X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTransforms%2FScalar%2FScalarReplAggregates.cpp;h=c5ca22145e3f7cd99826ab2651b045eb1867bb65;hb=88e6dc8bf14e8a98888f62173a6581386b8d29a0;hp=4a6aee391ccab9e4d8036dae74b686a54bbb93a1;hpb=fd93908ae8b9684fe71c239e3c6cfe13ff6a2663;p=oota-llvm.git diff --git a/lib/Transforms/Scalar/ScalarReplAggregates.cpp b/lib/Transforms/Scalar/ScalarReplAggregates.cpp index 4a6aee391cc..c5ca22145e3 100644 --- a/lib/Transforms/Scalar/ScalarReplAggregates.cpp +++ b/lib/Transforms/Scalar/ScalarReplAggregates.cpp @@ -2,8 +2,8 @@ // // The LLVM Compiler Infrastructure // -// This file was developed by the LLVM research group and is distributed under -// the University of Illinois Open Source License. See LICENSE.TXT for details. +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // @@ -19,26 +19,42 @@ // //===----------------------------------------------------------------------===// +#define DEBUG_TYPE "scalarrepl" #include "llvm/Transforms/Scalar.h" #include "llvm/Constants.h" #include "llvm/DerivedTypes.h" #include "llvm/Function.h" -#include "llvm/Pass.h" +#include "llvm/GlobalVariable.h" #include "llvm/Instructions.h" +#include "llvm/IntrinsicInst.h" +#include "llvm/Pass.h" #include "llvm/Analysis/Dominators.h" -#include "llvm/Support/GetElementPtrTypeIterator.h" #include "llvm/Target/TargetData.h" #include "llvm/Transforms/Utils/PromoteMemToReg.h" #include "llvm/Support/Debug.h" +#include "llvm/Support/GetElementPtrTypeIterator.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 { - Statistic<> NumReplaced("scalarrepl", "Number of allocas broken up"); - Statistic<> NumPromoted("scalarrepl", "Number of allocas promoted"); + struct VISIBILITY_HIDDEN SROA : public FunctionPass { + static char ID; // Pass identification, replacement for typeid + explicit SROA(signed T = -1) : FunctionPass((intptr_t)&ID) { + if (T == -1) + SRThreshold = 128; + else + SRThreshold = T; + } - struct SROA : public FunctionPass { bool runOnFunction(Function &F); bool performScalarRepl(Function &F); @@ -54,18 +70,69 @@ namespace { } private: - int isSafeElementUse(Value *Ptr); - int isSafeUseOfAllocation(Instruction *User); + /// 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; + + /// needsCanon - This is set to true if there is some use of the alloca + /// that requires canonicalization. + bool needsCanon : 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), needsCanon(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 CanonicalizeAllocaUsers(AllocationInst *AI); AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base); + + void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI, + SmallVector &NewElts); + + const Type *CanConvertToScalar(Value *V, bool &IsNotTrivial); + void ConvertToScalar(AllocationInst *AI, const Type *Ty); + void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset); + Value *ConvertUsesOfLoadToScalar(LoadInst *LI, AllocaInst *NewAI, + unsigned Offset); + Value *ConvertUsesOfStoreToScalar(StoreInst *SI, AllocaInst *NewAI, + unsigned Offset); + static Instruction *isOnlyCopiedFromConstantGlobal(AllocationInst *AI); }; - - RegisterOpt X("scalarrepl", "Scalar Replacement of Aggregates"); } +char SROA::ID = 0; +static RegisterPass X("scalarrepl", "Scalar Replacement of Aggregates"); + // Public interface to the ScalarReplAggregates pass -FunctionPass *llvm::createScalarReplAggregatesPass() { return new SROA(); } +FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) { + return new SROA(Threshold); +} bool SROA::runOnFunction(Function &F) { @@ -84,8 +151,7 @@ bool SROA::runOnFunction(Function &F) { bool SROA::performPromotion(Function &F) { std::vector Allocas; - const TargetData &TD = getAnalysis(); - DominatorTree &DT = getAnalysis(); + DominatorTree &DT = getAnalysis(); DominanceFrontier &DF = getAnalysis(); BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function @@ -99,12 +165,12 @@ bool SROA::performPromotion(Function &F) { // 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, TD)) + if (isAllocaPromotable(AI)) Allocas.push_back(AI); if (Allocas.empty()) break; - PromoteMemToReg(Allocas, DT, DF, TD); + PromoteMemToReg(Allocas, DT, DF); NumPromoted += Allocas.size(); Changed = true; } @@ -112,6 +178,13 @@ bool SROA::performPromotion(Function &F) { 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 @@ -126,106 +199,220 @@ bool SROA::performScalarRepl(Function &F) { if (AllocationInst *A = dyn_cast(I)) WorkList.push_back(A); + const TargetData &TD = getAnalysis(); + // 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 we can turn this aggregate value (potentially with casts) into a + // simple scalar value that can be mem2reg'd into a register value. + bool IsNotTrivial = false; + if (const Type *ActualType = CanConvertToScalar(AI, IsNotTrivial)) + if (IsNotTrivial && ActualType != Type::VoidTy) { + ConvertToScalar(AI, ActualType); + Changed = true; + continue; + } - // 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. - // - if (AI->isArrayAllocation() || - (!isa(AI->getAllocatedType()) && - !isa(AI->getAllocatedType()))) continue; - - // 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. + // 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. + if (!AI->isArrayAllocation() && + (isa(AI->getAllocatedType()) || + isa(AI->getAllocatedType())) && + AI->getAllocatedType()->isSized() && + // Do not promote any struct whose size is larger than "128" bytes. + TD.getABITypeSize(AI->getAllocatedType()) < SRThreshold && + // 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 + CanonicalizeAllocaUsers(AI); + // FALL THROUGH. + case 3: // Safe to scalar replace. + DoScalarReplacement(AI, WorkList); + Changed = true; + 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; - case 1: // Safe, but requires cleanup/canonicalizations first - CanonicalizeAllocaUsers(AI); - case 3: // Safe to scalar replace. - break; } + + // Otherwise, couldn't process this. + } - DEBUG(std::cerr << "Found inst to xform: " << *AI); - Changed = true; + return Changed; +} - std::vector 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->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->getName() + "." + utostr(i), AI); - ElementAllocas.push_back(NA); - WorkList.push_back(NA); // Add to worklist for recursive processing +/// 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; } - // 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()); - GetElementPtrInst *GEPI = cast(User); - // We now know that the GEP is of the form: GEP , 0, - unsigned Idx = - (unsigned)cast(GEPI->getOperand(2))->getRawValue(); - - 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. - // - std::string OldName = GEPI->getName(); // Steal the old name. - std::vector NewArgs; - NewArgs.push_back(Constant::getNullValue(Type::IntTy)); - NewArgs.insert(NewArgs.end(), GEPI->op_begin()+3, GEPI->op_end()); - GEPI->setName(""); - RepValue = new GetElementPtrInst(AllocaToUse, NewArgs, OldName, GEPI); + // 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]; - // Move all of the users over to the new GEP. - GEPI->replaceAllUsesWith(RepValue); - // Delete the old GEP - GEPI->eraseFromParent(); + 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) { + bool IsStartOfAggregateGEP = true; + for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i) { + if (!isa(GEPI->getOperand(i))) { + IsStartOfAggregateGEP = false; + break; + } + if (!cast(GEPI->getOperand(i))->isZero()) { + IsStartOfAggregateGEP = false; + break; + } + } + + if (IsStartOfAggregateGEP) + RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas); + } + - // Finally, delete the Alloca instruction - AI->getParent()->getInstList().erase(AI); - NumReplaced++; + // Move all of the users over to the new GEP. + GEPI->replaceAllUsesWith(RepValue); + // Delete the old GEP + GEPI->eraseFromParent(); } - return Changed; + // 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. +/// getelementptr instruction of an array aggregate allocation. isFirstElt +/// indicates whether Ptr is known to the start of the aggregate. /// -int SROA::isSafeElementUse(Value *Ptr) { +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); @@ -233,24 +420,55 @@ int SROA::isSafeElementUse(Value *Ptr) { 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 0; + 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))->isNullValue()) - return 0; // Using pointer arithmetic to navigate the array... + if (!isa(GEP->getOperand(1)) || + !cast(GEP->getOperand(1))->isZero()) + // Using pointer arithmetic to navigate the array. + return MarkUnsafe(Info); + + if (AreAllZeroIndices) { + for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i) { + if (!isa(GEP->getOperand(i)) || + !cast(GEP->getOperand(i))->isZero()) { + AreAllZeroIndices = false; + break; + } + } + } } - if (!isSafeElementUse(GEP)) return 0; + 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: - DEBUG(std::cerr << " Transformation preventing inst: " << *User); - return 0; + DOUT << " Transformation preventing inst: " << *User; + return MarkUnsafe(Info); } } - return 3; // All users look ok :) + return; // All users look ok :) } /// AllUsersAreLoads - Return true if all users of this value are loads. @@ -265,45 +483,345 @@ static bool AllUsersAreLoads(Value *Ptr) { /// isSafeUseOfAllocation - Check to see if this user is an allowed use for an /// aggregate allocation. /// -int SROA::isSafeUseOfAllocation(Instruction *User) { - if (!isa(User)) return 0; +void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI, + AllocaInfo &Info) { + if (BitCastInst *C = dyn_cast(User)) + return isSafeUseOfBitCastedAllocation(C, AI, Info); + + if (isa(User)) + return; // Loads (returning a first class aggregrate) are always rewritable + + if (isa(User) && User->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); - GetElementPtrInst *GEPI = cast(User); gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI); - // The GEP is safe to transform if it is of the form GEP , 0, + // 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 0; + I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) { + return MarkUnsafe(Info); + } ++I; - if (I == E) return 0; // ran out of GEP indices?? + if (I == E) return MarkUnsafe(Info); // ran out of GEP indices?? - // If this is a use of an array allocation, do a bit more checking for sanity. + 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)) { - uint64_t NumElements = AT->getNumElements(); - - if (ConstantInt *CI = dyn_cast(I.getOperand())) { - // Check to make sure that index falls within the array. If not, - // something funny is going on, so we won't do the optimization. - // - if (cast(GEPI->getOperand(2))->getRawValue() >= NumElements) - return 0; - - } else { + 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) - return AllUsersAreLoads(GEPI) ? 1 : 0; // Canonicalization required! - return 0; + if ((NumElements == 1 || NumElements == 2) && + AllUsersAreLoads(GEPI)) { + Info.needsCanon = 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; + + // Don't SROA pointers into vectors. + if (isa(*I)) + return MarkUnsafe(Info); + + // Otherwise, we must have an index into an array type. 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. + ConstantInt *IdxVal = dyn_cast(I.getOperand()); + if (!IdxVal) return MarkUnsafe(Info); + if (IdxVal->getZExtValue() >= cast(*I)->getNumElements()) + return MarkUnsafe(Info); + + IsAllZeroIndices &= IdxVal->isZero(); + } + // If there are any non-simple uses of this getelementptr, make sure to reject // them. - return isSafeElementUse(GEPI); + 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. + const TargetData &TD = getAnalysis(); + if (Length->getZExtValue() != + TD.getABITypeSize(AI->getType()->getElementType())) + return MarkUnsafe(Info); + + // We only know about memcpy/memset/memmove. + if (!isa(MI) && !isa(MI) && !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 { + 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) { + Constant *Zero = Constant::getNullValue(Type::Int32Ty); + const TargetData &TD = getAnalysis(); + + Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end(); + while (UI != UE) { + if (BitCastInst *BCU = dyn_cast(*UI)) { + RewriteBitCastUserOfAlloca(BCU, AI, NewElts); + ++UI; + BCU->eraseFromParent(); + continue; + } + + // Otherwise, must be memcpy/memmove/memset of the entire aggregate. Split + // into one per element. + MemIntrinsic *MI = dyn_cast(*UI); + + // If it's not a mem intrinsic, it must be some other user of a gep of the + // first pointer. Just leave these alone. + if (!MI) { + ++UI; + continue; + } + + // If this is a memcpy/memmove, construct the other pointer as the + // appropriate type. + Value *OtherPtr = 0; + if (MemCpyInst *MCI = dyn_cast(MI)) { + if (BCInst == MCI->getRawDest()) + OtherPtr = MCI->getRawSource(); + else { + assert(BCInst == MCI->getRawSource()); + OtherPtr = MCI->getRawDest(); + } + } else if (MemMoveInst *MMI = dyn_cast(MI)) { + if (BCInst == MMI->getRawDest()) + OtherPtr = MMI->getRawSource(); + else { + assert(BCInst == MMI->getRawSource()); + OtherPtr = MMI->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. + if (OtherPtr) { + // It is likely that OtherPtr is a bitcast, if so, remove it. + if (BitCastInst *BC = dyn_cast(OtherPtr)) + OtherPtr = BC->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()) + OtherPtr = new BitCastInst(OtherPtr, AI->getType(), 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; + + 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; + if (OtherPtr) { + Value *Idx[2] = { Zero, ConstantInt::get(Type::Int32Ty, i) }; + OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2, + OtherPtr->getNameStr()+"."+utostr(i), + MI); + } + + 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) || isa(MI)) { + Value *Elt = new LoadInst(SROADest ? OtherElt : EltPtr, "tmp", + MI); + new StoreInst(Elt, SROADest ? EltPtr : OtherElt, MI); + continue; + } else { + 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) + OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(), + MI); + + unsigned EltSize = TD.getABITypeSize(EltTy); + + // Finally, insert the meminst for this element. + if (isa(MI) || isa(MI)) { + Value *Ops[] = { + SROADest ? EltPtr : OtherElt, // Dest ptr + SROADest ? OtherElt : EltPtr, // Src ptr + ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size + Zero // Align + }; + 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); + } + } + + // Finally, MI is now dead, as we've modified its actions to occur on all of + // the elements of the aggregate. + ++UI; + MI->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.getABITypeSizeInBits(Ty); } /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of @@ -313,19 +831,28 @@ int SROA::isSafeUseOfAllocation(Instruction *User) { 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. - // - int isSafe = 3; + AllocaInfo Info; + for (Value::use_iterator I = AI->use_begin(), E = AI->use_end(); I != E; ++I) { - isSafe &= isSafeUseOfAllocation(cast(*I)); - if (isSafe == 0) { - DEBUG(std::cerr << "Cannot transform: " << *AI << " due to user: " - << **I); + isSafeUseOfAllocation(cast(*I), AI, Info); + if (Info.isUnsafe) { + DOUT << "Cannot transform: " << *AI << " due to user: " << **I; return 0; } } - // If we require cleanup, isSafe is now 1, otherwise it is 3. - return isSafe; + + // 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(), getAnalysis())) + return 0; + + // If we require cleanup, return 1, otherwise return 3. + return Info.needsCanon ? 1 : 3; } /// CanonicalizeAllocaUsers - If SROA reported that it can promote the specified @@ -336,7 +863,8 @@ void SROA::CanonicalizeAllocaUsers(AllocationInst *AI) { // up. for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E; ) { - GetElementPtrInst *GEPI = cast(*UI++); + GetElementPtrInst *GEPI = dyn_cast(*UI++); + if (!GEPI) continue; gep_type_iterator I = gep_type_begin(GEPI); ++I; @@ -345,29 +873,33 @@ void SROA::CanonicalizeAllocaUsers(AllocationInst *AI) { if (!isa(I.getOperand())) { if (NumElements == 1) { - GEPI->setOperand(2, Constant::getNullValue(Type::IntTy)); + GEPI->setOperand(2, Constant::getNullValue(Type::Int32Ty)); } else { 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 = BinaryOperator::createSetNE(I.getOperand(), + Value *IsOne = new ICmpInst(ICmpInst::ICMP_NE, I.getOperand(), Constant::getNullValue(I.getOperand()->getType()), - "isone", GEPI); + "isone", GEPI); // Insert the new GEP instructions, which are properly indexed. - std::vector Indices(GEPI->op_begin()+1, GEPI->op_end()); - Indices[1] = Constant::getNullValue(Type::IntTy); - Value *ZeroIdx = new GetElementPtrInst(GEPI->getOperand(0), Indices, - GEPI->getName()+".0", GEPI); - Indices[1] = ConstantInt::get(Type::IntTy, 1); - Value *OneIdx = new GetElementPtrInst(GEPI->getOperand(0), Indices, - GEPI->getName()+".1", GEPI); + 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 = new SelectInst(IsOne, One, Zero, LI->getName(), LI); + Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI); LI->replaceAllUsesWith(R); LI->eraseFromParent(); } @@ -377,3 +909,561 @@ void SROA::CanonicalizeAllocaUsers(AllocationInst *AI) { } } } + +/// MergeInType - Add the 'In' type to the accumulated type so far. If the +/// types are incompatible, return true, otherwise update Accum and return +/// false. +/// +/// There are three cases we handle here: +/// 1) An effectively-integer union, where the pieces are stored into as +/// smaller integers (common with byte swap and other idioms). +/// 2) A union of vector types of the same size and potentially its elements. +/// Here we turn element accesses into insert/extract element operations. +/// 3) A union of scalar types, such as int/float or int/pointer. Here we +/// merge together into integers, allowing the xform to work with #1 as +/// well. +static bool MergeInType(const Type *In, const Type *&Accum, + const TargetData &TD) { + // If this is our first type, just use it. + const VectorType *PTy; + if (Accum == Type::VoidTy || In == Accum) { + Accum = In; + } else if (In == Type::VoidTy) { + // Noop. + } else if (In->isInteger() && Accum->isInteger()) { // integer union. + // Otherwise pick whichever type is larger. + if (cast(In)->getBitWidth() > + cast(Accum)->getBitWidth()) + Accum = In; + } else if (isa(In) && isa(Accum)) { + // Pointer unions just stay as one of the pointers. + } else if (isa(In) || isa(Accum)) { + if ((PTy = dyn_cast(Accum)) && + PTy->getElementType() == In) { + // Accum is a vector, and we are accessing an element: ok. + } else if ((PTy = dyn_cast(In)) && + PTy->getElementType() == Accum) { + // In is a vector, and accum is an element: ok, remember In. + Accum = In; + } else if ((PTy = dyn_cast(In)) && isa(Accum) && + PTy->getBitWidth() == cast(Accum)->getBitWidth()) { + // Two vectors of the same size: keep Accum. + } else { + // Cannot insert an short into a <4 x int> or handle + // <2 x int> -> <4 x int> + return true; + } + } else { + // Pointer/FP/Integer unions merge together as integers. + switch (Accum->getTypeID()) { + case Type::PointerTyID: Accum = TD.getIntPtrType(); break; + case Type::FloatTyID: Accum = Type::Int32Ty; break; + case Type::DoubleTyID: Accum = Type::Int64Ty; break; + case Type::X86_FP80TyID: return true; + case Type::FP128TyID: return true; + case Type::PPC_FP128TyID: return true; + default: + assert(Accum->isInteger() && "Unknown FP type!"); + break; + } + + switch (In->getTypeID()) { + case Type::PointerTyID: In = TD.getIntPtrType(); break; + case Type::FloatTyID: In = Type::Int32Ty; break; + case Type::DoubleTyID: In = Type::Int64Ty; break; + case Type::X86_FP80TyID: return true; + case Type::FP128TyID: return true; + case Type::PPC_FP128TyID: return true; + default: + assert(In->isInteger() && "Unknown FP type!"); + break; + } + return MergeInType(In, Accum, TD); + } + return false; +} + +/// getUIntAtLeastAsBigAs - Return an unsigned integer type that is at least +/// as big as the specified type. If there is no suitable type, this returns +/// null. +const Type *getUIntAtLeastAsBigAs(unsigned NumBits) { + if (NumBits > 64) return 0; + if (NumBits > 32) return Type::Int64Ty; + if (NumBits > 16) return Type::Int32Ty; + if (NumBits > 8) return Type::Int16Ty; + return Type::Int8Ty; +} + +/// CanConvertToScalar - V is a pointer. If we can convert the pointee to a +/// single scalar integer type, return that type. Further, if the use is not +/// a completely trivial use that mem2reg could promote, set IsNotTrivial. If +/// there are no uses of this pointer, return Type::VoidTy to differentiate from +/// failure. +/// +const Type *SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial) { + const Type *UsedType = Type::VoidTy; // No uses, no forced type. + const TargetData &TD = getAnalysis(); + const PointerType *PTy = cast(V->getType()); + + 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)) { + // FIXME: Loads of a first class aggregrate value could be converted to a + // series of loads and insertvalues + if (!LI->getType()->isSingleValueType()) + return 0; + + if (MergeInType(LI->getType(), UsedType, TD)) + return 0; + + } else if (StoreInst *SI = dyn_cast(User)) { + // Storing the pointer, not into the value? + if (SI->getOperand(0) == V) return 0; + + // FIXME: Stores of a first class aggregrate value could be converted to a + // series of extractvalues and stores + if (!SI->getOperand(0)->getType()->isSingleValueType()) + return 0; + + // NOTE: We could handle storing of FP imms into integers here! + + if (MergeInType(SI->getOperand(0)->getType(), UsedType, TD)) + return 0; + } else if (BitCastInst *CI = dyn_cast(User)) { + IsNotTrivial = true; + const Type *SubTy = CanConvertToScalar(CI, IsNotTrivial); + if (!SubTy || MergeInType(SubTy, UsedType, TD)) return 0; + } else if (GetElementPtrInst *GEP = dyn_cast(User)) { + // Check to see if this is stepping over an element: GEP Ptr, int C + if (GEP->getNumOperands() == 2 && isa(GEP->getOperand(1))) { + unsigned Idx = cast(GEP->getOperand(1))->getZExtValue(); + unsigned ElSize = TD.getABITypeSize(PTy->getElementType()); + unsigned BitOffset = Idx*ElSize*8; + if (BitOffset > 64 || !isPowerOf2_32(ElSize)) return 0; + + IsNotTrivial = true; + const Type *SubElt = CanConvertToScalar(GEP, IsNotTrivial); + if (SubElt == 0) return 0; + if (SubElt != Type::VoidTy && SubElt->isInteger()) { + const Type *NewTy = + getUIntAtLeastAsBigAs(TD.getABITypeSizeInBits(SubElt)+BitOffset); + if (NewTy == 0 || MergeInType(NewTy, UsedType, TD)) return 0; + continue; + } + } else if (GEP->getNumOperands() == 3 && + isa(GEP->getOperand(1)) && + isa(GEP->getOperand(2)) && + cast(GEP->getOperand(1))->isZero()) { + // We are stepping into an element, e.g. a structure or an array: + // GEP Ptr, int 0, uint C + const Type *AggTy = PTy->getElementType(); + unsigned Idx = cast(GEP->getOperand(2))->getZExtValue(); + + if (const ArrayType *ATy = dyn_cast(AggTy)) { + if (Idx >= ATy->getNumElements()) return 0; // Out of range. + } else if (const VectorType *VectorTy = dyn_cast(AggTy)) { + // Getting an element of the vector. + if (Idx >= VectorTy->getNumElements()) return 0; // Out of range. + + // Merge in the vector type. + if (MergeInType(VectorTy, UsedType, TD)) return 0; + + const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial); + if (SubTy == 0) return 0; + + if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, TD)) + return 0; + + // We'll need to change this to an insert/extract element operation. + IsNotTrivial = true; + continue; // Everything looks ok + + } else if (isa(AggTy)) { + // Structs are always ok. + } else { + return 0; + } + const Type *NTy = getUIntAtLeastAsBigAs(TD.getABITypeSizeInBits(AggTy)); + if (NTy == 0 || MergeInType(NTy, UsedType, TD)) return 0; + const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial); + if (SubTy == 0) return 0; + if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, TD)) + return 0; + continue; // Everything looks ok + } + return 0; + } else { + // Cannot handle this! + return 0; + } + } + + return UsedType; +} + +/// ConvertToScalar - The specified alloca passes the CanConvertToScalar +/// predicate and is non-trivial. Convert it to something that can be trivially +/// promoted into a register by mem2reg. +void SROA::ConvertToScalar(AllocationInst *AI, const Type *ActualTy) { + DOUT << "CONVERT TO SCALAR: " << *AI << " TYPE = " + << *ActualTy << "\n"; + ++NumConverted; + + BasicBlock *EntryBlock = AI->getParent(); + assert(EntryBlock == &EntryBlock->getParent()->getEntryBlock() && + "Not in the entry block!"); + EntryBlock->getInstList().remove(AI); // Take the alloca out of the program. + + // Create and insert the alloca. + AllocaInst *NewAI = new AllocaInst(ActualTy, 0, AI->getName(), + EntryBlock->begin()); + ConvertUsesToScalar(AI, NewAI, 0); + delete AI; +} + + +/// 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, unsigned Offset) { + while (!Ptr->use_empty()) { + Instruction *User = cast(Ptr->use_back()); + + if (LoadInst *LI = dyn_cast(User)) { + Value *NV = ConvertUsesOfLoadToScalar(LI, NewAI, Offset); + LI->replaceAllUsesWith(NV); + LI->eraseFromParent(); + } else if (StoreInst *SI = dyn_cast(User)) { + assert(SI->getOperand(0) != Ptr && "Consistency error!"); + + Value *SV = ConvertUsesOfStoreToScalar(SI, NewAI, Offset); + new StoreInst(SV, NewAI, SI); + SI->eraseFromParent(); + + } else if (BitCastInst *CI = dyn_cast(User)) { + ConvertUsesToScalar(CI, NewAI, Offset); + CI->eraseFromParent(); + } else if (GetElementPtrInst *GEP = dyn_cast(User)) { + const PointerType *AggPtrTy = + cast(GEP->getOperand(0)->getType()); + const TargetData &TD = getAnalysis(); + unsigned AggSizeInBits = + TD.getABITypeSizeInBits(AggPtrTy->getElementType()); + + // Check to see if this is stepping over an element: GEP Ptr, int C + unsigned NewOffset = Offset; + if (GEP->getNumOperands() == 2) { + unsigned Idx = cast(GEP->getOperand(1))->getZExtValue(); + unsigned BitOffset = Idx*AggSizeInBits; + + NewOffset += BitOffset; + } else if (GEP->getNumOperands() == 3) { + // We know that operand #2 is zero. + unsigned Idx = cast(GEP->getOperand(2))->getZExtValue(); + const Type *AggTy = AggPtrTy->getElementType(); + if (const SequentialType *SeqTy = dyn_cast(AggTy)) { + unsigned ElSizeBits = + TD.getABITypeSizeInBits(SeqTy->getElementType()); + + NewOffset += ElSizeBits*Idx; + } else if (const StructType *STy = dyn_cast(AggTy)) { + unsigned EltBitOffset = + TD.getStructLayout(STy)->getElementOffsetInBits(Idx); + + NewOffset += EltBitOffset; + } else { + assert(0 && "Unsupported operation!"); + abort(); + } + } else { + assert(0 && "Unsupported operation!"); + abort(); + } + ConvertUsesToScalar(GEP, NewAI, NewOffset); + GEP->eraseFromParent(); + } else { + assert(0 && "Unsupported operation!"); + abort(); + } + } +} + +/// ConvertUsesOfLoadToScalar - Convert all of the users the specified load to +/// use the new alloca directly, returning the value that should replace the +/// load. 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. +Value *SROA::ConvertUsesOfLoadToScalar(LoadInst *LI, AllocaInst *NewAI, + unsigned Offset) { + // The load is a bit extract from NewAI shifted right by Offset bits. + Value *NV = new LoadInst(NewAI, LI->getName(), LI); + + if (NV->getType() == LI->getType() && Offset == 0) { + // We win, no conversion needed. + return NV; + } + + // If the result type of the 'union' is a pointer, then this must be ptr->ptr + // cast. Anything else would result in NV being an integer. + if (isa(NV->getType())) { + assert(isa(LI->getType())); + return new BitCastInst(NV, LI->getType(), LI->getName(), LI); + } + + if (const VectorType *VTy = dyn_cast(NV->getType())) { + // If the result alloca is a vector type, this is either an element + // access or a bitcast to another vector type. + if (isa(LI->getType())) + return new BitCastInst(NV, LI->getType(), LI->getName(), LI); + + // Otherwise it must be an element access. + const TargetData &TD = getAnalysis(); + unsigned Elt = 0; + if (Offset) { + unsigned EltSize = TD.getABITypeSizeInBits(VTy->getElementType()); + Elt = Offset/EltSize; + Offset -= EltSize*Elt; + } + NV = new ExtractElementInst(NV, ConstantInt::get(Type::Int32Ty, Elt), + "tmp", LI); + + // If we're done, return this element. + if (NV->getType() == LI->getType() && Offset == 0) + return NV; + } + + const IntegerType *NTy = cast(NV->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; + const TargetData &TD = getAnalysis(); + 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(LI->getType()) - 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()) + NV = BinaryOperator::CreateLShr(NV, + ConstantInt::get(NV->getType(),ShAmt), + LI->getName(), LI); + else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) + NV = BinaryOperator::CreateShl(NV, + ConstantInt::get(NV->getType(),-ShAmt), + LI->getName(), LI); + + // Finally, unconditionally truncate the integer to the right width. + unsigned LIBitWidth = TD.getTypeSizeInBits(LI->getType()); + if (LIBitWidth < NTy->getBitWidth()) + NV = new TruncInst(NV, IntegerType::get(LIBitWidth), + LI->getName(), LI); + + // If the result is an integer, this is a trunc or bitcast. + if (isa(LI->getType())) { + // Should be done. + } else if (LI->getType()->isFloatingPoint()) { + // Just do a bitcast, we know the sizes match up. + NV = new BitCastInst(NV, LI->getType(), LI->getName(), LI); + } else { + // Otherwise must be a pointer. + NV = new IntToPtrInst(NV, LI->getType(), LI->getName(), LI); + } + assert(NV->getType() == LI->getType() && "Didn't convert right?"); + return NV; +} + + +/// ConvertUsesOfStoreToScalar - Convert the specified store to a load+store +/// pair of the new alloca directly, returning the value that should be stored +/// to the alloca. 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. +Value *SROA::ConvertUsesOfStoreToScalar(StoreInst *SI, AllocaInst *NewAI, + unsigned Offset) { + + // Convert the stored type to the actual type, shift it left to insert + // then 'or' into place. + Value *SV = SI->getOperand(0); + const Type *AllocaType = NewAI->getType()->getElementType(); + if (SV->getType() == AllocaType && Offset == 0) { + // All is well. + } else if (const VectorType *PTy = dyn_cast(AllocaType)) { + Value *Old = new LoadInst(NewAI, NewAI->getName()+".in", SI); + + // If the result alloca is a vector type, this is either an element + // access or a bitcast to another vector type. + if (isa(SV->getType())) { + SV = new BitCastInst(SV, AllocaType, SV->getName(), SI); + } else { + // Must be an element insertion. + const TargetData &TD = getAnalysis(); + unsigned Elt = Offset/TD.getABITypeSizeInBits(PTy->getElementType()); + SV = InsertElementInst::Create(Old, SV, + ConstantInt::get(Type::Int32Ty, Elt), + "tmp", SI); + } + } else if (isa(AllocaType)) { + // If the alloca type is a pointer, then all the elements must be + // pointers. + if (SV->getType() != AllocaType) + SV = new BitCastInst(SV, AllocaType, SV->getName(), SI); + } else { + Value *Old = new LoadInst(NewAI, NewAI->getName()+".in", SI); + + // If SV is a float, convert it to the appropriate integer type. + // If it is a pointer, do the same, and also handle ptr->ptr casts + // here. + const TargetData &TD = getAnalysis(); + 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()) + SV = new BitCastInst(SV, IntegerType::get(SrcWidth), + SV->getName(), SI); + else if (isa(SV->getType())) + SV = new PtrToIntInst(SV, TD.getIntPtrType(), SV->getName(), SI); + + // Always zero extend the value if needed. + if (SV->getType() != AllocaType) + SV = new ZExtInst(SV, AllocaType, SV->getName(), SI); + + // 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 = BinaryOperator::CreateShl(SV, + ConstantInt::get(SV->getType(), ShAmt), + SV->getName(), SI); + Mask <<= ShAmt; + } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { + SV = BinaryOperator::CreateLShr(SV, + ConstantInt::get(SV->getType(),-ShAmt), + SV->getName(), SI); + 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 = BinaryOperator::CreateAnd(Old, ConstantInt::get(~Mask), + Old->getName()+".mask", SI); + SV = BinaryOperator::CreateOr(Old, SV, SV->getName()+".ins", SI); + } + } + 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 (isa(*UI)) { + // Ignore loads, they are always ok. + 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) && !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; +}