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

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//===- CodeGenPrepare.cpp - Prepare a function for code generation --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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/PointerIntPair.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.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/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/ISDOpcodes.h"
#include "llvm/CodeGen/MachineValueType.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.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/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/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/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetSubtargetInfo.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/BypassSlowDivision.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SimplifyLibCalls.h"
#include "llvm/Transforms/Utils/ValueMapper.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(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");
STATISTIC(NumMemCmpCalls, "Number of memcmp calls");
STATISTIC(NumMemCmpNotConstant, "Number of memcmp calls without constant size");
STATISTIC(NumMemCmpGreaterThanMax,
"Number of memcmp calls with size greater than max size");
STATISTIC(NumMemCmpInlined, "Number of inlined memcmp calls");
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<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<unsigned> MemCmpNumLoadsPerBlock(
"memcmp-num-loads-per-block", cl::Hidden, cl::init(1),
cl::desc("The number of loads per basic block for inline expansion of "
"memcmp that is only being compared against zero."));
namespace {
using SetOfInstrs = SmallPtrSet<Instruction *, 16>;
using TypeIsSExt = PointerIntPair<Type *, 1, bool>;
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 TargetLibraryInfo *TLInfo;
const LoopInfo *LI;
std::unique_ptr<BlockFrequencyInfo> BFI;
std::unique_ptr<BranchProbabilityInfo> BPI;
/// 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.
ValueMap<Value*, Value*> 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 SExt promoted.
ValueToSExts ValToSExtendedUses;
/// True if CFG is modified in any way.
bool ModifiedDT;
/// True if optimizing for size.
bool OptSize;
/// DataLayout for the Function being processed.
const DataLayout *DL = nullptr;
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<TargetTransformInfoWrapperPass>();
AU.addRequired<LoopInfoWrapperPass>();
}
private:
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 optimizeBlock(BasicBlock &BB, bool &ModifiedDT);
bool optimizeInst(Instruction *I, bool &ModifiedDT);
bool optimizeMemoryInst(Instruction *I, Value *Addr,
Type *AccessTy, unsigned AS);
bool optimizeInlineAsmInst(CallInst *CS);
bool optimizeCallInst(CallInst *CI, bool &ModifiedDT);
bool optimizeExt(Instruction *&I);
bool optimizeExtUses(Instruction *I);
bool optimizeLoadExt(LoadInst *I);
bool optimizeSelectInst(SelectInst *SI);
bool optimizeShuffleVectorInst(ShuffleVectorInst *SI);
bool optimizeSwitchInst(SwitchInst *CI);
bool optimizeExtractElementInst(Instruction *Inst);
bool dupRetToEnableTailCallOpts(BasicBlock *BB);
bool placeDbgValues(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 performAddressTypePromotion(
Instruction *&Inst,
bool AllowPromotionWithoutCommonHeader,
bool HasPromoted, TypePromotionTransaction &TPT,
SmallVectorImpl<Instruction *> &SpeculativelyMovedExts);
bool splitBranchCondition(Function &F);
bool simplifyOffsetableRelocate(Instruction &I);
bool splitIndirectCriticalEdges(Function &F);
};
} // end anonymous namespace
char CodeGenPrepare::ID = 0;
INITIALIZE_PASS_BEGIN(CodeGenPrepare, DEBUG_TYPE,
"Optimize for code generation", false, false)
INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
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();
BFI.reset();
BPI.reset();
ModifiedDT = false;
if (auto *TPC = getAnalysisIfAvailable<TargetPassConfig>()) {
TM = &TPC->getTM<TargetMachine>();
SubtargetInfo = TM->getSubtargetImpl(F);
TLI = SubtargetInfo->getTargetLowering();
TRI = SubtargetInfo->getRegisterInfo();
}
TLInfo = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
OptSize = F.optForSize();
if (ProfileGuidedSectionPrefix) {
ProfileSummaryInfo *PSI =
getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
if (PSI->isFunctionHotInCallGraph(&F))
F.setSectionPrefix(".hot");
else if (PSI->isFunctionColdInCallGraph(&F))
F.setSectionPrefix(".unlikely");
}
/// This optimization identifies DIV instructions that can be
/// profitably bypassed and carried out with a shorter, faster divide.
if (!OptSize && TLI && 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();
EverMadeChange |= bypassSlowDivision(BB, BypassWidths);
BB = Next;
}
}
// Eliminate blocks that contain only PHI nodes and an
// unconditional branch.
EverMadeChange |= eliminateMostlyEmptyBlocks(F);
// llvm.dbg.value is far away from the value then iSel may not be able
// handle it properly. iSel will drop llvm.dbg.value if it can not
// find a node corresponding to the value.
EverMadeChange |= placeDbgValues(F);
if (!DisableBranchOpts)
EverMadeChange |= splitBranchCondition(F);
// Split some critical edges where one of the sources is an indirect branch,
// to help generate sane code for PHIs involving such edges.
EverMadeChange |= splitIndirectCriticalEdges(F);
bool MadeChange = true;
while (MadeChange) {
MadeChange = false;
SeenChainsForSExt.clear();
ValToSExtendedUses.clear();
RemovedInsts.clear();
for (Function::iterator I = F.begin(); I != F.end(); ) {
BasicBlock *BB = &*I++;
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);
// Really free removed instructions during promotion.
for (Instruction *I : RemovedInsts)
I->deleteValue();
EverMadeChange |= MadeChange;
}
SunkAddrs.clear();
if (!DisableBranchOpts) {
MadeChange = false;
SmallPtrSet<BasicBlock*, 8> WorkList;
for (BasicBlock &BB : F) {
SmallVector<BasicBlock *, 2> Successors(succ_begin(&BB), succ_end(&BB));
MadeChange |= ConstantFoldTerminator(&BB, true);
if (!MadeChange) continue;
for (SmallVectorImpl<BasicBlock*>::iterator
II = Successors.begin(), IE = Successors.end(); II != IE; ++II)
if (pred_begin(*II) == pred_end(*II))
WorkList.insert(*II);
}
// Delete the dead blocks and any of their dead successors.
MadeChange |= !WorkList.empty();
while (!WorkList.empty()) {
BasicBlock *BB = *WorkList.begin();
WorkList.erase(BB);
SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB));
DeleteDeadBlock(BB);
for (SmallVectorImpl<BasicBlock*>::iterator
II = Successors.begin(), IE = Successors.end(); II != IE; ++II)
if (pred_begin(*II) == pred_end(*II))
WorkList.insert(*II);
}
// Merge pairs of basic blocks with unconditional branches, connected by
// a single edge.
if (EverMadeChange || MadeChange)
MadeChange |= eliminateFallThrough(F);
EverMadeChange |= MadeChange;
}
if (!DisableGCOpts) {
SmallVector<Instruction *, 2> Statepoints;
for (BasicBlock &BB : F)
for (Instruction &I : BB)
if (isStatepoint(I))
Statepoints.push_back(&I);
for (auto &I : Statepoints)
EverMadeChange |= simplifyOffsetableRelocate(*I);
}
return EverMadeChange;
}
/// 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.
for (Function::iterator I = std::next(F.begin()), E = F.end(); I != E;) {
BasicBlock *BB = &*I++;
// 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;
DEBUG(dbgs() << "To merge:\n"<< *SinglePred << "\n\n\n");
// Remember if SinglePred was the entry block of the function.
// If so, we will need to move BB back to the entry position.
bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
MergeBasicBlockIntoOnlyPred(BB, nullptr);
if (isEntry && BB != &BB->getParent()->getEntryBlock())
BB->moveBefore(&BB->getParent()->getEntryBlock());
// We have erased a block. Update the iterator.
I = BB->getIterator();
}
}
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;
}
// Return the unique indirectbr predecessor of a block. This may return null
// even if such a predecessor exists, if it's not useful for splitting.
// If a predecessor is found, OtherPreds will contain all other (non-indirectbr)
// predecessors of BB.
static BasicBlock *
findIBRPredecessor(BasicBlock *BB, SmallVectorImpl<BasicBlock *> &OtherPreds) {
// If the block doesn't have any PHIs, we don't care about it, since there's
// no point in splitting it.
PHINode *PN = dyn_cast<PHINode>(BB->begin());
if (!PN)
return nullptr;
// Verify we have exactly one IBR predecessor.
// Conservatively bail out if one of the other predecessors is not a "regular"
// terminator (that is, not a switch or a br).
BasicBlock *IBB = nullptr;
for (unsigned Pred = 0, E = PN->getNumIncomingValues(); Pred != E; ++Pred) {
BasicBlock *PredBB = PN->getIncomingBlock(Pred);
TerminatorInst *PredTerm = PredBB->getTerminator();
switch (PredTerm->getOpcode()) {
case Instruction::IndirectBr:
if (IBB)
return nullptr;
IBB = PredBB;
break;
case Instruction::Br:
case Instruction::Switch:
OtherPreds.push_back(PredBB);
continue;
default:
return nullptr;
}
}
return IBB;
}
// Split critical edges where the source of the edge is an indirectbr
// instruction. This isn't always possible, but we can handle some easy cases.
// This is useful because MI is unable to split such critical edges,
// which means it will not be able to sink instructions along those edges.
// This is especially painful for indirect branches with many successors, where
// we end up having to prepare all outgoing values in the origin block.
//
// Our normal algorithm for splitting critical edges requires us to update
// the outgoing edges of the edge origin block, but for an indirectbr this
// is hard, since it would require finding and updating the block addresses
// the indirect branch uses. But if a block only has a single indirectbr
// predecessor, with the others being regular branches, we can do it in a
// different way.
// Say we have A -> D, B -> D, I -> D where only I -> D is an indirectbr.
// We can split D into D0 and D1, where D0 contains only the PHIs from D,
// and D1 is the D block body. We can then duplicate D0 as D0A and D0B, and
// create the following structure:
// A -> D0A, B -> D0A, I -> D0B, D0A -> D1, D0B -> D1
bool CodeGenPrepare::splitIndirectCriticalEdges(Function &F) {
// Check whether the function has any indirectbrs, and collect which blocks
// they may jump to. Since most functions don't have indirect branches,
// this lowers the common case's overhead to O(Blocks) instead of O(Edges).
SmallSetVector<BasicBlock *, 16> Targets;
for (auto &BB : F) {
auto *IBI = dyn_cast<IndirectBrInst>(BB.getTerminator());
if (!IBI)
continue;
for (unsigned Succ = 0, E = IBI->getNumSuccessors(); Succ != E; ++Succ)
Targets.insert(IBI->getSuccessor(Succ));
}
if (Targets.empty())
return false;
bool Changed = false;
for (BasicBlock *Target : Targets) {
SmallVector<BasicBlock *, 16> OtherPreds;
BasicBlock *IBRPred = findIBRPredecessor(Target, OtherPreds);
// If we did not found an indirectbr, or the indirectbr is the only
// incoming edge, this isn't the kind of edge we're looking for.
if (!IBRPred || OtherPreds.empty())
continue;
// Don't even think about ehpads/landingpads.
Instruction *FirstNonPHI = Target->getFirstNonPHI();
if (FirstNonPHI->isEHPad() || Target->isLandingPad())
continue;
BasicBlock *BodyBlock = Target->splitBasicBlock(FirstNonPHI, ".split");
// It's possible Target was its own successor through an indirectbr.
// In this case, the indirectbr now comes from BodyBlock.
if (IBRPred == Target)
IBRPred = BodyBlock;
// At this point Target only has PHIs, and BodyBlock has the rest of the
// block's body. Create a copy of Target that will be used by the "direct"
// preds.
ValueToValueMapTy VMap;
BasicBlock *DirectSucc = CloneBasicBlock(Target, VMap, ".clone", &F);
for (BasicBlock *Pred : OtherPreds) {
// If the target is a loop to itself, then the terminator of the split
// block needs to be updated.
if (Pred == Target)
BodyBlock->getTerminator()->replaceUsesOfWith(Target, DirectSucc);
else
Pred->getTerminator()->replaceUsesOfWith(Target, DirectSucc);
}
// Ok, now fix up the PHIs. We know the two blocks only have PHIs, and that
// they are clones, so the number of PHIs are the same.
// (a) Remove the edge coming from IBRPred from the "Direct" PHI
// (b) Leave that as the only edge in the "Indirect" PHI.
// (c) Merge the two in the body block.
BasicBlock::iterator Indirect = Target->begin(),
End = Target->getFirstNonPHI()->getIterator();
BasicBlock::iterator Direct = DirectSucc->begin();
BasicBlock::iterator MergeInsert = BodyBlock->getFirstInsertionPt();
assert(&*End == Target->getTerminator() &&
"Block was expected to only contain PHIs");
while (Indirect != End) {
PHINode *DirPHI = cast<PHINode>(Direct);
PHINode *IndPHI = cast<PHINode>(Indirect);
// Now, clean up - the direct block shouldn't get the indirect value,
// and vice versa.
DirPHI->removeIncomingValue(IBRPred);
Direct++;
// Advance the pointer here, to avoid invalidation issues when the old
// PHI is erased.
Indirect++;
PHINode *NewIndPHI = PHINode::Create(IndPHI->getType(), 1, "ind", IndPHI);
NewIndPHI->addIncoming(IndPHI->getIncomingValueForBlock(IBRPred),
IBRPred);
// Create a PHI in the body block, to merge the direct and indirect
// predecessors.
PHINode *MergePHI =
PHINode::Create(IndPHI->getType(), 2, "merge", &*MergeInsert);
MergePHI->addIncoming(NewIndPHI, Target);
MergePHI->addIncoming(DirPHI, DirectSucc);
IndPHI->replaceAllUsesWith(MergePHI);
IndPHI->eraseFromParent();
}
Changed = true;
}
return Changed;
}
/// 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();
LoopList.insert(LoopList.end(), L->begin(), L->end());
if (BasicBlock *Preheader = L->getLoopPreheader())
Preheaders.insert(Preheader);
}
bool MadeChange = false;
// Note that this intentionally skips the entry block.
for (Function::iterator I = std::next(F.begin()), E = F.end(); I != E;) {
BasicBlock *BB = &*I++;
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;
// 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->getFirstNonPHI())
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 (pred_iterator PI = pred_begin(DestBB), E = pred_end(DestBB); PI != E;
++PI) {
BasicBlock *DestBBPred = *PI;
if (DestBBPred == BB)
continue;
bool HasAllSameValue = true;
BasicBlock::const_iterator DestBBI = DestBB->begin();
while (const PHINode *DestPN = dyn_cast<PHINode>(DestBBI++)) {
if (DestPN->getIncomingValueForBlock(BB) !=
DestPN->getIncomingValueForBlock(DestBBPred)) {
HasAllSameValue = false;
break;
}
}
if (HasAllSameValue)
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;
if (!BFI) {
Function &F = *BB->getParent();
LoopInfo LI{DominatorTree(F)};
BPI.reset(new BranchProbabilityInfo(F, LI));
BFI.reset(new BlockFrequencyInfo(F, *BPI, LI));
}
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.
BasicBlock::const_iterator BBI = BB->begin();
while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
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?
BBI = DestBB->begin();
while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
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);
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) {
// Remember if SinglePred was the entry block of the function. If so, we
// will need to move BB back to the entry position.
bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
MergeBasicBlockIntoOnlyPred(DestBB, nullptr);
if (isEntry && BB != &BB->getParent()->getEntryBlock())
BB->moveBefore(&BB->getParent()->getEntryBlock());
DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\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.
PHINode *PN;
for (BasicBlock::iterator BBI = DestBB->begin();
(PN = dyn_cast<PHINode>(BBI)); ++BBI) {
// 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 (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
PN->addIncoming(InVal, *PI);
}
}
}
// The PHIs are now updated, change everything that refers to BB to use
// DestBB and remove BB.
BB->replaceAllUsesWith(DestBB);
BB->eraseFromParent();
++NumBlocksElim;
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(Instruction &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 atleast 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;
}
/// SinkCast - 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);
}
// 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()) {
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.isCheapAddrSpaceCast(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);
}
/// Try to combine CI into a call to the llvm.uadd.with.overflow intrinsic if
/// possible.
///
/// Return true if any changes were made.
static bool CombineUAddWithOverflow(CmpInst *CI) {
Value *A, *B;
Instruction *AddI;
if (!match(CI,
m_UAddWithOverflow(m_Value(A), m_Value(B), m_Instruction(AddI))))
return false;
Type *Ty = AddI->getType();
if (!isa<IntegerType>(Ty))
return false;
// We don't want to move around uses of condition values this late, so we we
// check if it is legal to create the call to the intrinsic in the basic
// block containing the icmp:
if (AddI->getParent() != CI->getParent() && !AddI->hasOneUse())
return false;
#ifndef NDEBUG
// Someday m_UAddWithOverflow may get smarter, but this is a safe assumption
// for now:
if (AddI->hasOneUse())
assert(*AddI->user_begin() == CI && "expected!");
#endif
Module *M = CI->getModule();
Value *F = Intrinsic::getDeclaration(M, Intrinsic::uadd_with_overflow, Ty);
auto *InsertPt = AddI->hasOneUse() ? CI : AddI;
auto *UAddWithOverflow =
CallInst::Create(F, {A, B}, "uadd.overflow", InsertPt);
auto *UAdd = ExtractValueInst::Create(UAddWithOverflow, 0, "uadd", InsertPt);
auto *Overflow =
ExtractValueInst::Create(UAddWithOverflow, 1, "overflow", InsertPt);
CI->replaceAllUsesWith(Overflow);
AddI->replaceAllUsesWith(UAdd);
CI->eraseFromParent();
AddI->eraseFromParent();
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 *CI, const TargetLowering *TLI) {
BasicBlock *DefBB = CI->getParent();
// Avoid sinking soft-FP comparisons, since this can move them into a loop.
if (TLI && TLI->useSoftFloat() && isa<FCmpInst>(CI))
return false;
// Only insert a cmp in each block once.
DenseMap<BasicBlock*, CmpInst*> InsertedCmps;
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);
// 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();
// 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(CI->getOpcode(), CI->getPredicate(),
CI->getOperand(0), CI->getOperand(1), "", &*InsertPt);
// Propagate the debug info.
InsertedCmp->setDebugLoc(CI->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 (CI->use_empty()) {
CI->eraseFromParent();
MadeChange = true;
}
return MadeChange;
}
static bool OptimizeCmpExpression(CmpInst *CI, const TargetLowering *TLI) {
if (SinkCmpExpression(CI, TLI))
return true;
if (CombineUAddWithOverflow(CI))
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 for and mask 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;
DEBUG(dbgs() << "found 'and' feeding only icmp 0;\n");
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;
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;
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;
TruncInst *TruncI = dyn_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);
// Sink the trunc
BasicBlock::iterator TruncInsertPt = TruncUserBB->getFirstInsertionPt();
TruncInsertPt++;
assert(TruncInsertPt != TruncUserBB->end());
InsertedTrunc = CastInst::Create(TruncI->getOpcode(), InsertedShift,
TruncI->getType(), "", &*TruncInsertPt);
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 recoginze 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 trucate 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);
MadeChange = true;
}
// Replace a use of the shift with a use of the new shift.
TheUse = InsertedShift;
}
// If we removed all uses, nuke the shift.
if (ShiftI->use_empty())
ShiftI->eraseFromParent();
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 (!TLI || !DL)
return false;
// 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->getPrimitiveSizeInBits();
if (Ty->isVectorTy() || SizeInBits > DL->getLargestLegalIntTypeSizeInBits())
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);
Value *Cmp = Builder.CreateICmpEQ(CountZeros->getOperand(0), 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;
}
namespace {
// This class provides helper functions to expand a memcmp library call into an
// inline expansion.
class MemCmpExpansion {
struct ResultBlock {
BasicBlock *BB = nullptr;
PHINode *PhiSrc1 = nullptr;
PHINode *PhiSrc2 = nullptr;
ResultBlock() = default;
};
CallInst *CI;
ResultBlock ResBlock;
unsigned MaxLoadSize;
unsigned NumBlocks;
unsigned NumBlocksNonOneByte;
unsigned NumLoadsPerBlock;
std::vector<BasicBlock *> LoadCmpBlocks;
BasicBlock *EndBlock;
PHINode *PhiRes;
bool IsUsedForZeroCmp;
const DataLayout &DL;
IRBuilder<> Builder;
unsigned calculateNumBlocks(unsigned Size);
void createLoadCmpBlocks();
void createResultBlock();
void setupResultBlockPHINodes();
void setupEndBlockPHINodes();
void emitLoadCompareBlock(unsigned Index, unsigned LoadSize,
unsigned GEPIndex);
Value *getCompareLoadPairs(unsigned Index, unsigned Size,
unsigned &NumBytesProcessed);
void emitLoadCompareBlockMultipleLoads(unsigned Index, unsigned Size,
unsigned &NumBytesProcessed);
void emitLoadCompareByteBlock(unsigned Index, unsigned GEPIndex);
void emitMemCmpResultBlock();
Value *getMemCmpExpansionZeroCase(unsigned Size);
Value *getMemCmpEqZeroOneBlock(unsigned Size);
Value *getMemCmpOneBlock(unsigned Size);
unsigned getLoadSize(unsigned Size);
unsigned getNumLoads(unsigned Size);
public:
MemCmpExpansion(CallInst *CI, uint64_t Size, unsigned MaxLoadSize,
unsigned NumLoadsPerBlock, const DataLayout &DL);
Value *getMemCmpExpansion(uint64_t Size);
};
} // end anonymous namespace
// Initialize the basic block structure required for expansion of memcmp call
// with given maximum load size and memcmp size parameter.
// This structure includes:
// 1. A list of load compare blocks - LoadCmpBlocks.
// 2. An EndBlock, split from original instruction point, which is the block to
// return from.
// 3. ResultBlock, block to branch to for early exit when a
// LoadCmpBlock finds a difference.
MemCmpExpansion::MemCmpExpansion(CallInst *CI, uint64_t Size,
unsigned MaxLoadSize, unsigned LoadsPerBlock,
const DataLayout &TheDataLayout)
: CI(CI), MaxLoadSize(MaxLoadSize), NumLoadsPerBlock(LoadsPerBlock),
DL(TheDataLayout), Builder(CI) {
// A memcmp with zero-comparison with only one block of load and compare does
// not need to set up any extra blocks. This case could be handled in the DAG,
// but since we have all of the machinery to flexibly expand any memcpy here,
// we choose to handle this case too to avoid fragmented lowering.
IsUsedForZeroCmp = isOnlyUsedInZeroEqualityComparison(CI);
NumBlocks = calculateNumBlocks(Size);
if ((!IsUsedForZeroCmp && NumLoadsPerBlock != 1) || NumBlocks != 1) {
BasicBlock *StartBlock = CI->getParent();
EndBlock = StartBlock->splitBasicBlock(CI, "endblock");
setupEndBlockPHINodes();
createResultBlock();
// If return value of memcmp is not used in a zero equality, we need to
// calculate which source was larger. The calculation requires the
// two loaded source values of each load compare block.
// These will be saved in the phi nodes created by setupResultBlockPHINodes.
if (!IsUsedForZeroCmp)
setupResultBlockPHINodes();
// Create the number of required load compare basic blocks.
createLoadCmpBlocks();
// Update the terminator added by splitBasicBlock to branch to the first
// LoadCmpBlock.
StartBlock->getTerminator()->setSuccessor(0, LoadCmpBlocks[0]);
}
Builder.SetCurrentDebugLocation(CI->getDebugLoc());
}
void MemCmpExpansion::createLoadCmpBlocks() {
for (unsigned i = 0; i < NumBlocks; i++) {
BasicBlock *BB = BasicBlock::Create(CI->getContext(), "loadbb",
EndBlock->getParent(), EndBlock);
LoadCmpBlocks.push_back(BB);
}
}
void MemCmpExpansion::createResultBlock() {
ResBlock.BB = BasicBlock::Create(CI->getContext(), "res_block",
EndBlock->getParent(), EndBlock);
}
// This function creates the IR instructions for loading and comparing 1 byte.
// It loads 1 byte from each source of the memcmp parameters with the given
// GEPIndex. It then subtracts the two loaded values and adds this result to the
// final phi node for selecting the memcmp result.
void MemCmpExpansion::emitLoadCompareByteBlock(unsigned Index,
unsigned GEPIndex) {
Value *Source1 = CI->getArgOperand(0);
Value *Source2 = CI->getArgOperand(1);
Builder.SetInsertPoint(LoadCmpBlocks[Index]);
Type *LoadSizeType = Type::getInt8Ty(CI->getContext());
// Cast source to LoadSizeType*.
if (Source1->getType() != LoadSizeType)
Source1 = Builder.CreateBitCast(Source1, LoadSizeType->getPointerTo());
if (Source2->getType() != LoadSizeType)
Source2 = Builder.CreateBitCast(Source2, LoadSizeType->getPointerTo());
// Get the base address using the GEPIndex.
if (GEPIndex != 0) {
Source1 = Builder.CreateGEP(LoadSizeType, Source1,
ConstantInt::get(LoadSizeType, GEPIndex));
Source2 = Builder.CreateGEP(LoadSizeType, Source2,
ConstantInt::get(LoadSizeType, GEPIndex));
}
Value *LoadSrc1 = Builder.CreateLoad(LoadSizeType, Source1);
Value *LoadSrc2 = Builder.CreateLoad(LoadSizeType, Source2);
LoadSrc1 = Builder.CreateZExt(LoadSrc1, Type::getInt32Ty(CI->getContext()));
LoadSrc2 = Builder.CreateZExt(LoadSrc2, Type::getInt32Ty(CI->getContext()));
Value *Diff = Builder.CreateSub(LoadSrc1, LoadSrc2);
PhiRes->addIncoming(Diff, LoadCmpBlocks[Index]);
if (Index < (LoadCmpBlocks.size() - 1)) {
// Early exit branch if difference found to EndBlock. Otherwise, continue to
// next LoadCmpBlock,
Value *Cmp = Builder.CreateICmp(ICmpInst::ICMP_NE, Diff,
ConstantInt::get(Diff->getType(), 0));
BranchInst *CmpBr =
BranchInst::Create(EndBlock, LoadCmpBlocks[Index + 1], Cmp);
Builder.Insert(CmpBr);
} else {
// The last block has an unconditional branch to EndBlock.
BranchInst *CmpBr = BranchInst::Create(EndBlock);
Builder.Insert(CmpBr);
}
}
unsigned MemCmpExpansion::getNumLoads(unsigned Size) {
return (Size / MaxLoadSize) + countPopulation(Size % MaxLoadSize);
}
unsigned MemCmpExpansion::getLoadSize(unsigned Size) {
return MinAlign(PowerOf2Floor(Size), MaxLoadSize);
}
/// Generate an equality comparison for one or more pairs of loaded values.
/// This is used in the case where the memcmp() call is compared equal or not
/// equal to zero.
Value *MemCmpExpansion::getCompareLoadPairs(unsigned Index, unsigned Size,
unsigned &NumBytesProcessed) {
std::vector<Value *> XorList, OrList;
Value *Diff;
unsigned RemainingBytes = Size - NumBytesProcessed;
unsigned NumLoadsRemaining = getNumLoads(RemainingBytes);
unsigned NumLoads = std::min(NumLoadsRemaining, NumLoadsPerBlock);
// For a single-block expansion, start inserting before the memcmp call.
if (LoadCmpBlocks.empty())
Builder.SetInsertPoint(CI);
else
Builder.SetInsertPoint(LoadCmpBlocks[Index]);
Value *Cmp = nullptr;
for (unsigned i = 0; i < NumLoads; ++i) {
unsigned LoadSize = getLoadSize(RemainingBytes);
unsigned GEPIndex = NumBytesProcessed / LoadSize;
NumBytesProcessed += LoadSize;
RemainingBytes -= LoadSize;
Type *LoadSizeType = IntegerType::get(CI->getContext(), LoadSize * 8);
Type *MaxLoadType = IntegerType::get(CI->getContext(), MaxLoadSize * 8);
assert(LoadSize <= MaxLoadSize && "Unexpected load type");
Value *Source1 = CI->getArgOperand(0);
Value *Source2 = CI->getArgOperand(1);
// Cast source to LoadSizeType*.
if (Source1->getType() != LoadSizeType)
Source1 = Builder.CreateBitCast(Source1, LoadSizeType->getPointerTo());
if (Source2->getType() != LoadSizeType)
Source2 = Builder.CreateBitCast(Source2, LoadSizeType->getPointerTo());
// Get the base address using the GEPIndex.
if (GEPIndex != 0) {
Source1 = Builder.CreateGEP(LoadSizeType, Source1,
ConstantInt::get(LoadSizeType, GEPIndex));
Source2 = Builder.CreateGEP(LoadSizeType, Source2,
ConstantInt::get(LoadSizeType, GEPIndex));
}
// Get a constant or load a value for each source address.
Value *LoadSrc1 = nullptr;
if (auto *Source1C = dyn_cast<Constant>(Source1))
LoadSrc1 = ConstantFoldLoadFromConstPtr(Source1C, LoadSizeType, DL);
if (!LoadSrc1)
LoadSrc1 = Builder.CreateLoad(LoadSizeType, Source1);
Value *LoadSrc2 = nullptr;
if (auto *Source2C = dyn_cast<Constant>(Source2))
LoadSrc2 = ConstantFoldLoadFromConstPtr(Source2C, LoadSizeType, DL);
if (!LoadSrc2)
LoadSrc2 = Builder.CreateLoad(LoadSizeType, Source2);
if (NumLoads != 1) {
if (LoadSizeType != MaxLoadType) {
LoadSrc1 = Builder.CreateZExt(LoadSrc1, MaxLoadType);
LoadSrc2 = Builder.CreateZExt(LoadSrc2, MaxLoadType);
}
// If we have multiple loads per block, we need to generate a composite
// comparison using xor+or.
Diff = Builder.CreateXor(LoadSrc1, LoadSrc2);
Diff = Builder.CreateZExt(Diff, MaxLoadType);
XorList.push_back(Diff);
} else {
// If there's only one load per block, we just compare the loaded values.
Cmp = Builder.CreateICmpNE(LoadSrc1, LoadSrc2);
}
}
auto pairWiseOr = [&](std::vector<Value *> &InList) -> std::vector<Value *> {
std::vector<Value *> OutList;
for (unsigned i = 0; i < InList.size() - 1; i = i + 2) {
Value *Or = Builder.CreateOr(InList[i], InList[i + 1]);
OutList.push_back(Or);
}
if (InList.size() % 2 != 0)
OutList.push_back(InList.back());
return OutList;
};
if (!Cmp) {
// Pairwise OR the XOR results.
OrList = pairWiseOr(XorList);
// Pairwise OR the OR results until one result left.
while (OrList.size() != 1) {
OrList = pairWiseOr(OrList);
}
Cmp = Builder.CreateICmpNE(OrList[0], ConstantInt::get(Diff->getType(), 0));
}
return Cmp;
}
void MemCmpExpansion::emitLoadCompareBlockMultipleLoads(
unsigned Index, unsigned Size, unsigned &NumBytesProcessed) {
Value *Cmp = getCompareLoadPairs(Index, Size, NumBytesProcessed);
BasicBlock *NextBB = (Index == (LoadCmpBlocks.size() - 1))
? EndBlock
: LoadCmpBlocks[Index + 1];
// Early exit branch if difference found to ResultBlock. Otherwise,
// continue to next LoadCmpBlock or EndBlock.
BranchInst *CmpBr = BranchInst::Create(ResBlock.BB, NextBB, Cmp);
Builder.Insert(CmpBr);
// Add a phi edge for the last LoadCmpBlock to Endblock with a value of 0
// since early exit to ResultBlock was not taken (no difference was found in
// any of the bytes).
if (Index == LoadCmpBlocks.size() - 1) {
Value *Zero = ConstantInt::get(Type::getInt32Ty(CI->getContext()), 0);
PhiRes->addIncoming(Zero, LoadCmpBlocks[Index]);
}
}
// This function creates the IR intructions for loading and comparing using the
// given LoadSize. It loads the number of bytes specified by LoadSize from each
// source of the memcmp parameters. It then does a subtract to see if there was
// a difference in the loaded values. If a difference is found, it branches
// with an early exit to the ResultBlock for calculating which source was
// larger. Otherwise, it falls through to the either the next LoadCmpBlock or
// the EndBlock if this is the last LoadCmpBlock. Loading 1 byte is handled with
// a special case through emitLoadCompareByteBlock. The special handling can
// simply subtract the loaded values and add it to the result phi node.
void MemCmpExpansion::emitLoadCompareBlock(unsigned Index, unsigned LoadSize,
unsigned GEPIndex) {
if (LoadSize == 1) {
MemCmpExpansion::emitLoadCompareByteBlock(Index, GEPIndex);
return;
}
Type *LoadSizeType = IntegerType::get(CI->getContext(), LoadSize * 8);
Type *MaxLoadType = IntegerType::get(CI->getContext(), MaxLoadSize * 8);
assert(LoadSize <= MaxLoadSize && "Unexpected load type");
Value *Source1 = CI->getArgOperand(0);
Value *Source2 = CI->getArgOperand(1);
Builder.SetInsertPoint(LoadCmpBlocks[Index]);
// Cast source to LoadSizeType*.
if (Source1->getType() != LoadSizeType)
Source1 = Builder.CreateBitCast(Source1, LoadSizeType->getPointerTo());
if (Source2->getType() != LoadSizeType)
Source2 = Builder.CreateBitCast(Source2, LoadSizeType->getPointerTo());
// Get the base address using the GEPIndex.
if (GEPIndex != 0) {
Source1 = Builder.CreateGEP(LoadSizeType, Source1,
ConstantInt::get(LoadSizeType, GEPIndex));
Source2 = Builder.CreateGEP(LoadSizeType, Source2,
ConstantInt::get(LoadSizeType, GEPIndex));
}
// Load LoadSizeType from the base address.
Value *LoadSrc1 = Builder.CreateLoad(LoadSizeType, Source1);
Value *LoadSrc2 = Builder.CreateLoad(LoadSizeType, Source2);
if (DL.isLittleEndian()) {
Function *Bswap = Intrinsic::getDeclaration(CI->getModule(),
Intrinsic::bswap, LoadSizeType);
LoadSrc1 = Builder.CreateCall(Bswap, LoadSrc1);
LoadSrc2 = Builder.CreateCall(Bswap, LoadSrc2);
}
if (LoadSizeType != MaxLoadType) {
LoadSrc1 = Builder.CreateZExt(LoadSrc1, MaxLoadType);
LoadSrc2 = Builder.CreateZExt(LoadSrc2, MaxLoadType);
}
// Add the loaded values to the phi nodes for calculating memcmp result only
// if result is not used in a zero equality.
if (!IsUsedForZeroCmp) {
ResBlock.PhiSrc1->addIncoming(LoadSrc1, LoadCmpBlocks[Index]);
ResBlock.PhiSrc2->addIncoming(LoadSrc2, LoadCmpBlocks[Index]);
}
Value *Cmp = Builder.CreateICmp(ICmpInst::ICMP_EQ, LoadSrc1, LoadSrc2);
BasicBlock *NextBB = (Index == (LoadCmpBlocks.size() - 1))
? EndBlock
: LoadCmpBlocks[Index + 1];
// Early exit branch if difference found to ResultBlock. Otherwise, continue
// to next LoadCmpBlock or EndBlock.
BranchInst *CmpBr = BranchInst::Create(NextBB, ResBlock.BB, Cmp);
Builder.Insert(CmpBr);
// Add a phi edge for the last LoadCmpBlock to Endblock with a value of 0
// since early exit to ResultBlock was not taken (no difference was found in
// any of the bytes).
if (Index == LoadCmpBlocks.size() - 1) {
Value *Zero = ConstantInt::get(Type::getInt32Ty(CI->getContext()), 0);
PhiRes->addIncoming(Zero, LoadCmpBlocks[Index]);
}
}
// This function populates the ResultBlock with a sequence to calculate the
// memcmp result. It compares the two loaded source values and returns -1 if
// src1 < src2 and 1 if src1 > src2.
void MemCmpExpansion::emitMemCmpResultBlock() {
// Special case: if memcmp result is used in a zero equality, result does not
// need to be calculated and can simply return 1.
if (IsUsedForZeroCmp) {
BasicBlock::iterator InsertPt = ResBlock.BB->getFirstInsertionPt();
Builder.SetInsertPoint(ResBlock.BB, InsertPt);
Value *Res = ConstantInt::get(Type::getInt32Ty(CI->getContext()), 1);
PhiRes->addIncoming(Res, ResBlock.BB);
BranchInst *NewBr = BranchInst::Create(EndBlock);
Builder.Insert(NewBr);
return;
}
BasicBlock::iterator InsertPt = ResBlock.BB->getFirstInsertionPt();
Builder.SetInsertPoint(ResBlock.BB, InsertPt);
Value *Cmp = Builder.CreateICmp(ICmpInst::ICMP_ULT, ResBlock.PhiSrc1,
ResBlock.PhiSrc2);
Value *Res =
Builder.CreateSelect(Cmp, ConstantInt::get(Builder.getInt32Ty(), -1),
ConstantInt::get(Builder.getInt32Ty(), 1));
BranchInst *NewBr = BranchInst::Create(EndBlock);
Builder.Insert(NewBr);
PhiRes->addIncoming(Res, ResBlock.BB);
}
unsigned MemCmpExpansion::calculateNumBlocks(unsigned Size) {
unsigned NumBlocks = 0;
bool HaveOneByteLoad = false;
unsigned RemainingSize = Size;
unsigned LoadSize = MaxLoadSize;
while (RemainingSize) {
if (LoadSize == 1)
HaveOneByteLoad = true;
NumBlocks += RemainingSize / LoadSize;
RemainingSize = RemainingSize % LoadSize;
LoadSize = LoadSize / 2;
}
NumBlocksNonOneByte = HaveOneByteLoad ? (NumBlocks - 1) : NumBlocks;
if (IsUsedForZeroCmp)
NumBlocks = NumBlocks / NumLoadsPerBlock +
(NumBlocks % NumLoadsPerBlock != 0 ? 1 : 0);
return NumBlocks;
}
void MemCmpExpansion::setupResultBlockPHINodes() {
Type *MaxLoadType = IntegerType::get(CI->getContext(), MaxLoadSize * 8);
Builder.SetInsertPoint(ResBlock.BB);
ResBlock.PhiSrc1 =
Builder.CreatePHI(MaxLoadType, NumBlocksNonOneByte, "phi.src1");
ResBlock.PhiSrc2 =
Builder.CreatePHI(MaxLoadType, NumBlocksNonOneByte, "phi.src2");
}
void MemCmpExpansion::setupEndBlockPHINodes() {
Builder.SetInsertPoint(&EndBlock->front());
PhiRes = Builder.CreatePHI(Type::getInt32Ty(CI->getContext()), 2, "phi.res");
}
Value *MemCmpExpansion::getMemCmpExpansionZeroCase(unsigned Size) {
unsigned NumBytesProcessed = 0;
// This loop populates each of the LoadCmpBlocks with the IR sequence to
// handle multiple loads per block.
for (unsigned i = 0; i < NumBlocks; ++i)
emitLoadCompareBlockMultipleLoads(i, Size, NumBytesProcessed);
emitMemCmpResultBlock();
return PhiRes;
}
/// A memcmp expansion that compares equality with 0 and only has one block of
/// load and compare can bypass the compare, branch, and phi IR that is required
/// in the general case.
Value *MemCmpExpansion::getMemCmpEqZeroOneBlock(unsigned Size) {
unsigned NumBytesProcessed = 0;
Value *Cmp = getCompareLoadPairs(0, Size, NumBytesProcessed);
return Builder.CreateZExt(Cmp, Type::getInt32Ty(CI->getContext()));
}
/// A memcmp expansion that only has one block of load and compare can bypass
/// the compare, branch, and phi IR that is required in the general case.
Value *MemCmpExpansion::getMemCmpOneBlock(unsigned Size) {
assert(NumLoadsPerBlock == 1 && "Only handles one load pair per block");
Type *LoadSizeType = IntegerType::get(CI->getContext(), Size * 8);
Value *Source1 = CI->getArgOperand(0);
Value *Source2 = CI->getArgOperand(1);
// Cast source to LoadSizeType*.
if (Source1->getType() != LoadSizeType)
Source1 = Builder.CreateBitCast(Source1, LoadSizeType->getPointerTo());
if (Source2->getType() != LoadSizeType)
Source2 = Builder.CreateBitCast(Source2, LoadSizeType->getPointerTo());
// Load LoadSizeType from the base address.
Value *LoadSrc1 = Builder.CreateLoad(LoadSizeType, Source1);
Value *LoadSrc2 = Builder.CreateLoad(LoadSizeType, Source2);
if (DL.isLittleEndian() && Size != 1) {
Function *Bswap = Intrinsic::getDeclaration(CI->getModule(),
Intrinsic::bswap, LoadSizeType);
LoadSrc1 = Builder.CreateCall(Bswap, LoadSrc1);
LoadSrc2 = Builder.CreateCall(Bswap, LoadSrc2);
}
if (Size < 4) {
// The i8 and i16 cases don't need compares. We zext the loaded values and
// subtract them to get the suitable negative, zero, or positive i32 result.
LoadSrc1 = Builder.CreateZExt(LoadSrc1, Builder.getInt32Ty());
LoadSrc2 = Builder.CreateZExt(LoadSrc2, Builder.getInt32Ty());
return Builder.CreateSub(LoadSrc1, LoadSrc2);
}
// The result of memcmp is negative, zero, or positive, so produce that by
// subtracting 2 extended compare bits: sub (ugt, ult).
// If a target prefers to use selects to get -1/0/1, they should be able
// to transform this later. The inverse transform (going from selects to math)
// may not be possible in the DAG because the selects got converted into
// branches before we got there.
Value *CmpUGT = Builder.CreateICmpUGT(LoadSrc1, LoadSrc2);
Value *CmpULT = Builder.CreateICmpULT(LoadSrc1, LoadSrc2);
Value *ZextUGT = Builder.CreateZExt(CmpUGT, Builder.getInt32Ty());
Value *ZextULT = Builder.CreateZExt(CmpULT, Builder.getInt32Ty());
return Builder.CreateSub(ZextUGT, ZextULT);
}
// This function expands the memcmp call into an inline expansion and returns
// the memcmp result.
Value *MemCmpExpansion::getMemCmpExpansion(uint64_t Size) {
if (IsUsedForZeroCmp)
return NumBlocks == 1 ? getMemCmpEqZeroOneBlock(Size) :
getMemCmpExpansionZeroCase(Size);
// TODO: Handle more than one load pair per block in getMemCmpOneBlock().
if (NumBlocks == 1 && NumLoadsPerBlock == 1)
return getMemCmpOneBlock(Size);
// This loop calls emitLoadCompareBlock for comparing Size bytes of the two
// memcmp sources. It starts with loading using the maximum load size set by
// the target. It processes any remaining bytes using a load size which is the
// next smallest power of 2.
unsigned LoadSize = MaxLoadSize;
unsigned NumBytesToBeProcessed = Size;
unsigned Index = 0;
while (NumBytesToBeProcessed) {
// Calculate how many blocks we can create with the current load size.
unsigned NumBlocks = NumBytesToBeProcessed / LoadSize;
unsigned GEPIndex = (Size - NumBytesToBeProcessed) / LoadSize;
NumBytesToBeProcessed = NumBytesToBeProcessed % LoadSize;
// For each NumBlocks, populate the instruction sequence for loading and
// comparing LoadSize bytes.
while (NumBlocks--) {
emitLoadCompareBlock(Index, LoadSize, GEPIndex);
Index++;
GEPIndex++;
}
// Get the next LoadSize to use.
LoadSize = LoadSize / 2;
}
emitMemCmpResultBlock();
return PhiRes;
}
// This function checks to see if an expansion of memcmp can be generated.
// It checks for constant compare size that is less than the max inline size.
// If an expansion cannot occur, returns false to leave as a library call.
// Otherwise, the library call is replaced with a new IR instruction sequence.
/// We want to transform:
/// %call = call signext i32 @memcmp(i8* %0, i8* %1, i64 15)
/// To:
/// loadbb:
/// %0 = bitcast i32* %buffer2 to i8*
/// %1 = bitcast i32* %buffer1 to i8*
/// %2 = bitcast i8* %1 to i64*
/// %3 = bitcast i8* %0 to i64*
/// %4 = load i64, i64* %2
/// %5 = load i64, i64* %3
/// %6 = call i64 @llvm.bswap.i64(i64 %4)
/// %7 = call i64 @llvm.bswap.i64(i64 %5)
/// %8 = sub i64 %6, %7
/// %9 = icmp ne i64 %8, 0
/// br i1 %9, label %res_block, label %loadbb1
/// res_block: ; preds = %loadbb2,
/// %loadbb1, %loadbb
/// %phi.src1 = phi i64 [ %6, %loadbb ], [ %22, %loadbb1 ], [ %36, %loadbb2 ]
/// %phi.src2 = phi i64 [ %7, %loadbb ], [ %23, %loadbb1 ], [ %37, %loadbb2 ]
/// %10 = icmp ult i64 %phi.src1, %phi.src2
/// %11 = select i1 %10, i32 -1, i32 1
/// br label %endblock
/// loadbb1: ; preds = %loadbb
/// %12 = bitcast i32* %buffer2 to i8*
/// %13 = bitcast i32* %buffer1 to i8*
/// %14 = bitcast i8* %13 to i32*
/// %15 = bitcast i8* %12 to i32*
/// %16 = getelementptr i32, i32* %14, i32 2
/// %17 = getelementptr i32, i32* %15, i32 2
/// %18 = load i32, i32* %16
/// %19 = load i32, i32* %17
/// %20 = call i32 @llvm.bswap.i32(i32 %18)
/// %21 = call i32 @llvm.bswap.i32(i32 %19)
/// %22 = zext i32 %20 to i64
/// %23 = zext i32 %21 to i64
/// %24 = sub i64 %22, %23
/// %25 = icmp ne i64 %24, 0
/// br i1 %25, label %res_block, label %loadbb2
/// loadbb2: ; preds = %loadbb1
/// %26 = bitcast i32* %buffer2 to i8*
/// %27 = bitcast i32* %buffer1 to i8*
/// %28 = bitcast i8* %27 to i16*
/// %29 = bitcast i8* %26 to i16*
/// %30 = getelementptr i16, i16* %28, i16 6
/// %31 = getelementptr i16, i16* %29, i16 6
/// %32 = load i16, i16* %30
/// %33 = load i16, i16* %31
/// %34 = call i16 @llvm.bswap.i16(i16 %32)
/// %35 = call i16 @llvm.bswap.i16(i16 %33)
/// %36 = zext i16 %34 to i64
/// %37 = zext i16 %35 to i64
/// %38 = sub i64 %36, %37
/// %39 = icmp ne i64 %38, 0
/// br i1 %39, label %res_block, label %loadbb3
/// loadbb3: ; preds = %loadbb2
/// %40 = bitcast i32* %buffer2 to i8*
/// %41 = bitcast i32* %buffer1 to i8*
/// %42 = getelementptr i8, i8* %41, i8 14
/// %43 = getelementptr i8, i8* %40, i8 14
/// %44 = load i8, i8* %42
/// %45 = load i8, i8* %43
/// %46 = zext i8 %44 to i32
/// %47 = zext i8 %45 to i32
/// %48 = sub i32 %46, %47
/// br label %endblock
/// endblock: ; preds = %res_block,
/// %loadbb3
/// %phi.res = phi i32 [ %48, %loadbb3 ], [ %11, %res_block ]
/// ret i32 %phi.res
static bool expandMemCmp(CallInst *CI, const TargetTransformInfo *TTI,
const TargetLowering *TLI, const DataLayout *DL) {
NumMemCmpCalls++;
// TTI call to check if target would like to expand memcmp. Also, get the
// MaxLoadSize.
unsigned MaxLoadSize;
if (!TTI->expandMemCmp(CI, MaxLoadSize))
return false;
// Early exit from expansion if -Oz.
if (CI->getFunction()->optForMinSize())
return false;
// Early exit from expansion if size is not a constant.
ConstantInt *SizeCast = dyn_cast<ConstantInt>(CI->getArgOperand(2));
if (!SizeCast) {
NumMemCmpNotConstant++;
return false;
}
// Scale the max size down if the target can load more bytes than we need.
uint64_t SizeVal = SizeCast->getZExtValue();
if (MaxLoadSize > SizeVal)
MaxLoadSize = 1 << SizeCast->getValue().logBase2();
// Calculate how many load pairs are needed for the constant size.
unsigned NumLoads = 0;
unsigned RemainingSize = SizeVal;
unsigned LoadSize = MaxLoadSize;
while (RemainingSize) {
NumLoads += RemainingSize / LoadSize;
RemainingSize = RemainingSize % LoadSize;
LoadSize = LoadSize / 2;
}
// Don't expand if this will require more loads than desired by the target.
if (NumLoads > TLI->getMaxExpandSizeMemcmp(CI->getFunction()->optForSize())) {
NumMemCmpGreaterThanMax++;
return false;
}
NumMemCmpInlined++;
// MemCmpHelper object creates and sets up basic blocks required for
// expanding memcmp with size SizeVal.
unsigned NumLoadsPerBlock = MemCmpNumLoadsPerBlock;
MemCmpExpansion MemCmpHelper(CI, SizeVal, MaxLoadSize, NumLoadsPerBlock, *DL);
Value *Res = MemCmpHelper.getMemCmpExpansion(SizeVal);
// Replace call with result of expansion and erase call.
CI->replaceAllUsesWith(Res);
CI->eraseFromParent();
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 (TLI && isa<InlineAsm>(CI->getCalledValue())) {
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 && TLI->shouldAlignPointerArgs(CI, MinSize, PrefAlign)) {
for (auto &Arg : CI->arg_operands()) {
// 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->getPointerSizeInBits(
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(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(PrefAlign);
}
// If this is a memcpy (or similar) then we may be able to improve the
// alignment
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(CI)) {
unsigned Align = getKnownAlignment(MI->getDest(), *DL);
if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI))
Align = std::min(Align, getKnownAlignment(MTI->getSource(), *DL));
if (Align > MI->getAlignment())
MI->setAlignment(ConstantInt::get(MI->getAlignmentType(), Align));
}
}
// 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 (!OptSize && CI->hasFnAttr(Attribute::Cold))
for (auto &Arg : CI->arg_operands()) {
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::objectsize: {
// Lower all uses of llvm.objectsize.*
ConstantInt *RetVal =
lowerObjectSizeCall(II, *DL, TLInfo, /*MustSucceed=*/true);
// Substituting this 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);
replaceAndRecursivelySimplify(CI, RetVal, TLInfo, nullptr);
// If the iterator instruction was recursively deleted, start over at the
// start of the block.
if (IterHandle != CurValue) {
CurInstIterator = BB->begin();
SunkAddrs.clear();
}
return true;
}
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::invariant_group_barrier:
II->replaceAllUsesWith(II->getArgOperand(0));
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);
}
if (TLI) {
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);
if (Value *V = Simplifier.optimizeCall(CI)) {
CI->replaceAllUsesWith(V);
CI->eraseFromParent();
return true;
}
LibFunc Func;
if (TLInfo->getLibFunc(ImmutableCallSite(CI), Func) &&
Func == LibFunc_memcmp && expandMemCmp(CI, TTI, TLI, DL)) {
ModifiedDT = true;
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) {
if (!TLI)
return false;
ReturnInst *RetI = dyn_cast<ReturnInst>(BB->getTerminator());
if (!RetI)
return false;
PHINode *PN = nullptr;
BitCastInst *BCI = nullptr;
Value *V = RetI->getReturnValue();
if (V) {
BCI = dyn_cast<BitCastInst>(V);
if (BCI)
V = BCI->getOperand(0);
PN = dyn_cast<PHINode>(V);
if (!PN)
return false;
}
if (PN && PN->getParent() != BB)
return false;
// Make sure there are no instructions between the PHI and return, or that the
// return is the first instruction in the block.
if (PN) {
BasicBlock::iterator BI = BB->begin();
do { ++BI; } while (isa<DbgInfoIntrinsic>(BI));
if (&*BI == BCI)
// Also skip over the bitcast.
++BI;
if (&*BI != RetI)
return false;
} else {
BasicBlock::iterator BI = BB->begin();
while (isa<DbgInfoIntrinsic>(BI)) ++BI;
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<CallInst*, 4> TailCalls;
if (PN) {
for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) {
CallInst *CI = dyn_cast<CallInst>(PN->getIncomingValue(I));
// Make sure the phi value is indeed produced by the tail call.
if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) &&
TLI->mayBeEmittedAsTailCall(CI) &&
attributesPermitTailCall(F, CI, RetI, *TLI))
TailCalls.push_back(CI);
}
} else {
SmallPtrSet<BasicBlock*, 4> VisitedBBs;
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
if (!VisitedBBs.insert(*PI).second)
continue;
BasicBlock::InstListType &InstList = (*PI)->getInstList();
BasicBlock::InstListType::reverse_iterator RI = InstList.rbegin();
BasicBlock::InstListType::reverse_iterator RE = InstList.rend();
do { ++RI; } while (RI != RE && isa<DbgInfoIntrinsic>(&*RI));
if (RI == RE)
continue;
CallInst *CI = dyn_cast<CallInst>(&*RI);
if (CI && CI->use_empty() && TLI->mayBeEmittedAsTailCall(CI) &&
attributesPermitTailCall(F, CI, RetI, *TLI))
TailCalls.push_back(CI);
}
}
bool Changed = false;
for (unsigned i = 0, e = TailCalls.size(); i != e; ++i) {
CallInst *CI = TailCalls[i];
CallSite CS(CI);
// Conservatively require the attributes of the call to match those of the
// return. Ignore noalias because it doesn't affect the call sequence.
AttributeList CalleeAttrs = CS.getAttributes();
if (AttrBuilder(CalleeAttrs, AttributeList::ReturnIndex)
.removeAttribute(Attribute::NoAlias) !=
AttrBuilder(CalleeAttrs, AttributeList::ReturnIndex)
.removeAttribute(Attribute::NoAlias))
continue;
// Make sure the call instruction is followed by an unconditional branch to
// the return block.
BasicBlock *CallBB = CI->getParent();
BranchInst *BI = dyn_cast<BranchInst>(CallBB->getTerminator());
if (!BI || !BI->isUnconditional() || BI->getSuccessor(0) != BB)
continue;
// Duplicate the return into CallBB.
(void)FoldReturnIntoUncondBranch(RetI, BB, CallBB);
ModifiedDT = Changed = true;
++NumRetsDup;
}
// If we eliminated all predecessors of the block, delete the block now.
if (Changed && !BB->hasAddressTaken() && pred_begin(BB) == pred_end(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;
ExtAddrMode() = default;
void print(raw_ostream &OS) const;
void dump() const;
bool operator==(const ExtAddrMode& O) const {
return (BaseReg == O.BaseReg) && (ScaledReg == O.ScaledReg) &&
(BaseGV == O.BaseGV) && (BaseOffs == O.BaseOffs) &&
(HasBaseReg == O.HasBaseReg) && (Scale == O.Scale);
}
};
} // 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 (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 {
/// \brief 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.
class TypePromotionTransaction {
/// \brief 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:
/// \brief Constructor of the action.
/// The constructor performs the related action on the IR.
TypePromotionAction(Instruction *Inst) : Inst(Inst) {}
virtual ~TypePromotionAction() = default;
/// \brief 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;
/// \brief 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.
}
};
/// \brief 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 instructon: PrevInst is used.
union {
Instruction *PrevInst;
BasicBlock *BB;
} Point;
/// Remember whether or not the instruction had a previous instruction.
bool HasPrevInstruction;
public:
/// \brief 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();
}
/// \brief 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);
}
}
};
/// \brief Move an instruction before another.
class InstructionMoveBefore : public TypePromotionAction {
/// Original position of the instruction.
InsertionHandler Position;
public:
/// \brief Move \p Inst before \p Before.
InstructionMoveBefore(Instruction *Inst, Instruction *Before)
: TypePromotionAction(Inst), Position(Inst) {
DEBUG(dbgs() << "Do: move: " << *Inst << "\nbefore: " << *Before << "\n");
Inst->moveBefore(Before);
}
/// \brief Move the instruction back to its original position.
void undo() override {
DEBUG(dbgs() << "Undo: moveBefore: " << *Inst << "\n");
Position.insert(Inst);
}
};
/// \brief 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:
/// \brief Set \p Idx operand of \p Inst with \p NewVal.
OperandSetter(Instruction *Inst, unsigned Idx, Value *NewVal)
: TypePromotionAction(Inst), Idx(Idx) {
DEBUG(dbgs() << "Do: setOperand: " << Idx << "\n"
<< "for:" << *Inst << "\n"
<< "with:" << *NewVal << "\n");
Origin = Inst->getOperand(Idx);
Inst->setOperand(Idx, NewVal);
}
/// \brief Restore the original value of the instruction.
void undo() override {
DEBUG(dbgs() << "Undo: setOperand:" << Idx << "\n"
<< "for: " << *Inst << "\n"
<< "with: " << *Origin << "\n");
Inst->setOperand(Idx, Origin);
}
};
/// \brief 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:
/// \brief Remove \p Inst from the uses of the operands of \p Inst.
OperandsHider(Instruction *Inst) : TypePromotionAction(Inst) {
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()));
}
}
/// \brief Restore the original list of uses.
void undo() override {
DEBUG(dbgs() << "Undo: OperandsHider: " << *Inst << "\n");
for (unsigned It = 0, EndIt = OriginalValues.size(); It != EndIt; ++It)
Inst->setOperand(It, OriginalValues[It]);
}
};
/// \brief Build a truncate instruction.
class TruncBuilder : public TypePromotionAction {
Value *Val;
public:
/// \brief 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);
Val = Builder.CreateTrunc(Opnd, Ty, "promoted");
DEBUG(dbgs() << "Do: TruncBuilder: " << *Val << "\n");
}
/// \brief Get the built value.
Value *getBuiltValue() { return Val; }
/// \brief Remove the built instruction.
void undo() override {
DEBUG(dbgs() << "Undo: TruncBuilder: " << *Val << "\n");
if (Instruction *IVal = dyn_cast<Instruction>(Val))
IVal->eraseFromParent();
}
};
/// \brief Build a sign extension instruction.
class SExtBuilder : public TypePromotionAction {
Value *Val;
public:
/// \brief 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");
DEBUG(dbgs() << "Do: SExtBuilder: " << *Val << "\n");
}
/// \brief Get the built value.
Value *getBuiltValue() { return Val; }
/// \brief Remove the built instruction.
void undo() override {
DEBUG(dbgs() << "Undo: SExtBuilder: " << *Val << "\n");
if (Instruction *IVal = dyn_cast<Instruction>(Val))
IVal->eraseFromParent();
}
};
/// \brief Build a zero extension instruction.
class ZExtBuilder : public TypePromotionAction {
Value *Val;
public:
/// \brief 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);
Val = Builder.CreateZExt(Opnd, Ty, "promoted");
DEBUG(dbgs() << "Do: ZExtBuilder: " << *Val << "\n");
}
/// \brief Get the built value.
Value *getBuiltValue() { return Val; }
/// \brief Remove the built instruction.
void undo() override {
DEBUG(dbgs() << "Undo: ZExtBuilder: " << *Val << "\n");
if (Instruction *IVal = dyn_cast<Instruction>(Val))
IVal->eraseFromParent();
}
};
/// \brief Mutate an instruction to another type.
class TypeMutator : public TypePromotionAction {
/// Record the original type.
Type *OrigTy;
public:
/// \brief Mutate the type of \p Inst into \p NewTy.
TypeMutator(Instruction *Inst, Type *NewTy)
: TypePromotionAction(Inst), OrigTy(Inst->getType()) {
DEBUG(dbgs() << "Do: MutateType: " << *Inst << " with " << *NewTy
<< "\n");
Inst->mutateType(NewTy);
}
/// \brief Mutate the instruction back to its original type.
void undo() override {
DEBUG(dbgs() << "Undo: MutateType: " << *Inst << " with " << *OrigTy
<< "\n");
Inst->mutateType(OrigTy);
}
};
/// \brief 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;
using use_iterator = SmallVectorImpl<InstructionAndIdx>::iterator;
public:
/// \brief Replace all the use of \p Inst by \p New.
UsesReplacer(Instruction *Inst, Value *New) : TypePromotionAction(Inst) {
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()));
}
// Now, we can replace the uses.
Inst->replaceAllUsesWith(New);
}
/// \brief Reassign the original uses of Inst to Inst.
void undo() override {
DEBUG(dbgs() << "Undo: UsersReplacer: " << *Inst << "\n");
for (use_iterator UseIt = OriginalUses.begin(),
EndIt = OriginalUses.end();
UseIt != EndIt; ++UseIt) {
UseIt->Inst->setOperand(UseIt->Idx, Inst);
}
}
};
/// \brief 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:
/// \brief Remove all reference of \p Inst and optinally 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);
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; }
/// \brief Resurrect the instruction and reassign it to the proper uses if
/// new value was provided when build this action.
void undo() override {
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.
void 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(llvm::make_unique<TypePromotionTransaction::OperandSetter>(
Inst, Idx, NewVal));
}
void TypePromotionTransaction::eraseInstruction(Instruction *Inst,
Value *NewVal) {
Actions.push_back(
llvm::make_unique<TypePromotionTransaction::InstructionRemover>(
Inst, RemovedInsts, NewVal));
}
void TypePromotionTransaction::replaceAllUsesWith(Instruction *Inst,
Value *New) {
Actions.push_back(
llvm::make_unique<TypePromotionTransaction::UsesReplacer>(Inst, New));
}
void TypePromotionTransaction::mutateType(Instruction *Inst, Type *NewTy) {
Actions.push_back(
llvm::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(
llvm::make_unique<TypePromotionTransaction::InstructionMoveBefore>(
Inst, Before));
}
TypePromotionTransaction::ConstRestorationPt
TypePromotionTransaction::getRestorationPoint() const {
return !Actions.empty() ? Actions.back().get() : nullptr;
}
void TypePromotionTransaction::commit() {
for (CommitPt It = Actions.begin(), EndIt = Actions.end(); It != EndIt;
++It)
(*It)->commit();
Actions.clear();
}
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 {
/// \brief 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;
/// 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;
/// This is set to true when we should not do profitability checks.
/// When true, IsProfitableToFoldIntoAddressingMode always returns true.
bool IgnoreProfitability;
AddressingModeMatcher(SmallVectorImpl<Instruction *> &AMI,
const TargetLowering &TLI,
const TargetRegisterInfo &TRI,
Type *AT, unsigned AS,
Instruction *MI, ExtAddrMode &AM,
const SetOfInstrs &InsertedInsts,
InstrToOrigTy &PromotedInsts,
TypePromotionTransaction &TPT)
: AddrModeInsts(AMI), TLI(TLI), TRI(TRI),
DL(MI->getModule()->getDataLayout()), AccessTy(AT), AddrSpace(AS),
MemoryInst(MI), AddrMode(AM), InsertedInsts(InsertedInsts),
PromotedInsts(PromotedInsts), TPT(TPT) {
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 TargetRegisterInfo &TRI,
const SetOfInstrs &InsertedInsts,
InstrToOrigTy &PromotedInsts,
TypePromotionTransaction &TPT) {
ExtAddrMode Result;
bool Success = AddressingModeMatcher(AddrModeInsts, TLI, TRI,
AccessTy, AS,
MemoryInst, Result, InsertedInsts,
PromotedInsts, TPT).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 *V, unsigned Depth);
bool matchOperationAddr(User *Operation, 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;
};
} // 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.
ConstantInt *CI = nullptr; Value *AddLHS = nullptr;
if (isa<Instruction>(ScaleReg) && // not a constant expr.
match(ScaleReg, m_Add(m_Value(AddLHS), m_ConstantInt(CI)))) {
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;
}
}
// Otherwise, not (x+c)*scale, 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()->isPointerTy() || I->getType()->isIntegerTy();
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;
}
}
/// \brief 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 {
/// \brief Hepler class to perform type promotion.
class TypePromotionHelper {
/// \brief 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);
/// \brief 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);
}
/// \brief 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);
/// \brief 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);
/// \brief Given a sign/zero extend instruction \p Ext, return the approriate
/// 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.
const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(Inst);
if (BinOp && isa<OverflowingBinaryOperator>(BinOp) &&
((!IsSExt && BinOp->hasNoUnsignedWrap()) ||
(IsSExt && BinOp->hasNoSignedWrap())))
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;
InstrToOrigTy::const_iterator It = PromotedInsts.find(Opnd);
if (It != PromotedInsts.end() && It->second.getInt() == IsSExt)
OpndType = It->second.getPointer();
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.
PromotedInsts.insert(std::pair<Instruction *, TypeIsSExt>(
ExtOpnd, TypeIsSExt(ExtOpnd->getType(), IsSExt)));
// Step #1.
TPT.mutateType(ExtOpnd, Ext->getType());
// Step #2.
TPT.replaceAllUsesWith(Ext, ExtOpnd);
// Step #3.
Instruction *ExtForOpnd = Ext;
DEBUG(dbgs() << "Propagate Ext to operands\n");
for (int OpIdx = 0, EndOpIdx = ExtOpnd->getNumOperands(); OpIdx != EndOpIdx;
++OpIdx) {
DEBUG(dbgs() << "Operand:\n" << *(ExtOpnd->getOperand(OpIdx)) << '\n');
if (ExtOpnd->getOperand(OpIdx)->getType() == Ext->getType() ||
!shouldExtOperand(ExtOpnd, OpIdx)) {
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)) {
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)) {
DEBUG(dbgs() << "Statically extend\n");
TPT.setOperand(ExtOpnd, OpIdx, UndefValue::get(Ext->getType()));
continue;
}
// Otherwise we have to explicity sign extend the operand.
// Check if Ext was reused to extend an operand.
if (!ExtForOpnd) {
// If yes, create a new one.
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) {
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 {
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()->isPointerTy() ||
AddrInst->getOperand(0)->getType()->isIntegerTy()) &&
// 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.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();
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.
ConstantInt *RHS = dyn_cast<ConstantInt>(AddrInst->getOperand(1));
if (!RHS)
return false;
int64_t Scale = RHS->getSExtValue();
if (Opcode == Instruction::Shl)
Scale = 1LL << Scale;
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 {
uint64_t TypeSize = DL.getTypeAllocSize(GTI.getIndexedType());
if (ConstantInt *CI = dyn_cast<ConstantInt>(AddrInst->getOperand(i))) {
ConstantOffset += CI->getSExtValue()*TypeSize;
} else if (TypeSize) { // Scales of zero don't do anything.
// 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))
return true;
}
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;
// 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);
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)) {
// 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,
ImmutableCallSite(CI));
for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) {
TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i];
// 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!
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 the ultimately found memory instructions to MemoryUses.
static bool FindAllMemoryUses(
Instruction *I,
SmallVectorImpl<std::pair<Instruction *, unsigned>> &MemoryUses,
SmallPtrSetImpl<Instruction *> &ConsideredInsts, const TargetLowering &TLI,
const TargetRegisterInfo &TRI, 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;
const bool OptSize = I->getFunction()->optForSize();
// 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(std::make_pair(LI, U.getOperandNo()));
continue;
}
if (StoreInst *SI = dyn_cast<StoreInst>(UserI)) {
unsigned opNo = U.getOperandNo();
if (opNo != StoreInst::getPointerOperandIndex())
return true; // Storing addr, not into addr.
MemoryUses.push_back(std::make_pair(SI, opNo));
continue;
}
if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(UserI)) {
unsigned opNo = U.getOperandNo();
if (opNo != AtomicRMWInst::getPointerOperandIndex())
return true; // Storing addr, not into addr.
MemoryUses.push_back(std::make_pair(RMW, opNo));
continue;
}
if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(UserI)) {
unsigned opNo = U.getOperandNo();
if (opNo != AtomicCmpXchgInst::getPointerOperandIndex())
return true; // Storing addr, not into addr.
MemoryUses.push_back(std::make_pair(CmpX, opNo));
continue;
}
if (CallInst *CI = dyn_cast<CallInst>(UserI)) {
// If this is a cold call, we can sink the addressing calculation into
// the cold path. See optimizeCallInst
if (!OptSize && CI->hasFnAttr(Attribute::Cold))
continue;
InlineAsm *IA = dyn_cast<InlineAsm>(CI->getCalledValue());
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,
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<Instruction*,unsigned>, 16> MemoryUses;
SmallPtrSet<Instruction*, 16> ConsideredInsts;
if (FindAllMemoryUses(I, MemoryUses, ConsideredInsts, TLI, TRI))
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 (unsigned i = 0, e = MemoryUses.size(); i != e; ++i) {
Instruction *User = MemoryUses[i].first;
unsigned OpNo = MemoryUses[i].second;
// Get the access type of this use. If the use isn't a pointer, we don't
// know what it accesses.
Value *Address = User->getOperand(OpNo);
PointerType *AddrTy = dyn_cast<PointerType>(Address->getType());
if (!AddrTy)
return false;
Type *AddressAccessTy = AddrTy->getElementType();
unsigned AS = AddrTy->getAddressSpace();
// 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;
TypePromotionTransaction::ConstRestorationPt LastKnownGood =
TPT.getRestorationPoint();
AddressingModeMatcher Matcher(MatchedAddrModeInsts, TLI, TRI,
AddressAccessTy, AS,
MemoryInst, Result, InsertedInsts,
PromotedInsts, TPT);
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 nodes, and ensure that
// the addressing mode obtained from the non-PHI roots of the graph
// are equivalent.
bool AddrModeFound = false;
bool PhiSeen = false;
SmallVector<Instruction*, 16> AddrModeInsts;
ExtAddrMode AddrMode;
TypePromotionTransaction TPT(RemovedInsts);
TypePromotionTransaction::ConstRestorationPt LastKnownGood =
TPT.getRestorationPoint();
while (!worklist.empty()) {
Value *V = worklist.back();
worklist.pop_back();
// 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)) {
for (Value *IncValue : P->incoming_values())
worklist.push_back(IncValue);
PhiSeen = 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();
ExtAddrMode NewAddrMode = AddressingModeMatcher::Match(
V, AccessTy, AddrSpace, MemoryInst, AddrModeInsts, *TLI, *TRI,
InsertedInsts, PromotedInsts, TPT);
if (!AddrModeFound) {
AddrModeFound = true;
AddrMode = NewAddrMode;
continue;
}
if (NewAddrMode == AddrMode)
continue;
AddrModeFound = false;
break;
}
// If the addressing mode couldn't be determined, or if multiple different
// ones were determined, bail out now.
if (!AddrModeFound) {
TPT.rollback(LastKnownGood);
return false;
}
TPT.commit();
// If all the instructions matched are already in this BB, don't do anything.
// If we saw Phi node then it is not local definitely.
if (!PhiSeen && none_of(AddrModeInsts, [&](Value *V) {
return IsNonLocalValue(V, MemoryInst->getParent());
})) {
DEBUG(dbgs() << "CGP: Found local addrmode: " << AddrMode << "\n");
return false;
}
// 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.
Value *&SunkAddr = SunkAddrs[Addr];
if (SunkAddr) {
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() && TM &&
SubtargetInfo->useAA())) {
// By default, we use the GEP-based method when AA is used later. This
// prevents new inttoptr/ptrtoint pairs from degrading AA capabilities.
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 false;
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 false;
}
if (AddrMode.BaseGV) {
if (ResultPtr)
return false;
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 false;
} 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");
}
ResultIndex = V;
}
if (!ResultIndex) {
SunkAddr = ResultPtr;
} else {
if (ResultPtr->getType() != I8PtrTy)
ResultPtr = Builder.CreatePointerCast(ResultPtr, I8PtrTy);
SunkAddr = Builder.CreateGEP(I8Ty, ResultPtr, ResultIndex, "sunkaddr");
}
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 false;
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 false;
}
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);
// If we have no uses, recursively delete the value and all dead instructions
// using it.
if (Repl->use_empty()) {
// This can cause recursive deletion, which can invalidate our iterator.
// Use a WeakTrackingVH to hold onto it in case this happens.
Value *CurValue = &*CurInstIterator;
WeakTrackingVH IterHandle(CurValue);
BasicBlock *BB = CurInstIterator->getParent();
RecursivelyDeleteTriviallyDeadInstructions(Repl, TLInfo);
if (IterHandle != CurValue) {
// If the iterator instruction was recursively deleted, start over at the
// start of the block.
CurInstIterator = BB->begin();
SunkAddrs.clear();
}
}
++NumMemoryInsts;
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 (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) {
TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i];
// Compute the constraint code and ConstraintType to use.
TLI->ComputeConstraintToUse(OpInfo, SDValue());
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;
}
/// \brief 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;
}
/// \brief 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 || !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) {
DominatorTree DT(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 (DT.dominates(Inst, Pt)) {
Pt->replaceAllUsesWith(Inst);
RemovedInsts.insert(Pt);
Pt->removeFromParent();
Pt = Inst;
inserted = true;
Changed = true;
break;
}
if (!DT.dominates(Pt, Inst))
// Give up if we need to merge in a common dominator as the
// expermients 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;
}
/// 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) {
// ExtLoad formation and address type promotion infrastructure requires TLI to
// be effective.
if (!TLI)
return false;
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);
// CGP does not check if the zext would be speculatively executed when moved
// to the same basic block as the load. Preserving its original location
// would pessimize the debugging experience, as well as negatively impact
// the quality of sample pgo. We don't want to use "line 0" as that has a
// size cost in the line-table section and logically the zext can be seen as
// part of the load. Therefore we conservatively reuse the same debug
// location for the load and the zext.
ExtFedByLoad->setDebugLoc(LI->getDebugLoc());
++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 && !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()->isIntegerTy() || Load->getType()->isPointerTy()))
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();
APInt DemandBits(BitWidth, 0);
APInt WidestAndBits(BitWidth, 0);
while (!WorkList.empty()) {
Instruction *I = WorkList.back();
WorkList.pop_back();
// 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 = dyn_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::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 > TLI->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;
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());
}
return V;
}
/// If we have a SelectInst that will likely profit from branch prediction,
/// turn it into a branch.
bool CodeGenPrepare::optimizeSelectInst(SelectInst *SI) {
// 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 (DisableSelectToBranch || OptSize || !TLI || 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))
return false;
ModifiedDT = true;
// 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
// br i1 %cmp, 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 ]
//
// 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");
// 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);
}
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);
}
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);
BranchInst::Create(EndBlock, FalseBlock);
}
// 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<>(SI).CreateCondBr(SI->getCondition(), 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 (auto It = ASI.rbegin(); It != ASI.rend(); ++It) {
SelectInst *SI = *It;
// 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);
SI->replaceAllUsesWith(PN);
SI->eraseFromParent();
INS.erase(SI);
++NumSelectsExpanded;
}
// Instruct OptimizeBlock to skip to the next block.
CurInstIterator = StartBlock->end();
return true;
}
static bool isBroadcastShuffle(ShuffleVectorInst *SVI) {
SmallVector<int, 16> Mask(SVI->getShuffleMask());
int SplatElem = -1;
for (unsigned i = 0; i < Mask.size(); ++i) {
if (SplatElem != -1 && Mask[i] != -1 && Mask[i] != SplatElem)
return false;
SplatElem = Mask[i];
}
return true;
}
/// Some targets have expensive vector shifts if the lanes aren't all the same
/// (e.g. x86 only introduced "vpsllvd" and friends with AVX2). In these cases
/// it's often worth sinking a shufflevector splat down to its use so that
/// codegen can spot all lanes are identical.
bool CodeGenPrepare::optimizeShuffleVectorInst(ShuffleVectorInst *SVI) {
BasicBlock *DefBB = SVI->getParent();
// Only do this xform if variable vector shifts are particularly expensive.
if (!TLI || !TLI->isVectorShiftByScalarCheap(SVI->getType()))
return false;
// We only expect better codegen by sinking a shuffle if we can recognise a
// constant splat.
if (!isBroadcastShuffle(SVI))
return false;
// InsertedShuffles - Only insert a shuffle in each block once.
DenseMap<BasicBlock*, Instruction*> InsertedShuffles;
bool MadeChange = false;
for (User *U : SVI->users()) {
Instruction *UI = cast<Instruction>(U);
// Figure out which BB this ext is used in.
BasicBlock *UserBB = UI->getParent();
if (UserBB == DefBB) continue;
// For now only apply this when the splat is used by a shift instruction.
if (!UI->isShift()) continue;
// Everything checks out, sink the shuffle if the user's block doesn't
// already have a copy.
Instruction *&InsertedShuffle = InsertedShuffles[UserBB];
if (!InsertedShuffle) {
BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
assert(InsertPt != UserBB->end());
InsertedShuffle =
new ShuffleVectorInst(SVI->getOperand(0), SVI->getOperand(1),
SVI->getOperand(2), "", &*InsertPt);
}
UI->replaceUsesOfWith(SVI, InsertedShuffle);
MadeChange = true;
}
// If we removed all uses, nuke the shuffle.
if (SVI->use_empty()) {
SVI->eraseFromParent();
MadeChange = true;
}
return MadeChange;
}
bool CodeGenPrepare::optimizeSwitchInst(SwitchInst *SI) {
if (!TLI || !DL)
return false;
Value *Cond = SI->getCondition();
Type *OldType = Cond->getType();
LLVMContext &Context = Cond->getContext();
MVT RegType = TLI->getRegisterType(Context, TLI->getValueType(*DL, OldType));
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);
// Zero-extend the switch condition and case constants unless the switch
// condition is a function argument that is already being sign-extended.
// In that case, we can avoid an unnecessary mask/extension by sign-extending
// everything instead.
Instruction::CastOps ExtType = Instruction::ZExt;
if (auto *Arg = dyn_cast<Argument>(Cond))
if (Arg->hasSExtAttr())
ExtType = Instruction::SExt;
auto *ExtInst = CastInst::Create(ExtType, Cond, NewType);
ExtInst->insertBefore(SI);
SI->setCondition(ExtInst);
for (auto Case : SI->cases()) {
APInt NarrowConst = Case.getCaseValue()->getValue();
APInt WideConst = (ExtType == Instruction::ZExt) ?
NarrowConst.zext(RegWidth) : NarrowConst.sext(RegWidth);
Case.setValue(ConstantInt::get(Context, WideConst));
}
return true;
}
namespace {
/// \brief 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;
/// \brief 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();
}
/// \brief 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;
}
/// \brief 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;
}
/// \brief 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();
}
/// \brief 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);
/// \brief 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();
unsigned Align = ST->getAlignment();
// Check if this store is supported.
if (!TLI.allowsMisalignedMemoryAccesses(
TLI.getValueType(DL, ST->getValueOperand()->getType()), AS,
Align)) {
// 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.
uint64_t ScalarCost =
TTI.getVectorInstrCost(Transition->getOpcode(), PromotedType, Index);
uint64_t VectorCost = StoreExtractCombineCost;
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(), Arg0OVK, Arg1OVK);
VectorCost += TTI.getArithmeticInstrCost(Inst->getOpcode(), PromotedType,
Arg0OVK, Arg1OVK);
}
DEBUG(dbgs() << "Estimated cost of computation to be promoted:\nScalar: "
<< ScalarCost << "\nVector: " << VectorCost << '\n');
return ScalarCost > VectorCost;
}
/// \brief 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;
}
unsigned End = getTransitionType()->getVectorNumElements();
if (UseSplat)
return ConstantVector::getSplat(End, Val);
SmallVector<Constant *, 4> ConstVec;
UndefValue *UndefVal = UndefValue::get(Val->getType());
for (unsigned Idx = 0; Idx != End; ++Idx) {
if (Idx == ExtractIdx)
ConstVec.push_back(Val);
else
ConstVec.push_back(UndefVal);
}
return ConstantVector::get(ConstVec);
}
/// \brief 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");
}
/// \brief 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);
}
/// \brief 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));
}
/// \brief 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); }
/// \brief Record \p ToBePromoted as part of the chain to be promoted.
void enqueueForPromotion(Instruction *ToBePromoted) {
InstsToBePromoted.push_back(ToBePromoted);
}
/// \brief Set the instruction that will be combined with the transition.
void recordCombineInstruction(Instruction *ToBeCombined) {
assert(canCombine(ToBeCombined) && "Unsupported instruction to combine");
CombineInst = ToBeCombined;
}
/// \brief 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 || !TLI ||
(!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();
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());
DEBUG(dbgs() << "Use: " << *ToBePromoted << '\n');
if (ToBePromoted->getParent() != Parent) {
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)) {
DEBUG(dbgs() << "Assume " << *Inst << '\n'
<< "will be combined with: " << *ToBePromoted << '\n');
VPH.recordCombineInstruction(ToBePromoted);
bool Changed = VPH.promote();
NumStoreExtractExposed += Changed;
return Changed;
}
DEBUG(dbgs() << "Try promoting.\n");
if (!VPH.canPromote(ToBePromoted) || !VPH.shouldPromote(ToBePromoted))
return false;
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 efficent 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();
if (DL.getTypeStoreSizeInBits(StoreType) != DL.getTypeSizeInBits(StoreType) ||
DL.getTypeSizeInBits(StoreType) == 0)
return false;
unsigned HalfValBitSize = DL.getTypeSizeInBits(StoreType) / 2;
Type *SplitStoreType = Type::getIntNTy(SI.getContext(), HalfValBitSize);
if (DL.getTypeStoreSizeInBits(SplitStoreType) !=
DL.getTypeSizeInBits(SplitStoreType))
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());
auto CreateSplitStore = [&](Value *V, bool Upper) {
V = Builder.CreateZExtOrBitCast(V, SplitStoreType);
Value *Addr = Builder.CreateBitCast(
SI.getOperand(1),
SplitStoreType->getPointerTo(SI.getPointerAddressSpace()));
if (Upper)
Addr = Builder.CreateGEP(
SplitStoreType, Addr,
ConstantInt::get(Type::getInt32Ty(SI.getContext()), 1));
Builder.CreateAlignedStore(
V, Addr, Upper ? SI.getAlignment() / 2 : SI.getAlignment());
};
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::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::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();
unsigned ImmCost = TTI->getIntImmCost(NewIdx, GEPIIdx->getType());
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;
}
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;
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})) {
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 (TLI && 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 &&
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 (CmpInst *CI = dyn_cast<CmpInst>(I))
if (!TLI || !TLI->hasMultipleConditionRegisters())
return OptimizeCmpExpression(CI, TLI);
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
LI->setMetadata(LLVMContext::MD_invariant_group, nullptr);
if (TLI) {
bool Modified = optimizeLoadExt(LI);
unsigned AS = LI->getPointerAddressSpace();
Modified |= optimizeMemoryInst(I, I->getOperand(0), LI->getType(), AS);
return Modified;
}
return false;
}
if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
if (TLI && splitMergedValStore(*SI, *DL, *TLI))
return true;
SI->setMetadata(LLVMContext::MD_invariant_group, nullptr);
if (TLI) {
unsigned AS = SI->getPointerAddressSpace();
return optimizeMemoryInst(I, SI->getOperand(1),
SI->getOperand(0)->getType(), AS);
}
return false;
}
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 && TLI)
return sinkAndCmp0Expression(BinOp, *TLI, InsertedInsts);
if (BinOp && (BinOp->getOpcode() == Instruction::AShr ||
BinOp->getOpcode() == Instruction::LShr)) {
ConstantInt *CI = dyn_cast<ConstantInt>(BinOp->getOperand(1));
if (TLI && CI && TLI->hasExtractBitsInsn())
return OptimizeExtractBits(BinOp, CI, *TLI, *DL);
return false;
}
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);
GEPI->replaceAllUsesWith(NC);
GEPI->eraseFromParent();
++NumGEPsElim;
optimizeInst(NC, ModifiedDT);
return true;
}
if (tryUnmergingGEPsAcrossIndirectBr(GEPI, TTI)) {
return true;
}
return false;
}
if (CallInst *CI = dyn_cast<CallInst>(I))
return optimizeCallInst(CI, ModifiedDT);
if (SelectInst *SI = dyn_cast<SelectInst>(I))
return optimizeSelectInst(SI);
if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I))
return optimizeShuffleVectorInst(SVI);
if (auto *Switch = dyn_cast<SwitchInst>(I))
return optimizeSwitchInst(Switch);
if (isa<ExtractElementInst>(I))
return optimizeExtractElementInst(I);
return false;
}
/// Given an OR instruction, check to see if this is a bitreverse
/// idiom. If so, insert the new intrinsic and return true.
static bool makeBitReverse(Instruction &I, const DataLayout &DL,
const TargetLowering &TLI) {
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);
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 (TLI && MadeBitReverse) {
MadeBitReverse = false;
for (auto &I : reverse(BB)) {
if (makeBitReverse(I, *DL, *TLI)) {
MadeBitReverse = MadeChange = true;
ModifiedDT = true;
break;
}
}
}
MadeChange |= dupRetToEnableTailCallOpts(&BB);
return MadeChange;
}
// llvm.dbg.value is far away from the value then iSel may not be able
// handle it properly. iSel will drop llvm.dbg.value if it can not
// find a node corresponding to the value.
bool CodeGenPrepare::placeDbgValues(Function &F) {
bool MadeChange = false;
for (BasicBlock &BB : F) {
Instruction *PrevNonDbgInst = nullptr;
for (BasicBlock::iterator BI = BB.begin(), BE = BB.end(); BI != BE;) {
Instruction *Insn = &*BI++;
DbgValueInst *DVI = dyn_cast<DbgValueInst>(Insn);
// Leave dbg.values that refer to an alloca alone. These
// instrinsics describe the address of a variable (= the alloca)
// being taken. They should not be moved next to the alloca
// (and to the beginning of the scope), but rather stay close to
// where said address is used.
if (!DVI || (DVI->getValue() && isa<AllocaInst>(DVI->getValue()))) {
PrevNonDbgInst = Insn;
continue;
}
Instruction *VI = dyn_cast_or_null<Instruction>(DVI->getValue());
if (VI && VI != PrevNonDbgInst && !VI->isTerminator()) {
// 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;
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;
}
/// \brief 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;
}
/// \brief 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) {
if (!TM || !TM->Options.EnableFastISel || !TLI || 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"
BinaryOperator *LogicOp;
BasicBlock *TBB, *FBB;
if (!match(BB.getTerminator(), m_Br(m_OneUse(m_BinOp(LogicOp)), TBB, FBB)))
continue;
auto *Br1 = cast<BranchInst>(BB.getTerminator());
if (Br1->getMetadata(LLVMContext::MD_unpredictable))
continue;
unsigned Opc;
Value *Cond1, *Cond2;
if (match(LogicOp, m_And(m_OneUse(m_Value(Cond1)),
m_OneUse(m_Value(Cond2)))))
Opc = Instruction::And;
else if (match(LogicOp, m_Or(m_OneUse(m_Value(Cond1)),
m_OneUse(m_Value(Cond2)))))
Opc = Instruction::Or;
else
continue;
if (!match(Cond1, m_CombineOr(m_Cmp(), m_BinOp())) ||
!match(Cond2, m_CombineOr(m_Cmp(), m_BinOp())) )
continue;
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 conditon 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.
for (auto &I : *TBB) {
PHINode *PN = dyn_cast<PHINode>(&I);
if (!PN)
break;
int i;
while ((i = PN->getBasicBlockIndex(&BB)) >= 0)
PN->setIncomingBlock(i, TmpBB);
}
// Add another incoming edge form the new BB.
for (auto &I : *FBB) {
PHINode *PN = dyn_cast<PHINode>(&I);
if (!PN)
break;
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 orignal BB.
// Assuming the orignal 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 orignal BB.
// Assuming the orignal 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));
}
}
// Note: No point in getting fancy here, since the DT info is never
// available to CodeGenPrepare.
ModifiedDT = true;
MadeChange = true;
DEBUG(dbgs() << "After branch condition splitting\n"; BB.dump();
TmpBB->dump());
}
return MadeChange;
}
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