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(NumNewAllocas, "Number of new, smaller allocas introduced");
61 STATISTIC(NumPromoted, "Number of allocas promoted to SSA values");
62 STATISTIC(NumLoadsSpeculated, "Number of loads speculated to allow promotion");
63 STATISTIC(NumDeleted, "Number of instructions deleted");
64 STATISTIC(NumVectorized, "Number of vectorized aggregates");
66 /// Hidden option to force the pass to not use DomTree and mem2reg, instead
67 /// forming SSA values through the SSAUpdater infrastructure.
69 ForceSSAUpdater("force-ssa-updater", cl::init(false), cl::Hidden);
72 /// \brief A common base class for representing a half-open byte range.
74 /// \brief The beginning offset of the range.
77 /// \brief The ending offset, not included in the range.
80 ByteRange() : BeginOffset(), EndOffset() {}
81 ByteRange(uint64_t BeginOffset, uint64_t EndOffset)
82 : BeginOffset(BeginOffset), EndOffset(EndOffset) {}
84 /// \brief Support for ordering ranges.
86 /// This provides an ordering over ranges such that start offsets are
87 /// always increasing, and within equal start offsets, the end offsets are
88 /// decreasing. Thus the spanning range comes first in a cluster with the
89 /// same start position.
90 bool operator<(const ByteRange &RHS) const {
91 if (BeginOffset < RHS.BeginOffset) return true;
92 if (BeginOffset > RHS.BeginOffset) return false;
93 if (EndOffset > RHS.EndOffset) return true;
97 /// \brief Support comparison with a single offset to allow binary searches.
98 friend bool operator<(const ByteRange &LHS, uint64_t RHSOffset) {
99 return LHS.BeginOffset < RHSOffset;
102 friend LLVM_ATTRIBUTE_UNUSED bool operator<(uint64_t LHSOffset,
103 const ByteRange &RHS) {
104 return LHSOffset < RHS.BeginOffset;
107 bool operator==(const ByteRange &RHS) const {
108 return BeginOffset == RHS.BeginOffset && EndOffset == RHS.EndOffset;
110 bool operator!=(const ByteRange &RHS) const { return !operator==(RHS); }
113 /// \brief A partition of an alloca.
115 /// This structure represents a contiguous partition of the alloca. These are
116 /// formed by examining the uses of the alloca. During formation, they may
117 /// overlap but once an AllocaPartitioning is built, the Partitions within it
118 /// are all disjoint.
119 struct Partition : public ByteRange {
120 /// \brief Whether this partition is splittable into smaller partitions.
122 /// We flag partitions as splittable when they are formed entirely due to
123 /// accesses by trivially splittable operations such as memset and memcpy.
126 /// \brief Test whether a partition has been marked as dead.
127 bool isDead() const {
128 if (BeginOffset == UINT64_MAX) {
129 assert(EndOffset == UINT64_MAX);
135 /// \brief Kill a partition.
136 /// This is accomplished by setting both its beginning and end offset to
137 /// the maximum possible value.
139 assert(!isDead() && "He's Dead, Jim!");
140 BeginOffset = EndOffset = UINT64_MAX;
143 Partition() : ByteRange(), IsSplittable() {}
144 Partition(uint64_t BeginOffset, uint64_t EndOffset, bool IsSplittable)
145 : ByteRange(BeginOffset, EndOffset), IsSplittable(IsSplittable) {}
148 /// \brief A particular use of a partition of the alloca.
150 /// This structure is used to associate uses of a partition with it. They
151 /// mark the range of bytes which are referenced by a particular instruction,
152 /// and includes a handle to the user itself and the pointer value in use.
153 /// The bounds of these uses are determined by intersecting the bounds of the
154 /// memory use itself with a particular partition. As a consequence there is
155 /// intentionally overlap between various uses of the same partition.
156 class PartitionUse : public ByteRange {
157 /// \brief Combined storage for both the Use* and split state.
158 PointerIntPair<Use*, 1, bool> UsePtrAndIsSplit;
161 PartitionUse() : ByteRange(), UsePtrAndIsSplit() {}
162 PartitionUse(uint64_t BeginOffset, uint64_t EndOffset, Use *U,
164 : ByteRange(BeginOffset, EndOffset), UsePtrAndIsSplit(U, IsSplit) {}
166 /// \brief The use in question. Provides access to both user and used value.
168 /// Note that this may be null if the partition use is *dead*, that is, it
169 /// should be ignored.
170 Use *getUse() const { return UsePtrAndIsSplit.getPointer(); }
172 /// \brief Set the use for this partition use range.
173 void setUse(Use *U) { UsePtrAndIsSplit.setPointer(U); }
175 /// \brief Whether this use is split across multiple partitions.
176 bool isSplit() const { return UsePtrAndIsSplit.getInt(); }
181 template <> struct isPodLike<Partition> : llvm::true_type {};
182 template <> struct isPodLike<PartitionUse> : llvm::true_type {};
186 /// \brief Alloca partitioning representation.
188 /// This class represents a partitioning of an alloca into slices, and
189 /// information about the nature of uses of each slice of the alloca. The goal
190 /// is that this information is sufficient to decide if and how to split the
191 /// alloca apart and replace slices with scalars. It is also intended that this
192 /// structure can capture the relevant information needed both to decide about
193 /// and to enact these transformations.
194 class AllocaPartitioning {
196 /// \brief Construct a partitioning of a particular alloca.
198 /// Construction does most of the work for partitioning the alloca. This
199 /// performs the necessary walks of users and builds a partitioning from it.
200 AllocaPartitioning(const DataLayout &TD, AllocaInst &AI);
202 /// \brief Test whether a pointer to the allocation escapes our analysis.
204 /// If this is true, the partitioning is never fully built and should be
206 bool isEscaped() const { return PointerEscapingInstr; }
208 /// \brief Support for iterating over the partitions.
210 typedef SmallVectorImpl<Partition>::iterator iterator;
211 iterator begin() { return Partitions.begin(); }
212 iterator end() { return Partitions.end(); }
214 typedef SmallVectorImpl<Partition>::const_iterator const_iterator;
215 const_iterator begin() const { return Partitions.begin(); }
216 const_iterator end() const { return Partitions.end(); }
219 /// \brief Support for iterating over and manipulating a particular
220 /// partition's uses.
222 /// The iteration support provided for uses is more limited, but also
223 /// includes some manipulation routines to support rewriting the uses of
224 /// partitions during SROA.
226 typedef SmallVectorImpl<PartitionUse>::iterator use_iterator;
227 use_iterator use_begin(unsigned Idx) { return Uses[Idx].begin(); }
228 use_iterator use_begin(const_iterator I) { return Uses[I - begin()].begin(); }
229 use_iterator use_end(unsigned Idx) { return Uses[Idx].end(); }
230 use_iterator use_end(const_iterator I) { return Uses[I - begin()].end(); }
232 typedef SmallVectorImpl<PartitionUse>::const_iterator const_use_iterator;
233 const_use_iterator use_begin(unsigned Idx) const { return Uses[Idx].begin(); }
234 const_use_iterator use_begin(const_iterator I) const {
235 return Uses[I - begin()].begin();
237 const_use_iterator use_end(unsigned Idx) const { return Uses[Idx].end(); }
238 const_use_iterator use_end(const_iterator I) const {
239 return Uses[I - begin()].end();
242 unsigned use_size(unsigned Idx) const { return Uses[Idx].size(); }
243 unsigned use_size(const_iterator I) const { return Uses[I - begin()].size(); }
244 const PartitionUse &getUse(unsigned PIdx, unsigned UIdx) const {
245 return Uses[PIdx][UIdx];
247 const PartitionUse &getUse(const_iterator I, unsigned UIdx) const {
248 return Uses[I - begin()][UIdx];
251 void use_push_back(unsigned Idx, const PartitionUse &PU) {
252 Uses[Idx].push_back(PU);
254 void use_push_back(const_iterator I, const PartitionUse &PU) {
255 Uses[I - begin()].push_back(PU);
259 /// \brief Allow iterating the dead users for this alloca.
261 /// These are instructions which will never actually use the alloca as they
262 /// are outside the allocated range. They are safe to replace with undef and
265 typedef SmallVectorImpl<Instruction *>::const_iterator dead_user_iterator;
266 dead_user_iterator dead_user_begin() const { return DeadUsers.begin(); }
267 dead_user_iterator dead_user_end() const { return DeadUsers.end(); }
270 /// \brief Allow iterating the dead expressions referring to this alloca.
272 /// These are operands which have cannot actually be used to refer to the
273 /// alloca as they are outside its range and the user doesn't correct for
274 /// that. These mostly consist of PHI node inputs and the like which we just
275 /// need to replace with undef.
277 typedef SmallVectorImpl<Use *>::const_iterator dead_op_iterator;
278 dead_op_iterator dead_op_begin() const { return DeadOperands.begin(); }
279 dead_op_iterator dead_op_end() const { return DeadOperands.end(); }
282 /// \brief MemTransferInst auxiliary data.
283 /// This struct provides some auxiliary data about memory transfer
284 /// intrinsics such as memcpy and memmove. These intrinsics can use two
285 /// different ranges within the same alloca, and provide other challenges to
286 /// correctly represent. We stash extra data to help us untangle this
287 /// after the partitioning is complete.
288 struct MemTransferOffsets {
289 /// The destination begin and end offsets when the destination is within
290 /// this alloca. If the end offset is zero the destination is not within
292 uint64_t DestBegin, DestEnd;
294 /// The source begin and end offsets when the source is within this alloca.
295 /// If the end offset is zero, the source is not within this alloca.
296 uint64_t SourceBegin, SourceEnd;
298 /// Flag for whether an alloca is splittable.
301 MemTransferOffsets getMemTransferOffsets(MemTransferInst &II) const {
302 return MemTransferInstData.lookup(&II);
305 /// \brief Map from a PHI or select operand back to a partition.
307 /// When manipulating PHI nodes or selects, they can use more than one
308 /// partition of an alloca. We store a special mapping to allow finding the
309 /// partition referenced by each of these operands, if any.
310 iterator findPartitionForPHIOrSelectOperand(Use *U) {
311 SmallDenseMap<Use *, std::pair<unsigned, unsigned> >::const_iterator MapIt
312 = PHIOrSelectOpMap.find(U);
313 if (MapIt == PHIOrSelectOpMap.end())
316 return begin() + MapIt->second.first;
319 /// \brief Map from a PHI or select operand back to the specific use of
322 /// Similar to mapping these operands back to the partitions, this maps
323 /// directly to the use structure of that partition.
324 use_iterator findPartitionUseForPHIOrSelectOperand(Use *U) {
325 SmallDenseMap<Use *, std::pair<unsigned, unsigned> >::const_iterator MapIt
326 = PHIOrSelectOpMap.find(U);
327 assert(MapIt != PHIOrSelectOpMap.end());
328 return Uses[MapIt->second.first].begin() + MapIt->second.second;
331 /// \brief Compute a common type among the uses of a particular partition.
333 /// This routines walks all of the uses of a particular partition and tries
334 /// to find a common type between them. Untyped operations such as memset and
335 /// memcpy are ignored.
336 Type *getCommonType(iterator I) const;
338 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
339 void print(raw_ostream &OS, const_iterator I, StringRef Indent = " ") const;
340 void printUsers(raw_ostream &OS, const_iterator I,
341 StringRef Indent = " ") const;
342 void print(raw_ostream &OS) const;
343 void LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED dump(const_iterator I) const;
344 void LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED dump() const;
348 template <typename DerivedT, typename RetT = void> class BuilderBase;
349 class PartitionBuilder;
350 friend class AllocaPartitioning::PartitionBuilder;
352 friend class AllocaPartitioning::UseBuilder;
354 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
355 /// \brief Handle to alloca instruction to simplify method interfaces.
359 /// \brief The instruction responsible for this alloca having no partitioning.
361 /// When an instruction (potentially) escapes the pointer to the alloca, we
362 /// store a pointer to that here and abort trying to partition the alloca.
363 /// This will be null if the alloca is partitioned successfully.
364 Instruction *PointerEscapingInstr;
366 /// \brief The partitions of the alloca.
368 /// We store a vector of the partitions over the alloca here. This vector is
369 /// sorted by increasing begin offset, and then by decreasing end offset. See
370 /// the Partition inner class for more details. Initially (during
371 /// construction) there are overlaps, but we form a disjoint sequence of
372 /// partitions while finishing construction and a fully constructed object is
373 /// expected to always have this as a disjoint space.
374 SmallVector<Partition, 8> Partitions;
376 /// \brief The uses of the partitions.
378 /// This is essentially a mapping from each partition to a list of uses of
379 /// that partition. The mapping is done with a Uses vector that has the exact
380 /// same number of entries as the partition vector. Each entry is itself
381 /// a vector of the uses.
382 SmallVector<SmallVector<PartitionUse, 2>, 8> Uses;
384 /// \brief Instructions which will become dead if we rewrite the alloca.
386 /// Note that these are not separated by partition. This is because we expect
387 /// a partitioned alloca to be completely rewritten or not rewritten at all.
388 /// If rewritten, all these instructions can simply be removed and replaced
389 /// with undef as they come from outside of the allocated space.
390 SmallVector<Instruction *, 8> DeadUsers;
392 /// \brief Operands which will become dead if we rewrite the alloca.
394 /// These are operands that in their particular use can be replaced with
395 /// undef when we rewrite the alloca. These show up in out-of-bounds inputs
396 /// to PHI nodes and the like. They aren't entirely dead (there might be
397 /// a GEP back into the bounds using it elsewhere) and nor is the PHI, but we
398 /// want to swap this particular input for undef to simplify the use lists of
400 SmallVector<Use *, 8> DeadOperands;
402 /// \brief The underlying storage for auxiliary memcpy and memset info.
403 SmallDenseMap<MemTransferInst *, MemTransferOffsets, 4> MemTransferInstData;
405 /// \brief A side datastructure used when building up the partitions and uses.
407 /// This mapping is only really used during the initial building of the
408 /// partitioning so that we can retain information about PHI and select nodes
410 SmallDenseMap<Instruction *, std::pair<uint64_t, bool> > PHIOrSelectSizes;
412 /// \brief Auxiliary information for particular PHI or select operands.
413 SmallDenseMap<Use *, std::pair<unsigned, unsigned>, 4> PHIOrSelectOpMap;
415 /// \brief A utility routine called from the constructor.
417 /// This does what it says on the tin. It is the key of the alloca partition
418 /// splitting and merging. After it is called we have the desired disjoint
419 /// collection of partitions.
420 void splitAndMergePartitions();
424 static Value *foldSelectInst(SelectInst &SI) {
425 // If the condition being selected on is a constant or the same value is
426 // being selected between, fold the select. Yes this does (rarely) happen
428 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI.getCondition()))
429 return SI.getOperand(1+CI->isZero());
430 if (SI.getOperand(1) == SI.getOperand(2))
431 return SI.getOperand(1);
436 /// \brief Builder for the alloca partitioning.
438 /// This class builds an alloca partitioning by recursively visiting the uses
439 /// of an alloca and splitting the partitions for each load and store at each
441 class AllocaPartitioning::PartitionBuilder
442 : public PtrUseVisitor<PartitionBuilder> {
443 friend class PtrUseVisitor<PartitionBuilder>;
444 friend class InstVisitor<PartitionBuilder>;
445 typedef PtrUseVisitor<PartitionBuilder> Base;
447 const uint64_t AllocSize;
448 AllocaPartitioning &P;
450 SmallDenseMap<Instruction *, unsigned> MemTransferPartitionMap;
453 PartitionBuilder(const DataLayout &DL, AllocaInst &AI, AllocaPartitioning &P)
454 : PtrUseVisitor<PartitionBuilder>(DL),
455 AllocSize(DL.getTypeAllocSize(AI.getAllocatedType())),
459 void insertUse(Instruction &I, const APInt &Offset, uint64_t Size,
460 bool IsSplittable = false) {
461 // Completely skip uses which have a zero size or start either before or
462 // past the end of the allocation.
463 if (Size == 0 || Offset.isNegative() || Offset.uge(AllocSize)) {
464 DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte use @" << Offset
465 << " which has zero size or starts outside of the "
466 << AllocSize << " byte alloca:\n"
467 << " alloca: " << P.AI << "\n"
468 << " use: " << I << "\n");
472 uint64_t BeginOffset = Offset.getZExtValue();
473 uint64_t EndOffset = BeginOffset + Size;
475 // Clamp the end offset to the end of the allocation. Note that this is
476 // formulated to handle even the case where "BeginOffset + Size" overflows.
477 // This may appear superficially to be something we could ignore entirely,
478 // but that is not so! There may be widened loads or PHI-node uses where
479 // some instructions are dead but not others. We can't completely ignore
480 // them, and so have to record at least the information here.
481 assert(AllocSize >= BeginOffset); // Established above.
482 if (Size > AllocSize - BeginOffset) {
483 DEBUG(dbgs() << "WARNING: Clamping a " << Size << " byte use @" << Offset
484 << " to remain within the " << AllocSize << " byte alloca:\n"
485 << " alloca: " << P.AI << "\n"
486 << " use: " << I << "\n");
487 EndOffset = AllocSize;
490 Partition New(BeginOffset, EndOffset, IsSplittable);
491 P.Partitions.push_back(New);
494 void handleLoadOrStore(Type *Ty, Instruction &I, const APInt &Offset,
495 uint64_t Size, bool IsVolatile) {
496 // We allow splitting of loads and stores where the type is an integer type
497 // and cover the entire alloca. This prevents us from splitting over
499 // FIXME: In the great blue eventually, we should eagerly split all integer
500 // loads and stores, and then have a separate step that merges adjacent
501 // alloca partitions into a single partition suitable for integer widening.
502 // Or we should skip the merge step and rely on GVN and other passes to
503 // merge adjacent loads and stores that survive mem2reg.
505 Ty->isIntegerTy() && !IsVolatile && Offset == 0 && Size >= AllocSize;
507 insertUse(I, Offset, Size, IsSplittable);
510 void visitLoadInst(LoadInst &LI) {
511 assert((!LI.isSimple() || LI.getType()->isSingleValueType()) &&
512 "All simple FCA loads should have been pre-split");
515 return PI.setAborted(&LI);
517 uint64_t Size = DL.getTypeStoreSize(LI.getType());
518 return handleLoadOrStore(LI.getType(), LI, Offset, Size, LI.isVolatile());
521 void visitStoreInst(StoreInst &SI) {
522 Value *ValOp = SI.getValueOperand();
524 return PI.setEscapedAndAborted(&SI);
526 return PI.setAborted(&SI);
528 uint64_t Size = DL.getTypeStoreSize(ValOp->getType());
530 // If this memory access can be shown to *statically* extend outside the
531 // bounds of of the allocation, it's behavior is undefined, so simply
532 // ignore it. Note that this is more strict than the generic clamping
533 // behavior of insertUse. We also try to handle cases which might run the
535 // FIXME: We should instead consider the pointer to have escaped if this
536 // function is being instrumented for addressing bugs or race conditions.
537 if (Offset.isNegative() || Size > AllocSize ||
538 Offset.ugt(AllocSize - Size)) {
539 DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte store @" << Offset
540 << " which extends past the end of the " << AllocSize
542 << " alloca: " << P.AI << "\n"
543 << " use: " << SI << "\n");
547 assert((!SI.isSimple() || ValOp->getType()->isSingleValueType()) &&
548 "All simple FCA stores should have been pre-split");
549 handleLoadOrStore(ValOp->getType(), SI, Offset, Size, SI.isVolatile());
553 void visitMemSetInst(MemSetInst &II) {
554 assert(II.getRawDest() == *U && "Pointer use is not the destination?");
555 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
556 if ((Length && Length->getValue() == 0) ||
557 (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize)))
558 // Zero-length mem transfer intrinsics can be ignored entirely.
562 return PI.setAborted(&II);
564 insertUse(II, Offset,
565 Length ? Length->getLimitedValue()
566 : AllocSize - Offset.getLimitedValue(),
570 void visitMemTransferInst(MemTransferInst &II) {
571 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
572 if ((Length && Length->getValue() == 0) ||
573 (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize)))
574 // Zero-length mem transfer intrinsics can be ignored entirely.
578 return PI.setAborted(&II);
580 uint64_t RawOffset = Offset.getLimitedValue();
581 uint64_t Size = Length ? Length->getLimitedValue()
582 : AllocSize - RawOffset;
584 MemTransferOffsets &Offsets = P.MemTransferInstData[&II];
586 // Only intrinsics with a constant length can be split.
587 Offsets.IsSplittable = Length;
589 if (*U == II.getRawDest()) {
590 Offsets.DestBegin = RawOffset;
591 Offsets.DestEnd = RawOffset + Size;
593 if (*U == II.getRawSource()) {
594 Offsets.SourceBegin = RawOffset;
595 Offsets.SourceEnd = RawOffset + Size;
598 // If we have set up end offsets for both the source and the destination,
599 // we have found both sides of this transfer pointing at the same alloca.
600 bool SeenBothEnds = Offsets.SourceEnd && Offsets.DestEnd;
601 if (SeenBothEnds && II.getRawDest() != II.getRawSource()) {
602 unsigned PrevIdx = MemTransferPartitionMap[&II];
604 // Check if the begin offsets match and this is a non-volatile transfer.
605 // In that case, we can completely elide the transfer.
606 if (!II.isVolatile() && Offsets.SourceBegin == Offsets.DestBegin) {
607 P.Partitions[PrevIdx].kill();
611 // Otherwise we have an offset transfer within the same alloca. We can't
613 P.Partitions[PrevIdx].IsSplittable = Offsets.IsSplittable = false;
614 } else if (SeenBothEnds) {
615 // Handle the case where this exact use provides both ends of the
617 assert(II.getRawDest() == II.getRawSource());
619 // For non-volatile transfers this is a no-op.
620 if (!II.isVolatile())
623 // Otherwise just suppress splitting.
624 Offsets.IsSplittable = false;
628 // Insert the use now that we've fixed up the splittable nature.
629 insertUse(II, Offset, Size, Offsets.IsSplittable);
631 // Setup the mapping from intrinsic to partition of we've not seen both
632 // ends of this transfer.
634 unsigned NewIdx = P.Partitions.size() - 1;
636 = MemTransferPartitionMap.insert(std::make_pair(&II, NewIdx)).second;
638 "Already have intrinsic in map but haven't seen both ends");
643 // Disable SRoA for any intrinsics except for lifetime invariants.
644 // FIXME: What about debug intrinsics? This matches old behavior, but
645 // doesn't make sense.
646 void visitIntrinsicInst(IntrinsicInst &II) {
648 return PI.setAborted(&II);
650 if (II.getIntrinsicID() == Intrinsic::lifetime_start ||
651 II.getIntrinsicID() == Intrinsic::lifetime_end) {
652 ConstantInt *Length = cast<ConstantInt>(II.getArgOperand(0));
653 uint64_t Size = std::min(AllocSize - Offset.getLimitedValue(),
654 Length->getLimitedValue());
655 insertUse(II, Offset, Size, true);
659 Base::visitIntrinsicInst(II);
662 Instruction *hasUnsafePHIOrSelectUse(Instruction *Root, uint64_t &Size) {
663 // We consider any PHI or select that results in a direct load or store of
664 // the same offset to be a viable use for partitioning purposes. These uses
665 // are considered unsplittable and the size is the maximum loaded or stored
667 SmallPtrSet<Instruction *, 4> Visited;
668 SmallVector<std::pair<Instruction *, Instruction *>, 4> Uses;
669 Visited.insert(Root);
670 Uses.push_back(std::make_pair(cast<Instruction>(*U), Root));
671 // If there are no loads or stores, the access is dead. We mark that as
672 // a size zero access.
675 Instruction *I, *UsedI;
676 llvm::tie(UsedI, I) = Uses.pop_back_val();
678 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
679 Size = std::max(Size, DL.getTypeStoreSize(LI->getType()));
682 if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
683 Value *Op = SI->getOperand(0);
686 Size = std::max(Size, DL.getTypeStoreSize(Op->getType()));
690 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
691 if (!GEP->hasAllZeroIndices())
693 } else if (!isa<BitCastInst>(I) && !isa<PHINode>(I) &&
694 !isa<SelectInst>(I)) {
698 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE;
700 if (Visited.insert(cast<Instruction>(*UI)))
701 Uses.push_back(std::make_pair(I, cast<Instruction>(*UI)));
702 } while (!Uses.empty());
707 void visitPHINode(PHINode &PN) {
711 return PI.setAborted(&PN);
713 // See if we already have computed info on this node.
714 std::pair<uint64_t, bool> &PHIInfo = P.PHIOrSelectSizes[&PN];
716 PHIInfo.second = true;
717 insertUse(PN, Offset, PHIInfo.first);
721 // Check for an unsafe use of the PHI node.
722 if (Instruction *UnsafeI = hasUnsafePHIOrSelectUse(&PN, PHIInfo.first))
723 return PI.setAborted(UnsafeI);
725 insertUse(PN, Offset, PHIInfo.first);
728 void visitSelectInst(SelectInst &SI) {
731 if (Value *Result = foldSelectInst(SI)) {
733 // If the result of the constant fold will be the pointer, recurse
734 // through the select as if we had RAUW'ed it.
740 return PI.setAborted(&SI);
742 // See if we already have computed info on this node.
743 std::pair<uint64_t, bool> &SelectInfo = P.PHIOrSelectSizes[&SI];
744 if (SelectInfo.first) {
745 SelectInfo.second = true;
746 insertUse(SI, Offset, SelectInfo.first);
750 // Check for an unsafe use of the PHI node.
751 if (Instruction *UnsafeI = hasUnsafePHIOrSelectUse(&SI, SelectInfo.first))
752 return PI.setAborted(UnsafeI);
754 insertUse(SI, Offset, SelectInfo.first);
757 /// \brief Disable SROA entirely if there are unhandled users of the alloca.
758 void visitInstruction(Instruction &I) {
763 /// \brief Use adder for the alloca partitioning.
765 /// This class adds the uses of an alloca to all of the partitions which they
766 /// use. For splittable partitions, this can end up doing essentially a linear
767 /// walk of the partitions, but the number of steps remains bounded by the
768 /// total result instruction size:
769 /// - The number of partitions is a result of the number unsplittable
770 /// instructions using the alloca.
771 /// - The number of users of each partition is at worst the total number of
772 /// splittable instructions using the alloca.
773 /// Thus we will produce N * M instructions in the end, where N are the number
774 /// of unsplittable uses and M are the number of splittable. This visitor does
775 /// the exact same number of updates to the partitioning.
777 /// In the more common case, this visitor will leverage the fact that the
778 /// partition space is pre-sorted, and do a logarithmic search for the
779 /// partition needed, making the total visit a classical ((N + M) * log(N))
780 /// complexity operation.
781 class AllocaPartitioning::UseBuilder : public PtrUseVisitor<UseBuilder> {
782 friend class PtrUseVisitor<UseBuilder>;
783 friend class InstVisitor<UseBuilder>;
784 typedef PtrUseVisitor<UseBuilder> Base;
786 const uint64_t AllocSize;
787 AllocaPartitioning &P;
789 /// \brief Set to de-duplicate dead instructions found in the use walk.
790 SmallPtrSet<Instruction *, 4> VisitedDeadInsts;
793 UseBuilder(const DataLayout &TD, AllocaInst &AI, AllocaPartitioning &P)
794 : PtrUseVisitor<UseBuilder>(TD),
795 AllocSize(TD.getTypeAllocSize(AI.getAllocatedType())),
799 void markAsDead(Instruction &I) {
800 if (VisitedDeadInsts.insert(&I))
801 P.DeadUsers.push_back(&I);
804 void insertUse(Instruction &User, const APInt &Offset, uint64_t Size) {
805 // If the use has a zero size or extends outside of the allocation, record
806 // it as a dead use for elimination later.
807 if (Size == 0 || Offset.isNegative() || Offset.uge(AllocSize))
808 return markAsDead(User);
810 uint64_t BeginOffset = Offset.getZExtValue();
811 uint64_t EndOffset = BeginOffset + Size;
813 // Clamp the end offset to the end of the allocation. Note that this is
814 // formulated to handle even the case where "BeginOffset + Size" overflows.
815 assert(AllocSize >= BeginOffset); // Established above.
816 if (Size > AllocSize - BeginOffset)
817 EndOffset = AllocSize;
819 // NB: This only works if we have zero overlapping partitions.
820 iterator I = std::lower_bound(P.begin(), P.end(), BeginOffset);
821 if (I != P.begin() && llvm::prior(I)->EndOffset > BeginOffset)
823 iterator E = P.end();
824 bool IsSplit = llvm::next(I) != E && llvm::next(I)->BeginOffset < EndOffset;
825 for (; I != E && I->BeginOffset < EndOffset; ++I) {
826 PartitionUse NewPU(std::max(I->BeginOffset, BeginOffset),
827 std::min(I->EndOffset, EndOffset), U, IsSplit);
828 P.use_push_back(I, NewPU);
829 if (isa<PHINode>(U->getUser()) || isa<SelectInst>(U->getUser()))
830 P.PHIOrSelectOpMap[U]
831 = std::make_pair(I - P.begin(), P.Uses[I - P.begin()].size() - 1);
835 void visitBitCastInst(BitCastInst &BC) {
837 return markAsDead(BC);
839 return Base::visitBitCastInst(BC);
842 void visitGetElementPtrInst(GetElementPtrInst &GEPI) {
843 if (GEPI.use_empty())
844 return markAsDead(GEPI);
846 return Base::visitGetElementPtrInst(GEPI);
849 void visitLoadInst(LoadInst &LI) {
850 assert(IsOffsetKnown);
851 uint64_t Size = DL.getTypeStoreSize(LI.getType());
852 insertUse(LI, Offset, Size);
855 void visitStoreInst(StoreInst &SI) {
856 assert(IsOffsetKnown);
857 uint64_t Size = DL.getTypeStoreSize(SI.getOperand(0)->getType());
859 // If this memory access can be shown to *statically* extend outside the
860 // bounds of of the allocation, it's behavior is undefined, so simply
861 // ignore it. Note that this is more strict than the generic clamping
862 // behavior of insertUse.
863 if (Offset.isNegative() || Size > AllocSize ||
864 Offset.ugt(AllocSize - Size))
865 return markAsDead(SI);
867 insertUse(SI, Offset, Size);
870 void visitMemSetInst(MemSetInst &II) {
871 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
872 if ((Length && Length->getValue() == 0) ||
873 (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize)))
874 return markAsDead(II);
876 assert(IsOffsetKnown);
877 insertUse(II, Offset, Length ? Length->getLimitedValue()
878 : AllocSize - Offset.getLimitedValue());
881 void visitMemTransferInst(MemTransferInst &II) {
882 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
883 if ((Length && Length->getValue() == 0) ||
884 (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize)))
885 return markAsDead(II);
887 assert(IsOffsetKnown);
888 uint64_t Size = Length ? Length->getLimitedValue()
889 : AllocSize - Offset.getLimitedValue();
891 MemTransferOffsets &Offsets = P.MemTransferInstData[&II];
892 if (!II.isVolatile() && Offsets.DestEnd && Offsets.SourceEnd &&
893 Offsets.DestBegin == Offsets.SourceBegin)
894 return markAsDead(II); // Skip identity transfers without side-effects.
896 insertUse(II, Offset, Size);
899 void visitIntrinsicInst(IntrinsicInst &II) {
900 assert(IsOffsetKnown);
901 assert(II.getIntrinsicID() == Intrinsic::lifetime_start ||
902 II.getIntrinsicID() == Intrinsic::lifetime_end);
904 ConstantInt *Length = cast<ConstantInt>(II.getArgOperand(0));
905 insertUse(II, Offset, std::min(Length->getLimitedValue(),
906 AllocSize - Offset.getLimitedValue()));
909 void insertPHIOrSelect(Instruction &User, const APInt &Offset) {
910 uint64_t Size = P.PHIOrSelectSizes.lookup(&User).first;
912 // For PHI and select operands outside the alloca, we can't nuke the entire
913 // phi or select -- the other side might still be relevant, so we special
914 // case them here and use a separate structure to track the operands
915 // themselves which should be replaced with undef.
916 if ((Offset.isNegative() && Offset.uge(Size)) ||
917 (!Offset.isNegative() && Offset.uge(AllocSize))) {
918 P.DeadOperands.push_back(U);
922 insertUse(User, Offset, Size);
925 void visitPHINode(PHINode &PN) {
927 return markAsDead(PN);
929 assert(IsOffsetKnown);
930 insertPHIOrSelect(PN, Offset);
933 void visitSelectInst(SelectInst &SI) {
935 return markAsDead(SI);
937 if (Value *Result = foldSelectInst(SI)) {
939 // If the result of the constant fold will be the pointer, recurse
940 // through the select as if we had RAUW'ed it.
943 // Otherwise the operand to the select is dead, and we can replace it
945 P.DeadOperands.push_back(U);
950 assert(IsOffsetKnown);
951 insertPHIOrSelect(SI, Offset);
954 /// \brief Unreachable, we've already visited the alloca once.
955 void visitInstruction(Instruction &I) {
956 llvm_unreachable("Unhandled instruction in use builder.");
960 void AllocaPartitioning::splitAndMergePartitions() {
961 size_t NumDeadPartitions = 0;
963 // Track the range of splittable partitions that we pass when accumulating
964 // overlapping unsplittable partitions.
965 uint64_t SplitEndOffset = 0ull;
967 Partition New(0ull, 0ull, false);
969 for (unsigned i = 0, j = i, e = Partitions.size(); i != e; i = j) {
972 if (!Partitions[i].IsSplittable || New.BeginOffset == New.EndOffset) {
973 assert(New.BeginOffset == New.EndOffset);
976 assert(New.IsSplittable);
977 New.EndOffset = std::max(New.EndOffset, Partitions[i].EndOffset);
979 assert(New.BeginOffset != New.EndOffset);
981 // Scan the overlapping partitions.
982 while (j != e && New.EndOffset > Partitions[j].BeginOffset) {
983 // If the new partition we are forming is splittable, stop at the first
984 // unsplittable partition.
985 if (New.IsSplittable && !Partitions[j].IsSplittable)
988 // Grow the new partition to include any equally splittable range. 'j' is
989 // always equally splittable when New is splittable, but when New is not
990 // splittable, we may subsume some (or part of some) splitable partition
991 // without growing the new one.
992 if (New.IsSplittable == Partitions[j].IsSplittable) {
993 New.EndOffset = std::max(New.EndOffset, Partitions[j].EndOffset);
995 assert(!New.IsSplittable);
996 assert(Partitions[j].IsSplittable);
997 SplitEndOffset = std::max(SplitEndOffset, Partitions[j].EndOffset);
1000 Partitions[j].kill();
1001 ++NumDeadPartitions;
1005 // If the new partition is splittable, chop off the end as soon as the
1006 // unsplittable subsequent partition starts and ensure we eventually cover
1007 // the splittable area.
1008 if (j != e && New.IsSplittable) {
1009 SplitEndOffset = std::max(SplitEndOffset, New.EndOffset);
1010 New.EndOffset = std::min(New.EndOffset, Partitions[j].BeginOffset);
1013 // Add the new partition if it differs from the original one and is
1014 // non-empty. We can end up with an empty partition here if it was
1015 // splittable but there is an unsplittable one that starts at the same
1017 if (New != Partitions[i]) {
1018 if (New.BeginOffset != New.EndOffset)
1019 Partitions.push_back(New);
1020 // Mark the old one for removal.
1021 Partitions[i].kill();
1022 ++NumDeadPartitions;
1025 New.BeginOffset = New.EndOffset;
1026 if (!New.IsSplittable) {
1027 New.EndOffset = std::max(New.EndOffset, SplitEndOffset);
1028 if (j != e && !Partitions[j].IsSplittable)
1029 New.EndOffset = std::min(New.EndOffset, Partitions[j].BeginOffset);
1030 New.IsSplittable = true;
1031 // If there is a trailing splittable partition which won't be fused into
1032 // the next splittable partition go ahead and add it onto the partitions
1034 if (New.BeginOffset < New.EndOffset &&
1035 (j == e || !Partitions[j].IsSplittable ||
1036 New.EndOffset < Partitions[j].BeginOffset)) {
1037 Partitions.push_back(New);
1038 New.BeginOffset = New.EndOffset = 0ull;
1043 // Re-sort the partitions now that they have been split and merged into
1044 // disjoint set of partitions. Also remove any of the dead partitions we've
1045 // replaced in the process.
1046 std::sort(Partitions.begin(), Partitions.end());
1047 if (NumDeadPartitions) {
1048 assert(Partitions.back().isDead());
1049 assert((ptrdiff_t)NumDeadPartitions ==
1050 std::count(Partitions.begin(), Partitions.end(), Partitions.back()));
1052 Partitions.erase(Partitions.end() - NumDeadPartitions, Partitions.end());
1055 AllocaPartitioning::AllocaPartitioning(const DataLayout &TD, AllocaInst &AI)
1057 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1060 PointerEscapingInstr(0) {
1061 PartitionBuilder PB(TD, AI, *this);
1062 PartitionBuilder::PtrInfo PtrI = PB.visitPtr(AI);
1063 if (PtrI.isEscaped() || PtrI.isAborted()) {
1064 // FIXME: We should sink the escape vs. abort info into the caller nicely,
1065 // possibly by just storing the PtrInfo in the AllocaPartitioning.
1066 PointerEscapingInstr = PtrI.getEscapingInst() ? PtrI.getEscapingInst()
1067 : PtrI.getAbortingInst();
1068 assert(PointerEscapingInstr && "Did not track a bad instruction");
1072 // Sort the uses. This arranges for the offsets to be in ascending order,
1073 // and the sizes to be in descending order.
1074 std::sort(Partitions.begin(), Partitions.end());
1076 // Remove any partitions from the back which are marked as dead.
1077 while (!Partitions.empty() && Partitions.back().isDead())
1078 Partitions.pop_back();
1080 if (Partitions.size() > 1) {
1081 // Intersect splittability for all partitions with equal offsets and sizes.
1082 // Then remove all but the first so that we have a sequence of non-equal but
1083 // potentially overlapping partitions.
1084 for (iterator I = Partitions.begin(), J = I, E = Partitions.end(); I != E;
1087 while (J != E && *I == *J) {
1088 I->IsSplittable &= J->IsSplittable;
1092 Partitions.erase(std::unique(Partitions.begin(), Partitions.end()),
1095 // Split splittable and merge unsplittable partitions into a disjoint set
1096 // of partitions over the used space of the allocation.
1097 splitAndMergePartitions();
1100 // Now build up the user lists for each of these disjoint partitions by
1101 // re-walking the recursive users of the alloca.
1102 Uses.resize(Partitions.size());
1103 UseBuilder UB(TD, AI, *this);
1104 PtrI = UB.visitPtr(AI);
1105 assert(!PtrI.isEscaped() && "Previously analyzed pointer now escapes!");
1106 assert(!PtrI.isAborted() && "Early aborted the visit of the pointer.");
1109 Type *AllocaPartitioning::getCommonType(iterator I) const {
1111 for (const_use_iterator UI = use_begin(I), UE = use_end(I); UI != UE; ++UI) {
1112 Use *U = UI->getUse();
1114 continue; // Skip dead uses.
1115 if (isa<IntrinsicInst>(*U->getUser()))
1117 if (UI->BeginOffset != I->BeginOffset || UI->EndOffset != I->EndOffset)
1121 if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser()))
1122 UserTy = LI->getType();
1123 else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser()))
1124 UserTy = SI->getValueOperand()->getType();
1126 return 0; // Bail if we have weird uses.
1128 if (IntegerType *ITy = dyn_cast<IntegerType>(UserTy)) {
1129 // If the type is larger than the partition, skip it. We only encounter
1130 // this for split integer operations where we want to use the type of the
1131 // entity causing the split.
1132 if (ITy->getBitWidth() > (I->EndOffset - I->BeginOffset)*8)
1135 // If we have found an integer type use covering the alloca, use that
1136 // regardless of the other types, as integers are often used for a "bucket
1141 if (Ty && Ty != UserTy)
1149 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1151 void AllocaPartitioning::print(raw_ostream &OS, const_iterator I,
1152 StringRef Indent) const {
1153 OS << Indent << "partition #" << (I - begin())
1154 << " [" << I->BeginOffset << "," << I->EndOffset << ")"
1155 << (I->IsSplittable ? " (splittable)" : "")
1156 << (Uses[I - begin()].empty() ? " (zero uses)" : "")
1160 void AllocaPartitioning::printUsers(raw_ostream &OS, const_iterator I,
1161 StringRef Indent) const {
1162 for (const_use_iterator UI = use_begin(I), UE = use_end(I); UI != UE; ++UI) {
1164 continue; // Skip dead uses.
1165 OS << Indent << " [" << UI->BeginOffset << "," << UI->EndOffset << ") "
1166 << "used by: " << *UI->getUse()->getUser() << "\n";
1167 if (MemTransferInst *II =
1168 dyn_cast<MemTransferInst>(UI->getUse()->getUser())) {
1169 const MemTransferOffsets &MTO = MemTransferInstData.lookup(II);
1171 if (!MTO.IsSplittable)
1172 IsDest = UI->BeginOffset == MTO.DestBegin;
1174 IsDest = MTO.DestBegin != 0u;
1175 OS << Indent << " (original " << (IsDest ? "dest" : "source") << ": "
1176 << "[" << (IsDest ? MTO.DestBegin : MTO.SourceBegin)
1177 << "," << (IsDest ? MTO.DestEnd : MTO.SourceEnd) << ")\n";
1182 void AllocaPartitioning::print(raw_ostream &OS) const {
1183 if (PointerEscapingInstr) {
1184 OS << "No partitioning for alloca: " << AI << "\n"
1185 << " A pointer to this alloca escaped by:\n"
1186 << " " << *PointerEscapingInstr << "\n";
1190 OS << "Partitioning of alloca: " << AI << "\n";
1191 for (const_iterator I = begin(), E = end(); I != E; ++I) {
1197 void AllocaPartitioning::dump(const_iterator I) const { print(dbgs(), I); }
1198 void AllocaPartitioning::dump() const { print(dbgs()); }
1200 #endif // !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1204 /// \brief Implementation of LoadAndStorePromoter for promoting allocas.
1206 /// This subclass of LoadAndStorePromoter adds overrides to handle promoting
1207 /// the loads and stores of an alloca instruction, as well as updating its
1208 /// debug information. This is used when a domtree is unavailable and thus
1209 /// mem2reg in its full form can't be used to handle promotion of allocas to
1211 class AllocaPromoter : public LoadAndStorePromoter {
1215 SmallVector<DbgDeclareInst *, 4> DDIs;
1216 SmallVector<DbgValueInst *, 4> DVIs;
1219 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S,
1220 AllocaInst &AI, DIBuilder &DIB)
1221 : LoadAndStorePromoter(Insts, S), AI(AI), DIB(DIB) {}
1223 void run(const SmallVectorImpl<Instruction*> &Insts) {
1224 // Remember which alloca we're promoting (for isInstInList).
1225 if (MDNode *DebugNode = MDNode::getIfExists(AI.getContext(), &AI)) {
1226 for (Value::use_iterator UI = DebugNode->use_begin(),
1227 UE = DebugNode->use_end();
1229 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(*UI))
1230 DDIs.push_back(DDI);
1231 else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(*UI))
1232 DVIs.push_back(DVI);
1235 LoadAndStorePromoter::run(Insts);
1236 AI.eraseFromParent();
1237 while (!DDIs.empty())
1238 DDIs.pop_back_val()->eraseFromParent();
1239 while (!DVIs.empty())
1240 DVIs.pop_back_val()->eraseFromParent();
1243 virtual bool isInstInList(Instruction *I,
1244 const SmallVectorImpl<Instruction*> &Insts) const {
1245 if (LoadInst *LI = dyn_cast<LoadInst>(I))
1246 return LI->getOperand(0) == &AI;
1247 return cast<StoreInst>(I)->getPointerOperand() == &AI;
1250 virtual void updateDebugInfo(Instruction *Inst) const {
1251 for (SmallVector<DbgDeclareInst *, 4>::const_iterator I = DDIs.begin(),
1252 E = DDIs.end(); I != E; ++I) {
1253 DbgDeclareInst *DDI = *I;
1254 if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
1255 ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
1256 else if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
1257 ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
1259 for (SmallVector<DbgValueInst *, 4>::const_iterator I = DVIs.begin(),
1260 E = DVIs.end(); I != E; ++I) {
1261 DbgValueInst *DVI = *I;
1263 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
1264 // If an argument is zero extended then use argument directly. The ZExt
1265 // may be zapped by an optimization pass in future.
1266 if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
1267 Arg = dyn_cast<Argument>(ZExt->getOperand(0));
1268 if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
1269 Arg = dyn_cast<Argument>(SExt->getOperand(0));
1271 Arg = SI->getOperand(0);
1272 } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
1273 Arg = LI->getOperand(0);
1277 Instruction *DbgVal =
1278 DIB.insertDbgValueIntrinsic(Arg, 0, DIVariable(DVI->getVariable()),
1280 DbgVal->setDebugLoc(DVI->getDebugLoc());
1284 } // end anon namespace
1288 /// \brief An optimization pass providing Scalar Replacement of Aggregates.
1290 /// This pass takes allocations which can be completely analyzed (that is, they
1291 /// don't escape) and tries to turn them into scalar SSA values. There are
1292 /// a few steps to this process.
1294 /// 1) It takes allocations of aggregates and analyzes the ways in which they
1295 /// are used to try to split them into smaller allocations, ideally of
1296 /// a single scalar data type. It will split up memcpy and memset accesses
1297 /// as necessary and try to isolate individual scalar accesses.
1298 /// 2) It will transform accesses into forms which are suitable for SSA value
1299 /// promotion. This can be replacing a memset with a scalar store of an
1300 /// integer value, or it can involve speculating operations on a PHI or
1301 /// select to be a PHI or select of the results.
1302 /// 3) Finally, this will try to detect a pattern of accesses which map cleanly
1303 /// onto insert and extract operations on a vector value, and convert them to
1304 /// this form. By doing so, it will enable promotion of vector aggregates to
1305 /// SSA vector values.
1306 class SROA : public FunctionPass {
1307 const bool RequiresDomTree;
1310 const DataLayout *TD;
1313 /// \brief Worklist of alloca instructions to simplify.
1315 /// Each alloca in the function is added to this. Each new alloca formed gets
1316 /// added to it as well to recursively simplify unless that alloca can be
1317 /// directly promoted. Finally, each time we rewrite a use of an alloca other
1318 /// the one being actively rewritten, we add it back onto the list if not
1319 /// already present to ensure it is re-visited.
1320 SetVector<AllocaInst *, SmallVector<AllocaInst *, 16> > Worklist;
1322 /// \brief A collection of instructions to delete.
1323 /// We try to batch deletions to simplify code and make things a bit more
1325 SetVector<Instruction *, SmallVector<Instruction *, 8> > DeadInsts;
1327 /// \brief Post-promotion worklist.
1329 /// Sometimes we discover an alloca which has a high probability of becoming
1330 /// viable for SROA after a round of promotion takes place. In those cases,
1331 /// the alloca is enqueued here for re-processing.
1333 /// Note that we have to be very careful to clear allocas out of this list in
1334 /// the event they are deleted.
1335 SetVector<AllocaInst *, SmallVector<AllocaInst *, 16> > PostPromotionWorklist;
1337 /// \brief A collection of alloca instructions we can directly promote.
1338 std::vector<AllocaInst *> PromotableAllocas;
1341 SROA(bool RequiresDomTree = true)
1342 : FunctionPass(ID), RequiresDomTree(RequiresDomTree),
1343 C(0), TD(0), DT(0) {
1344 initializeSROAPass(*PassRegistry::getPassRegistry());
1346 bool runOnFunction(Function &F);
1347 void getAnalysisUsage(AnalysisUsage &AU) const;
1349 const char *getPassName() const { return "SROA"; }
1353 friend class PHIOrSelectSpeculator;
1354 friend class AllocaPartitionRewriter;
1355 friend class AllocaPartitionVectorRewriter;
1357 bool rewriteAllocaPartition(AllocaInst &AI,
1358 AllocaPartitioning &P,
1359 AllocaPartitioning::iterator PI);
1360 bool splitAlloca(AllocaInst &AI, AllocaPartitioning &P);
1361 bool runOnAlloca(AllocaInst &AI);
1362 void deleteDeadInstructions(SmallPtrSet<AllocaInst *, 4> &DeletedAllocas);
1363 bool promoteAllocas(Function &F);
1369 FunctionPass *llvm::createSROAPass(bool RequiresDomTree) {
1370 return new SROA(RequiresDomTree);
1373 INITIALIZE_PASS_BEGIN(SROA, "sroa", "Scalar Replacement Of Aggregates",
1375 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
1376 INITIALIZE_PASS_END(SROA, "sroa", "Scalar Replacement Of Aggregates",
1380 /// \brief Visitor to speculate PHIs and Selects where possible.
1381 class PHIOrSelectSpeculator : public InstVisitor<PHIOrSelectSpeculator> {
1382 // Befriend the base class so it can delegate to private visit methods.
1383 friend class llvm::InstVisitor<PHIOrSelectSpeculator>;
1385 const DataLayout &TD;
1386 AllocaPartitioning &P;
1390 PHIOrSelectSpeculator(const DataLayout &TD, AllocaPartitioning &P, SROA &Pass)
1391 : TD(TD), P(P), Pass(Pass) {}
1393 /// \brief Visit the users of an alloca partition and rewrite them.
1394 void visitUsers(AllocaPartitioning::const_iterator PI) {
1395 // Note that we need to use an index here as the underlying vector of uses
1396 // may be grown during speculation. However, we never need to re-visit the
1397 // new uses, and so we can use the initial size bound.
1398 for (unsigned Idx = 0, Size = P.use_size(PI); Idx != Size; ++Idx) {
1399 const PartitionUse &PU = P.getUse(PI, Idx);
1401 continue; // Skip dead use.
1403 visit(cast<Instruction>(PU.getUse()->getUser()));
1408 // By default, skip this instruction.
1409 void visitInstruction(Instruction &I) {}
1411 /// PHI instructions that use an alloca and are subsequently loaded can be
1412 /// rewritten to load both input pointers in the pred blocks and then PHI the
1413 /// results, allowing the load of the alloca to be promoted.
1415 /// %P2 = phi [i32* %Alloca, i32* %Other]
1416 /// %V = load i32* %P2
1418 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1420 /// %V2 = load i32* %Other
1422 /// %V = phi [i32 %V1, i32 %V2]
1424 /// We can do this to a select if its only uses are loads and if the operands
1425 /// to the select can be loaded unconditionally.
1427 /// FIXME: This should be hoisted into a generic utility, likely in
1428 /// Transforms/Util/Local.h
1429 bool isSafePHIToSpeculate(PHINode &PN, SmallVectorImpl<LoadInst *> &Loads) {
1430 // For now, we can only do this promotion if the load is in the same block
1431 // as the PHI, and if there are no stores between the phi and load.
1432 // TODO: Allow recursive phi users.
1433 // TODO: Allow stores.
1434 BasicBlock *BB = PN.getParent();
1435 unsigned MaxAlign = 0;
1436 for (Value::use_iterator UI = PN.use_begin(), UE = PN.use_end();
1438 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1439 if (LI == 0 || !LI->isSimple()) return false;
1441 // For now we only allow loads in the same block as the PHI. This is
1442 // a common case that happens when instcombine merges two loads through
1444 if (LI->getParent() != BB) return false;
1446 // Ensure that there are no instructions between the PHI and the load that
1448 for (BasicBlock::iterator BBI = &PN; &*BBI != LI; ++BBI)
1449 if (BBI->mayWriteToMemory())
1452 MaxAlign = std::max(MaxAlign, LI->getAlignment());
1453 Loads.push_back(LI);
1456 // We can only transform this if it is safe to push the loads into the
1457 // predecessor blocks. The only thing to watch out for is that we can't put
1458 // a possibly trapping load in the predecessor if it is a critical edge.
1459 for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) {
1460 TerminatorInst *TI = PN.getIncomingBlock(Idx)->getTerminator();
1461 Value *InVal = PN.getIncomingValue(Idx);
1463 // If the value is produced by the terminator of the predecessor (an
1464 // invoke) or it has side-effects, there is no valid place to put a load
1465 // in the predecessor.
1466 if (TI == InVal || TI->mayHaveSideEffects())
1469 // If the predecessor has a single successor, then the edge isn't
1471 if (TI->getNumSuccessors() == 1)
1474 // If this pointer is always safe to load, or if we can prove that there
1475 // is already a load in the block, then we can move the load to the pred
1477 if (InVal->isDereferenceablePointer() ||
1478 isSafeToLoadUnconditionally(InVal, TI, MaxAlign, &TD))
1487 void visitPHINode(PHINode &PN) {
1488 DEBUG(dbgs() << " original: " << PN << "\n");
1490 SmallVector<LoadInst *, 4> Loads;
1491 if (!isSafePHIToSpeculate(PN, Loads))
1494 assert(!Loads.empty());
1496 Type *LoadTy = cast<PointerType>(PN.getType())->getElementType();
1497 IRBuilder<> PHIBuilder(&PN);
1498 PHINode *NewPN = PHIBuilder.CreatePHI(LoadTy, PN.getNumIncomingValues(),
1499 PN.getName() + ".sroa.speculated");
1501 // Get the TBAA tag and alignment to use from one of the loads. It doesn't
1502 // matter which one we get and if any differ.
1503 LoadInst *SomeLoad = cast<LoadInst>(Loads.back());
1504 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa);
1505 unsigned Align = SomeLoad->getAlignment();
1507 // Rewrite all loads of the PN to use the new PHI.
1509 LoadInst *LI = Loads.pop_back_val();
1510 LI->replaceAllUsesWith(NewPN);
1511 Pass.DeadInsts.insert(LI);
1512 } while (!Loads.empty());
1514 // Inject loads into all of the pred blocks.
1515 for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) {
1516 BasicBlock *Pred = PN.getIncomingBlock(Idx);
1517 TerminatorInst *TI = Pred->getTerminator();
1518 Use *InUse = &PN.getOperandUse(PN.getOperandNumForIncomingValue(Idx));
1519 Value *InVal = PN.getIncomingValue(Idx);
1520 IRBuilder<> PredBuilder(TI);
1523 = PredBuilder.CreateLoad(InVal, (PN.getName() + ".sroa.speculate.load." +
1525 ++NumLoadsSpeculated;
1526 Load->setAlignment(Align);
1528 Load->setMetadata(LLVMContext::MD_tbaa, TBAATag);
1529 NewPN->addIncoming(Load, Pred);
1531 Instruction *Ptr = dyn_cast<Instruction>(InVal);
1533 // No uses to rewrite.
1536 // Try to lookup and rewrite any partition uses corresponding to this phi
1538 AllocaPartitioning::iterator PI
1539 = P.findPartitionForPHIOrSelectOperand(InUse);
1543 // Replace the Use in the PartitionUse for this operand with the Use
1545 AllocaPartitioning::use_iterator UI
1546 = P.findPartitionUseForPHIOrSelectOperand(InUse);
1547 assert(isa<PHINode>(*UI->getUse()->getUser()));
1548 UI->setUse(&Load->getOperandUse(Load->getPointerOperandIndex()));
1550 DEBUG(dbgs() << " speculated to: " << *NewPN << "\n");
1553 /// Select instructions that use an alloca and are subsequently loaded can be
1554 /// rewritten to load both input pointers and then select between the result,
1555 /// allowing the load of the alloca to be promoted.
1557 /// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
1558 /// %V = load i32* %P2
1560 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1561 /// %V2 = load i32* %Other
1562 /// %V = select i1 %cond, i32 %V1, i32 %V2
1564 /// We can do this to a select if its only uses are loads and if the operand
1565 /// to the select can be loaded unconditionally.
1566 bool isSafeSelectToSpeculate(SelectInst &SI,
1567 SmallVectorImpl<LoadInst *> &Loads) {
1568 Value *TValue = SI.getTrueValue();
1569 Value *FValue = SI.getFalseValue();
1570 bool TDerefable = TValue->isDereferenceablePointer();
1571 bool FDerefable = FValue->isDereferenceablePointer();
1573 for (Value::use_iterator UI = SI.use_begin(), UE = SI.use_end();
1575 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1576 if (LI == 0 || !LI->isSimple()) return false;
1578 // Both operands to the select need to be dereferencable, either
1579 // absolutely (e.g. allocas) or at this point because we can see other
1581 if (!TDerefable && !isSafeToLoadUnconditionally(TValue, LI,
1582 LI->getAlignment(), &TD))
1584 if (!FDerefable && !isSafeToLoadUnconditionally(FValue, LI,
1585 LI->getAlignment(), &TD))
1587 Loads.push_back(LI);
1593 void visitSelectInst(SelectInst &SI) {
1594 DEBUG(dbgs() << " original: " << SI << "\n");
1596 // If the select isn't safe to speculate, just use simple logic to emit it.
1597 SmallVector<LoadInst *, 4> Loads;
1598 if (!isSafeSelectToSpeculate(SI, Loads))
1601 IRBuilder<> IRB(&SI);
1602 Use *Ops[2] = { &SI.getOperandUse(1), &SI.getOperandUse(2) };
1603 AllocaPartitioning::iterator PIs[2];
1604 PartitionUse PUs[2];
1605 for (unsigned i = 0, e = 2; i != e; ++i) {
1606 PIs[i] = P.findPartitionForPHIOrSelectOperand(Ops[i]);
1607 if (PIs[i] != P.end()) {
1608 // If the pointer is within the partitioning, remove the select from
1609 // its uses. We'll add in the new loads below.
1610 AllocaPartitioning::use_iterator UI
1611 = P.findPartitionUseForPHIOrSelectOperand(Ops[i]);
1613 // Clear out the use here so that the offsets into the use list remain
1614 // stable but this use is ignored when rewriting.
1619 Value *TV = SI.getTrueValue();
1620 Value *FV = SI.getFalseValue();
1621 // Replace the loads of the select with a select of two loads.
1622 while (!Loads.empty()) {
1623 LoadInst *LI = Loads.pop_back_val();
1625 IRB.SetInsertPoint(LI);
1627 IRB.CreateLoad(TV, LI->getName() + ".sroa.speculate.load.true");
1629 IRB.CreateLoad(FV, LI->getName() + ".sroa.speculate.load.false");
1630 NumLoadsSpeculated += 2;
1632 // Transfer alignment and TBAA info if present.
1633 TL->setAlignment(LI->getAlignment());
1634 FL->setAlignment(LI->getAlignment());
1635 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) {
1636 TL->setMetadata(LLVMContext::MD_tbaa, Tag);
1637 FL->setMetadata(LLVMContext::MD_tbaa, Tag);
1640 Value *V = IRB.CreateSelect(SI.getCondition(), TL, FL,
1641 LI->getName() + ".sroa.speculated");
1643 LoadInst *Loads[2] = { TL, FL };
1644 for (unsigned i = 0, e = 2; i != e; ++i) {
1645 if (PIs[i] != P.end()) {
1646 Use *LoadUse = &Loads[i]->getOperandUse(0);
1647 assert(PUs[i].getUse()->get() == LoadUse->get());
1648 PUs[i].setUse(LoadUse);
1649 P.use_push_back(PIs[i], PUs[i]);
1653 DEBUG(dbgs() << " speculated to: " << *V << "\n");
1654 LI->replaceAllUsesWith(V);
1655 Pass.DeadInsts.insert(LI);
1661 /// \brief Build a GEP out of a base pointer and indices.
1663 /// This will return the BasePtr if that is valid, or build a new GEP
1664 /// instruction using the IRBuilder if GEP-ing is needed.
1665 static Value *buildGEP(IRBuilder<> &IRB, Value *BasePtr,
1666 SmallVectorImpl<Value *> &Indices,
1667 const Twine &Prefix) {
1668 if (Indices.empty())
1671 // A single zero index is a no-op, so check for this and avoid building a GEP
1673 if (Indices.size() == 1 && cast<ConstantInt>(Indices.back())->isZero())
1676 return IRB.CreateInBoundsGEP(BasePtr, Indices, Prefix + ".idx");
1679 /// \brief Get a natural GEP off of the BasePtr walking through Ty toward
1680 /// TargetTy without changing the offset of the pointer.
1682 /// This routine assumes we've already established a properly offset GEP with
1683 /// Indices, and arrived at the Ty type. The goal is to continue to GEP with
1684 /// zero-indices down through type layers until we find one the same as
1685 /// TargetTy. If we can't find one with the same type, we at least try to use
1686 /// one with the same size. If none of that works, we just produce the GEP as
1687 /// indicated by Indices to have the correct offset.
1688 static Value *getNaturalGEPWithType(IRBuilder<> &IRB, const DataLayout &TD,
1689 Value *BasePtr, Type *Ty, Type *TargetTy,
1690 SmallVectorImpl<Value *> &Indices,
1691 const Twine &Prefix) {
1693 return buildGEP(IRB, BasePtr, Indices, Prefix);
1695 // See if we can descend into a struct and locate a field with the correct
1697 unsigned NumLayers = 0;
1698 Type *ElementTy = Ty;
1700 if (ElementTy->isPointerTy())
1702 if (SequentialType *SeqTy = dyn_cast<SequentialType>(ElementTy)) {
1703 ElementTy = SeqTy->getElementType();
1704 // Note that we use the default address space as this index is over an
1705 // array or a vector, not a pointer.
1706 Indices.push_back(IRB.getInt(APInt(TD.getPointerSizeInBits(0), 0)));
1707 } else if (StructType *STy = dyn_cast<StructType>(ElementTy)) {
1708 if (STy->element_begin() == STy->element_end())
1709 break; // Nothing left to descend into.
1710 ElementTy = *STy->element_begin();
1711 Indices.push_back(IRB.getInt32(0));
1716 } while (ElementTy != TargetTy);
1717 if (ElementTy != TargetTy)
1718 Indices.erase(Indices.end() - NumLayers, Indices.end());
1720 return buildGEP(IRB, BasePtr, Indices, Prefix);
1723 /// \brief Recursively compute indices for a natural GEP.
1725 /// This is the recursive step for getNaturalGEPWithOffset that walks down the
1726 /// element types adding appropriate indices for the GEP.
1727 static Value *getNaturalGEPRecursively(IRBuilder<> &IRB, const DataLayout &TD,
1728 Value *Ptr, Type *Ty, APInt &Offset,
1730 SmallVectorImpl<Value *> &Indices,
1731 const Twine &Prefix) {
1733 return getNaturalGEPWithType(IRB, TD, Ptr, Ty, TargetTy, Indices, Prefix);
1735 // We can't recurse through pointer types.
1736 if (Ty->isPointerTy())
1739 // We try to analyze GEPs over vectors here, but note that these GEPs are
1740 // extremely poorly defined currently. The long-term goal is to remove GEPing
1741 // over a vector from the IR completely.
1742 if (VectorType *VecTy = dyn_cast<VectorType>(Ty)) {
1743 unsigned ElementSizeInBits = TD.getTypeSizeInBits(VecTy->getScalarType());
1744 if (ElementSizeInBits % 8)
1745 return 0; // GEPs over non-multiple of 8 size vector elements are invalid.
1746 APInt ElementSize(Offset.getBitWidth(), ElementSizeInBits / 8);
1747 APInt NumSkippedElements = Offset.sdiv(ElementSize);
1748 if (NumSkippedElements.ugt(VecTy->getNumElements()))
1750 Offset -= NumSkippedElements * ElementSize;
1751 Indices.push_back(IRB.getInt(NumSkippedElements));
1752 return getNaturalGEPRecursively(IRB, TD, Ptr, VecTy->getElementType(),
1753 Offset, TargetTy, Indices, Prefix);
1756 if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) {
1757 Type *ElementTy = ArrTy->getElementType();
1758 APInt ElementSize(Offset.getBitWidth(), TD.getTypeAllocSize(ElementTy));
1759 APInt NumSkippedElements = Offset.sdiv(ElementSize);
1760 if (NumSkippedElements.ugt(ArrTy->getNumElements()))
1763 Offset -= NumSkippedElements * ElementSize;
1764 Indices.push_back(IRB.getInt(NumSkippedElements));
1765 return getNaturalGEPRecursively(IRB, TD, Ptr, ElementTy, Offset, TargetTy,
1769 StructType *STy = dyn_cast<StructType>(Ty);
1773 const StructLayout *SL = TD.getStructLayout(STy);
1774 uint64_t StructOffset = Offset.getZExtValue();
1775 if (StructOffset >= SL->getSizeInBytes())
1777 unsigned Index = SL->getElementContainingOffset(StructOffset);
1778 Offset -= APInt(Offset.getBitWidth(), SL->getElementOffset(Index));
1779 Type *ElementTy = STy->getElementType(Index);
1780 if (Offset.uge(TD.getTypeAllocSize(ElementTy)))
1781 return 0; // The offset points into alignment padding.
1783 Indices.push_back(IRB.getInt32(Index));
1784 return getNaturalGEPRecursively(IRB, TD, Ptr, ElementTy, Offset, TargetTy,
1788 /// \brief Get a natural GEP from a base pointer to a particular offset and
1789 /// resulting in a particular type.
1791 /// The goal is to produce a "natural" looking GEP that works with the existing
1792 /// composite types to arrive at the appropriate offset and element type for
1793 /// a pointer. TargetTy is the element type the returned GEP should point-to if
1794 /// possible. We recurse by decreasing Offset, adding the appropriate index to
1795 /// Indices, and setting Ty to the result subtype.
1797 /// If no natural GEP can be constructed, this function returns null.
1798 static Value *getNaturalGEPWithOffset(IRBuilder<> &IRB, const DataLayout &TD,
1799 Value *Ptr, APInt Offset, Type *TargetTy,
1800 SmallVectorImpl<Value *> &Indices,
1801 const Twine &Prefix) {
1802 PointerType *Ty = cast<PointerType>(Ptr->getType());
1804 // Don't consider any GEPs through an i8* as natural unless the TargetTy is
1806 if (Ty == IRB.getInt8PtrTy() && TargetTy->isIntegerTy(8))
1809 Type *ElementTy = Ty->getElementType();
1810 if (!ElementTy->isSized())
1811 return 0; // We can't GEP through an unsized element.
1812 APInt ElementSize(Offset.getBitWidth(), TD.getTypeAllocSize(ElementTy));
1813 if (ElementSize == 0)
1814 return 0; // Zero-length arrays can't help us build a natural GEP.
1815 APInt NumSkippedElements = Offset.sdiv(ElementSize);
1817 Offset -= NumSkippedElements * ElementSize;
1818 Indices.push_back(IRB.getInt(NumSkippedElements));
1819 return getNaturalGEPRecursively(IRB, TD, Ptr, ElementTy, Offset, TargetTy,
1823 /// \brief Compute an adjusted pointer from Ptr by Offset bytes where the
1824 /// resulting pointer has PointerTy.
1826 /// This tries very hard to compute a "natural" GEP which arrives at the offset
1827 /// and produces the pointer type desired. Where it cannot, it will try to use
1828 /// the natural GEP to arrive at the offset and bitcast to the type. Where that
1829 /// fails, it will try to use an existing i8* and GEP to the byte offset and
1830 /// bitcast to the type.
1832 /// The strategy for finding the more natural GEPs is to peel off layers of the
1833 /// pointer, walking back through bit casts and GEPs, searching for a base
1834 /// pointer from which we can compute a natural GEP with the desired
1835 /// properties. The algorithm tries to fold as many constant indices into
1836 /// a single GEP as possible, thus making each GEP more independent of the
1837 /// surrounding code.
1838 static Value *getAdjustedPtr(IRBuilder<> &IRB, const DataLayout &TD,
1839 Value *Ptr, APInt Offset, Type *PointerTy,
1840 const Twine &Prefix) {
1841 // Even though we don't look through PHI nodes, we could be called on an
1842 // instruction in an unreachable block, which may be on a cycle.
1843 SmallPtrSet<Value *, 4> Visited;
1844 Visited.insert(Ptr);
1845 SmallVector<Value *, 4> Indices;
1847 // We may end up computing an offset pointer that has the wrong type. If we
1848 // never are able to compute one directly that has the correct type, we'll
1849 // fall back to it, so keep it around here.
1850 Value *OffsetPtr = 0;
1852 // Remember any i8 pointer we come across to re-use if we need to do a raw
1855 APInt Int8PtrOffset(Offset.getBitWidth(), 0);
1857 Type *TargetTy = PointerTy->getPointerElementType();
1860 // First fold any existing GEPs into the offset.
1861 while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
1862 APInt GEPOffset(Offset.getBitWidth(), 0);
1863 if (!GEP->accumulateConstantOffset(TD, GEPOffset))
1865 Offset += GEPOffset;
1866 Ptr = GEP->getPointerOperand();
1867 if (!Visited.insert(Ptr))
1871 // See if we can perform a natural GEP here.
1873 if (Value *P = getNaturalGEPWithOffset(IRB, TD, Ptr, Offset, TargetTy,
1875 if (P->getType() == PointerTy) {
1876 // Zap any offset pointer that we ended up computing in previous rounds.
1877 if (OffsetPtr && OffsetPtr->use_empty())
1878 if (Instruction *I = dyn_cast<Instruction>(OffsetPtr))
1879 I->eraseFromParent();
1887 // Stash this pointer if we've found an i8*.
1888 if (Ptr->getType()->isIntegerTy(8)) {
1890 Int8PtrOffset = Offset;
1893 // Peel off a layer of the pointer and update the offset appropriately.
1894 if (Operator::getOpcode(Ptr) == Instruction::BitCast) {
1895 Ptr = cast<Operator>(Ptr)->getOperand(0);
1896 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(Ptr)) {
1897 if (GA->mayBeOverridden())
1899 Ptr = GA->getAliasee();
1903 assert(Ptr->getType()->isPointerTy() && "Unexpected operand type!");
1904 } while (Visited.insert(Ptr));
1908 Int8Ptr = IRB.CreateBitCast(Ptr, IRB.getInt8PtrTy(),
1909 Prefix + ".raw_cast");
1910 Int8PtrOffset = Offset;
1913 OffsetPtr = Int8PtrOffset == 0 ? Int8Ptr :
1914 IRB.CreateInBoundsGEP(Int8Ptr, IRB.getInt(Int8PtrOffset),
1915 Prefix + ".raw_idx");
1919 // On the off chance we were targeting i8*, guard the bitcast here.
1920 if (Ptr->getType() != PointerTy)
1921 Ptr = IRB.CreateBitCast(Ptr, PointerTy, Prefix + ".cast");
1926 /// \brief Test whether we can convert a value from the old to the new type.
1928 /// This predicate should be used to guard calls to convertValue in order to
1929 /// ensure that we only try to convert viable values. The strategy is that we
1930 /// will peel off single element struct and array wrappings to get to an
1931 /// underlying value, and convert that value.
1932 static bool canConvertValue(const DataLayout &DL, Type *OldTy, Type *NewTy) {
1935 if (IntegerType *OldITy = dyn_cast<IntegerType>(OldTy))
1936 if (IntegerType *NewITy = dyn_cast<IntegerType>(NewTy))
1937 if (NewITy->getBitWidth() >= OldITy->getBitWidth())
1939 if (DL.getTypeSizeInBits(NewTy) != DL.getTypeSizeInBits(OldTy))
1941 if (!NewTy->isSingleValueType() || !OldTy->isSingleValueType())
1944 if (NewTy->isPointerTy() || OldTy->isPointerTy()) {
1945 if (NewTy->isPointerTy() && OldTy->isPointerTy())
1947 if (NewTy->isIntegerTy() || OldTy->isIntegerTy())
1955 /// \brief Generic routine to convert an SSA value to a value of a different
1958 /// This will try various different casting techniques, such as bitcasts,
1959 /// inttoptr, and ptrtoint casts. Use the \c canConvertValue predicate to test
1960 /// two types for viability with this routine.
1961 static Value *convertValue(const DataLayout &DL, IRBuilder<> &IRB, Value *V,
1963 assert(canConvertValue(DL, V->getType(), Ty) &&
1964 "Value not convertable to type");
1965 if (V->getType() == Ty)
1967 if (IntegerType *OldITy = dyn_cast<IntegerType>(V->getType()))
1968 if (IntegerType *NewITy = dyn_cast<IntegerType>(Ty))
1969 if (NewITy->getBitWidth() > OldITy->getBitWidth())
1970 return IRB.CreateZExt(V, NewITy);
1971 if (V->getType()->isIntegerTy() && Ty->isPointerTy())
1972 return IRB.CreateIntToPtr(V, Ty);
1973 if (V->getType()->isPointerTy() && Ty->isIntegerTy())
1974 return IRB.CreatePtrToInt(V, Ty);
1976 return IRB.CreateBitCast(V, Ty);
1979 /// \brief Test whether the given alloca partition can be promoted to a vector.
1981 /// This is a quick test to check whether we can rewrite a particular alloca
1982 /// partition (and its newly formed alloca) into a vector alloca with only
1983 /// whole-vector loads and stores such that it could be promoted to a vector
1984 /// SSA value. We only can ensure this for a limited set of operations, and we
1985 /// don't want to do the rewrites unless we are confident that the result will
1986 /// be promotable, so we have an early test here.
1987 static bool isVectorPromotionViable(const DataLayout &TD,
1989 AllocaPartitioning &P,
1990 uint64_t PartitionBeginOffset,
1991 uint64_t PartitionEndOffset,
1992 AllocaPartitioning::const_use_iterator I,
1993 AllocaPartitioning::const_use_iterator E) {
1994 VectorType *Ty = dyn_cast<VectorType>(AllocaTy);
1998 uint64_t ElementSize = TD.getTypeSizeInBits(Ty->getScalarType());
2000 // While the definition of LLVM vectors is bitpacked, we don't support sizes
2001 // that aren't byte sized.
2002 if (ElementSize % 8)
2004 assert((TD.getTypeSizeInBits(Ty) % 8) == 0 &&
2005 "vector size not a multiple of element size?");
2008 for (; I != E; ++I) {
2009 Use *U = I->getUse();
2011 continue; // Skip dead use.
2013 uint64_t BeginOffset = I->BeginOffset - PartitionBeginOffset;
2014 uint64_t BeginIndex = BeginOffset / ElementSize;
2015 if (BeginIndex * ElementSize != BeginOffset ||
2016 BeginIndex >= Ty->getNumElements())
2018 uint64_t EndOffset = I->EndOffset - PartitionBeginOffset;
2019 uint64_t EndIndex = EndOffset / ElementSize;
2020 if (EndIndex * ElementSize != EndOffset ||
2021 EndIndex > Ty->getNumElements())
2024 assert(EndIndex > BeginIndex && "Empty vector!");
2025 uint64_t NumElements = EndIndex - BeginIndex;
2027 = (NumElements == 1) ? Ty->getElementType()
2028 : VectorType::get(Ty->getElementType(), NumElements);
2030 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) {
2031 if (MI->isVolatile())
2033 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(U->getUser())) {
2034 const AllocaPartitioning::MemTransferOffsets &MTO
2035 = P.getMemTransferOffsets(*MTI);
2036 if (!MTO.IsSplittable)
2039 } else if (U->get()->getType()->getPointerElementType()->isStructTy()) {
2040 // Disable vector promotion when there are loads or stores of an FCA.
2042 } else if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) {
2043 if (LI->isVolatile())
2045 if (!canConvertValue(TD, PartitionTy, LI->getType()))
2047 } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
2048 if (SI->isVolatile())
2050 if (!canConvertValue(TD, SI->getValueOperand()->getType(), PartitionTy))
2059 /// \brief Test whether the given alloca partition's integer operations can be
2060 /// widened to promotable ones.
2062 /// This is a quick test to check whether we can rewrite the integer loads and
2063 /// stores to a particular alloca into wider loads and stores and be able to
2064 /// promote the resulting alloca.
2065 static bool isIntegerWideningViable(const DataLayout &TD,
2067 uint64_t AllocBeginOffset,
2068 AllocaPartitioning &P,
2069 AllocaPartitioning::const_use_iterator I,
2070 AllocaPartitioning::const_use_iterator E) {
2071 uint64_t SizeInBits = TD.getTypeSizeInBits(AllocaTy);
2072 // Don't create integer types larger than the maximum bitwidth.
2073 if (SizeInBits > IntegerType::MAX_INT_BITS)
2076 // Don't try to handle allocas with bit-padding.
2077 if (SizeInBits != TD.getTypeStoreSizeInBits(AllocaTy))
2080 // We need to ensure that an integer type with the appropriate bitwidth can
2081 // be converted to the alloca type, whatever that is. We don't want to force
2082 // the alloca itself to have an integer type if there is a more suitable one.
2083 Type *IntTy = Type::getIntNTy(AllocaTy->getContext(), SizeInBits);
2084 if (!canConvertValue(TD, AllocaTy, IntTy) ||
2085 !canConvertValue(TD, IntTy, AllocaTy))
2088 uint64_t Size = TD.getTypeStoreSize(AllocaTy);
2090 // Check the uses to ensure the uses are (likely) promotable integer uses.
2091 // Also ensure that the alloca has a covering load or store. We don't want
2092 // to widen the integer operations only to fail to promote due to some other
2093 // unsplittable entry (which we may make splittable later).
2094 bool WholeAllocaOp = false;
2095 for (; I != E; ++I) {
2096 Use *U = I->getUse();
2098 continue; // Skip dead use.
2100 uint64_t RelBegin = I->BeginOffset - AllocBeginOffset;
2101 uint64_t RelEnd = I->EndOffset - AllocBeginOffset;
2103 // We can't reasonably handle cases where the load or store extends past
2104 // the end of the aloca's type and into its padding.
2108 if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) {
2109 if (LI->isVolatile())
2111 if (RelBegin == 0 && RelEnd == Size)
2112 WholeAllocaOp = true;
2113 if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType())) {
2114 if (ITy->getBitWidth() < TD.getTypeStoreSizeInBits(ITy))
2118 // Non-integer loads need to be convertible from the alloca type so that
2119 // they are promotable.
2120 if (RelBegin != 0 || RelEnd != Size ||
2121 !canConvertValue(TD, AllocaTy, LI->getType()))
2123 } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
2124 Type *ValueTy = SI->getValueOperand()->getType();
2125 if (SI->isVolatile())
2127 if (RelBegin == 0 && RelEnd == Size)
2128 WholeAllocaOp = true;
2129 if (IntegerType *ITy = dyn_cast<IntegerType>(ValueTy)) {
2130 if (ITy->getBitWidth() < TD.getTypeStoreSizeInBits(ITy))
2134 // Non-integer stores need to be convertible to the alloca type so that
2135 // they are promotable.
2136 if (RelBegin != 0 || RelEnd != Size ||
2137 !canConvertValue(TD, ValueTy, AllocaTy))
2139 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) {
2140 if (MI->isVolatile() || !isa<Constant>(MI->getLength()))
2142 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(U->getUser())) {
2143 const AllocaPartitioning::MemTransferOffsets &MTO
2144 = P.getMemTransferOffsets(*MTI);
2145 if (!MTO.IsSplittable)
2148 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U->getUser())) {
2149 if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
2150 II->getIntrinsicID() != Intrinsic::lifetime_end)
2156 return WholeAllocaOp;
2159 static Value *extractInteger(const DataLayout &DL, IRBuilder<> &IRB, Value *V,
2160 IntegerType *Ty, uint64_t Offset,
2161 const Twine &Name) {
2162 DEBUG(dbgs() << " start: " << *V << "\n");
2163 IntegerType *IntTy = cast<IntegerType>(V->getType());
2164 assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) &&
2165 "Element extends past full value");
2166 uint64_t ShAmt = 8*Offset;
2167 if (DL.isBigEndian())
2168 ShAmt = 8*(DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset);
2170 V = IRB.CreateLShr(V, ShAmt, Name + ".shift");
2171 DEBUG(dbgs() << " shifted: " << *V << "\n");
2173 assert(Ty->getBitWidth() <= IntTy->getBitWidth() &&
2174 "Cannot extract to a larger integer!");
2176 V = IRB.CreateTrunc(V, Ty, Name + ".trunc");
2177 DEBUG(dbgs() << " trunced: " << *V << "\n");
2182 static Value *insertInteger(const DataLayout &DL, IRBuilder<> &IRB, Value *Old,
2183 Value *V, uint64_t Offset, const Twine &Name) {
2184 IntegerType *IntTy = cast<IntegerType>(Old->getType());
2185 IntegerType *Ty = cast<IntegerType>(V->getType());
2186 assert(Ty->getBitWidth() <= IntTy->getBitWidth() &&
2187 "Cannot insert a larger integer!");
2188 DEBUG(dbgs() << " start: " << *V << "\n");
2190 V = IRB.CreateZExt(V, IntTy, Name + ".ext");
2191 DEBUG(dbgs() << " extended: " << *V << "\n");
2193 assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) &&
2194 "Element store outside of alloca store");
2195 uint64_t ShAmt = 8*Offset;
2196 if (DL.isBigEndian())
2197 ShAmt = 8*(DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset);
2199 V = IRB.CreateShl(V, ShAmt, Name + ".shift");
2200 DEBUG(dbgs() << " shifted: " << *V << "\n");
2203 if (ShAmt || Ty->getBitWidth() < IntTy->getBitWidth()) {
2204 APInt Mask = ~Ty->getMask().zext(IntTy->getBitWidth()).shl(ShAmt);
2205 Old = IRB.CreateAnd(Old, Mask, Name + ".mask");
2206 DEBUG(dbgs() << " masked: " << *Old << "\n");
2207 V = IRB.CreateOr(Old, V, Name + ".insert");
2208 DEBUG(dbgs() << " inserted: " << *V << "\n");
2213 static Value *extractVector(IRBuilder<> &IRB, Value *V,
2214 unsigned BeginIndex, unsigned EndIndex,
2215 const Twine &Name) {
2216 VectorType *VecTy = cast<VectorType>(V->getType());
2217 unsigned NumElements = EndIndex - BeginIndex;
2218 assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
2220 if (NumElements == VecTy->getNumElements())
2223 if (NumElements == 1) {
2224 V = IRB.CreateExtractElement(V, IRB.getInt32(BeginIndex),
2226 DEBUG(dbgs() << " extract: " << *V << "\n");
2230 SmallVector<Constant*, 8> Mask;
2231 Mask.reserve(NumElements);
2232 for (unsigned i = BeginIndex; i != EndIndex; ++i)
2233 Mask.push_back(IRB.getInt32(i));
2234 V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()),
2235 ConstantVector::get(Mask),
2237 DEBUG(dbgs() << " shuffle: " << *V << "\n");
2241 static Value *insertVector(IRBuilder<> &IRB, Value *Old, Value *V,
2242 unsigned BeginIndex, const Twine &Name) {
2243 VectorType *VecTy = cast<VectorType>(Old->getType());
2244 assert(VecTy && "Can only insert a vector into a vector");
2246 VectorType *Ty = dyn_cast<VectorType>(V->getType());
2248 // Single element to insert.
2249 V = IRB.CreateInsertElement(Old, V, IRB.getInt32(BeginIndex),
2251 DEBUG(dbgs() << " insert: " << *V << "\n");
2255 assert(Ty->getNumElements() <= VecTy->getNumElements() &&
2256 "Too many elements!");
2257 if (Ty->getNumElements() == VecTy->getNumElements()) {
2258 assert(V->getType() == VecTy && "Vector type mismatch");
2261 unsigned EndIndex = BeginIndex + Ty->getNumElements();
2263 // When inserting a smaller vector into the larger to store, we first
2264 // use a shuffle vector to widen it with undef elements, and then
2265 // a second shuffle vector to select between the loaded vector and the
2267 SmallVector<Constant*, 8> Mask;
2268 Mask.reserve(VecTy->getNumElements());
2269 for (unsigned i = 0; i != VecTy->getNumElements(); ++i)
2270 if (i >= BeginIndex && i < EndIndex)
2271 Mask.push_back(IRB.getInt32(i - BeginIndex));
2273 Mask.push_back(UndefValue::get(IRB.getInt32Ty()));
2274 V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()),
2275 ConstantVector::get(Mask),
2277 DEBUG(dbgs() << " shuffle1: " << *V << "\n");
2280 for (unsigned i = 0; i != VecTy->getNumElements(); ++i)
2281 if (i >= BeginIndex && i < EndIndex)
2282 Mask.push_back(IRB.getInt32(i));
2284 Mask.push_back(IRB.getInt32(i + VecTy->getNumElements()));
2285 V = IRB.CreateShuffleVector(V, Old, ConstantVector::get(Mask),
2287 DEBUG(dbgs() << " shuffle2: " << *V << "\n");
2292 /// \brief Visitor to rewrite instructions using a partition of an alloca to
2293 /// use a new alloca.
2295 /// Also implements the rewriting to vector-based accesses when the partition
2296 /// passes the isVectorPromotionViable predicate. Most of the rewriting logic
2298 class AllocaPartitionRewriter : public InstVisitor<AllocaPartitionRewriter,
2300 // Befriend the base class so it can delegate to private visit methods.
2301 friend class llvm::InstVisitor<AllocaPartitionRewriter, bool>;
2303 const DataLayout &TD;
2304 AllocaPartitioning &P;
2306 AllocaInst &OldAI, &NewAI;
2307 const uint64_t NewAllocaBeginOffset, NewAllocaEndOffset;
2310 // If we are rewriting an alloca partition which can be written as pure
2311 // vector operations, we stash extra information here. When VecTy is
2312 // non-null, we have some strict guarantees about the rewritten alloca:
2313 // - The new alloca is exactly the size of the vector type here.
2314 // - The accesses all either map to the entire vector or to a single
2316 // - The set of accessing instructions is only one of those handled above
2317 // in isVectorPromotionViable. Generally these are the same access kinds
2318 // which are promotable via mem2reg.
2321 uint64_t ElementSize;
2323 // This is a convenience and flag variable that will be null unless the new
2324 // alloca's integer operations should be widened to this integer type due to
2325 // passing isIntegerWideningViable above. If it is non-null, the desired
2326 // integer type will be stored here for easy access during rewriting.
2329 // The offset of the partition user currently being rewritten.
2330 uint64_t BeginOffset, EndOffset;
2333 Instruction *OldPtr;
2335 // The name prefix to use when rewriting instructions for this alloca.
2336 std::string NamePrefix;
2339 AllocaPartitionRewriter(const DataLayout &TD, AllocaPartitioning &P,
2340 AllocaPartitioning::iterator PI,
2341 SROA &Pass, AllocaInst &OldAI, AllocaInst &NewAI,
2342 uint64_t NewBeginOffset, uint64_t NewEndOffset)
2343 : TD(TD), P(P), Pass(Pass),
2344 OldAI(OldAI), NewAI(NewAI),
2345 NewAllocaBeginOffset(NewBeginOffset),
2346 NewAllocaEndOffset(NewEndOffset),
2347 NewAllocaTy(NewAI.getAllocatedType()),
2348 VecTy(), ElementTy(), ElementSize(), IntTy(),
2349 BeginOffset(), EndOffset(), IsSplit(), OldUse(), OldPtr() {
2352 /// \brief Visit the users of the alloca partition and rewrite them.
2353 bool visitUsers(AllocaPartitioning::const_use_iterator I,
2354 AllocaPartitioning::const_use_iterator E) {
2355 if (isVectorPromotionViable(TD, NewAI.getAllocatedType(), P,
2356 NewAllocaBeginOffset, NewAllocaEndOffset,
2359 VecTy = cast<VectorType>(NewAI.getAllocatedType());
2360 ElementTy = VecTy->getElementType();
2361 assert((TD.getTypeSizeInBits(VecTy->getScalarType()) % 8) == 0 &&
2362 "Only multiple-of-8 sized vector elements are viable");
2363 ElementSize = TD.getTypeSizeInBits(VecTy->getScalarType()) / 8;
2364 } else if (isIntegerWideningViable(TD, NewAI.getAllocatedType(),
2365 NewAllocaBeginOffset, P, I, E)) {
2366 IntTy = Type::getIntNTy(NewAI.getContext(),
2367 TD.getTypeSizeInBits(NewAI.getAllocatedType()));
2369 bool CanSROA = true;
2370 for (; I != E; ++I) {
2372 continue; // Skip dead uses.
2373 BeginOffset = I->BeginOffset;
2374 EndOffset = I->EndOffset;
2375 IsSplit = I->isSplit();
2376 OldUse = I->getUse();
2377 OldPtr = cast<Instruction>(OldUse->get());
2378 NamePrefix = (Twine(NewAI.getName()) + "." + Twine(BeginOffset)).str();
2379 CanSROA &= visit(cast<Instruction>(OldUse->getUser()));
2395 // Every instruction which can end up as a user must have a rewrite rule.
2396 bool visitInstruction(Instruction &I) {
2397 DEBUG(dbgs() << " !!!! Cannot rewrite: " << I << "\n");
2398 llvm_unreachable("No rewrite rule for this instruction!");
2401 Twine getName(const Twine &Suffix) {
2402 return NamePrefix + Suffix;
2405 Value *getAdjustedAllocaPtr(IRBuilder<> &IRB, Type *PointerTy) {
2406 assert(BeginOffset >= NewAllocaBeginOffset);
2407 APInt Offset(TD.getPointerSizeInBits(), BeginOffset - NewAllocaBeginOffset);
2408 return getAdjustedPtr(IRB, TD, &NewAI, Offset, PointerTy, getName(""));
2411 /// \brief Compute suitable alignment to access an offset into the new alloca.
2412 unsigned getOffsetAlign(uint64_t Offset) {
2413 unsigned NewAIAlign = NewAI.getAlignment();
2415 NewAIAlign = TD.getABITypeAlignment(NewAI.getAllocatedType());
2416 return MinAlign(NewAIAlign, Offset);
2419 /// \brief Compute suitable alignment to access this partition of the new
2421 unsigned getPartitionAlign() {
2422 return getOffsetAlign(BeginOffset - NewAllocaBeginOffset);
2425 /// \brief Compute suitable alignment to access a type at an offset of the
2428 /// \returns zero if the type's ABI alignment is a suitable alignment,
2429 /// otherwise returns the maximal suitable alignment.
2430 unsigned getOffsetTypeAlign(Type *Ty, uint64_t Offset) {
2431 unsigned Align = getOffsetAlign(Offset);
2432 return Align == TD.getABITypeAlignment(Ty) ? 0 : Align;
2435 /// \brief Compute suitable alignment to access a type at the beginning of
2436 /// this partition of the new alloca.
2438 /// See \c getOffsetTypeAlign for details; this routine delegates to it.
2439 unsigned getPartitionTypeAlign(Type *Ty) {
2440 return getOffsetTypeAlign(Ty, BeginOffset - NewAllocaBeginOffset);
2443 unsigned getIndex(uint64_t Offset) {
2444 assert(VecTy && "Can only call getIndex when rewriting a vector");
2445 uint64_t RelOffset = Offset - NewAllocaBeginOffset;
2446 assert(RelOffset / ElementSize < UINT32_MAX && "Index out of bounds");
2447 uint32_t Index = RelOffset / ElementSize;
2448 assert(Index * ElementSize == RelOffset);
2452 void deleteIfTriviallyDead(Value *V) {
2453 Instruction *I = cast<Instruction>(V);
2454 if (isInstructionTriviallyDead(I))
2455 Pass.DeadInsts.insert(I);
2458 Value *rewriteVectorizedLoadInst(IRBuilder<> &IRB) {
2459 unsigned BeginIndex = getIndex(BeginOffset);
2460 unsigned EndIndex = getIndex(EndOffset);
2461 assert(EndIndex > BeginIndex && "Empty vector!");
2463 Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2465 return extractVector(IRB, V, BeginIndex, EndIndex, getName(".vec"));
2468 Value *rewriteIntegerLoad(IRBuilder<> &IRB, LoadInst &LI) {
2469 assert(IntTy && "We cannot insert an integer to the alloca");
2470 assert(!LI.isVolatile());
2471 Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2473 V = convertValue(TD, IRB, V, IntTy);
2474 assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2475 uint64_t Offset = BeginOffset - NewAllocaBeginOffset;
2476 if (Offset > 0 || EndOffset < NewAllocaEndOffset)
2477 V = extractInteger(TD, IRB, V, cast<IntegerType>(LI.getType()), Offset,
2478 getName(".extract"));
2482 bool visitLoadInst(LoadInst &LI) {
2483 DEBUG(dbgs() << " original: " << LI << "\n");
2484 Value *OldOp = LI.getOperand(0);
2485 assert(OldOp == OldPtr);
2487 uint64_t Size = EndOffset - BeginOffset;
2489 IRBuilder<> IRB(&LI);
2490 Type *TargetTy = IsSplit ? Type::getIntNTy(LI.getContext(), Size * 8)
2492 bool IsPtrAdjusted = false;
2495 V = rewriteVectorizedLoadInst(IRB);
2496 } else if (IntTy && LI.getType()->isIntegerTy()) {
2497 V = rewriteIntegerLoad(IRB, LI);
2498 } else if (BeginOffset == NewAllocaBeginOffset &&
2499 canConvertValue(TD, NewAllocaTy, LI.getType())) {
2500 V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2501 LI.isVolatile(), getName(".load"));
2503 Type *LTy = TargetTy->getPointerTo();
2504 V = IRB.CreateAlignedLoad(getAdjustedAllocaPtr(IRB, LTy),
2505 getPartitionTypeAlign(TargetTy),
2506 LI.isVolatile(), getName(".load"));
2507 IsPtrAdjusted = true;
2509 V = convertValue(TD, IRB, V, TargetTy);
2512 assert(!LI.isVolatile());
2513 assert(LI.getType()->isIntegerTy() &&
2514 "Only integer type loads and stores are split");
2515 assert(Size < TD.getTypeStoreSize(LI.getType()) &&
2516 "Split load isn't smaller than original load");
2517 assert(LI.getType()->getIntegerBitWidth() ==
2518 TD.getTypeStoreSizeInBits(LI.getType()) &&
2519 "Non-byte-multiple bit width");
2520 // Move the insertion point just past the load so that we can refer to it.
2521 IRB.SetInsertPoint(llvm::next(BasicBlock::iterator(&LI)));
2522 // Create a placeholder value with the same type as LI to use as the
2523 // basis for the new value. This allows us to replace the uses of LI with
2524 // the computed value, and then replace the placeholder with LI, leaving
2525 // LI only used for this computation.
2527 = new LoadInst(UndefValue::get(LI.getType()->getPointerTo()));
2528 V = insertInteger(TD, IRB, Placeholder, V, BeginOffset,
2529 getName(".insert"));
2530 LI.replaceAllUsesWith(V);
2531 Placeholder->replaceAllUsesWith(&LI);
2534 LI.replaceAllUsesWith(V);
2537 Pass.DeadInsts.insert(&LI);
2538 deleteIfTriviallyDead(OldOp);
2539 DEBUG(dbgs() << " to: " << *V << "\n");
2540 return !LI.isVolatile() && !IsPtrAdjusted;
2543 bool rewriteVectorizedStoreInst(IRBuilder<> &IRB, Value *V,
2544 StoreInst &SI, Value *OldOp) {
2545 unsigned BeginIndex = getIndex(BeginOffset);
2546 unsigned EndIndex = getIndex(EndOffset);
2547 assert(EndIndex > BeginIndex && "Empty vector!");
2548 unsigned NumElements = EndIndex - BeginIndex;
2549 assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
2551 = (NumElements == 1) ? ElementTy
2552 : VectorType::get(ElementTy, NumElements);
2553 if (V->getType() != PartitionTy)
2554 V = convertValue(TD, IRB, V, PartitionTy);
2556 // Mix in the existing elements.
2557 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2559 V = insertVector(IRB, Old, V, BeginIndex, getName(".vec"));
2561 StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment());
2562 Pass.DeadInsts.insert(&SI);
2565 DEBUG(dbgs() << " to: " << *Store << "\n");
2569 bool rewriteIntegerStore(IRBuilder<> &IRB, Value *V, StoreInst &SI) {
2570 assert(IntTy && "We cannot extract an integer from the alloca");
2571 assert(!SI.isVolatile());
2572 if (TD.getTypeSizeInBits(V->getType()) != IntTy->getBitWidth()) {
2573 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2574 getName(".oldload"));
2575 Old = convertValue(TD, IRB, Old, IntTy);
2576 assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2577 uint64_t Offset = BeginOffset - NewAllocaBeginOffset;
2578 V = insertInteger(TD, IRB, Old, SI.getValueOperand(), Offset,
2579 getName(".insert"));
2581 V = convertValue(TD, IRB, V, NewAllocaTy);
2582 StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment());
2583 Pass.DeadInsts.insert(&SI);
2585 DEBUG(dbgs() << " to: " << *Store << "\n");
2589 bool visitStoreInst(StoreInst &SI) {
2590 DEBUG(dbgs() << " original: " << SI << "\n");
2591 Value *OldOp = SI.getOperand(1);
2592 assert(OldOp == OldPtr);
2593 IRBuilder<> IRB(&SI);
2595 Value *V = SI.getValueOperand();
2597 // Strip all inbounds GEPs and pointer casts to try to dig out any root
2598 // alloca that should be re-examined after promoting this alloca.
2599 if (V->getType()->isPointerTy())
2600 if (AllocaInst *AI = dyn_cast<AllocaInst>(V->stripInBoundsOffsets()))
2601 Pass.PostPromotionWorklist.insert(AI);
2603 uint64_t Size = EndOffset - BeginOffset;
2604 if (Size < TD.getTypeStoreSize(V->getType())) {
2605 assert(!SI.isVolatile());
2606 assert(IsSplit && "A seemingly split store isn't splittable");
2607 assert(V->getType()->isIntegerTy() &&
2608 "Only integer type loads and stores are split");
2609 assert(V->getType()->getIntegerBitWidth() ==
2610 TD.getTypeStoreSizeInBits(V->getType()) &&
2611 "Non-byte-multiple bit width");
2612 IntegerType *NarrowTy = Type::getIntNTy(SI.getContext(), Size * 8);
2613 V = extractInteger(TD, IRB, V, NarrowTy, BeginOffset,
2614 getName(".extract"));
2618 return rewriteVectorizedStoreInst(IRB, V, SI, OldOp);
2619 if (IntTy && V->getType()->isIntegerTy())
2620 return rewriteIntegerStore(IRB, V, SI);
2623 if (BeginOffset == NewAllocaBeginOffset &&
2624 canConvertValue(TD, V->getType(), NewAllocaTy)) {
2625 V = convertValue(TD, IRB, V, NewAllocaTy);
2626 NewSI = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(),
2629 Value *NewPtr = getAdjustedAllocaPtr(IRB, V->getType()->getPointerTo());
2630 NewSI = IRB.CreateAlignedStore(V, NewPtr,
2631 getPartitionTypeAlign(V->getType()),
2635 Pass.DeadInsts.insert(&SI);
2636 deleteIfTriviallyDead(OldOp);
2638 DEBUG(dbgs() << " to: " << *NewSI << "\n");
2639 return NewSI->getPointerOperand() == &NewAI && !SI.isVolatile();
2642 /// \brief Compute an integer value from splatting an i8 across the given
2643 /// number of bytes.
2645 /// Note that this routine assumes an i8 is a byte. If that isn't true, don't
2646 /// call this routine.
2647 /// FIXME: Heed the advice above.
2649 /// \param V The i8 value to splat.
2650 /// \param Size The number of bytes in the output (assuming i8 is one byte)
2651 Value *getIntegerSplat(IRBuilder<> &IRB, Value *V, unsigned Size) {
2652 assert(Size > 0 && "Expected a positive number of bytes.");
2653 IntegerType *VTy = cast<IntegerType>(V->getType());
2654 assert(VTy->getBitWidth() == 8 && "Expected an i8 value for the byte");
2658 Type *SplatIntTy = Type::getIntNTy(VTy->getContext(), Size*8);
2659 V = IRB.CreateMul(IRB.CreateZExt(V, SplatIntTy, getName(".zext")),
2660 ConstantExpr::getUDiv(
2661 Constant::getAllOnesValue(SplatIntTy),
2662 ConstantExpr::getZExt(
2663 Constant::getAllOnesValue(V->getType()),
2665 getName(".isplat"));
2669 /// \brief Compute a vector splat for a given element value.
2670 Value *getVectorSplat(IRBuilder<> &IRB, Value *V, unsigned NumElements) {
2671 V = IRB.CreateVectorSplat(NumElements, V, NamePrefix);
2672 DEBUG(dbgs() << " splat: " << *V << "\n");
2676 bool visitMemSetInst(MemSetInst &II) {
2677 DEBUG(dbgs() << " original: " << II << "\n");
2678 IRBuilder<> IRB(&II);
2679 assert(II.getRawDest() == OldPtr);
2681 // If the memset has a variable size, it cannot be split, just adjust the
2682 // pointer to the new alloca.
2683 if (!isa<Constant>(II.getLength())) {
2684 II.setDest(getAdjustedAllocaPtr(IRB, II.getRawDest()->getType()));
2685 Type *CstTy = II.getAlignmentCst()->getType();
2686 II.setAlignment(ConstantInt::get(CstTy, getPartitionAlign()));
2688 deleteIfTriviallyDead(OldPtr);
2692 // Record this instruction for deletion.
2693 Pass.DeadInsts.insert(&II);
2695 Type *AllocaTy = NewAI.getAllocatedType();
2696 Type *ScalarTy = AllocaTy->getScalarType();
2698 // If this doesn't map cleanly onto the alloca type, and that type isn't
2699 // a single value type, just emit a memset.
2700 if (!VecTy && !IntTy &&
2701 (BeginOffset != NewAllocaBeginOffset ||
2702 EndOffset != NewAllocaEndOffset ||
2703 !AllocaTy->isSingleValueType() ||
2704 !TD.isLegalInteger(TD.getTypeSizeInBits(ScalarTy)) ||
2705 TD.getTypeSizeInBits(ScalarTy)%8 != 0)) {
2706 Type *SizeTy = II.getLength()->getType();
2707 Constant *Size = ConstantInt::get(SizeTy, EndOffset - BeginOffset);
2709 = IRB.CreateMemSet(getAdjustedAllocaPtr(IRB,
2710 II.getRawDest()->getType()),
2711 II.getValue(), Size, getPartitionAlign(),
2714 DEBUG(dbgs() << " to: " << *New << "\n");
2718 // If we can represent this as a simple value, we have to build the actual
2719 // value to store, which requires expanding the byte present in memset to
2720 // a sensible representation for the alloca type. This is essentially
2721 // splatting the byte to a sufficiently wide integer, splatting it across
2722 // any desired vector width, and bitcasting to the final type.
2726 // If this is a memset of a vectorized alloca, insert it.
2727 assert(ElementTy == ScalarTy);
2729 unsigned BeginIndex = getIndex(BeginOffset);
2730 unsigned EndIndex = getIndex(EndOffset);
2731 assert(EndIndex > BeginIndex && "Empty vector!");
2732 unsigned NumElements = EndIndex - BeginIndex;
2733 assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
2735 Value *Splat = getIntegerSplat(IRB, II.getValue(),
2736 TD.getTypeSizeInBits(ElementTy)/8);
2737 Splat = convertValue(TD, IRB, Splat, ElementTy);
2738 if (NumElements > 1)
2739 Splat = getVectorSplat(IRB, Splat, NumElements);
2741 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2742 getName(".oldload"));
2743 V = insertVector(IRB, Old, Splat, BeginIndex, getName(".vec"));
2745 // If this is a memset on an alloca where we can widen stores, insert the
2747 assert(!II.isVolatile());
2749 uint64_t Size = EndOffset - BeginOffset;
2750 V = getIntegerSplat(IRB, II.getValue(), Size);
2752 if (IntTy && (BeginOffset != NewAllocaBeginOffset ||
2753 EndOffset != NewAllocaBeginOffset)) {
2754 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2755 getName(".oldload"));
2756 Old = convertValue(TD, IRB, Old, IntTy);
2757 assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2758 uint64_t Offset = BeginOffset - NewAllocaBeginOffset;
2759 V = insertInteger(TD, IRB, Old, V, Offset, getName(".insert"));
2761 assert(V->getType() == IntTy &&
2762 "Wrong type for an alloca wide integer!");
2764 V = convertValue(TD, IRB, V, AllocaTy);
2766 // Established these invariants above.
2767 assert(BeginOffset == NewAllocaBeginOffset);
2768 assert(EndOffset == NewAllocaEndOffset);
2770 V = getIntegerSplat(IRB, II.getValue(),
2771 TD.getTypeSizeInBits(ScalarTy)/8);
2772 if (VectorType *AllocaVecTy = dyn_cast<VectorType>(AllocaTy))
2773 V = getVectorSplat(IRB, V, AllocaVecTy->getNumElements());
2775 V = convertValue(TD, IRB, V, AllocaTy);
2778 Value *New = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(),
2781 DEBUG(dbgs() << " to: " << *New << "\n");
2782 return !II.isVolatile();
2785 bool visitMemTransferInst(MemTransferInst &II) {
2786 // Rewriting of memory transfer instructions can be a bit tricky. We break
2787 // them into two categories: split intrinsics and unsplit intrinsics.
2789 DEBUG(dbgs() << " original: " << II << "\n");
2790 IRBuilder<> IRB(&II);
2792 assert(II.getRawSource() == OldPtr || II.getRawDest() == OldPtr);
2793 bool IsDest = II.getRawDest() == OldPtr;
2795 const AllocaPartitioning::MemTransferOffsets &MTO
2796 = P.getMemTransferOffsets(II);
2798 // Compute the relative offset within the transfer.
2799 unsigned IntPtrWidth = TD.getPointerSizeInBits();
2800 APInt RelOffset(IntPtrWidth, BeginOffset - (IsDest ? MTO.DestBegin
2801 : MTO.SourceBegin));
2803 unsigned Align = II.getAlignment();
2805 Align = MinAlign(RelOffset.zextOrTrunc(64).getZExtValue(),
2806 MinAlign(II.getAlignment(), getPartitionAlign()));
2808 // For unsplit intrinsics, we simply modify the source and destination
2809 // pointers in place. This isn't just an optimization, it is a matter of
2810 // correctness. With unsplit intrinsics we may be dealing with transfers
2811 // within a single alloca before SROA ran, or with transfers that have
2812 // a variable length. We may also be dealing with memmove instead of
2813 // memcpy, and so simply updating the pointers is the necessary for us to
2814 // update both source and dest of a single call.
2815 if (!MTO.IsSplittable) {
2816 Value *OldOp = IsDest ? II.getRawDest() : II.getRawSource();
2818 II.setDest(getAdjustedAllocaPtr(IRB, II.getRawDest()->getType()));
2820 II.setSource(getAdjustedAllocaPtr(IRB, II.getRawSource()->getType()));
2822 Type *CstTy = II.getAlignmentCst()->getType();
2823 II.setAlignment(ConstantInt::get(CstTy, Align));
2825 DEBUG(dbgs() << " to: " << II << "\n");
2826 deleteIfTriviallyDead(OldOp);
2829 // For split transfer intrinsics we have an incredibly useful assurance:
2830 // the source and destination do not reside within the same alloca, and at
2831 // least one of them does not escape. This means that we can replace
2832 // memmove with memcpy, and we don't need to worry about all manner of
2833 // downsides to splitting and transforming the operations.
2835 // If this doesn't map cleanly onto the alloca type, and that type isn't
2836 // a single value type, just emit a memcpy.
2838 = !VecTy && !IntTy && (BeginOffset != NewAllocaBeginOffset ||
2839 EndOffset != NewAllocaEndOffset ||
2840 !NewAI.getAllocatedType()->isSingleValueType());
2842 // If we're just going to emit a memcpy, the alloca hasn't changed, and the
2843 // size hasn't been shrunk based on analysis of the viable range, this is
2845 if (EmitMemCpy && &OldAI == &NewAI) {
2846 uint64_t OrigBegin = IsDest ? MTO.DestBegin : MTO.SourceBegin;
2847 uint64_t OrigEnd = IsDest ? MTO.DestEnd : MTO.SourceEnd;
2848 // Ensure the start lines up.
2849 assert(BeginOffset == OrigBegin);
2852 // Rewrite the size as needed.
2853 if (EndOffset != OrigEnd)
2854 II.setLength(ConstantInt::get(II.getLength()->getType(),
2855 EndOffset - BeginOffset));
2858 // Record this instruction for deletion.
2859 Pass.DeadInsts.insert(&II);
2861 // Strip all inbounds GEPs and pointer casts to try to dig out any root
2862 // alloca that should be re-examined after rewriting this instruction.
2863 Value *OtherPtr = IsDest ? II.getRawSource() : II.getRawDest();
2865 = dyn_cast<AllocaInst>(OtherPtr->stripInBoundsOffsets()))
2866 Pass.Worklist.insert(AI);
2869 Type *OtherPtrTy = IsDest ? II.getRawSource()->getType()
2870 : II.getRawDest()->getType();
2872 // Compute the other pointer, folding as much as possible to produce
2873 // a single, simple GEP in most cases.
2874 OtherPtr = getAdjustedPtr(IRB, TD, OtherPtr, RelOffset, OtherPtrTy,
2875 getName("." + OtherPtr->getName()));
2878 = getAdjustedAllocaPtr(IRB, IsDest ? II.getRawDest()->getType()
2879 : II.getRawSource()->getType());
2880 Type *SizeTy = II.getLength()->getType();
2881 Constant *Size = ConstantInt::get(SizeTy, EndOffset - BeginOffset);
2883 CallInst *New = IRB.CreateMemCpy(IsDest ? OurPtr : OtherPtr,
2884 IsDest ? OtherPtr : OurPtr,
2885 Size, Align, II.isVolatile());
2887 DEBUG(dbgs() << " to: " << *New << "\n");
2891 // Note that we clamp the alignment to 1 here as a 0 alignment for a memcpy
2892 // is equivalent to 1, but that isn't true if we end up rewriting this as
2897 bool IsWholeAlloca = BeginOffset == NewAllocaBeginOffset &&
2898 EndOffset == NewAllocaEndOffset;
2899 uint64_t Size = EndOffset - BeginOffset;
2900 unsigned BeginIndex = VecTy ? getIndex(BeginOffset) : 0;
2901 unsigned EndIndex = VecTy ? getIndex(EndOffset) : 0;
2902 unsigned NumElements = EndIndex - BeginIndex;
2903 IntegerType *SubIntTy
2904 = IntTy ? Type::getIntNTy(IntTy->getContext(), Size*8) : 0;
2906 Type *OtherPtrTy = NewAI.getType();
2907 if (VecTy && !IsWholeAlloca) {
2908 if (NumElements == 1)
2909 OtherPtrTy = VecTy->getElementType();
2911 OtherPtrTy = VectorType::get(VecTy->getElementType(), NumElements);
2913 OtherPtrTy = OtherPtrTy->getPointerTo();
2914 } else if (IntTy && !IsWholeAlloca) {
2915 OtherPtrTy = SubIntTy->getPointerTo();
2918 Value *SrcPtr = getAdjustedPtr(IRB, TD, OtherPtr, RelOffset, OtherPtrTy,
2919 getName("." + OtherPtr->getName()));
2920 Value *DstPtr = &NewAI;
2922 std::swap(SrcPtr, DstPtr);
2925 if (VecTy && !IsWholeAlloca && !IsDest) {
2926 Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2928 Src = extractVector(IRB, Src, BeginIndex, EndIndex, getName(".vec"));
2929 } else if (IntTy && !IsWholeAlloca && !IsDest) {
2930 Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2932 Src = convertValue(TD, IRB, Src, IntTy);
2933 assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2934 uint64_t Offset = BeginOffset - NewAllocaBeginOffset;
2935 Src = extractInteger(TD, IRB, Src, SubIntTy, Offset, getName(".extract"));
2937 Src = IRB.CreateAlignedLoad(SrcPtr, Align, II.isVolatile(),
2938 getName(".copyload"));
2941 if (VecTy && !IsWholeAlloca && IsDest) {
2942 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2943 getName(".oldload"));
2944 Src = insertVector(IRB, Old, Src, BeginIndex, getName(".vec"));
2945 } else if (IntTy && !IsWholeAlloca && IsDest) {
2946 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2947 getName(".oldload"));
2948 Old = convertValue(TD, IRB, Old, IntTy);
2949 assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2950 uint64_t Offset = BeginOffset - NewAllocaBeginOffset;
2951 Src = insertInteger(TD, IRB, Old, Src, Offset, getName(".insert"));
2952 Src = convertValue(TD, IRB, Src, NewAllocaTy);
2955 StoreInst *Store = cast<StoreInst>(
2956 IRB.CreateAlignedStore(Src, DstPtr, Align, II.isVolatile()));
2958 DEBUG(dbgs() << " to: " << *Store << "\n");
2959 return !II.isVolatile();
2962 bool visitIntrinsicInst(IntrinsicInst &II) {
2963 assert(II.getIntrinsicID() == Intrinsic::lifetime_start ||
2964 II.getIntrinsicID() == Intrinsic::lifetime_end);
2965 DEBUG(dbgs() << " original: " << II << "\n");
2966 IRBuilder<> IRB(&II);
2967 assert(II.getArgOperand(1) == OldPtr);
2969 // Record this instruction for deletion.
2970 Pass.DeadInsts.insert(&II);
2973 = ConstantInt::get(cast<IntegerType>(II.getArgOperand(0)->getType()),
2974 EndOffset - BeginOffset);
2975 Value *Ptr = getAdjustedAllocaPtr(IRB, II.getArgOperand(1)->getType());
2977 if (II.getIntrinsicID() == Intrinsic::lifetime_start)
2978 New = IRB.CreateLifetimeStart(Ptr, Size);
2980 New = IRB.CreateLifetimeEnd(Ptr, Size);
2983 DEBUG(dbgs() << " to: " << *New << "\n");
2987 bool visitPHINode(PHINode &PN) {
2988 DEBUG(dbgs() << " original: " << PN << "\n");
2990 // We would like to compute a new pointer in only one place, but have it be
2991 // as local as possible to the PHI. To do that, we re-use the location of
2992 // the old pointer, which necessarily must be in the right position to
2993 // dominate the PHI.
2994 IRBuilder<> PtrBuilder(cast<Instruction>(OldPtr));
2996 Value *NewPtr = getAdjustedAllocaPtr(PtrBuilder, OldPtr->getType());
2997 // Replace the operands which were using the old pointer.
2998 std::replace(PN.op_begin(), PN.op_end(), cast<Value>(OldPtr), NewPtr);
3000 DEBUG(dbgs() << " to: " << PN << "\n");
3001 deleteIfTriviallyDead(OldPtr);
3005 bool visitSelectInst(SelectInst &SI) {
3006 DEBUG(dbgs() << " original: " << SI << "\n");
3007 IRBuilder<> IRB(&SI);
3009 // Find the operand we need to rewrite here.
3010 bool IsTrueVal = SI.getTrueValue() == OldPtr;
3012 assert(SI.getFalseValue() != OldPtr && "Pointer is both operands!");
3014 assert(SI.getFalseValue() == OldPtr && "Pointer isn't an operand!");
3016 Value *NewPtr = getAdjustedAllocaPtr(IRB, OldPtr->getType());
3017 SI.setOperand(IsTrueVal ? 1 : 2, NewPtr);
3018 DEBUG(dbgs() << " to: " << SI << "\n");
3019 deleteIfTriviallyDead(OldPtr);
3027 /// \brief Visitor to rewrite aggregate loads and stores as scalar.
3029 /// This pass aggressively rewrites all aggregate loads and stores on
3030 /// a particular pointer (or any pointer derived from it which we can identify)
3031 /// with scalar loads and stores.
3032 class AggLoadStoreRewriter : public InstVisitor<AggLoadStoreRewriter, bool> {
3033 // Befriend the base class so it can delegate to private visit methods.
3034 friend class llvm::InstVisitor<AggLoadStoreRewriter, bool>;
3036 const DataLayout &TD;
3038 /// Queue of pointer uses to analyze and potentially rewrite.
3039 SmallVector<Use *, 8> Queue;
3041 /// Set to prevent us from cycling with phi nodes and loops.
3042 SmallPtrSet<User *, 8> Visited;
3044 /// The current pointer use being rewritten. This is used to dig up the used
3045 /// value (as opposed to the user).
3049 AggLoadStoreRewriter(const DataLayout &TD) : TD(TD) {}
3051 /// Rewrite loads and stores through a pointer and all pointers derived from
3053 bool rewrite(Instruction &I) {
3054 DEBUG(dbgs() << " Rewriting FCA loads and stores...\n");
3056 bool Changed = false;
3057 while (!Queue.empty()) {
3058 U = Queue.pop_back_val();
3059 Changed |= visit(cast<Instruction>(U->getUser()));
3065 /// Enqueue all the users of the given instruction for further processing.
3066 /// This uses a set to de-duplicate users.
3067 void enqueueUsers(Instruction &I) {
3068 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE;
3070 if (Visited.insert(*UI))
3071 Queue.push_back(&UI.getUse());
3074 // Conservative default is to not rewrite anything.
3075 bool visitInstruction(Instruction &I) { return false; }
3077 /// \brief Generic recursive split emission class.
3078 template <typename Derived>
3081 /// The builder used to form new instructions.
3083 /// The indices which to be used with insert- or extractvalue to select the
3084 /// appropriate value within the aggregate.
3085 SmallVector<unsigned, 4> Indices;
3086 /// The indices to a GEP instruction which will move Ptr to the correct slot
3087 /// within the aggregate.
3088 SmallVector<Value *, 4> GEPIndices;
3089 /// The base pointer of the original op, used as a base for GEPing the
3090 /// split operations.
3093 /// Initialize the splitter with an insertion point, Ptr and start with a
3094 /// single zero GEP index.
3095 OpSplitter(Instruction *InsertionPoint, Value *Ptr)
3096 : IRB(InsertionPoint), GEPIndices(1, IRB.getInt32(0)), Ptr(Ptr) {}
3099 /// \brief Generic recursive split emission routine.
3101 /// This method recursively splits an aggregate op (load or store) into
3102 /// scalar or vector ops. It splits recursively until it hits a single value
3103 /// and emits that single value operation via the template argument.
3105 /// The logic of this routine relies on GEPs and insertvalue and
3106 /// extractvalue all operating with the same fundamental index list, merely
3107 /// formatted differently (GEPs need actual values).
3109 /// \param Ty The type being split recursively into smaller ops.
3110 /// \param Agg The aggregate value being built up or stored, depending on
3111 /// whether this is splitting a load or a store respectively.
3112 void emitSplitOps(Type *Ty, Value *&Agg, const Twine &Name) {
3113 if (Ty->isSingleValueType())
3114 return static_cast<Derived *>(this)->emitFunc(Ty, Agg, Name);
3116 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
3117 unsigned OldSize = Indices.size();
3119 for (unsigned Idx = 0, Size = ATy->getNumElements(); Idx != Size;
3121 assert(Indices.size() == OldSize && "Did not return to the old size");
3122 Indices.push_back(Idx);
3123 GEPIndices.push_back(IRB.getInt32(Idx));
3124 emitSplitOps(ATy->getElementType(), Agg, Name + "." + Twine(Idx));
3125 GEPIndices.pop_back();
3131 if (StructType *STy = dyn_cast<StructType>(Ty)) {
3132 unsigned OldSize = Indices.size();
3134 for (unsigned Idx = 0, Size = STy->getNumElements(); Idx != Size;
3136 assert(Indices.size() == OldSize && "Did not return to the old size");
3137 Indices.push_back(Idx);
3138 GEPIndices.push_back(IRB.getInt32(Idx));
3139 emitSplitOps(STy->getElementType(Idx), Agg, Name + "." + Twine(Idx));
3140 GEPIndices.pop_back();
3146 llvm_unreachable("Only arrays and structs are aggregate loadable types");
3150 struct LoadOpSplitter : public OpSplitter<LoadOpSplitter> {
3151 LoadOpSplitter(Instruction *InsertionPoint, Value *Ptr)
3152 : OpSplitter<LoadOpSplitter>(InsertionPoint, Ptr) {}
3154 /// Emit a leaf load of a single value. This is called at the leaves of the
3155 /// recursive emission to actually load values.
3156 void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) {
3157 assert(Ty->isSingleValueType());
3158 // Load the single value and insert it using the indices.
3159 Value *GEP = IRB.CreateInBoundsGEP(Ptr, GEPIndices, Name + ".gep");
3160 Value *Load = IRB.CreateLoad(GEP, Name + ".load");
3161 Agg = IRB.CreateInsertValue(Agg, Load, Indices, Name + ".insert");
3162 DEBUG(dbgs() << " to: " << *Load << "\n");
3166 bool visitLoadInst(LoadInst &LI) {
3167 assert(LI.getPointerOperand() == *U);
3168 if (!LI.isSimple() || LI.getType()->isSingleValueType())
3171 // We have an aggregate being loaded, split it apart.
3172 DEBUG(dbgs() << " original: " << LI << "\n");
3173 LoadOpSplitter Splitter(&LI, *U);
3174 Value *V = UndefValue::get(LI.getType());
3175 Splitter.emitSplitOps(LI.getType(), V, LI.getName() + ".fca");
3176 LI.replaceAllUsesWith(V);
3177 LI.eraseFromParent();
3181 struct StoreOpSplitter : public OpSplitter<StoreOpSplitter> {
3182 StoreOpSplitter(Instruction *InsertionPoint, Value *Ptr)
3183 : OpSplitter<StoreOpSplitter>(InsertionPoint, Ptr) {}
3185 /// Emit a leaf store of a single value. This is called at the leaves of the
3186 /// recursive emission to actually produce stores.
3187 void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) {
3188 assert(Ty->isSingleValueType());
3189 // Extract the single value and store it using the indices.
3190 Value *Store = IRB.CreateStore(
3191 IRB.CreateExtractValue(Agg, Indices, Name + ".extract"),
3192 IRB.CreateInBoundsGEP(Ptr, GEPIndices, Name + ".gep"));
3194 DEBUG(dbgs() << " to: " << *Store << "\n");
3198 bool visitStoreInst(StoreInst &SI) {
3199 if (!SI.isSimple() || SI.getPointerOperand() != *U)
3201 Value *V = SI.getValueOperand();
3202 if (V->getType()->isSingleValueType())
3205 // We have an aggregate being stored, split it apart.
3206 DEBUG(dbgs() << " original: " << SI << "\n");
3207 StoreOpSplitter Splitter(&SI, *U);
3208 Splitter.emitSplitOps(V->getType(), V, V->getName() + ".fca");
3209 SI.eraseFromParent();
3213 bool visitBitCastInst(BitCastInst &BC) {
3218 bool visitGetElementPtrInst(GetElementPtrInst &GEPI) {
3223 bool visitPHINode(PHINode &PN) {
3228 bool visitSelectInst(SelectInst &SI) {
3235 /// \brief Strip aggregate type wrapping.
3237 /// This removes no-op aggregate types wrapping an underlying type. It will
3238 /// strip as many layers of types as it can without changing either the type
3239 /// size or the allocated size.
3240 static Type *stripAggregateTypeWrapping(const DataLayout &DL, Type *Ty) {
3241 if (Ty->isSingleValueType())
3244 uint64_t AllocSize = DL.getTypeAllocSize(Ty);
3245 uint64_t TypeSize = DL.getTypeSizeInBits(Ty);
3248 if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) {
3249 InnerTy = ArrTy->getElementType();
3250 } else if (StructType *STy = dyn_cast<StructType>(Ty)) {
3251 const StructLayout *SL = DL.getStructLayout(STy);
3252 unsigned Index = SL->getElementContainingOffset(0);
3253 InnerTy = STy->getElementType(Index);
3258 if (AllocSize > DL.getTypeAllocSize(InnerTy) ||
3259 TypeSize > DL.getTypeSizeInBits(InnerTy))
3262 return stripAggregateTypeWrapping(DL, InnerTy);
3265 /// \brief Try to find a partition of the aggregate type passed in for a given
3266 /// offset and size.
3268 /// This recurses through the aggregate type and tries to compute a subtype
3269 /// based on the offset and size. When the offset and size span a sub-section
3270 /// of an array, it will even compute a new array type for that sub-section,
3271 /// and the same for structs.
3273 /// Note that this routine is very strict and tries to find a partition of the
3274 /// type which produces the *exact* right offset and size. It is not forgiving
3275 /// when the size or offset cause either end of type-based partition to be off.
3276 /// Also, this is a best-effort routine. It is reasonable to give up and not
3277 /// return a type if necessary.
3278 static Type *getTypePartition(const DataLayout &TD, Type *Ty,
3279 uint64_t Offset, uint64_t Size) {
3280 if (Offset == 0 && TD.getTypeAllocSize(Ty) == Size)
3281 return stripAggregateTypeWrapping(TD, Ty);
3282 if (Offset > TD.getTypeAllocSize(Ty) ||
3283 (TD.getTypeAllocSize(Ty) - Offset) < Size)
3286 if (SequentialType *SeqTy = dyn_cast<SequentialType>(Ty)) {
3287 // We can't partition pointers...
3288 if (SeqTy->isPointerTy())
3291 Type *ElementTy = SeqTy->getElementType();
3292 uint64_t ElementSize = TD.getTypeAllocSize(ElementTy);
3293 uint64_t NumSkippedElements = Offset / ElementSize;
3294 if (ArrayType *ArrTy = dyn_cast<ArrayType>(SeqTy))
3295 if (NumSkippedElements >= ArrTy->getNumElements())
3297 if (VectorType *VecTy = dyn_cast<VectorType>(SeqTy))
3298 if (NumSkippedElements >= VecTy->getNumElements())
3300 Offset -= NumSkippedElements * ElementSize;
3302 // First check if we need to recurse.
3303 if (Offset > 0 || Size < ElementSize) {
3304 // Bail if the partition ends in a different array element.
3305 if ((Offset + Size) > ElementSize)
3307 // Recurse through the element type trying to peel off offset bytes.
3308 return getTypePartition(TD, ElementTy, Offset, Size);
3310 assert(Offset == 0);
3312 if (Size == ElementSize)
3313 return stripAggregateTypeWrapping(TD, ElementTy);
3314 assert(Size > ElementSize);
3315 uint64_t NumElements = Size / ElementSize;
3316 if (NumElements * ElementSize != Size)
3318 return ArrayType::get(ElementTy, NumElements);
3321 StructType *STy = dyn_cast<StructType>(Ty);
3325 const StructLayout *SL = TD.getStructLayout(STy);
3326 if (Offset >= SL->getSizeInBytes())
3328 uint64_t EndOffset = Offset + Size;
3329 if (EndOffset > SL->getSizeInBytes())
3332 unsigned Index = SL->getElementContainingOffset(Offset);
3333 Offset -= SL->getElementOffset(Index);
3335 Type *ElementTy = STy->getElementType(Index);
3336 uint64_t ElementSize = TD.getTypeAllocSize(ElementTy);
3337 if (Offset >= ElementSize)
3338 return 0; // The offset points into alignment padding.
3340 // See if any partition must be contained by the element.
3341 if (Offset > 0 || Size < ElementSize) {
3342 if ((Offset + Size) > ElementSize)
3344 return getTypePartition(TD, ElementTy, Offset, Size);
3346 assert(Offset == 0);
3348 if (Size == ElementSize)
3349 return stripAggregateTypeWrapping(TD, ElementTy);
3351 StructType::element_iterator EI = STy->element_begin() + Index,
3352 EE = STy->element_end();
3353 if (EndOffset < SL->getSizeInBytes()) {
3354 unsigned EndIndex = SL->getElementContainingOffset(EndOffset);
3355 if (Index == EndIndex)
3356 return 0; // Within a single element and its padding.
3358 // Don't try to form "natural" types if the elements don't line up with the
3360 // FIXME: We could potentially recurse down through the last element in the
3361 // sub-struct to find a natural end point.
3362 if (SL->getElementOffset(EndIndex) != EndOffset)
3365 assert(Index < EndIndex);
3366 EE = STy->element_begin() + EndIndex;
3369 // Try to build up a sub-structure.
3370 StructType *SubTy = StructType::get(STy->getContext(), makeArrayRef(EI, EE),
3372 const StructLayout *SubSL = TD.getStructLayout(SubTy);
3373 if (Size != SubSL->getSizeInBytes())
3374 return 0; // The sub-struct doesn't have quite the size needed.
3379 /// \brief Rewrite an alloca partition's users.
3381 /// This routine drives both of the rewriting goals of the SROA pass. It tries
3382 /// to rewrite uses of an alloca partition to be conducive for SSA value
3383 /// promotion. If the partition needs a new, more refined alloca, this will
3384 /// build that new alloca, preserving as much type information as possible, and
3385 /// rewrite the uses of the old alloca to point at the new one and have the
3386 /// appropriate new offsets. It also evaluates how successful the rewrite was
3387 /// at enabling promotion and if it was successful queues the alloca to be
3389 bool SROA::rewriteAllocaPartition(AllocaInst &AI,
3390 AllocaPartitioning &P,
3391 AllocaPartitioning::iterator PI) {
3392 uint64_t AllocaSize = PI->EndOffset - PI->BeginOffset;
3393 bool IsLive = false;
3394 for (AllocaPartitioning::use_iterator UI = P.use_begin(PI),
3396 UI != UE && !IsLive; ++UI)
3400 return false; // No live uses left of this partition.
3402 DEBUG(dbgs() << "Speculating PHIs and selects in partition "
3403 << "[" << PI->BeginOffset << "," << PI->EndOffset << ")\n");
3405 PHIOrSelectSpeculator Speculator(*TD, P, *this);
3406 DEBUG(dbgs() << " speculating ");
3407 DEBUG(P.print(dbgs(), PI, ""));
3408 Speculator.visitUsers(PI);
3410 // Try to compute a friendly type for this partition of the alloca. This
3411 // won't always succeed, in which case we fall back to a legal integer type
3412 // or an i8 array of an appropriate size.
3414 if (Type *PartitionTy = P.getCommonType(PI))
3415 if (TD->getTypeAllocSize(PartitionTy) >= AllocaSize)
3416 AllocaTy = PartitionTy;
3418 if (Type *PartitionTy = getTypePartition(*TD, AI.getAllocatedType(),
3419 PI->BeginOffset, AllocaSize))
3420 AllocaTy = PartitionTy;
3422 (AllocaTy->isArrayTy() &&
3423 AllocaTy->getArrayElementType()->isIntegerTy())) &&
3424 TD->isLegalInteger(AllocaSize * 8))
3425 AllocaTy = Type::getIntNTy(*C, AllocaSize * 8);
3427 AllocaTy = ArrayType::get(Type::getInt8Ty(*C), AllocaSize);
3428 assert(TD->getTypeAllocSize(AllocaTy) >= AllocaSize);
3430 // Check for the case where we're going to rewrite to a new alloca of the
3431 // exact same type as the original, and with the same access offsets. In that
3432 // case, re-use the existing alloca, but still run through the rewriter to
3433 // perform phi and select speculation.
3435 if (AllocaTy == AI.getAllocatedType()) {
3436 assert(PI->BeginOffset == 0 &&
3437 "Non-zero begin offset but same alloca type");
3438 assert(PI == P.begin() && "Begin offset is zero on later partition");
3441 unsigned Alignment = AI.getAlignment();
3443 // The minimum alignment which users can rely on when the explicit
3444 // alignment is omitted or zero is that required by the ABI for this
3446 Alignment = TD->getABITypeAlignment(AI.getAllocatedType());
3448 Alignment = MinAlign(Alignment, PI->BeginOffset);
3449 // If we will get at least this much alignment from the type alone, leave
3450 // the alloca's alignment unconstrained.
3451 if (Alignment <= TD->getABITypeAlignment(AllocaTy))
3453 NewAI = new AllocaInst(AllocaTy, 0, Alignment,
3454 AI.getName() + ".sroa." + Twine(PI - P.begin()),
3459 DEBUG(dbgs() << "Rewriting alloca partition "
3460 << "[" << PI->BeginOffset << "," << PI->EndOffset << ") to: "
3463 // Track the high watermark of the post-promotion worklist. We will reset it
3464 // to this point if the alloca is not in fact scheduled for promotion.
3465 unsigned PPWOldSize = PostPromotionWorklist.size();
3467 AllocaPartitionRewriter Rewriter(*TD, P, PI, *this, AI, *NewAI,
3468 PI->BeginOffset, PI->EndOffset);
3469 DEBUG(dbgs() << " rewriting ");
3470 DEBUG(P.print(dbgs(), PI, ""));
3471 bool Promotable = Rewriter.visitUsers(P.use_begin(PI), P.use_end(PI));
3473 DEBUG(dbgs() << " and queuing for promotion\n");
3474 PromotableAllocas.push_back(NewAI);
3475 } else if (NewAI != &AI) {
3476 // If we can't promote the alloca, iterate on it to check for new
3477 // refinements exposed by splitting the current alloca. Don't iterate on an
3478 // alloca which didn't actually change and didn't get promoted.
3479 Worklist.insert(NewAI);
3482 // Drop any post-promotion work items if promotion didn't happen.
3484 while (PostPromotionWorklist.size() > PPWOldSize)
3485 PostPromotionWorklist.pop_back();
3490 /// \brief Walks the partitioning of an alloca rewriting uses of each partition.
3491 bool SROA::splitAlloca(AllocaInst &AI, AllocaPartitioning &P) {
3492 bool Changed = false;
3493 for (AllocaPartitioning::iterator PI = P.begin(), PE = P.end(); PI != PE;
3495 Changed |= rewriteAllocaPartition(AI, P, PI);
3500 /// \brief Analyze an alloca for SROA.
3502 /// This analyzes the alloca to ensure we can reason about it, builds
3503 /// a partitioning of the alloca, and then hands it off to be split and
3504 /// rewritten as needed.
3505 bool SROA::runOnAlloca(AllocaInst &AI) {
3506 DEBUG(dbgs() << "SROA alloca: " << AI << "\n");
3507 ++NumAllocasAnalyzed;
3509 // Special case dead allocas, as they're trivial.
3510 if (AI.use_empty()) {
3511 AI.eraseFromParent();
3515 // Skip alloca forms that this analysis can't handle.
3516 if (AI.isArrayAllocation() || !AI.getAllocatedType()->isSized() ||
3517 TD->getTypeAllocSize(AI.getAllocatedType()) == 0)
3520 bool Changed = false;
3522 // First, split any FCA loads and stores touching this alloca to promote
3523 // better splitting and promotion opportunities.
3524 AggLoadStoreRewriter AggRewriter(*TD);
3525 Changed |= AggRewriter.rewrite(AI);
3527 // Build the partition set using a recursive instruction-visiting builder.
3528 AllocaPartitioning P(*TD, AI);
3529 DEBUG(P.print(dbgs()));
3533 // Delete all the dead users of this alloca before splitting and rewriting it.
3534 for (AllocaPartitioning::dead_user_iterator DI = P.dead_user_begin(),
3535 DE = P.dead_user_end();
3538 (*DI)->replaceAllUsesWith(UndefValue::get((*DI)->getType()));
3539 DeadInsts.insert(*DI);
3541 for (AllocaPartitioning::dead_op_iterator DO = P.dead_op_begin(),
3542 DE = P.dead_op_end();
3545 // Clobber the use with an undef value.
3546 **DO = UndefValue::get(OldV->getType());
3547 if (Instruction *OldI = dyn_cast<Instruction>(OldV))
3548 if (isInstructionTriviallyDead(OldI)) {
3550 DeadInsts.insert(OldI);
3554 // No partitions to split. Leave the dead alloca for a later pass to clean up.
3555 if (P.begin() == P.end())
3558 return splitAlloca(AI, P) || Changed;
3561 /// \brief Delete the dead instructions accumulated in this run.
3563 /// Recursively deletes the dead instructions we've accumulated. This is done
3564 /// at the very end to maximize locality of the recursive delete and to
3565 /// minimize the problems of invalidated instruction pointers as such pointers
3566 /// are used heavily in the intermediate stages of the algorithm.
3568 /// We also record the alloca instructions deleted here so that they aren't
3569 /// subsequently handed to mem2reg to promote.
3570 void SROA::deleteDeadInstructions(SmallPtrSet<AllocaInst*, 4> &DeletedAllocas) {
3571 while (!DeadInsts.empty()) {
3572 Instruction *I = DeadInsts.pop_back_val();
3573 DEBUG(dbgs() << "Deleting dead instruction: " << *I << "\n");
3575 I->replaceAllUsesWith(UndefValue::get(I->getType()));
3577 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
3578 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
3579 // Zero out the operand and see if it becomes trivially dead.
3581 if (isInstructionTriviallyDead(U))
3582 DeadInsts.insert(U);
3585 if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
3586 DeletedAllocas.insert(AI);
3589 I->eraseFromParent();
3593 /// \brief Promote the allocas, using the best available technique.
3595 /// This attempts to promote whatever allocas have been identified as viable in
3596 /// the PromotableAllocas list. If that list is empty, there is nothing to do.
3597 /// If there is a domtree available, we attempt to promote using the full power
3598 /// of mem2reg. Otherwise, we build and use the AllocaPromoter above which is
3599 /// based on the SSAUpdater utilities. This function returns whether any
3600 /// promotion occurred.
3601 bool SROA::promoteAllocas(Function &F) {
3602 if (PromotableAllocas.empty())
3605 NumPromoted += PromotableAllocas.size();
3607 if (DT && !ForceSSAUpdater) {
3608 DEBUG(dbgs() << "Promoting allocas with mem2reg...\n");
3609 PromoteMemToReg(PromotableAllocas, *DT);
3610 PromotableAllocas.clear();
3614 DEBUG(dbgs() << "Promoting allocas with SSAUpdater...\n");
3616 DIBuilder DIB(*F.getParent());
3617 SmallVector<Instruction*, 64> Insts;
3619 for (unsigned Idx = 0, Size = PromotableAllocas.size(); Idx != Size; ++Idx) {
3620 AllocaInst *AI = PromotableAllocas[Idx];
3621 for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end();
3623 Instruction *I = cast<Instruction>(*UI++);
3624 // FIXME: Currently the SSAUpdater infrastructure doesn't reason about
3625 // lifetime intrinsics and so we strip them (and the bitcasts+GEPs
3626 // leading to them) here. Eventually it should use them to optimize the
3627 // scalar values produced.
3628 if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) {
3629 assert(onlyUsedByLifetimeMarkers(I) &&
3630 "Found a bitcast used outside of a lifetime marker.");
3631 while (!I->use_empty())
3632 cast<Instruction>(*I->use_begin())->eraseFromParent();
3633 I->eraseFromParent();
3636 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
3637 assert(II->getIntrinsicID() == Intrinsic::lifetime_start ||
3638 II->getIntrinsicID() == Intrinsic::lifetime_end);
3639 II->eraseFromParent();
3645 AllocaPromoter(Insts, SSA, *AI, DIB).run(Insts);
3649 PromotableAllocas.clear();
3654 /// \brief A predicate to test whether an alloca belongs to a set.
3655 class IsAllocaInSet {
3656 typedef SmallPtrSet<AllocaInst *, 4> SetType;
3660 typedef AllocaInst *argument_type;
3662 IsAllocaInSet(const SetType &Set) : Set(Set) {}
3663 bool operator()(AllocaInst *AI) const { return Set.count(AI); }
3667 bool SROA::runOnFunction(Function &F) {
3668 DEBUG(dbgs() << "SROA function: " << F.getName() << "\n");
3669 C = &F.getContext();
3670 TD = getAnalysisIfAvailable<DataLayout>();
3672 DEBUG(dbgs() << " Skipping SROA -- no target data!\n");
3675 DT = getAnalysisIfAvailable<DominatorTree>();
3677 BasicBlock &EntryBB = F.getEntryBlock();
3678 for (BasicBlock::iterator I = EntryBB.begin(), E = llvm::prior(EntryBB.end());
3680 if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
3681 Worklist.insert(AI);
3683 bool Changed = false;
3684 // A set of deleted alloca instruction pointers which should be removed from
3685 // the list of promotable allocas.
3686 SmallPtrSet<AllocaInst *, 4> DeletedAllocas;
3689 while (!Worklist.empty()) {
3690 Changed |= runOnAlloca(*Worklist.pop_back_val());
3691 deleteDeadInstructions(DeletedAllocas);
3693 // Remove the deleted allocas from various lists so that we don't try to
3694 // continue processing them.
3695 if (!DeletedAllocas.empty()) {
3696 Worklist.remove_if(IsAllocaInSet(DeletedAllocas));
3697 PostPromotionWorklist.remove_if(IsAllocaInSet(DeletedAllocas));
3698 PromotableAllocas.erase(std::remove_if(PromotableAllocas.begin(),
3699 PromotableAllocas.end(),
3700 IsAllocaInSet(DeletedAllocas)),
3701 PromotableAllocas.end());
3702 DeletedAllocas.clear();
3706 Changed |= promoteAllocas(F);
3708 Worklist = PostPromotionWorklist;
3709 PostPromotionWorklist.clear();
3710 } while (!Worklist.empty());
3715 void SROA::getAnalysisUsage(AnalysisUsage &AU) const {
3716 if (RequiresDomTree)
3717 AU.addRequired<DominatorTree>();
3718 AU.setPreservesCFG();