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 #define DEBUG_TYPE "sroa"
27 #include "llvm/Transforms/Scalar.h"
28 #include "llvm/ADT/STLExtras.h"
29 #include "llvm/ADT/SetVector.h"
30 #include "llvm/ADT/SmallVector.h"
31 #include "llvm/ADT/Statistic.h"
32 #include "llvm/Analysis/Dominators.h"
33 #include "llvm/Analysis/Loads.h"
34 #include "llvm/Analysis/PtrUseVisitor.h"
35 #include "llvm/Analysis/ValueTracking.h"
36 #include "llvm/DIBuilder.h"
37 #include "llvm/DebugInfo.h"
38 #include "llvm/IR/Constants.h"
39 #include "llvm/IR/DataLayout.h"
40 #include "llvm/IR/DerivedTypes.h"
41 #include "llvm/IR/Function.h"
42 #include "llvm/IR/IRBuilder.h"
43 #include "llvm/IR/Instructions.h"
44 #include "llvm/IR/IntrinsicInst.h"
45 #include "llvm/IR/LLVMContext.h"
46 #include "llvm/IR/Operator.h"
47 #include "llvm/InstVisitor.h"
48 #include "llvm/Pass.h"
49 #include "llvm/Support/CommandLine.h"
50 #include "llvm/Support/Debug.h"
51 #include "llvm/Support/ErrorHandling.h"
52 #include "llvm/Support/MathExtras.h"
53 #include "llvm/Support/raw_ostream.h"
54 #include "llvm/Transforms/Utils/Local.h"
55 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
56 #include "llvm/Transforms/Utils/SSAUpdater.h"
59 STATISTIC(NumAllocasAnalyzed, "Number of allocas analyzed for replacement");
60 STATISTIC(NumAllocaPartitions, "Number of alloca partitions formed");
61 STATISTIC(MaxPartitionsPerAlloca, "Maximum number of partitions");
62 STATISTIC(NumAllocaPartitionUses, "Number of alloca partition uses found");
63 STATISTIC(MaxPartitionUsesPerAlloca, "Maximum number of partition uses");
64 STATISTIC(NumNewAllocas, "Number of new, smaller allocas introduced");
65 STATISTIC(NumPromoted, "Number of allocas promoted to SSA values");
66 STATISTIC(NumLoadsSpeculated, "Number of loads speculated to allow promotion");
67 STATISTIC(NumDeleted, "Number of instructions deleted");
68 STATISTIC(NumVectorized, "Number of vectorized aggregates");
70 /// Hidden option to force the pass to not use DomTree and mem2reg, instead
71 /// forming SSA values through the SSAUpdater infrastructure.
73 ForceSSAUpdater("force-ssa-updater", cl::init(false), cl::Hidden);
76 /// \brief Provide a typedef for IRBuilder that drops names in release builds.
78 typedef llvm::IRBuilderTy IRBuilderTy;
80 typedef llvm::IRBuilder<false> IRBuilderTy;
85 /// \brief A common base class for representing a half-open byte range.
87 /// \brief The beginning offset of the range.
90 /// \brief The ending offset, not included in the range.
93 ByteRange() : BeginOffset(), EndOffset() {}
94 ByteRange(uint64_t BeginOffset, uint64_t EndOffset)
95 : BeginOffset(BeginOffset), EndOffset(EndOffset) {}
97 /// \brief Support for ordering ranges.
99 /// This provides an ordering over ranges such that start offsets are
100 /// always increasing, and within equal start offsets, the end offsets are
101 /// decreasing. Thus the spanning range comes first in a cluster with the
102 /// same start position.
103 bool operator<(const ByteRange &RHS) const {
104 if (BeginOffset < RHS.BeginOffset) return true;
105 if (BeginOffset > RHS.BeginOffset) return false;
106 if (EndOffset > RHS.EndOffset) return true;
110 /// \brief Support comparison with a single offset to allow binary searches.
111 friend bool operator<(const ByteRange &LHS, uint64_t RHSOffset) {
112 return LHS.BeginOffset < RHSOffset;
115 friend LLVM_ATTRIBUTE_UNUSED bool operator<(uint64_t LHSOffset,
116 const ByteRange &RHS) {
117 return LHSOffset < RHS.BeginOffset;
120 bool operator==(const ByteRange &RHS) const {
121 return BeginOffset == RHS.BeginOffset && EndOffset == RHS.EndOffset;
123 bool operator!=(const ByteRange &RHS) const { return !operator==(RHS); }
126 /// \brief A partition of an alloca.
128 /// This structure represents a contiguous partition of the alloca. These are
129 /// formed by examining the uses of the alloca. During formation, they may
130 /// overlap but once an AllocaPartitioning is built, the Partitions within it
131 /// are all disjoint.
132 struct Partition : public ByteRange {
133 /// \brief Whether this partition is splittable into smaller partitions.
135 /// We flag partitions as splittable when they are formed entirely due to
136 /// accesses by trivially splittable operations such as memset and memcpy.
139 /// \brief Test whether a partition has been marked as dead.
140 bool isDead() const {
141 if (BeginOffset == UINT64_MAX) {
142 assert(EndOffset == UINT64_MAX);
148 /// \brief Kill a partition.
149 /// This is accomplished by setting both its beginning and end offset to
150 /// the maximum possible value.
152 assert(!isDead() && "He's Dead, Jim!");
153 BeginOffset = EndOffset = UINT64_MAX;
156 Partition() : ByteRange(), IsSplittable() {}
157 Partition(uint64_t BeginOffset, uint64_t EndOffset, bool IsSplittable)
158 : ByteRange(BeginOffset, EndOffset), IsSplittable(IsSplittable) {}
161 /// \brief A particular use of a partition of the alloca.
163 /// This structure is used to associate uses of a partition with it. They
164 /// mark the range of bytes which are referenced by a particular instruction,
165 /// and includes a handle to the user itself and the pointer value in use.
166 /// The bounds of these uses are determined by intersecting the bounds of the
167 /// memory use itself with a particular partition. As a consequence there is
168 /// intentionally overlap between various uses of the same partition.
169 class PartitionUse : public ByteRange {
170 /// \brief Combined storage for both the Use* and split state.
171 PointerIntPair<Use*, 1, bool> UsePtrAndIsSplit;
174 PartitionUse() : ByteRange(), UsePtrAndIsSplit() {}
175 PartitionUse(uint64_t BeginOffset, uint64_t EndOffset, Use *U,
177 : ByteRange(BeginOffset, EndOffset), UsePtrAndIsSplit(U, IsSplit) {}
179 /// \brief The use in question. Provides access to both user and used value.
181 /// Note that this may be null if the partition use is *dead*, that is, it
182 /// should be ignored.
183 Use *getUse() const { return UsePtrAndIsSplit.getPointer(); }
185 /// \brief Set the use for this partition use range.
186 void setUse(Use *U) { UsePtrAndIsSplit.setPointer(U); }
188 /// \brief Whether this use is split across multiple partitions.
189 bool isSplit() const { return UsePtrAndIsSplit.getInt(); }
194 template <> struct isPodLike<Partition> : llvm::true_type {};
195 template <> struct isPodLike<PartitionUse> : llvm::true_type {};
199 /// \brief Alloca partitioning representation.
201 /// This class represents a partitioning of an alloca into slices, and
202 /// information about the nature of uses of each slice of the alloca. The goal
203 /// is that this information is sufficient to decide if and how to split the
204 /// alloca apart and replace slices with scalars. It is also intended that this
205 /// structure can capture the relevant information needed both to decide about
206 /// and to enact these transformations.
207 class AllocaPartitioning {
209 /// \brief Construct a partitioning of a particular alloca.
211 /// Construction does most of the work for partitioning the alloca. This
212 /// performs the necessary walks of users and builds a partitioning from it.
213 AllocaPartitioning(const DataLayout &TD, AllocaInst &AI);
215 /// \brief Test whether a pointer to the allocation escapes our analysis.
217 /// If this is true, the partitioning is never fully built and should be
219 bool isEscaped() const { return PointerEscapingInstr; }
221 /// \brief Support for iterating over the partitions.
223 typedef SmallVectorImpl<Partition>::iterator iterator;
224 iterator begin() { return Partitions.begin(); }
225 iterator end() { return Partitions.end(); }
227 typedef SmallVectorImpl<Partition>::const_iterator const_iterator;
228 const_iterator begin() const { return Partitions.begin(); }
229 const_iterator end() const { return Partitions.end(); }
232 /// \brief Support for iterating over and manipulating a particular
233 /// partition's uses.
235 /// The iteration support provided for uses is more limited, but also
236 /// includes some manipulation routines to support rewriting the uses of
237 /// partitions during SROA.
239 typedef SmallVectorImpl<PartitionUse>::iterator use_iterator;
240 use_iterator use_begin(unsigned Idx) { return Uses[Idx].begin(); }
241 use_iterator use_begin(const_iterator I) { return Uses[I - begin()].begin(); }
242 use_iterator use_end(unsigned Idx) { return Uses[Idx].end(); }
243 use_iterator use_end(const_iterator I) { return Uses[I - begin()].end(); }
245 typedef SmallVectorImpl<PartitionUse>::const_iterator const_use_iterator;
246 const_use_iterator use_begin(unsigned Idx) const { return Uses[Idx].begin(); }
247 const_use_iterator use_begin(const_iterator I) const {
248 return Uses[I - begin()].begin();
250 const_use_iterator use_end(unsigned Idx) const { return Uses[Idx].end(); }
251 const_use_iterator use_end(const_iterator I) const {
252 return Uses[I - begin()].end();
255 unsigned use_size(unsigned Idx) const { return Uses[Idx].size(); }
256 unsigned use_size(const_iterator I) const { return Uses[I - begin()].size(); }
257 const PartitionUse &getUse(unsigned PIdx, unsigned UIdx) const {
258 return Uses[PIdx][UIdx];
260 const PartitionUse &getUse(const_iterator I, unsigned UIdx) const {
261 return Uses[I - begin()][UIdx];
264 void use_push_back(unsigned Idx, const PartitionUse &PU) {
265 Uses[Idx].push_back(PU);
267 void use_push_back(const_iterator I, const PartitionUse &PU) {
268 Uses[I - begin()].push_back(PU);
272 /// \brief Allow iterating the dead users for this alloca.
274 /// These are instructions which will never actually use the alloca as they
275 /// are outside the allocated range. They are safe to replace with undef and
278 typedef SmallVectorImpl<Instruction *>::const_iterator dead_user_iterator;
279 dead_user_iterator dead_user_begin() const { return DeadUsers.begin(); }
280 dead_user_iterator dead_user_end() const { return DeadUsers.end(); }
283 /// \brief Allow iterating the dead expressions referring to this alloca.
285 /// These are operands which have cannot actually be used to refer to the
286 /// alloca as they are outside its range and the user doesn't correct for
287 /// that. These mostly consist of PHI node inputs and the like which we just
288 /// need to replace with undef.
290 typedef SmallVectorImpl<Use *>::const_iterator dead_op_iterator;
291 dead_op_iterator dead_op_begin() const { return DeadOperands.begin(); }
292 dead_op_iterator dead_op_end() const { return DeadOperands.end(); }
295 /// \brief MemTransferInst auxiliary data.
296 /// This struct provides some auxiliary data about memory transfer
297 /// intrinsics such as memcpy and memmove. These intrinsics can use two
298 /// different ranges within the same alloca, and provide other challenges to
299 /// correctly represent. We stash extra data to help us untangle this
300 /// after the partitioning is complete.
301 struct MemTransferOffsets {
302 /// The destination begin and end offsets when the destination is within
303 /// this alloca. If the end offset is zero the destination is not within
305 uint64_t DestBegin, DestEnd;
307 /// The source begin and end offsets when the source is within this alloca.
308 /// If the end offset is zero, the source is not within this alloca.
309 uint64_t SourceBegin, SourceEnd;
311 /// Flag for whether an alloca is splittable.
314 MemTransferOffsets getMemTransferOffsets(MemTransferInst &II) const {
315 return MemTransferInstData.lookup(&II);
318 /// \brief Map from a PHI or select operand back to a partition.
320 /// When manipulating PHI nodes or selects, they can use more than one
321 /// partition of an alloca. We store a special mapping to allow finding the
322 /// partition referenced by each of these operands, if any.
323 iterator findPartitionForPHIOrSelectOperand(Use *U) {
324 SmallDenseMap<Use *, std::pair<unsigned, unsigned> >::const_iterator MapIt
325 = PHIOrSelectOpMap.find(U);
326 if (MapIt == PHIOrSelectOpMap.end())
329 return begin() + MapIt->second.first;
332 /// \brief Map from a PHI or select operand back to the specific use of
335 /// Similar to mapping these operands back to the partitions, this maps
336 /// directly to the use structure of that partition.
337 use_iterator findPartitionUseForPHIOrSelectOperand(Use *U) {
338 SmallDenseMap<Use *, std::pair<unsigned, unsigned> >::const_iterator MapIt
339 = PHIOrSelectOpMap.find(U);
340 assert(MapIt != PHIOrSelectOpMap.end());
341 return Uses[MapIt->second.first].begin() + MapIt->second.second;
344 /// \brief Compute a common type among the uses of a particular partition.
346 /// This routines walks all of the uses of a particular partition and tries
347 /// to find a common type between them. Untyped operations such as memset and
348 /// memcpy are ignored.
349 Type *getCommonType(iterator I) const;
351 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
352 void print(raw_ostream &OS, const_iterator I, StringRef Indent = " ") const;
353 void printUsers(raw_ostream &OS, const_iterator I,
354 StringRef Indent = " ") const;
355 void print(raw_ostream &OS) const;
356 void LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED dump(const_iterator I) const;
357 void LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED dump() const;
361 template <typename DerivedT, typename RetT = void> class BuilderBase;
362 class PartitionBuilder;
363 friend class AllocaPartitioning::PartitionBuilder;
365 friend class AllocaPartitioning::UseBuilder;
367 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
368 /// \brief Handle to alloca instruction to simplify method interfaces.
372 /// \brief The instruction responsible for this alloca having no partitioning.
374 /// When an instruction (potentially) escapes the pointer to the alloca, we
375 /// store a pointer to that here and abort trying to partition the alloca.
376 /// This will be null if the alloca is partitioned successfully.
377 Instruction *PointerEscapingInstr;
379 /// \brief The partitions of the alloca.
381 /// We store a vector of the partitions over the alloca here. This vector is
382 /// sorted by increasing begin offset, and then by decreasing end offset. See
383 /// the Partition inner class for more details. Initially (during
384 /// construction) there are overlaps, but we form a disjoint sequence of
385 /// partitions while finishing construction and a fully constructed object is
386 /// expected to always have this as a disjoint space.
387 SmallVector<Partition, 8> Partitions;
389 /// \brief The uses of the partitions.
391 /// This is essentially a mapping from each partition to a list of uses of
392 /// that partition. The mapping is done with a Uses vector that has the exact
393 /// same number of entries as the partition vector. Each entry is itself
394 /// a vector of the uses.
395 SmallVector<SmallVector<PartitionUse, 2>, 8> Uses;
397 /// \brief Instructions which will become dead if we rewrite the alloca.
399 /// Note that these are not separated by partition. This is because we expect
400 /// a partitioned alloca to be completely rewritten or not rewritten at all.
401 /// If rewritten, all these instructions can simply be removed and replaced
402 /// with undef as they come from outside of the allocated space.
403 SmallVector<Instruction *, 8> DeadUsers;
405 /// \brief Operands which will become dead if we rewrite the alloca.
407 /// These are operands that in their particular use can be replaced with
408 /// undef when we rewrite the alloca. These show up in out-of-bounds inputs
409 /// to PHI nodes and the like. They aren't entirely dead (there might be
410 /// a GEP back into the bounds using it elsewhere) and nor is the PHI, but we
411 /// want to swap this particular input for undef to simplify the use lists of
413 SmallVector<Use *, 8> DeadOperands;
415 /// \brief The underlying storage for auxiliary memcpy and memset info.
416 SmallDenseMap<MemTransferInst *, MemTransferOffsets, 4> MemTransferInstData;
418 /// \brief A side datastructure used when building up the partitions and uses.
420 /// This mapping is only really used during the initial building of the
421 /// partitioning so that we can retain information about PHI and select nodes
423 SmallDenseMap<Instruction *, std::pair<uint64_t, bool> > PHIOrSelectSizes;
425 /// \brief Auxiliary information for particular PHI or select operands.
426 SmallDenseMap<Use *, std::pair<unsigned, unsigned>, 4> PHIOrSelectOpMap;
428 /// \brief A utility routine called from the constructor.
430 /// This does what it says on the tin. It is the key of the alloca partition
431 /// splitting and merging. After it is called we have the desired disjoint
432 /// collection of partitions.
433 void splitAndMergePartitions();
437 static Value *foldSelectInst(SelectInst &SI) {
438 // If the condition being selected on is a constant or the same value is
439 // being selected between, fold the select. Yes this does (rarely) happen
441 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI.getCondition()))
442 return SI.getOperand(1+CI->isZero());
443 if (SI.getOperand(1) == SI.getOperand(2))
444 return SI.getOperand(1);
449 /// \brief Builder for the alloca partitioning.
451 /// This class builds an alloca partitioning by recursively visiting the uses
452 /// of an alloca and splitting the partitions for each load and store at each
454 class AllocaPartitioning::PartitionBuilder
455 : public PtrUseVisitor<PartitionBuilder> {
456 friend class PtrUseVisitor<PartitionBuilder>;
457 friend class InstVisitor<PartitionBuilder>;
458 typedef PtrUseVisitor<PartitionBuilder> Base;
460 const uint64_t AllocSize;
461 AllocaPartitioning &P;
463 SmallDenseMap<Instruction *, unsigned> MemTransferPartitionMap;
466 PartitionBuilder(const DataLayout &DL, AllocaInst &AI, AllocaPartitioning &P)
467 : PtrUseVisitor<PartitionBuilder>(DL),
468 AllocSize(DL.getTypeAllocSize(AI.getAllocatedType())),
472 void insertUse(Instruction &I, const APInt &Offset, uint64_t Size,
473 bool IsSplittable = false) {
474 // Completely skip uses which have a zero size or start either before or
475 // past the end of the allocation.
476 if (Size == 0 || Offset.isNegative() || Offset.uge(AllocSize)) {
477 DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte use @" << Offset
478 << " which has zero size or starts outside of the "
479 << AllocSize << " byte alloca:\n"
480 << " alloca: " << P.AI << "\n"
481 << " use: " << I << "\n");
485 uint64_t BeginOffset = Offset.getZExtValue();
486 uint64_t EndOffset = BeginOffset + Size;
488 // Clamp the end offset to the end of the allocation. Note that this is
489 // formulated to handle even the case where "BeginOffset + Size" overflows.
490 // This may appear superficially to be something we could ignore entirely,
491 // but that is not so! There may be widened loads or PHI-node uses where
492 // some instructions are dead but not others. We can't completely ignore
493 // them, and so have to record at least the information here.
494 assert(AllocSize >= BeginOffset); // Established above.
495 if (Size > AllocSize - BeginOffset) {
496 DEBUG(dbgs() << "WARNING: Clamping a " << Size << " byte use @" << Offset
497 << " to remain within the " << AllocSize << " byte alloca:\n"
498 << " alloca: " << P.AI << "\n"
499 << " use: " << I << "\n");
500 EndOffset = AllocSize;
503 Partition New(BeginOffset, EndOffset, IsSplittable);
504 P.Partitions.push_back(New);
507 void handleLoadOrStore(Type *Ty, Instruction &I, const APInt &Offset,
508 uint64_t Size, bool IsVolatile) {
509 // We allow splitting of loads and stores where the type is an integer type
510 // and cover the entire alloca. This prevents us from splitting over
512 // FIXME: In the great blue eventually, we should eagerly split all integer
513 // loads and stores, and then have a separate step that merges adjacent
514 // alloca partitions into a single partition suitable for integer widening.
515 // Or we should skip the merge step and rely on GVN and other passes to
516 // merge adjacent loads and stores that survive mem2reg.
518 Ty->isIntegerTy() && !IsVolatile && Offset == 0 && Size >= AllocSize;
520 insertUse(I, Offset, Size, IsSplittable);
523 void visitLoadInst(LoadInst &LI) {
524 assert((!LI.isSimple() || LI.getType()->isSingleValueType()) &&
525 "All simple FCA loads should have been pre-split");
528 return PI.setAborted(&LI);
530 uint64_t Size = DL.getTypeStoreSize(LI.getType());
531 return handleLoadOrStore(LI.getType(), LI, Offset, Size, LI.isVolatile());
534 void visitStoreInst(StoreInst &SI) {
535 Value *ValOp = SI.getValueOperand();
537 return PI.setEscapedAndAborted(&SI);
539 return PI.setAborted(&SI);
541 uint64_t Size = DL.getTypeStoreSize(ValOp->getType());
543 // If this memory access can be shown to *statically* extend outside the
544 // bounds of of the allocation, it's behavior is undefined, so simply
545 // ignore it. Note that this is more strict than the generic clamping
546 // behavior of insertUse. We also try to handle cases which might run the
548 // FIXME: We should instead consider the pointer to have escaped if this
549 // function is being instrumented for addressing bugs or race conditions.
550 if (Offset.isNegative() || Size > AllocSize ||
551 Offset.ugt(AllocSize - Size)) {
552 DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte store @" << Offset
553 << " which extends past the end of the " << AllocSize
555 << " alloca: " << P.AI << "\n"
556 << " use: " << SI << "\n");
560 assert((!SI.isSimple() || ValOp->getType()->isSingleValueType()) &&
561 "All simple FCA stores should have been pre-split");
562 handleLoadOrStore(ValOp->getType(), SI, Offset, Size, SI.isVolatile());
566 void visitMemSetInst(MemSetInst &II) {
567 assert(II.getRawDest() == *U && "Pointer use is not the destination?");
568 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
569 if ((Length && Length->getValue() == 0) ||
570 (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize)))
571 // Zero-length mem transfer intrinsics can be ignored entirely.
575 return PI.setAborted(&II);
577 insertUse(II, Offset,
578 Length ? Length->getLimitedValue()
579 : AllocSize - Offset.getLimitedValue(),
583 void visitMemTransferInst(MemTransferInst &II) {
584 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
585 if ((Length && Length->getValue() == 0) ||
586 (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize)))
587 // Zero-length mem transfer intrinsics can be ignored entirely.
591 return PI.setAborted(&II);
593 uint64_t RawOffset = Offset.getLimitedValue();
594 uint64_t Size = Length ? Length->getLimitedValue()
595 : AllocSize - RawOffset;
597 MemTransferOffsets &Offsets = P.MemTransferInstData[&II];
599 // Only intrinsics with a constant length can be split.
600 Offsets.IsSplittable = Length;
602 if (*U == II.getRawDest()) {
603 Offsets.DestBegin = RawOffset;
604 Offsets.DestEnd = RawOffset + Size;
606 if (*U == II.getRawSource()) {
607 Offsets.SourceBegin = RawOffset;
608 Offsets.SourceEnd = RawOffset + Size;
611 // If we have set up end offsets for both the source and the destination,
612 // we have found both sides of this transfer pointing at the same alloca.
613 bool SeenBothEnds = Offsets.SourceEnd && Offsets.DestEnd;
614 if (SeenBothEnds && II.getRawDest() != II.getRawSource()) {
615 unsigned PrevIdx = MemTransferPartitionMap[&II];
617 // Check if the begin offsets match and this is a non-volatile transfer.
618 // In that case, we can completely elide the transfer.
619 if (!II.isVolatile() && Offsets.SourceBegin == Offsets.DestBegin) {
620 P.Partitions[PrevIdx].kill();
624 // Otherwise we have an offset transfer within the same alloca. We can't
626 P.Partitions[PrevIdx].IsSplittable = Offsets.IsSplittable = false;
627 } else if (SeenBothEnds) {
628 // Handle the case where this exact use provides both ends of the
630 assert(II.getRawDest() == II.getRawSource());
632 // For non-volatile transfers this is a no-op.
633 if (!II.isVolatile())
636 // Otherwise just suppress splitting.
637 Offsets.IsSplittable = false;
641 // Insert the use now that we've fixed up the splittable nature.
642 insertUse(II, Offset, Size, Offsets.IsSplittable);
644 // Setup the mapping from intrinsic to partition of we've not seen both
645 // ends of this transfer.
647 unsigned NewIdx = P.Partitions.size() - 1;
649 = MemTransferPartitionMap.insert(std::make_pair(&II, NewIdx)).second;
651 "Already have intrinsic in map but haven't seen both ends");
656 // Disable SRoA for any intrinsics except for lifetime invariants.
657 // FIXME: What about debug intrinsics? This matches old behavior, but
658 // doesn't make sense.
659 void visitIntrinsicInst(IntrinsicInst &II) {
661 return PI.setAborted(&II);
663 if (II.getIntrinsicID() == Intrinsic::lifetime_start ||
664 II.getIntrinsicID() == Intrinsic::lifetime_end) {
665 ConstantInt *Length = cast<ConstantInt>(II.getArgOperand(0));
666 uint64_t Size = std::min(AllocSize - Offset.getLimitedValue(),
667 Length->getLimitedValue());
668 insertUse(II, Offset, Size, true);
672 Base::visitIntrinsicInst(II);
675 Instruction *hasUnsafePHIOrSelectUse(Instruction *Root, uint64_t &Size) {
676 // We consider any PHI or select that results in a direct load or store of
677 // the same offset to be a viable use for partitioning purposes. These uses
678 // are considered unsplittable and the size is the maximum loaded or stored
680 SmallPtrSet<Instruction *, 4> Visited;
681 SmallVector<std::pair<Instruction *, Instruction *>, 4> Uses;
682 Visited.insert(Root);
683 Uses.push_back(std::make_pair(cast<Instruction>(*U), Root));
684 // If there are no loads or stores, the access is dead. We mark that as
685 // a size zero access.
688 Instruction *I, *UsedI;
689 llvm::tie(UsedI, I) = Uses.pop_back_val();
691 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
692 Size = std::max(Size, DL.getTypeStoreSize(LI->getType()));
695 if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
696 Value *Op = SI->getOperand(0);
699 Size = std::max(Size, DL.getTypeStoreSize(Op->getType()));
703 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
704 if (!GEP->hasAllZeroIndices())
706 } else if (!isa<BitCastInst>(I) && !isa<PHINode>(I) &&
707 !isa<SelectInst>(I)) {
711 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE;
713 if (Visited.insert(cast<Instruction>(*UI)))
714 Uses.push_back(std::make_pair(I, cast<Instruction>(*UI)));
715 } while (!Uses.empty());
720 void visitPHINode(PHINode &PN) {
724 return PI.setAborted(&PN);
726 // See if we already have computed info on this node.
727 std::pair<uint64_t, bool> &PHIInfo = P.PHIOrSelectSizes[&PN];
729 PHIInfo.second = true;
730 insertUse(PN, Offset, PHIInfo.first);
734 // Check for an unsafe use of the PHI node.
735 if (Instruction *UnsafeI = hasUnsafePHIOrSelectUse(&PN, PHIInfo.first))
736 return PI.setAborted(UnsafeI);
738 insertUse(PN, Offset, PHIInfo.first);
741 void visitSelectInst(SelectInst &SI) {
744 if (Value *Result = foldSelectInst(SI)) {
746 // If the result of the constant fold will be the pointer, recurse
747 // through the select as if we had RAUW'ed it.
753 return PI.setAborted(&SI);
755 // See if we already have computed info on this node.
756 std::pair<uint64_t, bool> &SelectInfo = P.PHIOrSelectSizes[&SI];
757 if (SelectInfo.first) {
758 SelectInfo.second = true;
759 insertUse(SI, Offset, SelectInfo.first);
763 // Check for an unsafe use of the PHI node.
764 if (Instruction *UnsafeI = hasUnsafePHIOrSelectUse(&SI, SelectInfo.first))
765 return PI.setAborted(UnsafeI);
767 insertUse(SI, Offset, SelectInfo.first);
770 /// \brief Disable SROA entirely if there are unhandled users of the alloca.
771 void visitInstruction(Instruction &I) {
776 /// \brief Use adder for the alloca partitioning.
778 /// This class adds the uses of an alloca to all of the partitions which they
779 /// use. For splittable partitions, this can end up doing essentially a linear
780 /// walk of the partitions, but the number of steps remains bounded by the
781 /// total result instruction size:
782 /// - The number of partitions is a result of the number unsplittable
783 /// instructions using the alloca.
784 /// - The number of users of each partition is at worst the total number of
785 /// splittable instructions using the alloca.
786 /// Thus we will produce N * M instructions in the end, where N are the number
787 /// of unsplittable uses and M are the number of splittable. This visitor does
788 /// the exact same number of updates to the partitioning.
790 /// In the more common case, this visitor will leverage the fact that the
791 /// partition space is pre-sorted, and do a logarithmic search for the
792 /// partition needed, making the total visit a classical ((N + M) * log(N))
793 /// complexity operation.
794 class AllocaPartitioning::UseBuilder : public PtrUseVisitor<UseBuilder> {
795 friend class PtrUseVisitor<UseBuilder>;
796 friend class InstVisitor<UseBuilder>;
797 typedef PtrUseVisitor<UseBuilder> Base;
799 const uint64_t AllocSize;
800 AllocaPartitioning &P;
802 /// \brief Set to de-duplicate dead instructions found in the use walk.
803 SmallPtrSet<Instruction *, 4> VisitedDeadInsts;
806 UseBuilder(const DataLayout &TD, AllocaInst &AI, AllocaPartitioning &P)
807 : PtrUseVisitor<UseBuilder>(TD),
808 AllocSize(TD.getTypeAllocSize(AI.getAllocatedType())),
812 void markAsDead(Instruction &I) {
813 if (VisitedDeadInsts.insert(&I))
814 P.DeadUsers.push_back(&I);
817 void insertUse(Instruction &User, const APInt &Offset, uint64_t Size) {
818 // If the use has a zero size or extends outside of the allocation, record
819 // it as a dead use for elimination later.
820 if (Size == 0 || Offset.isNegative() || Offset.uge(AllocSize))
821 return markAsDead(User);
823 uint64_t BeginOffset = Offset.getZExtValue();
824 uint64_t EndOffset = BeginOffset + Size;
826 // Clamp the end offset to the end of the allocation. Note that this is
827 // formulated to handle even the case where "BeginOffset + Size" overflows.
828 assert(AllocSize >= BeginOffset); // Established above.
829 if (Size > AllocSize - BeginOffset)
830 EndOffset = AllocSize;
832 // NB: This only works if we have zero overlapping partitions.
833 iterator I = std::lower_bound(P.begin(), P.end(), BeginOffset);
834 if (I != P.begin() && llvm::prior(I)->EndOffset > BeginOffset)
836 iterator E = P.end();
837 bool IsSplit = llvm::next(I) != E && llvm::next(I)->BeginOffset < EndOffset;
838 for (; I != E && I->BeginOffset < EndOffset; ++I) {
839 PartitionUse NewPU(std::max(I->BeginOffset, BeginOffset),
840 std::min(I->EndOffset, EndOffset), U, IsSplit);
841 P.use_push_back(I, NewPU);
842 if (isa<PHINode>(U->getUser()) || isa<SelectInst>(U->getUser()))
843 P.PHIOrSelectOpMap[U]
844 = std::make_pair(I - P.begin(), P.Uses[I - P.begin()].size() - 1);
848 void visitBitCastInst(BitCastInst &BC) {
850 return markAsDead(BC);
852 return Base::visitBitCastInst(BC);
855 void visitGetElementPtrInst(GetElementPtrInst &GEPI) {
856 if (GEPI.use_empty())
857 return markAsDead(GEPI);
859 return Base::visitGetElementPtrInst(GEPI);
862 void visitLoadInst(LoadInst &LI) {
863 assert(IsOffsetKnown);
864 uint64_t Size = DL.getTypeStoreSize(LI.getType());
865 insertUse(LI, Offset, Size);
868 void visitStoreInst(StoreInst &SI) {
869 assert(IsOffsetKnown);
870 uint64_t Size = DL.getTypeStoreSize(SI.getOperand(0)->getType());
872 // If this memory access can be shown to *statically* extend outside the
873 // bounds of of the allocation, it's behavior is undefined, so simply
874 // ignore it. Note that this is more strict than the generic clamping
875 // behavior of insertUse.
876 if (Offset.isNegative() || Size > AllocSize ||
877 Offset.ugt(AllocSize - Size))
878 return markAsDead(SI);
880 insertUse(SI, Offset, Size);
883 void visitMemSetInst(MemSetInst &II) {
884 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
885 if ((Length && Length->getValue() == 0) ||
886 (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize)))
887 return markAsDead(II);
889 assert(IsOffsetKnown);
890 insertUse(II, Offset, Length ? Length->getLimitedValue()
891 : AllocSize - Offset.getLimitedValue());
894 void visitMemTransferInst(MemTransferInst &II) {
895 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
896 if ((Length && Length->getValue() == 0) ||
897 (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize)))
898 return markAsDead(II);
900 assert(IsOffsetKnown);
901 uint64_t Size = Length ? Length->getLimitedValue()
902 : AllocSize - Offset.getLimitedValue();
904 MemTransferOffsets &Offsets = P.MemTransferInstData[&II];
905 if (!II.isVolatile() && Offsets.DestEnd && Offsets.SourceEnd &&
906 Offsets.DestBegin == Offsets.SourceBegin)
907 return markAsDead(II); // Skip identity transfers without side-effects.
909 insertUse(II, Offset, Size);
912 void visitIntrinsicInst(IntrinsicInst &II) {
913 assert(IsOffsetKnown);
914 assert(II.getIntrinsicID() == Intrinsic::lifetime_start ||
915 II.getIntrinsicID() == Intrinsic::lifetime_end);
917 ConstantInt *Length = cast<ConstantInt>(II.getArgOperand(0));
918 insertUse(II, Offset, std::min(Length->getLimitedValue(),
919 AllocSize - Offset.getLimitedValue()));
922 void insertPHIOrSelect(Instruction &User, const APInt &Offset) {
923 uint64_t Size = P.PHIOrSelectSizes.lookup(&User).first;
925 // For PHI and select operands outside the alloca, we can't nuke the entire
926 // phi or select -- the other side might still be relevant, so we special
927 // case them here and use a separate structure to track the operands
928 // themselves which should be replaced with undef.
929 if ((Offset.isNegative() && Offset.uge(Size)) ||
930 (!Offset.isNegative() && Offset.uge(AllocSize))) {
931 P.DeadOperands.push_back(U);
935 insertUse(User, Offset, Size);
938 void visitPHINode(PHINode &PN) {
940 return markAsDead(PN);
942 assert(IsOffsetKnown);
943 insertPHIOrSelect(PN, Offset);
946 void visitSelectInst(SelectInst &SI) {
948 return markAsDead(SI);
950 if (Value *Result = foldSelectInst(SI)) {
952 // If the result of the constant fold will be the pointer, recurse
953 // through the select as if we had RAUW'ed it.
956 // Otherwise the operand to the select is dead, and we can replace it
958 P.DeadOperands.push_back(U);
963 assert(IsOffsetKnown);
964 insertPHIOrSelect(SI, Offset);
967 /// \brief Unreachable, we've already visited the alloca once.
968 void visitInstruction(Instruction &I) {
969 llvm_unreachable("Unhandled instruction in use builder.");
973 void AllocaPartitioning::splitAndMergePartitions() {
974 size_t NumDeadPartitions = 0;
976 // Track the range of splittable partitions that we pass when accumulating
977 // overlapping unsplittable partitions.
978 uint64_t SplitEndOffset = 0ull;
980 Partition New(0ull, 0ull, false);
982 for (unsigned i = 0, j = i, e = Partitions.size(); i != e; i = j) {
985 if (!Partitions[i].IsSplittable || New.BeginOffset == New.EndOffset) {
986 assert(New.BeginOffset == New.EndOffset);
989 assert(New.IsSplittable);
990 New.EndOffset = std::max(New.EndOffset, Partitions[i].EndOffset);
992 assert(New.BeginOffset != New.EndOffset);
994 // Scan the overlapping partitions.
995 while (j != e && New.EndOffset > Partitions[j].BeginOffset) {
996 // If the new partition we are forming is splittable, stop at the first
997 // unsplittable partition.
998 if (New.IsSplittable && !Partitions[j].IsSplittable)
1001 // Grow the new partition to include any equally splittable range. 'j' is
1002 // always equally splittable when New is splittable, but when New is not
1003 // splittable, we may subsume some (or part of some) splitable partition
1004 // without growing the new one.
1005 if (New.IsSplittable == Partitions[j].IsSplittable) {
1006 New.EndOffset = std::max(New.EndOffset, Partitions[j].EndOffset);
1008 assert(!New.IsSplittable);
1009 assert(Partitions[j].IsSplittable);
1010 SplitEndOffset = std::max(SplitEndOffset, Partitions[j].EndOffset);
1013 Partitions[j].kill();
1014 ++NumDeadPartitions;
1018 // If the new partition is splittable, chop off the end as soon as the
1019 // unsplittable subsequent partition starts and ensure we eventually cover
1020 // the splittable area.
1021 if (j != e && New.IsSplittable) {
1022 SplitEndOffset = std::max(SplitEndOffset, New.EndOffset);
1023 New.EndOffset = std::min(New.EndOffset, Partitions[j].BeginOffset);
1026 // Add the new partition if it differs from the original one and is
1027 // non-empty. We can end up with an empty partition here if it was
1028 // splittable but there is an unsplittable one that starts at the same
1030 if (New != Partitions[i]) {
1031 if (New.BeginOffset != New.EndOffset)
1032 Partitions.push_back(New);
1033 // Mark the old one for removal.
1034 Partitions[i].kill();
1035 ++NumDeadPartitions;
1038 New.BeginOffset = New.EndOffset;
1039 if (!New.IsSplittable) {
1040 New.EndOffset = std::max(New.EndOffset, SplitEndOffset);
1041 if (j != e && !Partitions[j].IsSplittable)
1042 New.EndOffset = std::min(New.EndOffset, Partitions[j].BeginOffset);
1043 New.IsSplittable = true;
1044 // If there is a trailing splittable partition which won't be fused into
1045 // the next splittable partition go ahead and add it onto the partitions
1047 if (New.BeginOffset < New.EndOffset &&
1048 (j == e || !Partitions[j].IsSplittable ||
1049 New.EndOffset < Partitions[j].BeginOffset)) {
1050 Partitions.push_back(New);
1051 New.BeginOffset = New.EndOffset = 0ull;
1056 // Re-sort the partitions now that they have been split and merged into
1057 // disjoint set of partitions. Also remove any of the dead partitions we've
1058 // replaced in the process.
1059 std::sort(Partitions.begin(), Partitions.end());
1060 if (NumDeadPartitions) {
1061 assert(Partitions.back().isDead());
1062 assert((ptrdiff_t)NumDeadPartitions ==
1063 std::count(Partitions.begin(), Partitions.end(), Partitions.back()));
1065 Partitions.erase(Partitions.end() - NumDeadPartitions, Partitions.end());
1068 AllocaPartitioning::AllocaPartitioning(const DataLayout &TD, AllocaInst &AI)
1070 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1073 PointerEscapingInstr(0) {
1074 PartitionBuilder PB(TD, AI, *this);
1075 PartitionBuilder::PtrInfo PtrI = PB.visitPtr(AI);
1076 if (PtrI.isEscaped() || PtrI.isAborted()) {
1077 // FIXME: We should sink the escape vs. abort info into the caller nicely,
1078 // possibly by just storing the PtrInfo in the AllocaPartitioning.
1079 PointerEscapingInstr = PtrI.getEscapingInst() ? PtrI.getEscapingInst()
1080 : PtrI.getAbortingInst();
1081 assert(PointerEscapingInstr && "Did not track a bad instruction");
1085 // Sort the uses. This arranges for the offsets to be in ascending order,
1086 // and the sizes to be in descending order.
1087 std::sort(Partitions.begin(), Partitions.end());
1089 // Remove any partitions from the back which are marked as dead.
1090 while (!Partitions.empty() && Partitions.back().isDead())
1091 Partitions.pop_back();
1093 if (Partitions.size() > 1) {
1094 // Intersect splittability for all partitions with equal offsets and sizes.
1095 // Then remove all but the first so that we have a sequence of non-equal but
1096 // potentially overlapping partitions.
1097 for (iterator I = Partitions.begin(), J = I, E = Partitions.end(); I != E;
1100 while (J != E && *I == *J) {
1101 I->IsSplittable &= J->IsSplittable;
1105 Partitions.erase(std::unique(Partitions.begin(), Partitions.end()),
1108 // Split splittable and merge unsplittable partitions into a disjoint set
1109 // of partitions over the used space of the allocation.
1110 splitAndMergePartitions();
1113 // Record how many partitions we end up with.
1114 NumAllocaPartitions += Partitions.size();
1115 MaxPartitionsPerAlloca = std::max<unsigned>(Partitions.size(), MaxPartitionsPerAlloca);
1117 // Now build up the user lists for each of these disjoint partitions by
1118 // re-walking the recursive users of the alloca.
1119 Uses.resize(Partitions.size());
1120 UseBuilder UB(TD, AI, *this);
1121 PtrI = UB.visitPtr(AI);
1122 assert(!PtrI.isEscaped() && "Previously analyzed pointer now escapes!");
1123 assert(!PtrI.isAborted() && "Early aborted the visit of the pointer.");
1125 unsigned NumUses = 0;
1126 #if !defined(NDEBUG) || defined(LLVM_ENABLE_STATS)
1127 for (unsigned Idx = 0, Size = Uses.size(); Idx != Size; ++Idx)
1128 NumUses += Uses[Idx].size();
1130 NumAllocaPartitionUses += NumUses;
1131 MaxPartitionUsesPerAlloca = std::max<unsigned>(NumUses, MaxPartitionUsesPerAlloca);
1134 Type *AllocaPartitioning::getCommonType(iterator I) const {
1136 for (const_use_iterator UI = use_begin(I), UE = use_end(I); UI != UE; ++UI) {
1137 Use *U = UI->getUse();
1139 continue; // Skip dead uses.
1140 if (isa<IntrinsicInst>(*U->getUser()))
1142 if (UI->BeginOffset != I->BeginOffset || UI->EndOffset != I->EndOffset)
1146 if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser()))
1147 UserTy = LI->getType();
1148 else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser()))
1149 UserTy = SI->getValueOperand()->getType();
1151 return 0; // Bail if we have weird uses.
1153 if (IntegerType *ITy = dyn_cast<IntegerType>(UserTy)) {
1154 // If the type is larger than the partition, skip it. We only encounter
1155 // this for split integer operations where we want to use the type of the
1156 // entity causing the split.
1157 if (ITy->getBitWidth() > (I->EndOffset - I->BeginOffset)*8)
1160 // If we have found an integer type use covering the alloca, use that
1161 // regardless of the other types, as integers are often used for a "bucket
1166 if (Ty && Ty != UserTy)
1174 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1176 void AllocaPartitioning::print(raw_ostream &OS, const_iterator I,
1177 StringRef Indent) const {
1178 OS << Indent << "partition #" << (I - begin())
1179 << " [" << I->BeginOffset << "," << I->EndOffset << ")"
1180 << (I->IsSplittable ? " (splittable)" : "")
1181 << (Uses[I - begin()].empty() ? " (zero uses)" : "")
1185 void AllocaPartitioning::printUsers(raw_ostream &OS, const_iterator I,
1186 StringRef Indent) const {
1187 for (const_use_iterator UI = use_begin(I), UE = use_end(I); UI != UE; ++UI) {
1189 continue; // Skip dead uses.
1190 OS << Indent << " [" << UI->BeginOffset << "," << UI->EndOffset << ") "
1191 << "used by: " << *UI->getUse()->getUser() << "\n";
1192 if (MemTransferInst *II =
1193 dyn_cast<MemTransferInst>(UI->getUse()->getUser())) {
1194 const MemTransferOffsets &MTO = MemTransferInstData.lookup(II);
1196 if (!MTO.IsSplittable)
1197 IsDest = UI->BeginOffset == MTO.DestBegin;
1199 IsDest = MTO.DestBegin != 0u;
1200 OS << Indent << " (original " << (IsDest ? "dest" : "source") << ": "
1201 << "[" << (IsDest ? MTO.DestBegin : MTO.SourceBegin)
1202 << "," << (IsDest ? MTO.DestEnd : MTO.SourceEnd) << ")\n";
1207 void AllocaPartitioning::print(raw_ostream &OS) const {
1208 if (PointerEscapingInstr) {
1209 OS << "No partitioning for alloca: " << AI << "\n"
1210 << " A pointer to this alloca escaped by:\n"
1211 << " " << *PointerEscapingInstr << "\n";
1215 OS << "Partitioning of alloca: " << AI << "\n";
1216 for (const_iterator I = begin(), E = end(); I != E; ++I) {
1222 void AllocaPartitioning::dump(const_iterator I) const { print(dbgs(), I); }
1223 void AllocaPartitioning::dump() const { print(dbgs()); }
1225 #endif // !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1229 /// \brief Implementation of LoadAndStorePromoter for promoting allocas.
1231 /// This subclass of LoadAndStorePromoter adds overrides to handle promoting
1232 /// the loads and stores of an alloca instruction, as well as updating its
1233 /// debug information. This is used when a domtree is unavailable and thus
1234 /// mem2reg in its full form can't be used to handle promotion of allocas to
1236 class AllocaPromoter : public LoadAndStorePromoter {
1240 SmallVector<DbgDeclareInst *, 4> DDIs;
1241 SmallVector<DbgValueInst *, 4> DVIs;
1244 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S,
1245 AllocaInst &AI, DIBuilder &DIB)
1246 : LoadAndStorePromoter(Insts, S), AI(AI), DIB(DIB) {}
1248 void run(const SmallVectorImpl<Instruction*> &Insts) {
1249 // Remember which alloca we're promoting (for isInstInList).
1250 if (MDNode *DebugNode = MDNode::getIfExists(AI.getContext(), &AI)) {
1251 for (Value::use_iterator UI = DebugNode->use_begin(),
1252 UE = DebugNode->use_end();
1254 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(*UI))
1255 DDIs.push_back(DDI);
1256 else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(*UI))
1257 DVIs.push_back(DVI);
1260 LoadAndStorePromoter::run(Insts);
1261 AI.eraseFromParent();
1262 while (!DDIs.empty())
1263 DDIs.pop_back_val()->eraseFromParent();
1264 while (!DVIs.empty())
1265 DVIs.pop_back_val()->eraseFromParent();
1268 virtual bool isInstInList(Instruction *I,
1269 const SmallVectorImpl<Instruction*> &Insts) const {
1270 if (LoadInst *LI = dyn_cast<LoadInst>(I))
1271 return LI->getOperand(0) == &AI;
1272 return cast<StoreInst>(I)->getPointerOperand() == &AI;
1275 virtual void updateDebugInfo(Instruction *Inst) const {
1276 for (SmallVector<DbgDeclareInst *, 4>::const_iterator I = DDIs.begin(),
1277 E = DDIs.end(); I != E; ++I) {
1278 DbgDeclareInst *DDI = *I;
1279 if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
1280 ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
1281 else if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
1282 ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
1284 for (SmallVector<DbgValueInst *, 4>::const_iterator I = DVIs.begin(),
1285 E = DVIs.end(); I != E; ++I) {
1286 DbgValueInst *DVI = *I;
1288 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
1289 // If an argument is zero extended then use argument directly. The ZExt
1290 // may be zapped by an optimization pass in future.
1291 if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
1292 Arg = dyn_cast<Argument>(ZExt->getOperand(0));
1293 if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
1294 Arg = dyn_cast<Argument>(SExt->getOperand(0));
1296 Arg = SI->getOperand(0);
1297 } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
1298 Arg = LI->getOperand(0);
1302 Instruction *DbgVal =
1303 DIB.insertDbgValueIntrinsic(Arg, 0, DIVariable(DVI->getVariable()),
1305 DbgVal->setDebugLoc(DVI->getDebugLoc());
1309 } // end anon namespace
1313 /// \brief An optimization pass providing Scalar Replacement of Aggregates.
1315 /// This pass takes allocations which can be completely analyzed (that is, they
1316 /// don't escape) and tries to turn them into scalar SSA values. There are
1317 /// a few steps to this process.
1319 /// 1) It takes allocations of aggregates and analyzes the ways in which they
1320 /// are used to try to split them into smaller allocations, ideally of
1321 /// a single scalar data type. It will split up memcpy and memset accesses
1322 /// as necessary and try to isolate individual scalar accesses.
1323 /// 2) It will transform accesses into forms which are suitable for SSA value
1324 /// promotion. This can be replacing a memset with a scalar store of an
1325 /// integer value, or it can involve speculating operations on a PHI or
1326 /// select to be a PHI or select of the results.
1327 /// 3) Finally, this will try to detect a pattern of accesses which map cleanly
1328 /// onto insert and extract operations on a vector value, and convert them to
1329 /// this form. By doing so, it will enable promotion of vector aggregates to
1330 /// SSA vector values.
1331 class SROA : public FunctionPass {
1332 const bool RequiresDomTree;
1335 const DataLayout *TD;
1338 /// \brief Worklist of alloca instructions to simplify.
1340 /// Each alloca in the function is added to this. Each new alloca formed gets
1341 /// added to it as well to recursively simplify unless that alloca can be
1342 /// directly promoted. Finally, each time we rewrite a use of an alloca other
1343 /// the one being actively rewritten, we add it back onto the list if not
1344 /// already present to ensure it is re-visited.
1345 SetVector<AllocaInst *, SmallVector<AllocaInst *, 16> > Worklist;
1347 /// \brief A collection of instructions to delete.
1348 /// We try to batch deletions to simplify code and make things a bit more
1350 SetVector<Instruction *, SmallVector<Instruction *, 8> > DeadInsts;
1352 /// \brief Post-promotion worklist.
1354 /// Sometimes we discover an alloca which has a high probability of becoming
1355 /// viable for SROA after a round of promotion takes place. In those cases,
1356 /// the alloca is enqueued here for re-processing.
1358 /// Note that we have to be very careful to clear allocas out of this list in
1359 /// the event they are deleted.
1360 SetVector<AllocaInst *, SmallVector<AllocaInst *, 16> > PostPromotionWorklist;
1362 /// \brief A collection of alloca instructions we can directly promote.
1363 std::vector<AllocaInst *> PromotableAllocas;
1366 SROA(bool RequiresDomTree = true)
1367 : FunctionPass(ID), RequiresDomTree(RequiresDomTree),
1368 C(0), TD(0), DT(0) {
1369 initializeSROAPass(*PassRegistry::getPassRegistry());
1371 bool runOnFunction(Function &F);
1372 void getAnalysisUsage(AnalysisUsage &AU) const;
1374 const char *getPassName() const { return "SROA"; }
1378 friend class PHIOrSelectSpeculator;
1379 friend class AllocaPartitionRewriter;
1380 friend class AllocaPartitionVectorRewriter;
1382 bool rewriteAllocaPartition(AllocaInst &AI,
1383 AllocaPartitioning &P,
1384 AllocaPartitioning::iterator PI);
1385 bool splitAlloca(AllocaInst &AI, AllocaPartitioning &P);
1386 bool runOnAlloca(AllocaInst &AI);
1387 void deleteDeadInstructions(SmallPtrSet<AllocaInst *, 4> &DeletedAllocas);
1388 bool promoteAllocas(Function &F);
1394 FunctionPass *llvm::createSROAPass(bool RequiresDomTree) {
1395 return new SROA(RequiresDomTree);
1398 INITIALIZE_PASS_BEGIN(SROA, "sroa", "Scalar Replacement Of Aggregates",
1400 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
1401 INITIALIZE_PASS_END(SROA, "sroa", "Scalar Replacement Of Aggregates",
1405 /// \brief Visitor to speculate PHIs and Selects where possible.
1406 class PHIOrSelectSpeculator : public InstVisitor<PHIOrSelectSpeculator> {
1407 // Befriend the base class so it can delegate to private visit methods.
1408 friend class llvm::InstVisitor<PHIOrSelectSpeculator>;
1410 const DataLayout &TD;
1411 AllocaPartitioning &P;
1415 PHIOrSelectSpeculator(const DataLayout &TD, AllocaPartitioning &P, SROA &Pass)
1416 : TD(TD), P(P), Pass(Pass) {}
1418 /// \brief Visit the users of an alloca partition and rewrite them.
1419 void visitUsers(AllocaPartitioning::const_iterator PI) {
1420 // Note that we need to use an index here as the underlying vector of uses
1421 // may be grown during speculation. However, we never need to re-visit the
1422 // new uses, and so we can use the initial size bound.
1423 for (unsigned Idx = 0, Size = P.use_size(PI); Idx != Size; ++Idx) {
1424 const PartitionUse &PU = P.getUse(PI, Idx);
1426 continue; // Skip dead use.
1428 visit(cast<Instruction>(PU.getUse()->getUser()));
1433 // By default, skip this instruction.
1434 void visitInstruction(Instruction &I) {}
1436 /// PHI instructions that use an alloca and are subsequently loaded can be
1437 /// rewritten to load both input pointers in the pred blocks and then PHI the
1438 /// results, allowing the load of the alloca to be promoted.
1440 /// %P2 = phi [i32* %Alloca, i32* %Other]
1441 /// %V = load i32* %P2
1443 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1445 /// %V2 = load i32* %Other
1447 /// %V = phi [i32 %V1, i32 %V2]
1449 /// We can do this to a select if its only uses are loads and if the operands
1450 /// to the select can be loaded unconditionally.
1452 /// FIXME: This should be hoisted into a generic utility, likely in
1453 /// Transforms/Util/Local.h
1454 bool isSafePHIToSpeculate(PHINode &PN, SmallVectorImpl<LoadInst *> &Loads) {
1455 // For now, we can only do this promotion if the load is in the same block
1456 // as the PHI, and if there are no stores between the phi and load.
1457 // TODO: Allow recursive phi users.
1458 // TODO: Allow stores.
1459 BasicBlock *BB = PN.getParent();
1460 unsigned MaxAlign = 0;
1461 for (Value::use_iterator UI = PN.use_begin(), UE = PN.use_end();
1463 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1464 if (LI == 0 || !LI->isSimple()) return false;
1466 // For now we only allow loads in the same block as the PHI. This is
1467 // a common case that happens when instcombine merges two loads through
1469 if (LI->getParent() != BB) return false;
1471 // Ensure that there are no instructions between the PHI and the load that
1473 for (BasicBlock::iterator BBI = &PN; &*BBI != LI; ++BBI)
1474 if (BBI->mayWriteToMemory())
1477 MaxAlign = std::max(MaxAlign, LI->getAlignment());
1478 Loads.push_back(LI);
1481 // We can only transform this if it is safe to push the loads into the
1482 // predecessor blocks. The only thing to watch out for is that we can't put
1483 // a possibly trapping load in the predecessor if it is a critical edge.
1484 for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) {
1485 TerminatorInst *TI = PN.getIncomingBlock(Idx)->getTerminator();
1486 Value *InVal = PN.getIncomingValue(Idx);
1488 // If the value is produced by the terminator of the predecessor (an
1489 // invoke) or it has side-effects, there is no valid place to put a load
1490 // in the predecessor.
1491 if (TI == InVal || TI->mayHaveSideEffects())
1494 // If the predecessor has a single successor, then the edge isn't
1496 if (TI->getNumSuccessors() == 1)
1499 // If this pointer is always safe to load, or if we can prove that there
1500 // is already a load in the block, then we can move the load to the pred
1502 if (InVal->isDereferenceablePointer() ||
1503 isSafeToLoadUnconditionally(InVal, TI, MaxAlign, &TD))
1512 void visitPHINode(PHINode &PN) {
1513 DEBUG(dbgs() << " original: " << PN << "\n");
1515 SmallVector<LoadInst *, 4> Loads;
1516 if (!isSafePHIToSpeculate(PN, Loads))
1519 assert(!Loads.empty());
1521 Type *LoadTy = cast<PointerType>(PN.getType())->getElementType();
1522 IRBuilderTy PHIBuilder(&PN);
1523 PHINode *NewPN = PHIBuilder.CreatePHI(LoadTy, PN.getNumIncomingValues(),
1524 PN.getName() + ".sroa.speculated");
1526 // Get the TBAA tag and alignment to use from one of the loads. It doesn't
1527 // matter which one we get and if any differ.
1528 LoadInst *SomeLoad = cast<LoadInst>(Loads.back());
1529 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa);
1530 unsigned Align = SomeLoad->getAlignment();
1532 // Rewrite all loads of the PN to use the new PHI.
1534 LoadInst *LI = Loads.pop_back_val();
1535 LI->replaceAllUsesWith(NewPN);
1536 Pass.DeadInsts.insert(LI);
1537 } while (!Loads.empty());
1539 // Inject loads into all of the pred blocks.
1540 for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) {
1541 BasicBlock *Pred = PN.getIncomingBlock(Idx);
1542 TerminatorInst *TI = Pred->getTerminator();
1543 Use *InUse = &PN.getOperandUse(PN.getOperandNumForIncomingValue(Idx));
1544 Value *InVal = PN.getIncomingValue(Idx);
1545 IRBuilderTy PredBuilder(TI);
1548 = PredBuilder.CreateLoad(InVal, (PN.getName() + ".sroa.speculate.load." +
1550 ++NumLoadsSpeculated;
1551 Load->setAlignment(Align);
1553 Load->setMetadata(LLVMContext::MD_tbaa, TBAATag);
1554 NewPN->addIncoming(Load, Pred);
1556 Instruction *Ptr = dyn_cast<Instruction>(InVal);
1558 // No uses to rewrite.
1561 // Try to lookup and rewrite any partition uses corresponding to this phi
1563 AllocaPartitioning::iterator PI
1564 = P.findPartitionForPHIOrSelectOperand(InUse);
1568 // Replace the Use in the PartitionUse for this operand with the Use
1570 AllocaPartitioning::use_iterator UI
1571 = P.findPartitionUseForPHIOrSelectOperand(InUse);
1572 assert(isa<PHINode>(*UI->getUse()->getUser()));
1573 UI->setUse(&Load->getOperandUse(Load->getPointerOperandIndex()));
1575 DEBUG(dbgs() << " speculated to: " << *NewPN << "\n");
1578 /// Select instructions that use an alloca and are subsequently loaded can be
1579 /// rewritten to load both input pointers and then select between the result,
1580 /// allowing the load of the alloca to be promoted.
1582 /// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
1583 /// %V = load i32* %P2
1585 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1586 /// %V2 = load i32* %Other
1587 /// %V = select i1 %cond, i32 %V1, i32 %V2
1589 /// We can do this to a select if its only uses are loads and if the operand
1590 /// to the select can be loaded unconditionally.
1591 bool isSafeSelectToSpeculate(SelectInst &SI,
1592 SmallVectorImpl<LoadInst *> &Loads) {
1593 Value *TValue = SI.getTrueValue();
1594 Value *FValue = SI.getFalseValue();
1595 bool TDerefable = TValue->isDereferenceablePointer();
1596 bool FDerefable = FValue->isDereferenceablePointer();
1598 for (Value::use_iterator UI = SI.use_begin(), UE = SI.use_end();
1600 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1601 if (LI == 0 || !LI->isSimple()) return false;
1603 // Both operands to the select need to be dereferencable, either
1604 // absolutely (e.g. allocas) or at this point because we can see other
1606 if (!TDerefable && !isSafeToLoadUnconditionally(TValue, LI,
1607 LI->getAlignment(), &TD))
1609 if (!FDerefable && !isSafeToLoadUnconditionally(FValue, LI,
1610 LI->getAlignment(), &TD))
1612 Loads.push_back(LI);
1618 void visitSelectInst(SelectInst &SI) {
1619 DEBUG(dbgs() << " original: " << SI << "\n");
1621 // If the select isn't safe to speculate, just use simple logic to emit it.
1622 SmallVector<LoadInst *, 4> Loads;
1623 if (!isSafeSelectToSpeculate(SI, Loads))
1626 IRBuilderTy IRB(&SI);
1627 Use *Ops[2] = { &SI.getOperandUse(1), &SI.getOperandUse(2) };
1628 AllocaPartitioning::iterator PIs[2];
1629 PartitionUse PUs[2];
1630 for (unsigned i = 0, e = 2; i != e; ++i) {
1631 PIs[i] = P.findPartitionForPHIOrSelectOperand(Ops[i]);
1632 if (PIs[i] != P.end()) {
1633 // If the pointer is within the partitioning, remove the select from
1634 // its uses. We'll add in the new loads below.
1635 AllocaPartitioning::use_iterator UI
1636 = P.findPartitionUseForPHIOrSelectOperand(Ops[i]);
1638 // Clear out the use here so that the offsets into the use list remain
1639 // stable but this use is ignored when rewriting.
1644 Value *TV = SI.getTrueValue();
1645 Value *FV = SI.getFalseValue();
1646 // Replace the loads of the select with a select of two loads.
1647 while (!Loads.empty()) {
1648 LoadInst *LI = Loads.pop_back_val();
1650 IRB.SetInsertPoint(LI);
1652 IRB.CreateLoad(TV, LI->getName() + ".sroa.speculate.load.true");
1654 IRB.CreateLoad(FV, LI->getName() + ".sroa.speculate.load.false");
1655 NumLoadsSpeculated += 2;
1657 // Transfer alignment and TBAA info if present.
1658 TL->setAlignment(LI->getAlignment());
1659 FL->setAlignment(LI->getAlignment());
1660 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) {
1661 TL->setMetadata(LLVMContext::MD_tbaa, Tag);
1662 FL->setMetadata(LLVMContext::MD_tbaa, Tag);
1665 Value *V = IRB.CreateSelect(SI.getCondition(), TL, FL,
1666 LI->getName() + ".sroa.speculated");
1668 LoadInst *Loads[2] = { TL, FL };
1669 for (unsigned i = 0, e = 2; i != e; ++i) {
1670 if (PIs[i] != P.end()) {
1671 Use *LoadUse = &Loads[i]->getOperandUse(0);
1672 assert(PUs[i].getUse()->get() == LoadUse->get());
1673 PUs[i].setUse(LoadUse);
1674 P.use_push_back(PIs[i], PUs[i]);
1678 DEBUG(dbgs() << " speculated to: " << *V << "\n");
1679 LI->replaceAllUsesWith(V);
1680 Pass.DeadInsts.insert(LI);
1686 /// \brief Build a GEP out of a base pointer and indices.
1688 /// This will return the BasePtr if that is valid, or build a new GEP
1689 /// instruction using the IRBuilder if GEP-ing is needed.
1690 static Value *buildGEP(IRBuilderTy &IRB, Value *BasePtr,
1691 SmallVectorImpl<Value *> &Indices,
1692 const Twine &Prefix) {
1693 if (Indices.empty())
1696 // A single zero index is a no-op, so check for this and avoid building a GEP
1698 if (Indices.size() == 1 && cast<ConstantInt>(Indices.back())->isZero())
1701 return IRB.CreateInBoundsGEP(BasePtr, Indices, Prefix + ".idx");
1704 /// \brief Get a natural GEP off of the BasePtr walking through Ty toward
1705 /// TargetTy without changing the offset of the pointer.
1707 /// This routine assumes we've already established a properly offset GEP with
1708 /// Indices, and arrived at the Ty type. The goal is to continue to GEP with
1709 /// zero-indices down through type layers until we find one the same as
1710 /// TargetTy. If we can't find one with the same type, we at least try to use
1711 /// one with the same size. If none of that works, we just produce the GEP as
1712 /// indicated by Indices to have the correct offset.
1713 static Value *getNaturalGEPWithType(IRBuilderTy &IRB, const DataLayout &TD,
1714 Value *BasePtr, Type *Ty, Type *TargetTy,
1715 SmallVectorImpl<Value *> &Indices,
1716 const Twine &Prefix) {
1718 return buildGEP(IRB, BasePtr, Indices, Prefix);
1720 // See if we can descend into a struct and locate a field with the correct
1722 unsigned NumLayers = 0;
1723 Type *ElementTy = Ty;
1725 if (ElementTy->isPointerTy())
1727 if (SequentialType *SeqTy = dyn_cast<SequentialType>(ElementTy)) {
1728 ElementTy = SeqTy->getElementType();
1729 // Note that we use the default address space as this index is over an
1730 // array or a vector, not a pointer.
1731 Indices.push_back(IRB.getInt(APInt(TD.getPointerSizeInBits(0), 0)));
1732 } else if (StructType *STy = dyn_cast<StructType>(ElementTy)) {
1733 if (STy->element_begin() == STy->element_end())
1734 break; // Nothing left to descend into.
1735 ElementTy = *STy->element_begin();
1736 Indices.push_back(IRB.getInt32(0));
1741 } while (ElementTy != TargetTy);
1742 if (ElementTy != TargetTy)
1743 Indices.erase(Indices.end() - NumLayers, Indices.end());
1745 return buildGEP(IRB, BasePtr, Indices, Prefix);
1748 /// \brief Recursively compute indices for a natural GEP.
1750 /// This is the recursive step for getNaturalGEPWithOffset that walks down the
1751 /// element types adding appropriate indices for the GEP.
1752 static Value *getNaturalGEPRecursively(IRBuilderTy &IRB, const DataLayout &TD,
1753 Value *Ptr, Type *Ty, APInt &Offset,
1755 SmallVectorImpl<Value *> &Indices,
1756 const Twine &Prefix) {
1758 return getNaturalGEPWithType(IRB, TD, Ptr, Ty, TargetTy, Indices, Prefix);
1760 // We can't recurse through pointer types.
1761 if (Ty->isPointerTy())
1764 // We try to analyze GEPs over vectors here, but note that these GEPs are
1765 // extremely poorly defined currently. The long-term goal is to remove GEPing
1766 // over a vector from the IR completely.
1767 if (VectorType *VecTy = dyn_cast<VectorType>(Ty)) {
1768 unsigned ElementSizeInBits = TD.getTypeSizeInBits(VecTy->getScalarType());
1769 if (ElementSizeInBits % 8)
1770 return 0; // GEPs over non-multiple of 8 size vector elements are invalid.
1771 APInt ElementSize(Offset.getBitWidth(), ElementSizeInBits / 8);
1772 APInt NumSkippedElements = Offset.sdiv(ElementSize);
1773 if (NumSkippedElements.ugt(VecTy->getNumElements()))
1775 Offset -= NumSkippedElements * ElementSize;
1776 Indices.push_back(IRB.getInt(NumSkippedElements));
1777 return getNaturalGEPRecursively(IRB, TD, Ptr, VecTy->getElementType(),
1778 Offset, TargetTy, Indices, Prefix);
1781 if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) {
1782 Type *ElementTy = ArrTy->getElementType();
1783 APInt ElementSize(Offset.getBitWidth(), TD.getTypeAllocSize(ElementTy));
1784 APInt NumSkippedElements = Offset.sdiv(ElementSize);
1785 if (NumSkippedElements.ugt(ArrTy->getNumElements()))
1788 Offset -= NumSkippedElements * ElementSize;
1789 Indices.push_back(IRB.getInt(NumSkippedElements));
1790 return getNaturalGEPRecursively(IRB, TD, Ptr, ElementTy, Offset, TargetTy,
1794 StructType *STy = dyn_cast<StructType>(Ty);
1798 const StructLayout *SL = TD.getStructLayout(STy);
1799 uint64_t StructOffset = Offset.getZExtValue();
1800 if (StructOffset >= SL->getSizeInBytes())
1802 unsigned Index = SL->getElementContainingOffset(StructOffset);
1803 Offset -= APInt(Offset.getBitWidth(), SL->getElementOffset(Index));
1804 Type *ElementTy = STy->getElementType(Index);
1805 if (Offset.uge(TD.getTypeAllocSize(ElementTy)))
1806 return 0; // The offset points into alignment padding.
1808 Indices.push_back(IRB.getInt32(Index));
1809 return getNaturalGEPRecursively(IRB, TD, Ptr, ElementTy, Offset, TargetTy,
1813 /// \brief Get a natural GEP from a base pointer to a particular offset and
1814 /// resulting in a particular type.
1816 /// The goal is to produce a "natural" looking GEP that works with the existing
1817 /// composite types to arrive at the appropriate offset and element type for
1818 /// a pointer. TargetTy is the element type the returned GEP should point-to if
1819 /// possible. We recurse by decreasing Offset, adding the appropriate index to
1820 /// Indices, and setting Ty to the result subtype.
1822 /// If no natural GEP can be constructed, this function returns null.
1823 static Value *getNaturalGEPWithOffset(IRBuilderTy &IRB, const DataLayout &TD,
1824 Value *Ptr, APInt Offset, Type *TargetTy,
1825 SmallVectorImpl<Value *> &Indices,
1826 const Twine &Prefix) {
1827 PointerType *Ty = cast<PointerType>(Ptr->getType());
1829 // Don't consider any GEPs through an i8* as natural unless the TargetTy is
1831 if (Ty == IRB.getInt8PtrTy() && TargetTy->isIntegerTy(8))
1834 Type *ElementTy = Ty->getElementType();
1835 if (!ElementTy->isSized())
1836 return 0; // We can't GEP through an unsized element.
1837 APInt ElementSize(Offset.getBitWidth(), TD.getTypeAllocSize(ElementTy));
1838 if (ElementSize == 0)
1839 return 0; // Zero-length arrays can't help us build a natural GEP.
1840 APInt NumSkippedElements = Offset.sdiv(ElementSize);
1842 Offset -= NumSkippedElements * ElementSize;
1843 Indices.push_back(IRB.getInt(NumSkippedElements));
1844 return getNaturalGEPRecursively(IRB, TD, Ptr, ElementTy, Offset, TargetTy,
1848 /// \brief Compute an adjusted pointer from Ptr by Offset bytes where the
1849 /// resulting pointer has PointerTy.
1851 /// This tries very hard to compute a "natural" GEP which arrives at the offset
1852 /// and produces the pointer type desired. Where it cannot, it will try to use
1853 /// the natural GEP to arrive at the offset and bitcast to the type. Where that
1854 /// fails, it will try to use an existing i8* and GEP to the byte offset and
1855 /// bitcast to the type.
1857 /// The strategy for finding the more natural GEPs is to peel off layers of the
1858 /// pointer, walking back through bit casts and GEPs, searching for a base
1859 /// pointer from which we can compute a natural GEP with the desired
1860 /// properties. The algorithm tries to fold as many constant indices into
1861 /// a single GEP as possible, thus making each GEP more independent of the
1862 /// surrounding code.
1863 static Value *getAdjustedPtr(IRBuilderTy &IRB, const DataLayout &TD,
1864 Value *Ptr, APInt Offset, Type *PointerTy,
1865 const Twine &Prefix) {
1866 // Even though we don't look through PHI nodes, we could be called on an
1867 // instruction in an unreachable block, which may be on a cycle.
1868 SmallPtrSet<Value *, 4> Visited;
1869 Visited.insert(Ptr);
1870 SmallVector<Value *, 4> Indices;
1872 // We may end up computing an offset pointer that has the wrong type. If we
1873 // never are able to compute one directly that has the correct type, we'll
1874 // fall back to it, so keep it around here.
1875 Value *OffsetPtr = 0;
1877 // Remember any i8 pointer we come across to re-use if we need to do a raw
1880 APInt Int8PtrOffset(Offset.getBitWidth(), 0);
1882 Type *TargetTy = PointerTy->getPointerElementType();
1885 // First fold any existing GEPs into the offset.
1886 while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
1887 APInt GEPOffset(Offset.getBitWidth(), 0);
1888 if (!GEP->accumulateConstantOffset(TD, GEPOffset))
1890 Offset += GEPOffset;
1891 Ptr = GEP->getPointerOperand();
1892 if (!Visited.insert(Ptr))
1896 // See if we can perform a natural GEP here.
1898 if (Value *P = getNaturalGEPWithOffset(IRB, TD, Ptr, Offset, TargetTy,
1900 if (P->getType() == PointerTy) {
1901 // Zap any offset pointer that we ended up computing in previous rounds.
1902 if (OffsetPtr && OffsetPtr->use_empty())
1903 if (Instruction *I = dyn_cast<Instruction>(OffsetPtr))
1904 I->eraseFromParent();
1912 // Stash this pointer if we've found an i8*.
1913 if (Ptr->getType()->isIntegerTy(8)) {
1915 Int8PtrOffset = Offset;
1918 // Peel off a layer of the pointer and update the offset appropriately.
1919 if (Operator::getOpcode(Ptr) == Instruction::BitCast) {
1920 Ptr = cast<Operator>(Ptr)->getOperand(0);
1921 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(Ptr)) {
1922 if (GA->mayBeOverridden())
1924 Ptr = GA->getAliasee();
1928 assert(Ptr->getType()->isPointerTy() && "Unexpected operand type!");
1929 } while (Visited.insert(Ptr));
1933 Int8Ptr = IRB.CreateBitCast(Ptr, IRB.getInt8PtrTy(),
1934 Prefix + ".raw_cast");
1935 Int8PtrOffset = Offset;
1938 OffsetPtr = Int8PtrOffset == 0 ? Int8Ptr :
1939 IRB.CreateInBoundsGEP(Int8Ptr, IRB.getInt(Int8PtrOffset),
1940 Prefix + ".raw_idx");
1944 // On the off chance we were targeting i8*, guard the bitcast here.
1945 if (Ptr->getType() != PointerTy)
1946 Ptr = IRB.CreateBitCast(Ptr, PointerTy, Prefix + ".cast");
1951 /// \brief Test whether we can convert a value from the old to the new type.
1953 /// This predicate should be used to guard calls to convertValue in order to
1954 /// ensure that we only try to convert viable values. The strategy is that we
1955 /// will peel off single element struct and array wrappings to get to an
1956 /// underlying value, and convert that value.
1957 static bool canConvertValue(const DataLayout &DL, Type *OldTy, Type *NewTy) {
1960 if (IntegerType *OldITy = dyn_cast<IntegerType>(OldTy))
1961 if (IntegerType *NewITy = dyn_cast<IntegerType>(NewTy))
1962 if (NewITy->getBitWidth() >= OldITy->getBitWidth())
1964 if (DL.getTypeSizeInBits(NewTy) != DL.getTypeSizeInBits(OldTy))
1966 if (!NewTy->isSingleValueType() || !OldTy->isSingleValueType())
1969 if (NewTy->isPointerTy() || OldTy->isPointerTy()) {
1970 if (NewTy->isPointerTy() && OldTy->isPointerTy())
1972 if (NewTy->isIntegerTy() || OldTy->isIntegerTy())
1980 /// \brief Generic routine to convert an SSA value to a value of a different
1983 /// This will try various different casting techniques, such as bitcasts,
1984 /// inttoptr, and ptrtoint casts. Use the \c canConvertValue predicate to test
1985 /// two types for viability with this routine.
1986 static Value *convertValue(const DataLayout &DL, IRBuilderTy &IRB, Value *V,
1988 assert(canConvertValue(DL, V->getType(), Ty) &&
1989 "Value not convertable to type");
1990 if (V->getType() == Ty)
1992 if (IntegerType *OldITy = dyn_cast<IntegerType>(V->getType()))
1993 if (IntegerType *NewITy = dyn_cast<IntegerType>(Ty))
1994 if (NewITy->getBitWidth() > OldITy->getBitWidth())
1995 return IRB.CreateZExt(V, NewITy);
1996 if (V->getType()->isIntegerTy() && Ty->isPointerTy())
1997 return IRB.CreateIntToPtr(V, Ty);
1998 if (V->getType()->isPointerTy() && Ty->isIntegerTy())
1999 return IRB.CreatePtrToInt(V, Ty);
2001 return IRB.CreateBitCast(V, Ty);
2004 /// \brief Test whether the given alloca partition can be promoted to a vector.
2006 /// This is a quick test to check whether we can rewrite a particular alloca
2007 /// partition (and its newly formed alloca) into a vector alloca with only
2008 /// whole-vector loads and stores such that it could be promoted to a vector
2009 /// SSA value. We only can ensure this for a limited set of operations, and we
2010 /// don't want to do the rewrites unless we are confident that the result will
2011 /// be promotable, so we have an early test here.
2012 static bool isVectorPromotionViable(const DataLayout &TD,
2014 AllocaPartitioning &P,
2015 uint64_t PartitionBeginOffset,
2016 uint64_t PartitionEndOffset,
2017 AllocaPartitioning::const_use_iterator I,
2018 AllocaPartitioning::const_use_iterator E) {
2019 VectorType *Ty = dyn_cast<VectorType>(AllocaTy);
2023 uint64_t ElementSize = TD.getTypeSizeInBits(Ty->getScalarType());
2025 // While the definition of LLVM vectors is bitpacked, we don't support sizes
2026 // that aren't byte sized.
2027 if (ElementSize % 8)
2029 assert((TD.getTypeSizeInBits(Ty) % 8) == 0 &&
2030 "vector size not a multiple of element size?");
2033 for (; I != E; ++I) {
2034 Use *U = I->getUse();
2036 continue; // Skip dead use.
2038 uint64_t BeginOffset = I->BeginOffset - PartitionBeginOffset;
2039 uint64_t BeginIndex = BeginOffset / ElementSize;
2040 if (BeginIndex * ElementSize != BeginOffset ||
2041 BeginIndex >= Ty->getNumElements())
2043 uint64_t EndOffset = I->EndOffset - PartitionBeginOffset;
2044 uint64_t EndIndex = EndOffset / ElementSize;
2045 if (EndIndex * ElementSize != EndOffset ||
2046 EndIndex > Ty->getNumElements())
2049 assert(EndIndex > BeginIndex && "Empty vector!");
2050 uint64_t NumElements = EndIndex - BeginIndex;
2052 = (NumElements == 1) ? Ty->getElementType()
2053 : VectorType::get(Ty->getElementType(), NumElements);
2055 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) {
2056 if (MI->isVolatile())
2058 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(U->getUser())) {
2059 const AllocaPartitioning::MemTransferOffsets &MTO
2060 = P.getMemTransferOffsets(*MTI);
2061 if (!MTO.IsSplittable)
2064 } else if (U->get()->getType()->getPointerElementType()->isStructTy()) {
2065 // Disable vector promotion when there are loads or stores of an FCA.
2067 } else if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) {
2068 if (LI->isVolatile())
2070 if (!canConvertValue(TD, PartitionTy, LI->getType()))
2072 } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
2073 if (SI->isVolatile())
2075 if (!canConvertValue(TD, SI->getValueOperand()->getType(), PartitionTy))
2084 /// \brief Test whether the given alloca partition's integer operations can be
2085 /// widened to promotable ones.
2087 /// This is a quick test to check whether we can rewrite the integer loads and
2088 /// stores to a particular alloca into wider loads and stores and be able to
2089 /// promote the resulting alloca.
2090 static bool isIntegerWideningViable(const DataLayout &TD,
2092 uint64_t AllocBeginOffset,
2093 AllocaPartitioning &P,
2094 AllocaPartitioning::const_use_iterator I,
2095 AllocaPartitioning::const_use_iterator E) {
2096 uint64_t SizeInBits = TD.getTypeSizeInBits(AllocaTy);
2097 // Don't create integer types larger than the maximum bitwidth.
2098 if (SizeInBits > IntegerType::MAX_INT_BITS)
2101 // Don't try to handle allocas with bit-padding.
2102 if (SizeInBits != TD.getTypeStoreSizeInBits(AllocaTy))
2105 // We need to ensure that an integer type with the appropriate bitwidth can
2106 // be converted to the alloca type, whatever that is. We don't want to force
2107 // the alloca itself to have an integer type if there is a more suitable one.
2108 Type *IntTy = Type::getIntNTy(AllocaTy->getContext(), SizeInBits);
2109 if (!canConvertValue(TD, AllocaTy, IntTy) ||
2110 !canConvertValue(TD, IntTy, AllocaTy))
2113 uint64_t Size = TD.getTypeStoreSize(AllocaTy);
2115 // Check the uses to ensure the uses are (likely) promotable integer uses.
2116 // Also ensure that the alloca has a covering load or store. We don't want
2117 // to widen the integer operations only to fail to promote due to some other
2118 // unsplittable entry (which we may make splittable later).
2119 bool WholeAllocaOp = false;
2120 for (; I != E; ++I) {
2121 Use *U = I->getUse();
2123 continue; // Skip dead use.
2125 uint64_t RelBegin = I->BeginOffset - AllocBeginOffset;
2126 uint64_t RelEnd = I->EndOffset - AllocBeginOffset;
2128 // We can't reasonably handle cases where the load or store extends past
2129 // the end of the aloca's type and into its padding.
2133 if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) {
2134 if (LI->isVolatile())
2136 if (RelBegin == 0 && RelEnd == Size)
2137 WholeAllocaOp = true;
2138 if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType())) {
2139 if (ITy->getBitWidth() < TD.getTypeStoreSizeInBits(ITy))
2143 // Non-integer loads need to be convertible from the alloca type so that
2144 // they are promotable.
2145 if (RelBegin != 0 || RelEnd != Size ||
2146 !canConvertValue(TD, AllocaTy, LI->getType()))
2148 } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
2149 Type *ValueTy = SI->getValueOperand()->getType();
2150 if (SI->isVolatile())
2152 if (RelBegin == 0 && RelEnd == Size)
2153 WholeAllocaOp = true;
2154 if (IntegerType *ITy = dyn_cast<IntegerType>(ValueTy)) {
2155 if (ITy->getBitWidth() < TD.getTypeStoreSizeInBits(ITy))
2159 // Non-integer stores need to be convertible to the alloca type so that
2160 // they are promotable.
2161 if (RelBegin != 0 || RelEnd != Size ||
2162 !canConvertValue(TD, ValueTy, AllocaTy))
2164 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) {
2165 if (MI->isVolatile() || !isa<Constant>(MI->getLength()))
2167 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(U->getUser())) {
2168 const AllocaPartitioning::MemTransferOffsets &MTO
2169 = P.getMemTransferOffsets(*MTI);
2170 if (!MTO.IsSplittable)
2173 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U->getUser())) {
2174 if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
2175 II->getIntrinsicID() != Intrinsic::lifetime_end)
2181 return WholeAllocaOp;
2184 static Value *extractInteger(const DataLayout &DL, IRBuilderTy &IRB, Value *V,
2185 IntegerType *Ty, uint64_t Offset,
2186 const Twine &Name) {
2187 DEBUG(dbgs() << " start: " << *V << "\n");
2188 IntegerType *IntTy = cast<IntegerType>(V->getType());
2189 assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) &&
2190 "Element extends past full value");
2191 uint64_t ShAmt = 8*Offset;
2192 if (DL.isBigEndian())
2193 ShAmt = 8*(DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset);
2195 V = IRB.CreateLShr(V, ShAmt, Name + ".shift");
2196 DEBUG(dbgs() << " shifted: " << *V << "\n");
2198 assert(Ty->getBitWidth() <= IntTy->getBitWidth() &&
2199 "Cannot extract to a larger integer!");
2201 V = IRB.CreateTrunc(V, Ty, Name + ".trunc");
2202 DEBUG(dbgs() << " trunced: " << *V << "\n");
2207 static Value *insertInteger(const DataLayout &DL, IRBuilderTy &IRB, Value *Old,
2208 Value *V, uint64_t Offset, const Twine &Name) {
2209 IntegerType *IntTy = cast<IntegerType>(Old->getType());
2210 IntegerType *Ty = cast<IntegerType>(V->getType());
2211 assert(Ty->getBitWidth() <= IntTy->getBitWidth() &&
2212 "Cannot insert a larger integer!");
2213 DEBUG(dbgs() << " start: " << *V << "\n");
2215 V = IRB.CreateZExt(V, IntTy, Name + ".ext");
2216 DEBUG(dbgs() << " extended: " << *V << "\n");
2218 assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) &&
2219 "Element store outside of alloca store");
2220 uint64_t ShAmt = 8*Offset;
2221 if (DL.isBigEndian())
2222 ShAmt = 8*(DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset);
2224 V = IRB.CreateShl(V, ShAmt, Name + ".shift");
2225 DEBUG(dbgs() << " shifted: " << *V << "\n");
2228 if (ShAmt || Ty->getBitWidth() < IntTy->getBitWidth()) {
2229 APInt Mask = ~Ty->getMask().zext(IntTy->getBitWidth()).shl(ShAmt);
2230 Old = IRB.CreateAnd(Old, Mask, Name + ".mask");
2231 DEBUG(dbgs() << " masked: " << *Old << "\n");
2232 V = IRB.CreateOr(Old, V, Name + ".insert");
2233 DEBUG(dbgs() << " inserted: " << *V << "\n");
2238 static Value *extractVector(IRBuilderTy &IRB, Value *V,
2239 unsigned BeginIndex, unsigned EndIndex,
2240 const Twine &Name) {
2241 VectorType *VecTy = cast<VectorType>(V->getType());
2242 unsigned NumElements = EndIndex - BeginIndex;
2243 assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
2245 if (NumElements == VecTy->getNumElements())
2248 if (NumElements == 1) {
2249 V = IRB.CreateExtractElement(V, IRB.getInt32(BeginIndex),
2251 DEBUG(dbgs() << " extract: " << *V << "\n");
2255 SmallVector<Constant*, 8> Mask;
2256 Mask.reserve(NumElements);
2257 for (unsigned i = BeginIndex; i != EndIndex; ++i)
2258 Mask.push_back(IRB.getInt32(i));
2259 V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()),
2260 ConstantVector::get(Mask),
2262 DEBUG(dbgs() << " shuffle: " << *V << "\n");
2266 static Value *insertVector(IRBuilderTy &IRB, Value *Old, Value *V,
2267 unsigned BeginIndex, const Twine &Name) {
2268 VectorType *VecTy = cast<VectorType>(Old->getType());
2269 assert(VecTy && "Can only insert a vector into a vector");
2271 VectorType *Ty = dyn_cast<VectorType>(V->getType());
2273 // Single element to insert.
2274 V = IRB.CreateInsertElement(Old, V, IRB.getInt32(BeginIndex),
2276 DEBUG(dbgs() << " insert: " << *V << "\n");
2280 assert(Ty->getNumElements() <= VecTy->getNumElements() &&
2281 "Too many elements!");
2282 if (Ty->getNumElements() == VecTy->getNumElements()) {
2283 assert(V->getType() == VecTy && "Vector type mismatch");
2286 unsigned EndIndex = BeginIndex + Ty->getNumElements();
2288 // When inserting a smaller vector into the larger to store, we first
2289 // use a shuffle vector to widen it with undef elements, and then
2290 // a second shuffle vector to select between the loaded vector and the
2292 SmallVector<Constant*, 8> Mask;
2293 Mask.reserve(VecTy->getNumElements());
2294 for (unsigned i = 0; i != VecTy->getNumElements(); ++i)
2295 if (i >= BeginIndex && i < EndIndex)
2296 Mask.push_back(IRB.getInt32(i - BeginIndex));
2298 Mask.push_back(UndefValue::get(IRB.getInt32Ty()));
2299 V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()),
2300 ConstantVector::get(Mask),
2302 DEBUG(dbgs() << " shuffle1: " << *V << "\n");
2305 for (unsigned i = 0; i != VecTy->getNumElements(); ++i)
2306 if (i >= BeginIndex && i < EndIndex)
2307 Mask.push_back(IRB.getInt32(i));
2309 Mask.push_back(IRB.getInt32(i + VecTy->getNumElements()));
2310 V = IRB.CreateShuffleVector(V, Old, ConstantVector::get(Mask),
2312 DEBUG(dbgs() << " shuffle2: " << *V << "\n");
2317 /// \brief Visitor to rewrite instructions using a partition of an alloca to
2318 /// use a new alloca.
2320 /// Also implements the rewriting to vector-based accesses when the partition
2321 /// passes the isVectorPromotionViable predicate. Most of the rewriting logic
2323 class AllocaPartitionRewriter : public InstVisitor<AllocaPartitionRewriter,
2325 // Befriend the base class so it can delegate to private visit methods.
2326 friend class llvm::InstVisitor<AllocaPartitionRewriter, bool>;
2328 const DataLayout &TD;
2329 AllocaPartitioning &P;
2331 AllocaInst &OldAI, &NewAI;
2332 const uint64_t NewAllocaBeginOffset, NewAllocaEndOffset;
2335 // If we are rewriting an alloca partition which can be written as pure
2336 // vector operations, we stash extra information here. When VecTy is
2337 // non-null, we have some strict guarantees about the rewritten alloca:
2338 // - The new alloca is exactly the size of the vector type here.
2339 // - The accesses all either map to the entire vector or to a single
2341 // - The set of accessing instructions is only one of those handled above
2342 // in isVectorPromotionViable. Generally these are the same access kinds
2343 // which are promotable via mem2reg.
2346 uint64_t ElementSize;
2348 // This is a convenience and flag variable that will be null unless the new
2349 // alloca's integer operations should be widened to this integer type due to
2350 // passing isIntegerWideningViable above. If it is non-null, the desired
2351 // integer type will be stored here for easy access during rewriting.
2354 // The offset of the partition user currently being rewritten.
2355 uint64_t BeginOffset, EndOffset;
2358 Instruction *OldPtr;
2360 // The name prefix to use when rewriting instructions for this alloca.
2361 std::string NamePrefix;
2364 AllocaPartitionRewriter(const DataLayout &TD, AllocaPartitioning &P,
2365 AllocaPartitioning::iterator PI,
2366 SROA &Pass, AllocaInst &OldAI, AllocaInst &NewAI,
2367 uint64_t NewBeginOffset, uint64_t NewEndOffset)
2368 : TD(TD), P(P), Pass(Pass),
2369 OldAI(OldAI), NewAI(NewAI),
2370 NewAllocaBeginOffset(NewBeginOffset),
2371 NewAllocaEndOffset(NewEndOffset),
2372 NewAllocaTy(NewAI.getAllocatedType()),
2373 VecTy(), ElementTy(), ElementSize(), IntTy(),
2374 BeginOffset(), EndOffset(), IsSplit(), OldUse(), OldPtr() {
2377 /// \brief Visit the users of the alloca partition and rewrite them.
2378 bool visitUsers(AllocaPartitioning::const_use_iterator I,
2379 AllocaPartitioning::const_use_iterator E) {
2380 if (isVectorPromotionViable(TD, NewAI.getAllocatedType(), P,
2381 NewAllocaBeginOffset, NewAllocaEndOffset,
2384 VecTy = cast<VectorType>(NewAI.getAllocatedType());
2385 ElementTy = VecTy->getElementType();
2386 assert((TD.getTypeSizeInBits(VecTy->getScalarType()) % 8) == 0 &&
2387 "Only multiple-of-8 sized vector elements are viable");
2388 ElementSize = TD.getTypeSizeInBits(VecTy->getScalarType()) / 8;
2389 } else if (isIntegerWideningViable(TD, NewAI.getAllocatedType(),
2390 NewAllocaBeginOffset, P, I, E)) {
2391 IntTy = Type::getIntNTy(NewAI.getContext(),
2392 TD.getTypeSizeInBits(NewAI.getAllocatedType()));
2394 bool CanSROA = true;
2395 for (; I != E; ++I) {
2397 continue; // Skip dead uses.
2398 BeginOffset = I->BeginOffset;
2399 EndOffset = I->EndOffset;
2400 IsSplit = I->isSplit();
2401 OldUse = I->getUse();
2402 OldPtr = cast<Instruction>(OldUse->get());
2403 NamePrefix = (Twine(NewAI.getName()) + "." + Twine(BeginOffset)).str();
2404 CanSROA &= visit(cast<Instruction>(OldUse->getUser()));
2420 // Every instruction which can end up as a user must have a rewrite rule.
2421 bool visitInstruction(Instruction &I) {
2422 DEBUG(dbgs() << " !!!! Cannot rewrite: " << I << "\n");
2423 llvm_unreachable("No rewrite rule for this instruction!");
2426 Twine getName(const Twine &Suffix) {
2427 return NamePrefix + Suffix;
2430 Value *getAdjustedAllocaPtr(IRBuilderTy &IRB, Type *PointerTy) {
2431 assert(BeginOffset >= NewAllocaBeginOffset);
2432 APInt Offset(TD.getPointerSizeInBits(), BeginOffset - NewAllocaBeginOffset);
2433 return getAdjustedPtr(IRB, TD, &NewAI, Offset, PointerTy, getName(""));
2436 /// \brief Compute suitable alignment to access an offset into the new alloca.
2437 unsigned getOffsetAlign(uint64_t Offset) {
2438 unsigned NewAIAlign = NewAI.getAlignment();
2440 NewAIAlign = TD.getABITypeAlignment(NewAI.getAllocatedType());
2441 return MinAlign(NewAIAlign, Offset);
2444 /// \brief Compute suitable alignment to access this partition of the new
2446 unsigned getPartitionAlign() {
2447 return getOffsetAlign(BeginOffset - NewAllocaBeginOffset);
2450 /// \brief Compute suitable alignment to access a type at an offset of the
2453 /// \returns zero if the type's ABI alignment is a suitable alignment,
2454 /// otherwise returns the maximal suitable alignment.
2455 unsigned getOffsetTypeAlign(Type *Ty, uint64_t Offset) {
2456 unsigned Align = getOffsetAlign(Offset);
2457 return Align == TD.getABITypeAlignment(Ty) ? 0 : Align;
2460 /// \brief Compute suitable alignment to access a type at the beginning of
2461 /// this partition of the new alloca.
2463 /// See \c getOffsetTypeAlign for details; this routine delegates to it.
2464 unsigned getPartitionTypeAlign(Type *Ty) {
2465 return getOffsetTypeAlign(Ty, BeginOffset - NewAllocaBeginOffset);
2468 unsigned getIndex(uint64_t Offset) {
2469 assert(VecTy && "Can only call getIndex when rewriting a vector");
2470 uint64_t RelOffset = Offset - NewAllocaBeginOffset;
2471 assert(RelOffset / ElementSize < UINT32_MAX && "Index out of bounds");
2472 uint32_t Index = RelOffset / ElementSize;
2473 assert(Index * ElementSize == RelOffset);
2477 void deleteIfTriviallyDead(Value *V) {
2478 Instruction *I = cast<Instruction>(V);
2479 if (isInstructionTriviallyDead(I))
2480 Pass.DeadInsts.insert(I);
2483 Value *rewriteVectorizedLoadInst(IRBuilderTy &IRB) {
2484 unsigned BeginIndex = getIndex(BeginOffset);
2485 unsigned EndIndex = getIndex(EndOffset);
2486 assert(EndIndex > BeginIndex && "Empty vector!");
2488 Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2490 return extractVector(IRB, V, BeginIndex, EndIndex, getName(".vec"));
2493 Value *rewriteIntegerLoad(IRBuilderTy &IRB, LoadInst &LI) {
2494 assert(IntTy && "We cannot insert an integer to the alloca");
2495 assert(!LI.isVolatile());
2496 Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2498 V = convertValue(TD, IRB, V, IntTy);
2499 assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2500 uint64_t Offset = BeginOffset - NewAllocaBeginOffset;
2501 if (Offset > 0 || EndOffset < NewAllocaEndOffset)
2502 V = extractInteger(TD, IRB, V, cast<IntegerType>(LI.getType()), Offset,
2503 getName(".extract"));
2507 bool visitLoadInst(LoadInst &LI) {
2508 DEBUG(dbgs() << " original: " << LI << "\n");
2509 Value *OldOp = LI.getOperand(0);
2510 assert(OldOp == OldPtr);
2512 uint64_t Size = EndOffset - BeginOffset;
2514 IRBuilderTy IRB(&LI);
2515 Type *TargetTy = IsSplit ? Type::getIntNTy(LI.getContext(), Size * 8)
2517 bool IsPtrAdjusted = false;
2520 V = rewriteVectorizedLoadInst(IRB);
2521 } else if (IntTy && LI.getType()->isIntegerTy()) {
2522 V = rewriteIntegerLoad(IRB, LI);
2523 } else if (BeginOffset == NewAllocaBeginOffset &&
2524 canConvertValue(TD, NewAllocaTy, LI.getType())) {
2525 V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2526 LI.isVolatile(), getName(".load"));
2528 Type *LTy = TargetTy->getPointerTo();
2529 V = IRB.CreateAlignedLoad(getAdjustedAllocaPtr(IRB, LTy),
2530 getPartitionTypeAlign(TargetTy),
2531 LI.isVolatile(), getName(".load"));
2532 IsPtrAdjusted = true;
2534 V = convertValue(TD, IRB, V, TargetTy);
2537 assert(!LI.isVolatile());
2538 assert(LI.getType()->isIntegerTy() &&
2539 "Only integer type loads and stores are split");
2540 assert(Size < TD.getTypeStoreSize(LI.getType()) &&
2541 "Split load isn't smaller than original load");
2542 assert(LI.getType()->getIntegerBitWidth() ==
2543 TD.getTypeStoreSizeInBits(LI.getType()) &&
2544 "Non-byte-multiple bit width");
2545 // Move the insertion point just past the load so that we can refer to it.
2546 IRB.SetInsertPoint(llvm::next(BasicBlock::iterator(&LI)));
2547 // Create a placeholder value with the same type as LI to use as the
2548 // basis for the new value. This allows us to replace the uses of LI with
2549 // the computed value, and then replace the placeholder with LI, leaving
2550 // LI only used for this computation.
2552 = new LoadInst(UndefValue::get(LI.getType()->getPointerTo()));
2553 V = insertInteger(TD, IRB, Placeholder, V, BeginOffset,
2554 getName(".insert"));
2555 LI.replaceAllUsesWith(V);
2556 Placeholder->replaceAllUsesWith(&LI);
2559 LI.replaceAllUsesWith(V);
2562 Pass.DeadInsts.insert(&LI);
2563 deleteIfTriviallyDead(OldOp);
2564 DEBUG(dbgs() << " to: " << *V << "\n");
2565 return !LI.isVolatile() && !IsPtrAdjusted;
2568 bool rewriteVectorizedStoreInst(IRBuilderTy &IRB, Value *V,
2569 StoreInst &SI, Value *OldOp) {
2570 unsigned BeginIndex = getIndex(BeginOffset);
2571 unsigned EndIndex = getIndex(EndOffset);
2572 assert(EndIndex > BeginIndex && "Empty vector!");
2573 unsigned NumElements = EndIndex - BeginIndex;
2574 assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
2576 = (NumElements == 1) ? ElementTy
2577 : VectorType::get(ElementTy, NumElements);
2578 if (V->getType() != PartitionTy)
2579 V = convertValue(TD, IRB, V, PartitionTy);
2581 // Mix in the existing elements.
2582 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2584 V = insertVector(IRB, Old, V, BeginIndex, getName(".vec"));
2586 StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment());
2587 Pass.DeadInsts.insert(&SI);
2590 DEBUG(dbgs() << " to: " << *Store << "\n");
2594 bool rewriteIntegerStore(IRBuilderTy &IRB, Value *V, StoreInst &SI) {
2595 assert(IntTy && "We cannot extract an integer from the alloca");
2596 assert(!SI.isVolatile());
2597 if (TD.getTypeSizeInBits(V->getType()) != IntTy->getBitWidth()) {
2598 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2599 getName(".oldload"));
2600 Old = convertValue(TD, IRB, Old, IntTy);
2601 assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2602 uint64_t Offset = BeginOffset - NewAllocaBeginOffset;
2603 V = insertInteger(TD, IRB, Old, SI.getValueOperand(), Offset,
2604 getName(".insert"));
2606 V = convertValue(TD, IRB, V, NewAllocaTy);
2607 StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment());
2608 Pass.DeadInsts.insert(&SI);
2610 DEBUG(dbgs() << " to: " << *Store << "\n");
2614 bool visitStoreInst(StoreInst &SI) {
2615 DEBUG(dbgs() << " original: " << SI << "\n");
2616 Value *OldOp = SI.getOperand(1);
2617 assert(OldOp == OldPtr);
2618 IRBuilderTy IRB(&SI);
2620 Value *V = SI.getValueOperand();
2622 // Strip all inbounds GEPs and pointer casts to try to dig out any root
2623 // alloca that should be re-examined after promoting this alloca.
2624 if (V->getType()->isPointerTy())
2625 if (AllocaInst *AI = dyn_cast<AllocaInst>(V->stripInBoundsOffsets()))
2626 Pass.PostPromotionWorklist.insert(AI);
2628 uint64_t Size = EndOffset - BeginOffset;
2629 if (Size < TD.getTypeStoreSize(V->getType())) {
2630 assert(!SI.isVolatile());
2631 assert(IsSplit && "A seemingly split store isn't splittable");
2632 assert(V->getType()->isIntegerTy() &&
2633 "Only integer type loads and stores are split");
2634 assert(V->getType()->getIntegerBitWidth() ==
2635 TD.getTypeStoreSizeInBits(V->getType()) &&
2636 "Non-byte-multiple bit width");
2637 IntegerType *NarrowTy = Type::getIntNTy(SI.getContext(), Size * 8);
2638 V = extractInteger(TD, IRB, V, NarrowTy, BeginOffset,
2639 getName(".extract"));
2643 return rewriteVectorizedStoreInst(IRB, V, SI, OldOp);
2644 if (IntTy && V->getType()->isIntegerTy())
2645 return rewriteIntegerStore(IRB, V, SI);
2648 if (BeginOffset == NewAllocaBeginOffset &&
2649 canConvertValue(TD, V->getType(), NewAllocaTy)) {
2650 V = convertValue(TD, IRB, V, NewAllocaTy);
2651 NewSI = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(),
2654 Value *NewPtr = getAdjustedAllocaPtr(IRB, V->getType()->getPointerTo());
2655 NewSI = IRB.CreateAlignedStore(V, NewPtr,
2656 getPartitionTypeAlign(V->getType()),
2660 Pass.DeadInsts.insert(&SI);
2661 deleteIfTriviallyDead(OldOp);
2663 DEBUG(dbgs() << " to: " << *NewSI << "\n");
2664 return NewSI->getPointerOperand() == &NewAI && !SI.isVolatile();
2667 /// \brief Compute an integer value from splatting an i8 across the given
2668 /// number of bytes.
2670 /// Note that this routine assumes an i8 is a byte. If that isn't true, don't
2671 /// call this routine.
2672 /// FIXME: Heed the advice above.
2674 /// \param V The i8 value to splat.
2675 /// \param Size The number of bytes in the output (assuming i8 is one byte)
2676 Value *getIntegerSplat(IRBuilderTy &IRB, Value *V, unsigned Size) {
2677 assert(Size > 0 && "Expected a positive number of bytes.");
2678 IntegerType *VTy = cast<IntegerType>(V->getType());
2679 assert(VTy->getBitWidth() == 8 && "Expected an i8 value for the byte");
2683 Type *SplatIntTy = Type::getIntNTy(VTy->getContext(), Size*8);
2684 V = IRB.CreateMul(IRB.CreateZExt(V, SplatIntTy, getName(".zext")),
2685 ConstantExpr::getUDiv(
2686 Constant::getAllOnesValue(SplatIntTy),
2687 ConstantExpr::getZExt(
2688 Constant::getAllOnesValue(V->getType()),
2690 getName(".isplat"));
2694 /// \brief Compute a vector splat for a given element value.
2695 Value *getVectorSplat(IRBuilderTy &IRB, Value *V, unsigned NumElements) {
2696 V = IRB.CreateVectorSplat(NumElements, V, NamePrefix);
2697 DEBUG(dbgs() << " splat: " << *V << "\n");
2701 bool visitMemSetInst(MemSetInst &II) {
2702 DEBUG(dbgs() << " original: " << II << "\n");
2703 IRBuilderTy IRB(&II);
2704 assert(II.getRawDest() == OldPtr);
2706 // If the memset has a variable size, it cannot be split, just adjust the
2707 // pointer to the new alloca.
2708 if (!isa<Constant>(II.getLength())) {
2709 II.setDest(getAdjustedAllocaPtr(IRB, II.getRawDest()->getType()));
2710 Type *CstTy = II.getAlignmentCst()->getType();
2711 II.setAlignment(ConstantInt::get(CstTy, getPartitionAlign()));
2713 deleteIfTriviallyDead(OldPtr);
2717 // Record this instruction for deletion.
2718 Pass.DeadInsts.insert(&II);
2720 Type *AllocaTy = NewAI.getAllocatedType();
2721 Type *ScalarTy = AllocaTy->getScalarType();
2723 // If this doesn't map cleanly onto the alloca type, and that type isn't
2724 // a single value type, just emit a memset.
2725 if (!VecTy && !IntTy &&
2726 (BeginOffset != NewAllocaBeginOffset ||
2727 EndOffset != NewAllocaEndOffset ||
2728 !AllocaTy->isSingleValueType() ||
2729 !TD.isLegalInteger(TD.getTypeSizeInBits(ScalarTy)) ||
2730 TD.getTypeSizeInBits(ScalarTy)%8 != 0)) {
2731 Type *SizeTy = II.getLength()->getType();
2732 Constant *Size = ConstantInt::get(SizeTy, EndOffset - BeginOffset);
2734 = IRB.CreateMemSet(getAdjustedAllocaPtr(IRB,
2735 II.getRawDest()->getType()),
2736 II.getValue(), Size, getPartitionAlign(),
2739 DEBUG(dbgs() << " to: " << *New << "\n");
2743 // If we can represent this as a simple value, we have to build the actual
2744 // value to store, which requires expanding the byte present in memset to
2745 // a sensible representation for the alloca type. This is essentially
2746 // splatting the byte to a sufficiently wide integer, splatting it across
2747 // any desired vector width, and bitcasting to the final type.
2751 // If this is a memset of a vectorized alloca, insert it.
2752 assert(ElementTy == ScalarTy);
2754 unsigned BeginIndex = getIndex(BeginOffset);
2755 unsigned EndIndex = getIndex(EndOffset);
2756 assert(EndIndex > BeginIndex && "Empty vector!");
2757 unsigned NumElements = EndIndex - BeginIndex;
2758 assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
2760 Value *Splat = getIntegerSplat(IRB, II.getValue(),
2761 TD.getTypeSizeInBits(ElementTy)/8);
2762 Splat = convertValue(TD, IRB, Splat, ElementTy);
2763 if (NumElements > 1)
2764 Splat = getVectorSplat(IRB, Splat, NumElements);
2766 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2767 getName(".oldload"));
2768 V = insertVector(IRB, Old, Splat, BeginIndex, getName(".vec"));
2770 // If this is a memset on an alloca where we can widen stores, insert the
2772 assert(!II.isVolatile());
2774 uint64_t Size = EndOffset - BeginOffset;
2775 V = getIntegerSplat(IRB, II.getValue(), Size);
2777 if (IntTy && (BeginOffset != NewAllocaBeginOffset ||
2778 EndOffset != NewAllocaBeginOffset)) {
2779 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2780 getName(".oldload"));
2781 Old = convertValue(TD, IRB, Old, IntTy);
2782 assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2783 uint64_t Offset = BeginOffset - NewAllocaBeginOffset;
2784 V = insertInteger(TD, IRB, Old, V, Offset, getName(".insert"));
2786 assert(V->getType() == IntTy &&
2787 "Wrong type for an alloca wide integer!");
2789 V = convertValue(TD, IRB, V, AllocaTy);
2791 // Established these invariants above.
2792 assert(BeginOffset == NewAllocaBeginOffset);
2793 assert(EndOffset == NewAllocaEndOffset);
2795 V = getIntegerSplat(IRB, II.getValue(),
2796 TD.getTypeSizeInBits(ScalarTy)/8);
2797 if (VectorType *AllocaVecTy = dyn_cast<VectorType>(AllocaTy))
2798 V = getVectorSplat(IRB, V, AllocaVecTy->getNumElements());
2800 V = convertValue(TD, IRB, V, AllocaTy);
2803 Value *New = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(),
2806 DEBUG(dbgs() << " to: " << *New << "\n");
2807 return !II.isVolatile();
2810 bool visitMemTransferInst(MemTransferInst &II) {
2811 // Rewriting of memory transfer instructions can be a bit tricky. We break
2812 // them into two categories: split intrinsics and unsplit intrinsics.
2814 DEBUG(dbgs() << " original: " << II << "\n");
2815 IRBuilderTy IRB(&II);
2817 assert(II.getRawSource() == OldPtr || II.getRawDest() == OldPtr);
2818 bool IsDest = II.getRawDest() == OldPtr;
2820 const AllocaPartitioning::MemTransferOffsets &MTO
2821 = P.getMemTransferOffsets(II);
2823 // Compute the relative offset within the transfer.
2824 unsigned IntPtrWidth = TD.getPointerSizeInBits();
2825 APInt RelOffset(IntPtrWidth, BeginOffset - (IsDest ? MTO.DestBegin
2826 : MTO.SourceBegin));
2828 unsigned Align = II.getAlignment();
2830 Align = MinAlign(RelOffset.zextOrTrunc(64).getZExtValue(),
2831 MinAlign(II.getAlignment(), getPartitionAlign()));
2833 // For unsplit intrinsics, we simply modify the source and destination
2834 // pointers in place. This isn't just an optimization, it is a matter of
2835 // correctness. With unsplit intrinsics we may be dealing with transfers
2836 // within a single alloca before SROA ran, or with transfers that have
2837 // a variable length. We may also be dealing with memmove instead of
2838 // memcpy, and so simply updating the pointers is the necessary for us to
2839 // update both source and dest of a single call.
2840 if (!MTO.IsSplittable) {
2841 Value *OldOp = IsDest ? II.getRawDest() : II.getRawSource();
2843 II.setDest(getAdjustedAllocaPtr(IRB, II.getRawDest()->getType()));
2845 II.setSource(getAdjustedAllocaPtr(IRB, II.getRawSource()->getType()));
2847 Type *CstTy = II.getAlignmentCst()->getType();
2848 II.setAlignment(ConstantInt::get(CstTy, Align));
2850 DEBUG(dbgs() << " to: " << II << "\n");
2851 deleteIfTriviallyDead(OldOp);
2854 // For split transfer intrinsics we have an incredibly useful assurance:
2855 // the source and destination do not reside within the same alloca, and at
2856 // least one of them does not escape. This means that we can replace
2857 // memmove with memcpy, and we don't need to worry about all manner of
2858 // downsides to splitting and transforming the operations.
2860 // If this doesn't map cleanly onto the alloca type, and that type isn't
2861 // a single value type, just emit a memcpy.
2863 = !VecTy && !IntTy && (BeginOffset != NewAllocaBeginOffset ||
2864 EndOffset != NewAllocaEndOffset ||
2865 !NewAI.getAllocatedType()->isSingleValueType());
2867 // If we're just going to emit a memcpy, the alloca hasn't changed, and the
2868 // size hasn't been shrunk based on analysis of the viable range, this is
2870 if (EmitMemCpy && &OldAI == &NewAI) {
2871 uint64_t OrigBegin = IsDest ? MTO.DestBegin : MTO.SourceBegin;
2872 uint64_t OrigEnd = IsDest ? MTO.DestEnd : MTO.SourceEnd;
2873 // Ensure the start lines up.
2874 assert(BeginOffset == OrigBegin);
2877 // Rewrite the size as needed.
2878 if (EndOffset != OrigEnd)
2879 II.setLength(ConstantInt::get(II.getLength()->getType(),
2880 EndOffset - BeginOffset));
2883 // Record this instruction for deletion.
2884 Pass.DeadInsts.insert(&II);
2886 // Strip all inbounds GEPs and pointer casts to try to dig out any root
2887 // alloca that should be re-examined after rewriting this instruction.
2888 Value *OtherPtr = IsDest ? II.getRawSource() : II.getRawDest();
2890 = dyn_cast<AllocaInst>(OtherPtr->stripInBoundsOffsets()))
2891 Pass.Worklist.insert(AI);
2894 Type *OtherPtrTy = IsDest ? II.getRawSource()->getType()
2895 : II.getRawDest()->getType();
2897 // Compute the other pointer, folding as much as possible to produce
2898 // a single, simple GEP in most cases.
2899 OtherPtr = getAdjustedPtr(IRB, TD, OtherPtr, RelOffset, OtherPtrTy,
2900 getName("." + OtherPtr->getName()));
2903 = getAdjustedAllocaPtr(IRB, IsDest ? II.getRawDest()->getType()
2904 : II.getRawSource()->getType());
2905 Type *SizeTy = II.getLength()->getType();
2906 Constant *Size = ConstantInt::get(SizeTy, EndOffset - BeginOffset);
2908 CallInst *New = IRB.CreateMemCpy(IsDest ? OurPtr : OtherPtr,
2909 IsDest ? OtherPtr : OurPtr,
2910 Size, Align, II.isVolatile());
2912 DEBUG(dbgs() << " to: " << *New << "\n");
2916 // Note that we clamp the alignment to 1 here as a 0 alignment for a memcpy
2917 // is equivalent to 1, but that isn't true if we end up rewriting this as
2922 bool IsWholeAlloca = BeginOffset == NewAllocaBeginOffset &&
2923 EndOffset == NewAllocaEndOffset;
2924 uint64_t Size = EndOffset - BeginOffset;
2925 unsigned BeginIndex = VecTy ? getIndex(BeginOffset) : 0;
2926 unsigned EndIndex = VecTy ? getIndex(EndOffset) : 0;
2927 unsigned NumElements = EndIndex - BeginIndex;
2928 IntegerType *SubIntTy
2929 = IntTy ? Type::getIntNTy(IntTy->getContext(), Size*8) : 0;
2931 Type *OtherPtrTy = NewAI.getType();
2932 if (VecTy && !IsWholeAlloca) {
2933 if (NumElements == 1)
2934 OtherPtrTy = VecTy->getElementType();
2936 OtherPtrTy = VectorType::get(VecTy->getElementType(), NumElements);
2938 OtherPtrTy = OtherPtrTy->getPointerTo();
2939 } else if (IntTy && !IsWholeAlloca) {
2940 OtherPtrTy = SubIntTy->getPointerTo();
2943 Value *SrcPtr = getAdjustedPtr(IRB, TD, OtherPtr, RelOffset, OtherPtrTy,
2944 getName("." + OtherPtr->getName()));
2945 Value *DstPtr = &NewAI;
2947 std::swap(SrcPtr, DstPtr);
2950 if (VecTy && !IsWholeAlloca && !IsDest) {
2951 Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2953 Src = extractVector(IRB, Src, BeginIndex, EndIndex, getName(".vec"));
2954 } else if (IntTy && !IsWholeAlloca && !IsDest) {
2955 Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2957 Src = convertValue(TD, IRB, Src, IntTy);
2958 assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2959 uint64_t Offset = BeginOffset - NewAllocaBeginOffset;
2960 Src = extractInteger(TD, IRB, Src, SubIntTy, Offset, getName(".extract"));
2962 Src = IRB.CreateAlignedLoad(SrcPtr, Align, II.isVolatile(),
2963 getName(".copyload"));
2966 if (VecTy && !IsWholeAlloca && IsDest) {
2967 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2968 getName(".oldload"));
2969 Src = insertVector(IRB, Old, Src, BeginIndex, getName(".vec"));
2970 } else if (IntTy && !IsWholeAlloca && IsDest) {
2971 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2972 getName(".oldload"));
2973 Old = convertValue(TD, IRB, Old, IntTy);
2974 assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2975 uint64_t Offset = BeginOffset - NewAllocaBeginOffset;
2976 Src = insertInteger(TD, IRB, Old, Src, Offset, getName(".insert"));
2977 Src = convertValue(TD, IRB, Src, NewAllocaTy);
2980 StoreInst *Store = cast<StoreInst>(
2981 IRB.CreateAlignedStore(Src, DstPtr, Align, II.isVolatile()));
2983 DEBUG(dbgs() << " to: " << *Store << "\n");
2984 return !II.isVolatile();
2987 bool visitIntrinsicInst(IntrinsicInst &II) {
2988 assert(II.getIntrinsicID() == Intrinsic::lifetime_start ||
2989 II.getIntrinsicID() == Intrinsic::lifetime_end);
2990 DEBUG(dbgs() << " original: " << II << "\n");
2991 IRBuilderTy IRB(&II);
2992 assert(II.getArgOperand(1) == OldPtr);
2994 // Record this instruction for deletion.
2995 Pass.DeadInsts.insert(&II);
2998 = ConstantInt::get(cast<IntegerType>(II.getArgOperand(0)->getType()),
2999 EndOffset - BeginOffset);
3000 Value *Ptr = getAdjustedAllocaPtr(IRB, II.getArgOperand(1)->getType());
3002 if (II.getIntrinsicID() == Intrinsic::lifetime_start)
3003 New = IRB.CreateLifetimeStart(Ptr, Size);
3005 New = IRB.CreateLifetimeEnd(Ptr, Size);
3008 DEBUG(dbgs() << " to: " << *New << "\n");
3012 bool visitPHINode(PHINode &PN) {
3013 DEBUG(dbgs() << " original: " << PN << "\n");
3015 // We would like to compute a new pointer in only one place, but have it be
3016 // as local as possible to the PHI. To do that, we re-use the location of
3017 // the old pointer, which necessarily must be in the right position to
3018 // dominate the PHI.
3019 IRBuilderTy PtrBuilder(cast<Instruction>(OldPtr));
3021 Value *NewPtr = getAdjustedAllocaPtr(PtrBuilder, OldPtr->getType());
3022 // Replace the operands which were using the old pointer.
3023 std::replace(PN.op_begin(), PN.op_end(), cast<Value>(OldPtr), NewPtr);
3025 DEBUG(dbgs() << " to: " << PN << "\n");
3026 deleteIfTriviallyDead(OldPtr);
3030 bool visitSelectInst(SelectInst &SI) {
3031 DEBUG(dbgs() << " original: " << SI << "\n");
3032 IRBuilderTy IRB(&SI);
3034 // Find the operand we need to rewrite here.
3035 bool IsTrueVal = SI.getTrueValue() == OldPtr;
3037 assert(SI.getFalseValue() != OldPtr && "Pointer is both operands!");
3039 assert(SI.getFalseValue() == OldPtr && "Pointer isn't an operand!");
3041 Value *NewPtr = getAdjustedAllocaPtr(IRB, OldPtr->getType());
3042 SI.setOperand(IsTrueVal ? 1 : 2, NewPtr);
3043 DEBUG(dbgs() << " to: " << SI << "\n");
3044 deleteIfTriviallyDead(OldPtr);
3052 /// \brief Visitor to rewrite aggregate loads and stores as scalar.
3054 /// This pass aggressively rewrites all aggregate loads and stores on
3055 /// a particular pointer (or any pointer derived from it which we can identify)
3056 /// with scalar loads and stores.
3057 class AggLoadStoreRewriter : public InstVisitor<AggLoadStoreRewriter, bool> {
3058 // Befriend the base class so it can delegate to private visit methods.
3059 friend class llvm::InstVisitor<AggLoadStoreRewriter, bool>;
3061 const DataLayout &TD;
3063 /// Queue of pointer uses to analyze and potentially rewrite.
3064 SmallVector<Use *, 8> Queue;
3066 /// Set to prevent us from cycling with phi nodes and loops.
3067 SmallPtrSet<User *, 8> Visited;
3069 /// The current pointer use being rewritten. This is used to dig up the used
3070 /// value (as opposed to the user).
3074 AggLoadStoreRewriter(const DataLayout &TD) : TD(TD) {}
3076 /// Rewrite loads and stores through a pointer and all pointers derived from
3078 bool rewrite(Instruction &I) {
3079 DEBUG(dbgs() << " Rewriting FCA loads and stores...\n");
3081 bool Changed = false;
3082 while (!Queue.empty()) {
3083 U = Queue.pop_back_val();
3084 Changed |= visit(cast<Instruction>(U->getUser()));
3090 /// Enqueue all the users of the given instruction for further processing.
3091 /// This uses a set to de-duplicate users.
3092 void enqueueUsers(Instruction &I) {
3093 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE;
3095 if (Visited.insert(*UI))
3096 Queue.push_back(&UI.getUse());
3099 // Conservative default is to not rewrite anything.
3100 bool visitInstruction(Instruction &I) { return false; }
3102 /// \brief Generic recursive split emission class.
3103 template <typename Derived>
3106 /// The builder used to form new instructions.
3108 /// The indices which to be used with insert- or extractvalue to select the
3109 /// appropriate value within the aggregate.
3110 SmallVector<unsigned, 4> Indices;
3111 /// The indices to a GEP instruction which will move Ptr to the correct slot
3112 /// within the aggregate.
3113 SmallVector<Value *, 4> GEPIndices;
3114 /// The base pointer of the original op, used as a base for GEPing the
3115 /// split operations.
3118 /// Initialize the splitter with an insertion point, Ptr and start with a
3119 /// single zero GEP index.
3120 OpSplitter(Instruction *InsertionPoint, Value *Ptr)
3121 : IRB(InsertionPoint), GEPIndices(1, IRB.getInt32(0)), Ptr(Ptr) {}
3124 /// \brief Generic recursive split emission routine.
3126 /// This method recursively splits an aggregate op (load or store) into
3127 /// scalar or vector ops. It splits recursively until it hits a single value
3128 /// and emits that single value operation via the template argument.
3130 /// The logic of this routine relies on GEPs and insertvalue and
3131 /// extractvalue all operating with the same fundamental index list, merely
3132 /// formatted differently (GEPs need actual values).
3134 /// \param Ty The type being split recursively into smaller ops.
3135 /// \param Agg The aggregate value being built up or stored, depending on
3136 /// whether this is splitting a load or a store respectively.
3137 void emitSplitOps(Type *Ty, Value *&Agg, const Twine &Name) {
3138 if (Ty->isSingleValueType())
3139 return static_cast<Derived *>(this)->emitFunc(Ty, Agg, Name);
3141 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
3142 unsigned OldSize = Indices.size();
3144 for (unsigned Idx = 0, Size = ATy->getNumElements(); Idx != Size;
3146 assert(Indices.size() == OldSize && "Did not return to the old size");
3147 Indices.push_back(Idx);
3148 GEPIndices.push_back(IRB.getInt32(Idx));
3149 emitSplitOps(ATy->getElementType(), Agg, Name + "." + Twine(Idx));
3150 GEPIndices.pop_back();
3156 if (StructType *STy = dyn_cast<StructType>(Ty)) {
3157 unsigned OldSize = Indices.size();
3159 for (unsigned Idx = 0, Size = STy->getNumElements(); Idx != Size;
3161 assert(Indices.size() == OldSize && "Did not return to the old size");
3162 Indices.push_back(Idx);
3163 GEPIndices.push_back(IRB.getInt32(Idx));
3164 emitSplitOps(STy->getElementType(Idx), Agg, Name + "." + Twine(Idx));
3165 GEPIndices.pop_back();
3171 llvm_unreachable("Only arrays and structs are aggregate loadable types");
3175 struct LoadOpSplitter : public OpSplitter<LoadOpSplitter> {
3176 LoadOpSplitter(Instruction *InsertionPoint, Value *Ptr)
3177 : OpSplitter<LoadOpSplitter>(InsertionPoint, Ptr) {}
3179 /// Emit a leaf load of a single value. This is called at the leaves of the
3180 /// recursive emission to actually load values.
3181 void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) {
3182 assert(Ty->isSingleValueType());
3183 // Load the single value and insert it using the indices.
3184 Value *GEP = IRB.CreateInBoundsGEP(Ptr, GEPIndices, Name + ".gep");
3185 Value *Load = IRB.CreateLoad(GEP, Name + ".load");
3186 Agg = IRB.CreateInsertValue(Agg, Load, Indices, Name + ".insert");
3187 DEBUG(dbgs() << " to: " << *Load << "\n");
3191 bool visitLoadInst(LoadInst &LI) {
3192 assert(LI.getPointerOperand() == *U);
3193 if (!LI.isSimple() || LI.getType()->isSingleValueType())
3196 // We have an aggregate being loaded, split it apart.
3197 DEBUG(dbgs() << " original: " << LI << "\n");
3198 LoadOpSplitter Splitter(&LI, *U);
3199 Value *V = UndefValue::get(LI.getType());
3200 Splitter.emitSplitOps(LI.getType(), V, LI.getName() + ".fca");
3201 LI.replaceAllUsesWith(V);
3202 LI.eraseFromParent();
3206 struct StoreOpSplitter : public OpSplitter<StoreOpSplitter> {
3207 StoreOpSplitter(Instruction *InsertionPoint, Value *Ptr)
3208 : OpSplitter<StoreOpSplitter>(InsertionPoint, Ptr) {}
3210 /// Emit a leaf store of a single value. This is called at the leaves of the
3211 /// recursive emission to actually produce stores.
3212 void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) {
3213 assert(Ty->isSingleValueType());
3214 // Extract the single value and store it using the indices.
3215 Value *Store = IRB.CreateStore(
3216 IRB.CreateExtractValue(Agg, Indices, Name + ".extract"),
3217 IRB.CreateInBoundsGEP(Ptr, GEPIndices, Name + ".gep"));
3219 DEBUG(dbgs() << " to: " << *Store << "\n");
3223 bool visitStoreInst(StoreInst &SI) {
3224 if (!SI.isSimple() || SI.getPointerOperand() != *U)
3226 Value *V = SI.getValueOperand();
3227 if (V->getType()->isSingleValueType())
3230 // We have an aggregate being stored, split it apart.
3231 DEBUG(dbgs() << " original: " << SI << "\n");
3232 StoreOpSplitter Splitter(&SI, *U);
3233 Splitter.emitSplitOps(V->getType(), V, V->getName() + ".fca");
3234 SI.eraseFromParent();
3238 bool visitBitCastInst(BitCastInst &BC) {
3243 bool visitGetElementPtrInst(GetElementPtrInst &GEPI) {
3248 bool visitPHINode(PHINode &PN) {
3253 bool visitSelectInst(SelectInst &SI) {
3260 /// \brief Strip aggregate type wrapping.
3262 /// This removes no-op aggregate types wrapping an underlying type. It will
3263 /// strip as many layers of types as it can without changing either the type
3264 /// size or the allocated size.
3265 static Type *stripAggregateTypeWrapping(const DataLayout &DL, Type *Ty) {
3266 if (Ty->isSingleValueType())
3269 uint64_t AllocSize = DL.getTypeAllocSize(Ty);
3270 uint64_t TypeSize = DL.getTypeSizeInBits(Ty);
3273 if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) {
3274 InnerTy = ArrTy->getElementType();
3275 } else if (StructType *STy = dyn_cast<StructType>(Ty)) {
3276 const StructLayout *SL = DL.getStructLayout(STy);
3277 unsigned Index = SL->getElementContainingOffset(0);
3278 InnerTy = STy->getElementType(Index);
3283 if (AllocSize > DL.getTypeAllocSize(InnerTy) ||
3284 TypeSize > DL.getTypeSizeInBits(InnerTy))
3287 return stripAggregateTypeWrapping(DL, InnerTy);
3290 /// \brief Try to find a partition of the aggregate type passed in for a given
3291 /// offset and size.
3293 /// This recurses through the aggregate type and tries to compute a subtype
3294 /// based on the offset and size. When the offset and size span a sub-section
3295 /// of an array, it will even compute a new array type for that sub-section,
3296 /// and the same for structs.
3298 /// Note that this routine is very strict and tries to find a partition of the
3299 /// type which produces the *exact* right offset and size. It is not forgiving
3300 /// when the size or offset cause either end of type-based partition to be off.
3301 /// Also, this is a best-effort routine. It is reasonable to give up and not
3302 /// return a type if necessary.
3303 static Type *getTypePartition(const DataLayout &TD, Type *Ty,
3304 uint64_t Offset, uint64_t Size) {
3305 if (Offset == 0 && TD.getTypeAllocSize(Ty) == Size)
3306 return stripAggregateTypeWrapping(TD, Ty);
3307 if (Offset > TD.getTypeAllocSize(Ty) ||
3308 (TD.getTypeAllocSize(Ty) - Offset) < Size)
3311 if (SequentialType *SeqTy = dyn_cast<SequentialType>(Ty)) {
3312 // We can't partition pointers...
3313 if (SeqTy->isPointerTy())
3316 Type *ElementTy = SeqTy->getElementType();
3317 uint64_t ElementSize = TD.getTypeAllocSize(ElementTy);
3318 uint64_t NumSkippedElements = Offset / ElementSize;
3319 if (ArrayType *ArrTy = dyn_cast<ArrayType>(SeqTy))
3320 if (NumSkippedElements >= ArrTy->getNumElements())
3322 if (VectorType *VecTy = dyn_cast<VectorType>(SeqTy))
3323 if (NumSkippedElements >= VecTy->getNumElements())
3325 Offset -= NumSkippedElements * ElementSize;
3327 // First check if we need to recurse.
3328 if (Offset > 0 || Size < ElementSize) {
3329 // Bail if the partition ends in a different array element.
3330 if ((Offset + Size) > ElementSize)
3332 // Recurse through the element type trying to peel off offset bytes.
3333 return getTypePartition(TD, ElementTy, Offset, Size);
3335 assert(Offset == 0);
3337 if (Size == ElementSize)
3338 return stripAggregateTypeWrapping(TD, ElementTy);
3339 assert(Size > ElementSize);
3340 uint64_t NumElements = Size / ElementSize;
3341 if (NumElements * ElementSize != Size)
3343 return ArrayType::get(ElementTy, NumElements);
3346 StructType *STy = dyn_cast<StructType>(Ty);
3350 const StructLayout *SL = TD.getStructLayout(STy);
3351 if (Offset >= SL->getSizeInBytes())
3353 uint64_t EndOffset = Offset + Size;
3354 if (EndOffset > SL->getSizeInBytes())
3357 unsigned Index = SL->getElementContainingOffset(Offset);
3358 Offset -= SL->getElementOffset(Index);
3360 Type *ElementTy = STy->getElementType(Index);
3361 uint64_t ElementSize = TD.getTypeAllocSize(ElementTy);
3362 if (Offset >= ElementSize)
3363 return 0; // The offset points into alignment padding.
3365 // See if any partition must be contained by the element.
3366 if (Offset > 0 || Size < ElementSize) {
3367 if ((Offset + Size) > ElementSize)
3369 return getTypePartition(TD, ElementTy, Offset, Size);
3371 assert(Offset == 0);
3373 if (Size == ElementSize)
3374 return stripAggregateTypeWrapping(TD, ElementTy);
3376 StructType::element_iterator EI = STy->element_begin() + Index,
3377 EE = STy->element_end();
3378 if (EndOffset < SL->getSizeInBytes()) {
3379 unsigned EndIndex = SL->getElementContainingOffset(EndOffset);
3380 if (Index == EndIndex)
3381 return 0; // Within a single element and its padding.
3383 // Don't try to form "natural" types if the elements don't line up with the
3385 // FIXME: We could potentially recurse down through the last element in the
3386 // sub-struct to find a natural end point.
3387 if (SL->getElementOffset(EndIndex) != EndOffset)
3390 assert(Index < EndIndex);
3391 EE = STy->element_begin() + EndIndex;
3394 // Try to build up a sub-structure.
3395 StructType *SubTy = StructType::get(STy->getContext(), makeArrayRef(EI, EE),
3397 const StructLayout *SubSL = TD.getStructLayout(SubTy);
3398 if (Size != SubSL->getSizeInBytes())
3399 return 0; // The sub-struct doesn't have quite the size needed.
3404 /// \brief Rewrite an alloca partition's users.
3406 /// This routine drives both of the rewriting goals of the SROA pass. It tries
3407 /// to rewrite uses of an alloca partition to be conducive for SSA value
3408 /// promotion. If the partition needs a new, more refined alloca, this will
3409 /// build that new alloca, preserving as much type information as possible, and
3410 /// rewrite the uses of the old alloca to point at the new one and have the
3411 /// appropriate new offsets. It also evaluates how successful the rewrite was
3412 /// at enabling promotion and if it was successful queues the alloca to be
3414 bool SROA::rewriteAllocaPartition(AllocaInst &AI,
3415 AllocaPartitioning &P,
3416 AllocaPartitioning::iterator PI) {
3417 uint64_t AllocaSize = PI->EndOffset - PI->BeginOffset;
3418 bool IsLive = false;
3419 for (AllocaPartitioning::use_iterator UI = P.use_begin(PI),
3421 UI != UE && !IsLive; ++UI)
3425 return false; // No live uses left of this partition.
3427 DEBUG(dbgs() << "Speculating PHIs and selects in partition "
3428 << "[" << PI->BeginOffset << "," << PI->EndOffset << ")\n");
3430 PHIOrSelectSpeculator Speculator(*TD, P, *this);
3431 DEBUG(dbgs() << " speculating ");
3432 DEBUG(P.print(dbgs(), PI, ""));
3433 Speculator.visitUsers(PI);
3435 // Try to compute a friendly type for this partition of the alloca. This
3436 // won't always succeed, in which case we fall back to a legal integer type
3437 // or an i8 array of an appropriate size.
3439 if (Type *PartitionTy = P.getCommonType(PI))
3440 if (TD->getTypeAllocSize(PartitionTy) >= AllocaSize)
3441 AllocaTy = PartitionTy;
3443 if (Type *PartitionTy = getTypePartition(*TD, AI.getAllocatedType(),
3444 PI->BeginOffset, AllocaSize))
3445 AllocaTy = PartitionTy;
3447 (AllocaTy->isArrayTy() &&
3448 AllocaTy->getArrayElementType()->isIntegerTy())) &&
3449 TD->isLegalInteger(AllocaSize * 8))
3450 AllocaTy = Type::getIntNTy(*C, AllocaSize * 8);
3452 AllocaTy = ArrayType::get(Type::getInt8Ty(*C), AllocaSize);
3453 assert(TD->getTypeAllocSize(AllocaTy) >= AllocaSize);
3455 // Check for the case where we're going to rewrite to a new alloca of the
3456 // exact same type as the original, and with the same access offsets. In that
3457 // case, re-use the existing alloca, but still run through the rewriter to
3458 // perform phi and select speculation.
3460 if (AllocaTy == AI.getAllocatedType()) {
3461 assert(PI->BeginOffset == 0 &&
3462 "Non-zero begin offset but same alloca type");
3463 assert(PI == P.begin() && "Begin offset is zero on later partition");
3466 unsigned Alignment = AI.getAlignment();
3468 // The minimum alignment which users can rely on when the explicit
3469 // alignment is omitted or zero is that required by the ABI for this
3471 Alignment = TD->getABITypeAlignment(AI.getAllocatedType());
3473 Alignment = MinAlign(Alignment, PI->BeginOffset);
3474 // If we will get at least this much alignment from the type alone, leave
3475 // the alloca's alignment unconstrained.
3476 if (Alignment <= TD->getABITypeAlignment(AllocaTy))
3478 NewAI = new AllocaInst(AllocaTy, 0, Alignment,
3479 AI.getName() + ".sroa." + Twine(PI - P.begin()),
3484 DEBUG(dbgs() << "Rewriting alloca partition "
3485 << "[" << PI->BeginOffset << "," << PI->EndOffset << ") to: "
3488 // Track the high watermark of the post-promotion worklist. We will reset it
3489 // to this point if the alloca is not in fact scheduled for promotion.
3490 unsigned PPWOldSize = PostPromotionWorklist.size();
3492 AllocaPartitionRewriter Rewriter(*TD, P, PI, *this, AI, *NewAI,
3493 PI->BeginOffset, PI->EndOffset);
3494 DEBUG(dbgs() << " rewriting ");
3495 DEBUG(P.print(dbgs(), PI, ""));
3496 bool Promotable = Rewriter.visitUsers(P.use_begin(PI), P.use_end(PI));
3498 DEBUG(dbgs() << " and queuing for promotion\n");
3499 PromotableAllocas.push_back(NewAI);
3500 } else if (NewAI != &AI) {
3501 // If we can't promote the alloca, iterate on it to check for new
3502 // refinements exposed by splitting the current alloca. Don't iterate on an
3503 // alloca which didn't actually change and didn't get promoted.
3504 Worklist.insert(NewAI);
3507 // Drop any post-promotion work items if promotion didn't happen.
3509 while (PostPromotionWorklist.size() > PPWOldSize)
3510 PostPromotionWorklist.pop_back();
3515 /// \brief Walks the partitioning of an alloca rewriting uses of each partition.
3516 bool SROA::splitAlloca(AllocaInst &AI, AllocaPartitioning &P) {
3517 bool Changed = false;
3518 for (AllocaPartitioning::iterator PI = P.begin(), PE = P.end(); PI != PE;
3520 Changed |= rewriteAllocaPartition(AI, P, PI);
3525 /// \brief Analyze an alloca for SROA.
3527 /// This analyzes the alloca to ensure we can reason about it, builds
3528 /// a partitioning of the alloca, and then hands it off to be split and
3529 /// rewritten as needed.
3530 bool SROA::runOnAlloca(AllocaInst &AI) {
3531 DEBUG(dbgs() << "SROA alloca: " << AI << "\n");
3532 ++NumAllocasAnalyzed;
3534 // Special case dead allocas, as they're trivial.
3535 if (AI.use_empty()) {
3536 AI.eraseFromParent();
3540 // Skip alloca forms that this analysis can't handle.
3541 if (AI.isArrayAllocation() || !AI.getAllocatedType()->isSized() ||
3542 TD->getTypeAllocSize(AI.getAllocatedType()) == 0)
3545 bool Changed = false;
3547 // First, split any FCA loads and stores touching this alloca to promote
3548 // better splitting and promotion opportunities.
3549 AggLoadStoreRewriter AggRewriter(*TD);
3550 Changed |= AggRewriter.rewrite(AI);
3552 // Build the partition set using a recursive instruction-visiting builder.
3553 AllocaPartitioning P(*TD, AI);
3554 DEBUG(P.print(dbgs()));
3558 // Delete all the dead users of this alloca before splitting and rewriting it.
3559 for (AllocaPartitioning::dead_user_iterator DI = P.dead_user_begin(),
3560 DE = P.dead_user_end();
3563 (*DI)->replaceAllUsesWith(UndefValue::get((*DI)->getType()));
3564 DeadInsts.insert(*DI);
3566 for (AllocaPartitioning::dead_op_iterator DO = P.dead_op_begin(),
3567 DE = P.dead_op_end();
3570 // Clobber the use with an undef value.
3571 **DO = UndefValue::get(OldV->getType());
3572 if (Instruction *OldI = dyn_cast<Instruction>(OldV))
3573 if (isInstructionTriviallyDead(OldI)) {
3575 DeadInsts.insert(OldI);
3579 // No partitions to split. Leave the dead alloca for a later pass to clean up.
3580 if (P.begin() == P.end())
3583 return splitAlloca(AI, P) || Changed;
3586 /// \brief Delete the dead instructions accumulated in this run.
3588 /// Recursively deletes the dead instructions we've accumulated. This is done
3589 /// at the very end to maximize locality of the recursive delete and to
3590 /// minimize the problems of invalidated instruction pointers as such pointers
3591 /// are used heavily in the intermediate stages of the algorithm.
3593 /// We also record the alloca instructions deleted here so that they aren't
3594 /// subsequently handed to mem2reg to promote.
3595 void SROA::deleteDeadInstructions(SmallPtrSet<AllocaInst*, 4> &DeletedAllocas) {
3596 while (!DeadInsts.empty()) {
3597 Instruction *I = DeadInsts.pop_back_val();
3598 DEBUG(dbgs() << "Deleting dead instruction: " << *I << "\n");
3600 I->replaceAllUsesWith(UndefValue::get(I->getType()));
3602 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
3603 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
3604 // Zero out the operand and see if it becomes trivially dead.
3606 if (isInstructionTriviallyDead(U))
3607 DeadInsts.insert(U);
3610 if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
3611 DeletedAllocas.insert(AI);
3614 I->eraseFromParent();
3618 /// \brief Promote the allocas, using the best available technique.
3620 /// This attempts to promote whatever allocas have been identified as viable in
3621 /// the PromotableAllocas list. If that list is empty, there is nothing to do.
3622 /// If there is a domtree available, we attempt to promote using the full power
3623 /// of mem2reg. Otherwise, we build and use the AllocaPromoter above which is
3624 /// based on the SSAUpdater utilities. This function returns whether any
3625 /// promotion occurred.
3626 bool SROA::promoteAllocas(Function &F) {
3627 if (PromotableAllocas.empty())
3630 NumPromoted += PromotableAllocas.size();
3632 if (DT && !ForceSSAUpdater) {
3633 DEBUG(dbgs() << "Promoting allocas with mem2reg...\n");
3634 PromoteMemToReg(PromotableAllocas, *DT);
3635 PromotableAllocas.clear();
3639 DEBUG(dbgs() << "Promoting allocas with SSAUpdater...\n");
3641 DIBuilder DIB(*F.getParent());
3642 SmallVector<Instruction*, 64> Insts;
3644 for (unsigned Idx = 0, Size = PromotableAllocas.size(); Idx != Size; ++Idx) {
3645 AllocaInst *AI = PromotableAllocas[Idx];
3646 for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end();
3648 Instruction *I = cast<Instruction>(*UI++);
3649 // FIXME: Currently the SSAUpdater infrastructure doesn't reason about
3650 // lifetime intrinsics and so we strip them (and the bitcasts+GEPs
3651 // leading to them) here. Eventually it should use them to optimize the
3652 // scalar values produced.
3653 if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) {
3654 assert(onlyUsedByLifetimeMarkers(I) &&
3655 "Found a bitcast used outside of a lifetime marker.");
3656 while (!I->use_empty())
3657 cast<Instruction>(*I->use_begin())->eraseFromParent();
3658 I->eraseFromParent();
3661 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
3662 assert(II->getIntrinsicID() == Intrinsic::lifetime_start ||
3663 II->getIntrinsicID() == Intrinsic::lifetime_end);
3664 II->eraseFromParent();
3670 AllocaPromoter(Insts, SSA, *AI, DIB).run(Insts);
3674 PromotableAllocas.clear();
3679 /// \brief A predicate to test whether an alloca belongs to a set.
3680 class IsAllocaInSet {
3681 typedef SmallPtrSet<AllocaInst *, 4> SetType;
3685 typedef AllocaInst *argument_type;
3687 IsAllocaInSet(const SetType &Set) : Set(Set) {}
3688 bool operator()(AllocaInst *AI) const { return Set.count(AI); }
3692 bool SROA::runOnFunction(Function &F) {
3693 DEBUG(dbgs() << "SROA function: " << F.getName() << "\n");
3694 C = &F.getContext();
3695 TD = getAnalysisIfAvailable<DataLayout>();
3697 DEBUG(dbgs() << " Skipping SROA -- no target data!\n");
3700 DT = getAnalysisIfAvailable<DominatorTree>();
3702 BasicBlock &EntryBB = F.getEntryBlock();
3703 for (BasicBlock::iterator I = EntryBB.begin(), E = llvm::prior(EntryBB.end());
3705 if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
3706 Worklist.insert(AI);
3708 bool Changed = false;
3709 // A set of deleted alloca instruction pointers which should be removed from
3710 // the list of promotable allocas.
3711 SmallPtrSet<AllocaInst *, 4> DeletedAllocas;
3714 while (!Worklist.empty()) {
3715 Changed |= runOnAlloca(*Worklist.pop_back_val());
3716 deleteDeadInstructions(DeletedAllocas);
3718 // Remove the deleted allocas from various lists so that we don't try to
3719 // continue processing them.
3720 if (!DeletedAllocas.empty()) {
3721 Worklist.remove_if(IsAllocaInSet(DeletedAllocas));
3722 PostPromotionWorklist.remove_if(IsAllocaInSet(DeletedAllocas));
3723 PromotableAllocas.erase(std::remove_if(PromotableAllocas.begin(),
3724 PromotableAllocas.end(),
3725 IsAllocaInSet(DeletedAllocas)),
3726 PromotableAllocas.end());
3727 DeletedAllocas.clear();
3731 Changed |= promoteAllocas(F);
3733 Worklist = PostPromotionWorklist;
3734 PostPromotionWorklist.clear();
3735 } while (!Worklist.empty());
3740 void SROA::getAnalysisUsage(AnalysisUsage &AU) const {
3741 if (RequiresDomTree)
3742 AU.addRequired<DominatorTree>();
3743 AU.setPreservesCFG();