forked from OSchip/llvm-project
1617 lines
60 KiB
C++
1617 lines
60 KiB
C++
//===- InstCombineLoadStoreAlloca.cpp -------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the visit functions for load, store and alloca.
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//
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//===----------------------------------------------------------------------===//
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#include "InstCombineInternal.h"
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#include "llvm/ADT/MapVector.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/Loads.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/IR/ConstantRange.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/DebugInfoMetadata.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/MDBuilder.h"
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#include "llvm/IR/PatternMatch.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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using namespace llvm;
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using namespace PatternMatch;
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#define DEBUG_TYPE "instcombine"
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STATISTIC(NumDeadStore, "Number of dead stores eliminated");
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STATISTIC(NumGlobalCopies, "Number of allocas copied from constant global");
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/// pointsToConstantGlobal - Return true if V (possibly indirectly) points to
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/// some part of a constant global variable. This intentionally only accepts
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/// constant expressions because we can't rewrite arbitrary instructions.
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static bool pointsToConstantGlobal(Value *V) {
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if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
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return GV->isConstant();
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if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
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if (CE->getOpcode() == Instruction::BitCast ||
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CE->getOpcode() == Instruction::AddrSpaceCast ||
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CE->getOpcode() == Instruction::GetElementPtr)
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return pointsToConstantGlobal(CE->getOperand(0));
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}
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return false;
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}
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/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
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/// pointer to an alloca. Ignore any reads of the pointer, return false if we
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/// see any stores or other unknown uses. If we see pointer arithmetic, keep
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/// track of whether it moves the pointer (with IsOffset) but otherwise traverse
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/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
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/// the alloca, and if the source pointer is a pointer to a constant global, we
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/// can optimize this.
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static bool
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isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
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SmallVectorImpl<Instruction *> &ToDelete) {
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// We track lifetime intrinsics as we encounter them. If we decide to go
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// ahead and replace the value with the global, this lets the caller quickly
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// eliminate the markers.
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SmallVector<std::pair<Value *, bool>, 35> ValuesToInspect;
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ValuesToInspect.emplace_back(V, false);
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while (!ValuesToInspect.empty()) {
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auto ValuePair = ValuesToInspect.pop_back_val();
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const bool IsOffset = ValuePair.second;
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for (auto &U : ValuePair.first->uses()) {
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auto *I = cast<Instruction>(U.getUser());
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if (auto *LI = dyn_cast<LoadInst>(I)) {
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// Ignore non-volatile loads, they are always ok.
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if (!LI->isSimple()) return false;
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continue;
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}
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if (isa<BitCastInst>(I) || isa<AddrSpaceCastInst>(I)) {
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// If uses of the bitcast are ok, we are ok.
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ValuesToInspect.emplace_back(I, IsOffset);
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continue;
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}
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if (auto *GEP = dyn_cast<GetElementPtrInst>(I)) {
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// If the GEP has all zero indices, it doesn't offset the pointer. If it
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// doesn't, it does.
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ValuesToInspect.emplace_back(I, IsOffset || !GEP->hasAllZeroIndices());
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continue;
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}
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if (auto *Call = dyn_cast<CallBase>(I)) {
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// If this is the function being called then we treat it like a load and
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// ignore it.
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if (Call->isCallee(&U))
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continue;
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unsigned DataOpNo = Call->getDataOperandNo(&U);
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bool IsArgOperand = Call->isArgOperand(&U);
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// Inalloca arguments are clobbered by the call.
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if (IsArgOperand && Call->isInAllocaArgument(DataOpNo))
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return false;
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// If this is a readonly/readnone call site, then we know it is just a
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// load (but one that potentially returns the value itself), so we can
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// ignore it if we know that the value isn't captured.
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if (Call->onlyReadsMemory() &&
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(Call->use_empty() || Call->doesNotCapture(DataOpNo)))
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continue;
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// If this is being passed as a byval argument, the caller is making a
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// copy, so it is only a read of the alloca.
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if (IsArgOperand && Call->isByValArgument(DataOpNo))
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continue;
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}
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// Lifetime intrinsics can be handled by the caller.
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if (I->isLifetimeStartOrEnd()) {
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assert(I->use_empty() && "Lifetime markers have no result to use!");
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ToDelete.push_back(I);
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continue;
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}
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// If this is isn't our memcpy/memmove, reject it as something we can't
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// handle.
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MemTransferInst *MI = dyn_cast<MemTransferInst>(I);
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if (!MI)
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return false;
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// If the transfer is using the alloca as a source of the transfer, then
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// ignore it since it is a load (unless the transfer is volatile).
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if (U.getOperandNo() == 1) {
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if (MI->isVolatile()) return false;
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continue;
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}
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// If we already have seen a copy, reject the second one.
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if (TheCopy) return false;
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// If the pointer has been offset from the start of the alloca, we can't
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// safely handle this.
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if (IsOffset) return false;
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// If the memintrinsic isn't using the alloca as the dest, reject it.
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if (U.getOperandNo() != 0) return false;
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// If the source of the memcpy/move is not a constant global, reject it.
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if (!pointsToConstantGlobal(MI->getSource()))
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return false;
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// Otherwise, the transform is safe. Remember the copy instruction.
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TheCopy = MI;
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}
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}
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return true;
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}
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/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
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/// modified by a copy from a constant global. If we can prove this, we can
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/// replace any uses of the alloca with uses of the global directly.
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static MemTransferInst *
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isOnlyCopiedFromConstantGlobal(AllocaInst *AI,
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SmallVectorImpl<Instruction *> &ToDelete) {
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MemTransferInst *TheCopy = nullptr;
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if (isOnlyCopiedFromConstantGlobal(AI, TheCopy, ToDelete))
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return TheCopy;
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return nullptr;
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}
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/// Returns true if V is dereferenceable for size of alloca.
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static bool isDereferenceableForAllocaSize(const Value *V, const AllocaInst *AI,
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const DataLayout &DL) {
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if (AI->isArrayAllocation())
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return false;
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uint64_t AllocaSize = DL.getTypeStoreSize(AI->getAllocatedType());
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if (!AllocaSize)
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return false;
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return isDereferenceableAndAlignedPointer(V, Align(AI->getAlignment()),
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APInt(64, AllocaSize), DL);
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}
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static Instruction *simplifyAllocaArraySize(InstCombiner &IC, AllocaInst &AI) {
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// Check for array size of 1 (scalar allocation).
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if (!AI.isArrayAllocation()) {
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// i32 1 is the canonical array size for scalar allocations.
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if (AI.getArraySize()->getType()->isIntegerTy(32))
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return nullptr;
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// Canonicalize it.
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Value *V = IC.Builder.getInt32(1);
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AI.setOperand(0, V);
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return &AI;
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}
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// Convert: alloca Ty, C - where C is a constant != 1 into: alloca [C x Ty], 1
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if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) {
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if (C->getValue().getActiveBits() <= 64) {
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Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getZExtValue());
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AllocaInst *New = IC.Builder.CreateAlloca(NewTy, nullptr, AI.getName());
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New->setAlignment(MaybeAlign(AI.getAlignment()));
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// Scan to the end of the allocation instructions, to skip over a block of
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// allocas if possible...also skip interleaved debug info
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//
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BasicBlock::iterator It(New);
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while (isa<AllocaInst>(*It) || isa<DbgInfoIntrinsic>(*It))
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++It;
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// Now that I is pointing to the first non-allocation-inst in the block,
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// insert our getelementptr instruction...
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//
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Type *IdxTy = IC.getDataLayout().getIntPtrType(AI.getType());
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Value *NullIdx = Constant::getNullValue(IdxTy);
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Value *Idx[2] = {NullIdx, NullIdx};
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Instruction *GEP = GetElementPtrInst::CreateInBounds(
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NewTy, New, Idx, New->getName() + ".sub");
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IC.InsertNewInstBefore(GEP, *It);
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// Now make everything use the getelementptr instead of the original
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// allocation.
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return IC.replaceInstUsesWith(AI, GEP);
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}
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}
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if (isa<UndefValue>(AI.getArraySize()))
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return IC.replaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
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// Ensure that the alloca array size argument has type intptr_t, so that
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// any casting is exposed early.
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Type *IntPtrTy = IC.getDataLayout().getIntPtrType(AI.getType());
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if (AI.getArraySize()->getType() != IntPtrTy) {
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Value *V = IC.Builder.CreateIntCast(AI.getArraySize(), IntPtrTy, false);
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AI.setOperand(0, V);
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return &AI;
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}
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return nullptr;
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}
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namespace {
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// If I and V are pointers in different address space, it is not allowed to
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// use replaceAllUsesWith since I and V have different types. A
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// non-target-specific transformation should not use addrspacecast on V since
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// the two address space may be disjoint depending on target.
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//
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// This class chases down uses of the old pointer until reaching the load
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// instructions, then replaces the old pointer in the load instructions with
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// the new pointer. If during the chasing it sees bitcast or GEP, it will
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// create new bitcast or GEP with the new pointer and use them in the load
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// instruction.
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class PointerReplacer {
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public:
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PointerReplacer(InstCombiner &IC) : IC(IC) {}
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void replacePointer(Instruction &I, Value *V);
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private:
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void findLoadAndReplace(Instruction &I);
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void replace(Instruction *I);
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Value *getReplacement(Value *I);
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SmallVector<Instruction *, 4> Path;
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MapVector<Value *, Value *> WorkMap;
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InstCombiner &IC;
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};
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} // end anonymous namespace
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void PointerReplacer::findLoadAndReplace(Instruction &I) {
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for (auto U : I.users()) {
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auto *Inst = dyn_cast<Instruction>(&*U);
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if (!Inst)
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return;
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LLVM_DEBUG(dbgs() << "Found pointer user: " << *U << '\n');
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if (isa<LoadInst>(Inst)) {
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for (auto P : Path)
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replace(P);
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replace(Inst);
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} else if (isa<GetElementPtrInst>(Inst) || isa<BitCastInst>(Inst)) {
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Path.push_back(Inst);
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findLoadAndReplace(*Inst);
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Path.pop_back();
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} else {
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return;
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}
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}
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}
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Value *PointerReplacer::getReplacement(Value *V) {
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auto Loc = WorkMap.find(V);
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if (Loc != WorkMap.end())
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return Loc->second;
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return nullptr;
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}
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void PointerReplacer::replace(Instruction *I) {
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if (getReplacement(I))
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return;
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if (auto *LT = dyn_cast<LoadInst>(I)) {
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auto *V = getReplacement(LT->getPointerOperand());
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assert(V && "Operand not replaced");
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auto *NewI = new LoadInst(I->getType(), V);
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NewI->takeName(LT);
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IC.InsertNewInstWith(NewI, *LT);
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IC.replaceInstUsesWith(*LT, NewI);
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WorkMap[LT] = NewI;
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} else if (auto *GEP = dyn_cast<GetElementPtrInst>(I)) {
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auto *V = getReplacement(GEP->getPointerOperand());
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assert(V && "Operand not replaced");
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SmallVector<Value *, 8> Indices;
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Indices.append(GEP->idx_begin(), GEP->idx_end());
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auto *NewI = GetElementPtrInst::Create(
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V->getType()->getPointerElementType(), V, Indices);
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IC.InsertNewInstWith(NewI, *GEP);
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NewI->takeName(GEP);
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WorkMap[GEP] = NewI;
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} else if (auto *BC = dyn_cast<BitCastInst>(I)) {
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auto *V = getReplacement(BC->getOperand(0));
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assert(V && "Operand not replaced");
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auto *NewT = PointerType::get(BC->getType()->getPointerElementType(),
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V->getType()->getPointerAddressSpace());
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auto *NewI = new BitCastInst(V, NewT);
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IC.InsertNewInstWith(NewI, *BC);
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NewI->takeName(BC);
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WorkMap[BC] = NewI;
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} else {
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llvm_unreachable("should never reach here");
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}
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}
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void PointerReplacer::replacePointer(Instruction &I, Value *V) {
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#ifndef NDEBUG
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auto *PT = cast<PointerType>(I.getType());
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auto *NT = cast<PointerType>(V->getType());
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assert(PT != NT && PT->getElementType() == NT->getElementType() &&
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"Invalid usage");
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#endif
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WorkMap[&I] = V;
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findLoadAndReplace(I);
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}
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Instruction *InstCombiner::visitAllocaInst(AllocaInst &AI) {
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if (auto *I = simplifyAllocaArraySize(*this, AI))
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return I;
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if (AI.getAllocatedType()->isSized()) {
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// If the alignment is 0 (unspecified), assign it the preferred alignment.
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if (AI.getAlignment() == 0)
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AI.setAlignment(
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MaybeAlign(DL.getPrefTypeAlignment(AI.getAllocatedType())));
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// Move all alloca's of zero byte objects to the entry block and merge them
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// together. Note that we only do this for alloca's, because malloc should
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// allocate and return a unique pointer, even for a zero byte allocation.
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if (DL.getTypeAllocSize(AI.getAllocatedType()) == 0) {
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// For a zero sized alloca there is no point in doing an array allocation.
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// This is helpful if the array size is a complicated expression not used
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// elsewhere.
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if (AI.isArrayAllocation()) {
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AI.setOperand(0, ConstantInt::get(AI.getArraySize()->getType(), 1));
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return &AI;
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}
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// Get the first instruction in the entry block.
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BasicBlock &EntryBlock = AI.getParent()->getParent()->getEntryBlock();
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Instruction *FirstInst = EntryBlock.getFirstNonPHIOrDbg();
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if (FirstInst != &AI) {
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// If the entry block doesn't start with a zero-size alloca then move
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// this one to the start of the entry block. There is no problem with
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// dominance as the array size was forced to a constant earlier already.
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AllocaInst *EntryAI = dyn_cast<AllocaInst>(FirstInst);
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if (!EntryAI || !EntryAI->getAllocatedType()->isSized() ||
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DL.getTypeAllocSize(EntryAI->getAllocatedType()) != 0) {
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AI.moveBefore(FirstInst);
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return &AI;
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}
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// If the alignment of the entry block alloca is 0 (unspecified),
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// assign it the preferred alignment.
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if (EntryAI->getAlignment() == 0)
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EntryAI->setAlignment(
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MaybeAlign(DL.getPrefTypeAlignment(EntryAI->getAllocatedType())));
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// Replace this zero-sized alloca with the one at the start of the entry
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// block after ensuring that the address will be aligned enough for both
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// types.
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const MaybeAlign MaxAlign(
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std::max(EntryAI->getAlignment(), AI.getAlignment()));
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EntryAI->setAlignment(MaxAlign);
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if (AI.getType() != EntryAI->getType())
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return new BitCastInst(EntryAI, AI.getType());
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return replaceInstUsesWith(AI, EntryAI);
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}
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}
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}
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if (AI.getAlignment()) {
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// Check to see if this allocation is only modified by a memcpy/memmove from
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// a constant global whose alignment is equal to or exceeds that of the
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// allocation. If this is the case, we can change all users to use
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// the constant global instead. This is commonly produced by the CFE by
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// constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
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// is only subsequently read.
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SmallVector<Instruction *, 4> ToDelete;
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if (MemTransferInst *Copy = isOnlyCopiedFromConstantGlobal(&AI, ToDelete)) {
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unsigned SourceAlign = getOrEnforceKnownAlignment(
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Copy->getSource(), AI.getAlignment(), DL, &AI, &AC, &DT);
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if (AI.getAlignment() <= SourceAlign &&
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isDereferenceableForAllocaSize(Copy->getSource(), &AI, DL)) {
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LLVM_DEBUG(dbgs() << "Found alloca equal to global: " << AI << '\n');
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LLVM_DEBUG(dbgs() << " memcpy = " << *Copy << '\n');
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for (unsigned i = 0, e = ToDelete.size(); i != e; ++i)
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eraseInstFromFunction(*ToDelete[i]);
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Constant *TheSrc = cast<Constant>(Copy->getSource());
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auto *SrcTy = TheSrc->getType();
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auto *DestTy = PointerType::get(AI.getType()->getPointerElementType(),
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SrcTy->getPointerAddressSpace());
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Constant *Cast =
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ConstantExpr::getPointerBitCastOrAddrSpaceCast(TheSrc, DestTy);
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if (AI.getType()->getPointerAddressSpace() ==
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SrcTy->getPointerAddressSpace()) {
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Instruction *NewI = replaceInstUsesWith(AI, Cast);
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eraseInstFromFunction(*Copy);
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++NumGlobalCopies;
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return NewI;
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} else {
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PointerReplacer PtrReplacer(*this);
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PtrReplacer.replacePointer(AI, Cast);
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++NumGlobalCopies;
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}
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}
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}
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}
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// At last, use the generic allocation site handler to aggressively remove
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// unused allocas.
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return visitAllocSite(AI);
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}
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// Are we allowed to form a atomic load or store of this type?
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static bool isSupportedAtomicType(Type *Ty) {
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return Ty->isIntOrPtrTy() || Ty->isFloatingPointTy();
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}
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/// Helper to combine a load to a new type.
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///
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/// This just does the work of combining a load to a new type. It handles
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/// metadata, etc., and returns the new instruction. The \c NewTy should be the
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/// loaded *value* type. This will convert it to a pointer, cast the operand to
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/// that pointer type, load it, etc.
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///
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/// Note that this will create all of the instructions with whatever insert
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/// point the \c InstCombiner currently is using.
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LoadInst *InstCombiner::combineLoadToNewType(LoadInst &LI, Type *NewTy,
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const Twine &Suffix) {
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assert((!LI.isAtomic() || isSupportedAtomicType(NewTy)) &&
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"can't fold an atomic load to requested type");
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Value *Ptr = LI.getPointerOperand();
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unsigned AS = LI.getPointerAddressSpace();
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Value *NewPtr = nullptr;
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if (!(match(Ptr, m_BitCast(m_Value(NewPtr))) &&
|
|
NewPtr->getType()->getPointerElementType() == NewTy &&
|
|
NewPtr->getType()->getPointerAddressSpace() == AS))
|
|
NewPtr = Builder.CreateBitCast(Ptr, NewTy->getPointerTo(AS));
|
|
|
|
unsigned Align = LI.getAlignment();
|
|
if (!Align)
|
|
// If old load did not have an explicit alignment specified,
|
|
// manually preserve the implied (ABI) alignment of the load.
|
|
// Else we may inadvertently incorrectly over-promise alignment.
|
|
Align = getDataLayout().getABITypeAlignment(LI.getType());
|
|
|
|
LoadInst *NewLoad = Builder.CreateAlignedLoad(
|
|
NewTy, NewPtr, Align, LI.isVolatile(), LI.getName() + Suffix);
|
|
NewLoad->setAtomic(LI.getOrdering(), LI.getSyncScopeID());
|
|
copyMetadataForLoad(*NewLoad, LI);
|
|
return NewLoad;
|
|
}
|
|
|
|
/// Combine a store to a new type.
|
|
///
|
|
/// Returns the newly created store instruction.
|
|
static StoreInst *combineStoreToNewValue(InstCombiner &IC, StoreInst &SI, Value *V) {
|
|
assert((!SI.isAtomic() || isSupportedAtomicType(V->getType())) &&
|
|
"can't fold an atomic store of requested type");
|
|
|
|
Value *Ptr = SI.getPointerOperand();
|
|
unsigned AS = SI.getPointerAddressSpace();
|
|
SmallVector<std::pair<unsigned, MDNode *>, 8> MD;
|
|
SI.getAllMetadata(MD);
|
|
|
|
StoreInst *NewStore = IC.Builder.CreateAlignedStore(
|
|
V, IC.Builder.CreateBitCast(Ptr, V->getType()->getPointerTo(AS)),
|
|
SI.getAlignment(), SI.isVolatile());
|
|
NewStore->setAtomic(SI.getOrdering(), SI.getSyncScopeID());
|
|
for (const auto &MDPair : MD) {
|
|
unsigned ID = MDPair.first;
|
|
MDNode *N = MDPair.second;
|
|
// Note, essentially every kind of metadata should be preserved here! This
|
|
// routine is supposed to clone a store instruction changing *only its
|
|
// type*. The only metadata it makes sense to drop is metadata which is
|
|
// invalidated when the pointer type changes. This should essentially
|
|
// never be the case in LLVM, but we explicitly switch over only known
|
|
// metadata to be conservatively correct. If you are adding metadata to
|
|
// LLVM which pertains to stores, you almost certainly want to add it
|
|
// here.
|
|
switch (ID) {
|
|
case LLVMContext::MD_dbg:
|
|
case LLVMContext::MD_tbaa:
|
|
case LLVMContext::MD_prof:
|
|
case LLVMContext::MD_fpmath:
|
|
case LLVMContext::MD_tbaa_struct:
|
|
case LLVMContext::MD_alias_scope:
|
|
case LLVMContext::MD_noalias:
|
|
case LLVMContext::MD_nontemporal:
|
|
case LLVMContext::MD_mem_parallel_loop_access:
|
|
case LLVMContext::MD_access_group:
|
|
// All of these directly apply.
|
|
NewStore->setMetadata(ID, N);
|
|
break;
|
|
case LLVMContext::MD_invariant_load:
|
|
case LLVMContext::MD_nonnull:
|
|
case LLVMContext::MD_range:
|
|
case LLVMContext::MD_align:
|
|
case LLVMContext::MD_dereferenceable:
|
|
case LLVMContext::MD_dereferenceable_or_null:
|
|
// These don't apply for stores.
|
|
break;
|
|
}
|
|
}
|
|
|
|
return NewStore;
|
|
}
|
|
|
|
/// Returns true if instruction represent minmax pattern like:
|
|
/// select ((cmp load V1, load V2), V1, V2).
|
|
static bool isMinMaxWithLoads(Value *V, Type *&LoadTy) {
|
|
assert(V->getType()->isPointerTy() && "Expected pointer type.");
|
|
// Ignore possible ty* to ixx* bitcast.
|
|
V = peekThroughBitcast(V);
|
|
// Check that select is select ((cmp load V1, load V2), V1, V2) - minmax
|
|
// pattern.
|
|
CmpInst::Predicate Pred;
|
|
Instruction *L1;
|
|
Instruction *L2;
|
|
Value *LHS;
|
|
Value *RHS;
|
|
if (!match(V, m_Select(m_Cmp(Pred, m_Instruction(L1), m_Instruction(L2)),
|
|
m_Value(LHS), m_Value(RHS))))
|
|
return false;
|
|
LoadTy = L1->getType();
|
|
return (match(L1, m_Load(m_Specific(LHS))) &&
|
|
match(L2, m_Load(m_Specific(RHS)))) ||
|
|
(match(L1, m_Load(m_Specific(RHS))) &&
|
|
match(L2, m_Load(m_Specific(LHS))));
|
|
}
|
|
|
|
/// Combine loads to match the type of their uses' value after looking
|
|
/// through intervening bitcasts.
|
|
///
|
|
/// The core idea here is that if the result of a load is used in an operation,
|
|
/// we should load the type most conducive to that operation. For example, when
|
|
/// loading an integer and converting that immediately to a pointer, we should
|
|
/// instead directly load a pointer.
|
|
///
|
|
/// However, this routine must never change the width of a load or the number of
|
|
/// loads as that would introduce a semantic change. This combine is expected to
|
|
/// be a semantic no-op which just allows loads to more closely model the types
|
|
/// of their consuming operations.
|
|
///
|
|
/// Currently, we also refuse to change the precise type used for an atomic load
|
|
/// or a volatile load. This is debatable, and might be reasonable to change
|
|
/// later. However, it is risky in case some backend or other part of LLVM is
|
|
/// relying on the exact type loaded to select appropriate atomic operations.
|
|
static Instruction *combineLoadToOperationType(InstCombiner &IC, LoadInst &LI) {
|
|
// FIXME: We could probably with some care handle both volatile and ordered
|
|
// atomic loads here but it isn't clear that this is important.
|
|
if (!LI.isUnordered())
|
|
return nullptr;
|
|
|
|
if (LI.use_empty())
|
|
return nullptr;
|
|
|
|
// swifterror values can't be bitcasted.
|
|
if (LI.getPointerOperand()->isSwiftError())
|
|
return nullptr;
|
|
|
|
Type *Ty = LI.getType();
|
|
const DataLayout &DL = IC.getDataLayout();
|
|
|
|
// Try to canonicalize loads which are only ever stored to operate over
|
|
// integers instead of any other type. We only do this when the loaded type
|
|
// is sized and has a size exactly the same as its store size and the store
|
|
// size is a legal integer type.
|
|
// Do not perform canonicalization if minmax pattern is found (to avoid
|
|
// infinite loop).
|
|
Type *Dummy;
|
|
if (!Ty->isIntegerTy() && Ty->isSized() &&
|
|
!(Ty->isVectorTy() && Ty->getVectorIsScalable()) &&
|
|
DL.isLegalInteger(DL.getTypeStoreSizeInBits(Ty)) &&
|
|
DL.typeSizeEqualsStoreSize(Ty) &&
|
|
!DL.isNonIntegralPointerType(Ty) &&
|
|
!isMinMaxWithLoads(
|
|
peekThroughBitcast(LI.getPointerOperand(), /*OneUseOnly=*/true),
|
|
Dummy)) {
|
|
if (all_of(LI.users(), [&LI](User *U) {
|
|
auto *SI = dyn_cast<StoreInst>(U);
|
|
return SI && SI->getPointerOperand() != &LI &&
|
|
!SI->getPointerOperand()->isSwiftError();
|
|
})) {
|
|
LoadInst *NewLoad = IC.combineLoadToNewType(
|
|
LI, Type::getIntNTy(LI.getContext(), DL.getTypeStoreSizeInBits(Ty)));
|
|
// Replace all the stores with stores of the newly loaded value.
|
|
for (auto UI = LI.user_begin(), UE = LI.user_end(); UI != UE;) {
|
|
auto *SI = cast<StoreInst>(*UI++);
|
|
IC.Builder.SetInsertPoint(SI);
|
|
combineStoreToNewValue(IC, *SI, NewLoad);
|
|
IC.eraseInstFromFunction(*SI);
|
|
}
|
|
assert(LI.use_empty() && "Failed to remove all users of the load!");
|
|
// Return the old load so the combiner can delete it safely.
|
|
return &LI;
|
|
}
|
|
}
|
|
|
|
// Fold away bit casts of the loaded value by loading the desired type.
|
|
// We can do this for BitCastInsts as well as casts from and to pointer types,
|
|
// as long as those are noops (i.e., the source or dest type have the same
|
|
// bitwidth as the target's pointers).
|
|
if (LI.hasOneUse())
|
|
if (auto* CI = dyn_cast<CastInst>(LI.user_back()))
|
|
if (CI->isNoopCast(DL))
|
|
if (!LI.isAtomic() || isSupportedAtomicType(CI->getDestTy())) {
|
|
LoadInst *NewLoad = IC.combineLoadToNewType(LI, CI->getDestTy());
|
|
CI->replaceAllUsesWith(NewLoad);
|
|
IC.eraseInstFromFunction(*CI);
|
|
return &LI;
|
|
}
|
|
|
|
// FIXME: We should also canonicalize loads of vectors when their elements are
|
|
// cast to other types.
|
|
return nullptr;
|
|
}
|
|
|
|
static Instruction *unpackLoadToAggregate(InstCombiner &IC, LoadInst &LI) {
|
|
// FIXME: We could probably with some care handle both volatile and atomic
|
|
// stores here but it isn't clear that this is important.
|
|
if (!LI.isSimple())
|
|
return nullptr;
|
|
|
|
Type *T = LI.getType();
|
|
if (!T->isAggregateType())
|
|
return nullptr;
|
|
|
|
StringRef Name = LI.getName();
|
|
assert(LI.getAlignment() && "Alignment must be set at this point");
|
|
|
|
if (auto *ST = dyn_cast<StructType>(T)) {
|
|
// If the struct only have one element, we unpack.
|
|
auto NumElements = ST->getNumElements();
|
|
if (NumElements == 1) {
|
|
LoadInst *NewLoad = IC.combineLoadToNewType(LI, ST->getTypeAtIndex(0U),
|
|
".unpack");
|
|
AAMDNodes AAMD;
|
|
LI.getAAMetadata(AAMD);
|
|
NewLoad->setAAMetadata(AAMD);
|
|
return IC.replaceInstUsesWith(LI, IC.Builder.CreateInsertValue(
|
|
UndefValue::get(T), NewLoad, 0, Name));
|
|
}
|
|
|
|
// We don't want to break loads with padding here as we'd loose
|
|
// the knowledge that padding exists for the rest of the pipeline.
|
|
const DataLayout &DL = IC.getDataLayout();
|
|
auto *SL = DL.getStructLayout(ST);
|
|
if (SL->hasPadding())
|
|
return nullptr;
|
|
|
|
auto Align = LI.getAlignment();
|
|
if (!Align)
|
|
Align = DL.getABITypeAlignment(ST);
|
|
|
|
auto *Addr = LI.getPointerOperand();
|
|
auto *IdxType = Type::getInt32Ty(T->getContext());
|
|
auto *Zero = ConstantInt::get(IdxType, 0);
|
|
|
|
Value *V = UndefValue::get(T);
|
|
for (unsigned i = 0; i < NumElements; i++) {
|
|
Value *Indices[2] = {
|
|
Zero,
|
|
ConstantInt::get(IdxType, i),
|
|
};
|
|
auto *Ptr = IC.Builder.CreateInBoundsGEP(ST, Addr, makeArrayRef(Indices),
|
|
Name + ".elt");
|
|
auto EltAlign = MinAlign(Align, SL->getElementOffset(i));
|
|
auto *L = IC.Builder.CreateAlignedLoad(ST->getElementType(i), Ptr,
|
|
EltAlign, Name + ".unpack");
|
|
// Propagate AA metadata. It'll still be valid on the narrowed load.
|
|
AAMDNodes AAMD;
|
|
LI.getAAMetadata(AAMD);
|
|
L->setAAMetadata(AAMD);
|
|
V = IC.Builder.CreateInsertValue(V, L, i);
|
|
}
|
|
|
|
V->setName(Name);
|
|
return IC.replaceInstUsesWith(LI, V);
|
|
}
|
|
|
|
if (auto *AT = dyn_cast<ArrayType>(T)) {
|
|
auto *ET = AT->getElementType();
|
|
auto NumElements = AT->getNumElements();
|
|
if (NumElements == 1) {
|
|
LoadInst *NewLoad = IC.combineLoadToNewType(LI, ET, ".unpack");
|
|
AAMDNodes AAMD;
|
|
LI.getAAMetadata(AAMD);
|
|
NewLoad->setAAMetadata(AAMD);
|
|
return IC.replaceInstUsesWith(LI, IC.Builder.CreateInsertValue(
|
|
UndefValue::get(T), NewLoad, 0, Name));
|
|
}
|
|
|
|
// Bail out if the array is too large. Ideally we would like to optimize
|
|
// arrays of arbitrary size but this has a terrible impact on compile time.
|
|
// The threshold here is chosen arbitrarily, maybe needs a little bit of
|
|
// tuning.
|
|
if (NumElements > IC.MaxArraySizeForCombine)
|
|
return nullptr;
|
|
|
|
const DataLayout &DL = IC.getDataLayout();
|
|
auto EltSize = DL.getTypeAllocSize(ET);
|
|
auto Align = LI.getAlignment();
|
|
if (!Align)
|
|
Align = DL.getABITypeAlignment(T);
|
|
|
|
auto *Addr = LI.getPointerOperand();
|
|
auto *IdxType = Type::getInt64Ty(T->getContext());
|
|
auto *Zero = ConstantInt::get(IdxType, 0);
|
|
|
|
Value *V = UndefValue::get(T);
|
|
uint64_t Offset = 0;
|
|
for (uint64_t i = 0; i < NumElements; i++) {
|
|
Value *Indices[2] = {
|
|
Zero,
|
|
ConstantInt::get(IdxType, i),
|
|
};
|
|
auto *Ptr = IC.Builder.CreateInBoundsGEP(AT, Addr, makeArrayRef(Indices),
|
|
Name + ".elt");
|
|
auto *L = IC.Builder.CreateAlignedLoad(
|
|
AT->getElementType(), Ptr, MinAlign(Align, Offset), Name + ".unpack");
|
|
AAMDNodes AAMD;
|
|
LI.getAAMetadata(AAMD);
|
|
L->setAAMetadata(AAMD);
|
|
V = IC.Builder.CreateInsertValue(V, L, i);
|
|
Offset += EltSize;
|
|
}
|
|
|
|
V->setName(Name);
|
|
return IC.replaceInstUsesWith(LI, V);
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
// If we can determine that all possible objects pointed to by the provided
|
|
// pointer value are, not only dereferenceable, but also definitively less than
|
|
// or equal to the provided maximum size, then return true. Otherwise, return
|
|
// false (constant global values and allocas fall into this category).
|
|
//
|
|
// FIXME: This should probably live in ValueTracking (or similar).
|
|
static bool isObjectSizeLessThanOrEq(Value *V, uint64_t MaxSize,
|
|
const DataLayout &DL) {
|
|
SmallPtrSet<Value *, 4> Visited;
|
|
SmallVector<Value *, 4> Worklist(1, V);
|
|
|
|
do {
|
|
Value *P = Worklist.pop_back_val();
|
|
P = P->stripPointerCasts();
|
|
|
|
if (!Visited.insert(P).second)
|
|
continue;
|
|
|
|
if (SelectInst *SI = dyn_cast<SelectInst>(P)) {
|
|
Worklist.push_back(SI->getTrueValue());
|
|
Worklist.push_back(SI->getFalseValue());
|
|
continue;
|
|
}
|
|
|
|
if (PHINode *PN = dyn_cast<PHINode>(P)) {
|
|
for (Value *IncValue : PN->incoming_values())
|
|
Worklist.push_back(IncValue);
|
|
continue;
|
|
}
|
|
|
|
if (GlobalAlias *GA = dyn_cast<GlobalAlias>(P)) {
|
|
if (GA->isInterposable())
|
|
return false;
|
|
Worklist.push_back(GA->getAliasee());
|
|
continue;
|
|
}
|
|
|
|
// If we know how big this object is, and it is less than MaxSize, continue
|
|
// searching. Otherwise, return false.
|
|
if (AllocaInst *AI = dyn_cast<AllocaInst>(P)) {
|
|
if (!AI->getAllocatedType()->isSized())
|
|
return false;
|
|
|
|
ConstantInt *CS = dyn_cast<ConstantInt>(AI->getArraySize());
|
|
if (!CS)
|
|
return false;
|
|
|
|
uint64_t TypeSize = DL.getTypeAllocSize(AI->getAllocatedType());
|
|
// Make sure that, even if the multiplication below would wrap as an
|
|
// uint64_t, we still do the right thing.
|
|
if ((CS->getValue().zextOrSelf(128)*APInt(128, TypeSize)).ugt(MaxSize))
|
|
return false;
|
|
continue;
|
|
}
|
|
|
|
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
|
|
if (!GV->hasDefinitiveInitializer() || !GV->isConstant())
|
|
return false;
|
|
|
|
uint64_t InitSize = DL.getTypeAllocSize(GV->getValueType());
|
|
if (InitSize > MaxSize)
|
|
return false;
|
|
continue;
|
|
}
|
|
|
|
return false;
|
|
} while (!Worklist.empty());
|
|
|
|
return true;
|
|
}
|
|
|
|
// If we're indexing into an object of a known size, and the outer index is
|
|
// not a constant, but having any value but zero would lead to undefined
|
|
// behavior, replace it with zero.
|
|
//
|
|
// For example, if we have:
|
|
// @f.a = private unnamed_addr constant [1 x i32] [i32 12], align 4
|
|
// ...
|
|
// %arrayidx = getelementptr inbounds [1 x i32]* @f.a, i64 0, i64 %x
|
|
// ... = load i32* %arrayidx, align 4
|
|
// Then we know that we can replace %x in the GEP with i64 0.
|
|
//
|
|
// FIXME: We could fold any GEP index to zero that would cause UB if it were
|
|
// not zero. Currently, we only handle the first such index. Also, we could
|
|
// also search through non-zero constant indices if we kept track of the
|
|
// offsets those indices implied.
|
|
static bool canReplaceGEPIdxWithZero(InstCombiner &IC, GetElementPtrInst *GEPI,
|
|
Instruction *MemI, unsigned &Idx) {
|
|
if (GEPI->getNumOperands() < 2)
|
|
return false;
|
|
|
|
// Find the first non-zero index of a GEP. If all indices are zero, return
|
|
// one past the last index.
|
|
auto FirstNZIdx = [](const GetElementPtrInst *GEPI) {
|
|
unsigned I = 1;
|
|
for (unsigned IE = GEPI->getNumOperands(); I != IE; ++I) {
|
|
Value *V = GEPI->getOperand(I);
|
|
if (const ConstantInt *CI = dyn_cast<ConstantInt>(V))
|
|
if (CI->isZero())
|
|
continue;
|
|
|
|
break;
|
|
}
|
|
|
|
return I;
|
|
};
|
|
|
|
// Skip through initial 'zero' indices, and find the corresponding pointer
|
|
// type. See if the next index is not a constant.
|
|
Idx = FirstNZIdx(GEPI);
|
|
if (Idx == GEPI->getNumOperands())
|
|
return false;
|
|
if (isa<Constant>(GEPI->getOperand(Idx)))
|
|
return false;
|
|
|
|
SmallVector<Value *, 4> Ops(GEPI->idx_begin(), GEPI->idx_begin() + Idx);
|
|
Type *AllocTy =
|
|
GetElementPtrInst::getIndexedType(GEPI->getSourceElementType(), Ops);
|
|
if (!AllocTy || !AllocTy->isSized())
|
|
return false;
|
|
const DataLayout &DL = IC.getDataLayout();
|
|
uint64_t TyAllocSize = DL.getTypeAllocSize(AllocTy);
|
|
|
|
// If there are more indices after the one we might replace with a zero, make
|
|
// sure they're all non-negative. If any of them are negative, the overall
|
|
// address being computed might be before the base address determined by the
|
|
// first non-zero index.
|
|
auto IsAllNonNegative = [&]() {
|
|
for (unsigned i = Idx+1, e = GEPI->getNumOperands(); i != e; ++i) {
|
|
KnownBits Known = IC.computeKnownBits(GEPI->getOperand(i), 0, MemI);
|
|
if (Known.isNonNegative())
|
|
continue;
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
};
|
|
|
|
// FIXME: If the GEP is not inbounds, and there are extra indices after the
|
|
// one we'll replace, those could cause the address computation to wrap
|
|
// (rendering the IsAllNonNegative() check below insufficient). We can do
|
|
// better, ignoring zero indices (and other indices we can prove small
|
|
// enough not to wrap).
|
|
if (Idx+1 != GEPI->getNumOperands() && !GEPI->isInBounds())
|
|
return false;
|
|
|
|
// Note that isObjectSizeLessThanOrEq will return true only if the pointer is
|
|
// also known to be dereferenceable.
|
|
return isObjectSizeLessThanOrEq(GEPI->getOperand(0), TyAllocSize, DL) &&
|
|
IsAllNonNegative();
|
|
}
|
|
|
|
// If we're indexing into an object with a variable index for the memory
|
|
// access, but the object has only one element, we can assume that the index
|
|
// will always be zero. If we replace the GEP, return it.
|
|
template <typename T>
|
|
static Instruction *replaceGEPIdxWithZero(InstCombiner &IC, Value *Ptr,
|
|
T &MemI) {
|
|
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Ptr)) {
|
|
unsigned Idx;
|
|
if (canReplaceGEPIdxWithZero(IC, GEPI, &MemI, Idx)) {
|
|
Instruction *NewGEPI = GEPI->clone();
|
|
NewGEPI->setOperand(Idx,
|
|
ConstantInt::get(GEPI->getOperand(Idx)->getType(), 0));
|
|
NewGEPI->insertBefore(GEPI);
|
|
MemI.setOperand(MemI.getPointerOperandIndex(), NewGEPI);
|
|
return NewGEPI;
|
|
}
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
static bool canSimplifyNullStoreOrGEP(StoreInst &SI) {
|
|
if (NullPointerIsDefined(SI.getFunction(), SI.getPointerAddressSpace()))
|
|
return false;
|
|
|
|
auto *Ptr = SI.getPointerOperand();
|
|
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Ptr))
|
|
Ptr = GEPI->getOperand(0);
|
|
return (isa<ConstantPointerNull>(Ptr) &&
|
|
!NullPointerIsDefined(SI.getFunction(), SI.getPointerAddressSpace()));
|
|
}
|
|
|
|
static bool canSimplifyNullLoadOrGEP(LoadInst &LI, Value *Op) {
|
|
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
|
|
const Value *GEPI0 = GEPI->getOperand(0);
|
|
if (isa<ConstantPointerNull>(GEPI0) &&
|
|
!NullPointerIsDefined(LI.getFunction(), GEPI->getPointerAddressSpace()))
|
|
return true;
|
|
}
|
|
if (isa<UndefValue>(Op) ||
|
|
(isa<ConstantPointerNull>(Op) &&
|
|
!NullPointerIsDefined(LI.getFunction(), LI.getPointerAddressSpace())))
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
|
|
Value *Op = LI.getOperand(0);
|
|
|
|
// Try to canonicalize the loaded type.
|
|
if (Instruction *Res = combineLoadToOperationType(*this, LI))
|
|
return Res;
|
|
|
|
// Attempt to improve the alignment.
|
|
unsigned KnownAlign = getOrEnforceKnownAlignment(
|
|
Op, DL.getPrefTypeAlignment(LI.getType()), DL, &LI, &AC, &DT);
|
|
unsigned LoadAlign = LI.getAlignment();
|
|
unsigned EffectiveLoadAlign =
|
|
LoadAlign != 0 ? LoadAlign : DL.getABITypeAlignment(LI.getType());
|
|
|
|
if (KnownAlign > EffectiveLoadAlign)
|
|
LI.setAlignment(MaybeAlign(KnownAlign));
|
|
else if (LoadAlign == 0)
|
|
LI.setAlignment(MaybeAlign(EffectiveLoadAlign));
|
|
|
|
// Replace GEP indices if possible.
|
|
if (Instruction *NewGEPI = replaceGEPIdxWithZero(*this, Op, LI)) {
|
|
Worklist.Add(NewGEPI);
|
|
return &LI;
|
|
}
|
|
|
|
if (Instruction *Res = unpackLoadToAggregate(*this, LI))
|
|
return Res;
|
|
|
|
// Do really simple store-to-load forwarding and load CSE, to catch cases
|
|
// where there are several consecutive memory accesses to the same location,
|
|
// separated by a few arithmetic operations.
|
|
BasicBlock::iterator BBI(LI);
|
|
bool IsLoadCSE = false;
|
|
if (Value *AvailableVal = FindAvailableLoadedValue(
|
|
&LI, LI.getParent(), BBI, DefMaxInstsToScan, AA, &IsLoadCSE)) {
|
|
if (IsLoadCSE)
|
|
combineMetadataForCSE(cast<LoadInst>(AvailableVal), &LI, false);
|
|
|
|
return replaceInstUsesWith(
|
|
LI, Builder.CreateBitOrPointerCast(AvailableVal, LI.getType(),
|
|
LI.getName() + ".cast"));
|
|
}
|
|
|
|
// None of the following transforms are legal for volatile/ordered atomic
|
|
// loads. Most of them do apply for unordered atomics.
|
|
if (!LI.isUnordered()) return nullptr;
|
|
|
|
// load(gep null, ...) -> unreachable
|
|
// load null/undef -> unreachable
|
|
// TODO: Consider a target hook for valid address spaces for this xforms.
|
|
if (canSimplifyNullLoadOrGEP(LI, Op)) {
|
|
// Insert a new store to null instruction before the load to indicate
|
|
// that this code is not reachable. We do this instead of inserting
|
|
// an unreachable instruction directly because we cannot modify the
|
|
// CFG.
|
|
StoreInst *SI = new StoreInst(UndefValue::get(LI.getType()),
|
|
Constant::getNullValue(Op->getType()), &LI);
|
|
SI->setDebugLoc(LI.getDebugLoc());
|
|
return replaceInstUsesWith(LI, UndefValue::get(LI.getType()));
|
|
}
|
|
|
|
if (Op->hasOneUse()) {
|
|
// Change select and PHI nodes to select values instead of addresses: this
|
|
// helps alias analysis out a lot, allows many others simplifications, and
|
|
// exposes redundancy in the code.
|
|
//
|
|
// Note that we cannot do the transformation unless we know that the
|
|
// introduced loads cannot trap! Something like this is valid as long as
|
|
// the condition is always false: load (select bool %C, int* null, int* %G),
|
|
// but it would not be valid if we transformed it to load from null
|
|
// unconditionally.
|
|
//
|
|
if (SelectInst *SI = dyn_cast<SelectInst>(Op)) {
|
|
// load (select (Cond, &V1, &V2)) --> select(Cond, load &V1, load &V2).
|
|
const MaybeAlign Alignment(LI.getAlignment());
|
|
if (isSafeToLoadUnconditionally(SI->getOperand(1), LI.getType(),
|
|
Alignment, DL, SI) &&
|
|
isSafeToLoadUnconditionally(SI->getOperand(2), LI.getType(),
|
|
Alignment, DL, SI)) {
|
|
LoadInst *V1 =
|
|
Builder.CreateLoad(LI.getType(), SI->getOperand(1),
|
|
SI->getOperand(1)->getName() + ".val");
|
|
LoadInst *V2 =
|
|
Builder.CreateLoad(LI.getType(), SI->getOperand(2),
|
|
SI->getOperand(2)->getName() + ".val");
|
|
assert(LI.isUnordered() && "implied by above");
|
|
V1->setAlignment(Alignment);
|
|
V1->setAtomic(LI.getOrdering(), LI.getSyncScopeID());
|
|
V2->setAlignment(Alignment);
|
|
V2->setAtomic(LI.getOrdering(), LI.getSyncScopeID());
|
|
return SelectInst::Create(SI->getCondition(), V1, V2);
|
|
}
|
|
|
|
// load (select (cond, null, P)) -> load P
|
|
if (isa<ConstantPointerNull>(SI->getOperand(1)) &&
|
|
!NullPointerIsDefined(SI->getFunction(),
|
|
LI.getPointerAddressSpace())) {
|
|
LI.setOperand(0, SI->getOperand(2));
|
|
return &LI;
|
|
}
|
|
|
|
// load (select (cond, P, null)) -> load P
|
|
if (isa<ConstantPointerNull>(SI->getOperand(2)) &&
|
|
!NullPointerIsDefined(SI->getFunction(),
|
|
LI.getPointerAddressSpace())) {
|
|
LI.setOperand(0, SI->getOperand(1));
|
|
return &LI;
|
|
}
|
|
}
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
/// Look for extractelement/insertvalue sequence that acts like a bitcast.
|
|
///
|
|
/// \returns underlying value that was "cast", or nullptr otherwise.
|
|
///
|
|
/// For example, if we have:
|
|
///
|
|
/// %E0 = extractelement <2 x double> %U, i32 0
|
|
/// %V0 = insertvalue [2 x double] undef, double %E0, 0
|
|
/// %E1 = extractelement <2 x double> %U, i32 1
|
|
/// %V1 = insertvalue [2 x double] %V0, double %E1, 1
|
|
///
|
|
/// and the layout of a <2 x double> is isomorphic to a [2 x double],
|
|
/// then %V1 can be safely approximated by a conceptual "bitcast" of %U.
|
|
/// Note that %U may contain non-undef values where %V1 has undef.
|
|
static Value *likeBitCastFromVector(InstCombiner &IC, Value *V) {
|
|
Value *U = nullptr;
|
|
while (auto *IV = dyn_cast<InsertValueInst>(V)) {
|
|
auto *E = dyn_cast<ExtractElementInst>(IV->getInsertedValueOperand());
|
|
if (!E)
|
|
return nullptr;
|
|
auto *W = E->getVectorOperand();
|
|
if (!U)
|
|
U = W;
|
|
else if (U != W)
|
|
return nullptr;
|
|
auto *CI = dyn_cast<ConstantInt>(E->getIndexOperand());
|
|
if (!CI || IV->getNumIndices() != 1 || CI->getZExtValue() != *IV->idx_begin())
|
|
return nullptr;
|
|
V = IV->getAggregateOperand();
|
|
}
|
|
if (!isa<UndefValue>(V) ||!U)
|
|
return nullptr;
|
|
|
|
auto *UT = cast<VectorType>(U->getType());
|
|
auto *VT = V->getType();
|
|
// Check that types UT and VT are bitwise isomorphic.
|
|
const auto &DL = IC.getDataLayout();
|
|
if (DL.getTypeStoreSizeInBits(UT) != DL.getTypeStoreSizeInBits(VT)) {
|
|
return nullptr;
|
|
}
|
|
if (auto *AT = dyn_cast<ArrayType>(VT)) {
|
|
if (AT->getNumElements() != UT->getNumElements())
|
|
return nullptr;
|
|
} else {
|
|
auto *ST = cast<StructType>(VT);
|
|
if (ST->getNumElements() != UT->getNumElements())
|
|
return nullptr;
|
|
for (const auto *EltT : ST->elements()) {
|
|
if (EltT != UT->getElementType())
|
|
return nullptr;
|
|
}
|
|
}
|
|
return U;
|
|
}
|
|
|
|
/// Combine stores to match the type of value being stored.
|
|
///
|
|
/// The core idea here is that the memory does not have any intrinsic type and
|
|
/// where we can we should match the type of a store to the type of value being
|
|
/// stored.
|
|
///
|
|
/// However, this routine must never change the width of a store or the number of
|
|
/// stores as that would introduce a semantic change. This combine is expected to
|
|
/// be a semantic no-op which just allows stores to more closely model the types
|
|
/// of their incoming values.
|
|
///
|
|
/// Currently, we also refuse to change the precise type used for an atomic or
|
|
/// volatile store. This is debatable, and might be reasonable to change later.
|
|
/// However, it is risky in case some backend or other part of LLVM is relying
|
|
/// on the exact type stored to select appropriate atomic operations.
|
|
///
|
|
/// \returns true if the store was successfully combined away. This indicates
|
|
/// the caller must erase the store instruction. We have to let the caller erase
|
|
/// the store instruction as otherwise there is no way to signal whether it was
|
|
/// combined or not: IC.EraseInstFromFunction returns a null pointer.
|
|
static bool combineStoreToValueType(InstCombiner &IC, StoreInst &SI) {
|
|
// FIXME: We could probably with some care handle both volatile and ordered
|
|
// atomic stores here but it isn't clear that this is important.
|
|
if (!SI.isUnordered())
|
|
return false;
|
|
|
|
// swifterror values can't be bitcasted.
|
|
if (SI.getPointerOperand()->isSwiftError())
|
|
return false;
|
|
|
|
Value *V = SI.getValueOperand();
|
|
|
|
// Fold away bit casts of the stored value by storing the original type.
|
|
if (auto *BC = dyn_cast<BitCastInst>(V)) {
|
|
V = BC->getOperand(0);
|
|
if (!SI.isAtomic() || isSupportedAtomicType(V->getType())) {
|
|
combineStoreToNewValue(IC, SI, V);
|
|
return true;
|
|
}
|
|
}
|
|
|
|
if (Value *U = likeBitCastFromVector(IC, V))
|
|
if (!SI.isAtomic() || isSupportedAtomicType(U->getType())) {
|
|
combineStoreToNewValue(IC, SI, U);
|
|
return true;
|
|
}
|
|
|
|
// FIXME: We should also canonicalize stores of vectors when their elements
|
|
// are cast to other types.
|
|
return false;
|
|
}
|
|
|
|
static bool unpackStoreToAggregate(InstCombiner &IC, StoreInst &SI) {
|
|
// FIXME: We could probably with some care handle both volatile and atomic
|
|
// stores here but it isn't clear that this is important.
|
|
if (!SI.isSimple())
|
|
return false;
|
|
|
|
Value *V = SI.getValueOperand();
|
|
Type *T = V->getType();
|
|
|
|
if (!T->isAggregateType())
|
|
return false;
|
|
|
|
if (auto *ST = dyn_cast<StructType>(T)) {
|
|
// If the struct only have one element, we unpack.
|
|
unsigned Count = ST->getNumElements();
|
|
if (Count == 1) {
|
|
V = IC.Builder.CreateExtractValue(V, 0);
|
|
combineStoreToNewValue(IC, SI, V);
|
|
return true;
|
|
}
|
|
|
|
// We don't want to break loads with padding here as we'd loose
|
|
// the knowledge that padding exists for the rest of the pipeline.
|
|
const DataLayout &DL = IC.getDataLayout();
|
|
auto *SL = DL.getStructLayout(ST);
|
|
if (SL->hasPadding())
|
|
return false;
|
|
|
|
auto Align = SI.getAlignment();
|
|
if (!Align)
|
|
Align = DL.getABITypeAlignment(ST);
|
|
|
|
SmallString<16> EltName = V->getName();
|
|
EltName += ".elt";
|
|
auto *Addr = SI.getPointerOperand();
|
|
SmallString<16> AddrName = Addr->getName();
|
|
AddrName += ".repack";
|
|
|
|
auto *IdxType = Type::getInt32Ty(ST->getContext());
|
|
auto *Zero = ConstantInt::get(IdxType, 0);
|
|
for (unsigned i = 0; i < Count; i++) {
|
|
Value *Indices[2] = {
|
|
Zero,
|
|
ConstantInt::get(IdxType, i),
|
|
};
|
|
auto *Ptr = IC.Builder.CreateInBoundsGEP(ST, Addr, makeArrayRef(Indices),
|
|
AddrName);
|
|
auto *Val = IC.Builder.CreateExtractValue(V, i, EltName);
|
|
auto EltAlign = MinAlign(Align, SL->getElementOffset(i));
|
|
llvm::Instruction *NS = IC.Builder.CreateAlignedStore(Val, Ptr, EltAlign);
|
|
AAMDNodes AAMD;
|
|
SI.getAAMetadata(AAMD);
|
|
NS->setAAMetadata(AAMD);
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
if (auto *AT = dyn_cast<ArrayType>(T)) {
|
|
// If the array only have one element, we unpack.
|
|
auto NumElements = AT->getNumElements();
|
|
if (NumElements == 1) {
|
|
V = IC.Builder.CreateExtractValue(V, 0);
|
|
combineStoreToNewValue(IC, SI, V);
|
|
return true;
|
|
}
|
|
|
|
// Bail out if the array is too large. Ideally we would like to optimize
|
|
// arrays of arbitrary size but this has a terrible impact on compile time.
|
|
// The threshold here is chosen arbitrarily, maybe needs a little bit of
|
|
// tuning.
|
|
if (NumElements > IC.MaxArraySizeForCombine)
|
|
return false;
|
|
|
|
const DataLayout &DL = IC.getDataLayout();
|
|
auto EltSize = DL.getTypeAllocSize(AT->getElementType());
|
|
auto Align = SI.getAlignment();
|
|
if (!Align)
|
|
Align = DL.getABITypeAlignment(T);
|
|
|
|
SmallString<16> EltName = V->getName();
|
|
EltName += ".elt";
|
|
auto *Addr = SI.getPointerOperand();
|
|
SmallString<16> AddrName = Addr->getName();
|
|
AddrName += ".repack";
|
|
|
|
auto *IdxType = Type::getInt64Ty(T->getContext());
|
|
auto *Zero = ConstantInt::get(IdxType, 0);
|
|
|
|
uint64_t Offset = 0;
|
|
for (uint64_t i = 0; i < NumElements; i++) {
|
|
Value *Indices[2] = {
|
|
Zero,
|
|
ConstantInt::get(IdxType, i),
|
|
};
|
|
auto *Ptr = IC.Builder.CreateInBoundsGEP(AT, Addr, makeArrayRef(Indices),
|
|
AddrName);
|
|
auto *Val = IC.Builder.CreateExtractValue(V, i, EltName);
|
|
auto EltAlign = MinAlign(Align, Offset);
|
|
Instruction *NS = IC.Builder.CreateAlignedStore(Val, Ptr, EltAlign);
|
|
AAMDNodes AAMD;
|
|
SI.getAAMetadata(AAMD);
|
|
NS->setAAMetadata(AAMD);
|
|
Offset += EltSize;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/// equivalentAddressValues - Test if A and B will obviously have the same
|
|
/// value. This includes recognizing that %t0 and %t1 will have the same
|
|
/// value in code like this:
|
|
/// %t0 = getelementptr \@a, 0, 3
|
|
/// store i32 0, i32* %t0
|
|
/// %t1 = getelementptr \@a, 0, 3
|
|
/// %t2 = load i32* %t1
|
|
///
|
|
static bool equivalentAddressValues(Value *A, Value *B) {
|
|
// Test if the values are trivially equivalent.
|
|
if (A == B) return true;
|
|
|
|
// Test if the values come form identical arithmetic instructions.
|
|
// This uses isIdenticalToWhenDefined instead of isIdenticalTo because
|
|
// its only used to compare two uses within the same basic block, which
|
|
// means that they'll always either have the same value or one of them
|
|
// will have an undefined value.
|
|
if (isa<BinaryOperator>(A) ||
|
|
isa<CastInst>(A) ||
|
|
isa<PHINode>(A) ||
|
|
isa<GetElementPtrInst>(A))
|
|
if (Instruction *BI = dyn_cast<Instruction>(B))
|
|
if (cast<Instruction>(A)->isIdenticalToWhenDefined(BI))
|
|
return true;
|
|
|
|
// Otherwise they may not be equivalent.
|
|
return false;
|
|
}
|
|
|
|
/// Converts store (bitcast (load (bitcast (select ...)))) to
|
|
/// store (load (select ...)), where select is minmax:
|
|
/// select ((cmp load V1, load V2), V1, V2).
|
|
static bool removeBitcastsFromLoadStoreOnMinMax(InstCombiner &IC,
|
|
StoreInst &SI) {
|
|
// bitcast?
|
|
if (!match(SI.getPointerOperand(), m_BitCast(m_Value())))
|
|
return false;
|
|
// load? integer?
|
|
Value *LoadAddr;
|
|
if (!match(SI.getValueOperand(), m_Load(m_BitCast(m_Value(LoadAddr)))))
|
|
return false;
|
|
auto *LI = cast<LoadInst>(SI.getValueOperand());
|
|
if (!LI->getType()->isIntegerTy())
|
|
return false;
|
|
Type *CmpLoadTy;
|
|
if (!isMinMaxWithLoads(LoadAddr, CmpLoadTy))
|
|
return false;
|
|
|
|
// Make sure we're not changing the size of the load/store.
|
|
const auto &DL = IC.getDataLayout();
|
|
if (DL.getTypeStoreSizeInBits(LI->getType()) !=
|
|
DL.getTypeStoreSizeInBits(CmpLoadTy))
|
|
return false;
|
|
|
|
if (!all_of(LI->users(), [LI, LoadAddr](User *U) {
|
|
auto *SI = dyn_cast<StoreInst>(U);
|
|
return SI && SI->getPointerOperand() != LI &&
|
|
peekThroughBitcast(SI->getPointerOperand()) != LoadAddr &&
|
|
!SI->getPointerOperand()->isSwiftError();
|
|
}))
|
|
return false;
|
|
|
|
IC.Builder.SetInsertPoint(LI);
|
|
LoadInst *NewLI = IC.combineLoadToNewType(*LI, CmpLoadTy);
|
|
// Replace all the stores with stores of the newly loaded value.
|
|
for (auto *UI : LI->users()) {
|
|
auto *USI = cast<StoreInst>(UI);
|
|
IC.Builder.SetInsertPoint(USI);
|
|
combineStoreToNewValue(IC, *USI, NewLI);
|
|
}
|
|
IC.replaceInstUsesWith(*LI, UndefValue::get(LI->getType()));
|
|
IC.eraseInstFromFunction(*LI);
|
|
return true;
|
|
}
|
|
|
|
Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
|
|
Value *Val = SI.getOperand(0);
|
|
Value *Ptr = SI.getOperand(1);
|
|
|
|
// Try to canonicalize the stored type.
|
|
if (combineStoreToValueType(*this, SI))
|
|
return eraseInstFromFunction(SI);
|
|
|
|
// Attempt to improve the alignment.
|
|
const Align KnownAlign = Align(getOrEnforceKnownAlignment(
|
|
Ptr, DL.getPrefTypeAlignment(Val->getType()), DL, &SI, &AC, &DT));
|
|
const MaybeAlign StoreAlign = MaybeAlign(SI.getAlignment());
|
|
const Align EffectiveStoreAlign =
|
|
StoreAlign ? *StoreAlign : Align(DL.getABITypeAlignment(Val->getType()));
|
|
|
|
if (KnownAlign > EffectiveStoreAlign)
|
|
SI.setAlignment(KnownAlign);
|
|
else if (!StoreAlign)
|
|
SI.setAlignment(EffectiveStoreAlign);
|
|
|
|
// Try to canonicalize the stored type.
|
|
if (unpackStoreToAggregate(*this, SI))
|
|
return eraseInstFromFunction(SI);
|
|
|
|
if (removeBitcastsFromLoadStoreOnMinMax(*this, SI))
|
|
return eraseInstFromFunction(SI);
|
|
|
|
// Replace GEP indices if possible.
|
|
if (Instruction *NewGEPI = replaceGEPIdxWithZero(*this, Ptr, SI)) {
|
|
Worklist.Add(NewGEPI);
|
|
return &SI;
|
|
}
|
|
|
|
// Don't hack volatile/ordered stores.
|
|
// FIXME: Some bits are legal for ordered atomic stores; needs refactoring.
|
|
if (!SI.isUnordered()) return nullptr;
|
|
|
|
// If the RHS is an alloca with a single use, zapify the store, making the
|
|
// alloca dead.
|
|
if (Ptr->hasOneUse()) {
|
|
if (isa<AllocaInst>(Ptr))
|
|
return eraseInstFromFunction(SI);
|
|
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr)) {
|
|
if (isa<AllocaInst>(GEP->getOperand(0))) {
|
|
if (GEP->getOperand(0)->hasOneUse())
|
|
return eraseInstFromFunction(SI);
|
|
}
|
|
}
|
|
}
|
|
|
|
// If we have a store to a location which is known constant, we can conclude
|
|
// that the store must be storing the constant value (else the memory
|
|
// wouldn't be constant), and this must be a noop.
|
|
if (AA->pointsToConstantMemory(Ptr))
|
|
return eraseInstFromFunction(SI);
|
|
|
|
// Do really simple DSE, to catch cases where there are several consecutive
|
|
// stores to the same location, separated by a few arithmetic operations. This
|
|
// situation often occurs with bitfield accesses.
|
|
BasicBlock::iterator BBI(SI);
|
|
for (unsigned ScanInsts = 6; BBI != SI.getParent()->begin() && ScanInsts;
|
|
--ScanInsts) {
|
|
--BBI;
|
|
// Don't count debug info directives, lest they affect codegen,
|
|
// and we skip pointer-to-pointer bitcasts, which are NOPs.
|
|
if (isa<DbgInfoIntrinsic>(BBI) ||
|
|
(isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())) {
|
|
ScanInsts++;
|
|
continue;
|
|
}
|
|
|
|
if (StoreInst *PrevSI = dyn_cast<StoreInst>(BBI)) {
|
|
// Prev store isn't volatile, and stores to the same location?
|
|
if (PrevSI->isUnordered() && equivalentAddressValues(PrevSI->getOperand(1),
|
|
SI.getOperand(1))) {
|
|
++NumDeadStore;
|
|
++BBI;
|
|
eraseInstFromFunction(*PrevSI);
|
|
continue;
|
|
}
|
|
break;
|
|
}
|
|
|
|
// If this is a load, we have to stop. However, if the loaded value is from
|
|
// the pointer we're loading and is producing the pointer we're storing,
|
|
// then *this* store is dead (X = load P; store X -> P).
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
|
|
if (LI == Val && equivalentAddressValues(LI->getOperand(0), Ptr)) {
|
|
assert(SI.isUnordered() && "can't eliminate ordering operation");
|
|
return eraseInstFromFunction(SI);
|
|
}
|
|
|
|
// Otherwise, this is a load from some other location. Stores before it
|
|
// may not be dead.
|
|
break;
|
|
}
|
|
|
|
// Don't skip over loads, throws or things that can modify memory.
|
|
if (BBI->mayWriteToMemory() || BBI->mayReadFromMemory() || BBI->mayThrow())
|
|
break;
|
|
}
|
|
|
|
// store X, null -> turns into 'unreachable' in SimplifyCFG
|
|
// store X, GEP(null, Y) -> turns into 'unreachable' in SimplifyCFG
|
|
if (canSimplifyNullStoreOrGEP(SI)) {
|
|
if (!isa<UndefValue>(Val)) {
|
|
SI.setOperand(0, UndefValue::get(Val->getType()));
|
|
if (Instruction *U = dyn_cast<Instruction>(Val))
|
|
Worklist.Add(U); // Dropped a use.
|
|
}
|
|
return nullptr; // Do not modify these!
|
|
}
|
|
|
|
// store undef, Ptr -> noop
|
|
if (isa<UndefValue>(Val))
|
|
return eraseInstFromFunction(SI);
|
|
|
|
// If this store is the second-to-last instruction in the basic block
|
|
// (excluding debug info and bitcasts of pointers) and if the block ends with
|
|
// an unconditional branch, try to move the store to the successor block.
|
|
BBI = SI.getIterator();
|
|
do {
|
|
++BBI;
|
|
} while (isa<DbgInfoIntrinsic>(BBI) ||
|
|
(isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy()));
|
|
|
|
if (BranchInst *BI = dyn_cast<BranchInst>(BBI))
|
|
if (BI->isUnconditional())
|
|
mergeStoreIntoSuccessor(SI);
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// Try to transform:
|
|
/// if () { *P = v1; } else { *P = v2 }
|
|
/// or:
|
|
/// *P = v1; if () { *P = v2; }
|
|
/// into a phi node with a store in the successor.
|
|
bool InstCombiner::mergeStoreIntoSuccessor(StoreInst &SI) {
|
|
assert(SI.isUnordered() &&
|
|
"This code has not been audited for volatile or ordered store case.");
|
|
|
|
// Check if the successor block has exactly 2 incoming edges.
|
|
BasicBlock *StoreBB = SI.getParent();
|
|
BasicBlock *DestBB = StoreBB->getTerminator()->getSuccessor(0);
|
|
if (!DestBB->hasNPredecessors(2))
|
|
return false;
|
|
|
|
// Capture the other block (the block that doesn't contain our store).
|
|
pred_iterator PredIter = pred_begin(DestBB);
|
|
if (*PredIter == StoreBB)
|
|
++PredIter;
|
|
BasicBlock *OtherBB = *PredIter;
|
|
|
|
// Bail out if all of the relevant blocks aren't distinct. This can happen,
|
|
// for example, if SI is in an infinite loop.
|
|
if (StoreBB == DestBB || OtherBB == DestBB)
|
|
return false;
|
|
|
|
// Verify that the other block ends in a branch and is not otherwise empty.
|
|
BasicBlock::iterator BBI(OtherBB->getTerminator());
|
|
BranchInst *OtherBr = dyn_cast<BranchInst>(BBI);
|
|
if (!OtherBr || BBI == OtherBB->begin())
|
|
return false;
|
|
|
|
// If the other block ends in an unconditional branch, check for the 'if then
|
|
// else' case. There is an instruction before the branch.
|
|
StoreInst *OtherStore = nullptr;
|
|
if (OtherBr->isUnconditional()) {
|
|
--BBI;
|
|
// Skip over debugging info.
|
|
while (isa<DbgInfoIntrinsic>(BBI) ||
|
|
(isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())) {
|
|
if (BBI==OtherBB->begin())
|
|
return false;
|
|
--BBI;
|
|
}
|
|
// If this isn't a store, isn't a store to the same location, or is not the
|
|
// right kind of store, bail out.
|
|
OtherStore = dyn_cast<StoreInst>(BBI);
|
|
if (!OtherStore || OtherStore->getOperand(1) != SI.getOperand(1) ||
|
|
!SI.isSameOperationAs(OtherStore))
|
|
return false;
|
|
} else {
|
|
// Otherwise, the other block ended with a conditional branch. If one of the
|
|
// destinations is StoreBB, then we have the if/then case.
|
|
if (OtherBr->getSuccessor(0) != StoreBB &&
|
|
OtherBr->getSuccessor(1) != StoreBB)
|
|
return false;
|
|
|
|
// Okay, we know that OtherBr now goes to Dest and StoreBB, so this is an
|
|
// if/then triangle. See if there is a store to the same ptr as SI that
|
|
// lives in OtherBB.
|
|
for (;; --BBI) {
|
|
// Check to see if we find the matching store.
|
|
if ((OtherStore = dyn_cast<StoreInst>(BBI))) {
|
|
if (OtherStore->getOperand(1) != SI.getOperand(1) ||
|
|
!SI.isSameOperationAs(OtherStore))
|
|
return false;
|
|
break;
|
|
}
|
|
// If we find something that may be using or overwriting the stored
|
|
// value, or if we run out of instructions, we can't do the transform.
|
|
if (BBI->mayReadFromMemory() || BBI->mayThrow() ||
|
|
BBI->mayWriteToMemory() || BBI == OtherBB->begin())
|
|
return false;
|
|
}
|
|
|
|
// In order to eliminate the store in OtherBr, we have to make sure nothing
|
|
// reads or overwrites the stored value in StoreBB.
|
|
for (BasicBlock::iterator I = StoreBB->begin(); &*I != &SI; ++I) {
|
|
// FIXME: This should really be AA driven.
|
|
if (I->mayReadFromMemory() || I->mayThrow() || I->mayWriteToMemory())
|
|
return false;
|
|
}
|
|
}
|
|
|
|
// Insert a PHI node now if we need it.
|
|
Value *MergedVal = OtherStore->getOperand(0);
|
|
// The debug locations of the original instructions might differ. Merge them.
|
|
DebugLoc MergedLoc = DILocation::getMergedLocation(SI.getDebugLoc(),
|
|
OtherStore->getDebugLoc());
|
|
if (MergedVal != SI.getOperand(0)) {
|
|
PHINode *PN = PHINode::Create(MergedVal->getType(), 2, "storemerge");
|
|
PN->addIncoming(SI.getOperand(0), SI.getParent());
|
|
PN->addIncoming(OtherStore->getOperand(0), OtherBB);
|
|
MergedVal = InsertNewInstBefore(PN, DestBB->front());
|
|
PN->setDebugLoc(MergedLoc);
|
|
}
|
|
|
|
// Advance to a place where it is safe to insert the new store and insert it.
|
|
BBI = DestBB->getFirstInsertionPt();
|
|
StoreInst *NewSI = new StoreInst(MergedVal, SI.getOperand(1), SI.isVolatile(),
|
|
MaybeAlign(SI.getAlignment()),
|
|
SI.getOrdering(), SI.getSyncScopeID());
|
|
InsertNewInstBefore(NewSI, *BBI);
|
|
NewSI->setDebugLoc(MergedLoc);
|
|
|
|
// If the two stores had AA tags, merge them.
|
|
AAMDNodes AATags;
|
|
SI.getAAMetadata(AATags);
|
|
if (AATags) {
|
|
OtherStore->getAAMetadata(AATags, /* Merge = */ true);
|
|
NewSI->setAAMetadata(AATags);
|
|
}
|
|
|
|
// Nuke the old stores.
|
|
eraseInstFromFunction(SI);
|
|
eraseInstFromFunction(*OtherStore);
|
|
return true;
|
|
}
|