#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/LLVMContext.h"
+#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/Loads.h"
+#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Utils/SSAUpdater.h"
+#include "llvm/Support/CallSite.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/IRBuilder.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
+#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
STATISTIC(NumReplaced, "Number of allocas broken up");
STATISTIC(NumPromoted, "Number of allocas promoted");
+STATISTIC(NumAdjusted, "Number of scalar allocas adjusted to allow promotion");
STATISTIC(NumConverted, "Number of aggregates converted to scalar");
STATISTIC(NumGlobals, "Number of allocas copied from constant global");
namespace {
struct SROA : public FunctionPass {
- static char ID; // Pass identification, replacement for typeid
- explicit SROA(signed T = -1) : FunctionPass(&ID) {
+ SROA(int T, bool hasDT, char &ID)
+ : FunctionPass(ID), HasDomTree(hasDT) {
if (T == -1)
SRThreshold = 128;
else
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<DominatorTree>();
- AU.addRequired<DominanceFrontier>();
- AU.setPreservesCFG();
- }
-
private:
+ bool HasDomTree;
TargetData *TD;
-
+
/// DeadInsts - Keep track of instructions we have made dead, so that
/// we can remove them after we are done working.
SmallVector<Value*, 32> DeadInsts;
/// information about the uses. All these fields are initialized to false
/// and set to true when something is learned.
struct AllocaInfo {
+ /// The alloca to promote.
+ AllocaInst *AI;
+
+ /// CheckedPHIs - This is a set of verified PHI nodes, to prevent infinite
+ /// looping and avoid redundant work.
+ SmallPtrSet<PHINode*, 8> CheckedPHIs;
+
/// isUnsafe - This is set to true if the alloca cannot be SROA'd.
bool isUnsafe : 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), isMemCpySrc(false), isMemCpyDst(false) {}
+ /// hasSubelementAccess - This is true if a subelement of the alloca is
+ /// ever accessed, or false if the alloca is only accessed with mem
+ /// intrinsics or load/store that only access the entire alloca at once.
+ bool hasSubelementAccess : 1;
+
+ /// hasALoadOrStore - This is true if there are any loads or stores to it.
+ /// The alloca may just be accessed with memcpy, for example, which would
+ /// not set this.
+ bool hasALoadOrStore : 1;
+
+ explicit AllocaInfo(AllocaInst *ai)
+ : AI(ai), isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false),
+ hasSubelementAccess(false), hasALoadOrStore(false) {}
};
-
+
unsigned SRThreshold;
- void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
+ void MarkUnsafe(AllocaInfo &I, Instruction *User) {
+ I.isUnsafe = true;
+ DEBUG(dbgs() << " Transformation preventing inst: " << *User << '\n');
+ }
bool isSafeAllocaToScalarRepl(AllocaInst *AI);
- void isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
- AllocaInfo &Info);
- void isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t &Offset,
- AllocaInfo &Info);
- void isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize,
- const Type *MemOpType, bool isStore, AllocaInfo &Info);
+ void isSafeForScalarRepl(Instruction *I, uint64_t Offset, AllocaInfo &Info);
+ void isSafePHISelectUseForScalarRepl(Instruction *User, uint64_t Offset,
+ AllocaInfo &Info);
+ void isSafeGEP(GetElementPtrInst *GEPI, uint64_t &Offset, AllocaInfo &Info);
+ void isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
+ const Type *MemOpType, bool isStore, AllocaInfo &Info,
+ Instruction *TheAccess, bool AllowWholeAccess);
bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size);
uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset,
const Type *&IdxTy);
-
- void DoScalarReplacement(AllocaInst *AI,
+
+ void DoScalarReplacement(AllocaInst *AI,
std::vector<AllocaInst*> &WorkList);
void DeleteDeadInstructions();
- AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocaInst *Base);
-
+
void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
SmallVector<AllocaInst*, 32> &NewElts);
void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
SmallVector<AllocaInst*, 32> &NewElts);
void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
SmallVector<AllocaInst*, 32> &NewElts);
+
+ static MemTransferInst *isOnlyCopiedFromConstantGlobal(AllocaInst *AI);
+ };
+
+ // SROA_DT - SROA that uses DominatorTree.
+ struct SROA_DT : public SROA {
+ static char ID;
+ public:
+ SROA_DT(int T = -1) : SROA(T, true, ID) {
+ initializeSROA_DTPass(*PassRegistry::getPassRegistry());
+ }
+
+ // 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<DominatorTree>();
+ AU.setPreservesCFG();
+ }
+ };
+
+ // SROA_SSAUp - SROA that uses SSAUpdater.
+ struct SROA_SSAUp : public SROA {
+ static char ID;
+ public:
+ SROA_SSAUp(int T = -1) : SROA(T, false, ID) {
+ initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry());
+ }
- 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(AllocaInst *AI);
+ // 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.setPreservesCFG();
+ }
};
+
}
-char SROA::ID = 0;
-static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates");
+char SROA_DT::ID = 0;
+char SROA_SSAUp::ID = 0;
+
+INITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl",
+ "Scalar Replacement of Aggregates (DT)", false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_END(SROA_DT, "scalarrepl",
+ "Scalar Replacement of Aggregates (DT)", false, false)
+
+INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa",
+ "Scalar Replacement of Aggregates (SSAUp)", false, false)
+INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa",
+ "Scalar Replacement of Aggregates (SSAUp)", false, false)
// Public interface to the ScalarReplAggregates pass
-FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) {
- return new SROA(Threshold);
+FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold,
+ bool UseDomTree) {
+ if (UseDomTree)
+ return new SROA_DT(Threshold);
+ return new SROA_SSAUp(Threshold);
}
-bool SROA::runOnFunction(Function &F) {
- TD = getAnalysisIfAvailable<TargetData>();
+//===----------------------------------------------------------------------===//
+// Convert To Scalar Optimization.
+//===----------------------------------------------------------------------===//
- bool Changed = performPromotion(F);
+namespace {
+/// ConvertToScalarInfo - This class implements the "Convert To Scalar"
+/// optimization, which scans the uses of an alloca and determines if it can
+/// rewrite it in terms of a single new alloca that can be mem2reg'd.
+class ConvertToScalarInfo {
+ /// AllocaSize - The size of the alloca being considered in bytes.
+ unsigned AllocaSize;
+ const TargetData &TD;
+
+ /// IsNotTrivial - This is set to true if there is some access to the object
+ /// which means that mem2reg can't promote it.
+ bool IsNotTrivial;
+
+ /// VectorTy - This tracks the type that we should promote the vector to if
+ /// it is possible to turn it into a vector. This starts out null, and if it
+ /// isn't possible to turn into a vector type, it gets set to VoidTy.
+ const Type *VectorTy;
+
+ /// HadAVector - True if there is at least one vector access to the alloca.
+ /// We don't want to turn random arrays into vectors and use vector element
+ /// insert/extract, but if there are element accesses to something that is
+ /// also declared as a vector, we do want to promote to a vector.
+ bool HadAVector;
+
+ /// HadNonMemTransferAccess - True if there is at least one access to the
+ /// alloca that is not a MemTransferInst. We don't want to turn structs into
+ /// large integers unless there is some potential for optimization.
+ bool HadNonMemTransferAccess;
+
+public:
+ explicit ConvertToScalarInfo(unsigned Size, const TargetData &td)
+ : AllocaSize(Size), TD(td), IsNotTrivial(false), VectorTy(0),
+ HadAVector(false), HadNonMemTransferAccess(false) { }
+
+ AllocaInst *TryConvert(AllocaInst *AI);
+
+private:
+ bool CanConvertToScalar(Value *V, uint64_t Offset);
+ void MergeInType(const Type *In, uint64_t Offset, bool IsLoadOrStore);
+ bool MergeInVectorType(const VectorType *VInTy, uint64_t Offset);
+ 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);
+};
+} // end anonymous namespace.
+
+
+/// TryConvert - Analyze the specified alloca, and if it is safe to do so,
+/// rewrite it to be a new alloca which is mem2reg'able. This returns the new
+/// alloca if possible or null if not.
+AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
+ // If we can't convert this scalar, or if mem2reg can trivially do it, bail
+ // out.
+ if (!CanConvertToScalar(AI, 0) || !IsNotTrivial)
+ return 0;
+
+ // 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.
+ const Type *NewTy;
+ if (VectorTy && VectorTy->isVectorTy() && HadAVector) {
+ DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
+ << *VectorTy << '\n');
+ NewTy = VectorTy; // Use the vector type.
+ } else {
+ unsigned BitWidth = AllocaSize * 8;
+ if (!HadAVector && !HadNonMemTransferAccess &&
+ !TD.fitsInLegalInteger(BitWidth))
+ return 0;
+
+ DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
+ // Create and insert the integer alloca.
+ NewTy = IntegerType::get(AI->getContext(), BitWidth);
+ }
+ AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
+ ConvertUsesToScalar(AI, NewAI, 0);
+ return NewAI;
+}
- // FIXME: ScalarRepl currently depends on TargetData more than it
- // theoretically needs to. It should be refactored in order to support
- // target-independent IR. Until this is done, just skip the actual
- // scalar-replacement portion of this pass.
- if (!TD) return Changed;
+/// MergeInType - Add the 'In' type to the accumulated vector type (VectorTy)
+/// so far at the offset specified by Offset (which is specified in bytes).
+///
+/// There are three 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 union of vector types with power-of-2 size differences, e.g. a float,
+/// <2 x float> and <4 x float>. Here we turn element accesses into insert
+/// and extract element operations, and <2 x float> accesses into a cast to
+/// <2 x double>, an extract, and a cast back to <2 x float>.
+/// 3) 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. We mark this by setting VectorTy
+/// to VoidTy.
+void ConvertToScalarInfo::MergeInType(const Type *In, uint64_t Offset,
+ bool IsLoadOrStore) {
+ // If we already decided to turn this into a blob of integer memory, there is
+ // nothing to be done.
+ if (VectorTy && VectorTy->isVoidTy())
+ return;
- 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
+ // If this could be contributing to a vector, analyze it.
+
+ // 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<VectorType>(In)) {
+ if (MergeInVectorType(VInTy, Offset))
+ return;
+ } else if (In->isFloatTy() || In->isDoubleTy() ||
+ (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
+ isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
+ // Full width accesses can be ignored, because they can always be turned
+ // into bitcasts.
+ unsigned EltSize = In->getPrimitiveSizeInBits()/8;
+ if (IsLoadOrStore && EltSize == AllocaSize)
+ return;
+ // 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.
+ if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 &&
+ (VectorTy == 0 ||
+ cast<VectorType>(VectorTy)->getElementType()
+ ->getPrimitiveSizeInBits()/8 == EltSize)) {
+ if (VectorTy == 0)
+ VectorTy = VectorType::get(In, AllocaSize/EltSize);
+ return;
+ }
}
- return Changed;
+ // Otherwise, we have a case that we can't handle with an optimized vector
+ // form. We can still turn this into a large integer.
+ VectorTy = Type::getVoidTy(In->getContext());
}
+/// MergeInVectorType - Handles the vector case of MergeInType, returning true
+/// if the type was successfully merged and false otherwise.
+bool ConvertToScalarInfo::MergeInVectorType(const VectorType *VInTy,
+ uint64_t Offset) {
+ // Remember if we saw a vector type.
+ HadAVector = true;
-bool SROA::performPromotion(Function &F) {
- std::vector<AllocaInst*> Allocas;
- DominatorTree &DT = getAnalysis<DominatorTree>();
- DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
+ // TODO: Support nonzero offsets?
+ if (Offset != 0)
+ return false;
- BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
+ // Only allow vectors that are a power-of-2 away from the size of the alloca.
+ if (!isPowerOf2_64(AllocaSize / (VInTy->getBitWidth() / 8)))
+ return false;
- bool Changed = false;
+ // If this the first vector we see, remember the type so that we know the
+ // element size.
+ if (!VectorTy) {
+ VectorTy = VInTy;
+ return true;
+ }
- while (1) {
- Allocas.clear();
+ unsigned BitWidth = cast<VectorType>(VectorTy)->getBitWidth();
+ unsigned InBitWidth = VInTy->getBitWidth();
- // 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<AllocaInst>(I)) // Is it an alloca?
- if (isAllocaPromotable(AI))
- Allocas.push_back(AI);
+ // Vectors of the same size can be converted using a simple bitcast.
+ if (InBitWidth == BitWidth && AllocaSize == (InBitWidth / 8))
+ return true;
- if (Allocas.empty()) break;
+ const Type *ElementTy = cast<VectorType>(VectorTy)->getElementType();
+ const Type *InElementTy = cast<VectorType>(VInTy)->getElementType();
- PromoteMemToReg(Allocas, DT, DF);
- NumPromoted += Allocas.size();
- Changed = true;
+ // Do not allow mixed integer and floating-point accesses from vectors of
+ // different sizes.
+ if (ElementTy->isFloatingPointTy() != InElementTy->isFloatingPointTy())
+ return false;
+
+ if (ElementTy->isFloatingPointTy()) {
+ // Only allow floating-point vectors of different sizes if they have the
+ // same element type.
+ // TODO: This could be loosened a bit, but would anything benefit?
+ if (ElementTy != InElementTy)
+ return false;
+
+ // There are no arbitrary-precision floating-point types, which limits the
+ // number of legal vector types with larger element types that we can form
+ // to bitcast and extract a subvector.
+ // TODO: We could support some more cases with mixed fp128 and double here.
+ if (!(BitWidth == 64 || BitWidth == 128) ||
+ !(InBitWidth == 64 || InBitWidth == 128))
+ return false;
+ } else {
+ assert(ElementTy->isIntegerTy() && "Vector elements must be either integer "
+ "or floating-point.");
+ unsigned BitWidth = ElementTy->getPrimitiveSizeInBits();
+ unsigned InBitWidth = InElementTy->getPrimitiveSizeInBits();
+
+ // Do not allow integer types smaller than a byte or types whose widths are
+ // not a multiple of a byte.
+ if (BitWidth < 8 || InBitWidth < 8 ||
+ BitWidth % 8 != 0 || InBitWidth % 8 != 0)
+ return false;
}
- return Changed;
-}
+ // Pick the largest of the two vector types.
+ if (InBitWidth > BitWidth)
+ VectorTy = VInTy;
-/// 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<StructType>(T))
- return ST->getNumElements();
- return cast<ArrayType>(T)->getNumElements();
+ return true;
}
-// 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<AllocaInst*> 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 (AllocaInst *A = dyn_cast<AllocaInst>(I))
- WorkList.push_back(A);
+/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
+/// its accesses to a 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 ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) {
+ for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
+ Instruction *User = cast<Instruction>(*UI);
- // Process the worklist
- bool Changed = false;
- while (!WorkList.empty()) {
- AllocaInst *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();
+ if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
+ // Don't break volatile loads.
+ if (LI->isVolatile())
+ return false;
+ // Don't touch MMX operations.
+ if (LI->getType()->isX86_MMXTy())
+ return false;
+ HadNonMemTransferAccess = true;
+ MergeInType(LI->getType(), Offset, true);
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)) {
- DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n');
- DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n');
- Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2));
- AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
- TheCopy->eraseFromParent(); // Don't mutate the global.
- AI->eraseFromParent();
- ++NumGlobals;
- Changed = true;
+ if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
+ // Storing the pointer, not into the value?
+ if (SI->getOperand(0) == V || SI->isVolatile()) return false;
+ // Don't touch MMX operations.
+ if (SI->getOperand(0)->getType()->isX86_MMXTy())
+ return false;
+ HadNonMemTransferAccess = true;
+ MergeInType(SI->getOperand(0)->getType(), Offset, 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->getTypeAllocSize(AI->getAllocatedType());
- // Do not promote [0 x %struct].
- if (AllocaSize == 0) continue;
+ if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
+ IsNotTrivial = true; // Can't be mem2reg'd.
+ if (!CanConvertToScalar(BCI, Offset))
+ return false;
+ continue;
+ }
- // Do not promote any struct whose size is too big.
- if (AllocaSize > SRThreshold) continue;
+ if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
+ // If this is a GEP with a variable indices, we can't handle it.
+ if (!GEP->hasAllConstantIndices())
+ return false;
- if ((isa<StructType>(AI->getAllocatedType()) ||
- isa<ArrayType>(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.
- if (isSafeAllocaToScalarRepl(AI)) {
- DoScalarReplacement(AI, WorkList);
- Changed = true;
- continue;
- }
+ // Compute the offset that this GEP adds to the pointer.
+ SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
+ uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
+ &Indices[0], Indices.size());
+ // See if all uses can be converted.
+ if (!CanConvertToScalar(GEP, Offset+GEPOffset))
+ return false;
+ IsNotTrivial = true; // Can't be mem2reg'd.
+ HadNonMemTransferAccess = 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<VectorType>(VectorTy) && HadAVector) {
- DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
- << *VectorTy << '\n');
-
- // Create and insert the vector alloca.
- NewAI = new AllocaInst(VectorTy, 0, "", AI->getParent()->begin());
- ConvertUsesToScalar(AI, NewAI, 0);
- } else {
- DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
-
- // Create and insert the integer alloca.
- const Type *NewTy = IntegerType::get(AI->getContext(), AllocaSize*8);
- NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
- ConvertUsesToScalar(AI, NewAI, 0);
- }
- NewAI->takeName(AI);
- AI->eraseFromParent();
- ++NumConverted;
- Changed = true;
+ // If this is a constant sized memset of a constant value (e.g. 0) we can
+ // handle it.
+ if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
+ // Store of constant value and constant size.
+ if (!isa<ConstantInt>(MSI->getValue()) ||
+ !isa<ConstantInt>(MSI->getLength()))
+ return false;
+ IsNotTrivial = true; // Can't be mem2reg'd.
+ HadNonMemTransferAccess = true;
continue;
}
-
- // Otherwise, couldn't process this alloca.
- }
- return Changed;
-}
+ // 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<MemTransferInst>(User)) {
+ ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
+ if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0)
+ return false;
-/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
-/// predicate, do SROA now.
-void SROA::DoScalarReplacement(AllocaInst *AI,
- std::vector<AllocaInst*> &WorkList) {
- DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
- SmallVector<AllocaInst*, 32> ElementAllocas;
- if (const StructType *ST = dyn_cast<StructType>(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() + "." + Twine(i), AI);
- ElementAllocas.push_back(NA);
- WorkList.push_back(NA); // Add to worklist for recursive processing
- }
- } else {
- const ArrayType *AT = cast<ArrayType>(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() + "." + Twine(i), AI);
- ElementAllocas.push_back(NA);
- WorkList.push_back(NA); // Add to worklist for recursive processing
+ IsNotTrivial = true; // Can't be mem2reg'd.
+ continue;
}
- }
-
- // Now that we have created the new alloca instructions, rewrite all the
- // uses of the old alloca.
- RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
- // Now erase any instructions that were made dead while rewriting the alloca.
- DeleteDeadInstructions();
- AI->eraseFromParent();
+ // Otherwise, we cannot handle this!
+ return false;
+ }
- NumReplaced++;
+ return true;
}
-/// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
-/// recursively including all their operands that become trivially dead.
-void SROA::DeleteDeadInstructions() {
- while (!DeadInsts.empty()) {
- Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
+/// 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 ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
+ uint64_t Offset) {
+ while (!Ptr->use_empty()) {
+ Instruction *User = cast<Instruction>(Ptr->use_back());
- for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
- if (Instruction *U = dyn_cast<Instruction>(*OI)) {
- // Zero out the operand and see if it becomes trivially dead.
- // (But, don't add allocas to the dead instruction list -- they are
- // already on the worklist and will be deleted separately.)
- *OI = 0;
- if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
- DeadInsts.push_back(U);
- }
+ if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
+ ConvertUsesToScalar(CI, NewAI, Offset);
+ CI->eraseFromParent();
+ continue;
+ }
- I->eraseFromParent();
- }
-}
-
-/// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
-/// performing scalar replacement of alloca AI. The results are flagged in
-/// the Info parameter. Offset indicates the position within AI that is
-/// referenced by this instruction.
-void SROA::isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
- AllocaInfo &Info) {
- for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
- Instruction *User = cast<Instruction>(*UI);
+ if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
+ // Compute the offset that this GEP adds to the pointer.
+ SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
+ uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
+ &Indices[0], Indices.size());
+ ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
+ GEP->eraseFromParent();
+ continue;
+ }
- if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
- isSafeForScalarRepl(BC, AI, Offset, Info);
- } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
- uint64_t GEPOffset = Offset;
- isSafeGEP(GEPI, AI, GEPOffset, Info);
- if (!Info.isUnsafe)
- isSafeForScalarRepl(GEPI, AI, GEPOffset, Info);
- } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) {
- ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
- if (Length)
- isSafeMemAccess(AI, Offset, Length->getZExtValue(), 0,
- UI.getOperandNo() == 1, Info);
- else
- MarkUnsafe(Info);
- } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
- if (!LI->isVolatile()) {
- const Type *LIType = LI->getType();
- isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(LIType),
- LIType, false, Info);
- } else
- MarkUnsafe(Info);
- } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
- // Store is ok if storing INTO the pointer, not storing the pointer
- if (!SI->isVolatile() && SI->getOperand(0) != I) {
- const Type *SIType = SI->getOperand(0)->getType();
- isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(SIType),
- SIType, true, Info);
- } else
- MarkUnsafe(Info);
- } else {
- DEBUG(errs() << " Transformation preventing inst: " << *User << '\n');
- MarkUnsafe(Info);
+ IRBuilder<> Builder(User);
+
+ if (LoadInst *LI = dyn_cast<LoadInst>(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 (Info.isUnsafe) return;
- }
-}
-/// isSafeGEP - Check if a GEP instruction can be handled for scalar
-/// replacement. It is safe when all the indices are constant, in-bounds
-/// references, and when the resulting offset corresponds to an element within
-/// the alloca type. The results are flagged in the Info parameter. Upon
-/// return, Offset is adjusted as specified by the GEP indices.
-void SROA::isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI,
- uint64_t &Offset, AllocaInfo &Info) {
- gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
- if (GEPIt == E)
- return;
+ if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
+ assert(SI->getOperand(0) != Ptr && "Consistency error!");
+ Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
+ Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
+ Builder);
+ Builder.CreateStore(New, NewAI);
+ SI->eraseFromParent();
- // Walk through the GEP type indices, checking the types that this indexes
- // into.
- for (; GEPIt != E; ++GEPIt) {
- // Ignore struct elements, no extra checking needed for these.
- if (isa<StructType>(*GEPIt))
+ // If the load we just inserted is now dead, then the inserted store
+ // overwrote the entire thing.
+ if (Old->use_empty())
+ Old->eraseFromParent();
continue;
+ }
- ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
- if (!IdxVal)
- return MarkUnsafe(Info);
- }
+ // 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<MemSetInst>(User)) {
+ assert(MSI->getRawDest() == Ptr && "Consistency error!");
+ unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
+ if (NumBytes != 0) {
+ unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
- // Compute the offset due to this GEP and check if the alloca has a
- // component element at that offset.
- SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
- Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
- &Indices[0], Indices.size());
- if (!TypeHasComponent(AI->getAllocatedType(), Offset, 0))
- MarkUnsafe(Info);
-}
+ // Compute the value replicated the right number of times.
+ APInt APVal(NumBytes*8, Val);
-/// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
-/// alloca or has an offset and size that corresponds to a component element
-/// within it. The offset checked here may have been formed from a GEP with a
-/// pointer bitcasted to a different type.
-void SROA::isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize,
- const Type *MemOpType, bool isStore,
- AllocaInfo &Info) {
- // Check if this is a load/store of the entire alloca.
- if (Offset == 0 && MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) {
- bool UsesAggregateType = (MemOpType == AI->getAllocatedType());
- // This is safe for MemIntrinsics (where MemOpType is 0), integer types
- // (which are essentially the same as the MemIntrinsics, especially with
- // regard to copying padding between elements), or references using the
- // aggregate type of the alloca.
- if (!MemOpType || isa<IntegerType>(MemOpType) || UsesAggregateType) {
- if (!UsesAggregateType) {
- if (isStore)
- Info.isMemCpyDst = true;
- else
- Info.isMemCpySrc = true;
+ // Splat the value if non-zero.
+ if (Val)
+ for (unsigned i = 1; i != NumBytes; ++i)
+ APVal |= APVal << 8;
+
+ Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
+ Value *New = ConvertScalar_InsertValue(
+ ConstantInt::get(User->getContext(), APVal),
+ Old, Offset, Builder);
+ Builder.CreateStore(New, NewAI);
+
+ // If the load we just inserted is now dead, then the memset overwrote
+ // the entire thing.
+ if (Old->use_empty())
+ Old->eraseFromParent();
}
- return;
+ MSI->eraseFromParent();
+ continue;
}
- }
- // Check if the offset/size correspond to a component within the alloca type.
- const Type *T = AI->getAllocatedType();
- if (TypeHasComponent(T, Offset, MemSize))
- return;
- return MarkUnsafe(Info);
-}
-
-/// TypeHasComponent - Return true if T has a component type with the
-/// specified offset and size. If Size is zero, do not check the size.
-bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) {
- const Type *EltTy;
- uint64_t EltSize;
- if (const StructType *ST = dyn_cast<StructType>(T)) {
- const StructLayout *Layout = TD->getStructLayout(ST);
- unsigned EltIdx = Layout->getElementContainingOffset(Offset);
- EltTy = ST->getContainedType(EltIdx);
- EltSize = TD->getTypeAllocSize(EltTy);
- Offset -= Layout->getElementOffset(EltIdx);
- } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
- EltTy = AT->getElementType();
- EltSize = TD->getTypeAllocSize(EltTy);
- if (Offset >= AT->getNumElements() * EltSize)
- return false;
- Offset %= EltSize;
- } else {
- return false;
- }
- if (Offset == 0 && (Size == 0 || EltSize == Size))
- return true;
- // Check if the component spans multiple elements.
- if (Offset + Size > EltSize)
- return false;
- return TypeHasComponent(EltTy, Offset, Size);
-}
+ // 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<MemTransferInst>(User)) {
+ assert(Offset == 0 && "must be store to start of alloca");
-/// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
-/// the instruction I, which references it, to use the separate elements.
-/// Offset indicates the position within AI that is referenced by this
-/// instruction.
-void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
- SmallVector<AllocaInst*, 32> &NewElts) {
- for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
- Instruction *User = cast<Instruction>(*UI);
+ // 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<AllocaInst>(GetUnderlyingObject(Ptr, &TD, 0));
- if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
- RewriteBitCast(BC, AI, Offset, NewElts);
- } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
- RewriteGEP(GEPI, AI, Offset, NewElts);
- } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
- ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
- uint64_t MemSize = Length->getZExtValue();
- if (Offset == 0 &&
- MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
- RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
- // Otherwise the intrinsic can only touch a single element and the
- // address operand will be updated, so nothing else needs to be done.
- } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
- const Type *LIType = LI->getType();
- if (LIType == AI->getAllocatedType()) {
- // 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)
- Value *Insert = UndefValue::get(LIType);
- for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
- Value *Load = new LoadInst(NewElts[i], "load", LI);
- Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
+ if (GetUnderlyingObject(MTI->getSource(), &TD, 0) != 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();
+ const PointerType* SPTy = cast<PointerType>(SrcPtr->getType());
+ const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
+ if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
+ AIPTy = PointerType::get(AIPTy->getElementType(),
+ SPTy->getAddressSpace());
}
- LI->replaceAllUsesWith(Insert);
- DeadInsts.push_back(LI);
- } else if (isa<IntegerType>(LIType) &&
- TD->getTypeAllocSize(LIType) ==
- TD->getTypeAllocSize(AI->getAllocatedType())) {
- // If this is a load of the entire alloca to an integer, rewrite it.
- RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
- }
- } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
- Value *Val = SI->getOperand(0);
- const Type *SIType = Val->getType();
- if (SIType == AI->getAllocatedType()) {
- // 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)
- for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
- Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
- new StoreInst(Extract, NewElts[i], SI);
+ SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy);
+
+ LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
+ SrcVal->setAlignment(MTI->getAlignment());
+ Builder.CreateStore(SrcVal, NewAI);
+ } else if (GetUnderlyingObject(MTI->getDest(), &TD, 0) != 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");
+
+ const PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType());
+ const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
+ if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
+ AIPTy = PointerType::get(AIPTy->getElementType(),
+ DPTy->getAddressSpace());
}
- DeadInsts.push_back(SI);
- } else if (isa<IntegerType>(SIType) &&
- TD->getTypeAllocSize(SIType) ==
- TD->getTypeAllocSize(AI->getAllocatedType())) {
- // If this is a store of the entire alloca from an integer, rewrite it.
- RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
+ Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy);
+
+ StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
+ NewStore->setAlignment(MTI->getAlignment());
+ } else {
+ // Noop transfer. Src == Dst
}
+
+ MTI->eraseFromParent();
+ continue;
}
+
+ llvm_unreachable("Unsupported operation!");
}
}
-/// RewriteBitCast - Update a bitcast reference to the alloca being replaced
-/// and recursively continue updating all of its uses.
-void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
- SmallVector<AllocaInst*, 32> &NewElts) {
- RewriteForScalarRepl(BC, AI, Offset, NewElts);
- if (BC->getOperand(0) != AI)
- return;
+/// getScaledElementType - Gets a scaled element type for a partial vector
+/// access of an alloca. The input type must be an integer or float, and
+/// the resulting type must be an integer, float or double.
+static const Type *getScaledElementType(const Type *OldTy,
+ unsigned NewBitWidth) {
+ assert((OldTy->isIntegerTy() || OldTy->isFloatTy()) && "Partial vector "
+ "accesses must be scaled from integer or float elements.");
- // The bitcast references the original alloca. Replace its uses with
- // references to the first new element alloca.
- Instruction *Val = NewElts[0];
- if (Val->getType() != BC->getDestTy()) {
- Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
- Val->takeName(BC);
- }
- BC->replaceAllUsesWith(Val);
- DeadInsts.push_back(BC);
-}
+ LLVMContext &Context = OldTy->getContext();
-/// FindElementAndOffset - Return the index of the element containing Offset
-/// within the specified type, which must be either a struct or an array.
-/// Sets T to the type of the element and Offset to the offset within that
-/// element. IdxTy is set to the type of the index result to be used in a
-/// GEP instruction.
-uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset,
- const Type *&IdxTy) {
- uint64_t Idx = 0;
- if (const StructType *ST = dyn_cast<StructType>(T)) {
- const StructLayout *Layout = TD->getStructLayout(ST);
- Idx = Layout->getElementContainingOffset(Offset);
- T = ST->getContainedType(Idx);
- Offset -= Layout->getElementOffset(Idx);
- IdxTy = Type::getInt32Ty(T->getContext());
- return Idx;
- }
- const ArrayType *AT = cast<ArrayType>(T);
- T = AT->getElementType();
- uint64_t EltSize = TD->getTypeAllocSize(T);
- Idx = Offset / EltSize;
- Offset -= Idx * EltSize;
- IdxTy = Type::getInt64Ty(T->getContext());
- return Idx;
+ if (OldTy->isIntegerTy())
+ return Type::getIntNTy(Context, NewBitWidth);
+ if (NewBitWidth == 32)
+ return Type::getFloatTy(Context);
+ if (NewBitWidth == 64)
+ return Type::getDoubleTy(Context);
+
+ llvm_unreachable("Invalid type for a partial vector access of an alloca!");
}
-/// RewriteGEP - Check if this GEP instruction moves the pointer across
-/// elements of the alloca that are being split apart, and if so, rewrite
-/// the GEP to be relative to the new element.
-void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
- SmallVector<AllocaInst*, 32> &NewElts) {
- uint64_t OldOffset = Offset;
- SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
- Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
- &Indices[0], Indices.size());
+/// 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 *ConvertToScalarInfo::
+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;
- RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
+ // 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<VectorType>(FromVal->getType())) {
+ unsigned ToTypeSize = TD.getTypeAllocSize(ToType);
+ if (ToTypeSize == AllocaSize)
+ return Builder.CreateBitCast(FromVal, ToType, "tmp");
- const Type *T = AI->getAllocatedType();
- const Type *IdxTy;
- uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
- if (GEPI->getOperand(0) == AI)
- OldIdx = ~0ULL; // Force the GEP to be rewritten.
+ if (ToType->isVectorTy()) {
+ assert(isPowerOf2_64(AllocaSize / ToTypeSize) &&
+ "Partial vector access of an alloca must have a power-of-2 size "
+ "ratio.");
+ assert(Offset == 0 && "Can't extract a value of a smaller vector type "
+ "from a nonzero offset.");
+
+ const Type *ToElementTy = cast<VectorType>(ToType)->getElementType();
+ const Type *CastElementTy = getScaledElementType(ToElementTy,
+ ToTypeSize * 8);
+ unsigned NumCastVectorElements = AllocaSize / ToTypeSize;
+
+ LLVMContext &Context = FromVal->getContext();
+ const Type *CastTy = VectorType::get(CastElementTy,
+ NumCastVectorElements);
+ Value *Cast = Builder.CreateBitCast(FromVal, CastTy, "tmp");
+ Value *Extract = Builder.CreateExtractElement(Cast, ConstantInt::get(
+ Type::getInt32Ty(Context), 0), "tmp");
+ return Builder.CreateBitCast(Extract, ToType, "tmp");
+ }
- T = AI->getAllocatedType();
- uint64_t EltOffset = Offset;
- uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
+ // Otherwise it must be an element access.
+ unsigned Elt = 0;
+ if (Offset) {
+ unsigned EltSize = TD.getTypeAllocSizeInBits(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::getInt32Ty(FromVal->getContext()), Elt), "tmp");
+ if (V->getType() != ToType)
+ V = Builder.CreateBitCast(V, ToType, "tmp");
+ return V;
+ }
- // If this GEP does not move the pointer across elements of the alloca
- // being split, then it does not needs to be rewritten.
- if (Idx == OldIdx)
- return;
+ // 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<StructType>(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;
+ }
- const Type *i32Ty = Type::getInt32Ty(AI->getContext());
- SmallVector<Value*, 8> NewArgs;
- NewArgs.push_back(Constant::getNullValue(i32Ty));
- while (EltOffset != 0) {
- uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
- NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
+ if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
+ uint64_t EltSize = TD.getTypeAllocSizeInBits(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;
}
- Instruction *Val = NewElts[Idx];
- if (NewArgs.size() > 1) {
- Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(),
- NewArgs.end(), "", GEPI);
- Val->takeName(GEPI);
+
+ // Otherwise, this must be a union that was converted to an integer value.
+ const IntegerType *NTy = cast<IntegerType>(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;
}
- if (Val->getType() != GEPI->getType())
- Val = new BitCastInst(Val, GEPI->getType(), Val->getNameStr(), GEPI);
- GEPI->replaceAllUsesWith(Val);
- DeadInsts.push_back(GEPI);
-}
-/// 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 *Inst,
- AllocaInst *AI,
- SmallVector<AllocaInst*, 32> &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;
- LLVMContext &Context = MI->getContext();
- unsigned MemAlignment = MI->getAlignment();
- if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
- if (Inst == MTI->getRawDest())
- OtherPtr = MTI->getRawSource();
- else {
- assert(Inst == MTI->getRawSource());
- OtherPtr = MTI->getRawDest();
- }
+ // 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(FromVal->getContext(),
+ LIBitWidth), "tmp");
+ else if (LIBitWidth > NTy->getBitWidth())
+ FromVal =
+ Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
+ LIBitWidth), "tmp");
+
+ // If the result is an integer, this is a trunc or bitcast.
+ if (ToType->isIntegerTy()) {
+ // Should be done.
+ } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
+ // 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;
+}
- // 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) {
+/// 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 *ConvertToScalarInfo::
+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();
+ LLVMContext &Context = Old->getContext();
- // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
- // optimization, but it's also required to detect the corner case where
- // both pointer operands are referencing the same memory, and where
- // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
- // function is only called for mem intrinsics that access the whole
- // aggregate, so non-zero GEPs are not an issue here.)
- while (1) {
- if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr)) {
- OtherPtr = BC->getOperand(0);
- continue;
- }
- if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr)) {
- // All zero GEPs are effectively bitcasts.
- if (GEP->hasAllZeroIndices()) {
- OtherPtr = GEP->getOperand(0);
- continue;
- }
- }
- break;
- }
- // Copying the alloca to itself is a no-op: just delete it.
- if (OtherPtr == AI || OtherPtr == NewElts[0]) {
- // This code will run twice for a no-op memcpy -- once for each operand.
- // Put only one reference to MI on the DeadInsts list.
- for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
- E = DeadInsts.end(); I != E; ++I)
- if (*I == MI) return;
- DeadInsts.push_back(MI);
- return;
+ if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
+ uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy);
+ uint64_t ValSize = TD.getTypeAllocSizeInBits(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");
+
+ if (SV->getType()->isVectorTy() && isPowerOf2_64(VecSize / ValSize)) {
+ assert(Offset == 0 && "Can't insert a value of a smaller vector type at "
+ "a nonzero offset.");
+
+ const Type *ToElementTy =
+ cast<VectorType>(SV->getType())->getElementType();
+ const Type *CastElementTy = getScaledElementType(ToElementTy, ValSize);
+ unsigned NumCastVectorElements = VecSize / ValSize;
+
+ LLVMContext &Context = SV->getContext();
+ const Type *OldCastTy = VectorType::get(CastElementTy,
+ NumCastVectorElements);
+ Value *OldCast = Builder.CreateBitCast(Old, OldCastTy, "tmp");
+
+ Value *SVCast = Builder.CreateBitCast(SV, CastElementTy, "tmp");
+ Value *Insert =
+ Builder.CreateInsertElement(OldCast, SVCast, ConstantInt::get(
+ Type::getInt32Ty(Context), 0), "tmp");
+ return Builder.CreateBitCast(Insert, AllocaType, "tmp");
}
-
- if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(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);
+
+ uint64_t EltSize = TD.getTypeAllocSizeInBits(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::getInt32Ty(SV->getContext()), Elt),
+ "tmp");
+ return SV;
}
-
- // Process each element of the aggregate.
- Value *TheFn = MI->getOperand(0);
- const Type *BytePtrTy = MI->getRawDest()->getType();
- bool SROADest = MI->getRawDest() == Inst;
-
- Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
- 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::getInt32Ty(MI->getContext()), i) };
- OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2,
- OtherPtr->getNameStr()+"."+Twine(i),
- MI);
- uint64_t EltOffset;
- const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
- if (const StructType *ST =
- dyn_cast<StructType>(OtherPtrTy->getElementType())) {
- EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
- } else {
- const Type *EltTy =
- cast<SequentialType>(OtherPtr->getType())->getElementType();
- EltOffset = TD->getTypeAllocSize(EltTy)*i;
+ // If SV is a first-class aggregate value, insert each value recursively.
+ if (const StructType *ST = dyn_cast<StructType>(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<ArrayType>(SV->getType())) {
+ uint64_t EltSize = TD.getTypeAllocSizeInBits(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()->isFloatingPointTy() || SV->getType()->isVectorTy())
+ SV = Builder.CreateBitCast(SV,
+ IntegerType::get(SV->getContext(),SrcWidth), "tmp");
+ else if (SV->getType()->isPointerTy())
+ SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "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(Context, ~Mask), "mask");
+ SV = Builder.CreateOr(Old, SV, "ins");
+ }
+ return SV;
+}
+
+
+//===----------------------------------------------------------------------===//
+// SRoA Driver
+//===----------------------------------------------------------------------===//
+
+
+bool SROA::runOnFunction(Function &F) {
+ TD = getAnalysisIfAvailable<TargetData>();
+
+ bool Changed = performPromotion(F);
+
+ // FIXME: ScalarRepl currently depends on TargetData more than it
+ // theoretically needs to. It should be refactored in order to support
+ // target-independent IR. Until this is done, just skip the actual
+ // scalar-replacement portion of this pass.
+ if (!TD) return Changed;
+
+ 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;
+}
+
+namespace {
+class AllocaPromoter : public LoadAndStorePromoter {
+ AllocaInst *AI;
+public:
+ AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S)
+ : LoadAndStorePromoter(Insts, S), AI(0) {}
+
+ void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) {
+ // Remember which alloca we're promoting (for isInstInList).
+ this->AI = AI;
+ LoadAndStorePromoter::run(Insts);
+ AI->eraseFromParent();
+ }
+
+ virtual bool isInstInList(Instruction *I,
+ const SmallVectorImpl<Instruction*> &Insts) const {
+ if (LoadInst *LI = dyn_cast<LoadInst>(I))
+ return LI->getOperand(0) == AI;
+ return cast<StoreInst>(I)->getPointerOperand() == AI;
+ }
+};
+} // end anon namespace
+
+/// isSafeSelectToSpeculate - Select instructions that use an alloca and are
+/// subsequently loaded can be rewritten to load both input pointers and then
+/// select between the result, allowing the load of the alloca to be promoted.
+/// From this:
+/// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
+/// %V = load i32* %P2
+/// to:
+/// %V1 = load i32* %Alloca -> will be mem2reg'd
+/// %V2 = load i32* %Other
+/// %V = select i1 %cond, i32 %V1, i32 %V2
+///
+/// We can do this to a select if its only uses are loads and if the operand to
+/// the select can be loaded unconditionally.
+static bool isSafeSelectToSpeculate(SelectInst *SI, const TargetData *TD) {
+ bool TDerefable = SI->getTrueValue()->isDereferenceablePointer();
+ bool FDerefable = SI->getFalseValue()->isDereferenceablePointer();
+
+ for (Value::use_iterator UI = SI->use_begin(), UE = SI->use_end();
+ UI != UE; ++UI) {
+ LoadInst *LI = dyn_cast<LoadInst>(*UI);
+ if (LI == 0 || LI->isVolatile()) return false;
+
+ // Both operands to the select need to be dereferencable, either absolutely
+ // (e.g. allocas) or at this point because we can see other accesses to it.
+ if (!TDerefable && !isSafeToLoadUnconditionally(SI->getTrueValue(), LI,
+ LI->getAlignment(), TD))
+ return false;
+ if (!FDerefable && !isSafeToLoadUnconditionally(SI->getFalseValue(), LI,
+ LI->getAlignment(), TD))
+ return false;
+ }
+
+ return true;
+}
+
+/// isSafePHIToSpeculate - PHI instructions that use an alloca and are
+/// subsequently loaded can be rewritten to load both input pointers in the pred
+/// blocks and then PHI the results, allowing the load of the alloca to be
+/// promoted.
+/// From this:
+/// %P2 = phi [i32* %Alloca, i32* %Other]
+/// %V = load i32* %P2
+/// to:
+/// %V1 = load i32* %Alloca -> will be mem2reg'd
+/// ...
+/// %V2 = load i32* %Other
+/// ...
+/// %V = phi [i32 %V1, i32 %V2]
+///
+/// We can do this to a select if its only uses are loads and if the operand to
+/// the select can be loaded unconditionally.
+static bool isSafePHIToSpeculate(PHINode *PN, const TargetData *TD) {
+ // For now, we can only do this promotion if the load is in the same block as
+ // the PHI, and if there are no stores between the phi and load.
+ // TODO: Allow recursive phi users.
+ // TODO: Allow stores.
+ BasicBlock *BB = PN->getParent();
+ unsigned MaxAlign = 0;
+ for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end();
+ UI != UE; ++UI) {
+ LoadInst *LI = dyn_cast<LoadInst>(*UI);
+ if (LI == 0 || LI->isVolatile()) return false;
+
+ // For now we only allow loads in the same block as the PHI. This is a
+ // common case that happens when instcombine merges two loads through a PHI.
+ if (LI->getParent() != BB) return false;
+
+ // Ensure that there are no instructions between the PHI and the load that
+ // could store.
+ for (BasicBlock::iterator BBI = PN; &*BBI != LI; ++BBI)
+ if (BBI->mayWriteToMemory())
+ return false;
+
+ MaxAlign = std::max(MaxAlign, LI->getAlignment());
+ }
+
+ // Okay, we know that we have one or more loads in the same block as the PHI.
+ // We can transform this if it is safe to push the loads into the predecessor
+ // blocks. The only thing to watch out for is that we can't put a possibly
+ // trapping load in the predecessor if it is a critical edge.
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ BasicBlock *Pred = PN->getIncomingBlock(i);
+
+ // If the predecessor has a single successor, then the edge isn't critical.
+ if (Pred->getTerminator()->getNumSuccessors() == 1)
+ continue;
+
+ Value *InVal = PN->getIncomingValue(i);
+
+ // If the InVal is an invoke in the pred, we can't put a load on the edge.
+ if (InvokeInst *II = dyn_cast<InvokeInst>(InVal))
+ if (II->getParent() == Pred)
+ return false;
+
+ // If this pointer is always safe to load, or if we can prove that there is
+ // already a load in the block, then we can move the load to the pred block.
+ if (InVal->isDereferenceablePointer() ||
+ isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign, TD))
+ continue;
+
+ return false;
+ }
+
+ return true;
+}
+
+
+/// tryToMakeAllocaBePromotable - This returns true if the alloca only has
+/// direct (non-volatile) loads and stores to it. If the alloca is close but
+/// not quite there, this will transform the code to allow promotion. As such,
+/// it is a non-pure predicate.
+static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const TargetData *TD) {
+ SetVector<Instruction*, SmallVector<Instruction*, 4>,
+ SmallPtrSet<Instruction*, 4> > InstsToRewrite;
+
+ for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end();
+ UI != UE; ++UI) {
+ User *U = *UI;
+ if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
+ if (LI->isVolatile())
+ return false;
+ continue;
+ }
+
+ if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
+ if (SI->getOperand(0) == AI || SI->isVolatile())
+ return false; // Don't allow a store OF the AI, only INTO the AI.
+ continue;
+ }
+
+ if (SelectInst *SI = dyn_cast<SelectInst>(U)) {
+ // If the condition being selected on is a constant, fold the select, yes
+ // this does (rarely) happen early on.
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) {
+ Value *Result = SI->getOperand(1+CI->isZero());
+ SI->replaceAllUsesWith(Result);
+ SI->eraseFromParent();
+
+ // This is very rare and we just scrambled the use list of AI, start
+ // over completely.
+ return tryToMakeAllocaBePromotable(AI, TD);
}
+
+ // If it is safe to turn "load (select c, AI, ptr)" into a select of two
+ // loads, then we can transform this by rewriting the select.
+ if (!isSafeSelectToSpeculate(SI, TD))
+ return false;
- // 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);
+ InstsToRewrite.insert(SI);
+ continue;
}
- Value *EltPtr = NewElts[i];
- const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
-
- // If we got down to a scalar, insert a load or store as appropriate.
- if (EltTy->isSingleValueType()) {
- if (isa<MemTransferInst>(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);
- }
+ if (PHINode *PN = dyn_cast<PHINode>(U)) {
+ if (PN->use_empty()) { // Dead PHIs can be stripped.
+ InstsToRewrite.insert(PN);
continue;
}
- assert(isa<MemSetInst>(MI));
- // If the stored element is zero (common case), just store a null
- // constant.
- Constant *StoreVal;
- if (ConstantInt *CI = dyn_cast<ConstantInt>(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->getScalarType();
+ // If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads
+ // in the pred blocks, then we can transform this by rewriting the PHI.
+ if (!isSafePHIToSpeculate(PN, TD))
+ return false;
+
+ InstsToRewrite.insert(PN);
+ continue;
+ }
+
+ return false;
+ }
- // 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(Context, TotalVal);
- if (isa<PointerType>(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<VectorType>(ValTy)->getNumElements();
- SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
- StoreVal = ConstantVector::get(&Elts[0], NumElts);
- }
+ // If there are no instructions to rewrite, then all uses are load/stores and
+ // we're done!
+ if (InstsToRewrite.empty())
+ return true;
+
+ // If we have instructions that need to be rewritten for this to be promotable
+ // take care of it now.
+ for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) {
+ if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) {
+ // Selects in InstsToRewrite only have load uses. Rewrite each as two
+ // loads with a new select.
+ while (!SI->use_empty()) {
+ LoadInst *LI = cast<LoadInst>(SI->use_back());
+
+ IRBuilder<> Builder(LI);
+ LoadInst *TrueLoad =
+ Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t");
+ LoadInst *FalseLoad =
+ Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".t");
+
+ // Transfer alignment and TBAA info if present.
+ TrueLoad->setAlignment(LI->getAlignment());
+ FalseLoad->setAlignment(LI->getAlignment());
+ if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) {
+ TrueLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
+ FalseLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
}
- new StoreInst(StoreVal, EltPtr, MI);
- continue;
+
+ Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad);
+ V->takeName(LI);
+ LI->replaceAllUsesWith(V);
+ LI->eraseFromParent();
}
- // Otherwise, if we're storing a byte variable, use a memset call for
- // this element.
+
+ // Now that all the loads are gone, the select is gone too.
+ SI->eraseFromParent();
+ continue;
}
- // Cast the element pointer to BytePtrTy.
- if (EltPtr->getType() != BytePtrTy)
- EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI);
+ // Otherwise, we have a PHI node which allows us to push the loads into the
+ // predecessors.
+ PHINode *PN = cast<PHINode>(InstsToRewrite[i]);
+ if (PN->use_empty()) {
+ PN->eraseFromParent();
+ continue;
+ }
- // Cast the other pointer (if we have one) to BytePtrTy.
- if (OtherElt && OtherElt->getType() != BytePtrTy)
- OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(),
- MI);
+ const Type *LoadTy = cast<PointerType>(PN->getType())->getElementType();
+ PHINode *NewPN = PHINode::Create(LoadTy, PN->getNumIncomingValues(),
+ PN->getName()+".ld", PN);
+
+ // Get the TBAA tag and alignment to use from one of the loads. It doesn't
+ // matter which one we get and if any differ, it doesn't matter.
+ LoadInst *SomeLoad = cast<LoadInst>(PN->use_back());
+ MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa);
+ unsigned Align = SomeLoad->getAlignment();
- unsigned EltSize = TD->getTypeAllocSize(EltTy);
+ // Rewrite all loads of the PN to use the new PHI.
+ while (!PN->use_empty()) {
+ LoadInst *LI = cast<LoadInst>(PN->use_back());
+ LI->replaceAllUsesWith(NewPN);
+ LI->eraseFromParent();
+ }
- // Finally, insert the meminst for this element.
- if (isa<MemTransferInst>(MI)) {
- Value *Ops[] = {
- SROADest ? EltPtr : OtherElt, // Dest ptr
- SROADest ? OtherElt : EltPtr, // Src ptr
- ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
- // Align
- ConstantInt::get(Type::getInt32Ty(MI->getContext()), OtherEltAlign)
- };
- CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
- } else {
- assert(isa<MemSetInst>(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);
+ // Inject loads into all of the pred blocks. Keep track of which blocks we
+ // insert them into in case we have multiple edges from the same block.
+ DenseMap<BasicBlock*, LoadInst*> InsertedLoads;
+
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ BasicBlock *Pred = PN->getIncomingBlock(i);
+ LoadInst *&Load = InsertedLoads[Pred];
+ if (Load == 0) {
+ Load = new LoadInst(PN->getIncomingValue(i),
+ PN->getName() + "." + Pred->getName(),
+ Pred->getTerminator());
+ Load->setAlignment(Align);
+ if (TBAATag) Load->setMetadata(LLVMContext::MD_tbaa, TBAATag);
+ }
+
+ NewPN->addIncoming(Load, Pred);
}
+
+ PN->eraseFromParent();
}
- DeadInsts.push_back(MI);
+
+ ++NumAdjusted;
+ return true;
}
-/// RewriteStoreUserOfWholeAlloca - We found a 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, AllocaInst *AI,
- SmallVector<AllocaInst*, 32> &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->getAllocatedType();
- uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
-
- // Handle tail padding by extending the operand
- if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
- SrcVal = new ZExtInst(SrcVal,
- IntegerType::get(SI->getContext(), AllocaSizeBits),
- "", SI);
- DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
- << '\n');
+bool SROA::performPromotion(Function &F) {
+ std::vector<AllocaInst*> Allocas;
+ DominatorTree *DT = 0;
+ if (HasDomTree)
+ DT = &getAnalysis<DominatorTree>();
- // 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<StructType>(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->getTypeAllocSizeInBits(FieldTy);
-
- Value *EltVal = SrcVal;
- if (Shift) {
- Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
- EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
- "sroa.store.elt", SI);
+ BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
+
+ bool Changed = false;
+ SmallVector<Instruction*, 64> Insts;
+ 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<AllocaInst>(I)) // Is it an alloca?
+ if (tryToMakeAllocaBePromotable(AI, TD))
+ Allocas.push_back(AI);
+
+ if (Allocas.empty()) break;
+
+ if (HasDomTree)
+ PromoteMemToReg(Allocas, *DT);
+ else {
+ SSAUpdater SSA;
+ for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
+ AllocaInst *AI = Allocas[i];
+
+ // Build list of instructions to promote.
+ for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
+ UI != E; ++UI)
+ Insts.push_back(cast<Instruction>(*UI));
+
+ AllocaPromoter(Insts, SSA).run(AI, Insts);
+ Insts.clear();
}
+ }
+ NumPromoted += Allocas.size();
+ Changed = true;
+ }
+
+ return Changed;
+}
+
+
+/// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
+/// SROA. It must be a struct or array type with a small number of elements.
+static bool ShouldAttemptScalarRepl(AllocaInst *AI) {
+ const Type *T = AI->getAllocatedType();
+ // Do not promote any struct into more than 32 separate vars.
+ if (const StructType *ST = dyn_cast<StructType>(T))
+ return ST->getNumElements() <= 32;
+ // Arrays are much less likely to be safe for SROA; only consider
+ // them if they are very small.
+ if (const ArrayType *AT = dyn_cast<ArrayType>(T))
+ return AT->getNumElements() <= 8;
+ return false;
+}
+
+
+// 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<AllocaInst*> WorkList;
+
+ // Scan the entry basic block, adding allocas to the worklist.
+ BasicBlock &BB = F.getEntryBlock();
+ for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
+ if (AllocaInst *A = dyn_cast<AllocaInst>(I))
+ WorkList.push_back(A);
+
+ // Process the worklist
+ bool Changed = false;
+ while (!WorkList.empty()) {
+ AllocaInst *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();
+ Changed = true;
+ 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 (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
+ DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n');
+ DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n');
+ Constant *TheSrc = cast<Constant>(TheCopy->getSource());
+ 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->getTypeAllocSize(AI->getAllocatedType());
+
+ // Do not promote [0 x %struct].
+ if (AllocaSize == 0) continue;
+
+ // Do not promote any struct whose size is too big.
+ if (AllocaSize > SRThreshold) continue;
+
+ // If the alloca looks like a good candidate for scalar replacement, and if
+ // all its users can be transformed, then split up the aggregate into its
+ // separate elements.
+ if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
+ 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.
+ if (AllocaInst *NewAI =
+ ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) {
+ 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(AllocaInst *AI,
+ std::vector<AllocaInst*> &WorkList) {
+ DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
+ SmallVector<AllocaInst*, 32> ElementAllocas;
+ if (const StructType *ST = dyn_cast<StructType>(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() + "." + Twine(i), AI);
+ ElementAllocas.push_back(NA);
+ WorkList.push_back(NA); // Add to worklist for recursive processing
+ }
+ } else {
+ const ArrayType *AT = cast<ArrayType>(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() + "." + Twine(i), AI);
+ ElementAllocas.push_back(NA);
+ WorkList.push_back(NA); // Add to worklist for recursive processing
+ }
+ }
+
+ // Now that we have created the new alloca instructions, rewrite all the
+ // uses of the old alloca.
+ RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
+
+ // Now erase any instructions that were made dead while rewriting the alloca.
+ DeleteDeadInstructions();
+ AI->eraseFromParent();
+
+ ++NumReplaced;
+}
+
+/// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
+/// recursively including all their operands that become trivially dead.
+void SROA::DeleteDeadInstructions() {
+ while (!DeadInsts.empty()) {
+ Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
+
+ for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
+ if (Instruction *U = dyn_cast<Instruction>(*OI)) {
+ // Zero out the operand and see if it becomes trivially dead.
+ // (But, don't add allocas to the dead instruction list -- they are
+ // already on the worklist and will be deleted separately.)
+ *OI = 0;
+ if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
+ DeadInsts.push_back(U);
+ }
+
+ I->eraseFromParent();
+ }
+}
+
+/// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
+/// performing scalar replacement of alloca AI. The results are flagged in
+/// the Info parameter. Offset indicates the position within AI that is
+/// referenced by this instruction.
+void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset,
+ AllocaInfo &Info) {
+ for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
+ Instruction *User = cast<Instruction>(*UI);
+
+ if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
+ isSafeForScalarRepl(BC, Offset, Info);
+ } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
+ uint64_t GEPOffset = Offset;
+ isSafeGEP(GEPI, GEPOffset, Info);
+ if (!Info.isUnsafe)
+ isSafeForScalarRepl(GEPI, GEPOffset, Info);
+ } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
+ ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
+ if (Length == 0)
+ return MarkUnsafe(Info, User);
+ isSafeMemAccess(Offset, Length->getZExtValue(), 0,
+ UI.getOperandNo() == 0, Info, MI,
+ true /*AllowWholeAccess*/);
+ } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
+ if (LI->isVolatile())
+ return MarkUnsafe(Info, User);
+ const Type *LIType = LI->getType();
+ isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
+ LIType, false, Info, LI, true /*AllowWholeAccess*/);
+ Info.hasALoadOrStore = true;
+
+ } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
+ // Store is ok if storing INTO the pointer, not storing the pointer
+ if (SI->isVolatile() || SI->getOperand(0) == I)
+ return MarkUnsafe(Info, User);
+
+ const Type *SIType = SI->getOperand(0)->getType();
+ isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
+ SIType, true, Info, SI, true /*AllowWholeAccess*/);
+ Info.hasALoadOrStore = true;
+ } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
+ isSafePHISelectUseForScalarRepl(User, Offset, Info);
+ } else {
+ return MarkUnsafe(Info, User);
+ }
+ if (Info.isUnsafe) return;
+ }
+}
+
+
+/// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer
+/// derived from the alloca, we can often still split the alloca into elements.
+/// This is useful if we have a large alloca where one element is phi'd
+/// together somewhere: we can SRoA and promote all the other elements even if
+/// we end up not being able to promote this one.
+///
+/// All we require is that the uses of the PHI do not index into other parts of
+/// the alloca. The most important use case for this is single load and stores
+/// that are PHI'd together, which can happen due to code sinking.
+void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset,
+ AllocaInfo &Info) {
+ // If we've already checked this PHI, don't do it again.
+ if (PHINode *PN = dyn_cast<PHINode>(I))
+ if (!Info.CheckedPHIs.insert(PN))
+ return;
+
+ for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
+ Instruction *User = cast<Instruction>(*UI);
+
+ if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
+ isSafePHISelectUseForScalarRepl(BC, Offset, Info);
+ } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
+ // Only allow "bitcast" GEPs for simplicity. We could generalize this,
+ // but would have to prove that we're staying inside of an element being
+ // promoted.
+ if (!GEPI->hasAllZeroIndices())
+ return MarkUnsafe(Info, User);
+ isSafePHISelectUseForScalarRepl(GEPI, Offset, Info);
+ } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
+ if (LI->isVolatile())
+ return MarkUnsafe(Info, User);
+ const Type *LIType = LI->getType();
+ isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
+ LIType, false, Info, LI, false /*AllowWholeAccess*/);
+ Info.hasALoadOrStore = true;
- // 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;
+ } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
+ // Store is ok if storing INTO the pointer, not storing the pointer
+ if (SI->isVolatile() || SI->getOperand(0) == I)
+ return MarkUnsafe(Info, User);
- if (FieldSizeBits != AllocaSizeBits)
- EltVal = new TruncInst(EltVal,
- IntegerType::get(SI->getContext(), 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<VectorType>(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);
+ const Type *SIType = SI->getOperand(0)->getType();
+ isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
+ SIType, true, Info, SI, false /*AllowWholeAccess*/);
+ Info.hasALoadOrStore = true;
+ } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
+ isSafePHISelectUseForScalarRepl(User, Offset, Info);
+ } else {
+ return MarkUnsafe(Info, User);
+ }
+ if (Info.isUnsafe) return;
+ }
+}
+
+/// isSafeGEP - Check if a GEP instruction can be handled for scalar
+/// replacement. It is safe when all the indices are constant, in-bounds
+/// references, and when the resulting offset corresponds to an element within
+/// the alloca type. The results are flagged in the Info parameter. Upon
+/// return, Offset is adjusted as specified by the GEP indices.
+void SROA::isSafeGEP(GetElementPtrInst *GEPI,
+ uint64_t &Offset, AllocaInfo &Info) {
+ gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
+ if (GEPIt == E)
+ return;
+
+ // Walk through the GEP type indices, checking the types that this indexes
+ // into.
+ for (; GEPIt != E; ++GEPIt) {
+ // Ignore struct elements, no extra checking needed for these.
+ if ((*GEPIt)->isStructTy())
+ continue;
+
+ ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
+ if (!IdxVal)
+ return MarkUnsafe(Info, GEPI);
+ }
+
+ // Compute the offset due to this GEP and check if the alloca has a
+ // component element at that offset.
+ SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
+ Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
+ &Indices[0], Indices.size());
+ if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset, 0))
+ MarkUnsafe(Info, GEPI);
+}
+
+/// isHomogeneousAggregate - Check if type T is a struct or array containing
+/// elements of the same type (which is always true for arrays). If so,
+/// return true with NumElts and EltTy set to the number of elements and the
+/// element type, respectively.
+static bool isHomogeneousAggregate(const Type *T, unsigned &NumElts,
+ const Type *&EltTy) {
+ if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
+ NumElts = AT->getNumElements();
+ EltTy = (NumElts == 0 ? 0 : AT->getElementType());
+ return true;
+ }
+ if (const StructType *ST = dyn_cast<StructType>(T)) {
+ NumElts = ST->getNumContainedTypes();
+ EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0));
+ for (unsigned n = 1; n < NumElts; ++n) {
+ if (ST->getContainedType(n) != EltTy)
+ return false;
}
-
+ return true;
+ }
+ return false;
+}
+
+/// isCompatibleAggregate - Check if T1 and T2 are either the same type or are
+/// "homogeneous" aggregates with the same element type and number of elements.
+static bool isCompatibleAggregate(const Type *T1, const Type *T2) {
+ if (T1 == T2)
+ return true;
+
+ unsigned NumElts1, NumElts2;
+ const Type *EltTy1, *EltTy2;
+ if (isHomogeneousAggregate(T1, NumElts1, EltTy1) &&
+ isHomogeneousAggregate(T2, NumElts2, EltTy2) &&
+ NumElts1 == NumElts2 &&
+ EltTy1 == EltTy2)
+ return true;
+
+ return false;
+}
+
+/// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
+/// alloca or has an offset and size that corresponds to a component element
+/// within it. The offset checked here may have been formed from a GEP with a
+/// pointer bitcasted to a different type.
+///
+/// If AllowWholeAccess is true, then this allows uses of the entire alloca as a
+/// unit. If false, it only allows accesses known to be in a single element.
+void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
+ const Type *MemOpType, bool isStore,
+ AllocaInfo &Info, Instruction *TheAccess,
+ bool AllowWholeAccess) {
+ // Check if this is a load/store of the entire alloca.
+ if (Offset == 0 && AllowWholeAccess &&
+ MemSize == TD->getTypeAllocSize(Info.AI->getAllocatedType())) {
+ // This can be safe for MemIntrinsics (where MemOpType is 0) and integer
+ // loads/stores (which are essentially the same as the MemIntrinsics with
+ // regard to copying padding between elements). But, if an alloca is
+ // flagged as both a source and destination of such operations, we'll need
+ // to check later for padding between elements.
+ if (!MemOpType || MemOpType->isIntegerTy()) {
+ if (isStore)
+ Info.isMemCpyDst = true;
+ else
+ Info.isMemCpySrc = true;
+ return;
+ }
+ // This is also safe for references using a type that is compatible with
+ // the type of the alloca, so that loads/stores can be rewritten using
+ // insertvalue/extractvalue.
+ if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) {
+ Info.hasSubelementAccess = true;
+ return;
+ }
+ }
+ // Check if the offset/size correspond to a component within the alloca type.
+ const Type *T = Info.AI->getAllocatedType();
+ if (TypeHasComponent(T, Offset, MemSize)) {
+ Info.hasSubelementAccess = true;
+ return;
+ }
+
+ return MarkUnsafe(Info, TheAccess);
+}
+
+/// TypeHasComponent - Return true if T has a component type with the
+/// specified offset and size. If Size is zero, do not check the size.
+bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) {
+ const Type *EltTy;
+ uint64_t EltSize;
+ if (const StructType *ST = dyn_cast<StructType>(T)) {
+ const StructLayout *Layout = TD->getStructLayout(ST);
+ unsigned EltIdx = Layout->getElementContainingOffset(Offset);
+ EltTy = ST->getContainedType(EltIdx);
+ EltSize = TD->getTypeAllocSize(EltTy);
+ Offset -= Layout->getElementOffset(EltIdx);
+ } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
+ EltTy = AT->getElementType();
+ EltSize = TD->getTypeAllocSize(EltTy);
+ if (Offset >= AT->getNumElements() * EltSize)
+ return false;
+ Offset %= EltSize;
} else {
- const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
- const Type *ArrayEltTy = ATy->getElementType();
- uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
- uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
+ return false;
+ }
+ if (Offset == 0 && (Size == 0 || EltSize == Size))
+ return true;
+ // Check if the component spans multiple elements.
+ if (Offset + Size > EltSize)
+ return false;
+ return TypeHasComponent(EltTy, Offset, Size);
+}
- uint64_t Shift;
+/// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
+/// the instruction I, which references it, to use the separate elements.
+/// Offset indicates the position within AI that is referenced by this
+/// instruction.
+void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
+ SmallVector<AllocaInst*, 32> &NewElts) {
+ for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) {
+ Use &TheUse = UI.getUse();
+ Instruction *User = cast<Instruction>(*UI++);
+
+ if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
+ RewriteBitCast(BC, AI, Offset, NewElts);
+ continue;
+ }
- if (TD->isBigEndian())
- Shift = AllocaSizeBits-ElementOffset;
- else
- Shift = 0;
+ if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
+ RewriteGEP(GEPI, AI, Offset, NewElts);
+ continue;
+ }
- for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
- // Ignore zero sized fields like {}, they obviously contain no data.
- if (ElementSizeBits == 0) continue;
+ if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
+ ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
+ uint64_t MemSize = Length->getZExtValue();
+ if (Offset == 0 &&
+ MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
+ RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
+ // Otherwise the intrinsic can only touch a single element and the
+ // address operand will be updated, so nothing else needs to be done.
+ continue;
+ }
+
+ if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
+ const Type *LIType = LI->getType();
- Value *EltVal = SrcVal;
- if (Shift) {
- Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
- EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
- "sroa.store.elt", SI);
+ if (isCompatibleAggregate(LIType, AI->getAllocatedType())) {
+ // 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)
+ Value *Insert = UndefValue::get(LIType);
+ for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
+ Value *Load = new LoadInst(NewElts[i], "load", LI);
+ Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
+ }
+ LI->replaceAllUsesWith(Insert);
+ DeadInsts.push_back(LI);
+ } else if (LIType->isIntegerTy() &&
+ TD->getTypeAllocSize(LIType) ==
+ TD->getTypeAllocSize(AI->getAllocatedType())) {
+ // If this is a load of the entire alloca to an integer, rewrite it.
+ RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
}
-
- // Truncate down to an integer of the right size.
- if (ElementSizeBits != AllocaSizeBits)
- EltVal = new TruncInst(EltVal,
- IntegerType::get(SI->getContext(),
- 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<VectorType>(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);
+ continue;
+ }
+
+ if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
+ Value *Val = SI->getOperand(0);
+ const Type *SIType = Val->getType();
+ if (isCompatibleAggregate(SIType, AI->getAllocatedType())) {
+ // 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)
+ for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
+ Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
+ new StoreInst(Extract, NewElts[i], SI);
+ }
+ DeadInsts.push_back(SI);
+ } else if (SIType->isIntegerTy() &&
+ TD->getTypeAllocSize(SIType) ==
+ TD->getTypeAllocSize(AI->getAllocatedType())) {
+ // If this is a store of the entire alloca from an integer, rewrite it.
+ RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
}
- new StoreInst(EltVal, DestField, SI);
+ continue;
+ }
+
+ if (isa<SelectInst>(User) || isa<PHINode>(User)) {
+ // If we have a PHI user of the alloca itself (as opposed to a GEP or
+ // bitcast) we have to rewrite it. GEP and bitcast uses will be RAUW'd to
+ // the new pointer.
+ if (!isa<AllocaInst>(I)) continue;
- if (TD->isBigEndian())
- Shift -= ElementOffset;
- else
- Shift += ElementOffset;
+ assert(Offset == 0 && NewElts[0] &&
+ "Direct alloca use should have a zero offset");
+
+ // If we have a use of the alloca, we know the derived uses will be
+ // utilizing just the first element of the scalarized result. Insert a
+ // bitcast of the first alloca before the user as required.
+ AllocaInst *NewAI = NewElts[0];
+ BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI);
+ NewAI->moveBefore(BCI);
+ TheUse = BCI;
+ continue;
}
}
-
- DeadInsts.push_back(SI);
}
-/// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
-/// an integer. Load the individual pieces to form the aggregate value.
-void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
- SmallVector<AllocaInst*, 32> &NewElts) {
- // Extract each element out of the NewElts according to its structure offset
- // and form the result value.
- const Type *AllocaEltTy = AI->getAllocatedType();
- uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
-
- DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
- << '\n');
-
- // 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<StructType>(AllocaEltTy)) {
- Layout = TD->getStructLayout(EltSTy);
- } else {
- const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
- ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
- }
-
- Value *ResultVal =
- Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
-
- 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<PointerType>(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(LI->getContext(),
- FieldSizeBits);
- if (!isa<IntegerType>(FieldTy) && !FieldTy->isFloatingPoint() &&
- !isa<VectorType>(FieldTy))
- SrcField = new BitCastInst(SrcField,
- PointerType::getUnqual(FieldIntTy),
- "", LI);
- SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
+/// RewriteBitCast - Update a bitcast reference to the alloca being replaced
+/// and recursively continue updating all of its uses.
+void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
+ SmallVector<AllocaInst*, 32> &NewElts) {
+ RewriteForScalarRepl(BC, AI, Offset, NewElts);
+ if (BC->getOperand(0) != AI)
+ return;
+
+ // The bitcast references the original alloca. Replace its uses with
+ // references to the first new element alloca.
+ Instruction *Val = NewElts[0];
+ if (Val->getType() != BC->getDestTy()) {
+ Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
+ Val->takeName(BC);
+ }
+ BC->replaceAllUsesWith(Val);
+ DeadInsts.push_back(BC);
+}
+
+/// FindElementAndOffset - Return the index of the element containing Offset
+/// within the specified type, which must be either a struct or an array.
+/// Sets T to the type of the element and Offset to the offset within that
+/// element. IdxTy is set to the type of the index result to be used in a
+/// GEP instruction.
+uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset,
+ const Type *&IdxTy) {
+ uint64_t Idx = 0;
+ if (const StructType *ST = dyn_cast<StructType>(T)) {
+ const StructLayout *Layout = TD->getStructLayout(ST);
+ Idx = Layout->getElementContainingOffset(Offset);
+ T = ST->getContainedType(Idx);
+ Offset -= Layout->getElementOffset(Idx);
+ IdxTy = Type::getInt32Ty(T->getContext());
+ return Idx;
+ }
+ const ArrayType *AT = cast<ArrayType>(T);
+ T = AT->getElementType();
+ uint64_t EltSize = TD->getTypeAllocSize(T);
+ Idx = Offset / EltSize;
+ Offset -= Idx * EltSize;
+ IdxTy = Type::getInt64Ty(T->getContext());
+ return Idx;
+}
- // 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);
+/// RewriteGEP - Check if this GEP instruction moves the pointer across
+/// elements of the alloca that are being split apart, and if so, rewrite
+/// the GEP to be relative to the new element.
+void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
+ SmallVector<AllocaInst*, 32> &NewElts) {
+ uint64_t OldOffset = Offset;
+ SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
+ Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
+ &Indices[0], Indices.size());
- // 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);
- }
+ RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
- ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
- }
+ const Type *T = AI->getAllocatedType();
+ const Type *IdxTy;
+ uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
+ if (GEPI->getOperand(0) == AI)
+ OldIdx = ~0ULL; // Force the GEP to be rewritten.
- // Handle tail padding by truncating the result
- if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
- ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
+ T = AI->getAllocatedType();
+ uint64_t EltOffset = Offset;
+ uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
- LI->replaceAllUsesWith(ResultVal);
- DeadInsts.push_back(LI);
+ // If this GEP does not move the pointer across elements of the alloca
+ // being split, then it does not needs to be rewritten.
+ if (Idx == OldIdx)
+ return;
+
+ const Type *i32Ty = Type::getInt32Ty(AI->getContext());
+ SmallVector<Value*, 8> NewArgs;
+ NewArgs.push_back(Constant::getNullValue(i32Ty));
+ while (EltOffset != 0) {
+ uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
+ NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
+ }
+ Instruction *Val = NewElts[Idx];
+ if (NewArgs.size() > 1) {
+ Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(),
+ NewArgs.end(), "", GEPI);
+ Val->takeName(GEPI);
+ }
+ if (Val->getType() != GEPI->getType())
+ Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
+ GEPI->replaceAllUsesWith(Val);
+ DeadInsts.push_back(GEPI);
}
-/// 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<StructType>(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;
+/// 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 *Inst,
+ AllocaInst *AI,
+ SmallVector<AllocaInst*, 32> &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<MemTransferInst>(MI)) { // memmove/memcopy
+ if (Inst == MTI->getRawDest())
+ OtherPtr = MTI->getRawSource();
+ else {
+ assert(Inst == MTI->getRawSource());
+ OtherPtr = MTI->getRawDest();
+ }
+ }
- // 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;
- }
+ // 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) {
+ unsigned AddrSpace =
+ cast<PointerType>(OtherPtr->getType())->getAddressSpace();
- PrevFieldBitOffset = FieldBitOffset;
- }
+ // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
+ // optimization, but it's also required to detect the corner case where
+ // both pointer operands are referencing the same memory, and where
+ // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
+ // function is only called for mem intrinsics that access the whole
+ // aggregate, so non-zero GEPs are not an issue here.)
+ OtherPtr = OtherPtr->stripPointerCasts();
- // Check for tail padding.
- if (unsigned EltCount = STy->getNumElements()) {
- unsigned PrevFieldEnd = PrevFieldBitOffset +
- TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
- if (PrevFieldEnd < SL->getSizeInBits())
- return true;
+ // Copying the alloca to itself is a no-op: just delete it.
+ if (OtherPtr == AI || OtherPtr == NewElts[0]) {
+ // This code will run twice for a no-op memcpy -- once for each operand.
+ // Put only one reference to MI on the DeadInsts list.
+ for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
+ E = DeadInsts.end(); I != E; ++I)
+ if (*I == MI) return;
+ DeadInsts.push_back(MI);
+ return;
}
- } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
- return HasPadding(ATy->getElementType(), TD);
- } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) {
- return HasPadding(VTy->getElementType(), TD);
- }
- return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
-}
+ // If the pointer is not the right type, insert a bitcast to the right
+ // type.
+ const Type *NewTy =
+ PointerType::get(AI->getType()->getElementType(), AddrSpace);
-/// 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.
-bool SROA::isSafeAllocaToScalarRepl(AllocaInst *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;
-
- isSafeForScalarRepl(AI, AI, 0, Info);
- if (Info.isUnsafe) {
- DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
- return false;
+ if (OtherPtr->getType() != NewTy)
+ OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
}
-
- // 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->getAllocatedType(), *TD))
- return false;
- return true;
-}
+ // Process each element of the aggregate.
+ bool SROADest = MI->getRawDest() == Inst;
-/// 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,
- LLVMContext &Context) {
- // If this could be contributing to a vector, analyze it.
- if (VecTy != Type::getVoidTy(Context)) { // 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<VectorType>(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->isFloatTy() || In->isDoubleTy() ||
- (isa<IntegerType>(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<VectorType>(VecTy)->getElementType()
- ->getPrimitiveSizeInBits()/8 == EltSize)) {
- if (VecTy == 0)
- VecTy = VectorType::get(In, AllocaSize/EltSize);
- return;
+ Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
+
+ 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::getInt32Ty(MI->getContext()), i) };
+ OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2,
+ OtherPtr->getName()+"."+Twine(i),
+ MI);
+ uint64_t EltOffset;
+ const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
+ const Type *OtherTy = OtherPtrTy->getElementType();
+ if (const StructType *ST = dyn_cast<StructType>(OtherTy)) {
+ EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
+ } else {
+ const Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
+ EltOffset = TD->getTypeAllocSize(EltTy)*i;
}
- }
- }
-
- // 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::getVoidTy(Context);
-}
-/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
-/// its accesses to a 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<Instruction>(*UI);
-
- if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
- // Don't break volatile loads.
- if (LI->isVolatile())
- return false;
- MergeInType(LI->getType(), Offset, VecTy,
- AllocaSize, *TD, V->getContext());
- SawVec |= isa<VectorType>(LI->getType());
- continue;
- }
-
- if (StoreInst *SI = dyn_cast<StoreInst>(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, V->getContext());
- SawVec |= isa<VectorType>(SI->getOperand(0)->getType());
- continue;
- }
-
- if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
- if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset,
- AllocaSize))
- return false;
- IsNotTrivial = true;
- continue;
+ // 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);
}
- if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(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<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
- uint64_t GEPOffset = TD->getIndexedOffset(GEP->getPointerOperandType(),
- &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;
- }
+ Value *EltPtr = NewElts[i];
+ const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
+
+ // If we got down to a scalar, insert a load or store as appropriate.
+ if (EltTy->isSingleValueType()) {
+ if (isa<MemTransferInst>(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<MemSetInst>(MI));
+
+ // If the stored element is zero (common case), just store a null
+ // constant.
+ Constant *StoreVal;
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
+ 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->getScalarType();
+
+ // 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(CI->getContext(), TotalVal);
+ if (ValTy->isPointerTy())
+ StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
+ else if (ValTy->isFloatingPointTy())
+ StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
+ assert(StoreVal->getType() == ValTy && "Type mismatch!");
- // If this is a constant sized memset of a constant value (e.g. 0) we can
- // handle it.
- if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
- // Store of constant value and constant size.
- if (isa<ConstantInt>(MSI->getValue()) &&
- isa<ConstantInt>(MSI->getLength())) {
- IsNotTrivial = true;
+ // If the requested value was a vector constant, create it.
+ if (EltTy != ValTy) {
+ unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
+ SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
+ StoreVal = ConstantVector::get(Elts);
+ }
+ }
+ new StoreInst(StoreVal, EltPtr, MI);
continue;
}
+ // Otherwise, if we're storing a byte variable, use a memset call for
+ // this element.
}
- // 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<MemTransferInst>(User)) {
- if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()))
- if (Len->getZExtValue() == AllocaSize && Offset == 0) {
- IsNotTrivial = true;
- continue;
- }
+ unsigned EltSize = TD->getTypeAllocSize(EltTy);
+
+ IRBuilder<> Builder(MI);
+
+ // Finally, insert the meminst for this element.
+ if (isa<MemSetInst>(MI)) {
+ Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize,
+ MI->isVolatile());
+ } else {
+ assert(isa<MemTransferInst>(MI));
+ Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr
+ Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr
+
+ if (isa<MemCpyInst>(MI))
+ Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile());
+ else
+ Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile());
}
-
- // Otherwise, we cannot handle this!
- return false;
}
-
- return true;
+ DeadInsts.push_back(MI);
}
-/// 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<Instruction>(Ptr->use_back());
+/// RewriteStoreUserOfWholeAlloca - We found a 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, AllocaInst *AI,
+ SmallVector<AllocaInst*, 32> &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->getAllocatedType();
+ uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
- if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
- ConvertUsesToScalar(CI, NewAI, Offset);
- CI->eraseFromParent();
- continue;
- }
+ IRBuilder<> Builder(SI);
+
+ // Handle tail padding by extending the operand
+ if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
+ SrcVal = Builder.CreateZExt(SrcVal,
+ IntegerType::get(SI->getContext(), AllocaSizeBits));
- if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
- // Compute the offset that this GEP adds to the pointer.
- SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
- uint64_t GEPOffset = TD->getIndexedOffset(GEP->getPointerOperandType(),
- &Indices[0], Indices.size());
- ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
- GEP->eraseFromParent();
- continue;
- }
-
- IRBuilder<> Builder(User->getParent(), User);
-
- if (LoadInst *LI = dyn_cast<LoadInst>(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<StoreInst>(User)) {
- assert(SI->getOperand(0) != Ptr && "Consistency error!");
- Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
- Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
- Builder);
- Builder.CreateStore(New, NewAI);
- SI->eraseFromParent();
-
- // If the load we just inserted is now dead, then the inserted store
- // overwrote the entire thing.
- if (Old->use_empty())
- Old->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<MemSetInst>(User)) {
- assert(MSI->getRawDest() == Ptr && "Consistency error!");
- unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
- if (NumBytes != 0) {
- unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
-
- // Compute the value replicated the right number of times.
- APInt APVal(NumBytes*8, Val);
+ DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
+ << '\n');
- // Splat the value if non-zero.
- if (Val)
- for (unsigned i = 1; i != NumBytes; ++i)
- APVal |= APVal << 8;
-
- Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
- Value *New = ConvertScalar_InsertValue(
- ConstantInt::get(User->getContext(), APVal),
- Old, Offset, Builder);
- Builder.CreateStore(New, NewAI);
-
- // If the load we just inserted is now dead, then the memset overwrote
- // the entire thing.
- if (Old->use_empty())
- Old->eraseFromParent();
+ // 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<StructType>(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->getTypeAllocSizeInBits(FieldTy);
+
+ Value *EltVal = SrcVal;
+ if (Shift) {
+ Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
+ EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
}
- 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<MemTransferInst>(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<AllocaInst>(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");
+ // Truncate down to an integer of the right size.
+ uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
- Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType());
- StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
- NewStore->setAlignment(MTI->getAlignment());
+ // Ignore zero sized fields like {}, they obviously contain no data.
+ if (FieldSizeBits == 0) continue;
+
+ if (FieldSizeBits != AllocaSizeBits)
+ EltVal = Builder.CreateTrunc(EltVal,
+ IntegerType::get(SI->getContext(), FieldSizeBits));
+ Value *DestField = NewElts[i];
+ if (EltVal->getType() == FieldTy) {
+ // Storing to an integer field of this size, just do it.
+ } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
+ // Bitcast to the right element type (for fp/vector values).
+ EltVal = Builder.CreateBitCast(EltVal, FieldTy);
} else {
- // Noop transfer. Src == Dst
+ // Otherwise, bitcast the dest pointer (for aggregates).
+ DestField = Builder.CreateBitCast(DestField,
+ PointerType::getUnqual(EltVal->getType()));
}
-
- MTI->eraseFromParent();
- continue;
+ new StoreInst(EltVal, DestField, SI);
}
-
- llvm_unreachable("Unsupported operation!");
- }
-}
-/// 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;
+ } else {
+ const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
+ const Type *ArrayEltTy = ATy->getElementType();
+ uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
+ uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
- // 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<VectorType>(FromVal->getType())) {
- if (isa<VectorType>(ToType))
- return Builder.CreateBitCast(FromVal, ToType, "tmp");
+ uint64_t Shift;
- // Otherwise it must be an element access.
- unsigned Elt = 0;
- if (Offset) {
- unsigned EltSize = TD->getTypeAllocSizeInBits(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::getInt32Ty(FromVal->getContext()), 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<StructType>(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<ArrayType>(ToType)) {
- uint64_t EltSize = TD->getTypeAllocSizeInBits(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");
+ 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 = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
+ }
+
+ // Truncate down to an integer of the right size.
+ if (ElementSizeBits != AllocaSizeBits)
+ EltVal = Builder.CreateTrunc(EltVal,
+ IntegerType::get(SI->getContext(),
+ ElementSizeBits));
+ Value *DestField = NewElts[i];
+ if (EltVal->getType() == ArrayEltTy) {
+ // Storing to an integer field of this size, just do it.
+ } else if (ArrayEltTy->isFloatingPointTy() ||
+ ArrayEltTy->isVectorTy()) {
+ // Bitcast to the right element type (for fp/vector values).
+ EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy);
+ } else {
+ // Otherwise, bitcast the dest pointer (for aggregates).
+ DestField = Builder.CreateBitCast(DestField,
+ PointerType::getUnqual(EltVal->getType()));
+ }
+ new StoreInst(EltVal, DestField, SI);
+
+ if (TD->isBigEndian())
+ Shift -= ElementOffset;
+ else
+ Shift += ElementOffset;
}
- return Res;
}
- // Otherwise, this must be a union that was converted to an integer value.
- const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
+ DeadInsts.push_back(SI);
+}
- // 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;
+/// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
+/// an integer. Load the individual pieces to form the aggregate value.
+void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
+ SmallVector<AllocaInst*, 32> &NewElts) {
+ // Extract each element out of the NewElts according to its structure offset
+ // and form the result value.
+ const Type *AllocaEltTy = AI->getAllocatedType();
+ uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
+
+ DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
+ << '\n');
+
+ // 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<StructType>(AllocaEltTy)) {
+ Layout = TD->getStructLayout(EltSTy);
} else {
- ShAmt = Offset;
+ const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
+ ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
}
- // 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");
+ Value *ResultVal =
+ Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
- // Finally, unconditionally truncate the integer to the right width.
- unsigned LIBitWidth = TD->getTypeSizeInBits(ToType);
- if (LIBitWidth < NTy->getBitWidth())
- FromVal =
- Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
- LIBitWidth), "tmp");
- else if (LIBitWidth > NTy->getBitWidth())
- FromVal =
- Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
- LIBitWidth), "tmp");
+ 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<PointerType>(SrcField->getType())->getElementType();
+ uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
- // If the result is an integer, this is a trunc or bitcast.
- if (isa<IntegerType>(ToType)) {
- // Should be done.
- } else if (ToType->isFloatingPoint() || isa<VectorType>(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;
-}
+ // Ignore zero sized fields like {}, they obviously contain no data.
+ if (FieldSizeBits == 0) continue;
-/// 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) {
+ const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
+ FieldSizeBits);
+ if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
+ !FieldTy->isVectorTy())
+ SrcField = new BitCastInst(SrcField,
+ PointerType::getUnqual(FieldIntTy),
+ "", LI);
+ SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
- // Convert the stored type to the actual type, shift it left to insert
- // then 'or' into place.
- const Type *AllocaType = Old->getType();
- LLVMContext &Context = Old->getContext();
+ // 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);
- if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
- uint64_t VecSize = TD->getTypeAllocSizeInBits(VTy);
- uint64_t ValSize = TD->getTypeAllocSizeInBits(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");
+ // 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);
- uint64_t EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
+ // 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;
- // 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::getInt32Ty(SV->getContext()), Elt),
- "tmp");
- return SV;
- }
-
- // If SV is a first-class aggregate value, insert each value recursively.
- if (const StructType *ST = dyn_cast<StructType>(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<ArrayType>(SV->getType())) {
- uint64_t EltSize = TD->getTypeAllocSizeInBits(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);
+ if (TD->isBigEndian())
+ Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
+
+ if (Shift) {
+ Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
+ SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
}
- return Old;
+
+ // Don't create an 'or x, 0' on the first iteration.
+ if (!isa<Constant>(ResultVal) ||
+ !cast<Constant>(ResultVal)->isNullValue())
+ ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
+ else
+ ResultVal = SrcField;
}
- // 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<VectorType>(SV->getType()))
- SV = Builder.CreateBitCast(SV,
- IntegerType::get(SV->getContext(),SrcWidth), "tmp");
- else if (isa<PointerType>(SV->getType()))
- SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(SV->getContext()), "tmp");
+ // Handle tail padding by truncating the result
+ if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
+ ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
- // 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;
- }
+ LI->replaceAllUsesWith(ResultVal);
+ DeadInsts.push_back(LI);
+}
+
+/// HasPadding - Return true if the specified type has any structure or
+/// alignment padding in between the elements that would be split apart
+/// by SROA; return false otherwise.
+static bool HasPadding(const Type *Ty, const TargetData &TD) {
+ if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
+ Ty = ATy->getElementType();
+ return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
}
- // 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;
+ // SROA currently handles only Arrays and Structs.
+ const StructType *STy = cast<StructType>(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);
+
+ // 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;
}
+ return false;
+}
- // 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);
+/// 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.
+bool SROA::isSafeAllocaToScalarRepl(AllocaInst *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(AI);
+
+ isSafeForScalarRepl(AI, 0, Info);
+ if (Info.isUnsafe) {
+ DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
+ return false;
}
- // 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(Context, ~Mask), "mask");
- SV = Builder.CreateOr(Old, SV, "ins");
+ // 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->getAllocatedType(), *TD))
+ return false;
+
+ // If the alloca never has an access to just *part* of it, but is accessed
+ // via loads and stores, then we should use ConvertToScalarInfo to promote
+ // the alloca instead of promoting each piece at a time and inserting fission
+ // and fusion code.
+ if (!Info.hasSubelementAccess && Info.hasALoadOrStore) {
+ // If the struct/array just has one element, use basic SRoA.
+ if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
+ if (ST->getNumElements() > 1) return false;
+ } else {
+ if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1)
+ return false;
+ }
}
- return SV;
+
+ return true;
}
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
return GV->isConstant();
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
- if (CE->getOpcode() == Instruction::BitCast ||
+ if (CE->getOpcode() == Instruction::BitCast ||
CE->getOpcode() == Instruction::GetElementPtr)
return PointsToConstantGlobal(CE->getOperand(0));
return false;
/// 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
+/// 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,
+static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
bool isOffset) {
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
- if (LoadInst *LI = dyn_cast<LoadInst>(*UI))
+ User *U = cast<Instruction>(*UI);
+
+ if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
// Ignore non-volatile loads, they are always ok.
- if (!LI->isVolatile())
- continue;
-
- if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) {
+ if (LI->isVolatile()) return false;
+ continue;
+ }
+
+ if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
// If uses of the bitcast are ok, we are ok.
if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
return false;
continue;
}
- if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
+ if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
// If the GEP has all zero indices, it doesn't offset the pointer. If it
// doesn't, it does.
if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
return false;
continue;
}
-
+
+ if (CallSite CS = U) {
+ // If this is a readonly/readnone call site, then we know it is just a
+ // load and we can ignore it.
+ if (CS.onlyReadsMemory())
+ continue;
+
+ // If this is the function being called then we treat it like a load and
+ // ignore it.
+ if (CS.isCallee(UI))
+ continue;
+
+ // If this is being passed as a byval argument, the caller is making a
+ // copy, so it is only a read of the alloca.
+ unsigned ArgNo = CS.getArgumentNo(UI);
+ if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal))
+ continue;
+ }
+
// If this is isn't our memcpy/memmove, reject it as something we can't
// handle.
- if (!isa<MemTransferInst>(*UI))
+ MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
+ if (MI == 0)
return false;
+ // If the transfer is using the alloca as a source of the transfer, then
+ // ignore it since it is a load (unless the transfer is volatile).
+ if (UI.getOperandNo() == 1) {
+ if (MI->isVolatile()) return false;
+ continue;
+ }
+
// 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<MemIntrinsic>(*UI);
-
+ if (UI.getOperandNo() != 0) return false;
+
// If the source of the memcpy/move is not a constant global, reject it.
- if (!PointsToConstantGlobal(MI->getOperand(2)))
+ if (!PointsToConstantGlobal(MI->getSource()))
return false;
-
+
// Otherwise, the transform is safe. Remember the copy instruction.
TheCopy = MI;
}
/// 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(AllocaInst *AI) {
- Instruction *TheCopy = 0;
+MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) {
+ MemTransferInst *TheCopy = 0;
if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))
return TheCopy;
return 0;
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