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-rw-r--r--lib/Transforms/Scalar/LoadCombine.cpp295
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diff --git a/lib/Transforms/Scalar/LoadCombine.cpp b/lib/Transforms/Scalar/LoadCombine.cpp
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--- a/lib/Transforms/Scalar/LoadCombine.cpp
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-//===- LoadCombine.cpp - Combine Adjacent Loads ---------------------------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-/// \file
-/// This transformation combines adjacent loads.
-///
-//===----------------------------------------------------------------------===//
-
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Analysis/AliasSetTracker.h"
-#include "llvm/Analysis/GlobalsModRef.h"
-#include "llvm/Analysis/TargetFolder.h"
-#include "llvm/IR/DataLayout.h"
-#include "llvm/IR/Dominators.h"
-#include "llvm/IR/Function.h"
-#include "llvm/IR/IRBuilder.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/Module.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/MathExtras.h"
-#include "llvm/Support/raw_ostream.h"
-#include "llvm/Transforms/Scalar.h"
-
-using namespace llvm;
-
-#define DEBUG_TYPE "load-combine"
-
-STATISTIC(NumLoadsAnalyzed, "Number of loads analyzed for combining");
-STATISTIC(NumLoadsCombined, "Number of loads combined");
-
-#define LDCOMBINE_NAME "Combine Adjacent Loads"
-
-namespace {
-struct PointerOffsetPair {
- Value *Pointer;
- APInt Offset;
-};
-
-struct LoadPOPPair {
- LoadInst *Load;
- PointerOffsetPair POP;
- /// \brief The new load needs to be created before the first load in IR order.
- unsigned InsertOrder;
-};
-
-class LoadCombine : public BasicBlockPass {
- LLVMContext *C;
- AliasAnalysis *AA;
- DominatorTree *DT;
-
-public:
- LoadCombine() : BasicBlockPass(ID), C(nullptr), AA(nullptr) {
- initializeLoadCombinePass(*PassRegistry::getPassRegistry());
- }
-
- using llvm::Pass::doInitialization;
- bool doInitialization(Function &) override;
- bool runOnBasicBlock(BasicBlock &BB) override;
- void getAnalysisUsage(AnalysisUsage &AU) const override {
- AU.setPreservesCFG();
- AU.addRequired<AAResultsWrapperPass>();
- AU.addRequired<DominatorTreeWrapperPass>();
- AU.addPreserved<GlobalsAAWrapperPass>();
- }
-
- StringRef getPassName() const override { return LDCOMBINE_NAME; }
- static char ID;
-
- typedef IRBuilder<TargetFolder> BuilderTy;
-
-private:
- BuilderTy *Builder;
-
- PointerOffsetPair getPointerOffsetPair(LoadInst &);
- bool combineLoads(DenseMap<const Value *, SmallVector<LoadPOPPair, 8>> &);
- bool aggregateLoads(SmallVectorImpl<LoadPOPPair> &);
- bool combineLoads(SmallVectorImpl<LoadPOPPair> &);
-};
-}
-
-bool LoadCombine::doInitialization(Function &F) {
- DEBUG(dbgs() << "LoadCombine function: " << F.getName() << "\n");
- C = &F.getContext();
- return true;
-}
-
-PointerOffsetPair LoadCombine::getPointerOffsetPair(LoadInst &LI) {
- auto &DL = LI.getModule()->getDataLayout();
-
- PointerOffsetPair POP;
- POP.Pointer = LI.getPointerOperand();
- unsigned BitWidth = DL.getPointerSizeInBits(LI.getPointerAddressSpace());
- POP.Offset = APInt(BitWidth, 0);
-
- while (isa<BitCastInst>(POP.Pointer) || isa<GetElementPtrInst>(POP.Pointer)) {
- if (auto *GEP = dyn_cast<GetElementPtrInst>(POP.Pointer)) {
- APInt LastOffset = POP.Offset;
- if (!GEP->accumulateConstantOffset(DL, POP.Offset)) {
- // Can't handle GEPs with variable indices.
- POP.Offset = LastOffset;
- return POP;
- }
- POP.Pointer = GEP->getPointerOperand();
- } else if (auto *BC = dyn_cast<BitCastInst>(POP.Pointer)) {
- POP.Pointer = BC->getOperand(0);
- }
- }
- return POP;
-}
-
-bool LoadCombine::combineLoads(
- DenseMap<const Value *, SmallVector<LoadPOPPair, 8>> &LoadMap) {
- bool Combined = false;
- for (auto &Loads : LoadMap) {
- if (Loads.second.size() < 2)
- continue;
- std::sort(Loads.second.begin(), Loads.second.end(),
- [](const LoadPOPPair &A, const LoadPOPPair &B) {
- return A.POP.Offset.slt(B.POP.Offset);
- });
- if (aggregateLoads(Loads.second))
- Combined = true;
- }
- return Combined;
-}
-
-/// \brief Try to aggregate loads from a sorted list of loads to be combined.
-///
-/// It is guaranteed that no writes occur between any of the loads. All loads
-/// have the same base pointer. There are at least two loads.
-bool LoadCombine::aggregateLoads(SmallVectorImpl<LoadPOPPair> &Loads) {
- assert(Loads.size() >= 2 && "Insufficient loads!");
- LoadInst *BaseLoad = nullptr;
- SmallVector<LoadPOPPair, 8> AggregateLoads;
- bool Combined = false;
- bool ValidPrevOffset = false;
- APInt PrevOffset;
- uint64_t PrevSize = 0;
- for (auto &L : Loads) {
- if (ValidPrevOffset == false) {
- BaseLoad = L.Load;
- PrevOffset = L.POP.Offset;
- PrevSize = L.Load->getModule()->getDataLayout().getTypeStoreSize(
- L.Load->getType());
- AggregateLoads.push_back(L);
- ValidPrevOffset = true;
- continue;
- }
- if (L.Load->getAlignment() > BaseLoad->getAlignment())
- continue;
- APInt PrevEnd = PrevOffset + PrevSize;
- if (L.POP.Offset.sgt(PrevEnd)) {
- // No other load will be combinable
- if (combineLoads(AggregateLoads))
- Combined = true;
- AggregateLoads.clear();
- ValidPrevOffset = false;
- continue;
- }
- if (L.POP.Offset != PrevEnd)
- // This load is offset less than the size of the last load.
- // FIXME: We may want to handle this case.
- continue;
- PrevOffset = L.POP.Offset;
- PrevSize = L.Load->getModule()->getDataLayout().getTypeStoreSize(
- L.Load->getType());
- AggregateLoads.push_back(L);
- }
- if (combineLoads(AggregateLoads))
- Combined = true;
- return Combined;
-}
-
-/// \brief Given a list of combinable load. Combine the maximum number of them.
-bool LoadCombine::combineLoads(SmallVectorImpl<LoadPOPPair> &Loads) {
- // Remove loads from the end while the size is not a power of 2.
- unsigned TotalSize = 0;
- for (const auto &L : Loads)
- TotalSize += L.Load->getType()->getPrimitiveSizeInBits();
- while (TotalSize != 0 && !isPowerOf2_32(TotalSize))
- TotalSize -= Loads.pop_back_val().Load->getType()->getPrimitiveSizeInBits();
- if (Loads.size() < 2)
- return false;
-
- DEBUG({
- dbgs() << "***** Combining Loads ******\n";
- for (const auto &L : Loads) {
- dbgs() << L.POP.Offset << ": " << *L.Load << "\n";
- }
- });
-
- // Find first load. This is where we put the new load.
- LoadPOPPair FirstLP;
- FirstLP.InsertOrder = -1u;
- for (const auto &L : Loads)
- if (L.InsertOrder < FirstLP.InsertOrder)
- FirstLP = L;
-
- unsigned AddressSpace =
- FirstLP.POP.Pointer->getType()->getPointerAddressSpace();
-
- Builder->SetInsertPoint(FirstLP.Load);
- Value *Ptr = Builder->CreateConstGEP1_64(
- Builder->CreatePointerCast(Loads[0].POP.Pointer,
- Builder->getInt8PtrTy(AddressSpace)),
- Loads[0].POP.Offset.getSExtValue());
- LoadInst *NewLoad = new LoadInst(
- Builder->CreatePointerCast(
- Ptr, PointerType::get(IntegerType::get(Ptr->getContext(), TotalSize),
- Ptr->getType()->getPointerAddressSpace())),
- Twine(Loads[0].Load->getName()) + ".combined", false,
- Loads[0].Load->getAlignment(), FirstLP.Load);
-
- for (const auto &L : Loads) {
- Builder->SetInsertPoint(L.Load);
- Value *V = Builder->CreateExtractInteger(
- L.Load->getModule()->getDataLayout(), NewLoad,
- cast<IntegerType>(L.Load->getType()),
- (L.POP.Offset - Loads[0].POP.Offset).getZExtValue(), "combine.extract");
- L.Load->replaceAllUsesWith(V);
- }
-
- NumLoadsCombined += Loads.size();
- return true;
-}
-
-bool LoadCombine::runOnBasicBlock(BasicBlock &BB) {
- if (skipBasicBlock(BB))
- return false;
-
- AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
- DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
-
- // Skip analysing dead blocks (not forward reachable from function entry).
- if (!DT->isReachableFromEntry(&BB)) {
- DEBUG(dbgs() << "LC: skipping unreachable " << BB.getName() <<
- " in " << BB.getParent()->getName() << "\n");
- return false;
- }
-
- IRBuilder<TargetFolder> TheBuilder(
- BB.getContext(), TargetFolder(BB.getModule()->getDataLayout()));
- Builder = &TheBuilder;
-
- DenseMap<const Value *, SmallVector<LoadPOPPair, 8>> LoadMap;
- AliasSetTracker AST(*AA);
-
- bool Combined = false;
- unsigned Index = 0;
- for (auto &I : BB) {
- if (I.mayThrow() || AST.containsUnknown(&I)) {
- if (combineLoads(LoadMap))
- Combined = true;
- LoadMap.clear();
- AST.clear();
- continue;
- }
- if (I.mayWriteToMemory()) {
- AST.add(&I);
- continue;
- }
- LoadInst *LI = dyn_cast<LoadInst>(&I);
- if (!LI)
- continue;
- ++NumLoadsAnalyzed;
- if (!LI->isSimple() || !LI->getType()->isIntegerTy())
- continue;
- auto POP = getPointerOffsetPair(*LI);
- if (!POP.Pointer)
- continue;
- LoadMap[POP.Pointer].push_back({LI, std::move(POP), Index++});
- AST.add(LI);
- }
- if (combineLoads(LoadMap))
- Combined = true;
- return Combined;
-}
-
-char LoadCombine::ID = 0;
-
-BasicBlockPass *llvm::createLoadCombinePass() {
- return new LoadCombine();
-}
-
-INITIALIZE_PASS_BEGIN(LoadCombine, "load-combine", LDCOMBINE_NAME, false, false)
-INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
-INITIALIZE_PASS_END(LoadCombine, "load-combine", LDCOMBINE_NAME, false, false)
generated by cgit v1.2.3 (git 2.25.1) at 2025-02-23 13:01:55 +0000