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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/CodeGen/Passes.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/CallSite.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/IRBuilder.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/IR/ValueMap.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetSubtargetInfo.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/BuildLibCalls.h"
#include "llvm/Transforms/Utils/BypassSlowDivision.h"
#include "llvm/Transforms/Utils/Local.h"
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(NumRetsDup, "Number of return instructions duplicated");
STATISTIC(NumDbgValueMoved, "Number of debug value instructions moved");
STATISTIC(NumSelectsExpanded, "Number of selects turned into branches");
STATISTIC(NumAndCmpsMoved, "Number of and/cmp's pushed into branches");
STATISTIC(NumStoreExtractExposed, "Number of store(extractelement) exposed");
static cl::opt<bool> DisableBranchOpts(
"disable-cgp-branch-opts", cl::Hidden, cl::init(false),
cl::desc("Disable branch optimizations in CodeGenPrepare"));
static cl::opt<bool> 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(false),
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"));
namespace {
typedef SmallPtrSet<Instruction *, 16> SetOfInstrs;
struct TypeIsSExt {
Type *Ty;
bool IsSExt;
TypeIsSExt(Type *Ty, bool IsSExt) : Ty(Ty), IsSExt(IsSExt) {}
};
typedef DenseMap<Instruction *, TypeIsSExt> InstrToOrigTy;
class TypePromotionTransaction;
class CodeGenPrepare : public FunctionPass {
/// TLI - Keep a pointer of a TargetLowering to consult for determining
/// transformation profitability.
const TargetMachine *TM;
const TargetLowering *TLI;
const TargetTransformInfo *TTI;
const TargetLibraryInfo *TLInfo;
DominatorTree *DT;
/// CurInstIterator - As we scan instructions optimizing them, this is the
/// next instruction to optimize. Xforms 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 truncates inserted for the current function.
SetOfInstrs InsertedTruncsSet;
/// Keeps track of the type of the related instruction before their
/// promotion for the current function.
InstrToOrigTy PromotedInsts;
/// ModifiedDT - If CFG is modified in anyway, dominator tree may need to
/// be updated.
bool ModifiedDT;
/// OptSize - True if optimizing for size.
bool OptSize;
public:
static char ID; // Pass identification, replacement for typeid
explicit CodeGenPrepare(const TargetMachine *TM = nullptr)
: FunctionPass(ID), TM(TM), TLI(nullptr), TTI(nullptr) {
initializeCodeGenPreparePass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &F) override;
const char *getPassName() const override { return "CodeGen Prepare"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addPreserved<DominatorTreeWrapperPass>();
AU.addRequired<TargetLibraryInfo>();
AU.addRequired<TargetTransformInfo>();
}
private:
bool EliminateFallThrough(Function &F);
bool EliminateMostlyEmptyBlocks(Function &F);
bool CanMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const;
void EliminateMostlyEmptyBlock(BasicBlock *BB);
bool OptimizeBlock(BasicBlock &BB);
bool OptimizeInst(Instruction *I);
bool OptimizeMemoryInst(Instruction *I, Value *Addr, Type *AccessTy);
bool OptimizeInlineAsmInst(CallInst *CS);
bool OptimizeCallInst(CallInst *CI);
bool MoveExtToFormExtLoad(Instruction *&I);
bool OptimizeExtUses(Instruction *I);
bool OptimizeSelectInst(SelectInst *SI);
bool OptimizeShuffleVectorInst(ShuffleVectorInst *SI);
bool OptimizeExtractElementInst(Instruction *Inst);
bool DupRetToEnableTailCallOpts(BasicBlock *BB);
bool PlaceDbgValues(Function &F);
bool sinkAndCmp(Function &F);
bool ExtLdPromotion(TypePromotionTransaction &TPT, LoadInst *&LI,
Instruction *&Inst,
const SmallVectorImpl<Instruction *> &Exts,
unsigned CreatedInst);
bool splitBranchCondition(Function &F);
};
}
char CodeGenPrepare::ID = 0;
INITIALIZE_TM_PASS(CodeGenPrepare, "codegenprepare",
"Optimize for code generation", false, false)
FunctionPass *llvm::createCodeGenPreparePass(const TargetMachine *TM) {
return new CodeGenPrepare(TM);
}
bool CodeGenPrepare::runOnFunction(Function &F) {
if (skipOptnoneFunction(F))
return false;
bool EverMadeChange = false;
// Clear per function information.
InsertedTruncsSet.clear();
PromotedInsts.clear();
ModifiedDT = false;
if (TM)
TLI = TM->getSubtargetImpl()->getTargetLowering();
TLInfo = &getAnalysis<TargetLibraryInfo>();
TTI = &getAnalysis<TargetTransformInfo>();
DominatorTreeWrapperPass *DTWP =
getAnalysisIfAvailable<DominatorTreeWrapperPass>();
DT = DTWP ? &DTWP->getDomTree() : nullptr;
OptSize = F.getAttributes().hasAttribute(AttributeSet::FunctionIndex,
Attribute::OptimizeForSize);
/// 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();
for (Function::iterator I = F.begin(); I != F.end(); I++)
EverMadeChange |= bypassSlowDivision(F, I, BypassWidths);
}
// 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 there is a mask, compare against zero, and branch that can be combined
// into a single target instruction, push the mask and compare into branch
// users. Do this before OptimizeBlock -> OptimizeInst ->
// OptimizeCmpExpression, which perturbs the pattern being searched for.
if (!DisableBranchOpts) {
EverMadeChange |= sinkAndCmp(F);
EverMadeChange |= splitBranchCondition(F);
}
bool MadeChange = true;
while (MadeChange) {
MadeChange = false;
for (Function::iterator I = F.begin(); I != F.end(); ) {
BasicBlock *BB = I++;
MadeChange |= OptimizeBlock(*BB);
}
EverMadeChange |= MadeChange;
}
SunkAddrs.clear();
if (!DisableBranchOpts) {
MadeChange = false;
SmallPtrSet<BasicBlock*, 8> WorkList;
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
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);
if (MadeChange)
ModifiedDT = true;
EverMadeChange |= MadeChange;
}
if (ModifiedDT && DT)
DT->recalculate(F);
return EverMadeChange;
}
/// EliminateFallThrough - 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, this);
if (isEntry && BB != &BB->getParent()->getEntryBlock())
BB->moveBefore(&BB->getParent()->getEntryBlock());
// We have erased a block. Update the iterator.
I = BB;
}
}
return Changed;
}
/// EliminateMostlyEmptyBlocks - 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) {
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++;
// If this block doesn't end with an uncond branch, ignore it.
BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
if (!BI || !BI->isUnconditional())
continue;
// If the instruction before the branch (skipping debug info) isn't a phi
// node, then other stuff is happening here.
BasicBlock::iterator BBI = BI;
if (BBI != BB->begin()) {
--BBI;
while (isa<DbgInfoIntrinsic>(BBI)) {
if (BBI == BB->begin())
break;
--BBI;
}
if (!isa<DbgInfoIntrinsic>(BBI) && !isa<PHINode>(BBI))
continue;
}
// Do not break infinite loops.
BasicBlock *DestBB = BI->getSuccessor(0);
if (DestBB == BB)
continue;
if (!CanMergeBlocks(BB, DestBB))
continue;
EliminateMostlyEmptyBlock(BB);
MadeChange = true;
}
return MadeChange;
}
/// CanMergeBlocks - Return true if we can merge BB into DestBB if there is a
/// single uncond 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;
}
/// EliminateMostlyEmptyBlock - Eliminate a basic block that have 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, this);
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);
if (DT && !ModifiedDT) {
BasicBlock *BBIDom = DT->getNode(BB)->getIDom()->getBlock();
BasicBlock *DestBBIDom = DT->getNode(DestBB)->getIDom()->getBlock();
BasicBlock *NewIDom = DT->findNearestCommonDominator(BBIDom, DestBBIDom);
DT->changeImmediateDominator(DestBB, NewIDom);
DT->eraseNode(BB);
}
BB->eraseFromParent();
++NumBlocksElim;
DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
}
/// 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;
// 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();
InsertedCast =
CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "",
InsertPt);
MadeChange = true;
}
// Replace a use of the cast with a use of the new cast.
TheUse = InsertedCast;
++NumCastUses;
}
// If we removed all uses, nuke the cast.
if (CI->use_empty()) {
CI->eraseFromParent();
MadeChange = true;
}
return MadeChange;
}
/// OptimizeNoopCopyExpression - 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){
// If this is a noop copy,
EVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
EVT DstVT = TLI.getValueType(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);
}
/// OptimizeCmpExpression - 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 OptimizeCmpExpression(CmpInst *CI) {
BasicBlock *DefBB = CI->getParent();
/// InsertedCmp - 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();
InsertedCmp =
CmpInst::Create(CI->getOpcode(),
CI->getPredicate(), CI->getOperand(0),
CI->getOperand(1), "", InsertPt);
MadeChange = true;
}
// Replace a use of the cmp with a use of the new cmp.
TheUse = InsertedCmp;
++NumCmpUses;
}
// If we removed all uses, nuke the cmp.
if (CI->use_empty())
CI->eraseFromParent();
return MadeChange;
}
/// isExtractBitsCandidateUse - Check if the candidates could
/// be combined with 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;
}
/// SinkShiftAndTruncate - 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) {
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(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();
// 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++;
InsertedTrunc = CastInst::Create(TruncI->getOpcode(), InsertedShift,
TruncI->getType(), "", TruncInsertPt);
MadeChange = true;
TruncTheUse = InsertedTrunc;
}
}
return MadeChange;
}
/// OptimizeExtractBits - 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) {
BasicBlock *DefBB = ShiftI->getParent();
/// Only insert instructions in each block once.
DenseMap<BasicBlock *, BinaryOperator *> InsertedShifts;
bool shiftIsLegal = TLI.isTypeLegal(TLI.getValueType(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(User->getType()))))
MadeChange =
SinkShiftAndTruncate(ShiftI, User, CI, InsertedShifts, TLI);
continue;
}
// If we have already inserted a shift into this block, use it.
BinaryOperator *&InsertedShift = InsertedShifts[UserBB];
if (!InsertedShift) {
BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
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;
}
namespace {
class CodeGenPrepareFortifiedLibCalls : public SimplifyFortifiedLibCalls {
protected:
void replaceCall(Value *With) override {
CI->replaceAllUsesWith(With);
CI->eraseFromParent();
}
bool isFoldable(unsigned SizeCIOp, unsigned, bool) const override {
if (ConstantInt *SizeCI =
dyn_cast<ConstantInt>(CI->getArgOperand(SizeCIOp)))
return SizeCI->isAllOnesValue();
return false;
}
};
} // end anonymous namespace
bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
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;
}
// Lower all uses of llvm.objectsize.*
IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI);
if (II && II->getIntrinsicID() == Intrinsic::objectsize) {
bool Min = (cast<ConstantInt>(II->getArgOperand(1))->getZExtValue() == 1);
Type *ReturnTy = CI->getType();
Constant *RetVal = ConstantInt::get(ReturnTy, Min ? 0 : -1ULL);
// Substituting this can cause recursive simplifications, which can
// invalidate our iterator. Use a WeakVH to hold onto it in case this
// happens.
WeakVH IterHandle(CurInstIterator);
replaceAndRecursivelySimplify(CI, RetVal,
TLI ? TLI->getDataLayout() : nullptr,
TLInfo, ModifiedDT ? nullptr : DT);
// If the iterator instruction was recursively deleted, start over at the
// start of the block.
if (IterHandle != CurInstIterator) {
CurInstIterator = BB->begin();
SunkAddrs.clear();
}
return true;
}
if (II && TLI) {
SmallVector<Value*, 2> PtrOps;
Type *AccessTy;
if (TLI->GetAddrModeArguments(II, PtrOps, AccessTy))
while (!PtrOps.empty())
if (OptimizeMemoryInst(II, PtrOps.pop_back_val(), AccessTy))
return true;
}
// From here on out we're working with named functions.
if (!CI->getCalledFunction()) return false;
// We'll need DataLayout from here on out.
const DataLayout *TD = TLI ? TLI->getDataLayout() : nullptr;
if (!TD) return false;
// Lower all default uses of _chk calls. This is very similar
// to what InstCombineCalls does, but here we are only lowering calls
// that have the default "don't know" as the objectsize. Anything else
// should be left alone.
CodeGenPrepareFortifiedLibCalls Simplifier;
return Simplifier.fold(CI, TD, TLInfo);
}
/// DupRetToEnableTailCallOpts - 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 *RI = dyn_cast<ReturnInst>(BB->getTerminator());
if (!RI)
return false;
PHINode *PN = nullptr;
BitCastInst *BCI = nullptr;
Value *V = RI->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;
// It's not safe to eliminate the sign / zero extension of the return value.
// See llvm::isInTailCallPosition().
const Function *F = BB->getParent();
AttributeSet CallerAttrs = F->getAttributes();
if (CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::ZExt) ||
CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::SExt))
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 != RI)
return false;
} else {
BasicBlock::iterator BI = BB->begin();
while (isa<DbgInfoIntrinsic>(BI)) ++BI;
if (&*BI != RI)
return false;
}
/// Only dup the ReturnInst if the CallInst is likely to be emitted as a tail
/// call.
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))
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))
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.
AttributeSet CalleeAttrs = CS.getAttributes();
if (AttrBuilder(CalleeAttrs, AttributeSet::ReturnIndex).
removeAttribute(Attribute::NoAlias) !=
AttrBuilder(CalleeAttrs, AttributeSet::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(RI, 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 {
/// ExtAddrMode - This is an extended version of TargetLowering::AddrMode
/// which holds actual Value*'s for register values.
struct ExtAddrMode : public TargetLowering::AddrMode {
Value *BaseReg;
Value *ScaledReg;
ExtAddrMode() : BaseReg(nullptr), ScaledReg(nullptr) {}
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);
}
};
#ifndef NDEBUG
static inline raw_ostream &operator<<(raw_ostream &OS, const ExtAddrMode &AM) {
AM.print(OS);
return OS;
}
#endif
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 << ']';
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void ExtAddrMode::dump() const {
print(dbgs());
dbgs() << '\n';
}
#endif
/// \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() {}
/// \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;
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 implied 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;
typedef SmallVectorImpl<InstructionAndIdx>::iterator use_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;
public:
/// \brief Remove all reference of \p Inst and optinally replace all its
/// uses with New.
/// \pre If !Inst->use_empty(), then New != nullptr
InstructionRemover(Instruction *Inst, Value *New = nullptr)
: TypePromotionAction(Inst), Inserter(Inst), Hider(Inst),
Replacer(nullptr) {
if (New)
Replacer = new UsesReplacer(Inst, New);
DEBUG(dbgs() << "Do: InstructionRemover: " << *Inst << "\n");
Inst->removeFromParent();
}
~InstructionRemover() { delete Replacer; }
/// \brief Really remove the instruction.
void commit() override { delete Inst; }
/// \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();
}
};
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.
typedef const TypePromotionAction *ConstRestorationPt;
/// 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;
typedef SmallVectorImpl<std::unique_ptr<TypePromotionAction>>::iterator CommitPt;
};
void TypePromotionTransaction::setOperand(Instruction *Inst, unsigned Idx,
Value *NewVal) {
Actions.push_back(
make_unique<TypePromotionTransaction::OperandSetter>(Inst, Idx, NewVal));
}
void TypePromotionTransaction::eraseInstruction(Instruction *Inst,
Value *NewVal) {
Actions.push_back(
make_unique<TypePromotionTransaction::InstructionRemover>(Inst, NewVal));
}
void TypePromotionTransaction::replaceAllUsesWith(Instruction *Inst,
Value *New) {
Actions.push_back(make_unique<TypePromotionTransaction::UsesReplacer>(Inst, New));
}
void TypePromotionTransaction::mutateType(Instruction *Inst, Type *NewTy) {
Actions.push_back(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(
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();
}
}
/// \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;
/// 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;
Instruction *MemoryInst;
/// AddrMode - 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 truncate instruction inserted by other CodeGenPrepare optimizations.
const SetOfInstrs &InsertedTruncs;
/// A map from the instructions to their type before promotion.
InstrToOrigTy &PromotedInsts;
/// The ongoing transaction where every action should be registered.
TypePromotionTransaction &TPT;
/// IgnoreProfitability - 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 &T, Type *AT,
Instruction *MI, ExtAddrMode &AM,
const SetOfInstrs &InsertedTruncs,
InstrToOrigTy &PromotedInsts,
TypePromotionTransaction &TPT)
: AddrModeInsts(AMI), TLI(T), AccessTy(AT), MemoryInst(MI), AddrMode(AM),
InsertedTruncs(InsertedTruncs), PromotedInsts(PromotedInsts), TPT(TPT) {
IgnoreProfitability = false;
}
public:
/// Match - 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 InsertedTruncs The truncate instruction 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,
Instruction *MemoryInst,
SmallVectorImpl<Instruction*> &AddrModeInsts,
const TargetLowering &TLI,
const SetOfInstrs &InsertedTruncs,
InstrToOrigTy &PromotedInsts,
TypePromotionTransaction &TPT) {
ExtAddrMode Result;
bool Success = AddressingModeMatcher(AddrModeInsts, TLI, AccessTy,
MemoryInst, Result, InsertedTruncs,
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 MatchedSize, unsigned SizeWithPromotion,
Value *PromotedOperand) const;
};
/// MatchScaledValue - 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(TestAddrMode, AccessTy))
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(TestAddrMode, AccessTy)) {
AddrModeInsts.push_back(cast<Instruction>(ScaleReg));
AddrMode = TestAddrMode;
return true;
}
}
// Otherwise, not (x+c)*scale, just return what we have.
return true;
}
/// MightBeFoldableInst - 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, 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(PromotedInst->getType()));
}
/// \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) {
if (isa<SelectInst>(Inst) && OpIdx == 0)
return false;
return true;
}
/// \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 CreatedInsts[out] contains how many non-free instructions have been
/// 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 &CreatedInsts,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs);
/// \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 CreatedInsts[out] contains how many non-free instructions have been
/// 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 &CreatedInsts,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs, bool IsSExt);
/// \see promoteOperandForOther.
static Value *
signExtendOperandForOther(Instruction *Ext, TypePromotionTransaction &TPT,
InstrToOrigTy &PromotedInsts,
unsigned &CreatedInsts,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs) {
return promoteOperandForOther(Ext, TPT, PromotedInsts, CreatedInsts, Exts,
Truncs, true);
}
/// \see promoteOperandForOther.
static Value *
zeroExtendOperandForOther(Instruction *Ext, TypePromotionTransaction &TPT,
InstrToOrigTy &PromotedInsts,
unsigned &CreatedInsts,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs) {
return promoteOperandForOther(Ext, TPT, PromotedInsts, CreatedInsts, Exts,
Truncs, false);
}
public:
/// Type for the utility function that promotes the operand of Ext.
typedef Value *(*Action)(Instruction *Ext, TypePromotionTransaction &TPT,
InstrToOrigTy &PromotedInsts, unsigned &CreatedInsts,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs);
/// \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 InsertedTruncs keeps track of all the truncate instructions inserted by
/// the others 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 &InsertedTruncs,
const TargetLowering &TLI,
const InstrToOrigTy &PromotedInsts);
};
bool TypePromotionHelper::canGetThrough(const Instruction *Inst,
Type *ConsideredExtType,
const InstrToOrigTy &PromotedInsts,
bool IsSExt) {
// 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.IsSExt == IsSExt)
OpndType = It->second.Ty;
else if ((IsSExt && isa<SExtInst>(Opnd)) || (!IsSExt && isa<ZExtInst>(Opnd)))
OpndType = Opnd->getOperand(0)->getType();
else
return false;
// #2 check that the truncate just drop extended bits.
if (Inst->getType()->getIntegerBitWidth() >= OpndType->getIntegerBitWidth())
return true;
return false;
}
TypePromotionHelper::Action TypePromotionHelper::getAction(
Instruction *Ext, const SetOfInstrs &InsertedTruncs,
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) && InsertedTruncs.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(
llvm::Instruction *SExt, TypePromotionTransaction &TPT,
InstrToOrigTy &PromotedInsts, unsigned &CreatedInsts,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs) {
// 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;
if (isa<ZExtInst>(SExtOpnd)) {
// Replace s|zext(zext(opnd))
// => zext(opnd).
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));
}
CreatedInsts = 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 && Exts)
Exts->push_back(ExtInst);
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 &CreatedInsts,
SmallVectorImpl<Instruction *> *Exts,
SmallVectorImpl<Instruction *> *Truncs, 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));
CreatedInsts = 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)) {
ITrunc->removeFromParent();
// Insert it just after the definition.
ITrunc->insertAfter(ExtOpnd);
if (Truncs)
Truncs->push_back(ITrunc);
}
TPT.replaceAllUsesWith(ExtOpnd, Trunc);
// Restore the operand of Ext (which has been replace 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");
ExtForOpnd =
cast<Instruction>(IsSExt ? TPT.createSExt(Ext, Opnd, Ext->getType())
: TPT.createZExt(Ext, Opnd, Ext->getType()));
++CreatedInsts;
}
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);
// 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;
}
/// IsPromotionProfitable - Check whether or not promoting an instruction
/// to a wider type was profitable.
/// \p MatchedSize gives the number of instructions that have been matched
/// in the addressing mode after the promotion was applied.
/// \p SizeWithPromotion gives the number of created instructions for
/// the promotion plus the number of instructions that have been
/// matched in the addressing mode before the promotion.
/// \p PromotedOperand is the value that has been promoted.
/// \return True if the promotion is profitable, false otherwise.
bool
AddressingModeMatcher::IsPromotionProfitable(unsigned MatchedSize,
unsigned SizeWithPromotion,
Value *PromotedOperand) const {
// We folded less instructions than what we created to promote the operand.
// This is not profitable.
if (MatchedSize < SizeWithPromotion)
return false;
if (MatchedSize > SizeWithPromotion)
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, PromotedOperand);
}
/// MatchOperationAddr - 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:
// This inttoptr is a no-op if the integer type is pointer sized.
if (TLI.getValueType(AddrInst->getOperand(0)->getType()) ==
TLI.getPointerTy(AddrInst->getType()->getPointerAddressSpace()))
return MatchAddr(AddrInst->getOperand(0), Depth);
return false;
case Instruction::BitCast:
case Instruction::AddrSpaceCast:
// 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::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;
const DataLayout *TD = TLI.getDataLayout();
gep_type_iterator GTI = gep_type_begin(AddrInst);
for (unsigned i = 1, e = AddrInst->getNumOperands(); i != e; ++i, ++GTI) {
if (StructType *STy = dyn_cast<StructType>(*GTI)) {
const StructLayout *SL = TD->getStructLayout(STy);
unsigned Idx =
cast<ConstantInt>(AddrInst->getOperand(i))->getZExtValue();
ConstantOffset += SL->getElementOffset(Idx);
} else {
uint64_t TypeSize = TD->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(AddrMode, AccessTy)){
// 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, InsertedTruncs, TLI, PromotedInsts);
if (!TPH)
return false;
TypePromotionTransaction::ConstRestorationPt LastKnownGood =
TPT.getRestorationPoint();
unsigned CreatedInsts = 0;
Value *PromotedOperand =
TPH(Ext, TPT, PromotedInsts, CreatedInsts, nullptr, nullptr);
// 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) ||
!IsPromotionProfitable(AddrModeInsts.size(), OldSize + CreatedInsts,
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;
}
/// MatchAddr - 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(AddrMode, AccessTy))
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(AddrMode, AccessTy))
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 move 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(AddrMode, AccessTy))
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(AddrMode, AccessTy))
return true;
AddrMode.Scale = 0;
AddrMode.ScaledReg = nullptr;
}
// Couldn't match.
TPT.rollback(LastKnownGood);
return false;
}
/// IsOperandAMemoryOperand - 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) {
TargetLowering::AsmOperandInfoVector TargetConstraints = TLI.ParseConstraints(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;
}
/// FindAllMemoryUses - 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) {
// If we already considered this instruction, we're done.
if (!ConsideredInsts.insert(I).second)
return false;
// If this is an obviously unfoldable instruction, bail out.
if (!MightBeFoldableInst(I))
return true;
// Loop over all the uses, recursively processing them.
for (Use &U : I->uses()) {
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 == 0) return true; // Storing addr, not into addr.
MemoryUses.push_back(std::make_pair(SI, opNo));
continue;
}
if (CallInst *CI = dyn_cast<CallInst>(UserI)) {
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))
return true;
continue;
}
if (FindAllMemoryUses(UserI, MemoryUses, ConsideredInsts, TLI))
return true;
}
return false;
}
/// ValueAlreadyLiveAtInst - Retrn 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());
}
/// IsProfitableToFoldIntoAddressingMode - 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 are ultimately load/store/inlineasm's,
// check to see if their addressing modes will include this instruction. If
// so, we can fold it into all uses, so it doesn't matter if it has multiple
// uses.
SmallVector<std::pair<Instruction*,unsigned>, 16> MemoryUses;
SmallPtrSet<Instruction*, 16> ConsideredInsts;
if (FindAllMemoryUses(I, MemoryUses, ConsideredInsts, TLI))
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 uses and see if they could
// *actually* fold the instruction.
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);
if (!Address->getType()->isPointerTy())
return false;
Type *AddressAccessTy = Address->getType()->getPointerElementType();
// 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, AddressAccessTy,
MemoryInst, Result, InsertedTruncs,
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 (std::find(MatchedAddrModeInsts.begin(), MatchedAddrModeInsts.end(),
I) == MatchedAddrModeInsts.end())
return false;
MatchedAddrModeInsts.clear();
}
return true;
}
} // end anonymous namespace
/// IsNonLocalValue - 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;
}
/// OptimizeMemoryInst - 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
/// stuff into the block as possible.
///
/// This method is used to optimize both load/store and inline asms with memory
/// operands.
bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
Type *AccessTy) {
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.
Value *Consensus = nullptr;
unsigned NumUsesConsensus = 0;
bool IsNumUsesConsensusValid = false;
SmallVector<Instruction*, 16> AddrModeInsts;
ExtAddrMode AddrMode;
TypePromotionTransaction TPT;
TypePromotionTransaction::ConstRestorationPt LastKnownGood =
TPT.getRestorationPoint();
while (!worklist.empty()) {
Value *V = worklist.back();
worklist.pop_back();
// Break use-def graph loops.
if (!Visited.insert(V).second) {
Consensus = nullptr;
break;
}
// For a PHI node, push all of its incoming values.
if (PHINode *P = dyn_cast<PHINode>(V)) {
for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i)
worklist.push_back(P->getIncomingValue(i));
continue;
}
// For non-PHIs, determine the addressing mode being computed.
SmallVector<Instruction*, 16> NewAddrModeInsts;
ExtAddrMode NewAddrMode = AddressingModeMatcher::Match(
V, AccessTy, MemoryInst, NewAddrModeInsts, *TLI, InsertedTruncsSet,
PromotedInsts, TPT);
// This check is broken into two cases with very similar code to avoid using
// getNumUses() as much as possible. Some values have a lot of uses, so
// calling getNumUses() unconditionally caused a significant compile-time
// regression.
if (!Consensus) {
Consensus = V;
AddrMode = NewAddrMode;
AddrModeInsts = NewAddrModeInsts;
continue;
} else if (NewAddrMode == AddrMode) {
if (!IsNumUsesConsensusValid) {
NumUsesConsensus = Consensus->getNumUses();
IsNumUsesConsensusValid = true;
}
// Ensure that the obtained addressing mode is equivalent to that obtained
// for all other roots of the PHI traversal. Also, when choosing one
// such root as representative, select the one with the most uses in order
// to keep the cost modeling heuristics in AddressingModeMatcher
// applicable.
unsigned NumUses = V->getNumUses();
if (NumUses > NumUsesConsensus) {
Consensus = V;
NumUsesConsensus = NumUses;
AddrModeInsts = NewAddrModeInsts;
}
continue;
}
Consensus = nullptr;
break;
}
// If the addressing mode couldn't be determined, or if multiple different
// ones were determined, bail out now.
if (!Consensus) {
TPT.rollback(LastKnownGood);
return false;
}
TPT.commit();
// Check to see if any of the instructions supersumed by this addr mode are
// non-local to I's BB.
bool AnyNonLocal = false;
for (unsigned i = 0, e = AddrModeInsts.size(); i != e; ++i) {
if (IsNonLocalValue(AddrModeInsts[i], MemoryInst->getParent())) {
AnyNonLocal = true;
break;
}
}
// If all the instructions matched are already in this BB, don't do anything.
if (!AnyNonLocal) {
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.CreateBitCast(SunkAddr, Addr->getType());
} else if (AddrSinkUsingGEPs || (!AddrSinkUsingGEPs.getNumOccurrences() &&
TM && TM->getSubtarget<TargetSubtargetInfo>().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 = TLI->getDataLayout()->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;
}
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 (!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());
// 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 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>(ResultIndex);
if (I && (ResultIndex != AddrMode.BaseReg))
I->eraseFromParent();
return false;
}
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.CreateBitCast(ResultPtr, I8PtrTy);
ResultPtr = Builder.CreateGEP(ResultPtr, ResultIndex, "sunkaddr");
}
ResultIndex = V;
}
if (!ResultIndex) {
SunkAddr = ResultPtr;
} else {
if (ResultPtr->getType() != I8PtrTy)
ResultPtr = Builder.CreateBitCast(ResultPtr, I8PtrTy);
SunkAddr = Builder.CreateGEP(ResultPtr, ResultIndex, "sunkaddr");
}
if (SunkAddr->getType() != Addr->getType())
SunkAddr = Builder.CreateBitCast(SunkAddr, Addr->getType());
}
} else {
DEBUG(dbgs() << "CGP: SINKING nonlocal addrmode: " << AddrMode << " for "
<< *MemoryInst << "\n");
Type *IntPtrTy = TLI->getDataLayout()->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 WeakVH to hold onto it in case this happens.
WeakVH IterHandle(CurInstIterator);
BasicBlock *BB = CurInstIterator->getParent();
RecursivelyDeleteTriviallyDeadInstructions(Repl, TLInfo);
if (IterHandle != CurInstIterator) {
// If the iterator instruction was recursively deleted, start over at the
// start of the block.
CurInstIterator = BB->begin();
SunkAddrs.clear();
}
}
++NumMemoryInsts;
return true;
}
/// OptimizeInlineAsmInst - 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;
TargetLowering::AsmOperandInfoVector
TargetConstraints = TLI->ParseConstraints(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());
} else if (OpInfo.Type == InlineAsm::isInput)
ArgNo++;
}
return MadeChange;
}
/// \brief Check if all the uses of \p Inst are equivalent (or free) zero or
/// sign extensions.
static bool hasSameExtUse(Instruction *Inst, const TargetLowering &TLI) {
assert(!Inst->use_empty() && "Input must have at least one use");
const Instruction *FirstUser = cast<Instruction>(*Inst->user_begin());
bool IsSExt = isa<SExtInst>(FirstUser);
Type *ExtTy = FirstUser->getType();
for (const User *U : Inst->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 = Inst
// b = sext ty1 a to ty2
// c = sext ty1 a to ty3
// Assuming ty2 is shorter than ty3, this could be turned into:
// a = Inst
// 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 form ExtLd by promoting \p Exts until they reach a
/// load instruction.
/// If an ext(load) can be formed, it is returned via \p LI for the load
/// and \p Inst for the extension.
/// Otherwise LI == nullptr and Inst == nullptr.
/// When some promotion happened, \p TPT contains the proper state to
/// revert them.
///
/// \return true when promoting was necessary to expose the ext(load)
/// opportunity, false otherwise.
///
/// Example:
/// \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
/// Thanks to the promotion, we can match zext(load i32*) to i64.
bool CodeGenPrepare::ExtLdPromotion(TypePromotionTransaction &TPT,
LoadInst *&LI, Instruction *&Inst,
const SmallVectorImpl<Instruction *> &Exts,
unsigned CreatedInsts = 0) {
// Iterate over all the extensions to see if one form an ext(load).
for (auto I : Exts) {
// Check if we directly have ext(load).
if ((LI = dyn_cast<LoadInst>(I->getOperand(0)))) {
Inst = I;
// No promotion happened here.
return false;
}
// Check whether or not we want to do any promotion.
if (!TLI || !TLI->enableExtLdPromotion() || DisableExtLdPromotion)
continue;
// Get the action to perform the promotion.
TypePromotionHelper::Action TPH = TypePromotionHelper::getAction(
I, InsertedTruncsSet, *TLI, PromotedInsts);
// Check if we can promote.
if (!TPH)
continue;
// Save the current state.
TypePromotionTransaction::ConstRestorationPt LastKnownGood =
TPT.getRestorationPoint();
SmallVector<Instruction *, 4> NewExts;
unsigned NewCreatedInsts = 0;
// Promote.
Value *PromotedVal =
TPH(I, TPT, PromotedInsts, NewCreatedInsts, &NewExts, nullptr);
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.
unsigned TotalCreatedInsts = CreatedInsts + NewCreatedInsts;
if (!StressExtLdPromotion &&
(TotalCreatedInsts > 1 ||
!isPromotedInstructionLegal(*TLI, PromotedVal))) {
// The promotion is not profitable, rollback to the previous state.
TPT.rollback(LastKnownGood);
continue;
}
// The promotion is profitable.
// Check if it exposes an ext(load).
(void)ExtLdPromotion(TPT, LI, Inst, NewExts, TotalCreatedInsts);
if (LI && (StressExtLdPromotion || NewCreatedInsts == 0 ||
// If we have created a new extension, i.e., now we have two
// extensions. We must make sure one of them is merged with
// the load, otherwise we may degrade the code quality.
(LI->hasOneUse() || hasSameExtUse(LI, *TLI))))
// Promotion happened.
return true;
// If this does not help to expose an ext(load) then, rollback.
TPT.rollback(LastKnownGood);
}
// None of the extension can form an ext(load).
LI = nullptr;
Inst = nullptr;
return false;
}
/// MoveExtToFormExtLoad - 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.
/// \p I[in/out] the extension may be modified during the process if some
/// promotions apply.
///
bool CodeGenPrepare::MoveExtToFormExtLoad(Instruction *&I) {
// Try to promote a chain of computation if it allows to form
// an extended load.
TypePromotionTransaction TPT;
TypePromotionTransaction::ConstRestorationPt LastKnownGood =
TPT.getRestorationPoint();
SmallVector<Instruction *, 1> Exts;
Exts.push_back(I);
// Look for a load being extended.
LoadInst *LI = nullptr;
Instruction *OldExt = I;
bool HasPromoted = ExtLdPromotion(TPT, LI, I, Exts);
if (!LI || !I) {
assert(!HasPromoted && !LI && "If we did not match any load instruction "
"the code must remain the same");
I = OldExt;
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() == I->getParent())
return false;
EVT VT = TLI->getValueType(I->getType());
EVT LoadVT = TLI->getValueType(LI->getType());
// If the load has other users and the truncate is not free, this probably
// isn't worthwhile.
if (!LI->hasOneUse() && TLI &&
(TLI->isTypeLegal(LoadVT) || !TLI->isTypeLegal(VT)) &&
!TLI->isTruncateFree(I->getType(), LI->getType())) {
I = OldExt;
TPT.rollback(LastKnownGood);
return false;
}
// Check whether the target supports casts folded into loads.
unsigned LType;
if (isa<ZExtInst>(I))
LType = ISD::ZEXTLOAD;
else {
assert(isa<SExtInst>(I) && "Unexpected ext type!");
LType = ISD::SEXTLOAD;
}
if (TLI && !TLI->isLoadExtLegal(LType, LoadVT)) {
I = OldExt;
TPT.rollback(LastKnownGood);
return false;
}
// Move the extend into the same block as the load, so that SelectionDAG
// can fold it.
TPT.commit();
I->removeFromParent();
I->insertAfter(LI);
++NumExtsMoved;
return true;
}
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();
InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt);
InsertedTruncsSet.insert(InsertedTrunc);
}
// Replace a use of the {s|z}ext source with a use of the result.
U = InsertedTrunc;
++NumExtUses;
MadeChange = true;
}
return MadeChange;
}
/// isFormingBranchFromSelectProfitable - Returns true if a SelectInst should be
/// turned into an explicit branch.
static bool isFormingBranchFromSelectProfitable(SelectInst *SI) {
// FIXME: This should use the same heuristics as IfConversion to determine
// whether a select is better represented as a branch. This requires that
// branch probability metadata is preserved for the select, which is not the
// case currently.
CmpInst *Cmp = dyn_cast<CmpInst>(SI->getCondition());
// If the branch is predicted right, an out of order CPU can avoid blocking on
// the compare. Emit cmovs on compares with a memory operand as branches to
// avoid stalls on the load from memory. 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)
return false;
Value *CmpOp0 = Cmp->getOperand(0);
Value *CmpOp1 = Cmp->getOperand(1);
// We check that the memory operand has one use to avoid uses of the loaded
// value directly after the compare, making branches unprofitable.
return Cmp->hasOneUse() &&
((isa<LoadInst>(CmpOp0) && CmpOp0->hasOneUse()) ||
(isa<LoadInst>(CmpOp1) && CmpOp1->hasOneUse()));
}
/// If we have a SelectInst that will likely profit from branch prediction,
/// turn it into a branch.
bool CodeGenPrepare::OptimizeSelectInst(SelectInst *SI) {
bool VectorCond = !SI->getCondition()->getType()->isIntegerTy(1);
// Can we convert the 'select' to CF ?
if (DisableSelectToBranch || OptSize || !TLI || VectorCond)
return false;
TargetLowering::SelectSupportKind SelectKind;
if (VectorCond)
SelectKind = TargetLowering::VectorMaskSelect;
else if (SI->getType()->isVectorTy())
SelectKind = TargetLowering::ScalarCondVectorVal;
else
SelectKind = TargetLowering::ScalarValSelect;
// Do we have efficient codegen support for this kind of 'selects' ?
if (TLI->isSelectSupported(SelectKind)) {
// We have efficient codegen support for the select instruction.
// Check if it is profitable to keep this 'select'.
if (!TLI->isPredictableSelectExpensive() ||
!isFormingBranchFromSelectProfitable(SI))
return false;
}
ModifiedDT = true;
// First, we split the block containing the select into 2 blocks.
BasicBlock *StartBlock = SI->getParent();
BasicBlock::iterator SplitPt = ++(BasicBlock::iterator(SI));
BasicBlock *NextBlock = StartBlock->splitBasicBlock(SplitPt, "select.end");
// Create a new block serving as the landing pad for the branch.
BasicBlock *SmallBlock = BasicBlock::Create(SI->getContext(), "select.mid",
NextBlock->getParent(), NextBlock);
// Move the unconditional branch from the block with the select in it into our
// landing pad block.
StartBlock->getTerminator()->eraseFromParent();
BranchInst::Create(NextBlock, SmallBlock);
// Insert the real conditional branch based on the original condition.
BranchInst::Create(NextBlock, SmallBlock, SI->getCondition(), SI);
// The select itself is replaced with a PHI Node.
PHINode *PN = PHINode::Create(SI->getType(), 2, "", NextBlock->begin());
PN->takeName(SI);
PN->addIncoming(SI->getTrueValue(), StartBlock);
PN->addIncoming(SI->getFalseValue(), SmallBlock);
SI->replaceAllUsesWith(PN);
SI->eraseFromParent();
// Instruct OptimizeBlock to skip to the next block.
CurInstIterator = StartBlock->end();
++NumSelectsExpanded;
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();
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;
}
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 {
/// 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;
/// \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(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
/// accross 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 = UINT_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 TargetLowering &TLI, const TargetTransformInfo &TTI,
Instruction *Transition, unsigned CombineCost)
: TLI(TLI), TTI(TTI), Transition(Transition),
StoreExtractCombineCost(CombineCost), CombineInst(nullptr) {
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(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 of 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
assert(0 && "Did you modified shouldPromote and forgot to update this?");
ToBePromoted->setOperand(U.getOperandNo(), NewVal);
}
Transition->removeFromParent();
Transition->insertAfter(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 = UINT_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(*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;
}
bool CodeGenPrepare::OptimizeInst(Instruction *I) {
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, TLI ? TLI->getDataLayout() : nullptr,
TLInfo, DT)) {
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))
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(CI->getType())) ==
TargetLowering::TypeExpandInteger) {
return SinkCast(CI);
} else {
bool MadeChange = MoveExtToFormExtLoad(I);
return MadeChange | OptimizeExtUses(I);
}
}
return false;
}
if (CmpInst *CI = dyn_cast<CmpInst>(I))
if (!TLI || !TLI->hasMultipleConditionRegisters())
return OptimizeCmpExpression(CI);
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (TLI)
return OptimizeMemoryInst(I, I->getOperand(0), LI->getType());
return false;
}
if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
if (TLI)
return OptimizeMemoryInst(I, SI->getOperand(1),
SI->getOperand(0)->getType());
return false;
}
BinaryOperator *BinOp = dyn_cast<BinaryOperator>(I);
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);
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);
return true;
}
return false;
}
if (CallInst *CI = dyn_cast<CallInst>(I))
return OptimizeCallInst(CI);
if (SelectInst *SI = dyn_cast<SelectInst>(I))
return OptimizeSelectInst(SI);
if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I))
return OptimizeShuffleVectorInst(SVI);
if (isa<ExtractElementInst>(I))
return OptimizeExtractElementInst(I);
return false;
}
// 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) {
SunkAddrs.clear();
bool MadeChange = false;
CurInstIterator = BB.begin();
while (CurInstIterator != BB.end())
MadeChange |= OptimizeInst(CurInstIterator++);
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 (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
Instruction *PrevNonDbgInst = nullptr;
for (BasicBlock::iterator BI = I->begin(), BE = I->end(); BI != BE;) {
Instruction *Insn = BI; ++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()) {
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;
}
// If there is a sequence that branches based on comparing a single bit
// against zero that can be combined into a single instruction, and the
// target supports folding these into a single instruction, sink the
// mask and compare into the branch uses. Do this before OptimizeBlock ->
// OptimizeInst -> OptimizeCmpExpression, which perturbs the pattern being
// searched for.
bool CodeGenPrepare::sinkAndCmp(Function &F) {
if (!EnableAndCmpSinking)
return false;
if (!TLI || !TLI->isMaskAndBranchFoldingLegal())
return false;
bool MadeChange = false;
for (Function::iterator I = F.begin(), E = F.end(); I != E; ) {
BasicBlock *BB = I++;
// Does this BB end with the following?
// %andVal = and %val, #single-bit-set
// %icmpVal = icmp %andResult, 0
// br i1 %cmpVal label %dest1, label %dest2"
BranchInst *Brcc = dyn_cast<BranchInst>(BB->getTerminator());
if (!Brcc || !Brcc->isConditional())
continue;
ICmpInst *Cmp = dyn_cast<ICmpInst>(Brcc->getOperand(0));
if (!Cmp || Cmp->getParent() != BB)
continue;
ConstantInt *Zero = dyn_cast<ConstantInt>(Cmp->getOperand(1));
if (!Zero || !Zero->isZero())
continue;
Instruction *And = dyn_cast<Instruction>(Cmp->getOperand(0));
if (!And || And->getOpcode() != Instruction::And || And->getParent() != BB)
continue;
ConstantInt* Mask = dyn_cast<ConstantInt>(And->getOperand(1));
if (!Mask || !Mask->getUniqueInteger().isPowerOf2())
continue;
DEBUG(dbgs() << "found and; icmp ?,0; brcc\n"); DEBUG(BB->dump());
// Push the "and; icmp" for any users that are conditional branches.
// Since there can only be one branch use per BB, we don't need to keep
// track of which BBs we insert into.
for (Value::use_iterator UI = Cmp->use_begin(), E = Cmp->use_end();
UI != E; ) {
Use &TheUse = *UI;
// Find brcc use.
BranchInst *BrccUser = dyn_cast<BranchInst>(*UI);
++UI;
if (!BrccUser || !BrccUser->isConditional())
continue;
BasicBlock *UserBB = BrccUser->getParent();
if (UserBB == BB) continue;
DEBUG(dbgs() << "found Brcc use\n");
// Sink the "and; icmp" to use.
MadeChange = true;
BinaryOperator *NewAnd =
BinaryOperator::CreateAnd(And->getOperand(0), And->getOperand(1), "",
BrccUser);
CmpInst *NewCmp =
CmpInst::Create(Cmp->getOpcode(), Cmp->getPredicate(), NewAnd, Zero,
"", BrccUser);
TheUse = NewCmp;
++NumAndCmpsMoved;
DEBUG(BrccUser->getParent()->dump());
}
}
return MadeChange;
}
/// \brief Retrieve the probabilities of a conditional branch. Returns true on
/// success, or returns false if no or invalid metadata was found.
static bool extractBranchMetadata(BranchInst *BI,
uint64_t &ProbTrue, uint64_t &ProbFalse) {
assert(BI->isConditional() &&
"Looking for probabilities on unconditional branch?");
auto *ProfileData = BI->getMetadata(LLVMContext::MD_prof);
if (!ProfileData || ProfileData->getNumOperands() != 3)
return false;
const auto *CITrue =
mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(1));
const auto *CIFalse =
mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(2));
if (!CITrue || !CIFalse)
return false;
ProbTrue = CITrue->getValue().getZExtValue();
ProbFalse = CIFalse->getValue().getZExtValue();
return true;
}
/// \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 / UINT32_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 != true ||
!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;
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 *InsertBefore = std::next(Function::iterator(BB))
.getNodePtrUnchecked();
auto TmpBB = BasicBlock::Create(BB.getContext(),
BB.getName() + ".cond.split",
BB.getParent(), InsertBefore);
// Update original basic block by using the first condition directly by the
// branch instruction and removing the no longer needed and/or instruction.
auto *Br1 = cast<BranchInst>(BB.getTerminator());
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 succesor'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 perfrom 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 (extractBranchMetadata(Br1, 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 (extractBranchMetadata(Br1, 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));
}
}
// Request DOM Tree update.
// Note: No point in getting fancy here, since the DT info is never
// available to CodeGenPrepare and the existing update code is broken
// anyways.
ModifiedDT = true;
MadeChange = true;
DEBUG(dbgs() << "After branch condition splitting\n"; BB.dump();
TmpBB->dump());
}
return MadeChange;
}
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