ScalarReplAggregates.cpp revision c4f78208b399111cc4f5d97ed1875566819f34b4
14e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom//===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===// 24e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// 34e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// The LLVM Compiler Infrastructure 44e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// 54e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// This file is distributed under the University of Illinois Open Source 64e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// License. See LICENSE.TXT for details. 74e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// 84e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom//===----------------------------------------------------------------------===// 94e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// 104e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// This transformation implements the well known scalar replacement of 114e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// aggregates transformation. This xform breaks up alloca instructions of 124e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// aggregate type (structure or array) into individual alloca instructions for 134e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// each member (if possible). Then, if possible, it transforms the individual 144e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// alloca instructions into nice clean scalar SSA form. 154e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// 164e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// This combines a simple SRoA algorithm with the Mem2Reg algorithm because 174e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// often interact, especially for C++ programs. As such, iterating between 184e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// SRoA, then Mem2Reg until we run out of things to promote works well. 194e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom// 204e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom//===----------------------------------------------------------------------===// 214e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 224e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#define DEBUG_TYPE "scalarrepl" 234e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Transforms/Scalar.h" 244e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Constants.h" 254e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/DerivedTypes.h" 264e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Function.h" 274e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/GlobalVariable.h" 284e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Instructions.h" 294e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/IntrinsicInst.h" 304e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/LLVMContext.h" 314e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Module.h" 324e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Pass.h" 334e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Analysis/DIBuilder.h" 344e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Analysis/Dominators.h" 354e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Analysis/Loads.h" 364e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Analysis/ValueTracking.h" 374e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Target/TargetData.h" 384e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Transforms/Utils/PromoteMemToReg.h" 394e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Transforms/Utils/Local.h" 404e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Transforms/Utils/SSAUpdater.h" 414e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Support/CallSite.h" 424e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Support/Debug.h" 434e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Support/ErrorHandling.h" 444e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Support/GetElementPtrTypeIterator.h" 454e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Support/IRBuilder.h" 464e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Support/MathExtras.h" 474e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/Support/raw_ostream.h" 484e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/ADT/SetVector.h" 494e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/ADT/SmallVector.h" 504e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom#include "llvm/ADT/Statistic.h" 514e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstromusing namespace llvm; 524e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 534e0e02a98b7d235f19972c6a214fda924d6b958bBrian CarlstromSTATISTIC(NumReplaced, "Number of allocas broken up"); 544e0e02a98b7d235f19972c6a214fda924d6b958bBrian CarlstromSTATISTIC(NumPromoted, "Number of allocas promoted"); 554e0e02a98b7d235f19972c6a214fda924d6b958bBrian CarlstromSTATISTIC(NumAdjusted, "Number of scalar allocas adjusted to allow promotion"); 564e0e02a98b7d235f19972c6a214fda924d6b958bBrian CarlstromSTATISTIC(NumConverted, "Number of aggregates converted to scalar"); 574e0e02a98b7d235f19972c6a214fda924d6b958bBrian CarlstromSTATISTIC(NumGlobals, "Number of allocas copied from constant global"); 584e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 594e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstromnamespace { 604e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom struct SROA : public FunctionPass { 614e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom SROA(int T, bool hasDT, char &ID) 624e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom : FunctionPass(ID), HasDomTree(hasDT) { 634e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom if (T == -1) 644e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom SRThreshold = 128; 654e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom else 664e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom SRThreshold = T; 674e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom } 684e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 694e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom bool runOnFunction(Function &F); 704e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 714e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom bool performScalarRepl(Function &F); 724e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom bool performPromotion(Function &F); 734e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 744e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom private: 754e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom bool HasDomTree; 764e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom TargetData *TD; 774e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 784e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// DeadInsts - Keep track of instructions we have made dead, so that 794e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// we can remove them after we are done working. 804e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom SmallVector<Value*, 32> DeadInsts; 814e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 824e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// AllocaInfo - When analyzing uses of an alloca instruction, this captures 834e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// information about the uses. All these fields are initialized to false 844e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// and set to true when something is learned. 854e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom struct AllocaInfo { 864e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// The alloca to promote. 874e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom AllocaInst *AI; 884e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 894e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// CheckedPHIs - This is a set of verified PHI nodes, to prevent infinite 904e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// looping and avoid redundant work. 914e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom SmallPtrSet<PHINode*, 8> CheckedPHIs; 924e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 934e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// isUnsafe - This is set to true if the alloca cannot be SROA'd. 944e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom bool isUnsafe : 1; 954e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 964e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// isMemCpySrc - This is true if this aggregate is memcpy'd from. 974e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom bool isMemCpySrc : 1; 984e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 994e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// isMemCpyDst - This is true if this aggregate is memcpy'd into. 1004e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom bool isMemCpyDst : 1; 1014e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1024e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// hasSubelementAccess - This is true if a subelement of the alloca is 1034e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// ever accessed, or false if the alloca is only accessed with mem 1044e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// intrinsics or load/store that only access the entire alloca at once. 1054e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom bool hasSubelementAccess : 1; 1064e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1074e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// hasALoadOrStore - This is true if there are any loads or stores to it. 1084e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// The alloca may just be accessed with memcpy, for example, which would 1094e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom /// not set this. 1104e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom bool hasALoadOrStore : 1; 1114e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1124e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom explicit AllocaInfo(AllocaInst *ai) 1134e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom : AI(ai), isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false), 1144e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom hasSubelementAccess(false), hasALoadOrStore(false) {} 1154e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom }; 1164e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1174e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom unsigned SRThreshold; 1184e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1194e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom void MarkUnsafe(AllocaInfo &I, Instruction *User) { 1204e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom I.isUnsafe = true; 1214e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom DEBUG(dbgs() << " Transformation preventing inst: " << *User << '\n'); 1224e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom } 1234e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1244e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom bool isSafeAllocaToScalarRepl(AllocaInst *AI); 1254e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1264e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom void isSafeForScalarRepl(Instruction *I, uint64_t Offset, AllocaInfo &Info); 1274e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom void isSafePHISelectUseForScalarRepl(Instruction *User, uint64_t Offset, 1284e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom AllocaInfo &Info); 1294e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom void isSafeGEP(GetElementPtrInst *GEPI, uint64_t &Offset, AllocaInfo &Info); 1304e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom void isSafeMemAccess(uint64_t Offset, uint64_t MemSize, 1314e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom const Type *MemOpType, bool isStore, AllocaInfo &Info, 1324e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom Instruction *TheAccess, bool AllowWholeAccess); 1334e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size); 1344e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset, 1354e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom const Type *&IdxTy); 1364e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1374e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom void DoScalarReplacement(AllocaInst *AI, 1384e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom std::vector<AllocaInst*> &WorkList); 1394e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom void DeleteDeadInstructions(); 1404e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1414e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 1424e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom SmallVector<AllocaInst*, 32> &NewElts); 14343c12e3d4f9bbbbd4a8ba7b149686437514bc6b6Brian Carlstrom void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, 1444e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom SmallVector<AllocaInst*, 32> &NewElts); 1454e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, 1464e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom SmallVector<AllocaInst*, 32> &NewElts); 1474e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, 1484e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom AllocaInst *AI, 1494e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom SmallVector<AllocaInst*, 32> &NewElts); 1504e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, 1514e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom SmallVector<AllocaInst*, 32> &NewElts); 1524e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, 1534e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom SmallVector<AllocaInst*, 32> &NewElts); 1544e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1554e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom static MemTransferInst *isOnlyCopiedFromConstantGlobal(AllocaInst *AI); 1564e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom }; 1574e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1584e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom // SROA_DT - SROA that uses DominatorTree. 1594e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom struct SROA_DT : public SROA { 1604e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom static char ID; 1614e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom public: 1624e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom SROA_DT(int T = -1) : SROA(T, true, ID) { 1634e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom initializeSROA_DTPass(*PassRegistry::getPassRegistry()); 1644e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom } 1654e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1664e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom // getAnalysisUsage - This pass does not require any passes, but we know it 1674e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom // will not alter the CFG, so say so. 1684e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom virtual void getAnalysisUsage(AnalysisUsage &AU) const { 1694e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom AU.addRequired<DominatorTree>(); 1704e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom AU.setPreservesCFG(); 1714e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom } 1724e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom }; 1734e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1744e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom // SROA_SSAUp - SROA that uses SSAUpdater. 1754e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom struct SROA_SSAUp : public SROA { 1764e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom static char ID; 1774e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom public: 1784e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom SROA_SSAUp(int T = -1) : SROA(T, false, ID) { 1794e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry()); 1804e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom } 1814e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1824e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom // getAnalysisUsage - This pass does not require any passes, but we know it 1834e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom // will not alter the CFG, so say so. 1844e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom virtual void getAnalysisUsage(AnalysisUsage &AU) const { 1854e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom AU.setPreservesCFG(); 1864e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom } 1874e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom }; 1884e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1894e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom} 1904e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1914e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstromchar SROA_DT::ID = 0; 1924e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstromchar SROA_SSAUp::ID = 0; 1934e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 1944e0e02a98b7d235f19972c6a214fda924d6b958bBrian CarlstromINITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl", 1954e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom "Scalar Replacement of Aggregates (DT)", false, false) 1964e0e02a98b7d235f19972c6a214fda924d6b958bBrian CarlstromINITIALIZE_PASS_DEPENDENCY(DominatorTree) 1974e0e02a98b7d235f19972c6a214fda924d6b958bBrian CarlstromINITIALIZE_PASS_END(SROA_DT, "scalarrepl", 1984e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom "Scalar Replacement of Aggregates (DT)", false, false) 1994e0e02a98b7d235f19972c6a214fda924d6b958bBrian Carlstrom 2004e0e02a98b7d235f19972c6a214fda924d6b958bBrian CarlstromINITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa", 201 "Scalar Replacement of Aggregates (SSAUp)", false, false) 202INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa", 203 "Scalar Replacement of Aggregates (SSAUp)", false, false) 204 205// Public interface to the ScalarReplAggregates pass 206FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold, 207 bool UseDomTree) { 208 if (UseDomTree) 209 return new SROA_DT(Threshold); 210 return new SROA_SSAUp(Threshold); 211} 212 213 214//===----------------------------------------------------------------------===// 215// Convert To Scalar Optimization. 216//===----------------------------------------------------------------------===// 217 218namespace { 219/// ConvertToScalarInfo - This class implements the "Convert To Scalar" 220/// optimization, which scans the uses of an alloca and determines if it can 221/// rewrite it in terms of a single new alloca that can be mem2reg'd. 222class ConvertToScalarInfo { 223 /// AllocaSize - The size of the alloca being considered in bytes. 224 unsigned AllocaSize; 225 const TargetData &TD; 226 227 /// IsNotTrivial - This is set to true if there is some access to the object 228 /// which means that mem2reg can't promote it. 229 bool IsNotTrivial; 230 231 /// VectorTy - This tracks the type that we should promote the vector to if 232 /// it is possible to turn it into a vector. This starts out null, and if it 233 /// isn't possible to turn into a vector type, it gets set to VoidTy. 234 const Type *VectorTy; 235 236 /// HadAVector - True if there is at least one vector access to the alloca. 237 /// We don't want to turn random arrays into vectors and use vector element 238 /// insert/extract, but if there are element accesses to something that is 239 /// also declared as a vector, we do want to promote to a vector. 240 bool HadAVector; 241 242 /// HadNonMemTransferAccess - True if there is at least one access to the 243 /// alloca that is not a MemTransferInst. We don't want to turn structs into 244 /// large integers unless there is some potential for optimization. 245 bool HadNonMemTransferAccess; 246 247public: 248 explicit ConvertToScalarInfo(unsigned Size, const TargetData &td) 249 : AllocaSize(Size), TD(td), IsNotTrivial(false), VectorTy(0), 250 HadAVector(false), HadNonMemTransferAccess(false) { } 251 252 AllocaInst *TryConvert(AllocaInst *AI); 253 254private: 255 bool CanConvertToScalar(Value *V, uint64_t Offset); 256 void MergeInType(const Type *In, uint64_t Offset, bool IsLoadOrStore); 257 bool MergeInVectorType(const VectorType *VInTy, uint64_t Offset); 258 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset); 259 260 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType, 261 uint64_t Offset, IRBuilder<> &Builder); 262 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal, 263 uint64_t Offset, IRBuilder<> &Builder); 264}; 265} // end anonymous namespace. 266 267 268/// TryConvert - Analyze the specified alloca, and if it is safe to do so, 269/// rewrite it to be a new alloca which is mem2reg'able. This returns the new 270/// alloca if possible or null if not. 271AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) { 272 // If we can't convert this scalar, or if mem2reg can trivially do it, bail 273 // out. 274 if (!CanConvertToScalar(AI, 0) || !IsNotTrivial) 275 return 0; 276 277 // If we were able to find a vector type that can handle this with 278 // insert/extract elements, and if there was at least one use that had 279 // a vector type, promote this to a vector. We don't want to promote 280 // random stuff that doesn't use vectors (e.g. <9 x double>) because then 281 // we just get a lot of insert/extracts. If at least one vector is 282 // involved, then we probably really do have a union of vector/array. 283 const Type *NewTy; 284 if (VectorTy && VectorTy->isVectorTy() && HadAVector) { 285 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = " 286 << *VectorTy << '\n'); 287 NewTy = VectorTy; // Use the vector type. 288 } else { 289 unsigned BitWidth = AllocaSize * 8; 290 if (!HadAVector && !HadNonMemTransferAccess && 291 !TD.fitsInLegalInteger(BitWidth)) 292 return 0; 293 294 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n"); 295 // Create and insert the integer alloca. 296 NewTy = IntegerType::get(AI->getContext(), BitWidth); 297 } 298 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin()); 299 ConvertUsesToScalar(AI, NewAI, 0); 300 return NewAI; 301} 302 303/// MergeInType - Add the 'In' type to the accumulated vector type (VectorTy) 304/// so far at the offset specified by Offset (which is specified in bytes). 305/// 306/// There are three cases we handle here: 307/// 1) A union of vector types of the same size and potentially its elements. 308/// Here we turn element accesses into insert/extract element operations. 309/// This promotes a <4 x float> with a store of float to the third element 310/// into a <4 x float> that uses insert element. 311/// 2) A union of vector types with power-of-2 size differences, e.g. a float, 312/// <2 x float> and <4 x float>. Here we turn element accesses into insert 313/// and extract element operations, and <2 x float> accesses into a cast to 314/// <2 x double>, an extract, and a cast back to <2 x float>. 315/// 3) A fully general blob of memory, which we turn into some (potentially 316/// large) integer type with extract and insert operations where the loads 317/// and stores would mutate the memory. We mark this by setting VectorTy 318/// to VoidTy. 319void ConvertToScalarInfo::MergeInType(const Type *In, uint64_t Offset, 320 bool IsLoadOrStore) { 321 // If we already decided to turn this into a blob of integer memory, there is 322 // nothing to be done. 323 if (VectorTy && VectorTy->isVoidTy()) 324 return; 325 326 // If this could be contributing to a vector, analyze it. 327 328 // If the In type is a vector that is the same size as the alloca, see if it 329 // matches the existing VecTy. 330 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) { 331 if (MergeInVectorType(VInTy, Offset)) 332 return; 333 } else if (In->isFloatTy() || In->isDoubleTy() || 334 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 && 335 isPowerOf2_32(In->getPrimitiveSizeInBits()))) { 336 // Full width accesses can be ignored, because they can always be turned 337 // into bitcasts. 338 unsigned EltSize = In->getPrimitiveSizeInBits()/8; 339 if (IsLoadOrStore && EltSize == AllocaSize) 340 return; 341 342 // If we're accessing something that could be an element of a vector, see 343 // if the implied vector agrees with what we already have and if Offset is 344 // compatible with it. 345 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 && 346 (!VectorTy || Offset * 8 < VectorTy->getPrimitiveSizeInBits())) { 347 if (!VectorTy) { 348 VectorTy = VectorType::get(In, AllocaSize/EltSize); 349 return; 350 } 351 352 unsigned CurrentEltSize = cast<VectorType>(VectorTy)->getElementType() 353 ->getPrimitiveSizeInBits()/8; 354 if (EltSize == CurrentEltSize) 355 return; 356 357 if (In->isIntegerTy() && isPowerOf2_32(AllocaSize / EltSize)) 358 return; 359 } 360 } 361 362 // Otherwise, we have a case that we can't handle with an optimized vector 363 // form. We can still turn this into a large integer. 364 VectorTy = Type::getVoidTy(In->getContext()); 365} 366 367/// MergeInVectorType - Handles the vector case of MergeInType, returning true 368/// if the type was successfully merged and false otherwise. 369bool ConvertToScalarInfo::MergeInVectorType(const VectorType *VInTy, 370 uint64_t Offset) { 371 // Remember if we saw a vector type. 372 HadAVector = true; 373 374 // TODO: Support nonzero offsets? 375 if (Offset != 0) 376 return false; 377 378 // Only allow vectors that are a power-of-2 away from the size of the alloca. 379 if (!isPowerOf2_64(AllocaSize / (VInTy->getBitWidth() / 8))) 380 return false; 381 382 // If this the first vector we see, remember the type so that we know the 383 // element size. 384 if (!VectorTy) { 385 VectorTy = VInTy; 386 return true; 387 } 388 389 unsigned BitWidth = cast<VectorType>(VectorTy)->getBitWidth(); 390 unsigned InBitWidth = VInTy->getBitWidth(); 391 392 // Vectors of the same size can be converted using a simple bitcast. 393 if (InBitWidth == BitWidth && AllocaSize == (InBitWidth / 8)) 394 return true; 395 396 const Type *ElementTy = cast<VectorType>(VectorTy)->getElementType(); 397 const Type *InElementTy = cast<VectorType>(VInTy)->getElementType(); 398 399 // Do not allow mixed integer and floating-point accesses from vectors of 400 // different sizes. 401 if (ElementTy->isFloatingPointTy() != InElementTy->isFloatingPointTy()) 402 return false; 403 404 if (ElementTy->isFloatingPointTy()) { 405 // Only allow floating-point vectors of different sizes if they have the 406 // same element type. 407 // TODO: This could be loosened a bit, but would anything benefit? 408 if (ElementTy != InElementTy) 409 return false; 410 411 // There are no arbitrary-precision floating-point types, which limits the 412 // number of legal vector types with larger element types that we can form 413 // to bitcast and extract a subvector. 414 // TODO: We could support some more cases with mixed fp128 and double here. 415 if (!(BitWidth == 64 || BitWidth == 128) || 416 !(InBitWidth == 64 || InBitWidth == 128)) 417 return false; 418 } else { 419 assert(ElementTy->isIntegerTy() && "Vector elements must be either integer " 420 "or floating-point."); 421 unsigned BitWidth = ElementTy->getPrimitiveSizeInBits(); 422 unsigned InBitWidth = InElementTy->getPrimitiveSizeInBits(); 423 424 // Do not allow integer types smaller than a byte or types whose widths are 425 // not a multiple of a byte. 426 if (BitWidth < 8 || InBitWidth < 8 || 427 BitWidth % 8 != 0 || InBitWidth % 8 != 0) 428 return false; 429 } 430 431 // Pick the largest of the two vector types. 432 if (InBitWidth > BitWidth) 433 VectorTy = VInTy; 434 435 return true; 436} 437 438/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all 439/// its accesses to a single vector type, return true and set VecTy to 440/// the new type. If we could convert the alloca into a single promotable 441/// integer, return true but set VecTy to VoidTy. Further, if the use is not a 442/// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset 443/// is the current offset from the base of the alloca being analyzed. 444/// 445/// If we see at least one access to the value that is as a vector type, set the 446/// SawVec flag. 447bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) { 448 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 449 Instruction *User = cast<Instruction>(*UI); 450 451 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 452 // Don't break volatile loads. 453 if (LI->isVolatile()) 454 return false; 455 // Don't touch MMX operations. 456 if (LI->getType()->isX86_MMXTy()) 457 return false; 458 HadNonMemTransferAccess = true; 459 MergeInType(LI->getType(), Offset, true); 460 continue; 461 } 462 463 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 464 // Storing the pointer, not into the value? 465 if (SI->getOperand(0) == V || SI->isVolatile()) return false; 466 // Don't touch MMX operations. 467 if (SI->getOperand(0)->getType()->isX86_MMXTy()) 468 return false; 469 HadNonMemTransferAccess = true; 470 MergeInType(SI->getOperand(0)->getType(), Offset, true); 471 continue; 472 } 473 474 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { 475 IsNotTrivial = true; // Can't be mem2reg'd. 476 if (!CanConvertToScalar(BCI, Offset)) 477 return false; 478 continue; 479 } 480 481 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 482 // If this is a GEP with a variable indices, we can't handle it. 483 if (!GEP->hasAllConstantIndices()) 484 return false; 485 486 // Compute the offset that this GEP adds to the pointer. 487 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 488 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(), 489 &Indices[0], Indices.size()); 490 // See if all uses can be converted. 491 if (!CanConvertToScalar(GEP, Offset+GEPOffset)) 492 return false; 493 IsNotTrivial = true; // Can't be mem2reg'd. 494 HadNonMemTransferAccess = true; 495 continue; 496 } 497 498 // If this is a constant sized memset of a constant value (e.g. 0) we can 499 // handle it. 500 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 501 // Store of constant value and constant size. 502 if (!isa<ConstantInt>(MSI->getValue()) || 503 !isa<ConstantInt>(MSI->getLength())) 504 return false; 505 IsNotTrivial = true; // Can't be mem2reg'd. 506 HadNonMemTransferAccess = true; 507 continue; 508 } 509 510 // If this is a memcpy or memmove into or out of the whole allocation, we 511 // can handle it like a load or store of the scalar type. 512 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 513 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()); 514 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0) 515 return false; 516 517 IsNotTrivial = true; // Can't be mem2reg'd. 518 continue; 519 } 520 521 // Otherwise, we cannot handle this! 522 return false; 523 } 524 525 return true; 526} 527 528/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca 529/// directly. This happens when we are converting an "integer union" to a 530/// single integer scalar, or when we are converting a "vector union" to a 531/// vector with insert/extractelement instructions. 532/// 533/// Offset is an offset from the original alloca, in bits that need to be 534/// shifted to the right. By the end of this, there should be no uses of Ptr. 535void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, 536 uint64_t Offset) { 537 while (!Ptr->use_empty()) { 538 Instruction *User = cast<Instruction>(Ptr->use_back()); 539 540 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 541 ConvertUsesToScalar(CI, NewAI, Offset); 542 CI->eraseFromParent(); 543 continue; 544 } 545 546 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 547 // Compute the offset that this GEP adds to the pointer. 548 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 549 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(), 550 &Indices[0], Indices.size()); 551 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8); 552 GEP->eraseFromParent(); 553 continue; 554 } 555 556 IRBuilder<> Builder(User); 557 558 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 559 // The load is a bit extract from NewAI shifted right by Offset bits. 560 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp"); 561 Value *NewLoadVal 562 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder); 563 LI->replaceAllUsesWith(NewLoadVal); 564 LI->eraseFromParent(); 565 continue; 566 } 567 568 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 569 assert(SI->getOperand(0) != Ptr && "Consistency error!"); 570 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); 571 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset, 572 Builder); 573 Builder.CreateStore(New, NewAI); 574 SI->eraseFromParent(); 575 576 // If the load we just inserted is now dead, then the inserted store 577 // overwrote the entire thing. 578 if (Old->use_empty()) 579 Old->eraseFromParent(); 580 continue; 581 } 582 583 // If this is a constant sized memset of a constant value (e.g. 0) we can 584 // transform it into a store of the expanded constant value. 585 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 586 assert(MSI->getRawDest() == Ptr && "Consistency error!"); 587 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue(); 588 if (NumBytes != 0) { 589 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue(); 590 591 // Compute the value replicated the right number of times. 592 APInt APVal(NumBytes*8, Val); 593 594 // Splat the value if non-zero. 595 if (Val) 596 for (unsigned i = 1; i != NumBytes; ++i) 597 APVal |= APVal << 8; 598 599 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); 600 Value *New = ConvertScalar_InsertValue( 601 ConstantInt::get(User->getContext(), APVal), 602 Old, Offset, Builder); 603 Builder.CreateStore(New, NewAI); 604 605 // If the load we just inserted is now dead, then the memset overwrote 606 // the entire thing. 607 if (Old->use_empty()) 608 Old->eraseFromParent(); 609 } 610 MSI->eraseFromParent(); 611 continue; 612 } 613 614 // If this is a memcpy or memmove into or out of the whole allocation, we 615 // can handle it like a load or store of the scalar type. 616 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 617 assert(Offset == 0 && "must be store to start of alloca"); 618 619 // If the source and destination are both to the same alloca, then this is 620 // a noop copy-to-self, just delete it. Otherwise, emit a load and store 621 // as appropriate. 622 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, &TD, 0)); 623 624 if (GetUnderlyingObject(MTI->getSource(), &TD, 0) != OrigAI) { 625 // Dest must be OrigAI, change this to be a load from the original 626 // pointer (bitcasted), then a store to our new alloca. 627 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?"); 628 Value *SrcPtr = MTI->getSource(); 629 const PointerType* SPTy = cast<PointerType>(SrcPtr->getType()); 630 const PointerType* AIPTy = cast<PointerType>(NewAI->getType()); 631 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) { 632 AIPTy = PointerType::get(AIPTy->getElementType(), 633 SPTy->getAddressSpace()); 634 } 635 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy); 636 637 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval"); 638 SrcVal->setAlignment(MTI->getAlignment()); 639 Builder.CreateStore(SrcVal, NewAI); 640 } else if (GetUnderlyingObject(MTI->getDest(), &TD, 0) != OrigAI) { 641 // Src must be OrigAI, change this to be a load from NewAI then a store 642 // through the original dest pointer (bitcasted). 643 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?"); 644 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval"); 645 646 const PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType()); 647 const PointerType* AIPTy = cast<PointerType>(NewAI->getType()); 648 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) { 649 AIPTy = PointerType::get(AIPTy->getElementType(), 650 DPTy->getAddressSpace()); 651 } 652 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy); 653 654 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr); 655 NewStore->setAlignment(MTI->getAlignment()); 656 } else { 657 // Noop transfer. Src == Dst 658 } 659 660 MTI->eraseFromParent(); 661 continue; 662 } 663 664 llvm_unreachable("Unsupported operation!"); 665 } 666} 667 668/// getScaledElementType - Gets a scaled element type for a partial vector 669/// access of an alloca. The input types must be integer or floating-point 670/// scalar or vector types, and the resulting type is an integer, float or 671/// double. 672static const Type *getScaledElementType(const Type *Ty1, const Type *Ty2, 673 unsigned NewBitWidth) { 674 bool IsFP1 = Ty1->isFloatingPointTy() || 675 (Ty1->isVectorTy() && 676 cast<VectorType>(Ty1)->getElementType()->isFloatingPointTy()); 677 bool IsFP2 = Ty2->isFloatingPointTy() || 678 (Ty2->isVectorTy() && 679 cast<VectorType>(Ty2)->getElementType()->isFloatingPointTy()); 680 681 LLVMContext &Context = Ty1->getContext(); 682 683 // Prefer floating-point types over integer types, as integer types may have 684 // been created by earlier scalar replacement. 685 if (IsFP1 || IsFP2) { 686 if (NewBitWidth == 32) 687 return Type::getFloatTy(Context); 688 if (NewBitWidth == 64) 689 return Type::getDoubleTy(Context); 690 } 691 692 return Type::getIntNTy(Context, NewBitWidth); 693} 694 695/// CreateShuffleVectorCast - Creates a shuffle vector to convert one vector 696/// to another vector of the same element type which has the same allocation 697/// size but different primitive sizes (e.g. <3 x i32> and <4 x i32>). 698static Value *CreateShuffleVectorCast(Value *FromVal, const Type *ToType, 699 IRBuilder<> &Builder) { 700 const Type *FromType = FromVal->getType(); 701 const VectorType *FromVTy = cast<VectorType>(FromType); 702 const VectorType *ToVTy = cast<VectorType>(ToType); 703 assert((ToVTy->getElementType() == FromVTy->getElementType()) && 704 "Vectors must have the same element type"); 705 Value *UnV = UndefValue::get(FromType); 706 unsigned numEltsFrom = FromVTy->getNumElements(); 707 unsigned numEltsTo = ToVTy->getNumElements(); 708 709 SmallVector<Constant*, 3> Args; 710 const Type* Int32Ty = Builder.getInt32Ty(); 711 unsigned minNumElts = std::min(numEltsFrom, numEltsTo); 712 unsigned i; 713 for (i=0; i != minNumElts; ++i) 714 Args.push_back(ConstantInt::get(Int32Ty, i)); 715 716 if (i < numEltsTo) { 717 Constant* UnC = UndefValue::get(Int32Ty); 718 for (; i != numEltsTo; ++i) 719 Args.push_back(UnC); 720 } 721 Constant *Mask = ConstantVector::get(Args); 722 return Builder.CreateShuffleVector(FromVal, UnV, Mask, "tmpV"); 723} 724 725/// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer 726/// or vector value FromVal, extracting the bits from the offset specified by 727/// Offset. This returns the value, which is of type ToType. 728/// 729/// This happens when we are converting an "integer union" to a single 730/// integer scalar, or when we are converting a "vector union" to a vector with 731/// insert/extractelement instructions. 732/// 733/// Offset is an offset from the original alloca, in bits that need to be 734/// shifted to the right. 735Value *ConvertToScalarInfo:: 736ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType, 737 uint64_t Offset, IRBuilder<> &Builder) { 738 // If the load is of the whole new alloca, no conversion is needed. 739 const Type *FromType = FromVal->getType(); 740 if (FromType == ToType && Offset == 0) 741 return FromVal; 742 743 // If the result alloca is a vector type, this is either an element 744 // access or a bitcast to another vector type of the same size. 745 if (const VectorType *VTy = dyn_cast<VectorType>(FromType)) { 746 unsigned FromTypeSize = TD.getTypeAllocSize(FromType); 747 unsigned ToTypeSize = TD.getTypeAllocSize(ToType); 748 if (FromTypeSize == ToTypeSize) { 749 // If the two types have the same primitive size, use a bit cast. 750 // Otherwise, it is two vectors with the same element type that has 751 // the same allocation size but different number of elements so use 752 // a shuffle vector. 753 if (FromType->getPrimitiveSizeInBits() == 754 ToType->getPrimitiveSizeInBits()) 755 return Builder.CreateBitCast(FromVal, ToType, "tmp"); 756 else 757 return CreateShuffleVectorCast(FromVal, ToType, Builder); 758 } 759 760 if (isPowerOf2_64(FromTypeSize / ToTypeSize)) { 761 assert(!(ToType->isVectorTy() && Offset != 0) && "Can't extract a value " 762 "of a smaller vector type at a nonzero offset."); 763 764 const Type *CastElementTy = getScaledElementType(FromType, ToType, 765 ToTypeSize * 8); 766 unsigned NumCastVectorElements = FromTypeSize / ToTypeSize; 767 768 LLVMContext &Context = FromVal->getContext(); 769 const Type *CastTy = VectorType::get(CastElementTy, 770 NumCastVectorElements); 771 Value *Cast = Builder.CreateBitCast(FromVal, CastTy, "tmp"); 772 773 unsigned EltSize = TD.getTypeAllocSizeInBits(CastElementTy); 774 unsigned Elt = Offset/EltSize; 775 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); 776 Value *Extract = Builder.CreateExtractElement(Cast, ConstantInt::get( 777 Type::getInt32Ty(Context), Elt), "tmp"); 778 return Builder.CreateBitCast(Extract, ToType, "tmp"); 779 } 780 781 // Otherwise it must be an element access. 782 unsigned Elt = 0; 783 if (Offset) { 784 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType()); 785 Elt = Offset/EltSize; 786 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); 787 } 788 // Return the element extracted out of it. 789 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get( 790 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp"); 791 if (V->getType() != ToType) 792 V = Builder.CreateBitCast(V, ToType, "tmp"); 793 return V; 794 } 795 796 // If ToType is a first class aggregate, extract out each of the pieces and 797 // use insertvalue's to form the FCA. 798 if (const StructType *ST = dyn_cast<StructType>(ToType)) { 799 const StructLayout &Layout = *TD.getStructLayout(ST); 800 Value *Res = UndefValue::get(ST); 801 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 802 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i), 803 Offset+Layout.getElementOffsetInBits(i), 804 Builder); 805 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 806 } 807 return Res; 808 } 809 810 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) { 811 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType()); 812 Value *Res = UndefValue::get(AT); 813 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 814 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(), 815 Offset+i*EltSize, Builder); 816 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 817 } 818 return Res; 819 } 820 821 // Otherwise, this must be a union that was converted to an integer value. 822 const IntegerType *NTy = cast<IntegerType>(FromVal->getType()); 823 824 // If this is a big-endian system and the load is narrower than the 825 // full alloca type, we need to do a shift to get the right bits. 826 int ShAmt = 0; 827 if (TD.isBigEndian()) { 828 // On big-endian machines, the lowest bit is stored at the bit offset 829 // from the pointer given by getTypeStoreSizeInBits. This matters for 830 // integers with a bitwidth that is not a multiple of 8. 831 ShAmt = TD.getTypeStoreSizeInBits(NTy) - 832 TD.getTypeStoreSizeInBits(ToType) - Offset; 833 } else { 834 ShAmt = Offset; 835 } 836 837 // Note: we support negative bitwidths (with shl) which are not defined. 838 // We do this to support (f.e.) loads off the end of a structure where 839 // only some bits are used. 840 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth()) 841 FromVal = Builder.CreateLShr(FromVal, 842 ConstantInt::get(FromVal->getType(), 843 ShAmt), "tmp"); 844 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) 845 FromVal = Builder.CreateShl(FromVal, 846 ConstantInt::get(FromVal->getType(), 847 -ShAmt), "tmp"); 848 849 // Finally, unconditionally truncate the integer to the right width. 850 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType); 851 if (LIBitWidth < NTy->getBitWidth()) 852 FromVal = 853 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(), 854 LIBitWidth), "tmp"); 855 else if (LIBitWidth > NTy->getBitWidth()) 856 FromVal = 857 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(), 858 LIBitWidth), "tmp"); 859 860 // If the result is an integer, this is a trunc or bitcast. 861 if (ToType->isIntegerTy()) { 862 // Should be done. 863 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) { 864 // Just do a bitcast, we know the sizes match up. 865 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp"); 866 } else { 867 // Otherwise must be a pointer. 868 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp"); 869 } 870 assert(FromVal->getType() == ToType && "Didn't convert right?"); 871 return FromVal; 872} 873 874/// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer 875/// or vector value "Old" at the offset specified by Offset. 876/// 877/// This happens when we are converting an "integer union" to a 878/// single integer scalar, or when we are converting a "vector union" to a 879/// vector with insert/extractelement instructions. 880/// 881/// Offset is an offset from the original alloca, in bits that need to be 882/// shifted to the right. 883Value *ConvertToScalarInfo:: 884ConvertScalar_InsertValue(Value *SV, Value *Old, 885 uint64_t Offset, IRBuilder<> &Builder) { 886 // Convert the stored type to the actual type, shift it left to insert 887 // then 'or' into place. 888 const Type *AllocaType = Old->getType(); 889 LLVMContext &Context = Old->getContext(); 890 891 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) { 892 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy); 893 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType()); 894 895 // Changing the whole vector with memset or with an access of a different 896 // vector type? 897 if (ValSize == VecSize) { 898 // If the two types have the same primitive size, use a bit cast. 899 // Otherwise, it is two vectors with the same element type that has 900 // the same allocation size but different number of elements so use 901 // a shuffle vector. 902 if (VTy->getPrimitiveSizeInBits() == 903 SV->getType()->getPrimitiveSizeInBits()) 904 return Builder.CreateBitCast(SV, AllocaType, "tmp"); 905 else 906 return CreateShuffleVectorCast(SV, VTy, Builder); 907 } 908 909 if (isPowerOf2_64(VecSize / ValSize)) { 910 assert(!(SV->getType()->isVectorTy() && Offset != 0) && "Can't insert a " 911 "value of a smaller vector type at a nonzero offset."); 912 913 const Type *CastElementTy = getScaledElementType(VTy, SV->getType(), 914 ValSize); 915 unsigned NumCastVectorElements = VecSize / ValSize; 916 917 LLVMContext &Context = SV->getContext(); 918 const Type *OldCastTy = VectorType::get(CastElementTy, 919 NumCastVectorElements); 920 Value *OldCast = Builder.CreateBitCast(Old, OldCastTy, "tmp"); 921 922 Value *SVCast = Builder.CreateBitCast(SV, CastElementTy, "tmp"); 923 924 unsigned EltSize = TD.getTypeAllocSizeInBits(CastElementTy); 925 unsigned Elt = Offset/EltSize; 926 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); 927 Value *Insert = 928 Builder.CreateInsertElement(OldCast, SVCast, ConstantInt::get( 929 Type::getInt32Ty(Context), Elt), "tmp"); 930 return Builder.CreateBitCast(Insert, AllocaType, "tmp"); 931 } 932 933 // Must be an element insertion. 934 assert(SV->getType() == VTy->getElementType()); 935 uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType()); 936 unsigned Elt = Offset/EltSize; 937 return Builder.CreateInsertElement(Old, SV, 938 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt), 939 "tmp"); 940 } 941 942 // If SV is a first-class aggregate value, insert each value recursively. 943 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) { 944 const StructLayout &Layout = *TD.getStructLayout(ST); 945 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 946 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 947 Old = ConvertScalar_InsertValue(Elt, Old, 948 Offset+Layout.getElementOffsetInBits(i), 949 Builder); 950 } 951 return Old; 952 } 953 954 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) { 955 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType()); 956 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 957 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 958 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder); 959 } 960 return Old; 961 } 962 963 // If SV is a float, convert it to the appropriate integer type. 964 // If it is a pointer, do the same. 965 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType()); 966 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType); 967 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType()); 968 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType); 969 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy()) 970 SV = Builder.CreateBitCast(SV, 971 IntegerType::get(SV->getContext(),SrcWidth), "tmp"); 972 else if (SV->getType()->isPointerTy()) 973 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "tmp"); 974 975 // Zero extend or truncate the value if needed. 976 if (SV->getType() != AllocaType) { 977 if (SV->getType()->getPrimitiveSizeInBits() < 978 AllocaType->getPrimitiveSizeInBits()) 979 SV = Builder.CreateZExt(SV, AllocaType, "tmp"); 980 else { 981 // Truncation may be needed if storing more than the alloca can hold 982 // (undefined behavior). 983 SV = Builder.CreateTrunc(SV, AllocaType, "tmp"); 984 SrcWidth = DestWidth; 985 SrcStoreWidth = DestStoreWidth; 986 } 987 } 988 989 // If this is a big-endian system and the store is narrower than the 990 // full alloca type, we need to do a shift to get the right bits. 991 int ShAmt = 0; 992 if (TD.isBigEndian()) { 993 // On big-endian machines, the lowest bit is stored at the bit offset 994 // from the pointer given by getTypeStoreSizeInBits. This matters for 995 // integers with a bitwidth that is not a multiple of 8. 996 ShAmt = DestStoreWidth - SrcStoreWidth - Offset; 997 } else { 998 ShAmt = Offset; 999 } 1000 1001 // Note: we support negative bitwidths (with shr) which are not defined. 1002 // We do this to support (f.e.) stores off the end of a structure where 1003 // only some bits in the structure are set. 1004 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth)); 1005 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) { 1006 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), 1007 ShAmt), "tmp"); 1008 Mask <<= ShAmt; 1009 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { 1010 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), 1011 -ShAmt), "tmp"); 1012 Mask = Mask.lshr(-ShAmt); 1013 } 1014 1015 // Mask out the bits we are about to insert from the old value, and or 1016 // in the new bits. 1017 if (SrcWidth != DestWidth) { 1018 assert(DestWidth > SrcWidth); 1019 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask"); 1020 SV = Builder.CreateOr(Old, SV, "ins"); 1021 } 1022 return SV; 1023} 1024 1025 1026//===----------------------------------------------------------------------===// 1027// SRoA Driver 1028//===----------------------------------------------------------------------===// 1029 1030 1031bool SROA::runOnFunction(Function &F) { 1032 TD = getAnalysisIfAvailable<TargetData>(); 1033 1034 bool Changed = performPromotion(F); 1035 1036 // FIXME: ScalarRepl currently depends on TargetData more than it 1037 // theoretically needs to. It should be refactored in order to support 1038 // target-independent IR. Until this is done, just skip the actual 1039 // scalar-replacement portion of this pass. 1040 if (!TD) return Changed; 1041 1042 while (1) { 1043 bool LocalChange = performScalarRepl(F); 1044 if (!LocalChange) break; // No need to repromote if no scalarrepl 1045 Changed = true; 1046 LocalChange = performPromotion(F); 1047 if (!LocalChange) break; // No need to re-scalarrepl if no promotion 1048 } 1049 1050 return Changed; 1051} 1052 1053namespace { 1054class AllocaPromoter : public LoadAndStorePromoter { 1055 AllocaInst *AI; 1056public: 1057 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S, 1058 DbgDeclareInst *DD, DIBuilder *&DB) 1059 : LoadAndStorePromoter(Insts, S, DD, DB), AI(0) {} 1060 1061 void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) { 1062 // Remember which alloca we're promoting (for isInstInList). 1063 this->AI = AI; 1064 LoadAndStorePromoter::run(Insts); 1065 AI->eraseFromParent(); 1066 } 1067 1068 virtual bool isInstInList(Instruction *I, 1069 const SmallVectorImpl<Instruction*> &Insts) const { 1070 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 1071 return LI->getOperand(0) == AI; 1072 return cast<StoreInst>(I)->getPointerOperand() == AI; 1073 } 1074}; 1075} // end anon namespace 1076 1077/// isSafeSelectToSpeculate - Select instructions that use an alloca and are 1078/// subsequently loaded can be rewritten to load both input pointers and then 1079/// select between the result, allowing the load of the alloca to be promoted. 1080/// From this: 1081/// %P2 = select i1 %cond, i32* %Alloca, i32* %Other 1082/// %V = load i32* %P2 1083/// to: 1084/// %V1 = load i32* %Alloca -> will be mem2reg'd 1085/// %V2 = load i32* %Other 1086/// %V = select i1 %cond, i32 %V1, i32 %V2 1087/// 1088/// We can do this to a select if its only uses are loads and if the operand to 1089/// the select can be loaded unconditionally. 1090static bool isSafeSelectToSpeculate(SelectInst *SI, const TargetData *TD) { 1091 bool TDerefable = SI->getTrueValue()->isDereferenceablePointer(); 1092 bool FDerefable = SI->getFalseValue()->isDereferenceablePointer(); 1093 1094 for (Value::use_iterator UI = SI->use_begin(), UE = SI->use_end(); 1095 UI != UE; ++UI) { 1096 LoadInst *LI = dyn_cast<LoadInst>(*UI); 1097 if (LI == 0 || LI->isVolatile()) return false; 1098 1099 // Both operands to the select need to be dereferencable, either absolutely 1100 // (e.g. allocas) or at this point because we can see other accesses to it. 1101 if (!TDerefable && !isSafeToLoadUnconditionally(SI->getTrueValue(), LI, 1102 LI->getAlignment(), TD)) 1103 return false; 1104 if (!FDerefable && !isSafeToLoadUnconditionally(SI->getFalseValue(), LI, 1105 LI->getAlignment(), TD)) 1106 return false; 1107 } 1108 1109 return true; 1110} 1111 1112/// isSafePHIToSpeculate - PHI instructions that use an alloca and are 1113/// subsequently loaded can be rewritten to load both input pointers in the pred 1114/// blocks and then PHI the results, allowing the load of the alloca to be 1115/// promoted. 1116/// From this: 1117/// %P2 = phi [i32* %Alloca, i32* %Other] 1118/// %V = load i32* %P2 1119/// to: 1120/// %V1 = load i32* %Alloca -> will be mem2reg'd 1121/// ... 1122/// %V2 = load i32* %Other 1123/// ... 1124/// %V = phi [i32 %V1, i32 %V2] 1125/// 1126/// We can do this to a select if its only uses are loads and if the operand to 1127/// the select can be loaded unconditionally. 1128static bool isSafePHIToSpeculate(PHINode *PN, const TargetData *TD) { 1129 // For now, we can only do this promotion if the load is in the same block as 1130 // the PHI, and if there are no stores between the phi and load. 1131 // TODO: Allow recursive phi users. 1132 // TODO: Allow stores. 1133 BasicBlock *BB = PN->getParent(); 1134 unsigned MaxAlign = 0; 1135 for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end(); 1136 UI != UE; ++UI) { 1137 LoadInst *LI = dyn_cast<LoadInst>(*UI); 1138 if (LI == 0 || LI->isVolatile()) return false; 1139 1140 // For now we only allow loads in the same block as the PHI. This is a 1141 // common case that happens when instcombine merges two loads through a PHI. 1142 if (LI->getParent() != BB) return false; 1143 1144 // Ensure that there are no instructions between the PHI and the load that 1145 // could store. 1146 for (BasicBlock::iterator BBI = PN; &*BBI != LI; ++BBI) 1147 if (BBI->mayWriteToMemory()) 1148 return false; 1149 1150 MaxAlign = std::max(MaxAlign, LI->getAlignment()); 1151 } 1152 1153 // Okay, we know that we have one or more loads in the same block as the PHI. 1154 // We can transform this if it is safe to push the loads into the predecessor 1155 // blocks. The only thing to watch out for is that we can't put a possibly 1156 // trapping load in the predecessor if it is a critical edge. 1157 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 1158 BasicBlock *Pred = PN->getIncomingBlock(i); 1159 1160 // If the predecessor has a single successor, then the edge isn't critical. 1161 if (Pred->getTerminator()->getNumSuccessors() == 1) 1162 continue; 1163 1164 Value *InVal = PN->getIncomingValue(i); 1165 1166 // If the InVal is an invoke in the pred, we can't put a load on the edge. 1167 if (InvokeInst *II = dyn_cast<InvokeInst>(InVal)) 1168 if (II->getParent() == Pred) 1169 return false; 1170 1171 // If this pointer is always safe to load, or if we can prove that there is 1172 // already a load in the block, then we can move the load to the pred block. 1173 if (InVal->isDereferenceablePointer() || 1174 isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign, TD)) 1175 continue; 1176 1177 return false; 1178 } 1179 1180 return true; 1181} 1182 1183 1184/// tryToMakeAllocaBePromotable - This returns true if the alloca only has 1185/// direct (non-volatile) loads and stores to it. If the alloca is close but 1186/// not quite there, this will transform the code to allow promotion. As such, 1187/// it is a non-pure predicate. 1188static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const TargetData *TD) { 1189 SetVector<Instruction*, SmallVector<Instruction*, 4>, 1190 SmallPtrSet<Instruction*, 4> > InstsToRewrite; 1191 1192 for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end(); 1193 UI != UE; ++UI) { 1194 User *U = *UI; 1195 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 1196 if (LI->isVolatile()) 1197 return false; 1198 continue; 1199 } 1200 1201 if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 1202 if (SI->getOperand(0) == AI || SI->isVolatile()) 1203 return false; // Don't allow a store OF the AI, only INTO the AI. 1204 continue; 1205 } 1206 1207 if (SelectInst *SI = dyn_cast<SelectInst>(U)) { 1208 // If the condition being selected on is a constant, fold the select, yes 1209 // this does (rarely) happen early on. 1210 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) { 1211 Value *Result = SI->getOperand(1+CI->isZero()); 1212 SI->replaceAllUsesWith(Result); 1213 SI->eraseFromParent(); 1214 1215 // This is very rare and we just scrambled the use list of AI, start 1216 // over completely. 1217 return tryToMakeAllocaBePromotable(AI, TD); 1218 } 1219 1220 // If it is safe to turn "load (select c, AI, ptr)" into a select of two 1221 // loads, then we can transform this by rewriting the select. 1222 if (!isSafeSelectToSpeculate(SI, TD)) 1223 return false; 1224 1225 InstsToRewrite.insert(SI); 1226 continue; 1227 } 1228 1229 if (PHINode *PN = dyn_cast<PHINode>(U)) { 1230 if (PN->use_empty()) { // Dead PHIs can be stripped. 1231 InstsToRewrite.insert(PN); 1232 continue; 1233 } 1234 1235 // If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads 1236 // in the pred blocks, then we can transform this by rewriting the PHI. 1237 if (!isSafePHIToSpeculate(PN, TD)) 1238 return false; 1239 1240 InstsToRewrite.insert(PN); 1241 continue; 1242 } 1243 1244 return false; 1245 } 1246 1247 // If there are no instructions to rewrite, then all uses are load/stores and 1248 // we're done! 1249 if (InstsToRewrite.empty()) 1250 return true; 1251 1252 // If we have instructions that need to be rewritten for this to be promotable 1253 // take care of it now. 1254 for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) { 1255 if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) { 1256 // Selects in InstsToRewrite only have load uses. Rewrite each as two 1257 // loads with a new select. 1258 while (!SI->use_empty()) { 1259 LoadInst *LI = cast<LoadInst>(SI->use_back()); 1260 1261 IRBuilder<> Builder(LI); 1262 LoadInst *TrueLoad = 1263 Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t"); 1264 LoadInst *FalseLoad = 1265 Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".t"); 1266 1267 // Transfer alignment and TBAA info if present. 1268 TrueLoad->setAlignment(LI->getAlignment()); 1269 FalseLoad->setAlignment(LI->getAlignment()); 1270 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) { 1271 TrueLoad->setMetadata(LLVMContext::MD_tbaa, Tag); 1272 FalseLoad->setMetadata(LLVMContext::MD_tbaa, Tag); 1273 } 1274 1275 Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad); 1276 V->takeName(LI); 1277 LI->replaceAllUsesWith(V); 1278 LI->eraseFromParent(); 1279 } 1280 1281 // Now that all the loads are gone, the select is gone too. 1282 SI->eraseFromParent(); 1283 continue; 1284 } 1285 1286 // Otherwise, we have a PHI node which allows us to push the loads into the 1287 // predecessors. 1288 PHINode *PN = cast<PHINode>(InstsToRewrite[i]); 1289 if (PN->use_empty()) { 1290 PN->eraseFromParent(); 1291 continue; 1292 } 1293 1294 const Type *LoadTy = cast<PointerType>(PN->getType())->getElementType(); 1295 PHINode *NewPN = PHINode::Create(LoadTy, PN->getNumIncomingValues(), 1296 PN->getName()+".ld", PN); 1297 1298 // Get the TBAA tag and alignment to use from one of the loads. It doesn't 1299 // matter which one we get and if any differ, it doesn't matter. 1300 LoadInst *SomeLoad = cast<LoadInst>(PN->use_back()); 1301 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa); 1302 unsigned Align = SomeLoad->getAlignment(); 1303 1304 // Rewrite all loads of the PN to use the new PHI. 1305 while (!PN->use_empty()) { 1306 LoadInst *LI = cast<LoadInst>(PN->use_back()); 1307 LI->replaceAllUsesWith(NewPN); 1308 LI->eraseFromParent(); 1309 } 1310 1311 // Inject loads into all of the pred blocks. Keep track of which blocks we 1312 // insert them into in case we have multiple edges from the same block. 1313 DenseMap<BasicBlock*, LoadInst*> InsertedLoads; 1314 1315 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 1316 BasicBlock *Pred = PN->getIncomingBlock(i); 1317 LoadInst *&Load = InsertedLoads[Pred]; 1318 if (Load == 0) { 1319 Load = new LoadInst(PN->getIncomingValue(i), 1320 PN->getName() + "." + Pred->getName(), 1321 Pred->getTerminator()); 1322 Load->setAlignment(Align); 1323 if (TBAATag) Load->setMetadata(LLVMContext::MD_tbaa, TBAATag); 1324 } 1325 1326 NewPN->addIncoming(Load, Pred); 1327 } 1328 1329 PN->eraseFromParent(); 1330 } 1331 1332 ++NumAdjusted; 1333 return true; 1334} 1335 1336bool SROA::performPromotion(Function &F) { 1337 std::vector<AllocaInst*> Allocas; 1338 DominatorTree *DT = 0; 1339 if (HasDomTree) 1340 DT = &getAnalysis<DominatorTree>(); 1341 1342 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 1343 1344 bool Changed = false; 1345 SmallVector<Instruction*, 64> Insts; 1346 DIBuilder *DIB = 0; 1347 while (1) { 1348 Allocas.clear(); 1349 1350 // Find allocas that are safe to promote, by looking at all instructions in 1351 // the entry node 1352 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 1353 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 1354 if (tryToMakeAllocaBePromotable(AI, TD)) 1355 Allocas.push_back(AI); 1356 1357 if (Allocas.empty()) break; 1358 1359 if (HasDomTree) 1360 PromoteMemToReg(Allocas, *DT); 1361 else { 1362 SSAUpdater SSA; 1363 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) { 1364 AllocaInst *AI = Allocas[i]; 1365 1366 // Build list of instructions to promote. 1367 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); 1368 UI != E; ++UI) 1369 Insts.push_back(cast<Instruction>(*UI)); 1370 1371 DbgDeclareInst *DDI = FindAllocaDbgDeclare(AI); 1372 if (DDI && !DIB) 1373 DIB = new DIBuilder(*AI->getParent()->getParent()->getParent()); 1374 AllocaPromoter(Insts, SSA, DDI, DIB).run(AI, Insts); 1375 Insts.clear(); 1376 } 1377 } 1378 NumPromoted += Allocas.size(); 1379 Changed = true; 1380 } 1381 1382 // FIXME: Is there a better way to handle the lazy initialization of DIB 1383 // so that there doesn't need to be an explicit delete? 1384 delete DIB; 1385 1386 return Changed; 1387} 1388 1389 1390/// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for 1391/// SROA. It must be a struct or array type with a small number of elements. 1392static bool ShouldAttemptScalarRepl(AllocaInst *AI) { 1393 const Type *T = AI->getAllocatedType(); 1394 // Do not promote any struct into more than 32 separate vars. 1395 if (const StructType *ST = dyn_cast<StructType>(T)) 1396 return ST->getNumElements() <= 32; 1397 // Arrays are much less likely to be safe for SROA; only consider 1398 // them if they are very small. 1399 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) 1400 return AT->getNumElements() <= 8; 1401 return false; 1402} 1403 1404 1405// performScalarRepl - This algorithm is a simple worklist driven algorithm, 1406// which runs on all of the malloc/alloca instructions in the function, removing 1407// them if they are only used by getelementptr instructions. 1408// 1409bool SROA::performScalarRepl(Function &F) { 1410 std::vector<AllocaInst*> WorkList; 1411 1412 // Scan the entry basic block, adding allocas to the worklist. 1413 BasicBlock &BB = F.getEntryBlock(); 1414 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 1415 if (AllocaInst *A = dyn_cast<AllocaInst>(I)) 1416 WorkList.push_back(A); 1417 1418 // Process the worklist 1419 bool Changed = false; 1420 while (!WorkList.empty()) { 1421 AllocaInst *AI = WorkList.back(); 1422 WorkList.pop_back(); 1423 1424 // Handle dead allocas trivially. These can be formed by SROA'ing arrays 1425 // with unused elements. 1426 if (AI->use_empty()) { 1427 AI->eraseFromParent(); 1428 Changed = true; 1429 continue; 1430 } 1431 1432 // If this alloca is impossible for us to promote, reject it early. 1433 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized()) 1434 continue; 1435 1436 // Check to see if this allocation is only modified by a memcpy/memmove from 1437 // a constant global. If this is the case, we can change all users to use 1438 // the constant global instead. This is commonly produced by the CFE by 1439 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' 1440 // is only subsequently read. 1441 if (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) { 1442 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n'); 1443 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n'); 1444 Constant *TheSrc = cast<Constant>(TheCopy->getSource()); 1445 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType())); 1446 TheCopy->eraseFromParent(); // Don't mutate the global. 1447 AI->eraseFromParent(); 1448 ++NumGlobals; 1449 Changed = true; 1450 continue; 1451 } 1452 1453 // Check to see if we can perform the core SROA transformation. We cannot 1454 // transform the allocation instruction if it is an array allocation 1455 // (allocations OF arrays are ok though), and an allocation of a scalar 1456 // value cannot be decomposed at all. 1457 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType()); 1458 1459 // Do not promote [0 x %struct]. 1460 if (AllocaSize == 0) continue; 1461 1462 // Do not promote any struct whose size is too big. 1463 if (AllocaSize > SRThreshold) continue; 1464 1465 // If the alloca looks like a good candidate for scalar replacement, and if 1466 // all its users can be transformed, then split up the aggregate into its 1467 // separate elements. 1468 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) { 1469 DoScalarReplacement(AI, WorkList); 1470 Changed = true; 1471 continue; 1472 } 1473 1474 // If we can turn this aggregate value (potentially with casts) into a 1475 // simple scalar value that can be mem2reg'd into a register value. 1476 // IsNotTrivial tracks whether this is something that mem2reg could have 1477 // promoted itself. If so, we don't want to transform it needlessly. Note 1478 // that we can't just check based on the type: the alloca may be of an i32 1479 // but that has pointer arithmetic to set byte 3 of it or something. 1480 if (AllocaInst *NewAI = 1481 ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) { 1482 NewAI->takeName(AI); 1483 AI->eraseFromParent(); 1484 ++NumConverted; 1485 Changed = true; 1486 continue; 1487 } 1488 1489 // Otherwise, couldn't process this alloca. 1490 } 1491 1492 return Changed; 1493} 1494 1495/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl 1496/// predicate, do SROA now. 1497void SROA::DoScalarReplacement(AllocaInst *AI, 1498 std::vector<AllocaInst*> &WorkList) { 1499 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n'); 1500 SmallVector<AllocaInst*, 32> ElementAllocas; 1501 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 1502 ElementAllocas.reserve(ST->getNumContainedTypes()); 1503 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { 1504 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0, 1505 AI->getAlignment(), 1506 AI->getName() + "." + Twine(i), AI); 1507 ElementAllocas.push_back(NA); 1508 WorkList.push_back(NA); // Add to worklist for recursive processing 1509 } 1510 } else { 1511 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType()); 1512 ElementAllocas.reserve(AT->getNumElements()); 1513 const Type *ElTy = AT->getElementType(); 1514 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 1515 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(), 1516 AI->getName() + "." + Twine(i), AI); 1517 ElementAllocas.push_back(NA); 1518 WorkList.push_back(NA); // Add to worklist for recursive processing 1519 } 1520 } 1521 1522 // Now that we have created the new alloca instructions, rewrite all the 1523 // uses of the old alloca. 1524 RewriteForScalarRepl(AI, AI, 0, ElementAllocas); 1525 1526 // Now erase any instructions that were made dead while rewriting the alloca. 1527 DeleteDeadInstructions(); 1528 AI->eraseFromParent(); 1529 1530 ++NumReplaced; 1531} 1532 1533/// DeleteDeadInstructions - Erase instructions on the DeadInstrs list, 1534/// recursively including all their operands that become trivially dead. 1535void SROA::DeleteDeadInstructions() { 1536 while (!DeadInsts.empty()) { 1537 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val()); 1538 1539 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) 1540 if (Instruction *U = dyn_cast<Instruction>(*OI)) { 1541 // Zero out the operand and see if it becomes trivially dead. 1542 // (But, don't add allocas to the dead instruction list -- they are 1543 // already on the worklist and will be deleted separately.) 1544 *OI = 0; 1545 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U)) 1546 DeadInsts.push_back(U); 1547 } 1548 1549 I->eraseFromParent(); 1550 } 1551} 1552 1553/// isSafeForScalarRepl - Check if instruction I is a safe use with regard to 1554/// performing scalar replacement of alloca AI. The results are flagged in 1555/// the Info parameter. Offset indicates the position within AI that is 1556/// referenced by this instruction. 1557void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset, 1558 AllocaInfo &Info) { 1559 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { 1560 Instruction *User = cast<Instruction>(*UI); 1561 1562 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 1563 isSafeForScalarRepl(BC, Offset, Info); 1564 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1565 uint64_t GEPOffset = Offset; 1566 isSafeGEP(GEPI, GEPOffset, Info); 1567 if (!Info.isUnsafe) 1568 isSafeForScalarRepl(GEPI, GEPOffset, Info); 1569 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 1570 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 1571 if (Length == 0) 1572 return MarkUnsafe(Info, User); 1573 isSafeMemAccess(Offset, Length->getZExtValue(), 0, 1574 UI.getOperandNo() == 0, Info, MI, 1575 true /*AllowWholeAccess*/); 1576 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1577 if (LI->isVolatile()) 1578 return MarkUnsafe(Info, User); 1579 const Type *LIType = LI->getType(); 1580 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType), 1581 LIType, false, Info, LI, true /*AllowWholeAccess*/); 1582 Info.hasALoadOrStore = true; 1583 1584 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1585 // Store is ok if storing INTO the pointer, not storing the pointer 1586 if (SI->isVolatile() || SI->getOperand(0) == I) 1587 return MarkUnsafe(Info, User); 1588 1589 const Type *SIType = SI->getOperand(0)->getType(); 1590 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType), 1591 SIType, true, Info, SI, true /*AllowWholeAccess*/); 1592 Info.hasALoadOrStore = true; 1593 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) { 1594 isSafePHISelectUseForScalarRepl(User, Offset, Info); 1595 } else { 1596 return MarkUnsafe(Info, User); 1597 } 1598 if (Info.isUnsafe) return; 1599 } 1600} 1601 1602 1603/// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer 1604/// derived from the alloca, we can often still split the alloca into elements. 1605/// This is useful if we have a large alloca where one element is phi'd 1606/// together somewhere: we can SRoA and promote all the other elements even if 1607/// we end up not being able to promote this one. 1608/// 1609/// All we require is that the uses of the PHI do not index into other parts of 1610/// the alloca. The most important use case for this is single load and stores 1611/// that are PHI'd together, which can happen due to code sinking. 1612void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset, 1613 AllocaInfo &Info) { 1614 // If we've already checked this PHI, don't do it again. 1615 if (PHINode *PN = dyn_cast<PHINode>(I)) 1616 if (!Info.CheckedPHIs.insert(PN)) 1617 return; 1618 1619 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { 1620 Instruction *User = cast<Instruction>(*UI); 1621 1622 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 1623 isSafePHISelectUseForScalarRepl(BC, Offset, Info); 1624 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1625 // Only allow "bitcast" GEPs for simplicity. We could generalize this, 1626 // but would have to prove that we're staying inside of an element being 1627 // promoted. 1628 if (!GEPI->hasAllZeroIndices()) 1629 return MarkUnsafe(Info, User); 1630 isSafePHISelectUseForScalarRepl(GEPI, Offset, Info); 1631 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1632 if (LI->isVolatile()) 1633 return MarkUnsafe(Info, User); 1634 const Type *LIType = LI->getType(); 1635 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType), 1636 LIType, false, Info, LI, false /*AllowWholeAccess*/); 1637 Info.hasALoadOrStore = true; 1638 1639 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1640 // Store is ok if storing INTO the pointer, not storing the pointer 1641 if (SI->isVolatile() || SI->getOperand(0) == I) 1642 return MarkUnsafe(Info, User); 1643 1644 const Type *SIType = SI->getOperand(0)->getType(); 1645 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType), 1646 SIType, true, Info, SI, false /*AllowWholeAccess*/); 1647 Info.hasALoadOrStore = true; 1648 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) { 1649 isSafePHISelectUseForScalarRepl(User, Offset, Info); 1650 } else { 1651 return MarkUnsafe(Info, User); 1652 } 1653 if (Info.isUnsafe) return; 1654 } 1655} 1656 1657/// isSafeGEP - Check if a GEP instruction can be handled for scalar 1658/// replacement. It is safe when all the indices are constant, in-bounds 1659/// references, and when the resulting offset corresponds to an element within 1660/// the alloca type. The results are flagged in the Info parameter. Upon 1661/// return, Offset is adjusted as specified by the GEP indices. 1662void SROA::isSafeGEP(GetElementPtrInst *GEPI, 1663 uint64_t &Offset, AllocaInfo &Info) { 1664 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI); 1665 if (GEPIt == E) 1666 return; 1667 1668 // Walk through the GEP type indices, checking the types that this indexes 1669 // into. 1670 for (; GEPIt != E; ++GEPIt) { 1671 // Ignore struct elements, no extra checking needed for these. 1672 if ((*GEPIt)->isStructTy()) 1673 continue; 1674 1675 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand()); 1676 if (!IdxVal) 1677 return MarkUnsafe(Info, GEPI); 1678 } 1679 1680 // Compute the offset due to this GEP and check if the alloca has a 1681 // component element at that offset. 1682 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); 1683 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), 1684 &Indices[0], Indices.size()); 1685 if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset, 0)) 1686 MarkUnsafe(Info, GEPI); 1687} 1688 1689/// isHomogeneousAggregate - Check if type T is a struct or array containing 1690/// elements of the same type (which is always true for arrays). If so, 1691/// return true with NumElts and EltTy set to the number of elements and the 1692/// element type, respectively. 1693static bool isHomogeneousAggregate(const Type *T, unsigned &NumElts, 1694 const Type *&EltTy) { 1695 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) { 1696 NumElts = AT->getNumElements(); 1697 EltTy = (NumElts == 0 ? 0 : AT->getElementType()); 1698 return true; 1699 } 1700 if (const StructType *ST = dyn_cast<StructType>(T)) { 1701 NumElts = ST->getNumContainedTypes(); 1702 EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0)); 1703 for (unsigned n = 1; n < NumElts; ++n) { 1704 if (ST->getContainedType(n) != EltTy) 1705 return false; 1706 } 1707 return true; 1708 } 1709 return false; 1710} 1711 1712/// isCompatibleAggregate - Check if T1 and T2 are either the same type or are 1713/// "homogeneous" aggregates with the same element type and number of elements. 1714static bool isCompatibleAggregate(const Type *T1, const Type *T2) { 1715 if (T1 == T2) 1716 return true; 1717 1718 unsigned NumElts1, NumElts2; 1719 const Type *EltTy1, *EltTy2; 1720 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) && 1721 isHomogeneousAggregate(T2, NumElts2, EltTy2) && 1722 NumElts1 == NumElts2 && 1723 EltTy1 == EltTy2) 1724 return true; 1725 1726 return false; 1727} 1728 1729/// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI 1730/// alloca or has an offset and size that corresponds to a component element 1731/// within it. The offset checked here may have been formed from a GEP with a 1732/// pointer bitcasted to a different type. 1733/// 1734/// If AllowWholeAccess is true, then this allows uses of the entire alloca as a 1735/// unit. If false, it only allows accesses known to be in a single element. 1736void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize, 1737 const Type *MemOpType, bool isStore, 1738 AllocaInfo &Info, Instruction *TheAccess, 1739 bool AllowWholeAccess) { 1740 // Check if this is a load/store of the entire alloca. 1741 if (Offset == 0 && AllowWholeAccess && 1742 MemSize == TD->getTypeAllocSize(Info.AI->getAllocatedType())) { 1743 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer 1744 // loads/stores (which are essentially the same as the MemIntrinsics with 1745 // regard to copying padding between elements). But, if an alloca is 1746 // flagged as both a source and destination of such operations, we'll need 1747 // to check later for padding between elements. 1748 if (!MemOpType || MemOpType->isIntegerTy()) { 1749 if (isStore) 1750 Info.isMemCpyDst = true; 1751 else 1752 Info.isMemCpySrc = true; 1753 return; 1754 } 1755 // This is also safe for references using a type that is compatible with 1756 // the type of the alloca, so that loads/stores can be rewritten using 1757 // insertvalue/extractvalue. 1758 if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) { 1759 Info.hasSubelementAccess = true; 1760 return; 1761 } 1762 } 1763 // Check if the offset/size correspond to a component within the alloca type. 1764 const Type *T = Info.AI->getAllocatedType(); 1765 if (TypeHasComponent(T, Offset, MemSize)) { 1766 Info.hasSubelementAccess = true; 1767 return; 1768 } 1769 1770 return MarkUnsafe(Info, TheAccess); 1771} 1772 1773/// TypeHasComponent - Return true if T has a component type with the 1774/// specified offset and size. If Size is zero, do not check the size. 1775bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) { 1776 const Type *EltTy; 1777 uint64_t EltSize; 1778 if (const StructType *ST = dyn_cast<StructType>(T)) { 1779 const StructLayout *Layout = TD->getStructLayout(ST); 1780 unsigned EltIdx = Layout->getElementContainingOffset(Offset); 1781 EltTy = ST->getContainedType(EltIdx); 1782 EltSize = TD->getTypeAllocSize(EltTy); 1783 Offset -= Layout->getElementOffset(EltIdx); 1784 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) { 1785 EltTy = AT->getElementType(); 1786 EltSize = TD->getTypeAllocSize(EltTy); 1787 if (Offset >= AT->getNumElements() * EltSize) 1788 return false; 1789 Offset %= EltSize; 1790 } else { 1791 return false; 1792 } 1793 if (Offset == 0 && (Size == 0 || EltSize == Size)) 1794 return true; 1795 // Check if the component spans multiple elements. 1796 if (Offset + Size > EltSize) 1797 return false; 1798 return TypeHasComponent(EltTy, Offset, Size); 1799} 1800 1801/// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite 1802/// the instruction I, which references it, to use the separate elements. 1803/// Offset indicates the position within AI that is referenced by this 1804/// instruction. 1805void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 1806 SmallVector<AllocaInst*, 32> &NewElts) { 1807 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) { 1808 Use &TheUse = UI.getUse(); 1809 Instruction *User = cast<Instruction>(*UI++); 1810 1811 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 1812 RewriteBitCast(BC, AI, Offset, NewElts); 1813 continue; 1814 } 1815 1816 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1817 RewriteGEP(GEPI, AI, Offset, NewElts); 1818 continue; 1819 } 1820 1821 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 1822 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 1823 uint64_t MemSize = Length->getZExtValue(); 1824 if (Offset == 0 && 1825 MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) 1826 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts); 1827 // Otherwise the intrinsic can only touch a single element and the 1828 // address operand will be updated, so nothing else needs to be done. 1829 continue; 1830 } 1831 1832 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1833 const Type *LIType = LI->getType(); 1834 1835 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) { 1836 // Replace: 1837 // %res = load { i32, i32 }* %alloc 1838 // with: 1839 // %load.0 = load i32* %alloc.0 1840 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0 1841 // %load.1 = load i32* %alloc.1 1842 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1 1843 // (Also works for arrays instead of structs) 1844 Value *Insert = UndefValue::get(LIType); 1845 IRBuilder<> Builder(LI); 1846 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1847 Value *Load = Builder.CreateLoad(NewElts[i], "load"); 1848 Insert = Builder.CreateInsertValue(Insert, Load, i, "insert"); 1849 } 1850 LI->replaceAllUsesWith(Insert); 1851 DeadInsts.push_back(LI); 1852 } else if (LIType->isIntegerTy() && 1853 TD->getTypeAllocSize(LIType) == 1854 TD->getTypeAllocSize(AI->getAllocatedType())) { 1855 // If this is a load of the entire alloca to an integer, rewrite it. 1856 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts); 1857 } 1858 continue; 1859 } 1860 1861 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1862 Value *Val = SI->getOperand(0); 1863 const Type *SIType = Val->getType(); 1864 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) { 1865 // Replace: 1866 // store { i32, i32 } %val, { i32, i32 }* %alloc 1867 // with: 1868 // %val.0 = extractvalue { i32, i32 } %val, 0 1869 // store i32 %val.0, i32* %alloc.0 1870 // %val.1 = extractvalue { i32, i32 } %val, 1 1871 // store i32 %val.1, i32* %alloc.1 1872 // (Also works for arrays instead of structs) 1873 IRBuilder<> Builder(SI); 1874 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1875 Value *Extract = Builder.CreateExtractValue(Val, i, Val->getName()); 1876 Builder.CreateStore(Extract, NewElts[i]); 1877 } 1878 DeadInsts.push_back(SI); 1879 } else if (SIType->isIntegerTy() && 1880 TD->getTypeAllocSize(SIType) == 1881 TD->getTypeAllocSize(AI->getAllocatedType())) { 1882 // If this is a store of the entire alloca from an integer, rewrite it. 1883 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts); 1884 } 1885 continue; 1886 } 1887 1888 if (isa<SelectInst>(User) || isa<PHINode>(User)) { 1889 // If we have a PHI user of the alloca itself (as opposed to a GEP or 1890 // bitcast) we have to rewrite it. GEP and bitcast uses will be RAUW'd to 1891 // the new pointer. 1892 if (!isa<AllocaInst>(I)) continue; 1893 1894 assert(Offset == 0 && NewElts[0] && 1895 "Direct alloca use should have a zero offset"); 1896 1897 // If we have a use of the alloca, we know the derived uses will be 1898 // utilizing just the first element of the scalarized result. Insert a 1899 // bitcast of the first alloca before the user as required. 1900 AllocaInst *NewAI = NewElts[0]; 1901 BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI); 1902 NewAI->moveBefore(BCI); 1903 TheUse = BCI; 1904 continue; 1905 } 1906 } 1907} 1908 1909/// RewriteBitCast - Update a bitcast reference to the alloca being replaced 1910/// and recursively continue updating all of its uses. 1911void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, 1912 SmallVector<AllocaInst*, 32> &NewElts) { 1913 RewriteForScalarRepl(BC, AI, Offset, NewElts); 1914 if (BC->getOperand(0) != AI) 1915 return; 1916 1917 // The bitcast references the original alloca. Replace its uses with 1918 // references to the first new element alloca. 1919 Instruction *Val = NewElts[0]; 1920 if (Val->getType() != BC->getDestTy()) { 1921 Val = new BitCastInst(Val, BC->getDestTy(), "", BC); 1922 Val->takeName(BC); 1923 } 1924 BC->replaceAllUsesWith(Val); 1925 DeadInsts.push_back(BC); 1926} 1927 1928/// FindElementAndOffset - Return the index of the element containing Offset 1929/// within the specified type, which must be either a struct or an array. 1930/// Sets T to the type of the element and Offset to the offset within that 1931/// element. IdxTy is set to the type of the index result to be used in a 1932/// GEP instruction. 1933uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset, 1934 const Type *&IdxTy) { 1935 uint64_t Idx = 0; 1936 if (const StructType *ST = dyn_cast<StructType>(T)) { 1937 const StructLayout *Layout = TD->getStructLayout(ST); 1938 Idx = Layout->getElementContainingOffset(Offset); 1939 T = ST->getContainedType(Idx); 1940 Offset -= Layout->getElementOffset(Idx); 1941 IdxTy = Type::getInt32Ty(T->getContext()); 1942 return Idx; 1943 } 1944 const ArrayType *AT = cast<ArrayType>(T); 1945 T = AT->getElementType(); 1946 uint64_t EltSize = TD->getTypeAllocSize(T); 1947 Idx = Offset / EltSize; 1948 Offset -= Idx * EltSize; 1949 IdxTy = Type::getInt64Ty(T->getContext()); 1950 return Idx; 1951} 1952 1953/// RewriteGEP - Check if this GEP instruction moves the pointer across 1954/// elements of the alloca that are being split apart, and if so, rewrite 1955/// the GEP to be relative to the new element. 1956void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, 1957 SmallVector<AllocaInst*, 32> &NewElts) { 1958 uint64_t OldOffset = Offset; 1959 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); 1960 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), 1961 &Indices[0], Indices.size()); 1962 1963 RewriteForScalarRepl(GEPI, AI, Offset, NewElts); 1964 1965 const Type *T = AI->getAllocatedType(); 1966 const Type *IdxTy; 1967 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy); 1968 if (GEPI->getOperand(0) == AI) 1969 OldIdx = ~0ULL; // Force the GEP to be rewritten. 1970 1971 T = AI->getAllocatedType(); 1972 uint64_t EltOffset = Offset; 1973 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy); 1974 1975 // If this GEP does not move the pointer across elements of the alloca 1976 // being split, then it does not needs to be rewritten. 1977 if (Idx == OldIdx) 1978 return; 1979 1980 const Type *i32Ty = Type::getInt32Ty(AI->getContext()); 1981 SmallVector<Value*, 8> NewArgs; 1982 NewArgs.push_back(Constant::getNullValue(i32Ty)); 1983 while (EltOffset != 0) { 1984 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy); 1985 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx)); 1986 } 1987 Instruction *Val = NewElts[Idx]; 1988 if (NewArgs.size() > 1) { 1989 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(), 1990 NewArgs.end(), "", GEPI); 1991 Val->takeName(GEPI); 1992 } 1993 if (Val->getType() != GEPI->getType()) 1994 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI); 1995 GEPI->replaceAllUsesWith(Val); 1996 DeadInsts.push_back(GEPI); 1997} 1998 1999/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI. 2000/// Rewrite it to copy or set the elements of the scalarized memory. 2001void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, 2002 AllocaInst *AI, 2003 SmallVector<AllocaInst*, 32> &NewElts) { 2004 // If this is a memcpy/memmove, construct the other pointer as the 2005 // appropriate type. The "Other" pointer is the pointer that goes to memory 2006 // that doesn't have anything to do with the alloca that we are promoting. For 2007 // memset, this Value* stays null. 2008 Value *OtherPtr = 0; 2009 unsigned MemAlignment = MI->getAlignment(); 2010 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy 2011 if (Inst == MTI->getRawDest()) 2012 OtherPtr = MTI->getRawSource(); 2013 else { 2014 assert(Inst == MTI->getRawSource()); 2015 OtherPtr = MTI->getRawDest(); 2016 } 2017 } 2018 2019 // If there is an other pointer, we want to convert it to the same pointer 2020 // type as AI has, so we can GEP through it safely. 2021 if (OtherPtr) { 2022 unsigned AddrSpace = 2023 cast<PointerType>(OtherPtr->getType())->getAddressSpace(); 2024 2025 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an 2026 // optimization, but it's also required to detect the corner case where 2027 // both pointer operands are referencing the same memory, and where 2028 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This 2029 // function is only called for mem intrinsics that access the whole 2030 // aggregate, so non-zero GEPs are not an issue here.) 2031 OtherPtr = OtherPtr->stripPointerCasts(); 2032 2033 // Copying the alloca to itself is a no-op: just delete it. 2034 if (OtherPtr == AI || OtherPtr == NewElts[0]) { 2035 // This code will run twice for a no-op memcpy -- once for each operand. 2036 // Put only one reference to MI on the DeadInsts list. 2037 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(), 2038 E = DeadInsts.end(); I != E; ++I) 2039 if (*I == MI) return; 2040 DeadInsts.push_back(MI); 2041 return; 2042 } 2043 2044 // If the pointer is not the right type, insert a bitcast to the right 2045 // type. 2046 const Type *NewTy = 2047 PointerType::get(AI->getType()->getElementType(), AddrSpace); 2048 2049 if (OtherPtr->getType() != NewTy) 2050 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI); 2051 } 2052 2053 // Process each element of the aggregate. 2054 bool SROADest = MI->getRawDest() == Inst; 2055 2056 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext())); 2057 2058 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 2059 // If this is a memcpy/memmove, emit a GEP of the other element address. 2060 Value *OtherElt = 0; 2061 unsigned OtherEltAlign = MemAlignment; 2062 2063 if (OtherPtr) { 2064 Value *Idx[2] = { Zero, 2065 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) }; 2066 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2, 2067 OtherPtr->getName()+"."+Twine(i), 2068 MI); 2069 uint64_t EltOffset; 2070 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType()); 2071 const Type *OtherTy = OtherPtrTy->getElementType(); 2072 if (const StructType *ST = dyn_cast<StructType>(OtherTy)) { 2073 EltOffset = TD->getStructLayout(ST)->getElementOffset(i); 2074 } else { 2075 const Type *EltTy = cast<SequentialType>(OtherTy)->getElementType(); 2076 EltOffset = TD->getTypeAllocSize(EltTy)*i; 2077 } 2078 2079 // The alignment of the other pointer is the guaranteed alignment of the 2080 // element, which is affected by both the known alignment of the whole 2081 // mem intrinsic and the alignment of the element. If the alignment of 2082 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the 2083 // known alignment is just 4 bytes. 2084 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset); 2085 } 2086 2087 Value *EltPtr = NewElts[i]; 2088 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType(); 2089 2090 // If we got down to a scalar, insert a load or store as appropriate. 2091 if (EltTy->isSingleValueType()) { 2092 if (isa<MemTransferInst>(MI)) { 2093 if (SROADest) { 2094 // From Other to Alloca. 2095 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI); 2096 new StoreInst(Elt, EltPtr, MI); 2097 } else { 2098 // From Alloca to Other. 2099 Value *Elt = new LoadInst(EltPtr, "tmp", MI); 2100 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI); 2101 } 2102 continue; 2103 } 2104 assert(isa<MemSetInst>(MI)); 2105 2106 // If the stored element is zero (common case), just store a null 2107 // constant. 2108 Constant *StoreVal; 2109 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) { 2110 if (CI->isZero()) { 2111 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0> 2112 } else { 2113 // If EltTy is a vector type, get the element type. 2114 const Type *ValTy = EltTy->getScalarType(); 2115 2116 // Construct an integer with the right value. 2117 unsigned EltSize = TD->getTypeSizeInBits(ValTy); 2118 APInt OneVal(EltSize, CI->getZExtValue()); 2119 APInt TotalVal(OneVal); 2120 // Set each byte. 2121 for (unsigned i = 0; 8*i < EltSize; ++i) { 2122 TotalVal = TotalVal.shl(8); 2123 TotalVal |= OneVal; 2124 } 2125 2126 // Convert the integer value to the appropriate type. 2127 StoreVal = ConstantInt::get(CI->getContext(), TotalVal); 2128 if (ValTy->isPointerTy()) 2129 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy); 2130 else if (ValTy->isFloatingPointTy()) 2131 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy); 2132 assert(StoreVal->getType() == ValTy && "Type mismatch!"); 2133 2134 // If the requested value was a vector constant, create it. 2135 if (EltTy != ValTy) { 2136 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements(); 2137 SmallVector<Constant*, 16> Elts(NumElts, StoreVal); 2138 StoreVal = ConstantVector::get(Elts); 2139 } 2140 } 2141 new StoreInst(StoreVal, EltPtr, MI); 2142 continue; 2143 } 2144 // Otherwise, if we're storing a byte variable, use a memset call for 2145 // this element. 2146 } 2147 2148 unsigned EltSize = TD->getTypeAllocSize(EltTy); 2149 2150 IRBuilder<> Builder(MI); 2151 2152 // Finally, insert the meminst for this element. 2153 if (isa<MemSetInst>(MI)) { 2154 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize, 2155 MI->isVolatile()); 2156 } else { 2157 assert(isa<MemTransferInst>(MI)); 2158 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr 2159 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr 2160 2161 if (isa<MemCpyInst>(MI)) 2162 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile()); 2163 else 2164 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile()); 2165 } 2166 } 2167 DeadInsts.push_back(MI); 2168} 2169 2170/// RewriteStoreUserOfWholeAlloca - We found a store of an integer that 2171/// overwrites the entire allocation. Extract out the pieces of the stored 2172/// integer and store them individually. 2173void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, 2174 SmallVector<AllocaInst*, 32> &NewElts){ 2175 // Extract each element out of the integer according to its structure offset 2176 // and store the element value to the individual alloca. 2177 Value *SrcVal = SI->getOperand(0); 2178 const Type *AllocaEltTy = AI->getAllocatedType(); 2179 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 2180 2181 IRBuilder<> Builder(SI); 2182 2183 // Handle tail padding by extending the operand 2184 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits) 2185 SrcVal = Builder.CreateZExt(SrcVal, 2186 IntegerType::get(SI->getContext(), AllocaSizeBits)); 2187 2188 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI 2189 << '\n'); 2190 2191 // There are two forms here: AI could be an array or struct. Both cases 2192 // have different ways to compute the element offset. 2193 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 2194 const StructLayout *Layout = TD->getStructLayout(EltSTy); 2195 2196 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 2197 // Get the number of bits to shift SrcVal to get the value. 2198 const Type *FieldTy = EltSTy->getElementType(i); 2199 uint64_t Shift = Layout->getElementOffsetInBits(i); 2200 2201 if (TD->isBigEndian()) 2202 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy); 2203 2204 Value *EltVal = SrcVal; 2205 if (Shift) { 2206 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 2207 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt"); 2208 } 2209 2210 // Truncate down to an integer of the right size. 2211 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 2212 2213 // Ignore zero sized fields like {}, they obviously contain no data. 2214 if (FieldSizeBits == 0) continue; 2215 2216 if (FieldSizeBits != AllocaSizeBits) 2217 EltVal = Builder.CreateTrunc(EltVal, 2218 IntegerType::get(SI->getContext(), FieldSizeBits)); 2219 Value *DestField = NewElts[i]; 2220 if (EltVal->getType() == FieldTy) { 2221 // Storing to an integer field of this size, just do it. 2222 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) { 2223 // Bitcast to the right element type (for fp/vector values). 2224 EltVal = Builder.CreateBitCast(EltVal, FieldTy); 2225 } else { 2226 // Otherwise, bitcast the dest pointer (for aggregates). 2227 DestField = Builder.CreateBitCast(DestField, 2228 PointerType::getUnqual(EltVal->getType())); 2229 } 2230 new StoreInst(EltVal, DestField, SI); 2231 } 2232 2233 } else { 2234 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy); 2235 const Type *ArrayEltTy = ATy->getElementType(); 2236 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 2237 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy); 2238 2239 uint64_t Shift; 2240 2241 if (TD->isBigEndian()) 2242 Shift = AllocaSizeBits-ElementOffset; 2243 else 2244 Shift = 0; 2245 2246 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 2247 // Ignore zero sized fields like {}, they obviously contain no data. 2248 if (ElementSizeBits == 0) continue; 2249 2250 Value *EltVal = SrcVal; 2251 if (Shift) { 2252 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 2253 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt"); 2254 } 2255 2256 // Truncate down to an integer of the right size. 2257 if (ElementSizeBits != AllocaSizeBits) 2258 EltVal = Builder.CreateTrunc(EltVal, 2259 IntegerType::get(SI->getContext(), 2260 ElementSizeBits)); 2261 Value *DestField = NewElts[i]; 2262 if (EltVal->getType() == ArrayEltTy) { 2263 // Storing to an integer field of this size, just do it. 2264 } else if (ArrayEltTy->isFloatingPointTy() || 2265 ArrayEltTy->isVectorTy()) { 2266 // Bitcast to the right element type (for fp/vector values). 2267 EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy); 2268 } else { 2269 // Otherwise, bitcast the dest pointer (for aggregates). 2270 DestField = Builder.CreateBitCast(DestField, 2271 PointerType::getUnqual(EltVal->getType())); 2272 } 2273 new StoreInst(EltVal, DestField, SI); 2274 2275 if (TD->isBigEndian()) 2276 Shift -= ElementOffset; 2277 else 2278 Shift += ElementOffset; 2279 } 2280 } 2281 2282 DeadInsts.push_back(SI); 2283} 2284 2285/// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to 2286/// an integer. Load the individual pieces to form the aggregate value. 2287void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, 2288 SmallVector<AllocaInst*, 32> &NewElts) { 2289 // Extract each element out of the NewElts according to its structure offset 2290 // and form the result value. 2291 const Type *AllocaEltTy = AI->getAllocatedType(); 2292 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 2293 2294 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI 2295 << '\n'); 2296 2297 // There are two forms here: AI could be an array or struct. Both cases 2298 // have different ways to compute the element offset. 2299 const StructLayout *Layout = 0; 2300 uint64_t ArrayEltBitOffset = 0; 2301 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 2302 Layout = TD->getStructLayout(EltSTy); 2303 } else { 2304 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType(); 2305 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 2306 } 2307 2308 Value *ResultVal = 2309 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits)); 2310 2311 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 2312 // Load the value from the alloca. If the NewElt is an aggregate, cast 2313 // the pointer to an integer of the same size before doing the load. 2314 Value *SrcField = NewElts[i]; 2315 const Type *FieldTy = 2316 cast<PointerType>(SrcField->getType())->getElementType(); 2317 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 2318 2319 // Ignore zero sized fields like {}, they obviously contain no data. 2320 if (FieldSizeBits == 0) continue; 2321 2322 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(), 2323 FieldSizeBits); 2324 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() && 2325 !FieldTy->isVectorTy()) 2326 SrcField = new BitCastInst(SrcField, 2327 PointerType::getUnqual(FieldIntTy), 2328 "", LI); 2329 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI); 2330 2331 // If SrcField is a fp or vector of the right size but that isn't an 2332 // integer type, bitcast to an integer so we can shift it. 2333 if (SrcField->getType() != FieldIntTy) 2334 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI); 2335 2336 // Zero extend the field to be the same size as the final alloca so that 2337 // we can shift and insert it. 2338 if (SrcField->getType() != ResultVal->getType()) 2339 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI); 2340 2341 // Determine the number of bits to shift SrcField. 2342 uint64_t Shift; 2343 if (Layout) // Struct case. 2344 Shift = Layout->getElementOffsetInBits(i); 2345 else // Array case. 2346 Shift = i*ArrayEltBitOffset; 2347 2348 if (TD->isBigEndian()) 2349 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth(); 2350 2351 if (Shift) { 2352 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift); 2353 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI); 2354 } 2355 2356 // Don't create an 'or x, 0' on the first iteration. 2357 if (!isa<Constant>(ResultVal) || 2358 !cast<Constant>(ResultVal)->isNullValue()) 2359 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI); 2360 else 2361 ResultVal = SrcField; 2362 } 2363 2364 // Handle tail padding by truncating the result 2365 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits) 2366 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI); 2367 2368 LI->replaceAllUsesWith(ResultVal); 2369 DeadInsts.push_back(LI); 2370} 2371 2372/// HasPadding - Return true if the specified type has any structure or 2373/// alignment padding in between the elements that would be split apart 2374/// by SROA; return false otherwise. 2375static bool HasPadding(const Type *Ty, const TargetData &TD) { 2376 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 2377 Ty = ATy->getElementType(); 2378 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty); 2379 } 2380 2381 // SROA currently handles only Arrays and Structs. 2382 const StructType *STy = cast<StructType>(Ty); 2383 const StructLayout *SL = TD.getStructLayout(STy); 2384 unsigned PrevFieldBitOffset = 0; 2385 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 2386 unsigned FieldBitOffset = SL->getElementOffsetInBits(i); 2387 2388 // Check to see if there is any padding between this element and the 2389 // previous one. 2390 if (i) { 2391 unsigned PrevFieldEnd = 2392 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1)); 2393 if (PrevFieldEnd < FieldBitOffset) 2394 return true; 2395 } 2396 PrevFieldBitOffset = FieldBitOffset; 2397 } 2398 // Check for tail padding. 2399 if (unsigned EltCount = STy->getNumElements()) { 2400 unsigned PrevFieldEnd = PrevFieldBitOffset + 2401 TD.getTypeSizeInBits(STy->getElementType(EltCount-1)); 2402 if (PrevFieldEnd < SL->getSizeInBits()) 2403 return true; 2404 } 2405 return false; 2406} 2407 2408/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of 2409/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, 2410/// or 1 if safe after canonicalization has been performed. 2411bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) { 2412 // Loop over the use list of the alloca. We can only transform it if all of 2413 // the users are safe to transform. 2414 AllocaInfo Info(AI); 2415 2416 isSafeForScalarRepl(AI, 0, Info); 2417 if (Info.isUnsafe) { 2418 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n'); 2419 return false; 2420 } 2421 2422 // Okay, we know all the users are promotable. If the aggregate is a memcpy 2423 // source and destination, we have to be careful. In particular, the memcpy 2424 // could be moving around elements that live in structure padding of the LLVM 2425 // types, but may actually be used. In these cases, we refuse to promote the 2426 // struct. 2427 if (Info.isMemCpySrc && Info.isMemCpyDst && 2428 HasPadding(AI->getAllocatedType(), *TD)) 2429 return false; 2430 2431 // If the alloca never has an access to just *part* of it, but is accessed 2432 // via loads and stores, then we should use ConvertToScalarInfo to promote 2433 // the alloca instead of promoting each piece at a time and inserting fission 2434 // and fusion code. 2435 if (!Info.hasSubelementAccess && Info.hasALoadOrStore) { 2436 // If the struct/array just has one element, use basic SRoA. 2437 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 2438 if (ST->getNumElements() > 1) return false; 2439 } else { 2440 if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1) 2441 return false; 2442 } 2443 } 2444 2445 return true; 2446} 2447 2448 2449 2450/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to 2451/// some part of a constant global variable. This intentionally only accepts 2452/// constant expressions because we don't can't rewrite arbitrary instructions. 2453static bool PointsToConstantGlobal(Value *V) { 2454 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 2455 return GV->isConstant(); 2456 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 2457 if (CE->getOpcode() == Instruction::BitCast || 2458 CE->getOpcode() == Instruction::GetElementPtr) 2459 return PointsToConstantGlobal(CE->getOperand(0)); 2460 return false; 2461} 2462 2463/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) 2464/// pointer to an alloca. Ignore any reads of the pointer, return false if we 2465/// see any stores or other unknown uses. If we see pointer arithmetic, keep 2466/// track of whether it moves the pointer (with isOffset) but otherwise traverse 2467/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to 2468/// the alloca, and if the source pointer is a pointer to a constant global, we 2469/// can optimize this. 2470static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy, 2471 bool isOffset) { 2472 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 2473 User *U = cast<Instruction>(*UI); 2474 2475 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 2476 // Ignore non-volatile loads, they are always ok. 2477 if (LI->isVolatile()) return false; 2478 continue; 2479 } 2480 2481 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) { 2482 // If uses of the bitcast are ok, we are ok. 2483 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset)) 2484 return false; 2485 continue; 2486 } 2487 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { 2488 // If the GEP has all zero indices, it doesn't offset the pointer. If it 2489 // doesn't, it does. 2490 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, 2491 isOffset || !GEP->hasAllZeroIndices())) 2492 return false; 2493 continue; 2494 } 2495 2496 if (CallSite CS = U) { 2497 // If this is the function being called then we treat it like a load and 2498 // ignore it. 2499 if (CS.isCallee(UI)) 2500 continue; 2501 2502 // If this is a readonly/readnone call site, then we know it is just a 2503 // load (but one that potentially returns the value itself), so we can 2504 // ignore it if we know that the value isn't captured. 2505 unsigned ArgNo = CS.getArgumentNo(UI); 2506 if (CS.onlyReadsMemory() && 2507 (CS.getInstruction()->use_empty() || 2508 CS.paramHasAttr(ArgNo+1, Attribute::NoCapture))) 2509 continue; 2510 2511 // If this is being passed as a byval argument, the caller is making a 2512 // copy, so it is only a read of the alloca. 2513 if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal)) 2514 continue; 2515 } 2516 2517 // If this is isn't our memcpy/memmove, reject it as something we can't 2518 // handle. 2519 MemTransferInst *MI = dyn_cast<MemTransferInst>(U); 2520 if (MI == 0) 2521 return false; 2522 2523 // If the transfer is using the alloca as a source of the transfer, then 2524 // ignore it since it is a load (unless the transfer is volatile). 2525 if (UI.getOperandNo() == 1) { 2526 if (MI->isVolatile()) return false; 2527 continue; 2528 } 2529 2530 // If we already have seen a copy, reject the second one. 2531 if (TheCopy) return false; 2532 2533 // If the pointer has been offset from the start of the alloca, we can't 2534 // safely handle this. 2535 if (isOffset) return false; 2536 2537 // If the memintrinsic isn't using the alloca as the dest, reject it. 2538 if (UI.getOperandNo() != 0) return false; 2539 2540 // If the source of the memcpy/move is not a constant global, reject it. 2541 if (!PointsToConstantGlobal(MI->getSource())) 2542 return false; 2543 2544 // Otherwise, the transform is safe. Remember the copy instruction. 2545 TheCopy = MI; 2546 } 2547 return true; 2548} 2549 2550/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only 2551/// modified by a copy from a constant global. If we can prove this, we can 2552/// replace any uses of the alloca with uses of the global directly. 2553MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) { 2554 MemTransferInst *TheCopy = 0; 2555 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false)) 2556 return TheCopy; 2557 return 0; 2558} 2559