DEBUG(dbgs() << "Undo: OperandsHider: " << *Inst << "\n");
for (unsigned It = 0, EndIt = OriginalValues.size(); It != EndIt; ++It)
Inst->setOperand(It, OriginalValues[It]);
}
};
/// Build a truncate instruction.
class TruncBuilder : public TypePromotionAction {
Value *Val;
public:
/// Build a truncate instruction of \p Opnd producing a \p Ty
/// result.
/// trunc Opnd to Ty.
TruncBuilder(Instruction *Opnd, Type *Ty) : TypePromotionAction(Opnd) {
IRBuilder<> Builder(Opnd);
Builder.SetCurrentDebugLocation(DebugLoc());
Val = Builder.CreateTrunc(Opnd, Ty, "promoted");
LLVM_DEBUG(dbgs() << "Do: TruncBuilder: " << *Val << "\n");
}
/// Get the built value.
Value *getBuiltValue() { return Val; }
/// Remove the built instruction.
void undo() override {
LLVM_DEBUG(dbgs() << "Undo: TruncBuilder: " << *Val << "\n");
if (Instruction *IVal = dyn_cast<Instruction>(Val))
IVal->eraseFromParent();
}
};
/// Build a sign extension instruction.
class SExtBuilder : public TypePromotionAction {
Value *Val;
public:
/// Build a sign extension instruction of \p Opnd producing a \p Ty
/// result.
/// sext Opnd to Ty.
SExtBuilder(Instruction *InsertPt, Value *Opnd, Type *Ty)
: TypePromotionAction(InsertPt) {
IRBuilder<> Builder(InsertPt);
Val = Builder.CreateSExt(Opnd, Ty, "promoted");
LLVM_DEBUG(dbgs() << "Do: SExtBuilder: " << *Val << "\n");
}
/// Get the built value.
Value *getBuiltValue() { return Val; }
/// Remove the built instruction.
void undo() override {
LLVM_DEBUG(dbgs() << "Undo: SExtBuilder: " << *Val << "\n");
if (Instruction *IVal = dyn_cast<Instruction>(Val))
IVal->eraseFromParent();
}
};
/// Build a zero extension instruction.
class ZExtBuilder : public TypePromotionAction {
Value *Val;
public:
/// Build a zero extension instruction of \p Opnd producing a \p Ty
/// result.
/// zext Opnd to Ty.
ZExtBuilder(Instruction *InsertPt, Value *Opnd, Type *Ty)
: TypePromotionAction(InsertPt) {
IRBuilder<> Builder(InsertPt);
Builder.SetCurrentDebugLocation(DebugLoc());
Val = Builder.CreateZExt(Opnd, Ty, "promoted");
LLVM_DEBUG(dbgs() << "Do: ZExtBuilder: " << *Val << "\n");
}
/// Get the built value.
Value *getBuiltValue() { return Val; }
/// Remove the built instruction.
void undo() override {
LLVM_DEBUG(dbgs() << "Undo: ZExtBuilder: " << *Val << "\n");
if (Instruction *IVal = dyn_cast<Instruction>(Val))
IVal->eraseFromParent();
}
};
/// Mutate an instruction to another type.
class TypeMutator : public TypePromotionAction {
/// Record the original type.
Type *OrigTy;
public:
/// Mutate the type of \p Inst into \p NewTy.
TypeMutator(Instruction *Inst, Type *NewTy)
: TypePromotionAction(Inst), OrigTy(Inst->getType()) {
LLVM_DEBUG(dbgs() << "Do: MutateType: " << *Inst << " with " << *NewTy
<< "\n");
Inst->mutateType(NewTy);
}
/// Mutate the instruction back to its original type.
void undo() override {
LLVM_DEBUG(dbgs() << "Undo: MutateType: " << *Inst << " with " << *OrigTy
<< "\n");
Inst->mutateType(OrigTy);
}
};
/// Replace the uses of an instruction by another instruction.
class UsesReplacer : public TypePromotionAction {
/// Helper structure to keep track of the replaced uses.
struct InstructionAndIdx {
/// The instruction using the instruction.
Instruction *Inst;
/// The index where this instruction is used for Inst.
unsigned Idx;
InstructionAndIdx(Instruction *Inst, unsigned Idx)
: Inst(Inst), Idx(Idx) {}
};
/// Keep track of the original uses (pair Instruction, Index).
SmallVector<InstructionAndIdx, 4> OriginalUses;
/// Keep track of the debug users.
SmallVector<DbgValueInst *, 1> DbgValues;
/// Keep track of the new value so that we can undo it by replacing
/// instances of the new value with the original value.
Value *New;
using use_iterator = SmallVectorImpl<InstructionAndIdx>::iterator;
public:
/// Replace all the use of \p Inst by \p New.
UsesReplacer(Instruction *Inst, Value *New)
: TypePromotionAction(Inst), New(New) {
LLVM_DEBUG(dbgs() << "Do: UsersReplacer: " << *Inst << " with " << *New
<< "\n");
// Record the original uses.
for (Use &U : Inst->uses()) {
Instruction *UserI = cast<Instruction>(U.getUser());
OriginalUses.push_back(InstructionAndIdx(UserI, U.getOperandNo()));
}
// Record the debug uses separately. They are not in the instruction's
// use list, but they are replaced by RAUW.
findDbgValues(DbgValues, Inst);
// Now, we can replace the uses.
Inst->replaceAllUsesWith(New);
}
/// Reassign the original uses of Inst to Inst.
void undo() override {
LLVM_DEBUG(dbgs() << "Undo: UsersReplacer: " << *Inst << "\n");
for (InstructionAndIdx &Use : OriginalUses)
Use.Inst->setOperand(Use.Idx, Inst);
// RAUW has replaced all original uses with references to the new value,
// including the debug uses. Since we are undoing the replacements,
// the original debug uses must also be reinstated to maintain the
// correctness and utility of debug value instructions.
for (auto *DVI : DbgValues)
DVI->replaceVariableLocationOp(New, Inst);
}
};
/// Remove an instruction from the IR.
class InstructionRemover : public TypePromotionAction {
/// Original position of the instruction.
InsertionHandler Inserter;
/// Helper structure to hide all the link to the instruction. In other
/// words, this helps to do as if the instruction was removed.
OperandsHider Hider;
/// Keep track of the uses replaced, if any.
UsesReplacer *Replacer = nullptr;
/// Keep track of instructions removed.
SetOfInstrs &RemovedInsts;
public:
/// Remove all reference of \p Inst and optionally replace all its
/// uses with New.
/// \p RemovedInsts Keep track of the instructions removed by this Action.
/// \pre If !Inst->use_empty(), then New != nullptr
InstructionRemover(Instruction *Inst, SetOfInstrs &RemovedInsts,
Value *New = nullptr)
: TypePromotionAction(Inst), Inserter(Inst), Hider(Inst),
RemovedInsts(RemovedInsts) {
if (New)
Replacer = new UsesReplacer(Inst, New);
LLVM_DEBUG(dbgs() << "Do: InstructionRemover: " << *Inst << "\n");
RemovedInsts.insert(Inst);
/// The instructions removed here will be freed after completing
/// optimizeBlock() for all blocks as we need to keep track of the
/// removed instructions during promotion.
Inst->removeFromParent();
}
~InstructionRemover() override { delete Replacer; }
/// Resurrect the instruction and reassign it to the proper uses if
/// new value was provided when build this action.
void undo() override {
LLVM_DEBUG(dbgs() << "Undo: InstructionRemover: " << *Inst << "\n");
Inserter.insert(Inst);
if (Replacer)
Replacer->undo();
Hider.undo();
RemovedInsts.erase(Inst);
}
};
public:
/// Restoration point.
/// The restoration point is a pointer to an action instead of an iterator
/// because the iterator may be invalidated but not the pointer.
using ConstRestorationPt = const TypePromotionAction *;
TypePromotionTransaction(SetOfInstrs &RemovedInsts)
: RemovedInsts(RemovedInsts) {}
/// Advocate every changes made in that transaction. Return true if any change
/// happen.
bool commit();
/// Undo all the changes made after the given point.
void rollback(ConstRestorationPt Point);
/// Get the current restoration point.
ConstRestorationPt getRestorationPoint() const;
/// \name API for IR modification with state keeping to support rollback.
/// @{
/// Same as Instruction::setOperand.
void setOperand(Instruction *Inst, unsigned Idx, Value *NewVal);
/// Same as Instruction::eraseFromParent.
void eraseInstruction(Instruction *Inst, Value *NewVal = nullptr);
/// Same as Value::replaceAllUsesWith.
void replaceAllUsesWith(Instruction *Inst, Value *New);
/// Same as Value::mutateType.
void mutateType(Instruction *Inst, Type *NewTy);
/// Same as IRBuilder::createTrunc.
Value *createTrunc(Instruction *Opnd, Type *Ty);
/// Same as IRBuilder::createSExt.
Value *createSExt(Instruction *Inst, Value *Opnd, Type *Ty);
/// Same as IRBuilder::createZExt.
Value *createZExt(Instruction *Inst, Value *Opnd, Type *Ty);
/// Same as Instruction::moveBefore.
void moveBefore(Instruction *Inst, Instruction *Before);
/// @}
private:
/// The ordered list of actions made so far.
SmallVector<std::unique_ptr<TypePromotionAction>, 16> Actions;
using CommitPt = SmallVectorImpl<std::unique_ptr<TypePromotionAction>>::iterator;
SetOfInstrs &RemovedInsts;
};
} // end anonymous namespace
void TypePromotionTransaction::setOperand(Instruction *Inst, unsigned Idx,
Value *NewVal) {
Actions.push_back(std::make_unique<TypePromotionTransaction::OperandSetter>(
Inst, Idx, NewVal));
}
void TypePromotionTransaction::eraseInstruction(Instruction *Inst,
Value *NewVal) {
Actions.push_back(
std::make_unique<TypePromotionTransaction::InstructionRemover>(
Inst, RemovedInsts, NewVal));
}
void TypePromotionTransaction::replaceAllUsesWith(Instruction *Inst,
Value *New) {
Actions.push_back(
std::make_unique<TypePromotionTransaction::UsesReplacer>(Inst, New));
}
void TypePromotionTransaction::mutateType(Instruction *Inst, Type *NewTy) {
Actions.push_back(
std::make_unique<TypePromotionTransaction::TypeMutator>(Inst, NewTy));
}
Value *TypePromotionTransaction::createTrunc(Instruction *Opnd,
Type *Ty) {
std::unique_ptr<TruncBuilder> Ptr(new TruncBuilder(Opnd, Ty));
Value *Val = Ptr->getBuiltValue();
Actions.push_back(std::move(Ptr));
return Val;
}
Value *TypePromotionTransaction::createSExt(Instruction *Inst,
Value *Opnd, Type *Ty) {
std::unique_ptr<SExtBuilder> Ptr(new SExtBuilder(Inst, Opnd, Ty));
Value *Val = Ptr->getBuiltValue();
Actions.push_back(std::move(Ptr));
return Val;
}
Value *TypePromotionTransaction::createZExt(Instruction *Inst,
Value *Opnd, Type *Ty) {
std::unique_ptr<ZExtBuilder> Ptr(new ZExtBuilder(Inst, Opnd, Ty));
Value *Val = Ptr->getBuiltValue();
Actions.push_back(std::move(Ptr));
return Val;
}
void TypePromotionTransaction::moveBefore(Instruction *Inst,
Instruction *Before) {
Actions.push_back(
std::make_unique<TypePromotionTransaction::InstructionMoveBefore>(
Inst, Before));
}
TypePromotionTransaction::ConstRestorationPt
TypePromotionTransaction::getRestorationPoint() const {
return !Actions.empty() ? Actions.back().get() : nullptr;
}
bool TypePromotionTransaction::commit() {
for (std::unique_ptr<TypePromotionAction> &Action : Actions)
Action->commit();
bool Modified = !Actions.empty();
Actions.clear();
return Modified;
}
void TypePromotionTransaction::rollback(
TypePromotionTransaction::ConstRestorationPt Point) {
while (!Actions.empty() && Point != Actions.back().get()) {
std::unique_ptr<TypePromotionAction> Curr = Actions.pop_back_val();
Curr->undo();
}
}
namespace {
/// A helper class for matching addressing modes.
///
/// This encapsulates the logic for matching the target-legal addressing modes.
class AddressingModeMatcher {
SmallVectorImpl<Instruction*> &AddrModeInsts;
const TargetLowering &TLI;
const TargetRegisterInfo &TRI;
const DataLayout &DL;
const LoopInfo &LI;
const std::function<const DominatorTree &()> getDTFn;
/// AccessTy/MemoryInst - This is the type for the access (e.g. double) and
/// the memory instruction that we're computing this address for.
Type *AccessTy;
unsigned AddrSpace;
Instruction *MemoryInst;
/// This is the addressing mode that we're building up. This is
/// part of the return value of this addressing mode matching stuff.
ExtAddrMode &AddrMode;
/// The instructions inserted by other CodeGenPrepare optimizations.
const SetOfInstrs &InsertedInsts;
/// A map from the instructions to their type before promotion.
InstrToOrigTy &PromotedInsts;
/// The ongoing transaction where every action should be registered.
TypePromotionTransaction &TPT;
// A GEP which has too large offset to be folded into the addressing mode.
std::pair<AssertingVH<GetElementPtrInst>, int64_t> &LargeOffsetGEP;
/// This is set to true when we should not do profitability checks.
/// When true, IsProfitableToFoldIntoAddressingMode always returns true.
bool IgnoreProfitability;
/// True if we are optimizing for size.
bool OptSize;
ProfileSummaryInfo *PSI;
BlockFrequencyInfo *BFI;
AddressingModeMatcher(
SmallVectorImpl<Instruction *> &AMI, const TargetLowering &TLI,
const TargetRegisterInfo &TRI, const LoopInfo &LI,
const std::function<const DominatorTree &()> getDTFn,
Type *AT, unsigned AS, Instruction *MI, ExtAddrMode &AM,
const SetOfInstrs &InsertedInsts, InstrToOrigTy &PromotedInsts,
TypePromotionTransaction &TPT,
std::pair<AssertingVH<GetElementPtrInst>, int64_t> &LargeOffsetGEP,
bool OptSize, ProfileSummaryInfo *PSI, BlockFrequencyInfo *BFI)
: AddrModeInsts(AMI), TLI(TLI), TRI(TRI),
DL(MI->getModule()->getDataLayout()), LI(LI), getDTFn(getDTFn),
AccessTy(AT), AddrSpace(AS), MemoryInst(MI), AddrMode(AM),
InsertedInsts(InsertedInsts), PromotedInsts(PromotedInsts), TPT(TPT),
LargeOffsetGEP(LargeOffsetGEP), OptSize(OptSize), PSI(PSI), BFI(BFI) {
IgnoreProfitability = false;
}
public:
/// Find the maximal addressing mode that a load/store of V can fold,
/// give an access type of AccessTy. This returns a list of involved
/// instructions in AddrModeInsts.
/// \p InsertedInsts The instructions inserted by other CodeGenPrepare
/// optimizations.
/// \p PromotedInsts maps the instructions to their type before promotion.
/// \p The ongoing transaction where every action should be registered.
static ExtAddrMode
Match(Value *V, Type *AccessTy, unsigned AS, Instruction *MemoryInst,
SmallVectorImpl<Instruction *> &AddrModeInsts,
const TargetLowering &TLI, const LoopInfo &LI,
const std::function<const DominatorTree &()> getDTFn,
const TargetRegisterInfo &TRI, const SetOfInstrs &InsertedInsts,
InstrToOrigTy &PromotedInsts, TypePromotionTransaction &TPT,
std::pair<AssertingVH<GetElementPtrInst>, int64_t> &LargeOffsetGEP,
bool OptSize, ProfileSummaryInfo *PSI, BlockFrequencyInfo *BFI) {
ExtAddrMode Result;
bool Success = AddressingModeMatcher(
AddrModeInsts, TLI, TRI, LI, getDTFn, AccessTy, AS, MemoryInst, Result,
InsertedInsts, PromotedInsts, TPT, LargeOffsetGEP, OptSize, PSI,
BFI).matchAddr(V, 0);
(void)Success; assert(Success && "Couldn't select *anything*?");
return Result;
}
private:
bool matchScaledValue(Value *ScaleReg, int64_t Scale, unsigned Depth);
bool matchAddr(Value *Addr, unsigned Depth);
bool matchOperationAddr(User *AddrInst, unsigned Opcode, unsigned Depth,
bool *MovedAway = nullptr);
bool isProfitableToFoldIntoAddressingMode(Instruction *I,
ExtAddrMode &AMBefore,
ExtAddrMode &AMAfter);
bool valueAlreadyLiveAtInst(Value *Val, Value *KnownLive1, Value *KnownLive2);
bool isPromotionProfitable(unsigned NewCost, unsigned OldCost,
Value *PromotedOperand) const;
};
class PhiNodeSet;
/// An iterator for PhiNodeSet.
class PhiNodeSetIterator {
PhiNodeSet * const Set;
size_t CurrentIndex = 0;
public:
/// The constructor. Start should point to either a valid element, or be equal
/// to the size of the underlying SmallVector of the PhiNodeSet.
PhiNodeSetIterator(PhiNodeSet * const Set, size_t Start);
PHINode * operator*() const;
PhiNodeSetIterator& operator++();
bool operator==(const PhiNodeSetIterator &RHS) const;
bool operator!=(const PhiNodeSetIterator &RHS) const;
};
/// Keeps a set of PHINodes.
///
/// This is a minimal set implementation for a specific use case:
/// It is very fast when there are very few elements, but also provides good
/// performance when there are many. It is similar to SmallPtrSet, but also
/// provides iteration by insertion order, which is deterministic and stable
/// across runs. It is also similar to SmallSetVector, but provides removing
/// elements in O(1) time. This is achieved by not actually removing the element
/// from the underlying vector, so comes at the cost of using more memory, but
/// that is fine, since PhiNodeSets are used as short lived objects.
class PhiNodeSet {
friend class PhiNodeSetIterator;
using MapType = SmallDenseMap<PHINode *, size_t, 32>;
using iterator = PhiNodeSetIterator;
/// Keeps the elements in the order of their insertion in the underlying
/// vector. To achieve constant time removal, it never deletes any element.
SmallVector<PHINode *, 32> NodeList;
/// Keeps the elements in the underlying set implementation. This (and not the
/// NodeList defined above) is the source of truth on whether an element
/// is actually in the collection.
MapType NodeMap;
/// Points to the first valid (not deleted) element when the set is not empty
/// and the value is not zero. Equals to the size of the underlying vector
/// when the set is empty. When the value is 0, as in the beginning, the
/// first element may or may not be valid.
size_t FirstValidElement = 0;
public:
/// Inserts a new element to the collection.
/// \returns true if the element is actually added, i.e. was not in the
/// collection before the operation.
bool insert(PHINode *Ptr) {
if (NodeMap.insert(std::make_pair(Ptr, NodeList.size())).second) {
NodeList.push_back(Ptr);
return true;
}
return false;
}
/// Removes the element from the collection.
/// \returns whether the element is actually removed, i.e. was in the
/// collection before the operation.
bool erase(PHINode *Ptr) {
if (NodeMap.erase(Ptr)) {
SkipRemovedElements(FirstValidElement);
return true;
}
return false;
}
/// Removes all elements and clears the collection.
void clear() {
NodeMap.clear();
NodeList.clear();
FirstValidElement = 0;
}
/// \returns an iterator that will iterate the elements in the order of
/// insertion.
iterator begin() {
if (FirstValidElement == 0)
SkipRemovedElements(FirstValidElement);
return PhiNodeSetIterator(this, FirstValidElement);
}
/// \returns an iterator that points to the end of the collection.
iterator end() { return PhiNodeSetIterator(this, NodeList.size()); }
/// Returns the number of elements in the collection.
size_t size() const {
return NodeMap.size();
}
/// \returns 1 if the given element is in the collection, and 0 if otherwise.
size_t count(PHINode *Ptr) const {
return NodeMap.count(Ptr);
}
private:
/// Updates the CurrentIndex so that it will point to a valid element.
///
/// If the element of NodeList at CurrentIndex is valid, it does not
/// change it. If there are no more valid elements, it updates CurrentIndex
/// to point to the end of the NodeList.
void SkipRemovedElements(size_t &CurrentIndex) {
while (CurrentIndex < NodeList.size()) {
auto it = NodeMap.find(NodeList[CurrentIndex]);
// If the element has been deleted and added again later, NodeMap will
// point to a different index, so CurrentIndex will still be invalid.
if (it != NodeMap.end() && it->second == CurrentIndex)
break;
++CurrentIndex;
}
}
};
PhiNodeSetIterator::PhiNodeSetIterator(PhiNodeSet *const Set, size_t Start)
: Set(Set), CurrentIndex(Start) {}
PHINode * PhiNodeSetIterator::operator*() const {
assert(CurrentIndex < Set->NodeList.size() &&
"PhiNodeSet access out of range");
return Set->NodeList[CurrentIndex];
}
PhiNodeSetIterator& PhiNodeSetIterator::operator++() {
assert(CurrentIndex < Set->NodeList.size() &&
"PhiNodeSet access out of range");
++CurrentIndex;
Set->SkipRemovedElements(CurrentIndex);
return *this;
}
bool PhiNodeSetIterator::operator==(const PhiNodeSetIterator &RHS) const {
return CurrentIndex == RHS.CurrentIndex;
}
bool PhiNodeSetIterator::operator!=(const PhiNodeSetIterator &RHS) const {
return !((*this) == RHS);
}
/// Keep track of simplification of Phi nodes.
/// Accept the set of all phi nodes and erase phi node from this set
/// if it is simplified.
class SimplificationTracker {
DenseMap<Value *, Value *> Storage;
const SimplifyQuery &SQ;
// Tracks newly created Phi nodes. The elements are iterated by insertion
// order.
PhiNodeSet AllPhiNodes;
// Tracks newly created Select nodes.
SmallPtrSet<SelectInst *, 32> AllSelectNodes;
public:
SimplificationTracker(const SimplifyQuery &sq)
: SQ(sq) {}
Value *Get(Value *V) {
do {
auto SV = Storage.find(V);
if (SV == Storage.end())
return V;
V = SV->second;
} while (true);
}
Value *Simplify(Value *Val) {
SmallVector<Value *, 32> WorkList;
SmallPtrSet<Value *, 32> Visited;
WorkList.push_back(Val);
while (!WorkList.empty()) {
auto *P = WorkList.pop_back_val();
if (!Visited.insert(P).second)
continue;
if (auto *PI = dyn_cast<Instruction>(P))
if (Value *V = SimplifyInstruction(cast<Instruction>(PI), SQ)) {
for (auto *U : PI->users())
WorkList.push_back(cast<Value>(U));
Put(PI, V);
PI->replaceAllUsesWith(V);
if (auto *PHI = dyn_cast<PHINode>(PI))
AllPhiNodes.erase(PHI);
if (auto *Select = dyn_cast<SelectInst>(PI))
AllSelectNodes.erase(Select);
PI->eraseFromParent();
}
}
return Get(Val);
}
void Put(Value *From, Value *To) {
Storage.insert({ From, To });
}
void ReplacePhi(PHINode *From, PHINode *To) {
Value* OldReplacement = Get(From);
while (OldReplacement != From) {
From = To;
To = dyn_cast<PHINode>(OldReplacement);
OldReplacement = Get(From);
}
assert(To && Get(To) == To && "Replacement PHI node is already replaced.");
Put(From, To);
From->replaceAllUsesWith(To);
AllPhiNodes.erase(From);
From->eraseFromParent();
}
PhiNodeSet& newPhiNodes() { return AllPhiNodes; }
void insertNewPhi(PHINode *PN) { AllPhiNodes.insert(PN); }
void insertNewSelect(SelectInst *SI) { AllSelectNodes.insert(SI); }
unsigned countNewPhiNodes() const { return AllPhiNodes.size(); }
unsigned countNewSelectNodes() const { return AllSelectNodes.size(); }
void destroyNewNodes(Type *CommonType) {
// For safe erasing, replace the uses with dummy value first.
auto *Dummy = UndefValue::get(CommonType);
for (auto *I : AllPhiNodes) {
I->replaceAllUsesWith(Dummy);
I->eraseFromParent();
}
AllPhiNodes.clear();
for (auto *I : AllSelectNodes) {
I->replaceAllUsesWith(Dummy);
I->eraseFromParent();
}
AllSelectNodes.clear();
}
};
/// A helper class for combining addressing modes.
class AddressingModeCombiner {
typedef DenseMap<Value *, Value *> FoldAddrToValueMapping;
typedef std::pair<PHINode *, PHINode *> PHIPair;
private:
/// The addressing modes we've collected.
SmallVector<ExtAddrMode, 16> AddrModes;
/// The field in which the AddrModes differ, when we have more than one.
ExtAddrMode::FieldName DifferentField = ExtAddrMode::NoField;
/// Are the AddrModes that we have all just equal to their original values?
bool AllAddrModesTrivial = true;
/// Common Type for all different fields in addressing modes.
Type *CommonType = nullptr;
/// SimplifyQuery for simplifyInstruction utility.
const SimplifyQuery &SQ;
/// Original Address.
Value *Original;
public:
AddressingModeCombiner(const SimplifyQuery &_SQ, Value *OriginalValue)
: SQ(_SQ), Original(OriginalValue) {}
/// Get the combined AddrMode
const ExtAddrMode &getAddrMode() const {
return AddrModes[0];
}
/// Add a new AddrMode if it's compatible with the AddrModes we already
/// have.
/// \return True iff we succeeded in doing so.
bool addNewAddrMode(ExtAddrMode &NewAddrMode) {
// Take note of if we have any non-trivial AddrModes, as we need to detect
// when all AddrModes are trivial as then we would introduce a phi or select
// which just duplicates what's already there.
AllAddrModesTrivial = AllAddrModesTrivial && NewAddrMode.isTrivial();
// If this is the first addrmode then everything is fine.
if (AddrModes.empty()) {
AddrModes.emplace_back(NewAddrMode);
return true;
}
// Figure out how different this is from the other address modes, which we
// can do just by comparing against the first one given that we only care
// about the cumulative difference.
ExtAddrMode::FieldName ThisDifferentField =
AddrModes[0].compare(NewAddrMode);
if (DifferentField == ExtAddrMode::NoField)
DifferentField = ThisDifferentField;
else if (DifferentField != ThisDifferentField)
DifferentField = ExtAddrMode::MultipleFields;
// If NewAddrMode differs in more than one dimension we cannot handle it.
bool CanHandle = DifferentField != ExtAddrMode::MultipleFields;
// If Scale Field is different then we reject.
CanHandle = CanHandle && DifferentField != ExtAddrMode::ScaleField;
// We also must reject the case when base offset is different and
// scale reg is not null, we cannot handle this case due to merge of
// different offsets will be used as ScaleReg.
CanHandle = CanHandle && (DifferentField != ExtAddrMode::BaseOffsField ||
!NewAddrMode.ScaledReg);
// We also must reject the case when GV is different and BaseReg installed
// due to we want to use base reg as a merge of GV values.
CanHandle = CanHandle && (DifferentField != ExtAddrMode::BaseGVField ||
!NewAddrMode.HasBaseReg);
// Even if NewAddMode is the same we still need to collect it due to
// original value is different. And later we will need all original values
// as anchors during finding the common Phi node.
if (CanHandle)
AddrModes.emplace_back(NewAddrMode);
else
AddrModes.clear();
return CanHandle;
}
/// Combine the addressing modes we've collected into a single
/// addressing mode.
/// \return True iff we successfully combined them or we only had one so
/// didn't need to combine them anyway.
bool combineAddrModes() {
// If we have no AddrModes then they can't be combined.
if (AddrModes.size() == 0)
return false;
// A single AddrMode can trivially be combined.
if (AddrModes.size() == 1 || DifferentField == ExtAddrMode::NoField)
return true;
// If the AddrModes we collected are all just equal to the value they are
// derived from then combining them wouldn't do anything useful.
if (AllAddrModesTrivial)
return false;
if (!addrModeCombiningAllowed())
return false;
// Build a map between <original value, basic block where we saw it> to
// value of base register.
// Bail out if there is no common type.
FoldAddrToValueMapping Map;
if (!initializeMap(Map))
return false;
Value *CommonValue = findCommon(Map);
if (CommonValue)
AddrModes[0].SetCombinedField(DifferentField, CommonValue, AddrModes);
return CommonValue != nullptr;
}
private:
/// Initialize Map with anchor values. For address seen
/// we set the value of different field saw in this address.
/// At the same time we find a common type for different field we will
/// use to create new Phi/Select nodes. Keep it in CommonType field.
/// Return false if there is no common type found.
bool initializeMap(FoldAddrToValueMapping &Map) {
// Keep track of keys where the value is null. We will need to replace it
// with constant null when we know the common type.
SmallVector<Value *, 2> NullValue;
Type *IntPtrTy = SQ.DL.getIntPtrType(AddrModes[0].OriginalValue->getType());
for (auto &AM : AddrModes) {
Value *DV = AM.GetFieldAsValue(DifferentField, IntPtrTy);
if (DV) {
auto *Type = DV->getType();
if (CommonType && CommonType != Type)
return false;
CommonType = Type;
Map[AM.OriginalValue] = DV;
} else {
NullValue.push_back(AM.OriginalValue);
}
}
assert(CommonType && "At least one non-null value must be!");
for (auto *V : NullValue)
Map[V] = Constant::getNullValue(CommonType);
return true;
}
/// We have mapping between value A and other value B where B was a field in
/// addressing mode represented by A. Also we have an original value C
/// representing an address we start with. Traversing from C through phi and
/// selects we ended up with A's in a map. This utility function tries to find
/// a value V which is a field in addressing mode C and traversing through phi
/// nodes and selects we will end up in corresponded values B in a map.
/// The utility will create a new Phi/Selects if needed.
// The simple example looks as follows:
// BB1:
// p1 = b1 + 40
// br cond BB2, BB3
// BB2:
// p2 = b2 + 40
// br BB3
// BB3:
// p = phi [p1, BB1], [p2, BB2]
// v = load p
// Map is
// p1 -> b1
// p2 -> b2
// Request is
// p -> ?
// The function tries to find or build phi [b1, BB1], [b2, BB2] in BB3.
Value *findCommon(FoldAddrToValueMapping &Map) {
// Tracks the simplification of newly created phi nodes. The reason we use
// this mapping is because we will add new created Phi nodes in AddrToBase.
// Simplification of Phi nodes is recursive, so some Phi node may
// be simplified after we added it to AddrToBase. In reality this
// simplification is possible only if original phi/selects were not
// simplified yet.
// Using this mapping we can find the current value in AddrToBase.
SimplificationTracker ST(SQ);
// First step, DFS to create PHI nodes for all intermediate blocks.
// Also fill traverse order for the second step.
SmallVector<Value *, 32> TraverseOrder;
InsertPlaceholders(Map, TraverseOrder, ST);
// Second Step, fill new nodes by merged values and simplify if possible.
FillPlaceholders(Map, TraverseOrder, ST);
if (!AddrSinkNewSelects && ST.countNewSelectNodes() > 0) {
ST.destroyNewNodes(CommonType);
return nullptr;
}
// Now we'd like to match New Phi nodes to existed ones.
unsigned PhiNotMatchedCount = 0;
if (!MatchPhiSet(ST, AddrSinkNewPhis, PhiNotMatchedCount)) {
ST.destroyNewNodes(CommonType);
return nullptr;
}
auto *Result = ST.Get(Map.find(Original)->second);
if (Result) {
NumMemoryInstsPhiCreated += ST.countNewPhiNodes() + PhiNotMatchedCount;
NumMemoryInstsSelectCreated += ST.countNewSelectNodes();
}
return Result;
}
/// Try to match PHI node to Candidate.
/// Matcher tracks the matched Phi nodes.
bool MatchPhiNode(PHINode *PHI, PHINode *Candidate,
SmallSetVector<PHIPair, 8> &Matcher,
PhiNodeSet &PhiNodesToMatch) {
SmallVector<PHIPair, 8> WorkList;
Matcher.insert({ PHI, Candidate });
SmallSet<PHINode *, 8> MatchedPHIs;
MatchedPHIs.insert(PHI);
WorkList.push_back({ PHI, Candidate });
SmallSet<PHIPair, 8> Visited;
while (!WorkList.empty()) {
auto Item = WorkList.pop_back_val();
if (!Visited.insert(Item).second)
continue;
// We iterate over all incoming values to Phi to compare them.
// If values are different and both of them Phi and the first one is a
// Phi we added (subject to match) and both of them is in the same basic
// block then we can match our pair if values match. So we state that
// these values match and add it to work list to verify that.
for (auto B : Item.first->blocks()) {
Value *FirstValue = Item.first->getIncomingValueForBlock(B);
Value *SecondValue = Item.second->getIncomingValueForBlock(B);
if (FirstValue == SecondValue)
continue;
PHINode *FirstPhi = dyn_cast<PHINode>(FirstValue);
PHINode *SecondPhi = dyn_cast<PHINode>(SecondValue);
// One of them is not Phi or
// The first one is not Phi node from the set we'd like to match or
// Phi nodes from different basic blocks then
// we will not be able to match.
if (!FirstPhi || !SecondPhi || !PhiNodesToMatch.count(FirstPhi) ||
FirstPhi->getParent() != SecondPhi->getParent())
return false;
// If we already matched them then continue.
if (Matcher.count({ FirstPhi, SecondPhi }))
continue;
// So the values are different and does not match. So we need them to
// match. (But we register no more than one match per PHI node, so that
// we won't later try to replace them twice.)
if (MatchedPHIs.insert(FirstPhi).second)
Matcher.insert({ FirstPhi, SecondPhi });
// But me must check it.
WorkList.push_back({ FirstPhi, SecondPhi });
}
}
return true;
}
/// For the given set of PHI nodes (in the SimplificationTracker) try
/// to find their equivalents.
/// Returns false if this matching fails and creation of new Phi is disabled.
bool MatchPhiSet(SimplificationTracker &ST, bool AllowNewPhiNodes,
unsigned &PhiNotMatchedCount) {
// Matched and PhiNodesToMatch iterate their elements in a deterministic
// order, so the replacements (ReplacePhi) are also done in a deterministic
// order.
SmallSetVector<PHIPair, 8> Matched;
SmallPtrSet<PHINode *, 8> WillNotMatch;
PhiNodeSet &PhiNodesToMatch = ST.newPhiNodes();
while (PhiNodesToMatch.size()) {
PHINode *PHI = *PhiNodesToMatch.begin();
// Add us, if no Phi nodes in the basic block we do not match.
WillNotMatch.clear();
WillNotMatch.insert(PHI);
// Traverse all Phis until we found equivalent or fail to do that.
bool IsMatched = false;
for (auto &P : PHI->getParent()->phis()) {
// Skip new Phi nodes.
if (PhiNodesToMatch.count(&P))
continue;
if ((IsMatched = MatchPhiNode(PHI, &P, Matched, PhiNodesToMatch)))
break;
// If it does not match, collect all Phi nodes from matcher.
// if we end up with no match, them all these Phi nodes will not match
// later.
for (auto M : Matched)
WillNotMatch.insert(M.first);
Matched.clear();
}
if (IsMatched) {
// Replace all matched values and erase them.
for (auto MV : Matched)
ST.ReplacePhi(MV.first, MV.second);
Matched.clear();
continue;
}
// If we are not allowed to create new nodes then bail out.
if (!AllowNewPhiNodes)
return false;
// Just remove all seen values in matcher. They will not match anything.
PhiNotMatchedCount += WillNotMatch.size();
for (auto *P : WillNotMatch)
PhiNodesToMatch.erase(P);
}
return true;
}
/// Fill the placeholders with values from predecessors and simplify them.
void FillPlaceholders(FoldAddrToValueMapping &Map,
SmallVectorImpl<Value *> &TraverseOrder,
SimplificationTracker &ST) {
while (!TraverseOrder.empty()) {
Value *Current = TraverseOrder.pop_back_val();
assert(Map.find(Current) != Map.end() && "No node to fill!!!");
Value *V = Map[Current];
if (SelectInst *Select = dyn_cast<SelectInst>(V)) {
// CurrentValue also must be Select.
auto *CurrentSelect = cast<SelectInst>(Current);
auto *TrueValue = CurrentSelect->getTrueValue();
assert(Map.find(TrueValue) != Map.end() && "No True Value!");
Select->setTrueValue(ST.Get(Map[TrueValue]));
auto *FalseValue = CurrentSelect->getFalseValue();
assert(Map.find(FalseValue) != Map.end() && "No False Value!");
Select->setFalseValue(ST.Get(Map[FalseValue]));
} else {
// Must be a Phi node then.
auto *PHI = cast<PHINode>(V);
// Fill the Phi node with values from predecessors.
for (auto *B : predecessors(PHI->getParent())) {
Value *PV = cast<PHINode>(Current)->getIncomingValueForBlock(B);
assert(Map.find(PV) != Map.end() && "No predecessor Value!");
PHI->addIncoming(ST.Get(Map[PV]), B);
}
}
Map[Current] = ST.Simplify(V);
}
}
/// Starting from original value recursively iterates over def-use chain up to
/// known ending values represented in a map. For each traversed phi/select
/// inserts a placeholder Phi or Select.
/// Reports all new created Phi/Select nodes by adding them to set.
/// Also reports and order in what values have been traversed.
void InsertPlaceholders(FoldAddrToValueMapping &Map,
SmallVectorImpl<Value *> &TraverseOrder,
SimplificationTracker &ST) {
SmallVector<Value *, 32> Worklist;
assert((isa<PHINode>(Original) || isa<SelectInst>(Original)) &&
"Address must be a Phi or Select node");
auto *Dummy = UndefValue::get(CommonType);
Worklist.push_back(Original);
while (!Worklist.empty()) {
Value *Current = Worklist.pop_back_val();
// if it is already visited or it is an ending value then skip it.
if (Map.find(Current) != Map.end())
continue;
TraverseOrder.push_back(Current);
// CurrentValue must be a Phi node or select. All others must be covered
// by anchors.
if (SelectInst *CurrentSelect = dyn_cast<SelectInst>(Current)) {
// Is it OK to get metadata from OrigSelect?!
// Create a Select placeholder with dummy value.
SelectInst *Select = SelectInst::Create(
CurrentSelect->getCondition(), Dummy, Dummy,
CurrentSelect->getName(), CurrentSelect, CurrentSelect);
Map[Current] = Select;
ST.insertNewSelect(Select);
// We are interested in True and False values.
Worklist.push_back(CurrentSelect->getTrueValue());
Worklist.push_back(CurrentSelect->getFalseValue());
} else {
// It must be a Phi node then.
PHINode *CurrentPhi = cast<PHINode>(Current);
unsigned PredCount = CurrentPhi->getNumIncomingValues();
PHINode *PHI =
PHINode::Create(CommonType, PredCount, "sunk_phi", CurrentPhi);
Map[Current] = PHI;
ST.insertNewPhi(PHI);
append_range(Worklist, CurrentPhi->incoming_values());
}
}
}
bool addrModeCombiningAllowed() {
if (DisableComplexAddrModes)
return false;
switch (DifferentField) {
default:
return false;
case ExtAddrMode::BaseRegField:
return AddrSinkCombineBaseReg;
case ExtAddrMode::BaseGVField:
return AddrSinkCombineBaseGV;
case ExtAddrMode::BaseOffsField:
return AddrSinkCombineBaseOffs;
case ExtAddrMode::ScaledRegField:
return AddrSinkCombineScaledReg;
}
}
};
} // end anonymous namespace
/// Try adding ScaleReg*Scale to the current addressing mode.
/// Return true and update AddrMode if this addr mode is legal for the target,
/// false if not.
bool AddressingModeMatcher::matchScaledValue(Value *ScaleReg, int64_t Scale,
unsigned Depth) {
// If Scale is 1, then this is the same as adding ScaleReg to the addressing
// mode. Just process that directly.
if (Scale == 1)
return matchAddr(ScaleReg, Depth);
// If the scale is 0, it takes nothing to add this.
if (Scale == 0)
return true;
// If we already have a scale of this value, we can add to it, otherwise, we
// need an available scale field.
if (AddrMode.Scale != 0 && AddrMode.ScaledReg != ScaleReg)
return false;
ExtAddrMode TestAddrMode = AddrMode;
// Add scale to turn X*4+X*3 -> X*7. This could also do things like
// [A+B + A*7] -> [B+A*8].
TestAddrMode.Scale += Scale;
TestAddrMode.ScaledReg = ScaleReg;
// If the new address isn't legal, bail out.
if (!TLI.isLegalAddressingMode(DL, TestAddrMode, AccessTy, AddrSpace))
return false;
// It was legal, so commit it.
AddrMode = TestAddrMode;
// Okay, we decided that we can add ScaleReg+Scale to AddrMode. Check now
// to see if ScaleReg is actually X+C. If so, we can turn this into adding
// X*Scale + C*Scale to addr mode. If we found available IV increment, do not
// go any further: we can reuse it and cannot eliminate it.
ConstantInt *CI = nullptr; Value *AddLHS = nullptr;
if (isa<Instruction>(ScaleReg) && // not a constant expr.
match(ScaleReg, m_Add(m_Value(AddLHS), m_ConstantInt(CI))) &&
!isIVIncrement(ScaleReg, &LI) && CI->getValue().isSignedIntN(64)) {
TestAddrMode.InBounds = false;
TestAddrMode.ScaledReg = AddLHS;
TestAddrMode.BaseOffs += CI->getSExtValue() * TestAddrMode.Scale;
// If this addressing mode is legal, commit it and remember that we folded
// this instruction.
if (TLI.isLegalAddressingMode(DL, TestAddrMode, AccessTy, AddrSpace)) {
AddrModeInsts.push_back(cast<Instruction>(ScaleReg));
AddrMode = TestAddrMode;
return true;
}
// Restore status quo.
TestAddrMode = AddrMode;
}
// If this is an add recurrence with a constant step, return the increment
// instruction and the canonicalized step.
auto GetConstantStep = [this](const Value * V)
->Optional<std::pair<Instruction *, APInt> > {
auto *PN = dyn_cast<PHINode>(V);
if (!PN)
return None;
auto IVInc = getIVIncrement(PN, &LI);
if (!IVInc)
return None;
// TODO: The result of the intrinsics above is two-compliment. However when
// IV inc is expressed as add or sub, iv.next is potentially a poison value.
// If it has nuw or nsw flags, we need to make sure that these flags are
// inferrable at the point of memory instruction. Otherwise we are replacing
// well-defined two-compliment computation with poison. Currently, to avoid
// potentially complex analysis needed to prove this, we reject such cases.
if (auto *OIVInc = dyn_cast<OverflowingBinaryOperator>(IVInc->first))
if (OIVInc->hasNoSignedWrap() || OIVInc->hasNoUnsignedWrap())
return None;
if (auto *ConstantStep = dyn_cast<ConstantInt>(IVInc->second))
return std::make_pair(IVInc->first, ConstantStep->getValue());
return None;
};
// Try to account for the following special case:
// 1. ScaleReg is an inductive variable;
// 2. We use it with non-zero offset;
// 3. IV's increment is available at the point of memory instruction.
//
// In this case, we may reuse the IV increment instead of the IV Phi to
// achieve the following advantages:
// 1. If IV step matches the offset, we will have no need in the offset;
// 2. Even if they don't match, we will reduce the overlap of living IV
// and IV increment, that will potentially lead to better register
// assignment.
if (AddrMode.BaseOffs) {
if (auto IVStep = GetConstantStep(ScaleReg)) {
Instruction *IVInc = IVStep->first;
// The following assert is important to ensure a lack of infinite loops.
// This transforms is (intentionally) the inverse of the one just above.
// If they don't agree on the definition of an increment, we'd alternate
// back and forth indefinitely.
assert(isIVIncrement(IVInc, &LI) && "implied by GetConstantStep");
APInt Step = IVStep->second;
APInt Offset = Step * AddrMode.Scale;
if (Offset.isSignedIntN(64)) {
TestAddrMode.InBounds = false;
TestAddrMode.ScaledReg = IVInc;
TestAddrMode.BaseOffs -= Offset.getLimitedValue();
// If this addressing mode is legal, commit it..
// (Note that we defer the (expensive) domtree base legality check
// to the very last possible point.)
if (TLI.isLegalAddressingMode(DL, TestAddrMode, AccessTy, AddrSpace) &&
getDTFn().dominates(IVInc, MemoryInst)) {
AddrModeInsts.push_back(cast<Instruction>(IVInc));
AddrMode = TestAddrMode;
return true;
}
// Restore status quo.
TestAddrMode = AddrMode;
}
}
}
// Otherwise, just return what we have.
return true;
}
/// This is a little filter, which returns true if an addressing computation
/// involving I might be folded into a load/store accessing it.
/// This doesn't need to be perfect, but needs to accept at least
/// the set of instructions that MatchOperationAddr can.
static bool MightBeFoldableInst(Instruction *I) {
switch (I->getOpcode()) {
case Instruction::BitCast:
case Instruction::AddrSpaceCast:
// Don't touch identity bitcasts.
if (I->getType() == I->getOperand(0)->getType())
return false;
return I->getType()->isIntOrPtrTy();
case Instruction::PtrToInt:
// PtrToInt is always a noop, as we know that the int type is pointer sized.
return true;
case Instruction::IntToPtr:
// We know the input is intptr_t, so this is foldable.
return true;
case Instruction::Add:
return true;
case Instruction::Mul:
case Instruction::Shl:
// Can only handle X*C and X << C.
return isa<ConstantInt>(I->getOperand(1));
case Instruction::GetElementPtr:
return true;
default:
return false;
}
}
/// Check whether or not \p Val is a legal instruction for \p TLI.
/// \note \p Val is assumed to be the product of some type promotion.
/// Therefore if \p Val has an undefined state in \p TLI, this is assumed
/// to be legal, as the non-promoted value would have had the same state.
static bool isPromotedInstructionLegal(const TargetLowering &TLI,
const DataLayout &DL, Value *Val) {
Instruction *PromotedInst = dyn_cast<Instruction>(Val);
if (!PromotedInst)
return false;
int ISDOpcode = TLI.InstructionOpcodeToISD(PromotedInst->getOpcode());
// If the ISDOpcode is undefined, it was undefined before the promotion.
if (!ISDOpcode)
return true;
// Otherwise, check if the promoted instruction is legal or not.
return TLI.isOperationLegalOrCustom(
ISDOpcode, TLI.getValueType(DL, PromotedInst->getType()));
}
namespace {
/// Hepler class to perform type promotion.
class TypePromotionHelper {
/// Utility function to add a promoted instruction \p ExtOpnd to
/// \p PromotedInsts and record the type of extension we have seen.
static void addPromotedInst(InstrToOrigTy &PromotedInsts,
Instruction *ExtOpnd,
bool IsSExt) {
ExtType ExtTy = IsSExt ? SignExtension : ZeroExtension;
InstrToOrigTy::iterator It = PromotedInsts.find(ExtOpnd);
if (It != PromotedInsts.end()) {
// If the new extension is same as original, the information in
// PromotedInsts[ExtOpnd] is still correct.
if (It->second.getInt() == ExtTy)
return;
// Now the new extension is different from old extension, we make
// the type information invalid by setting extension type to
// BothExtension.
ExtTy = BothExtension;
}
PromotedInsts[ExtOpnd] = TypeIsSExt(ExtOpnd->getType(), ExtTy);
}
/// Utility function to query the original type of instruction \p Opnd
/// with a matched extension type. If the extension doesn't match, we
/// cannot use the information we had on the original type.
/// BothExtension doesn't match any extension type.
static const Type *getOrigType(const InstrToOrigTy &PromotedInsts,
Instruction *Opnd,
bool IsSExt) {
ExtType ExtTy = IsSExt ? SignExtension : ZeroExtension;
InstrToOrigTy::const_iterator It = PromotedInsts.find(Opnd);
if (It != PromotedInsts.end() && It->second.getInt() == ExtTy)
return It->second.getPointer();
return nullptr;
}
/// Utility function to check whether or not a sign or zero extension
/// of \p Inst with \p ConsideredExtType can be moved through \p Inst by
/// either using the operands of \p Inst or promoting \p Inst.
/// The type of the extension is defined by \p IsSExt.
/// In other words, check if:
/// ext (Ty Inst opnd1 opnd2 ... opndN) to ConsideredExtType.
/// #1 Promotion applies:
/// ConsideredExtType Inst (ext opnd1 to ConsideredExtType, ...).
/// #2 Operand reuses:
/// ext opnd1 to ConsideredExtType.
/// \p PromotedInsts maps the instructions to their type before promotion.
static bool canGetThrough(const Instruction *Inst, Type *ConsideredExtType,
const InstrToOrigTy &PromotedInsts, bool IsSExt);
/// Utility function to determine if \p OpIdx should be promoted when
/// promoting \p Inst.
static bool shouldExtOperand(const Instruction *Inst, int OpIdx) {
return !(isa<SelectInst>(Inst) && OpIdx == 0);
}
/// Utility function to promote the operand of \p Ext when this
/// operand is a promotable trunc or sext or zext.
/// \p PromotedInsts maps the instructions to their type before promotion.
/// \p CreatedInstsCost[out] contains the cost of all instructions
/// created to promote the operand of Ext.
/// Newly added extensions are inserted in \p Exts.
/// Newly added truncates are inserted in \p Truncs.
/// Should never be called directly.
/// \return The promoted value which is used instead of Ext.
static Value *promoteOperandForTruncAndAnyExt(
Instruction *Ext, TypePromotionTransaction &TPT,
InstrToOrigTy &PromotedInsts, unsigned &CreatedInstsCost,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs, const TargetLowering &TLI);
/// Utility function to promote the operand of \p Ext when this
/// operand is promotable and is not a supported trunc or sext.
/// \p PromotedInsts maps the instructions to their type before promotion.
/// \p CreatedInstsCost[out] contains the cost of all the instructions
/// created to promote the operand of Ext.
/// Newly added extensions are inserted in \p Exts.
/// Newly added truncates are inserted in \p Truncs.
/// Should never be called directly.
/// \return The promoted value which is used instead of Ext.
static Value *promoteOperandForOther(Instruction *Ext,
TypePromotionTransaction &TPT,
InstrToOrigTy &PromotedInsts,
unsigned &CreatedInstsCost,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs,
const TargetLowering &TLI, bool IsSExt);
/// \see promoteOperandForOther.
static Value *signExtendOperandForOther(
Instruction *Ext, TypePromotionTransaction &TPT,
InstrToOrigTy &PromotedInsts, unsigned &CreatedInstsCost,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs, const TargetLowering &TLI) {
return promoteOperandForOther(Ext, TPT, PromotedInsts, CreatedInstsCost,
Exts, Truncs, TLI, true);
}
/// \see promoteOperandForOther.
static Value *zeroExtendOperandForOther(
Instruction *Ext, TypePromotionTransaction &TPT,
InstrToOrigTy &PromotedInsts, unsigned &CreatedInstsCost,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs, const TargetLowering &TLI) {
return promoteOperandForOther(Ext, TPT, PromotedInsts, CreatedInstsCost,
Exts, Truncs, TLI, false);
}
public:
/// Type for the utility function that promotes the operand of Ext.
using Action = Value *(*)(Instruction *Ext, TypePromotionTransaction &TPT,
InstrToOrigTy &PromotedInsts,
unsigned &CreatedInstsCost,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs,
const TargetLowering &TLI);
/// Given a sign/zero extend instruction \p Ext, return the appropriate
/// action to promote the operand of \p Ext instead of using Ext.
/// \return NULL if no promotable action is possible with the current
/// sign extension.
/// \p InsertedInsts keeps track of all the instructions inserted by the
/// other CodeGenPrepare optimizations. This information is important
/// because we do not want to promote these instructions as CodeGenPrepare
/// will reinsert them later. Thus creating an infinite loop: create/remove.
/// \p PromotedInsts maps the instructions to their type before promotion.
static Action getAction(Instruction *Ext, const SetOfInstrs &InsertedInsts,
const TargetLowering &TLI,
const InstrToOrigTy &PromotedInsts);
};
} // end anonymous namespace
bool TypePromotionHelper::canGetThrough(const Instruction *Inst,
Type *ConsideredExtType,
const InstrToOrigTy &PromotedInsts,
bool IsSExt) {
// The promotion helper does not know how to deal with vector types yet.
// To be able to fix that, we would need to fix the places where we
// statically extend, e.g., constants and such.
if (Inst->getType()->isVectorTy())
return false;
// We can always get through zext.
if (isa<ZExtInst>(Inst))
return true;
// sext(sext) is ok too.
if (IsSExt && isa<SExtInst>(Inst))
return true;
// We can get through binary operator, if it is legal. In other words, the
// binary operator must have a nuw or nsw flag.
if (const auto *BinOp = dyn_cast<BinaryOperator>(Inst))
if (isa<OverflowingBinaryOperator>(BinOp) &&
((!IsSExt && BinOp->hasNoUnsignedWrap()) ||
(IsSExt && BinOp->hasNoSignedWrap())))
return true;
// ext(and(opnd, cst)) --> and(ext(opnd), ext(cst))
if ((Inst->getOpcode() == Instruction::And ||
Inst->getOpcode() == Instruction::Or))
return true;
// ext(xor(opnd, cst)) --> xor(ext(opnd), ext(cst))
if (Inst->getOpcode() == Instruction::Xor) {
// Make sure it is not a NOT.
if (const auto *Cst = dyn_cast<ConstantInt>(Inst->getOperand(1)))
if (!Cst->getValue().isAllOnes())
return true;
}
// zext(shrl(opnd, cst)) --> shrl(zext(opnd), zext(cst))
// It may change a poisoned value into a regular value, like
// zext i32 (shrl i8 %val, 12) --> shrl i32 (zext i8 %val), 12
// poisoned value regular value
// It should be OK since undef covers valid value.
if (Inst->getOpcode() == Instruction::LShr && !IsSExt)
return true;
// and(ext(shl(opnd, cst)), cst) --> and(shl(ext(opnd), ext(cst)), cst)
// It may change a poisoned value into a regular value, like
// zext i32 (shl i8 %val, 12) --> shl i32 (zext i8 %val), 12
// poisoned value regular value
// It should be OK since undef covers valid value.
if (Inst->getOpcode() == Instruction::Shl && Inst->hasOneUse()) {
const auto *ExtInst = cast<const Instruction>(*Inst->user_begin());
if (ExtInst->hasOneUse()) {
const auto *AndInst = dyn_cast<const Instruction>(*ExtInst->user_begin());
if (AndInst && AndInst->getOpcode() == Instruction::And) {
const auto *Cst = dyn_cast<ConstantInt>(AndInst->getOperand(1));
if (Cst &&
Cst->getValue().isIntN(Inst->getType()->getIntegerBitWidth()))
return true;
}
}
}
// Check if we can do the following simplification.
// ext(trunc(opnd)) --> ext(opnd)
if (!isa<TruncInst>(Inst))
return false;
Value *OpndVal = Inst->getOperand(0);
// Check if we can use this operand in the extension.
// If the type is larger than the result type of the extension, we cannot.
if (!OpndVal->getType()->isIntegerTy() ||
OpndVal->getType()->getIntegerBitWidth() >
ConsideredExtType->getIntegerBitWidth())
return false;
// If the operand of the truncate is not an instruction, we will not have
// any information on the dropped bits.
// (Actually we could for constant but it is not worth the extra logic).
Instruction *Opnd = dyn_cast<Instruction>(OpndVal);
if (!Opnd)
return false;
// Check if the source of the type is narrow enough.
// I.e., check that trunc just drops extended bits of the same kind of
// the extension.
// #1 get the type of the operand and check the kind of the extended bits.
const Type *OpndType = getOrigType(PromotedInsts, Opnd, IsSExt);
if (OpndType)
;
else if ((IsSExt && isa<SExtInst>(Opnd)) || (!IsSExt && isa<ZExtInst>(Opnd)))
OpndType = Opnd->getOperand(0)->getType();
else
return false;
// #2 check that the truncate just drops extended bits.
return Inst->getType()->getIntegerBitWidth() >=
OpndType->getIntegerBitWidth();
}
TypePromotionHelper::Action TypePromotionHelper::getAction(
Instruction *Ext, const SetOfInstrs &InsertedInsts,
const TargetLowering &TLI, const InstrToOrigTy &PromotedInsts) {
assert((isa<SExtInst>(Ext) || isa<ZExtInst>(Ext)) &&
"Unexpected instruction type");
Instruction *ExtOpnd = dyn_cast<Instruction>(Ext->getOperand(0));
Type *ExtTy = Ext->getType();
bool IsSExt = isa<SExtInst>(Ext);
// If the operand of the extension is not an instruction, we cannot
// get through.
// If it, check we can get through.
if (!ExtOpnd || !canGetThrough(ExtOpnd, ExtTy, PromotedInsts, IsSExt))
return nullptr;
// Do not promote if the operand has been added by codegenprepare.
// Otherwise, it means we are undoing an optimization that is likely to be
// redone, thus causing potential infinite loop.
if (isa<TruncInst>(ExtOpnd) && InsertedInsts.count(ExtOpnd))
return nullptr;
// SExt or Trunc instructions.
// Return the related handler.
if (isa<SExtInst>(ExtOpnd) || isa<TruncInst>(ExtOpnd) ||
isa<ZExtInst>(ExtOpnd))
return promoteOperandForTruncAndAnyExt;
// Regular instruction.
// Abort early if we will have to insert non-free instructions.
if (!ExtOpnd->hasOneUse() && !TLI.isTruncateFree(ExtTy, ExtOpnd->getType()))
return nullptr;
return IsSExt ? signExtendOperandForOther : zeroExtendOperandForOther;
}
Value *TypePromotionHelper::promoteOperandForTruncAndAnyExt(
Instruction *SExt, TypePromotionTransaction &TPT,
InstrToOrigTy &PromotedInsts, unsigned &CreatedInstsCost,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs, const TargetLowering &TLI) {
// By construction, the operand of SExt is an instruction. Otherwise we cannot
// get through it and this method should not be called.
Instruction *SExtOpnd = cast<Instruction>(SExt->getOperand(0));
Value *ExtVal = SExt;
bool HasMergedNonFreeExt = false;
if (isa<ZExtInst>(SExtOpnd)) {
// Replace s|zext(zext(opnd))
// => zext(opnd).
HasMergedNonFreeExt = !TLI.isExtFree(SExtOpnd);
Value *ZExt =
TPT.createZExt(SExt, SExtOpnd->getOperand(0), SExt->getType());
TPT.replaceAllUsesWith(SExt, ZExt);
TPT.eraseInstruction(SExt);
ExtVal = ZExt;
} else {
// Replace z|sext(trunc(opnd)) or sext(sext(opnd))
// => z|sext(opnd).
TPT.setOperand(SExt, 0, SExtOpnd->getOperand(0));
}
CreatedInstsCost = 0;
// Remove dead code.
if (SExtOpnd->use_empty())
TPT.eraseInstruction(SExtOpnd);
// Check if the extension is still needed.
Instruction *ExtInst = dyn_cast<Instruction>(ExtVal);
if (!ExtInst || ExtInst->getType() != ExtInst->getOperand(0)->getType()) {
if (ExtInst) {
if (Exts)
Exts->push_back(ExtInst);
CreatedInstsCost = !TLI.isExtFree(ExtInst) && !HasMergedNonFreeExt;
}
return ExtVal;
}
// At this point we have: ext ty opnd to ty.
// Reassign the uses of ExtInst to the opnd and remove ExtInst.
Value *NextVal = ExtInst->getOperand(0);
TPT.eraseInstruction(ExtInst, NextVal);
return NextVal;
}
Value *TypePromotionHelper::promoteOperandForOther(
Instruction *Ext, TypePromotionTransaction &TPT,
InstrToOrigTy &PromotedInsts, unsigned &CreatedInstsCost,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs, const TargetLowering &TLI,
bool IsSExt) {
// By construction, the operand of Ext is an instruction. Otherwise we cannot
// get through it and this method should not be called.
Instruction *ExtOpnd = cast<Instruction>(Ext->getOperand(0));
CreatedInstsCost = 0;
if (!ExtOpnd->hasOneUse()) {
// ExtOpnd will be promoted.
// All its uses, but Ext, will need to use a truncated value of the
// promoted version.
// Create the truncate now.
Value *Trunc = TPT.createTrunc(Ext, ExtOpnd->getType());
if (Instruction *ITrunc = dyn_cast<Instruction>(Trunc)) {
// Insert it just after the definition.
ITrunc->moveAfter(ExtOpnd);
if (Truncs)
Truncs->push_back(ITrunc);
}
TPT.replaceAllUsesWith(ExtOpnd, Trunc);
// Restore the operand of Ext (which has been replaced by the previous call
// to replaceAllUsesWith) to avoid creating a cycle trunc <-> sext.
TPT.setOperand(Ext, 0, ExtOpnd);
}
// Get through the Instruction:
// 1. Update its type.
// 2. Replace the uses of Ext by Inst.
// 3. Extend each operand that needs to be extended.
// Remember the original type of the instruction before promotion.
// This is useful to know that the high bits are sign extended bits.
addPromotedInst(PromotedInsts, ExtOpnd, IsSExt);
// Step #1.
TPT.mutateType(ExtOpnd, Ext->getType());
// Step #2.
TPT.replaceAllUsesWith(Ext, ExtOpnd);
// Step #3.
Instruction *ExtForOpnd = Ext;
LLVM_DEBUG(dbgs() << "Propagate Ext to operands\n");
for (int OpIdx = 0, EndOpIdx = ExtOpnd->getNumOperands(); OpIdx != EndOpIdx;
++OpIdx) {
LLVM_DEBUG(dbgs() << "Operand:\n" << *(ExtOpnd->getOperand(OpIdx)) << '\n');
if (ExtOpnd->getOperand(OpIdx)->getType() == Ext->getType() ||
!shouldExtOperand(ExtOpnd, OpIdx)) {
LLVM_DEBUG(dbgs() << "No need to propagate\n");
continue;
}
// Check if we can statically extend the operand.
Value *Opnd = ExtOpnd->getOperand(OpIdx);
if (const ConstantInt *Cst = dyn_cast<ConstantInt>(Opnd)) {
LLVM_DEBUG(dbgs() << "Statically extend\n");
unsigned BitWidth = Ext->getType()->getIntegerBitWidth();
APInt CstVal = IsSExt ? Cst->getValue().sext(BitWidth)
: Cst->getValue().zext(BitWidth);
TPT.setOperand(ExtOpnd, OpIdx, ConstantInt::get(Ext->getType(), CstVal));
continue;
}
// UndefValue are typed, so we have to statically sign extend them.
if (isa<UndefValue>(Opnd)) {
LLVM_DEBUG(dbgs() << "Statically extend\n");
TPT.setOperand(ExtOpnd, OpIdx, UndefValue::get(Ext->getType()));
continue;
}
// Otherwise we have to explicitly sign extend the operand.
// Check if Ext was reused to extend an operand.
if (!ExtForOpnd) {
// If yes, create a new one.
LLVM_DEBUG(dbgs() << "More operands to ext\n");
Value *ValForExtOpnd = IsSExt ? TPT.createSExt(Ext, Opnd, Ext->getType())
: TPT.createZExt(Ext, Opnd, Ext->getType());
if (!isa<Instruction>(ValForExtOpnd)) {
TPT.setOperand(ExtOpnd, OpIdx, ValForExtOpnd);
continue;
}
ExtForOpnd = cast<Instruction>(ValForExtOpnd);
}
if (Exts)
Exts->push_back(ExtForOpnd);
TPT.setOperand(ExtForOpnd, 0, Opnd);
// Move the sign extension before the insertion point.
TPT.moveBefore(ExtForOpnd, ExtOpnd);
TPT.setOperand(ExtOpnd, OpIdx, ExtForOpnd);
CreatedInstsCost += !TLI.isExtFree(ExtForOpnd);
// If more sext are required, new instructions will have to be created.
ExtForOpnd = nullptr;
}
if (ExtForOpnd == Ext) {
LLVM_DEBUG(dbgs() << "Extension is useless now\n");
TPT.eraseInstruction(Ext);
}
return ExtOpnd;
}
/// Check whether or not promoting an instruction to a wider type is profitable.
/// \p NewCost gives the cost of extension instructions created by the
/// promotion.
/// \p OldCost gives the cost of extension instructions before the promotion
/// plus the number of instructions that have been
/// matched in the addressing mode the promotion.
/// \p PromotedOperand is the value that has been promoted.
/// \return True if the promotion is profitable, false otherwise.
bool AddressingModeMatcher::isPromotionProfitable(
unsigned NewCost, unsigned OldCost, Value *PromotedOperand) const {
LLVM_DEBUG(dbgs() << "OldCost: " << OldCost << "\tNewCost: " << NewCost
<< '\n');
// The cost of the new extensions is greater than the cost of the
// old extension plus what we folded.
// This is not profitable.
if (NewCost > OldCost)
return false;
if (NewCost < OldCost)
return true;
// The promotion is neutral but it may help folding the sign extension in
// loads for instance.
// Check that we did not create an illegal instruction.
return isPromotedInstructionLegal(TLI, DL, PromotedOperand);
}
/// Given an instruction or constant expr, see if we can fold the operation
/// into the addressing mode. If so, update the addressing mode and return
/// true, otherwise return false without modifying AddrMode.
/// If \p MovedAway is not NULL, it contains the information of whether or
/// not AddrInst has to be folded into the addressing mode on success.
/// If \p MovedAway == true, \p AddrInst will not be part of the addressing
/// because it has been moved away.
/// Thus AddrInst must not be added in the matched instructions.
/// This state can happen when AddrInst is a sext, since it may be moved away.
/// Therefore, AddrInst may not be valid when MovedAway is true and it must
/// not be referenced anymore.
bool AddressingModeMatcher::matchOperationAddr(User *AddrInst, unsigned Opcode,
unsigned Depth,
bool *MovedAway) {
// Avoid exponential behavior on extremely deep expression trees.
if (Depth >= 5) return false;
// By default, all matched instructions stay in place.
if (MovedAway)
*MovedAway = false;
switch (Opcode) {
case Instruction::PtrToInt:
// PtrToInt is always a noop, as we know that the int type is pointer sized.
return matchAddr(AddrInst->getOperand(0), Depth);
case Instruction::IntToPtr: {
auto AS = AddrInst->getType()->getPointerAddressSpace();
auto PtrTy = MVT::getIntegerVT(DL.getPointerSizeInBits(AS));
// This inttoptr is a no-op if the integer type is pointer sized.
if (TLI.getValueType(DL, AddrInst->getOperand(0)->getType()) == PtrTy)
return matchAddr(AddrInst->getOperand(0), Depth);
return false;
}
case Instruction::BitCast:
// BitCast is always a noop, and we can handle it as long as it is
// int->int or pointer->pointer (we don't want int<->fp or something).
if (AddrInst->getOperand(0)->getType()->isIntOrPtrTy() &&
// Don't touch identity bitcasts. These were probably put here by LSR,
// and we don't want to mess around with them. Assume it knows what it
// is doing.
AddrInst->getOperand(0)->getType() != AddrInst->getType())
return matchAddr(AddrInst->getOperand(0), Depth);
return false;
case Instruction::AddrSpaceCast: {
unsigned SrcAS
= AddrInst->getOperand(0)->getType()->getPointerAddressSpace();
unsigned DestAS = AddrInst->getType()->getPointerAddressSpace();
if (TLI.getTargetMachine().isNoopAddrSpaceCast(SrcAS, DestAS))
return matchAddr(AddrInst->getOperand(0), Depth);
return false;
}
case Instruction::Add: {
// Check to see if we can merge in the RHS then the LHS. If so, we win.
ExtAddrMode BackupAddrMode = AddrMode;
unsigned OldSize = AddrModeInsts.size();
// Start a transaction at this point.
// The LHS may match but not the RHS.
// Therefore, we need a higher level restoration point to undo partially
// matched operation.
TypePromotionTransaction::ConstRestorationPt LastKnownGood =
TPT.getRestorationPoint();
AddrMode.InBounds = false;
if (matchAddr(AddrInst->getOperand(1), Depth+1) &&
matchAddr(AddrInst->getOperand(0), Depth+1))
return true;
// Restore the old addr mode info.
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
TPT.rollback(LastKnownGood);
// Otherwise this was over-aggressive. Try merging in the LHS then the RHS.
if (matchAddr(AddrInst->getOperand(0), Depth+1) &&
matchAddr(AddrInst->getOperand(1), Depth+1))
return true;
// Otherwise we definitely can't merge the ADD in.
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
TPT.rollback(LastKnownGood);
break;
}
//case Instruction::Or:
// TODO: We can handle "Or Val, Imm" iff this OR is equivalent to an ADD.
//break;
case Instruction::Mul:
case Instruction::Shl: {
// Can only handle X*C and X << C.
AddrMode.InBounds = false;
ConstantInt *RHS = dyn_cast<ConstantInt>(AddrInst->getOperand(1));
if (!RHS || RHS->getBitWidth() > 64)
return false;
int64_t Scale = Opcode == Instruction::Shl
? 1LL << RHS->getLimitedValue(RHS->getBitWidth() - 1)
: RHS->getSExtValue();
return matchScaledValue(AddrInst->getOperand(0), Scale, Depth);
}
case Instruction::GetElementPtr: {
// Scan the GEP. We check it if it contains constant offsets and at most
// one variable offset.
int VariableOperand = -1;
unsigned VariableScale = 0;
int64_t ConstantOffset = 0;
gep_type_iterator GTI = gep_type_begin(AddrInst);
for (unsigned i = 1, e = AddrInst->getNumOperands(); i != e; ++i, ++GTI) {
if (StructType *STy = GTI.getStructTypeOrNull()) {
const StructLayout *SL = DL.getStructLayout(STy);
unsigned Idx =
cast<ConstantInt>(AddrInst->getOperand(i))->getZExtValue();
ConstantOffset += SL->getElementOffset(Idx);
} else {
TypeSize TS = DL.getTypeAllocSize(GTI.getIndexedType());
if (TS.isNonZero()) {
// The optimisations below currently only work for fixed offsets.
if (TS.isScalable())
return false;
int64_t TypeSize = TS.getFixedSize();
if (ConstantInt *CI =
dyn_cast<ConstantInt>(AddrInst->getOperand(i))) {
const APInt &CVal = CI->getValue();
if (CVal.getMinSignedBits() <= 64) {
ConstantOffset += CVal.getSExtValue() * TypeSize;
continue;
}
}
// We only allow one variable index at the moment.
if (VariableOperand != -1)
return false;
// Remember the variable index.
VariableOperand = i;
VariableScale = TypeSize;
}
}
}
// A common case is for the GEP to only do a constant offset. In this case,
// just add it to the disp field and check validity.
if (VariableOperand == -1) {
AddrMode.BaseOffs += ConstantOffset;
if (ConstantOffset == 0 ||
TLI.isLegalAddressingMode(DL, AddrMode, AccessTy, AddrSpace)) {
// Check to see if we can fold the base pointer in too.
if (matchAddr(AddrInst->getOperand(0), Depth+1)) {
if (!cast<GEPOperator>(AddrInst)->isInBounds())
AddrMode.InBounds = false;
return true;
}
} else if (EnableGEPOffsetSplit && isa<GetElementPtrInst>(AddrInst) &&
TLI.shouldConsiderGEPOffsetSplit() && Depth == 0 &&
ConstantOffset > 0) {
// Record GEPs with non-zero offsets as candidates for splitting in the
// event that the offset cannot fit into the r+i addressing mode.
// Simple and common case that only one GEP is used in calculating the
// address for the memory access.
Value *Base = AddrInst->getOperand(0);
auto *BaseI = dyn_cast<Instruction>(Base);
auto *GEP = cast<GetElementPtrInst>(AddrInst);
if (isa<Argument>(Base) || isa<GlobalValue>(Base) ||
(BaseI && !isa<CastInst>(BaseI) &&
!isa<GetElementPtrInst>(BaseI))) {
// Make sure the parent block allows inserting non-PHI instructions
// before the terminator.
BasicBlock *Parent =
BaseI ? BaseI->getParent() : &GEP->getFunction()->getEntryBlock();
if (!Parent->getTerminator()->isEHPad())
LargeOffsetGEP = std::make_pair(GEP, ConstantOffset);
}
}
AddrMode.BaseOffs -= ConstantOffset;
return false;
}
// Save the valid addressing mode in case we can't match.
ExtAddrMode BackupAddrMode = AddrMode;
unsigned OldSize = AddrModeInsts.size();
// See if the scale and offset amount is valid for this target.
AddrMode.BaseOffs += ConstantOffset;
if (!cast<GEPOperator>(AddrInst)->isInBounds())
AddrMode.InBounds = false;
// Match the base operand of the GEP.
if (!matchAddr(AddrInst->getOperand(0), Depth+1)) {
// If it couldn't be matched, just stuff the value in a register.
if (AddrMode.HasBaseReg) {
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
return false;
}
AddrMode.HasBaseReg = true;
AddrMode.BaseReg = AddrInst->getOperand(0);
}
// Match the remaining variable portion of the GEP.
if (!matchScaledValue(AddrInst->getOperand(VariableOperand), VariableScale,
Depth)) {
// If it couldn't be matched, try stuffing the base into a register
// instead of matching it, and retrying the match of the scale.
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
if (AddrMode.HasBaseReg)
return false;
AddrMode.HasBaseReg = true;
AddrMode.BaseReg = AddrInst->getOperand(0);
AddrMode.BaseOffs += ConstantOffset;
if (!matchScaledValue(AddrInst->getOperand(VariableOperand),
VariableScale, Depth)) {
// If even that didn't work, bail.
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
return false;
}
}
return true;
}
case Instruction::SExt:
case Instruction::ZExt: {
Instruction *Ext = dyn_cast<Instruction>(AddrInst);
if (!Ext)
return false;
// Try to move this ext out of the way of the addressing mode.
// Ask for a method for doing so.
TypePromotionHelper::Action TPH =
TypePromotionHelper::getAction(Ext, InsertedInsts, TLI, PromotedInsts);
if (!TPH)
return false;
TypePromotionTransaction::ConstRestorationPt LastKnownGood =
TPT.getRestorationPoint();
unsigned CreatedInstsCost = 0;
unsigned ExtCost = !TLI.isExtFree(Ext);
Value *PromotedOperand =
TPH(Ext, TPT, PromotedInsts, CreatedInstsCost, nullptr, nullptr, TLI);
// SExt has been moved away.
// Thus either it will be rematched later in the recursive calls or it is
// gone. Anyway, we must not fold it into the addressing mode at this point.
// E.g.,
// op = add opnd, 1
// idx = ext op
// addr = gep base, idx
// is now:
// promotedOpnd = ext opnd <- no match here
// op = promoted_add promotedOpnd, 1 <- match (later in recursive calls)
// addr = gep base, op <- match
if (MovedAway)
*MovedAway = true;
assert(PromotedOperand &&
"TypePromotionHelper should have filtered out those cases");
ExtAddrMode BackupAddrMode = AddrMode;
unsigned OldSize = AddrModeInsts.size();
if (!matchAddr(PromotedOperand, Depth) ||
// The total of the new cost is equal to the cost of the created
// instructions.
// The total of the old cost is equal to the cost of the extension plus
// what we have saved in the addressing mode.
!isPromotionProfitable(CreatedInstsCost,
ExtCost + (AddrModeInsts.size() - OldSize),
PromotedOperand)) {
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
LLVM_DEBUG(dbgs() << "Sign extension does not pay off: rollback\n");
TPT.rollback(LastKnownGood);
return false;
}
return true;
}
}
return false;
}
/// If we can, try to add the value of 'Addr' into the current addressing mode.
/// If Addr can't be added to AddrMode this returns false and leaves AddrMode
/// unmodified. This assumes that Addr is either a pointer type or intptr_t
/// for the target.
///
bool AddressingModeMatcher::matchAddr(Value *Addr, unsigned Depth) {
// Start a transaction at this point that we will rollback if the matching
// fails.
TypePromotionTransaction::ConstRestorationPt LastKnownGood =
TPT.getRestorationPoint();
if (ConstantInt *CI = dyn_cast<ConstantInt>(Addr)) {
if (CI->getValue().isSignedIntN(64)) {
// Fold in immediates if legal for the target.
AddrMode.BaseOffs += CI->getSExtValue();
if (TLI.isLegalAddressingMode(DL, AddrMode, AccessTy, AddrSpace))
return true;
AddrMode.BaseOffs -= CI->getSExtValue();
}
} else if (GlobalValue *GV = dyn_cast<GlobalValue>(Addr)) {
// If this is a global variable, try to fold it into the addressing mode.
if (!AddrMode.BaseGV) {
AddrMode.BaseGV = GV;
if (TLI.isLegalAddressingMode(DL, AddrMode, AccessTy, AddrSpace))
return true;
AddrMode.BaseGV = nullptr;
}
} else if (Instruction *I = dyn_cast<Instruction>(Addr)) {
ExtAddrMode BackupAddrMode = AddrMode;
unsigned OldSize = AddrModeInsts.size();
// Check to see if it is possible to fold this operation.
bool MovedAway = false;
if (matchOperationAddr(I, I->getOpcode(), Depth, &MovedAway)) {
// This instruction may have been moved away. If so, there is nothing
// to check here.
if (MovedAway)
return true;
// Okay, it's possible to fold this. Check to see if it is actually
// *profitable* to do so. We use a simple cost model to avoid increasing
// register pressure too much.
if (I->hasOneUse() ||
isProfitableToFoldIntoAddressingMode(I, BackupAddrMode, AddrMode)) {
AddrModeInsts.push_back(I);
return true;
}
// It isn't profitable to do this, roll back.
//cerr << "NOT FOLDING: " << *I;
AddrMode = BackupAddrMode;
AddrModeInsts.resize(OldSize);
TPT.rollback(LastKnownGood);
}
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Addr)) {
if (matchOperationAddr(CE, CE->getOpcode(), Depth))
return true;
TPT.rollback(LastKnownGood);
} else if (isa<ConstantPointerNull>(Addr)) {
// Null pointer gets folded without affecting the addressing mode.
return true;
}
// Worse case, the target should support [reg] addressing modes. :)
if (!AddrMode.HasBaseReg) {
AddrMode.HasBaseReg = true;
AddrMode.BaseReg = Addr;
// Still check for legality in case the target supports [imm] but not [i+r].
if (TLI.isLegalAddressingMode(DL, AddrMode, AccessTy, AddrSpace))
return true;
AddrMode.HasBaseReg = false;
AddrMode.BaseReg = nullptr;
}
// If the base register is already taken, see if we can do [r+r].
if (AddrMode.Scale == 0) {
AddrMode.Scale = 1;
AddrMode.ScaledReg = Addr;
if (TLI.isLegalAddressingMode(DL, AddrMode, AccessTy, AddrSpace))
return true;
AddrMode.Scale = 0;
AddrMode.ScaledReg = nullptr;
}
// Couldn't match.
TPT.rollback(LastKnownGood);
return false;
}
/// Check to see if all uses of OpVal by the specified inline asm call are due
/// to memory operands. If so, return true, otherwise return false.
static bool IsOperandAMemoryOperand(CallInst *CI, InlineAsm *IA, Value *OpVal,
const TargetLowering &TLI,
const TargetRegisterInfo &TRI) {
const Function *F = CI->getFunction();
TargetLowering::AsmOperandInfoVector TargetConstraints =
TLI.ParseConstraints(F->getParent()->getDataLayout(), &TRI, *CI);
for (TargetLowering::AsmOperandInfo &OpInfo : TargetConstraints) {
// Compute the constraint code and ConstraintType to use.
TLI.ComputeConstraintToUse(OpInfo, SDValue());
// If this asm operand is our Value*, and if it isn't an indirect memory
// operand, we can't fold it! TODO: Also handle C_Address?
if (OpInfo.CallOperandVal == OpVal &&
(OpInfo.ConstraintType != TargetLowering::C_Memory ||
!OpInfo.isIndirect))
return false;
}
return true;
}
// Max number of memory uses to look at before aborting the search to conserve
// compile time.
static constexpr int MaxMemoryUsesToScan = 20;
/// Recursively walk all the uses of I until we find a memory use.
/// If we find an obviously non-foldable instruction, return true.
/// Add accessed addresses and types to MemoryUses.
static bool FindAllMemoryUses(
Instruction *I, SmallVectorImpl<std::pair<Value *, Type *>> &MemoryUses,
SmallPtrSetImpl<Instruction *> &ConsideredInsts, const TargetLowering &TLI,
const TargetRegisterInfo &TRI, bool OptSize, ProfileSummaryInfo *PSI,
BlockFrequencyInfo *BFI, int SeenInsts = 0) {
// If we already considered this instruction, we're done.
if (!ConsideredInsts.insert(I).second)
return false;
// If this is an obviously unfoldable instruction, bail out.
if (!MightBeFoldableInst(I))
return true;
// Loop over all the uses, recursively processing them.
for (Use &U : I->uses()) {
// Conservatively return true if we're seeing a large number or a deep chain
// of users. This avoids excessive compilation times in pathological cases.
if (SeenInsts++ >= MaxMemoryUsesToScan)
return true;
Instruction *UserI = cast<Instruction>(U.getUser());
if (LoadInst *LI = dyn_cast<LoadInst>(UserI)) {
MemoryUses.push_back({U.get(), LI->getType()});
continue;
}
if (StoreInst *SI = dyn_cast<StoreInst>(UserI)) {
if (U.getOperandNo() != StoreInst::getPointerOperandIndex())
return true; // Storing addr, not into addr.
MemoryUses.push_back({U.get(), SI->getValueOperand()->getType()});
continue;
}
if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(UserI)) {
if (U.getOperandNo() != AtomicRMWInst::getPointerOperandIndex())
return true; // Storing addr, not into addr.
MemoryUses.push_back({U.get(), RMW->getValOperand()->getType()});
continue;
}
if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(UserI)) {
if (U.getOperandNo() != AtomicCmpXchgInst::getPointerOperandIndex())
return true; // Storing addr, not into addr.
MemoryUses.push_back({U.get(), CmpX->getCompareOperand()->getType()});
continue;
}
if (CallInst *CI = dyn_cast<CallInst>(UserI)) {
if (CI->hasFnAttr(Attribute::Cold)) {
// If this is a cold call, we can sink the addressing calculation into
// the cold path. See optimizeCallInst
bool OptForSize = OptSize ||
llvm::shouldOptimizeForSize(CI->getParent(), PSI, BFI);
if (!OptForSize)
continue;
}
InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledOperand());
if (!IA) return true;
// If this is a memory operand, we're cool, otherwise bail out.
if (!IsOperandAMemoryOperand(CI, IA, I, TLI, TRI))
return true;
continue;
}
if (FindAllMemoryUses(UserI, MemoryUses, ConsideredInsts, TLI, TRI, OptSize,
PSI, BFI, SeenInsts))
return true;
}
return false;
}
/// Return true if Val is already known to be live at the use site that we're
/// folding it into. If so, there is no cost to include it in the addressing
/// mode. KnownLive1 and KnownLive2 are two values that we know are live at the
/// instruction already.
bool AddressingModeMatcher::valueAlreadyLiveAtInst(Value *Val,Value *KnownLive1,
Value *KnownLive2) {
// If Val is either of the known-live values, we know it is live!
if (Val == nullptr || Val == KnownLive1 || Val == KnownLive2)
return true;
// All values other than instructions and arguments (e.g. constants) are live.
if (!isa<Instruction>(Val) && !isa<Argument>(Val)) return true;
// If Val is a constant sized alloca in the entry block, it is live, this is
// true because it is just a reference to the stack/frame pointer, which is
// live for the whole function.
if (AllocaInst *AI = dyn_cast<AllocaInst>(Val))
if (AI->isStaticAlloca())
return true;
// Check to see if this value is already used in the memory instruction's
// block. If so, it's already live into the block at the very least, so we
// can reasonably fold it.
return Val->isUsedInBasicBlock(MemoryInst->getParent());
}
/// It is possible for the addressing mode of the machine to fold the specified
/// instruction into a load or store that ultimately uses it.
/// However, the specified instruction has multiple uses.
/// Given this, it may actually increase register pressure to fold it
/// into the load. For example, consider this code:
///
/// X = ...
/// Y = X+1
/// use(Y) -> nonload/store
/// Z = Y+1
/// load Z
///
/// In this case, Y has multiple uses, and can be folded into the load of Z
/// (yielding load [X+2]). However, doing this will cause both "X" and "X+1" to
/// be live at the use(Y) line. If we don't fold Y into load Z, we use one
/// fewer register. Since Y can't be folded into "use(Y)" we don't increase the
/// number of computations either.
///
/// Note that this (like most of CodeGenPrepare) is just a rough heuristic. If
/// X was live across 'load Z' for other reasons, we actually *would* want to
/// fold the addressing mode in the Z case. This would make Y die earlier.
bool AddressingModeMatcher::
isProfitableToFoldIntoAddressingMode(Instruction *I, ExtAddrMode &AMBefore,
ExtAddrMode &AMAfter) {
if (IgnoreProfitability) return true;
// AMBefore is the addressing mode before this instruction was folded into it,
// and AMAfter is the addressing mode after the instruction was folded. Get
// the set of registers referenced by AMAfter and subtract out those
// referenced by AMBefore: this is the set of values which folding in this
// address extends the lifetime of.
//
// Note that there are only two potential values being referenced here,
// BaseReg and ScaleReg (global addresses are always available, as are any
// folded immediates).
Value *BaseReg = AMAfter.BaseReg, *ScaledReg = AMAfter.ScaledReg;
// If the BaseReg or ScaledReg was referenced by the previous addrmode, their
// lifetime wasn't extended by adding this instruction.
if (valueAlreadyLiveAtInst(BaseReg, AMBefore.BaseReg, AMBefore.ScaledReg))
BaseReg = nullptr;
if (valueAlreadyLiveAtInst(ScaledReg, AMBefore.BaseReg, AMBefore.ScaledReg))
ScaledReg = nullptr;
// If folding this instruction (and it's subexprs) didn't extend any live
// ranges, we're ok with it.
if (!BaseReg && !ScaledReg)
return true;
// If all uses of this instruction can have the address mode sunk into them,
// we can remove the addressing mode and effectively trade one live register
// for another (at worst.) In this context, folding an addressing mode into
// the use is just a particularly nice way of sinking it.
SmallVector<std::pair<Value *, Type *>, 16> MemoryUses;
SmallPtrSet<Instruction*, 16> ConsideredInsts;
if (FindAllMemoryUses(I, MemoryUses, ConsideredInsts, TLI, TRI, OptSize,
PSI, BFI))
return false; // Has a non-memory, non-foldable use!
// Now that we know that all uses of this instruction are part of a chain of
// computation involving only operations that could theoretically be folded
// into a memory use, loop over each of these memory operation uses and see
// if they could *actually* fold the instruction. The assumption is that
// addressing modes are cheap and that duplicating the computation involved
// many times is worthwhile, even on a fastpath. For sinking candidates
// (i.e. cold call sites), this serves as a way to prevent excessive code
// growth since most architectures have some reasonable small and fast way to
// compute an effective address. (i.e LEA on x86)
SmallVector<Instruction*, 32> MatchedAddrModeInsts;
for (const std::pair<Value *, Type *> &Pair : MemoryUses) {
Value *Address = Pair.first;
Type *AddressAccessTy = Pair.second;
unsigned AS = Address->getType()->getPointerAddressSpace();
// Do a match against the root of this address, ignoring profitability. This
// will tell us if the addressing mode for the memory operation will
// *actually* cover the shared instruction.
ExtAddrMode Result;
std::pair<AssertingVH<GetElementPtrInst>, int64_t> LargeOffsetGEP(nullptr,
0);
TypePromotionTransaction::ConstRestorationPt LastKnownGood =
TPT.getRestorationPoint();
AddressingModeMatcher Matcher(MatchedAddrModeInsts, TLI, TRI, LI, getDTFn,
AddressAccessTy, AS, MemoryInst, Result,
InsertedInsts, PromotedInsts, TPT,
LargeOffsetGEP, OptSize, PSI, BFI);
Matcher.IgnoreProfitability = true;
bool Success = Matcher.matchAddr(Address, 0);
(void)Success; assert(Success && "Couldn't select *anything*?");
// The match was to check the profitability, the changes made are not
// part of the original matcher. Therefore, they should be dropped
// otherwise the original matcher will not present the right state.
TPT.rollback(LastKnownGood);
// If the match didn't cover I, then it won't be shared by it.
if (!is_contained(MatchedAddrModeInsts, I))
return false;
MatchedAddrModeInsts.clear();
}
return true;
}
/// Return true if the specified values are defined in a
/// different basic block than BB.
static bool IsNonLocalValue(Value *V, BasicBlock *BB) {
if (Instruction *I = dyn_cast<Instruction>(V))
return I->getParent() != BB;
return false;
}
/// Sink addressing mode computation immediate before MemoryInst if doing so
/// can be done without increasing register pressure. The need for the
/// register pressure constraint means this can end up being an all or nothing
/// decision for all uses of the same addressing computation.
///
/// Load and Store Instructions often have addressing modes that can do
/// significant amounts of computation. As such, instruction selection will try
/// to get the load or store to do as much computation as possible for the
/// program. The problem is that isel can only see within a single block. As
/// such, we sink as much legal addressing mode work into the block as possible.
///
/// This method is used to optimize both load/store and inline asms with memory
/// operands. It's also used to sink addressing computations feeding into cold
/// call sites into their (cold) basic block.
///
/// The motivation for handling sinking into cold blocks is that doing so can
/// both enable other address mode sinking (by satisfying the register pressure
/// constraint above), and reduce register pressure globally (by removing the
/// addressing mode computation from the fast path entirely.).
bool CodeGenPrepare::optimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
Type *AccessTy, unsigned AddrSpace) {
Value *Repl = Addr;
// Try to collapse single-value PHI nodes. This is necessary to undo
// unprofitable PRE transformations.
SmallVector<Value*, 8> worklist;
SmallPtrSet<Value*, 16> Visited;
worklist.push_back(Addr);
// Use a worklist to iteratively look through PHI and select nodes, and
// ensure that the addressing mode obtained from the non-PHI/select roots of
// the graph are compatible.
bool PhiOrSelectSeen = false;
SmallVector<Instruction*, 16> AddrModeInsts;
const SimplifyQuery SQ(*DL, TLInfo);
AddressingModeCombiner AddrModes(SQ, Addr);
TypePromotionTransaction TPT(RemovedInsts);
TypePromotionTransaction::ConstRestorationPt LastKnownGood =
TPT.getRestorationPoint();
while (!worklist.empty()) {
Value *V = worklist.pop_back_val();
// We allow traversing cyclic Phi nodes.
// In case of success after this loop we ensure that traversing through
// Phi nodes ends up with all cases to compute address of the form
// BaseGV + Base + Scale * Index + Offset
// where Scale and Offset are constans and BaseGV, Base and Index
// are exactly the same Values in all cases.
// It means that BaseGV, Scale and Offset dominate our memory instruction
// and have the same value as they had in address computation represented
// as Phi. So we can safely sink address computation to memory instruction.
if (!Visited.insert(V).second)
continue;
// For a PHI node, push all of its incoming values.
if (PHINode *P = dyn_cast<PHINode>(V)) {
append_range(worklist, P->incoming_values());
PhiOrSelectSeen = true;
continue;
}
// Similar for select.
if (SelectInst *SI = dyn_cast<SelectInst>(V)) {
worklist.push_back(SI->getFalseValue());
worklist.push_back(SI->getTrueValue());
PhiOrSelectSeen = true;
continue;
}
// For non-PHIs, determine the addressing mode being computed. Note that
// the result may differ depending on what other uses our candidate
// addressing instructions might have.
AddrModeInsts.clear();
std::pair<AssertingVH<GetElementPtrInst>, int64_t> LargeOffsetGEP(nullptr,
0);
// Defer the query (and possible computation of) the dom tree to point of
// actual use. It's expected that most address matches don't actually need
// the domtree.
auto getDTFn = [MemoryInst, this]() -> const DominatorTree & {
Function *F = MemoryInst->getParent()->getParent();
return this->getDT(*F);
};
ExtAddrMode NewAddrMode = AddressingModeMatcher::Match(
V, AccessTy, AddrSpace, MemoryInst, AddrModeInsts, *TLI, *LI, getDTFn,
*TRI, InsertedInsts, PromotedInsts, TPT, LargeOffsetGEP, OptSize, PSI,
BFI.get());
GetElementPtrInst *GEP = LargeOffsetGEP.first;
if (GEP && !NewGEPBases.count(GEP)) {
// If splitting the underlying data structure can reduce the offset of a
// GEP, collect the GEP. Skip the GEPs that are the new bases of
// previously split data structures.
LargeOffsetGEPMap[GEP->getPointerOperand()].push_back(LargeOffsetGEP);
if (LargeOffsetGEPID.find(GEP) == LargeOffsetGEPID.end())
LargeOffsetGEPID[GEP] = LargeOffsetGEPID.size();
}
NewAddrMode.OriginalValue = V;
if (!AddrModes.addNewAddrMode(NewAddrMode))
break;
}
// Try to combine the AddrModes we've collected. If we couldn't collect any,
// or we have multiple but either couldn't combine them or combining them
// wouldn't do anything useful, bail out now.
if (!AddrModes.combineAddrModes()) {
TPT.rollback(LastKnownGood);
return false;
}
bool Modified = TPT.commit();
// Get the combined AddrMode (or the only AddrMode, if we only had one).
ExtAddrMode AddrMode = AddrModes.getAddrMode();
// If all the instructions matched are already in this BB, don't do anything.
// If we saw a Phi node then it is not local definitely, and if we saw a select
// then we want to push the address calculation past it even if it's already
// in this BB.
if (!PhiOrSelectSeen && none_of(AddrModeInsts, [&](Value *V) {
return IsNonLocalValue(V, MemoryInst->getParent());
})) {
LLVM_DEBUG(dbgs() << "CGP: Found local addrmode: " << AddrMode
<< "\n");
return Modified;
}
// Insert this computation right after this user. Since our caller is
// scanning from the top of the BB to the bottom, reuse of the expr are
// guaranteed to happen later.
IRBuilder<> Builder(MemoryInst);
// Now that we determined the addressing expression we want to use and know
// that we have to sink it into this block. Check to see if we have already
// done this for some other load/store instr in this block. If so, reuse
// the computation. Before attempting reuse, check if the address is valid
// as it may have been erased.
WeakTrackingVH SunkAddrVH = SunkAddrs[Addr];
Value * SunkAddr = SunkAddrVH.pointsToAliveValue() ? SunkAddrVH : nullptr;
if (SunkAddr) {
LLVM_DEBUG(dbgs() << "CGP: Reusing nonlocal addrmode: " << AddrMode
<< " for " << *MemoryInst << "\n");
if (SunkAddr->getType() != Addr->getType())
SunkAddr = Builder.CreatePointerCast(SunkAddr, Addr->getType());
} else if (AddrSinkUsingGEPs || (!AddrSinkUsingGEPs.getNumOccurrences() &&
SubtargetInfo->addrSinkUsingGEPs())) {
// By default, we use the GEP-based method when AA is used later. This
// prevents new inttoptr/ptrtoint pairs from degrading AA capabilities.
LLVM_DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode
<< " for " << *MemoryInst << "\n");
Type *IntPtrTy = DL->getIntPtrType(Addr->getType());
Value *ResultPtr = nullptr, *ResultIndex = nullptr;
// First, find the pointer.
if (AddrMode.BaseReg && AddrMode.BaseReg->getType()->isPointerTy()) {
ResultPtr = AddrMode.BaseReg;
AddrMode.BaseReg = nullptr;
}
if (AddrMode.Scale && AddrMode.ScaledReg->getType()->isPointerTy()) {
// We can't add more than one pointer together, nor can we scale a
// pointer (both of which seem meaningless).
if (ResultPtr || AddrMode.Scale != 1)
return Modified;
ResultPtr = AddrMode.ScaledReg;
AddrMode.Scale = 0;
}
// It is only safe to sign extend the BaseReg if we know that the math
// required to create it did not overflow before we extend it. Since
// the original IR value was tossed in favor of a constant back when
// the AddrMode was created we need to bail out gracefully if widths
// do not match instead of extending it.
//
// (See below for code to add the scale.)
if (AddrMode.Scale) {
Type *ScaledRegTy = AddrMode.ScaledReg->getType();
if (cast<IntegerType>(IntPtrTy)->getBitWidth() >
cast<IntegerType>(ScaledRegTy)->getBitWidth())
return Modified;
}
if (AddrMode.BaseGV) {
if (ResultPtr)
return Modified;
ResultPtr = AddrMode.BaseGV;
}
// If the real base value actually came from an inttoptr, then the matcher
// will look through it and provide only the integer value. In that case,
// use it here.
if (!DL->isNonIntegralPointerType(Addr->getType())) {
if (!ResultPtr && AddrMode.BaseReg) {
ResultPtr = Builder.CreateIntToPtr(AddrMode.BaseReg, Addr->getType(),
"sunkaddr");
AddrMode.BaseReg = nullptr;
} else if (!ResultPtr && AddrMode.Scale == 1) {
ResultPtr = Builder.CreateIntToPtr(AddrMode.ScaledReg, Addr->getType(),
"sunkaddr");
AddrMode.Scale = 0;
}
}
if (!ResultPtr &&
!AddrMode.BaseReg && !AddrMode.Scale && !AddrMode.BaseOffs) {
SunkAddr = Constant::getNullValue(Addr->getType());
} else if (!ResultPtr) {
return Modified;
} else {
Type *I8PtrTy =
Builder.getInt8PtrTy(Addr->getType()->getPointerAddressSpace());
Type *I8Ty = Builder.getInt8Ty();
// Start with the base register. Do this first so that subsequent address
// matching finds it last, which will prevent it from trying to match it
// as the scaled value in case it happens to be a mul. That would be
// problematic if we've sunk a different mul for the scale, because then
// we'd end up sinking both muls.
if (AddrMode.BaseReg) {
Value *V = AddrMode.BaseReg;
if (V->getType() != IntPtrTy)
V = Builder.CreateIntCast(V, IntPtrTy, /*isSigned=*/true, "sunkaddr");
ResultIndex = V;
}
// Add the scale value.
if (AddrMode.Scale) {
Value *V = AddrMode.ScaledReg;
if (V->getType() == IntPtrTy) {
// done.
} else {
assert(cast<IntegerType>(IntPtrTy)->getBitWidth() <
cast<IntegerType>(V->getType())->getBitWidth() &&
"We can't transform if ScaledReg is too narrow");
V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr");
}
if (AddrMode.Scale != 1)
V = Builder.CreateMul(V, ConstantInt::get(IntPtrTy, AddrMode.Scale),
"sunkaddr");
if (ResultIndex)
ResultIndex = Builder.CreateAdd(ResultIndex, V, "sunkaddr");
else
ResultIndex = V;
}
// Add in the Base Offset if present.
if (AddrMode.BaseOffs) {
Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
if (ResultIndex) {
// We need to add this separately from the scale above to help with
// SDAG consecutive load/store merging.
if (ResultPtr->getType() != I8PtrTy)
ResultPtr = Builder.CreatePointerCast(ResultPtr, I8PtrTy);
ResultPtr = Builder.CreateGEP(I8Ty, ResultPtr, ResultIndex,
"sunkaddr", AddrMode.InBounds);
}
ResultIndex = V;
}
if (!ResultIndex) {
SunkAddr = ResultPtr;
} else {
if (ResultPtr->getType() != I8PtrTy)
ResultPtr = Builder.CreatePointerCast(ResultPtr, I8PtrTy);
SunkAddr = Builder.CreateGEP(I8Ty, ResultPtr, ResultIndex, "sunkaddr",
AddrMode.InBounds);
}
if (SunkAddr->getType() != Addr->getType())
SunkAddr = Builder.CreatePointerCast(SunkAddr, Addr->getType());
}
} else {
// We'd require a ptrtoint/inttoptr down the line, which we can't do for
// non-integral pointers, so in that case bail out now.
Type *BaseTy = AddrMode.BaseReg ? AddrMode.BaseReg->getType() : nullptr;
Type *ScaleTy = AddrMode.Scale ? AddrMode.ScaledReg->getType() : nullptr;
PointerType *BasePtrTy = dyn_cast_or_null<PointerType>(BaseTy);
PointerType *ScalePtrTy = dyn_cast_or_null<PointerType>(ScaleTy);
if (DL->isNonIntegralPointerType(Addr->getType()) ||
(BasePtrTy && DL->isNonIntegralPointerType(BasePtrTy)) ||
(ScalePtrTy && DL->isNonIntegralPointerType(ScalePtrTy)) ||
(AddrMode.BaseGV &&
DL->isNonIntegralPointerType(AddrMode.BaseGV->getType())))
return Modified;
LLVM_DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode
<< " for " << *MemoryInst << "\n");
Type *IntPtrTy = DL->getIntPtrType(Addr->getType());
Value *Result = nullptr;
// Start with the base register. Do this first so that subsequent address
// matching finds it last, which will prevent it from trying to match it
// as the scaled value in case it happens to be a mul. That would be
// problematic if we've sunk a different mul for the scale, because then
// we'd end up sinking both muls.
if (AddrMode.BaseReg) {
Value *V = AddrMode.BaseReg;
if (V->getType()->isPointerTy())
V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr");
if (V->getType() != IntPtrTy)
V = Builder.CreateIntCast(V, IntPtrTy, /*isSigned=*/true, "sunkaddr");
Result = V;
}
// Add the scale value.
if (AddrMode.Scale) {
Value *V = AddrMode.ScaledReg;
if (V->getType() == IntPtrTy) {
// done.
} else if (V->getType()->isPointerTy()) {
V = Builder.CreatePtrToInt(V, IntPtrTy, "sunkaddr");
} else if (cast<IntegerType>(IntPtrTy)->getBitWidth() <
cast<IntegerType>(V->getType())->getBitWidth()) {
V = Builder.CreateTrunc(V, IntPtrTy, "sunkaddr");
} else {
// It is only safe to sign extend the BaseReg if we know that the math
// required to create it did not overflow before we extend it. Since
// the original IR value was tossed in favor of a constant back when
// the AddrMode was created we need to bail out gracefully if widths
// do not match instead of extending it.
Instruction *I = dyn_cast_or_null<Instruction>(Result);
if (I && (Result != AddrMode.BaseReg))
I->eraseFromParent();
return Modified;
}
if (AddrMode.Scale != 1)
V = Builder.CreateMul(V, ConstantInt::get(IntPtrTy, AddrMode.Scale),
"sunkaddr");
if (Result)
Result = Builder.CreateAdd(Result, V, "sunkaddr");
else
Result = V;
}
// Add in the BaseGV if present.
if (AddrMode.BaseGV) {
Value *V = Builder.CreatePtrToInt(AddrMode.BaseGV, IntPtrTy, "sunkaddr");
if (Result)
Result = Builder.CreateAdd(Result, V, "sunkaddr");
else
Result = V;
}
// Add in the Base Offset if present.
if (AddrMode.BaseOffs) {
Value *V = ConstantInt::get(IntPtrTy, AddrMode.BaseOffs);
if (Result)
Result = Builder.CreateAdd(Result, V, "sunkaddr");
else
Result = V;
}
if (!Result)
SunkAddr = Constant::getNullValue(Addr->getType());
else
SunkAddr = Builder.CreateIntToPtr(Result, Addr->getType(), "sunkaddr");
}
MemoryInst->replaceUsesOfWith(Repl, SunkAddr);
// Store the newly computed address into the cache. In the case we reused a
// value, this should be idempotent.
SunkAddrs[Addr] = WeakTrackingVH(SunkAddr);
// If we have no uses, recursively delete the value and all dead instructions
// using it.
if (Repl->use_empty()) {
resetIteratorIfInvalidatedWhileCalling(CurInstIterator->getParent(), [&]() {
RecursivelyDeleteTriviallyDeadInstructions(
Repl, TLInfo, nullptr,
[&](Value *V) { removeAllAssertingVHReferences(V); });
});
}
++NumMemoryInsts;
return true;
}
/// Rewrite GEP input to gather/scatter to enable SelectionDAGBuilder to find
/// a uniform base to use for ISD::MGATHER/MSCATTER. SelectionDAGBuilder can
/// only handle a 2 operand GEP in the same basic block or a splat constant
/// vector. The 2 operands to the GEP must have a scalar pointer and a vector
/// index.
///
/// If the existing GEP has a vector base pointer that is splat, we can look
/// through the splat to find the scalar pointer. If we can't find a scalar
/// pointer there's nothing we can do.
///
/// If we have a GEP with more than 2 indices where the middle indices are all
/// zeroes, we can replace it with 2 GEPs where the second has 2 operands.
///
/// If the final index isn't a vector or is a splat, we can emit a scalar GEP
/// followed by a GEP with an all zeroes vector index. This will enable
/// SelectionDAGBuilder to use the scalar GEP as the uniform base and have a
/// zero index.
bool CodeGenPrepare::optimizeGatherScatterInst(Instruction *MemoryInst,
Value *Ptr) {
Value *NewAddr;
if (const auto *GEP = dyn_cast<GetElementPtrInst>(Ptr)) {
// Don't optimize GEPs that don't have indices.
if (!GEP->hasIndices())
return false;
// If the GEP and the gather/scatter aren't in the same BB, don't optimize.
// FIXME: We should support this by sinking the GEP.
if (MemoryInst->getParent() != GEP->getParent())
return false;
SmallVector<Value *, 2> Ops(GEP->operands());
bool RewriteGEP = false;
if (Ops[0]->getType()->isVectorTy()) {
Ops[0] = getSplatValue(Ops[0]);
if (!Ops[0])
return false;
RewriteGEP = true;
}
unsigned FinalIndex = Ops.size() - 1;
// Ensure all but the last index is 0.
// FIXME: This isn't strictly required. All that's required is that they are
// all scalars or splats.
for (unsigned i = 1; i < FinalIndex; ++i) {
auto *C = dyn_cast<Constant>(Ops[i]);
if (!C)
return false;
if (isa<VectorType>(C->getType()))
C = C->getSplatValue();
auto *CI = dyn_cast_or_null<ConstantInt>(C);
if (!CI || !CI->isZero())
return false;
// Scalarize the index if needed.
Ops[i] = CI;
}
// Try to scalarize the final index.
if (Ops[FinalIndex]->getType()->isVectorTy()) {
if (Value *V = getSplatValue(Ops[FinalIndex])) {
auto *C = dyn_cast<ConstantInt>(V);
// Don't scalarize all zeros vector.
if (!C || !C->isZero()) {
Ops[FinalIndex] = V;
RewriteGEP = true;
}
}
}
// If we made any changes or the we have extra operands, we need to generate
// new instructions.
if (!RewriteGEP && Ops.size() == 2)
return false;
auto NumElts = cast<VectorType>(Ptr->getType())->getElementCount();
IRBuilder<> Builder(MemoryInst);
Type *SourceTy = GEP->getSourceElementType();
Type *ScalarIndexTy = DL->getIndexType(Ops[0]->getType()->getScalarType());
// If the final index isn't a vector, emit a scalar GEP containing all ops
// and a vector GEP with all zeroes final index.
if (!Ops[FinalIndex]->getType()->isVectorTy()) {
NewAddr = Builder.CreateGEP(SourceTy, Ops[0],
makeArrayRef(Ops).drop_front());
auto *IndexTy = VectorType::get(ScalarIndexTy, NumElts);
auto *SecondTy = GetElementPtrInst::getIndexedType(
SourceTy, makeArrayRef(Ops).drop_front());
NewAddr =
Builder.CreateGEP(SecondTy, NewAddr, Constant::getNullValue(IndexTy));
} else {
Value *Base = Ops[0];
Value *Index = Ops[FinalIndex];
// Create a scalar GEP if there are more than 2 operands.
if (Ops.size() != 2) {
// Replace the last index with 0.
Ops[FinalIndex] = Constant::getNullValue(ScalarIndexTy);
Base = Builder.CreateGEP(SourceTy, Base,
makeArrayRef(Ops).drop_front());
SourceTy = GetElementPtrInst::getIndexedType(
SourceTy, makeArrayRef(Ops).drop_front());
}
// Now create the GEP with scalar pointer and vector index.
NewAddr = Builder.CreateGEP(SourceTy, Base, Index);
}
} else if (!isa<Constant>(Ptr)) {
// Not a GEP, maybe its a splat and we can create a GEP to enable
// SelectionDAGBuilder to use it as a uniform base.
Value *V = getSplatValue(Ptr);
if (!V)
return false;
auto NumElts = cast<VectorType>(Ptr->getType())->getElementCount();
IRBuilder<> Builder(MemoryInst);
// Emit a vector GEP with a scalar pointer and all 0s vector index.
Type *ScalarIndexTy = DL->getIndexType(V->getType()->getScalarType());
auto *IndexTy = VectorType::get(ScalarIndexTy, NumElts);
Type *ScalarTy;
if (cast<IntrinsicInst>(MemoryInst)->getIntrinsicID() ==
Intrinsic::masked_gather) {
ScalarTy = MemoryInst->getType()->getScalarType();
} else {
assert(cast<IntrinsicInst>(MemoryInst)->getIntrinsicID() ==
Intrinsic::masked_scatter);
ScalarTy = MemoryInst->getOperand(0)->getType()->getScalarType();
}
NewAddr = Builder.CreateGEP(ScalarTy, V, Constant::getNullValue(IndexTy));
} else {
// Constant, SelectionDAGBuilder knows to check if its a splat.
return false;
}
MemoryInst->replaceUsesOfWith(Ptr, NewAddr);
// If we have no uses, recursively delete the value and all dead instructions
// using it.
if (Ptr->use_empty())
RecursivelyDeleteTriviallyDeadInstructions(
Ptr, TLInfo, nullptr,
[&](Value *V) { removeAllAssertingVHReferences(V); });
return true;
}
/// If there are any memory operands, use OptimizeMemoryInst to sink their
/// address computing into the block when possible / profitable.
bool CodeGenPrepare::optimizeInlineAsmInst(CallInst *CS) {
bool MadeChange = false;
const TargetRegisterInfo *TRI =
TM->getSubtargetImpl(*CS->getFunction())->getRegisterInfo();
TargetLowering::AsmOperandInfoVector TargetConstraints =
TLI->ParseConstraints(*DL, TRI, *CS);
unsigned ArgNo = 0;
for (TargetLowering::AsmOperandInfo &OpInfo : TargetConstraints) {
// Compute the constraint code and ConstraintType to use.
TLI->ComputeConstraintToUse(OpInfo, SDValue());
// TODO: Also handle C_Address?
if (OpInfo.ConstraintType == TargetLowering::C_Memory &&
OpInfo.isIndirect) {
Value *OpVal = CS->getArgOperand(ArgNo++);
MadeChange |= optimizeMemoryInst(CS, OpVal, OpVal->getType(), ~0u);
} else if (OpInfo.Type == InlineAsm::isInput)
ArgNo++;
}
return MadeChange;
}
/// Check if all the uses of \p Val are equivalent (or free) zero or
/// sign extensions.
static bool hasSameExtUse(Value *Val, const TargetLowering &TLI) {
assert(!Val->use_empty() && "Input must have at least one use");
const Instruction *FirstUser = cast<Instruction>(*Val->user_begin());
bool IsSExt = isa<SExtInst>(FirstUser);
Type *ExtTy = FirstUser->getType();
for (const User *U : Val->users()) {
const Instruction *UI = cast<Instruction>(U);
if ((IsSExt && !isa<SExtInst>(UI)) || (!IsSExt && !isa<ZExtInst>(UI)))
return false;
Type *CurTy = UI->getType();
// Same input and output types: Same instruction after CSE.
if (CurTy == ExtTy)
continue;
// If IsSExt is true, we are in this situation:
// a = Val
// b = sext ty1 a to ty2
// c = sext ty1 a to ty3
// Assuming ty2 is shorter than ty3, this could be turned into:
// a = Val
// b = sext ty1 a to ty2
// c = sext ty2 b to ty3
// However, the last sext is not free.
if (IsSExt)
return false;
// This is a ZExt, maybe this is free to extend from one type to another.
// In that case, we would not account for a different use.
Type *NarrowTy;
Type *LargeTy;
if (ExtTy->getScalarType()->getIntegerBitWidth() >
CurTy->getScalarType()->getIntegerBitWidth()) {
NarrowTy = CurTy;
LargeTy = ExtTy;
} else {
NarrowTy = ExtTy;
LargeTy = CurTy;
}
if (!TLI.isZExtFree(NarrowTy, LargeTy))
return false;
}
// All uses are the same or can be derived from one another for free.
return true;
}
/// Try to speculatively promote extensions in \p Exts and continue
/// promoting through newly promoted operands recursively as far as doing so is
/// profitable. Save extensions profitably moved up, in \p ProfitablyMovedExts.
/// When some promotion happened, \p TPT contains the proper state to revert
/// them.
///
/// \return true if some promotion happened, false otherwise.
bool CodeGenPrepare::tryToPromoteExts(
TypePromotionTransaction &TPT, const SmallVectorImpl<Instruction *> &Exts,
SmallVectorImpl<Instruction *> &ProfitablyMovedExts,
unsigned CreatedInstsCost) {
bool Promoted = false;
// Iterate over all the extensions to try to promote them.
for (auto *I : Exts) {
// Early check if we directly have ext(load).
if (isa<LoadInst>(I->getOperand(0))) {
ProfitablyMovedExts.push_back(I);
continue;
}
// Check whether or not we want to do any promotion. The reason we have
// this check inside the for loop is to catch the case where an extension
// is directly fed by a load because in such case the extension can be moved
// up without any promotion on its operands.
if (!TLI->enableExtLdPromotion() || DisableExtLdPromotion)
return false;
// Get the action to perform the promotion.
TypePromotionHelper::Action TPH =
TypePromotionHelper::getAction(I, InsertedInsts, *TLI, PromotedInsts);
// Check if we can promote.
if (!TPH) {
// Save the current extension as we cannot move up through its operand.
ProfitablyMovedExts.push_back(I);
continue;
}
// Save the current state.
TypePromotionTransaction::ConstRestorationPt LastKnownGood =
TPT.getRestorationPoint();
SmallVector<Instruction *, 4> NewExts;
unsigned NewCreatedInstsCost = 0;
unsigned ExtCost = !TLI->isExtFree(I);
// Promote.
Value *PromotedVal = TPH(I, TPT, PromotedInsts, NewCreatedInstsCost,
&NewExts, nullptr, *TLI);
assert(PromotedVal &&
"TypePromotionHelper should have filtered out those cases");
// We would be able to merge only one extension in a load.
// Therefore, if we have more than 1 new extension we heuristically
// cut this search path, because it means we degrade the code quality.
// With exactly 2, the transformation is neutral, because we will merge
// one extension but leave one. However, we optimistically keep going,
// because the new extension may be removed too.
long long TotalCreatedInstsCost = CreatedInstsCost + NewCreatedInstsCost;
// FIXME: It would be possible to propagate a negative value instead of
// conservatively ceiling it to 0.
TotalCreatedInstsCost =
std::max((long long)0, (TotalCreatedInstsCost - ExtCost));
if (!StressExtLdPromotion &&
(TotalCreatedInstsCost > 1 ||
!isPromotedInstructionLegal(*TLI, *DL, PromotedVal))) {
// This promotion is not profitable, rollback to the previous state, and
// save the current extension in ProfitablyMovedExts as the latest
// speculative promotion turned out to be unprofitable.
TPT.rollback(LastKnownGood);
ProfitablyMovedExts.push_back(I);
continue;
}
// Continue promoting NewExts as far as doing so is profitable.
SmallVector<Instruction *, 2> NewlyMovedExts;
(void)tryToPromoteExts(TPT, NewExts, NewlyMovedExts, TotalCreatedInstsCost);
bool NewPromoted = false;
for (auto *ExtInst : NewlyMovedExts) {
Instruction *MovedExt = cast<Instruction>(ExtInst);
Value *ExtOperand = MovedExt->getOperand(0);
// If we have reached to a load, we need this extra profitability check
// as it could potentially be merged into an ext(load).
if (isa<LoadInst>(ExtOperand) &&
!(StressExtLdPromotion || NewCreatedInstsCost <= ExtCost ||
(ExtOperand->hasOneUse() || hasSameExtUse(ExtOperand, *TLI))))
continue;
ProfitablyMovedExts.push_back(MovedExt);
NewPromoted = true;
}
// If none of speculative promotions for NewExts is profitable, rollback
// and save the current extension (I) as the last profitable extension.
if (!NewPromoted) {
TPT.rollback(LastKnownGood);
ProfitablyMovedExts.push_back(I);
continue;
}
// The promotion is profitable.
Promoted = true;
}
return Promoted;
}
/// Merging redundant sexts when one is dominating the other.
bool CodeGenPrepare::mergeSExts(Function &F) {
bool Changed = false;
for (auto &Entry : ValToSExtendedUses) {
SExts &Insts = Entry.second;
SExts CurPts;
for (Instruction *Inst : Insts) {
if (RemovedInsts.count(Inst) || !isa<SExtInst>(Inst) ||
Inst->getOperand(0) != Entry.first)
continue;
bool inserted = false;
for (auto &Pt : CurPts) {
if (getDT(F).dominates(Inst, Pt)) {
Pt->replaceAllUsesWith(Inst);
RemovedInsts.insert(Pt);
Pt->removeFromParent();
Pt = Inst;
inserted = true;
Changed = true;
break;
}
if (!getDT(F).dominates(Pt, Inst))
// Give up if we need to merge in a common dominator as the
// experiments show it is not profitable.
continue;
Inst->replaceAllUsesWith(Pt);
RemovedInsts.insert(Inst);
Inst->removeFromParent();
inserted = true;
Changed = true;
break;
}
if (!inserted)
CurPts.push_back(Inst);
}
}
return Changed;
}
// Splitting large data structures so that the GEPs accessing them can have
// smaller offsets so that they can be sunk to the same blocks as their users.
// For example, a large struct starting from %base is split into two parts
// where the second part starts from %new_base.
//
// Before:
// BB0:
// %base =
//
// BB1:
// %gep0 = gep %base, off0
// %gep1 = gep %base, off1
// %gep2 = gep %base, off2
//
// BB2:
// %load1 = load %gep0
// %load2 = load %gep1
// %load3 = load %gep2
//
// After:
// BB0:
// %base =
// %new_base = gep %base, off0
//
// BB1:
// %new_gep0 = %new_base
// %new_gep1 = gep %new_base, off1 - off0
// %new_gep2 = gep %new_base, off2 - off0
//
// BB2:
// %load1 = load i32, i32* %new_gep0
// %load2 = load i32, i32* %new_gep1
// %load3 = load i32, i32* %new_gep2
//
// %new_gep1 and %new_gep2 can be sunk to BB2 now after the splitting because
// their offsets are smaller enough to fit into the addressing mode.
bool CodeGenPrepare::splitLargeGEPOffsets() {
bool Changed = false;
for (auto &Entry : LargeOffsetGEPMap) {
Value *OldBase = Entry.first;
SmallVectorImpl<std::pair<AssertingVH<GetElementPtrInst>, int64_t>>
&LargeOffsetGEPs = Entry.second;
auto compareGEPOffset =
[&](const std::pair<GetElementPtrInst *, int64_t> &LHS,
const std::pair<GetElementPtrInst *, int64_t> &RHS) {
if (LHS.first == RHS.first)
return false;
if (LHS.second != RHS.second)
return LHS.second < RHS.second;
return LargeOffsetGEPID[LHS.first] < LargeOffsetGEPID[RHS.first];
};
// Sorting all the GEPs of the same data structures based on the offsets.
llvm::sort(LargeOffsetGEPs, compareGEPOffset);
LargeOffsetGEPs.erase(
std::unique(LargeOffsetGEPs.begin(), LargeOffsetGEPs.end()),
LargeOffsetGEPs.end());
// Skip if all the GEPs have the same offsets.
if (LargeOffsetGEPs.front().second == LargeOffsetGEPs.back().second)
continue;
GetElementPtrInst *BaseGEP = LargeOffsetGEPs.begin()->first;
int64_t BaseOffset = LargeOffsetGEPs.begin()->second;
Value *NewBaseGEP = nullptr;
auto *LargeOffsetGEP = LargeOffsetGEPs.begin();
while (LargeOffsetGEP != LargeOffsetGEPs.end()) {
GetElementPtrInst *GEP = LargeOffsetGEP->first;
int64_t Offset = LargeOffsetGEP->second;
if (Offset != BaseOffset) {
TargetLowering::AddrMode AddrMode;
AddrMode.BaseOffs = Offset - BaseOffset;
// The result type of the GEP might not be the type of the memory
// access.
if (!TLI->isLegalAddressingMode(*DL, AddrMode,
GEP->getResultElementType(),
GEP->getAddressSpace())) {
// We need to create a new base if the offset to the current base is
// too large to fit into the addressing mode. So, a very large struct
// may be split into several parts.
BaseGEP = GEP;
BaseOffset = Offset;
NewBaseGEP = nullptr;
}
}
// Generate a new GEP to replace the current one.
LLVMContext &Ctx = GEP->getContext();
Type *IntPtrTy = DL->getIntPtrType(GEP->getType());
Type *I8PtrTy =
Type::getInt8PtrTy(Ctx, GEP->getType()->getPointerAddressSpace());
Type *I8Ty = Type::getInt8Ty(Ctx);
if (!NewBaseGEP) {
// Create a new base if we don't have one yet. Find the insertion
// pointer for the new base first.
BasicBlock::iterator NewBaseInsertPt;
BasicBlock *NewBaseInsertBB;
if (auto *BaseI = dyn_cast<Instruction>(OldBase)) {
// If the base of the struct is an instruction, the new base will be
// inserted close to it.
NewBaseInsertBB = BaseI->getParent();
if (isa<PHINode>(BaseI))
NewBaseInsertPt = NewBaseInsertBB->getFirstInsertionPt();
else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(BaseI)) {
NewBaseInsertBB =
SplitEdge(NewBaseInsertBB, Invoke->getNormalDest());
NewBaseInsertPt = NewBaseInsertBB->getFirstInsertionPt();
} else
NewBaseInsertPt = std::next(BaseI->getIterator());
} else {
// If the current base is an argument or global value, the new base
// will be inserted to the entry block.
NewBaseInsertBB = &BaseGEP->getFunction()->getEntryBlock();
NewBaseInsertPt = NewBaseInsertBB->getFirstInsertionPt();
}
IRBuilder<> NewBaseBuilder(NewBaseInsertBB, NewBaseInsertPt);
// Create a new base.
Value *BaseIndex = ConstantInt::get(IntPtrTy, BaseOffset);
NewBaseGEP = OldBase;
if (NewBaseGEP->getType() != I8PtrTy)
NewBaseGEP = NewBaseBuilder.CreatePointerCast(NewBaseGEP, I8PtrTy);
NewBaseGEP =
NewBaseBuilder.CreateGEP(I8Ty, NewBaseGEP, BaseIndex, "splitgep");
NewGEPBases.insert(NewBaseGEP);
}
IRBuilder<> Builder(GEP);
Value *NewGEP = NewBaseGEP;
if (Offset == BaseOffset) {
if (GEP->getType() != I8PtrTy)
NewGEP = Builder.CreatePointerCast(NewGEP, GEP->getType());
} else {
// Calculate the new offset for the new GEP.
Value *Index = ConstantInt::get(IntPtrTy, Offset - BaseOffset);
NewGEP = Builder.CreateGEP(I8Ty, NewBaseGEP, Index);
if (GEP->getType() != I8PtrTy)
NewGEP = Builder.CreatePointerCast(NewGEP, GEP->getType());
}
GEP->replaceAllUsesWith(NewGEP);
LargeOffsetGEPID.erase(GEP);
LargeOffsetGEP = LargeOffsetGEPs.erase(LargeOffsetGEP);
GEP->eraseFromParent();
Changed = true;
}
}
return Changed;
}
bool CodeGenPrepare::optimizePhiType(
PHINode *I, SmallPtrSetImpl<PHINode *> &Visited,
SmallPtrSetImpl<Instruction *> &DeletedInstrs) {
// We are looking for a collection on interconnected phi nodes that together
// only use loads/bitcasts and are used by stores/bitcasts, and the bitcasts
// are of the same type. Convert the whole set of nodes to the type of the
// bitcast.
Type *PhiTy = I->getType();
Type *ConvertTy = nullptr;
if (Visited.count(I) ||
(!I->getType()->isIntegerTy() && !I->getType()->isFloatingPointTy()))
return false;
SmallVector<Instruction *, 4> Worklist;
Worklist.push_back(cast<Instruction>(I));
SmallPtrSet<PHINode *, 4> PhiNodes;
PhiNodes.insert(I);
Visited.insert(I);
SmallPtrSet<Instruction *, 4> Defs;
SmallPtrSet<Instruction *, 4> Uses;
// This works by adding extra bitcasts between load/stores and removing
// existing bicasts. If we have a phi(bitcast(load)) or a store(bitcast(phi))
// we can get in the situation where we remove a bitcast in one iteration
// just to add it again in the next. We need to ensure that at least one
// bitcast we remove are anchored to something that will not change back.
bool AnyAnchored = false;
while (!Worklist.empty()) {
Instruction *II = Worklist.pop_back_val();
if (auto *Phi = dyn_cast<PHINode>(II)) {
// Handle Defs, which might also be PHI's
for (Value *V : Phi->incoming_values()) {
if (auto *OpPhi = dyn_cast<PHINode>(V)) {
if (!PhiNodes.count(OpPhi)) {
if (Visited.count(OpPhi))
return false;
PhiNodes.insert(OpPhi);
Visited.insert(OpPhi);
Worklist.push_back(OpPhi);
}
} else if (auto *OpLoad = dyn_cast<LoadInst>(V)) {
if (!OpLoad->isSimple())
return false;
if (!Defs.count(OpLoad)) {
Defs.insert(OpLoad);
Worklist.push_back(OpLoad);
}
} else if (auto *OpEx = dyn_cast<ExtractElementInst>(V)) {
if (!Defs.count(OpEx)) {
Defs.insert(OpEx);
Worklist.push_back(OpEx);
}
} else if (auto *OpBC = dyn_cast<BitCastInst>(V)) {
if (!ConvertTy)
ConvertTy = OpBC->getOperand(0)->getType();
if (OpBC->getOperand(0)->getType() != ConvertTy)
return false;
if (!Defs.count(OpBC)) {
Defs.insert(OpBC);
Worklist.push_back(OpBC);
AnyAnchored |= !isa<LoadInst>(OpBC->getOperand(0)) &&
!isa<ExtractElementInst>(OpBC->getOperand(0));
}
} else if (!isa<UndefValue>(V)) {
return false;
}
}
}
// Handle uses which might also be phi's
for (User *V : II->users()) {
if (auto *OpPhi = dyn_cast<PHINode>(V)) {
if (!PhiNodes.count(OpPhi)) {
if (Visited.count(OpPhi))
return false;
PhiNodes.insert(OpPhi);
Visited.insert(OpPhi);
Worklist.push_back(OpPhi);
}
} else if (auto *OpStore = dyn_cast<StoreInst>(V)) {
if (!OpStore->isSimple() || OpStore->getOperand(0) != II)
return false;
Uses.insert(OpStore);
} else if (auto *OpBC = dyn_cast<BitCastInst>(V)) {
if (!ConvertTy)
ConvertTy = OpBC->getType();
if (OpBC->getType() != ConvertTy)
return false;
Uses.insert(OpBC);
AnyAnchored |=
any_of(OpBC->users(), [](User *U) { return !isa<StoreInst>(U); });
} else {
return false;
}
}
}
if (!ConvertTy || !AnyAnchored || !TLI->shouldConvertPhiType(PhiTy, ConvertTy))
return false;
LLVM_DEBUG(dbgs() << "Converting " << *I << "\n and connected nodes to "
<< *ConvertTy << "\n");
// Create all the new phi nodes of the new type, and bitcast any loads to the
// correct type.
ValueToValueMap ValMap;
ValMap[UndefValue::get(PhiTy)] = UndefValue::get(ConvertTy);
for (Instruction *D : Defs) {
if (isa<BitCastInst>(D)) {
ValMap[D] = D->getOperand(0);
DeletedInstrs.insert(D);
} else {
ValMap[D] =
new BitCastInst(D, ConvertTy, D->getName() + ".bc", D->getNextNode());
}
}
for (PHINode *Phi : PhiNodes)
ValMap[Phi] = PHINode::Create(ConvertTy, Phi->getNumIncomingValues(),
Phi->getName() + ".tc", Phi);
// Pipe together all the PhiNodes.
for (PHINode *Phi : PhiNodes) {
PHINode *NewPhi = cast<PHINode>(ValMap[Phi]);
for (int i = 0, e = Phi->getNumIncomingValues(); i < e; i++)
NewPhi->addIncoming(ValMap[Phi->getIncomingValue(i)],
Phi->getIncomingBlock(i));
Visited.insert(NewPhi);
}
// And finally pipe up the stores and bitcasts
for (Instruction *U : Uses) {
if (isa<BitCastInst>(U)) {
DeletedInstrs.insert(U);
U->replaceAllUsesWith(ValMap[U->getOperand(0)]);
} else {
U->setOperand(0,
new BitCastInst(ValMap[U->getOperand(0)], PhiTy, "bc", U));
}
}
// Save the removed phis to be deleted later.
for (PHINode *Phi : PhiNodes)
DeletedInstrs.insert(Phi);
return true;
}
bool CodeGenPrepare::optimizePhiTypes(Function &F) {
if (!OptimizePhiTypes)
return false;
bool Changed = false;
SmallPtrSet<PHINode *, 4> Visited;
SmallPtrSet<Instruction *, 4> DeletedInstrs;
// Attempt to optimize all the phis in the functions to the correct type.
for (auto &BB : F)
for (auto &Phi : BB.phis())
Changed |= optimizePhiType(&Phi, Visited, DeletedInstrs);
// Remove any old phi's that have been converted.
for (auto *I : DeletedInstrs) {
I->replaceAllUsesWith(UndefValue::get(I->getType()));
I->eraseFromParent();
}
return Changed;
}
/// Return true, if an ext(load) can be formed from an extension in
/// \p MovedExts.
bool CodeGenPrepare::canFormExtLd(
const SmallVectorImpl<Instruction *> &MovedExts, LoadInst *&LI,
Instruction *&Inst, bool HasPromoted) {
for (auto *MovedExtInst : MovedExts) {
if (isa<LoadInst>(MovedExtInst->getOperand(0))) {
LI = cast<LoadInst>(MovedExtInst->getOperand(0));
Inst = MovedExtInst;
break;
}
}
if (!LI)
return false;
// If they're already in the same block, there's nothing to do.
// Make the cheap checks first if we did not promote.
// If we promoted, we need to check if it is indeed profitable.
if (!HasPromoted && LI->getParent() == Inst->getParent())
return false;
return TLI->isExtLoad(LI, Inst, *DL);
}
/// Move a zext or sext fed by a load into the same basic block as the load,
/// unless conditions are unfavorable. This allows SelectionDAG to fold the
/// extend into the load.
///
/// E.g.,
/// \code
/// %ld = load i32* %addr
/// %add = add nuw i32 %ld, 4
/// %zext = zext i32 %add to i64
// \endcode
/// =>
/// \code
/// %ld = load i32* %addr
/// %zext = zext i32 %ld to i64
/// %add = add nuw i64 %zext, 4
/// \encode
/// Note that the promotion in %add to i64 is done in tryToPromoteExts(), which
/// allow us to match zext(load i32*) to i64.
///
/// Also, try to promote the computations used to obtain a sign extended
/// value used into memory accesses.
/// E.g.,
/// \code
/// a = add nsw i32 b, 3
/// d = sext i32 a to i64
/// e = getelementptr ..., i64 d
/// \endcode
/// =>
/// \code
/// f = sext i32 b to i64
/// a = add nsw i64 f, 3
/// e = getelementptr ..., i64 a
/// \endcode
///
/// \p Inst[in/out] the extension may be modified during the process if some
/// promotions apply.
bool CodeGenPrepare::optimizeExt(Instruction *&Inst) {
bool AllowPromotionWithoutCommonHeader = false;
/// See if it is an interesting sext operations for the address type
/// promotion before trying to promote it, e.g., the ones with the right
/// type and used in memory accesses.
bool ATPConsiderable = TTI->shouldConsiderAddressTypePromotion(
*Inst, AllowPromotionWithoutCommonHeader);
TypePromotionTransaction TPT(RemovedInsts);
TypePromotionTransaction::ConstRestorationPt LastKnownGood =
TPT.getRestorationPoint();
SmallVector<Instruction *, 1> Exts;
SmallVector<Instruction *, 2> SpeculativelyMovedExts;
Exts.push_back(Inst);
bool HasPromoted = tryToPromoteExts(TPT, Exts, SpeculativelyMovedExts);
// Look for a load being extended.
LoadInst *LI = nullptr;
Instruction *ExtFedByLoad;
// Try to promote a chain of computation if it allows to form an extended
// load.
if (canFormExtLd(SpeculativelyMovedExts, LI, ExtFedByLoad, HasPromoted)) {
assert(LI && ExtFedByLoad && "Expect a valid load and extension");
TPT.commit();
// Move the extend into the same block as the load.
ExtFedByLoad->moveAfter(LI);
++NumExtsMoved;
Inst = ExtFedByLoad;
return true;
}
// Continue promoting SExts if known as considerable depending on targets.
if (ATPConsiderable &&
performAddressTypePromotion(Inst, AllowPromotionWithoutCommonHeader,
HasPromoted, TPT, SpeculativelyMovedExts))
return true;
TPT.rollback(LastKnownGood);
return false;
}
// Perform address type promotion if doing so is profitable.
// If AllowPromotionWithoutCommonHeader == false, we should find other sext
// instructions that sign extended the same initial value. However, if
// AllowPromotionWithoutCommonHeader == true, we expect promoting the
// extension is just profitable.
bool CodeGenPrepare::performAddressTypePromotion(
Instruction *&Inst, bool AllowPromotionWithoutCommonHeader,
bool HasPromoted, TypePromotionTransaction &TPT,
SmallVectorImpl<Instruction *> &SpeculativelyMovedExts) {
bool Promoted = false;
SmallPtrSet<Instruction *, 1> UnhandledExts;
bool AllSeenFirst = true;
for (auto *I : SpeculativelyMovedExts) {
Value *HeadOfChain = I->getOperand(0);
DenseMap<Value *, Instruction *>::iterator AlreadySeen =
SeenChainsForSExt.find(HeadOfChain);
// If there is an unhandled SExt which has the same header, try to promote
// it as well.
if (AlreadySeen != SeenChainsForSExt.end()) {
if (AlreadySeen->second != nullptr)
UnhandledExts.insert(AlreadySeen->second);
AllSeenFirst = false;
}
}
if (!AllSeenFirst || (AllowPromotionWithoutCommonHeader &&
SpeculativelyMovedExts.size() == 1)) {
TPT.commit();
if (HasPromoted)
Promoted = true;
for (auto *I : SpeculativelyMovedExts) {
Value *HeadOfChain = I->getOperand(0);
SeenChainsForSExt[HeadOfChain] = nullptr;
ValToSExtendedUses[HeadOfChain].push_back(I);
}
// Update Inst as promotion happen.
Inst = SpeculativelyMovedExts.pop_back_val();
} else {
// This is the first chain visited from the header, keep the current chain
// as unhandled. Defer to promote this until we encounter another SExt
// chain derived from the same header.
for (auto *I : SpeculativelyMovedExts) {
Value *HeadOfChain = I->getOperand(0);
SeenChainsForSExt[HeadOfChain] = Inst;
}
return false;
}
if (!AllSeenFirst && !UnhandledExts.empty())
for (auto *VisitedSExt : UnhandledExts) {
if (RemovedInsts.count(VisitedSExt))
continue;
TypePromotionTransaction TPT(RemovedInsts);
SmallVector<Instruction *, 1> Exts;
SmallVector<Instruction *, 2> Chains;
Exts.push_back(VisitedSExt);
bool HasPromoted = tryToPromoteExts(TPT, Exts, Chains);
TPT.commit();
if (HasPromoted)
Promoted = true;
for (auto *I : Chains) {
Value *HeadOfChain = I->getOperand(0);
// Mark this as handled.
SeenChainsForSExt[HeadOfChain] = nullptr;
ValToSExtendedUses[HeadOfChain].push_back(I);
}
}
return Promoted;
}
bool CodeGenPrepare::optimizeExtUses(Instruction *I) {
BasicBlock *DefBB = I->getParent();
// If the result of a {s|z}ext and its source are both live out, rewrite all
// other uses of the source with result of extension.
Value *Src = I->getOperand(0);
if (Src->hasOneUse())
return false;
// Only do this xform if truncating is free.
if (!TLI->isTruncateFree(I->getType(), Src->getType()))
return false;
// Only safe to perform the optimization if the source is also defined in
// this block.
if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent())
return false;
bool DefIsLiveOut = false;
for (User *U : I->users()) {
Instruction *UI = cast<Instruction>(U);
// Figure out which BB this ext is used in.
BasicBlock *UserBB = UI->getParent();
if (UserBB == DefBB) continue;
DefIsLiveOut = true;
break;
}
if (!DefIsLiveOut)
return false;
// Make sure none of the uses are PHI nodes.
for (User *U : Src->users()) {
Instruction *UI = cast<Instruction>(U);
BasicBlock *UserBB = UI->getParent();
if (UserBB == DefBB) continue;
// Be conservative. We don't want this xform to end up introducing
// reloads just before load / store instructions.
if (isa<PHINode>(UI) || isa<LoadInst>(UI) || isa<StoreInst>(UI))
return false;
}
// InsertedTruncs - Only insert one trunc in each block once.
DenseMap<BasicBlock*, Instruction*> InsertedTruncs;
bool MadeChange = false;
for (Use &U : Src->uses()) {
Instruction *User = cast<Instruction>(U.getUser());
// Figure out which BB this ext is used in.
BasicBlock *UserBB = User->getParent();
if (UserBB == DefBB) continue;
// Both src and def are live in this block. Rewrite the use.
Instruction *&InsertedTrunc = InsertedTruncs[UserBB];
if (!InsertedTrunc) {
BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
assert(InsertPt != UserBB->end());
InsertedTrunc = new TruncInst(I, Src->getType(), "", &*InsertPt);
InsertedInsts.insert(InsertedTrunc);
}
// Replace a use of the {s|z}ext source with a use of the result.
U = InsertedTrunc;
++NumExtUses;
MadeChange = true;
}
return MadeChange;
}
// Find loads whose uses only use some of the loaded value's bits. Add an "and"
// just after the load if the target can fold this into one extload instruction,
// with the hope of eliminating some of the other later "and" instructions using
// the loaded value. "and"s that are made trivially redundant by the insertion
// of the new "and" are removed by this function, while others (e.g. those whose
// path from the load goes through a phi) are left for isel to potentially
// remove.
//
// For example:
//
// b0:
// x = load i32
// ...
// b1:
// y = and x, 0xff
// z = use y
//
// becomes:
//
// b0:
// x = load i32
// x' = and x, 0xff
// ...
// b1:
// z = use x'
//
// whereas:
//
// b0:
// x1 = load i32
// ...
// b1:
// x2 = load i32
// ...
// b2:
// x = phi x1, x2
// y = and x, 0xff
//
// becomes (after a call to optimizeLoadExt for each load):
//
// b0:
// x1 = load i32
// x1' = and x1, 0xff
// ...
// b1:
// x2 = load i32
// x2' = and x2, 0xff
// ...
// b2:
// x = phi x1', x2'
// y = and x, 0xff
bool CodeGenPrepare::optimizeLoadExt(LoadInst *Load) {
if (!Load->isSimple() || !Load->getType()->isIntOrPtrTy())
return false;
// Skip loads we've already transformed.
if (Load->hasOneUse() &&
InsertedInsts.count(cast<Instruction>(*Load->user_begin())))
return false;
// Look at all uses of Load, looking through phis, to determine how many bits
// of the loaded value are needed.
SmallVector<Instruction *, 8> WorkList;
SmallPtrSet<Instruction *, 16> Visited;
SmallVector<Instruction *, 8> AndsToMaybeRemove;
for (auto *U : Load->users())
WorkList.push_back(cast<Instruction>(U));
EVT LoadResultVT = TLI->getValueType(*DL, Load->getType());
unsigned BitWidth = LoadResultVT.getSizeInBits();
// If the BitWidth is 0, do not try to optimize the type
if (BitWidth == 0)
return false;
APInt DemandBits(BitWidth, 0);
APInt WidestAndBits(BitWidth, 0);
while (!WorkList.empty()) {
Instruction *I = WorkList.pop_back_val();
// Break use-def graph loops.
if (!Visited.insert(I).second)
continue;
// For a PHI node, push all of its users.
if (auto *Phi = dyn_cast<PHINode>(I)) {
for (auto *U : Phi->users())
WorkList.push_back(cast<Instruction>(U));
continue;
}
switch (I->getOpcode()) {
case Instruction::And: {
auto *AndC = dyn_cast<ConstantInt>(I->getOperand(1));
if (!AndC)
return false;
APInt AndBits = AndC->getValue();
DemandBits |= AndBits;
// Keep track of the widest and mask we see.
if (AndBits.ugt(WidestAndBits))
WidestAndBits = AndBits;
if (AndBits == WidestAndBits && I->getOperand(0) == Load)
AndsToMaybeRemove.push_back(I);
break;
}
case Instruction::Shl: {
auto *ShlC = dyn_cast<ConstantInt>(I->getOperand(1));
if (!ShlC)
return false;
uint64_t ShiftAmt = ShlC->getLimitedValue(BitWidth - 1);
DemandBits.setLowBits(BitWidth - ShiftAmt);
break;
}
case Instruction::Trunc: {
EVT TruncVT = TLI->getValueType(*DL, I->getType());
unsigned TruncBitWidth = TruncVT.getSizeInBits();
DemandBits.setLowBits(TruncBitWidth);
break;
}
default:
return false;
}
}
uint32_t ActiveBits = DemandBits.getActiveBits();
// Avoid hoisting (and (load x) 1) since it is unlikely to be folded by the
// target even if isLoadExtLegal says an i1 EXTLOAD is valid. For example,
// for the AArch64 target isLoadExtLegal(ZEXTLOAD, i32, i1) returns true, but
// (and (load x) 1) is not matched as a single instruction, rather as a LDR
// followed by an AND.
// TODO: Look into removing this restriction by fixing backends to either
// return false for isLoadExtLegal for i1 or have them select this pattern to
// a single instruction.
//
// Also avoid hoisting if we didn't see any ands with the exact DemandBits
// mask, since these are the only ands that will be removed by isel.
if (ActiveBits <= 1 || !DemandBits.isMask(ActiveBits) ||
WidestAndBits != DemandBits)
return false;
LLVMContext &Ctx = Load->getType()->getContext();
Type *TruncTy = Type::getIntNTy(Ctx, ActiveBits);
EVT TruncVT = TLI->getValueType(*DL, TruncTy);
// Reject cases that won't be matched as extloads.
if (!LoadResultVT.bitsGT(TruncVT) || !TruncVT.isRound() ||
!TLI->isLoadExtLegal(ISD::ZEXTLOAD, LoadResultVT, TruncVT))
return false;
IRBuilder<> Builder(Load->getNextNode());
auto *NewAnd = cast<Instruction>(
Builder.CreateAnd(Load, ConstantInt::get(Ctx, DemandBits)));
// Mark this instruction as "inserted by CGP", so that other
// optimizations don't touch it.
InsertedInsts.insert(NewAnd);
// Replace all uses of load with new and (except for the use of load in the
// new and itself).
Load->replaceAllUsesWith(NewAnd);
NewAnd->setOperand(0, Load);
// Remove any and instructions that are now redundant.
for (auto *And : AndsToMaybeRemove)
// Check that the and mask is the same as the one we decided to put on the
// new and.
if (cast<ConstantInt>(And->getOperand(1))->getValue() == DemandBits) {
And->replaceAllUsesWith(NewAnd);
if (&*CurInstIterator == And)
CurInstIterator = std::next(And->getIterator());
And->eraseFromParent();
++NumAndUses;
}
++NumAndsAdded;
return true;
}
/// Check if V (an operand of a select instruction) is an expensive instruction
/// that is only used once.
static bool sinkSelectOperand(const TargetTransformInfo *TTI, Value *V) {
auto *I = dyn_cast<Instruction>(V);
// If it's safe to speculatively execute, then it should not have side
// effects; therefore, it's safe to sink and possibly *not* execute.
return I && I->hasOneUse() && isSafeToSpeculativelyExecute(I) &&
TTI->getUserCost(I, TargetTransformInfo::TCK_SizeAndLatency) >=
TargetTransformInfo::TCC_Expensive;
}
/// Returns true if a SelectInst should be turned into an explicit branch.
static bool isFormingBranchFromSelectProfitable(const TargetTransformInfo *TTI,
const TargetLowering *TLI,
SelectInst *SI) {
// If even a predictable select is cheap, then a branch can't be cheaper.
if (!TLI->isPredictableSelectExpensive())
return false;
// FIXME: This should use the same heuristics as IfConversion to determine
// whether a select is better represented as a branch.
// If metadata tells us that the select condition is obviously predictable,
// then we want to replace the select with a branch.
uint64_t TrueWeight, FalseWeight;
if (SI->extractProfMetadata(TrueWeight, FalseWeight)) {
uint64_t Max = std::max(TrueWeight, FalseWeight);
uint64_t Sum = TrueWeight + FalseWeight;
if (Sum != 0) {
auto Probability = BranchProbability::getBranchProbability(Max, Sum);
if (Probability > TTI->getPredictableBranchThreshold())
return true;
}
}
CmpInst *Cmp = dyn_cast<CmpInst>(SI->getCondition());
// If a branch is predictable, an out-of-order CPU can avoid blocking on its
// comparison condition. If the compare has more than one use, there's
// probably another cmov or setcc around, so it's not worth emitting a branch.
if (!Cmp || !Cmp->hasOneUse())
return false;
// If either operand of the select is expensive and only needed on one side
// of the select, we should form a branch.
if (sinkSelectOperand(TTI, SI->getTrueValue()) ||
sinkSelectOperand(TTI, SI->getFalseValue()))
return true;
return false;
}
/// If \p isTrue is true, return the true value of \p SI, otherwise return
/// false value of \p SI. If the true/false value of \p SI is defined by any
/// select instructions in \p Selects, look through the defining select
/// instruction until the true/false value is not defined in \p Selects.
static Value *getTrueOrFalseValue(
SelectInst *SI, bool isTrue,
const SmallPtrSet<const Instruction *, 2> &Selects) {
Value *V = nullptr;
for (SelectInst *DefSI = SI; DefSI != nullptr && Selects.count(DefSI);
DefSI = dyn_cast<SelectInst>(V)) {
assert(DefSI->getCondition() == SI->getCondition() &&
"The condition of DefSI does not match with SI");
V = (isTrue ? DefSI->getTrueValue() : DefSI->getFalseValue());
}
assert(V && "Failed to get select true/false value");
return V;
}
bool CodeGenPrepare::optimizeShiftInst(BinaryOperator *Shift) {
assert(Shift->isShift() && "Expected a shift");
// If this is (1) a vector shift, (2) shifts by scalars are cheaper than
// general vector shifts, and (3) the shift amount is a select-of-splatted
// values, hoist the shifts before the select:
// shift Op0, (select Cond, TVal, FVal) -->
// select Cond, (shift Op0, TVal), (shift Op0, FVal)
//
// This is inverting a generic IR transform when we know that the cost of a
// general vector shift is more than the cost of 2 shift-by-scalars.
// We can't do this effectively in SDAG because we may not be able to
// determine if the select operands are splats from within a basic block.
Type *Ty = Shift->getType();
if (!Ty->isVectorTy() || !TLI->isVectorShiftByScalarCheap(Ty))
return false;
Value *Cond, *TVal, *FVal;
if (!match(Shift->getOperand(1),
m_OneUse(m_Select(m_Value(Cond), m_Value(TVal), m_Value(FVal)))))
return false;
if (!isSplatValue(TVal) || !isSplatValue(FVal))
return false;
IRBuilder<> Builder(Shift);
BinaryOperator::BinaryOps Opcode = Shift->getOpcode();
Value *NewTVal = Builder.CreateBinOp(Opcode, Shift->getOperand(0), TVal);
Value *NewFVal = Builder.CreateBinOp(Opcode, Shift->getOperand(0), FVal);
Value *NewSel = Builder.CreateSelect(Cond, NewTVal, NewFVal);
Shift->replaceAllUsesWith(NewSel);
Shift->eraseFromParent();
return true;
}
bool CodeGenPrepare::optimizeFunnelShift(IntrinsicInst *Fsh) {
Intrinsic::ID Opcode = Fsh->getIntrinsicID();
assert((Opcode == Intrinsic::fshl || Opcode == Intrinsic::fshr) &&
"Expected a funnel shift");
// If this is (1) a vector funnel shift, (2) shifts by scalars are cheaper
// than general vector shifts, and (3) the shift amount is select-of-splatted
// values, hoist the funnel shifts before the select:
// fsh Op0, Op1, (select Cond, TVal, FVal) -->
// select Cond, (fsh Op0, Op1, TVal), (fsh Op0, Op1, FVal)
//
// This is inverting a generic IR transform when we know that the cost of a
// general vector shift is more than the cost of 2 shift-by-scalars.
// We can't do this effectively in SDAG because we may not be able to
// determine if the select operands are splats from within a basic block.
Type *Ty = Fsh->getType();
if (!Ty->isVectorTy() || !TLI->isVectorShiftByScalarCheap(Ty))
return false;
Value *Cond, *TVal, *FVal;
if (!match(Fsh->getOperand(2),
m_OneUse(m_Select(m_Value(Cond), m_Value(TVal), m_Value(FVal)))))
return false;
if (!isSplatValue(TVal) || !isSplatValue(FVal))
return false;
IRBuilder<> Builder(Fsh);
Value *X = Fsh->getOperand(0), *Y = Fsh->getOperand(1);
Value *NewTVal = Builder.CreateIntrinsic(Opcode, Ty, { X, Y, TVal });
Value *NewFVal = Builder.CreateIntrinsic(Opcode, Ty, { X, Y, FVal });
Value *NewSel = Builder.CreateSelect(Cond, NewTVal, NewFVal);
Fsh->replaceAllUsesWith(NewSel);
Fsh->eraseFromParent();
return true;
}
/// If we have a SelectInst that will likely profit from branch prediction,
/// turn it into a branch.
bool CodeGenPrepare::optimizeSelectInst(SelectInst *SI) {
if (DisableSelectToBranch)
return false;
// Find all consecutive select instructions that share the same condition.
SmallVector<SelectInst *, 2> ASI;
ASI.push_back(SI);
for (BasicBlock::iterator It = ++BasicBlock::iterator(SI);
It != SI->getParent()->end(); ++It) {
SelectInst *I = dyn_cast<SelectInst>(&*It);
if (I && SI->getCondition() == I->getCondition()) {
ASI.push_back(I);
} else {
break;
}
}
SelectInst *LastSI = ASI.back();
// Increment the current iterator to skip all the rest of select instructions
// because they will be either "not lowered" or "all lowered" to branch.
CurInstIterator = std::next(LastSI->getIterator());
bool VectorCond = !SI->getCondition()->getType()->isIntegerTy(1);
// Can we convert the 'select' to CF ?
if (VectorCond || SI->getMetadata(LLVMContext::MD_unpredictable))
return false;
TargetLowering::SelectSupportKind SelectKind;
if (VectorCond)
SelectKind = TargetLowering::VectorMaskSelect;
else if (SI->getType()->isVectorTy())
SelectKind = TargetLowering::ScalarCondVectorVal;
else
SelectKind = TargetLowering::ScalarValSelect;
if (TLI->isSelectSupported(SelectKind) &&
(!isFormingBranchFromSelectProfitable(TTI, TLI, SI) || OptSize ||
llvm::shouldOptimizeForSize(SI->getParent(), PSI, BFI.get())))
return false;
// The DominatorTree needs to be rebuilt by any consumers after this
// transformation. We simply reset here rather than setting the ModifiedDT
// flag to avoid restarting the function walk in runOnFunction for each
// select optimized.
DT.reset();
// Transform a sequence like this:
// start:
// %cmp = cmp uge i32 %a, %b
// %sel = select i1 %cmp, i32 %c, i32 %d
//
// Into:
// start:
// %cmp = cmp uge i32 %a, %b
// %cmp.frozen = freeze %cmp
// br i1 %cmp.frozen, label %select.true, label %select.false
// select.true:
// br label %select.end
// select.false:
// br label %select.end
// select.end:
// %sel = phi i32 [ %c, %select.true ], [ %d, %select.false ]
//
// %cmp should be frozen, otherwise it may introduce undefined behavior.
// In addition, we may sink instructions that produce %c or %d from
// the entry block into the destination(s) of the new branch.
// If the true or false blocks do not contain a sunken instruction, that
// block and its branch may be optimized away. In that case, one side of the
// first branch will point directly to select.end, and the corresponding PHI
// predecessor block will be the start block.
// First, we split the block containing the select into 2 blocks.
BasicBlock *StartBlock = SI->getParent();
BasicBlock::iterator SplitPt = ++(BasicBlock::iterator(LastSI));
BasicBlock *EndBlock = StartBlock->splitBasicBlock(SplitPt, "select.end");
BFI->setBlockFreq(EndBlock, BFI->getBlockFreq(StartBlock).getFrequency());
// Delete the unconditional branch that was just created by the split.
StartBlock->getTerminator()->eraseFromParent();
// These are the new basic blocks for the conditional branch.
// At least one will become an actual new basic block.
BasicBlock *TrueBlock = nullptr;
BasicBlock *FalseBlock = nullptr;
BranchInst *TrueBranch = nullptr;
BranchInst *FalseBranch = nullptr;
// Sink expensive instructions into the conditional blocks to avoid executing
// them speculatively.
for (SelectInst *SI : ASI) {
if (sinkSelectOperand(TTI, SI->getTrueValue())) {
if (TrueBlock == nullptr) {
TrueBlock = BasicBlock::Create(SI->getContext(), "select.true.sink",
EndBlock->getParent(), EndBlock);
TrueBranch = BranchInst::Create(EndBlock, TrueBlock);
TrueBranch->setDebugLoc(SI->getDebugLoc());
}
auto *TrueInst = cast<Instruction>(SI->getTrueValue());
TrueInst->moveBefore(TrueBranch);
}
if (sinkSelectOperand(TTI, SI->getFalseValue())) {
if (FalseBlock == nullptr) {
FalseBlock = BasicBlock::Create(SI->getContext(), "select.false.sink",
EndBlock->getParent(), EndBlock);
FalseBranch = BranchInst::Create(EndBlock, FalseBlock);
FalseBranch->setDebugLoc(SI->getDebugLoc());
}
auto *FalseInst = cast<Instruction>(SI->getFalseValue());
FalseInst->moveBefore(FalseBranch);
}
}
// If there was nothing to sink, then arbitrarily choose the 'false' side
// for a new input value to the PHI.
if (TrueBlock == FalseBlock) {
assert(TrueBlock == nullptr &&
"Unexpected basic block transform while optimizing select");
FalseBlock = BasicBlock::Create(SI->getContext(), "select.false",
EndBlock->getParent(), EndBlock);
auto *FalseBranch = BranchInst::Create(EndBlock, FalseBlock);
FalseBranch->setDebugLoc(SI->getDebugLoc());
}
// Insert the real conditional branch based on the original condition.
// If we did not create a new block for one of the 'true' or 'false' paths
// of the condition, it means that side of the branch goes to the end block
// directly and the path originates from the start block from the point of
// view of the new PHI.
BasicBlock *TT, *FT;
if (TrueBlock == nullptr) {
TT = EndBlock;
FT = FalseBlock;
TrueBlock = StartBlock;
} else if (FalseBlock == nullptr) {
TT = TrueBlock;
FT = EndBlock;
FalseBlock = StartBlock;
} else {
TT = TrueBlock;
FT = FalseBlock;
}
IRBuilder<> IB(SI);
auto *CondFr = IB.CreateFreeze(SI->getCondition(), SI->getName() + ".frozen");
IB.CreateCondBr(CondFr, TT, FT, SI);
SmallPtrSet<const Instruction *, 2> INS;
INS.insert(ASI.begin(), ASI.end());
// Use reverse iterator because later select may use the value of the
// earlier select, and we need to propagate value through earlier select
// to get the PHI operand.
for (SelectInst *SI : llvm::reverse(ASI)) {
// The select itself is replaced with a PHI Node.
PHINode *PN = PHINode::Create(SI->getType(), 2, "", &EndBlock->front());
PN->takeName(SI);
PN->addIncoming(getTrueOrFalseValue(SI, true, INS), TrueBlock);
PN->addIncoming(getTrueOrFalseValue(SI, false, INS), FalseBlock);
PN->setDebugLoc(SI->getDebugLoc());
SI->replaceAllUsesWith(PN);
SI->eraseFromParent();
INS.erase(SI);
++NumSelectsExpanded;
}
// Instruct OptimizeBlock to skip to the next block.
CurInstIterator = StartBlock->end();
return true;
}
/// Some targets only accept certain types for splat inputs. For example a VDUP
/// in MVE takes a GPR (integer) register, and the instruction that incorporate
/// a VDUP (such as a VADD qd, qm, rm) also require a gpr register.
bool CodeGenPrepare::optimizeShuffleVectorInst(ShuffleVectorInst *SVI) {
// Accept shuf(insertelem(undef/poison, val, 0), undef/poison, <0,0,..>) only
if (!match(SVI, m_Shuffle(m_InsertElt(m_Undef(), m_Value(), m_ZeroInt()),
m_Undef(), m_ZeroMask())))
return false;
Type *NewType = TLI->shouldConvertSplatType(SVI);
if (!NewType)
return false;
auto *SVIVecType = cast<FixedVectorType>(SVI->getType());
assert(!NewType->isVectorTy() && "Expected a scalar type!");
assert(NewType->getScalarSizeInBits() == SVIVecType->getScalarSizeInBits() &&
"Expected a type of the same size!");
auto *NewVecType =
FixedVectorType::get(NewType, SVIVecType->getNumElements());
// Create a bitcast (shuffle (insert (bitcast(..))))
IRBuilder<> Builder(SVI->getContext());
Builder.SetInsertPoint(SVI);
Value *BC1 = Builder.CreateBitCast(
cast<Instruction>(SVI->getOperand(0))->getOperand(1), NewType);
Value *Shuffle = Builder.CreateVectorSplat(NewVecType->getNumElements(), BC1);
Value *BC2 = Builder.CreateBitCast(Shuffle, SVIVecType);
SVI->replaceAllUsesWith(BC2);
RecursivelyDeleteTriviallyDeadInstructions(
SVI, TLInfo, nullptr, [&](Value *V) { removeAllAssertingVHReferences(V); });
// Also hoist the bitcast up to its operand if it they are not in the same
// block.
if (auto *BCI = dyn_cast<Instruction>(BC1))
if (auto *Op = dyn_cast<Instruction>(BCI->getOperand(0)))
if (BCI->getParent() != Op->getParent() && !isa<PHINode>(Op) &&
!Op->isTerminator() && !Op->isEHPad())
BCI->moveAfter(Op);
return true;
}
bool CodeGenPrepare::tryToSinkFreeOperands(Instruction *I) {
// If the operands of I can be folded into a target instruction together with
// I, duplicate and sink them.
SmallVector<Use *, 4> OpsToSink;
if (!TLI->shouldSinkOperands(I, OpsToSink))
return false;
// OpsToSink can contain multiple uses in a use chain (e.g.
// (%u1 with %u1 = shufflevector), (%u2 with %u2 = zext %u1)). The dominating
// uses must come first, so we process the ops in reverse order so as to not
// create invalid IR.
BasicBlock *TargetBB = I->getParent();
bool Changed = false;
SmallVector<Use *, 4> ToReplace;
Instruction *InsertPoint = I;
DenseMap<const Instruction *, unsigned long> InstOrdering;
unsigned long InstNumber = 0;
for (const auto &I : *TargetBB)
InstOrdering[&I] = InstNumber++;
for (Use *U : reverse(OpsToSink)) {
auto *UI = cast<Instruction>(U->get());
if (isa<PHINode>(UI))
continue;
if (UI->getParent() == TargetBB) {
if (InstOrdering[UI] < InstOrdering[InsertPoint])
InsertPoint = UI;
continue;
}
ToReplace.push_back(U);
}
SetVector<Instruction *> MaybeDead;
DenseMap<Instruction *, Instruction *> NewInstructions;
for (Use *U : ToReplace) {
auto *UI = cast<Instruction>(U->get());
Instruction *NI = UI->clone();
NewInstructions[UI] = NI;
MaybeDead.insert(UI);
LLVM_DEBUG(dbgs() << "Sinking " << *UI << " to user " << *I << "\n");
NI->insertBefore(InsertPoint);
InsertPoint = NI;
InsertedInsts.insert(NI);
// Update the use for the new instruction, making sure that we update the
// sunk instruction uses, if it is part of a chain that has already been
// sunk.
Instruction *OldI = cast<Instruction>(U->getUser());
if (NewInstructions.count(OldI))
NewInstructions[OldI]->setOperand(U->getOperandNo(), NI);
else
U->set(NI);
Changed = true;
}
// Remove instructions that are dead after sinking.
for (auto *I : MaybeDead) {
if (!I->hasNUsesOrMore(1)) {
LLVM_DEBUG(dbgs() << "Removing dead instruction: " << *I << "\n");
I->eraseFromParent();
}
}
return Changed;
}
bool CodeGenPrepare::optimizeSwitchType(SwitchInst *SI) {
Value *Cond = SI->getCondition();
Type *OldType = Cond->getType();
LLVMContext &Context = Cond->getContext();
EVT OldVT = TLI->getValueType(*DL, OldType);
MVT RegType = TLI->getPreferredSwitchConditionType(Context, OldVT);
unsigned RegWidth = RegType.getSizeInBits();
if (RegWidth <= cast<IntegerType>(OldType)->getBitWidth())
return false;
// If the register width is greater than the type width, expand the condition
// of the switch instruction and each case constant to the width of the
// register. By widening the type of the switch condition, subsequent
// comparisons (for case comparisons) will not need to be extended to the
// preferred register width, so we will potentially eliminate N-1 extends,
// where N is the number of cases in the switch.
auto *NewType = Type::getIntNTy(Context, RegWidth);
// Extend the switch condition and case constants using the target preferred
// extend unless the switch condition is a function argument with an extend
// attribute. In that case, we can avoid an unnecessary mask/extension by
// matching the argument extension instead.
Instruction::CastOps ExtType = Instruction::ZExt;
// Some targets prefer SExt over ZExt.
if (TLI->isSExtCheaperThanZExt(OldVT, RegType))
ExtType = Instruction::SExt;
if (auto *Arg = dyn_cast<Argument>(Cond)) {
if (Arg->hasSExtAttr())
ExtType = Instruction::SExt;
if (Arg->hasZExtAttr())
ExtType = Instruction::ZExt;
}
auto *ExtInst = CastInst::Create(ExtType, Cond, NewType);
ExtInst->insertBefore(SI);
ExtInst->setDebugLoc(SI->getDebugLoc());
SI->setCondition(ExtInst);
for (auto Case : SI->cases()) {
const APInt &NarrowConst = Case.getCaseValue()->getValue();
APInt WideConst = (ExtType == Instruction::ZExt) ?
NarrowConst.zext(RegWidth) : NarrowConst.sext(RegWidth);
Case.setValue(ConstantInt::get(Context, WideConst));
}
return true;
}
bool CodeGenPrepare::optimizeSwitchPhiConstants(SwitchInst *SI) {
// The SCCP optimization tends to produce code like this:
// switch(x) { case 42: phi(42, ...) }
// Materializing the constant for the phi-argument needs instructions; So we
// change the code to:
// switch(x) { case 42: phi(x, ...) }
Value *Condition = SI->getCondition();
// Avoid endless loop in degenerate case.
if (isa<ConstantInt>(*Condition))
return false;
bool Changed = false;
BasicBlock *SwitchBB = SI->getParent();
Type *ConditionType = Condition->getType();
for (const SwitchInst::CaseHandle &Case : SI->cases()) {
ConstantInt *CaseValue = Case.getCaseValue();
BasicBlock *CaseBB = Case.getCaseSuccessor();
// Set to true if we previously checked that `CaseBB` is only reached by
// a single case from this switch.
bool CheckedForSinglePred = false;
for (PHINode &PHI : CaseBB->phis()) {
Type *PHIType = PHI.getType();
// If ZExt is free then we can also catch patterns like this:
// switch((i32)x) { case 42: phi((i64)42, ...); }
// and replace `(i64)42` with `zext i32 %x to i64`.
bool TryZExt =
PHIType->isIntegerTy() &&
PHIType->getIntegerBitWidth() > ConditionType->getIntegerBitWidth() &&
TLI->isZExtFree(ConditionType, PHIType);
if (PHIType == ConditionType || TryZExt) {
// Set to true to skip this case because of multiple preds.
bool SkipCase = false;
Value *Replacement = nullptr;
for (unsigned I = 0, E = PHI.getNumIncomingValues(); I != E; I++) {
Value *PHIValue = PHI.getIncomingValue(I);
if (PHIValue != CaseValue) {
if (!TryZExt)
continue;
ConstantInt *PHIValueInt = dyn_cast<ConstantInt>(PHIValue);
if (!PHIValueInt ||
PHIValueInt->getValue() !=
CaseValue->getValue().zext(PHIType->getIntegerBitWidth()))
continue;
}
if (PHI.getIncomingBlock(I) != SwitchBB)
continue;
// We cannot optimize if there are multiple case labels jumping to
// this block. This check may get expensive when there are many
// case labels so we test for it last.
if (!CheckedForSinglePred) {
CheckedForSinglePred = true;
if (SI->findCaseDest(CaseBB) == nullptr) {
SkipCase = true;
break;
}
}
if (Replacement == nullptr) {
if (PHIValue == CaseValue) {
Replacement = Condition;
} else {
IRBuilder<> Builder(SI);
Replacement = Builder.CreateZExt(Condition, PHIType);
}
}
PHI.setIncomingValue(I, Replacement);
Changed = true;
}
if (SkipCase)
break;
}
}
}
return Changed;
}
bool CodeGenPrepare::optimizeSwitchInst(SwitchInst *SI) {
bool Changed = optimizeSwitchType(SI);
Changed |= optimizeSwitchPhiConstants(SI);
return Changed;
}
namespace {
/// Helper class to promote a scalar operation to a vector one.
/// This class is used to move downward extractelement transition.
/// E.g.,
/// a = vector_op <2 x i32>
/// b = extractelement <2 x i32> a, i32 0
/// c = scalar_op b
/// store c
///
/// =>
/// a = vector_op <2 x i32>
/// c = vector_op a (equivalent to scalar_op on the related lane)
/// * d = extractelement <2 x i32> c, i32 0
/// * store d
/// Assuming both extractelement and store can be combine, we get rid of the
/// transition.
class VectorPromoteHelper {
/// DataLayout associated with the current module.
const DataLayout &DL;
/// Used to perform some checks on the legality of vector operations.
const TargetLowering &TLI;
/// Used to estimated the cost of the promoted chain.
const TargetTransformInfo &TTI;
/// The transition being moved downwards.
Instruction *Transition;
/// The sequence of instructions to be promoted.
SmallVector<Instruction *, 4> InstsToBePromoted;
/// Cost of combining a store and an extract.
unsigned StoreExtractCombineCost;
/// Instruction that will be combined with the transition.
Instruction *CombineInst = nullptr;
/// The instruction that represents the current end of the transition.
/// Since we are faking the promotion until we reach the end of the chain
/// of computation, we need a way to get the current end of the transition.
Instruction *getEndOfTransition() const {
if (InstsToBePromoted.empty())
return Transition;
return InstsToBePromoted.back();
}
/// Return the index of the original value in the transition.
/// E.g., for "extractelement <2 x i32> c, i32 1" the original value,
/// c, is at index 0.
unsigned getTransitionOriginalValueIdx() const {
assert(isa<ExtractElementInst>(Transition) &&
"Other kind of transitions are not supported yet");
return 0;
}
/// Return the index of the index in the transition.
/// E.g., for "extractelement <2 x i32> c, i32 0" the index
/// is at index 1.
unsigned getTransitionIdx() const {
assert(isa<ExtractElementInst>(Transition) &&
"Other kind of transitions are not supported yet");
return 1;
}
/// Get the type of the transition.
/// This is the type of the original value.
/// E.g., for "extractelement <2 x i32> c, i32 1" the type of the
/// transition is <2 x i32>.
Type *getTransitionType() const {
return Transition->getOperand(getTransitionOriginalValueIdx())->getType();
}
/// Promote \p ToBePromoted by moving \p Def downward through.
/// I.e., we have the following sequence:
/// Def = Transition <ty1> a to <ty2>
/// b = ToBePromoted <ty2> Def, ...
/// =>
/// b = ToBePromoted <ty1> a, ...
/// Def = Transition <ty1> ToBePromoted to <ty2>
void promoteImpl(Instruction *ToBePromoted);
/// Check whether or not it is profitable to promote all the
/// instructions enqueued to be promoted.
bool isProfitableToPromote() {
Value *ValIdx = Transition->getOperand(getTransitionOriginalValueIdx());
unsigned Index = isa<ConstantInt>(ValIdx)
? cast<ConstantInt>(ValIdx)->getZExtValue()
: -1;
Type *PromotedType = getTransitionType();
StoreInst *ST = cast<StoreInst>(CombineInst);
unsigned AS = ST->getPointerAddressSpace();
// Check if this store is supported.
if (!TLI.allowsMisalignedMemoryAccesses(
TLI.getValueType(DL, ST->getValueOperand()->getType()), AS,
ST->getAlign())) {
// If this is not supported, there is no way we can combine
// the extract with the store.
return false;
}
// The scalar chain of computation has to pay for the transition
// scalar to vector.
// The vector chain has to account for the combining cost.
InstructionCost ScalarCost =
TTI.getVectorInstrCost(Transition->getOpcode(), PromotedType, Index);
InstructionCost VectorCost = StoreExtractCombineCost;
enum TargetTransformInfo::TargetCostKind CostKind =
TargetTransformInfo::TCK_RecipThroughput;
for (const auto &Inst : InstsToBePromoted) {
// Compute the cost.
// By construction, all instructions being promoted are arithmetic ones.
// Moreover, one argument is a constant that can be viewed as a splat
// constant.
Value *Arg0 = Inst->getOperand(0);
bool IsArg0Constant = isa<UndefValue>(Arg0) || isa<ConstantInt>(Arg0) ||
isa<ConstantFP>(Arg0);
TargetTransformInfo::OperandValueKind Arg0OVK =
IsArg0Constant ? TargetTransformInfo::OK_UniformConstantValue
: TargetTransformInfo::OK_AnyValue;
TargetTransformInfo::OperandValueKind Arg1OVK =
!IsArg0Constant ? TargetTransformInfo::OK_UniformConstantValue
: TargetTransformInfo::OK_AnyValue;
ScalarCost += TTI.getArithmeticInstrCost(
Inst->getOpcode(), Inst->getType(), CostKind, Arg0OVK, Arg1OVK);
VectorCost += TTI.getArithmeticInstrCost(Inst->getOpcode(), PromotedType,
CostKind,
Arg0OVK, Arg1OVK);
}
LLVM_DEBUG(
dbgs() << "Estimated cost of computation to be promoted:\nScalar: "
<< ScalarCost << "\nVector: " << VectorCost << '\n');
return ScalarCost > VectorCost;
}
/// Generate a constant vector with \p Val with the same
/// number of elements as the transition.
/// \p UseSplat defines whether or not \p Val should be replicated
/// across the whole vector.
/// In other words, if UseSplat == true, we generate <Val, Val, ..., Val>,
/// otherwise we generate a vector with as many undef as possible:
/// <undef, ..., undef, Val, undef, ..., undef> where \p Val is only
/// used at the index of the extract.
Value *getConstantVector(Constant *Val, bool UseSplat) const {
unsigned ExtractIdx = std::numeric_limits<unsigned>::max();
if (!UseSplat) {
// If we cannot determine where the constant must be, we have to
// use a splat constant.
Value *ValExtractIdx = Transition->getOperand(getTransitionIdx());
if (ConstantInt *CstVal = dyn_cast<ConstantInt>(ValExtractIdx))
ExtractIdx = CstVal->getSExtValue();
else
UseSplat = true;
}
ElementCount EC = cast<VectorType>(getTransitionType())->getElementCount();
if (UseSplat)
return ConstantVector::getSplat(EC, Val);
if (!EC.isScalable()) {
SmallVector<Constant *, 4> ConstVec;
UndefValue *UndefVal = UndefValue::get(Val->getType());
for (unsigned Idx = 0; Idx != EC.getKnownMinValue(); ++Idx) {
if (Idx == ExtractIdx)
ConstVec.push_back(Val);
else
ConstVec.push_back(UndefVal);
}
return ConstantVector::get(ConstVec);
} else
llvm_unreachable(
"Generate scalable vector for non-splat is unimplemented");
}
/// Check if promoting to a vector type an operand at \p OperandIdx
/// in \p Use can trigger undefined behavior.
static bool canCauseUndefinedBehavior(const Instruction *Use,
unsigned OperandIdx) {
// This is not safe to introduce undef when the operand is on
// the right hand side of a division-like instruction.
if (OperandIdx != 1)
return false;
switch (Use->getOpcode()) {
default:
return false;
case Instruction::SDiv:
case Instruction::UDiv:
case Instruction::SRem:
case Instruction::URem:
return true;
case Instruction::FDiv:
case Instruction::FRem:
return !Use->hasNoNaNs();
}
llvm_unreachable(nullptr);
}
public:
VectorPromoteHelper(const DataLayout &DL, const TargetLowering &TLI,
const TargetTransformInfo &TTI, Instruction *Transition,
unsigned CombineCost)
: DL(DL), TLI(TLI), TTI(TTI), Transition(Transition),
StoreExtractCombineCost(CombineCost) {
assert(Transition && "Do not know how to promote null");
}
/// Check if we can promote \p ToBePromoted to \p Type.
bool canPromote(const Instruction *ToBePromoted) const {
// We could support CastInst too.
return isa<BinaryOperator>(ToBePromoted);
}
/// Check if it is profitable to promote \p ToBePromoted
/// by moving downward the transition through.
bool shouldPromote(const Instruction *ToBePromoted) const {
// Promote only if all the operands can be statically expanded.
// Indeed, we do not want to introduce any new kind of transitions.
for (const Use &U : ToBePromoted->operands()) {
const Value *Val = U.get();
if (Val == getEndOfTransition()) {
// If the use is a division and the transition is on the rhs,
// we cannot promote the operation, otherwise we may create a
// division by zero.
if (canCauseUndefinedBehavior(ToBePromoted, U.getOperandNo()))
return false;
continue;
}
if (!isa<ConstantInt>(Val) && !isa<UndefValue>(Val) &&
!isa<ConstantFP>(Val))
return false;
}
// Check that the resulting operation is legal.
int ISDOpcode = TLI.InstructionOpcodeToISD(ToBePromoted->getOpcode());
if (!ISDOpcode)
return false;
return StressStoreExtract ||
TLI.isOperationLegalOrCustom(
ISDOpcode, TLI.getValueType(DL, getTransitionType(), true));
}
/// Check whether or not \p Use can be combined
/// with the transition.
/// I.e., is it possible to do Use(Transition) => AnotherUse?
bool canCombine(const Instruction *Use) { return isa<StoreInst>(Use); }
/// Record \p ToBePromoted as part of the chain to be promoted.
void enqueueForPromotion(Instruction *ToBePromoted) {
InstsToBePromoted.push_back(ToBePromoted);
}
/// Set the instruction that will be combined with the transition.
void recordCombineInstruction(Instruction *ToBeCombined) {
assert(canCombine(ToBeCombined) && "Unsupported instruction to combine");
CombineInst = ToBeCombined;
}
/// Promote all the instructions enqueued for promotion if it is
/// is profitable.
/// \return True if the promotion happened, false otherwise.
bool promote() {
// Check if there is something to promote.
// Right now, if we do not have anything to combine with,
// we assume the promotion is not profitable.
if (InstsToBePromoted.empty() || !CombineInst)
return false;
// Check cost.
if (!StressStoreExtract && !isProfitableToPromote())
return false;
// Promote.
for (auto &ToBePromoted : InstsToBePromoted)
promoteImpl(ToBePromoted);
InstsToBePromoted.clear();
return true;
}
};
} // end anonymous namespace
void VectorPromoteHelper::promoteImpl(Instruction *ToBePromoted) {
// At this point, we know that all the operands of ToBePromoted but Def
// can be statically promoted.
// For Def, we need to use its parameter in ToBePromoted:
// b = ToBePromoted ty1 a
// Def = Transition ty1 b to ty2
// Move the transition down.
// 1. Replace all uses of the promoted operation by the transition.
// = ... b => = ... Def.
assert(ToBePromoted->getType() == Transition->getType() &&
"The type of the result of the transition does not match "
"the final type");
ToBePromoted->replaceAllUsesWith(Transition);
// 2. Update the type of the uses.
// b = ToBePromoted ty2 Def => b = ToBePromoted ty1 Def.
Type *TransitionTy = getTransitionType();
ToBePromoted->mutateType(TransitionTy);
// 3. Update all the operands of the promoted operation with promoted
// operands.
// b = ToBePromoted ty1 Def => b = ToBePromoted ty1 a.
for (Use &U : ToBePromoted->operands()) {
Value *Val = U.get();
Value *NewVal = nullptr;
if (Val == Transition)
NewVal = Transition->getOperand(getTransitionOriginalValueIdx());
else if (isa<UndefValue>(Val) || isa<ConstantInt>(Val) ||
isa<ConstantFP>(Val)) {
// Use a splat constant if it is not safe to use undef.
NewVal = getConstantVector(
cast<Constant>(Val),
isa<UndefValue>(Val) ||
canCauseUndefinedBehavior(ToBePromoted, U.getOperandNo()));
} else
llvm_unreachable("Did you modified shouldPromote and forgot to update "
"this?");
ToBePromoted->setOperand(U.getOperandNo(), NewVal);
}
Transition->moveAfter(ToBePromoted);
Transition->setOperand(getTransitionOriginalValueIdx(), ToBePromoted);
}
/// Some targets can do store(extractelement) with one instruction.
/// Try to push the extractelement towards the stores when the target
/// has this feature and this is profitable.
bool CodeGenPrepare::optimizeExtractElementInst(Instruction *Inst) {
unsigned CombineCost = std::numeric_limits<unsigned>::max();
if (DisableStoreExtract ||
(!StressStoreExtract &&
!TLI->canCombineStoreAndExtract(Inst->getOperand(0)->getType(),
Inst->getOperand(1), CombineCost)))
return false;
// At this point we know that Inst is a vector to scalar transition.
// Try to move it down the def-use chain, until:
// - We can combine the transition with its single use
// => we got rid of the transition.
// - We escape the current basic block
// => we would need to check that we are moving it at a cheaper place and
// we do not do that for now.
BasicBlock *Parent = Inst->getParent();
LLVM_DEBUG(dbgs() << "Found an interesting transition: " << *Inst << '\n');
VectorPromoteHelper VPH(*DL, *TLI, *TTI, Inst, CombineCost);
// If the transition has more than one use, assume this is not going to be
// beneficial.
while (Inst->hasOneUse()) {
Instruction *ToBePromoted = cast<Instruction>(*Inst->user_begin());
LLVM_DEBUG(dbgs() << "Use: " << *ToBePromoted << '\n');
if (ToBePromoted->getParent() != Parent) {
LLVM_DEBUG(dbgs() << "Instruction to promote is in a different block ("
<< ToBePromoted->getParent()->getName()
<< ") than the transition (" << Parent->getName()
<< ").\n");
return false;
}
if (VPH.canCombine(ToBePromoted)) {
LLVM_DEBUG(dbgs() << "Assume " << *Inst << '\n'
<< "will be combined with: " << *ToBePromoted << '\n');
VPH.recordCombineInstruction(ToBePromoted);
bool Changed = VPH.promote();
NumStoreExtractExposed += Changed;
return Changed;
}
LLVM_DEBUG(dbgs() << "Try promoting.\n");
if (!VPH.canPromote(ToBePromoted) || !VPH.shouldPromote(ToBePromoted))
return false;
LLVM_DEBUG(dbgs() << "Promoting is possible... Enqueue for promotion!\n");
VPH.enqueueForPromotion(ToBePromoted);
Inst = ToBePromoted;
}
return false;
}
/// For the instruction sequence of store below, F and I values
/// are bundled together as an i64 value before being stored into memory.
/// Sometimes it is more efficient to generate separate stores for F and I,
/// which can remove the bitwise instructions or sink them to colder places.
///
/// (store (or (zext (bitcast F to i32) to i64),
/// (shl (zext I to i64), 32)), addr) -->
/// (store F, addr) and (store I, addr+4)
///
/// Similarly, splitting for other merged store can also be beneficial, like:
/// For pair of {i32, i32}, i64 store --> two i32 stores.
/// For pair of {i32, i16}, i64 store --> two i32 stores.
/// For pair of {i16, i16}, i32 store --> two i16 stores.
/// For pair of {i16, i8}, i32 store --> two i16 stores.
/// For pair of {i8, i8}, i16 store --> two i8 stores.
///
/// We allow each target to determine specifically which kind of splitting is
/// supported.
///
/// The store patterns are commonly seen from the simple code snippet below
/// if only std::make_pair(...) is sroa transformed before inlined into hoo.
/// void goo(const std::pair<int, float> &);
/// hoo() {
/// ...
/// goo(std::make_pair(tmp, ftmp));
/// ...
/// }
///
/// Although we already have similar splitting in DAG Combine, we duplicate
/// it in CodeGenPrepare to catch the case in which pattern is across
/// multiple BBs. The logic in DAG Combine is kept to catch case generated
/// during code expansion.
static bool splitMergedValStore(StoreInst &SI, const DataLayout &DL,
const TargetLowering &TLI) {
// Handle simple but common cases only.
Type *StoreType = SI.getValueOperand()->getType();
// The code below assumes shifting a value by <number of bits>,
// whereas scalable vectors would have to be shifted by
// <2log(vscale) + number of bits> in order to store the
// low/high parts. Bailing out for now.
if (isa<ScalableVectorType>(StoreType))
return false;
if (!DL.typeSizeEqualsStoreSize(StoreType) ||
DL.getTypeSizeInBits(StoreType) == 0)
return false;
unsigned HalfValBitSize = DL.getTypeSizeInBits(StoreType) / 2;
Type *SplitStoreType = Type::getIntNTy(SI.getContext(), HalfValBitSize);
if (!DL.typeSizeEqualsStoreSize(SplitStoreType))
return false;
// Don't split the store if it is volatile.
if (SI.isVolatile())
return false;
// Match the following patterns:
// (store (or (zext LValue to i64),
// (shl (zext HValue to i64), 32)), HalfValBitSize)
// or
// (store (or (shl (zext HValue to i64), 32)), HalfValBitSize)
// (zext LValue to i64),
// Expect both operands of OR and the first operand of SHL have only
// one use.
Value *LValue, *HValue;
if (!match(SI.getValueOperand(),
m_c_Or(m_OneUse(m_ZExt(m_Value(LValue))),
m_OneUse(m_Shl(m_OneUse(m_ZExt(m_Value(HValue))),
m_SpecificInt(HalfValBitSize))))))
return false;
// Check LValue and HValue are int with size less or equal than 32.
if (!LValue->getType()->isIntegerTy() ||
DL.getTypeSizeInBits(LValue->getType()) > HalfValBitSize ||
!HValue->getType()->isIntegerTy() ||
DL.getTypeSizeInBits(HValue->getType()) > HalfValBitSize)
return false;
// If LValue/HValue is a bitcast instruction, use the EVT before bitcast
// as the input of target query.
auto *LBC = dyn_cast<BitCastInst>(LValue);
auto *HBC = dyn_cast<BitCastInst>(HValue);
EVT LowTy = LBC ? EVT::getEVT(LBC->getOperand(0)->getType())
: EVT::getEVT(LValue->getType());
EVT HighTy = HBC ? EVT::getEVT(HBC->getOperand(0)->getType())
: EVT::getEVT(HValue->getType());
if (!ForceSplitStore && !TLI.isMultiStoresCheaperThanBitsMerge(LowTy, HighTy))
return false;
// Start to split store.
IRBuilder<> Builder(SI.getContext());
Builder.SetInsertPoint(&SI);
// If LValue/HValue is a bitcast in another BB, create a new one in current
// BB so it may be merged with the splitted stores by dag combiner.
if (LBC && LBC->getParent() != SI.getParent())
LValue = Builder.CreateBitCast(LBC->getOperand(0), LBC->getType());
if (HBC && HBC->getParent() != SI.getParent())
HValue = Builder.CreateBitCast(HBC->getOperand(0), HBC->getType());
bool IsLE = SI.getModule()->getDataLayout().isLittleEndian();
auto CreateSplitStore = [&](Value *V, bool Upper) {
V = Builder.CreateZExtOrBitCast(V, SplitStoreType);
Value *Addr = Builder.CreateBitCast(
SI.getOperand(1),
SplitStoreType->getPointerTo(SI.getPointerAddressSpace()));
Align Alignment = SI.getAlign();
const bool IsOffsetStore = (IsLE && Upper) || (!IsLE && !Upper);
if (IsOffsetStore) {
Addr = Builder.CreateGEP(
SplitStoreType, Addr,
ConstantInt::get(Type::getInt32Ty(SI.getContext()), 1));
// When splitting the store in half, naturally one half will retain the
// alignment of the original wider store, regardless of whether it was
// over-aligned or not, while the other will require adjustment.
Alignment = commonAlignment(Alignment, HalfValBitSize / 8);
}
Builder.CreateAlignedStore(V, Addr, Alignment);
};
CreateSplitStore(LValue, false);
CreateSplitStore(HValue, true);
// Delete the old store.
SI.eraseFromParent();
return true;
}
// Return true if the GEP has two operands, the first operand is of a sequential
// type, and the second operand is a constant.
static bool GEPSequentialConstIndexed(GetElementPtrInst *GEP) {
gep_type_iterator I = gep_type_begin(*GEP);
return GEP->getNumOperands() == 2 &&
I.isSequential() &&
isa<ConstantInt>(GEP->getOperand(1));
}
// Try unmerging GEPs to reduce liveness interference (register pressure) across
// IndirectBr edges. Since IndirectBr edges tend to touch on many blocks,
// reducing liveness interference across those edges benefits global register
// allocation. Currently handles only certain cases.
//
// For example, unmerge %GEPI and %UGEPI as below.
//
// ---------- BEFORE ----------
// SrcBlock:
// ...
// %GEPIOp = ...
// ...
// %GEPI = gep %GEPIOp, Idx
// ...
// indirectbr ... [ label %DstB0, label %DstB1, ... label %DstBi ... ]
// (* %GEPI is alive on the indirectbr edges due to other uses ahead)
// (* %GEPIOp is alive on the indirectbr edges only because of it's used by
// %UGEPI)
//
// DstB0: ... (there may be a gep similar to %UGEPI to be unmerged)
// DstB1: ... (there may be a gep similar to %UGEPI to be unmerged)
// ...
//
// DstBi:
// ...
// %UGEPI = gep %GEPIOp, UIdx
// ...
// ---------------------------
//
// ---------- AFTER ----------
// SrcBlock:
// ... (same as above)
// (* %GEPI is still alive on the indirectbr edges)
// (* %GEPIOp is no longer alive on the indirectbr edges as a result of the
// unmerging)
// ...
//
// DstBi:
// ...
// %UGEPI = gep %GEPI, (UIdx-Idx)
// ...
// ---------------------------
//
// The register pressure on the IndirectBr edges is reduced because %GEPIOp is
// no longer alive on them.
//
// We try to unmerge GEPs here in CodGenPrepare, as opposed to limiting merging
// of GEPs in the first place in InstCombiner::visitGetElementPtrInst() so as
// not to disable further simplications and optimizations as a result of GEP
// merging.
//
// Note this unmerging may increase the length of the data flow critical path
// (the path from %GEPIOp to %UGEPI would go through %GEPI), which is a tradeoff
// between the register pressure and the length of data-flow critical
// path. Restricting this to the uncommon IndirectBr case would minimize the
// impact of potentially longer critical path, if any, and the impact on compile
// time.
static bool tryUnmergingGEPsAcrossIndirectBr(GetElementPtrInst *GEPI,
const TargetTransformInfo *TTI) {
BasicBlock *SrcBlock = GEPI->getParent();
// Check that SrcBlock ends with an IndirectBr. If not, give up. The common
// (non-IndirectBr) cases exit early here.
if (!isa<IndirectBrInst>(SrcBlock->getTerminator()))
return false;
// Check that GEPI is a simple gep with a single constant index.
if (!GEPSequentialConstIndexed(GEPI))
return false;
ConstantInt *GEPIIdx = cast<ConstantInt>(GEPI->getOperand(1));
// Check that GEPI is a cheap one.
if (TTI->getIntImmCost(GEPIIdx->getValue(), GEPIIdx->getType(),
TargetTransformInfo::TCK_SizeAndLatency)
> TargetTransformInfo::TCC_Basic)
return false;
Value *GEPIOp = GEPI->getOperand(0);
// Check that GEPIOp is an instruction that's also defined in SrcBlock.
if (!isa<Instruction>(GEPIOp))
return false;
auto *GEPIOpI = cast<Instruction>(GEPIOp);
if (GEPIOpI->getParent() != SrcBlock)
return false;
// Check that GEP is used outside the block, meaning it's alive on the
// IndirectBr edge(s).
if (find_if(GEPI->users(), [&](User *Usr) {
if (auto *I = dyn_cast<Instruction>(Usr)) {
if (I->getParent() != SrcBlock) {
return true;
}
}
return false;
}) == GEPI->users().end())
return false;
// The second elements of the GEP chains to be unmerged.
std::vector<GetElementPtrInst *> UGEPIs;
// Check each user of GEPIOp to check if unmerging would make GEPIOp not alive
// on IndirectBr edges.
for (User *Usr : GEPIOp->users()) {
if (Usr == GEPI) continue;
// Check if Usr is an Instruction. If not, give up.
if (!isa<Instruction>(Usr))
return false;
auto *UI = cast<Instruction>(Usr);
// Check if Usr in the same block as GEPIOp, which is fine, skip.
if (UI->getParent() == SrcBlock)
continue;
// Check if Usr is a GEP. If not, give up.
if (!isa<GetElementPtrInst>(Usr))
return false;
auto *UGEPI = cast<GetElementPtrInst>(Usr);
// Check if UGEPI is a simple gep with a single constant index and GEPIOp is
// the pointer operand to it. If so, record it in the vector. If not, give
// up.
if (!GEPSequentialConstIndexed(UGEPI))
return false;
if (UGEPI->getOperand(0) != GEPIOp)
return false;
if (GEPIIdx->getType() !=
cast<ConstantInt>(UGEPI->getOperand(1))->getType())
return false;
ConstantInt *UGEPIIdx = cast<ConstantInt>(UGEPI->getOperand(1));
if (TTI->getIntImmCost(UGEPIIdx->getValue(), UGEPIIdx->getType(),
TargetTransformInfo::TCK_SizeAndLatency)
> TargetTransformInfo::TCC_Basic)
return false;
UGEPIs.push_back(UGEPI);
}
if (UGEPIs.size() == 0)
return false;
// Check the materializing cost of (Uidx-Idx).
for (GetElementPtrInst *UGEPI : UGEPIs) {
ConstantInt *UGEPIIdx = cast<ConstantInt>(UGEPI->getOperand(1));
APInt NewIdx = UGEPIIdx->getValue() - GEPIIdx->getValue();
InstructionCost ImmCost = TTI->getIntImmCost(
NewIdx, GEPIIdx->getType(), TargetTransformInfo::TCK_SizeAndLatency);
if (ImmCost > TargetTransformInfo::TCC_Basic)
return false;
}
// Now unmerge between GEPI and UGEPIs.
for (GetElementPtrInst *UGEPI : UGEPIs) {
UGEPI->setOperand(0, GEPI);
ConstantInt *UGEPIIdx = cast<ConstantInt>(UGEPI->getOperand(1));
Constant *NewUGEPIIdx =
ConstantInt::get(GEPIIdx->getType(),
UGEPIIdx->getValue() - GEPIIdx->getValue());
UGEPI->setOperand(1, NewUGEPIIdx);
// If GEPI is not inbounds but UGEPI is inbounds, change UGEPI to not
// inbounds to avoid UB.
if (!GEPI->isInBounds()) {
UGEPI->setIsInBounds(false);
}
}
// After unmerging, verify that GEPIOp is actually only used in SrcBlock (not
// alive on IndirectBr edges).
assert(find_if(GEPIOp->users(), [&](User *Usr) {
return cast<Instruction>(Usr)->getParent() != SrcBlock;
}) == GEPIOp->users().end() && "GEPIOp is used outside SrcBlock");
return true;
}
static bool optimizeBranch(BranchInst *Branch, const TargetLowering &TLI) {
// Try and convert
// %c = icmp ult %x, 8
// br %c, bla, blb
// %tc = lshr %x, 3
// to
// %tc = lshr %x, 3
// %c = icmp eq %tc, 0
// br %c, bla, blb
// Creating the cmp to zero can be better for the backend, especially if the
// lshr produces flags that can be used automatically.
if (!TLI.preferZeroCompareBranch() || !Branch->isConditional())
return false;
ICmpInst *Cmp = dyn_cast<ICmpInst>(Branch->getCondition());
if (!Cmp || !isa<ConstantInt>(Cmp->getOperand(1)) || !Cmp->hasOneUse())
return false;
Value *X = Cmp->getOperand(0);
APInt CmpC = cast<ConstantInt>(Cmp->getOperand(1))->getValue();
for (auto *U : X->users()) {
Instruction *UI = dyn_cast<Instruction>(U);
// A quick dominance check
if (!UI ||
(UI->getParent() != Branch->getParent() &&
UI->getParent() != Branch->getSuccessor(0) &&
UI->getParent() != Branch->getSuccessor(1)) ||
(UI->getParent() != Branch->getParent() &&
!UI->getParent()->getSinglePredecessor()))
continue;
if (CmpC.isPowerOf2() && Cmp->getPredicate() == ICmpInst::ICMP_ULT &&
match(UI, m_Shr(m_Specific(X), m_SpecificInt(CmpC.logBase2())))) {
IRBuilder<> Builder(Branch);
if (UI->getParent() != Branch->getParent())
UI->moveBefore(Branch);
Value *NewCmp = Builder.CreateCmp(ICmpInst::ICMP_EQ, UI,
ConstantInt::get(UI->getType(), 0));
LLVM_DEBUG(dbgs() << "Converting " << *Cmp << "\n");
LLVM_DEBUG(dbgs() << " to compare on zero: " << *NewCmp << "\n");
Cmp->replaceAllUsesWith(NewCmp);
return true;
}
if (Cmp->isEquality() &&
(match(UI, m_Add(m_Specific(X), m_SpecificInt(-CmpC))) ||
match(UI, m_Sub(m_Specific(X), m_SpecificInt(CmpC))))) {
IRBuilder<> Builder(Branch);
if (UI->getParent() != Branch->getParent())
UI->moveBefore(Branch);
Value *NewCmp = Builder.CreateCmp(Cmp->getPredicate(), UI,
ConstantInt::get(UI->getType(), 0));
LLVM_DEBUG(dbgs() << "Converting " << *Cmp << "\n");
LLVM_DEBUG(dbgs() << " to compare on zero: " << *NewCmp << "\n");
Cmp->replaceAllUsesWith(NewCmp);
return true;
}
}
return false;
}
bool CodeGenPrepare::optimizeInst(Instruction *I, bool &ModifiedDT) {
// Bail out if we inserted the instruction to prevent optimizations from
// stepping on each other's toes.
if (InsertedInsts.count(I))
return false;
// TODO: Move into the switch on opcode below here.
if (PHINode *P = dyn_cast<PHINode>(I)) {
// It is possible for very late stage optimizations (such as SimplifyCFG)
// to introduce PHI nodes too late to be cleaned up. If we detect such a
// trivial PHI, go ahead and zap it here.
if (Value *V = SimplifyInstruction(P, {*DL, TLInfo})) {
LargeOffsetGEPMap.erase(P);
P->replaceAllUsesWith(V);
P->eraseFromParent();
++NumPHIsElim;
return true;
}
return false;
}
if (CastInst *CI = dyn_cast<CastInst>(I)) {
// If the source of the cast is a constant, then this should have
// already been constant folded. The only reason NOT to constant fold
// it is if something (e.g. LSR) was careful to place the constant
// evaluation in a block other than then one that uses it (e.g. to hoist
// the address of globals out of a loop). If this is the case, we don't
// want to forward-subst the cast.
if (isa<Constant>(CI->getOperand(0)))
return false;
if (OptimizeNoopCopyExpression(CI, *TLI, *DL))
return true;
if (isa<ZExtInst>(I) || isa<SExtInst>(I)) {
/// Sink a zext or sext into its user blocks if the target type doesn't
/// fit in one register
if (TLI->getTypeAction(CI->getContext(),
TLI->getValueType(*DL, CI->getType())) ==
TargetLowering::TypeExpandInteger) {
return SinkCast(CI);
} else {
bool MadeChange = optimizeExt(I);
return MadeChange | optimizeExtUses(I);
}
}
return false;
}
if (auto *Cmp = dyn_cast<CmpInst>(I))
if (optimizeCmp(Cmp, ModifiedDT))
return true;
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
LI->setMetadata(LLVMContext::MD_invariant_group, nullptr);
bool Modified = optimizeLoadExt(LI);
unsigned AS = LI->getPointerAddressSpace();
Modified |= optimizeMemoryInst(I, I->getOperand(0), LI->getType(), AS);
return Modified;
}
if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
if (splitMergedValStore(*SI, *DL, *TLI))
return true;
SI->setMetadata(LLVMContext::MD_invariant_group, nullptr);
unsigned AS = SI->getPointerAddressSpace();
return optimizeMemoryInst(I, SI->getOperand(1),
SI->getOperand(0)->getType(), AS);
}
if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) {
unsigned AS = RMW->getPointerAddressSpace();
return optimizeMemoryInst(I, RMW->getPointerOperand(),
RMW->getType(), AS);
}
if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(I)) {
unsigned AS = CmpX->getPointerAddressSpace();
return optimizeMemoryInst(I, CmpX->getPointerOperand(),
CmpX->getCompareOperand()->getType(), AS);
}
BinaryOperator *BinOp = dyn_cast<BinaryOperator>(I);
if (BinOp && BinOp->getOpcode() == Instruction::And && EnableAndCmpSinking &&
sinkAndCmp0Expression(BinOp, *TLI, InsertedInsts))
return true;
// TODO: Move this into the switch on opcode - it handles shifts already.
if (BinOp && (BinOp->getOpcode() == Instruction::AShr ||
BinOp->getOpcode() == Instruction::LShr)) {
ConstantInt *CI = dyn_cast<ConstantInt>(BinOp->getOperand(1));
if (CI && TLI->hasExtractBitsInsn())
if (OptimizeExtractBits(BinOp, CI, *TLI, *DL))
return true;
}
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
if (GEPI->hasAllZeroIndices()) {
/// The GEP operand must be a pointer, so must its result -> BitCast
Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(),
GEPI->getName(), GEPI);
NC->setDebugLoc(GEPI->getDebugLoc());
GEPI->replaceAllUsesWith(NC);
GEPI->eraseFromParent();
++NumGEPsElim;
optimizeInst(NC, ModifiedDT);
return true;
}
if (tryUnmergingGEPsAcrossIndirectBr(GEPI, TTI)) {
return true;
}
return false;
}
if (FreezeInst *FI = dyn_cast<FreezeInst>(I)) {
// freeze(icmp a, const)) -> icmp (freeze a), const
// This helps generate efficient conditional jumps.
Instruction *CmpI = nullptr;
if (ICmpInst *II = dyn_cast<ICmpInst>(FI->getOperand(0)))
CmpI = II;
else if (FCmpInst *F = dyn_cast<FCmpInst>(FI->getOperand(0)))
CmpI = F->getFastMathFlags().none() ? F : nullptr;
if (CmpI && CmpI->hasOneUse()) {
auto Op0 = CmpI->getOperand(0), Op1 = CmpI->getOperand(1);
bool Const0 = isa<ConstantInt>(Op0) || isa<ConstantFP>(Op0) ||
isa<ConstantPointerNull>(Op0);
bool Const1 = isa<ConstantInt>(Op1) || isa<ConstantFP>(Op1) ||
isa<ConstantPointerNull>(Op1);
if (Const0 || Const1) {
if (!Const0 || !Const1) {
auto *F = new FreezeInst(Const0 ? Op1 : Op0, "", CmpI);
F->takeName(FI);
CmpI->setOperand(Const0 ? 1 : 0, F);
}
FI->replaceAllUsesWith(CmpI);
FI->eraseFromParent();
return true;
}
}
return false;
}
if (tryToSinkFreeOperands(I))
return true;
switch (I->getOpcode()) {
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
return optimizeShiftInst(cast<BinaryOperator>(I));
case Instruction::Call:
return optimizeCallInst(cast<CallInst>(I), ModifiedDT);
case Instruction::Select:
return optimizeSelectInst(cast<SelectInst>(I));
case Instruction::ShuffleVector:
return optimizeShuffleVectorInst(cast<ShuffleVectorInst>(I));
case Instruction::Switch:
return optimizeSwitchInst(cast<SwitchInst>(I));
case Instruction::ExtractElement:
return optimizeExtractElementInst(cast<ExtractElementInst>(I));
case Instruction::Br:
return optimizeBranch(cast<BranchInst>(I), *TLI);
}
return false;
}
/// Given an OR instruction, check to see if this is a bitreverse
/// idiom. If so, insert the new intrinsic and return true.
bool CodeGenPrepare::makeBitReverse(Instruction &I) {
if (!I.getType()->isIntegerTy() ||
!TLI->isOperationLegalOrCustom(ISD::BITREVERSE,
TLI->getValueType(*DL, I.getType(), true)))
return false;
SmallVector<Instruction*, 4> Insts;
if (!recognizeBSwapOrBitReverseIdiom(&I, false, true, Insts))
return false;
Instruction *LastInst = Insts.back();
I.replaceAllUsesWith(LastInst);
RecursivelyDeleteTriviallyDeadInstructions(
&I, TLInfo, nullptr, [&](Value *V) { removeAllAssertingVHReferences(V); });
return true;
}
// In this pass we look for GEP and cast instructions that are used
// across basic blocks and rewrite them to improve basic-block-at-a-time
// selection.
bool CodeGenPrepare::optimizeBlock(BasicBlock &BB, bool &ModifiedDT) {
SunkAddrs.clear();
bool MadeChange = false;
CurInstIterator = BB.begin();
while (CurInstIterator != BB.end()) {
MadeChange |= optimizeInst(&*CurInstIterator++, ModifiedDT);
if (ModifiedDT)
return true;
}
bool MadeBitReverse = true;
while (MadeBitReverse) {
MadeBitReverse = false;
for (auto &I : reverse(BB)) {
if (makeBitReverse(I)) {
MadeBitReverse = MadeChange = true;
break;
}
}
}
MadeChange |= dupRetToEnableTailCallOpts(&BB, ModifiedDT);
return MadeChange;
}
// Some CGP optimizations may move or alter what's computed in a block. Check
// whether a dbg.value intrinsic could be pointed at a more appropriate operand.
bool CodeGenPrepare::fixupDbgValue(Instruction *I) {
assert(isa<DbgValueInst>(I));
DbgValueInst &DVI = *cast<DbgValueInst>(I);
// Does this dbg.value refer to a sunk address calculation?
bool AnyChange = false;
SmallDenseSet<Value *> LocationOps(DVI.location_ops().begin(),
DVI.location_ops().end());
for (Value *Location : LocationOps) {
WeakTrackingVH SunkAddrVH = SunkAddrs[Location];
Value *SunkAddr = SunkAddrVH.pointsToAliveValue() ? SunkAddrVH : nullptr;
if (SunkAddr) {
// Point dbg.value at locally computed address, which should give the best
// opportunity to be accurately lowered. This update may change the type
// of pointer being referred to; however this makes no difference to
// debugging information, and we can't generate bitcasts that may affect
// codegen.
DVI.replaceVariableLocationOp(Location, SunkAddr);
AnyChange = true;
}
}
return AnyChange;
}
// A llvm.dbg.value may be using a value before its definition, due to
// optimizations in this pass and others. Scan for such dbg.values, and rescue
// them by moving the dbg.value to immediately after the value definition.
// FIXME: Ideally this should never be necessary, and this has the potential
// to re-order dbg.value intrinsics.
bool CodeGenPrepare::placeDbgValues(Function &F) {
bool MadeChange = false;
DominatorTree DT(F);
for (BasicBlock &BB : F) {
for (Instruction &Insn : llvm::make_early_inc_range(BB)) {
DbgValueInst *DVI = dyn_cast<DbgValueInst>(&Insn);
if (!DVI)
continue;
SmallVector<Instruction *, 4> VIs;
for (Value *V : DVI->getValues())
if (Instruction *VI = dyn_cast_or_null<Instruction>(V))
VIs.push_back(VI);
// This DVI may depend on multiple instructions, complicating any
// potential sink. This block takes the defensive approach, opting to
// "undef" the DVI if it has more than one instruction and any of them do
// not dominate DVI.
for (Instruction *VI : VIs) {
if (VI->isTerminator())
continue;
// If VI is a phi in a block with an EHPad terminator, we can't insert
// after it.
if (isa<PHINode>(VI) && VI->getParent()->getTerminator()->isEHPad())
continue;
// If the defining instruction dominates the dbg.value, we do not need
// to move the dbg.value.
if (DT.dominates(VI, DVI))
continue;
// If we depend on multiple instructions and any of them doesn't
// dominate this DVI, we probably can't salvage it: moving it to
// after any of the instructions could cause us to lose the others.
if (VIs.size() > 1) {
LLVM_DEBUG(
dbgs()
<< "Unable to find valid location for Debug Value, undefing:\n"
<< *DVI);
DVI->setUndef();
break;
}
LLVM_DEBUG(dbgs() << "Moving Debug Value before :\n"
<< *DVI << ' ' << *VI);
DVI->removeFromParent();
if (isa<PHINode>(VI))
DVI->insertBefore(&*VI->getParent()->getFirstInsertionPt());
else
DVI->insertAfter(VI);
MadeChange = true;
++NumDbgValueMoved;
}
}
}
return MadeChange;
}
// Group scattered pseudo probes in a block to favor SelectionDAG. Scattered
// probes can be chained dependencies of other regular DAG nodes and block DAG
// combine optimizations.
bool CodeGenPrepare::placePseudoProbes(Function &F) {
bool MadeChange = false;
for (auto &Block : F) {
// Move the rest probes to the beginning of the block.
auto FirstInst = Block.getFirstInsertionPt();
while (FirstInst != Block.end() && FirstInst->isDebugOrPseudoInst())
++FirstInst;
BasicBlock::iterator I(FirstInst);
I++;
while (I != Block.end()) {
if (auto *II = dyn_cast<PseudoProbeInst>(I++)) {
II->moveBefore(&*FirstInst);
MadeChange = true;
}
}
}
return MadeChange;
}
/// Scale down both weights to fit into uint32_t.
static void scaleWeights(uint64_t &NewTrue, uint64_t &NewFalse) {
uint64_t NewMax = (NewTrue > NewFalse) ? NewTrue : NewFalse;
uint32_t Scale = (NewMax / std::numeric_limits<uint32_t>::max()) + 1;
NewTrue = NewTrue / Scale;
NewFalse = NewFalse / Scale;
}
/// Some targets prefer to split a conditional branch like:
/// \code
/// %0 = icmp ne i32 %a, 0
/// %1 = icmp ne i32 %b, 0
/// %or.cond = or i1 %0, %1
/// br i1 %or.cond, label %TrueBB, label %FalseBB
/// \endcode
/// into multiple branch instructions like:
/// \code
/// bb1:
/// %0 = icmp ne i32 %a, 0
/// br i1 %0, label %TrueBB, label %bb2
/// bb2:
/// %1 = icmp ne i32 %b, 0
/// br i1 %1, label %TrueBB, label %FalseBB
/// \endcode
/// This usually allows instruction selection to do even further optimizations
/// and combine the compare with the branch instruction. Currently this is
/// applied for targets which have "cheap" jump instructions.
///
/// FIXME: Remove the (equivalent?) implementation in SelectionDAG.
///
bool CodeGenPrepare::splitBranchCondition(Function &F, bool &ModifiedDT) {
if (!TM->Options.EnableFastISel || TLI->isJumpExpensive())
return false;
bool MadeChange = false;
for (auto &BB : F) {
// Does this BB end with the following?
// %cond1 = icmp|fcmp|binary instruction ...
// %cond2 = icmp|fcmp|binary instruction ...
// %cond.or = or|and i1 %cond1, cond2
// br i1 %cond.or label %dest1, label %dest2"
Instruction *LogicOp;
BasicBlock *TBB, *FBB;
if (!match(BB.getTerminator(),
m_Br(m_OneUse(m_Instruction(LogicOp)), TBB, FBB)))
continue;
auto *Br1 = cast<BranchInst>(BB.getTerminator());
if (Br1->getMetadata(LLVMContext::MD_unpredictable))
continue;
// The merging of mostly empty BB can cause a degenerate branch.
if (TBB == FBB)
continue;
unsigned Opc;
Value *Cond1, *Cond2;
if (match(LogicOp,
m_LogicalAnd(m_OneUse(m_Value(Cond1)), m_OneUse(m_Value(Cond2)))))
Opc = Instruction::And;
else if (match(LogicOp, m_LogicalOr(m_OneUse(m_Value(Cond1)),
m_OneUse(m_Value(Cond2)))))
Opc = Instruction::Or;
else
continue;
auto IsGoodCond = [](Value *Cond) {
return match(
Cond,
m_CombineOr(m_Cmp(), m_CombineOr(m_LogicalAnd(m_Value(), m_Value()),
m_LogicalOr(m_Value(), m_Value()))));
};
if (!IsGoodCond(Cond1) || !IsGoodCond(Cond2))
continue;
LLVM_DEBUG(dbgs() << "Before branch condition splitting\n"; BB.dump());
// Create a new BB.
auto *TmpBB =
BasicBlock::Create(BB.getContext(), BB.getName() + ".cond.split",
BB.getParent(), BB.getNextNode());
// Update original basic block by using the first condition directly by the
// branch instruction and removing the no longer needed and/or instruction.
Br1->setCondition(Cond1);
LogicOp->eraseFromParent();
// Depending on the condition we have to either replace the true or the
// false successor of the original branch instruction.
if (Opc == Instruction::And)
Br1->setSuccessor(0, TmpBB);
else
Br1->setSuccessor(1, TmpBB);
// Fill in the new basic block.
auto *Br2 = IRBuilder<>(TmpBB).CreateCondBr(Cond2, TBB, FBB);
if (auto *I = dyn_cast<Instruction>(Cond2)) {
I->removeFromParent();
I->insertBefore(Br2);
}
// Update PHI nodes in both successors. The original BB needs to be
// replaced in one successor's PHI nodes, because the branch comes now from
// the newly generated BB (NewBB). In the other successor we need to add one
// incoming edge to the PHI nodes, because both branch instructions target
// now the same successor. Depending on the original branch condition
// (and/or) we have to swap the successors (TrueDest, FalseDest), so that
// we perform the correct update for the PHI nodes.
// This doesn't change the successor order of the just created branch
// instruction (or any other instruction).
if (Opc == Instruction::Or)
std::swap(TBB, FBB);
// Replace the old BB with the new BB.
TBB->replacePhiUsesWith(&BB, TmpBB);
// Add another incoming edge form the new BB.
for (PHINode &PN : FBB->phis()) {
auto *Val = PN.getIncomingValueForBlock(&BB);
PN.addIncoming(Val, TmpBB);
}
// Update the branch weights (from SelectionDAGBuilder::
// FindMergedConditions).
if (Opc == Instruction::Or) {
// Codegen X | Y as:
// BB1:
// jmp_if_X TBB
// jmp TmpBB
// TmpBB:
// jmp_if_Y TBB
// jmp FBB
//
// We have flexibility in setting Prob for BB1 and Prob for NewBB.
// The requirement is that
// TrueProb for BB1 + (FalseProb for BB1 * TrueProb for TmpBB)
// = TrueProb for original BB.
// Assuming the original weights are A and B, one choice is to set BB1's
// weights to A and A+2B, and set TmpBB's weights to A and 2B. This choice
// assumes that
// TrueProb for BB1 == FalseProb for BB1 * TrueProb for TmpBB.
// Another choice is to assume TrueProb for BB1 equals to TrueProb for
// TmpBB, but the math is more complicated.
uint64_t TrueWeight, FalseWeight;
if (Br1->extractProfMetadata(TrueWeight, FalseWeight)) {
uint64_t NewTrueWeight = TrueWeight;
uint64_t NewFalseWeight = TrueWeight + 2 * FalseWeight;
scaleWeights(NewTrueWeight, NewFalseWeight);
Br1->setMetadata(LLVMContext::MD_prof, MDBuilder(Br1->getContext())
.createBranchWeights(TrueWeight, FalseWeight));
NewTrueWeight = TrueWeight;
NewFalseWeight = 2 * FalseWeight;
scaleWeights(NewTrueWeight, NewFalseWeight);
Br2->setMetadata(LLVMContext::MD_prof, MDBuilder(Br2->getContext())
.createBranchWeights(TrueWeight, FalseWeight));
}
} else {
// Codegen X & Y as:
// BB1:
// jmp_if_X TmpBB
// jmp FBB
// TmpBB:
// jmp_if_Y TBB
// jmp FBB
//
// This requires creation of TmpBB after CurBB.
// We have flexibility in setting Prob for BB1 and Prob for TmpBB.
// The requirement is that
// FalseProb for BB1 + (TrueProb for BB1 * FalseProb for TmpBB)
// = FalseProb for original BB.
// Assuming the original weights are A and B, one choice is to set BB1's
// weights to 2A+B and B, and set TmpBB's weights to 2A and B. This choice
// assumes that
// FalseProb for BB1 == TrueProb for BB1 * FalseProb for TmpBB.
uint64_t TrueWeight, FalseWeight;
if (Br1->extractProfMetadata(TrueWeight, FalseWeight)) {
uint64_t NewTrueWeight = 2 * TrueWeight + FalseWeight;
uint64_t NewFalseWeight = FalseWeight;
scaleWeights(NewTrueWeight, NewFalseWeight);
Br1->setMetadata(LLVMContext::MD_prof, MDBuilder(Br1->getContext())
.createBranchWeights(TrueWeight, FalseWeight));
NewTrueWeight = 2 * TrueWeight;
NewFalseWeight = FalseWeight;
scaleWeights(NewTrueWeight, NewFalseWeight);
Br2->setMetadata(LLVMContext::MD_prof, MDBuilder(Br2->getContext())
.createBranchWeights(TrueWeight, FalseWeight));
}
}
ModifiedDT = true;
MadeChange = true;
LLVM_DEBUG(dbgs() << "After branch condition splitting\n"; BB.dump();
TmpBB->dump());
}
return MadeChange;
}
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