1 //===- SROA.cpp - Scalar Replacement Of Aggregates ------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 /// This transformation implements the well known scalar replacement of
11 /// aggregates transformation. It tries to identify promotable elements of an
12 /// aggregate alloca, and promote them to registers. It will also try to
13 /// convert uses of an element (or set of elements) of an alloca into a vector
14 /// or bitfield-style integer scalar if appropriate.
16 /// It works to do this with minimal slicing of the alloca so that regions
17 /// which are merely transferred in and out of external memory remain unchanged
18 /// and are not decomposed to scalar code.
20 /// Because this also performs alloca promotion, it can be thought of as also
21 /// serving the purpose of SSA formation. The algorithm iterates on the
22 /// function until all opportunities for promotion have been realized.
24 //===----------------------------------------------------------------------===//
26 #include "llvm/Transforms/Scalar.h"
27 #include "llvm/ADT/STLExtras.h"
28 #include "llvm/ADT/SetVector.h"
29 #include "llvm/ADT/SmallVector.h"
30 #include "llvm/ADT/Statistic.h"
31 #include "llvm/Analysis/AssumptionCache.h"
32 #include "llvm/Analysis/Loads.h"
33 #include "llvm/Analysis/PtrUseVisitor.h"
34 #include "llvm/Analysis/ValueTracking.h"
35 #include "llvm/IR/Constants.h"
36 #include "llvm/IR/DIBuilder.h"
37 #include "llvm/IR/DataLayout.h"
38 #include "llvm/IR/DebugInfo.h"
39 #include "llvm/IR/DerivedTypes.h"
40 #include "llvm/IR/Dominators.h"
41 #include "llvm/IR/Function.h"
42 #include "llvm/IR/IRBuilder.h"
43 #include "llvm/IR/InstVisitor.h"
44 #include "llvm/IR/Instructions.h"
45 #include "llvm/IR/IntrinsicInst.h"
46 #include "llvm/IR/LLVMContext.h"
47 #include "llvm/IR/Operator.h"
48 #include "llvm/Pass.h"
49 #include "llvm/Support/CommandLine.h"
50 #include "llvm/Support/Compiler.h"
51 #include "llvm/Support/Debug.h"
52 #include "llvm/Support/ErrorHandling.h"
53 #include "llvm/Support/MathExtras.h"
54 #include "llvm/Support/TimeValue.h"
55 #include "llvm/Support/raw_ostream.h"
56 #include "llvm/Transforms/Utils/Local.h"
57 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
58 #include "llvm/Transforms/Utils/SSAUpdater.h"
60 #if __cplusplus >= 201103L && !defined(NDEBUG)
61 // We only use this for a debug check in C++11
67 #define DEBUG_TYPE "sroa"
69 STATISTIC(NumAllocasAnalyzed, "Number of allocas analyzed for replacement");
70 STATISTIC(NumAllocaPartitions, "Number of alloca partitions formed");
71 STATISTIC(MaxPartitionsPerAlloca, "Maximum number of partitions per alloca");
72 STATISTIC(NumAllocaPartitionUses, "Number of alloca partition uses rewritten");
73 STATISTIC(MaxUsesPerAllocaPartition, "Maximum number of uses of a partition");
74 STATISTIC(NumNewAllocas, "Number of new, smaller allocas introduced");
75 STATISTIC(NumPromoted, "Number of allocas promoted to SSA values");
76 STATISTIC(NumLoadsSpeculated, "Number of loads speculated to allow promotion");
77 STATISTIC(NumDeleted, "Number of instructions deleted");
78 STATISTIC(NumVectorized, "Number of vectorized aggregates");
80 /// Hidden option to force the pass to not use DomTree and mem2reg, instead
81 /// forming SSA values through the SSAUpdater infrastructure.
82 static cl::opt<bool> ForceSSAUpdater("force-ssa-updater", cl::init(false),
85 /// Hidden option to enable randomly shuffling the slices to help uncover
86 /// instability in their order.
87 static cl::opt<bool> SROARandomShuffleSlices("sroa-random-shuffle-slices",
88 cl::init(false), cl::Hidden);
90 /// Hidden option to experiment with completely strict handling of inbounds
92 static cl::opt<bool> SROAStrictInbounds("sroa-strict-inbounds", cl::init(false),
96 /// \brief A custom IRBuilder inserter which prefixes all names if they are
98 template <bool preserveNames = true>
99 class IRBuilderPrefixedInserter
100 : public IRBuilderDefaultInserter<preserveNames> {
104 void SetNamePrefix(const Twine &P) { Prefix = P.str(); }
107 void InsertHelper(Instruction *I, const Twine &Name, BasicBlock *BB,
108 BasicBlock::iterator InsertPt) const {
109 IRBuilderDefaultInserter<preserveNames>::InsertHelper(
110 I, Name.isTriviallyEmpty() ? Name : Prefix + Name, BB, InsertPt);
114 // Specialization for not preserving the name is trivial.
116 class IRBuilderPrefixedInserter<false>
117 : public IRBuilderDefaultInserter<false> {
119 void SetNamePrefix(const Twine &P) {}
122 /// \brief Provide a typedef for IRBuilder that drops names in release builds.
124 typedef llvm::IRBuilder<true, ConstantFolder, IRBuilderPrefixedInserter<true>>
127 typedef llvm::IRBuilder<false, ConstantFolder, IRBuilderPrefixedInserter<false>>
133 /// \brief A used slice of an alloca.
135 /// This structure represents a slice of an alloca used by some instruction. It
136 /// stores both the begin and end offsets of this use, a pointer to the use
137 /// itself, and a flag indicating whether we can classify the use as splittable
138 /// or not when forming partitions of the alloca.
140 /// \brief The beginning offset of the range.
141 uint64_t BeginOffset;
143 /// \brief The ending offset, not included in the range.
146 /// \brief Storage for both the use of this slice and whether it can be
148 PointerIntPair<Use *, 1, bool> UseAndIsSplittable;
151 Slice() : BeginOffset(), EndOffset() {}
152 Slice(uint64_t BeginOffset, uint64_t EndOffset, Use *U, bool IsSplittable)
153 : BeginOffset(BeginOffset), EndOffset(EndOffset),
154 UseAndIsSplittable(U, IsSplittable) {}
156 uint64_t beginOffset() const { return BeginOffset; }
157 uint64_t endOffset() const { return EndOffset; }
159 bool isSplittable() const { return UseAndIsSplittable.getInt(); }
160 void makeUnsplittable() { UseAndIsSplittable.setInt(false); }
162 Use *getUse() const { return UseAndIsSplittable.getPointer(); }
164 bool isDead() const { return getUse() == nullptr; }
165 void kill() { UseAndIsSplittable.setPointer(nullptr); }
167 /// \brief Support for ordering ranges.
169 /// This provides an ordering over ranges such that start offsets are
170 /// always increasing, and within equal start offsets, the end offsets are
171 /// decreasing. Thus the spanning range comes first in a cluster with the
172 /// same start position.
173 bool operator<(const Slice &RHS) const {
174 if (beginOffset() < RHS.beginOffset())
176 if (beginOffset() > RHS.beginOffset())
178 if (isSplittable() != RHS.isSplittable())
179 return !isSplittable();
180 if (endOffset() > RHS.endOffset())
185 /// \brief Support comparison with a single offset to allow binary searches.
186 friend LLVM_ATTRIBUTE_UNUSED bool operator<(const Slice &LHS,
187 uint64_t RHSOffset) {
188 return LHS.beginOffset() < RHSOffset;
190 friend LLVM_ATTRIBUTE_UNUSED bool operator<(uint64_t LHSOffset,
192 return LHSOffset < RHS.beginOffset();
195 bool operator==(const Slice &RHS) const {
196 return isSplittable() == RHS.isSplittable() &&
197 beginOffset() == RHS.beginOffset() && endOffset() == RHS.endOffset();
199 bool operator!=(const Slice &RHS) const { return !operator==(RHS); }
201 } // end anonymous namespace
204 template <typename T> struct isPodLike;
205 template <> struct isPodLike<Slice> { static const bool value = true; };
209 /// \brief Representation of the alloca slices.
211 /// This class represents the slices of an alloca which are formed by its
212 /// various uses. If a pointer escapes, we can't fully build a representation
213 /// for the slices used and we reflect that in this structure. The uses are
214 /// stored, sorted by increasing beginning offset and with unsplittable slices
215 /// starting at a particular offset before splittable slices.
218 /// \brief Construct the slices of a particular alloca.
219 AllocaSlices(const DataLayout &DL, AllocaInst &AI);
221 /// \brief Test whether a pointer to the allocation escapes our analysis.
223 /// If this is true, the slices are never fully built and should be
225 bool isEscaped() const { return PointerEscapingInstr; }
227 /// \brief Support for iterating over the slices.
229 typedef SmallVectorImpl<Slice>::iterator iterator;
230 typedef iterator_range<iterator> range;
231 iterator begin() { return Slices.begin(); }
232 iterator end() { return Slices.end(); }
234 typedef SmallVectorImpl<Slice>::const_iterator const_iterator;
235 typedef iterator_range<const_iterator> const_range;
236 const_iterator begin() const { return Slices.begin(); }
237 const_iterator end() const { return Slices.end(); }
240 /// \brief Erase a range of slices.
241 void erase(iterator Start, iterator Stop) { Slices.erase(Start, Stop); }
243 /// \brief Insert new slices for this alloca.
245 /// This moves the slices into the alloca's slices collection, and re-sorts
246 /// everything so that the usual ordering properties of the alloca's slices
248 void insert(ArrayRef<Slice> NewSlices) {
249 int OldSize = Slices.size();
250 Slices.append(NewSlices.begin(), NewSlices.end());
251 auto SliceI = Slices.begin() + OldSize;
252 std::sort(SliceI, Slices.end());
253 std::inplace_merge(Slices.begin(), SliceI, Slices.end());
256 // Forward declare an iterator to befriend it.
257 class partition_iterator;
259 /// \brief A partition of the slices.
261 /// An ephemeral representation for a range of slices which can be viewed as
262 /// a partition of the alloca. This range represents a span of the alloca's
263 /// memory which cannot be split, and provides access to all of the slices
264 /// overlapping some part of the partition.
266 /// Objects of this type are produced by traversing the alloca's slices, but
267 /// are only ephemeral and not persistent.
270 friend class AllocaSlices;
271 friend class AllocaSlices::partition_iterator;
273 /// \brief The begining and ending offsets of the alloca for this partition.
274 uint64_t BeginOffset, EndOffset;
276 /// \brief The start end end iterators of this partition.
279 /// \brief A collection of split slice tails overlapping the partition.
280 SmallVector<Slice *, 4> SplitTails;
282 /// \brief Raw constructor builds an empty partition starting and ending at
283 /// the given iterator.
284 Partition(iterator SI) : SI(SI), SJ(SI) {}
287 /// \brief The start offset of this partition.
289 /// All of the contained slices start at or after this offset.
290 uint64_t beginOffset() const { return BeginOffset; }
292 /// \brief The end offset of this partition.
294 /// All of the contained slices end at or before this offset.
295 uint64_t endOffset() const { return EndOffset; }
297 /// \brief The size of the partition.
299 /// Note that this can never be zero.
300 uint64_t size() const {
301 assert(BeginOffset < EndOffset && "Partitions must span some bytes!");
302 return EndOffset - BeginOffset;
305 /// \brief Test whether this partition contains no slices, and merely spans
306 /// a region occupied by split slices.
307 bool empty() const { return SI == SJ; }
309 /// \name Iterate slices that start within the partition.
310 /// These may be splittable or unsplittable. They have a begin offset >= the
311 /// partition begin offset.
313 // FIXME: We should probably define a "concat_iterator" helper and use that
314 // to stitch together pointee_iterators over the split tails and the
315 // contiguous iterators of the partition. That would give a much nicer
316 // interface here. We could then additionally expose filtered iterators for
317 // split, unsplit, and unsplittable splices based on the usage patterns.
318 iterator begin() const { return SI; }
319 iterator end() const { return SJ; }
322 /// \brief Get the sequence of split slice tails.
324 /// These tails are of slices which start before this partition but are
325 /// split and overlap into the partition. We accumulate these while forming
327 ArrayRef<Slice *> splitSliceTails() const { return SplitTails; }
330 /// \brief An iterator over partitions of the alloca's slices.
332 /// This iterator implements the core algorithm for partitioning the alloca's
333 /// slices. It is a forward iterator as we don't support backtracking for
334 /// efficiency reasons, and re-use a single storage area to maintain the
335 /// current set of split slices.
337 /// It is templated on the slice iterator type to use so that it can operate
338 /// with either const or non-const slice iterators.
339 class partition_iterator
340 : public iterator_facade_base<partition_iterator,
341 std::forward_iterator_tag, Partition> {
342 friend class AllocaSlices;
344 /// \brief Most of the state for walking the partitions is held in a class
345 /// with a nice interface for examining them.
348 /// \brief We need to keep the end of the slices to know when to stop.
349 AllocaSlices::iterator SE;
351 /// \brief We also need to keep track of the maximum split end offset seen.
352 /// FIXME: Do we really?
353 uint64_t MaxSplitSliceEndOffset;
355 /// \brief Sets the partition to be empty at given iterator, and sets the
357 partition_iterator(AllocaSlices::iterator SI, AllocaSlices::iterator SE)
358 : P(SI), SE(SE), MaxSplitSliceEndOffset(0) {
359 // If not already at the end, advance our state to form the initial
365 /// \brief Advance the iterator to the next partition.
367 /// Requires that the iterator not be at the end of the slices.
369 assert((P.SI != SE || !P.SplitTails.empty()) &&
370 "Cannot advance past the end of the slices!");
372 // Clear out any split uses which have ended.
373 if (!P.SplitTails.empty()) {
374 if (P.EndOffset >= MaxSplitSliceEndOffset) {
375 // If we've finished all splits, this is easy.
376 P.SplitTails.clear();
377 MaxSplitSliceEndOffset = 0;
379 // Remove the uses which have ended in the prior partition. This
380 // cannot change the max split slice end because we just checked that
381 // the prior partition ended prior to that max.
384 P.SplitTails.begin(), P.SplitTails.end(),
385 [&](Slice *S) { return S->endOffset() <= P.EndOffset; }),
387 assert(std::any_of(P.SplitTails.begin(), P.SplitTails.end(),
389 return S->endOffset() == MaxSplitSliceEndOffset;
391 "Could not find the current max split slice offset!");
392 assert(std::all_of(P.SplitTails.begin(), P.SplitTails.end(),
394 return S->endOffset() <= MaxSplitSliceEndOffset;
396 "Max split slice end offset is not actually the max!");
400 // If P.SI is already at the end, then we've cleared the split tail and
401 // now have an end iterator.
403 assert(P.SplitTails.empty() && "Failed to clear the split slices!");
407 // If we had a non-empty partition previously, set up the state for
408 // subsequent partitions.
410 // Accumulate all the splittable slices which started in the old
411 // partition into the split list.
413 if (S.isSplittable() && S.endOffset() > P.EndOffset) {
414 P.SplitTails.push_back(&S);
415 MaxSplitSliceEndOffset =
416 std::max(S.endOffset(), MaxSplitSliceEndOffset);
419 // Start from the end of the previous partition.
422 // If P.SI is now at the end, we at most have a tail of split slices.
424 P.BeginOffset = P.EndOffset;
425 P.EndOffset = MaxSplitSliceEndOffset;
429 // If the we have split slices and the next slice is after a gap and is
430 // not splittable immediately form an empty partition for the split
431 // slices up until the next slice begins.
432 if (!P.SplitTails.empty() && P.SI->beginOffset() != P.EndOffset &&
433 !P.SI->isSplittable()) {
434 P.BeginOffset = P.EndOffset;
435 P.EndOffset = P.SI->beginOffset();
440 // OK, we need to consume new slices. Set the end offset based on the
441 // current slice, and step SJ past it. The beginning offset of the
442 // parttion is the beginning offset of the next slice unless we have
443 // pre-existing split slices that are continuing, in which case we begin
444 // at the prior end offset.
445 P.BeginOffset = P.SplitTails.empty() ? P.SI->beginOffset() : P.EndOffset;
446 P.EndOffset = P.SI->endOffset();
449 // There are two strategies to form a partition based on whether the
450 // partition starts with an unsplittable slice or a splittable slice.
451 if (!P.SI->isSplittable()) {
452 // When we're forming an unsplittable region, it must always start at
453 // the first slice and will extend through its end.
454 assert(P.BeginOffset == P.SI->beginOffset());
456 // Form a partition including all of the overlapping slices with this
457 // unsplittable slice.
458 while (P.SJ != SE && P.SJ->beginOffset() < P.EndOffset) {
459 if (!P.SJ->isSplittable())
460 P.EndOffset = std::max(P.EndOffset, P.SJ->endOffset());
464 // We have a partition across a set of overlapping unsplittable
469 // If we're starting with a splittable slice, then we need to form
470 // a synthetic partition spanning it and any other overlapping splittable
472 assert(P.SI->isSplittable() && "Forming a splittable partition!");
474 // Collect all of the overlapping splittable slices.
475 while (P.SJ != SE && P.SJ->beginOffset() < P.EndOffset &&
476 P.SJ->isSplittable()) {
477 P.EndOffset = std::max(P.EndOffset, P.SJ->endOffset());
481 // Back upiP.EndOffset if we ended the span early when encountering an
482 // unsplittable slice. This synthesizes the early end offset of
483 // a partition spanning only splittable slices.
484 if (P.SJ != SE && P.SJ->beginOffset() < P.EndOffset) {
485 assert(!P.SJ->isSplittable());
486 P.EndOffset = P.SJ->beginOffset();
491 bool operator==(const partition_iterator &RHS) const {
492 assert(SE == RHS.SE &&
493 "End iterators don't match between compared partition iterators!");
495 // The observed positions of partitions is marked by the P.SI iterator and
496 // the emptyness of the split slices. The latter is only relevant when
497 // P.SI == SE, as the end iterator will additionally have an empty split
498 // slices list, but the prior may have the same P.SI and a tail of split
500 if (P.SI == RHS.P.SI &&
501 P.SplitTails.empty() == RHS.P.SplitTails.empty()) {
502 assert(P.SJ == RHS.P.SJ &&
503 "Same set of slices formed two different sized partitions!");
504 assert(P.SplitTails.size() == RHS.P.SplitTails.size() &&
505 "Same slice position with differently sized non-empty split "
512 partition_iterator &operator++() {
517 Partition &operator*() { return P; }
520 /// \brief A forward range over the partitions of the alloca's slices.
522 /// This accesses an iterator range over the partitions of the alloca's
523 /// slices. It computes these partitions on the fly based on the overlapping
524 /// offsets of the slices and the ability to split them. It will visit "empty"
525 /// partitions to cover regions of the alloca only accessed via split
527 iterator_range<partition_iterator> partitions() {
528 return make_range(partition_iterator(begin(), end()),
529 partition_iterator(end(), end()));
532 /// \brief Access the dead users for this alloca.
533 ArrayRef<Instruction *> getDeadUsers() const { return DeadUsers; }
535 /// \brief Access the dead operands referring to this alloca.
537 /// These are operands which have cannot actually be used to refer to the
538 /// alloca as they are outside its range and the user doesn't correct for
539 /// that. These mostly consist of PHI node inputs and the like which we just
540 /// need to replace with undef.
541 ArrayRef<Use *> getDeadOperands() const { return DeadOperands; }
543 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
544 void print(raw_ostream &OS, const_iterator I, StringRef Indent = " ") const;
545 void printSlice(raw_ostream &OS, const_iterator I,
546 StringRef Indent = " ") const;
547 void printUse(raw_ostream &OS, const_iterator I,
548 StringRef Indent = " ") const;
549 void print(raw_ostream &OS) const;
550 void dump(const_iterator I) const;
555 template <typename DerivedT, typename RetT = void> class BuilderBase;
557 friend class AllocaSlices::SliceBuilder;
559 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
560 /// \brief Handle to alloca instruction to simplify method interfaces.
564 /// \brief The instruction responsible for this alloca not having a known set
567 /// When an instruction (potentially) escapes the pointer to the alloca, we
568 /// store a pointer to that here and abort trying to form slices of the
569 /// alloca. This will be null if the alloca slices are analyzed successfully.
570 Instruction *PointerEscapingInstr;
572 /// \brief The slices of the alloca.
574 /// We store a vector of the slices formed by uses of the alloca here. This
575 /// vector is sorted by increasing begin offset, and then the unsplittable
576 /// slices before the splittable ones. See the Slice inner class for more
578 SmallVector<Slice, 8> Slices;
580 /// \brief Instructions which will become dead if we rewrite the alloca.
582 /// Note that these are not separated by slice. This is because we expect an
583 /// alloca to be completely rewritten or not rewritten at all. If rewritten,
584 /// all these instructions can simply be removed and replaced with undef as
585 /// they come from outside of the allocated space.
586 SmallVector<Instruction *, 8> DeadUsers;
588 /// \brief Operands which will become dead if we rewrite the alloca.
590 /// These are operands that in their particular use can be replaced with
591 /// undef when we rewrite the alloca. These show up in out-of-bounds inputs
592 /// to PHI nodes and the like. They aren't entirely dead (there might be
593 /// a GEP back into the bounds using it elsewhere) and nor is the PHI, but we
594 /// want to swap this particular input for undef to simplify the use lists of
596 SmallVector<Use *, 8> DeadOperands;
600 static Value *foldSelectInst(SelectInst &SI) {
601 // If the condition being selected on is a constant or the same value is
602 // being selected between, fold the select. Yes this does (rarely) happen
604 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI.getCondition()))
605 return SI.getOperand(1 + CI->isZero());
606 if (SI.getOperand(1) == SI.getOperand(2))
607 return SI.getOperand(1);
612 /// \brief A helper that folds a PHI node or a select.
613 static Value *foldPHINodeOrSelectInst(Instruction &I) {
614 if (PHINode *PN = dyn_cast<PHINode>(&I)) {
615 // If PN merges together the same value, return that value.
616 return PN->hasConstantValue();
618 return foldSelectInst(cast<SelectInst>(I));
621 /// \brief Builder for the alloca slices.
623 /// This class builds a set of alloca slices by recursively visiting the uses
624 /// of an alloca and making a slice for each load and store at each offset.
625 class AllocaSlices::SliceBuilder : public PtrUseVisitor<SliceBuilder> {
626 friend class PtrUseVisitor<SliceBuilder>;
627 friend class InstVisitor<SliceBuilder>;
628 typedef PtrUseVisitor<SliceBuilder> Base;
630 const uint64_t AllocSize;
633 SmallDenseMap<Instruction *, unsigned> MemTransferSliceMap;
634 SmallDenseMap<Instruction *, uint64_t> PHIOrSelectSizes;
636 /// \brief Set to de-duplicate dead instructions found in the use walk.
637 SmallPtrSet<Instruction *, 4> VisitedDeadInsts;
640 SliceBuilder(const DataLayout &DL, AllocaInst &AI, AllocaSlices &AS)
641 : PtrUseVisitor<SliceBuilder>(DL),
642 AllocSize(DL.getTypeAllocSize(AI.getAllocatedType())), AS(AS) {}
645 void markAsDead(Instruction &I) {
646 if (VisitedDeadInsts.insert(&I).second)
647 AS.DeadUsers.push_back(&I);
650 void insertUse(Instruction &I, const APInt &Offset, uint64_t Size,
651 bool IsSplittable = false) {
652 // Completely skip uses which have a zero size or start either before or
653 // past the end of the allocation.
654 if (Size == 0 || Offset.uge(AllocSize)) {
655 DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte use @" << Offset
656 << " which has zero size or starts outside of the "
657 << AllocSize << " byte alloca:\n"
658 << " alloca: " << AS.AI << "\n"
659 << " use: " << I << "\n");
660 return markAsDead(I);
663 uint64_t BeginOffset = Offset.getZExtValue();
664 uint64_t EndOffset = BeginOffset + Size;
666 // Clamp the end offset to the end of the allocation. Note that this is
667 // formulated to handle even the case where "BeginOffset + Size" overflows.
668 // This may appear superficially to be something we could ignore entirely,
669 // but that is not so! There may be widened loads or PHI-node uses where
670 // some instructions are dead but not others. We can't completely ignore
671 // them, and so have to record at least the information here.
672 assert(AllocSize >= BeginOffset); // Established above.
673 if (Size > AllocSize - BeginOffset) {
674 DEBUG(dbgs() << "WARNING: Clamping a " << Size << " byte use @" << Offset
675 << " to remain within the " << AllocSize << " byte alloca:\n"
676 << " alloca: " << AS.AI << "\n"
677 << " use: " << I << "\n");
678 EndOffset = AllocSize;
681 AS.Slices.push_back(Slice(BeginOffset, EndOffset, U, IsSplittable));
684 void visitBitCastInst(BitCastInst &BC) {
686 return markAsDead(BC);
688 return Base::visitBitCastInst(BC);
691 void visitGetElementPtrInst(GetElementPtrInst &GEPI) {
692 if (GEPI.use_empty())
693 return markAsDead(GEPI);
695 if (SROAStrictInbounds && GEPI.isInBounds()) {
696 // FIXME: This is a manually un-factored variant of the basic code inside
697 // of GEPs with checking of the inbounds invariant specified in the
698 // langref in a very strict sense. If we ever want to enable
699 // SROAStrictInbounds, this code should be factored cleanly into
700 // PtrUseVisitor, but it is easier to experiment with SROAStrictInbounds
701 // by writing out the code here where we have tho underlying allocation
702 // size readily available.
703 APInt GEPOffset = Offset;
704 const DataLayout &DL = GEPI.getModule()->getDataLayout();
705 for (gep_type_iterator GTI = gep_type_begin(GEPI),
706 GTE = gep_type_end(GEPI);
708 ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand());
712 // Handle a struct index, which adds its field offset to the pointer.
713 if (StructType *STy = dyn_cast<StructType>(*GTI)) {
714 unsigned ElementIdx = OpC->getZExtValue();
715 const StructLayout *SL = DL.getStructLayout(STy);
717 APInt(Offset.getBitWidth(), SL->getElementOffset(ElementIdx));
719 // For array or vector indices, scale the index by the size of the
721 APInt Index = OpC->getValue().sextOrTrunc(Offset.getBitWidth());
722 GEPOffset += Index * APInt(Offset.getBitWidth(),
723 DL.getTypeAllocSize(GTI.getIndexedType()));
726 // If this index has computed an intermediate pointer which is not
727 // inbounds, then the result of the GEP is a poison value and we can
728 // delete it and all uses.
729 if (GEPOffset.ugt(AllocSize))
730 return markAsDead(GEPI);
734 return Base::visitGetElementPtrInst(GEPI);
737 void handleLoadOrStore(Type *Ty, Instruction &I, const APInt &Offset,
738 uint64_t Size, bool IsVolatile) {
739 // We allow splitting of non-volatile loads and stores where the type is an
740 // integer type. These may be used to implement 'memcpy' or other "transfer
741 // of bits" patterns.
742 bool IsSplittable = Ty->isIntegerTy() && !IsVolatile;
744 insertUse(I, Offset, Size, IsSplittable);
747 void visitLoadInst(LoadInst &LI) {
748 assert((!LI.isSimple() || LI.getType()->isSingleValueType()) &&
749 "All simple FCA loads should have been pre-split");
752 return PI.setAborted(&LI);
754 const DataLayout &DL = LI.getModule()->getDataLayout();
755 uint64_t Size = DL.getTypeStoreSize(LI.getType());
756 return handleLoadOrStore(LI.getType(), LI, Offset, Size, LI.isVolatile());
759 void visitStoreInst(StoreInst &SI) {
760 Value *ValOp = SI.getValueOperand();
762 return PI.setEscapedAndAborted(&SI);
764 return PI.setAborted(&SI);
766 const DataLayout &DL = SI.getModule()->getDataLayout();
767 uint64_t Size = DL.getTypeStoreSize(ValOp->getType());
769 // If this memory access can be shown to *statically* extend outside the
770 // bounds of of the allocation, it's behavior is undefined, so simply
771 // ignore it. Note that this is more strict than the generic clamping
772 // behavior of insertUse. We also try to handle cases which might run the
774 // FIXME: We should instead consider the pointer to have escaped if this
775 // function is being instrumented for addressing bugs or race conditions.
776 if (Size > AllocSize || Offset.ugt(AllocSize - Size)) {
777 DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte store @" << Offset
778 << " which extends past the end of the " << AllocSize
780 << " alloca: " << AS.AI << "\n"
781 << " use: " << SI << "\n");
782 return markAsDead(SI);
785 assert((!SI.isSimple() || ValOp->getType()->isSingleValueType()) &&
786 "All simple FCA stores should have been pre-split");
787 handleLoadOrStore(ValOp->getType(), SI, Offset, Size, SI.isVolatile());
790 void visitMemSetInst(MemSetInst &II) {
791 assert(II.getRawDest() == *U && "Pointer use is not the destination?");
792 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
793 if ((Length && Length->getValue() == 0) ||
794 (IsOffsetKnown && Offset.uge(AllocSize)))
795 // Zero-length mem transfer intrinsics can be ignored entirely.
796 return markAsDead(II);
799 return PI.setAborted(&II);
801 insertUse(II, Offset, Length ? Length->getLimitedValue()
802 : AllocSize - Offset.getLimitedValue(),
806 void visitMemTransferInst(MemTransferInst &II) {
807 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
808 if (Length && Length->getValue() == 0)
809 // Zero-length mem transfer intrinsics can be ignored entirely.
810 return markAsDead(II);
812 // Because we can visit these intrinsics twice, also check to see if the
813 // first time marked this instruction as dead. If so, skip it.
814 if (VisitedDeadInsts.count(&II))
818 return PI.setAborted(&II);
820 // This side of the transfer is completely out-of-bounds, and so we can
821 // nuke the entire transfer. However, we also need to nuke the other side
822 // if already added to our partitions.
823 // FIXME: Yet another place we really should bypass this when
824 // instrumenting for ASan.
825 if (Offset.uge(AllocSize)) {
826 SmallDenseMap<Instruction *, unsigned>::iterator MTPI =
827 MemTransferSliceMap.find(&II);
828 if (MTPI != MemTransferSliceMap.end())
829 AS.Slices[MTPI->second].kill();
830 return markAsDead(II);
833 uint64_t RawOffset = Offset.getLimitedValue();
834 uint64_t Size = Length ? Length->getLimitedValue() : AllocSize - RawOffset;
836 // Check for the special case where the same exact value is used for both
838 if (*U == II.getRawDest() && *U == II.getRawSource()) {
839 // For non-volatile transfers this is a no-op.
840 if (!II.isVolatile())
841 return markAsDead(II);
843 return insertUse(II, Offset, Size, /*IsSplittable=*/false);
846 // If we have seen both source and destination for a mem transfer, then
847 // they both point to the same alloca.
849 SmallDenseMap<Instruction *, unsigned>::iterator MTPI;
850 std::tie(MTPI, Inserted) =
851 MemTransferSliceMap.insert(std::make_pair(&II, AS.Slices.size()));
852 unsigned PrevIdx = MTPI->second;
854 Slice &PrevP = AS.Slices[PrevIdx];
856 // Check if the begin offsets match and this is a non-volatile transfer.
857 // In that case, we can completely elide the transfer.
858 if (!II.isVolatile() && PrevP.beginOffset() == RawOffset) {
860 return markAsDead(II);
863 // Otherwise we have an offset transfer within the same alloca. We can't
865 PrevP.makeUnsplittable();
868 // Insert the use now that we've fixed up the splittable nature.
869 insertUse(II, Offset, Size, /*IsSplittable=*/Inserted && Length);
871 // Check that we ended up with a valid index in the map.
872 assert(AS.Slices[PrevIdx].getUse()->getUser() == &II &&
873 "Map index doesn't point back to a slice with this user.");
876 // Disable SRoA for any intrinsics except for lifetime invariants.
877 // FIXME: What about debug intrinsics? This matches old behavior, but
878 // doesn't make sense.
879 void visitIntrinsicInst(IntrinsicInst &II) {
881 return PI.setAborted(&II);
883 if (II.getIntrinsicID() == Intrinsic::lifetime_start ||
884 II.getIntrinsicID() == Intrinsic::lifetime_end) {
885 ConstantInt *Length = cast<ConstantInt>(II.getArgOperand(0));
886 uint64_t Size = std::min(AllocSize - Offset.getLimitedValue(),
887 Length->getLimitedValue());
888 insertUse(II, Offset, Size, true);
892 Base::visitIntrinsicInst(II);
895 Instruction *hasUnsafePHIOrSelectUse(Instruction *Root, uint64_t &Size) {
896 // We consider any PHI or select that results in a direct load or store of
897 // the same offset to be a viable use for slicing purposes. These uses
898 // are considered unsplittable and the size is the maximum loaded or stored
900 SmallPtrSet<Instruction *, 4> Visited;
901 SmallVector<std::pair<Instruction *, Instruction *>, 4> Uses;
902 Visited.insert(Root);
903 Uses.push_back(std::make_pair(cast<Instruction>(*U), Root));
904 const DataLayout &DL = Root->getModule()->getDataLayout();
905 // If there are no loads or stores, the access is dead. We mark that as
906 // a size zero access.
909 Instruction *I, *UsedI;
910 std::tie(UsedI, I) = Uses.pop_back_val();
912 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
913 Size = std::max(Size, DL.getTypeStoreSize(LI->getType()));
916 if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
917 Value *Op = SI->getOperand(0);
920 Size = std::max(Size, DL.getTypeStoreSize(Op->getType()));
924 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
925 if (!GEP->hasAllZeroIndices())
927 } else if (!isa<BitCastInst>(I) && !isa<PHINode>(I) &&
928 !isa<SelectInst>(I)) {
932 for (User *U : I->users())
933 if (Visited.insert(cast<Instruction>(U)).second)
934 Uses.push_back(std::make_pair(I, cast<Instruction>(U)));
935 } while (!Uses.empty());
940 void visitPHINodeOrSelectInst(Instruction &I) {
941 assert(isa<PHINode>(I) || isa<SelectInst>(I));
943 return markAsDead(I);
945 // TODO: We could use SimplifyInstruction here to fold PHINodes and
946 // SelectInsts. However, doing so requires to change the current
947 // dead-operand-tracking mechanism. For instance, suppose neither loading
948 // from %U nor %other traps. Then "load (select undef, %U, %other)" does not
949 // trap either. However, if we simply replace %U with undef using the
950 // current dead-operand-tracking mechanism, "load (select undef, undef,
951 // %other)" may trap because the select may return the first operand
953 if (Value *Result = foldPHINodeOrSelectInst(I)) {
955 // If the result of the constant fold will be the pointer, recurse
956 // through the PHI/select as if we had RAUW'ed it.
959 // Otherwise the operand to the PHI/select is dead, and we can replace
961 AS.DeadOperands.push_back(U);
967 return PI.setAborted(&I);
969 // See if we already have computed info on this node.
970 uint64_t &Size = PHIOrSelectSizes[&I];
972 // This is a new PHI/Select, check for an unsafe use of it.
973 if (Instruction *UnsafeI = hasUnsafePHIOrSelectUse(&I, Size))
974 return PI.setAborted(UnsafeI);
977 // For PHI and select operands outside the alloca, we can't nuke the entire
978 // phi or select -- the other side might still be relevant, so we special
979 // case them here and use a separate structure to track the operands
980 // themselves which should be replaced with undef.
981 // FIXME: This should instead be escaped in the event we're instrumenting
982 // for address sanitization.
983 if (Offset.uge(AllocSize)) {
984 AS.DeadOperands.push_back(U);
988 insertUse(I, Offset, Size);
991 void visitPHINode(PHINode &PN) { visitPHINodeOrSelectInst(PN); }
993 void visitSelectInst(SelectInst &SI) { visitPHINodeOrSelectInst(SI); }
995 /// \brief Disable SROA entirely if there are unhandled users of the alloca.
996 void visitInstruction(Instruction &I) { PI.setAborted(&I); }
999 AllocaSlices::AllocaSlices(const DataLayout &DL, AllocaInst &AI)
1001 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1004 PointerEscapingInstr(nullptr) {
1005 SliceBuilder PB(DL, AI, *this);
1006 SliceBuilder::PtrInfo PtrI = PB.visitPtr(AI);
1007 if (PtrI.isEscaped() || PtrI.isAborted()) {
1008 // FIXME: We should sink the escape vs. abort info into the caller nicely,
1009 // possibly by just storing the PtrInfo in the AllocaSlices.
1010 PointerEscapingInstr = PtrI.getEscapingInst() ? PtrI.getEscapingInst()
1011 : PtrI.getAbortingInst();
1012 assert(PointerEscapingInstr && "Did not track a bad instruction");
1016 Slices.erase(std::remove_if(Slices.begin(), Slices.end(),
1017 [](const Slice &S) {
1022 #if __cplusplus >= 201103L && !defined(NDEBUG)
1023 if (SROARandomShuffleSlices) {
1024 std::mt19937 MT(static_cast<unsigned>(sys::TimeValue::now().msec()));
1025 std::shuffle(Slices.begin(), Slices.end(), MT);
1029 // Sort the uses. This arranges for the offsets to be in ascending order,
1030 // and the sizes to be in descending order.
1031 std::sort(Slices.begin(), Slices.end());
1034 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1036 void AllocaSlices::print(raw_ostream &OS, const_iterator I,
1037 StringRef Indent) const {
1038 printSlice(OS, I, Indent);
1040 printUse(OS, I, Indent);
1043 void AllocaSlices::printSlice(raw_ostream &OS, const_iterator I,
1044 StringRef Indent) const {
1045 OS << Indent << "[" << I->beginOffset() << "," << I->endOffset() << ")"
1046 << " slice #" << (I - begin())
1047 << (I->isSplittable() ? " (splittable)" : "");
1050 void AllocaSlices::printUse(raw_ostream &OS, const_iterator I,
1051 StringRef Indent) const {
1052 OS << Indent << " used by: " << *I->getUse()->getUser() << "\n";
1055 void AllocaSlices::print(raw_ostream &OS) const {
1056 if (PointerEscapingInstr) {
1057 OS << "Can't analyze slices for alloca: " << AI << "\n"
1058 << " A pointer to this alloca escaped by:\n"
1059 << " " << *PointerEscapingInstr << "\n";
1063 OS << "Slices of alloca: " << AI << "\n";
1064 for (const_iterator I = begin(), E = end(); I != E; ++I)
1068 LLVM_DUMP_METHOD void AllocaSlices::dump(const_iterator I) const {
1071 LLVM_DUMP_METHOD void AllocaSlices::dump() const { print(dbgs()); }
1073 #endif // !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1076 /// \brief Implementation of LoadAndStorePromoter for promoting allocas.
1078 /// This subclass of LoadAndStorePromoter adds overrides to handle promoting
1079 /// the loads and stores of an alloca instruction, as well as updating its
1080 /// debug information. This is used when a domtree is unavailable and thus
1081 /// mem2reg in its full form can't be used to handle promotion of allocas to
1083 class AllocaPromoter : public LoadAndStorePromoter {
1087 SmallVector<DbgDeclareInst *, 4> DDIs;
1088 SmallVector<DbgValueInst *, 4> DVIs;
1091 AllocaPromoter(ArrayRef<const Instruction *> Insts,
1093 AllocaInst &AI, DIBuilder &DIB)
1094 : LoadAndStorePromoter(Insts, S), AI(AI), DIB(DIB) {}
1096 void run(const SmallVectorImpl<Instruction *> &Insts) {
1097 // Retain the debug information attached to the alloca for use when
1098 // rewriting loads and stores.
1099 if (auto *L = LocalAsMetadata::getIfExists(&AI)) {
1100 if (auto *DINode = MetadataAsValue::getIfExists(AI.getContext(), L)) {
1101 for (User *U : DINode->users())
1102 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(U))
1103 DDIs.push_back(DDI);
1104 else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(U))
1105 DVIs.push_back(DVI);
1109 LoadAndStorePromoter::run(Insts);
1111 // While we have the debug information, clear it off of the alloca. The
1112 // caller takes care of deleting the alloca.
1113 while (!DDIs.empty())
1114 DDIs.pop_back_val()->eraseFromParent();
1115 while (!DVIs.empty())
1116 DVIs.pop_back_val()->eraseFromParent();
1120 isInstInList(Instruction *I,
1121 const SmallVectorImpl<Instruction *> &Insts) const override {
1123 if (LoadInst *LI = dyn_cast<LoadInst>(I))
1124 Ptr = LI->getOperand(0);
1126 Ptr = cast<StoreInst>(I)->getPointerOperand();
1128 // Only used to detect cycles, which will be rare and quickly found as
1129 // we're walking up a chain of defs rather than down through uses.
1130 SmallPtrSet<Value *, 4> Visited;
1136 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Ptr))
1137 Ptr = BCI->getOperand(0);
1138 else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Ptr))
1139 Ptr = GEPI->getPointerOperand();
1143 } while (Visited.insert(Ptr).second);
1148 void updateDebugInfo(Instruction *Inst) const override {
1149 for (DbgDeclareInst *DDI : DDIs)
1150 if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
1151 ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
1152 else if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
1153 ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
1154 for (DbgValueInst *DVI : DVIs) {
1155 Value *Arg = nullptr;
1156 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
1157 // If an argument is zero extended then use argument directly. The ZExt
1158 // may be zapped by an optimization pass in future.
1159 if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
1160 Arg = dyn_cast<Argument>(ZExt->getOperand(0));
1161 else if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
1162 Arg = dyn_cast<Argument>(SExt->getOperand(0));
1164 Arg = SI->getValueOperand();
1165 } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
1166 Arg = LI->getPointerOperand();
1170 DIB.insertDbgValueIntrinsic(Arg, 0, DVI->getVariable(),
1171 DVI->getExpression(), DVI->getDebugLoc(),
1176 } // end anon namespace
1179 /// \brief An optimization pass providing Scalar Replacement of Aggregates.
1181 /// This pass takes allocations which can be completely analyzed (that is, they
1182 /// don't escape) and tries to turn them into scalar SSA values. There are
1183 /// a few steps to this process.
1185 /// 1) It takes allocations of aggregates and analyzes the ways in which they
1186 /// are used to try to split them into smaller allocations, ideally of
1187 /// a single scalar data type. It will split up memcpy and memset accesses
1188 /// as necessary and try to isolate individual scalar accesses.
1189 /// 2) It will transform accesses into forms which are suitable for SSA value
1190 /// promotion. This can be replacing a memset with a scalar store of an
1191 /// integer value, or it can involve speculating operations on a PHI or
1192 /// select to be a PHI or select of the results.
1193 /// 3) Finally, this will try to detect a pattern of accesses which map cleanly
1194 /// onto insert and extract operations on a vector value, and convert them to
1195 /// this form. By doing so, it will enable promotion of vector aggregates to
1196 /// SSA vector values.
1197 class SROA : public FunctionPass {
1198 const bool RequiresDomTree;
1202 AssumptionCache *AC;
1204 /// \brief Worklist of alloca instructions to simplify.
1206 /// Each alloca in the function is added to this. Each new alloca formed gets
1207 /// added to it as well to recursively simplify unless that alloca can be
1208 /// directly promoted. Finally, each time we rewrite a use of an alloca other
1209 /// the one being actively rewritten, we add it back onto the list if not
1210 /// already present to ensure it is re-visited.
1211 SetVector<AllocaInst *, SmallVector<AllocaInst *, 16>> Worklist;
1213 /// \brief A collection of instructions to delete.
1214 /// We try to batch deletions to simplify code and make things a bit more
1216 SetVector<Instruction *, SmallVector<Instruction *, 8>> DeadInsts;
1218 /// \brief Post-promotion worklist.
1220 /// Sometimes we discover an alloca which has a high probability of becoming
1221 /// viable for SROA after a round of promotion takes place. In those cases,
1222 /// the alloca is enqueued here for re-processing.
1224 /// Note that we have to be very careful to clear allocas out of this list in
1225 /// the event they are deleted.
1226 SetVector<AllocaInst *, SmallVector<AllocaInst *, 16>> PostPromotionWorklist;
1228 /// \brief A collection of alloca instructions we can directly promote.
1229 std::vector<AllocaInst *> PromotableAllocas;
1231 /// \brief A worklist of PHIs to speculate prior to promoting allocas.
1233 /// All of these PHIs have been checked for the safety of speculation and by
1234 /// being speculated will allow promoting allocas currently in the promotable
1236 SetVector<PHINode *, SmallVector<PHINode *, 2>> SpeculatablePHIs;
1238 /// \brief A worklist of select instructions to speculate prior to promoting
1241 /// All of these select instructions have been checked for the safety of
1242 /// speculation and by being speculated will allow promoting allocas
1243 /// currently in the promotable queue.
1244 SetVector<SelectInst *, SmallVector<SelectInst *, 2>> SpeculatableSelects;
1247 SROA(bool RequiresDomTree = true)
1248 : FunctionPass(ID), RequiresDomTree(RequiresDomTree), C(nullptr),
1250 initializeSROAPass(*PassRegistry::getPassRegistry());
1252 bool runOnFunction(Function &F) override;
1253 void getAnalysisUsage(AnalysisUsage &AU) const override;
1255 const char *getPassName() const override { return "SROA"; }
1259 friend class PHIOrSelectSpeculator;
1260 friend class AllocaSliceRewriter;
1262 bool presplitLoadsAndStores(AllocaInst &AI, AllocaSlices &AS);
1263 AllocaInst *rewritePartition(AllocaInst &AI, AllocaSlices &AS,
1264 AllocaSlices::Partition &P);
1265 bool splitAlloca(AllocaInst &AI, AllocaSlices &AS);
1266 bool runOnAlloca(AllocaInst &AI);
1267 void clobberUse(Use &U);
1268 void deleteDeadInstructions(SmallPtrSetImpl<AllocaInst *> &DeletedAllocas);
1269 bool promoteAllocas(Function &F);
1275 FunctionPass *llvm::createSROAPass(bool RequiresDomTree) {
1276 return new SROA(RequiresDomTree);
1279 INITIALIZE_PASS_BEGIN(SROA, "sroa", "Scalar Replacement Of Aggregates", false,
1281 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
1282 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
1283 INITIALIZE_PASS_END(SROA, "sroa", "Scalar Replacement Of Aggregates", false,
1286 /// Walk the range of a partitioning looking for a common type to cover this
1287 /// sequence of slices.
1288 static Type *findCommonType(AllocaSlices::const_iterator B,
1289 AllocaSlices::const_iterator E,
1290 uint64_t EndOffset) {
1292 bool TyIsCommon = true;
1293 IntegerType *ITy = nullptr;
1295 // Note that we need to look at *every* alloca slice's Use to ensure we
1296 // always get consistent results regardless of the order of slices.
1297 for (AllocaSlices::const_iterator I = B; I != E; ++I) {
1298 Use *U = I->getUse();
1299 if (isa<IntrinsicInst>(*U->getUser()))
1301 if (I->beginOffset() != B->beginOffset() || I->endOffset() != EndOffset)
1304 Type *UserTy = nullptr;
1305 if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) {
1306 UserTy = LI->getType();
1307 } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
1308 UserTy = SI->getValueOperand()->getType();
1311 if (IntegerType *UserITy = dyn_cast_or_null<IntegerType>(UserTy)) {
1312 // If the type is larger than the partition, skip it. We only encounter
1313 // this for split integer operations where we want to use the type of the
1314 // entity causing the split. Also skip if the type is not a byte width
1316 if (UserITy->getBitWidth() % 8 != 0 ||
1317 UserITy->getBitWidth() / 8 > (EndOffset - B->beginOffset()))
1320 // Track the largest bitwidth integer type used in this way in case there
1321 // is no common type.
1322 if (!ITy || ITy->getBitWidth() < UserITy->getBitWidth())
1326 // To avoid depending on the order of slices, Ty and TyIsCommon must not
1327 // depend on types skipped above.
1328 if (!UserTy || (Ty && Ty != UserTy))
1329 TyIsCommon = false; // Give up on anything but an iN type.
1334 return TyIsCommon ? Ty : ITy;
1337 /// PHI instructions that use an alloca and are subsequently loaded can be
1338 /// rewritten to load both input pointers in the pred blocks and then PHI the
1339 /// results, allowing the load of the alloca to be promoted.
1341 /// %P2 = phi [i32* %Alloca, i32* %Other]
1342 /// %V = load i32* %P2
1344 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1346 /// %V2 = load i32* %Other
1348 /// %V = phi [i32 %V1, i32 %V2]
1350 /// We can do this to a select if its only uses are loads and if the operands
1351 /// to the select can be loaded unconditionally.
1353 /// FIXME: This should be hoisted into a generic utility, likely in
1354 /// Transforms/Util/Local.h
1355 static bool isSafePHIToSpeculate(PHINode &PN) {
1356 // For now, we can only do this promotion if the load is in the same block
1357 // as the PHI, and if there are no stores between the phi and load.
1358 // TODO: Allow recursive phi users.
1359 // TODO: Allow stores.
1360 BasicBlock *BB = PN.getParent();
1361 unsigned MaxAlign = 0;
1362 bool HaveLoad = false;
1363 for (User *U : PN.users()) {
1364 LoadInst *LI = dyn_cast<LoadInst>(U);
1365 if (!LI || !LI->isSimple())
1368 // For now we only allow loads in the same block as the PHI. This is
1369 // a common case that happens when instcombine merges two loads through
1371 if (LI->getParent() != BB)
1374 // Ensure that there are no instructions between the PHI and the load that
1376 for (BasicBlock::iterator BBI = &PN; &*BBI != LI; ++BBI)
1377 if (BBI->mayWriteToMemory())
1380 MaxAlign = std::max(MaxAlign, LI->getAlignment());
1387 const DataLayout &DL = PN.getModule()->getDataLayout();
1389 // We can only transform this if it is safe to push the loads into the
1390 // predecessor blocks. The only thing to watch out for is that we can't put
1391 // a possibly trapping load in the predecessor if it is a critical edge.
1392 for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) {
1393 TerminatorInst *TI = PN.getIncomingBlock(Idx)->getTerminator();
1394 Value *InVal = PN.getIncomingValue(Idx);
1396 // If the value is produced by the terminator of the predecessor (an
1397 // invoke) or it has side-effects, there is no valid place to put a load
1398 // in the predecessor.
1399 if (TI == InVal || TI->mayHaveSideEffects())
1402 // If the predecessor has a single successor, then the edge isn't
1404 if (TI->getNumSuccessors() == 1)
1407 // If this pointer is always safe to load, or if we can prove that there
1408 // is already a load in the block, then we can move the load to the pred
1410 if (isDereferenceablePointer(InVal, DL) ||
1411 isSafeToLoadUnconditionally(InVal, TI, MaxAlign))
1420 static void speculatePHINodeLoads(PHINode &PN) {
1421 DEBUG(dbgs() << " original: " << PN << "\n");
1423 Type *LoadTy = cast<PointerType>(PN.getType())->getElementType();
1424 IRBuilderTy PHIBuilder(&PN);
1425 PHINode *NewPN = PHIBuilder.CreatePHI(LoadTy, PN.getNumIncomingValues(),
1426 PN.getName() + ".sroa.speculated");
1428 // Get the AA tags and alignment to use from one of the loads. It doesn't
1429 // matter which one we get and if any differ.
1430 LoadInst *SomeLoad = cast<LoadInst>(PN.user_back());
1433 SomeLoad->getAAMetadata(AATags);
1434 unsigned Align = SomeLoad->getAlignment();
1436 // Rewrite all loads of the PN to use the new PHI.
1437 while (!PN.use_empty()) {
1438 LoadInst *LI = cast<LoadInst>(PN.user_back());
1439 LI->replaceAllUsesWith(NewPN);
1440 LI->eraseFromParent();
1443 // Inject loads into all of the pred blocks.
1444 for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) {
1445 BasicBlock *Pred = PN.getIncomingBlock(Idx);
1446 TerminatorInst *TI = Pred->getTerminator();
1447 Value *InVal = PN.getIncomingValue(Idx);
1448 IRBuilderTy PredBuilder(TI);
1450 LoadInst *Load = PredBuilder.CreateLoad(
1451 InVal, (PN.getName() + ".sroa.speculate.load." + Pred->getName()));
1452 ++NumLoadsSpeculated;
1453 Load->setAlignment(Align);
1455 Load->setAAMetadata(AATags);
1456 NewPN->addIncoming(Load, Pred);
1459 DEBUG(dbgs() << " speculated to: " << *NewPN << "\n");
1460 PN.eraseFromParent();
1463 /// Select instructions that use an alloca and are subsequently loaded can be
1464 /// rewritten to load both input pointers and then select between the result,
1465 /// allowing the load of the alloca to be promoted.
1467 /// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
1468 /// %V = load i32* %P2
1470 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1471 /// %V2 = load i32* %Other
1472 /// %V = select i1 %cond, i32 %V1, i32 %V2
1474 /// We can do this to a select if its only uses are loads and if the operand
1475 /// to the select can be loaded unconditionally.
1476 static bool isSafeSelectToSpeculate(SelectInst &SI) {
1477 Value *TValue = SI.getTrueValue();
1478 Value *FValue = SI.getFalseValue();
1479 const DataLayout &DL = SI.getModule()->getDataLayout();
1480 bool TDerefable = isDereferenceablePointer(TValue, DL);
1481 bool FDerefable = isDereferenceablePointer(FValue, DL);
1483 for (User *U : SI.users()) {
1484 LoadInst *LI = dyn_cast<LoadInst>(U);
1485 if (!LI || !LI->isSimple())
1488 // Both operands to the select need to be dereferencable, either
1489 // absolutely (e.g. allocas) or at this point because we can see other
1492 !isSafeToLoadUnconditionally(TValue, LI, LI->getAlignment()))
1495 !isSafeToLoadUnconditionally(FValue, LI, LI->getAlignment()))
1502 static void speculateSelectInstLoads(SelectInst &SI) {
1503 DEBUG(dbgs() << " original: " << SI << "\n");
1505 IRBuilderTy IRB(&SI);
1506 Value *TV = SI.getTrueValue();
1507 Value *FV = SI.getFalseValue();
1508 // Replace the loads of the select with a select of two loads.
1509 while (!SI.use_empty()) {
1510 LoadInst *LI = cast<LoadInst>(SI.user_back());
1511 assert(LI->isSimple() && "We only speculate simple loads");
1513 IRB.SetInsertPoint(LI);
1515 IRB.CreateLoad(TV, LI->getName() + ".sroa.speculate.load.true");
1517 IRB.CreateLoad(FV, LI->getName() + ".sroa.speculate.load.false");
1518 NumLoadsSpeculated += 2;
1520 // Transfer alignment and AA info if present.
1521 TL->setAlignment(LI->getAlignment());
1522 FL->setAlignment(LI->getAlignment());
1525 LI->getAAMetadata(Tags);
1527 TL->setAAMetadata(Tags);
1528 FL->setAAMetadata(Tags);
1531 Value *V = IRB.CreateSelect(SI.getCondition(), TL, FL,
1532 LI->getName() + ".sroa.speculated");
1534 DEBUG(dbgs() << " speculated to: " << *V << "\n");
1535 LI->replaceAllUsesWith(V);
1536 LI->eraseFromParent();
1538 SI.eraseFromParent();
1541 /// \brief Build a GEP out of a base pointer and indices.
1543 /// This will return the BasePtr if that is valid, or build a new GEP
1544 /// instruction using the IRBuilder if GEP-ing is needed.
1545 static Value *buildGEP(IRBuilderTy &IRB, Value *BasePtr,
1546 SmallVectorImpl<Value *> &Indices, Twine NamePrefix) {
1547 if (Indices.empty())
1550 // A single zero index is a no-op, so check for this and avoid building a GEP
1552 if (Indices.size() == 1 && cast<ConstantInt>(Indices.back())->isZero())
1555 return IRB.CreateInBoundsGEP(nullptr, BasePtr, Indices,
1556 NamePrefix + "sroa_idx");
1559 /// \brief Get a natural GEP off of the BasePtr walking through Ty toward
1560 /// TargetTy without changing the offset of the pointer.
1562 /// This routine assumes we've already established a properly offset GEP with
1563 /// Indices, and arrived at the Ty type. The goal is to continue to GEP with
1564 /// zero-indices down through type layers until we find one the same as
1565 /// TargetTy. If we can't find one with the same type, we at least try to use
1566 /// one with the same size. If none of that works, we just produce the GEP as
1567 /// indicated by Indices to have the correct offset.
1568 static Value *getNaturalGEPWithType(IRBuilderTy &IRB, const DataLayout &DL,
1569 Value *BasePtr, Type *Ty, Type *TargetTy,
1570 SmallVectorImpl<Value *> &Indices,
1573 return buildGEP(IRB, BasePtr, Indices, NamePrefix);
1575 // Pointer size to use for the indices.
1576 unsigned PtrSize = DL.getPointerTypeSizeInBits(BasePtr->getType());
1578 // See if we can descend into a struct and locate a field with the correct
1580 unsigned NumLayers = 0;
1581 Type *ElementTy = Ty;
1583 if (ElementTy->isPointerTy())
1586 if (ArrayType *ArrayTy = dyn_cast<ArrayType>(ElementTy)) {
1587 ElementTy = ArrayTy->getElementType();
1588 Indices.push_back(IRB.getIntN(PtrSize, 0));
1589 } else if (VectorType *VectorTy = dyn_cast<VectorType>(ElementTy)) {
1590 ElementTy = VectorTy->getElementType();
1591 Indices.push_back(IRB.getInt32(0));
1592 } else if (StructType *STy = dyn_cast<StructType>(ElementTy)) {
1593 if (STy->element_begin() == STy->element_end())
1594 break; // Nothing left to descend into.
1595 ElementTy = *STy->element_begin();
1596 Indices.push_back(IRB.getInt32(0));
1601 } while (ElementTy != TargetTy);
1602 if (ElementTy != TargetTy)
1603 Indices.erase(Indices.end() - NumLayers, Indices.end());
1605 return buildGEP(IRB, BasePtr, Indices, NamePrefix);
1608 /// \brief Recursively compute indices for a natural GEP.
1610 /// This is the recursive step for getNaturalGEPWithOffset that walks down the
1611 /// element types adding appropriate indices for the GEP.
1612 static Value *getNaturalGEPRecursively(IRBuilderTy &IRB, const DataLayout &DL,
1613 Value *Ptr, Type *Ty, APInt &Offset,
1615 SmallVectorImpl<Value *> &Indices,
1618 return getNaturalGEPWithType(IRB, DL, Ptr, Ty, TargetTy, Indices,
1621 // We can't recurse through pointer types.
1622 if (Ty->isPointerTy())
1625 // We try to analyze GEPs over vectors here, but note that these GEPs are
1626 // extremely poorly defined currently. The long-term goal is to remove GEPing
1627 // over a vector from the IR completely.
1628 if (VectorType *VecTy = dyn_cast<VectorType>(Ty)) {
1629 unsigned ElementSizeInBits = DL.getTypeSizeInBits(VecTy->getScalarType());
1630 if (ElementSizeInBits % 8 != 0) {
1631 // GEPs over non-multiple of 8 size vector elements are invalid.
1634 APInt ElementSize(Offset.getBitWidth(), ElementSizeInBits / 8);
1635 APInt NumSkippedElements = Offset.sdiv(ElementSize);
1636 if (NumSkippedElements.ugt(VecTy->getNumElements()))
1638 Offset -= NumSkippedElements * ElementSize;
1639 Indices.push_back(IRB.getInt(NumSkippedElements));
1640 return getNaturalGEPRecursively(IRB, DL, Ptr, VecTy->getElementType(),
1641 Offset, TargetTy, Indices, NamePrefix);
1644 if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) {
1645 Type *ElementTy = ArrTy->getElementType();
1646 APInt ElementSize(Offset.getBitWidth(), DL.getTypeAllocSize(ElementTy));
1647 APInt NumSkippedElements = Offset.sdiv(ElementSize);
1648 if (NumSkippedElements.ugt(ArrTy->getNumElements()))
1651 Offset -= NumSkippedElements * ElementSize;
1652 Indices.push_back(IRB.getInt(NumSkippedElements));
1653 return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy,
1654 Indices, NamePrefix);
1657 StructType *STy = dyn_cast<StructType>(Ty);
1661 const StructLayout *SL = DL.getStructLayout(STy);
1662 uint64_t StructOffset = Offset.getZExtValue();
1663 if (StructOffset >= SL->getSizeInBytes())
1665 unsigned Index = SL->getElementContainingOffset(StructOffset);
1666 Offset -= APInt(Offset.getBitWidth(), SL->getElementOffset(Index));
1667 Type *ElementTy = STy->getElementType(Index);
1668 if (Offset.uge(DL.getTypeAllocSize(ElementTy)))
1669 return nullptr; // The offset points into alignment padding.
1671 Indices.push_back(IRB.getInt32(Index));
1672 return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy,
1673 Indices, NamePrefix);
1676 /// \brief Get a natural GEP from a base pointer to a particular offset and
1677 /// resulting in a particular type.
1679 /// The goal is to produce a "natural" looking GEP that works with the existing
1680 /// composite types to arrive at the appropriate offset and element type for
1681 /// a pointer. TargetTy is the element type the returned GEP should point-to if
1682 /// possible. We recurse by decreasing Offset, adding the appropriate index to
1683 /// Indices, and setting Ty to the result subtype.
1685 /// If no natural GEP can be constructed, this function returns null.
1686 static Value *getNaturalGEPWithOffset(IRBuilderTy &IRB, const DataLayout &DL,
1687 Value *Ptr, APInt Offset, Type *TargetTy,
1688 SmallVectorImpl<Value *> &Indices,
1690 PointerType *Ty = cast<PointerType>(Ptr->getType());
1692 // Don't consider any GEPs through an i8* as natural unless the TargetTy is
1694 if (Ty == IRB.getInt8PtrTy(Ty->getAddressSpace()) && TargetTy->isIntegerTy(8))
1697 Type *ElementTy = Ty->getElementType();
1698 if (!ElementTy->isSized())
1699 return nullptr; // We can't GEP through an unsized element.
1700 APInt ElementSize(Offset.getBitWidth(), DL.getTypeAllocSize(ElementTy));
1701 if (ElementSize == 0)
1702 return nullptr; // Zero-length arrays can't help us build a natural GEP.
1703 APInt NumSkippedElements = Offset.sdiv(ElementSize);
1705 Offset -= NumSkippedElements * ElementSize;
1706 Indices.push_back(IRB.getInt(NumSkippedElements));
1707 return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy,
1708 Indices, NamePrefix);
1711 /// \brief Compute an adjusted pointer from Ptr by Offset bytes where the
1712 /// resulting pointer has PointerTy.
1714 /// This tries very hard to compute a "natural" GEP which arrives at the offset
1715 /// and produces the pointer type desired. Where it cannot, it will try to use
1716 /// the natural GEP to arrive at the offset and bitcast to the type. Where that
1717 /// fails, it will try to use an existing i8* and GEP to the byte offset and
1718 /// bitcast to the type.
1720 /// The strategy for finding the more natural GEPs is to peel off layers of the
1721 /// pointer, walking back through bit casts and GEPs, searching for a base
1722 /// pointer from which we can compute a natural GEP with the desired
1723 /// properties. The algorithm tries to fold as many constant indices into
1724 /// a single GEP as possible, thus making each GEP more independent of the
1725 /// surrounding code.
1726 static Value *getAdjustedPtr(IRBuilderTy &IRB, const DataLayout &DL, Value *Ptr,
1727 APInt Offset, Type *PointerTy, Twine NamePrefix) {
1728 // Even though we don't look through PHI nodes, we could be called on an
1729 // instruction in an unreachable block, which may be on a cycle.
1730 SmallPtrSet<Value *, 4> Visited;
1731 Visited.insert(Ptr);
1732 SmallVector<Value *, 4> Indices;
1734 // We may end up computing an offset pointer that has the wrong type. If we
1735 // never are able to compute one directly that has the correct type, we'll
1736 // fall back to it, so keep it and the base it was computed from around here.
1737 Value *OffsetPtr = nullptr;
1738 Value *OffsetBasePtr;
1740 // Remember any i8 pointer we come across to re-use if we need to do a raw
1742 Value *Int8Ptr = nullptr;
1743 APInt Int8PtrOffset(Offset.getBitWidth(), 0);
1745 Type *TargetTy = PointerTy->getPointerElementType();
1748 // First fold any existing GEPs into the offset.
1749 while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
1750 APInt GEPOffset(Offset.getBitWidth(), 0);
1751 if (!GEP->accumulateConstantOffset(DL, GEPOffset))
1753 Offset += GEPOffset;
1754 Ptr = GEP->getPointerOperand();
1755 if (!Visited.insert(Ptr).second)
1759 // See if we can perform a natural GEP here.
1761 if (Value *P = getNaturalGEPWithOffset(IRB, DL, Ptr, Offset, TargetTy,
1762 Indices, NamePrefix)) {
1763 // If we have a new natural pointer at the offset, clear out any old
1764 // offset pointer we computed. Unless it is the base pointer or
1765 // a non-instruction, we built a GEP we don't need. Zap it.
1766 if (OffsetPtr && OffsetPtr != OffsetBasePtr)
1767 if (Instruction *I = dyn_cast<Instruction>(OffsetPtr)) {
1768 assert(I->use_empty() && "Built a GEP with uses some how!");
1769 I->eraseFromParent();
1772 OffsetBasePtr = Ptr;
1773 // If we also found a pointer of the right type, we're done.
1774 if (P->getType() == PointerTy)
1778 // Stash this pointer if we've found an i8*.
1779 if (Ptr->getType()->isIntegerTy(8)) {
1781 Int8PtrOffset = Offset;
1784 // Peel off a layer of the pointer and update the offset appropriately.
1785 if (Operator::getOpcode(Ptr) == Instruction::BitCast) {
1786 Ptr = cast<Operator>(Ptr)->getOperand(0);
1787 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(Ptr)) {
1788 if (GA->mayBeOverridden())
1790 Ptr = GA->getAliasee();
1794 assert(Ptr->getType()->isPointerTy() && "Unexpected operand type!");
1795 } while (Visited.insert(Ptr).second);
1799 Int8Ptr = IRB.CreateBitCast(
1800 Ptr, IRB.getInt8PtrTy(PointerTy->getPointerAddressSpace()),
1801 NamePrefix + "sroa_raw_cast");
1802 Int8PtrOffset = Offset;
1805 OffsetPtr = Int8PtrOffset == 0
1807 : IRB.CreateInBoundsGEP(IRB.getInt8Ty(), Int8Ptr,
1808 IRB.getInt(Int8PtrOffset),
1809 NamePrefix + "sroa_raw_idx");
1813 // On the off chance we were targeting i8*, guard the bitcast here.
1814 if (Ptr->getType() != PointerTy)
1815 Ptr = IRB.CreateBitCast(Ptr, PointerTy, NamePrefix + "sroa_cast");
1820 /// \brief Compute the adjusted alignment for a load or store from an offset.
1821 static unsigned getAdjustedAlignment(Instruction *I, uint64_t Offset,
1822 const DataLayout &DL) {
1825 if (auto *LI = dyn_cast<LoadInst>(I)) {
1826 Alignment = LI->getAlignment();
1828 } else if (auto *SI = dyn_cast<StoreInst>(I)) {
1829 Alignment = SI->getAlignment();
1830 Ty = SI->getValueOperand()->getType();
1832 llvm_unreachable("Only loads and stores are allowed!");
1836 Alignment = DL.getABITypeAlignment(Ty);
1838 return MinAlign(Alignment, Offset);
1841 /// \brief Test whether we can convert a value from the old to the new type.
1843 /// This predicate should be used to guard calls to convertValue in order to
1844 /// ensure that we only try to convert viable values. The strategy is that we
1845 /// will peel off single element struct and array wrappings to get to an
1846 /// underlying value, and convert that value.
1847 static bool canConvertValue(const DataLayout &DL, Type *OldTy, Type *NewTy) {
1850 if (IntegerType *OldITy = dyn_cast<IntegerType>(OldTy))
1851 if (IntegerType *NewITy = dyn_cast<IntegerType>(NewTy))
1852 if (NewITy->getBitWidth() >= OldITy->getBitWidth())
1854 if (DL.getTypeSizeInBits(NewTy) != DL.getTypeSizeInBits(OldTy))
1856 if (!NewTy->isSingleValueType() || !OldTy->isSingleValueType())
1859 // We can convert pointers to integers and vice-versa. Same for vectors
1860 // of pointers and integers.
1861 OldTy = OldTy->getScalarType();
1862 NewTy = NewTy->getScalarType();
1863 if (NewTy->isPointerTy() || OldTy->isPointerTy()) {
1864 if (NewTy->isPointerTy() && OldTy->isPointerTy())
1866 if (NewTy->isIntegerTy() || OldTy->isIntegerTy())
1874 /// \brief Generic routine to convert an SSA value to a value of a different
1877 /// This will try various different casting techniques, such as bitcasts,
1878 /// inttoptr, and ptrtoint casts. Use the \c canConvertValue predicate to test
1879 /// two types for viability with this routine.
1880 static Value *convertValue(const DataLayout &DL, IRBuilderTy &IRB, Value *V,
1882 Type *OldTy = V->getType();
1883 assert(canConvertValue(DL, OldTy, NewTy) && "Value not convertable to type");
1888 if (IntegerType *OldITy = dyn_cast<IntegerType>(OldTy))
1889 if (IntegerType *NewITy = dyn_cast<IntegerType>(NewTy))
1890 if (NewITy->getBitWidth() > OldITy->getBitWidth())
1891 return IRB.CreateZExt(V, NewITy);
1893 // See if we need inttoptr for this type pair. A cast involving both scalars
1894 // and vectors requires and additional bitcast.
1895 if (OldTy->getScalarType()->isIntegerTy() &&
1896 NewTy->getScalarType()->isPointerTy()) {
1897 // Expand <2 x i32> to i8* --> <2 x i32> to i64 to i8*
1898 if (OldTy->isVectorTy() && !NewTy->isVectorTy())
1899 return IRB.CreateIntToPtr(IRB.CreateBitCast(V, DL.getIntPtrType(NewTy)),
1902 // Expand i128 to <2 x i8*> --> i128 to <2 x i64> to <2 x i8*>
1903 if (!OldTy->isVectorTy() && NewTy->isVectorTy())
1904 return IRB.CreateIntToPtr(IRB.CreateBitCast(V, DL.getIntPtrType(NewTy)),
1907 return IRB.CreateIntToPtr(V, NewTy);
1910 // See if we need ptrtoint for this type pair. A cast involving both scalars
1911 // and vectors requires and additional bitcast.
1912 if (OldTy->getScalarType()->isPointerTy() &&
1913 NewTy->getScalarType()->isIntegerTy()) {
1914 // Expand <2 x i8*> to i128 --> <2 x i8*> to <2 x i64> to i128
1915 if (OldTy->isVectorTy() && !NewTy->isVectorTy())
1916 return IRB.CreateBitCast(IRB.CreatePtrToInt(V, DL.getIntPtrType(OldTy)),
1919 // Expand i8* to <2 x i32> --> i8* to i64 to <2 x i32>
1920 if (!OldTy->isVectorTy() && NewTy->isVectorTy())
1921 return IRB.CreateBitCast(IRB.CreatePtrToInt(V, DL.getIntPtrType(OldTy)),
1924 return IRB.CreatePtrToInt(V, NewTy);
1927 return IRB.CreateBitCast(V, NewTy);
1930 /// \brief Test whether the given slice use can be promoted to a vector.
1932 /// This function is called to test each entry in a partioning which is slated
1933 /// for a single slice.
1934 static bool isVectorPromotionViableForSlice(AllocaSlices::Partition &P,
1935 const Slice &S, VectorType *Ty,
1936 uint64_t ElementSize,
1937 const DataLayout &DL) {
1938 // First validate the slice offsets.
1939 uint64_t BeginOffset =
1940 std::max(S.beginOffset(), P.beginOffset()) - P.beginOffset();
1941 uint64_t BeginIndex = BeginOffset / ElementSize;
1942 if (BeginIndex * ElementSize != BeginOffset ||
1943 BeginIndex >= Ty->getNumElements())
1945 uint64_t EndOffset =
1946 std::min(S.endOffset(), P.endOffset()) - P.beginOffset();
1947 uint64_t EndIndex = EndOffset / ElementSize;
1948 if (EndIndex * ElementSize != EndOffset || EndIndex > Ty->getNumElements())
1951 assert(EndIndex > BeginIndex && "Empty vector!");
1952 uint64_t NumElements = EndIndex - BeginIndex;
1953 Type *SliceTy = (NumElements == 1)
1954 ? Ty->getElementType()
1955 : VectorType::get(Ty->getElementType(), NumElements);
1958 Type::getIntNTy(Ty->getContext(), NumElements * ElementSize * 8);
1960 Use *U = S.getUse();
1962 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) {
1963 if (MI->isVolatile())
1965 if (!S.isSplittable())
1966 return false; // Skip any unsplittable intrinsics.
1967 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U->getUser())) {
1968 if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
1969 II->getIntrinsicID() != Intrinsic::lifetime_end)
1971 } else if (U->get()->getType()->getPointerElementType()->isStructTy()) {
1972 // Disable vector promotion when there are loads or stores of an FCA.
1974 } else if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) {
1975 if (LI->isVolatile())
1977 Type *LTy = LI->getType();
1978 if (P.beginOffset() > S.beginOffset() || P.endOffset() < S.endOffset()) {
1979 assert(LTy->isIntegerTy());
1982 if (!canConvertValue(DL, SliceTy, LTy))
1984 } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
1985 if (SI->isVolatile())
1987 Type *STy = SI->getValueOperand()->getType();
1988 if (P.beginOffset() > S.beginOffset() || P.endOffset() < S.endOffset()) {
1989 assert(STy->isIntegerTy());
1992 if (!canConvertValue(DL, STy, SliceTy))
2001 /// \brief Test whether the given alloca partitioning and range of slices can be
2002 /// promoted to a vector.
2004 /// This is a quick test to check whether we can rewrite a particular alloca
2005 /// partition (and its newly formed alloca) into a vector alloca with only
2006 /// whole-vector loads and stores such that it could be promoted to a vector
2007 /// SSA value. We only can ensure this for a limited set of operations, and we
2008 /// don't want to do the rewrites unless we are confident that the result will
2009 /// be promotable, so we have an early test here.
2010 static VectorType *isVectorPromotionViable(AllocaSlices::Partition &P,
2011 const DataLayout &DL) {
2012 // Collect the candidate types for vector-based promotion. Also track whether
2013 // we have different element types.
2014 SmallVector<VectorType *, 4> CandidateTys;
2015 Type *CommonEltTy = nullptr;
2016 bool HaveCommonEltTy = true;
2017 auto CheckCandidateType = [&](Type *Ty) {
2018 if (auto *VTy = dyn_cast<VectorType>(Ty)) {
2019 CandidateTys.push_back(VTy);
2021 CommonEltTy = VTy->getElementType();
2022 else if (CommonEltTy != VTy->getElementType())
2023 HaveCommonEltTy = false;
2026 // Consider any loads or stores that are the exact size of the slice.
2027 for (const Slice &S : P)
2028 if (S.beginOffset() == P.beginOffset() &&
2029 S.endOffset() == P.endOffset()) {
2030 if (auto *LI = dyn_cast<LoadInst>(S.getUse()->getUser()))
2031 CheckCandidateType(LI->getType());
2032 else if (auto *SI = dyn_cast<StoreInst>(S.getUse()->getUser()))
2033 CheckCandidateType(SI->getValueOperand()->getType());
2036 // If we didn't find a vector type, nothing to do here.
2037 if (CandidateTys.empty())
2040 // Remove non-integer vector types if we had multiple common element types.
2041 // FIXME: It'd be nice to replace them with integer vector types, but we can't
2042 // do that until all the backends are known to produce good code for all
2043 // integer vector types.
2044 if (!HaveCommonEltTy) {
2045 CandidateTys.erase(std::remove_if(CandidateTys.begin(), CandidateTys.end(),
2046 [](VectorType *VTy) {
2047 return !VTy->getElementType()->isIntegerTy();
2049 CandidateTys.end());
2051 // If there were no integer vector types, give up.
2052 if (CandidateTys.empty())
2055 // Rank the remaining candidate vector types. This is easy because we know
2056 // they're all integer vectors. We sort by ascending number of elements.
2057 auto RankVectorTypes = [&DL](VectorType *RHSTy, VectorType *LHSTy) {
2058 assert(DL.getTypeSizeInBits(RHSTy) == DL.getTypeSizeInBits(LHSTy) &&
2059 "Cannot have vector types of different sizes!");
2060 assert(RHSTy->getElementType()->isIntegerTy() &&
2061 "All non-integer types eliminated!");
2062 assert(LHSTy->getElementType()->isIntegerTy() &&
2063 "All non-integer types eliminated!");
2064 return RHSTy->getNumElements() < LHSTy->getNumElements();
2066 std::sort(CandidateTys.begin(), CandidateTys.end(), RankVectorTypes);
2068 std::unique(CandidateTys.begin(), CandidateTys.end(), RankVectorTypes),
2069 CandidateTys.end());
2071 // The only way to have the same element type in every vector type is to
2072 // have the same vector type. Check that and remove all but one.
2074 for (VectorType *VTy : CandidateTys) {
2075 assert(VTy->getElementType() == CommonEltTy &&
2076 "Unaccounted for element type!");
2077 assert(VTy == CandidateTys[0] &&
2078 "Different vector types with the same element type!");
2081 CandidateTys.resize(1);
2084 // Try each vector type, and return the one which works.
2085 auto CheckVectorTypeForPromotion = [&](VectorType *VTy) {
2086 uint64_t ElementSize = DL.getTypeSizeInBits(VTy->getElementType());
2088 // While the definition of LLVM vectors is bitpacked, we don't support sizes
2089 // that aren't byte sized.
2090 if (ElementSize % 8)
2092 assert((DL.getTypeSizeInBits(VTy) % 8) == 0 &&
2093 "vector size not a multiple of element size?");
2096 for (const Slice &S : P)
2097 if (!isVectorPromotionViableForSlice(P, S, VTy, ElementSize, DL))
2100 for (const Slice *S : P.splitSliceTails())
2101 if (!isVectorPromotionViableForSlice(P, *S, VTy, ElementSize, DL))
2106 for (VectorType *VTy : CandidateTys)
2107 if (CheckVectorTypeForPromotion(VTy))
2113 /// \brief Test whether a slice of an alloca is valid for integer widening.
2115 /// This implements the necessary checking for the \c isIntegerWideningViable
2116 /// test below on a single slice of the alloca.
2117 static bool isIntegerWideningViableForSlice(const Slice &S,
2118 uint64_t AllocBeginOffset,
2120 const DataLayout &DL,
2121 bool &WholeAllocaOp) {
2122 uint64_t Size = DL.getTypeStoreSize(AllocaTy);
2124 uint64_t RelBegin = S.beginOffset() - AllocBeginOffset;
2125 uint64_t RelEnd = S.endOffset() - AllocBeginOffset;
2127 // We can't reasonably handle cases where the load or store extends past
2128 // the end of the aloca's type and into its padding.
2132 Use *U = S.getUse();
2134 if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) {
2135 if (LI->isVolatile())
2137 // Note that we don't count vector loads or stores as whole-alloca
2138 // operations which enable integer widening because we would prefer to use
2139 // vector widening instead.
2140 if (!isa<VectorType>(LI->getType()) && RelBegin == 0 && RelEnd == Size)
2141 WholeAllocaOp = true;
2142 if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType())) {
2143 if (ITy->getBitWidth() < DL.getTypeStoreSizeInBits(ITy))
2145 } else if (RelBegin != 0 || RelEnd != Size ||
2146 !canConvertValue(DL, AllocaTy, LI->getType())) {
2147 // Non-integer loads need to be convertible from the alloca type so that
2148 // they are promotable.
2151 } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
2152 Type *ValueTy = SI->getValueOperand()->getType();
2153 if (SI->isVolatile())
2155 // Note that we don't count vector loads or stores as whole-alloca
2156 // operations which enable integer widening because we would prefer to use
2157 // vector widening instead.
2158 if (!isa<VectorType>(ValueTy) && RelBegin == 0 && RelEnd == Size)
2159 WholeAllocaOp = true;
2160 if (IntegerType *ITy = dyn_cast<IntegerType>(ValueTy)) {
2161 if (ITy->getBitWidth() < DL.getTypeStoreSizeInBits(ITy))
2163 } else if (RelBegin != 0 || RelEnd != Size ||
2164 !canConvertValue(DL, ValueTy, AllocaTy)) {
2165 // Non-integer stores need to be convertible to the alloca type so that
2166 // they are promotable.
2169 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) {
2170 if (MI->isVolatile() || !isa<Constant>(MI->getLength()))
2172 if (!S.isSplittable())
2173 return false; // Skip any unsplittable intrinsics.
2174 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U->getUser())) {
2175 if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
2176 II->getIntrinsicID() != Intrinsic::lifetime_end)
2185 /// \brief Test whether the given alloca partition's integer operations can be
2186 /// widened to promotable ones.
2188 /// This is a quick test to check whether we can rewrite the integer loads and
2189 /// stores to a particular alloca into wider loads and stores and be able to
2190 /// promote the resulting alloca.
2191 static bool isIntegerWideningViable(AllocaSlices::Partition &P, Type *AllocaTy,
2192 const DataLayout &DL) {
2193 uint64_t SizeInBits = DL.getTypeSizeInBits(AllocaTy);
2194 // Don't create integer types larger than the maximum bitwidth.
2195 if (SizeInBits > IntegerType::MAX_INT_BITS)
2198 // Don't try to handle allocas with bit-padding.
2199 if (SizeInBits != DL.getTypeStoreSizeInBits(AllocaTy))
2202 // We need to ensure that an integer type with the appropriate bitwidth can
2203 // be converted to the alloca type, whatever that is. We don't want to force
2204 // the alloca itself to have an integer type if there is a more suitable one.
2205 Type *IntTy = Type::getIntNTy(AllocaTy->getContext(), SizeInBits);
2206 if (!canConvertValue(DL, AllocaTy, IntTy) ||
2207 !canConvertValue(DL, IntTy, AllocaTy))
2210 // While examining uses, we ensure that the alloca has a covering load or
2211 // store. We don't want to widen the integer operations only to fail to
2212 // promote due to some other unsplittable entry (which we may make splittable
2213 // later). However, if there are only splittable uses, go ahead and assume
2214 // that we cover the alloca.
2215 // FIXME: We shouldn't consider split slices that happen to start in the
2216 // partition here...
2217 bool WholeAllocaOp =
2218 P.begin() != P.end() ? false : DL.isLegalInteger(SizeInBits);
2220 for (const Slice &S : P)
2221 if (!isIntegerWideningViableForSlice(S, P.beginOffset(), AllocaTy, DL,
2225 for (const Slice *S : P.splitSliceTails())
2226 if (!isIntegerWideningViableForSlice(*S, P.beginOffset(), AllocaTy, DL,
2230 return WholeAllocaOp;
2233 static Value *extractInteger(const DataLayout &DL, IRBuilderTy &IRB, Value *V,
2234 IntegerType *Ty, uint64_t Offset,
2235 const Twine &Name) {
2236 DEBUG(dbgs() << " start: " << *V << "\n");
2237 IntegerType *IntTy = cast<IntegerType>(V->getType());
2238 assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) &&
2239 "Element extends past full value");
2240 uint64_t ShAmt = 8 * Offset;
2241 if (DL.isBigEndian())
2242 ShAmt = 8 * (DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset);
2244 V = IRB.CreateLShr(V, ShAmt, Name + ".shift");
2245 DEBUG(dbgs() << " shifted: " << *V << "\n");
2247 assert(Ty->getBitWidth() <= IntTy->getBitWidth() &&
2248 "Cannot extract to a larger integer!");
2250 V = IRB.CreateTrunc(V, Ty, Name + ".trunc");
2251 DEBUG(dbgs() << " trunced: " << *V << "\n");
2256 static Value *insertInteger(const DataLayout &DL, IRBuilderTy &IRB, Value *Old,
2257 Value *V, uint64_t Offset, const Twine &Name) {
2258 IntegerType *IntTy = cast<IntegerType>(Old->getType());
2259 IntegerType *Ty = cast<IntegerType>(V->getType());
2260 assert(Ty->getBitWidth() <= IntTy->getBitWidth() &&
2261 "Cannot insert a larger integer!");
2262 DEBUG(dbgs() << " start: " << *V << "\n");
2264 V = IRB.CreateZExt(V, IntTy, Name + ".ext");
2265 DEBUG(dbgs() << " extended: " << *V << "\n");
2267 assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) &&
2268 "Element store outside of alloca store");
2269 uint64_t ShAmt = 8 * Offset;
2270 if (DL.isBigEndian())
2271 ShAmt = 8 * (DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset);
2273 V = IRB.CreateShl(V, ShAmt, Name + ".shift");
2274 DEBUG(dbgs() << " shifted: " << *V << "\n");
2277 if (ShAmt || Ty->getBitWidth() < IntTy->getBitWidth()) {
2278 APInt Mask = ~Ty->getMask().zext(IntTy->getBitWidth()).shl(ShAmt);
2279 Old = IRB.CreateAnd(Old, Mask, Name + ".mask");
2280 DEBUG(dbgs() << " masked: " << *Old << "\n");
2281 V = IRB.CreateOr(Old, V, Name + ".insert");
2282 DEBUG(dbgs() << " inserted: " << *V << "\n");
2287 static Value *extractVector(IRBuilderTy &IRB, Value *V, unsigned BeginIndex,
2288 unsigned EndIndex, const Twine &Name) {
2289 VectorType *VecTy = cast<VectorType>(V->getType());
2290 unsigned NumElements = EndIndex - BeginIndex;
2291 assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
2293 if (NumElements == VecTy->getNumElements())
2296 if (NumElements == 1) {
2297 V = IRB.CreateExtractElement(V, IRB.getInt32(BeginIndex),
2299 DEBUG(dbgs() << " extract: " << *V << "\n");
2303 SmallVector<Constant *, 8> Mask;
2304 Mask.reserve(NumElements);
2305 for (unsigned i = BeginIndex; i != EndIndex; ++i)
2306 Mask.push_back(IRB.getInt32(i));
2307 V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()),
2308 ConstantVector::get(Mask), Name + ".extract");
2309 DEBUG(dbgs() << " shuffle: " << *V << "\n");
2313 static Value *insertVector(IRBuilderTy &IRB, Value *Old, Value *V,
2314 unsigned BeginIndex, const Twine &Name) {
2315 VectorType *VecTy = cast<VectorType>(Old->getType());
2316 assert(VecTy && "Can only insert a vector into a vector");
2318 VectorType *Ty = dyn_cast<VectorType>(V->getType());
2320 // Single element to insert.
2321 V = IRB.CreateInsertElement(Old, V, IRB.getInt32(BeginIndex),
2323 DEBUG(dbgs() << " insert: " << *V << "\n");
2327 assert(Ty->getNumElements() <= VecTy->getNumElements() &&
2328 "Too many elements!");
2329 if (Ty->getNumElements() == VecTy->getNumElements()) {
2330 assert(V->getType() == VecTy && "Vector type mismatch");
2333 unsigned EndIndex = BeginIndex + Ty->getNumElements();
2335 // When inserting a smaller vector into the larger to store, we first
2336 // use a shuffle vector to widen it with undef elements, and then
2337 // a second shuffle vector to select between the loaded vector and the
2339 SmallVector<Constant *, 8> Mask;
2340 Mask.reserve(VecTy->getNumElements());
2341 for (unsigned i = 0; i != VecTy->getNumElements(); ++i)
2342 if (i >= BeginIndex && i < EndIndex)
2343 Mask.push_back(IRB.getInt32(i - BeginIndex));
2345 Mask.push_back(UndefValue::get(IRB.getInt32Ty()));
2346 V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()),
2347 ConstantVector::get(Mask), Name + ".expand");
2348 DEBUG(dbgs() << " shuffle: " << *V << "\n");
2351 for (unsigned i = 0; i != VecTy->getNumElements(); ++i)
2352 Mask.push_back(IRB.getInt1(i >= BeginIndex && i < EndIndex));
2354 V = IRB.CreateSelect(ConstantVector::get(Mask), V, Old, Name + "blend");
2356 DEBUG(dbgs() << " blend: " << *V << "\n");
2361 /// \brief Visitor to rewrite instructions using p particular slice of an alloca
2362 /// to use a new alloca.
2364 /// Also implements the rewriting to vector-based accesses when the partition
2365 /// passes the isVectorPromotionViable predicate. Most of the rewriting logic
2367 class AllocaSliceRewriter : public InstVisitor<AllocaSliceRewriter, bool> {
2368 // Befriend the base class so it can delegate to private visit methods.
2369 friend class llvm::InstVisitor<AllocaSliceRewriter, bool>;
2370 typedef llvm::InstVisitor<AllocaSliceRewriter, bool> Base;
2372 const DataLayout &DL;
2375 AllocaInst &OldAI, &NewAI;
2376 const uint64_t NewAllocaBeginOffset, NewAllocaEndOffset;
2379 // This is a convenience and flag variable that will be null unless the new
2380 // alloca's integer operations should be widened to this integer type due to
2381 // passing isIntegerWideningViable above. If it is non-null, the desired
2382 // integer type will be stored here for easy access during rewriting.
2385 // If we are rewriting an alloca partition which can be written as pure
2386 // vector operations, we stash extra information here. When VecTy is
2387 // non-null, we have some strict guarantees about the rewritten alloca:
2388 // - The new alloca is exactly the size of the vector type here.
2389 // - The accesses all either map to the entire vector or to a single
2391 // - The set of accessing instructions is only one of those handled above
2392 // in isVectorPromotionViable. Generally these are the same access kinds
2393 // which are promotable via mem2reg.
2396 uint64_t ElementSize;
2398 // The original offset of the slice currently being rewritten relative to
2399 // the original alloca.
2400 uint64_t BeginOffset, EndOffset;
2401 // The new offsets of the slice currently being rewritten relative to the
2403 uint64_t NewBeginOffset, NewEndOffset;
2409 Instruction *OldPtr;
2411 // Track post-rewrite users which are PHI nodes and Selects.
2412 SmallPtrSetImpl<PHINode *> &PHIUsers;
2413 SmallPtrSetImpl<SelectInst *> &SelectUsers;
2415 // Utility IR builder, whose name prefix is setup for each visited use, and
2416 // the insertion point is set to point to the user.
2420 AllocaSliceRewriter(const DataLayout &DL, AllocaSlices &AS, SROA &Pass,
2421 AllocaInst &OldAI, AllocaInst &NewAI,
2422 uint64_t NewAllocaBeginOffset,
2423 uint64_t NewAllocaEndOffset, bool IsIntegerPromotable,
2424 VectorType *PromotableVecTy,
2425 SmallPtrSetImpl<PHINode *> &PHIUsers,
2426 SmallPtrSetImpl<SelectInst *> &SelectUsers)
2427 : DL(DL), AS(AS), Pass(Pass), OldAI(OldAI), NewAI(NewAI),
2428 NewAllocaBeginOffset(NewAllocaBeginOffset),
2429 NewAllocaEndOffset(NewAllocaEndOffset),
2430 NewAllocaTy(NewAI.getAllocatedType()),
2431 IntTy(IsIntegerPromotable
2434 DL.getTypeSizeInBits(NewAI.getAllocatedType()))
2436 VecTy(PromotableVecTy),
2437 ElementTy(VecTy ? VecTy->getElementType() : nullptr),
2438 ElementSize(VecTy ? DL.getTypeSizeInBits(ElementTy) / 8 : 0),
2439 BeginOffset(), EndOffset(), IsSplittable(), IsSplit(), OldUse(),
2440 OldPtr(), PHIUsers(PHIUsers), SelectUsers(SelectUsers),
2441 IRB(NewAI.getContext(), ConstantFolder()) {
2443 assert((DL.getTypeSizeInBits(ElementTy) % 8) == 0 &&
2444 "Only multiple-of-8 sized vector elements are viable");
2447 assert((!IntTy && !VecTy) || (IntTy && !VecTy) || (!IntTy && VecTy));
2450 bool visit(AllocaSlices::const_iterator I) {
2451 bool CanSROA = true;
2452 BeginOffset = I->beginOffset();
2453 EndOffset = I->endOffset();
2454 IsSplittable = I->isSplittable();
2456 BeginOffset < NewAllocaBeginOffset || EndOffset > NewAllocaEndOffset;
2457 DEBUG(dbgs() << " rewriting " << (IsSplit ? "split " : ""));
2458 DEBUG(AS.printSlice(dbgs(), I, ""));
2459 DEBUG(dbgs() << "\n");
2461 // Compute the intersecting offset range.
2462 assert(BeginOffset < NewAllocaEndOffset);
2463 assert(EndOffset > NewAllocaBeginOffset);
2464 NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset);
2465 NewEndOffset = std::min(EndOffset, NewAllocaEndOffset);
2467 SliceSize = NewEndOffset - NewBeginOffset;
2469 OldUse = I->getUse();
2470 OldPtr = cast<Instruction>(OldUse->get());
2472 Instruction *OldUserI = cast<Instruction>(OldUse->getUser());
2473 IRB.SetInsertPoint(OldUserI);
2474 IRB.SetCurrentDebugLocation(OldUserI->getDebugLoc());
2475 IRB.SetNamePrefix(Twine(NewAI.getName()) + "." + Twine(BeginOffset) + ".");
2477 CanSROA &= visit(cast<Instruction>(OldUse->getUser()));
2484 // Make sure the other visit overloads are visible.
2487 // Every instruction which can end up as a user must have a rewrite rule.
2488 bool visitInstruction(Instruction &I) {
2489 DEBUG(dbgs() << " !!!! Cannot rewrite: " << I << "\n");
2490 llvm_unreachable("No rewrite rule for this instruction!");
2493 Value *getNewAllocaSlicePtr(IRBuilderTy &IRB, Type *PointerTy) {
2494 // Note that the offset computation can use BeginOffset or NewBeginOffset
2495 // interchangeably for unsplit slices.
2496 assert(IsSplit || BeginOffset == NewBeginOffset);
2497 uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
2500 StringRef OldName = OldPtr->getName();
2501 // Skip through the last '.sroa.' component of the name.
2502 size_t LastSROAPrefix = OldName.rfind(".sroa.");
2503 if (LastSROAPrefix != StringRef::npos) {
2504 OldName = OldName.substr(LastSROAPrefix + strlen(".sroa."));
2505 // Look for an SROA slice index.
2506 size_t IndexEnd = OldName.find_first_not_of("0123456789");
2507 if (IndexEnd != StringRef::npos && OldName[IndexEnd] == '.') {
2508 // Strip the index and look for the offset.
2509 OldName = OldName.substr(IndexEnd + 1);
2510 size_t OffsetEnd = OldName.find_first_not_of("0123456789");
2511 if (OffsetEnd != StringRef::npos && OldName[OffsetEnd] == '.')
2512 // Strip the offset.
2513 OldName = OldName.substr(OffsetEnd + 1);
2516 // Strip any SROA suffixes as well.
2517 OldName = OldName.substr(0, OldName.find(".sroa_"));
2520 return getAdjustedPtr(IRB, DL, &NewAI,
2521 APInt(DL.getPointerSizeInBits(), Offset), PointerTy,
2523 Twine(OldName) + "."
2530 /// \brief Compute suitable alignment to access this slice of the *new*
2533 /// You can optionally pass a type to this routine and if that type's ABI
2534 /// alignment is itself suitable, this will return zero.
2535 unsigned getSliceAlign(Type *Ty = nullptr) {
2536 unsigned NewAIAlign = NewAI.getAlignment();
2538 NewAIAlign = DL.getABITypeAlignment(NewAI.getAllocatedType());
2540 MinAlign(NewAIAlign, NewBeginOffset - NewAllocaBeginOffset);
2541 return (Ty && Align == DL.getABITypeAlignment(Ty)) ? 0 : Align;
2544 unsigned getIndex(uint64_t Offset) {
2545 assert(VecTy && "Can only call getIndex when rewriting a vector");
2546 uint64_t RelOffset = Offset - NewAllocaBeginOffset;
2547 assert(RelOffset / ElementSize < UINT32_MAX && "Index out of bounds");
2548 uint32_t Index = RelOffset / ElementSize;
2549 assert(Index * ElementSize == RelOffset);
2553 void deleteIfTriviallyDead(Value *V) {
2554 Instruction *I = cast<Instruction>(V);
2555 if (isInstructionTriviallyDead(I))
2556 Pass.DeadInsts.insert(I);
2559 Value *rewriteVectorizedLoadInst() {
2560 unsigned BeginIndex = getIndex(NewBeginOffset);
2561 unsigned EndIndex = getIndex(NewEndOffset);
2562 assert(EndIndex > BeginIndex && "Empty vector!");
2564 Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "load");
2565 return extractVector(IRB, V, BeginIndex, EndIndex, "vec");
2568 Value *rewriteIntegerLoad(LoadInst &LI) {
2569 assert(IntTy && "We cannot insert an integer to the alloca");
2570 assert(!LI.isVolatile());
2571 Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "load");
2572 V = convertValue(DL, IRB, V, IntTy);
2573 assert(NewBeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2574 uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
2575 if (Offset > 0 || NewEndOffset < NewAllocaEndOffset)
2576 V = extractInteger(DL, IRB, V, cast<IntegerType>(LI.getType()), Offset,
2581 bool visitLoadInst(LoadInst &LI) {
2582 DEBUG(dbgs() << " original: " << LI << "\n");
2583 Value *OldOp = LI.getOperand(0);
2584 assert(OldOp == OldPtr);
2586 Type *TargetTy = IsSplit ? Type::getIntNTy(LI.getContext(), SliceSize * 8)
2588 bool IsPtrAdjusted = false;
2591 V = rewriteVectorizedLoadInst();
2592 } else if (IntTy && LI.getType()->isIntegerTy()) {
2593 V = rewriteIntegerLoad(LI);
2594 } else if (NewBeginOffset == NewAllocaBeginOffset &&
2595 canConvertValue(DL, NewAllocaTy, LI.getType())) {
2596 V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), LI.isVolatile(),
2599 Type *LTy = TargetTy->getPointerTo();
2600 V = IRB.CreateAlignedLoad(getNewAllocaSlicePtr(IRB, LTy),
2601 getSliceAlign(TargetTy), LI.isVolatile(),
2603 IsPtrAdjusted = true;
2605 V = convertValue(DL, IRB, V, TargetTy);
2608 assert(!LI.isVolatile());
2609 assert(LI.getType()->isIntegerTy() &&
2610 "Only integer type loads and stores are split");
2611 assert(SliceSize < DL.getTypeStoreSize(LI.getType()) &&
2612 "Split load isn't smaller than original load");
2613 assert(LI.getType()->getIntegerBitWidth() ==
2614 DL.getTypeStoreSizeInBits(LI.getType()) &&
2615 "Non-byte-multiple bit width");
2616 // Move the insertion point just past the load so that we can refer to it.
2617 IRB.SetInsertPoint(std::next(BasicBlock::iterator(&LI)));
2618 // Create a placeholder value with the same type as LI to use as the
2619 // basis for the new value. This allows us to replace the uses of LI with
2620 // the computed value, and then replace the placeholder with LI, leaving
2621 // LI only used for this computation.
2622 Value *Placeholder =
2623 new LoadInst(UndefValue::get(LI.getType()->getPointerTo()));
2624 V = insertInteger(DL, IRB, Placeholder, V, NewBeginOffset - BeginOffset,
2626 LI.replaceAllUsesWith(V);
2627 Placeholder->replaceAllUsesWith(&LI);
2630 LI.replaceAllUsesWith(V);
2633 Pass.DeadInsts.insert(&LI);
2634 deleteIfTriviallyDead(OldOp);
2635 DEBUG(dbgs() << " to: " << *V << "\n");
2636 return !LI.isVolatile() && !IsPtrAdjusted;
2639 bool rewriteVectorizedStoreInst(Value *V, StoreInst &SI, Value *OldOp) {
2640 if (V->getType() != VecTy) {
2641 unsigned BeginIndex = getIndex(NewBeginOffset);
2642 unsigned EndIndex = getIndex(NewEndOffset);
2643 assert(EndIndex > BeginIndex && "Empty vector!");
2644 unsigned NumElements = EndIndex - BeginIndex;
2645 assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
2646 Type *SliceTy = (NumElements == 1)
2648 : VectorType::get(ElementTy, NumElements);
2649 if (V->getType() != SliceTy)
2650 V = convertValue(DL, IRB, V, SliceTy);
2652 // Mix in the existing elements.
2653 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "load");
2654 V = insertVector(IRB, Old, V, BeginIndex, "vec");
2656 StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment());
2657 Pass.DeadInsts.insert(&SI);
2660 DEBUG(dbgs() << " to: " << *Store << "\n");
2664 bool rewriteIntegerStore(Value *V, StoreInst &SI) {
2665 assert(IntTy && "We cannot extract an integer from the alloca");
2666 assert(!SI.isVolatile());
2667 if (DL.getTypeSizeInBits(V->getType()) != IntTy->getBitWidth()) {
2669 IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "oldload");
2670 Old = convertValue(DL, IRB, Old, IntTy);
2671 assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2672 uint64_t Offset = BeginOffset - NewAllocaBeginOffset;
2673 V = insertInteger(DL, IRB, Old, SI.getValueOperand(), Offset, "insert");
2675 V = convertValue(DL, IRB, V, NewAllocaTy);
2676 StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment());
2677 Pass.DeadInsts.insert(&SI);
2679 DEBUG(dbgs() << " to: " << *Store << "\n");
2683 bool visitStoreInst(StoreInst &SI) {
2684 DEBUG(dbgs() << " original: " << SI << "\n");
2685 Value *OldOp = SI.getOperand(1);
2686 assert(OldOp == OldPtr);
2688 Value *V = SI.getValueOperand();
2690 // Strip all inbounds GEPs and pointer casts to try to dig out any root
2691 // alloca that should be re-examined after promoting this alloca.
2692 if (V->getType()->isPointerTy())
2693 if (AllocaInst *AI = dyn_cast<AllocaInst>(V->stripInBoundsOffsets()))
2694 Pass.PostPromotionWorklist.insert(AI);
2696 if (SliceSize < DL.getTypeStoreSize(V->getType())) {
2697 assert(!SI.isVolatile());
2698 assert(V->getType()->isIntegerTy() &&
2699 "Only integer type loads and stores are split");
2700 assert(V->getType()->getIntegerBitWidth() ==
2701 DL.getTypeStoreSizeInBits(V->getType()) &&
2702 "Non-byte-multiple bit width");
2703 IntegerType *NarrowTy = Type::getIntNTy(SI.getContext(), SliceSize * 8);
2704 V = extractInteger(DL, IRB, V, NarrowTy, NewBeginOffset - BeginOffset,
2709 return rewriteVectorizedStoreInst(V, SI, OldOp);
2710 if (IntTy && V->getType()->isIntegerTy())
2711 return rewriteIntegerStore(V, SI);
2714 if (NewBeginOffset == NewAllocaBeginOffset &&
2715 NewEndOffset == NewAllocaEndOffset &&
2716 canConvertValue(DL, V->getType(), NewAllocaTy)) {
2717 V = convertValue(DL, IRB, V, NewAllocaTy);
2718 NewSI = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(),
2721 Value *NewPtr = getNewAllocaSlicePtr(IRB, V->getType()->getPointerTo());
2722 NewSI = IRB.CreateAlignedStore(V, NewPtr, getSliceAlign(V->getType()),
2726 Pass.DeadInsts.insert(&SI);
2727 deleteIfTriviallyDead(OldOp);
2729 DEBUG(dbgs() << " to: " << *NewSI << "\n");
2730 return NewSI->getPointerOperand() == &NewAI && !SI.isVolatile();
2733 /// \brief Compute an integer value from splatting an i8 across the given
2734 /// number of bytes.
2736 /// Note that this routine assumes an i8 is a byte. If that isn't true, don't
2737 /// call this routine.
2738 /// FIXME: Heed the advice above.
2740 /// \param V The i8 value to splat.
2741 /// \param Size The number of bytes in the output (assuming i8 is one byte)
2742 Value *getIntegerSplat(Value *V, unsigned Size) {
2743 assert(Size > 0 && "Expected a positive number of bytes.");
2744 IntegerType *VTy = cast<IntegerType>(V->getType());
2745 assert(VTy->getBitWidth() == 8 && "Expected an i8 value for the byte");
2749 Type *SplatIntTy = Type::getIntNTy(VTy->getContext(), Size * 8);
2751 IRB.CreateZExt(V, SplatIntTy, "zext"),
2752 ConstantExpr::getUDiv(
2753 Constant::getAllOnesValue(SplatIntTy),
2754 ConstantExpr::getZExt(Constant::getAllOnesValue(V->getType()),
2760 /// \brief Compute a vector splat for a given element value.
2761 Value *getVectorSplat(Value *V, unsigned NumElements) {
2762 V = IRB.CreateVectorSplat(NumElements, V, "vsplat");
2763 DEBUG(dbgs() << " splat: " << *V << "\n");
2767 bool visitMemSetInst(MemSetInst &II) {
2768 DEBUG(dbgs() << " original: " << II << "\n");
2769 assert(II.getRawDest() == OldPtr);
2771 // If the memset has a variable size, it cannot be split, just adjust the
2772 // pointer to the new alloca.
2773 if (!isa<Constant>(II.getLength())) {
2775 assert(NewBeginOffset == BeginOffset);
2776 II.setDest(getNewAllocaSlicePtr(IRB, OldPtr->getType()));
2777 Type *CstTy = II.getAlignmentCst()->getType();
2778 II.setAlignment(ConstantInt::get(CstTy, getSliceAlign()));
2780 deleteIfTriviallyDead(OldPtr);
2784 // Record this instruction for deletion.
2785 Pass.DeadInsts.insert(&II);
2787 Type *AllocaTy = NewAI.getAllocatedType();
2788 Type *ScalarTy = AllocaTy->getScalarType();
2790 // If this doesn't map cleanly onto the alloca type, and that type isn't
2791 // a single value type, just emit a memset.
2792 if (!VecTy && !IntTy &&
2793 (BeginOffset > NewAllocaBeginOffset || EndOffset < NewAllocaEndOffset ||
2794 SliceSize != DL.getTypeStoreSize(AllocaTy) ||
2795 !AllocaTy->isSingleValueType() ||
2796 !DL.isLegalInteger(DL.getTypeSizeInBits(ScalarTy)) ||
2797 DL.getTypeSizeInBits(ScalarTy) % 8 != 0)) {
2798 Type *SizeTy = II.getLength()->getType();
2799 Constant *Size = ConstantInt::get(SizeTy, NewEndOffset - NewBeginOffset);
2800 CallInst *New = IRB.CreateMemSet(
2801 getNewAllocaSlicePtr(IRB, OldPtr->getType()), II.getValue(), Size,
2802 getSliceAlign(), II.isVolatile());
2804 DEBUG(dbgs() << " to: " << *New << "\n");
2808 // If we can represent this as a simple value, we have to build the actual
2809 // value to store, which requires expanding the byte present in memset to
2810 // a sensible representation for the alloca type. This is essentially
2811 // splatting the byte to a sufficiently wide integer, splatting it across
2812 // any desired vector width, and bitcasting to the final type.
2816 // If this is a memset of a vectorized alloca, insert it.
2817 assert(ElementTy == ScalarTy);
2819 unsigned BeginIndex = getIndex(NewBeginOffset);
2820 unsigned EndIndex = getIndex(NewEndOffset);
2821 assert(EndIndex > BeginIndex && "Empty vector!");
2822 unsigned NumElements = EndIndex - BeginIndex;
2823 assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
2826 getIntegerSplat(II.getValue(), DL.getTypeSizeInBits(ElementTy) / 8);
2827 Splat = convertValue(DL, IRB, Splat, ElementTy);
2828 if (NumElements > 1)
2829 Splat = getVectorSplat(Splat, NumElements);
2832 IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "oldload");
2833 V = insertVector(IRB, Old, Splat, BeginIndex, "vec");
2835 // If this is a memset on an alloca where we can widen stores, insert the
2837 assert(!II.isVolatile());
2839 uint64_t Size = NewEndOffset - NewBeginOffset;
2840 V = getIntegerSplat(II.getValue(), Size);
2842 if (IntTy && (BeginOffset != NewAllocaBeginOffset ||
2843 EndOffset != NewAllocaBeginOffset)) {
2845 IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "oldload");
2846 Old = convertValue(DL, IRB, Old, IntTy);
2847 uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
2848 V = insertInteger(DL, IRB, Old, V, Offset, "insert");
2850 assert(V->getType() == IntTy &&
2851 "Wrong type for an alloca wide integer!");
2853 V = convertValue(DL, IRB, V, AllocaTy);
2855 // Established these invariants above.
2856 assert(NewBeginOffset == NewAllocaBeginOffset);
2857 assert(NewEndOffset == NewAllocaEndOffset);
2859 V = getIntegerSplat(II.getValue(), DL.getTypeSizeInBits(ScalarTy) / 8);
2860 if (VectorType *AllocaVecTy = dyn_cast<VectorType>(AllocaTy))
2861 V = getVectorSplat(V, AllocaVecTy->getNumElements());
2863 V = convertValue(DL, IRB, V, AllocaTy);
2866 Value *New = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(),
2869 DEBUG(dbgs() << " to: " << *New << "\n");
2870 return !II.isVolatile();
2873 bool visitMemTransferInst(MemTransferInst &II) {
2874 // Rewriting of memory transfer instructions can be a bit tricky. We break
2875 // them into two categories: split intrinsics and unsplit intrinsics.
2877 DEBUG(dbgs() << " original: " << II << "\n");
2879 bool IsDest = &II.getRawDestUse() == OldUse;
2880 assert((IsDest && II.getRawDest() == OldPtr) ||
2881 (!IsDest && II.getRawSource() == OldPtr));
2883 unsigned SliceAlign = getSliceAlign();
2885 // For unsplit intrinsics, we simply modify the source and destination
2886 // pointers in place. This isn't just an optimization, it is a matter of
2887 // correctness. With unsplit intrinsics we may be dealing with transfers
2888 // within a single alloca before SROA ran, or with transfers that have
2889 // a variable length. We may also be dealing with memmove instead of
2890 // memcpy, and so simply updating the pointers is the necessary for us to
2891 // update both source and dest of a single call.
2892 if (!IsSplittable) {
2893 Value *AdjustedPtr = getNewAllocaSlicePtr(IRB, OldPtr->getType());
2895 II.setDest(AdjustedPtr);
2897 II.setSource(AdjustedPtr);
2899 if (II.getAlignment() > SliceAlign) {
2900 Type *CstTy = II.getAlignmentCst()->getType();
2902 ConstantInt::get(CstTy, MinAlign(II.getAlignment(), SliceAlign)));
2905 DEBUG(dbgs() << " to: " << II << "\n");
2906 deleteIfTriviallyDead(OldPtr);
2909 // For split transfer intrinsics we have an incredibly useful assurance:
2910 // the source and destination do not reside within the same alloca, and at
2911 // least one of them does not escape. This means that we can replace
2912 // memmove with memcpy, and we don't need to worry about all manner of
2913 // downsides to splitting and transforming the operations.
2915 // If this doesn't map cleanly onto the alloca type, and that type isn't
2916 // a single value type, just emit a memcpy.
2919 (BeginOffset > NewAllocaBeginOffset || EndOffset < NewAllocaEndOffset ||
2920 SliceSize != DL.getTypeStoreSize(NewAI.getAllocatedType()) ||
2921 !NewAI.getAllocatedType()->isSingleValueType());
2923 // If we're just going to emit a memcpy, the alloca hasn't changed, and the
2924 // size hasn't been shrunk based on analysis of the viable range, this is
2926 if (EmitMemCpy && &OldAI == &NewAI) {
2927 // Ensure the start lines up.
2928 assert(NewBeginOffset == BeginOffset);
2930 // Rewrite the size as needed.
2931 if (NewEndOffset != EndOffset)
2932 II.setLength(ConstantInt::get(II.getLength()->getType(),
2933 NewEndOffset - NewBeginOffset));
2936 // Record this instruction for deletion.
2937 Pass.DeadInsts.insert(&II);
2939 // Strip all inbounds GEPs and pointer casts to try to dig out any root
2940 // alloca that should be re-examined after rewriting this instruction.
2941 Value *OtherPtr = IsDest ? II.getRawSource() : II.getRawDest();
2942 if (AllocaInst *AI =
2943 dyn_cast<AllocaInst>(OtherPtr->stripInBoundsOffsets())) {
2944 assert(AI != &OldAI && AI != &NewAI &&
2945 "Splittable transfers cannot reach the same alloca on both ends.");
2946 Pass.Worklist.insert(AI);
2949 Type *OtherPtrTy = OtherPtr->getType();
2950 unsigned OtherAS = OtherPtrTy->getPointerAddressSpace();
2952 // Compute the relative offset for the other pointer within the transfer.
2953 unsigned IntPtrWidth = DL.getPointerSizeInBits(OtherAS);
2954 APInt OtherOffset(IntPtrWidth, NewBeginOffset - BeginOffset);
2955 unsigned OtherAlign = MinAlign(II.getAlignment() ? II.getAlignment() : 1,
2956 OtherOffset.zextOrTrunc(64).getZExtValue());
2959 // Compute the other pointer, folding as much as possible to produce
2960 // a single, simple GEP in most cases.
2961 OtherPtr = getAdjustedPtr(IRB, DL, OtherPtr, OtherOffset, OtherPtrTy,
2962 OtherPtr->getName() + ".");
2964 Value *OurPtr = getNewAllocaSlicePtr(IRB, OldPtr->getType());
2965 Type *SizeTy = II.getLength()->getType();
2966 Constant *Size = ConstantInt::get(SizeTy, NewEndOffset - NewBeginOffset);
2968 CallInst *New = IRB.CreateMemCpy(
2969 IsDest ? OurPtr : OtherPtr, IsDest ? OtherPtr : OurPtr, Size,
2970 MinAlign(SliceAlign, OtherAlign), II.isVolatile());
2972 DEBUG(dbgs() << " to: " << *New << "\n");
2976 bool IsWholeAlloca = NewBeginOffset == NewAllocaBeginOffset &&
2977 NewEndOffset == NewAllocaEndOffset;
2978 uint64_t Size = NewEndOffset - NewBeginOffset;
2979 unsigned BeginIndex = VecTy ? getIndex(NewBeginOffset) : 0;
2980 unsigned EndIndex = VecTy ? getIndex(NewEndOffset) : 0;
2981 unsigned NumElements = EndIndex - BeginIndex;
2982 IntegerType *SubIntTy =
2983 IntTy ? Type::getIntNTy(IntTy->getContext(), Size * 8) : nullptr;
2985 // Reset the other pointer type to match the register type we're going to
2986 // use, but using the address space of the original other pointer.
2987 if (VecTy && !IsWholeAlloca) {
2988 if (NumElements == 1)
2989 OtherPtrTy = VecTy->getElementType();
2991 OtherPtrTy = VectorType::get(VecTy->getElementType(), NumElements);
2993 OtherPtrTy = OtherPtrTy->getPointerTo(OtherAS);
2994 } else if (IntTy && !IsWholeAlloca) {
2995 OtherPtrTy = SubIntTy->getPointerTo(OtherAS);
2997 OtherPtrTy = NewAllocaTy->getPointerTo(OtherAS);
3000 Value *SrcPtr = getAdjustedPtr(IRB, DL, OtherPtr, OtherOffset, OtherPtrTy,
3001 OtherPtr->getName() + ".");
3002 unsigned SrcAlign = OtherAlign;
3003 Value *DstPtr = &NewAI;
3004 unsigned DstAlign = SliceAlign;
3006 std::swap(SrcPtr, DstPtr);
3007 std::swap(SrcAlign, DstAlign);
3011 if (VecTy && !IsWholeAlloca && !IsDest) {
3012 Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "load");
3013 Src = extractVector(IRB, Src, BeginIndex, EndIndex, "vec");
3014 } else if (IntTy && !IsWholeAlloca && !IsDest) {
3015 Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "load");
3016 Src = convertValue(DL, IRB, Src, IntTy);
3017 uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
3018 Src = extractInteger(DL, IRB, Src, SubIntTy, Offset, "extract");
3021 IRB.CreateAlignedLoad(SrcPtr, SrcAlign, II.isVolatile(), "copyload");
3024 if (VecTy && !IsWholeAlloca && IsDest) {
3026 IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "oldload");
3027 Src = insertVector(IRB, Old, Src, BeginIndex, "vec");
3028 } else if (IntTy && !IsWholeAlloca && IsDest) {
3030 IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), "oldload");
3031 Old = convertValue(DL, IRB, Old, IntTy);
3032 uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
3033 Src = insertInteger(DL, IRB, Old, Src, Offset, "insert");
3034 Src = convertValue(DL, IRB, Src, NewAllocaTy);
3037 StoreInst *Store = cast<StoreInst>(
3038 IRB.CreateAlignedStore(Src, DstPtr, DstAlign, II.isVolatile()));
3040 DEBUG(dbgs() << " to: " << *Store << "\n");
3041 return !II.isVolatile();
3044 bool visitIntrinsicInst(IntrinsicInst &II) {
3045 assert(II.getIntrinsicID() == Intrinsic::lifetime_start ||
3046 II.getIntrinsicID() == Intrinsic::lifetime_end);
3047 DEBUG(dbgs() << " original: " << II << "\n");
3048 assert(II.getArgOperand(1) == OldPtr);
3050 // Record this instruction for deletion.
3051 Pass.DeadInsts.insert(&II);
3054 ConstantInt::get(cast<IntegerType>(II.getArgOperand(0)->getType()),
3055 NewEndOffset - NewBeginOffset);
3056 Value *Ptr = getNewAllocaSlicePtr(IRB, OldPtr->getType());
3058 if (II.getIntrinsicID() == Intrinsic::lifetime_start)
3059 New = IRB.CreateLifetimeStart(Ptr, Size);
3061 New = IRB.CreateLifetimeEnd(Ptr, Size);
3064 DEBUG(dbgs() << " to: " << *New << "\n");
3068 bool visitPHINode(PHINode &PN) {
3069 DEBUG(dbgs() << " original: " << PN << "\n");
3070 assert(BeginOffset >= NewAllocaBeginOffset && "PHIs are unsplittable");
3071 assert(EndOffset <= NewAllocaEndOffset && "PHIs are unsplittable");
3073 // We would like to compute a new pointer in only one place, but have it be
3074 // as local as possible to the PHI. To do that, we re-use the location of
3075 // the old pointer, which necessarily must be in the right position to
3076 // dominate the PHI.
3077 IRBuilderTy PtrBuilder(IRB);
3078 if (isa<PHINode>(OldPtr))
3079 PtrBuilder.SetInsertPoint(OldPtr->getParent()->getFirstInsertionPt());
3081 PtrBuilder.SetInsertPoint(OldPtr);
3082 PtrBuilder.SetCurrentDebugLocation(OldPtr->getDebugLoc());
3084 Value *NewPtr = getNewAllocaSlicePtr(PtrBuilder, OldPtr->getType());
3085 // Replace the operands which were using the old pointer.
3086 std::replace(PN.op_begin(), PN.op_end(), cast<Value>(OldPtr), NewPtr);
3088 DEBUG(dbgs() << " to: " << PN << "\n");
3089 deleteIfTriviallyDead(OldPtr);
3091 // PHIs can't be promoted on their own, but often can be speculated. We
3092 // check the speculation outside of the rewriter so that we see the
3093 // fully-rewritten alloca.
3094 PHIUsers.insert(&PN);
3098 bool visitSelectInst(SelectInst &SI) {
3099 DEBUG(dbgs() << " original: " << SI << "\n");
3100 assert((SI.getTrueValue() == OldPtr || SI.getFalseValue() == OldPtr) &&
3101 "Pointer isn't an operand!");
3102 assert(BeginOffset >= NewAllocaBeginOffset && "Selects are unsplittable");
3103 assert(EndOffset <= NewAllocaEndOffset && "Selects are unsplittable");
3105 Value *NewPtr = getNewAllocaSlicePtr(IRB, OldPtr->getType());
3106 // Replace the operands which were using the old pointer.
3107 if (SI.getOperand(1) == OldPtr)
3108 SI.setOperand(1, NewPtr);
3109 if (SI.getOperand(2) == OldPtr)
3110 SI.setOperand(2, NewPtr);
3112 DEBUG(dbgs() << " to: " << SI << "\n");
3113 deleteIfTriviallyDead(OldPtr);
3115 // Selects can't be promoted on their own, but often can be speculated. We
3116 // check the speculation outside of the rewriter so that we see the
3117 // fully-rewritten alloca.
3118 SelectUsers.insert(&SI);
3125 /// \brief Visitor to rewrite aggregate loads and stores as scalar.
3127 /// This pass aggressively rewrites all aggregate loads and stores on
3128 /// a particular pointer (or any pointer derived from it which we can identify)
3129 /// with scalar loads and stores.
3130 class AggLoadStoreRewriter : public InstVisitor<AggLoadStoreRewriter, bool> {
3131 // Befriend the base class so it can delegate to private visit methods.
3132 friend class llvm::InstVisitor<AggLoadStoreRewriter, bool>;
3134 const DataLayout &DL;
3136 /// Queue of pointer uses to analyze and potentially rewrite.
3137 SmallVector<Use *, 8> Queue;
3139 /// Set to prevent us from cycling with phi nodes and loops.
3140 SmallPtrSet<User *, 8> Visited;
3142 /// The current pointer use being rewritten. This is used to dig up the used
3143 /// value (as opposed to the user).
3147 AggLoadStoreRewriter(const DataLayout &DL) : DL(DL) {}
3149 /// Rewrite loads and stores through a pointer and all pointers derived from
3151 bool rewrite(Instruction &I) {
3152 DEBUG(dbgs() << " Rewriting FCA loads and stores...\n");
3154 bool Changed = false;
3155 while (!Queue.empty()) {
3156 U = Queue.pop_back_val();
3157 Changed |= visit(cast<Instruction>(U->getUser()));
3163 /// Enqueue all the users of the given instruction for further processing.
3164 /// This uses a set to de-duplicate users.
3165 void enqueueUsers(Instruction &I) {
3166 for (Use &U : I.uses())
3167 if (Visited.insert(U.getUser()).second)
3168 Queue.push_back(&U);
3171 // Conservative default is to not rewrite anything.
3172 bool visitInstruction(Instruction &I) { return false; }
3174 /// \brief Generic recursive split emission class.
3175 template <typename Derived> class OpSplitter {
3177 /// The builder used to form new instructions.
3179 /// The indices which to be used with insert- or extractvalue to select the
3180 /// appropriate value within the aggregate.
3181 SmallVector<unsigned, 4> Indices;
3182 /// The indices to a GEP instruction which will move Ptr to the correct slot
3183 /// within the aggregate.
3184 SmallVector<Value *, 4> GEPIndices;
3185 /// The base pointer of the original op, used as a base for GEPing the
3186 /// split operations.
3189 /// Initialize the splitter with an insertion point, Ptr and start with a
3190 /// single zero GEP index.
3191 OpSplitter(Instruction *InsertionPoint, Value *Ptr)
3192 : IRB(InsertionPoint), GEPIndices(1, IRB.getInt32(0)), Ptr(Ptr) {}
3195 /// \brief Generic recursive split emission routine.
3197 /// This method recursively splits an aggregate op (load or store) into
3198 /// scalar or vector ops. It splits recursively until it hits a single value
3199 /// and emits that single value operation via the template argument.
3201 /// The logic of this routine relies on GEPs and insertvalue and
3202 /// extractvalue all operating with the same fundamental index list, merely
3203 /// formatted differently (GEPs need actual values).
3205 /// \param Ty The type being split recursively into smaller ops.
3206 /// \param Agg The aggregate value being built up or stored, depending on
3207 /// whether this is splitting a load or a store respectively.
3208 void emitSplitOps(Type *Ty, Value *&Agg, const Twine &Name) {
3209 if (Ty->isSingleValueType())
3210 return static_cast<Derived *>(this)->emitFunc(Ty, Agg, Name);
3212 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
3213 unsigned OldSize = Indices.size();
3215 for (unsigned Idx = 0, Size = ATy->getNumElements(); Idx != Size;
3217 assert(Indices.size() == OldSize && "Did not return to the old size");
3218 Indices.push_back(Idx);
3219 GEPIndices.push_back(IRB.getInt32(Idx));
3220 emitSplitOps(ATy->getElementType(), Agg, Name + "." + Twine(Idx));
3221 GEPIndices.pop_back();
3227 if (StructType *STy = dyn_cast<StructType>(Ty)) {
3228 unsigned OldSize = Indices.size();
3230 for (unsigned Idx = 0, Size = STy->getNumElements(); Idx != Size;
3232 assert(Indices.size() == OldSize && "Did not return to the old size");
3233 Indices.push_back(Idx);
3234 GEPIndices.push_back(IRB.getInt32(Idx));
3235 emitSplitOps(STy->getElementType(Idx), Agg, Name + "." + Twine(Idx));
3236 GEPIndices.pop_back();
3242 llvm_unreachable("Only arrays and structs are aggregate loadable types");
3246 struct LoadOpSplitter : public OpSplitter<LoadOpSplitter> {
3247 LoadOpSplitter(Instruction *InsertionPoint, Value *Ptr)
3248 : OpSplitter<LoadOpSplitter>(InsertionPoint, Ptr) {}
3250 /// Emit a leaf load of a single value. This is called at the leaves of the
3251 /// recursive emission to actually load values.
3252 void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) {
3253 assert(Ty->isSingleValueType());
3254 // Load the single value and insert it using the indices.
3256 IRB.CreateInBoundsGEP(nullptr, Ptr, GEPIndices, Name + ".gep");
3257 Value *Load = IRB.CreateLoad(GEP, Name + ".load");
3258 Agg = IRB.CreateInsertValue(Agg, Load, Indices, Name + ".insert");
3259 DEBUG(dbgs() << " to: " << *Load << "\n");
3263 bool visitLoadInst(LoadInst &LI) {
3264 assert(LI.getPointerOperand() == *U);
3265 if (!LI.isSimple() || LI.getType()->isSingleValueType())
3268 // We have an aggregate being loaded, split it apart.
3269 DEBUG(dbgs() << " original: " << LI << "\n");
3270 LoadOpSplitter Splitter(&LI, *U);
3271 Value *V = UndefValue::get(LI.getType());
3272 Splitter.emitSplitOps(LI.getType(), V, LI.getName() + ".fca");
3273 LI.replaceAllUsesWith(V);
3274 LI.eraseFromParent();
3278 struct StoreOpSplitter : public OpSplitter<StoreOpSplitter> {
3279 StoreOpSplitter(Instruction *InsertionPoint, Value *Ptr)
3280 : OpSplitter<StoreOpSplitter>(InsertionPoint, Ptr) {}
3282 /// Emit a leaf store of a single value. This is called at the leaves of the
3283 /// recursive emission to actually produce stores.
3284 void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) {
3285 assert(Ty->isSingleValueType());
3286 // Extract the single value and store it using the indices.
3287 Value *Store = IRB.CreateStore(
3288 IRB.CreateExtractValue(Agg, Indices, Name + ".extract"),
3289 IRB.CreateInBoundsGEP(nullptr, Ptr, GEPIndices, Name + ".gep"));
3291 DEBUG(dbgs() << " to: " << *Store << "\n");
3295 bool visitStoreInst(StoreInst &SI) {
3296 if (!SI.isSimple() || SI.getPointerOperand() != *U)
3298 Value *V = SI.getValueOperand();
3299 if (V->getType()->isSingleValueType())
3302 // We have an aggregate being stored, split it apart.
3303 DEBUG(dbgs() << " original: " << SI << "\n");
3304 StoreOpSplitter Splitter(&SI, *U);
3305 Splitter.emitSplitOps(V->getType(), V, V->getName() + ".fca");
3306 SI.eraseFromParent();
3310 bool visitBitCastInst(BitCastInst &BC) {
3315 bool visitGetElementPtrInst(GetElementPtrInst &GEPI) {
3320 bool visitPHINode(PHINode &PN) {
3325 bool visitSelectInst(SelectInst &SI) {
3332 /// \brief Strip aggregate type wrapping.
3334 /// This removes no-op aggregate types wrapping an underlying type. It will
3335 /// strip as many layers of types as it can without changing either the type
3336 /// size or the allocated size.
3337 static Type *stripAggregateTypeWrapping(const DataLayout &DL, Type *Ty) {
3338 if (Ty->isSingleValueType())
3341 uint64_t AllocSize = DL.getTypeAllocSize(Ty);
3342 uint64_t TypeSize = DL.getTypeSizeInBits(Ty);
3345 if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) {
3346 InnerTy = ArrTy->getElementType();
3347 } else if (StructType *STy = dyn_cast<StructType>(Ty)) {
3348 const StructLayout *SL = DL.getStructLayout(STy);
3349 unsigned Index = SL->getElementContainingOffset(0);
3350 InnerTy = STy->getElementType(Index);
3355 if (AllocSize > DL.getTypeAllocSize(InnerTy) ||
3356 TypeSize > DL.getTypeSizeInBits(InnerTy))
3359 return stripAggregateTypeWrapping(DL, InnerTy);
3362 /// \brief Try to find a partition of the aggregate type passed in for a given
3363 /// offset and size.
3365 /// This recurses through the aggregate type and tries to compute a subtype
3366 /// based on the offset and size. When the offset and size span a sub-section
3367 /// of an array, it will even compute a new array type for that sub-section,
3368 /// and the same for structs.
3370 /// Note that this routine is very strict and tries to find a partition of the
3371 /// type which produces the *exact* right offset and size. It is not forgiving
3372 /// when the size or offset cause either end of type-based partition to be off.
3373 /// Also, this is a best-effort routine. It is reasonable to give up and not
3374 /// return a type if necessary.
3375 static Type *getTypePartition(const DataLayout &DL, Type *Ty, uint64_t Offset,
3377 if (Offset == 0 && DL.getTypeAllocSize(Ty) == Size)
3378 return stripAggregateTypeWrapping(DL, Ty);
3379 if (Offset > DL.getTypeAllocSize(Ty) ||
3380 (DL.getTypeAllocSize(Ty) - Offset) < Size)
3383 if (SequentialType *SeqTy = dyn_cast<SequentialType>(Ty)) {
3384 // We can't partition pointers...
3385 if (SeqTy->isPointerTy())
3388 Type *ElementTy = SeqTy->getElementType();
3389 uint64_t ElementSize = DL.getTypeAllocSize(ElementTy);
3390 uint64_t NumSkippedElements = Offset / ElementSize;
3391 if (ArrayType *ArrTy = dyn_cast<ArrayType>(SeqTy)) {
3392 if (NumSkippedElements >= ArrTy->getNumElements())
3394 } else if (VectorType *VecTy = dyn_cast<VectorType>(SeqTy)) {
3395 if (NumSkippedElements >= VecTy->getNumElements())
3398 Offset -= NumSkippedElements * ElementSize;
3400 // First check if we need to recurse.
3401 if (Offset > 0 || Size < ElementSize) {
3402 // Bail if the partition ends in a different array element.
3403 if ((Offset + Size) > ElementSize)
3405 // Recurse through the element type trying to peel off offset bytes.
3406 return getTypePartition(DL, ElementTy, Offset, Size);
3408 assert(Offset == 0);
3410 if (Size == ElementSize)
3411 return stripAggregateTypeWrapping(DL, ElementTy);
3412 assert(Size > ElementSize);
3413 uint64_t NumElements = Size / ElementSize;
3414 if (NumElements * ElementSize != Size)
3416 return ArrayType::get(ElementTy, NumElements);
3419 StructType *STy = dyn_cast<StructType>(Ty);
3423 const StructLayout *SL = DL.getStructLayout(STy);
3424 if (Offset >= SL->getSizeInBytes())
3426 uint64_t EndOffset = Offset + Size;
3427 if (EndOffset > SL->getSizeInBytes())
3430 unsigned Index = SL->getElementContainingOffset(Offset);
3431 Offset -= SL->getElementOffset(Index);
3433 Type *ElementTy = STy->getElementType(Index);
3434 uint64_t ElementSize = DL.getTypeAllocSize(ElementTy);
3435 if (Offset >= ElementSize)
3436 return nullptr; // The offset points into alignment padding.
3438 // See if any partition must be contained by the element.
3439 if (Offset > 0 || Size < ElementSize) {
3440 if ((Offset + Size) > ElementSize)
3442 return getTypePartition(DL, ElementTy, Offset, Size);
3444 assert(Offset == 0);
3446 if (Size == ElementSize)
3447 return stripAggregateTypeWrapping(DL, ElementTy);
3449 StructType::element_iterator EI = STy->element_begin() + Index,
3450 EE = STy->element_end();
3451 if (EndOffset < SL->getSizeInBytes()) {
3452 unsigned EndIndex = SL->getElementContainingOffset(EndOffset);
3453 if (Index == EndIndex)
3454 return nullptr; // Within a single element and its padding.
3456 // Don't try to form "natural" types if the elements don't line up with the
3458 // FIXME: We could potentially recurse down through the last element in the
3459 // sub-struct to find a natural end point.
3460 if (SL->getElementOffset(EndIndex) != EndOffset)
3463 assert(Index < EndIndex);
3464 EE = STy->element_begin() + EndIndex;
3467 // Try to build up a sub-structure.
3469 StructType::get(STy->getContext(), makeArrayRef(EI, EE), STy->isPacked());
3470 const StructLayout *SubSL = DL.getStructLayout(SubTy);
3471 if (Size != SubSL->getSizeInBytes())
3472 return nullptr; // The sub-struct doesn't have quite the size needed.
3477 /// \brief Pre-split loads and stores to simplify rewriting.
3479 /// We want to break up the splittable load+store pairs as much as
3480 /// possible. This is important to do as a preprocessing step, as once we
3481 /// start rewriting the accesses to partitions of the alloca we lose the
3482 /// necessary information to correctly split apart paired loads and stores
3483 /// which both point into this alloca. The case to consider is something like
3486 /// %a = alloca [12 x i8]
3487 /// %gep1 = getelementptr [12 x i8]* %a, i32 0, i32 0
3488 /// %gep2 = getelementptr [12 x i8]* %a, i32 0, i32 4
3489 /// %gep3 = getelementptr [12 x i8]* %a, i32 0, i32 8
3490 /// %iptr1 = bitcast i8* %gep1 to i64*
3491 /// %iptr2 = bitcast i8* %gep2 to i64*
3492 /// %fptr1 = bitcast i8* %gep1 to float*
3493 /// %fptr2 = bitcast i8* %gep2 to float*
3494 /// %fptr3 = bitcast i8* %gep3 to float*
3495 /// store float 0.0, float* %fptr1
3496 /// store float 1.0, float* %fptr2
3497 /// %v = load i64* %iptr1
3498 /// store i64 %v, i64* %iptr2
3499 /// %f1 = load float* %fptr2
3500 /// %f2 = load float* %fptr3
3502 /// Here we want to form 3 partitions of the alloca, each 4 bytes large, and
3503 /// promote everything so we recover the 2 SSA values that should have been
3504 /// there all along.
3506 /// \returns true if any changes are made.
3507 bool SROA::presplitLoadsAndStores(AllocaInst &AI, AllocaSlices &AS) {
3508 DEBUG(dbgs() << "Pre-splitting loads and stores\n");
3510 // Track the loads and stores which are candidates for pre-splitting here, in
3511 // the order they first appear during the partition scan. These give stable
3512 // iteration order and a basis for tracking which loads and stores we
3514 SmallVector<LoadInst *, 4> Loads;
3515 SmallVector<StoreInst *, 4> Stores;
3517 // We need to accumulate the splits required of each load or store where we
3518 // can find them via a direct lookup. This is important to cross-check loads
3519 // and stores against each other. We also track the slice so that we can kill
3520 // all the slices that end up split.
3521 struct SplitOffsets {
3523 std::vector<uint64_t> Splits;
3525 SmallDenseMap<Instruction *, SplitOffsets, 8> SplitOffsetsMap;
3527 // Track loads out of this alloca which cannot, for any reason, be pre-split.
3528 // This is important as we also cannot pre-split stores of those loads!
3529 // FIXME: This is all pretty gross. It means that we can be more aggressive
3530 // in pre-splitting when the load feeding the store happens to come from
3531 // a separate alloca. Put another way, the effectiveness of SROA would be
3532 // decreased by a frontend which just concatenated all of its local allocas
3533 // into one big flat alloca. But defeating such patterns is exactly the job
3534 // SROA is tasked with! Sadly, to not have this discrepancy we would have
3535 // change store pre-splitting to actually force pre-splitting of the load
3536 // that feeds it *and all stores*. That makes pre-splitting much harder, but
3537 // maybe it would make it more principled?
3538 SmallPtrSet<LoadInst *, 8> UnsplittableLoads;
3540 DEBUG(dbgs() << " Searching for candidate loads and stores\n");
3541 for (auto &P : AS.partitions()) {
3542 for (Slice &S : P) {
3543 Instruction *I = cast<Instruction>(S.getUse()->getUser());
3544 if (!S.isSplittable() ||S.endOffset() <= P.endOffset()) {
3545 // If this was a load we have to track that it can't participate in any
3547 if (auto *LI = dyn_cast<LoadInst>(I))
3548 UnsplittableLoads.insert(LI);
3551 assert(P.endOffset() > S.beginOffset() &&
3552 "Empty or backwards partition!");
3554 // Determine if this is a pre-splittable slice.
3555 if (auto *LI = dyn_cast<LoadInst>(I)) {
3556 assert(!LI->isVolatile() && "Cannot split volatile loads!");
3558 // The load must be used exclusively to store into other pointers for
3559 // us to be able to arbitrarily pre-split it. The stores must also be
3560 // simple to avoid changing semantics.
3561 auto IsLoadSimplyStored = [](LoadInst *LI) {
3562 for (User *LU : LI->users()) {
3563 auto *SI = dyn_cast<StoreInst>(LU);
3564 if (!SI || !SI->isSimple())
3569 if (!IsLoadSimplyStored(LI)) {
3570 UnsplittableLoads.insert(LI);
3574 Loads.push_back(LI);
3575 } else if (auto *SI = dyn_cast<StoreInst>(S.getUse()->getUser())) {
3577 S.getUse() != &SI->getOperandUse(SI->getPointerOperandIndex()))
3579 auto *StoredLoad = dyn_cast<LoadInst>(SI->getValueOperand());
3580 if (!StoredLoad || !StoredLoad->isSimple())
3582 assert(!SI->isVolatile() && "Cannot split volatile stores!");
3584 Stores.push_back(SI);
3586 // Other uses cannot be pre-split.
3590 // Record the initial split.
3591 DEBUG(dbgs() << " Candidate: " << *I << "\n");
3592 auto &Offsets = SplitOffsetsMap[I];
3593 assert(Offsets.Splits.empty() &&
3594 "Should not have splits the first time we see an instruction!");
3596 Offsets.Splits.push_back(P.endOffset() - S.beginOffset());
3599 // Now scan the already split slices, and add a split for any of them which
3600 // we're going to pre-split.
3601 for (Slice *S : P.splitSliceTails()) {
3602 auto SplitOffsetsMapI =
3603 SplitOffsetsMap.find(cast<Instruction>(S->getUse()->getUser()));
3604 if (SplitOffsetsMapI == SplitOffsetsMap.end())
3606 auto &Offsets = SplitOffsetsMapI->second;
3608 assert(Offsets.S == S && "Found a mismatched slice!");
3609 assert(!Offsets.Splits.empty() &&
3610 "Cannot have an empty set of splits on the second partition!");
3611 assert(Offsets.Splits.back() ==
3612 P.beginOffset() - Offsets.S->beginOffset() &&
3613 "Previous split does not end where this one begins!");
3615 // Record each split. The last partition's end isn't needed as the size
3616 // of the slice dictates that.
3617 if (S->endOffset() > P.endOffset())
3618 Offsets.Splits.push_back(P.endOffset() - Offsets.S->beginOffset());
3622 // We may have split loads where some of their stores are split stores. For
3623 // such loads and stores, we can only pre-split them if their splits exactly
3624 // match relative to their starting offset. We have to verify this prior to
3627 std::remove_if(Stores.begin(), Stores.end(),
3628 [&UnsplittableLoads, &SplitOffsetsMap](StoreInst *SI) {
3629 // Lookup the load we are storing in our map of split
3631 auto *LI = cast<LoadInst>(SI->getValueOperand());
3632 // If it was completely unsplittable, then we're done,
3633 // and this store can't be pre-split.
3634 if (UnsplittableLoads.count(LI))
3637 auto LoadOffsetsI = SplitOffsetsMap.find(LI);
3638 if (LoadOffsetsI == SplitOffsetsMap.end())
3639 return false; // Unrelated loads are definitely safe.
3640 auto &LoadOffsets = LoadOffsetsI->second;
3642 // Now lookup the store's offsets.
3643 auto &StoreOffsets = SplitOffsetsMap[SI];
3645 // If the relative offsets of each split in the load and
3646 // store match exactly, then we can split them and we
3647 // don't need to remove them here.
3648 if (LoadOffsets.Splits == StoreOffsets.Splits)
3652 << " Mismatched splits for load and store:\n"
3653 << " " << *LI << "\n"
3654 << " " << *SI << "\n");
3656 // We've found a store and load that we need to split
3657 // with mismatched relative splits. Just give up on them
3658 // and remove both instructions from our list of
3660 UnsplittableLoads.insert(LI);
3664 // Now we have to go *back* through all te stores, because a later store may
3665 // have caused an earlier store's load to become unsplittable and if it is
3666 // unsplittable for the later store, then we can't rely on it being split in
3667 // the earlier store either.
3668 Stores.erase(std::remove_if(Stores.begin(), Stores.end(),
3669 [&UnsplittableLoads](StoreInst *SI) {
3671 cast<LoadInst>(SI->getValueOperand());
3672 return UnsplittableLoads.count(LI);
3675 // Once we've established all the loads that can't be split for some reason,
3676 // filter any that made it into our list out.
3677 Loads.erase(std::remove_if(Loads.begin(), Loads.end(),
3678 [&UnsplittableLoads](LoadInst *LI) {
3679 return UnsplittableLoads.count(LI);
3684 // If no loads or stores are left, there is no pre-splitting to be done for
3686 if (Loads.empty() && Stores.empty())
3689 // From here on, we can't fail and will be building new accesses, so rig up
3691 IRBuilderTy IRB(&AI);
3693 // Collect the new slices which we will merge into the alloca slices.
3694 SmallVector<Slice, 4> NewSlices;
3696 // Track any allocas we end up splitting loads and stores for so we iterate
3698 SmallPtrSet<AllocaInst *, 4> ResplitPromotableAllocas;
3700 // At this point, we have collected all of the loads and stores we can
3701 // pre-split, and the specific splits needed for them. We actually do the
3702 // splitting in a specific order in order to handle when one of the loads in
3703 // the value operand to one of the stores.
3705 // First, we rewrite all of the split loads, and just accumulate each split
3706 // load in a parallel structure. We also build the slices for them and append
3707 // them to the alloca slices.
3708 SmallDenseMap<LoadInst *, std::vector<LoadInst *>, 1> SplitLoadsMap;
3709 std::vector<LoadInst *> SplitLoads;
3710 const DataLayout &DL = AI.getModule()->getDataLayout();
3711 for (LoadInst *LI : Loads) {
3714 IntegerType *Ty = cast<IntegerType>(LI->getType());
3715 uint64_t LoadSize = Ty->getBitWidth() / 8;
3716 assert(LoadSize > 0 && "Cannot have a zero-sized integer load!");
3718 auto &Offsets = SplitOffsetsMap[LI];
3719 assert(LoadSize == Offsets.S->endOffset() - Offsets.S->beginOffset() &&
3720 "Slice size should always match load size exactly!");
3721 uint64_t BaseOffset = Offsets.S->beginOffset();
3722 assert(BaseOffset + LoadSize > BaseOffset &&
3723 "Cannot represent alloca access size using 64-bit integers!");
3725 Instruction *BasePtr = cast<Instruction>(LI->getPointerOperand());
3726 IRB.SetInsertPoint(BasicBlock::iterator(LI));
3728 DEBUG(dbgs() << " Splitting load: " << *LI << "\n");
3730 uint64_t PartOffset = 0, PartSize = Offsets.Splits.front();
3731 int Idx = 0, Size = Offsets.Splits.size();
3733 auto *PartTy = Type::getIntNTy(Ty->getContext(), PartSize * 8);
3734 auto *PartPtrTy = PartTy->getPointerTo(LI->getPointerAddressSpace());
3735 LoadInst *PLoad = IRB.CreateAlignedLoad(
3736 getAdjustedPtr(IRB, DL, BasePtr,
3737 APInt(DL.getPointerSizeInBits(), PartOffset),
3738 PartPtrTy, BasePtr->getName() + "."),
3739 getAdjustedAlignment(LI, PartOffset, DL), /*IsVolatile*/ false,
3742 // Append this load onto the list of split loads so we can find it later
3743 // to rewrite the stores.
3744 SplitLoads.push_back(PLoad);
3746 // Now build a new slice for the alloca.
3747 NewSlices.push_back(
3748 Slice(BaseOffset + PartOffset, BaseOffset + PartOffset + PartSize,
3749 &PLoad->getOperandUse(PLoad->getPointerOperandIndex()),
3750 /*IsSplittable*/ false));
3751 DEBUG(dbgs() << " new slice [" << NewSlices.back().beginOffset()
3752 << ", " << NewSlices.back().endOffset() << "): " << *PLoad
3755 // See if we've handled all the splits.
3759 // Setup the next partition.
3760 PartOffset = Offsets.Splits[Idx];
3762 PartSize = (Idx < Size ? Offsets.Splits[Idx] : LoadSize) - PartOffset;
3765 // Now that we have the split loads, do the slow walk over all uses of the
3766 // load and rewrite them as split stores, or save the split loads to use
3767 // below if the store is going to be split there anyways.
3768 bool DeferredStores = false;
3769 for (User *LU : LI->users()) {
3770 StoreInst *SI = cast<StoreInst>(LU);
3771 if (!Stores.empty() && SplitOffsetsMap.count(SI)) {
3772 DeferredStores = true;
3773 DEBUG(dbgs() << " Deferred splitting of store: " << *SI << "\n");
3777 Value *StoreBasePtr = SI->getPointerOperand();
3778 IRB.SetInsertPoint(BasicBlock::iterator(SI));
3780 DEBUG(dbgs() << " Splitting store of load: " << *SI << "\n");
3782 for (int Idx = 0, Size = SplitLoads.size(); Idx < Size; ++Idx) {
3783 LoadInst *PLoad = SplitLoads[Idx];
3784 uint64_t PartOffset = Idx == 0 ? 0 : Offsets.Splits[Idx - 1];
3786 PLoad->getType()->getPointerTo(SI->getPointerAddressSpace());
3788 StoreInst *PStore = IRB.CreateAlignedStore(
3789 PLoad, getAdjustedPtr(IRB, DL, StoreBasePtr,
3790 APInt(DL.getPointerSizeInBits(), PartOffset),
3791 PartPtrTy, StoreBasePtr->getName() + "."),
3792 getAdjustedAlignment(SI, PartOffset, DL), /*IsVolatile*/ false);
3794 DEBUG(dbgs() << " +" << PartOffset << ":" << *PStore << "\n");
3797 // We want to immediately iterate on any allocas impacted by splitting
3798 // this store, and we have to track any promotable alloca (indicated by
3799 // a direct store) as needing to be resplit because it is no longer
3801 if (AllocaInst *OtherAI = dyn_cast<AllocaInst>(StoreBasePtr)) {
3802 ResplitPromotableAllocas.insert(OtherAI);
3803 Worklist.insert(OtherAI);
3804 } else if (AllocaInst *OtherAI = dyn_cast<AllocaInst>(
3805 StoreBasePtr->stripInBoundsOffsets())) {
3806 Worklist.insert(OtherAI);
3809 // Mark the original store as dead.
3810 DeadInsts.insert(SI);
3813 // Save the split loads if there are deferred stores among the users.
3815 SplitLoadsMap.insert(std::make_pair(LI, std::move(SplitLoads)));
3817 // Mark the original load as dead and kill the original slice.
3818 DeadInsts.insert(LI);
3822 // Second, we rewrite all of the split stores. At this point, we know that
3823 // all loads from this alloca have been split already. For stores of such
3824 // loads, we can simply look up the pre-existing split loads. For stores of
3825 // other loads, we split those loads first and then write split stores of
3827 for (StoreInst *SI : Stores) {
3828 auto *LI = cast<LoadInst>(SI->getValueOperand());
3829 IntegerType *Ty = cast<IntegerType>(LI->getType());
3830 uint64_t StoreSize = Ty->getBitWidth() / 8;
3831 assert(StoreSize > 0 && "Cannot have a zero-sized integer store!");
3833 auto &Offsets = SplitOffsetsMap[SI];
3834 assert(StoreSize == Offsets.S->endOffset() - Offsets.S->beginOffset() &&
3835 "Slice size should always match load size exactly!");
3836 uint64_t BaseOffset = Offsets.S->beginOffset();
3837 assert(BaseOffset + StoreSize > BaseOffset &&
3838 "Cannot represent alloca access size using 64-bit integers!");
3840 Value *LoadBasePtr = LI->getPointerOperand();
3841 Instruction *StoreBasePtr = cast<Instruction>(SI->getPointerOperand());
3843 DEBUG(dbgs() << " Splitting store: " << *SI << "\n");
3845 // Check whether we have an already split load.
3846 auto SplitLoadsMapI = SplitLoadsMap.find(LI);
3847 std::vector<LoadInst *> *SplitLoads = nullptr;
3848 if (SplitLoadsMapI != SplitLoadsMap.end()) {
3849 SplitLoads = &SplitLoadsMapI->second;
3850 assert(SplitLoads->size() == Offsets.Splits.size() + 1 &&
3851 "Too few split loads for the number of splits in the store!");
3853 DEBUG(dbgs() << " of load: " << *LI << "\n");
3856 uint64_t PartOffset = 0, PartSize = Offsets.Splits.front();
3857 int Idx = 0, Size = Offsets.Splits.size();
3859 auto *PartTy = Type::getIntNTy(Ty->getContext(), PartSize * 8);
3860 auto *PartPtrTy = PartTy->getPointerTo(SI->getPointerAddressSpace());
3862 // Either lookup a split load or create one.
3865 PLoad = (*SplitLoads)[Idx];
3867 IRB.SetInsertPoint(BasicBlock::iterator(LI));
3868 PLoad = IRB.CreateAlignedLoad(
3869 getAdjustedPtr(IRB, DL, LoadBasePtr,
3870 APInt(DL.getPointerSizeInBits(), PartOffset),
3871 PartPtrTy, LoadBasePtr->getName() + "."),
3872 getAdjustedAlignment(LI, PartOffset, DL), /*IsVolatile*/ false,
3876 // And store this partition.
3877 IRB.SetInsertPoint(BasicBlock::iterator(SI));
3878 StoreInst *PStore = IRB.CreateAlignedStore(
3879 PLoad, getAdjustedPtr(IRB, DL, StoreBasePtr,
3880 APInt(DL.getPointerSizeInBits(), PartOffset),
3881 PartPtrTy, StoreBasePtr->getName() + "."),
3882 getAdjustedAlignment(SI, PartOffset, DL), /*IsVolatile*/ false);
3884 // Now build a new slice for the alloca.
3885 NewSlices.push_back(
3886 Slice(BaseOffset + PartOffset, BaseOffset + PartOffset + PartSize,
3887 &PStore->getOperandUse(PStore->getPointerOperandIndex()),
3888 /*IsSplittable*/ false));
3889 DEBUG(dbgs() << " new slice [" << NewSlices.back().beginOffset()
3890 << ", " << NewSlices.back().endOffset() << "): " << *PStore
3893 DEBUG(dbgs() << " of split load: " << *PLoad << "\n");
3896 // See if we've finished all the splits.
3900 // Setup the next partition.
3901 PartOffset = Offsets.Splits[Idx];
3903 PartSize = (Idx < Size ? Offsets.Splits[Idx] : StoreSize) - PartOffset;
3906 // We want to immediately iterate on any allocas impacted by splitting
3907 // this load, which is only relevant if it isn't a load of this alloca and
3908 // thus we didn't already split the loads above. We also have to keep track
3909 // of any promotable allocas we split loads on as they can no longer be
3912 if (AllocaInst *OtherAI = dyn_cast<AllocaInst>(LoadBasePtr)) {
3913 assert(OtherAI != &AI && "We can't re-split our own alloca!");
3914 ResplitPromotableAllocas.insert(OtherAI);
3915 Worklist.insert(OtherAI);
3916 } else if (AllocaInst *OtherAI = dyn_cast<AllocaInst>(
3917 LoadBasePtr->stripInBoundsOffsets())) {
3918 assert(OtherAI != &AI && "We can't re-split our own alloca!");
3919 Worklist.insert(OtherAI);
3923 // Mark the original store as dead now that we've split it up and kill its
3924 // slice. Note that we leave the original load in place unless this store
3925 // was its ownly use. It may in turn be split up if it is an alloca load
3926 // for some other alloca, but it may be a normal load. This may introduce
3927 // redundant loads, but where those can be merged the rest of the optimizer
3928 // should handle the merging, and this uncovers SSA splits which is more
3929 // important. In practice, the original loads will almost always be fully
3930 // split and removed eventually, and the splits will be merged by any
3931 // trivial CSE, including instcombine.
3932 if (LI->hasOneUse()) {
3933 assert(*LI->user_begin() == SI && "Single use isn't this store!");
3934 DeadInsts.insert(LI);
3936 DeadInsts.insert(SI);
3940 // Remove the killed slices that have ben pre-split.
3941 AS.erase(std::remove_if(AS.begin(), AS.end(), [](const Slice &S) {
3945 // Insert our new slices. This will sort and merge them into the sorted
3947 AS.insert(NewSlices);
3949 DEBUG(dbgs() << " Pre-split slices:\n");
3951 for (auto I = AS.begin(), E = AS.end(); I != E; ++I)
3952 DEBUG(AS.print(dbgs(), I, " "));
3955 // Finally, don't try to promote any allocas that new require re-splitting.
3956 // They have already been added to the worklist above.
3957 PromotableAllocas.erase(
3959 PromotableAllocas.begin(), PromotableAllocas.end(),
3960 [&](AllocaInst *AI) { return ResplitPromotableAllocas.count(AI); }),
3961 PromotableAllocas.end());
3966 /// \brief Rewrite an alloca partition's users.
3968 /// This routine drives both of the rewriting goals of the SROA pass. It tries
3969 /// to rewrite uses of an alloca partition to be conducive for SSA value
3970 /// promotion. If the partition needs a new, more refined alloca, this will
3971 /// build that new alloca, preserving as much type information as possible, and
3972 /// rewrite the uses of the old alloca to point at the new one and have the
3973 /// appropriate new offsets. It also evaluates how successful the rewrite was
3974 /// at enabling promotion and if it was successful queues the alloca to be
3976 AllocaInst *SROA::rewritePartition(AllocaInst &AI, AllocaSlices &AS,
3977 AllocaSlices::Partition &P) {
3978 // Try to compute a friendly type for this partition of the alloca. This
3979 // won't always succeed, in which case we fall back to a legal integer type
3980 // or an i8 array of an appropriate size.
3981 Type *SliceTy = nullptr;
3982 const DataLayout &DL = AI.getModule()->getDataLayout();
3983 if (Type *CommonUseTy = findCommonType(P.begin(), P.end(), P.endOffset()))
3984 if (DL.getTypeAllocSize(CommonUseTy) >= P.size())
3985 SliceTy = CommonUseTy;
3987 if (Type *TypePartitionTy = getTypePartition(DL, AI.getAllocatedType(),
3988 P.beginOffset(), P.size()))
3989 SliceTy = TypePartitionTy;
3990 if ((!SliceTy || (SliceTy->isArrayTy() &&
3991 SliceTy->getArrayElementType()->isIntegerTy())) &&
3992 DL.isLegalInteger(P.size() * 8))
3993 SliceTy = Type::getIntNTy(*C, P.size() * 8);
3995 SliceTy = ArrayType::get(Type::getInt8Ty(*C), P.size());
3996 assert(DL.getTypeAllocSize(SliceTy) >= P.size());
3998 bool IsIntegerPromotable = isIntegerWideningViable(P, SliceTy, DL);
4001 IsIntegerPromotable ? nullptr : isVectorPromotionViable(P, DL);
4005 // Check for the case where we're going to rewrite to a new alloca of the
4006 // exact same type as the original, and with the same access offsets. In that
4007 // case, re-use the existing alloca, but still run through the rewriter to
4008 // perform phi and select speculation.
4010 if (SliceTy == AI.getAllocatedType()) {
4011 assert(P.beginOffset() == 0 &&
4012 "Non-zero begin offset but same alloca type");
4014 // FIXME: We should be able to bail at this point with "nothing changed".
4015 // FIXME: We might want to defer PHI speculation until after here.
4016 // FIXME: return nullptr;
4018 unsigned Alignment = AI.getAlignment();
4020 // The minimum alignment which users can rely on when the explicit
4021 // alignment is omitted or zero is that required by the ABI for this
4023 Alignment = DL.getABITypeAlignment(AI.getAllocatedType());
4025 Alignment = MinAlign(Alignment, P.beginOffset());
4026 // If we will get at least this much alignment from the type alone, leave
4027 // the alloca's alignment unconstrained.
4028 if (Alignment <= DL.getABITypeAlignment(SliceTy))
4030 NewAI = new AllocaInst(
4031 SliceTy, nullptr, Alignment,
4032 AI.getName() + ".sroa." + Twine(P.begin() - AS.begin()), &AI);
4036 DEBUG(dbgs() << "Rewriting alloca partition "
4037 << "[" << P.beginOffset() << "," << P.endOffset()
4038 << ") to: " << *NewAI << "\n");
4040 // Track the high watermark on the worklist as it is only relevant for
4041 // promoted allocas. We will reset it to this point if the alloca is not in
4042 // fact scheduled for promotion.
4043 unsigned PPWOldSize = PostPromotionWorklist.size();
4044 unsigned NumUses = 0;
4045 SmallPtrSet<PHINode *, 8> PHIUsers;
4046 SmallPtrSet<SelectInst *, 8> SelectUsers;
4048 AllocaSliceRewriter Rewriter(DL, AS, *this, AI, *NewAI, P.beginOffset(),
4049 P.endOffset(), IsIntegerPromotable, VecTy,
4050 PHIUsers, SelectUsers);
4051 bool Promotable = true;
4052 for (Slice *S : P.splitSliceTails()) {
4053 Promotable &= Rewriter.visit(S);
4056 for (Slice &S : P) {
4057 Promotable &= Rewriter.visit(&S);
4061 NumAllocaPartitionUses += NumUses;
4062 MaxUsesPerAllocaPartition =
4063 std::max<unsigned>(NumUses, MaxUsesPerAllocaPartition);
4065 // Now that we've processed all the slices in the new partition, check if any
4066 // PHIs or Selects would block promotion.
4067 for (SmallPtrSetImpl<PHINode *>::iterator I = PHIUsers.begin(),
4070 if (!isSafePHIToSpeculate(**I)) {
4073 SelectUsers.clear();
4076 for (SmallPtrSetImpl<SelectInst *>::iterator I = SelectUsers.begin(),
4077 E = SelectUsers.end();
4079 if (!isSafeSelectToSpeculate(**I)) {
4082 SelectUsers.clear();
4087 if (PHIUsers.empty() && SelectUsers.empty()) {
4088 // Promote the alloca.
4089 PromotableAllocas.push_back(NewAI);
4091 // If we have either PHIs or Selects to speculate, add them to those
4092 // worklists and re-queue the new alloca so that we promote in on the
4094 for (PHINode *PHIUser : PHIUsers)
4095 SpeculatablePHIs.insert(PHIUser);
4096 for (SelectInst *SelectUser : SelectUsers)
4097 SpeculatableSelects.insert(SelectUser);
4098 Worklist.insert(NewAI);
4101 // If we can't promote the alloca, iterate on it to check for new
4102 // refinements exposed by splitting the current alloca. Don't iterate on an
4103 // alloca which didn't actually change and didn't get promoted.
4105 Worklist.insert(NewAI);
4107 // Drop any post-promotion work items if promotion didn't happen.
4108 while (PostPromotionWorklist.size() > PPWOldSize)
4109 PostPromotionWorklist.pop_back();
4115 /// \brief Walks the slices of an alloca and form partitions based on them,
4116 /// rewriting each of their uses.
4117 bool SROA::splitAlloca(AllocaInst &AI, AllocaSlices &AS) {
4118 if (AS.begin() == AS.end())
4121 unsigned NumPartitions = 0;
4122 bool Changed = false;
4123 const DataLayout &DL = AI.getModule()->getDataLayout();
4125 // First try to pre-split loads and stores.
4126 Changed |= presplitLoadsAndStores(AI, AS);
4128 // Now that we have identified any pre-splitting opportunities, mark any
4129 // splittable (non-whole-alloca) loads and stores as unsplittable. If we fail
4130 // to split these during pre-splitting, we want to force them to be
4131 // rewritten into a partition.
4132 bool IsSorted = true;
4133 for (Slice &S : AS) {
4134 if (!S.isSplittable())
4136 // FIXME: We currently leave whole-alloca splittable loads and stores. This
4137 // used to be the only splittable loads and stores and we need to be
4138 // confident that the above handling of splittable loads and stores is
4139 // completely sufficient before we forcibly disable the remaining handling.
4140 if (S.beginOffset() == 0 &&
4141 S.endOffset() >= DL.getTypeAllocSize(AI.getAllocatedType()))
4143 if (isa<LoadInst>(S.getUse()->getUser()) ||
4144 isa<StoreInst>(S.getUse()->getUser())) {
4145 S.makeUnsplittable();
4150 std::sort(AS.begin(), AS.end());
4152 /// \brief Describes the allocas introduced by rewritePartition
4153 /// in order to migrate the debug info.
4158 Piece(AllocaInst *AI, uint64_t O, uint64_t S)
4159 : Alloca(AI), Offset(O), Size(S) {}
4161 SmallVector<Piece, 4> Pieces;
4163 // Rewrite each partition.
4164 for (auto &P : AS.partitions()) {
4165 if (AllocaInst *NewAI = rewritePartition(AI, AS, P)) {
4168 uint64_t SizeOfByte = 8;
4169 uint64_t AllocaSize = DL.getTypeSizeInBits(NewAI->getAllocatedType());
4170 // Don't include any padding.
4171 uint64_t Size = std::min(AllocaSize, P.size() * SizeOfByte);
4172 Pieces.push_back(Piece(NewAI, P.beginOffset() * SizeOfByte, Size));
4178 NumAllocaPartitions += NumPartitions;
4179 MaxPartitionsPerAlloca =
4180 std::max<unsigned>(NumPartitions, MaxPartitionsPerAlloca);
4182 // Migrate debug information from the old alloca to the new alloca(s)
4183 // and the individial partitions.
4184 if (DbgDeclareInst *DbgDecl = FindAllocaDbgDeclare(&AI)) {
4185 auto *Var = DbgDecl->getVariable();
4186 auto *Expr = DbgDecl->getExpression();
4187 DIBuilder DIB(*AI.getParent()->getParent()->getParent(),
4188 /*AllowUnresolved*/ false);
4189 bool IsSplit = Pieces.size() > 1;
4190 for (auto Piece : Pieces) {
4191 // Create a piece expression describing the new partition or reuse AI's
4192 // expression if there is only one partition.
4193 auto *PieceExpr = Expr;
4194 if (IsSplit || Expr->isBitPiece()) {
4195 // If this alloca is already a scalar replacement of a larger aggregate,
4196 // Piece.Offset describes the offset inside the scalar.
4197 uint64_t Offset = Expr->isBitPiece() ? Expr->getBitPieceOffset() : 0;
4198 uint64_t Start = Offset + Piece.Offset;
4199 uint64_t Size = Piece.Size;
4200 if (Expr->isBitPiece()) {
4201 uint64_t AbsEnd = Expr->getBitPieceOffset() + Expr->getBitPieceSize();
4202 if (Start >= AbsEnd)
4203 // No need to describe a SROAed padding.
4205 Size = std::min(Size, AbsEnd - Start);
4207 PieceExpr = DIB.createBitPieceExpression(Start, Size);
4210 // Remove any existing dbg.declare intrinsic describing the same alloca.
4211 if (DbgDeclareInst *OldDDI = FindAllocaDbgDeclare(Piece.Alloca))
4212 OldDDI->eraseFromParent();
4214 DIB.insertDeclare(Piece.Alloca, Var, PieceExpr, DbgDecl->getDebugLoc(),
4221 /// \brief Clobber a use with undef, deleting the used value if it becomes dead.
4222 void SROA::clobberUse(Use &U) {
4224 // Replace the use with an undef value.
4225 U = UndefValue::get(OldV->getType());
4227 // Check for this making an instruction dead. We have to garbage collect
4228 // all the dead instructions to ensure the uses of any alloca end up being
4230 if (Instruction *OldI = dyn_cast<Instruction>(OldV))
4231 if (isInstructionTriviallyDead(OldI)) {
4232 DeadInsts.insert(OldI);
4236 /// \brief Analyze an alloca for SROA.
4238 /// This analyzes the alloca to ensure we can reason about it, builds
4239 /// the slices of the alloca, and then hands it off to be split and
4240 /// rewritten as needed.
4241 bool SROA::runOnAlloca(AllocaInst &AI) {
4242 DEBUG(dbgs() << "SROA alloca: " << AI << "\n");
4243 ++NumAllocasAnalyzed;
4245 // Special case dead allocas, as they're trivial.
4246 if (AI.use_empty()) {
4247 AI.eraseFromParent();
4250 const DataLayout &DL = AI.getModule()->getDataLayout();
4252 // Skip alloca forms that this analysis can't handle.
4253 if (AI.isArrayAllocation() || !AI.getAllocatedType()->isSized() ||
4254 DL.getTypeAllocSize(AI.getAllocatedType()) == 0)
4257 bool Changed = false;
4259 // First, split any FCA loads and stores touching this alloca to promote
4260 // better splitting and promotion opportunities.
4261 AggLoadStoreRewriter AggRewriter(DL);
4262 Changed |= AggRewriter.rewrite(AI);
4264 // Build the slices using a recursive instruction-visiting builder.
4265 AllocaSlices AS(DL, AI);
4266 DEBUG(AS.print(dbgs()));
4270 // Delete all the dead users of this alloca before splitting and rewriting it.
4271 for (Instruction *DeadUser : AS.getDeadUsers()) {
4272 // Free up everything used by this instruction.
4273 for (Use &DeadOp : DeadUser->operands())
4276 // Now replace the uses of this instruction.
4277 DeadUser->replaceAllUsesWith(UndefValue::get(DeadUser->getType()));
4279 // And mark it for deletion.
4280 DeadInsts.insert(DeadUser);
4283 for (Use *DeadOp : AS.getDeadOperands()) {
4284 clobberUse(*DeadOp);
4288 // No slices to split. Leave the dead alloca for a later pass to clean up.
4289 if (AS.begin() == AS.end())
4292 Changed |= splitAlloca(AI, AS);
4294 DEBUG(dbgs() << " Speculating PHIs\n");
4295 while (!SpeculatablePHIs.empty())
4296 speculatePHINodeLoads(*SpeculatablePHIs.pop_back_val());
4298 DEBUG(dbgs() << " Speculating Selects\n");
4299 while (!SpeculatableSelects.empty())
4300 speculateSelectInstLoads(*SpeculatableSelects.pop_back_val());
4305 /// \brief Delete the dead instructions accumulated in this run.
4307 /// Recursively deletes the dead instructions we've accumulated. This is done
4308 /// at the very end to maximize locality of the recursive delete and to
4309 /// minimize the problems of invalidated instruction pointers as such pointers
4310 /// are used heavily in the intermediate stages of the algorithm.
4312 /// We also record the alloca instructions deleted here so that they aren't
4313 /// subsequently handed to mem2reg to promote.
4314 void SROA::deleteDeadInstructions(
4315 SmallPtrSetImpl<AllocaInst *> &DeletedAllocas) {
4316 while (!DeadInsts.empty()) {
4317 Instruction *I = DeadInsts.pop_back_val();
4318 DEBUG(dbgs() << "Deleting dead instruction: " << *I << "\n");
4320 I->replaceAllUsesWith(UndefValue::get(I->getType()));
4322 for (Use &Operand : I->operands())
4323 if (Instruction *U = dyn_cast<Instruction>(Operand)) {
4324 // Zero out the operand and see if it becomes trivially dead.
4326 if (isInstructionTriviallyDead(U))
4327 DeadInsts.insert(U);
4330 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
4331 DeletedAllocas.insert(AI);
4332 if (DbgDeclareInst *DbgDecl = FindAllocaDbgDeclare(AI))
4333 DbgDecl->eraseFromParent();
4337 I->eraseFromParent();
4341 static void enqueueUsersInWorklist(Instruction &I,
4342 SmallVectorImpl<Instruction *> &Worklist,
4343 SmallPtrSetImpl<Instruction *> &Visited) {
4344 for (User *U : I.users())
4345 if (Visited.insert(cast<Instruction>(U)).second)
4346 Worklist.push_back(cast<Instruction>(U));
4349 /// \brief Promote the allocas, using the best available technique.
4351 /// This attempts to promote whatever allocas have been identified as viable in
4352 /// the PromotableAllocas list. If that list is empty, there is nothing to do.
4353 /// If there is a domtree available, we attempt to promote using the full power
4354 /// of mem2reg. Otherwise, we build and use the AllocaPromoter above which is
4355 /// based on the SSAUpdater utilities. This function returns whether any
4356 /// promotion occurred.
4357 bool SROA::promoteAllocas(Function &F) {
4358 if (PromotableAllocas.empty())
4361 NumPromoted += PromotableAllocas.size();
4363 if (DT && !ForceSSAUpdater) {
4364 DEBUG(dbgs() << "Promoting allocas with mem2reg...\n");
4365 PromoteMemToReg(PromotableAllocas, *DT, nullptr, AC);
4366 PromotableAllocas.clear();
4370 DEBUG(dbgs() << "Promoting allocas with SSAUpdater...\n");
4372 DIBuilder DIB(*F.getParent(), /*AllowUnresolved*/ false);
4373 SmallVector<Instruction *, 64> Insts;
4375 // We need a worklist to walk the uses of each alloca.
4376 SmallVector<Instruction *, 8> Worklist;
4377 SmallPtrSet<Instruction *, 8> Visited;
4378 SmallVector<Instruction *, 32> DeadInsts;
4380 for (unsigned Idx = 0, Size = PromotableAllocas.size(); Idx != Size; ++Idx) {
4381 AllocaInst *AI = PromotableAllocas[Idx];
4386 enqueueUsersInWorklist(*AI, Worklist, Visited);
4388 while (!Worklist.empty()) {
4389 Instruction *I = Worklist.pop_back_val();
4391 // FIXME: Currently the SSAUpdater infrastructure doesn't reason about
4392 // lifetime intrinsics and so we strip them (and the bitcasts+GEPs
4393 // leading to them) here. Eventually it should use them to optimize the
4394 // scalar values produced.
4395 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
4396 assert(II->getIntrinsicID() == Intrinsic::lifetime_start ||
4397 II->getIntrinsicID() == Intrinsic::lifetime_end);
4398 II->eraseFromParent();
4402 // Push the loads and stores we find onto the list. SROA will already
4403 // have validated that all loads and stores are viable candidates for
4405 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
4406 assert(LI->getType() == AI->getAllocatedType());
4407 Insts.push_back(LI);
4410 if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
4411 assert(SI->getValueOperand()->getType() == AI->getAllocatedType());
4412 Insts.push_back(SI);
4416 // For everything else, we know that only no-op bitcasts and GEPs will
4417 // make it this far, just recurse through them and recall them for later
4419 DeadInsts.push_back(I);
4420 enqueueUsersInWorklist(*I, Worklist, Visited);
4422 AllocaPromoter(Insts, SSA, *AI, DIB).run(Insts);
4423 while (!DeadInsts.empty())
4424 DeadInsts.pop_back_val()->eraseFromParent();
4425 AI->eraseFromParent();
4428 PromotableAllocas.clear();
4432 bool SROA::runOnFunction(Function &F) {
4433 if (skipOptnoneFunction(F))
4436 DEBUG(dbgs() << "SROA function: " << F.getName() << "\n");
4437 C = &F.getContext();
4438 DominatorTreeWrapperPass *DTWP =
4439 getAnalysisIfAvailable<DominatorTreeWrapperPass>();
4440 DT = DTWP ? &DTWP->getDomTree() : nullptr;
4441 AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
4443 BasicBlock &EntryBB = F.getEntryBlock();
4444 for (BasicBlock::iterator I = EntryBB.begin(), E = std::prev(EntryBB.end());
4446 if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
4447 Worklist.insert(AI);
4450 bool Changed = false;
4451 // A set of deleted alloca instruction pointers which should be removed from
4452 // the list of promotable allocas.
4453 SmallPtrSet<AllocaInst *, 4> DeletedAllocas;
4456 while (!Worklist.empty()) {
4457 Changed |= runOnAlloca(*Worklist.pop_back_val());
4458 deleteDeadInstructions(DeletedAllocas);
4460 // Remove the deleted allocas from various lists so that we don't try to
4461 // continue processing them.
4462 if (!DeletedAllocas.empty()) {
4463 auto IsInSet = [&](AllocaInst *AI) { return DeletedAllocas.count(AI); };
4464 Worklist.remove_if(IsInSet);
4465 PostPromotionWorklist.remove_if(IsInSet);
4466 PromotableAllocas.erase(std::remove_if(PromotableAllocas.begin(),
4467 PromotableAllocas.end(),
4469 PromotableAllocas.end());
4470 DeletedAllocas.clear();
4474 Changed |= promoteAllocas(F);
4476 Worklist = PostPromotionWorklist;
4477 PostPromotionWorklist.clear();
4478 } while (!Worklist.empty());
4483 void SROA::getAnalysisUsage(AnalysisUsage &AU) const {
4484 AU.addRequired<AssumptionCacheTracker>();
4485 if (RequiresDomTree)
4486 AU.addRequired<DominatorTreeWrapperPass>();
4487 AU.setPreservesCFG();