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Diffstat (limited to 'gnu/llvm/lib/Transforms/Scalar/SROA.cpp')
| -rw-r--r-- | gnu/llvm/lib/Transforms/Scalar/SROA.cpp | 4592 |
1 files changed, 0 insertions, 4592 deletions
diff --git a/gnu/llvm/lib/Transforms/Scalar/SROA.cpp b/gnu/llvm/lib/Transforms/Scalar/SROA.cpp deleted file mode 100644 index 68ca6c47c8f..00000000000 --- a/gnu/llvm/lib/Transforms/Scalar/SROA.cpp +++ /dev/null @@ -1,4592 +0,0 @@ -//===- 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. -/// -//===----------------------------------------------------------------------===// - -#include "llvm/Transforms/Scalar/SROA.h" -#include "llvm/ADT/APInt.h" -#include "llvm/ADT/ArrayRef.h" -#include "llvm/ADT/DenseMap.h" -#include "llvm/ADT/PointerIntPair.h" -#include "llvm/ADT/STLExtras.h" -#include "llvm/ADT/SetVector.h" -#include "llvm/ADT/SmallBitVector.h" -#include "llvm/ADT/SmallPtrSet.h" -#include "llvm/ADT/SmallVector.h" -#include "llvm/ADT/Statistic.h" -#include "llvm/ADT/StringRef.h" -#include "llvm/ADT/Twine.h" -#include "llvm/ADT/iterator.h" -#include "llvm/ADT/iterator_range.h" -#include "llvm/Analysis/AssumptionCache.h" -#include "llvm/Analysis/GlobalsModRef.h" -#include "llvm/Analysis/Loads.h" -#include "llvm/Analysis/PtrUseVisitor.h" -#include "llvm/Transforms/Utils/Local.h" -#include "llvm/Config/llvm-config.h" -#include "llvm/IR/BasicBlock.h" -#include "llvm/IR/Constant.h" -#include "llvm/IR/ConstantFolder.h" -#include "llvm/IR/Constants.h" -#include "llvm/IR/DIBuilder.h" -#include "llvm/IR/DataLayout.h" -#include "llvm/IR/DebugInfoMetadata.h" -#include "llvm/IR/DerivedTypes.h" -#include "llvm/IR/Dominators.h" -#include "llvm/IR/Function.h" -#include "llvm/IR/GetElementPtrTypeIterator.h" -#include "llvm/IR/GlobalAlias.h" -#include "llvm/IR/IRBuilder.h" -#include "llvm/IR/InstVisitor.h" -#include "llvm/IR/InstrTypes.h" -#include "llvm/IR/Instruction.h" -#include "llvm/IR/Instructions.h" -#include "llvm/IR/IntrinsicInst.h" -#include "llvm/IR/Intrinsics.h" -#include "llvm/IR/LLVMContext.h" -#include "llvm/IR/Metadata.h" -#include "llvm/IR/Module.h" -#include "llvm/IR/Operator.h" -#include "llvm/IR/PassManager.h" -#include "llvm/IR/Type.h" -#include "llvm/IR/Use.h" -#include "llvm/IR/User.h" -#include "llvm/IR/Value.h" -#include "llvm/Pass.h" -#include "llvm/Support/Casting.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/Scalar.h" -#include "llvm/Transforms/Utils/PromoteMemToReg.h" -#include <algorithm> -#include <cassert> -#include <chrono> -#include <cstddef> -#include <cstdint> -#include <cstring> -#include <iterator> -#include <string> -#include <tuple> -#include <utility> -#include <vector> - -#ifndef NDEBUG -// We only use this for a debug check. -#include <random> -#endif - -using namespace llvm; -using namespace llvm::sroa; - -#define DEBUG_TYPE "sroa" - -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 enable randomly shuffling the slices to help uncover -/// instability in their order. -static cl::opt<bool> SROARandomShuffleSlices("sroa-random-shuffle-slices", - cl::init(false), cl::Hidden); - -/// Hidden option to experiment with completely strict handling of inbounds -/// GEPs. -static cl::opt<bool> SROAStrictInbounds("sroa-strict-inbounds", cl::init(false), - cl::Hidden); - -namespace { - -/// A custom IRBuilder inserter which prefixes all names, but only in -/// Assert builds. -class IRBuilderPrefixedInserter : public IRBuilderDefaultInserter { - std::string Prefix; - - const Twine getNameWithPrefix(const Twine &Name) const { - return Name.isTriviallyEmpty() ? Name : Prefix + Name; - } - -public: - void SetNamePrefix(const Twine &P) { Prefix = P.str(); } - -protected: - void InsertHelper(Instruction *I, const Twine &Name, BasicBlock *BB, - BasicBlock::iterator InsertPt) const { - IRBuilderDefaultInserter::InsertHelper(I, getNameWithPrefix(Name), BB, - InsertPt); - } -}; - -/// Provide a type for IRBuilder that drops names in release builds. -using IRBuilderTy = IRBuilder<ConstantFolder, IRBuilderPrefixedInserter>; - -/// 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 { - /// The beginning offset of the range. - uint64_t BeginOffset = 0; - - /// The ending offset, not included in the range. - uint64_t EndOffset = 0; - - /// Storage for both the use of this slice and whether it can be - /// split. - PointerIntPair<Use *, 1, bool> UseAndIsSplittable; - -public: - Slice() = default; - - 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() == nullptr; } - void kill() { UseAndIsSplittable.setPointer(nullptr); } - - /// 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; - } - - /// 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; }; - -} // end namespace llvm - -/// 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 llvm::sroa::AllocaSlices { -public: - /// Construct the slices of a particular alloca. - AllocaSlices(const DataLayout &DL, AllocaInst &AI); - - /// 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; } - - /// Support for iterating over the slices. - /// @{ - using iterator = SmallVectorImpl<Slice>::iterator; - using range = iterator_range<iterator>; - - iterator begin() { return Slices.begin(); } - iterator end() { return Slices.end(); } - - using const_iterator = SmallVectorImpl<Slice>::const_iterator; - using const_range = iterator_range<const_iterator>; - - const_iterator begin() const { return Slices.begin(); } - const_iterator end() const { return Slices.end(); } - /// @} - - /// Erase a range of slices. - void erase(iterator Start, iterator Stop) { Slices.erase(Start, Stop); } - - /// Insert new slices for this alloca. - /// - /// This moves the slices into the alloca's slices collection, and re-sorts - /// everything so that the usual ordering properties of the alloca's slices - /// hold. - void insert(ArrayRef<Slice> NewSlices) { - int OldSize = Slices.size(); - Slices.append(NewSlices.begin(), NewSlices.end()); - auto SliceI = Slices.begin() + OldSize; - llvm::sort(SliceI, Slices.end()); - std::inplace_merge(Slices.begin(), SliceI, Slices.end()); - } - - // Forward declare the iterator and range accessor for walking the - // partitions. - class partition_iterator; - iterator_range<partition_iterator> partitions(); - - /// Access the dead users for this alloca. - ArrayRef<Instruction *> getDeadUsers() const { return DeadUsers; } - - /// Access the dead operands 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. - ArrayRef<Use *> getDeadOperands() const { return DeadOperands; } - -#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 dump(const_iterator I) const; - void 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) - /// Handle to alloca instruction to simplify method interfaces. - AllocaInst &AI; -#endif - - /// 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; - - /// 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; - - /// 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; - - /// 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; -}; - -/// A partition of the slices. -/// -/// An ephemeral representation for a range of slices which can be viewed as -/// a partition of the alloca. This range represents a span of the alloca's -/// memory which cannot be split, and provides access to all of the slices -/// overlapping some part of the partition. -/// -/// Objects of this type are produced by traversing the alloca's slices, but -/// are only ephemeral and not persistent. -class llvm::sroa::Partition { -private: - friend class AllocaSlices; - friend class AllocaSlices::partition_iterator; - - using iterator = AllocaSlices::iterator; - - /// The beginning and ending offsets of the alloca for this - /// partition. - uint64_t BeginOffset, EndOffset; - - /// The start and end iterators of this partition. - iterator SI, SJ; - - /// A collection of split slice tails overlapping the partition. - SmallVector<Slice *, 4> SplitTails; - - /// Raw constructor builds an empty partition starting and ending at - /// the given iterator. - Partition(iterator SI) : SI(SI), SJ(SI) {} - -public: - /// The start offset of this partition. - /// - /// All of the contained slices start at or after this offset. - uint64_t beginOffset() const { return BeginOffset; } - - /// The end offset of this partition. - /// - /// All of the contained slices end at or before this offset. - uint64_t endOffset() const { return EndOffset; } - - /// The size of the partition. - /// - /// Note that this can never be zero. - uint64_t size() const { - assert(BeginOffset < EndOffset && "Partitions must span some bytes!"); - return EndOffset - BeginOffset; - } - - /// Test whether this partition contains no slices, and merely spans - /// a region occupied by split slices. - bool empty() const { return SI == SJ; } - - /// \name Iterate slices that start within the partition. - /// These may be splittable or unsplittable. They have a begin offset >= the - /// partition begin offset. - /// @{ - // FIXME: We should probably define a "concat_iterator" helper and use that - // to stitch together pointee_iterators over the split tails and the - // contiguous iterators of the partition. That would give a much nicer - // interface here. We could then additionally expose filtered iterators for - // split, unsplit, and unsplittable splices based on the usage patterns. - iterator begin() const { return SI; } - iterator end() const { return SJ; } - /// @} - - /// Get the sequence of split slice tails. - /// - /// These tails are of slices which start before this partition but are - /// split and overlap into the partition. We accumulate these while forming - /// partitions. - ArrayRef<Slice *> splitSliceTails() const { return SplitTails; } -}; - -/// An iterator over partitions of the alloca's slices. -/// -/// This iterator implements the core algorithm for partitioning the alloca's -/// slices. It is a forward iterator as we don't support backtracking for -/// efficiency reasons, and re-use a single storage area to maintain the -/// current set of split slices. -/// -/// It is templated on the slice iterator type to use so that it can operate -/// with either const or non-const slice iterators. -class AllocaSlices::partition_iterator - : public iterator_facade_base<partition_iterator, std::forward_iterator_tag, - Partition> { - friend class AllocaSlices; - - /// Most of the state for walking the partitions is held in a class - /// with a nice interface for examining them. - Partition P; - - /// We need to keep the end of the slices to know when to stop. - AllocaSlices::iterator SE; - - /// We also need to keep track of the maximum split end offset seen. - /// FIXME: Do we really? - uint64_t MaxSplitSliceEndOffset = 0; - - /// Sets the partition to be empty at given iterator, and sets the - /// end iterator. - partition_iterator(AllocaSlices::iterator SI, AllocaSlices::iterator SE) - : P(SI), SE(SE) { - // If not already at the end, advance our state to form the initial - // partition. - if (SI != SE) - advance(); - } - - /// Advance the iterator to the next partition. - /// - /// Requires that the iterator not be at the end of the slices. - void advance() { - assert((P.SI != SE || !P.SplitTails.empty()) && - "Cannot advance past the end of the slices!"); - - // Clear out any split uses which have ended. - if (!P.SplitTails.empty()) { - if (P.EndOffset >= MaxSplitSliceEndOffset) { - // If we've finished all splits, this is easy. - P.SplitTails.clear(); - MaxSplitSliceEndOffset = 0; - } else { - // Remove the uses which have ended in the prior partition. This - // cannot change the max split slice end because we just checked that - // the prior partition ended prior to that max. - P.SplitTails.erase(llvm::remove_if(P.SplitTails, - [&](Slice *S) { - return S->endOffset() <= - P.EndOffset; - }), - P.SplitTails.end()); - assert(llvm::any_of(P.SplitTails, - [&](Slice *S) { - return S->endOffset() == MaxSplitSliceEndOffset; - }) && - "Could not find the current max split slice offset!"); - assert(llvm::all_of(P.SplitTails, - [&](Slice *S) { - return S->endOffset() <= MaxSplitSliceEndOffset; - }) && - "Max split slice end offset is not actually the max!"); - } - } - - // If P.SI is already at the end, then we've cleared the split tail and - // now have an end iterator. - if (P.SI == SE) { - assert(P.SplitTails.empty() && "Failed to clear the split slices!"); - return; - } - - // If we had a non-empty partition previously, set up the state for - // subsequent partitions. - if (P.SI != P.SJ) { - // Accumulate all the splittable slices which started in the old - // partition into the split list. - for (Slice &S : P) - if (S.isSplittable() && S.endOffset() > P.EndOffset) { - P.SplitTails.push_back(&S); - MaxSplitSliceEndOffset = - std::max(S.endOffset(), MaxSplitSliceEndOffset); - } - - // Start from the end of the previous partition. - P.SI = P.SJ; - - // If P.SI is now at the end, we at most have a tail of split slices. - if (P.SI == SE) { - P.BeginOffset = P.EndOffset; - P.EndOffset = MaxSplitSliceEndOffset; - return; - } - - // If the we have split slices and the next slice is after a gap and is - // not splittable immediately form an empty partition for the split - // slices up until the next slice begins. - if (!P.SplitTails.empty() && P.SI->beginOffset() != P.EndOffset && - !P.SI->isSplittable()) { - P.BeginOffset = P.EndOffset; - P.EndOffset = P.SI->beginOffset(); - return; - } - } - - // OK, we need to consume new slices. Set the end offset based on the - // current slice, and step SJ past it. The beginning offset of the - // partition is the beginning offset of the next slice unless we have - // pre-existing split slices that are continuing, in which case we begin - // at the prior end offset. - P.BeginOffset = P.SplitTails.empty() ? P.SI->beginOffset() : P.EndOffset; - P.EndOffset = P.SI->endOffset(); - ++P.SJ; - - // There are two strategies to form a partition based on whether the - // partition starts with an unsplittable slice or a splittable slice. - if (!P.SI->isSplittable()) { - // When we're forming an unsplittable region, it must always start at - // the first slice and will extend through its end. - assert(P.BeginOffset == P.SI->beginOffset()); - - // Form a partition including all of the overlapping slices with this - // unsplittable slice. - while (P.SJ != SE && P.SJ->beginOffset() < P.EndOffset) { - if (!P.SJ->isSplittable()) - P.EndOffset = std::max(P.EndOffset, P.SJ->endOffset()); - ++P.SJ; - } - - // We have a partition across a set of overlapping unsplittable - // partitions. - return; - } - - // If we're starting with a splittable slice, then we need to form - // a synthetic partition spanning it and any other overlapping splittable - // splices. - assert(P.SI->isSplittable() && "Forming a splittable partition!"); - - // Collect all of the overlapping splittable slices. - while (P.SJ != SE && P.SJ->beginOffset() < P.EndOffset && - P.SJ->isSplittable()) { - P.EndOffset = std::max(P.EndOffset, P.SJ->endOffset()); - ++P.SJ; - } - - // Back upiP.EndOffset if we ended the span early when encountering an - // unsplittable slice. This synthesizes the early end offset of - // a partition spanning only splittable slices. - if (P.SJ != SE && P.SJ->beginOffset() < P.EndOffset) { - assert(!P.SJ->isSplittable()); - P.EndOffset = P.SJ->beginOffset(); - } - } - -public: - bool operator==(const partition_iterator &RHS) const { - assert(SE == RHS.SE && - "End iterators don't match between compared partition iterators!"); - - // The observed positions of partitions is marked by the P.SI iterator and - // the emptiness of the split slices. The latter is only relevant when - // P.SI == SE, as the end iterator will additionally have an empty split - // slices list, but the prior may have the same P.SI and a tail of split - // slices. - if (P.SI == RHS.P.SI && P.SplitTails.empty() == RHS.P.SplitTails.empty()) { - assert(P.SJ == RHS.P.SJ && - "Same set of slices formed two different sized partitions!"); - assert(P.SplitTails.size() == RHS.P.SplitTails.size() && - "Same slice position with differently sized non-empty split " - "slice tails!"); - return true; - } - return false; - } - - partition_iterator &operator++() { - advance(); - return *this; - } - - Partition &operator*() { return P; } -}; - -/// A forward range over the partitions of the alloca's slices. -/// -/// This accesses an iterator range over the partitions of the alloca's -/// slices. It computes these partitions on the fly based on the overlapping -/// offsets of the slices and the ability to split them. It will visit "empty" -/// partitions to cover regions of the alloca only accessed via split -/// slices. -iterator_range<AllocaSlices::partition_iterator> AllocaSlices::partitions() { - return make_range(partition_iterator(begin(), end()), - partition_iterator(end(), end())); -} - -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 nullptr; -} - -/// A helper that folds a PHI node or a select. -static Value *foldPHINodeOrSelectInst(Instruction &I) { - if (PHINode *PN = dyn_cast<PHINode>(&I)) { - // If PN merges together the same value, return that value. - return PN->hasConstantValue(); - } - return foldSelectInst(cast<SelectInst>(I)); -} - -/// 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>; - - using Base = PtrUseVisitor<SliceBuilder>; - - const uint64_t AllocSize; - AllocaSlices &AS; - - SmallDenseMap<Instruction *, unsigned> MemTransferSliceMap; - SmallDenseMap<Instruction *, uint64_t> PHIOrSelectSizes; - - /// Set to de-duplicate dead instructions found in the use walk. - SmallPtrSet<Instruction *, 4> VisitedDeadInsts; - -public: - SliceBuilder(const DataLayout &DL, AllocaInst &AI, AllocaSlices &AS) - : PtrUseVisitor<SliceBuilder>(DL), - AllocSize(DL.getTypeAllocSize(AI.getAllocatedType())), AS(AS) {} - -private: - void markAsDead(Instruction &I) { - if (VisitedDeadInsts.insert(&I).second) - AS.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.uge(AllocSize)) { - LLVM_DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte use @" - << Offset - << " which has zero size or starts outside of the " - << AllocSize << " byte alloca:\n" - << " alloca: " << AS.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) { - LLVM_DEBUG(dbgs() << "WARNING: Clamping a " << Size << " byte use @" - << Offset << " to remain within the " << AllocSize - << " byte alloca:\n" - << " alloca: " << AS.AI << "\n" - << " use: " << I << "\n"); - EndOffset = AllocSize; - } - - AS.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); - - if (SROAStrictInbounds && GEPI.isInBounds()) { - // FIXME: This is a manually un-factored variant of the basic code inside - // of GEPs with checking of the inbounds invariant specified in the - // langref in a very strict sense. If we ever want to enable - // SROAStrictInbounds, this code should be factored cleanly into - // PtrUseVisitor, but it is easier to experiment with SROAStrictInbounds - // by writing out the code here where we have the underlying allocation - // size readily available. - APInt GEPOffset = Offset; - const DataLayout &DL = GEPI.getModule()->getDataLayout(); - for (gep_type_iterator GTI = gep_type_begin(GEPI), - GTE = gep_type_end(GEPI); - GTI != GTE; ++GTI) { - ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand()); - if (!OpC) - break; - - // Handle a struct index, which adds its field offset to the pointer. - if (StructType *STy = GTI.getStructTypeOrNull()) { - unsigned ElementIdx = OpC->getZExtValue(); - const StructLayout *SL = DL.getStructLayout(STy); - GEPOffset += - APInt(Offset.getBitWidth(), SL->getElementOffset(ElementIdx)); - } else { - // For array or vector indices, scale the index by the size of the - // type. - APInt Index = OpC->getValue().sextOrTrunc(Offset.getBitWidth()); - GEPOffset += Index * APInt(Offset.getBitWidth(), - DL.getTypeAllocSize(GTI.getIndexedType())); - } - - // If this index has computed an intermediate pointer which is not - // inbounds, then the result of the GEP is a poison value and we can - // delete it and all uses. - if (GEPOffset.ugt(AllocSize)) - 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 non-volatile loads and stores where the type is an - // integer type. These may be used to implement 'memcpy' or other "transfer - // of bits" patterns. - bool IsSplittable = Ty->isIntegerTy() && !IsVolatile; - - 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); - - const DataLayout &DL = LI.getModule()->getDataLayout(); - 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); - - const DataLayout &DL = SI.getModule()->getDataLayout(); - uint64_t Size = DL.getTypeStoreSize(ValOp->getType()); - - // If this memory access can be shown to *statically* extend outside the - // bounds 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 (Size > AllocSize || Offset.ugt(AllocSize - Size)) { - LLVM_DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte store @" - << Offset << " which extends past the end of the " - << AllocSize << " byte alloca:\n" - << " alloca: " << AS.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.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) - // Zero-length mem transfer intrinsics can be ignored entirely. - return markAsDead(II); - - // Because we can visit these intrinsics twice, also check to see if the - // first time marked this instruction as dead. If so, skip it. - if (VisitedDeadInsts.count(&II)) - return; - - if (!IsOffsetKnown) - return PI.setAborted(&II); - - // This side of the transfer is completely out-of-bounds, and so we can - // nuke the entire transfer. However, we also need to nuke the other side - // if already added to our partitions. - // FIXME: Yet another place we really should bypass this when - // instrumenting for ASan. - if (Offset.uge(AllocSize)) { - SmallDenseMap<Instruction *, unsigned>::iterator MTPI = - MemTransferSliceMap.find(&II); - if (MTPI != MemTransferSliceMap.end()) - AS.Slices[MTPI->second].kill(); - return markAsDead(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; - std::tie(MTPI, Inserted) = - MemTransferSliceMap.insert(std::make_pair(&II, AS.Slices.size())); - unsigned PrevIdx = MTPI->second; - if (!Inserted) { - Slice &PrevP = AS.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(AS.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.isLifetimeStartOrEnd()) { - 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)); - const DataLayout &DL = Root->getModule()->getDataLayout(); - // 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; - std::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 (User *U : I->users()) - if (Visited.insert(cast<Instruction>(U)).second) - Uses.push_back(std::make_pair(I, cast<Instruction>(U))); - } while (!Uses.empty()); - - return nullptr; - } - - void visitPHINodeOrSelectInst(Instruction &I) { - assert(isa<PHINode>(I) || isa<SelectInst>(I)); - if (I.use_empty()) - return markAsDead(I); - - // TODO: We could use SimplifyInstruction here to fold PHINodes and - // SelectInsts. However, doing so requires to change the current - // dead-operand-tracking mechanism. For instance, suppose neither loading - // from %U nor %other traps. Then "load (select undef, %U, %other)" does not - // trap either. However, if we simply replace %U with undef using the - // current dead-operand-tracking mechanism, "load (select undef, undef, - // %other)" may trap because the select may return the first operand - // "undef". - if (Value *Result = foldPHINodeOrSelectInst(I)) { - if (Result == *U) - // If the result of the constant fold will be the pointer, recurse - // through the PHI/select as if we had RAUW'ed it. - enqueueUsers(I); - else - // Otherwise the operand to the PHI/select is dead, and we can replace - // it with undef. - AS.DeadOperands.push_back(U); - - return; - } - - if (!IsOffsetKnown) - return PI.setAborted(&I); - - // See if we already have computed info on this node. - uint64_t &Size = PHIOrSelectSizes[&I]; - if (!Size) { - // This is a new PHI/Select, check for an unsafe use of it. - if (Instruction *UnsafeI = hasUnsafePHIOrSelectUse(&I, Size)) - 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.uge(AllocSize)) { - AS.DeadOperands.push_back(U); - return; - } - - insertUse(I, Offset, Size); - } - - void visitPHINode(PHINode &PN) { visitPHINodeOrSelectInst(PN); } - - void visitSelectInst(SelectInst &SI) { visitPHINodeOrSelectInst(SI); } - - /// 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(nullptr) { - 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( - llvm::remove_if(Slices, [](const Slice &S) { return S.isDead(); }), - Slices.end()); - -#ifndef NDEBUG - if (SROARandomShuffleSlices) { - std::mt19937 MT(static_cast<unsigned>( - std::chrono::system_clock::now().time_since_epoch().count())); - std::shuffle(Slices.begin(), Slices.end(), MT); - } -#endif - - // Sort the uses. This arranges for the offsets to be in ascending order, - // and the sizes to be in descending order. - llvm::sort(Slices); -} - -#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) - -void AllocaSlices::print(raw_ostream &OS, const_iterator I, - StringRef Indent) const { - printSlice(OS, I, Indent); - OS << "\n"; - 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)" : ""); -} - -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); -} - -LLVM_DUMP_METHOD void AllocaSlices::dump(const_iterator I) const { - print(dbgs(), I); -} -LLVM_DUMP_METHOD void AllocaSlices::dump() const { print(dbgs()); } - -#endif // !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) - -/// 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 = nullptr; - bool TyIsCommon = true; - IntegerType *ITy = nullptr; - - // Note that we need to look at *every* alloca slice's Use to ensure we - // always get consistent results regardless of the order of slices. - 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 = nullptr; - if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) { - UserTy = LI->getType(); - } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) { - UserTy = SI->getValueOperand()->getType(); - } - - if (IntegerType *UserITy = dyn_cast_or_null<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 (UserITy->getBitWidth() % 8 != 0 || - UserITy->getBitWidth() / 8 > (EndOffset - B->beginOffset())) - continue; - - // Track the largest bitwidth integer type used in this way in case there - // is no common type. - if (!ITy || ITy->getBitWidth() < UserITy->getBitWidth()) - ITy = UserITy; - } - - // To avoid depending on the order of slices, Ty and TyIsCommon must not - // depend on types skipped above. - if (!UserTy || (Ty && Ty != UserTy)) - TyIsCommon = false; // Give up on anything but an iN type. - else - Ty = UserTy; - } - - return TyIsCommon ? Ty : ITy; -} - -/// 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) { - // 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 (User *U : PN.users()) { - LoadInst *LI = dyn_cast<LoadInst>(U); - if (!LI || !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; - - const DataLayout &DL = PN.getModule()->getDataLayout(); - - // 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) { - Instruction *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 (isSafeToLoadUnconditionally(InVal, MaxAlign, DL, TI)) - continue; - - return false; - } - - return true; -} - -static void speculatePHINodeLoads(PHINode &PN) { - LLVM_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 AA tags 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.user_back()); - - AAMDNodes AATags; - SomeLoad->getAAMetadata(AATags); - unsigned Align = SomeLoad->getAlignment(); - - // Rewrite all loads of the PN to use the new PHI. - while (!PN.use_empty()) { - LoadInst *LI = cast<LoadInst>(PN.user_back()); - LI->replaceAllUsesWith(NewPN); - LI->eraseFromParent(); - } - - // Inject loads into all of the pred blocks. - DenseMap<BasicBlock*, Value*> InjectedLoads; - for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) { - BasicBlock *Pred = PN.getIncomingBlock(Idx); - Value *InVal = PN.getIncomingValue(Idx); - - // A PHI node is allowed to have multiple (duplicated) entries for the same - // basic block, as long as the value is the same. So if we already injected - // a load in the predecessor, then we should reuse the same load for all - // duplicated entries. - if (Value* V = InjectedLoads.lookup(Pred)) { - NewPN->addIncoming(V, Pred); - continue; - } - - Instruction *TI = Pred->getTerminator(); - IRBuilderTy PredBuilder(TI); - - LoadInst *Load = PredBuilder.CreateLoad( - InVal, (PN.getName() + ".sroa.speculate.load." + Pred->getName())); - ++NumLoadsSpeculated; - Load->setAlignment(Align); - if (AATags) - Load->setAAMetadata(AATags); - NewPN->addIncoming(Load, Pred); - InjectedLoads[Pred] = Load; - } - - LLVM_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) { - Value *TValue = SI.getTrueValue(); - Value *FValue = SI.getFalseValue(); - const DataLayout &DL = SI.getModule()->getDataLayout(); - - for (User *U : SI.users()) { - LoadInst *LI = dyn_cast<LoadInst>(U); - if (!LI || !LI->isSimple()) - return false; - - // Both operands to the select need to be dereferenceable, either - // absolutely (e.g. allocas) or at this point because we can see other - // accesses to it. - if (!isSafeToLoadUnconditionally(TValue, LI->getAlignment(), DL, LI)) - return false; - if (!isSafeToLoadUnconditionally(FValue, LI->getAlignment(), DL, LI)) - return false; - } - - return true; -} - -static void speculateSelectInstLoads(SelectInst &SI) { - LLVM_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.user_back()); - 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 AA info if present. - TL->setAlignment(LI->getAlignment()); - FL->setAlignment(LI->getAlignment()); - - AAMDNodes Tags; - LI->getAAMetadata(Tags); - if (Tags) { - TL->setAAMetadata(Tags); - FL->setAAMetadata(Tags); - } - - Value *V = IRB.CreateSelect(SI.getCondition(), TL, FL, - LI->getName() + ".sroa.speculated"); - - LLVM_DEBUG(dbgs() << " speculated to: " << *V << "\n"); - LI->replaceAllUsesWith(V); - LI->eraseFromParent(); - } - SI.eraseFromParent(); -} - -/// 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, Twine NamePrefix) { - 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(nullptr, BasePtr, Indices, - NamePrefix + "sroa_idx"); -} - -/// 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, - Twine NamePrefix) { - if (Ty == TargetTy) - return buildGEP(IRB, BasePtr, Indices, NamePrefix); - - // Offset size to use for the indices. - unsigned OffsetSize = DL.getIndexTypeSizeInBits(BasePtr->getType()); - - // 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 (ArrayType *ArrayTy = dyn_cast<ArrayType>(ElementTy)) { - ElementTy = ArrayTy->getElementType(); - Indices.push_back(IRB.getIntN(OffsetSize, 0)); - } else if (VectorType *VectorTy = dyn_cast<VectorType>(ElementTy)) { - ElementTy = VectorTy->getElementType(); - Indices.push_back(IRB.getInt32(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, NamePrefix); -} - -/// 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, - Twine NamePrefix) { - if (Offset == 0) - return getNaturalGEPWithType(IRB, DL, Ptr, Ty, TargetTy, Indices, - NamePrefix); - - // We can't recurse through pointer types. - if (Ty->isPointerTy()) - return nullptr; - - // 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 != 0) { - // GEPs over non-multiple of 8 size vector elements are invalid. - return nullptr; - } - APInt ElementSize(Offset.getBitWidth(), ElementSizeInBits / 8); - APInt NumSkippedElements = Offset.sdiv(ElementSize); - if (NumSkippedElements.ugt(VecTy->getNumElements())) - return nullptr; - Offset -= NumSkippedElements * ElementSize; - Indices.push_back(IRB.getInt(NumSkippedElements)); - return getNaturalGEPRecursively(IRB, DL, Ptr, VecTy->getElementType(), - Offset, TargetTy, Indices, NamePrefix); - } - - 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 nullptr; - - Offset -= NumSkippedElements * ElementSize; - Indices.push_back(IRB.getInt(NumSkippedElements)); - return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy, - Indices, NamePrefix); - } - - StructType *STy = dyn_cast<StructType>(Ty); - if (!STy) - return nullptr; - - const StructLayout *SL = DL.getStructLayout(STy); - uint64_t StructOffset = Offset.getZExtValue(); - if (StructOffset >= SL->getSizeInBytes()) - return nullptr; - unsigned Index = SL->getElementContainingOffset(StructOffset); - Offset -= APInt(Offset.getBitWidth(), SL->getElementOffset(Index)); - Type *ElementTy = STy->getElementType(Index); - if (Offset.uge(DL.getTypeAllocSize(ElementTy))) - return nullptr; // The offset points into alignment padding. - - Indices.push_back(IRB.getInt32(Index)); - return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy, - Indices, NamePrefix); -} - -/// 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, - Twine NamePrefix) { - 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(Ty->getAddressSpace()) && TargetTy->isIntegerTy(8)) - return nullptr; - - Type *ElementTy = Ty->getElementType(); - if (!ElementTy->isSized()) - return nullptr; // We can't GEP through an unsized element. - APInt ElementSize(Offset.getBitWidth(), DL.getTypeAllocSize(ElementTy)); - if (ElementSize == 0) - return nullptr; // 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, NamePrefix); -} - -/// 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, Twine NamePrefix) { - // 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 and the base it was computed from around here. - Value *OffsetPtr = nullptr; - Value *OffsetBasePtr; - - // Remember any i8 pointer we come across to re-use if we need to do a raw - // byte offset. - Value *Int8Ptr = nullptr; - 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).second) - break; - } - - // See if we can perform a natural GEP here. - Indices.clear(); - if (Value *P = getNaturalGEPWithOffset(IRB, DL, Ptr, Offset, TargetTy, - Indices, NamePrefix)) { - // If we have a new natural pointer at the offset, clear out any old - // offset pointer we computed. Unless it is the base pointer or - // a non-instruction, we built a GEP we don't need. Zap it. - if (OffsetPtr && OffsetPtr != OffsetBasePtr) - if (Instruction *I = dyn_cast<Instruction>(OffsetPtr)) { - assert(I->use_empty() && "Built a GEP with uses some how!"); - I->eraseFromParent(); - } - OffsetPtr = P; - OffsetBasePtr = Ptr; - // If we also found a pointer of the right type, we're done. - if (P->getType() == PointerTy) - return 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->isInterposable()) - break; - Ptr = GA->getAliasee(); - } else { - break; - } - assert(Ptr->getType()->isPointerTy() && "Unexpected operand type!"); - } while (Visited.insert(Ptr).second); - - if (!OffsetPtr) { - if (!Int8Ptr) { - Int8Ptr = IRB.CreateBitCast( - Ptr, IRB.getInt8PtrTy(PointerTy->getPointerAddressSpace()), - NamePrefix + "sroa_raw_cast"); - Int8PtrOffset = Offset; - } - - OffsetPtr = Int8PtrOffset == 0 - ? Int8Ptr - : IRB.CreateInBoundsGEP(IRB.getInt8Ty(), Int8Ptr, - IRB.getInt(Int8PtrOffset), - NamePrefix + "sroa_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, NamePrefix + "sroa_cast"); - - return Ptr; -} - -/// Compute the adjusted alignment for a load or store from an offset. -static unsigned getAdjustedAlignment(Instruction *I, uint64_t Offset, - const DataLayout &DL) { - unsigned Alignment; - Type *Ty; - if (auto *LI = dyn_cast<LoadInst>(I)) { - Alignment = LI->getAlignment(); - Ty = LI->getType(); - } else if (auto *SI = dyn_cast<StoreInst>(I)) { - Alignment = SI->getAlignment(); - Ty = SI->getValueOperand()->getType(); - } else { - llvm_unreachable("Only loads and stores are allowed!"); - } - - if (!Alignment) - Alignment = DL.getABITypeAlignment(Ty); - - return MinAlign(Alignment, Offset); -} - -/// 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; - - // For integer types, we can't handle any bit-width differences. This would - // break both vector conversions with extension and introduce endianness - // issues when in conjunction with loads and stores. - if (isa<IntegerType>(OldTy) && isa<IntegerType>(NewTy)) { - assert(cast<IntegerType>(OldTy)->getBitWidth() != - cast<IntegerType>(NewTy)->getBitWidth() && - "We can't have the same bitwidth for different int types"); - return false; - } - - 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 cast<PointerType>(NewTy)->getPointerAddressSpace() == - cast<PointerType>(OldTy)->getPointerAddressSpace(); - } - - // We can convert integers to integral pointers, but not to non-integral - // pointers. - if (OldTy->isIntegerTy()) - return !DL.isNonIntegralPointerType(NewTy); - - // We can convert integral pointers to integers, but non-integral pointers - // need to remain pointers. - if (!DL.isNonIntegralPointerType(OldTy)) - return NewTy->isIntegerTy(); - - return false; - } - - return true; -} - -/// 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; - - assert(!(isa<IntegerType>(OldTy) && isa<IntegerType>(NewTy)) && - "Integer types must be the exact same to convert."); - - // See if we need inttoptr for this type pair. A cast involving both scalars - // and vectors requires and additional bitcast. - if (OldTy->isIntOrIntVectorTy() && NewTy->isPtrOrPtrVectorTy()) { - // 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->isPtrOrPtrVectorTy() && NewTy->isIntOrIntVectorTy()) { - // 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); -} - -/// Test whether the given slice use can be promoted to a vector. -/// -/// This function is called to test each entry in a partition which is slated -/// for a single slice. -static bool isVectorPromotionViableForSlice(Partition &P, const Slice &S, - VectorType *Ty, - uint64_t ElementSize, - const DataLayout &DL) { - // First validate the slice offsets. - uint64_t BeginOffset = - std::max(S.beginOffset(), P.beginOffset()) - P.beginOffset(); - uint64_t BeginIndex = BeginOffset / ElementSize; - if (BeginIndex * ElementSize != BeginOffset || - BeginIndex >= Ty->getNumElements()) - return false; - uint64_t EndOffset = - std::min(S.endOffset(), P.endOffset()) - P.beginOffset(); - 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 = S.getUse(); - - if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) { - if (MI->isVolatile()) - return false; - if (!S.isSplittable()) - return false; // Skip any unsplittable intrinsics. - } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U->getUser())) { - if (!II->isLifetimeStartOrEnd()) - return false; - } 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 (P.beginOffset() > S.beginOffset() || P.endOffset() < S.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 (P.beginOffset() > S.beginOffset() || P.endOffset() < S.endOffset()) { - assert(STy->isIntegerTy()); - STy = SplitIntTy; - } - if (!canConvertValue(DL, STy, SliceTy)) - return false; - } else { - return false; - } - - return true; -} - -/// 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 VectorType *isVectorPromotionViable(Partition &P, const DataLayout &DL) { - // Collect the candidate types for vector-based promotion. Also track whether - // we have different element types. - SmallVector<VectorType *, 4> CandidateTys; - Type *CommonEltTy = nullptr; - bool HaveCommonEltTy = true; - auto CheckCandidateType = [&](Type *Ty) { - if (auto *VTy = dyn_cast<VectorType>(Ty)) { - CandidateTys.push_back(VTy); - if (!CommonEltTy) - CommonEltTy = VTy->getElementType(); - else if (CommonEltTy != VTy->getElementType()) - HaveCommonEltTy = false; - } - }; - // Consider any loads or stores that are the exact size of the slice. - for (const Slice &S : P) - if (S.beginOffset() == P.beginOffset() && - S.endOffset() == P.endOffset()) { - if (auto *LI = dyn_cast<LoadInst>(S.getUse()->getUser())) - CheckCandidateType(LI->getType()); - else if (auto *SI = dyn_cast<StoreInst>(S.getUse()->getUser())) - CheckCandidateType(SI->getValueOperand()->getType()); - } - - // If we didn't find a vector type, nothing to do here. - if (CandidateTys.empty()) - return nullptr; - - // Remove non-integer vector types if we had multiple common element types. - // FIXME: It'd be nice to replace them with integer vector types, but we can't - // do that until all the backends are known to produce good code for all - // integer vector types. - if (!HaveCommonEltTy) { - CandidateTys.erase( - llvm::remove_if(CandidateTys, - [](VectorType *VTy) { - return !VTy->getElementType()->isIntegerTy(); - }), - CandidateTys.end()); - - // If there were no integer vector types, give up. - if (CandidateTys.empty()) - return nullptr; - - // Rank the remaining candidate vector types. This is easy because we know - // they're all integer vectors. We sort by ascending number of elements. - auto RankVectorTypes = [&DL](VectorType *RHSTy, VectorType *LHSTy) { - (void)DL; - assert(DL.getTypeSizeInBits(RHSTy) == DL.getTypeSizeInBits(LHSTy) && - "Cannot have vector types of different sizes!"); - assert(RHSTy->getElementType()->isIntegerTy() && - "All non-integer types eliminated!"); - assert(LHSTy->getElementType()->isIntegerTy() && - "All non-integer types eliminated!"); - return RHSTy->getNumElements() < LHSTy->getNumElements(); - }; - llvm::sort(CandidateTys, RankVectorTypes); - CandidateTys.erase( - std::unique(CandidateTys.begin(), CandidateTys.end(), RankVectorTypes), - CandidateTys.end()); - } else { -// The only way to have the same element type in every vector type is to -// have the same vector type. Check that and remove all but one. -#ifndef NDEBUG - for (VectorType *VTy : CandidateTys) { - assert(VTy->getElementType() == CommonEltTy && - "Unaccounted for element type!"); - assert(VTy == CandidateTys[0] && - "Different vector types with the same element type!"); - } -#endif - CandidateTys.resize(1); - } - - // Try each vector type, and return the one which works. - auto CheckVectorTypeForPromotion = [&](VectorType *VTy) { - uint64_t ElementSize = DL.getTypeSizeInBits(VTy->getElementType()); - - // 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(VTy) % 8) == 0 && - "vector size not a multiple of element size?"); - ElementSize /= 8; - - for (const Slice &S : P) - if (!isVectorPromotionViableForSlice(P, S, VTy, ElementSize, DL)) - return false; - - for (const Slice *S : P.splitSliceTails()) - if (!isVectorPromotionViableForSlice(P, *S, VTy, ElementSize, DL)) - return false; - - return true; - }; - for (VectorType *VTy : CandidateTys) - if (CheckVectorTypeForPromotion(VTy)) - return VTy; - - return nullptr; -} - -/// 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 Slice &S, - uint64_t AllocBeginOffset, - Type *AllocaTy, - const DataLayout &DL, - bool &WholeAllocaOp) { - uint64_t Size = DL.getTypeStoreSize(AllocaTy); - - uint64_t RelBegin = S.beginOffset() - AllocBeginOffset; - uint64_t RelEnd = S.endOffset() - AllocBeginOffset; - - // We can't reasonably handle cases where the load or store extends past - // the end of the alloca's type and into its padding. - if (RelEnd > Size) - return false; - - Use *U = S.getUse(); - - if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) { - if (LI->isVolatile()) - return false; - // We can't handle loads that extend past the allocated memory. - if (DL.getTypeStoreSize(LI->getType()) > Size) - return false; - // So far, AllocaSliceRewriter does not support widening split slice tails - // in rewriteIntegerLoad. - if (S.beginOffset() < AllocBeginOffset) - return false; - // Note that we don't count vector loads or stores as whole-alloca - // operations which enable integer widening because we would prefer to use - // vector widening instead. - if (!isa<VectorType>(LI->getType()) && 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; - // We can't handle stores that extend past the allocated memory. - if (DL.getTypeStoreSize(ValueTy) > Size) - return false; - // So far, AllocaSliceRewriter does not support widening split slice tails - // in rewriteIntegerStore. - if (S.beginOffset() < AllocBeginOffset) - return false; - // Note that we don't count vector loads or stores as whole-alloca - // operations which enable integer widening because we would prefer to use - // vector widening instead. - if (!isa<VectorType>(ValueTy) && 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 (!S.isSplittable()) - return false; // Skip any unsplittable intrinsics. - } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U->getUser())) { - if (!II->isLifetimeStartOrEnd()) - return false; - } else { - return false; - } - - return true; -} - -/// 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(Partition &P, Type *AllocaTy, - const DataLayout &DL) { - 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; - - // 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. - // FIXME: We shouldn't consider split slices that happen to start in the - // partition here... - bool WholeAllocaOp = - P.begin() != P.end() ? false : DL.isLegalInteger(SizeInBits); - - for (const Slice &S : P) - if (!isIntegerWideningViableForSlice(S, P.beginOffset(), AllocaTy, DL, - WholeAllocaOp)) - return false; - - for (const Slice *S : P.splitSliceTails()) - if (!isIntegerWideningViableForSlice(*S, P.beginOffset(), AllocaTy, DL, - WholeAllocaOp)) - return false; - - return WholeAllocaOp; -} - -static Value *extractInteger(const DataLayout &DL, IRBuilderTy &IRB, Value *V, - IntegerType *Ty, uint64_t Offset, - const Twine &Name) { - LLVM_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"); - LLVM_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"); - LLVM_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!"); - LLVM_DEBUG(dbgs() << " start: " << *V << "\n"); - if (Ty != IntTy) { - V = IRB.CreateZExt(V, IntTy, Name + ".ext"); - LLVM_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"); - LLVM_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"); - LLVM_DEBUG(dbgs() << " masked: " << *Old << "\n"); - V = IRB.CreateOr(Old, V, Name + ".insert"); - LLVM_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"); - LLVM_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"); - LLVM_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"); - LLVM_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"); - LLVM_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"); - - LLVM_DEBUG(dbgs() << " blend: " << *V << "\n"); - return V; -} - -/// 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 llvm::sroa::AllocaSliceRewriter - : public InstVisitor<AllocaSliceRewriter, bool> { - // Befriend the base class so it can delegate to private visit methods. - friend class InstVisitor<AllocaSliceRewriter, bool>; - - using Base = InstVisitor<AllocaSliceRewriter, bool>; - - const DataLayout &DL; - AllocaSlices &AS; - SROA &Pass; - AllocaInst &OldAI, &NewAI; - const uint64_t NewAllocaBeginOffset, NewAllocaEndOffset; - Type *NewAllocaTy; - - // 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; - - // 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; - - // The original offset of the slice currently being rewritten relative to - // the original alloca. - uint64_t BeginOffset = 0; - uint64_t EndOffset = 0; - - // The new offsets of the slice currently being rewritten relative to the - // original alloca. - uint64_t NewBeginOffset, NewEndOffset; - - uint64_t SliceSize; - bool IsSplittable = false; - bool IsSplit = false; - Use *OldUse = nullptr; - Instruction *OldPtr = nullptr; - - // Track post-rewrite users which are PHI nodes and Selects. - SmallSetVector<PHINode *, 8> &PHIUsers; - SmallSetVector<SelectInst *, 8> &SelectUsers; - - // 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 &AS, SROA &Pass, - AllocaInst &OldAI, AllocaInst &NewAI, - uint64_t NewAllocaBeginOffset, - uint64_t NewAllocaEndOffset, bool IsIntegerPromotable, - VectorType *PromotableVecTy, - SmallSetVector<PHINode *, 8> &PHIUsers, - SmallSetVector<SelectInst *, 8> &SelectUsers) - : DL(DL), AS(AS), Pass(Pass), OldAI(OldAI), NewAI(NewAI), - NewAllocaBeginOffset(NewAllocaBeginOffset), - NewAllocaEndOffset(NewAllocaEndOffset), - NewAllocaTy(NewAI.getAllocatedType()), - IntTy(IsIntegerPromotable - ? Type::getIntNTy( - NewAI.getContext(), - DL.getTypeSizeInBits(NewAI.getAllocatedType())) - : nullptr), - VecTy(PromotableVecTy), - ElementTy(VecTy ? VecTy->getElementType() : nullptr), - ElementSize(VecTy ? DL.getTypeSizeInBits(ElementTy) / 8 : 0), - PHIUsers(PHIUsers), SelectUsers(SelectUsers), - IRB(NewAI.getContext(), ConstantFolder()) { - if (VecTy) { - assert((DL.getTypeSizeInBits(ElementTy) % 8) == 0 && - "Only multiple-of-8 sized vector elements are viable"); - ++NumVectorized; - } - assert((!IntTy && !VecTy) || (IntTy && !VecTy) || (!IntTy && VecTy)); - } - - bool visit(AllocaSlices::const_iterator I) { - bool CanSROA = true; - BeginOffset = I->beginOffset(); - EndOffset = I->endOffset(); - IsSplittable = I->isSplittable(); - IsSplit = - BeginOffset < NewAllocaBeginOffset || EndOffset > NewAllocaEndOffset; - LLVM_DEBUG(dbgs() << " rewriting " << (IsSplit ? "split " : "")); - LLVM_DEBUG(AS.printSlice(dbgs(), I, "")); - LLVM_DEBUG(dbgs() << "\n"); - - // Compute the intersecting offset range. - assert(BeginOffset < NewAllocaEndOffset); - assert(EndOffset > NewAllocaBeginOffset); - NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset); - NewEndOffset = std::min(EndOffset, NewAllocaEndOffset); - - SliceSize = NewEndOffset - NewBeginOffset; - - 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; - } - -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) { - LLVM_DEBUG(dbgs() << " !!!! Cannot rewrite: " << I << "\n"); - llvm_unreachable("No rewrite rule for this instruction!"); - } - - Value *getNewAllocaSlicePtr(IRBuilderTy &IRB, Type *PointerTy) { - // Note that the offset computation can use BeginOffset or NewBeginOffset - // interchangeably for unsplit slices. - assert(IsSplit || BeginOffset == NewBeginOffset); - uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset; - -#ifndef NDEBUG - StringRef OldName = OldPtr->getName(); - // Skip through the last '.sroa.' component of the name. - size_t LastSROAPrefix = OldName.rfind(".sroa."); - if (LastSROAPrefix != StringRef::npos) { - OldName = OldName.substr(LastSROAPrefix + strlen(".sroa.")); - // Look for an SROA slice index. - size_t IndexEnd = OldName.find_first_not_of("0123456789"); - if (IndexEnd != StringRef::npos && OldName[IndexEnd] == '.') { - // Strip the index and look for the offset. - OldName = OldName.substr(IndexEnd + 1); - size_t OffsetEnd = OldName.find_first_not_of("0123456789"); - if (OffsetEnd != StringRef::npos && OldName[OffsetEnd] == '.') - // Strip the offset. - OldName = OldName.substr(OffsetEnd + 1); - } - } - // Strip any SROA suffixes as well. - OldName = OldName.substr(0, OldName.find(".sroa_")); -#endif - - return getAdjustedPtr(IRB, DL, &NewAI, - APInt(DL.getIndexTypeSizeInBits(PointerTy), Offset), - PointerTy, -#ifndef NDEBUG - Twine(OldName) + "." -#else - Twine() -#endif - ); - } - - /// Compute suitable alignment to access this slice of the *new* - /// alloca. - /// - /// You can optionally pass a type to this routine and if that type's ABI - /// alignment is itself suitable, this will return zero. - unsigned getSliceAlign(Type *Ty = nullptr) { - unsigned NewAIAlign = NewAI.getAlignment(); - if (!NewAIAlign) - NewAIAlign = DL.getABITypeAlignment(NewAI.getAllocatedType()); - unsigned Align = - MinAlign(NewAIAlign, NewBeginOffset - NewAllocaBeginOffset); - return (Ty && 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() { - 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) { - 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) { - IntegerType *ExtractTy = Type::getIntNTy(LI.getContext(), SliceSize * 8); - V = extractInteger(DL, IRB, V, ExtractTy, Offset, "extract"); - } - // It is possible that the extracted type is not the load type. This - // happens if there is a load past the end of the alloca, and as - // a consequence the slice is narrower but still a candidate for integer - // lowering. To handle this case, we just zero extend the extracted - // integer. - assert(cast<IntegerType>(LI.getType())->getBitWidth() >= SliceSize * 8 && - "Can only handle an extract for an overly wide load"); - if (cast<IntegerType>(LI.getType())->getBitWidth() > SliceSize * 8) - V = IRB.CreateZExt(V, LI.getType()); - return V; - } - - bool visitLoadInst(LoadInst &LI) { - LLVM_DEBUG(dbgs() << " original: " << LI << "\n"); - Value *OldOp = LI.getOperand(0); - assert(OldOp == OldPtr); - - AAMDNodes AATags; - LI.getAAMetadata(AATags); - - unsigned AS = LI.getPointerAddressSpace(); - - Type *TargetTy = IsSplit ? Type::getIntNTy(LI.getContext(), SliceSize * 8) - : LI.getType(); - const bool IsLoadPastEnd = DL.getTypeStoreSize(TargetTy) > SliceSize; - bool IsPtrAdjusted = false; - Value *V; - if (VecTy) { - V = rewriteVectorizedLoadInst(); - } else if (IntTy && LI.getType()->isIntegerTy()) { - V = rewriteIntegerLoad(LI); - } else if (NewBeginOffset == NewAllocaBeginOffset && - NewEndOffset == NewAllocaEndOffset && - (canConvertValue(DL, NewAllocaTy, TargetTy) || - (IsLoadPastEnd && NewAllocaTy->isIntegerTy() && - TargetTy->isIntegerTy()))) { - LoadInst *NewLI = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), - LI.isVolatile(), LI.getName()); - if (AATags) - NewLI->setAAMetadata(AATags); - if (LI.isVolatile()) - NewLI->setAtomic(LI.getOrdering(), LI.getSyncScopeID()); - - // Any !nonnull metadata or !range metadata on the old load is also valid - // on the new load. This is even true in some cases even when the loads - // are different types, for example by mapping !nonnull metadata to - // !range metadata by modeling the null pointer constant converted to the - // integer type. - // FIXME: Add support for range metadata here. Currently the utilities - // for this don't propagate range metadata in trivial cases from one - // integer load to another, don't handle non-addrspace-0 null pointers - // correctly, and don't have any support for mapping ranges as the - // integer type becomes winder or narrower. - if (MDNode *N = LI.getMetadata(LLVMContext::MD_nonnull)) - copyNonnullMetadata(LI, N, *NewLI); - - // Try to preserve nonnull metadata - V = NewLI; - - // If this is an integer load past the end of the slice (which means the - // bytes outside the slice are undef or this load is dead) just forcibly - // fix the integer size with correct handling of endianness. - if (auto *AITy = dyn_cast<IntegerType>(NewAllocaTy)) - if (auto *TITy = dyn_cast<IntegerType>(TargetTy)) - if (AITy->getBitWidth() < TITy->getBitWidth()) { - V = IRB.CreateZExt(V, TITy, "load.ext"); - if (DL.isBigEndian()) - V = IRB.CreateShl(V, TITy->getBitWidth() - AITy->getBitWidth(), - "endian_shift"); - } - } else { - Type *LTy = TargetTy->getPointerTo(AS); - LoadInst *NewLI = IRB.CreateAlignedLoad(getNewAllocaSlicePtr(IRB, LTy), - getSliceAlign(TargetTy), - LI.isVolatile(), LI.getName()); - if (AATags) - NewLI->setAAMetadata(AATags); - if (LI.isVolatile()) - NewLI->setAtomic(LI.getOrdering(), LI.getSyncScopeID()); - - V = NewLI; - 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(SliceSize < 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(&*std::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(AS))); - V = insertInteger(DL, IRB, Placeholder, V, NewBeginOffset - BeginOffset, - "insert"); - LI.replaceAllUsesWith(V); - Placeholder->replaceAllUsesWith(&LI); - Placeholder->deleteValue(); - } else { - LI.replaceAllUsesWith(V); - } - - Pass.DeadInsts.insert(&LI); - deleteIfTriviallyDead(OldOp); - LLVM_DEBUG(dbgs() << " to: " << *V << "\n"); - return !LI.isVolatile() && !IsPtrAdjusted; - } - - bool rewriteVectorizedStoreInst(Value *V, StoreInst &SI, Value *OldOp, - AAMDNodes AATags) { - 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()); - if (AATags) - Store->setAAMetadata(AATags); - Pass.DeadInsts.insert(&SI); - - LLVM_DEBUG(dbgs() << " to: " << *Store << "\n"); - return true; - } - - bool rewriteIntegerStore(Value *V, StoreInst &SI, AAMDNodes AATags) { - 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()); - Store->copyMetadata(SI, {LLVMContext::MD_mem_parallel_loop_access, - LLVMContext::MD_access_group}); - if (AATags) - Store->setAAMetadata(AATags); - Pass.DeadInsts.insert(&SI); - LLVM_DEBUG(dbgs() << " to: " << *Store << "\n"); - return true; - } - - bool visitStoreInst(StoreInst &SI) { - LLVM_DEBUG(dbgs() << " original: " << SI << "\n"); - Value *OldOp = SI.getOperand(1); - assert(OldOp == OldPtr); - - AAMDNodes AATags; - SI.getAAMetadata(AATags); - - 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); - - if (SliceSize < 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(), SliceSize * 8); - V = extractInteger(DL, IRB, V, NarrowTy, NewBeginOffset - BeginOffset, - "extract"); - } - - if (VecTy) - return rewriteVectorizedStoreInst(V, SI, OldOp, AATags); - if (IntTy && V->getType()->isIntegerTy()) - return rewriteIntegerStore(V, SI, AATags); - - const bool IsStorePastEnd = DL.getTypeStoreSize(V->getType()) > SliceSize; - StoreInst *NewSI; - if (NewBeginOffset == NewAllocaBeginOffset && - NewEndOffset == NewAllocaEndOffset && - (canConvertValue(DL, V->getType(), NewAllocaTy) || - (IsStorePastEnd && NewAllocaTy->isIntegerTy() && - V->getType()->isIntegerTy()))) { - // If this is an integer store past the end of slice (and thus the bytes - // past that point are irrelevant or this is unreachable), truncate the - // value prior to storing. - if (auto *VITy = dyn_cast<IntegerType>(V->getType())) - if (auto *AITy = dyn_cast<IntegerType>(NewAllocaTy)) - if (VITy->getBitWidth() > AITy->getBitWidth()) { - if (DL.isBigEndian()) - V = IRB.CreateLShr(V, VITy->getBitWidth() - AITy->getBitWidth(), - "endian_shift"); - V = IRB.CreateTrunc(V, AITy, "load.trunc"); - } - - V = convertValue(DL, IRB, V, NewAllocaTy); - NewSI = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(), - SI.isVolatile()); - } else { - unsigned AS = SI.getPointerAddressSpace(); - Value *NewPtr = getNewAllocaSlicePtr(IRB, V->getType()->getPointerTo(AS)); - NewSI = IRB.CreateAlignedStore(V, NewPtr, getSliceAlign(V->getType()), - SI.isVolatile()); - } - NewSI->copyMetadata(SI, {LLVMContext::MD_mem_parallel_loop_access, - LLVMContext::MD_access_group}); - if (AATags) - NewSI->setAAMetadata(AATags); - if (SI.isVolatile()) - NewSI->setAtomic(SI.getOrdering(), SI.getSyncScopeID()); - Pass.DeadInsts.insert(&SI); - deleteIfTriviallyDead(OldOp); - - LLVM_DEBUG(dbgs() << " to: " << *NewSI << "\n"); - return NewSI->getPointerOperand() == &NewAI && !SI.isVolatile(); - } - - /// 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; - } - - /// Compute a vector splat for a given element value. - Value *getVectorSplat(Value *V, unsigned NumElements) { - V = IRB.CreateVectorSplat(NumElements, V, "vsplat"); - LLVM_DEBUG(dbgs() << " splat: " << *V << "\n"); - return V; - } - - bool visitMemSetInst(MemSetInst &II) { - LLVM_DEBUG(dbgs() << " original: " << II << "\n"); - assert(II.getRawDest() == OldPtr); - - AAMDNodes AATags; - II.getAAMetadata(AATags); - - // 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(NewBeginOffset == BeginOffset); - II.setDest(getNewAllocaSlicePtr(IRB, OldPtr->getType())); - II.setDestAlignment(getSliceAlign()); - - deleteIfTriviallyDead(OldPtr); - return false; - } - - // Record this instruction for deletion. - Pass.DeadInsts.insert(&II); - - Type *AllocaTy = NewAI.getAllocatedType(); - Type *ScalarTy = AllocaTy->getScalarType(); - - // 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 || - SliceSize != DL.getTypeStoreSize(AllocaTy) || - !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( - getNewAllocaSlicePtr(IRB, OldPtr->getType()), II.getValue(), Size, - getSliceAlign(), II.isVolatile()); - if (AATags) - New->setAAMetadata(AATags); - LLVM_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); - } - - StoreInst *New = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(), - II.isVolatile()); - if (AATags) - New->setAAMetadata(AATags); - LLVM_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. - - LLVM_DEBUG(dbgs() << " original: " << II << "\n"); - - AAMDNodes AATags; - II.getAAMetadata(AATags); - - bool IsDest = &II.getRawDestUse() == OldUse; - assert((IsDest && II.getRawDest() == OldPtr) || - (!IsDest && II.getRawSource() == OldPtr)); - - unsigned SliceAlign = getSliceAlign(); - - // 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 *AdjustedPtr = getNewAllocaSlicePtr(IRB, OldPtr->getType()); - if (IsDest) { - II.setDest(AdjustedPtr); - II.setDestAlignment(SliceAlign); - } - else { - II.setSource(AdjustedPtr); - II.setSourceAlignment(SliceAlign); - } - - LLVM_DEBUG(dbgs() << " to: " << II << "\n"); - deleteIfTriviallyDead(OldPtr); - 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 || - SliceSize != DL.getTypeStoreSize(NewAI.getAllocatedType()) || - !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())) { - assert(AI != &OldAI && AI != &NewAI && - "Splittable transfers cannot reach the same alloca on both ends."); - Pass.Worklist.insert(AI); - } - - Type *OtherPtrTy = OtherPtr->getType(); - unsigned OtherAS = OtherPtrTy->getPointerAddressSpace(); - - // Compute the relative offset for the other pointer within the transfer. - unsigned OffsetWidth = DL.getIndexSizeInBits(OtherAS); - APInt OtherOffset(OffsetWidth, NewBeginOffset - BeginOffset); - unsigned OtherAlign = - IsDest ? II.getSourceAlignment() : II.getDestAlignment(); - OtherAlign = MinAlign(OtherAlign ? OtherAlign : 1, - OtherOffset.zextOrTrunc(64).getZExtValue()); - - if (EmitMemCpy) { - // Compute the other pointer, folding as much as possible to produce - // a single, simple GEP in most cases. - OtherPtr = getAdjustedPtr(IRB, DL, OtherPtr, OtherOffset, OtherPtrTy, - OtherPtr->getName() + "."); - - Value *OurPtr = getNewAllocaSlicePtr(IRB, OldPtr->getType()); - Type *SizeTy = II.getLength()->getType(); - Constant *Size = ConstantInt::get(SizeTy, NewEndOffset - NewBeginOffset); - - Value *DestPtr, *SrcPtr; - unsigned DestAlign, SrcAlign; - // Note: IsDest is true iff we're copying into the new alloca slice - if (IsDest) { - DestPtr = OurPtr; - DestAlign = SliceAlign; - SrcPtr = OtherPtr; - SrcAlign = OtherAlign; - } else { - DestPtr = OtherPtr; - DestAlign = OtherAlign; - SrcPtr = OurPtr; - SrcAlign = SliceAlign; - } - CallInst *New = IRB.CreateMemCpy(DestPtr, DestAlign, SrcPtr, SrcAlign, - Size, II.isVolatile()); - if (AATags) - New->setAAMetadata(AATags); - LLVM_DEBUG(dbgs() << " to: " << *New << "\n"); - return false; - } - - 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) : nullptr; - - // Reset the other pointer type to match the register type we're going to - // use, but using the address space of the original other pointer. - if (VecTy && !IsWholeAlloca) { - if (NumElements == 1) - OtherPtrTy = VecTy->getElementType(); - else - OtherPtrTy = VectorType::get(VecTy->getElementType(), NumElements); - - OtherPtrTy = OtherPtrTy->getPointerTo(OtherAS); - } else if (IntTy && !IsWholeAlloca) { - OtherPtrTy = SubIntTy->getPointerTo(OtherAS); - } else { - OtherPtrTy = NewAllocaTy->getPointerTo(OtherAS); - } - - Value *SrcPtr = getAdjustedPtr(IRB, DL, OtherPtr, OtherOffset, OtherPtrTy, - OtherPtr->getName() + "."); - unsigned SrcAlign = OtherAlign; - Value *DstPtr = &NewAI; - unsigned DstAlign = SliceAlign; - if (!IsDest) { - std::swap(SrcPtr, DstPtr); - std::swap(SrcAlign, DstAlign); - } - - 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 { - LoadInst *Load = IRB.CreateAlignedLoad(SrcPtr, SrcAlign, II.isVolatile(), - "copyload"); - if (AATags) - Load->setAAMetadata(AATags); - Src = Load; - } - - 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, DstAlign, II.isVolatile())); - if (AATags) - Store->setAAMetadata(AATags); - LLVM_DEBUG(dbgs() << " to: " << *Store << "\n"); - return !II.isVolatile(); - } - - bool visitIntrinsicInst(IntrinsicInst &II) { - assert(II.isLifetimeStartOrEnd()); - LLVM_DEBUG(dbgs() << " original: " << II << "\n"); - assert(II.getArgOperand(1) == OldPtr); - - // Record this instruction for deletion. - Pass.DeadInsts.insert(&II); - - // Lifetime intrinsics are only promotable if they cover the whole alloca. - // Therefore, we drop lifetime intrinsics which don't cover the whole - // alloca. - // (In theory, intrinsics which partially cover an alloca could be - // promoted, but PromoteMemToReg doesn't handle that case.) - // FIXME: Check whether the alloca is promotable before dropping the - // lifetime intrinsics? - if (NewBeginOffset != NewAllocaBeginOffset || - NewEndOffset != NewAllocaEndOffset) - return true; - - ConstantInt *Size = - ConstantInt::get(cast<IntegerType>(II.getArgOperand(0)->getType()), - NewEndOffset - NewBeginOffset); - // Lifetime intrinsics always expect an i8* so directly get such a pointer - // for the new alloca slice. - Type *PointerTy = IRB.getInt8PtrTy(OldPtr->getType()->getPointerAddressSpace()); - Value *Ptr = getNewAllocaSlicePtr(IRB, PointerTy); - Value *New; - if (II.getIntrinsicID() == Intrinsic::lifetime_start) - New = IRB.CreateLifetimeStart(Ptr, Size); - else - New = IRB.CreateLifetimeEnd(Ptr, Size); - - (void)New; - LLVM_DEBUG(dbgs() << " to: " << *New << "\n"); - - return true; - } - - void fixLoadStoreAlign(Instruction &Root) { - // This algorithm implements the same visitor loop as - // hasUnsafePHIOrSelectUse, and fixes the alignment of each load - // or store found. - SmallPtrSet<Instruction *, 4> Visited; - SmallVector<Instruction *, 4> Uses; - Visited.insert(&Root); - Uses.push_back(&Root); - do { - Instruction *I = Uses.pop_back_val(); - - if (LoadInst *LI = dyn_cast<LoadInst>(I)) { - unsigned LoadAlign = LI->getAlignment(); - if (!LoadAlign) - LoadAlign = DL.getABITypeAlignment(LI->getType()); - LI->setAlignment(std::min(LoadAlign, getSliceAlign())); - continue; - } - if (StoreInst *SI = dyn_cast<StoreInst>(I)) { - unsigned StoreAlign = SI->getAlignment(); - if (!StoreAlign) { - Value *Op = SI->getOperand(0); - StoreAlign = DL.getABITypeAlignment(Op->getType()); - } - SI->setAlignment(std::min(StoreAlign, getSliceAlign())); - continue; - } - - assert(isa<BitCastInst>(I) || isa<PHINode>(I) || - isa<SelectInst>(I) || isa<GetElementPtrInst>(I)); - for (User *U : I->users()) - if (Visited.insert(cast<Instruction>(U)).second) - Uses.push_back(cast<Instruction>(U)); - } while (!Uses.empty()); - } - - bool visitPHINode(PHINode &PN) { - LLVM_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(IRB); - if (isa<PHINode>(OldPtr)) - PtrBuilder.SetInsertPoint(&*OldPtr->getParent()->getFirstInsertionPt()); - else - PtrBuilder.SetInsertPoint(OldPtr); - PtrBuilder.SetCurrentDebugLocation(OldPtr->getDebugLoc()); - - Value *NewPtr = getNewAllocaSlicePtr(PtrBuilder, OldPtr->getType()); - // Replace the operands which were using the old pointer. - std::replace(PN.op_begin(), PN.op_end(), cast<Value>(OldPtr), NewPtr); - - LLVM_DEBUG(dbgs() << " to: " << PN << "\n"); - deleteIfTriviallyDead(OldPtr); - - // Fix the alignment of any loads or stores using this PHI node. - fixLoadStoreAlign(PN); - - // PHIs can't be promoted on their own, but often can be speculated. We - // check the speculation outside of the rewriter so that we see the - // fully-rewritten alloca. - PHIUsers.insert(&PN); - return true; - } - - bool visitSelectInst(SelectInst &SI) { - LLVM_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 = getNewAllocaSlicePtr(IRB, 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); - - LLVM_DEBUG(dbgs() << " to: " << SI << "\n"); - deleteIfTriviallyDead(OldPtr); - - // Fix the alignment of any loads or stores using this select. - fixLoadStoreAlign(SI); - - // Selects can't be promoted on their own, but often can be speculated. We - // check the speculation outside of the rewriter so that we see the - // fully-rewritten alloca. - SelectUsers.insert(&SI); - return true; - } -}; - -namespace { - -/// 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 InstVisitor<AggLoadStoreRewriter, bool>; - - /// 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; - - /// Used to calculate offsets, and hence alignment, of subobjects. - const DataLayout &DL; - -public: - AggLoadStoreRewriter(const DataLayout &DL) : DL(DL) {} - - /// Rewrite loads and stores through a pointer and all pointers derived from - /// it. - bool rewrite(Instruction &I) { - LLVM_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 (Use &U : I.uses()) - if (Visited.insert(U.getUser()).second) - Queue.push_back(&U); - } - - // Conservative default is to not rewrite anything. - bool visitInstruction(Instruction &I) { return false; } - - /// 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; - - /// The base pointee type being GEPed into. - Type *BaseTy; - - /// Known alignment of the base pointer. - unsigned BaseAlign; - - /// To calculate offset of each component so we can correctly deduce - /// alignments. - const DataLayout &DL; - - /// Initialize the splitter with an insertion point, Ptr and start with a - /// single zero GEP index. - OpSplitter(Instruction *InsertionPoint, Value *Ptr, Type *BaseTy, - unsigned BaseAlign, const DataLayout &DL) - : IRB(InsertionPoint), GEPIndices(1, IRB.getInt32(0)), Ptr(Ptr), - BaseTy(BaseTy), BaseAlign(BaseAlign), DL(DL) {} - - public: - /// 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()) { - unsigned Offset = DL.getIndexedOffsetInType(BaseTy, GEPIndices); - return static_cast<Derived *>(this)->emitFunc( - Ty, Agg, MinAlign(BaseAlign, Offset), 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> { - AAMDNodes AATags; - - LoadOpSplitter(Instruction *InsertionPoint, Value *Ptr, Type *BaseTy, - AAMDNodes AATags, unsigned BaseAlign, const DataLayout &DL) - : OpSplitter<LoadOpSplitter>(InsertionPoint, Ptr, BaseTy, BaseAlign, - DL), AATags(AATags) {} - - /// 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, unsigned Align, const Twine &Name) { - assert(Ty->isSingleValueType()); - // Load the single value and insert it using the indices. - Value *GEP = - IRB.CreateInBoundsGEP(nullptr, Ptr, GEPIndices, Name + ".gep"); - LoadInst *Load = IRB.CreateAlignedLoad(GEP, Align, Name + ".load"); - if (AATags) - Load->setAAMetadata(AATags); - Agg = IRB.CreateInsertValue(Agg, Load, Indices, Name + ".insert"); - LLVM_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. - LLVM_DEBUG(dbgs() << " original: " << LI << "\n"); - AAMDNodes AATags; - LI.getAAMetadata(AATags); - LoadOpSplitter Splitter(&LI, *U, LI.getType(), AATags, - getAdjustedAlignment(&LI, 0, DL), DL); - 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, Type *BaseTy, - AAMDNodes AATags, unsigned BaseAlign, const DataLayout &DL) - : OpSplitter<StoreOpSplitter>(InsertionPoint, Ptr, BaseTy, BaseAlign, - DL), - AATags(AATags) {} - AAMDNodes AATags; - /// 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, unsigned Align, const Twine &Name) { - assert(Ty->isSingleValueType()); - // Extract the single value and store it using the indices. - // - // The gep and extractvalue values are factored out of the CreateStore - // call to make the output independent of the argument evaluation order. - Value *ExtractValue = - IRB.CreateExtractValue(Agg, Indices, Name + ".extract"); - Value *InBoundsGEP = - IRB.CreateInBoundsGEP(nullptr, Ptr, GEPIndices, Name + ".gep"); - StoreInst *Store = - IRB.CreateAlignedStore(ExtractValue, InBoundsGEP, Align); - if (AATags) - Store->setAAMetadata(AATags); - LLVM_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. - LLVM_DEBUG(dbgs() << " original: " << SI << "\n"); - AAMDNodes AATags; - SI.getAAMetadata(AATags); - StoreOpSplitter Splitter(&SI, *U, V->getType(), AATags, - getAdjustedAlignment(&SI, 0, DL), DL); - 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; - } -}; - -} // end anonymous namespace - -/// 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); -} - -/// 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 nullptr; - - if (SequentialType *SeqTy = dyn_cast<SequentialType>(Ty)) { - Type *ElementTy = SeqTy->getElementType(); - uint64_t ElementSize = DL.getTypeAllocSize(ElementTy); - uint64_t NumSkippedElements = Offset / ElementSize; - if (NumSkippedElements >= SeqTy->getNumElements()) - return nullptr; - 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 nullptr; - // 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 nullptr; - return ArrayType::get(ElementTy, NumElements); - } - - StructType *STy = dyn_cast<StructType>(Ty); - if (!STy) - return nullptr; - - const StructLayout *SL = DL.getStructLayout(STy); - if (Offset >= SL->getSizeInBytes()) - return nullptr; - uint64_t EndOffset = Offset + Size; - if (EndOffset > SL->getSizeInBytes()) - return nullptr; - - unsigned Index = SL->getElementContainingOffset(Offset); - Offset -= SL->getElementOffset(Index); - - Type *ElementTy = STy->getElementType(Index); - uint64_t ElementSize = DL.getTypeAllocSize(ElementTy); - if (Offset >= ElementSize) - return nullptr; // 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 nullptr; - 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 nullptr; // 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 nullptr; - - 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 nullptr; // The sub-struct doesn't have quite the size needed. - - return SubTy; -} - -/// Pre-split loads and stores to simplify rewriting. -/// -/// We want to break up the splittable load+store pairs as much as -/// possible. This is important to do as a preprocessing step, as once we -/// start rewriting the accesses to partitions of the alloca we lose the -/// necessary information to correctly split apart paired loads and stores -/// which both point into this alloca. The case to consider is something like -/// the following: -/// -/// %a = alloca [12 x i8] -/// %gep1 = getelementptr [12 x i8]* %a, i32 0, i32 0 -/// %gep2 = getelementptr [12 x i8]* %a, i32 0, i32 4 -/// %gep3 = getelementptr [12 x i8]* %a, i32 0, i32 8 -/// %iptr1 = bitcast i8* %gep1 to i64* -/// %iptr2 = bitcast i8* %gep2 to i64* -/// %fptr1 = bitcast i8* %gep1 to float* -/// %fptr2 = bitcast i8* %gep2 to float* -/// %fptr3 = bitcast i8* %gep3 to float* -/// store float 0.0, float* %fptr1 -/// store float 1.0, float* %fptr2 -/// %v = load i64* %iptr1 -/// store i64 %v, i64* %iptr2 -/// %f1 = load float* %fptr2 -/// %f2 = load float* %fptr3 -/// -/// Here we want to form 3 partitions of the alloca, each 4 bytes large, and -/// promote everything so we recover the 2 SSA values that should have been -/// there all along. -/// -/// \returns true if any changes are made. -bool SROA::presplitLoadsAndStores(AllocaInst &AI, AllocaSlices &AS) { - LLVM_DEBUG(dbgs() << "Pre-splitting loads and stores\n"); - - // Track the loads and stores which are candidates for pre-splitting here, in - // the order they first appear during the partition scan. These give stable - // iteration order and a basis for tracking which loads and stores we - // actually split. - SmallVector<LoadInst *, 4> Loads; - SmallVector<StoreInst *, 4> Stores; - - // We need to accumulate the splits required of each load or store where we - // can find them via a direct lookup. This is important to cross-check loads - // and stores against each other. We also track the slice so that we can kill - // all the slices that end up split. - struct SplitOffsets { - Slice *S; - std::vector<uint64_t> Splits; - }; - SmallDenseMap<Instruction *, SplitOffsets, 8> SplitOffsetsMap; - - // Track loads out of this alloca which cannot, for any reason, be pre-split. - // This is important as we also cannot pre-split stores of those loads! - // FIXME: This is all pretty gross. It means that we can be more aggressive - // in pre-splitting when the load feeding the store happens to come from - // a separate alloca. Put another way, the effectiveness of SROA would be - // decreased by a frontend which just concatenated all of its local allocas - // into one big flat alloca. But defeating such patterns is exactly the job - // SROA is tasked with! Sadly, to not have this discrepancy we would have - // change store pre-splitting to actually force pre-splitting of the load - // that feeds it *and all stores*. That makes pre-splitting much harder, but - // maybe it would make it more principled? - SmallPtrSet<LoadInst *, 8> UnsplittableLoads; - - LLVM_DEBUG(dbgs() << " Searching for candidate loads and stores\n"); - for (auto &P : AS.partitions()) { - for (Slice &S : P) { - Instruction *I = cast<Instruction>(S.getUse()->getUser()); - if (!S.isSplittable() || S.endOffset() <= P.endOffset()) { - // If this is a load we have to track that it can't participate in any - // pre-splitting. If this is a store of a load we have to track that - // that load also can't participate in any pre-splitting. - if (auto *LI = dyn_cast<LoadInst>(I)) - UnsplittableLoads.insert(LI); - else if (auto *SI = dyn_cast<StoreInst>(I)) - if (auto *LI = dyn_cast<LoadInst>(SI->getValueOperand())) - UnsplittableLoads.insert(LI); - continue; - } - assert(P.endOffset() > S.beginOffset() && - "Empty or backwards partition!"); - - // Determine if this is a pre-splittable slice. - if (auto *LI = dyn_cast<LoadInst>(I)) { - assert(!LI->isVolatile() && "Cannot split volatile loads!"); - - // The load must be used exclusively to store into other pointers for - // us to be able to arbitrarily pre-split it. The stores must also be - // simple to avoid changing semantics. - auto IsLoadSimplyStored = [](LoadInst *LI) { - for (User *LU : LI->users()) { - auto *SI = dyn_cast<StoreInst>(LU); - if (!SI || !SI->isSimple()) - return false; - } - return true; - }; - if (!IsLoadSimplyStored(LI)) { - UnsplittableLoads.insert(LI); - continue; - } - - Loads.push_back(LI); - } else if (auto *SI = dyn_cast<StoreInst>(I)) { - if (S.getUse() != &SI->getOperandUse(SI->getPointerOperandIndex())) - // Skip stores *of* pointers. FIXME: This shouldn't even be possible! - continue; - auto *StoredLoad = dyn_cast<LoadInst>(SI->getValueOperand()); - if (!StoredLoad || !StoredLoad->isSimple()) - continue; - assert(!SI->isVolatile() && "Cannot split volatile stores!"); - - Stores.push_back(SI); - } else { - // Other uses cannot be pre-split. - continue; - } - - // Record the initial split. - LLVM_DEBUG(dbgs() << " Candidate: " << *I << "\n"); - auto &Offsets = SplitOffsetsMap[I]; - assert(Offsets.Splits.empty() && - "Should not have splits the first time we see an instruction!"); - Offsets.S = &S; - Offsets.Splits.push_back(P.endOffset() - S.beginOffset()); - } - - // Now scan the already split slices, and add a split for any of them which - // we're going to pre-split. - for (Slice *S : P.splitSliceTails()) { - auto SplitOffsetsMapI = - SplitOffsetsMap.find(cast<Instruction>(S->getUse()->getUser())); - if (SplitOffsetsMapI == SplitOffsetsMap.end()) - continue; - auto &Offsets = SplitOffsetsMapI->second; - - assert(Offsets.S == S && "Found a mismatched slice!"); - assert(!Offsets.Splits.empty() && - "Cannot have an empty set of splits on the second partition!"); - assert(Offsets.Splits.back() == - P.beginOffset() - Offsets.S->beginOffset() && - "Previous split does not end where this one begins!"); - - // Record each split. The last partition's end isn't needed as the size - // of the slice dictates that. - if (S->endOffset() > P.endOffset()) - Offsets.Splits.push_back(P.endOffset() - Offsets.S->beginOffset()); - } - } - - // We may have split loads where some of their stores are split stores. For - // such loads and stores, we can only pre-split them if their splits exactly - // match relative to their starting offset. We have to verify this prior to - // any rewriting. - Stores.erase( - llvm::remove_if(Stores, - [&UnsplittableLoads, &SplitOffsetsMap](StoreInst *SI) { - // Lookup the load we are storing in our map of split - // offsets. - auto *LI = cast<LoadInst>(SI->getValueOperand()); - // If it was completely unsplittable, then we're done, - // and this store can't be pre-split. - if (UnsplittableLoads.count(LI)) - return true; - - auto LoadOffsetsI = SplitOffsetsMap.find(LI); - if (LoadOffsetsI == SplitOffsetsMap.end()) - return false; // Unrelated loads are definitely safe. - auto &LoadOffsets = LoadOffsetsI->second; - - // Now lookup the store's offsets. - auto &StoreOffsets = SplitOffsetsMap[SI]; - - // If the relative offsets of each split in the load and - // store match exactly, then we can split them and we - // don't need to remove them here. - if (LoadOffsets.Splits == StoreOffsets.Splits) - return false; - - LLVM_DEBUG( - dbgs() - << " Mismatched splits for load and store:\n" - << " " << *LI << "\n" - << " " << *SI << "\n"); - - // We've found a store and load that we need to split - // with mismatched relative splits. Just give up on them - // and remove both instructions from our list of - // candidates. - UnsplittableLoads.insert(LI); - return true; - }), - Stores.end()); - // Now we have to go *back* through all the stores, because a later store may - // have caused an earlier store's load to become unsplittable and if it is - // unsplittable for the later store, then we can't rely on it being split in - // the earlier store either. - Stores.erase(llvm::remove_if(Stores, - [&UnsplittableLoads](StoreInst *SI) { - auto *LI = - cast<LoadInst>(SI->getValueOperand()); - return UnsplittableLoads.count(LI); - }), - Stores.end()); - // Once we've established all the loads that can't be split for some reason, - // filter any that made it into our list out. - Loads.erase(llvm::remove_if(Loads, - [&UnsplittableLoads](LoadInst *LI) { - return UnsplittableLoads.count(LI); - }), - Loads.end()); - - // If no loads or stores are left, there is no pre-splitting to be done for - // this alloca. - if (Loads.empty() && Stores.empty()) - return false; - - // From here on, we can't fail and will be building new accesses, so rig up - // an IR builder. - IRBuilderTy IRB(&AI); - - // Collect the new slices which we will merge into the alloca slices. - SmallVector<Slice, 4> NewSlices; - - // Track any allocas we end up splitting loads and stores for so we iterate - // on them. - SmallPtrSet<AllocaInst *, 4> ResplitPromotableAllocas; - - // At this point, we have collected all of the loads and stores we can - // pre-split, and the specific splits needed for them. We actually do the - // splitting in a specific order in order to handle when one of the loads in - // the value operand to one of the stores. - // - // First, we rewrite all of the split loads, and just accumulate each split - // load in a parallel structure. We also build the slices for them and append - // them to the alloca slices. - SmallDenseMap<LoadInst *, std::vector<LoadInst *>, 1> SplitLoadsMap; - std::vector<LoadInst *> SplitLoads; - const DataLayout &DL = AI.getModule()->getDataLayout(); - for (LoadInst *LI : Loads) { - SplitLoads.clear(); - - IntegerType *Ty = cast<IntegerType>(LI->getType()); - uint64_t LoadSize = Ty->getBitWidth() / 8; - assert(LoadSize > 0 && "Cannot have a zero-sized integer load!"); - - auto &Offsets = SplitOffsetsMap[LI]; - assert(LoadSize == Offsets.S->endOffset() - Offsets.S->beginOffset() && - "Slice size should always match load size exactly!"); - uint64_t BaseOffset = Offsets.S->beginOffset(); - assert(BaseOffset + LoadSize > BaseOffset && - "Cannot represent alloca access size using 64-bit integers!"); - - Instruction *BasePtr = cast<Instruction>(LI->getPointerOperand()); - IRB.SetInsertPoint(LI); - - LLVM_DEBUG(dbgs() << " Splitting load: " << *LI << "\n"); - - uint64_t PartOffset = 0, PartSize = Offsets.Splits.front(); - int Idx = 0, Size = Offsets.Splits.size(); - for (;;) { - auto *PartTy = Type::getIntNTy(Ty->getContext(), PartSize * 8); - auto AS = LI->getPointerAddressSpace(); - auto *PartPtrTy = PartTy->getPointerTo(AS); - LoadInst *PLoad = IRB.CreateAlignedLoad( - getAdjustedPtr(IRB, DL, BasePtr, - APInt(DL.getIndexSizeInBits(AS), PartOffset), - PartPtrTy, BasePtr->getName() + "."), - getAdjustedAlignment(LI, PartOffset, DL), /*IsVolatile*/ false, - LI->getName()); - PLoad->copyMetadata(*LI, {LLVMContext::MD_mem_parallel_loop_access, - LLVMContext::MD_access_group}); - - // Append this load onto the list of split loads so we can find it later - // to rewrite the stores. - SplitLoads.push_back(PLoad); - - // Now build a new slice for the alloca. - NewSlices.push_back( - Slice(BaseOffset + PartOffset, BaseOffset + PartOffset + PartSize, - &PLoad->getOperandUse(PLoad->getPointerOperandIndex()), - /*IsSplittable*/ false)); - LLVM_DEBUG(dbgs() << " new slice [" << NewSlices.back().beginOffset() - << ", " << NewSlices.back().endOffset() - << "): " << *PLoad << "\n"); - - // See if we've handled all the splits. - if (Idx >= Size) - break; - - // Setup the next partition. - PartOffset = Offsets.Splits[Idx]; - ++Idx; - PartSize = (Idx < Size ? Offsets.Splits[Idx] : LoadSize) - PartOffset; - } - - // Now that we have the split loads, do the slow walk over all uses of the - // load and rewrite them as split stores, or save the split loads to use - // below if the store is going to be split there anyways. - bool DeferredStores = false; - for (User *LU : LI->users()) { - StoreInst *SI = cast<StoreInst>(LU); - if (!Stores.empty() && SplitOffsetsMap.count(SI)) { - DeferredStores = true; - LLVM_DEBUG(dbgs() << " Deferred splitting of store: " << *SI - << "\n"); - continue; - } - - Value *StoreBasePtr = SI->getPointerOperand(); - IRB.SetInsertPoint(SI); - - LLVM_DEBUG(dbgs() << " Splitting store of load: " << *SI << "\n"); - - for (int Idx = 0, Size = SplitLoads.size(); Idx < Size; ++Idx) { - LoadInst *PLoad = SplitLoads[Idx]; - uint64_t PartOffset = Idx == 0 ? 0 : Offsets.Splits[Idx - 1]; - auto *PartPtrTy = - PLoad->getType()->getPointerTo(SI->getPointerAddressSpace()); - - auto AS = SI->getPointerAddressSpace(); - StoreInst *PStore = IRB.CreateAlignedStore( - PLoad, - getAdjustedPtr(IRB, DL, StoreBasePtr, - APInt(DL.getIndexSizeInBits(AS), PartOffset), - PartPtrTy, StoreBasePtr->getName() + "."), - getAdjustedAlignment(SI, PartOffset, DL), /*IsVolatile*/ false); - PStore->copyMetadata(*LI, {LLVMContext::MD_mem_parallel_loop_access, - LLVMContext::MD_access_group}); - LLVM_DEBUG(dbgs() << " +" << PartOffset << ":" << *PStore << "\n"); - } - - // We want to immediately iterate on any allocas impacted by splitting - // this store, and we have to track any promotable alloca (indicated by - // a direct store) as needing to be resplit because it is no longer - // promotable. - if (AllocaInst *OtherAI = dyn_cast<AllocaInst>(StoreBasePtr)) { - ResplitPromotableAllocas.insert(OtherAI); - Worklist.insert(OtherAI); - } else if (AllocaInst *OtherAI = dyn_cast<AllocaInst>( - StoreBasePtr->stripInBoundsOffsets())) { - Worklist.insert(OtherAI); - } - - // Mark the original store as dead. - DeadInsts.insert(SI); - } - - // Save the split loads if there are deferred stores among the users. - if (DeferredStores) - SplitLoadsMap.insert(std::make_pair(LI, std::move(SplitLoads))); - - // Mark the original load as dead and kill the original slice. - DeadInsts.insert(LI); - Offsets.S->kill(); - } - - // Second, we rewrite all of the split stores. At this point, we know that - // all loads from this alloca have been split already. For stores of such - // loads, we can simply look up the pre-existing split loads. For stores of - // other loads, we split those loads first and then write split stores of - // them. - for (StoreInst *SI : Stores) { - auto *LI = cast<LoadInst>(SI->getValueOperand()); - IntegerType *Ty = cast<IntegerType>(LI->getType()); - uint64_t StoreSize = Ty->getBitWidth() / 8; - assert(StoreSize > 0 && "Cannot have a zero-sized integer store!"); - - auto &Offsets = SplitOffsetsMap[SI]; - assert(StoreSize == Offsets.S->endOffset() - Offsets.S->beginOffset() && - "Slice size should always match load size exactly!"); - uint64_t BaseOffset = Offsets.S->beginOffset(); - assert(BaseOffset + StoreSize > BaseOffset && - "Cannot represent alloca access size using 64-bit integers!"); - - Value *LoadBasePtr = LI->getPointerOperand(); - Instruction *StoreBasePtr = cast<Instruction>(SI->getPointerOperand()); - - LLVM_DEBUG(dbgs() << " Splitting store: " << *SI << "\n"); - - // Check whether we have an already split load. - auto SplitLoadsMapI = SplitLoadsMap.find(LI); - std::vector<LoadInst *> *SplitLoads = nullptr; - if (SplitLoadsMapI != SplitLoadsMap.end()) { - SplitLoads = &SplitLoadsMapI->second; - assert(SplitLoads->size() == Offsets.Splits.size() + 1 && - "Too few split loads for the number of splits in the store!"); - } else { - LLVM_DEBUG(dbgs() << " of load: " << *LI << "\n"); - } - - uint64_t PartOffset = 0, PartSize = Offsets.Splits.front(); - int Idx = 0, Size = Offsets.Splits.size(); - for (;;) { - auto *PartTy = Type::getIntNTy(Ty->getContext(), PartSize * 8); - auto *LoadPartPtrTy = PartTy->getPointerTo(LI->getPointerAddressSpace()); - auto *StorePartPtrTy = PartTy->getPointerTo(SI->getPointerAddressSpace()); - - // Either lookup a split load or create one. - LoadInst *PLoad; - if (SplitLoads) { - PLoad = (*SplitLoads)[Idx]; - } else { - IRB.SetInsertPoint(LI); - auto AS = LI->getPointerAddressSpace(); - PLoad = IRB.CreateAlignedLoad( - getAdjustedPtr(IRB, DL, LoadBasePtr, - APInt(DL.getIndexSizeInBits(AS), PartOffset), - LoadPartPtrTy, LoadBasePtr->getName() + "."), - getAdjustedAlignment(LI, PartOffset, DL), /*IsVolatile*/ false, - LI->getName()); - } - - // And store this partition. - IRB.SetInsertPoint(SI); - auto AS = SI->getPointerAddressSpace(); - StoreInst *PStore = IRB.CreateAlignedStore( - PLoad, - getAdjustedPtr(IRB, DL, StoreBasePtr, - APInt(DL.getIndexSizeInBits(AS), PartOffset), - StorePartPtrTy, StoreBasePtr->getName() + "."), - getAdjustedAlignment(SI, PartOffset, DL), /*IsVolatile*/ false); - - // Now build a new slice for the alloca. - NewSlices.push_back( - Slice(BaseOffset + PartOffset, BaseOffset + PartOffset + PartSize, - &PStore->getOperandUse(PStore->getPointerOperandIndex()), - /*IsSplittable*/ false)); - LLVM_DEBUG(dbgs() << " new slice [" << NewSlices.back().beginOffset() - << ", " << NewSlices.back().endOffset() - << "): " << *PStore << "\n"); - if (!SplitLoads) { - LLVM_DEBUG(dbgs() << " of split load: " << *PLoad << "\n"); - } - - // See if we've finished all the splits. - if (Idx >= Size) - break; - - // Setup the next partition. - PartOffset = Offsets.Splits[Idx]; - ++Idx; - PartSize = (Idx < Size ? Offsets.Splits[Idx] : StoreSize) - PartOffset; - } - - // We want to immediately iterate on any allocas impacted by splitting - // this load, which is only relevant if it isn't a load of this alloca and - // thus we didn't already split the loads above. We also have to keep track - // of any promotable allocas we split loads on as they can no longer be - // promoted. - if (!SplitLoads) { - if (AllocaInst *OtherAI = dyn_cast<AllocaInst>(LoadBasePtr)) { - assert(OtherAI != &AI && "We can't re-split our own alloca!"); - ResplitPromotableAllocas.insert(OtherAI); - Worklist.insert(OtherAI); - } else if (AllocaInst *OtherAI = dyn_cast<AllocaInst>( - LoadBasePtr->stripInBoundsOffsets())) { - assert(OtherAI != &AI && "We can't re-split our own alloca!"); - Worklist.insert(OtherAI); - } - } - - // Mark the original store as dead now that we've split it up and kill its - // slice. Note that we leave the original load in place unless this store - // was its only use. It may in turn be split up if it is an alloca load - // for some other alloca, but it may be a normal load. This may introduce - // redundant loads, but where those can be merged the rest of the optimizer - // should handle the merging, and this uncovers SSA splits which is more - // important. In practice, the original loads will almost always be fully - // split and removed eventually, and the splits will be merged by any - // trivial CSE, including instcombine. - if (LI->hasOneUse()) { - assert(*LI->user_begin() == SI && "Single use isn't this store!"); - DeadInsts.insert(LI); - } - DeadInsts.insert(SI); - Offsets.S->kill(); - } - - // Remove the killed slices that have ben pre-split. - AS.erase(llvm::remove_if(AS, [](const Slice &S) { return S.isDead(); }), - AS.end()); - - // Insert our new slices. This will sort and merge them into the sorted - // sequence. - AS.insert(NewSlices); - - LLVM_DEBUG(dbgs() << " Pre-split slices:\n"); -#ifndef NDEBUG - for (auto I = AS.begin(), E = AS.end(); I != E; ++I) - LLVM_DEBUG(AS.print(dbgs(), I, " ")); -#endif - - // Finally, don't try to promote any allocas that new require re-splitting. - // They have already been added to the worklist above. - PromotableAllocas.erase( - llvm::remove_if( - PromotableAllocas, - [&](AllocaInst *AI) { return ResplitPromotableAllocas.count(AI); }), - PromotableAllocas.end()); - - return true; -} - -/// 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. -AllocaInst *SROA::rewritePartition(AllocaInst &AI, AllocaSlices &AS, - Partition &P) { - // 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 = nullptr; - const DataLayout &DL = AI.getModule()->getDataLayout(); - if (Type *CommonUseTy = findCommonType(P.begin(), P.end(), P.endOffset())) - if (DL.getTypeAllocSize(CommonUseTy) >= P.size()) - SliceTy = CommonUseTy; - if (!SliceTy) - if (Type *TypePartitionTy = getTypePartition(DL, AI.getAllocatedType(), - P.beginOffset(), P.size())) - SliceTy = TypePartitionTy; - if ((!SliceTy || (SliceTy->isArrayTy() && - SliceTy->getArrayElementType()->isIntegerTy())) && - DL.isLegalInteger(P.size() * 8)) - SliceTy = Type::getIntNTy(*C, P.size() * 8); - if (!SliceTy) - SliceTy = ArrayType::get(Type::getInt8Ty(*C), P.size()); - assert(DL.getTypeAllocSize(SliceTy) >= P.size()); - - bool IsIntegerPromotable = isIntegerWideningViable(P, SliceTy, DL); - - VectorType *VecTy = - IsIntegerPromotable ? nullptr : isVectorPromotionViable(P, DL); - if (VecTy) - SliceTy = VecTy; - - // 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. - // P.beginOffset() can be non-zero even with the same type in a case with - // out-of-bounds access (e.g. @PR35657 function in SROA/basictest.ll). - AllocaInst *NewAI; - if (SliceTy == AI.getAllocatedType() && P.beginOffset() == 0) { - 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. - // FIXME: return nullptr; - } 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, P.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, AI.getType()->getAddressSpace(), nullptr, Alignment, - AI.getName() + ".sroa." + Twine(P.begin() - AS.begin()), &AI); - // Copy the old AI debug location over to the new one. - NewAI->setDebugLoc(AI.getDebugLoc()); - ++NumNewAllocas; - } - - LLVM_DEBUG(dbgs() << "Rewriting alloca partition " - << "[" << P.beginOffset() << "," << P.endOffset() - << ") to: " << *NewAI << "\n"); - - // Track the high watermark on the worklist as it is 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 NumUses = 0; - SmallSetVector<PHINode *, 8> PHIUsers; - SmallSetVector<SelectInst *, 8> SelectUsers; - - AllocaSliceRewriter Rewriter(DL, AS, *this, AI, *NewAI, P.beginOffset(), - P.endOffset(), IsIntegerPromotable, VecTy, - PHIUsers, SelectUsers); - bool Promotable = true; - for (Slice *S : P.splitSliceTails()) { - Promotable &= Rewriter.visit(S); - ++NumUses; - } - for (Slice &S : P) { - Promotable &= Rewriter.visit(&S); - ++NumUses; - } - - NumAllocaPartitionUses += NumUses; - MaxUsesPerAllocaPartition.updateMax(NumUses); - - // Now that we've processed all the slices in the new partition, check if any - // PHIs or Selects would block promotion. - for (PHINode *PHI : PHIUsers) - if (!isSafePHIToSpeculate(*PHI)) { - Promotable = false; - PHIUsers.clear(); - SelectUsers.clear(); - break; - } - - for (SelectInst *Sel : SelectUsers) - if (!isSafeSelectToSpeculate(*Sel)) { - Promotable = false; - PHIUsers.clear(); - SelectUsers.clear(); - break; - } - - if (Promotable) { - if (PHIUsers.empty() && SelectUsers.empty()) { - // Promote the alloca. - PromotableAllocas.push_back(NewAI); - } else { - // If we have either PHIs or Selects to speculate, add them to those - // worklists and re-queue the new alloca so that we promote in on the - // next iteration. - for (PHINode *PHIUser : PHIUsers) - SpeculatablePHIs.insert(PHIUser); - for (SelectInst *SelectUser : SelectUsers) - SpeculatableSelects.insert(SelectUser); - Worklist.insert(NewAI); - } - } else { - // Drop any post-promotion work items if promotion didn't happen. - while (PostPromotionWorklist.size() > PPWOldSize) - PostPromotionWorklist.pop_back(); - - // We couldn't promote and we didn't create a new partition, nothing - // happened. - if (NewAI == &AI) - return nullptr; - - // 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. - Worklist.insert(NewAI); - } - - return NewAI; -} - -/// Walks the slices of an alloca and form partitions based on them, -/// rewriting each of their uses. -bool SROA::splitAlloca(AllocaInst &AI, AllocaSlices &AS) { - if (AS.begin() == AS.end()) - return false; - - unsigned NumPartitions = 0; - bool Changed = false; - const DataLayout &DL = AI.getModule()->getDataLayout(); - - // First try to pre-split loads and stores. - Changed |= presplitLoadsAndStores(AI, AS); - - // Now that we have identified any pre-splitting opportunities, - // mark loads and stores unsplittable except for the following case. - // We leave a slice splittable if all other slices are disjoint or fully - // included in the slice, such as whole-alloca loads and stores. - // If we fail to split these during pre-splitting, we want to force them - // to be rewritten into a partition. - bool IsSorted = true; - - uint64_t AllocaSize = DL.getTypeAllocSize(AI.getAllocatedType()); - const uint64_t MaxBitVectorSize = 1024; - if (AllocaSize <= MaxBitVectorSize) { - // If a byte boundary is included in any load or store, a slice starting or - // ending at the boundary is not splittable. - SmallBitVector SplittableOffset(AllocaSize + 1, true); - for (Slice &S : AS) - for (unsigned O = S.beginOffset() + 1; - O < S.endOffset() && O < AllocaSize; O++) - SplittableOffset.reset(O); - - for (Slice &S : AS) { - if (!S.isSplittable()) - continue; - - if ((S.beginOffset() > AllocaSize || SplittableOffset[S.beginOffset()]) && - (S.endOffset() > AllocaSize || SplittableOffset[S.endOffset()])) - continue; - - if (isa<LoadInst>(S.getUse()->getUser()) || - isa<StoreInst>(S.getUse()->getUser())) { - S.makeUnsplittable(); - IsSorted = false; - } - } - } - else { - // We only allow whole-alloca splittable loads and stores - // for a large alloca to avoid creating too large BitVector. - for (Slice &S : AS) { - if (!S.isSplittable()) - continue; - - if (S.beginOffset() == 0 && S.endOffset() >= AllocaSize) - continue; - - if (isa<LoadInst>(S.getUse()->getUser()) || - isa<StoreInst>(S.getUse()->getUser())) { - S.makeUnsplittable(); - IsSorted = false; - } - } - } - - if (!IsSorted) - llvm::sort(AS); - - /// Describes the allocas introduced by rewritePartition in order to migrate - /// the debug info. - struct Fragment { - AllocaInst *Alloca; - uint64_t Offset; - uint64_t Size; - Fragment(AllocaInst *AI, uint64_t O, uint64_t S) - : Alloca(AI), Offset(O), Size(S) {} - }; - SmallVector<Fragment, 4> Fragments; - - // Rewrite each partition. - for (auto &P : AS.partitions()) { - if (AllocaInst *NewAI = rewritePartition(AI, AS, P)) { - Changed = true; - if (NewAI != &AI) { - uint64_t SizeOfByte = 8; - uint64_t AllocaSize = DL.getTypeSizeInBits(NewAI->getAllocatedType()); - // Don't include any padding. - uint64_t Size = std::min(AllocaSize, P.size() * SizeOfByte); - Fragments.push_back(Fragment(NewAI, P.beginOffset() * SizeOfByte, Size)); - } - } - ++NumPartitions; - } - - NumAllocaPartitions += NumPartitions; - MaxPartitionsPerAlloca.updateMax(NumPartitions); - - // Migrate debug information from the old alloca to the new alloca(s) - // and the individual partitions. - TinyPtrVector<DbgVariableIntrinsic *> DbgDeclares = FindDbgAddrUses(&AI); - if (!DbgDeclares.empty()) { - auto *Var = DbgDeclares.front()->getVariable(); - auto *Expr = DbgDeclares.front()->getExpression(); - auto VarSize = Var->getSizeInBits(); - DIBuilder DIB(*AI.getModule(), /*AllowUnresolved*/ false); - uint64_t AllocaSize = DL.getTypeSizeInBits(AI.getAllocatedType()); - for (auto Fragment : Fragments) { - // Create a fragment expression describing the new partition or reuse AI's - // expression if there is only one partition. - auto *FragmentExpr = Expr; - if (Fragment.Size < AllocaSize || Expr->isFragment()) { - // If this alloca is already a scalar replacement of a larger aggregate, - // Fragment.Offset describes the offset inside the scalar. - auto ExprFragment = Expr->getFragmentInfo(); - uint64_t Offset = ExprFragment ? ExprFragment->OffsetInBits : 0; - uint64_t Start = Offset + Fragment.Offset; - uint64_t Size = Fragment.Size; - if (ExprFragment) { - uint64_t AbsEnd = - ExprFragment->OffsetInBits + ExprFragment->SizeInBits; - if (Start >= AbsEnd) - // No need to describe a SROAed padding. - continue; - Size = std::min(Size, AbsEnd - Start); - } - // The new, smaller fragment is stenciled out from the old fragment. - if (auto OrigFragment = FragmentExpr->getFragmentInfo()) { - assert(Start >= OrigFragment->OffsetInBits && - "new fragment is outside of original fragment"); - Start -= OrigFragment->OffsetInBits; - } - - // The alloca may be larger than the variable. - if (VarSize) { - if (Size > *VarSize) - Size = *VarSize; - if (Size == 0 || Start + Size > *VarSize) - continue; - } - - // Avoid creating a fragment expression that covers the entire variable. - if (!VarSize || *VarSize != Size) { - if (auto E = - DIExpression::createFragmentExpression(Expr, Start, Size)) - FragmentExpr = *E; - else - continue; - } - } - - // Remove any existing intrinsics describing the same alloca. - for (DbgVariableIntrinsic *OldDII : FindDbgAddrUses(Fragment.Alloca)) - OldDII->eraseFromParent(); - - DIB.insertDeclare(Fragment.Alloca, Var, FragmentExpr, - DbgDeclares.front()->getDebugLoc(), &AI); - } - } - return Changed; -} - -/// Clobber a use with undef, deleting the used value if it becomes dead. -void SROA::clobberUse(Use &U) { - Value *OldV = U; - // Replace the use with an undef value. - U = UndefValue::get(OldV->getType()); - - // Check for this making an instruction dead. We have to garbage collect - // all the dead instructions to ensure the uses of any alloca end up being - // minimal. - if (Instruction *OldI = dyn_cast<Instruction>(OldV)) - if (isInstructionTriviallyDead(OldI)) { - DeadInsts.insert(OldI); - } -} - -/// 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) { - LLVM_DEBUG(dbgs() << "SROA alloca: " << AI << "\n"); - ++NumAllocasAnalyzed; - - // Special case dead allocas, as they're trivial. - if (AI.use_empty()) { - AI.eraseFromParent(); - return true; - } - const DataLayout &DL = AI.getModule()->getDataLayout(); - - // 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 AS(DL, AI); - LLVM_DEBUG(AS.print(dbgs())); - if (AS.isEscaped()) - return Changed; - - // Delete all the dead users of this alloca before splitting and rewriting it. - for (Instruction *DeadUser : AS.getDeadUsers()) { - // Free up everything used by this instruction. - for (Use &DeadOp : DeadUser->operands()) - clobberUse(DeadOp); - - // Now replace the uses of this instruction. - DeadUser->replaceAllUsesWith(UndefValue::get(DeadUser->getType())); - - // And mark it for deletion. - DeadInsts.insert(DeadUser); - Changed = true; - } - for (Use *DeadOp : AS.getDeadOperands()) { - clobberUse(*DeadOp); - Changed = true; - } - - // No slices to split. Leave the dead alloca for a later pass to clean up. - if (AS.begin() == AS.end()) - return Changed; - - Changed |= splitAlloca(AI, AS); - - LLVM_DEBUG(dbgs() << " Speculating PHIs\n"); - while (!SpeculatablePHIs.empty()) - speculatePHINodeLoads(*SpeculatablePHIs.pop_back_val()); - - LLVM_DEBUG(dbgs() << " Speculating Selects\n"); - while (!SpeculatableSelects.empty()) - speculateSelectInstLoads(*SpeculatableSelects.pop_back_val()); - - return Changed; -} - -/// 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. -bool SROA::deleteDeadInstructions( - SmallPtrSetImpl<AllocaInst *> &DeletedAllocas) { - bool Changed = false; - while (!DeadInsts.empty()) { - Instruction *I = DeadInsts.pop_back_val(); - LLVM_DEBUG(dbgs() << "Deleting dead instruction: " << *I << "\n"); - - // If the instruction is an alloca, find the possible dbg.declare connected - // to it, and remove it too. We must do this before calling RAUW or we will - // not be able to find it. - if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) { - DeletedAllocas.insert(AI); - for (DbgVariableIntrinsic *OldDII : FindDbgAddrUses(AI)) - OldDII->eraseFromParent(); - } - - I->replaceAllUsesWith(UndefValue::get(I->getType())); - - for (Use &Operand : I->operands()) - if (Instruction *U = dyn_cast<Instruction>(Operand)) { - // Zero out the operand and see if it becomes trivially dead. - Operand = nullptr; - if (isInstructionTriviallyDead(U)) - DeadInsts.insert(U); - } - - ++NumDeleted; - I->eraseFromParent(); - Changed = true; - } - return Changed; -} - -/// 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. -/// This function returns whether any promotion occurred. -bool SROA::promoteAllocas(Function &F) { - if (PromotableAllocas.empty()) - return false; - - NumPromoted += PromotableAllocas.size(); - - LLVM_DEBUG(dbgs() << "Promoting allocas with mem2reg...\n"); - PromoteMemToReg(PromotableAllocas, *DT, AC); - PromotableAllocas.clear(); - return true; -} - -PreservedAnalyses SROA::runImpl(Function &F, DominatorTree &RunDT, - AssumptionCache &RunAC) { - LLVM_DEBUG(dbgs() << "SROA function: " << F.getName() << "\n"); - C = &F.getContext(); - DT = &RunDT; - AC = &RunAC; - - BasicBlock &EntryBB = F.getEntryBlock(); - for (BasicBlock::iterator I = EntryBB.begin(), E = std::prev(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()); - Changed |= deleteDeadInstructions(DeletedAllocas); - - // Remove the deleted allocas from various lists so that we don't try to - // continue processing them. - if (!DeletedAllocas.empty()) { - auto IsInSet = [&](AllocaInst *AI) { return DeletedAllocas.count(AI); }; - Worklist.remove_if(IsInSet); - PostPromotionWorklist.remove_if(IsInSet); - PromotableAllocas.erase(llvm::remove_if(PromotableAllocas, IsInSet), - PromotableAllocas.end()); - DeletedAllocas.clear(); - } - } - - Changed |= promoteAllocas(F); - - Worklist = PostPromotionWorklist; - PostPromotionWorklist.clear(); - } while (!Worklist.empty()); - - if (!Changed) - return PreservedAnalyses::all(); - - PreservedAnalyses PA; - PA.preserveSet<CFGAnalyses>(); - PA.preserve<GlobalsAA>(); - return PA; -} - -PreservedAnalyses SROA::run(Function &F, FunctionAnalysisManager &AM) { - return runImpl(F, AM.getResult<DominatorTreeAnalysis>(F), - AM.getResult<AssumptionAnalysis>(F)); -} - -/// A legacy pass for the legacy pass manager that wraps the \c SROA pass. -/// -/// This is in the llvm namespace purely to allow it to be a friend of the \c -/// SROA pass. -class llvm::sroa::SROALegacyPass : public FunctionPass { - /// The SROA implementation. - SROA Impl; - -public: - static char ID; - - SROALegacyPass() : FunctionPass(ID) { - initializeSROALegacyPassPass(*PassRegistry::getPassRegistry()); - } - - bool runOnFunction(Function &F) override { - if (skipFunction(F)) - return false; - - auto PA = Impl.runImpl( - F, getAnalysis<DominatorTreeWrapperPass>().getDomTree(), - getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F)); - return !PA.areAllPreserved(); - } - - void getAnalysisUsage(AnalysisUsage &AU) const override { - AU.addRequired<AssumptionCacheTracker>(); - AU.addRequired<DominatorTreeWrapperPass>(); - AU.addPreserved<GlobalsAAWrapperPass>(); - AU.setPreservesCFG(); - } - - StringRef getPassName() const override { return "SROA"; } -}; - -char SROALegacyPass::ID = 0; - -FunctionPass *llvm::createSROAPass() { return new SROALegacyPass(); } - -INITIALIZE_PASS_BEGIN(SROALegacyPass, "sroa", - "Scalar Replacement Of Aggregates", false, false) -INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) -INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) -INITIALIZE_PASS_END(SROALegacyPass, "sroa", "Scalar Replacement Of Aggregates", - false, false) |