//===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This transformation implements the well known scalar replacement of // aggregates transformation. This xform breaks up alloca instructions of // aggregate type (structure or array) into individual alloca instructions for // each member (if possible). Then, if possible, it transforms the individual // alloca instructions into nice clean scalar SSA form. // // This combines a simple SRoA algorithm with the Mem2Reg algorithm because // often interact, especially for C++ programs. As such, iterating between // SRoA, then Mem2Reg until we run out of things to promote works well. // //===----------------------------------------------------------------------===// #define DEBUG_TYPE "scalarrepl" #include "llvm/Transforms/Scalar.h" #include "llvm/Constants.h" #include "llvm/DerivedTypes.h" #include "llvm/Function.h" #include "llvm/GlobalVariable.h" #include "llvm/Instructions.h" #include "llvm/IntrinsicInst.h" #include "llvm/Pass.h" #include "llvm/Analysis/Dominators.h" #include "llvm/Target/TargetData.h" #include "llvm/Transforms/Utils/PromoteMemToReg.h" #include "llvm/Transforms/Utils/Local.h" #include "llvm/Support/Debug.h" #include "llvm/Support/GetElementPtrTypeIterator.h" #include "llvm/Support/IRBuilder.h" #include "llvm/Support/MathExtras.h" #include "llvm/Support/Compiler.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/Statistic.h" #include "llvm/ADT/StringExtras.h" using namespace llvm; STATISTIC(NumReplaced, "Number of allocas broken up"); STATISTIC(NumPromoted, "Number of allocas promoted"); STATISTIC(NumConverted, "Number of aggregates converted to scalar"); STATISTIC(NumGlobals, "Number of allocas copied from constant global"); namespace { struct VISIBILITY_HIDDEN SROA : public FunctionPass { static char ID; // Pass identification, replacement for typeid explicit SROA(signed T = -1) : FunctionPass(&ID) { if (T == -1) SRThreshold = 128; else SRThreshold = T; } bool runOnFunction(Function &F); bool performScalarRepl(Function &F); bool performPromotion(Function &F); // getAnalysisUsage - This pass does not require any passes, but we know it // will not alter the CFG, so say so. virtual void getAnalysisUsage(AnalysisUsage &AU) const { AU.addRequired(); AU.addRequired(); AU.addRequired(); AU.setPreservesCFG(); } private: TargetData *TD; /// AllocaInfo - When analyzing uses of an alloca instruction, this captures /// information about the uses. All these fields are initialized to false /// and set to true when something is learned. struct AllocaInfo { /// isUnsafe - This is set to true if the alloca cannot be SROA'd. bool isUnsafe : 1; /// needsCleanup - This is set to true if there is some use of the alloca /// that requires cleanup. bool needsCleanup : 1; /// isMemCpySrc - This is true if this aggregate is memcpy'd from. bool isMemCpySrc : 1; /// isMemCpyDst - This is true if this aggregate is memcpy'd into. bool isMemCpyDst : 1; AllocaInfo() : isUnsafe(false), needsCleanup(false), isMemCpySrc(false), isMemCpyDst(false) {} }; unsigned SRThreshold; void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; } int isSafeAllocaToScalarRepl(AllocationInst *AI); void isSafeUseOfAllocation(Instruction *User, AllocationInst *AI, AllocaInfo &Info); void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI, AllocaInfo &Info); void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI, unsigned OpNo, AllocaInfo &Info); void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocationInst *AI, AllocaInfo &Info); void DoScalarReplacement(AllocationInst *AI, std::vector &WorkList); void CleanupGEP(GetElementPtrInst *GEP); void CleanupAllocaUsers(AllocationInst *AI); AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base); void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI, SmallVector &NewElts); void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst, AllocationInst *AI, SmallVector &NewElts); void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocationInst *AI, SmallVector &NewElts); void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI, SmallVector &NewElts); bool CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy, bool &SawVec, uint64_t Offset, unsigned AllocaSize); void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset); Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType, uint64_t Offset, IRBuilder<> &Builder); Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal, uint64_t Offset, IRBuilder<> &Builder); static Instruction *isOnlyCopiedFromConstantGlobal(AllocationInst *AI); }; } char SROA::ID = 0; static RegisterPass X("scalarrepl", "Scalar Replacement of Aggregates"); // Public interface to the ScalarReplAggregates pass FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) { return new SROA(Threshold); } bool SROA::runOnFunction(Function &F) { TD = &getAnalysis(); bool Changed = performPromotion(F); while (1) { bool LocalChange = performScalarRepl(F); if (!LocalChange) break; // No need to repromote if no scalarrepl Changed = true; LocalChange = performPromotion(F); if (!LocalChange) break; // No need to re-scalarrepl if no promotion } return Changed; } bool SROA::performPromotion(Function &F) { std::vector Allocas; DominatorTree &DT = getAnalysis(); DominanceFrontier &DF = getAnalysis(); BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function bool Changed = false; while (1) { Allocas.clear(); // Find allocas that are safe to promote, by looking at all instructions in // the entry node for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) if (AllocaInst *AI = dyn_cast(I)) // Is it an alloca? if (isAllocaPromotable(AI)) Allocas.push_back(AI); if (Allocas.empty()) break; PromoteMemToReg(Allocas, DT, DF); NumPromoted += Allocas.size(); Changed = true; } return Changed; } /// getNumSAElements - Return the number of elements in the specific struct or /// array. static uint64_t getNumSAElements(const Type *T) { if (const StructType *ST = dyn_cast(T)) return ST->getNumElements(); return cast(T)->getNumElements(); } // performScalarRepl - This algorithm is a simple worklist driven algorithm, // which runs on all of the malloc/alloca instructions in the function, removing // them if they are only used by getelementptr instructions. // bool SROA::performScalarRepl(Function &F) { std::vector WorkList; // Scan the entry basic block, adding any alloca's and mallocs to the worklist BasicBlock &BB = F.getEntryBlock(); for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) if (AllocationInst *A = dyn_cast(I)) WorkList.push_back(A); // Process the worklist bool Changed = false; while (!WorkList.empty()) { AllocationInst *AI = WorkList.back(); WorkList.pop_back(); // Handle dead allocas trivially. These can be formed by SROA'ing arrays // with unused elements. if (AI->use_empty()) { AI->eraseFromParent(); continue; } // If this alloca is impossible for us to promote, reject it early. if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized()) continue; // Check to see if this allocation is only modified by a memcpy/memmove from // a constant global. If this is the case, we can change all users to use // the constant global instead. This is commonly produced by the CFE by // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' // is only subsequently read. if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) { DOUT << "Found alloca equal to global: " << *AI; DOUT << " memcpy = " << *TheCopy; Constant *TheSrc = cast(TheCopy->getOperand(2)); AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType())); TheCopy->eraseFromParent(); // Don't mutate the global. AI->eraseFromParent(); ++NumGlobals; Changed = true; continue; } // Check to see if we can perform the core SROA transformation. We cannot // transform the allocation instruction if it is an array allocation // (allocations OF arrays are ok though), and an allocation of a scalar // value cannot be decomposed at all. uint64_t AllocaSize = TD->getTypePaddedSize(AI->getAllocatedType()); // Do not promote any struct whose size is too big. if (AllocaSize > SRThreshold) continue; if ((isa(AI->getAllocatedType()) || isa(AI->getAllocatedType())) && // Do not promote any struct into more than "32" separate vars. getNumSAElements(AI->getAllocatedType()) <= SRThreshold/4) { // Check that all of the users of the allocation are capable of being // transformed. switch (isSafeAllocaToScalarRepl(AI)) { default: assert(0 && "Unexpected value!"); case 0: // Not safe to scalar replace. break; case 1: // Safe, but requires cleanup/canonicalizations first CleanupAllocaUsers(AI); // FALL THROUGH. case 3: // Safe to scalar replace. DoScalarReplacement(AI, WorkList); Changed = true; continue; } } // If we can turn this aggregate value (potentially with casts) into a // simple scalar value that can be mem2reg'd into a register value. // IsNotTrivial tracks whether this is something that mem2reg could have // promoted itself. If so, we don't want to transform it needlessly. Note // that we can't just check based on the type: the alloca may be of an i32 // but that has pointer arithmetic to set byte 3 of it or something. bool IsNotTrivial = false; const Type *VectorTy = 0; bool HadAVector = false; if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector, 0, unsigned(AllocaSize)) && IsNotTrivial) { AllocaInst *NewAI; // If we were able to find a vector type that can handle this with // insert/extract elements, and if there was at least one use that had // a vector type, promote this to a vector. We don't want to promote // random stuff that doesn't use vectors (e.g. <9 x double>) because then // we just get a lot of insert/extracts. If at least one vector is // involved, then we probably really do have a union of vector/array. if (VectorTy && isa(VectorTy) && HadAVector) { DOUT << "CONVERT TO VECTOR: " << *AI << " TYPE = " << *VectorTy <<"\n"; // Create and insert the vector alloca. NewAI = new AllocaInst(VectorTy, 0, "", AI->getParent()->begin()); ConvertUsesToScalar(AI, NewAI, 0); } else { DOUT << "CONVERT TO SCALAR INTEGER: " << *AI << "\n"; // Create and insert the integer alloca. const Type *NewTy = IntegerType::get(AllocaSize*8); NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin()); ConvertUsesToScalar(AI, NewAI, 0); } NewAI->takeName(AI); AI->eraseFromParent(); ++NumConverted; Changed = true; continue; } // Otherwise, couldn't process this alloca. } return Changed; } /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl /// predicate, do SROA now. void SROA::DoScalarReplacement(AllocationInst *AI, std::vector &WorkList) { DOUT << "Found inst to SROA: " << *AI; SmallVector ElementAllocas; if (const StructType *ST = dyn_cast(AI->getAllocatedType())) { ElementAllocas.reserve(ST->getNumContainedTypes()); for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0, AI->getAlignment(), AI->getName() + "." + utostr(i), AI); ElementAllocas.push_back(NA); WorkList.push_back(NA); // Add to worklist for recursive processing } } else { const ArrayType *AT = cast(AI->getAllocatedType()); ElementAllocas.reserve(AT->getNumElements()); const Type *ElTy = AT->getElementType(); for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(), AI->getName() + "." + utostr(i), AI); ElementAllocas.push_back(NA); WorkList.push_back(NA); // Add to worklist for recursive processing } } // Now that we have created the alloca instructions that we want to use, // expand the getelementptr instructions to use them. // while (!AI->use_empty()) { Instruction *User = cast(AI->use_back()); if (BitCastInst *BCInst = dyn_cast(User)) { RewriteBitCastUserOfAlloca(BCInst, AI, ElementAllocas); BCInst->eraseFromParent(); continue; } // Replace: // %res = load { i32, i32 }* %alloc // with: // %load.0 = load i32* %alloc.0 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0 // %load.1 = load i32* %alloc.1 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1 // (Also works for arrays instead of structs) if (LoadInst *LI = dyn_cast(User)) { Value *Insert = UndefValue::get(LI->getType()); for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) { Value *Load = new LoadInst(ElementAllocas[i], "load", LI); Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI); } LI->replaceAllUsesWith(Insert); LI->eraseFromParent(); continue; } // Replace: // store { i32, i32 } %val, { i32, i32 }* %alloc // with: // %val.0 = extractvalue { i32, i32 } %val, 0 // store i32 %val.0, i32* %alloc.0 // %val.1 = extractvalue { i32, i32 } %val, 1 // store i32 %val.1, i32* %alloc.1 // (Also works for arrays instead of structs) if (StoreInst *SI = dyn_cast(User)) { Value *Val = SI->getOperand(0); for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) { Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI); new StoreInst(Extract, ElementAllocas[i], SI); } SI->eraseFromParent(); continue; } GetElementPtrInst *GEPI = cast(User); // We now know that the GEP is of the form: GEP , 0, unsigned Idx = (unsigned)cast(GEPI->getOperand(2))->getZExtValue(); assert(Idx < ElementAllocas.size() && "Index out of range?"); AllocaInst *AllocaToUse = ElementAllocas[Idx]; Value *RepValue; if (GEPI->getNumOperands() == 3) { // Do not insert a new getelementptr instruction with zero indices, only // to have it optimized out later. RepValue = AllocaToUse; } else { // We are indexing deeply into the structure, so we still need a // getelement ptr instruction to finish the indexing. This may be // expanded itself once the worklist is rerun. // SmallVector NewArgs; NewArgs.push_back(Constant::getNullValue(Type::Int32Ty)); NewArgs.append(GEPI->op_begin()+3, GEPI->op_end()); RepValue = GetElementPtrInst::Create(AllocaToUse, NewArgs.begin(), NewArgs.end(), "", GEPI); RepValue->takeName(GEPI); } // If this GEP is to the start of the aggregate, check for memcpys. if (Idx == 0 && GEPI->hasAllZeroIndices()) RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas); // Move all of the users over to the new GEP. GEPI->replaceAllUsesWith(RepValue); // Delete the old GEP GEPI->eraseFromParent(); } // Finally, delete the Alloca instruction AI->eraseFromParent(); NumReplaced++; } /// isSafeElementUse - Check to see if this use is an allowed use for a /// getelementptr instruction of an array aggregate allocation. isFirstElt /// indicates whether Ptr is known to the start of the aggregate. /// void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI, AllocaInfo &Info) { for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); I != E; ++I) { Instruction *User = cast(*I); switch (User->getOpcode()) { case Instruction::Load: break; case Instruction::Store: // Store is ok if storing INTO the pointer, not storing the pointer if (User->getOperand(0) == Ptr) return MarkUnsafe(Info); break; case Instruction::GetElementPtr: { GetElementPtrInst *GEP = cast(User); bool AreAllZeroIndices = isFirstElt; if (GEP->getNumOperands() > 1) { if (!isa(GEP->getOperand(1)) || !cast(GEP->getOperand(1))->isZero()) // Using pointer arithmetic to navigate the array. return MarkUnsafe(Info); if (AreAllZeroIndices) AreAllZeroIndices = GEP->hasAllZeroIndices(); } isSafeElementUse(GEP, AreAllZeroIndices, AI, Info); if (Info.isUnsafe) return; break; } case Instruction::BitCast: if (isFirstElt) { isSafeUseOfBitCastedAllocation(cast(User), AI, Info); if (Info.isUnsafe) return; break; } DOUT << " Transformation preventing inst: " << *User; return MarkUnsafe(Info); case Instruction::Call: if (MemIntrinsic *MI = dyn_cast(User)) { if (isFirstElt) { isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info); if (Info.isUnsafe) return; break; } } DOUT << " Transformation preventing inst: " << *User; return MarkUnsafe(Info); default: DOUT << " Transformation preventing inst: " << *User; return MarkUnsafe(Info); } } return; // All users look ok :) } /// AllUsersAreLoads - Return true if all users of this value are loads. static bool AllUsersAreLoads(Value *Ptr) { for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); I != E; ++I) if (cast(*I)->getOpcode() != Instruction::Load) return false; return true; } /// isSafeUseOfAllocation - Check to see if this user is an allowed use for an /// aggregate allocation. /// void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI, AllocaInfo &Info) { if (BitCastInst *C = dyn_cast(User)) return isSafeUseOfBitCastedAllocation(C, AI, Info); if (LoadInst *LI = dyn_cast(User)) if (!LI->isVolatile()) return;// Loads (returning a first class aggregrate) are always rewritable if (StoreInst *SI = dyn_cast(User)) if (!SI->isVolatile() && SI->getOperand(0) != AI) return;// Store is ok if storing INTO the pointer, not storing the pointer GetElementPtrInst *GEPI = dyn_cast(User); if (GEPI == 0) return MarkUnsafe(Info); gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI); // The GEP is not safe to transform if not of the form "GEP , 0, ". if (I == E || I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) { return MarkUnsafe(Info); } ++I; if (I == E) return MarkUnsafe(Info); // ran out of GEP indices?? bool IsAllZeroIndices = true; // If the first index is a non-constant index into an array, see if we can // handle it as a special case. if (const ArrayType *AT = dyn_cast(*I)) { if (!isa(I.getOperand())) { IsAllZeroIndices = 0; uint64_t NumElements = AT->getNumElements(); // If this is an array index and the index is not constant, we cannot // promote... that is unless the array has exactly one or two elements in // it, in which case we CAN promote it, but we have to canonicalize this // out if this is the only problem. if ((NumElements == 1 || NumElements == 2) && AllUsersAreLoads(GEPI)) { Info.needsCleanup = true; return; // Canonicalization required! } return MarkUnsafe(Info); } } // Walk through the GEP type indices, checking the types that this indexes // into. for (; I != E; ++I) { // Ignore struct elements, no extra checking needed for these. if (isa(*I)) continue; ConstantInt *IdxVal = dyn_cast(I.getOperand()); if (!IdxVal) return MarkUnsafe(Info); // Are all indices still zero? IsAllZeroIndices &= IdxVal->isZero(); if (const ArrayType *AT = dyn_cast(*I)) { // This GEP indexes an array. Verify that this is an in-range constant // integer. Specifically, consider A[0][i]. We cannot know that the user // isn't doing invalid things like allowing i to index an out-of-range // subscript that accesses A[1]. Because of this, we have to reject SROA // of any accesses into structs where any of the components are variables. if (IdxVal->getZExtValue() >= AT->getNumElements()) return MarkUnsafe(Info); } else if (const VectorType *VT = dyn_cast(*I)) { if (IdxVal->getZExtValue() >= VT->getNumElements()) return MarkUnsafe(Info); } } // If there are any non-simple uses of this getelementptr, make sure to reject // them. return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info); } /// isSafeMemIntrinsicOnAllocation - Return true if the specified memory /// intrinsic can be promoted by SROA. At this point, we know that the operand /// of the memintrinsic is a pointer to the beginning of the allocation. void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI, unsigned OpNo, AllocaInfo &Info) { // If not constant length, give up. ConstantInt *Length = dyn_cast(MI->getLength()); if (!Length) return MarkUnsafe(Info); // If not the whole aggregate, give up. if (Length->getZExtValue() != TD->getTypePaddedSize(AI->getType()->getElementType())) return MarkUnsafe(Info); // We only know about memcpy/memset/memmove. if (!isa(MI)) return MarkUnsafe(Info); // Otherwise, we can transform it. Determine whether this is a memcpy/set // into or out of the aggregate. if (OpNo == 1) Info.isMemCpyDst = true; else { assert(OpNo == 2); Info.isMemCpySrc = true; } } /// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast /// are void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI, AllocaInfo &Info) { for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end(); UI != E; ++UI) { if (BitCastInst *BCU = dyn_cast(UI)) { isSafeUseOfBitCastedAllocation(BCU, AI, Info); } else if (MemIntrinsic *MI = dyn_cast(UI)) { isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info); } else if (StoreInst *SI = dyn_cast(UI)) { if (SI->isVolatile()) return MarkUnsafe(Info); // If storing the entire alloca in one chunk through a bitcasted pointer // to integer, we can transform it. This happens (for example) when you // cast a {i32,i32}* to i64* and store through it. This is similar to the // memcpy case and occurs in various "byval" cases and emulated memcpys. if (isa(SI->getOperand(0)->getType()) && TD->getTypePaddedSize(SI->getOperand(0)->getType()) == TD->getTypePaddedSize(AI->getType()->getElementType())) { Info.isMemCpyDst = true; continue; } return MarkUnsafe(Info); } else if (LoadInst *LI = dyn_cast(UI)) { if (LI->isVolatile()) return MarkUnsafe(Info); // If loading the entire alloca in one chunk through a bitcasted pointer // to integer, we can transform it. This happens (for example) when you // cast a {i32,i32}* to i64* and load through it. This is similar to the // memcpy case and occurs in various "byval" cases and emulated memcpys. if (isa(LI->getType()) && TD->getTypePaddedSize(LI->getType()) == TD->getTypePaddedSize(AI->getType()->getElementType())) { Info.isMemCpySrc = true; continue; } return MarkUnsafe(Info); } else if (isa(UI)) { // If one user is DbgInfoIntrinsic then check if all users are // DbgInfoIntrinsics. if (OnlyUsedByDbgInfoIntrinsics(BC)) { Info.needsCleanup = true; return; } else MarkUnsafe(Info); } else { return MarkUnsafe(Info); } if (Info.isUnsafe) return; } } /// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes /// to its first element. Transform users of the cast to use the new values /// instead. void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI, SmallVector &NewElts) { Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end(); while (UI != UE) { Instruction *User = cast(*UI++); if (BitCastInst *BCU = dyn_cast(User)) { RewriteBitCastUserOfAlloca(BCU, AI, NewElts); if (BCU->use_empty()) BCU->eraseFromParent(); continue; } if (MemIntrinsic *MI = dyn_cast(User)) { // This must be memcpy/memmove/memset of the entire aggregate. // Split into one per element. RewriteMemIntrinUserOfAlloca(MI, BCInst, AI, NewElts); continue; } if (StoreInst *SI = dyn_cast(User)) { // If this is a store of the entire alloca from an integer, rewrite it. RewriteStoreUserOfWholeAlloca(SI, AI, NewElts); continue; } if (LoadInst *LI = dyn_cast(User)) { // If this is a load of the entire alloca to an integer, rewrite it. RewriteLoadUserOfWholeAlloca(LI, AI, NewElts); continue; } // Otherwise it must be some other user of a gep of the first pointer. Just // leave these alone. continue; } } /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI. /// Rewrite it to copy or set the elements of the scalarized memory. void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst, AllocationInst *AI, SmallVector &NewElts) { // If this is a memcpy/memmove, construct the other pointer as the // appropriate type. The "Other" pointer is the pointer that goes to memory // that doesn't have anything to do with the alloca that we are promoting. For // memset, this Value* stays null. Value *OtherPtr = 0; unsigned MemAlignment = MI->getAlignment(); if (MemTransferInst *MTI = dyn_cast(MI)) { // memmove/memcopy if (BCInst == MTI->getRawDest()) OtherPtr = MTI->getRawSource(); else { assert(BCInst == MTI->getRawSource()); OtherPtr = MTI->getRawDest(); } } // If there is an other pointer, we want to convert it to the same pointer // type as AI has, so we can GEP through it safely. if (OtherPtr) { // It is likely that OtherPtr is a bitcast, if so, remove it. if (BitCastInst *BC = dyn_cast(OtherPtr)) OtherPtr = BC->getOperand(0); // All zero GEPs are effectively bitcasts. if (GetElementPtrInst *GEP = dyn_cast(OtherPtr)) if (GEP->hasAllZeroIndices()) OtherPtr = GEP->getOperand(0); if (ConstantExpr *BCE = dyn_cast(OtherPtr)) if (BCE->getOpcode() == Instruction::BitCast) OtherPtr = BCE->getOperand(0); // If the pointer is not the right type, insert a bitcast to the right // type. if (OtherPtr->getType() != AI->getType()) { // Preserve address space of OtherPtrTy const PointerType* OtherPtrTy = cast(OtherPtr->getType()); const PointerType* AIPtrTy = cast(AI->getType()); if (OtherPtrTy->getElementType() != AIPtrTy->getElementType()) { Type *NewOtherPtrTy = PointerType::get(AIPtrTy->getElementType(), OtherPtrTy->getAddressSpace()); OtherPtr = new BitCastInst(OtherPtr, NewOtherPtrTy, OtherPtr->getName(), MI); } } } // Process each element of the aggregate. Value *TheFn = MI->getOperand(0); const Type *BytePtrTy = MI->getRawDest()->getType(); bool SROADest = MI->getRawDest() == BCInst; Constant *Zero = Constant::getNullValue(Type::Int32Ty); for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { // If this is a memcpy/memmove, emit a GEP of the other element address. Value *OtherElt = 0; unsigned OtherEltAlign = MemAlignment; if (OtherPtr) { Value *Idx[2] = { Zero, ConstantInt::get(Type::Int32Ty, i) }; OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2, OtherPtr->getNameStr()+"."+utostr(i), MI); uint64_t EltOffset; const PointerType *OtherPtrTy = cast(OtherPtr->getType()); if (const StructType *ST = dyn_cast(OtherPtrTy->getElementType())) { EltOffset = TD->getStructLayout(ST)->getElementOffset(i); } else { const Type *EltTy = cast(OtherPtr->getType())->getElementType(); EltOffset = TD->getTypePaddedSize(EltTy)*i; } // The alignment of the other pointer is the guaranteed alignment of the // element, which is affected by both the known alignment of the whole // mem intrinsic and the alignment of the element. If the alignment of // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the // known alignment is just 4 bytes. OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset); } Value *EltPtr = NewElts[i]; const Type *EltTy = cast(EltPtr->getType())->getElementType(); // If we got down to a scalar, insert a load or store as appropriate. if (EltTy->isSingleValueType()) { if (isa(MI)) { if (SROADest) { // From Other to Alloca. Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI); new StoreInst(Elt, EltPtr, MI); } else { // From Alloca to Other. Value *Elt = new LoadInst(EltPtr, "tmp", MI); new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI); } continue; } assert(isa(MI)); // If the stored element is zero (common case), just store a null // constant. Constant *StoreVal; if (ConstantInt *CI = dyn_cast(MI->getOperand(2))) { if (CI->isZero()) { StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0> } else { // If EltTy is a vector type, get the element type. const Type *ValTy = EltTy; if (const VectorType *VTy = dyn_cast(ValTy)) ValTy = VTy->getElementType(); // Construct an integer with the right value. unsigned EltSize = TD->getTypeSizeInBits(ValTy); APInt OneVal(EltSize, CI->getZExtValue()); APInt TotalVal(OneVal); // Set each byte. for (unsigned i = 0; 8*i < EltSize; ++i) { TotalVal = TotalVal.shl(8); TotalVal |= OneVal; } // Convert the integer value to the appropriate type. StoreVal = ConstantInt::get(TotalVal); if (isa(ValTy)) StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy); else if (ValTy->isFloatingPoint()) StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy); assert(StoreVal->getType() == ValTy && "Type mismatch!"); // If the requested value was a vector constant, create it. if (EltTy != ValTy) { unsigned NumElts = cast(ValTy)->getNumElements(); SmallVector Elts(NumElts, StoreVal); StoreVal = ConstantVector::get(&Elts[0], NumElts); } } new StoreInst(StoreVal, EltPtr, MI); continue; } // Otherwise, if we're storing a byte variable, use a memset call for // this element. } // Cast the element pointer to BytePtrTy. if (EltPtr->getType() != BytePtrTy) EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI); // Cast the other pointer (if we have one) to BytePtrTy. if (OtherElt && OtherElt->getType() != BytePtrTy) { // Preserve address space of OtherElt const PointerType* OtherPTy = cast(OtherElt->getType()); const PointerType* PTy = cast(BytePtrTy); if (OtherPTy->getElementType() != PTy->getElementType()) { Type *NewOtherPTy = PointerType::get(PTy->getElementType(), OtherPTy->getAddressSpace()); OtherElt = new BitCastInst(OtherElt, NewOtherPTy, OtherElt->getNameStr(), MI); } } unsigned EltSize = TD->getTypePaddedSize(EltTy); // Finally, insert the meminst for this element. if (isa(MI)) { Value *Ops[] = { SROADest ? EltPtr : OtherElt, // Dest ptr SROADest ? OtherElt : EltPtr, // Src ptr ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size ConstantInt::get(Type::Int32Ty, OtherEltAlign) // Align }; if (MI->getIntrinsicID() == Intrinsic::memcpyany) { // In case we fold a memcpyany of A to B with memcpyany of B to C, // we will need to change the function to be a memcpyany of A to C. const Type *Tys[] = { Ops[0]->getType(), Ops[1]->getType(), Ops[2]->getType(), Ops[3]->getType() }; Module *M = MI->getParent()->getParent()->getParent(); TheFn = Intrinsic::getDeclaration(M, Intrinsic::memcpyany, Tys, 4); } CallInst::Create(TheFn, Ops, Ops + 4, "", MI); } else { assert(isa(MI)); Value *Ops[] = { EltPtr, MI->getOperand(2), // Dest, Value, ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size Zero // Align }; CallInst::Create(TheFn, Ops, Ops + 4, "", MI); } } MI->eraseFromParent(); } /// RewriteStoreUserOfWholeAlloca - We found an store of an integer that /// overwrites the entire allocation. Extract out the pieces of the stored /// integer and store them individually. void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocationInst *AI, SmallVector &NewElts){ // Extract each element out of the integer according to its structure offset // and store the element value to the individual alloca. Value *SrcVal = SI->getOperand(0); const Type *AllocaEltTy = AI->getType()->getElementType(); uint64_t AllocaSizeBits = TD->getTypePaddedSizeInBits(AllocaEltTy); // If this isn't a store of an integer to the whole alloca, it may be a store // to the first element. Just ignore the store in this case and normal SROA // will handle it. We don't handle types here that have tail padding, like // an alloca of type {i1}. if (!isa(SrcVal->getType()) || TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits) return; DOUT << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << *SI; // There are two forms here: AI could be an array or struct. Both cases // have different ways to compute the element offset. if (const StructType *EltSTy = dyn_cast(AllocaEltTy)) { const StructLayout *Layout = TD->getStructLayout(EltSTy); for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { // Get the number of bits to shift SrcVal to get the value. const Type *FieldTy = EltSTy->getElementType(i); uint64_t Shift = Layout->getElementOffsetInBits(i); if (TD->isBigEndian()) Shift = AllocaSizeBits-Shift-TD->getTypePaddedSizeInBits(FieldTy); Value *EltVal = SrcVal; if (Shift) { Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, "sroa.store.elt", SI); } // Truncate down to an integer of the right size. uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); // Ignore zero sized fields like {}, they obviously contain no data. if (FieldSizeBits == 0) continue; if (FieldSizeBits != AllocaSizeBits) EltVal = new TruncInst(EltVal, IntegerType::get(FieldSizeBits), "", SI); Value *DestField = NewElts[i]; if (EltVal->getType() == FieldTy) { // Storing to an integer field of this size, just do it. } else if (FieldTy->isFloatingPoint() || isa(FieldTy)) { // Bitcast to the right element type (for fp/vector values). EltVal = new BitCastInst(EltVal, FieldTy, "", SI); } else { // Otherwise, bitcast the dest pointer (for aggregates). DestField = new BitCastInst(DestField, PointerType::getUnqual(EltVal->getType()), "", SI); } new StoreInst(EltVal, DestField, SI); } } else { const ArrayType *ATy = cast(AllocaEltTy); const Type *ArrayEltTy = ATy->getElementType(); uint64_t ElementOffset = TD->getTypePaddedSizeInBits(ArrayEltTy); uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy); uint64_t Shift; if (TD->isBigEndian()) Shift = AllocaSizeBits-ElementOffset; else Shift = 0; for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { // Ignore zero sized fields like {}, they obviously contain no data. if (ElementSizeBits == 0) continue; Value *EltVal = SrcVal; if (Shift) { Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, "sroa.store.elt", SI); } // Truncate down to an integer of the right size. if (ElementSizeBits != AllocaSizeBits) EltVal = new TruncInst(EltVal, IntegerType::get(ElementSizeBits),"",SI); Value *DestField = NewElts[i]; if (EltVal->getType() == ArrayEltTy) { // Storing to an integer field of this size, just do it. } else if (ArrayEltTy->isFloatingPoint() || isa(ArrayEltTy)) { // Bitcast to the right element type (for fp/vector values). EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI); } else { // Otherwise, bitcast the dest pointer (for aggregates). DestField = new BitCastInst(DestField, PointerType::getUnqual(EltVal->getType()), "", SI); } new StoreInst(EltVal, DestField, SI); if (TD->isBigEndian()) Shift -= ElementOffset; else Shift += ElementOffset; } } SI->eraseFromParent(); } /// RewriteLoadUserOfWholeAlloca - We found an load of the entire allocation to /// an integer. Load the individual pieces to form the aggregate value. void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI, SmallVector &NewElts) { // Extract each element out of the NewElts according to its structure offset // and form the result value. const Type *AllocaEltTy = AI->getType()->getElementType(); uint64_t AllocaSizeBits = TD->getTypePaddedSizeInBits(AllocaEltTy); // If this isn't a load of the whole alloca to an integer, it may be a load // of the first element. Just ignore the load in this case and normal SROA // will handle it. We don't handle types here that have tail padding, like // an alloca of type {i1}. if (!isa(LI->getType()) || TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits) return; DOUT << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << *LI; // There are two forms here: AI could be an array or struct. Both cases // have different ways to compute the element offset. const StructLayout *Layout = 0; uint64_t ArrayEltBitOffset = 0; if (const StructType *EltSTy = dyn_cast(AllocaEltTy)) { Layout = TD->getStructLayout(EltSTy); } else { const Type *ArrayEltTy = cast(AllocaEltTy)->getElementType(); ArrayEltBitOffset = TD->getTypePaddedSizeInBits(ArrayEltTy); } Value *ResultVal = Constant::getNullValue(LI->getType()); for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { // Load the value from the alloca. If the NewElt is an aggregate, cast // the pointer to an integer of the same size before doing the load. Value *SrcField = NewElts[i]; const Type *FieldTy = cast(SrcField->getType())->getElementType(); uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); // Ignore zero sized fields like {}, they obviously contain no data. if (FieldSizeBits == 0) continue; const IntegerType *FieldIntTy = IntegerType::get(FieldSizeBits); if (!isa(FieldTy) && !FieldTy->isFloatingPoint() && !isa(FieldTy)) SrcField = new BitCastInst(SrcField, PointerType::getUnqual(FieldIntTy), "", LI); SrcField = new LoadInst(SrcField, "sroa.load.elt", LI); // If SrcField is a fp or vector of the right size but that isn't an // integer type, bitcast to an integer so we can shift it. if (SrcField->getType() != FieldIntTy) SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI); // Zero extend the field to be the same size as the final alloca so that // we can shift and insert it. if (SrcField->getType() != ResultVal->getType()) SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI); // Determine the number of bits to shift SrcField. uint64_t Shift; if (Layout) // Struct case. Shift = Layout->getElementOffsetInBits(i); else // Array case. Shift = i*ArrayEltBitOffset; if (TD->isBigEndian()) Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth(); if (Shift) { Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift); SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI); } ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI); } LI->replaceAllUsesWith(ResultVal); LI->eraseFromParent(); } /// HasPadding - Return true if the specified type has any structure or /// alignment padding, false otherwise. static bool HasPadding(const Type *Ty, const TargetData &TD) { if (const StructType *STy = dyn_cast(Ty)) { const StructLayout *SL = TD.getStructLayout(STy); unsigned PrevFieldBitOffset = 0; for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { unsigned FieldBitOffset = SL->getElementOffsetInBits(i); // Padding in sub-elements? if (HasPadding(STy->getElementType(i), TD)) return true; // Check to see if there is any padding between this element and the // previous one. if (i) { unsigned PrevFieldEnd = PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1)); if (PrevFieldEnd < FieldBitOffset) return true; } PrevFieldBitOffset = FieldBitOffset; } // Check for tail padding. if (unsigned EltCount = STy->getNumElements()) { unsigned PrevFieldEnd = PrevFieldBitOffset + TD.getTypeSizeInBits(STy->getElementType(EltCount-1)); if (PrevFieldEnd < SL->getSizeInBits()) return true; } } else if (const ArrayType *ATy = dyn_cast(Ty)) { return HasPadding(ATy->getElementType(), TD); } else if (const VectorType *VTy = dyn_cast(Ty)) { return HasPadding(VTy->getElementType(), TD); } return TD.getTypeSizeInBits(Ty) != TD.getTypePaddedSizeInBits(Ty); } /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, /// or 1 if safe after canonicalization has been performed. /// int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) { // Loop over the use list of the alloca. We can only transform it if all of // the users are safe to transform. AllocaInfo Info; for (Value::use_iterator I = AI->use_begin(), E = AI->use_end(); I != E; ++I) { isSafeUseOfAllocation(cast(*I), AI, Info); if (Info.isUnsafe) { DOUT << "Cannot transform: " << *AI << " due to user: " << **I; return 0; } } // Okay, we know all the users are promotable. If the aggregate is a memcpy // source and destination, we have to be careful. In particular, the memcpy // could be moving around elements that live in structure padding of the LLVM // types, but may actually be used. In these cases, we refuse to promote the // struct. if (Info.isMemCpySrc && Info.isMemCpyDst && HasPadding(AI->getType()->getElementType(), *TD)) return 0; // If we require cleanup, return 1, otherwise return 3. return Info.needsCleanup ? 1 : 3; } /// CleanupGEP - GEP is used by an Alloca, which can be prompted after the GEP /// is canonicalized here. void SROA::CleanupGEP(GetElementPtrInst *GEPI) { gep_type_iterator I = gep_type_begin(GEPI); ++I; const ArrayType *AT = dyn_cast(*I); if (!AT) return; uint64_t NumElements = AT->getNumElements(); if (isa(I.getOperand())) return; if (NumElements == 1) { GEPI->setOperand(2, Constant::getNullValue(Type::Int32Ty)); return; } assert(NumElements == 2 && "Unhandled case!"); // All users of the GEP must be loads. At each use of the GEP, insert // two loads of the appropriate indexed GEP and select between them. Value *IsOne = new ICmpInst(ICmpInst::ICMP_NE, I.getOperand(), Constant::getNullValue(I.getOperand()->getType()), "isone", GEPI); // Insert the new GEP instructions, which are properly indexed. SmallVector Indices(GEPI->op_begin()+1, GEPI->op_end()); Indices[1] = Constant::getNullValue(Type::Int32Ty); Value *ZeroIdx = GetElementPtrInst::Create(GEPI->getOperand(0), Indices.begin(), Indices.end(), GEPI->getName()+".0", GEPI); Indices[1] = ConstantInt::get(Type::Int32Ty, 1); Value *OneIdx = GetElementPtrInst::Create(GEPI->getOperand(0), Indices.begin(), Indices.end(), GEPI->getName()+".1", GEPI); // Replace all loads of the variable index GEP with loads from both // indexes and a select. while (!GEPI->use_empty()) { LoadInst *LI = cast(GEPI->use_back()); Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI); Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI); Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI); LI->replaceAllUsesWith(R); LI->eraseFromParent(); } GEPI->eraseFromParent(); } /// CleanupAllocaUsers - If SROA reported that it can promote the specified /// allocation, but only if cleaned up, perform the cleanups required. void SROA::CleanupAllocaUsers(AllocationInst *AI) { // At this point, we know that the end result will be SROA'd and promoted, so // we can insert ugly code if required so long as sroa+mem2reg will clean it // up. for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E; ) { User *U = *UI++; if (GetElementPtrInst *GEPI = dyn_cast(U)) CleanupGEP(GEPI); else if (Instruction *I = dyn_cast(U)) { SmallVector DbgInUses; if (!isa(I) && OnlyUsedByDbgInfoIntrinsics(I, &DbgInUses)) { // Safe to remove debug info uses. while (!DbgInUses.empty()) { DbgInfoIntrinsic *DI = DbgInUses.back(); DbgInUses.pop_back(); DI->eraseFromParent(); } I->eraseFromParent(); } } } } /// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at /// the offset specified by Offset (which is specified in bytes). /// /// There are two cases we handle here: /// 1) A union of vector types of the same size and potentially its elements. /// Here we turn element accesses into insert/extract element operations. /// This promotes a <4 x float> with a store of float to the third element /// into a <4 x float> that uses insert element. /// 2) A fully general blob of memory, which we turn into some (potentially /// large) integer type with extract and insert operations where the loads /// and stores would mutate the memory. static void MergeInType(const Type *In, uint64_t Offset, const Type *&VecTy, unsigned AllocaSize, const TargetData &TD) { // If this could be contributing to a vector, analyze it. if (VecTy != Type::VoidTy) { // either null or a vector type. // If the In type is a vector that is the same size as the alloca, see if it // matches the existing VecTy. if (const VectorType *VInTy = dyn_cast(In)) { if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) { // If we're storing/loading a vector of the right size, allow it as a // vector. If this the first vector we see, remember the type so that // we know the element size. if (VecTy == 0) VecTy = VInTy; return; } } else if (In == Type::FloatTy || In == Type::DoubleTy || (isa(In) && In->getPrimitiveSizeInBits() >= 8 && isPowerOf2_32(In->getPrimitiveSizeInBits()))) { // If we're accessing something that could be an element of a vector, see // if the implied vector agrees with what we already have and if Offset is // compatible with it. unsigned EltSize = In->getPrimitiveSizeInBits()/8; if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 && (VecTy == 0 || cast(VecTy)->getElementType() ->getPrimitiveSizeInBits()/8 == EltSize)) { if (VecTy == 0) VecTy = VectorType::get(In, AllocaSize/EltSize); return; } } } // Otherwise, we have a case that we can't handle with an optimized vector // form. We can still turn this into a large integer. VecTy = Type::VoidTy; } /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all /// its accesses to use a to single vector type, return true, and set VecTy to /// the new type. If we could convert the alloca into a single promotable /// integer, return true but set VecTy to VoidTy. Further, if the use is not a /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset /// is the current offset from the base of the alloca being analyzed. /// /// If we see at least one access to the value that is as a vector type, set the /// SawVec flag. /// bool SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy, bool &SawVec, uint64_t Offset, unsigned AllocaSize) { for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { Instruction *User = cast(*UI); if (LoadInst *LI = dyn_cast(User)) { // Don't break volatile loads. if (LI->isVolatile()) return false; MergeInType(LI->getType(), Offset, VecTy, AllocaSize, *TD); SawVec |= isa(LI->getType()); continue; } if (StoreInst *SI = dyn_cast(User)) { // Storing the pointer, not into the value? if (SI->getOperand(0) == V || SI->isVolatile()) return 0; MergeInType(SI->getOperand(0)->getType(), Offset, VecTy, AllocaSize, *TD); SawVec |= isa(SI->getOperand(0)->getType()); continue; } if (BitCastInst *BCI = dyn_cast(User)) { if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset, AllocaSize)) return false; IsNotTrivial = true; continue; } if (GetElementPtrInst *GEP = dyn_cast(User)) { // If this is a GEP with a variable indices, we can't handle it. if (!GEP->hasAllConstantIndices()) return false; // Compute the offset that this GEP adds to the pointer. SmallVector Indices(GEP->op_begin()+1, GEP->op_end()); uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(), &Indices[0], Indices.size()); // See if all uses can be converted. if (!CanConvertToScalar(GEP, IsNotTrivial, VecTy, SawVec,Offset+GEPOffset, AllocaSize)) return false; IsNotTrivial = true; continue; } // If this is a constant sized memset of a constant value (e.g. 0) we can // handle it. if (MemSetInst *MSI = dyn_cast(User)) { // Store of constant value and constant size. if (isa(MSI->getValue()) && isa(MSI->getLength())) { IsNotTrivial = true; continue; } } // If this is a memcpy or memmove into or out of the whole allocation, we // can handle it like a load or store of the scalar type. if (MemTransferInst *MTI = dyn_cast(User)) { if (ConstantInt *Len = dyn_cast(MTI->getLength())) if (Len->getZExtValue() == AllocaSize && Offset == 0) { IsNotTrivial = true; continue; } } // Ignore dbg intrinsic. if (isa(User)) continue; // Otherwise, we cannot handle this! return false; } return true; } /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca /// directly. This happens when we are converting an "integer union" to a /// single integer scalar, or when we are converting a "vector union" to a /// vector with insert/extractelement instructions. /// /// Offset is an offset from the original alloca, in bits that need to be /// shifted to the right. By the end of this, there should be no uses of Ptr. void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) { while (!Ptr->use_empty()) { Instruction *User = cast(Ptr->use_back()); if (BitCastInst *CI = dyn_cast(User)) { ConvertUsesToScalar(CI, NewAI, Offset); CI->eraseFromParent(); continue; } if (GetElementPtrInst *GEP = dyn_cast(User)) { // Compute the offset that this GEP adds to the pointer. SmallVector Indices(GEP->op_begin()+1, GEP->op_end()); uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(), &Indices[0], Indices.size()); ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8); GEP->eraseFromParent(); continue; } IRBuilder<> Builder(User->getParent(), User); if (LoadInst *LI = dyn_cast(User)) { // The load is a bit extract from NewAI shifted right by Offset bits. Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp"); Value *NewLoadVal = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder); LI->replaceAllUsesWith(NewLoadVal); LI->eraseFromParent(); continue; } if (StoreInst *SI = dyn_cast(User)) { assert(SI->getOperand(0) != Ptr && "Consistency error!"); Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str()); Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset, Builder); Builder.CreateStore(New, NewAI); SI->eraseFromParent(); continue; } // If this is a constant sized memset of a constant value (e.g. 0) we can // transform it into a store of the expanded constant value. if (MemSetInst *MSI = dyn_cast(User)) { assert(MSI->getRawDest() == Ptr && "Consistency error!"); unsigned NumBytes = cast(MSI->getLength())->getZExtValue(); if (NumBytes != 0) { unsigned Val = cast(MSI->getValue())->getZExtValue(); // Compute the value replicated the right number of times. APInt APVal(NumBytes*8, Val); // Splat the value if non-zero. if (Val) for (unsigned i = 1; i != NumBytes; ++i) APVal |= APVal << 8; Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str()); Value *New = ConvertScalar_InsertValue(ConstantInt::get(APVal), Old, Offset, Builder); Builder.CreateStore(New, NewAI); } MSI->eraseFromParent(); continue; } // If this is a memcpy or memmove into or out of the whole allocation, we // can handle it like a load or store of the scalar type. if (MemTransferInst *MTI = dyn_cast(User)) { assert(Offset == 0 && "must be store to start of alloca"); // If the source and destination are both to the same alloca, then this is // a noop copy-to-self, just delete it. Otherwise, emit a load and store // as appropriate. AllocaInst *OrigAI = cast(Ptr->getUnderlyingObject()); if (MTI->getSource()->getUnderlyingObject() != OrigAI) { // Dest must be OrigAI, change this to be a load from the original // pointer (bitcasted), then a store to our new alloca. assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?"); Value *SrcPtr = MTI->getSource(); SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType()); LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval"); SrcVal->setAlignment(MTI->getAlignment()); Builder.CreateStore(SrcVal, NewAI); } else if (MTI->getDest()->getUnderlyingObject() != OrigAI) { // Src must be OrigAI, change this to be a load from NewAI then a store // through the original dest pointer (bitcasted). assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?"); LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval"); Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType()); StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr); NewStore->setAlignment(MTI->getAlignment()); } else { // Noop transfer. Src == Dst } MTI->eraseFromParent(); continue; } // If user is a dbg info intrinsic then it is safe to remove it. if (isa(User)) { User->eraseFromParent(); continue; } assert(0 && "Unsupported operation!"); abort(); } } /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer /// or vector value FromVal, extracting the bits from the offset specified by /// Offset. This returns the value, which is of type ToType. /// /// This happens when we are converting an "integer union" to a single /// integer scalar, or when we are converting a "vector union" to a vector with /// insert/extractelement instructions. /// /// Offset is an offset from the original alloca, in bits that need to be /// shifted to the right. Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType, uint64_t Offset, IRBuilder<> &Builder) { // If the load is of the whole new alloca, no conversion is needed. if (FromVal->getType() == ToType && Offset == 0) return FromVal; // If the result alloca is a vector type, this is either an element // access or a bitcast to another vector type of the same size. if (const VectorType *VTy = dyn_cast(FromVal->getType())) { if (isa(ToType)) return Builder.CreateBitCast(FromVal, ToType, "tmp"); // Otherwise it must be an element access. unsigned Elt = 0; if (Offset) { unsigned EltSize = TD->getTypePaddedSizeInBits(VTy->getElementType()); Elt = Offset/EltSize; assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); } // Return the element extracted out of it. Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(Type::Int32Ty,Elt), "tmp"); if (V->getType() != ToType) V = Builder.CreateBitCast(V, ToType, "tmp"); return V; } // If ToType is a first class aggregate, extract out each of the pieces and // use insertvalue's to form the FCA. if (const StructType *ST = dyn_cast(ToType)) { const StructLayout &Layout = *TD->getStructLayout(ST); Value *Res = UndefValue::get(ST); for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i), Offset+Layout.getElementOffsetInBits(i), Builder); Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); } return Res; } if (const ArrayType *AT = dyn_cast(ToType)) { uint64_t EltSize = TD->getTypePaddedSizeInBits(AT->getElementType()); Value *Res = UndefValue::get(AT); for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(), Offset+i*EltSize, Builder); Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); } return Res; } // Otherwise, this must be a union that was converted to an integer value. const IntegerType *NTy = cast(FromVal->getType()); // If this is a big-endian system and the load is narrower than the // full alloca type, we need to do a shift to get the right bits. int ShAmt = 0; if (TD->isBigEndian()) { // On big-endian machines, the lowest bit is stored at the bit offset // from the pointer given by getTypeStoreSizeInBits. This matters for // integers with a bitwidth that is not a multiple of 8. ShAmt = TD->getTypeStoreSizeInBits(NTy) - TD->getTypeStoreSizeInBits(ToType) - Offset; } else { ShAmt = Offset; } // Note: we support negative bitwidths (with shl) which are not defined. // We do this to support (f.e.) loads off the end of a structure where // only some bits are used. if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth()) FromVal = Builder.CreateLShr(FromVal, ConstantInt::get(FromVal->getType(), ShAmt), "tmp"); else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) FromVal = Builder.CreateShl(FromVal, ConstantInt::get(FromVal->getType(), -ShAmt), "tmp"); // Finally, unconditionally truncate the integer to the right width. unsigned LIBitWidth = TD->getTypeSizeInBits(ToType); if (LIBitWidth < NTy->getBitWidth()) FromVal = Builder.CreateTrunc(FromVal, IntegerType::get(LIBitWidth), "tmp"); else if (LIBitWidth > NTy->getBitWidth()) FromVal = Builder.CreateZExt(FromVal, IntegerType::get(LIBitWidth), "tmp"); // If the result is an integer, this is a trunc or bitcast. if (isa(ToType)) { // Should be done. } else if (ToType->isFloatingPoint() || isa(ToType)) { // Just do a bitcast, we know the sizes match up. FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp"); } else { // Otherwise must be a pointer. FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp"); } assert(FromVal->getType() == ToType && "Didn't convert right?"); return FromVal; } /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer /// or vector value "Old" at the offset specified by Offset. /// /// This happens when we are converting an "integer union" to a /// single integer scalar, or when we are converting a "vector union" to a /// vector with insert/extractelement instructions. /// /// Offset is an offset from the original alloca, in bits that need to be /// shifted to the right. Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old, uint64_t Offset, IRBuilder<> &Builder) { // Convert the stored type to the actual type, shift it left to insert // then 'or' into place. const Type *AllocaType = Old->getType(); if (const VectorType *VTy = dyn_cast(AllocaType)) { uint64_t VecSize = TD->getTypePaddedSizeInBits(VTy); uint64_t ValSize = TD->getTypePaddedSizeInBits(SV->getType()); // Changing the whole vector with memset or with an access of a different // vector type? if (ValSize == VecSize) return Builder.CreateBitCast(SV, AllocaType, "tmp"); uint64_t EltSize = TD->getTypePaddedSizeInBits(VTy->getElementType()); // Must be an element insertion. unsigned Elt = Offset/EltSize; if (SV->getType() != VTy->getElementType()) SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp"); SV = Builder.CreateInsertElement(Old, SV, ConstantInt::get(Type::Int32Ty, Elt), "tmp"); return SV; } // If SV is a first-class aggregate value, insert each value recursively. if (const StructType *ST = dyn_cast(SV->getType())) { const StructLayout &Layout = *TD->getStructLayout(ST); for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); Old = ConvertScalar_InsertValue(Elt, Old, Offset+Layout.getElementOffsetInBits(i), Builder); } return Old; } if (const ArrayType *AT = dyn_cast(SV->getType())) { uint64_t EltSize = TD->getTypePaddedSizeInBits(AT->getElementType()); for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder); } return Old; } // If SV is a float, convert it to the appropriate integer type. // If it is a pointer, do the same. unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType()); unsigned DestWidth = TD->getTypeSizeInBits(AllocaType); unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType()); unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType); if (SV->getType()->isFloatingPoint() || isa(SV->getType())) SV = Builder.CreateBitCast(SV, IntegerType::get(SrcWidth), "tmp"); else if (isa(SV->getType())) SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(), "tmp"); // Zero extend or truncate the value if needed. if (SV->getType() != AllocaType) { if (SV->getType()->getPrimitiveSizeInBits() < AllocaType->getPrimitiveSizeInBits()) SV = Builder.CreateZExt(SV, AllocaType, "tmp"); else { // Truncation may be needed if storing more than the alloca can hold // (undefined behavior). SV = Builder.CreateTrunc(SV, AllocaType, "tmp"); SrcWidth = DestWidth; SrcStoreWidth = DestStoreWidth; } } // If this is a big-endian system and the store is narrower than the // full alloca type, we need to do a shift to get the right bits. int ShAmt = 0; if (TD->isBigEndian()) { // On big-endian machines, the lowest bit is stored at the bit offset // from the pointer given by getTypeStoreSizeInBits. This matters for // integers with a bitwidth that is not a multiple of 8. ShAmt = DestStoreWidth - SrcStoreWidth - Offset; } else { ShAmt = Offset; } // Note: we support negative bitwidths (with shr) which are not defined. // We do this to support (f.e.) stores off the end of a structure where // only some bits in the structure are set. APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth)); if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) { SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), ShAmt), "tmp"); Mask <<= ShAmt; } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), -ShAmt), "tmp"); Mask = Mask.lshr(-ShAmt); } // Mask out the bits we are about to insert from the old value, and or // in the new bits. if (SrcWidth != DestWidth) { assert(DestWidth > SrcWidth); Old = Builder.CreateAnd(Old, ConstantInt::get(~Mask), "mask"); SV = Builder.CreateOr(Old, SV, "ins"); } return SV; } /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to /// some part of a constant global variable. This intentionally only accepts /// constant expressions because we don't can't rewrite arbitrary instructions. static bool PointsToConstantGlobal(Value *V) { if (GlobalVariable *GV = dyn_cast(V)) return GV->isConstant(); if (ConstantExpr *CE = dyn_cast(V)) if (CE->getOpcode() == Instruction::BitCast || CE->getOpcode() == Instruction::GetElementPtr) return PointsToConstantGlobal(CE->getOperand(0)); return false; } /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) /// pointer to an alloca. Ignore any reads of the pointer, return false if we /// see any stores or other unknown uses. If we see pointer arithmetic, keep /// track of whether it moves the pointer (with isOffset) but otherwise traverse /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to /// the alloca, and if the source pointer is a pointer to a constant global, we /// can optimize this. static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy, bool isOffset) { for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { if (LoadInst *LI = dyn_cast(*UI)) // Ignore non-volatile loads, they are always ok. if (!LI->isVolatile()) continue; if (BitCastInst *BCI = dyn_cast(*UI)) { // If uses of the bitcast are ok, we are ok. if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset)) return false; continue; } if (GetElementPtrInst *GEP = dyn_cast(*UI)) { // If the GEP has all zero indices, it doesn't offset the pointer. If it // doesn't, it does. if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, isOffset || !GEP->hasAllZeroIndices())) return false; continue; } // If this is isn't our memcpy/memmove, reject it as something we can't // handle. if (!isa(*UI)) return false; // If we already have seen a copy, reject the second one. if (TheCopy) return false; // If the pointer has been offset from the start of the alloca, we can't // safely handle this. if (isOffset) return false; // If the memintrinsic isn't using the alloca as the dest, reject it. if (UI.getOperandNo() != 1) return false; MemIntrinsic *MI = cast(*UI); // If the source of the memcpy/move is not a constant global, reject it. if (!PointsToConstantGlobal(MI->getOperand(2))) return false; // Otherwise, the transform is safe. Remember the copy instruction. TheCopy = MI; } return true; } /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only /// modified by a copy from a constant global. If we can prove this, we can /// replace any uses of the alloca with uses of the global directly. Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocationInst *AI) { Instruction *TheCopy = 0; if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false)) return TheCopy; return 0; }