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Diffstat (limited to 'lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp')
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp | 613 |
1 files changed, 613 insertions, 0 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp new file mode 100644 index 0000000..6c0ecc9 --- /dev/null +++ b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp @@ -0,0 +1,613 @@ +//===- InstCombineLoadStoreAlloca.cpp -------------------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements the visit functions for load, store and alloca. +// +//===----------------------------------------------------------------------===// + +#include "InstCombine.h" +#include "llvm/IntrinsicInst.h" +#include "llvm/Target/TargetData.h" +#include "llvm/Transforms/Utils/BasicBlockUtils.h" +#include "llvm/Transforms/Utils/Local.h" +#include "llvm/ADT/Statistic.h" +using namespace llvm; + +STATISTIC(NumDeadStore, "Number of dead stores eliminated"); + +Instruction *InstCombiner::visitAllocaInst(AllocaInst &AI) { + // Convert: alloca Ty, C - where C is a constant != 1 into: alloca [C x Ty], 1 + if (AI.isArrayAllocation()) { // Check C != 1 + if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) { + const Type *NewTy = + ArrayType::get(AI.getAllocatedType(), C->getZExtValue()); + assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!"); + AllocaInst *New = Builder->CreateAlloca(NewTy, 0, AI.getName()); + New->setAlignment(AI.getAlignment()); + + // Scan to the end of the allocation instructions, to skip over a block of + // allocas if possible...also skip interleaved debug info + // + BasicBlock::iterator It = New; + while (isa<AllocaInst>(*It) || isa<DbgInfoIntrinsic>(*It)) ++It; + + // Now that I is pointing to the first non-allocation-inst in the block, + // insert our getelementptr instruction... + // + Value *NullIdx =Constant::getNullValue(Type::getInt32Ty(AI.getContext())); + Value *Idx[2]; + Idx[0] = NullIdx; + Idx[1] = NullIdx; + Value *V = GetElementPtrInst::CreateInBounds(New, Idx, Idx + 2, + New->getName()+".sub", It); + + // Now make everything use the getelementptr instead of the original + // allocation. + return ReplaceInstUsesWith(AI, V); + } else if (isa<UndefValue>(AI.getArraySize())) { + return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType())); + } + } + + if (TD && isa<AllocaInst>(AI) && AI.getAllocatedType()->isSized()) { + // If alloca'ing a zero byte object, replace the alloca with a null pointer. + // Note that we only do this for alloca's, because malloc should allocate + // and return a unique pointer, even for a zero byte allocation. + if (TD->getTypeAllocSize(AI.getAllocatedType()) == 0) + return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType())); + + // If the alignment is 0 (unspecified), assign it the preferred alignment. + if (AI.getAlignment() == 0) + AI.setAlignment(TD->getPrefTypeAlignment(AI.getAllocatedType())); + } + + return 0; +} + + +/// InstCombineLoadCast - Fold 'load (cast P)' -> cast (load P)' when possible. +static Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI, + const TargetData *TD) { + User *CI = cast<User>(LI.getOperand(0)); + Value *CastOp = CI->getOperand(0); + + const PointerType *DestTy = cast<PointerType>(CI->getType()); + const Type *DestPTy = DestTy->getElementType(); + if (const PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType())) { + + // If the address spaces don't match, don't eliminate the cast. + if (DestTy->getAddressSpace() != SrcTy->getAddressSpace()) + return 0; + + const Type *SrcPTy = SrcTy->getElementType(); + + if (DestPTy->isInteger() || isa<PointerType>(DestPTy) || + isa<VectorType>(DestPTy)) { + // If the source is an array, the code below will not succeed. Check to + // see if a trivial 'gep P, 0, 0' will help matters. Only do this for + // constants. + if (const ArrayType *ASrcTy = dyn_cast<ArrayType>(SrcPTy)) + if (Constant *CSrc = dyn_cast<Constant>(CastOp)) + if (ASrcTy->getNumElements() != 0) { + Value *Idxs[2]; + Idxs[0] = Constant::getNullValue(Type::getInt32Ty(LI.getContext())); + Idxs[1] = Idxs[0]; + CastOp = ConstantExpr::getGetElementPtr(CSrc, Idxs, 2); + SrcTy = cast<PointerType>(CastOp->getType()); + SrcPTy = SrcTy->getElementType(); + } + + if (IC.getTargetData() && + (SrcPTy->isInteger() || isa<PointerType>(SrcPTy) || + isa<VectorType>(SrcPTy)) && + // Do not allow turning this into a load of an integer, which is then + // casted to a pointer, this pessimizes pointer analysis a lot. + (isa<PointerType>(SrcPTy) == isa<PointerType>(LI.getType())) && + IC.getTargetData()->getTypeSizeInBits(SrcPTy) == + IC.getTargetData()->getTypeSizeInBits(DestPTy)) { + + // Okay, we are casting from one integer or pointer type to another of + // the same size. Instead of casting the pointer before the load, cast + // the result of the loaded value. + Value *NewLoad = + IC.Builder->CreateLoad(CastOp, LI.isVolatile(), CI->getName()); + // Now cast the result of the load. + return new BitCastInst(NewLoad, LI.getType()); + } + } + } + return 0; +} + +Instruction *InstCombiner::visitLoadInst(LoadInst &LI) { + Value *Op = LI.getOperand(0); + + // Attempt to improve the alignment. + if (TD) { + unsigned KnownAlign = + GetOrEnforceKnownAlignment(Op, TD->getPrefTypeAlignment(LI.getType())); + if (KnownAlign > + (LI.getAlignment() == 0 ? TD->getABITypeAlignment(LI.getType()) : + LI.getAlignment())) + LI.setAlignment(KnownAlign); + } + + // load (cast X) --> cast (load X) iff safe. + if (isa<CastInst>(Op)) + if (Instruction *Res = InstCombineLoadCast(*this, LI, TD)) + return Res; + + // None of the following transforms are legal for volatile loads. + if (LI.isVolatile()) return 0; + + // Do really simple store-to-load forwarding and load CSE, to catch cases + // where there are several consequtive memory accesses to the same location, + // separated by a few arithmetic operations. + BasicBlock::iterator BBI = &LI; + if (Value *AvailableVal = FindAvailableLoadedValue(Op, LI.getParent(), BBI,6)) + return ReplaceInstUsesWith(LI, AvailableVal); + + // load(gep null, ...) -> unreachable + if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) { + const Value *GEPI0 = GEPI->getOperand(0); + // TODO: Consider a target hook for valid address spaces for this xform. + if (isa<ConstantPointerNull>(GEPI0) && GEPI->getPointerAddressSpace() == 0){ + // 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. + new StoreInst(UndefValue::get(LI.getType()), + Constant::getNullValue(Op->getType()), &LI); + return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType())); + } + } + + // load null/undef -> unreachable + // TODO: Consider a target hook for valid address spaces for this xform. + if (isa<UndefValue>(Op) || + (isa<ConstantPointerNull>(Op) && LI.getPointerAddressSpace() == 0)) { + // 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. + new StoreInst(UndefValue::get(LI.getType()), + Constant::getNullValue(Op->getType()), &LI); + return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType())); + } + + // Instcombine load (constantexpr_cast global) -> cast (load global) + if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op)) + if (CE->isCast()) + if (Instruction *Res = InstCombineLoadCast(*this, LI, TD)) + return Res; + + 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). + if (isSafeToLoadUnconditionally(SI->getOperand(1), SI) && + isSafeToLoadUnconditionally(SI->getOperand(2), SI)) { + Value *V1 = Builder->CreateLoad(SI->getOperand(1), + SI->getOperand(1)->getName()+".val"); + Value *V2 = Builder->CreateLoad(SI->getOperand(2), + SI->getOperand(2)->getName()+".val"); + return SelectInst::Create(SI->getCondition(), V1, V2); + } + + // load (select (cond, null, P)) -> load P + if (Constant *C = dyn_cast<Constant>(SI->getOperand(1))) + if (C->isNullValue()) { + LI.setOperand(0, SI->getOperand(2)); + return &LI; + } + + // load (select (cond, P, null)) -> load P + if (Constant *C = dyn_cast<Constant>(SI->getOperand(2))) + if (C->isNullValue()) { + LI.setOperand(0, SI->getOperand(1)); + return &LI; + } + } + } + return 0; +} + +/// InstCombineStoreToCast - Fold store V, (cast P) -> store (cast V), P +/// when possible. This makes it generally easy to do alias analysis and/or +/// SROA/mem2reg of the memory object. +static Instruction *InstCombineStoreToCast(InstCombiner &IC, StoreInst &SI) { + User *CI = cast<User>(SI.getOperand(1)); + Value *CastOp = CI->getOperand(0); + + const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType(); + const PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType()); + if (SrcTy == 0) return 0; + + const Type *SrcPTy = SrcTy->getElementType(); + + if (!DestPTy->isInteger() && !isa<PointerType>(DestPTy)) + return 0; + + /// NewGEPIndices - If SrcPTy is an aggregate type, we can emit a "noop gep" + /// to its first element. This allows us to handle things like: + /// store i32 xxx, (bitcast {foo*, float}* %P to i32*) + /// on 32-bit hosts. + SmallVector<Value*, 4> NewGEPIndices; + + // If the source is an array, the code below will not succeed. Check to + // see if a trivial 'gep P, 0, 0' will help matters. Only do this for + // constants. + if (isa<ArrayType>(SrcPTy) || isa<StructType>(SrcPTy)) { + // Index through pointer. + Constant *Zero = Constant::getNullValue(Type::getInt32Ty(SI.getContext())); + NewGEPIndices.push_back(Zero); + + while (1) { + if (const StructType *STy = dyn_cast<StructType>(SrcPTy)) { + if (!STy->getNumElements()) /* Struct can be empty {} */ + break; + NewGEPIndices.push_back(Zero); + SrcPTy = STy->getElementType(0); + } else if (const ArrayType *ATy = dyn_cast<ArrayType>(SrcPTy)) { + NewGEPIndices.push_back(Zero); + SrcPTy = ATy->getElementType(); + } else { + break; + } + } + + SrcTy = PointerType::get(SrcPTy, SrcTy->getAddressSpace()); + } + + if (!SrcPTy->isInteger() && !isa<PointerType>(SrcPTy)) + return 0; + + // If the pointers point into different address spaces or if they point to + // values with different sizes, we can't do the transformation. + if (!IC.getTargetData() || + SrcTy->getAddressSpace() != + cast<PointerType>(CI->getType())->getAddressSpace() || + IC.getTargetData()->getTypeSizeInBits(SrcPTy) != + IC.getTargetData()->getTypeSizeInBits(DestPTy)) + return 0; + + // Okay, we are casting from one integer or pointer type to another of + // the same size. Instead of casting the pointer before + // the store, cast the value to be stored. + Value *NewCast; + Value *SIOp0 = SI.getOperand(0); + Instruction::CastOps opcode = Instruction::BitCast; + const Type* CastSrcTy = SIOp0->getType(); + const Type* CastDstTy = SrcPTy; + if (isa<PointerType>(CastDstTy)) { + if (CastSrcTy->isInteger()) + opcode = Instruction::IntToPtr; + } else if (isa<IntegerType>(CastDstTy)) { + if (isa<PointerType>(SIOp0->getType())) + opcode = Instruction::PtrToInt; + } + + // SIOp0 is a pointer to aggregate and this is a store to the first field, + // emit a GEP to index into its first field. + if (!NewGEPIndices.empty()) + CastOp = IC.Builder->CreateInBoundsGEP(CastOp, NewGEPIndices.begin(), + NewGEPIndices.end()); + + NewCast = IC.Builder->CreateCast(opcode, SIOp0, CastDstTy, + SIOp0->getName()+".c"); + return new StoreInst(NewCast, CastOp); +} + +/// 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; +} + +// If this instruction has two uses, one of which is a llvm.dbg.declare, +// return the llvm.dbg.declare. +DbgDeclareInst *InstCombiner::hasOneUsePlusDeclare(Value *V) { + if (!V->hasNUses(2)) + return 0; + for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); + UI != E; ++UI) { + if (DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(UI)) + return DI; + if (isa<BitCastInst>(UI) && UI->hasOneUse()) { + if (DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(UI->use_begin())) + return DI; + } + } + return 0; +} + +Instruction *InstCombiner::visitStoreInst(StoreInst &SI) { + Value *Val = SI.getOperand(0); + Value *Ptr = SI.getOperand(1); + + // If the RHS is an alloca with a single use, zapify the store, making the + // alloca dead. + // If the RHS is an alloca with a two uses, the other one being a + // llvm.dbg.declare, zapify the store and the declare, making the + // alloca dead. We must do this to prevent declare's from affecting + // codegen. + if (!SI.isVolatile()) { + 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 (DbgDeclareInst *DI = hasOneUsePlusDeclare(GEP->getOperand(0))) { + EraseInstFromFunction(*DI); + return EraseInstFromFunction(SI); + } + } + } + } + if (DbgDeclareInst *DI = hasOneUsePlusDeclare(Ptr)) { + EraseInstFromFunction(*DI); + return EraseInstFromFunction(SI); + } + } + + // Attempt to improve the alignment. + if (TD) { + unsigned KnownAlign = + GetOrEnforceKnownAlignment(Ptr, TD->getPrefTypeAlignment(Val->getType())); + if (KnownAlign > + (SI.getAlignment() == 0 ? TD->getABITypeAlignment(Val->getType()) : + SI.getAlignment())) + SI.setAlignment(KnownAlign); + } + + // 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. + // It is necessary for correctness to skip those that feed into a + // llvm.dbg.declare, as these are not present when debugging is off. + if (isa<DbgInfoIntrinsic>(BBI) || + (isa<BitCastInst>(BBI) && isa<PointerType>(BBI->getType()))) { + ScanInsts++; + continue; + } + + if (StoreInst *PrevSI = dyn_cast<StoreInst>(BBI)) { + // Prev store isn't volatile, and stores to the same location? + if (!PrevSI->isVolatile() &&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) && + !SI.isVolatile()) + 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 or things that can modify memory. + if (BBI->mayWriteToMemory() || BBI->mayReadFromMemory()) + break; + } + + + if (SI.isVolatile()) return 0; // Don't hack volatile stores. + + // store X, null -> turns into 'unreachable' in SimplifyCFG + if (isa<ConstantPointerNull>(Ptr) && SI.getPointerAddressSpace() == 0) { + 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 0; // Do not modify these! + } + + // store undef, Ptr -> noop + if (isa<UndefValue>(Val)) + return EraseInstFromFunction(SI); + + // If the pointer destination is a cast, see if we can fold the cast into the + // source instead. + if (isa<CastInst>(Ptr)) + if (Instruction *Res = InstCombineStoreToCast(*this, SI)) + return Res; + if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) + if (CE->isCast()) + if (Instruction *Res = InstCombineStoreToCast(*this, SI)) + return Res; + + + // If this store is the last instruction in the basic block (possibly + // excepting debug info instructions and the pointer bitcasts that feed + // into them), and if the block ends with an unconditional branch, try + // to move it to the successor block. + BBI = &SI; + do { + ++BBI; + } while (isa<DbgInfoIntrinsic>(BBI) || + (isa<BitCastInst>(BBI) && isa<PointerType>(BBI->getType()))); + if (BranchInst *BI = dyn_cast<BranchInst>(BBI)) + if (BI->isUnconditional()) + if (SimplifyStoreAtEndOfBlock(SI)) + return 0; // xform done! + + return 0; +} + +/// SimplifyStoreAtEndOfBlock - Turn things like: +/// if () { *P = v1; } else { *P = v2 } +/// into a phi node with a store in the successor. +/// +/// Simplify things like: +/// *P = v1; if () { *P = v2; } +/// into a phi node with a store in the successor. +/// +bool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) { + BasicBlock *StoreBB = SI.getParent(); + + // Check to see if the successor block has exactly two incoming edges. If + // so, see if the other predecessor contains a store to the same location. + // if so, insert a PHI node (if needed) and move the stores down. + BasicBlock *DestBB = StoreBB->getTerminator()->getSuccessor(0); + + // Determine whether Dest has exactly two predecessors and, if so, compute + // the other predecessor. + pred_iterator PI = pred_begin(DestBB); + BasicBlock *OtherBB = 0; + if (*PI != StoreBB) + OtherBB = *PI; + ++PI; + if (PI == pred_end(DestBB)) + return false; + + if (*PI != StoreBB) { + if (OtherBB) + return false; + OtherBB = *PI; + } + if (++PI != pred_end(DestBB)) + return false; + + // Bail out if all 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 = 0; + if (OtherBr->isUnconditional()) { + --BBI; + // Skip over debugging info. + while (isa<DbgInfoIntrinsic>(BBI) || + (isa<BitCastInst>(BBI) && isa<PointerType>(BBI->getType()))) { + if (BBI==OtherBB->begin()) + return false; + --BBI; + } + // If this isn't a store, isn't a store to the same location, or if the + // alignments differ, bail out. + OtherStore = dyn_cast<StoreInst>(BBI); + if (!OtherStore || OtherStore->getOperand(1) != SI.getOperand(1) || + OtherStore->getAlignment() != SI.getAlignment()) + 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) || + OtherStore->getAlignment() != SI.getAlignment()) + 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 xform. + if (BBI->mayReadFromMemory() || 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->mayWriteToMemory()) + return false; + } + } + + // Insert a PHI node now if we need it. + Value *MergedVal = OtherStore->getOperand(0); + if (MergedVal != SI.getOperand(0)) { + PHINode *PN = PHINode::Create(MergedVal->getType(), "storemerge"); + PN->reserveOperandSpace(2); + PN->addIncoming(SI.getOperand(0), SI.getParent()); + PN->addIncoming(OtherStore->getOperand(0), OtherBB); + MergedVal = InsertNewInstBefore(PN, DestBB->front()); + } + + // Advance to a place where it is safe to insert the new store and + // insert it. + BBI = DestBB->getFirstNonPHI(); + InsertNewInstBefore(new StoreInst(MergedVal, SI.getOperand(1), + OtherStore->isVolatile(), + SI.getAlignment()), *BBI); + + // Nuke the old stores. + EraseInstFromFunction(SI); + EraseInstFromFunction(*OtherStore); + return true; +} |
