InstCombineLoadStoreAlloca.cpp revision 0ccae0b1f6b95e4500adb45649472389a1f111a7
18d9b8d717e665945b31b0742b901561fb433ceceChris Lattner//===- InstCombineLoadStoreAlloca.cpp -------------------------------------===// 28d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// 38d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// The LLVM Compiler Infrastructure 48d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// 58d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// This file is distributed under the University of Illinois Open Source 68d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// License. See LICENSE.TXT for details. 78d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// 88d9b8d717e665945b31b0742b901561fb433ceceChris Lattner//===----------------------------------------------------------------------===// 98d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// 108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// This file implements the visit functions for load, store and alloca. 118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// 128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner//===----------------------------------------------------------------------===// 138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner#include "InstCombine.h" 158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner#include "llvm/IntrinsicInst.h" 16dd9344f3face8f1978a7f9f393c31b628144d1f6Dan Gohman#include "llvm/Analysis/Loads.h" 178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner#include "llvm/Target/TargetData.h" 188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner#include "llvm/Transforms/Utils/BasicBlockUtils.h" 198d9b8d717e665945b31b0742b901561fb433ceceChris Lattner#include "llvm/Transforms/Utils/Local.h" 208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner#include "llvm/ADT/Statistic.h" 218d9b8d717e665945b31b0742b901561fb433ceceChris Lattnerusing namespace llvm; 228d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 238d9b8d717e665945b31b0742b901561fb433ceceChris LattnerSTATISTIC(NumDeadStore, "Number of dead stores eliminated"); 248d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 258d9b8d717e665945b31b0742b901561fb433ceceChris LattnerInstruction *InstCombiner::visitAllocaInst(AllocaInst &AI) { 2605d62537276197b3351d9887f4967590b6a3b901Dan Gohman // Ensure that the alloca array size argument has type intptr_t, so that 2705d62537276197b3351d9887f4967590b6a3b901Dan Gohman // any casting is exposed early. 2805d62537276197b3351d9887f4967590b6a3b901Dan Gohman if (TD) { 29db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *IntPtrTy = TD->getIntPtrType(AI.getContext()); 3005d62537276197b3351d9887f4967590b6a3b901Dan Gohman if (AI.getArraySize()->getType() != IntPtrTy) { 3105d62537276197b3351d9887f4967590b6a3b901Dan Gohman Value *V = Builder->CreateIntCast(AI.getArraySize(), 3205d62537276197b3351d9887f4967590b6a3b901Dan Gohman IntPtrTy, false); 3305d62537276197b3351d9887f4967590b6a3b901Dan Gohman AI.setOperand(0, V); 3405d62537276197b3351d9887f4967590b6a3b901Dan Gohman return &AI; 3505d62537276197b3351d9887f4967590b6a3b901Dan Gohman } 3605d62537276197b3351d9887f4967590b6a3b901Dan Gohman } 3705d62537276197b3351d9887f4967590b6a3b901Dan Gohman 388d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Convert: alloca Ty, C - where C is a constant != 1 into: alloca [C x Ty], 1 398d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (AI.isArrayAllocation()) { // Check C != 1 408d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) { 41db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *NewTy = 428d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ArrayType::get(AI.getAllocatedType(), C->getZExtValue()); 438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!"); 448d9b8d717e665945b31b0742b901561fb433ceceChris Lattner AllocaInst *New = Builder->CreateAlloca(NewTy, 0, AI.getName()); 458d9b8d717e665945b31b0742b901561fb433ceceChris Lattner New->setAlignment(AI.getAlignment()); 468d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 478d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Scan to the end of the allocation instructions, to skip over a block of 488d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // allocas if possible...also skip interleaved debug info 498d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // 508d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock::iterator It = New; 518d9b8d717e665945b31b0742b901561fb433ceceChris Lattner while (isa<AllocaInst>(*It) || isa<DbgInfoIntrinsic>(*It)) ++It; 528d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 538d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Now that I is pointing to the first non-allocation-inst in the block, 548d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // insert our getelementptr instruction... 558d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // 568d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *NullIdx =Constant::getNullValue(Type::getInt32Ty(AI.getContext())); 578d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *Idx[2]; 588d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Idx[0] = NullIdx; 598d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Idx[1] = NullIdx; 60e6f364b6c44eda14cd4ad54366ea5cc7246b9500Eli Friedman Instruction *GEP = 61a9203109f4ac95aa7e9624f2838e3d89623ec902Jay Foad GetElementPtrInst::CreateInBounds(New, Idx, New->getName()+".sub"); 62e6f364b6c44eda14cd4ad54366ea5cc7246b9500Eli Friedman InsertNewInstBefore(GEP, *It); 638d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 648d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Now make everything use the getelementptr instead of the original 658d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // allocation. 66e6f364b6c44eda14cd4ad54366ea5cc7246b9500Eli Friedman return ReplaceInstUsesWith(AI, GEP); 678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } else if (isa<UndefValue>(AI.getArraySize())) { 688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType())); 698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 708d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (TD && isa<AllocaInst>(AI) && AI.getAllocatedType()->isSized()) { 738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If alloca'ing a zero byte object, replace the alloca with a null pointer. 748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Note that we only do this for alloca's, because malloc should allocate 758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // and return a unique pointer, even for a zero byte allocation. 768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (TD->getTypeAllocSize(AI.getAllocatedType()) == 0) 778d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType())); 788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the alignment is 0 (unspecified), assign it the preferred alignment. 808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (AI.getAlignment() == 0) 818d9b8d717e665945b31b0742b901561fb433ceceChris Lattner AI.setAlignment(TD->getPrefTypeAlignment(AI.getAllocatedType())); 828d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 888d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// InstCombineLoadCast - Fold 'load (cast P)' -> cast (load P)' when possible. 898d9b8d717e665945b31b0742b901561fb433ceceChris Lattnerstatic Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI, 908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner const TargetData *TD) { 918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner User *CI = cast<User>(LI.getOperand(0)); 928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *CastOp = CI->getOperand(0); 938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 94db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner PointerType *DestTy = cast<PointerType>(CI->getType()); 95db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *DestPTy = DestTy->getElementType(); 96db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner if (PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType())) { 978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the address spaces don't match, don't eliminate the cast. 998d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (DestTy->getAddressSpace() != SrcTy->getAddressSpace()) 1008d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 1018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 102db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *SrcPTy = SrcTy->getElementType(); 1038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1041df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (DestPTy->isIntegerTy() || DestPTy->isPointerTy() || 1051df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands DestPTy->isVectorTy()) { 1068d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the source is an array, the code below will not succeed. Check to 1078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // see if a trivial 'gep P, 0, 0' will help matters. Only do this for 1088d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // constants. 109db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner if (ArrayType *ASrcTy = dyn_cast<ArrayType>(SrcPTy)) 1108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Constant *CSrc = dyn_cast<Constant>(CastOp)) 1118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (ASrcTy->getNumElements() != 0) { 1128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *Idxs[2]; 1138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Idxs[0] = Constant::getNullValue(Type::getInt32Ty(LI.getContext())); 1148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Idxs[1] = Idxs[0]; 1158908ff207d8dc0daccde3dc5710dc805ec98e1faJay Foad CastOp = ConstantExpr::getGetElementPtr(CSrc, Idxs); 1168d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcTy = cast<PointerType>(CastOp->getType()); 1178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcPTy = SrcTy->getElementType(); 1188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 1198d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (IC.getTargetData() && 1211df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (SrcPTy->isIntegerTy() || SrcPTy->isPointerTy() || 1221df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands SrcPTy->isVectorTy()) && 1238d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Do not allow turning this into a load of an integer, which is then 1248d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // casted to a pointer, this pessimizes pointer analysis a lot. 1251df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (SrcPTy->isPointerTy() == LI.getType()->isPointerTy()) && 1268d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.getTargetData()->getTypeSizeInBits(SrcPTy) == 1278d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.getTargetData()->getTypeSizeInBits(DestPTy)) { 1288d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1298d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Okay, we are casting from one integer or pointer type to another of 1308d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the same size. Instead of casting the pointer before the load, cast 1318d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the result of the loaded value. 1326ecfccfd55274187368b86d7f2e65f77d1921c36Bob Wilson LoadInst *NewLoad = 1338d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.Builder->CreateLoad(CastOp, LI.isVolatile(), CI->getName()); 1346ecfccfd55274187368b86d7f2e65f77d1921c36Bob Wilson NewLoad->setAlignment(LI.getAlignment()); 135cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman NewLoad->setAtomic(LI.getOrdering(), LI.getSynchScope()); 1368d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Now cast the result of the load. 1378d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return new BitCastInst(NewLoad, LI.getType()); 1388d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 1398d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 1408d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 1418d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 1428d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 1438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1448d9b8d717e665945b31b0742b901561fb433ceceChris LattnerInstruction *InstCombiner::visitLoadInst(LoadInst &LI) { 1458d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *Op = LI.getOperand(0); 1468d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1478d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Attempt to improve the alignment. 1488d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (TD) { 1498d9b8d717e665945b31b0742b901561fb433ceceChris Lattner unsigned KnownAlign = 150687140c818ba4b896329a83324714140b6580ef8Chris Lattner getOrEnforceKnownAlignment(Op, TD->getPrefTypeAlignment(LI.getType()),TD); 1510fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman unsigned LoadAlign = LI.getAlignment(); 1520fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman unsigned EffectiveLoadAlign = LoadAlign != 0 ? LoadAlign : 1530fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman TD->getABITypeAlignment(LI.getType()); 1540fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman 1550fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman if (KnownAlign > EffectiveLoadAlign) 1568d9b8d717e665945b31b0742b901561fb433ceceChris Lattner LI.setAlignment(KnownAlign); 1570fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman else if (LoadAlign == 0) 1580fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman LI.setAlignment(EffectiveLoadAlign); 1598d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 1608d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1618d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load (cast X) --> cast (load X) iff safe. 1628d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<CastInst>(Op)) 1638d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *Res = InstCombineLoadCast(*this, LI, TD)) 1648d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return Res; 1658d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 166cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // None of the following transforms are legal for volatile/atomic loads. 167cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // FIXME: Some of it is okay for atomic loads; needs refactoring. 168cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (!LI.isSimple()) return 0; 1698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1708d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Do really simple store-to-load forwarding and load CSE, to catch cases 171ab4c366274a582dd8146b2820c6b999cad5fce36Duncan Sands // where there are several consecutive memory accesses to the same location, 1728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // separated by a few arithmetic operations. 1738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock::iterator BBI = &LI; 1748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Value *AvailableVal = FindAvailableLoadedValue(Op, LI.getParent(), BBI,6)) 1758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(LI, AvailableVal); 1768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1778d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load(gep null, ...) -> unreachable 1788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) { 1798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner const Value *GEPI0 = GEPI->getOperand(0); 1808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // TODO: Consider a target hook for valid address spaces for this xform. 1818d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<ConstantPointerNull>(GEPI0) && GEPI->getPointerAddressSpace() == 0){ 1828d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Insert a new store to null instruction before the load to indicate 1838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // that this code is not reachable. We do this instead of inserting 1848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // an unreachable instruction directly because we cannot modify the 1858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // CFG. 1868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner new StoreInst(UndefValue::get(LI.getType()), 1878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Constant::getNullValue(Op->getType()), &LI); 1888d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType())); 1898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 1908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 1918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load null/undef -> unreachable 1938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // TODO: Consider a target hook for valid address spaces for this xform. 1948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<UndefValue>(Op) || 1958d9b8d717e665945b31b0742b901561fb433ceceChris Lattner (isa<ConstantPointerNull>(Op) && LI.getPointerAddressSpace() == 0)) { 1968d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Insert a new store to null instruction before the load to indicate that 1978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // this code is not reachable. We do this instead of inserting an 1988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // unreachable instruction directly because we cannot modify the CFG. 1998d9b8d717e665945b31b0742b901561fb433ceceChris Lattner new StoreInst(UndefValue::get(LI.getType()), 2008d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Constant::getNullValue(Op->getType()), &LI); 2018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType())); 2028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Instcombine load (constantexpr_cast global) -> cast (load global) 2058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op)) 2068d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (CE->isCast()) 2078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *Res = InstCombineLoadCast(*this, LI, TD)) 2088d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return Res; 2098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Op->hasOneUse()) { 2118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Change select and PHI nodes to select values instead of addresses: this 2128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // helps alias analysis out a lot, allows many others simplifications, and 2138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // exposes redundancy in the code. 2148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // 2158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Note that we cannot do the transformation unless we know that the 2168d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // introduced loads cannot trap! Something like this is valid as long as 2178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the condition is always false: load (select bool %C, int* null, int* %G), 2188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // but it would not be valid if we transformed it to load from null 2198d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // unconditionally. 2208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // 2218d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (SelectInst *SI = dyn_cast<SelectInst>(Op)) { 2228d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load (select (Cond, &V1, &V2)) --> select(Cond, load &V1, load &V2). 22349db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson unsigned Align = LI.getAlignment(); 22449db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson if (isSafeToLoadUnconditionally(SI->getOperand(1), SI, Align, TD) && 22549db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson isSafeToLoadUnconditionally(SI->getOperand(2), SI, Align, TD)) { 2266ecfccfd55274187368b86d7f2e65f77d1921c36Bob Wilson LoadInst *V1 = Builder->CreateLoad(SI->getOperand(1), 22749db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson SI->getOperand(1)->getName()+".val"); 2286ecfccfd55274187368b86d7f2e65f77d1921c36Bob Wilson LoadInst *V2 = Builder->CreateLoad(SI->getOperand(2), 22949db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson SI->getOperand(2)->getName()+".val"); 23049db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson V1->setAlignment(Align); 23149db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson V2->setAlignment(Align); 2328d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return SelectInst::Create(SI->getCondition(), V1, V2); 2338d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2348d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2358d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load (select (cond, null, P)) -> load P 2368d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Constant *C = dyn_cast<Constant>(SI->getOperand(1))) 2378d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (C->isNullValue()) { 2388d9b8d717e665945b31b0742b901561fb433ceceChris Lattner LI.setOperand(0, SI->getOperand(2)); 2398d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return &LI; 2408d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2418d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2428d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load (select (cond, P, null)) -> load P 2438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Constant *C = dyn_cast<Constant>(SI->getOperand(2))) 2448d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (C->isNullValue()) { 2458d9b8d717e665945b31b0742b901561fb433ceceChris Lattner LI.setOperand(0, SI->getOperand(1)); 2468d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return &LI; 2478d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2488d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2498d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2508d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 2518d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 2528d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2538d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// InstCombineStoreToCast - Fold store V, (cast P) -> store (cast V), P 2548d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// when possible. This makes it generally easy to do alias analysis and/or 2558d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// SROA/mem2reg of the memory object. 2568d9b8d717e665945b31b0742b901561fb433ceceChris Lattnerstatic Instruction *InstCombineStoreToCast(InstCombiner &IC, StoreInst &SI) { 2578d9b8d717e665945b31b0742b901561fb433ceceChris Lattner User *CI = cast<User>(SI.getOperand(1)); 2588d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *CastOp = CI->getOperand(0); 2598d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 260db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *DestPTy = cast<PointerType>(CI->getType())->getElementType(); 261db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType()); 2628d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (SrcTy == 0) return 0; 2638d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 264db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *SrcPTy = SrcTy->getElementType(); 2658d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2661df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (!DestPTy->isIntegerTy() && !DestPTy->isPointerTy()) 2678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 2688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner /// NewGEPIndices - If SrcPTy is an aggregate type, we can emit a "noop gep" 2708d9b8d717e665945b31b0742b901561fb433ceceChris Lattner /// to its first element. This allows us to handle things like: 2718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner /// store i32 xxx, (bitcast {foo*, float}* %P to i32*) 2728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner /// on 32-bit hosts. 2738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SmallVector<Value*, 4> NewGEPIndices; 2748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the source is an array, the code below will not succeed. Check to 2768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // see if a trivial 'gep P, 0, 0' will help matters. Only do this for 2778d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // constants. 2781df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (SrcPTy->isArrayTy() || SrcPTy->isStructTy()) { 2798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Index through pointer. 2808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Constant *Zero = Constant::getNullValue(Type::getInt32Ty(SI.getContext())); 2818d9b8d717e665945b31b0742b901561fb433ceceChris Lattner NewGEPIndices.push_back(Zero); 2828d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner while (1) { 284db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner if (StructType *STy = dyn_cast<StructType>(SrcPTy)) { 2858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!STy->getNumElements()) /* Struct can be empty {} */ 2868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 2878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner NewGEPIndices.push_back(Zero); 2888d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcPTy = STy->getElementType(0); 289db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner } else if (ArrayType *ATy = dyn_cast<ArrayType>(SrcPTy)) { 2908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner NewGEPIndices.push_back(Zero); 2918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcPTy = ATy->getElementType(); 2928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } else { 2938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 2948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2958d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2968d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcTy = PointerType::get(SrcPTy, SrcTy->getAddressSpace()); 2988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2998d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3001df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (!SrcPTy->isIntegerTy() && !SrcPTy->isPointerTy()) 3018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 3028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the pointers point into different address spaces or if they point to 3048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // values with different sizes, we can't do the transformation. 3058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!IC.getTargetData() || 3068d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcTy->getAddressSpace() != 3078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner cast<PointerType>(CI->getType())->getAddressSpace() || 3088d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.getTargetData()->getTypeSizeInBits(SrcPTy) != 3098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.getTargetData()->getTypeSizeInBits(DestPTy)) 3108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 3118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Okay, we are casting from one integer or pointer type to another of 3138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the same size. Instead of casting the pointer before 3148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the store, cast the value to be stored. 3158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *NewCast; 3168d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *SIOp0 = SI.getOperand(0); 3178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Instruction::CastOps opcode = Instruction::BitCast; 318db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type* CastSrcTy = SIOp0->getType(); 319db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type* CastDstTy = SrcPTy; 3201df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (CastDstTy->isPointerTy()) { 321b0bc6c361da9009e8414efde317d9bbff755f6c0Duncan Sands if (CastSrcTy->isIntegerTy()) 3228d9b8d717e665945b31b0742b901561fb433ceceChris Lattner opcode = Instruction::IntToPtr; 3231df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands } else if (CastDstTy->isIntegerTy()) { 3241df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (SIOp0->getType()->isPointerTy()) 3258d9b8d717e665945b31b0742b901561fb433ceceChris Lattner opcode = Instruction::PtrToInt; 3268d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3278d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3288d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // SIOp0 is a pointer to aggregate and this is a store to the first field, 3298d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // emit a GEP to index into its first field. 3308d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!NewGEPIndices.empty()) 3310a2a60ace9b79164b71794ce7ff981171c61e442Jay Foad CastOp = IC.Builder->CreateInBoundsGEP(CastOp, NewGEPIndices); 3328d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3338d9b8d717e665945b31b0742b901561fb433ceceChris Lattner NewCast = IC.Builder->CreateCast(opcode, SIOp0, CastDstTy, 3348d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SIOp0->getName()+".c"); 33517a0bf996fb61cdd43cec2cfc7db53145bbc767aDan Gohman SI.setOperand(0, NewCast); 33617a0bf996fb61cdd43cec2cfc7db53145bbc767aDan Gohman SI.setOperand(1, CastOp); 33717a0bf996fb61cdd43cec2cfc7db53145bbc767aDan Gohman return &SI; 3388d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 3398d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3408d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// equivalentAddressValues - Test if A and B will obviously have the same 3418d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// value. This includes recognizing that %t0 and %t1 will have the same 3428d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// value in code like this: 3438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// %t0 = getelementptr \@a, 0, 3 3448d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// store i32 0, i32* %t0 3458d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// %t1 = getelementptr \@a, 0, 3 3468d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// %t2 = load i32* %t1 3478d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// 3488d9b8d717e665945b31b0742b901561fb433ceceChris Lattnerstatic bool equivalentAddressValues(Value *A, Value *B) { 3498d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Test if the values are trivially equivalent. 3508d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (A == B) return true; 3518d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3528d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Test if the values come form identical arithmetic instructions. 3538d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // This uses isIdenticalToWhenDefined instead of isIdenticalTo because 3548d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // its only used to compare two uses within the same basic block, which 3558d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // means that they'll always either have the same value or one of them 3568d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // will have an undefined value. 3578d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<BinaryOperator>(A) || 3588d9b8d717e665945b31b0742b901561fb433ceceChris Lattner isa<CastInst>(A) || 3598d9b8d717e665945b31b0742b901561fb433ceceChris Lattner isa<PHINode>(A) || 3608d9b8d717e665945b31b0742b901561fb433ceceChris Lattner isa<GetElementPtrInst>(A)) 3618d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *BI = dyn_cast<Instruction>(B)) 3628d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (cast<Instruction>(A)->isIdenticalToWhenDefined(BI)) 3638d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return true; 3648d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3658d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Otherwise they may not be equivalent. 3668d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 3678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 3688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3698d9b8d717e665945b31b0742b901561fb433ceceChris LattnerInstruction *InstCombiner::visitStoreInst(StoreInst &SI) { 3708d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *Val = SI.getOperand(0); 3718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *Ptr = SI.getOperand(1); 3728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Attempt to improve the alignment. 3748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (TD) { 3758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner unsigned KnownAlign = 376687140c818ba4b896329a83324714140b6580ef8Chris Lattner getOrEnforceKnownAlignment(Ptr, TD->getPrefTypeAlignment(Val->getType()), 377687140c818ba4b896329a83324714140b6580ef8Chris Lattner TD); 3780fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman unsigned StoreAlign = SI.getAlignment(); 3790fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman unsigned EffectiveStoreAlign = StoreAlign != 0 ? StoreAlign : 3800fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman TD->getABITypeAlignment(Val->getType()); 3810fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman 3820ccae0b1f6b95e4500adb45649472389a1f111a7Bill Wendling if (KnownAlign > EffectiveStoreAlign) 3838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SI.setAlignment(KnownAlign); 3840ccae0b1f6b95e4500adb45649472389a1f111a7Bill Wendling else if (StoreAlign == 0) 3850ccae0b1f6b95e4500adb45649472389a1f111a7Bill Wendling SI.setAlignment(EffectiveStoreAlign); 3868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 388cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // Don't hack volatile/atomic stores. 389cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // FIXME: Some bits are legal for atomic stores; needs refactoring. 390cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (!SI.isSimple()) return 0; 391cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman 392cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // If the RHS is an alloca with a single use, zapify the store, making the 393cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // alloca dead. 394cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (Ptr->hasOneUse()) { 395cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (isa<AllocaInst>(Ptr)) 396cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman return EraseInstFromFunction(SI); 397cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr)) { 398cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (isa<AllocaInst>(GEP->getOperand(0))) { 399cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (GEP->getOperand(0)->hasOneUse()) 400cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman return EraseInstFromFunction(SI); 401cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman } 402cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman } 403cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman } 404cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman 4058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Do really simple DSE, to catch cases where there are several consecutive 4068d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // stores to the same location, separated by a few arithmetic operations. This 4078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // situation often occurs with bitfield accesses. 4088d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock::iterator BBI = &SI; 4098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner for (unsigned ScanInsts = 6; BBI != SI.getParent()->begin() && ScanInsts; 4108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner --ScanInsts) { 4118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner --BBI; 41229fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez // Don't count debug info directives, lest they affect codegen, 41329fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez // and we skip pointer-to-pointer bitcasts, which are NOPs. 41429fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez if (isa<DbgInfoIntrinsic>(BBI) || 4151df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())) { 4168d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ScanInsts++; 4178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner continue; 4188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4198d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (StoreInst *PrevSI = dyn_cast<StoreInst>(BBI)) { 4218d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Prev store isn't volatile, and stores to the same location? 422cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (PrevSI->isSimple() && equivalentAddressValues(PrevSI->getOperand(1), 423cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman SI.getOperand(1))) { 4248d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ++NumDeadStore; 4258d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ++BBI; 4268d9b8d717e665945b31b0742b901561fb433ceceChris Lattner EraseInstFromFunction(*PrevSI); 4278d9b8d717e665945b31b0742b901561fb433ceceChris Lattner continue; 4288d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4298d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 4308d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4318d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4328d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If this is a load, we have to stop. However, if the loaded value is from 4338d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the pointer we're loading and is producing the pointer we're storing, 4348d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // then *this* store is dead (X = load P; store X -> P). 4358d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) { 436948d9e7ec7c4f8da50d2640d3564b01d40ffd4b1Jin-Gu Kang if (LI == Val && equivalentAddressValues(LI->getOperand(0), Ptr) && 437cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman LI->isSimple()) 438948d9e7ec7c4f8da50d2640d3564b01d40ffd4b1Jin-Gu Kang return EraseInstFromFunction(SI); 4398d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4408d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Otherwise, this is a load from some other location. Stores before it 4418d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // may not be dead. 4428d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 4438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4448d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4458d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Don't skip over loads or things that can modify memory. 4468d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BBI->mayWriteToMemory() || BBI->mayReadFromMemory()) 4478d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 4488d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4498d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4508d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // store X, null -> turns into 'unreachable' in SimplifyCFG 4518d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<ConstantPointerNull>(Ptr) && SI.getPointerAddressSpace() == 0) { 4528d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!isa<UndefValue>(Val)) { 4538d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SI.setOperand(0, UndefValue::get(Val->getType())); 4548d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *U = dyn_cast<Instruction>(Val)) 4558d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Worklist.Add(U); // Dropped a use. 4568d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4578d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; // Do not modify these! 4588d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4598d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4608d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // store undef, Ptr -> noop 4618d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<UndefValue>(Val)) 4628d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return EraseInstFromFunction(SI); 4638d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4648d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the pointer destination is a cast, see if we can fold the cast into the 4658d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // source instead. 4668d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<CastInst>(Ptr)) 4678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *Res = InstCombineStoreToCast(*this, SI)) 4688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return Res; 4698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 4708d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (CE->isCast()) 4718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *Res = InstCombineStoreToCast(*this, SI)) 4728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return Res; 4738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If this store is the last instruction in the basic block (possibly 476a4c77622f7f9f7546f0eae7c171ab56df125dc9aVictor Hernandez // excepting debug info instructions), and if the block ends with an 477a4c77622f7f9f7546f0eae7c171ab56df125dc9aVictor Hernandez // unconditional branch, try to move it to the successor block. 4788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BBI = &SI; 4798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner do { 4808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ++BBI; 48129fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez } while (isa<DbgInfoIntrinsic>(BBI) || 4821df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())); 4838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BranchInst *BI = dyn_cast<BranchInst>(BBI)) 4848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BI->isUnconditional()) 4858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (SimplifyStoreAtEndOfBlock(SI)) 4868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; // xform done! 4878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4888d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 4898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 4908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// SimplifyStoreAtEndOfBlock - Turn things like: 4928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// if () { *P = v1; } else { *P = v2 } 4938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// into a phi node with a store in the successor. 4948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// 4958d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// Simplify things like: 4968d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// *P = v1; if () { *P = v2; } 4978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// into a phi node with a store in the successor. 4988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// 4998d9b8d717e665945b31b0742b901561fb433ceceChris Lattnerbool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) { 5008d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock *StoreBB = SI.getParent(); 5018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Check to see if the successor block has exactly two incoming edges. If 5038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // so, see if the other predecessor contains a store to the same location. 5048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // if so, insert a PHI node (if needed) and move the stores down. 5058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock *DestBB = StoreBB->getTerminator()->getSuccessor(0); 5068d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Determine whether Dest has exactly two predecessors and, if so, compute 5088d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the other predecessor. 5098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner pred_iterator PI = pred_begin(DestBB); 510a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif BasicBlock *P = *PI; 5118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock *OtherBB = 0; 512a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif 513a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif if (P != StoreBB) 514a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif OtherBB = P; 515a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif 516a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif if (++PI == pred_end(DestBB)) 5178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 519a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif P = *PI; 520a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif if (P != StoreBB) { 5218d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (OtherBB) 5228d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 523a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif OtherBB = P; 5248d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5258d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (++PI != pred_end(DestBB)) 5268d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5278d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5288d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Bail out if all the relevant blocks aren't distinct (this can happen, 5298d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // for example, if SI is in an infinite loop) 5308d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (StoreBB == DestBB || OtherBB == DestBB) 5318d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5328d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5338d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Verify that the other block ends in a branch and is not otherwise empty. 5348d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock::iterator BBI = OtherBB->getTerminator(); 5358d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BranchInst *OtherBr = dyn_cast<BranchInst>(BBI); 5368d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!OtherBr || BBI == OtherBB->begin()) 5378d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5388d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5398d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the other block ends in an unconditional branch, check for the 'if then 5408d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // else' case. there is an instruction before the branch. 5418d9b8d717e665945b31b0742b901561fb433ceceChris Lattner StoreInst *OtherStore = 0; 5428d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (OtherBr->isUnconditional()) { 5438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner --BBI; 5448d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Skip over debugging info. 54529fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez while (isa<DbgInfoIntrinsic>(BBI) || 5461df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())) { 5478d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BBI==OtherBB->begin()) 5488d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5498d9b8d717e665945b31b0742b901561fb433ceceChris Lattner --BBI; 5508d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 551cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // If this isn't a store, isn't a store to the same location, or is not the 552cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // right kind of store, bail out. 5538d9b8d717e665945b31b0742b901561fb433ceceChris Lattner OtherStore = dyn_cast<StoreInst>(BBI); 5548d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!OtherStore || OtherStore->getOperand(1) != SI.getOperand(1) || 555cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman !SI.isSameOperationAs(OtherStore)) 5568d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5578d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } else { 5588d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Otherwise, the other block ended with a conditional branch. If one of the 5598d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // destinations is StoreBB, then we have the if/then case. 5608d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (OtherBr->getSuccessor(0) != StoreBB && 5618d9b8d717e665945b31b0742b901561fb433ceceChris Lattner OtherBr->getSuccessor(1) != StoreBB) 5628d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5638d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5648d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Okay, we know that OtherBr now goes to Dest and StoreBB, so this is an 5658d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // if/then triangle. See if there is a store to the same ptr as SI that 5668d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // lives in OtherBB. 5678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner for (;; --BBI) { 5688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Check to see if we find the matching store. 5698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if ((OtherStore = dyn_cast<StoreInst>(BBI))) { 5708d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (OtherStore->getOperand(1) != SI.getOperand(1) || 571cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman !SI.isSameOperationAs(OtherStore)) 5728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 5748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If we find something that may be using or overwriting the stored 5768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // value, or if we run out of instructions, we can't do the xform. 5778d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BBI->mayReadFromMemory() || BBI->mayWriteToMemory() || 5788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BBI == OtherBB->begin()) 5798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5818d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5828d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // In order to eliminate the store in OtherBr, we have to 5838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // make sure nothing reads or overwrites the stored value in 5848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // StoreBB. 5858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner for (BasicBlock::iterator I = StoreBB->begin(); &*I != &SI; ++I) { 5868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // FIXME: This should really be AA driven. 5878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (I->mayReadFromMemory() || I->mayWriteToMemory()) 5888d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Insert a PHI node now if we need it. 5938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *MergedVal = OtherStore->getOperand(0); 5948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (MergedVal != SI.getOperand(0)) { 5953ecfc861b4365f341c5c969b40e1afccde676e6fJay Foad PHINode *PN = PHINode::Create(MergedVal->getType(), 2, "storemerge"); 5968d9b8d717e665945b31b0742b901561fb433ceceChris Lattner PN->addIncoming(SI.getOperand(0), SI.getParent()); 5978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner PN->addIncoming(OtherStore->getOperand(0), OtherBB); 5988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner MergedVal = InsertNewInstBefore(PN, DestBB->front()); 5998d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 6008d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 6018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Advance to a place where it is safe to insert the new store and 6028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // insert it. 6035b6f42f57e730c2d968c313a27fa505a3c3e5efaBill Wendling BBI = DestBB->getFirstInsertionPt(); 604a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman StoreInst *NewSI = new StoreInst(MergedVal, SI.getOperand(1), 605cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman SI.isVolatile(), 606cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman SI.getAlignment(), 607cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman SI.getOrdering(), 608cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman SI.getSynchScope()); 609a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman InsertNewInstBefore(NewSI, *BBI); 610a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman NewSI->setDebugLoc(OtherStore->getDebugLoc()); 611a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman 6128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Nuke the old stores. 6138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner EraseInstFromFunction(SI); 6148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner EraseInstFromFunction(*OtherStore); 6158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return true; 6168d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 617