InstCombineLoadStoreAlloca.cpp revision 8908ff207d8dc0daccde3dc5710dc805ec98e1fa
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 = 61e6f364b6c44eda14cd4ad54366ea5cc7246b9500Eli Friedman GetElementPtrInst::CreateInBounds(New, Idx, Idx + 2, 62e6f364b6c44eda14cd4ad54366ea5cc7246b9500Eli Friedman New->getName()+".sub"); 63e6f364b6c44eda14cd4ad54366ea5cc7246b9500Eli Friedman InsertNewInstBefore(GEP, *It); 648d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 658d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Now make everything use the getelementptr instead of the original 668d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // allocation. 67e6f364b6c44eda14cd4ad54366ea5cc7246b9500Eli Friedman return ReplaceInstUsesWith(AI, GEP); 688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } else if (isa<UndefValue>(AI.getArraySize())) { 698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType())); 708d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (TD && isa<AllocaInst>(AI) && AI.getAllocatedType()->isSized()) { 748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If alloca'ing a zero byte object, replace the alloca with a null pointer. 758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Note that we only do this for alloca's, because malloc should allocate 768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // and return a unique pointer, even for a zero byte allocation. 778d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (TD->getTypeAllocSize(AI.getAllocatedType()) == 0) 788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType())); 798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the alignment is 0 (unspecified), assign it the preferred alignment. 818d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (AI.getAlignment() == 0) 828d9b8d717e665945b31b0742b901561fb433ceceChris Lattner AI.setAlignment(TD->getPrefTypeAlignment(AI.getAllocatedType())); 838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 888d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// InstCombineLoadCast - Fold 'load (cast P)' -> cast (load P)' when possible. 908d9b8d717e665945b31b0742b901561fb433ceceChris Lattnerstatic Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI, 918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner const TargetData *TD) { 928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner User *CI = cast<User>(LI.getOperand(0)); 938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *CastOp = CI->getOperand(0); 948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 95db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner PointerType *DestTy = cast<PointerType>(CI->getType()); 96db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *DestPTy = DestTy->getElementType(); 97db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner if (PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType())) { 988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 998d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the address spaces don't match, don't eliminate the cast. 1008d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (DestTy->getAddressSpace() != SrcTy->getAddressSpace()) 1018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 1028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 103db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *SrcPTy = SrcTy->getElementType(); 1048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1051df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (DestPTy->isIntegerTy() || DestPTy->isPointerTy() || 1061df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands DestPTy->isVectorTy()) { 1078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the source is an array, the code below will not succeed. Check to 1088d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // see if a trivial 'gep P, 0, 0' will help matters. Only do this for 1098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // constants. 110db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner if (ArrayType *ASrcTy = dyn_cast<ArrayType>(SrcPTy)) 1118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Constant *CSrc = dyn_cast<Constant>(CastOp)) 1128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (ASrcTy->getNumElements() != 0) { 1138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *Idxs[2]; 1148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Idxs[0] = Constant::getNullValue(Type::getInt32Ty(LI.getContext())); 1158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Idxs[1] = Idxs[0]; 1168908ff207d8dc0daccde3dc5710dc805ec98e1faJay Foad CastOp = ConstantExpr::getGetElementPtr(CSrc, Idxs); 1178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcTy = cast<PointerType>(CastOp->getType()); 1188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcPTy = SrcTy->getElementType(); 1198d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 1208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1218d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (IC.getTargetData() && 1221df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (SrcPTy->isIntegerTy() || SrcPTy->isPointerTy() || 1231df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands SrcPTy->isVectorTy()) && 1248d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Do not allow turning this into a load of an integer, which is then 1258d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // casted to a pointer, this pessimizes pointer analysis a lot. 1261df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (SrcPTy->isPointerTy() == LI.getType()->isPointerTy()) && 1278d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.getTargetData()->getTypeSizeInBits(SrcPTy) == 1288d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.getTargetData()->getTypeSizeInBits(DestPTy)) { 1298d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1308d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Okay, we are casting from one integer or pointer type to another of 1318d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the same size. Instead of casting the pointer before the load, cast 1328d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the result of the loaded value. 1336ecfccfd55274187368b86d7f2e65f77d1921c36Bob Wilson LoadInst *NewLoad = 1348d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.Builder->CreateLoad(CastOp, LI.isVolatile(), CI->getName()); 1356ecfccfd55274187368b86d7f2e65f77d1921c36Bob Wilson NewLoad->setAlignment(LI.getAlignment()); 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 1668d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // None of the following transforms are legal for volatile loads. 1678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (LI.isVolatile()) return 0; 1688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Do really simple store-to-load forwarding and load CSE, to catch cases 170ab4c366274a582dd8146b2820c6b999cad5fce36Duncan Sands // where there are several consecutive memory accesses to the same location, 1718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // separated by a few arithmetic operations. 1728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock::iterator BBI = &LI; 1738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Value *AvailableVal = FindAvailableLoadedValue(Op, LI.getParent(), BBI,6)) 1748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(LI, AvailableVal); 1758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load(gep null, ...) -> unreachable 1778d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) { 1788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner const Value *GEPI0 = GEPI->getOperand(0); 1798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // TODO: Consider a target hook for valid address spaces for this xform. 1808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<ConstantPointerNull>(GEPI0) && GEPI->getPointerAddressSpace() == 0){ 1818d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Insert a new store to null instruction before the load to indicate 1828d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // that this code is not reachable. We do this instead of inserting 1838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // an unreachable instruction directly because we cannot modify the 1848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // CFG. 1858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner new StoreInst(UndefValue::get(LI.getType()), 1868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Constant::getNullValue(Op->getType()), &LI); 1878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType())); 1888d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 1898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 1908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load null/undef -> unreachable 1928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // TODO: Consider a target hook for valid address spaces for this xform. 1938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<UndefValue>(Op) || 1948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner (isa<ConstantPointerNull>(Op) && LI.getPointerAddressSpace() == 0)) { 1958d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Insert a new store to null instruction before the load to indicate that 1968d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // this code is not reachable. We do this instead of inserting an 1978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // unreachable instruction directly because we cannot modify the CFG. 1988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner new StoreInst(UndefValue::get(LI.getType()), 1998d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Constant::getNullValue(Op->getType()), &LI); 2008d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType())); 2018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Instcombine load (constantexpr_cast global) -> cast (load global) 2048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op)) 2058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (CE->isCast()) 2068d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *Res = InstCombineLoadCast(*this, LI, TD)) 2078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return Res; 2088d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Op->hasOneUse()) { 2108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Change select and PHI nodes to select values instead of addresses: this 2118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // helps alias analysis out a lot, allows many others simplifications, and 2128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // exposes redundancy in the code. 2138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // 2148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Note that we cannot do the transformation unless we know that the 2158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // introduced loads cannot trap! Something like this is valid as long as 2168d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the condition is always false: load (select bool %C, int* null, int* %G), 2178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // but it would not be valid if we transformed it to load from null 2188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // unconditionally. 2198d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // 2208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (SelectInst *SI = dyn_cast<SelectInst>(Op)) { 2218d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load (select (Cond, &V1, &V2)) --> select(Cond, load &V1, load &V2). 22249db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson unsigned Align = LI.getAlignment(); 22349db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson if (isSafeToLoadUnconditionally(SI->getOperand(1), SI, Align, TD) && 22449db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson isSafeToLoadUnconditionally(SI->getOperand(2), SI, Align, TD)) { 2256ecfccfd55274187368b86d7f2e65f77d1921c36Bob Wilson LoadInst *V1 = Builder->CreateLoad(SI->getOperand(1), 22649db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson SI->getOperand(1)->getName()+".val"); 2276ecfccfd55274187368b86d7f2e65f77d1921c36Bob Wilson LoadInst *V2 = Builder->CreateLoad(SI->getOperand(2), 22849db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson SI->getOperand(2)->getName()+".val"); 22949db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson V1->setAlignment(Align); 23049db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson V2->setAlignment(Align); 2318d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return SelectInst::Create(SI->getCondition(), V1, V2); 2328d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2338d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2348d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load (select (cond, null, P)) -> load P 2358d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Constant *C = dyn_cast<Constant>(SI->getOperand(1))) 2368d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (C->isNullValue()) { 2378d9b8d717e665945b31b0742b901561fb433ceceChris Lattner LI.setOperand(0, SI->getOperand(2)); 2388d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return &LI; 2398d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2408d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2418d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load (select (cond, P, null)) -> load P 2428d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Constant *C = dyn_cast<Constant>(SI->getOperand(2))) 2438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (C->isNullValue()) { 2448d9b8d717e665945b31b0742b901561fb433ceceChris Lattner LI.setOperand(0, SI->getOperand(1)); 2458d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return &LI; 2468d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2478d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2488d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2498d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 2508d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 2518d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2528d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// InstCombineStoreToCast - Fold store V, (cast P) -> store (cast V), P 2538d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// when possible. This makes it generally easy to do alias analysis and/or 2548d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// SROA/mem2reg of the memory object. 2558d9b8d717e665945b31b0742b901561fb433ceceChris Lattnerstatic Instruction *InstCombineStoreToCast(InstCombiner &IC, StoreInst &SI) { 2568d9b8d717e665945b31b0742b901561fb433ceceChris Lattner User *CI = cast<User>(SI.getOperand(1)); 2578d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *CastOp = CI->getOperand(0); 2588d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 259db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *DestPTy = cast<PointerType>(CI->getType())->getElementType(); 260db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType()); 2618d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (SrcTy == 0) return 0; 2628d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 263db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *SrcPTy = SrcTy->getElementType(); 2648d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2651df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (!DestPTy->isIntegerTy() && !DestPTy->isPointerTy()) 2668d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 2678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner /// NewGEPIndices - If SrcPTy is an aggregate type, we can emit a "noop gep" 2698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner /// to its first element. This allows us to handle things like: 2708d9b8d717e665945b31b0742b901561fb433ceceChris Lattner /// store i32 xxx, (bitcast {foo*, float}* %P to i32*) 2718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner /// on 32-bit hosts. 2728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SmallVector<Value*, 4> NewGEPIndices; 2738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the source is an array, the code below will not succeed. Check to 2758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // see if a trivial 'gep P, 0, 0' will help matters. Only do this for 2768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // constants. 2771df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (SrcPTy->isArrayTy() || SrcPTy->isStructTy()) { 2788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Index through pointer. 2798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Constant *Zero = Constant::getNullValue(Type::getInt32Ty(SI.getContext())); 2808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner NewGEPIndices.push_back(Zero); 2818d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2828d9b8d717e665945b31b0742b901561fb433ceceChris Lattner while (1) { 283db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner if (StructType *STy = dyn_cast<StructType>(SrcPTy)) { 2848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!STy->getNumElements()) /* Struct can be empty {} */ 2858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 2868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner NewGEPIndices.push_back(Zero); 2878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcPTy = STy->getElementType(0); 288db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner } else if (ArrayType *ATy = dyn_cast<ArrayType>(SrcPTy)) { 2898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner NewGEPIndices.push_back(Zero); 2908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcPTy = ATy->getElementType(); 2918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } else { 2928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 2938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2958d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2968d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcTy = PointerType::get(SrcPTy, SrcTy->getAddressSpace()); 2978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2991df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (!SrcPTy->isIntegerTy() && !SrcPTy->isPointerTy()) 3008d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 3018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the pointers point into different address spaces or if they point to 3038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // values with different sizes, we can't do the transformation. 3048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!IC.getTargetData() || 3058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcTy->getAddressSpace() != 3068d9b8d717e665945b31b0742b901561fb433ceceChris Lattner cast<PointerType>(CI->getType())->getAddressSpace() || 3078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.getTargetData()->getTypeSizeInBits(SrcPTy) != 3088d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.getTargetData()->getTypeSizeInBits(DestPTy)) 3098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 3108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Okay, we are casting from one integer or pointer type to another of 3128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the same size. Instead of casting the pointer before 3138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the store, cast the value to be stored. 3148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *NewCast; 3158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *SIOp0 = SI.getOperand(0); 3168d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Instruction::CastOps opcode = Instruction::BitCast; 317db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type* CastSrcTy = SIOp0->getType(); 318db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type* CastDstTy = SrcPTy; 3191df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (CastDstTy->isPointerTy()) { 320b0bc6c361da9009e8414efde317d9bbff755f6c0Duncan Sands if (CastSrcTy->isIntegerTy()) 3218d9b8d717e665945b31b0742b901561fb433ceceChris Lattner opcode = Instruction::IntToPtr; 3221df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands } else if (CastDstTy->isIntegerTy()) { 3231df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (SIOp0->getType()->isPointerTy()) 3248d9b8d717e665945b31b0742b901561fb433ceceChris Lattner opcode = Instruction::PtrToInt; 3258d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3268d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3278d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // SIOp0 is a pointer to aggregate and this is a store to the first field, 3288d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // emit a GEP to index into its first field. 3298d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!NewGEPIndices.empty()) 3308d9b8d717e665945b31b0742b901561fb433ceceChris Lattner CastOp = IC.Builder->CreateInBoundsGEP(CastOp, NewGEPIndices.begin(), 3318d9b8d717e665945b31b0742b901561fb433ceceChris Lattner NewGEPIndices.end()); 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 // If the RHS is an alloca with a single use, zapify the store, making the 3748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // alloca dead. 3758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!SI.isVolatile()) { 3768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Ptr->hasOneUse()) { 3778d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<AllocaInst>(Ptr)) 3788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return EraseInstFromFunction(SI); 3798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr)) { 3808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<AllocaInst>(GEP->getOperand(0))) { 3818d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (GEP->getOperand(0)->hasOneUse()) 3828d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return EraseInstFromFunction(SI); 3838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3888d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Attempt to improve the alignment. 3898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (TD) { 3908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner unsigned KnownAlign = 391687140c818ba4b896329a83324714140b6580ef8Chris Lattner getOrEnforceKnownAlignment(Ptr, TD->getPrefTypeAlignment(Val->getType()), 392687140c818ba4b896329a83324714140b6580ef8Chris Lattner TD); 3930fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman unsigned StoreAlign = SI.getAlignment(); 3940fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman unsigned EffectiveStoreAlign = StoreAlign != 0 ? StoreAlign : 3950fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman TD->getABITypeAlignment(Val->getType()); 3960fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman 3970fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman if (KnownAlign > EffectiveStoreAlign) 3988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SI.setAlignment(KnownAlign); 3990fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman else if (StoreAlign == 0) 4000fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman SI.setAlignment(EffectiveStoreAlign); 4018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Do really simple DSE, to catch cases where there are several consecutive 4048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // stores to the same location, separated by a few arithmetic operations. This 4058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // situation often occurs with bitfield accesses. 4068d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock::iterator BBI = &SI; 4078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner for (unsigned ScanInsts = 6; BBI != SI.getParent()->begin() && ScanInsts; 4088d9b8d717e665945b31b0742b901561fb433ceceChris Lattner --ScanInsts) { 4098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner --BBI; 41029fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez // Don't count debug info directives, lest they affect codegen, 41129fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez // and we skip pointer-to-pointer bitcasts, which are NOPs. 41229fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez if (isa<DbgInfoIntrinsic>(BBI) || 4131df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())) { 4148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ScanInsts++; 4158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner continue; 4168d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (StoreInst *PrevSI = dyn_cast<StoreInst>(BBI)) { 4198d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Prev store isn't volatile, and stores to the same location? 4208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!PrevSI->isVolatile() &&equivalentAddressValues(PrevSI->getOperand(1), 4218d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SI.getOperand(1))) { 4228d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ++NumDeadStore; 4238d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ++BBI; 4248d9b8d717e665945b31b0742b901561fb433ceceChris Lattner EraseInstFromFunction(*PrevSI); 4258d9b8d717e665945b31b0742b901561fb433ceceChris Lattner continue; 4268d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4278d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 4288d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4298d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4308d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If this is a load, we have to stop. However, if the loaded value is from 4318d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the pointer we're loading and is producing the pointer we're storing, 4328d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // then *this* store is dead (X = load P; store X -> P). 4338d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) { 434948d9e7ec7c4f8da50d2640d3564b01d40ffd4b1Jin-Gu Kang if (LI == Val && equivalentAddressValues(LI->getOperand(0), Ptr) && 435948d9e7ec7c4f8da50d2640d3564b01d40ffd4b1Jin-Gu Kang !SI.isVolatile()) 436948d9e7ec7c4f8da50d2640d3564b01d40ffd4b1Jin-Gu Kang return EraseInstFromFunction(SI); 4378d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4388d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Otherwise, this is a load from some other location. Stores before it 4398d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // may not be dead. 4408d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 4418d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4428d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Don't skip over loads or things that can modify memory. 4448d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BBI->mayWriteToMemory() || BBI->mayReadFromMemory()) 4458d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 4468d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4478d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4488d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4498d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (SI.isVolatile()) return 0; // Don't hack volatile stores. 4508d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4518d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // store X, null -> turns into 'unreachable' in SimplifyCFG 4528d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<ConstantPointerNull>(Ptr) && SI.getPointerAddressSpace() == 0) { 4538d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!isa<UndefValue>(Val)) { 4548d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SI.setOperand(0, UndefValue::get(Val->getType())); 4558d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *U = dyn_cast<Instruction>(Val)) 4568d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Worklist.Add(U); // Dropped a use. 4578d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4588d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; // Do not modify these! 4598d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4608d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4618d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // store undef, Ptr -> noop 4628d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<UndefValue>(Val)) 4638d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return EraseInstFromFunction(SI); 4648d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4658d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the pointer destination is a cast, see if we can fold the cast into the 4668d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // source instead. 4678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<CastInst>(Ptr)) 4688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *Res = InstCombineStoreToCast(*this, SI)) 4698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return Res; 4708d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 4718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (CE->isCast()) 4728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *Res = InstCombineStoreToCast(*this, SI)) 4738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return Res; 4748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If this store is the last instruction in the basic block (possibly 477a4c77622f7f9f7546f0eae7c171ab56df125dc9aVictor Hernandez // excepting debug info instructions), and if the block ends with an 478a4c77622f7f9f7546f0eae7c171ab56df125dc9aVictor Hernandez // unconditional branch, try to move it to the successor block. 4798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BBI = &SI; 4808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner do { 4818d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ++BBI; 48229fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez } while (isa<DbgInfoIntrinsic>(BBI) || 4831df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())); 4848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BranchInst *BI = dyn_cast<BranchInst>(BBI)) 4858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BI->isUnconditional()) 4868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (SimplifyStoreAtEndOfBlock(SI)) 4878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; // xform done! 4888d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 4908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 4918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// SimplifyStoreAtEndOfBlock - Turn things like: 4938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// if () { *P = v1; } else { *P = v2 } 4948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// into a phi node with a store in the successor. 4958d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// 4968d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// Simplify things like: 4978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// *P = v1; if () { *P = v2; } 4988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// into a phi node with a store in the successor. 4998d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// 5008d9b8d717e665945b31b0742b901561fb433ceceChris Lattnerbool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) { 5018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock *StoreBB = SI.getParent(); 5028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Check to see if the successor block has exactly two incoming edges. If 5048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // so, see if the other predecessor contains a store to the same location. 5058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // if so, insert a PHI node (if needed) and move the stores down. 5068d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock *DestBB = StoreBB->getTerminator()->getSuccessor(0); 5078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5088d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Determine whether Dest has exactly two predecessors and, if so, compute 5098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the other predecessor. 5108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner pred_iterator PI = pred_begin(DestBB); 511a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif BasicBlock *P = *PI; 5128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock *OtherBB = 0; 513a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif 514a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif if (P != StoreBB) 515a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif OtherBB = P; 516a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif 517a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif if (++PI == pred_end(DestBB)) 5188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5198d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 520a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif P = *PI; 521a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif if (P != StoreBB) { 5228d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (OtherBB) 5238d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 524a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif OtherBB = P; 5258d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5268d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (++PI != pred_end(DestBB)) 5278d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5288d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5298d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Bail out if all the relevant blocks aren't distinct (this can happen, 5308d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // for example, if SI is in an infinite loop) 5318d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (StoreBB == DestBB || OtherBB == DestBB) 5328d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5338d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5348d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Verify that the other block ends in a branch and is not otherwise empty. 5358d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock::iterator BBI = OtherBB->getTerminator(); 5368d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BranchInst *OtherBr = dyn_cast<BranchInst>(BBI); 5378d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!OtherBr || BBI == OtherBB->begin()) 5388d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5398d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5408d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the other block ends in an unconditional branch, check for the 'if then 5418d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // else' case. there is an instruction before the branch. 5428d9b8d717e665945b31b0742b901561fb433ceceChris Lattner StoreInst *OtherStore = 0; 5438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (OtherBr->isUnconditional()) { 5448d9b8d717e665945b31b0742b901561fb433ceceChris Lattner --BBI; 5458d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Skip over debugging info. 54629fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez while (isa<DbgInfoIntrinsic>(BBI) || 5471df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())) { 5488d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BBI==OtherBB->begin()) 5498d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5508d9b8d717e665945b31b0742b901561fb433ceceChris Lattner --BBI; 5518d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5528d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If this isn't a store, isn't a store to the same location, or if the 5538d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // alignments differ, bail out. 5548d9b8d717e665945b31b0742b901561fb433ceceChris Lattner OtherStore = dyn_cast<StoreInst>(BBI); 5558d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!OtherStore || OtherStore->getOperand(1) != SI.getOperand(1) || 5568d9b8d717e665945b31b0742b901561fb433ceceChris Lattner OtherStore->getAlignment() != SI.getAlignment()) 5578d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5588d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } else { 5598d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Otherwise, the other block ended with a conditional branch. If one of the 5608d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // destinations is StoreBB, then we have the if/then case. 5618d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (OtherBr->getSuccessor(0) != StoreBB && 5628d9b8d717e665945b31b0742b901561fb433ceceChris Lattner OtherBr->getSuccessor(1) != StoreBB) 5638d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5648d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5658d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Okay, we know that OtherBr now goes to Dest and StoreBB, so this is an 5668d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // if/then triangle. See if there is a store to the same ptr as SI that 5678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // lives in OtherBB. 5688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner for (;; --BBI) { 5698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Check to see if we find the matching store. 5708d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if ((OtherStore = dyn_cast<StoreInst>(BBI))) { 5718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (OtherStore->getOperand(1) != SI.getOperand(1) || 5728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner OtherStore->getAlignment() != SI.getAlignment()) 5738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 5758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If we find something that may be using or overwriting the stored 5778d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // value, or if we run out of instructions, we can't do the xform. 5788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BBI->mayReadFromMemory() || BBI->mayWriteToMemory() || 5798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BBI == OtherBB->begin()) 5808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5818d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5828d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // In order to eliminate the store in OtherBr, we have to 5848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // make sure nothing reads or overwrites the stored value in 5858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // StoreBB. 5868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner for (BasicBlock::iterator I = StoreBB->begin(); &*I != &SI; ++I) { 5878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // FIXME: This should really be AA driven. 5888d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (I->mayReadFromMemory() || I->mayWriteToMemory()) 5898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Insert a PHI node now if we need it. 5948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *MergedVal = OtherStore->getOperand(0); 5958d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (MergedVal != SI.getOperand(0)) { 5963ecfc861b4365f341c5c969b40e1afccde676e6fJay Foad PHINode *PN = PHINode::Create(MergedVal->getType(), 2, "storemerge"); 5978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner PN->addIncoming(SI.getOperand(0), SI.getParent()); 5988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner PN->addIncoming(OtherStore->getOperand(0), OtherBB); 5998d9b8d717e665945b31b0742b901561fb433ceceChris Lattner MergedVal = InsertNewInstBefore(PN, DestBB->front()); 6008d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 6018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 6028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Advance to a place where it is safe to insert the new store and 6038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // insert it. 6048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BBI = DestBB->getFirstNonPHI(); 605a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman StoreInst *NewSI = new StoreInst(MergedVal, SI.getOperand(1), 606a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman OtherStore->isVolatile(), 607a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman SI.getAlignment()); 608a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman InsertNewInstBefore(NewSI, *BBI); 609a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman NewSI->setDebugLoc(OtherStore->getDebugLoc()); 610a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman 6118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Nuke the old stores. 6128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner EraseInstFromFunction(SI); 6138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner EraseInstFromFunction(*OtherStore); 6148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return true; 6158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 616