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[ExpandMemCmpPass] Preserve Dominator Tree, if available

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This finishes getting rid of all the avoidable Dominator Tree recalculations
in X86 optimized codegen pipeline.
This commit is contained in:
Roman Lebedev 2021-01-29 22:46:34 +03:00
parent e695f6dc77
commit f23effe39b
4 changed files with 75 additions and 33 deletions
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105
lib/CodeGen/ExpandMemCmp.cpp
View File

@ -13,6 +13,7 @@
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/DomTreeUpdater.h"
#include "llvm/Analysis/LazyBlockFrequencyInfo.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
@ -21,11 +22,13 @@
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/InitializePasses.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SizeOpts.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
@ -75,6 +78,7 @@ class MemCmpExpansion {
PHINode *PhiRes;
const bool IsUsedForZeroCmp;
const DataLayout &DL;
DomTreeUpdater *DTU;
IRBuilder<> Builder;
// Represents the decomposition in blocks of the expansion. For example,
// comparing 33 bytes on X86+sse can be done with 2x16-byte loads and
@ -123,7 +127,8 @@ class MemCmpExpansion {
public:
MemCmpExpansion(CallInst *CI, uint64_t Size,
const TargetTransformInfo::MemCmpExpansionOptions &Options,
const bool IsUsedForZeroCmp, const DataLayout &TheDataLayout);
const bool IsUsedForZeroCmp, const DataLayout &TheDataLayout,
DomTreeUpdater *DTU);
unsigned getNumBlocks();
uint64_t getNumLoads() const { return LoadSequence.size(); }
@ -212,10 +217,12 @@ MemCmpExpansion::computeOverlappingLoadSequence(uint64_t Size,
MemCmpExpansion::MemCmpExpansion(
CallInst *const CI, uint64_t Size,
const TargetTransformInfo::MemCmpExpansionOptions &Options,
const bool IsUsedForZeroCmp, const DataLayout &TheDataLayout)
const bool IsUsedForZeroCmp, const DataLayout &TheDataLayout,
DomTreeUpdater *DTU)
: CI(CI), Size(Size), MaxLoadSize(0), NumLoadsNonOneByte(0),
NumLoadsPerBlockForZeroCmp(Options.NumLoadsPerBlock),
IsUsedForZeroCmp(IsUsedForZeroCmp), DL(TheDataLayout), Builder(CI) {
IsUsedForZeroCmp(IsUsedForZeroCmp), DL(TheDataLayout), DTU(DTU),
Builder(CI) {
assert(Size > 0 && "zero blocks");
// Scale the max size down if the target can load more bytes than we need.
llvm::ArrayRef<unsigned> LoadSizes(Options.LoadSizes);
@ -325,13 +332,14 @@ MemCmpExpansion::LoadPair MemCmpExpansion::getLoadPair(Type *LoadSizeType,
// final phi node for selecting the memcmp result.
void MemCmpExpansion::emitLoadCompareByteBlock(unsigned BlockIndex,
unsigned OffsetBytes) {
Builder.SetInsertPoint(LoadCmpBlocks[BlockIndex]);
BasicBlock *BB = LoadCmpBlocks[BlockIndex];
Builder.SetInsertPoint(BB);
const LoadPair Loads =
getLoadPair(Type::getInt8Ty(CI->getContext()), /*NeedsBSwap=*/false,
Type::getInt32Ty(CI->getContext()), OffsetBytes);
Value *Diff = Builder.CreateSub(Loads.Lhs, Loads.Rhs);
PhiRes->addIncoming(Diff, LoadCmpBlocks[BlockIndex]);
PhiRes->addIncoming(Diff, BB);
if (BlockIndex < (LoadCmpBlocks.size() - 1)) {
// Early exit branch if difference found to EndBlock. Otherwise, continue to
@ -340,10 +348,16 @@ void MemCmpExpansion::emitLoadCompareByteBlock(unsigned BlockIndex,
ConstantInt::get(Diff->getType(), 0));
BranchInst *CmpBr =
BranchInst::Create(EndBlock, LoadCmpBlocks[BlockIndex + 1], Cmp);
if (DTU)
DTU->applyUpdates(
{{DominatorTree::Insert, BB, EndBlock},
{DominatorTree::Insert, BB, LoadCmpBlocks[BlockIndex + 1]}});
Builder.Insert(CmpBr);
} else {
// The last block has an unconditional branch to EndBlock.
BranchInst *CmpBr = BranchInst::Create(EndBlock);
if (DTU)
DTU->applyUpdates({{DominatorTree::Insert, BB, EndBlock}});
Builder.Insert(CmpBr);
}
}
@ -428,8 +442,12 @@ void MemCmpExpansion::emitLoadCompareBlockMultipleLoads(unsigned BlockIndex,
: LoadCmpBlocks[BlockIndex + 1];
// Early exit branch if difference found to ResultBlock. Otherwise,
// continue to next LoadCmpBlock or EndBlock.
BasicBlock *BB = Builder.GetInsertBlock();
BranchInst *CmpBr = BranchInst::Create(ResBlock.BB, NextBB, Cmp);
Builder.Insert(CmpBr);
if (DTU)
DTU->applyUpdates({{DominatorTree::Insert, BB, ResBlock.BB},
{DominatorTree::Insert, BB, NextBB}});
// Add a phi edge for the last LoadCmpBlock to Endblock with a value of 0
// since early exit to ResultBlock was not taken (no difference was found in
@ -482,8 +500,12 @@ void MemCmpExpansion::emitLoadCompareBlock(unsigned BlockIndex) {
: LoadCmpBlocks[BlockIndex + 1];
// Early exit branch if difference found to ResultBlock. Otherwise, continue
// to next LoadCmpBlock or EndBlock.
BasicBlock *BB = Builder.GetInsertBlock();
BranchInst *CmpBr = BranchInst::Create(NextBB, ResBlock.BB, Cmp);
Builder.Insert(CmpBr);
if (DTU)
DTU->applyUpdates({{DominatorTree::Insert, BB, NextBB},
{DominatorTree::Insert, BB, ResBlock.BB}});
// Add a phi edge for the last LoadCmpBlock to Endblock with a value of 0
// since early exit to ResultBlock was not taken (no difference was found in
@ -507,6 +529,8 @@ void MemCmpExpansion::emitMemCmpResultBlock() {
PhiRes->addIncoming(Res, ResBlock.BB);
BranchInst *NewBr = BranchInst::Create(EndBlock);
Builder.Insert(NewBr);
if (DTU)
DTU->applyUpdates({{DominatorTree::Insert, ResBlock.BB, EndBlock}});
return;
}
BasicBlock::iterator InsertPt = ResBlock.BB->getFirstInsertionPt();
@ -519,9 +543,11 @@ void MemCmpExpansion::emitMemCmpResultBlock() {
Builder.CreateSelect(Cmp, ConstantInt::get(Builder.getInt32Ty(), -1),
ConstantInt::get(Builder.getInt32Ty(), 1));
PhiRes->addIncoming(Res, ResBlock.BB);
BranchInst *NewBr = BranchInst::Create(EndBlock);
Builder.Insert(NewBr);
PhiRes->addIncoming(Res, ResBlock.BB);
if (DTU)
DTU->applyUpdates({{DominatorTree::Insert, ResBlock.BB, EndBlock}});
}
void MemCmpExpansion::setupResultBlockPHINodes() {
@ -597,7 +623,8 @@ Value *MemCmpExpansion::getMemCmpExpansion() {
// Create the basic block framework for a multi-block expansion.
if (getNumBlocks() != 1) {
BasicBlock *StartBlock = CI->getParent();
EndBlock = StartBlock->splitBasicBlock(CI, "endblock");
EndBlock = SplitBlock(StartBlock, CI, DTU, /*LI=*/nullptr,
/*MSSAU=*/nullptr, "endblock");
setupEndBlockPHINodes();
createResultBlock();
@ -610,9 +637,12 @@ Value *MemCmpExpansion::getMemCmpExpansion() {
// Create the number of required load compare basic blocks.
createLoadCmpBlocks();
// Update the terminator added by splitBasicBlock to branch to the first
// Update the terminator added by SplitBlock to branch to the first
// LoadCmpBlock.
StartBlock->getTerminator()->setSuccessor(0, LoadCmpBlocks[0]);
if (DTU)
DTU->applyUpdates({{DominatorTree::Insert, StartBlock, LoadCmpBlocks[0]},
{DominatorTree::Delete, StartBlock, EndBlock}});
}
Builder.SetCurrentDebugLocation(CI->getDebugLoc());
@ -707,7 +737,8 @@ Value *MemCmpExpansion::getMemCmpExpansion() {
/// ret i32 %phi.res
static bool expandMemCmp(CallInst *CI, const TargetTransformInfo *TTI,
const TargetLowering *TLI, const DataLayout *DL,
ProfileSummaryInfo *PSI, BlockFrequencyInfo *BFI) {
ProfileSummaryInfo *PSI, BlockFrequencyInfo *BFI,
DomTreeUpdater *DTU) {
NumMemCmpCalls++;
// Early exit from expansion if -Oz.
@ -744,7 +775,7 @@ static bool expandMemCmp(CallInst *CI, const TargetTransformInfo *TTI,
if (!OptForSize && MaxLoadsPerMemcmp.getNumOccurrences())
Options.MaxNumLoads = MaxLoadsPerMemcmp;
MemCmpExpansion Expansion(CI, SizeVal, Options, IsUsedForZeroCmp, *DL);
MemCmpExpansion Expansion(CI, SizeVal, Options, IsUsedForZeroCmp, *DL, DTU);
// Don't expand if this will require more loads than desired by the target.
if (Expansion.getNumLoads() == 0) {
@ -763,8 +794,6 @@ static bool expandMemCmp(CallInst *CI, const TargetTransformInfo *TTI,
return true;
}
class ExpandMemCmpPass : public FunctionPass {
public:
static char ID;
@ -791,7 +820,10 @@ public:
auto *BFI = (PSI && PSI->hasProfileSummary()) ?
&getAnalysis<LazyBlockFrequencyInfoPass>().getBFI() :
nullptr;
auto PA = runImpl(F, TLI, TTI, TL, PSI, BFI);
DominatorTree *DT = nullptr;
if (auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>())
DT = &DTWP->getDomTree();
auto PA = runImpl(F, TLI, TTI, TL, PSI, BFI, DT);
return !PA.areAllPreserved();
}
@ -800,25 +832,28 @@ private:
AU.addRequired<TargetLibraryInfoWrapperPass>();
AU.addRequired<TargetTransformInfoWrapperPass>();
AU.addRequired<ProfileSummaryInfoWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
LazyBlockFrequencyInfoPass::getLazyBFIAnalysisUsage(AU);
FunctionPass::getAnalysisUsage(AU);
}
PreservedAnalyses runImpl(Function &F, const TargetLibraryInfo *TLI,
const TargetTransformInfo *TTI,
const TargetLowering* TL,
ProfileSummaryInfo *PSI, BlockFrequencyInfo *BFI);
const TargetLowering *TL, ProfileSummaryInfo *PSI,
BlockFrequencyInfo *BFI, DominatorTree *DT);
// Returns true if a change was made.
bool runOnBlock(BasicBlock &BB, const TargetLibraryInfo *TLI,
const TargetTransformInfo *TTI, const TargetLowering* TL,
const DataLayout& DL, ProfileSummaryInfo *PSI,
BlockFrequencyInfo *BFI);
const TargetTransformInfo *TTI, const TargetLowering *TL,
const DataLayout &DL, ProfileSummaryInfo *PSI,
BlockFrequencyInfo *BFI, DomTreeUpdater *DTU);
};
bool ExpandMemCmpPass::runOnBlock(
BasicBlock &BB, const TargetLibraryInfo *TLI,
const TargetTransformInfo *TTI, const TargetLowering* TL,
const DataLayout& DL, ProfileSummaryInfo *PSI, BlockFrequencyInfo *BFI) {
bool ExpandMemCmpPass::runOnBlock(BasicBlock &BB, const TargetLibraryInfo *TLI,
const TargetTransformInfo *TTI,
const TargetLowering *TL,
const DataLayout &DL, ProfileSummaryInfo *PSI,
BlockFrequencyInfo *BFI,
DomTreeUpdater *DTU) {
for (Instruction& I : BB) {
CallInst *CI = dyn_cast<CallInst>(&I);
if (!CI) {
@ -827,22 +862,27 @@ bool ExpandMemCmpPass::runOnBlock(
LibFunc Func;
if (TLI->getLibFunc(*CI, Func) &&
(Func == LibFunc_memcmp || Func == LibFunc_bcmp) &&
expandMemCmp(CI, TTI, TL, &DL, PSI, BFI)) {
expandMemCmp(CI, TTI, TL, &DL, PSI, BFI, DTU)) {
return true;
}
}
return false;
}
PreservedAnalyses
ExpandMemCmpPass::runImpl(Function &F, const TargetLibraryInfo *TLI,
const TargetTransformInfo *TTI,
const TargetLowering *TL, ProfileSummaryInfo *PSI,
BlockFrequencyInfo *BFI, DominatorTree *DT) {
Optional<DomTreeUpdater> DTU;
if (DT)
DTU.emplace(DT, DomTreeUpdater::UpdateStrategy::Lazy);
PreservedAnalyses ExpandMemCmpPass::runImpl(
Function &F, const TargetLibraryInfo *TLI, const TargetTransformInfo *TTI,
const TargetLowering* TL, ProfileSummaryInfo *PSI,
BlockFrequencyInfo *BFI) {
const DataLayout& DL = F.getParent()->getDataLayout();
bool MadeChanges = false;
for (auto BBIt = F.begin(); BBIt != F.end();) {
if (runOnBlock(*BBIt, TLI, TTI, TL, DL, PSI, BFI)) {
if (runOnBlock(*BBIt, TLI, TTI, TL, DL, PSI, BFI,
DTU.hasValue() ? DTU.getPointer() : nullptr)) {
MadeChanges = true;
// If changes were made, restart the function from the beginning, since
// the structure of the function was changed.
@ -854,7 +894,11 @@ PreservedAnalyses ExpandMemCmpPass::runImpl(
if (MadeChanges)
for (BasicBlock &BB : F)
SimplifyInstructionsInBlock(&BB);
return MadeChanges ? PreservedAnalyses::none() : PreservedAnalyses::all();
if (!MadeChanges)
return PreservedAnalyses::all();
PreservedAnalyses PA;
PA.preserve<DominatorTreeAnalysis>();
return PA;
}
} // namespace
@ -866,6 +910,7 @@ INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LazyBlockFrequencyInfoPass)
INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_END(ExpandMemCmpPass, "expandmemcmp",
"Expand memcmp() to load/stores", false, false)

1
test/CodeGen/AArch64/O3-pipeline.ll
View File

@ -49,7 +49,6 @@
; CHECK-NEXT: Shadow Stack GC Lowering
; CHECK-NEXT: Lower constant intrinsics
; CHECK-NEXT: Remove unreachable blocks from the CFG
; CHECK-NEXT: Dominator Tree Construction
; CHECK-NEXT: Natural Loop Information
; CHECK-NEXT: Post-Dominator Tree Construction
; CHECK-NEXT: Branch Probability Analysis

1
test/CodeGen/ARM/O3-pipeline.ll
View File

@ -29,7 +29,6 @@
; CHECK-NEXT: Shadow Stack GC Lowering
; CHECK-NEXT: Lower constant intrinsics
; CHECK-NEXT: Remove unreachable blocks from the CFG
; CHECK-NEXT: Dominator Tree Construction
; CHECK-NEXT: Natural Loop Information
; CHECK-NEXT: Post-Dominator Tree Construction
; CHECK-NEXT: Branch Probability Analysis

1
test/CodeGen/X86/opt-pipeline.ll
View File

@ -46,7 +46,6 @@
; CHECK-NEXT: Shadow Stack GC Lowering
; CHECK-NEXT: Lower constant intrinsics
; CHECK-NEXT: Remove unreachable blocks from the CFG
; CHECK-NEXT: Dominator Tree Construction
; CHECK-NEXT: Natural Loop Information
; CHECK-NEXT: Post-Dominator Tree Construction
; CHECK-NEXT: Branch Probability Analysis