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Diffstat (limited to 'contrib/llvm/lib/Transforms/Scalar/SROA.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/Scalar/SROA.cpp | 3590 |
1 files changed, 3590 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Transforms/Scalar/SROA.cpp b/contrib/llvm/lib/Transforms/Scalar/SROA.cpp new file mode 100644 index 0000000..9f3fc83 --- /dev/null +++ b/contrib/llvm/lib/Transforms/Scalar/SROA.cpp @@ -0,0 +1,3590 @@ +//===- SROA.cpp - Scalar Replacement Of Aggregates ------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +/// \file +/// This transformation implements the well known scalar replacement of +/// aggregates transformation. It tries to identify promotable elements of an +/// aggregate alloca, and promote them to registers. It will also try to +/// convert uses of an element (or set of elements) of an alloca into a vector +/// or bitfield-style integer scalar if appropriate. +/// +/// It works to do this with minimal slicing of the alloca so that regions +/// which are merely transferred in and out of external memory remain unchanged +/// and are not decomposed to scalar code. +/// +/// Because this also performs alloca promotion, it can be thought of as also +/// serving the purpose of SSA formation. The algorithm iterates on the +/// function until all opportunities for promotion have been realized. +/// +//===----------------------------------------------------------------------===// + +#define DEBUG_TYPE "sroa" +#include "llvm/Transforms/Scalar.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/SetVector.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/Analysis/Dominators.h" +#include "llvm/Analysis/Loads.h" +#include "llvm/Analysis/PtrUseVisitor.h" +#include "llvm/Analysis/ValueTracking.h" +#include "llvm/DIBuilder.h" +#include "llvm/DebugInfo.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/DataLayout.h" +#include "llvm/IR/DerivedTypes.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/IRBuilder.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/Operator.h" +#include "llvm/InstVisitor.h" +#include "llvm/Pass.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Compiler.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/MathExtras.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Transforms/Utils/Local.h" +#include "llvm/Transforms/Utils/PromoteMemToReg.h" +#include "llvm/Transforms/Utils/SSAUpdater.h" +using namespace llvm; + +STATISTIC(NumAllocasAnalyzed, "Number of allocas analyzed for replacement"); +STATISTIC(NumAllocaPartitions, "Number of alloca partitions formed"); +STATISTIC(MaxPartitionsPerAlloca, "Maximum number of partitions per alloca"); +STATISTIC(NumAllocaPartitionUses, "Number of alloca partition uses rewritten"); +STATISTIC(MaxUsesPerAllocaPartition, "Maximum number of uses of a partition"); +STATISTIC(NumNewAllocas, "Number of new, smaller allocas introduced"); +STATISTIC(NumPromoted, "Number of allocas promoted to SSA values"); +STATISTIC(NumLoadsSpeculated, "Number of loads speculated to allow promotion"); +STATISTIC(NumDeleted, "Number of instructions deleted"); +STATISTIC(NumVectorized, "Number of vectorized aggregates"); + +/// Hidden option to force the pass to not use DomTree and mem2reg, instead +/// forming SSA values through the SSAUpdater infrastructure. +static cl::opt<bool> +ForceSSAUpdater("force-ssa-updater", cl::init(false), cl::Hidden); + +namespace { +/// \brief A custom IRBuilder inserter which prefixes all names if they are +/// preserved. +template <bool preserveNames = true> +class IRBuilderPrefixedInserter : + public IRBuilderDefaultInserter<preserveNames> { + std::string Prefix; + +public: + void SetNamePrefix(const Twine &P) { Prefix = P.str(); } + +protected: + void InsertHelper(Instruction *I, const Twine &Name, BasicBlock *BB, + BasicBlock::iterator InsertPt) const { + IRBuilderDefaultInserter<preserveNames>::InsertHelper( + I, Name.isTriviallyEmpty() ? Name : Prefix + Name, BB, InsertPt); + } +}; + +// Specialization for not preserving the name is trivial. +template <> +class IRBuilderPrefixedInserter<false> : + public IRBuilderDefaultInserter<false> { +public: + void SetNamePrefix(const Twine &P) {} +}; + +/// \brief Provide a typedef for IRBuilder that drops names in release builds. +#ifndef NDEBUG +typedef llvm::IRBuilder<true, ConstantFolder, + IRBuilderPrefixedInserter<true> > IRBuilderTy; +#else +typedef llvm::IRBuilder<false, ConstantFolder, + IRBuilderPrefixedInserter<false> > IRBuilderTy; +#endif +} + +namespace { +/// \brief A used slice of an alloca. +/// +/// This structure represents a slice of an alloca used by some instruction. It +/// stores both the begin and end offsets of this use, a pointer to the use +/// itself, and a flag indicating whether we can classify the use as splittable +/// or not when forming partitions of the alloca. +class Slice { + /// \brief The beginning offset of the range. + uint64_t BeginOffset; + + /// \brief The ending offset, not included in the range. + uint64_t EndOffset; + + /// \brief Storage for both the use of this slice and whether it can be + /// split. + PointerIntPair<Use *, 1, bool> UseAndIsSplittable; + +public: + Slice() : BeginOffset(), EndOffset() {} + Slice(uint64_t BeginOffset, uint64_t EndOffset, Use *U, bool IsSplittable) + : BeginOffset(BeginOffset), EndOffset(EndOffset), + UseAndIsSplittable(U, IsSplittable) {} + + uint64_t beginOffset() const { return BeginOffset; } + uint64_t endOffset() const { return EndOffset; } + + bool isSplittable() const { return UseAndIsSplittable.getInt(); } + void makeUnsplittable() { UseAndIsSplittable.setInt(false); } + + Use *getUse() const { return UseAndIsSplittable.getPointer(); } + + bool isDead() const { return getUse() == 0; } + void kill() { UseAndIsSplittable.setPointer(0); } + + /// \brief Support for ordering ranges. + /// + /// This provides an ordering over ranges such that start offsets are + /// always increasing, and within equal start offsets, the end offsets are + /// decreasing. Thus the spanning range comes first in a cluster with the + /// same start position. + bool operator<(const Slice &RHS) const { + if (beginOffset() < RHS.beginOffset()) return true; + if (beginOffset() > RHS.beginOffset()) return false; + if (isSplittable() != RHS.isSplittable()) return !isSplittable(); + if (endOffset() > RHS.endOffset()) return true; + return false; + } + + /// \brief Support comparison with a single offset to allow binary searches. + friend LLVM_ATTRIBUTE_UNUSED bool operator<(const Slice &LHS, + uint64_t RHSOffset) { + return LHS.beginOffset() < RHSOffset; + } + friend LLVM_ATTRIBUTE_UNUSED bool operator<(uint64_t LHSOffset, + const Slice &RHS) { + return LHSOffset < RHS.beginOffset(); + } + + bool operator==(const Slice &RHS) const { + return isSplittable() == RHS.isSplittable() && + beginOffset() == RHS.beginOffset() && endOffset() == RHS.endOffset(); + } + bool operator!=(const Slice &RHS) const { return !operator==(RHS); } +}; +} // end anonymous namespace + +namespace llvm { +template <typename T> struct isPodLike; +template <> struct isPodLike<Slice> { + static const bool value = true; +}; +} + +namespace { +/// \brief Representation of the alloca slices. +/// +/// This class represents the slices of an alloca which are formed by its +/// various uses. If a pointer escapes, we can't fully build a representation +/// for the slices used and we reflect that in this structure. The uses are +/// stored, sorted by increasing beginning offset and with unsplittable slices +/// starting at a particular offset before splittable slices. +class AllocaSlices { +public: + /// \brief Construct the slices of a particular alloca. + AllocaSlices(const DataLayout &DL, AllocaInst &AI); + + /// \brief Test whether a pointer to the allocation escapes our analysis. + /// + /// If this is true, the slices are never fully built and should be + /// ignored. + bool isEscaped() const { return PointerEscapingInstr; } + + /// \brief Support for iterating over the slices. + /// @{ + typedef SmallVectorImpl<Slice>::iterator iterator; + iterator begin() { return Slices.begin(); } + iterator end() { return Slices.end(); } + + typedef SmallVectorImpl<Slice>::const_iterator const_iterator; + const_iterator begin() const { return Slices.begin(); } + const_iterator end() const { return Slices.end(); } + /// @} + + /// \brief Allow iterating the dead users for this alloca. + /// + /// These are instructions which will never actually use the alloca as they + /// are outside the allocated range. They are safe to replace with undef and + /// delete. + /// @{ + typedef SmallVectorImpl<Instruction *>::const_iterator dead_user_iterator; + dead_user_iterator dead_user_begin() const { return DeadUsers.begin(); } + dead_user_iterator dead_user_end() const { return DeadUsers.end(); } + /// @} + + /// \brief Allow iterating the dead expressions referring to this alloca. + /// + /// These are operands which have cannot actually be used to refer to the + /// alloca as they are outside its range and the user doesn't correct for + /// that. These mostly consist of PHI node inputs and the like which we just + /// need to replace with undef. + /// @{ + typedef SmallVectorImpl<Use *>::const_iterator dead_op_iterator; + dead_op_iterator dead_op_begin() const { return DeadOperands.begin(); } + dead_op_iterator dead_op_end() const { return DeadOperands.end(); } + /// @} + +#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) + void print(raw_ostream &OS, const_iterator I, StringRef Indent = " ") const; + void printSlice(raw_ostream &OS, const_iterator I, + StringRef Indent = " ") const; + void printUse(raw_ostream &OS, const_iterator I, + StringRef Indent = " ") const; + void print(raw_ostream &OS) const; + void LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED dump(const_iterator I) const; + void LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED dump() const; +#endif + +private: + template <typename DerivedT, typename RetT = void> class BuilderBase; + class SliceBuilder; + friend class AllocaSlices::SliceBuilder; + +#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) + /// \brief Handle to alloca instruction to simplify method interfaces. + AllocaInst &AI; +#endif + + /// \brief The instruction responsible for this alloca not having a known set + /// of slices. + /// + /// When an instruction (potentially) escapes the pointer to the alloca, we + /// store a pointer to that here and abort trying to form slices of the + /// alloca. This will be null if the alloca slices are analyzed successfully. + Instruction *PointerEscapingInstr; + + /// \brief The slices of the alloca. + /// + /// We store a vector of the slices formed by uses of the alloca here. This + /// vector is sorted by increasing begin offset, and then the unsplittable + /// slices before the splittable ones. See the Slice inner class for more + /// details. + SmallVector<Slice, 8> Slices; + + /// \brief Instructions which will become dead if we rewrite the alloca. + /// + /// Note that these are not separated by slice. This is because we expect an + /// alloca to be completely rewritten or not rewritten at all. If rewritten, + /// all these instructions can simply be removed and replaced with undef as + /// they come from outside of the allocated space. + SmallVector<Instruction *, 8> DeadUsers; + + /// \brief Operands which will become dead if we rewrite the alloca. + /// + /// These are operands that in their particular use can be replaced with + /// undef when we rewrite the alloca. These show up in out-of-bounds inputs + /// to PHI nodes and the like. They aren't entirely dead (there might be + /// a GEP back into the bounds using it elsewhere) and nor is the PHI, but we + /// want to swap this particular input for undef to simplify the use lists of + /// the alloca. + SmallVector<Use *, 8> DeadOperands; +}; +} + +static Value *foldSelectInst(SelectInst &SI) { + // If the condition being selected on is a constant or the same value is + // being selected between, fold the select. Yes this does (rarely) happen + // early on. + if (ConstantInt *CI = dyn_cast<ConstantInt>(SI.getCondition())) + return SI.getOperand(1+CI->isZero()); + if (SI.getOperand(1) == SI.getOperand(2)) + return SI.getOperand(1); + + return 0; +} + +/// \brief Builder for the alloca slices. +/// +/// This class builds a set of alloca slices by recursively visiting the uses +/// of an alloca and making a slice for each load and store at each offset. +class AllocaSlices::SliceBuilder : public PtrUseVisitor<SliceBuilder> { + friend class PtrUseVisitor<SliceBuilder>; + friend class InstVisitor<SliceBuilder>; + typedef PtrUseVisitor<SliceBuilder> Base; + + const uint64_t AllocSize; + AllocaSlices &S; + + SmallDenseMap<Instruction *, unsigned> MemTransferSliceMap; + SmallDenseMap<Instruction *, uint64_t> PHIOrSelectSizes; + + /// \brief Set to de-duplicate dead instructions found in the use walk. + SmallPtrSet<Instruction *, 4> VisitedDeadInsts; + +public: + SliceBuilder(const DataLayout &DL, AllocaInst &AI, AllocaSlices &S) + : PtrUseVisitor<SliceBuilder>(DL), + AllocSize(DL.getTypeAllocSize(AI.getAllocatedType())), S(S) {} + +private: + void markAsDead(Instruction &I) { + if (VisitedDeadInsts.insert(&I)) + S.DeadUsers.push_back(&I); + } + + void insertUse(Instruction &I, const APInt &Offset, uint64_t Size, + bool IsSplittable = false) { + // Completely skip uses which have a zero size or start either before or + // past the end of the allocation. + if (Size == 0 || Offset.isNegative() || Offset.uge(AllocSize)) { + DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte use @" << Offset + << " which has zero size or starts outside of the " + << AllocSize << " byte alloca:\n" + << " alloca: " << S.AI << "\n" + << " use: " << I << "\n"); + return markAsDead(I); + } + + uint64_t BeginOffset = Offset.getZExtValue(); + uint64_t EndOffset = BeginOffset + Size; + + // Clamp the end offset to the end of the allocation. Note that this is + // formulated to handle even the case where "BeginOffset + Size" overflows. + // This may appear superficially to be something we could ignore entirely, + // but that is not so! There may be widened loads or PHI-node uses where + // some instructions are dead but not others. We can't completely ignore + // them, and so have to record at least the information here. + assert(AllocSize >= BeginOffset); // Established above. + if (Size > AllocSize - BeginOffset) { + DEBUG(dbgs() << "WARNING: Clamping a " << Size << " byte use @" << Offset + << " to remain within the " << AllocSize << " byte alloca:\n" + << " alloca: " << S.AI << "\n" + << " use: " << I << "\n"); + EndOffset = AllocSize; + } + + S.Slices.push_back(Slice(BeginOffset, EndOffset, U, IsSplittable)); + } + + void visitBitCastInst(BitCastInst &BC) { + if (BC.use_empty()) + return markAsDead(BC); + + return Base::visitBitCastInst(BC); + } + + void visitGetElementPtrInst(GetElementPtrInst &GEPI) { + if (GEPI.use_empty()) + return markAsDead(GEPI); + + return Base::visitGetElementPtrInst(GEPI); + } + + void handleLoadOrStore(Type *Ty, Instruction &I, const APInt &Offset, + uint64_t Size, bool IsVolatile) { + // We allow splitting of loads and stores where the type is an integer type + // and cover the entire alloca. This prevents us from splitting over + // eagerly. + // FIXME: In the great blue eventually, we should eagerly split all integer + // loads and stores, and then have a separate step that merges adjacent + // alloca partitions into a single partition suitable for integer widening. + // Or we should skip the merge step and rely on GVN and other passes to + // merge adjacent loads and stores that survive mem2reg. + bool IsSplittable = + Ty->isIntegerTy() && !IsVolatile && Offset == 0 && Size >= AllocSize; + + insertUse(I, Offset, Size, IsSplittable); + } + + void visitLoadInst(LoadInst &LI) { + assert((!LI.isSimple() || LI.getType()->isSingleValueType()) && + "All simple FCA loads should have been pre-split"); + + if (!IsOffsetKnown) + return PI.setAborted(&LI); + + uint64_t Size = DL.getTypeStoreSize(LI.getType()); + return handleLoadOrStore(LI.getType(), LI, Offset, Size, LI.isVolatile()); + } + + void visitStoreInst(StoreInst &SI) { + Value *ValOp = SI.getValueOperand(); + if (ValOp == *U) + return PI.setEscapedAndAborted(&SI); + if (!IsOffsetKnown) + return PI.setAborted(&SI); + + uint64_t Size = DL.getTypeStoreSize(ValOp->getType()); + + // If this memory access can be shown to *statically* extend outside the + // bounds of of the allocation, it's behavior is undefined, so simply + // ignore it. Note that this is more strict than the generic clamping + // behavior of insertUse. We also try to handle cases which might run the + // risk of overflow. + // FIXME: We should instead consider the pointer to have escaped if this + // function is being instrumented for addressing bugs or race conditions. + if (Offset.isNegative() || Size > AllocSize || + Offset.ugt(AllocSize - Size)) { + DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte store @" << Offset + << " which extends past the end of the " << AllocSize + << " byte alloca:\n" + << " alloca: " << S.AI << "\n" + << " use: " << SI << "\n"); + return markAsDead(SI); + } + + assert((!SI.isSimple() || ValOp->getType()->isSingleValueType()) && + "All simple FCA stores should have been pre-split"); + handleLoadOrStore(ValOp->getType(), SI, Offset, Size, SI.isVolatile()); + } + + + void visitMemSetInst(MemSetInst &II) { + assert(II.getRawDest() == *U && "Pointer use is not the destination?"); + ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength()); + if ((Length && Length->getValue() == 0) || + (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize))) + // Zero-length mem transfer intrinsics can be ignored entirely. + return markAsDead(II); + + if (!IsOffsetKnown) + return PI.setAborted(&II); + + insertUse(II, Offset, + Length ? Length->getLimitedValue() + : AllocSize - Offset.getLimitedValue(), + (bool)Length); + } + + void visitMemTransferInst(MemTransferInst &II) { + ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength()); + if ((Length && Length->getValue() == 0) || + (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize))) + // Zero-length mem transfer intrinsics can be ignored entirely. + return markAsDead(II); + + if (!IsOffsetKnown) + return PI.setAborted(&II); + + uint64_t RawOffset = Offset.getLimitedValue(); + uint64_t Size = Length ? Length->getLimitedValue() + : AllocSize - RawOffset; + + // Check for the special case where the same exact value is used for both + // source and dest. + if (*U == II.getRawDest() && *U == II.getRawSource()) { + // For non-volatile transfers this is a no-op. + if (!II.isVolatile()) + return markAsDead(II); + + return insertUse(II, Offset, Size, /*IsSplittable=*/false); + } + + // If we have seen both source and destination for a mem transfer, then + // they both point to the same alloca. + bool Inserted; + SmallDenseMap<Instruction *, unsigned>::iterator MTPI; + llvm::tie(MTPI, Inserted) = + MemTransferSliceMap.insert(std::make_pair(&II, S.Slices.size())); + unsigned PrevIdx = MTPI->second; + if (!Inserted) { + Slice &PrevP = S.Slices[PrevIdx]; + + // Check if the begin offsets match and this is a non-volatile transfer. + // In that case, we can completely elide the transfer. + if (!II.isVolatile() && PrevP.beginOffset() == RawOffset) { + PrevP.kill(); + return markAsDead(II); + } + + // Otherwise we have an offset transfer within the same alloca. We can't + // split those. + PrevP.makeUnsplittable(); + } + + // Insert the use now that we've fixed up the splittable nature. + insertUse(II, Offset, Size, /*IsSplittable=*/Inserted && Length); + + // Check that we ended up with a valid index in the map. + assert(S.Slices[PrevIdx].getUse()->getUser() == &II && + "Map index doesn't point back to a slice with this user."); + } + + // Disable SRoA for any intrinsics except for lifetime invariants. + // FIXME: What about debug intrinsics? This matches old behavior, but + // doesn't make sense. + void visitIntrinsicInst(IntrinsicInst &II) { + if (!IsOffsetKnown) + return PI.setAborted(&II); + + if (II.getIntrinsicID() == Intrinsic::lifetime_start || + II.getIntrinsicID() == Intrinsic::lifetime_end) { + ConstantInt *Length = cast<ConstantInt>(II.getArgOperand(0)); + uint64_t Size = std::min(AllocSize - Offset.getLimitedValue(), + Length->getLimitedValue()); + insertUse(II, Offset, Size, true); + return; + } + + Base::visitIntrinsicInst(II); + } + + Instruction *hasUnsafePHIOrSelectUse(Instruction *Root, uint64_t &Size) { + // We consider any PHI or select that results in a direct load or store of + // the same offset to be a viable use for slicing purposes. These uses + // are considered unsplittable and the size is the maximum loaded or stored + // size. + SmallPtrSet<Instruction *, 4> Visited; + SmallVector<std::pair<Instruction *, Instruction *>, 4> Uses; + Visited.insert(Root); + Uses.push_back(std::make_pair(cast<Instruction>(*U), Root)); + // If there are no loads or stores, the access is dead. We mark that as + // a size zero access. + Size = 0; + do { + Instruction *I, *UsedI; + llvm::tie(UsedI, I) = Uses.pop_back_val(); + + if (LoadInst *LI = dyn_cast<LoadInst>(I)) { + Size = std::max(Size, DL.getTypeStoreSize(LI->getType())); + continue; + } + if (StoreInst *SI = dyn_cast<StoreInst>(I)) { + Value *Op = SI->getOperand(0); + if (Op == UsedI) + return SI; + Size = std::max(Size, DL.getTypeStoreSize(Op->getType())); + continue; + } + + if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) { + if (!GEP->hasAllZeroIndices()) + return GEP; + } else if (!isa<BitCastInst>(I) && !isa<PHINode>(I) && + !isa<SelectInst>(I)) { + return I; + } + + for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE; + ++UI) + if (Visited.insert(cast<Instruction>(*UI))) + Uses.push_back(std::make_pair(I, cast<Instruction>(*UI))); + } while (!Uses.empty()); + + return 0; + } + + void visitPHINode(PHINode &PN) { + if (PN.use_empty()) + return markAsDead(PN); + if (!IsOffsetKnown) + return PI.setAborted(&PN); + + // See if we already have computed info on this node. + uint64_t &PHISize = PHIOrSelectSizes[&PN]; + if (!PHISize) { + // This is a new PHI node, check for an unsafe use of the PHI node. + if (Instruction *UnsafeI = hasUnsafePHIOrSelectUse(&PN, PHISize)) + return PI.setAborted(UnsafeI); + } + + // For PHI and select operands outside the alloca, we can't nuke the entire + // phi or select -- the other side might still be relevant, so we special + // case them here and use a separate structure to track the operands + // themselves which should be replaced with undef. + // FIXME: This should instead be escaped in the event we're instrumenting + // for address sanitization. + if ((Offset.isNegative() && (-Offset).uge(PHISize)) || + (!Offset.isNegative() && Offset.uge(AllocSize))) { + S.DeadOperands.push_back(U); + return; + } + + insertUse(PN, Offset, PHISize); + } + + void visitSelectInst(SelectInst &SI) { + if (SI.use_empty()) + return markAsDead(SI); + if (Value *Result = foldSelectInst(SI)) { + if (Result == *U) + // If the result of the constant fold will be the pointer, recurse + // through the select as if we had RAUW'ed it. + enqueueUsers(SI); + else + // Otherwise the operand to the select is dead, and we can replace it + // with undef. + S.DeadOperands.push_back(U); + + return; + } + if (!IsOffsetKnown) + return PI.setAborted(&SI); + + // See if we already have computed info on this node. + uint64_t &SelectSize = PHIOrSelectSizes[&SI]; + if (!SelectSize) { + // This is a new Select, check for an unsafe use of it. + if (Instruction *UnsafeI = hasUnsafePHIOrSelectUse(&SI, SelectSize)) + return PI.setAborted(UnsafeI); + } + + // For PHI and select operands outside the alloca, we can't nuke the entire + // phi or select -- the other side might still be relevant, so we special + // case them here and use a separate structure to track the operands + // themselves which should be replaced with undef. + // FIXME: This should instead be escaped in the event we're instrumenting + // for address sanitization. + if ((Offset.isNegative() && Offset.uge(SelectSize)) || + (!Offset.isNegative() && Offset.uge(AllocSize))) { + S.DeadOperands.push_back(U); + return; + } + + insertUse(SI, Offset, SelectSize); + } + + /// \brief Disable SROA entirely if there are unhandled users of the alloca. + void visitInstruction(Instruction &I) { + PI.setAborted(&I); + } +}; + +AllocaSlices::AllocaSlices(const DataLayout &DL, AllocaInst &AI) + : +#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) + AI(AI), +#endif + PointerEscapingInstr(0) { + SliceBuilder PB(DL, AI, *this); + SliceBuilder::PtrInfo PtrI = PB.visitPtr(AI); + if (PtrI.isEscaped() || PtrI.isAborted()) { + // FIXME: We should sink the escape vs. abort info into the caller nicely, + // possibly by just storing the PtrInfo in the AllocaSlices. + PointerEscapingInstr = PtrI.getEscapingInst() ? PtrI.getEscapingInst() + : PtrI.getAbortingInst(); + assert(PointerEscapingInstr && "Did not track a bad instruction"); + return; + } + + Slices.erase(std::remove_if(Slices.begin(), Slices.end(), + std::mem_fun_ref(&Slice::isDead)), + Slices.end()); + + // Sort the uses. This arranges for the offsets to be in ascending order, + // and the sizes to be in descending order. + std::sort(Slices.begin(), Slices.end()); +} + +#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) + +void AllocaSlices::print(raw_ostream &OS, const_iterator I, + StringRef Indent) const { + printSlice(OS, I, Indent); + printUse(OS, I, Indent); +} + +void AllocaSlices::printSlice(raw_ostream &OS, const_iterator I, + StringRef Indent) const { + OS << Indent << "[" << I->beginOffset() << "," << I->endOffset() << ")" + << " slice #" << (I - begin()) + << (I->isSplittable() ? " (splittable)" : "") << "\n"; +} + +void AllocaSlices::printUse(raw_ostream &OS, const_iterator I, + StringRef Indent) const { + OS << Indent << " used by: " << *I->getUse()->getUser() << "\n"; +} + +void AllocaSlices::print(raw_ostream &OS) const { + if (PointerEscapingInstr) { + OS << "Can't analyze slices for alloca: " << AI << "\n" + << " A pointer to this alloca escaped by:\n" + << " " << *PointerEscapingInstr << "\n"; + return; + } + + OS << "Slices of alloca: " << AI << "\n"; + for (const_iterator I = begin(), E = end(); I != E; ++I) + print(OS, I); +} + +void AllocaSlices::dump(const_iterator I) const { print(dbgs(), I); } +void AllocaSlices::dump() const { print(dbgs()); } + +#endif // !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) + +namespace { +/// \brief Implementation of LoadAndStorePromoter for promoting allocas. +/// +/// This subclass of LoadAndStorePromoter adds overrides to handle promoting +/// the loads and stores of an alloca instruction, as well as updating its +/// debug information. This is used when a domtree is unavailable and thus +/// mem2reg in its full form can't be used to handle promotion of allocas to +/// scalar values. +class AllocaPromoter : public LoadAndStorePromoter { + AllocaInst &AI; + DIBuilder &DIB; + + SmallVector<DbgDeclareInst *, 4> DDIs; + SmallVector<DbgValueInst *, 4> DVIs; + +public: + AllocaPromoter(const SmallVectorImpl<Instruction *> &Insts, SSAUpdater &S, + AllocaInst &AI, DIBuilder &DIB) + : LoadAndStorePromoter(Insts, S), AI(AI), DIB(DIB) {} + + void run(const SmallVectorImpl<Instruction*> &Insts) { + // Retain the debug information attached to the alloca for use when + // rewriting loads and stores. + if (MDNode *DebugNode = MDNode::getIfExists(AI.getContext(), &AI)) { + for (Value::use_iterator UI = DebugNode->use_begin(), + UE = DebugNode->use_end(); + UI != UE; ++UI) + if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(*UI)) + DDIs.push_back(DDI); + else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(*UI)) + DVIs.push_back(DVI); + } + + LoadAndStorePromoter::run(Insts); + + // While we have the debug information, clear it off of the alloca. The + // caller takes care of deleting the alloca. + while (!DDIs.empty()) + DDIs.pop_back_val()->eraseFromParent(); + while (!DVIs.empty()) + DVIs.pop_back_val()->eraseFromParent(); + } + + virtual bool isInstInList(Instruction *I, + const SmallVectorImpl<Instruction*> &Insts) const { + Value *Ptr; + if (LoadInst *LI = dyn_cast<LoadInst>(I)) + Ptr = LI->getOperand(0); + else + Ptr = cast<StoreInst>(I)->getPointerOperand(); + + // Only used to detect cycles, which will be rare and quickly found as + // we're walking up a chain of defs rather than down through uses. + SmallPtrSet<Value *, 4> Visited; + + do { + if (Ptr == &AI) + return true; + + if (BitCastInst *BCI = dyn_cast<BitCastInst>(Ptr)) + Ptr = BCI->getOperand(0); + else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Ptr)) + Ptr = GEPI->getPointerOperand(); + else + return false; + + } while (Visited.insert(Ptr)); + + return false; + } + + virtual void updateDebugInfo(Instruction *Inst) const { + for (SmallVectorImpl<DbgDeclareInst *>::const_iterator I = DDIs.begin(), + E = DDIs.end(); I != E; ++I) { + DbgDeclareInst *DDI = *I; + if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) + ConvertDebugDeclareToDebugValue(DDI, SI, DIB); + else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) + ConvertDebugDeclareToDebugValue(DDI, LI, DIB); + } + for (SmallVectorImpl<DbgValueInst *>::const_iterator I = DVIs.begin(), + E = DVIs.end(); I != E; ++I) { + DbgValueInst *DVI = *I; + Value *Arg = 0; + if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { + // If an argument is zero extended then use argument directly. The ZExt + // may be zapped by an optimization pass in future. + if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0))) + Arg = dyn_cast<Argument>(ZExt->getOperand(0)); + else if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0))) + Arg = dyn_cast<Argument>(SExt->getOperand(0)); + if (!Arg) + Arg = SI->getValueOperand(); + } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) { + Arg = LI->getPointerOperand(); + } else { + continue; + } + Instruction *DbgVal = + DIB.insertDbgValueIntrinsic(Arg, 0, DIVariable(DVI->getVariable()), + Inst); + DbgVal->setDebugLoc(DVI->getDebugLoc()); + } + } +}; +} // end anon namespace + + +namespace { +/// \brief An optimization pass providing Scalar Replacement of Aggregates. +/// +/// This pass takes allocations which can be completely analyzed (that is, they +/// don't escape) and tries to turn them into scalar SSA values. There are +/// a few steps to this process. +/// +/// 1) It takes allocations of aggregates and analyzes the ways in which they +/// are used to try to split them into smaller allocations, ideally of +/// a single scalar data type. It will split up memcpy and memset accesses +/// as necessary and try to isolate individual scalar accesses. +/// 2) It will transform accesses into forms which are suitable for SSA value +/// promotion. This can be replacing a memset with a scalar store of an +/// integer value, or it can involve speculating operations on a PHI or +/// select to be a PHI or select of the results. +/// 3) Finally, this will try to detect a pattern of accesses which map cleanly +/// onto insert and extract operations on a vector value, and convert them to +/// this form. By doing so, it will enable promotion of vector aggregates to +/// SSA vector values. +class SROA : public FunctionPass { + const bool RequiresDomTree; + + LLVMContext *C; + const DataLayout *DL; + DominatorTree *DT; + + /// \brief Worklist of alloca instructions to simplify. + /// + /// Each alloca in the function is added to this. Each new alloca formed gets + /// added to it as well to recursively simplify unless that alloca can be + /// directly promoted. Finally, each time we rewrite a use of an alloca other + /// the one being actively rewritten, we add it back onto the list if not + /// already present to ensure it is re-visited. + SetVector<AllocaInst *, SmallVector<AllocaInst *, 16> > Worklist; + + /// \brief A collection of instructions to delete. + /// We try to batch deletions to simplify code and make things a bit more + /// efficient. + SetVector<Instruction *, SmallVector<Instruction *, 8> > DeadInsts; + + /// \brief Post-promotion worklist. + /// + /// Sometimes we discover an alloca which has a high probability of becoming + /// viable for SROA after a round of promotion takes place. In those cases, + /// the alloca is enqueued here for re-processing. + /// + /// Note that we have to be very careful to clear allocas out of this list in + /// the event they are deleted. + SetVector<AllocaInst *, SmallVector<AllocaInst *, 16> > PostPromotionWorklist; + + /// \brief A collection of alloca instructions we can directly promote. + std::vector<AllocaInst *> PromotableAllocas; + + /// \brief A worklist of PHIs to speculate prior to promoting allocas. + /// + /// All of these PHIs have been checked for the safety of speculation and by + /// being speculated will allow promoting allocas currently in the promotable + /// queue. + SetVector<PHINode *, SmallVector<PHINode *, 2> > SpeculatablePHIs; + + /// \brief A worklist of select instructions to speculate prior to promoting + /// allocas. + /// + /// All of these select instructions have been checked for the safety of + /// speculation and by being speculated will allow promoting allocas + /// currently in the promotable queue. + SetVector<SelectInst *, SmallVector<SelectInst *, 2> > SpeculatableSelects; + +public: + SROA(bool RequiresDomTree = true) + : FunctionPass(ID), RequiresDomTree(RequiresDomTree), + C(0), DL(0), DT(0) { + initializeSROAPass(*PassRegistry::getPassRegistry()); + } + bool runOnFunction(Function &F); + void getAnalysisUsage(AnalysisUsage &AU) const; + + const char *getPassName() const { return "SROA"; } + static char ID; + +private: + friend class PHIOrSelectSpeculator; + friend class AllocaSliceRewriter; + + bool rewritePartition(AllocaInst &AI, AllocaSlices &S, + AllocaSlices::iterator B, AllocaSlices::iterator E, + int64_t BeginOffset, int64_t EndOffset, + ArrayRef<AllocaSlices::iterator> SplitUses); + bool splitAlloca(AllocaInst &AI, AllocaSlices &S); + bool runOnAlloca(AllocaInst &AI); + void deleteDeadInstructions(SmallPtrSet<AllocaInst *, 4> &DeletedAllocas); + bool promoteAllocas(Function &F); +}; +} + +char SROA::ID = 0; + +FunctionPass *llvm::createSROAPass(bool RequiresDomTree) { + return new SROA(RequiresDomTree); +} + +INITIALIZE_PASS_BEGIN(SROA, "sroa", "Scalar Replacement Of Aggregates", + false, false) +INITIALIZE_PASS_DEPENDENCY(DominatorTree) +INITIALIZE_PASS_END(SROA, "sroa", "Scalar Replacement Of Aggregates", + false, false) + +/// Walk the range of a partitioning looking for a common type to cover this +/// sequence of slices. +static Type *findCommonType(AllocaSlices::const_iterator B, + AllocaSlices::const_iterator E, + uint64_t EndOffset) { + Type *Ty = 0; + bool IgnoreNonIntegralTypes = false; + for (AllocaSlices::const_iterator I = B; I != E; ++I) { + Use *U = I->getUse(); + if (isa<IntrinsicInst>(*U->getUser())) + continue; + if (I->beginOffset() != B->beginOffset() || I->endOffset() != EndOffset) + continue; + + Type *UserTy = 0; + if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) { + UserTy = LI->getType(); + } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) { + UserTy = SI->getValueOperand()->getType(); + } else { + IgnoreNonIntegralTypes = true; // Give up on anything but an iN type. + continue; + } + + if (IntegerType *ITy = dyn_cast<IntegerType>(UserTy)) { + // If the type is larger than the partition, skip it. We only encounter + // this for split integer operations where we want to use the type of the + // entity causing the split. Also skip if the type is not a byte width + // multiple. + if (ITy->getBitWidth() % 8 != 0 || + ITy->getBitWidth() / 8 > (EndOffset - B->beginOffset())) + continue; + + // If we have found an integer type use covering the alloca, use that + // regardless of the other types, as integers are often used for + // a "bucket of bits" type. + // + // NB: This *must* be the only return from inside the loop so that the + // order of slices doesn't impact the computed type. + return ITy; + } else if (IgnoreNonIntegralTypes) { + continue; + } + + if (Ty && Ty != UserTy) + IgnoreNonIntegralTypes = true; // Give up on anything but an iN type. + + Ty = UserTy; + } + return Ty; +} + +/// 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 operands +/// to the select can be loaded unconditionally. +/// +/// FIXME: This should be hoisted into a generic utility, likely in +/// Transforms/Util/Local.h +static bool isSafePHIToSpeculate(PHINode &PN, + const DataLayout *DL = 0) { + // 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; + bool HaveLoad = false; + 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->isSimple()) + 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()); + HaveLoad = true; + } + + if (!HaveLoad) + return false; + + // We can only 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 Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) { + TerminatorInst *TI = PN.getIncomingBlock(Idx)->getTerminator(); + Value *InVal = PN.getIncomingValue(Idx); + + // If the value is produced by the terminator of the predecessor (an + // invoke) or it has side-effects, there is no valid place to put a load + // in the predecessor. + if (TI == InVal || TI->mayHaveSideEffects()) + return false; + + // If the predecessor has a single successor, then the edge isn't + // critical. + if (TI->getNumSuccessors() == 1) + continue; + + // 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, TI, MaxAlign, DL)) + continue; + + return false; + } + + return true; +} + +static void speculatePHINodeLoads(PHINode &PN) { + DEBUG(dbgs() << " original: " << PN << "\n"); + + Type *LoadTy = cast<PointerType>(PN.getType())->getElementType(); + IRBuilderTy PHIBuilder(&PN); + PHINode *NewPN = PHIBuilder.CreatePHI(LoadTy, PN.getNumIncomingValues(), + PN.getName() + ".sroa.speculated"); + + // 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. + LoadInst *SomeLoad = cast<LoadInst>(*PN.use_begin()); + MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa); + unsigned Align = SomeLoad->getAlignment(); + + // Rewrite all loads of the PN to use the new PHI. + while (!PN.use_empty()) { + LoadInst *LI = cast<LoadInst>(*PN.use_begin()); + LI->replaceAllUsesWith(NewPN); + LI->eraseFromParent(); + } + + // Inject loads into all of the pred blocks. + for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) { + BasicBlock *Pred = PN.getIncomingBlock(Idx); + TerminatorInst *TI = Pred->getTerminator(); + Value *InVal = PN.getIncomingValue(Idx); + IRBuilderTy PredBuilder(TI); + + LoadInst *Load = PredBuilder.CreateLoad( + InVal, (PN.getName() + ".sroa.speculate.load." + Pred->getName())); + ++NumLoadsSpeculated; + Load->setAlignment(Align); + if (TBAATag) + Load->setMetadata(LLVMContext::MD_tbaa, TBAATag); + NewPN->addIncoming(Load, Pred); + } + + DEBUG(dbgs() << " speculated to: " << *NewPN << "\n"); + PN.eraseFromParent(); +} + +/// 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 DataLayout *DL = 0) { + Value *TValue = SI.getTrueValue(); + Value *FValue = SI.getFalseValue(); + bool TDerefable = TValue->isDereferenceablePointer(); + bool FDerefable = FValue->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->isSimple()) + 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(TValue, LI, LI->getAlignment(), DL)) + return false; + if (!FDerefable && + !isSafeToLoadUnconditionally(FValue, LI, LI->getAlignment(), DL)) + return false; + } + + return true; +} + +static void speculateSelectInstLoads(SelectInst &SI) { + DEBUG(dbgs() << " original: " << SI << "\n"); + + IRBuilderTy IRB(&SI); + Value *TV = SI.getTrueValue(); + Value *FV = SI.getFalseValue(); + // Replace the loads of the select with a select of two loads. + while (!SI.use_empty()) { + LoadInst *LI = cast<LoadInst>(*SI.use_begin()); + assert(LI->isSimple() && "We only speculate simple loads"); + + IRB.SetInsertPoint(LI); + LoadInst *TL = + IRB.CreateLoad(TV, LI->getName() + ".sroa.speculate.load.true"); + LoadInst *FL = + IRB.CreateLoad(FV, LI->getName() + ".sroa.speculate.load.false"); + NumLoadsSpeculated += 2; + + // Transfer alignment and TBAA info if present. + TL->setAlignment(LI->getAlignment()); + FL->setAlignment(LI->getAlignment()); + if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) { + TL->setMetadata(LLVMContext::MD_tbaa, Tag); + FL->setMetadata(LLVMContext::MD_tbaa, Tag); + } + + Value *V = IRB.CreateSelect(SI.getCondition(), TL, FL, + LI->getName() + ".sroa.speculated"); + + DEBUG(dbgs() << " speculated to: " << *V << "\n"); + LI->replaceAllUsesWith(V); + LI->eraseFromParent(); + } + SI.eraseFromParent(); +} + +/// \brief Build a GEP out of a base pointer and indices. +/// +/// This will return the BasePtr if that is valid, or build a new GEP +/// instruction using the IRBuilder if GEP-ing is needed. +static Value *buildGEP(IRBuilderTy &IRB, Value *BasePtr, + SmallVectorImpl<Value *> &Indices) { + if (Indices.empty()) + return BasePtr; + + // A single zero index is a no-op, so check for this and avoid building a GEP + // in that case. + if (Indices.size() == 1 && cast<ConstantInt>(Indices.back())->isZero()) + return BasePtr; + + return IRB.CreateInBoundsGEP(BasePtr, Indices, "idx"); +} + +/// \brief Get a natural GEP off of the BasePtr walking through Ty toward +/// TargetTy without changing the offset of the pointer. +/// +/// This routine assumes we've already established a properly offset GEP with +/// Indices, and arrived at the Ty type. The goal is to continue to GEP with +/// zero-indices down through type layers until we find one the same as +/// TargetTy. If we can't find one with the same type, we at least try to use +/// one with the same size. If none of that works, we just produce the GEP as +/// indicated by Indices to have the correct offset. +static Value *getNaturalGEPWithType(IRBuilderTy &IRB, const DataLayout &DL, + Value *BasePtr, Type *Ty, Type *TargetTy, + SmallVectorImpl<Value *> &Indices) { + if (Ty == TargetTy) + return buildGEP(IRB, BasePtr, Indices); + + // See if we can descend into a struct and locate a field with the correct + // type. + unsigned NumLayers = 0; + Type *ElementTy = Ty; + do { + if (ElementTy->isPointerTy()) + break; + if (SequentialType *SeqTy = dyn_cast<SequentialType>(ElementTy)) { + ElementTy = SeqTy->getElementType(); + // Note that we use the default address space as this index is over an + // array or a vector, not a pointer. + Indices.push_back(IRB.getInt(APInt(DL.getPointerSizeInBits(0), 0))); + } else if (StructType *STy = dyn_cast<StructType>(ElementTy)) { + if (STy->element_begin() == STy->element_end()) + break; // Nothing left to descend into. + ElementTy = *STy->element_begin(); + Indices.push_back(IRB.getInt32(0)); + } else { + break; + } + ++NumLayers; + } while (ElementTy != TargetTy); + if (ElementTy != TargetTy) + Indices.erase(Indices.end() - NumLayers, Indices.end()); + + return buildGEP(IRB, BasePtr, Indices); +} + +/// \brief Recursively compute indices for a natural GEP. +/// +/// This is the recursive step for getNaturalGEPWithOffset that walks down the +/// element types adding appropriate indices for the GEP. +static Value *getNaturalGEPRecursively(IRBuilderTy &IRB, const DataLayout &DL, + Value *Ptr, Type *Ty, APInt &Offset, + Type *TargetTy, + SmallVectorImpl<Value *> &Indices) { + if (Offset == 0) + return getNaturalGEPWithType(IRB, DL, Ptr, Ty, TargetTy, Indices); + + // We can't recurse through pointer types. + if (Ty->isPointerTy()) + return 0; + + // We try to analyze GEPs over vectors here, but note that these GEPs are + // extremely poorly defined currently. The long-term goal is to remove GEPing + // over a vector from the IR completely. + if (VectorType *VecTy = dyn_cast<VectorType>(Ty)) { + unsigned ElementSizeInBits = DL.getTypeSizeInBits(VecTy->getScalarType()); + if (ElementSizeInBits % 8) + return 0; // GEPs over non-multiple of 8 size vector elements are invalid. + APInt ElementSize(Offset.getBitWidth(), ElementSizeInBits / 8); + APInt NumSkippedElements = Offset.sdiv(ElementSize); + if (NumSkippedElements.ugt(VecTy->getNumElements())) + return 0; + Offset -= NumSkippedElements * ElementSize; + Indices.push_back(IRB.getInt(NumSkippedElements)); + return getNaturalGEPRecursively(IRB, DL, Ptr, VecTy->getElementType(), + Offset, TargetTy, Indices); + } + + if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) { + Type *ElementTy = ArrTy->getElementType(); + APInt ElementSize(Offset.getBitWidth(), DL.getTypeAllocSize(ElementTy)); + APInt NumSkippedElements = Offset.sdiv(ElementSize); + if (NumSkippedElements.ugt(ArrTy->getNumElements())) + return 0; + + Offset -= NumSkippedElements * ElementSize; + Indices.push_back(IRB.getInt(NumSkippedElements)); + return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy, + Indices); + } + + StructType *STy = dyn_cast<StructType>(Ty); + if (!STy) + return 0; + + const StructLayout *SL = DL.getStructLayout(STy); + uint64_t StructOffset = Offset.getZExtValue(); + if (StructOffset >= SL->getSizeInBytes()) + return 0; + unsigned Index = SL->getElementContainingOffset(StructOffset); + Offset -= APInt(Offset.getBitWidth(), SL->getElementOffset(Index)); + Type *ElementTy = STy->getElementType(Index); + if (Offset.uge(DL.getTypeAllocSize(ElementTy))) + return 0; // The offset points into alignment padding. + + Indices.push_back(IRB.getInt32(Index)); + return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy, + Indices); +} + +/// \brief Get a natural GEP from a base pointer to a particular offset and +/// resulting in a particular type. +/// +/// The goal is to produce a "natural" looking GEP that works with the existing +/// composite types to arrive at the appropriate offset and element type for +/// a pointer. TargetTy is the element type the returned GEP should point-to if +/// possible. We recurse by decreasing Offset, adding the appropriate index to +/// Indices, and setting Ty to the result subtype. +/// +/// If no natural GEP can be constructed, this function returns null. +static Value *getNaturalGEPWithOffset(IRBuilderTy &IRB, const DataLayout &DL, + Value *Ptr, APInt Offset, Type *TargetTy, + SmallVectorImpl<Value *> &Indices) { + PointerType *Ty = cast<PointerType>(Ptr->getType()); + + // Don't consider any GEPs through an i8* as natural unless the TargetTy is + // an i8. + if (Ty == IRB.getInt8PtrTy() && TargetTy->isIntegerTy(8)) + return 0; + + Type *ElementTy = Ty->getElementType(); + if (!ElementTy->isSized()) + return 0; // We can't GEP through an unsized element. + APInt ElementSize(Offset.getBitWidth(), DL.getTypeAllocSize(ElementTy)); + if (ElementSize == 0) + return 0; // Zero-length arrays can't help us build a natural GEP. + APInt NumSkippedElements = Offset.sdiv(ElementSize); + + Offset -= NumSkippedElements * ElementSize; + Indices.push_back(IRB.getInt(NumSkippedElements)); + return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy, + Indices); +} + +/// \brief Compute an adjusted pointer from Ptr by Offset bytes where the +/// resulting pointer has PointerTy. +/// +/// This tries very hard to compute a "natural" GEP which arrives at the offset +/// and produces the pointer type desired. Where it cannot, it will try to use +/// the natural GEP to arrive at the offset and bitcast to the type. Where that +/// fails, it will try to use an existing i8* and GEP to the byte offset and +/// bitcast to the type. +/// +/// The strategy for finding the more natural GEPs is to peel off layers of the +/// pointer, walking back through bit casts and GEPs, searching for a base +/// pointer from which we can compute a natural GEP with the desired +/// properties. The algorithm tries to fold as many constant indices into +/// a single GEP as possible, thus making each GEP more independent of the +/// surrounding code. +static Value *getAdjustedPtr(IRBuilderTy &IRB, const DataLayout &DL, + Value *Ptr, APInt Offset, Type *PointerTy) { + // Even though we don't look through PHI nodes, we could be called on an + // instruction in an unreachable block, which may be on a cycle. + SmallPtrSet<Value *, 4> Visited; + Visited.insert(Ptr); + SmallVector<Value *, 4> Indices; + + // We may end up computing an offset pointer that has the wrong type. If we + // never are able to compute one directly that has the correct type, we'll + // fall back to it, so keep it around here. + Value *OffsetPtr = 0; + + // Remember any i8 pointer we come across to re-use if we need to do a raw + // byte offset. + Value *Int8Ptr = 0; + APInt Int8PtrOffset(Offset.getBitWidth(), 0); + + Type *TargetTy = PointerTy->getPointerElementType(); + + do { + // First fold any existing GEPs into the offset. + while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) { + APInt GEPOffset(Offset.getBitWidth(), 0); + if (!GEP->accumulateConstantOffset(DL, GEPOffset)) + break; + Offset += GEPOffset; + Ptr = GEP->getPointerOperand(); + if (!Visited.insert(Ptr)) + break; + } + + // See if we can perform a natural GEP here. + Indices.clear(); + if (Value *P = getNaturalGEPWithOffset(IRB, DL, Ptr, Offset, TargetTy, + Indices)) { + if (P->getType() == PointerTy) { + // Zap any offset pointer that we ended up computing in previous rounds. + if (OffsetPtr && OffsetPtr->use_empty()) + if (Instruction *I = dyn_cast<Instruction>(OffsetPtr)) + I->eraseFromParent(); + return P; + } + if (!OffsetPtr) { + OffsetPtr = P; + } + } + + // Stash this pointer if we've found an i8*. + if (Ptr->getType()->isIntegerTy(8)) { + Int8Ptr = Ptr; + Int8PtrOffset = Offset; + } + + // Peel off a layer of the pointer and update the offset appropriately. + if (Operator::getOpcode(Ptr) == Instruction::BitCast) { + Ptr = cast<Operator>(Ptr)->getOperand(0); + } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(Ptr)) { + if (GA->mayBeOverridden()) + break; + Ptr = GA->getAliasee(); + } else { + break; + } + assert(Ptr->getType()->isPointerTy() && "Unexpected operand type!"); + } while (Visited.insert(Ptr)); + + if (!OffsetPtr) { + if (!Int8Ptr) { + Int8Ptr = IRB.CreateBitCast(Ptr, IRB.getInt8PtrTy(), + "raw_cast"); + Int8PtrOffset = Offset; + } + + OffsetPtr = Int8PtrOffset == 0 ? Int8Ptr : + IRB.CreateInBoundsGEP(Int8Ptr, IRB.getInt(Int8PtrOffset), + "raw_idx"); + } + Ptr = OffsetPtr; + + // On the off chance we were targeting i8*, guard the bitcast here. + if (Ptr->getType() != PointerTy) + Ptr = IRB.CreateBitCast(Ptr, PointerTy, "cast"); + + return Ptr; +} + +/// \brief Test whether we can convert a value from the old to the new type. +/// +/// This predicate should be used to guard calls to convertValue in order to +/// ensure that we only try to convert viable values. The strategy is that we +/// will peel off single element struct and array wrappings to get to an +/// underlying value, and convert that value. +static bool canConvertValue(const DataLayout &DL, Type *OldTy, Type *NewTy) { + if (OldTy == NewTy) + return true; + if (IntegerType *OldITy = dyn_cast<IntegerType>(OldTy)) + if (IntegerType *NewITy = dyn_cast<IntegerType>(NewTy)) + if (NewITy->getBitWidth() >= OldITy->getBitWidth()) + return true; + if (DL.getTypeSizeInBits(NewTy) != DL.getTypeSizeInBits(OldTy)) + return false; + if (!NewTy->isSingleValueType() || !OldTy->isSingleValueType()) + return false; + + // We can convert pointers to integers and vice-versa. Same for vectors + // of pointers and integers. + OldTy = OldTy->getScalarType(); + NewTy = NewTy->getScalarType(); + if (NewTy->isPointerTy() || OldTy->isPointerTy()) { + if (NewTy->isPointerTy() && OldTy->isPointerTy()) + return true; + if (NewTy->isIntegerTy() || OldTy->isIntegerTy()) + return true; + return false; + } + + return true; +} + +/// \brief Generic routine to convert an SSA value to a value of a different +/// type. +/// +/// This will try various different casting techniques, such as bitcasts, +/// inttoptr, and ptrtoint casts. Use the \c canConvertValue predicate to test +/// two types for viability with this routine. +static Value *convertValue(const DataLayout &DL, IRBuilderTy &IRB, Value *V, + Type *NewTy) { + Type *OldTy = V->getType(); + assert(canConvertValue(DL, OldTy, NewTy) && "Value not convertable to type"); + + if (OldTy == NewTy) + return V; + + if (IntegerType *OldITy = dyn_cast<IntegerType>(OldTy)) + if (IntegerType *NewITy = dyn_cast<IntegerType>(NewTy)) + if (NewITy->getBitWidth() > OldITy->getBitWidth()) + return IRB.CreateZExt(V, NewITy); + + // See if we need inttoptr for this type pair. A cast involving both scalars + // and vectors requires and additional bitcast. + if (OldTy->getScalarType()->isIntegerTy() && + NewTy->getScalarType()->isPointerTy()) { + // Expand <2 x i32> to i8* --> <2 x i32> to i64 to i8* + if (OldTy->isVectorTy() && !NewTy->isVectorTy()) + return IRB.CreateIntToPtr(IRB.CreateBitCast(V, DL.getIntPtrType(NewTy)), + NewTy); + + // Expand i128 to <2 x i8*> --> i128 to <2 x i64> to <2 x i8*> + if (!OldTy->isVectorTy() && NewTy->isVectorTy()) + return IRB.CreateIntToPtr(IRB.CreateBitCast(V, DL.getIntPtrType(NewTy)), + NewTy); + + return IRB.CreateIntToPtr(V, NewTy); + } + + // See if we need ptrtoint for this type pair. A cast involving both scalars + // and vectors requires and additional bitcast. + if (OldTy->getScalarType()->isPointerTy() && + NewTy->getScalarType()->isIntegerTy()) { + // Expand <2 x i8*> to i128 --> <2 x i8*> to <2 x i64> to i128 + if (OldTy->isVectorTy() && !NewTy->isVectorTy()) + return IRB.CreateBitCast(IRB.CreatePtrToInt(V, DL.getIntPtrType(OldTy)), + NewTy); + + // Expand i8* to <2 x i32> --> i8* to i64 to <2 x i32> + if (!OldTy->isVectorTy() && NewTy->isVectorTy()) + return IRB.CreateBitCast(IRB.CreatePtrToInt(V, DL.getIntPtrType(OldTy)), + NewTy); + + return IRB.CreatePtrToInt(V, NewTy); + } + + return IRB.CreateBitCast(V, NewTy); +} + +/// \brief Test whether the given slice use can be promoted to a vector. +/// +/// This function is called to test each entry in a partioning which is slated +/// for a single slice. +static bool isVectorPromotionViableForSlice( + const DataLayout &DL, AllocaSlices &S, uint64_t SliceBeginOffset, + uint64_t SliceEndOffset, VectorType *Ty, uint64_t ElementSize, + AllocaSlices::const_iterator I) { + // First validate the slice offsets. + uint64_t BeginOffset = + std::max(I->beginOffset(), SliceBeginOffset) - SliceBeginOffset; + uint64_t BeginIndex = BeginOffset / ElementSize; + if (BeginIndex * ElementSize != BeginOffset || + BeginIndex >= Ty->getNumElements()) + return false; + uint64_t EndOffset = + std::min(I->endOffset(), SliceEndOffset) - SliceBeginOffset; + uint64_t EndIndex = EndOffset / ElementSize; + if (EndIndex * ElementSize != EndOffset || EndIndex > Ty->getNumElements()) + return false; + + assert(EndIndex > BeginIndex && "Empty vector!"); + uint64_t NumElements = EndIndex - BeginIndex; + Type *SliceTy = + (NumElements == 1) ? Ty->getElementType() + : VectorType::get(Ty->getElementType(), NumElements); + + Type *SplitIntTy = + Type::getIntNTy(Ty->getContext(), NumElements * ElementSize * 8); + + Use *U = I->getUse(); + + if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) { + if (MI->isVolatile()) + return false; + if (!I->isSplittable()) + return false; // Skip any unsplittable intrinsics. + } else if (U->get()->getType()->getPointerElementType()->isStructTy()) { + // Disable vector promotion when there are loads or stores of an FCA. + return false; + } else if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) { + if (LI->isVolatile()) + return false; + Type *LTy = LI->getType(); + if (SliceBeginOffset > I->beginOffset() || + SliceEndOffset < I->endOffset()) { + assert(LTy->isIntegerTy()); + LTy = SplitIntTy; + } + if (!canConvertValue(DL, SliceTy, LTy)) + return false; + } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) { + if (SI->isVolatile()) + return false; + Type *STy = SI->getValueOperand()->getType(); + if (SliceBeginOffset > I->beginOffset() || + SliceEndOffset < I->endOffset()) { + assert(STy->isIntegerTy()); + STy = SplitIntTy; + } + if (!canConvertValue(DL, STy, SliceTy)) + return false; + } else { + return false; + } + + return true; +} + +/// \brief Test whether the given alloca partitioning and range of slices can be +/// promoted to a vector. +/// +/// This is a quick test to check whether we can rewrite a particular alloca +/// partition (and its newly formed alloca) into a vector alloca with only +/// whole-vector loads and stores such that it could be promoted to a vector +/// SSA value. We only can ensure this for a limited set of operations, and we +/// don't want to do the rewrites unless we are confident that the result will +/// be promotable, so we have an early test here. +static bool +isVectorPromotionViable(const DataLayout &DL, Type *AllocaTy, AllocaSlices &S, + uint64_t SliceBeginOffset, uint64_t SliceEndOffset, + AllocaSlices::const_iterator I, + AllocaSlices::const_iterator E, + ArrayRef<AllocaSlices::iterator> SplitUses) { + VectorType *Ty = dyn_cast<VectorType>(AllocaTy); + if (!Ty) + return false; + + uint64_t ElementSize = DL.getTypeSizeInBits(Ty->getScalarType()); + + // While the definition of LLVM vectors is bitpacked, we don't support sizes + // that aren't byte sized. + if (ElementSize % 8) + return false; + assert((DL.getTypeSizeInBits(Ty) % 8) == 0 && + "vector size not a multiple of element size?"); + ElementSize /= 8; + + for (; I != E; ++I) + if (!isVectorPromotionViableForSlice(DL, S, SliceBeginOffset, + SliceEndOffset, Ty, ElementSize, I)) + return false; + + for (ArrayRef<AllocaSlices::iterator>::const_iterator SUI = SplitUses.begin(), + SUE = SplitUses.end(); + SUI != SUE; ++SUI) + if (!isVectorPromotionViableForSlice(DL, S, SliceBeginOffset, + SliceEndOffset, Ty, ElementSize, *SUI)) + return false; + + return true; +} + +/// \brief Test whether a slice of an alloca is valid for integer widening. +/// +/// This implements the necessary checking for the \c isIntegerWideningViable +/// test below on a single slice of the alloca. +static bool isIntegerWideningViableForSlice(const DataLayout &DL, + Type *AllocaTy, + uint64_t AllocBeginOffset, + uint64_t Size, AllocaSlices &S, + AllocaSlices::const_iterator I, + bool &WholeAllocaOp) { + uint64_t RelBegin = I->beginOffset() - AllocBeginOffset; + uint64_t RelEnd = I->endOffset() - AllocBeginOffset; + + // We can't reasonably handle cases where the load or store extends past + // the end of the aloca's type and into its padding. + if (RelEnd > Size) + return false; + + Use *U = I->getUse(); + + if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) { + if (LI->isVolatile()) + return false; + if (RelBegin == 0 && RelEnd == Size) + WholeAllocaOp = true; + if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType())) { + if (ITy->getBitWidth() < DL.getTypeStoreSizeInBits(ITy)) + return false; + } else if (RelBegin != 0 || RelEnd != Size || + !canConvertValue(DL, AllocaTy, LI->getType())) { + // Non-integer loads need to be convertible from the alloca type so that + // they are promotable. + return false; + } + } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) { + Type *ValueTy = SI->getValueOperand()->getType(); + if (SI->isVolatile()) + return false; + if (RelBegin == 0 && RelEnd == Size) + WholeAllocaOp = true; + if (IntegerType *ITy = dyn_cast<IntegerType>(ValueTy)) { + if (ITy->getBitWidth() < DL.getTypeStoreSizeInBits(ITy)) + return false; + } else if (RelBegin != 0 || RelEnd != Size || + !canConvertValue(DL, ValueTy, AllocaTy)) { + // Non-integer stores need to be convertible to the alloca type so that + // they are promotable. + return false; + } + } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) { + if (MI->isVolatile() || !isa<Constant>(MI->getLength())) + return false; + if (!I->isSplittable()) + return false; // Skip any unsplittable intrinsics. + } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U->getUser())) { + if (II->getIntrinsicID() != Intrinsic::lifetime_start && + II->getIntrinsicID() != Intrinsic::lifetime_end) + return false; + } else { + return false; + } + + return true; +} + +/// \brief Test whether the given alloca partition's integer operations can be +/// widened to promotable ones. +/// +/// This is a quick test to check whether we can rewrite the integer loads and +/// stores to a particular alloca into wider loads and stores and be able to +/// promote the resulting alloca. +static bool +isIntegerWideningViable(const DataLayout &DL, Type *AllocaTy, + uint64_t AllocBeginOffset, AllocaSlices &S, + AllocaSlices::const_iterator I, + AllocaSlices::const_iterator E, + ArrayRef<AllocaSlices::iterator> SplitUses) { + uint64_t SizeInBits = DL.getTypeSizeInBits(AllocaTy); + // Don't create integer types larger than the maximum bitwidth. + if (SizeInBits > IntegerType::MAX_INT_BITS) + return false; + + // Don't try to handle allocas with bit-padding. + if (SizeInBits != DL.getTypeStoreSizeInBits(AllocaTy)) + return false; + + // We need to ensure that an integer type with the appropriate bitwidth can + // be converted to the alloca type, whatever that is. We don't want to force + // the alloca itself to have an integer type if there is a more suitable one. + Type *IntTy = Type::getIntNTy(AllocaTy->getContext(), SizeInBits); + if (!canConvertValue(DL, AllocaTy, IntTy) || + !canConvertValue(DL, IntTy, AllocaTy)) + return false; + + uint64_t Size = DL.getTypeStoreSize(AllocaTy); + + // While examining uses, we ensure that the alloca has a covering load or + // store. We don't want to widen the integer operations only to fail to + // promote due to some other unsplittable entry (which we may make splittable + // later). However, if there are only splittable uses, go ahead and assume + // that we cover the alloca. + bool WholeAllocaOp = (I != E) ? false : DL.isLegalInteger(SizeInBits); + + for (; I != E; ++I) + if (!isIntegerWideningViableForSlice(DL, AllocaTy, AllocBeginOffset, Size, + S, I, WholeAllocaOp)) + return false; + + for (ArrayRef<AllocaSlices::iterator>::const_iterator SUI = SplitUses.begin(), + SUE = SplitUses.end(); + SUI != SUE; ++SUI) + if (!isIntegerWideningViableForSlice(DL, AllocaTy, AllocBeginOffset, Size, + S, *SUI, WholeAllocaOp)) + return false; + + return WholeAllocaOp; +} + +static Value *extractInteger(const DataLayout &DL, IRBuilderTy &IRB, Value *V, + IntegerType *Ty, uint64_t Offset, + const Twine &Name) { + DEBUG(dbgs() << " start: " << *V << "\n"); + IntegerType *IntTy = cast<IntegerType>(V->getType()); + assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) && + "Element extends past full value"); + uint64_t ShAmt = 8*Offset; + if (DL.isBigEndian()) + ShAmt = 8*(DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset); + if (ShAmt) { + V = IRB.CreateLShr(V, ShAmt, Name + ".shift"); + DEBUG(dbgs() << " shifted: " << *V << "\n"); + } + assert(Ty->getBitWidth() <= IntTy->getBitWidth() && + "Cannot extract to a larger integer!"); + if (Ty != IntTy) { + V = IRB.CreateTrunc(V, Ty, Name + ".trunc"); + DEBUG(dbgs() << " trunced: " << *V << "\n"); + } + return V; +} + +static Value *insertInteger(const DataLayout &DL, IRBuilderTy &IRB, Value *Old, + Value *V, uint64_t Offset, const Twine &Name) { + IntegerType *IntTy = cast<IntegerType>(Old->getType()); + IntegerType *Ty = cast<IntegerType>(V->getType()); + assert(Ty->getBitWidth() <= IntTy->getBitWidth() && + "Cannot insert a larger integer!"); + DEBUG(dbgs() << " start: " << *V << "\n"); + if (Ty != IntTy) { + V = IRB.CreateZExt(V, IntTy, Name + ".ext"); + DEBUG(dbgs() << " extended: " << *V << "\n"); + } + assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) && + "Element store outside of alloca store"); + uint64_t ShAmt = 8*Offset; + if (DL.isBigEndian()) + ShAmt = 8*(DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset); + if (ShAmt) { + V = IRB.CreateShl(V, ShAmt, Name + ".shift"); + DEBUG(dbgs() << " shifted: " << *V << "\n"); + } + + if (ShAmt || Ty->getBitWidth() < IntTy->getBitWidth()) { + APInt Mask = ~Ty->getMask().zext(IntTy->getBitWidth()).shl(ShAmt); + Old = IRB.CreateAnd(Old, Mask, Name + ".mask"); + DEBUG(dbgs() << " masked: " << *Old << "\n"); + V = IRB.CreateOr(Old, V, Name + ".insert"); + DEBUG(dbgs() << " inserted: " << *V << "\n"); + } + return V; +} + +static Value *extractVector(IRBuilderTy &IRB, Value *V, + unsigned BeginIndex, unsigned EndIndex, + const Twine &Name) { + VectorType *VecTy = cast<VectorType>(V->getType()); + unsigned NumElements = EndIndex - BeginIndex; + assert(NumElements <= VecTy->getNumElements() && "Too many elements!"); + + if (NumElements == VecTy->getNumElements()) + return V; + + if (NumElements == 1) { + V = IRB.CreateExtractElement(V, IRB.getInt32(BeginIndex), + Name + ".extract"); + DEBUG(dbgs() << " extract: " << *V << "\n"); + return V; + } + + SmallVector<Constant*, 8> Mask; + Mask.reserve(NumElements); + for (unsigned i = BeginIndex; i != EndIndex; ++i) + Mask.push_back(IRB.getInt32(i)); + V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()), + ConstantVector::get(Mask), + Name + ".extract"); + DEBUG(dbgs() << " shuffle: " << *V << "\n"); + return V; +} + +static Value *insertVector(IRBuilderTy &IRB, Value *Old, Value *V, + unsigned BeginIndex, const Twine &Name) { + VectorType *VecTy = cast<VectorType>(Old->getType()); + assert(VecTy && "Can only insert a vector into a vector"); + + VectorType *Ty = dyn_cast<VectorType>(V->getType()); + if (!Ty) { + // Single element to insert. + V = IRB.CreateInsertElement(Old, V, IRB.getInt32(BeginIndex), + Name + ".insert"); + DEBUG(dbgs() << " insert: " << *V << "\n"); + return V; + } + + assert(Ty->getNumElements() <= VecTy->getNumElements() && + "Too many elements!"); + if (Ty->getNumElements() == VecTy->getNumElements()) { + assert(V->getType() == VecTy && "Vector type mismatch"); + return V; + } + unsigned EndIndex = BeginIndex + Ty->getNumElements(); + + // When inserting a smaller vector into the larger to store, we first + // use a shuffle vector to widen it with undef elements, and then + // a second shuffle vector to select between the loaded vector and the + // incoming vector. + SmallVector<Constant*, 8> Mask; + Mask.reserve(VecTy->getNumElements()); + for (unsigned i = 0; i != VecTy->getNumElements(); ++i) + if (i >= BeginIndex && i < EndIndex) + Mask.push_back(IRB.getInt32(i - BeginIndex)); + else + Mask.push_back(UndefValue::get(IRB.getInt32Ty())); + V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()), + ConstantVector::get(Mask), + Name + ".expand"); + DEBUG(dbgs() << " shuffle: " << *V << "\n"); + + Mask.clear(); + for (unsigned i = 0; i != VecTy->getNumElements(); ++i) + Mask.push_back(IRB.getInt1(i >= BeginIndex && i < EndIndex)); + + V = IRB.CreateSelect(ConstantVector::get(Mask), V, Old, Name + "blend"); + + DEBUG(dbgs() << " blend: " << *V << "\n"); + return V; +} + +namespace { +/// \brief Visitor to rewrite instructions using p particular slice of an alloca +/// to use a new alloca. +/// +/// Also implements the rewriting to vector-based accesses when the partition +/// passes the isVectorPromotionViable predicate. Most of the rewriting logic +/// lives here. +class AllocaSliceRewriter : public InstVisitor<AllocaSliceRewriter, bool> { + // Befriend the base class so it can delegate to private visit methods. + friend class llvm::InstVisitor<AllocaSliceRewriter, bool>; + typedef llvm::InstVisitor<AllocaSliceRewriter, bool> Base; + + const DataLayout &DL; + AllocaSlices &S; + SROA &Pass; + AllocaInst &OldAI, &NewAI; + const uint64_t NewAllocaBeginOffset, NewAllocaEndOffset; + Type *NewAllocaTy; + + // If we are rewriting an alloca partition which can be written as pure + // vector operations, we stash extra information here. When VecTy is + // non-null, we have some strict guarantees about the rewritten alloca: + // - The new alloca is exactly the size of the vector type here. + // - The accesses all either map to the entire vector or to a single + // element. + // - The set of accessing instructions is only one of those handled above + // in isVectorPromotionViable. Generally these are the same access kinds + // which are promotable via mem2reg. + VectorType *VecTy; + Type *ElementTy; + uint64_t ElementSize; + + // This is a convenience and flag variable that will be null unless the new + // alloca's integer operations should be widened to this integer type due to + // passing isIntegerWideningViable above. If it is non-null, the desired + // integer type will be stored here for easy access during rewriting. + IntegerType *IntTy; + + // The offset of the slice currently being rewritten. + uint64_t BeginOffset, EndOffset; + bool IsSplittable; + bool IsSplit; + Use *OldUse; + Instruction *OldPtr; + + // Output members carrying state about the result of visiting and rewriting + // the slice of the alloca. + bool IsUsedByRewrittenSpeculatableInstructions; + + // Utility IR builder, whose name prefix is setup for each visited use, and + // the insertion point is set to point to the user. + IRBuilderTy IRB; + +public: + AllocaSliceRewriter(const DataLayout &DL, AllocaSlices &S, SROA &Pass, + AllocaInst &OldAI, AllocaInst &NewAI, + uint64_t NewBeginOffset, uint64_t NewEndOffset, + bool IsVectorPromotable = false, + bool IsIntegerPromotable = false) + : DL(DL), S(S), Pass(Pass), OldAI(OldAI), NewAI(NewAI), + NewAllocaBeginOffset(NewBeginOffset), NewAllocaEndOffset(NewEndOffset), + NewAllocaTy(NewAI.getAllocatedType()), + VecTy(IsVectorPromotable ? cast<VectorType>(NewAllocaTy) : 0), + ElementTy(VecTy ? VecTy->getElementType() : 0), + ElementSize(VecTy ? DL.getTypeSizeInBits(ElementTy) / 8 : 0), + IntTy(IsIntegerPromotable + ? Type::getIntNTy( + NewAI.getContext(), + DL.getTypeSizeInBits(NewAI.getAllocatedType())) + : 0), + BeginOffset(), EndOffset(), IsSplittable(), IsSplit(), OldUse(), + OldPtr(), IsUsedByRewrittenSpeculatableInstructions(false), + IRB(NewAI.getContext(), ConstantFolder()) { + if (VecTy) { + assert((DL.getTypeSizeInBits(ElementTy) % 8) == 0 && + "Only multiple-of-8 sized vector elements are viable"); + ++NumVectorized; + } + assert((!IsVectorPromotable && !IsIntegerPromotable) || + IsVectorPromotable != IsIntegerPromotable); + } + + bool visit(AllocaSlices::const_iterator I) { + bool CanSROA = true; + BeginOffset = I->beginOffset(); + EndOffset = I->endOffset(); + IsSplittable = I->isSplittable(); + IsSplit = + BeginOffset < NewAllocaBeginOffset || EndOffset > NewAllocaEndOffset; + + OldUse = I->getUse(); + OldPtr = cast<Instruction>(OldUse->get()); + + Instruction *OldUserI = cast<Instruction>(OldUse->getUser()); + IRB.SetInsertPoint(OldUserI); + IRB.SetCurrentDebugLocation(OldUserI->getDebugLoc()); + IRB.SetNamePrefix(Twine(NewAI.getName()) + "." + Twine(BeginOffset) + "."); + + CanSROA &= visit(cast<Instruction>(OldUse->getUser())); + if (VecTy || IntTy) + assert(CanSROA); + return CanSROA; + } + + /// \brief Query whether this slice is used by speculatable instructions after + /// rewriting. + /// + /// These instructions (PHIs and Selects currently) require the alloca slice + /// to run back through the rewriter. Thus, they are promotable, but not on + /// this iteration. This is distinct from a slice which is unpromotable for + /// some other reason, in which case we don't even want to perform the + /// speculation. This can be querried at any time and reflects whether (at + /// that point) a visit call has rewritten a speculatable instruction on the + /// current slice. + bool isUsedByRewrittenSpeculatableInstructions() const { + return IsUsedByRewrittenSpeculatableInstructions; + } + +private: + // Make sure the other visit overloads are visible. + using Base::visit; + + // Every instruction which can end up as a user must have a rewrite rule. + bool visitInstruction(Instruction &I) { + DEBUG(dbgs() << " !!!! Cannot rewrite: " << I << "\n"); + llvm_unreachable("No rewrite rule for this instruction!"); + } + + Value *getAdjustedAllocaPtr(IRBuilderTy &IRB, uint64_t Offset, + Type *PointerTy) { + assert(Offset >= NewAllocaBeginOffset); + return getAdjustedPtr(IRB, DL, &NewAI, APInt(DL.getPointerSizeInBits(), + Offset - NewAllocaBeginOffset), + PointerTy); + } + + /// \brief Compute suitable alignment to access an offset into the new alloca. + unsigned getOffsetAlign(uint64_t Offset) { + unsigned NewAIAlign = NewAI.getAlignment(); + if (!NewAIAlign) + NewAIAlign = DL.getABITypeAlignment(NewAI.getAllocatedType()); + return MinAlign(NewAIAlign, Offset); + } + + /// \brief Compute suitable alignment to access a type at an offset of the + /// new alloca. + /// + /// \returns zero if the type's ABI alignment is a suitable alignment, + /// otherwise returns the maximal suitable alignment. + unsigned getOffsetTypeAlign(Type *Ty, uint64_t Offset) { + unsigned Align = getOffsetAlign(Offset); + return Align == DL.getABITypeAlignment(Ty) ? 0 : Align; + } + + unsigned getIndex(uint64_t Offset) { + assert(VecTy && "Can only call getIndex when rewriting a vector"); + uint64_t RelOffset = Offset - NewAllocaBeginOffset; + assert(RelOffset / ElementSize < UINT32_MAX && "Index out of bounds"); + uint32_t Index = RelOffset / ElementSize; + assert(Index * ElementSize == RelOffset); + return Index; + } + + void deleteIfTriviallyDead(Value *V) { + Instruction *I = cast<Instruction>(V); + if (isInstructionTriviallyDead(I)) + Pass.DeadInsts.insert(I); + } + + Value *rewriteVectorizedLoadInst(uint64_t NewBeginOffset, + uint64_t NewEndOffset) { + unsigned BeginIndex = getIndex(NewBeginOffset); + unsigned EndIndex = getIndex(NewEndOffset); + assert(EndIndex > BeginIndex && "Empty vector!"); + + Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), + "load"); + return extractVector(IRB, V, BeginIndex, EndIndex, "vec"); + } + + Value *rewriteIntegerLoad(LoadInst &LI, uint64_t NewBeginOffset, + uint64_t NewEndOffset) { + assert(IntTy && "We cannot insert an integer to the alloca"); + assert(!LI.isVolatile()); + Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), + "load"); + V = convertValue(DL, IRB, V, IntTy); + assert(NewBeginOffset >= NewAllocaBeginOffset && "Out of bounds offset"); + uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset; + if (Offset > 0 || NewEndOffset < NewAllocaEndOffset) + V = extractInteger(DL, IRB, V, cast<IntegerType>(LI.getType()), Offset, + "extract"); + return V; + } + + bool visitLoadInst(LoadInst &LI) { + DEBUG(dbgs() << " original: " << LI << "\n"); + Value *OldOp = LI.getOperand(0); + assert(OldOp == OldPtr); + + // Compute the intersecting offset range. + assert(BeginOffset < NewAllocaEndOffset); + assert(EndOffset > NewAllocaBeginOffset); + uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset); + uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset); + + uint64_t Size = NewEndOffset - NewBeginOffset; + + Type *TargetTy = IsSplit ? Type::getIntNTy(LI.getContext(), Size * 8) + : LI.getType(); + bool IsPtrAdjusted = false; + Value *V; + if (VecTy) { + V = rewriteVectorizedLoadInst(NewBeginOffset, NewEndOffset); + } else if (IntTy && LI.getType()->isIntegerTy()) { + V = rewriteIntegerLoad(LI, NewBeginOffset, NewEndOffset); + } else if (NewBeginOffset == NewAllocaBeginOffset && + canConvertValue(DL, NewAllocaTy, LI.getType())) { + V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), + LI.isVolatile(), "load"); + } else { + Type *LTy = TargetTy->getPointerTo(); + V = IRB.CreateAlignedLoad( + getAdjustedAllocaPtr(IRB, NewBeginOffset, LTy), + getOffsetTypeAlign(TargetTy, NewBeginOffset - NewAllocaBeginOffset), + LI.isVolatile(), "load"); + IsPtrAdjusted = true; + } + V = convertValue(DL, IRB, V, TargetTy); + + if (IsSplit) { + assert(!LI.isVolatile()); + assert(LI.getType()->isIntegerTy() && + "Only integer type loads and stores are split"); + assert(Size < DL.getTypeStoreSize(LI.getType()) && + "Split load isn't smaller than original load"); + assert(LI.getType()->getIntegerBitWidth() == + DL.getTypeStoreSizeInBits(LI.getType()) && + "Non-byte-multiple bit width"); + // Move the insertion point just past the load so that we can refer to it. + IRB.SetInsertPoint(llvm::next(BasicBlock::iterator(&LI))); + // Create a placeholder value with the same type as LI to use as the + // basis for the new value. This allows us to replace the uses of LI with + // the computed value, and then replace the placeholder with LI, leaving + // LI only used for this computation. + Value *Placeholder + = new LoadInst(UndefValue::get(LI.getType()->getPointerTo())); + V = insertInteger(DL, IRB, Placeholder, V, NewBeginOffset, + "insert"); + LI.replaceAllUsesWith(V); + Placeholder->replaceAllUsesWith(&LI); + delete Placeholder; + } else { + LI.replaceAllUsesWith(V); + } + + Pass.DeadInsts.insert(&LI); + deleteIfTriviallyDead(OldOp); + DEBUG(dbgs() << " to: " << *V << "\n"); + return !LI.isVolatile() && !IsPtrAdjusted; + } + + bool rewriteVectorizedStoreInst(Value *V, StoreInst &SI, Value *OldOp, + uint64_t NewBeginOffset, + uint64_t NewEndOffset) { + if (V->getType() != VecTy) { + unsigned BeginIndex = getIndex(NewBeginOffset); + unsigned EndIndex = getIndex(NewEndOffset); + assert(EndIndex > BeginIndex && "Empty vector!"); + unsigned NumElements = EndIndex - BeginIndex; + assert(NumElements <= VecTy->getNumElements() && "Too many elements!"); + Type *SliceTy = + (NumElements == 1) ? ElementTy + : VectorType::get(ElementTy, NumElements); + if (V->getType() != SliceTy) + V = convertValue(DL, IRB, V, SliceTy); + + // Mix in the existing elements. + Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), + "load"); + V = insertVector(IRB, Old, V, BeginIndex, "vec"); + } + StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment()); + Pass.DeadInsts.insert(&SI); + + (void)Store; + DEBUG(dbgs() << " to: " << *Store << "\n"); + return true; + } + + bool rewriteIntegerStore(Value *V, StoreInst &SI, + uint64_t NewBeginOffset, uint64_t NewEndOffset) { + assert(IntTy && "We cannot extract an integer from the alloca"); + assert(!SI.isVolatile()); + if (DL.getTypeSizeInBits(V->getType()) != IntTy->getBitWidth()) { + Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), + "oldload"); + Old = convertValue(DL, IRB, Old, IntTy); + assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset"); + uint64_t Offset = BeginOffset - NewAllocaBeginOffset; + V = insertInteger(DL, IRB, Old, SI.getValueOperand(), Offset, + "insert"); + } + V = convertValue(DL, IRB, V, NewAllocaTy); + StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment()); + Pass.DeadInsts.insert(&SI); + (void)Store; + DEBUG(dbgs() << " to: " << *Store << "\n"); + return true; + } + + bool visitStoreInst(StoreInst &SI) { + DEBUG(dbgs() << " original: " << SI << "\n"); + Value *OldOp = SI.getOperand(1); + assert(OldOp == OldPtr); + + Value *V = SI.getValueOperand(); + + // Strip all inbounds GEPs and pointer casts to try to dig out any root + // alloca that should be re-examined after promoting this alloca. + if (V->getType()->isPointerTy()) + if (AllocaInst *AI = dyn_cast<AllocaInst>(V->stripInBoundsOffsets())) + Pass.PostPromotionWorklist.insert(AI); + + // Compute the intersecting offset range. + assert(BeginOffset < NewAllocaEndOffset); + assert(EndOffset > NewAllocaBeginOffset); + uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset); + uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset); + + uint64_t Size = NewEndOffset - NewBeginOffset; + if (Size < DL.getTypeStoreSize(V->getType())) { + assert(!SI.isVolatile()); + assert(V->getType()->isIntegerTy() && + "Only integer type loads and stores are split"); + assert(V->getType()->getIntegerBitWidth() == + DL.getTypeStoreSizeInBits(V->getType()) && + "Non-byte-multiple bit width"); + IntegerType *NarrowTy = Type::getIntNTy(SI.getContext(), Size * 8); + V = extractInteger(DL, IRB, V, NarrowTy, NewBeginOffset, + "extract"); + } + + if (VecTy) + return rewriteVectorizedStoreInst(V, SI, OldOp, NewBeginOffset, + NewEndOffset); + if (IntTy && V->getType()->isIntegerTy()) + return rewriteIntegerStore(V, SI, NewBeginOffset, NewEndOffset); + + StoreInst *NewSI; + if (NewBeginOffset == NewAllocaBeginOffset && + NewEndOffset == NewAllocaEndOffset && + canConvertValue(DL, V->getType(), NewAllocaTy)) { + V = convertValue(DL, IRB, V, NewAllocaTy); + NewSI = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(), + SI.isVolatile()); + } else { + Value *NewPtr = getAdjustedAllocaPtr(IRB, NewBeginOffset, + V->getType()->getPointerTo()); + NewSI = IRB.CreateAlignedStore( + V, NewPtr, getOffsetTypeAlign( + V->getType(), NewBeginOffset - NewAllocaBeginOffset), + SI.isVolatile()); + } + (void)NewSI; + Pass.DeadInsts.insert(&SI); + deleteIfTriviallyDead(OldOp); + + DEBUG(dbgs() << " to: " << *NewSI << "\n"); + return NewSI->getPointerOperand() == &NewAI && !SI.isVolatile(); + } + + /// \brief Compute an integer value from splatting an i8 across the given + /// number of bytes. + /// + /// Note that this routine assumes an i8 is a byte. If that isn't true, don't + /// call this routine. + /// FIXME: Heed the advice above. + /// + /// \param V The i8 value to splat. + /// \param Size The number of bytes in the output (assuming i8 is one byte) + Value *getIntegerSplat(Value *V, unsigned Size) { + assert(Size > 0 && "Expected a positive number of bytes."); + IntegerType *VTy = cast<IntegerType>(V->getType()); + assert(VTy->getBitWidth() == 8 && "Expected an i8 value for the byte"); + if (Size == 1) + return V; + + Type *SplatIntTy = Type::getIntNTy(VTy->getContext(), Size*8); + V = IRB.CreateMul(IRB.CreateZExt(V, SplatIntTy, "zext"), + ConstantExpr::getUDiv( + Constant::getAllOnesValue(SplatIntTy), + ConstantExpr::getZExt( + Constant::getAllOnesValue(V->getType()), + SplatIntTy)), + "isplat"); + return V; + } + + /// \brief Compute a vector splat for a given element value. + Value *getVectorSplat(Value *V, unsigned NumElements) { + V = IRB.CreateVectorSplat(NumElements, V, "vsplat"); + DEBUG(dbgs() << " splat: " << *V << "\n"); + return V; + } + + bool visitMemSetInst(MemSetInst &II) { + DEBUG(dbgs() << " original: " << II << "\n"); + assert(II.getRawDest() == OldPtr); + + // If the memset has a variable size, it cannot be split, just adjust the + // pointer to the new alloca. + if (!isa<Constant>(II.getLength())) { + assert(!IsSplit); + assert(BeginOffset >= NewAllocaBeginOffset); + II.setDest( + getAdjustedAllocaPtr(IRB, BeginOffset, II.getRawDest()->getType())); + Type *CstTy = II.getAlignmentCst()->getType(); + II.setAlignment(ConstantInt::get(CstTy, getOffsetAlign(BeginOffset))); + + deleteIfTriviallyDead(OldPtr); + return false; + } + + // Record this instruction for deletion. + Pass.DeadInsts.insert(&II); + + Type *AllocaTy = NewAI.getAllocatedType(); + Type *ScalarTy = AllocaTy->getScalarType(); + + // Compute the intersecting offset range. + assert(BeginOffset < NewAllocaEndOffset); + assert(EndOffset > NewAllocaBeginOffset); + uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset); + uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset); + uint64_t SliceOffset = NewBeginOffset - NewAllocaBeginOffset; + + // If this doesn't map cleanly onto the alloca type, and that type isn't + // a single value type, just emit a memset. + if (!VecTy && !IntTy && + (BeginOffset > NewAllocaBeginOffset || + EndOffset < NewAllocaEndOffset || + !AllocaTy->isSingleValueType() || + !DL.isLegalInteger(DL.getTypeSizeInBits(ScalarTy)) || + DL.getTypeSizeInBits(ScalarTy)%8 != 0)) { + Type *SizeTy = II.getLength()->getType(); + Constant *Size = ConstantInt::get(SizeTy, NewEndOffset - NewBeginOffset); + CallInst *New = IRB.CreateMemSet( + getAdjustedAllocaPtr(IRB, NewBeginOffset, II.getRawDest()->getType()), + II.getValue(), Size, getOffsetAlign(SliceOffset), II.isVolatile()); + (void)New; + DEBUG(dbgs() << " to: " << *New << "\n"); + return false; + } + + // If we can represent this as a simple value, we have to build the actual + // value to store, which requires expanding the byte present in memset to + // a sensible representation for the alloca type. This is essentially + // splatting the byte to a sufficiently wide integer, splatting it across + // any desired vector width, and bitcasting to the final type. + Value *V; + + if (VecTy) { + // If this is a memset of a vectorized alloca, insert it. + assert(ElementTy == ScalarTy); + + unsigned BeginIndex = getIndex(NewBeginOffset); + unsigned EndIndex = getIndex(NewEndOffset); + assert(EndIndex > BeginIndex && "Empty vector!"); + unsigned NumElements = EndIndex - BeginIndex; + assert(NumElements <= VecTy->getNumElements() && "Too many elements!"); + + Value *Splat = + getIntegerSplat(II.getValue(), DL.getTypeSizeInBits(ElementTy) / 8); + Splat = convertValue(DL, IRB, Splat, ElementTy); + if (NumElements > 1) + Splat = getVectorSplat(Splat, NumElements); + + Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), + "oldload"); + V = insertVector(IRB, Old, Splat, BeginIndex, "vec"); + } else if (IntTy) { + // If this is a memset on an alloca where we can widen stores, insert the + // set integer. + assert(!II.isVolatile()); + + uint64_t Size = NewEndOffset - NewBeginOffset; + V = getIntegerSplat(II.getValue(), Size); + + if (IntTy && (BeginOffset != NewAllocaBeginOffset || + EndOffset != NewAllocaBeginOffset)) { + Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), + "oldload"); + Old = convertValue(DL, IRB, Old, IntTy); + uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset; + V = insertInteger(DL, IRB, Old, V, Offset, "insert"); + } else { + assert(V->getType() == IntTy && + "Wrong type for an alloca wide integer!"); + } + V = convertValue(DL, IRB, V, AllocaTy); + } else { + // Established these invariants above. + assert(NewBeginOffset == NewAllocaBeginOffset); + assert(NewEndOffset == NewAllocaEndOffset); + + V = getIntegerSplat(II.getValue(), DL.getTypeSizeInBits(ScalarTy) / 8); + if (VectorType *AllocaVecTy = dyn_cast<VectorType>(AllocaTy)) + V = getVectorSplat(V, AllocaVecTy->getNumElements()); + + V = convertValue(DL, IRB, V, AllocaTy); + } + + Value *New = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(), + II.isVolatile()); + (void)New; + DEBUG(dbgs() << " to: " << *New << "\n"); + return !II.isVolatile(); + } + + bool visitMemTransferInst(MemTransferInst &II) { + // Rewriting of memory transfer instructions can be a bit tricky. We break + // them into two categories: split intrinsics and unsplit intrinsics. + + DEBUG(dbgs() << " original: " << II << "\n"); + + // Compute the intersecting offset range. + assert(BeginOffset < NewAllocaEndOffset); + assert(EndOffset > NewAllocaBeginOffset); + uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset); + uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset); + + assert(II.getRawSource() == OldPtr || II.getRawDest() == OldPtr); + bool IsDest = II.getRawDest() == OldPtr; + + // Compute the relative offset within the transfer. + unsigned IntPtrWidth = DL.getPointerSizeInBits(); + APInt RelOffset(IntPtrWidth, NewBeginOffset - BeginOffset); + + unsigned Align = II.getAlignment(); + uint64_t SliceOffset = NewBeginOffset - NewAllocaBeginOffset; + if (Align > 1) + Align = + MinAlign(RelOffset.zextOrTrunc(64).getZExtValue(), + MinAlign(II.getAlignment(), getOffsetAlign(SliceOffset))); + + // For unsplit intrinsics, we simply modify the source and destination + // pointers in place. This isn't just an optimization, it is a matter of + // correctness. With unsplit intrinsics we may be dealing with transfers + // within a single alloca before SROA ran, or with transfers that have + // a variable length. We may also be dealing with memmove instead of + // memcpy, and so simply updating the pointers is the necessary for us to + // update both source and dest of a single call. + if (!IsSplittable) { + Value *OldOp = IsDest ? II.getRawDest() : II.getRawSource(); + if (IsDest) + II.setDest( + getAdjustedAllocaPtr(IRB, BeginOffset, II.getRawDest()->getType())); + else + II.setSource(getAdjustedAllocaPtr(IRB, BeginOffset, + II.getRawSource()->getType())); + + Type *CstTy = II.getAlignmentCst()->getType(); + II.setAlignment(ConstantInt::get(CstTy, Align)); + + DEBUG(dbgs() << " to: " << II << "\n"); + deleteIfTriviallyDead(OldOp); + return false; + } + // For split transfer intrinsics we have an incredibly useful assurance: + // the source and destination do not reside within the same alloca, and at + // least one of them does not escape. This means that we can replace + // memmove with memcpy, and we don't need to worry about all manner of + // downsides to splitting and transforming the operations. + + // If this doesn't map cleanly onto the alloca type, and that type isn't + // a single value type, just emit a memcpy. + bool EmitMemCpy + = !VecTy && !IntTy && (BeginOffset > NewAllocaBeginOffset || + EndOffset < NewAllocaEndOffset || + !NewAI.getAllocatedType()->isSingleValueType()); + + // If we're just going to emit a memcpy, the alloca hasn't changed, and the + // size hasn't been shrunk based on analysis of the viable range, this is + // a no-op. + if (EmitMemCpy && &OldAI == &NewAI) { + // Ensure the start lines up. + assert(NewBeginOffset == BeginOffset); + + // Rewrite the size as needed. + if (NewEndOffset != EndOffset) + II.setLength(ConstantInt::get(II.getLength()->getType(), + NewEndOffset - NewBeginOffset)); + return false; + } + // Record this instruction for deletion. + Pass.DeadInsts.insert(&II); + + // Strip all inbounds GEPs and pointer casts to try to dig out any root + // alloca that should be re-examined after rewriting this instruction. + Value *OtherPtr = IsDest ? II.getRawSource() : II.getRawDest(); + if (AllocaInst *AI + = dyn_cast<AllocaInst>(OtherPtr->stripInBoundsOffsets())) + Pass.Worklist.insert(AI); + + if (EmitMemCpy) { + Type *OtherPtrTy = IsDest ? II.getRawSource()->getType() + : II.getRawDest()->getType(); + + // Compute the other pointer, folding as much as possible to produce + // a single, simple GEP in most cases. + OtherPtr = getAdjustedPtr(IRB, DL, OtherPtr, RelOffset, OtherPtrTy); + + Value *OurPtr = getAdjustedAllocaPtr( + IRB, NewBeginOffset, + IsDest ? II.getRawDest()->getType() : II.getRawSource()->getType()); + Type *SizeTy = II.getLength()->getType(); + Constant *Size = ConstantInt::get(SizeTy, NewEndOffset - NewBeginOffset); + + CallInst *New = IRB.CreateMemCpy(IsDest ? OurPtr : OtherPtr, + IsDest ? OtherPtr : OurPtr, + Size, Align, II.isVolatile()); + (void)New; + DEBUG(dbgs() << " to: " << *New << "\n"); + return false; + } + + // Note that we clamp the alignment to 1 here as a 0 alignment for a memcpy + // is equivalent to 1, but that isn't true if we end up rewriting this as + // a load or store. + if (!Align) + Align = 1; + + bool IsWholeAlloca = NewBeginOffset == NewAllocaBeginOffset && + NewEndOffset == NewAllocaEndOffset; + uint64_t Size = NewEndOffset - NewBeginOffset; + unsigned BeginIndex = VecTy ? getIndex(NewBeginOffset) : 0; + unsigned EndIndex = VecTy ? getIndex(NewEndOffset) : 0; + unsigned NumElements = EndIndex - BeginIndex; + IntegerType *SubIntTy + = IntTy ? Type::getIntNTy(IntTy->getContext(), Size*8) : 0; + + Type *OtherPtrTy = NewAI.getType(); + if (VecTy && !IsWholeAlloca) { + if (NumElements == 1) + OtherPtrTy = VecTy->getElementType(); + else + OtherPtrTy = VectorType::get(VecTy->getElementType(), NumElements); + + OtherPtrTy = OtherPtrTy->getPointerTo(); + } else if (IntTy && !IsWholeAlloca) { + OtherPtrTy = SubIntTy->getPointerTo(); + } + + Value *SrcPtr = getAdjustedPtr(IRB, DL, OtherPtr, RelOffset, OtherPtrTy); + Value *DstPtr = &NewAI; + if (!IsDest) + std::swap(SrcPtr, DstPtr); + + Value *Src; + if (VecTy && !IsWholeAlloca && !IsDest) { + Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), + "load"); + Src = extractVector(IRB, Src, BeginIndex, EndIndex, "vec"); + } else if (IntTy && !IsWholeAlloca && !IsDest) { + Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), + "load"); + Src = convertValue(DL, IRB, Src, IntTy); + uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset; + Src = extractInteger(DL, IRB, Src, SubIntTy, Offset, "extract"); + } else { + Src = IRB.CreateAlignedLoad(SrcPtr, Align, II.isVolatile(), + "copyload"); + } + + if (VecTy && !IsWholeAlloca && IsDest) { + Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), + "oldload"); + Src = insertVector(IRB, Old, Src, BeginIndex, "vec"); + } else if (IntTy && !IsWholeAlloca && IsDest) { + Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), + "oldload"); + Old = convertValue(DL, IRB, Old, IntTy); + uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset; + Src = insertInteger(DL, IRB, Old, Src, Offset, "insert"); + Src = convertValue(DL, IRB, Src, NewAllocaTy); + } + + StoreInst *Store = cast<StoreInst>( + IRB.CreateAlignedStore(Src, DstPtr, Align, II.isVolatile())); + (void)Store; + DEBUG(dbgs() << " to: " << *Store << "\n"); + return !II.isVolatile(); + } + + bool visitIntrinsicInst(IntrinsicInst &II) { + assert(II.getIntrinsicID() == Intrinsic::lifetime_start || + II.getIntrinsicID() == Intrinsic::lifetime_end); + DEBUG(dbgs() << " original: " << II << "\n"); + assert(II.getArgOperand(1) == OldPtr); + + // Compute the intersecting offset range. + assert(BeginOffset < NewAllocaEndOffset); + assert(EndOffset > NewAllocaBeginOffset); + uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset); + uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset); + + // Record this instruction for deletion. + Pass.DeadInsts.insert(&II); + + ConstantInt *Size + = ConstantInt::get(cast<IntegerType>(II.getArgOperand(0)->getType()), + NewEndOffset - NewBeginOffset); + Value *Ptr = + getAdjustedAllocaPtr(IRB, NewBeginOffset, II.getArgOperand(1)->getType()); + Value *New; + if (II.getIntrinsicID() == Intrinsic::lifetime_start) + New = IRB.CreateLifetimeStart(Ptr, Size); + else + New = IRB.CreateLifetimeEnd(Ptr, Size); + + (void)New; + DEBUG(dbgs() << " to: " << *New << "\n"); + return true; + } + + bool visitPHINode(PHINode &PN) { + DEBUG(dbgs() << " original: " << PN << "\n"); + assert(BeginOffset >= NewAllocaBeginOffset && "PHIs are unsplittable"); + assert(EndOffset <= NewAllocaEndOffset && "PHIs are unsplittable"); + + // We would like to compute a new pointer in only one place, but have it be + // as local as possible to the PHI. To do that, we re-use the location of + // the old pointer, which necessarily must be in the right position to + // dominate the PHI. + IRBuilderTy PtrBuilder(OldPtr); + PtrBuilder.SetNamePrefix(Twine(NewAI.getName()) + "." + Twine(BeginOffset) + + "."); + + Value *NewPtr = + getAdjustedAllocaPtr(PtrBuilder, BeginOffset, OldPtr->getType()); + // Replace the operands which were using the old pointer. + std::replace(PN.op_begin(), PN.op_end(), cast<Value>(OldPtr), NewPtr); + + DEBUG(dbgs() << " to: " << PN << "\n"); + deleteIfTriviallyDead(OldPtr); + + // Check whether we can speculate this PHI node, and if so remember that + // fact and queue it up for another iteration after the speculation + // occurs. + if (isSafePHIToSpeculate(PN, &DL)) { + Pass.SpeculatablePHIs.insert(&PN); + IsUsedByRewrittenSpeculatableInstructions = true; + return true; + } + + return false; // PHIs can't be promoted on their own. + } + + bool visitSelectInst(SelectInst &SI) { + DEBUG(dbgs() << " original: " << SI << "\n"); + assert((SI.getTrueValue() == OldPtr || SI.getFalseValue() == OldPtr) && + "Pointer isn't an operand!"); + assert(BeginOffset >= NewAllocaBeginOffset && "Selects are unsplittable"); + assert(EndOffset <= NewAllocaEndOffset && "Selects are unsplittable"); + + Value *NewPtr = getAdjustedAllocaPtr(IRB, BeginOffset, OldPtr->getType()); + // Replace the operands which were using the old pointer. + if (SI.getOperand(1) == OldPtr) + SI.setOperand(1, NewPtr); + if (SI.getOperand(2) == OldPtr) + SI.setOperand(2, NewPtr); + + DEBUG(dbgs() << " to: " << SI << "\n"); + deleteIfTriviallyDead(OldPtr); + + // Check whether we can speculate this select instruction, and if so + // remember that fact and queue it up for another iteration after the + // speculation occurs. + if (isSafeSelectToSpeculate(SI, &DL)) { + Pass.SpeculatableSelects.insert(&SI); + IsUsedByRewrittenSpeculatableInstructions = true; + return true; + } + + return false; // Selects can't be promoted on their own. + } + +}; +} + +namespace { +/// \brief Visitor to rewrite aggregate loads and stores as scalar. +/// +/// This pass aggressively rewrites all aggregate loads and stores on +/// a particular pointer (or any pointer derived from it which we can identify) +/// with scalar loads and stores. +class AggLoadStoreRewriter : public InstVisitor<AggLoadStoreRewriter, bool> { + // Befriend the base class so it can delegate to private visit methods. + friend class llvm::InstVisitor<AggLoadStoreRewriter, bool>; + + const DataLayout &DL; + + /// Queue of pointer uses to analyze and potentially rewrite. + SmallVector<Use *, 8> Queue; + + /// Set to prevent us from cycling with phi nodes and loops. + SmallPtrSet<User *, 8> Visited; + + /// The current pointer use being rewritten. This is used to dig up the used + /// value (as opposed to the user). + Use *U; + +public: + AggLoadStoreRewriter(const DataLayout &DL) : DL(DL) {} + + /// Rewrite loads and stores through a pointer and all pointers derived from + /// it. + bool rewrite(Instruction &I) { + DEBUG(dbgs() << " Rewriting FCA loads and stores...\n"); + enqueueUsers(I); + bool Changed = false; + while (!Queue.empty()) { + U = Queue.pop_back_val(); + Changed |= visit(cast<Instruction>(U->getUser())); + } + return Changed; + } + +private: + /// Enqueue all the users of the given instruction for further processing. + /// This uses a set to de-duplicate users. + void enqueueUsers(Instruction &I) { + for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE; + ++UI) + if (Visited.insert(*UI)) + Queue.push_back(&UI.getUse()); + } + + // Conservative default is to not rewrite anything. + bool visitInstruction(Instruction &I) { return false; } + + /// \brief Generic recursive split emission class. + template <typename Derived> + class OpSplitter { + protected: + /// The builder used to form new instructions. + IRBuilderTy IRB; + /// The indices which to be used with insert- or extractvalue to select the + /// appropriate value within the aggregate. + SmallVector<unsigned, 4> Indices; + /// The indices to a GEP instruction which will move Ptr to the correct slot + /// within the aggregate. + SmallVector<Value *, 4> GEPIndices; + /// The base pointer of the original op, used as a base for GEPing the + /// split operations. + Value *Ptr; + + /// Initialize the splitter with an insertion point, Ptr and start with a + /// single zero GEP index. + OpSplitter(Instruction *InsertionPoint, Value *Ptr) + : IRB(InsertionPoint), GEPIndices(1, IRB.getInt32(0)), Ptr(Ptr) {} + + public: + /// \brief Generic recursive split emission routine. + /// + /// This method recursively splits an aggregate op (load or store) into + /// scalar or vector ops. It splits recursively until it hits a single value + /// and emits that single value operation via the template argument. + /// + /// The logic of this routine relies on GEPs and insertvalue and + /// extractvalue all operating with the same fundamental index list, merely + /// formatted differently (GEPs need actual values). + /// + /// \param Ty The type being split recursively into smaller ops. + /// \param Agg The aggregate value being built up or stored, depending on + /// whether this is splitting a load or a store respectively. + void emitSplitOps(Type *Ty, Value *&Agg, const Twine &Name) { + if (Ty->isSingleValueType()) + return static_cast<Derived *>(this)->emitFunc(Ty, Agg, Name); + + if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { + unsigned OldSize = Indices.size(); + (void)OldSize; + for (unsigned Idx = 0, Size = ATy->getNumElements(); Idx != Size; + ++Idx) { + assert(Indices.size() == OldSize && "Did not return to the old size"); + Indices.push_back(Idx); + GEPIndices.push_back(IRB.getInt32(Idx)); + emitSplitOps(ATy->getElementType(), Agg, Name + "." + Twine(Idx)); + GEPIndices.pop_back(); + Indices.pop_back(); + } + return; + } + + if (StructType *STy = dyn_cast<StructType>(Ty)) { + unsigned OldSize = Indices.size(); + (void)OldSize; + for (unsigned Idx = 0, Size = STy->getNumElements(); Idx != Size; + ++Idx) { + assert(Indices.size() == OldSize && "Did not return to the old size"); + Indices.push_back(Idx); + GEPIndices.push_back(IRB.getInt32(Idx)); + emitSplitOps(STy->getElementType(Idx), Agg, Name + "." + Twine(Idx)); + GEPIndices.pop_back(); + Indices.pop_back(); + } + return; + } + + llvm_unreachable("Only arrays and structs are aggregate loadable types"); + } + }; + + struct LoadOpSplitter : public OpSplitter<LoadOpSplitter> { + LoadOpSplitter(Instruction *InsertionPoint, Value *Ptr) + : OpSplitter<LoadOpSplitter>(InsertionPoint, Ptr) {} + + /// Emit a leaf load of a single value. This is called at the leaves of the + /// recursive emission to actually load values. + void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) { + assert(Ty->isSingleValueType()); + // Load the single value and insert it using the indices. + Value *GEP = IRB.CreateInBoundsGEP(Ptr, GEPIndices, Name + ".gep"); + Value *Load = IRB.CreateLoad(GEP, Name + ".load"); + Agg = IRB.CreateInsertValue(Agg, Load, Indices, Name + ".insert"); + DEBUG(dbgs() << " to: " << *Load << "\n"); + } + }; + + bool visitLoadInst(LoadInst &LI) { + assert(LI.getPointerOperand() == *U); + if (!LI.isSimple() || LI.getType()->isSingleValueType()) + return false; + + // We have an aggregate being loaded, split it apart. + DEBUG(dbgs() << " original: " << LI << "\n"); + LoadOpSplitter Splitter(&LI, *U); + Value *V = UndefValue::get(LI.getType()); + Splitter.emitSplitOps(LI.getType(), V, LI.getName() + ".fca"); + LI.replaceAllUsesWith(V); + LI.eraseFromParent(); + return true; + } + + struct StoreOpSplitter : public OpSplitter<StoreOpSplitter> { + StoreOpSplitter(Instruction *InsertionPoint, Value *Ptr) + : OpSplitter<StoreOpSplitter>(InsertionPoint, Ptr) {} + + /// Emit a leaf store of a single value. This is called at the leaves of the + /// recursive emission to actually produce stores. + void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) { + assert(Ty->isSingleValueType()); + // Extract the single value and store it using the indices. + Value *Store = IRB.CreateStore( + IRB.CreateExtractValue(Agg, Indices, Name + ".extract"), + IRB.CreateInBoundsGEP(Ptr, GEPIndices, Name + ".gep")); + (void)Store; + DEBUG(dbgs() << " to: " << *Store << "\n"); + } + }; + + bool visitStoreInst(StoreInst &SI) { + if (!SI.isSimple() || SI.getPointerOperand() != *U) + return false; + Value *V = SI.getValueOperand(); + if (V->getType()->isSingleValueType()) + return false; + + // We have an aggregate being stored, split it apart. + DEBUG(dbgs() << " original: " << SI << "\n"); + StoreOpSplitter Splitter(&SI, *U); + Splitter.emitSplitOps(V->getType(), V, V->getName() + ".fca"); + SI.eraseFromParent(); + return true; + } + + bool visitBitCastInst(BitCastInst &BC) { + enqueueUsers(BC); + return false; + } + + bool visitGetElementPtrInst(GetElementPtrInst &GEPI) { + enqueueUsers(GEPI); + return false; + } + + bool visitPHINode(PHINode &PN) { + enqueueUsers(PN); + return false; + } + + bool visitSelectInst(SelectInst &SI) { + enqueueUsers(SI); + return false; + } +}; +} + +/// \brief Strip aggregate type wrapping. +/// +/// This removes no-op aggregate types wrapping an underlying type. It will +/// strip as many layers of types as it can without changing either the type +/// size or the allocated size. +static Type *stripAggregateTypeWrapping(const DataLayout &DL, Type *Ty) { + if (Ty->isSingleValueType()) + return Ty; + + uint64_t AllocSize = DL.getTypeAllocSize(Ty); + uint64_t TypeSize = DL.getTypeSizeInBits(Ty); + + Type *InnerTy; + if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) { + InnerTy = ArrTy->getElementType(); + } else if (StructType *STy = dyn_cast<StructType>(Ty)) { + const StructLayout *SL = DL.getStructLayout(STy); + unsigned Index = SL->getElementContainingOffset(0); + InnerTy = STy->getElementType(Index); + } else { + return Ty; + } + + if (AllocSize > DL.getTypeAllocSize(InnerTy) || + TypeSize > DL.getTypeSizeInBits(InnerTy)) + return Ty; + + return stripAggregateTypeWrapping(DL, InnerTy); +} + +/// \brief Try to find a partition of the aggregate type passed in for a given +/// offset and size. +/// +/// This recurses through the aggregate type and tries to compute a subtype +/// based on the offset and size. When the offset and size span a sub-section +/// of an array, it will even compute a new array type for that sub-section, +/// and the same for structs. +/// +/// Note that this routine is very strict and tries to find a partition of the +/// type which produces the *exact* right offset and size. It is not forgiving +/// when the size or offset cause either end of type-based partition to be off. +/// Also, this is a best-effort routine. It is reasonable to give up and not +/// return a type if necessary. +static Type *getTypePartition(const DataLayout &DL, Type *Ty, + uint64_t Offset, uint64_t Size) { + if (Offset == 0 && DL.getTypeAllocSize(Ty) == Size) + return stripAggregateTypeWrapping(DL, Ty); + if (Offset > DL.getTypeAllocSize(Ty) || + (DL.getTypeAllocSize(Ty) - Offset) < Size) + return 0; + + if (SequentialType *SeqTy = dyn_cast<SequentialType>(Ty)) { + // We can't partition pointers... + if (SeqTy->isPointerTy()) + return 0; + + Type *ElementTy = SeqTy->getElementType(); + uint64_t ElementSize = DL.getTypeAllocSize(ElementTy); + uint64_t NumSkippedElements = Offset / ElementSize; + if (ArrayType *ArrTy = dyn_cast<ArrayType>(SeqTy)) { + if (NumSkippedElements >= ArrTy->getNumElements()) + return 0; + } else if (VectorType *VecTy = dyn_cast<VectorType>(SeqTy)) { + if (NumSkippedElements >= VecTy->getNumElements()) + return 0; + } + Offset -= NumSkippedElements * ElementSize; + + // First check if we need to recurse. + if (Offset > 0 || Size < ElementSize) { + // Bail if the partition ends in a different array element. + if ((Offset + Size) > ElementSize) + return 0; + // Recurse through the element type trying to peel off offset bytes. + return getTypePartition(DL, ElementTy, Offset, Size); + } + assert(Offset == 0); + + if (Size == ElementSize) + return stripAggregateTypeWrapping(DL, ElementTy); + assert(Size > ElementSize); + uint64_t NumElements = Size / ElementSize; + if (NumElements * ElementSize != Size) + return 0; + return ArrayType::get(ElementTy, NumElements); + } + + StructType *STy = dyn_cast<StructType>(Ty); + if (!STy) + return 0; + + const StructLayout *SL = DL.getStructLayout(STy); + if (Offset >= SL->getSizeInBytes()) + return 0; + uint64_t EndOffset = Offset + Size; + if (EndOffset > SL->getSizeInBytes()) + return 0; + + unsigned Index = SL->getElementContainingOffset(Offset); + Offset -= SL->getElementOffset(Index); + + Type *ElementTy = STy->getElementType(Index); + uint64_t ElementSize = DL.getTypeAllocSize(ElementTy); + if (Offset >= ElementSize) + return 0; // The offset points into alignment padding. + + // See if any partition must be contained by the element. + if (Offset > 0 || Size < ElementSize) { + if ((Offset + Size) > ElementSize) + return 0; + return getTypePartition(DL, ElementTy, Offset, Size); + } + assert(Offset == 0); + + if (Size == ElementSize) + return stripAggregateTypeWrapping(DL, ElementTy); + + StructType::element_iterator EI = STy->element_begin() + Index, + EE = STy->element_end(); + if (EndOffset < SL->getSizeInBytes()) { + unsigned EndIndex = SL->getElementContainingOffset(EndOffset); + if (Index == EndIndex) + return 0; // Within a single element and its padding. + + // Don't try to form "natural" types if the elements don't line up with the + // expected size. + // FIXME: We could potentially recurse down through the last element in the + // sub-struct to find a natural end point. + if (SL->getElementOffset(EndIndex) != EndOffset) + return 0; + + assert(Index < EndIndex); + EE = STy->element_begin() + EndIndex; + } + + // Try to build up a sub-structure. + StructType *SubTy = StructType::get(STy->getContext(), makeArrayRef(EI, EE), + STy->isPacked()); + const StructLayout *SubSL = DL.getStructLayout(SubTy); + if (Size != SubSL->getSizeInBytes()) + return 0; // The sub-struct doesn't have quite the size needed. + + return SubTy; +} + +/// \brief Rewrite an alloca partition's users. +/// +/// This routine drives both of the rewriting goals of the SROA pass. It tries +/// to rewrite uses of an alloca partition to be conducive for SSA value +/// promotion. If the partition needs a new, more refined alloca, this will +/// build that new alloca, preserving as much type information as possible, and +/// rewrite the uses of the old alloca to point at the new one and have the +/// appropriate new offsets. It also evaluates how successful the rewrite was +/// at enabling promotion and if it was successful queues the alloca to be +/// promoted. +bool SROA::rewritePartition(AllocaInst &AI, AllocaSlices &S, + AllocaSlices::iterator B, AllocaSlices::iterator E, + int64_t BeginOffset, int64_t EndOffset, + ArrayRef<AllocaSlices::iterator> SplitUses) { + assert(BeginOffset < EndOffset); + uint64_t SliceSize = EndOffset - BeginOffset; + + // Try to compute a friendly type for this partition of the alloca. This + // won't always succeed, in which case we fall back to a legal integer type + // or an i8 array of an appropriate size. + Type *SliceTy = 0; + if (Type *CommonUseTy = findCommonType(B, E, EndOffset)) + if (DL->getTypeAllocSize(CommonUseTy) >= SliceSize) + SliceTy = CommonUseTy; + if (!SliceTy) + if (Type *TypePartitionTy = getTypePartition(*DL, AI.getAllocatedType(), + BeginOffset, SliceSize)) + SliceTy = TypePartitionTy; + if ((!SliceTy || (SliceTy->isArrayTy() && + SliceTy->getArrayElementType()->isIntegerTy())) && + DL->isLegalInteger(SliceSize * 8)) + SliceTy = Type::getIntNTy(*C, SliceSize * 8); + if (!SliceTy) + SliceTy = ArrayType::get(Type::getInt8Ty(*C), SliceSize); + assert(DL->getTypeAllocSize(SliceTy) >= SliceSize); + + bool IsVectorPromotable = isVectorPromotionViable( + *DL, SliceTy, S, BeginOffset, EndOffset, B, E, SplitUses); + + bool IsIntegerPromotable = + !IsVectorPromotable && + isIntegerWideningViable(*DL, SliceTy, BeginOffset, S, B, E, SplitUses); + + // Check for the case where we're going to rewrite to a new alloca of the + // exact same type as the original, and with the same access offsets. In that + // case, re-use the existing alloca, but still run through the rewriter to + // perform phi and select speculation. + AllocaInst *NewAI; + if (SliceTy == AI.getAllocatedType()) { + assert(BeginOffset == 0 && + "Non-zero begin offset but same alloca type"); + NewAI = &AI; + // FIXME: We should be able to bail at this point with "nothing changed". + // FIXME: We might want to defer PHI speculation until after here. + } else { + unsigned Alignment = AI.getAlignment(); + if (!Alignment) { + // The minimum alignment which users can rely on when the explicit + // alignment is omitted or zero is that required by the ABI for this + // type. + Alignment = DL->getABITypeAlignment(AI.getAllocatedType()); + } + Alignment = MinAlign(Alignment, BeginOffset); + // If we will get at least this much alignment from the type alone, leave + // the alloca's alignment unconstrained. + if (Alignment <= DL->getABITypeAlignment(SliceTy)) + Alignment = 0; + NewAI = new AllocaInst(SliceTy, 0, Alignment, + AI.getName() + ".sroa." + Twine(B - S.begin()), &AI); + ++NumNewAllocas; + } + + DEBUG(dbgs() << "Rewriting alloca partition " + << "[" << BeginOffset << "," << EndOffset << ") to: " << *NewAI + << "\n"); + + // Track the high watermark on several worklists that are only relevant for + // promoted allocas. We will reset it to this point if the alloca is not in + // fact scheduled for promotion. + unsigned PPWOldSize = PostPromotionWorklist.size(); + unsigned SPOldSize = SpeculatablePHIs.size(); + unsigned SSOldSize = SpeculatableSelects.size(); + unsigned NumUses = 0; + + AllocaSliceRewriter Rewriter(*DL, S, *this, AI, *NewAI, BeginOffset, + EndOffset, IsVectorPromotable, + IsIntegerPromotable); + bool Promotable = true; + for (ArrayRef<AllocaSlices::iterator>::const_iterator SUI = SplitUses.begin(), + SUE = SplitUses.end(); + SUI != SUE; ++SUI) { + DEBUG(dbgs() << " rewriting split "); + DEBUG(S.printSlice(dbgs(), *SUI, "")); + Promotable &= Rewriter.visit(*SUI); + ++NumUses; + } + for (AllocaSlices::iterator I = B; I != E; ++I) { + DEBUG(dbgs() << " rewriting "); + DEBUG(S.printSlice(dbgs(), I, "")); + Promotable &= Rewriter.visit(I); + ++NumUses; + } + + NumAllocaPartitionUses += NumUses; + MaxUsesPerAllocaPartition = + std::max<unsigned>(NumUses, MaxUsesPerAllocaPartition); + + if (Promotable && !Rewriter.isUsedByRewrittenSpeculatableInstructions()) { + DEBUG(dbgs() << " and queuing for promotion\n"); + PromotableAllocas.push_back(NewAI); + } else if (NewAI != &AI || + (Promotable && + Rewriter.isUsedByRewrittenSpeculatableInstructions())) { + // If we can't promote the alloca, iterate on it to check for new + // refinements exposed by splitting the current alloca. Don't iterate on an + // alloca which didn't actually change and didn't get promoted. + // + // Alternatively, if we could promote the alloca but have speculatable + // instructions then we will speculate them after finishing our processing + // of the original alloca. Mark the new one for re-visiting in the next + // iteration so the speculated operations can be rewritten. + // + // FIXME: We should actually track whether the rewriter changed anything. + Worklist.insert(NewAI); + } + + // Drop any post-promotion work items if promotion didn't happen. + if (!Promotable) { + while (PostPromotionWorklist.size() > PPWOldSize) + PostPromotionWorklist.pop_back(); + while (SpeculatablePHIs.size() > SPOldSize) + SpeculatablePHIs.pop_back(); + while (SpeculatableSelects.size() > SSOldSize) + SpeculatableSelects.pop_back(); + } + + return true; +} + +namespace { +struct IsSliceEndLessOrEqualTo { + uint64_t UpperBound; + + IsSliceEndLessOrEqualTo(uint64_t UpperBound) : UpperBound(UpperBound) {} + + bool operator()(const AllocaSlices::iterator &I) { + return I->endOffset() <= UpperBound; + } +}; +} + +static void +removeFinishedSplitUses(SmallVectorImpl<AllocaSlices::iterator> &SplitUses, + uint64_t &MaxSplitUseEndOffset, uint64_t Offset) { + if (Offset >= MaxSplitUseEndOffset) { + SplitUses.clear(); + MaxSplitUseEndOffset = 0; + return; + } + + size_t SplitUsesOldSize = SplitUses.size(); + SplitUses.erase(std::remove_if(SplitUses.begin(), SplitUses.end(), + IsSliceEndLessOrEqualTo(Offset)), + SplitUses.end()); + if (SplitUsesOldSize == SplitUses.size()) + return; + + // Recompute the max. While this is linear, so is remove_if. + MaxSplitUseEndOffset = 0; + for (SmallVectorImpl<AllocaSlices::iterator>::iterator + SUI = SplitUses.begin(), + SUE = SplitUses.end(); + SUI != SUE; ++SUI) + MaxSplitUseEndOffset = std::max((*SUI)->endOffset(), MaxSplitUseEndOffset); +} + +/// \brief Walks the slices of an alloca and form partitions based on them, +/// rewriting each of their uses. +bool SROA::splitAlloca(AllocaInst &AI, AllocaSlices &S) { + if (S.begin() == S.end()) + return false; + + unsigned NumPartitions = 0; + bool Changed = false; + SmallVector<AllocaSlices::iterator, 4> SplitUses; + uint64_t MaxSplitUseEndOffset = 0; + + uint64_t BeginOffset = S.begin()->beginOffset(); + + for (AllocaSlices::iterator SI = S.begin(), SJ = llvm::next(SI), SE = S.end(); + SI != SE; SI = SJ) { + uint64_t MaxEndOffset = SI->endOffset(); + + if (!SI->isSplittable()) { + // When we're forming an unsplittable region, it must always start at the + // first slice and will extend through its end. + assert(BeginOffset == SI->beginOffset()); + + // Form a partition including all of the overlapping slices with this + // unsplittable slice. + while (SJ != SE && SJ->beginOffset() < MaxEndOffset) { + if (!SJ->isSplittable()) + MaxEndOffset = std::max(MaxEndOffset, SJ->endOffset()); + ++SJ; + } + } else { + assert(SI->isSplittable()); // Established above. + + // Collect all of the overlapping splittable slices. + while (SJ != SE && SJ->beginOffset() < MaxEndOffset && + SJ->isSplittable()) { + MaxEndOffset = std::max(MaxEndOffset, SJ->endOffset()); + ++SJ; + } + + // Back up MaxEndOffset and SJ if we ended the span early when + // encountering an unsplittable slice. + if (SJ != SE && SJ->beginOffset() < MaxEndOffset) { + assert(!SJ->isSplittable()); + MaxEndOffset = SJ->beginOffset(); + } + } + + // Check if we have managed to move the end offset forward yet. If so, + // we'll have to rewrite uses and erase old split uses. + if (BeginOffset < MaxEndOffset) { + // Rewrite a sequence of overlapping slices. + Changed |= + rewritePartition(AI, S, SI, SJ, BeginOffset, MaxEndOffset, SplitUses); + ++NumPartitions; + + removeFinishedSplitUses(SplitUses, MaxSplitUseEndOffset, MaxEndOffset); + } + + // Accumulate all the splittable slices from the [SI,SJ) region which + // overlap going forward. + for (AllocaSlices::iterator SK = SI; SK != SJ; ++SK) + if (SK->isSplittable() && SK->endOffset() > MaxEndOffset) { + SplitUses.push_back(SK); + MaxSplitUseEndOffset = std::max(SK->endOffset(), MaxSplitUseEndOffset); + } + + // If we're already at the end and we have no split uses, we're done. + if (SJ == SE && SplitUses.empty()) + break; + + // If we have no split uses or no gap in offsets, we're ready to move to + // the next slice. + if (SplitUses.empty() || (SJ != SE && MaxEndOffset == SJ->beginOffset())) { + BeginOffset = SJ->beginOffset(); + continue; + } + + // Even if we have split slices, if the next slice is splittable and the + // split slices reach it, we can simply set up the beginning offset of the + // next iteration to bridge between them. + if (SJ != SE && SJ->isSplittable() && + MaxSplitUseEndOffset > SJ->beginOffset()) { + BeginOffset = MaxEndOffset; + continue; + } + + // Otherwise, we have a tail of split slices. Rewrite them with an empty + // range of slices. + uint64_t PostSplitEndOffset = + SJ == SE ? MaxSplitUseEndOffset : SJ->beginOffset(); + + Changed |= rewritePartition(AI, S, SJ, SJ, MaxEndOffset, PostSplitEndOffset, + SplitUses); + ++NumPartitions; + + if (SJ == SE) + break; // Skip the rest, we don't need to do any cleanup. + + removeFinishedSplitUses(SplitUses, MaxSplitUseEndOffset, + PostSplitEndOffset); + + // Now just reset the begin offset for the next iteration. + BeginOffset = SJ->beginOffset(); + } + + NumAllocaPartitions += NumPartitions; + MaxPartitionsPerAlloca = + std::max<unsigned>(NumPartitions, MaxPartitionsPerAlloca); + + return Changed; +} + +/// \brief Analyze an alloca for SROA. +/// +/// This analyzes the alloca to ensure we can reason about it, builds +/// the slices of the alloca, and then hands it off to be split and +/// rewritten as needed. +bool SROA::runOnAlloca(AllocaInst &AI) { + DEBUG(dbgs() << "SROA alloca: " << AI << "\n"); + ++NumAllocasAnalyzed; + + // Special case dead allocas, as they're trivial. + if (AI.use_empty()) { + AI.eraseFromParent(); + return true; + } + + // Skip alloca forms that this analysis can't handle. + if (AI.isArrayAllocation() || !AI.getAllocatedType()->isSized() || + DL->getTypeAllocSize(AI.getAllocatedType()) == 0) + return false; + + bool Changed = false; + + // First, split any FCA loads and stores touching this alloca to promote + // better splitting and promotion opportunities. + AggLoadStoreRewriter AggRewriter(*DL); + Changed |= AggRewriter.rewrite(AI); + + // Build the slices using a recursive instruction-visiting builder. + AllocaSlices S(*DL, AI); + DEBUG(S.print(dbgs())); + if (S.isEscaped()) + return Changed; + + // Delete all the dead users of this alloca before splitting and rewriting it. + for (AllocaSlices::dead_user_iterator DI = S.dead_user_begin(), + DE = S.dead_user_end(); + DI != DE; ++DI) { + Changed = true; + (*DI)->replaceAllUsesWith(UndefValue::get((*DI)->getType())); + DeadInsts.insert(*DI); + } + for (AllocaSlices::dead_op_iterator DO = S.dead_op_begin(), + DE = S.dead_op_end(); + DO != DE; ++DO) { + Value *OldV = **DO; + // Clobber the use with an undef value. + **DO = UndefValue::get(OldV->getType()); + if (Instruction *OldI = dyn_cast<Instruction>(OldV)) + if (isInstructionTriviallyDead(OldI)) { + Changed = true; + DeadInsts.insert(OldI); + } + } + + // No slices to split. Leave the dead alloca for a later pass to clean up. + if (S.begin() == S.end()) + return Changed; + + Changed |= splitAlloca(AI, S); + + DEBUG(dbgs() << " Speculating PHIs\n"); + while (!SpeculatablePHIs.empty()) + speculatePHINodeLoads(*SpeculatablePHIs.pop_back_val()); + + DEBUG(dbgs() << " Speculating Selects\n"); + while (!SpeculatableSelects.empty()) + speculateSelectInstLoads(*SpeculatableSelects.pop_back_val()); + + return Changed; +} + +/// \brief Delete the dead instructions accumulated in this run. +/// +/// Recursively deletes the dead instructions we've accumulated. This is done +/// at the very end to maximize locality of the recursive delete and to +/// minimize the problems of invalidated instruction pointers as such pointers +/// are used heavily in the intermediate stages of the algorithm. +/// +/// We also record the alloca instructions deleted here so that they aren't +/// subsequently handed to mem2reg to promote. +void SROA::deleteDeadInstructions(SmallPtrSet<AllocaInst*, 4> &DeletedAllocas) { + while (!DeadInsts.empty()) { + Instruction *I = DeadInsts.pop_back_val(); + DEBUG(dbgs() << "Deleting dead instruction: " << *I << "\n"); + + I->replaceAllUsesWith(UndefValue::get(I->getType())); + + 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. + *OI = 0; + if (isInstructionTriviallyDead(U)) + DeadInsts.insert(U); + } + + if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) + DeletedAllocas.insert(AI); + + ++NumDeleted; + I->eraseFromParent(); + } +} + +static void enqueueUsersInWorklist(Instruction &I, + SmallVectorImpl<Instruction *> &Worklist, + SmallPtrSet<Instruction *, 8> &Visited) { + for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE; + ++UI) + if (Visited.insert(cast<Instruction>(*UI))) + Worklist.push_back(cast<Instruction>(*UI)); +} + +/// \brief Promote the allocas, using the best available technique. +/// +/// This attempts to promote whatever allocas have been identified as viable in +/// the PromotableAllocas list. If that list is empty, there is nothing to do. +/// If there is a domtree available, we attempt to promote using the full power +/// of mem2reg. Otherwise, we build and use the AllocaPromoter above which is +/// based on the SSAUpdater utilities. This function returns whether any +/// promotion occurred. +bool SROA::promoteAllocas(Function &F) { + if (PromotableAllocas.empty()) + return false; + + NumPromoted += PromotableAllocas.size(); + + if (DT && !ForceSSAUpdater) { + DEBUG(dbgs() << "Promoting allocas with mem2reg...\n"); + PromoteMemToReg(PromotableAllocas, *DT); + PromotableAllocas.clear(); + return true; + } + + DEBUG(dbgs() << "Promoting allocas with SSAUpdater...\n"); + SSAUpdater SSA; + DIBuilder DIB(*F.getParent()); + SmallVector<Instruction *, 64> Insts; + + // We need a worklist to walk the uses of each alloca. + SmallVector<Instruction *, 8> Worklist; + SmallPtrSet<Instruction *, 8> Visited; + SmallVector<Instruction *, 32> DeadInsts; + + for (unsigned Idx = 0, Size = PromotableAllocas.size(); Idx != Size; ++Idx) { + AllocaInst *AI = PromotableAllocas[Idx]; + Insts.clear(); + Worklist.clear(); + Visited.clear(); + + enqueueUsersInWorklist(*AI, Worklist, Visited); + + while (!Worklist.empty()) { + Instruction *I = Worklist.pop_back_val(); + + // FIXME: Currently the SSAUpdater infrastructure doesn't reason about + // lifetime intrinsics and so we strip them (and the bitcasts+GEPs + // leading to them) here. Eventually it should use them to optimize the + // scalar values produced. + if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { + assert(II->getIntrinsicID() == Intrinsic::lifetime_start || + II->getIntrinsicID() == Intrinsic::lifetime_end); + II->eraseFromParent(); + continue; + } + + // Push the loads and stores we find onto the list. SROA will already + // have validated that all loads and stores are viable candidates for + // promotion. + if (LoadInst *LI = dyn_cast<LoadInst>(I)) { + assert(LI->getType() == AI->getAllocatedType()); + Insts.push_back(LI); + continue; + } + if (StoreInst *SI = dyn_cast<StoreInst>(I)) { + assert(SI->getValueOperand()->getType() == AI->getAllocatedType()); + Insts.push_back(SI); + continue; + } + + // For everything else, we know that only no-op bitcasts and GEPs will + // make it this far, just recurse through them and recall them for later + // removal. + DeadInsts.push_back(I); + enqueueUsersInWorklist(*I, Worklist, Visited); + } + AllocaPromoter(Insts, SSA, *AI, DIB).run(Insts); + while (!DeadInsts.empty()) + DeadInsts.pop_back_val()->eraseFromParent(); + AI->eraseFromParent(); + } + + PromotableAllocas.clear(); + return true; +} + +namespace { + /// \brief A predicate to test whether an alloca belongs to a set. + class IsAllocaInSet { + typedef SmallPtrSet<AllocaInst *, 4> SetType; + const SetType &Set; + + public: + typedef AllocaInst *argument_type; + + IsAllocaInSet(const SetType &Set) : Set(Set) {} + bool operator()(AllocaInst *AI) const { return Set.count(AI); } + }; +} + +bool SROA::runOnFunction(Function &F) { + DEBUG(dbgs() << "SROA function: " << F.getName() << "\n"); + C = &F.getContext(); + DL = getAnalysisIfAvailable<DataLayout>(); + if (!DL) { + DEBUG(dbgs() << " Skipping SROA -- no target data!\n"); + return false; + } + DT = getAnalysisIfAvailable<DominatorTree>(); + + BasicBlock &EntryBB = F.getEntryBlock(); + for (BasicBlock::iterator I = EntryBB.begin(), E = llvm::prior(EntryBB.end()); + I != E; ++I) + if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) + Worklist.insert(AI); + + bool Changed = false; + // A set of deleted alloca instruction pointers which should be removed from + // the list of promotable allocas. + SmallPtrSet<AllocaInst *, 4> DeletedAllocas; + + do { + while (!Worklist.empty()) { + Changed |= runOnAlloca(*Worklist.pop_back_val()); + deleteDeadInstructions(DeletedAllocas); + + // Remove the deleted allocas from various lists so that we don't try to + // continue processing them. + if (!DeletedAllocas.empty()) { + Worklist.remove_if(IsAllocaInSet(DeletedAllocas)); + PostPromotionWorklist.remove_if(IsAllocaInSet(DeletedAllocas)); + PromotableAllocas.erase(std::remove_if(PromotableAllocas.begin(), + PromotableAllocas.end(), + IsAllocaInSet(DeletedAllocas)), + PromotableAllocas.end()); + DeletedAllocas.clear(); + } + } + + Changed |= promoteAllocas(F); + + Worklist = PostPromotionWorklist; + PostPromotionWorklist.clear(); + } while (!Worklist.empty()); + + return Changed; +} + +void SROA::getAnalysisUsage(AnalysisUsage &AU) const { + if (RequiresDomTree) + AU.addRequired<DominatorTree>(); + AU.setPreservesCFG(); +} |
