1 //===- SROA.cpp - Scalar Replacement Of Aggregates ------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 /// \file
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.
15 ///
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.
19 ///
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.
23 ///
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/Compiler.h"
51 #include "llvm/Support/Debug.h"
52 #include "llvm/Support/ErrorHandling.h"
53 #include "llvm/Support/MathExtras.h"
54 #include "llvm/Support/raw_ostream.h"
55 #include "llvm/Transforms/Utils/Local.h"
56 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
57 #include "llvm/Transforms/Utils/SSAUpdater.h"
58 using namespace llvm;
60 STATISTIC(NumAllocasAnalyzed, "Number of allocas analyzed for replacement");
61 STATISTIC(NumAllocaPartitions, "Number of alloca partitions formed");
62 STATISTIC(MaxPartitionsPerAlloca, "Maximum number of partitions per alloca");
63 STATISTIC(NumAllocaPartitionUses, "Number of alloca partition uses rewritten");
64 STATISTIC(MaxUsesPerAllocaPartition, "Maximum number of uses of a partition");
65 STATISTIC(NumNewAllocas, "Number of new, smaller allocas introduced");
66 STATISTIC(NumPromoted, "Number of allocas promoted to SSA values");
67 STATISTIC(NumLoadsSpeculated, "Number of loads speculated to allow promotion");
68 STATISTIC(NumDeleted, "Number of instructions deleted");
69 STATISTIC(NumVectorized, "Number of vectorized aggregates");
71 /// Hidden option to force the pass to not use DomTree and mem2reg, instead
72 /// forming SSA values through the SSAUpdater infrastructure.
73 static cl::opt<bool>
74 ForceSSAUpdater("force-ssa-updater", cl::init(false), cl::Hidden);
76 namespace {
77 /// \brief A custom IRBuilder inserter which prefixes all names if they are
78 /// preserved.
79 template <bool preserveNames = true>
80 class IRBuilderPrefixedInserter :
81 public IRBuilderDefaultInserter<preserveNames> {
82 std::string Prefix;
84 public:
85 void SetNamePrefix(const Twine &P) { Prefix = P.str(); }
87 protected:
88 void InsertHelper(Instruction *I, const Twine &Name, BasicBlock *BB,
89 BasicBlock::iterator InsertPt) const {
90 IRBuilderDefaultInserter<preserveNames>::InsertHelper(
91 I, Name.isTriviallyEmpty() ? Name : Prefix + Name, BB, InsertPt);
92 }
93 };
95 // Specialization for not preserving the name is trivial.
96 template <>
97 class IRBuilderPrefixedInserter<false> :
98 public IRBuilderDefaultInserter<false> {
99 public:
100 void SetNamePrefix(const Twine &P) {}
101 };
103 /// \brief Provide a typedef for IRBuilder that drops names in release builds.
104 #ifndef NDEBUG
105 typedef llvm::IRBuilder<true, ConstantFolder,
106 IRBuilderPrefixedInserter<true> > IRBuilderTy;
107 #else
108 typedef llvm::IRBuilder<false, ConstantFolder,
109 IRBuilderPrefixedInserter<false> > IRBuilderTy;
110 #endif
111 }
113 namespace {
114 /// \brief A used slice of an alloca.
115 ///
116 /// This structure represents a slice of an alloca used by some instruction. It
117 /// stores both the begin and end offsets of this use, a pointer to the use
118 /// itself, and a flag indicating whether we can classify the use as splittable
119 /// or not when forming partitions of the alloca.
120 class Slice {
121 /// \brief The beginning offset of the range.
122 uint64_t BeginOffset;
124 /// \brief The ending offset, not included in the range.
125 uint64_t EndOffset;
127 /// \brief Storage for both the use of this slice and whether it can be
128 /// split.
129 PointerIntPair<Use *, 1, bool> UseAndIsSplittable;
131 public:
132 Slice() : BeginOffset(), EndOffset() {}
133 Slice(uint64_t BeginOffset, uint64_t EndOffset, Use *U, bool IsSplittable)
134 : BeginOffset(BeginOffset), EndOffset(EndOffset),
135 UseAndIsSplittable(U, IsSplittable) {}
137 uint64_t beginOffset() const { return BeginOffset; }
138 uint64_t endOffset() const { return EndOffset; }
140 bool isSplittable() const { return UseAndIsSplittable.getInt(); }
141 void makeUnsplittable() { UseAndIsSplittable.setInt(false); }
143 Use *getUse() const { return UseAndIsSplittable.getPointer(); }
145 bool isDead() const { return getUse() == 0; }
146 void kill() { UseAndIsSplittable.setPointer(0); }
148 /// \brief Support for ordering ranges.
149 ///
150 /// This provides an ordering over ranges such that start offsets are
151 /// always increasing, and within equal start offsets, the end offsets are
152 /// decreasing. Thus the spanning range comes first in a cluster with the
153 /// same start position.
154 bool operator<(const Slice &RHS) const {
155 if (beginOffset() < RHS.beginOffset()) return true;
156 if (beginOffset() > RHS.beginOffset()) return false;
157 if (isSplittable() != RHS.isSplittable()) return !isSplittable();
158 if (endOffset() > RHS.endOffset()) return true;
159 return false;
160 }
162 /// \brief Support comparison with a single offset to allow binary searches.
163 friend LLVM_ATTRIBUTE_UNUSED bool operator<(const Slice &LHS,
164 uint64_t RHSOffset) {
165 return LHS.beginOffset() < RHSOffset;
166 }
167 friend LLVM_ATTRIBUTE_UNUSED bool operator<(uint64_t LHSOffset,
168 const Slice &RHS) {
169 return LHSOffset < RHS.beginOffset();
170 }
172 bool operator==(const Slice &RHS) const {
173 return isSplittable() == RHS.isSplittable() &&
174 beginOffset() == RHS.beginOffset() && endOffset() == RHS.endOffset();
175 }
176 bool operator!=(const Slice &RHS) const { return !operator==(RHS); }
177 };
178 } // end anonymous namespace
180 namespace llvm {
181 template <typename T> struct isPodLike;
182 template <> struct isPodLike<Slice> {
183 static const bool value = true;
184 };
185 }
187 namespace {
188 /// \brief Representation of the alloca slices.
189 ///
190 /// This class represents the slices of an alloca which are formed by its
191 /// various uses. If a pointer escapes, we can't fully build a representation
192 /// for the slices used and we reflect that in this structure. The uses are
193 /// stored, sorted by increasing beginning offset and with unsplittable slices
194 /// starting at a particular offset before splittable slices.
195 class AllocaSlices {
196 public:
197 /// \brief Construct the slices of a particular alloca.
198 AllocaSlices(const DataLayout &DL, AllocaInst &AI);
200 /// \brief Test whether a pointer to the allocation escapes our analysis.
201 ///
202 /// If this is true, the slices are never fully built and should be
203 /// ignored.
204 bool isEscaped() const { return PointerEscapingInstr; }
206 /// \brief Support for iterating over the slices.
207 /// @{
208 typedef SmallVectorImpl<Slice>::iterator iterator;
209 iterator begin() { return Slices.begin(); }
210 iterator end() { return Slices.end(); }
212 typedef SmallVectorImpl<Slice>::const_iterator const_iterator;
213 const_iterator begin() const { return Slices.begin(); }
214 const_iterator end() const { return Slices.end(); }
215 /// @}
217 /// \brief Allow iterating the dead users for this alloca.
218 ///
219 /// These are instructions which will never actually use the alloca as they
220 /// are outside the allocated range. They are safe to replace with undef and
221 /// delete.
222 /// @{
223 typedef SmallVectorImpl<Instruction *>::const_iterator dead_user_iterator;
224 dead_user_iterator dead_user_begin() const { return DeadUsers.begin(); }
225 dead_user_iterator dead_user_end() const { return DeadUsers.end(); }
226 /// @}
228 /// \brief Allow iterating the dead expressions referring to this alloca.
229 ///
230 /// These are operands which have cannot actually be used to refer to the
231 /// alloca as they are outside its range and the user doesn't correct for
232 /// that. These mostly consist of PHI node inputs and the like which we just
233 /// need to replace with undef.
234 /// @{
235 typedef SmallVectorImpl<Use *>::const_iterator dead_op_iterator;
236 dead_op_iterator dead_op_begin() const { return DeadOperands.begin(); }
237 dead_op_iterator dead_op_end() const { return DeadOperands.end(); }
238 /// @}
240 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
241 void print(raw_ostream &OS, const_iterator I, StringRef Indent = " ") const;
242 void printSlice(raw_ostream &OS, const_iterator I,
243 StringRef Indent = " ") const;
244 void printUse(raw_ostream &OS, const_iterator I,
245 StringRef Indent = " ") const;
246 void print(raw_ostream &OS) const;
247 void LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED dump(const_iterator I) const;
248 void LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED dump() const;
249 #endif
251 private:
252 template <typename DerivedT, typename RetT = void> class BuilderBase;
253 class SliceBuilder;
254 friend class AllocaSlices::SliceBuilder;
256 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
257 /// \brief Handle to alloca instruction to simplify method interfaces.
258 AllocaInst &AI;
259 #endif
261 /// \brief The instruction responsible for this alloca not having a known set
262 /// of slices.
263 ///
264 /// When an instruction (potentially) escapes the pointer to the alloca, we
265 /// store a pointer to that here and abort trying to form slices of the
266 /// alloca. This will be null if the alloca slices are analyzed successfully.
267 Instruction *PointerEscapingInstr;
269 /// \brief The slices of the alloca.
270 ///
271 /// We store a vector of the slices formed by uses of the alloca here. This
272 /// vector is sorted by increasing begin offset, and then the unsplittable
273 /// slices before the splittable ones. See the Slice inner class for more
274 /// details.
275 SmallVector<Slice, 8> Slices;
277 /// \brief Instructions which will become dead if we rewrite the alloca.
278 ///
279 /// Note that these are not separated by slice. This is because we expect an
280 /// alloca to be completely rewritten or not rewritten at all. If rewritten,
281 /// all these instructions can simply be removed and replaced with undef as
282 /// they come from outside of the allocated space.
283 SmallVector<Instruction *, 8> DeadUsers;
285 /// \brief Operands which will become dead if we rewrite the alloca.
286 ///
287 /// These are operands that in their particular use can be replaced with
288 /// undef when we rewrite the alloca. These show up in out-of-bounds inputs
289 /// to PHI nodes and the like. They aren't entirely dead (there might be
290 /// a GEP back into the bounds using it elsewhere) and nor is the PHI, but we
291 /// want to swap this particular input for undef to simplify the use lists of
292 /// the alloca.
293 SmallVector<Use *, 8> DeadOperands;
294 };
295 }
297 static Value *foldSelectInst(SelectInst &SI) {
298 // If the condition being selected on is a constant or the same value is
299 // being selected between, fold the select. Yes this does (rarely) happen
300 // early on.
301 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI.getCondition()))
302 return SI.getOperand(1+CI->isZero());
303 if (SI.getOperand(1) == SI.getOperand(2))
304 return SI.getOperand(1);
306 return 0;
307 }
309 /// \brief Builder for the alloca slices.
310 ///
311 /// This class builds a set of alloca slices by recursively visiting the uses
312 /// of an alloca and making a slice for each load and store at each offset.
313 class AllocaSlices::SliceBuilder : public PtrUseVisitor<SliceBuilder> {
314 friend class PtrUseVisitor<SliceBuilder>;
315 friend class InstVisitor<SliceBuilder>;
316 typedef PtrUseVisitor<SliceBuilder> Base;
318 const uint64_t AllocSize;
319 AllocaSlices &S;
321 SmallDenseMap<Instruction *, unsigned> MemTransferSliceMap;
322 SmallDenseMap<Instruction *, uint64_t> PHIOrSelectSizes;
324 /// \brief Set to de-duplicate dead instructions found in the use walk.
325 SmallPtrSet<Instruction *, 4> VisitedDeadInsts;
327 public:
328 SliceBuilder(const DataLayout &DL, AllocaInst &AI, AllocaSlices &S)
329 : PtrUseVisitor<SliceBuilder>(DL),
330 AllocSize(DL.getTypeAllocSize(AI.getAllocatedType())), S(S) {}
332 private:
333 void markAsDead(Instruction &I) {
334 if (VisitedDeadInsts.insert(&I))
335 S.DeadUsers.push_back(&I);
336 }
338 void insertUse(Instruction &I, const APInt &Offset, uint64_t Size,
339 bool IsSplittable = false) {
340 // Completely skip uses which have a zero size or start either before or
341 // past the end of the allocation.
342 if (Size == 0 || Offset.isNegative() || Offset.uge(AllocSize)) {
343 DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte use @" << Offset
344 << " which has zero size or starts outside of the "
345 << AllocSize << " byte alloca:\n"
346 << " alloca: " << S.AI << "\n"
347 << " use: " << I << "\n");
348 return markAsDead(I);
349 }
351 uint64_t BeginOffset = Offset.getZExtValue();
352 uint64_t EndOffset = BeginOffset + Size;
354 // Clamp the end offset to the end of the allocation. Note that this is
355 // formulated to handle even the case where "BeginOffset + Size" overflows.
356 // This may appear superficially to be something we could ignore entirely,
357 // but that is not so! There may be widened loads or PHI-node uses where
358 // some instructions are dead but not others. We can't completely ignore
359 // them, and so have to record at least the information here.
360 assert(AllocSize >= BeginOffset); // Established above.
361 if (Size > AllocSize - BeginOffset) {
362 DEBUG(dbgs() << "WARNING: Clamping a " << Size << " byte use @" << Offset
363 << " to remain within the " << AllocSize << " byte alloca:\n"
364 << " alloca: " << S.AI << "\n"
365 << " use: " << I << "\n");
366 EndOffset = AllocSize;
367 }
369 S.Slices.push_back(Slice(BeginOffset, EndOffset, U, IsSplittable));
370 }
372 void visitBitCastInst(BitCastInst &BC) {
373 if (BC.use_empty())
374 return markAsDead(BC);
376 return Base::visitBitCastInst(BC);
377 }
379 void visitGetElementPtrInst(GetElementPtrInst &GEPI) {
380 if (GEPI.use_empty())
381 return markAsDead(GEPI);
383 return Base::visitGetElementPtrInst(GEPI);
384 }
386 void handleLoadOrStore(Type *Ty, Instruction &I, const APInt &Offset,
387 uint64_t Size, bool IsVolatile) {
388 // We allow splitting of loads and stores where the type is an integer type
389 // and cover the entire alloca. This prevents us from splitting over
390 // eagerly.
391 // FIXME: In the great blue eventually, we should eagerly split all integer
392 // loads and stores, and then have a separate step that merges adjacent
393 // alloca partitions into a single partition suitable for integer widening.
394 // Or we should skip the merge step and rely on GVN and other passes to
395 // merge adjacent loads and stores that survive mem2reg.
396 bool IsSplittable =
397 Ty->isIntegerTy() && !IsVolatile && Offset == 0 && Size >= AllocSize;
399 insertUse(I, Offset, Size, IsSplittable);
400 }
402 void visitLoadInst(LoadInst &LI) {
403 assert((!LI.isSimple() || LI.getType()->isSingleValueType()) &&
404 "All simple FCA loads should have been pre-split");
406 if (!IsOffsetKnown)
407 return PI.setAborted(&LI);
409 uint64_t Size = DL.getTypeStoreSize(LI.getType());
410 return handleLoadOrStore(LI.getType(), LI, Offset, Size, LI.isVolatile());
411 }
413 void visitStoreInst(StoreInst &SI) {
414 Value *ValOp = SI.getValueOperand();
415 if (ValOp == *U)
416 return PI.setEscapedAndAborted(&SI);
417 if (!IsOffsetKnown)
418 return PI.setAborted(&SI);
420 uint64_t Size = DL.getTypeStoreSize(ValOp->getType());
422 // If this memory access can be shown to *statically* extend outside the
423 // bounds of of the allocation, it's behavior is undefined, so simply
424 // ignore it. Note that this is more strict than the generic clamping
425 // behavior of insertUse. We also try to handle cases which might run the
426 // risk of overflow.
427 // FIXME: We should instead consider the pointer to have escaped if this
428 // function is being instrumented for addressing bugs or race conditions.
429 if (Offset.isNegative() || Size > AllocSize ||
430 Offset.ugt(AllocSize - Size)) {
431 DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte store @" << Offset
432 << " which extends past the end of the " << AllocSize
433 << " byte alloca:\n"
434 << " alloca: " << S.AI << "\n"
435 << " use: " << SI << "\n");
436 return markAsDead(SI);
437 }
439 assert((!SI.isSimple() || ValOp->getType()->isSingleValueType()) &&
440 "All simple FCA stores should have been pre-split");
441 handleLoadOrStore(ValOp->getType(), SI, Offset, Size, SI.isVolatile());
442 }
445 void visitMemSetInst(MemSetInst &II) {
446 assert(II.getRawDest() == *U && "Pointer use is not the destination?");
447 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
448 if ((Length && Length->getValue() == 0) ||
449 (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize)))
450 // Zero-length mem transfer intrinsics can be ignored entirely.
451 return markAsDead(II);
453 if (!IsOffsetKnown)
454 return PI.setAborted(&II);
456 insertUse(II, Offset,
457 Length ? Length->getLimitedValue()
458 : AllocSize - Offset.getLimitedValue(),
459 (bool)Length);
460 }
462 void visitMemTransferInst(MemTransferInst &II) {
463 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
464 if ((Length && Length->getValue() == 0) ||
465 (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize)))
466 // Zero-length mem transfer intrinsics can be ignored entirely.
467 return markAsDead(II);
469 if (!IsOffsetKnown)
470 return PI.setAborted(&II);
472 uint64_t RawOffset = Offset.getLimitedValue();
473 uint64_t Size = Length ? Length->getLimitedValue()
474 : AllocSize - RawOffset;
476 // Check for the special case where the same exact value is used for both
477 // source and dest.
478 if (*U == II.getRawDest() && *U == II.getRawSource()) {
479 // For non-volatile transfers this is a no-op.
480 if (!II.isVolatile())
481 return markAsDead(II);
483 return insertUse(II, Offset, Size, /*IsSplittable=*/false);
484 }
486 // If we have seen both source and destination for a mem transfer, then
487 // they both point to the same alloca.
488 bool Inserted;
489 SmallDenseMap<Instruction *, unsigned>::iterator MTPI;
490 llvm::tie(MTPI, Inserted) =
491 MemTransferSliceMap.insert(std::make_pair(&II, S.Slices.size()));
492 unsigned PrevIdx = MTPI->second;
493 if (!Inserted) {
494 Slice &PrevP = S.Slices[PrevIdx];
496 // Check if the begin offsets match and this is a non-volatile transfer.
497 // In that case, we can completely elide the transfer.
498 if (!II.isVolatile() && PrevP.beginOffset() == RawOffset) {
499 PrevP.kill();
500 return markAsDead(II);
501 }
503 // Otherwise we have an offset transfer within the same alloca. We can't
504 // split those.
505 PrevP.makeUnsplittable();
506 }
508 // Insert the use now that we've fixed up the splittable nature.
509 insertUse(II, Offset, Size, /*IsSplittable=*/Inserted && Length);
511 // Check that we ended up with a valid index in the map.
512 assert(S.Slices[PrevIdx].getUse()->getUser() == &II &&
513 "Map index doesn't point back to a slice with this user.");
514 }
516 // Disable SRoA for any intrinsics except for lifetime invariants.
517 // FIXME: What about debug intrinsics? This matches old behavior, but
518 // doesn't make sense.
519 void visitIntrinsicInst(IntrinsicInst &II) {
520 if (!IsOffsetKnown)
521 return PI.setAborted(&II);
523 if (II.getIntrinsicID() == Intrinsic::lifetime_start ||
524 II.getIntrinsicID() == Intrinsic::lifetime_end) {
525 ConstantInt *Length = cast<ConstantInt>(II.getArgOperand(0));
526 uint64_t Size = std::min(AllocSize - Offset.getLimitedValue(),
527 Length->getLimitedValue());
528 insertUse(II, Offset, Size, true);
529 return;
530 }
532 Base::visitIntrinsicInst(II);
533 }
535 Instruction *hasUnsafePHIOrSelectUse(Instruction *Root, uint64_t &Size) {
536 // We consider any PHI or select that results in a direct load or store of
537 // the same offset to be a viable use for slicing purposes. These uses
538 // are considered unsplittable and the size is the maximum loaded or stored
539 // size.
540 SmallPtrSet<Instruction *, 4> Visited;
541 SmallVector<std::pair<Instruction *, Instruction *>, 4> Uses;
542 Visited.insert(Root);
543 Uses.push_back(std::make_pair(cast<Instruction>(*U), Root));
544 // If there are no loads or stores, the access is dead. We mark that as
545 // a size zero access.
546 Size = 0;
547 do {
548 Instruction *I, *UsedI;
549 llvm::tie(UsedI, I) = Uses.pop_back_val();
551 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
552 Size = std::max(Size, DL.getTypeStoreSize(LI->getType()));
553 continue;
554 }
555 if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
556 Value *Op = SI->getOperand(0);
557 if (Op == UsedI)
558 return SI;
559 Size = std::max(Size, DL.getTypeStoreSize(Op->getType()));
560 continue;
561 }
563 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
564 if (!GEP->hasAllZeroIndices())
565 return GEP;
566 } else if (!isa<BitCastInst>(I) && !isa<PHINode>(I) &&
567 !isa<SelectInst>(I)) {
568 return I;
569 }
571 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE;
572 ++UI)
573 if (Visited.insert(cast<Instruction>(*UI)))
574 Uses.push_back(std::make_pair(I, cast<Instruction>(*UI)));
575 } while (!Uses.empty());
577 return 0;
578 }
580 void visitPHINode(PHINode &PN) {
581 if (PN.use_empty())
582 return markAsDead(PN);
583 if (!IsOffsetKnown)
584 return PI.setAborted(&PN);
586 // See if we already have computed info on this node.
587 uint64_t &PHISize = PHIOrSelectSizes[&PN];
588 if (!PHISize) {
589 // This is a new PHI node, check for an unsafe use of the PHI node.
590 if (Instruction *UnsafeI = hasUnsafePHIOrSelectUse(&PN, PHISize))
591 return PI.setAborted(UnsafeI);
592 }
594 // For PHI and select operands outside the alloca, we can't nuke the entire
595 // phi or select -- the other side might still be relevant, so we special
596 // case them here and use a separate structure to track the operands
597 // themselves which should be replaced with undef.
598 // FIXME: This should instead be escaped in the event we're instrumenting
599 // for address sanitization.
600 if ((Offset.isNegative() && (-Offset).uge(PHISize)) ||
601 (!Offset.isNegative() && Offset.uge(AllocSize))) {
602 S.DeadOperands.push_back(U);
603 return;
604 }
606 insertUse(PN, Offset, PHISize);
607 }
609 void visitSelectInst(SelectInst &SI) {
610 if (SI.use_empty())
611 return markAsDead(SI);
612 if (Value *Result = foldSelectInst(SI)) {
613 if (Result == *U)
614 // If the result of the constant fold will be the pointer, recurse
615 // through the select as if we had RAUW'ed it.
616 enqueueUsers(SI);
617 else
618 // Otherwise the operand to the select is dead, and we can replace it
619 // with undef.
620 S.DeadOperands.push_back(U);
622 return;
623 }
624 if (!IsOffsetKnown)
625 return PI.setAborted(&SI);
627 // See if we already have computed info on this node.
628 uint64_t &SelectSize = PHIOrSelectSizes[&SI];
629 if (!SelectSize) {
630 // This is a new Select, check for an unsafe use of it.
631 if (Instruction *UnsafeI = hasUnsafePHIOrSelectUse(&SI, SelectSize))
632 return PI.setAborted(UnsafeI);
633 }
635 // For PHI and select operands outside the alloca, we can't nuke the entire
636 // phi or select -- the other side might still be relevant, so we special
637 // case them here and use a separate structure to track the operands
638 // themselves which should be replaced with undef.
639 // FIXME: This should instead be escaped in the event we're instrumenting
640 // for address sanitization.
641 if ((Offset.isNegative() && Offset.uge(SelectSize)) ||
642 (!Offset.isNegative() && Offset.uge(AllocSize))) {
643 S.DeadOperands.push_back(U);
644 return;
645 }
647 insertUse(SI, Offset, SelectSize);
648 }
650 /// \brief Disable SROA entirely if there are unhandled users of the alloca.
651 void visitInstruction(Instruction &I) {
652 PI.setAborted(&I);
653 }
654 };
656 AllocaSlices::AllocaSlices(const DataLayout &DL, AllocaInst &AI)
657 :
658 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
659 AI(AI),
660 #endif
661 PointerEscapingInstr(0) {
662 SliceBuilder PB(DL, AI, *this);
663 SliceBuilder::PtrInfo PtrI = PB.visitPtr(AI);
664 if (PtrI.isEscaped() || PtrI.isAborted()) {
665 // FIXME: We should sink the escape vs. abort info into the caller nicely,
666 // possibly by just storing the PtrInfo in the AllocaSlices.
667 PointerEscapingInstr = PtrI.getEscapingInst() ? PtrI.getEscapingInst()
668 : PtrI.getAbortingInst();
669 assert(PointerEscapingInstr && "Did not track a bad instruction");
670 return;
671 }
673 Slices.erase(std::remove_if(Slices.begin(), Slices.end(),
674 std::mem_fun_ref(&Slice::isDead)),
675 Slices.end());
677 // Sort the uses. This arranges for the offsets to be in ascending order,
678 // and the sizes to be in descending order.
679 std::sort(Slices.begin(), Slices.end());
680 }
682 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
684 void AllocaSlices::print(raw_ostream &OS, const_iterator I,
685 StringRef Indent) const {
686 printSlice(OS, I, Indent);
687 printUse(OS, I, Indent);
688 }
690 void AllocaSlices::printSlice(raw_ostream &OS, const_iterator I,
691 StringRef Indent) const {
692 OS << Indent << "[" << I->beginOffset() << "," << I->endOffset() << ")"
693 << " slice #" << (I - begin())
694 << (I->isSplittable() ? " (splittable)" : "") << "\n";
695 }
697 void AllocaSlices::printUse(raw_ostream &OS, const_iterator I,
698 StringRef Indent) const {
699 OS << Indent << " used by: " << *I->getUse()->getUser() << "\n";
700 }
702 void AllocaSlices::print(raw_ostream &OS) const {
703 if (PointerEscapingInstr) {
704 OS << "Can't analyze slices for alloca: " << AI << "\n"
705 << " A pointer to this alloca escaped by:\n"
706 << " " << *PointerEscapingInstr << "\n";
707 return;
708 }
710 OS << "Slices of alloca: " << AI << "\n";
711 for (const_iterator I = begin(), E = end(); I != E; ++I)
712 print(OS, I);
713 }
715 void AllocaSlices::dump(const_iterator I) const { print(dbgs(), I); }
716 void AllocaSlices::dump() const { print(dbgs()); }
718 #endif // !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
720 namespace {
721 /// \brief Implementation of LoadAndStorePromoter for promoting allocas.
722 ///
723 /// This subclass of LoadAndStorePromoter adds overrides to handle promoting
724 /// the loads and stores of an alloca instruction, as well as updating its
725 /// debug information. This is used when a domtree is unavailable and thus
726 /// mem2reg in its full form can't be used to handle promotion of allocas to
727 /// scalar values.
728 class AllocaPromoter : public LoadAndStorePromoter {
729 AllocaInst &AI;
730 DIBuilder &DIB;
732 SmallVector<DbgDeclareInst *, 4> DDIs;
733 SmallVector<DbgValueInst *, 4> DVIs;
735 public:
736 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S,
737 AllocaInst &AI, DIBuilder &DIB)
738 : LoadAndStorePromoter(Insts, S), AI(AI), DIB(DIB) {}
740 void run(const SmallVectorImpl<Instruction*> &Insts) {
741 // Remember which alloca we're promoting (for isInstInList).
742 if (MDNode *DebugNode = MDNode::getIfExists(AI.getContext(), &AI)) {
743 for (Value::use_iterator UI = DebugNode->use_begin(),
744 UE = DebugNode->use_end();
745 UI != UE; ++UI)
746 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(*UI))
747 DDIs.push_back(DDI);
748 else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(*UI))
749 DVIs.push_back(DVI);
750 }
752 LoadAndStorePromoter::run(Insts);
753 AI.eraseFromParent();
754 while (!DDIs.empty())
755 DDIs.pop_back_val()->eraseFromParent();
756 while (!DVIs.empty())
757 DVIs.pop_back_val()->eraseFromParent();
758 }
760 virtual bool isInstInList(Instruction *I,
761 const SmallVectorImpl<Instruction*> &Insts) const {
762 if (LoadInst *LI = dyn_cast<LoadInst>(I))
763 return LI->getOperand(0) == &AI;
764 return cast<StoreInst>(I)->getPointerOperand() == &AI;
765 }
767 virtual void updateDebugInfo(Instruction *Inst) const {
768 for (SmallVectorImpl<DbgDeclareInst *>::const_iterator I = DDIs.begin(),
769 E = DDIs.end(); I != E; ++I) {
770 DbgDeclareInst *DDI = *I;
771 if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
772 ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
773 else if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
774 ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
775 }
776 for (SmallVectorImpl<DbgValueInst *>::const_iterator I = DVIs.begin(),
777 E = DVIs.end(); I != E; ++I) {
778 DbgValueInst *DVI = *I;
779 Value *Arg = 0;
780 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
781 // If an argument is zero extended then use argument directly. The ZExt
782 // may be zapped by an optimization pass in future.
783 if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
784 Arg = dyn_cast<Argument>(ZExt->getOperand(0));
785 else if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
786 Arg = dyn_cast<Argument>(SExt->getOperand(0));
787 if (!Arg)
788 Arg = SI->getValueOperand();
789 } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
790 Arg = LI->getPointerOperand();
791 } else {
792 continue;
793 }
794 Instruction *DbgVal =
795 DIB.insertDbgValueIntrinsic(Arg, 0, DIVariable(DVI->getVariable()),
796 Inst);
797 DbgVal->setDebugLoc(DVI->getDebugLoc());
798 }
799 }
800 };
801 } // end anon namespace
804 namespace {
805 /// \brief An optimization pass providing Scalar Replacement of Aggregates.
806 ///
807 /// This pass takes allocations which can be completely analyzed (that is, they
808 /// don't escape) and tries to turn them into scalar SSA values. There are
809 /// a few steps to this process.
810 ///
811 /// 1) It takes allocations of aggregates and analyzes the ways in which they
812 /// are used to try to split them into smaller allocations, ideally of
813 /// a single scalar data type. It will split up memcpy and memset accesses
814 /// as necessary and try to isolate individual scalar accesses.
815 /// 2) It will transform accesses into forms which are suitable for SSA value
816 /// promotion. This can be replacing a memset with a scalar store of an
817 /// integer value, or it can involve speculating operations on a PHI or
818 /// select to be a PHI or select of the results.
819 /// 3) Finally, this will try to detect a pattern of accesses which map cleanly
820 /// onto insert and extract operations on a vector value, and convert them to
821 /// this form. By doing so, it will enable promotion of vector aggregates to
822 /// SSA vector values.
823 class SROA : public FunctionPass {
824 const bool RequiresDomTree;
826 LLVMContext *C;
827 const DataLayout *DL;
828 DominatorTree *DT;
830 /// \brief Worklist of alloca instructions to simplify.
831 ///
832 /// Each alloca in the function is added to this. Each new alloca formed gets
833 /// added to it as well to recursively simplify unless that alloca can be
834 /// directly promoted. Finally, each time we rewrite a use of an alloca other
835 /// the one being actively rewritten, we add it back onto the list if not
836 /// already present to ensure it is re-visited.
837 SetVector<AllocaInst *, SmallVector<AllocaInst *, 16> > Worklist;
839 /// \brief A collection of instructions to delete.
840 /// We try to batch deletions to simplify code and make things a bit more
841 /// efficient.
842 SetVector<Instruction *, SmallVector<Instruction *, 8> > DeadInsts;
844 /// \brief Post-promotion worklist.
845 ///
846 /// Sometimes we discover an alloca which has a high probability of becoming
847 /// viable for SROA after a round of promotion takes place. In those cases,
848 /// the alloca is enqueued here for re-processing.
849 ///
850 /// Note that we have to be very careful to clear allocas out of this list in
851 /// the event they are deleted.
852 SetVector<AllocaInst *, SmallVector<AllocaInst *, 16> > PostPromotionWorklist;
854 /// \brief A collection of alloca instructions we can directly promote.
855 std::vector<AllocaInst *> PromotableAllocas;
857 /// \brief A worklist of PHIs to speculate prior to promoting allocas.
858 ///
859 /// All of these PHIs have been checked for the safety of speculation and by
860 /// being speculated will allow promoting allocas currently in the promotable
861 /// queue.
862 SetVector<PHINode *, SmallVector<PHINode *, 2> > SpeculatablePHIs;
864 /// \brief A worklist of select instructions to speculate prior to promoting
865 /// allocas.
866 ///
867 /// All of these select instructions have been checked for the safety of
868 /// speculation and by being speculated will allow promoting allocas
869 /// currently in the promotable queue.
870 SetVector<SelectInst *, SmallVector<SelectInst *, 2> > SpeculatableSelects;
872 public:
873 SROA(bool RequiresDomTree = true)
874 : FunctionPass(ID), RequiresDomTree(RequiresDomTree),
875 C(0), DL(0), DT(0) {
876 initializeSROAPass(*PassRegistry::getPassRegistry());
877 }
878 bool runOnFunction(Function &F);
879 void getAnalysisUsage(AnalysisUsage &AU) const;
881 const char *getPassName() const { return "SROA"; }
882 static char ID;
884 private:
885 friend class PHIOrSelectSpeculator;
886 friend class AllocaSliceRewriter;
888 bool rewritePartition(AllocaInst &AI, AllocaSlices &S,
889 AllocaSlices::iterator B, AllocaSlices::iterator E,
890 int64_t BeginOffset, int64_t EndOffset,
891 ArrayRef<AllocaSlices::iterator> SplitUses);
892 bool splitAlloca(AllocaInst &AI, AllocaSlices &S);
893 bool runOnAlloca(AllocaInst &AI);
894 void deleteDeadInstructions(SmallPtrSet<AllocaInst *, 4> &DeletedAllocas);
895 bool promoteAllocas(Function &F);
896 };
897 }
899 char SROA::ID = 0;
901 FunctionPass *llvm::createSROAPass(bool RequiresDomTree) {
902 return new SROA(RequiresDomTree);
903 }
905 INITIALIZE_PASS_BEGIN(SROA, "sroa", "Scalar Replacement Of Aggregates",
906 false, false)
907 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
908 INITIALIZE_PASS_END(SROA, "sroa", "Scalar Replacement Of Aggregates",
909 false, false)
911 /// Walk the range of a partitioning looking for a common type to cover this
912 /// sequence of slices.
913 static Type *findCommonType(AllocaSlices::const_iterator B,
914 AllocaSlices::const_iterator E,
915 uint64_t EndOffset) {
916 Type *Ty = 0;
917 for (AllocaSlices::const_iterator I = B; I != E; ++I) {
918 Use *U = I->getUse();
919 if (isa<IntrinsicInst>(*U->getUser()))
920 continue;
921 if (I->beginOffset() != B->beginOffset() || I->endOffset() != EndOffset)
922 continue;
924 Type *UserTy = 0;
925 if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser()))
926 UserTy = LI->getType();
927 else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser()))
928 UserTy = SI->getValueOperand()->getType();
929 else
930 return 0; // Bail if we have weird uses.
932 if (IntegerType *ITy = dyn_cast<IntegerType>(UserTy)) {
933 // If the type is larger than the partition, skip it. We only encounter
934 // this for split integer operations where we want to use the type of the
935 // entity causing the split.
936 if (ITy->getBitWidth() / 8 > (EndOffset - B->beginOffset()))
937 continue;
939 // If we have found an integer type use covering the alloca, use that
940 // regardless of the other types, as integers are often used for a
941 // "bucket
942 // of bits" type.
943 return ITy;
944 }
946 if (Ty && Ty != UserTy)
947 return 0;
949 Ty = UserTy;
950 }
951 return Ty;
952 }
954 /// PHI instructions that use an alloca and are subsequently loaded can be
955 /// rewritten to load both input pointers in the pred blocks and then PHI the
956 /// results, allowing the load of the alloca to be promoted.
957 /// From this:
958 /// %P2 = phi [i32* %Alloca, i32* %Other]
959 /// %V = load i32* %P2
960 /// to:
961 /// %V1 = load i32* %Alloca -> will be mem2reg'd
962 /// ...
963 /// %V2 = load i32* %Other
964 /// ...
965 /// %V = phi [i32 %V1, i32 %V2]
966 ///
967 /// We can do this to a select if its only uses are loads and if the operands
968 /// to the select can be loaded unconditionally.
969 ///
970 /// FIXME: This should be hoisted into a generic utility, likely in
971 /// Transforms/Util/Local.h
972 static bool isSafePHIToSpeculate(PHINode &PN,
973 const DataLayout *DL = 0) {
974 // For now, we can only do this promotion if the load is in the same block
975 // as the PHI, and if there are no stores between the phi and load.
976 // TODO: Allow recursive phi users.
977 // TODO: Allow stores.
978 BasicBlock *BB = PN.getParent();
979 unsigned MaxAlign = 0;
980 bool HaveLoad = false;
981 for (Value::use_iterator UI = PN.use_begin(), UE = PN.use_end(); UI != UE;
982 ++UI) {
983 LoadInst *LI = dyn_cast<LoadInst>(*UI);
984 if (LI == 0 || !LI->isSimple())
985 return false;
987 // For now we only allow loads in the same block as the PHI. This is
988 // a common case that happens when instcombine merges two loads through
989 // a PHI.
990 if (LI->getParent() != BB)
991 return false;
993 // Ensure that there are no instructions between the PHI and the load that
994 // could store.
995 for (BasicBlock::iterator BBI = &PN; &*BBI != LI; ++BBI)
996 if (BBI->mayWriteToMemory())
997 return false;
999 MaxAlign = std::max(MaxAlign, LI->getAlignment());
1000 HaveLoad = true;
1001 }
1003 if (!HaveLoad)
1004 return false;
1006 // We can only transform this if it is safe to push the loads into the
1007 // predecessor blocks. The only thing to watch out for is that we can't put
1008 // a possibly trapping load in the predecessor if it is a critical edge.
1009 for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) {
1010 TerminatorInst *TI = PN.getIncomingBlock(Idx)->getTerminator();
1011 Value *InVal = PN.getIncomingValue(Idx);
1013 // If the value is produced by the terminator of the predecessor (an
1014 // invoke) or it has side-effects, there is no valid place to put a load
1015 // in the predecessor.
1016 if (TI == InVal || TI->mayHaveSideEffects())
1017 return false;
1019 // If the predecessor has a single successor, then the edge isn't
1020 // critical.
1021 if (TI->getNumSuccessors() == 1)
1022 continue;
1024 // If this pointer is always safe to load, or if we can prove that there
1025 // is already a load in the block, then we can move the load to the pred
1026 // block.
1027 if (InVal->isDereferenceablePointer() ||
1028 isSafeToLoadUnconditionally(InVal, TI, MaxAlign, DL))
1029 continue;
1031 return false;
1032 }
1034 return true;
1035 }
1037 static void speculatePHINodeLoads(PHINode &PN) {
1038 DEBUG(dbgs() << " original: " << PN << "\n");
1040 Type *LoadTy = cast<PointerType>(PN.getType())->getElementType();
1041 IRBuilderTy PHIBuilder(&PN);
1042 PHINode *NewPN = PHIBuilder.CreatePHI(LoadTy, PN.getNumIncomingValues(),
1043 PN.getName() + ".sroa.speculated");
1045 // Get the TBAA tag and alignment to use from one of the loads. It doesn't
1046 // matter which one we get and if any differ.
1047 LoadInst *SomeLoad = cast<LoadInst>(*PN.use_begin());
1048 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa);
1049 unsigned Align = SomeLoad->getAlignment();
1051 // Rewrite all loads of the PN to use the new PHI.
1052 while (!PN.use_empty()) {
1053 LoadInst *LI = cast<LoadInst>(*PN.use_begin());
1054 LI->replaceAllUsesWith(NewPN);
1055 LI->eraseFromParent();
1056 }
1058 // Inject loads into all of the pred blocks.
1059 for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) {
1060 BasicBlock *Pred = PN.getIncomingBlock(Idx);
1061 TerminatorInst *TI = Pred->getTerminator();
1062 Value *InVal = PN.getIncomingValue(Idx);
1063 IRBuilderTy PredBuilder(TI);
1065 LoadInst *Load = PredBuilder.CreateLoad(
1066 InVal, (PN.getName() + ".sroa.speculate.load." + Pred->getName()));
1067 ++NumLoadsSpeculated;
1068 Load->setAlignment(Align);
1069 if (TBAATag)
1070 Load->setMetadata(LLVMContext::MD_tbaa, TBAATag);
1071 NewPN->addIncoming(Load, Pred);
1072 }
1074 DEBUG(dbgs() << " speculated to: " << *NewPN << "\n");
1075 PN.eraseFromParent();
1076 }
1078 /// Select instructions that use an alloca and are subsequently loaded can be
1079 /// rewritten to load both input pointers and then select between the result,
1080 /// allowing the load of the alloca to be promoted.
1081 /// From this:
1082 /// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
1083 /// %V = load i32* %P2
1084 /// to:
1085 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1086 /// %V2 = load i32* %Other
1087 /// %V = select i1 %cond, i32 %V1, i32 %V2
1088 ///
1089 /// We can do this to a select if its only uses are loads and if the operand
1090 /// to the select can be loaded unconditionally.
1091 static bool isSafeSelectToSpeculate(SelectInst &SI, const DataLayout *DL = 0) {
1092 Value *TValue = SI.getTrueValue();
1093 Value *FValue = SI.getFalseValue();
1094 bool TDerefable = TValue->isDereferenceablePointer();
1095 bool FDerefable = FValue->isDereferenceablePointer();
1097 for (Value::use_iterator UI = SI.use_begin(), UE = SI.use_end(); UI != UE;
1098 ++UI) {
1099 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1100 if (LI == 0 || !LI->isSimple())
1101 return false;
1103 // Both operands to the select need to be dereferencable, either
1104 // absolutely (e.g. allocas) or at this point because we can see other
1105 // accesses to it.
1106 if (!TDerefable &&
1107 !isSafeToLoadUnconditionally(TValue, LI, LI->getAlignment(), DL))
1108 return false;
1109 if (!FDerefable &&
1110 !isSafeToLoadUnconditionally(FValue, LI, LI->getAlignment(), DL))
1111 return false;
1112 }
1114 return true;
1115 }
1117 static void speculateSelectInstLoads(SelectInst &SI) {
1118 DEBUG(dbgs() << " original: " << SI << "\n");
1120 IRBuilderTy IRB(&SI);
1121 Value *TV = SI.getTrueValue();
1122 Value *FV = SI.getFalseValue();
1123 // Replace the loads of the select with a select of two loads.
1124 while (!SI.use_empty()) {
1125 LoadInst *LI = cast<LoadInst>(*SI.use_begin());
1126 assert(LI->isSimple() && "We only speculate simple loads");
1128 IRB.SetInsertPoint(LI);
1129 LoadInst *TL =
1130 IRB.CreateLoad(TV, LI->getName() + ".sroa.speculate.load.true");
1131 LoadInst *FL =
1132 IRB.CreateLoad(FV, LI->getName() + ".sroa.speculate.load.false");
1133 NumLoadsSpeculated += 2;
1135 // Transfer alignment and TBAA info if present.
1136 TL->setAlignment(LI->getAlignment());
1137 FL->setAlignment(LI->getAlignment());
1138 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) {
1139 TL->setMetadata(LLVMContext::MD_tbaa, Tag);
1140 FL->setMetadata(LLVMContext::MD_tbaa, Tag);
1141 }
1143 Value *V = IRB.CreateSelect(SI.getCondition(), TL, FL,
1144 LI->getName() + ".sroa.speculated");
1146 DEBUG(dbgs() << " speculated to: " << *V << "\n");
1147 LI->replaceAllUsesWith(V);
1148 LI->eraseFromParent();
1149 }
1150 SI.eraseFromParent();
1151 }
1153 /// \brief Build a GEP out of a base pointer and indices.
1154 ///
1155 /// This will return the BasePtr if that is valid, or build a new GEP
1156 /// instruction using the IRBuilder if GEP-ing is needed.
1157 static Value *buildGEP(IRBuilderTy &IRB, Value *BasePtr,
1158 SmallVectorImpl<Value *> &Indices) {
1159 if (Indices.empty())
1160 return BasePtr;
1162 // A single zero index is a no-op, so check for this and avoid building a GEP
1163 // in that case.
1164 if (Indices.size() == 1 && cast<ConstantInt>(Indices.back())->isZero())
1165 return BasePtr;
1167 return IRB.CreateInBoundsGEP(BasePtr, Indices, "idx");
1168 }
1170 /// \brief Get a natural GEP off of the BasePtr walking through Ty toward
1171 /// TargetTy without changing the offset of the pointer.
1172 ///
1173 /// This routine assumes we've already established a properly offset GEP with
1174 /// Indices, and arrived at the Ty type. The goal is to continue to GEP with
1175 /// zero-indices down through type layers until we find one the same as
1176 /// TargetTy. If we can't find one with the same type, we at least try to use
1177 /// one with the same size. If none of that works, we just produce the GEP as
1178 /// indicated by Indices to have the correct offset.
1179 static Value *getNaturalGEPWithType(IRBuilderTy &IRB, const DataLayout &DL,
1180 Value *BasePtr, Type *Ty, Type *TargetTy,
1181 SmallVectorImpl<Value *> &Indices) {
1182 if (Ty == TargetTy)
1183 return buildGEP(IRB, BasePtr, Indices);
1185 // See if we can descend into a struct and locate a field with the correct
1186 // type.
1187 unsigned NumLayers = 0;
1188 Type *ElementTy = Ty;
1189 do {
1190 if (ElementTy->isPointerTy())
1191 break;
1192 if (SequentialType *SeqTy = dyn_cast<SequentialType>(ElementTy)) {
1193 ElementTy = SeqTy->getElementType();
1194 // Note that we use the default address space as this index is over an
1195 // array or a vector, not a pointer.
1196 Indices.push_back(IRB.getInt(APInt(DL.getPointerSizeInBits(0), 0)));
1197 } else if (StructType *STy = dyn_cast<StructType>(ElementTy)) {
1198 if (STy->element_begin() == STy->element_end())
1199 break; // Nothing left to descend into.
1200 ElementTy = *STy->element_begin();
1201 Indices.push_back(IRB.getInt32(0));
1202 } else {
1203 break;
1204 }
1205 ++NumLayers;
1206 } while (ElementTy != TargetTy);
1207 if (ElementTy != TargetTy)
1208 Indices.erase(Indices.end() - NumLayers, Indices.end());
1210 return buildGEP(IRB, BasePtr, Indices);
1211 }
1213 /// \brief Recursively compute indices for a natural GEP.
1214 ///
1215 /// This is the recursive step for getNaturalGEPWithOffset that walks down the
1216 /// element types adding appropriate indices for the GEP.
1217 static Value *getNaturalGEPRecursively(IRBuilderTy &IRB, const DataLayout &DL,
1218 Value *Ptr, Type *Ty, APInt &Offset,
1219 Type *TargetTy,
1220 SmallVectorImpl<Value *> &Indices) {
1221 if (Offset == 0)
1222 return getNaturalGEPWithType(IRB, DL, Ptr, Ty, TargetTy, Indices);
1224 // We can't recurse through pointer types.
1225 if (Ty->isPointerTy())
1226 return 0;
1228 // We try to analyze GEPs over vectors here, but note that these GEPs are
1229 // extremely poorly defined currently. The long-term goal is to remove GEPing
1230 // over a vector from the IR completely.
1231 if (VectorType *VecTy = dyn_cast<VectorType>(Ty)) {
1232 unsigned ElementSizeInBits = DL.getTypeSizeInBits(VecTy->getScalarType());
1233 if (ElementSizeInBits % 8)
1234 return 0; // GEPs over non-multiple of 8 size vector elements are invalid.
1235 APInt ElementSize(Offset.getBitWidth(), ElementSizeInBits / 8);
1236 APInt NumSkippedElements = Offset.sdiv(ElementSize);
1237 if (NumSkippedElements.ugt(VecTy->getNumElements()))
1238 return 0;
1239 Offset -= NumSkippedElements * ElementSize;
1240 Indices.push_back(IRB.getInt(NumSkippedElements));
1241 return getNaturalGEPRecursively(IRB, DL, Ptr, VecTy->getElementType(),
1242 Offset, TargetTy, Indices);
1243 }
1245 if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) {
1246 Type *ElementTy = ArrTy->getElementType();
1247 APInt ElementSize(Offset.getBitWidth(), DL.getTypeAllocSize(ElementTy));
1248 APInt NumSkippedElements = Offset.sdiv(ElementSize);
1249 if (NumSkippedElements.ugt(ArrTy->getNumElements()))
1250 return 0;
1252 Offset -= NumSkippedElements * ElementSize;
1253 Indices.push_back(IRB.getInt(NumSkippedElements));
1254 return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy,
1255 Indices);
1256 }
1258 StructType *STy = dyn_cast<StructType>(Ty);
1259 if (!STy)
1260 return 0;
1262 const StructLayout *SL = DL.getStructLayout(STy);
1263 uint64_t StructOffset = Offset.getZExtValue();
1264 if (StructOffset >= SL->getSizeInBytes())
1265 return 0;
1266 unsigned Index = SL->getElementContainingOffset(StructOffset);
1267 Offset -= APInt(Offset.getBitWidth(), SL->getElementOffset(Index));
1268 Type *ElementTy = STy->getElementType(Index);
1269 if (Offset.uge(DL.getTypeAllocSize(ElementTy)))
1270 return 0; // The offset points into alignment padding.
1272 Indices.push_back(IRB.getInt32(Index));
1273 return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy,
1274 Indices);
1275 }
1277 /// \brief Get a natural GEP from a base pointer to a particular offset and
1278 /// resulting in a particular type.
1279 ///
1280 /// The goal is to produce a "natural" looking GEP that works with the existing
1281 /// composite types to arrive at the appropriate offset and element type for
1282 /// a pointer. TargetTy is the element type the returned GEP should point-to if
1283 /// possible. We recurse by decreasing Offset, adding the appropriate index to
1284 /// Indices, and setting Ty to the result subtype.
1285 ///
1286 /// If no natural GEP can be constructed, this function returns null.
1287 static Value *getNaturalGEPWithOffset(IRBuilderTy &IRB, const DataLayout &DL,
1288 Value *Ptr, APInt Offset, Type *TargetTy,
1289 SmallVectorImpl<Value *> &Indices) {
1290 PointerType *Ty = cast<PointerType>(Ptr->getType());
1292 // Don't consider any GEPs through an i8* as natural unless the TargetTy is
1293 // an i8.
1294 if (Ty == IRB.getInt8PtrTy() && TargetTy->isIntegerTy(8))
1295 return 0;
1297 Type *ElementTy = Ty->getElementType();
1298 if (!ElementTy->isSized())
1299 return 0; // We can't GEP through an unsized element.
1300 APInt ElementSize(Offset.getBitWidth(), DL.getTypeAllocSize(ElementTy));
1301 if (ElementSize == 0)
1302 return 0; // Zero-length arrays can't help us build a natural GEP.
1303 APInt NumSkippedElements = Offset.sdiv(ElementSize);
1305 Offset -= NumSkippedElements * ElementSize;
1306 Indices.push_back(IRB.getInt(NumSkippedElements));
1307 return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy,
1308 Indices);
1309 }
1311 /// \brief Compute an adjusted pointer from Ptr by Offset bytes where the
1312 /// resulting pointer has PointerTy.
1313 ///
1314 /// This tries very hard to compute a "natural" GEP which arrives at the offset
1315 /// and produces the pointer type desired. Where it cannot, it will try to use
1316 /// the natural GEP to arrive at the offset and bitcast to the type. Where that
1317 /// fails, it will try to use an existing i8* and GEP to the byte offset and
1318 /// bitcast to the type.
1319 ///
1320 /// The strategy for finding the more natural GEPs is to peel off layers of the
1321 /// pointer, walking back through bit casts and GEPs, searching for a base
1322 /// pointer from which we can compute a natural GEP with the desired
1323 /// properties. The algorithm tries to fold as many constant indices into
1324 /// a single GEP as possible, thus making each GEP more independent of the
1325 /// surrounding code.
1326 static Value *getAdjustedPtr(IRBuilderTy &IRB, const DataLayout &DL,
1327 Value *Ptr, APInt Offset, Type *PointerTy) {
1328 // Even though we don't look through PHI nodes, we could be called on an
1329 // instruction in an unreachable block, which may be on a cycle.
1330 SmallPtrSet<Value *, 4> Visited;
1331 Visited.insert(Ptr);
1332 SmallVector<Value *, 4> Indices;
1334 // We may end up computing an offset pointer that has the wrong type. If we
1335 // never are able to compute one directly that has the correct type, we'll
1336 // fall back to it, so keep it around here.
1337 Value *OffsetPtr = 0;
1339 // Remember any i8 pointer we come across to re-use if we need to do a raw
1340 // byte offset.
1341 Value *Int8Ptr = 0;
1342 APInt Int8PtrOffset(Offset.getBitWidth(), 0);
1344 Type *TargetTy = PointerTy->getPointerElementType();
1346 do {
1347 // First fold any existing GEPs into the offset.
1348 while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
1349 APInt GEPOffset(Offset.getBitWidth(), 0);
1350 if (!GEP->accumulateConstantOffset(DL, GEPOffset))
1351 break;
1352 Offset += GEPOffset;
1353 Ptr = GEP->getPointerOperand();
1354 if (!Visited.insert(Ptr))
1355 break;
1356 }
1358 // See if we can perform a natural GEP here.
1359 Indices.clear();
1360 if (Value *P = getNaturalGEPWithOffset(IRB, DL, Ptr, Offset, TargetTy,
1361 Indices)) {
1362 if (P->getType() == PointerTy) {
1363 // Zap any offset pointer that we ended up computing in previous rounds.
1364 if (OffsetPtr && OffsetPtr->use_empty())
1365 if (Instruction *I = dyn_cast<Instruction>(OffsetPtr))
1366 I->eraseFromParent();
1367 return P;
1368 }
1369 if (!OffsetPtr) {
1370 OffsetPtr = P;
1371 }
1372 }
1374 // Stash this pointer if we've found an i8*.
1375 if (Ptr->getType()->isIntegerTy(8)) {
1376 Int8Ptr = Ptr;
1377 Int8PtrOffset = Offset;
1378 }
1380 // Peel off a layer of the pointer and update the offset appropriately.
1381 if (Operator::getOpcode(Ptr) == Instruction::BitCast) {
1382 Ptr = cast<Operator>(Ptr)->getOperand(0);
1383 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(Ptr)) {
1384 if (GA->mayBeOverridden())
1385 break;
1386 Ptr = GA->getAliasee();
1387 } else {
1388 break;
1389 }
1390 assert(Ptr->getType()->isPointerTy() && "Unexpected operand type!");
1391 } while (Visited.insert(Ptr));
1393 if (!OffsetPtr) {
1394 if (!Int8Ptr) {
1395 Int8Ptr = IRB.CreateBitCast(Ptr, IRB.getInt8PtrTy(),
1396 "raw_cast");
1397 Int8PtrOffset = Offset;
1398 }
1400 OffsetPtr = Int8PtrOffset == 0 ? Int8Ptr :
1401 IRB.CreateInBoundsGEP(Int8Ptr, IRB.getInt(Int8PtrOffset),
1402 "raw_idx");
1403 }
1404 Ptr = OffsetPtr;
1406 // On the off chance we were targeting i8*, guard the bitcast here.
1407 if (Ptr->getType() != PointerTy)
1408 Ptr = IRB.CreateBitCast(Ptr, PointerTy, "cast");
1410 return Ptr;
1411 }
1413 /// \brief Test whether we can convert a value from the old to the new type.
1414 ///
1415 /// This predicate should be used to guard calls to convertValue in order to
1416 /// ensure that we only try to convert viable values. The strategy is that we
1417 /// will peel off single element struct and array wrappings to get to an
1418 /// underlying value, and convert that value.
1419 static bool canConvertValue(const DataLayout &DL, Type *OldTy, Type *NewTy) {
1420 if (OldTy == NewTy)
1421 return true;
1422 if (IntegerType *OldITy = dyn_cast<IntegerType>(OldTy))
1423 if (IntegerType *NewITy = dyn_cast<IntegerType>(NewTy))
1424 if (NewITy->getBitWidth() >= OldITy->getBitWidth())
1425 return true;
1426 if (DL.getTypeSizeInBits(NewTy) != DL.getTypeSizeInBits(OldTy))
1427 return false;
1428 if (!NewTy->isSingleValueType() || !OldTy->isSingleValueType())
1429 return false;
1431 if (NewTy->isPointerTy() || OldTy->isPointerTy()) {
1432 if (NewTy->isPointerTy() && OldTy->isPointerTy())
1433 return true;
1434 if (NewTy->isIntegerTy() || OldTy->isIntegerTy())
1435 return true;
1436 return false;
1437 }
1439 return true;
1440 }
1442 /// \brief Generic routine to convert an SSA value to a value of a different
1443 /// type.
1444 ///
1445 /// This will try various different casting techniques, such as bitcasts,
1446 /// inttoptr, and ptrtoint casts. Use the \c canConvertValue predicate to test
1447 /// two types for viability with this routine.
1448 static Value *convertValue(const DataLayout &DL, IRBuilderTy &IRB, Value *V,
1449 Type *Ty) {
1450 assert(canConvertValue(DL, V->getType(), Ty) &&
1451 "Value not convertable to type");
1452 if (V->getType() == Ty)
1453 return V;
1454 if (IntegerType *OldITy = dyn_cast<IntegerType>(V->getType()))
1455 if (IntegerType *NewITy = dyn_cast<IntegerType>(Ty))
1456 if (NewITy->getBitWidth() > OldITy->getBitWidth())
1457 return IRB.CreateZExt(V, NewITy);
1458 if (V->getType()->isIntegerTy() && Ty->isPointerTy())
1459 return IRB.CreateIntToPtr(V, Ty);
1460 if (V->getType()->isPointerTy() && Ty->isIntegerTy())
1461 return IRB.CreatePtrToInt(V, Ty);
1463 return IRB.CreateBitCast(V, Ty);
1464 }
1466 /// \brief Test whether the given slice use can be promoted to a vector.
1467 ///
1468 /// This function is called to test each entry in a partioning which is slated
1469 /// for a single slice.
1470 static bool isVectorPromotionViableForSlice(
1471 const DataLayout &DL, AllocaSlices &S, uint64_t SliceBeginOffset,
1472 uint64_t SliceEndOffset, VectorType *Ty, uint64_t ElementSize,
1473 AllocaSlices::const_iterator I) {
1474 // First validate the slice offsets.
1475 uint64_t BeginOffset =
1476 std::max(I->beginOffset(), SliceBeginOffset) - SliceBeginOffset;
1477 uint64_t BeginIndex = BeginOffset / ElementSize;
1478 if (BeginIndex * ElementSize != BeginOffset ||
1479 BeginIndex >= Ty->getNumElements())
1480 return false;
1481 uint64_t EndOffset =
1482 std::min(I->endOffset(), SliceEndOffset) - SliceBeginOffset;
1483 uint64_t EndIndex = EndOffset / ElementSize;
1484 if (EndIndex * ElementSize != EndOffset || EndIndex > Ty->getNumElements())
1485 return false;
1487 assert(EndIndex > BeginIndex && "Empty vector!");
1488 uint64_t NumElements = EndIndex - BeginIndex;
1489 Type *SliceTy =
1490 (NumElements == 1) ? Ty->getElementType()
1491 : VectorType::get(Ty->getElementType(), NumElements);
1493 Type *SplitIntTy =
1494 Type::getIntNTy(Ty->getContext(), NumElements * ElementSize * 8);
1496 Use *U = I->getUse();
1498 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) {
1499 if (MI->isVolatile())
1500 return false;
1501 if (!I->isSplittable())
1502 return false; // Skip any unsplittable intrinsics.
1503 } else if (U->get()->getType()->getPointerElementType()->isStructTy()) {
1504 // Disable vector promotion when there are loads or stores of an FCA.
1505 return false;
1506 } else if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) {
1507 if (LI->isVolatile())
1508 return false;
1509 Type *LTy = LI->getType();
1510 if (SliceBeginOffset > I->beginOffset() ||
1511 SliceEndOffset < I->endOffset()) {
1512 assert(LTy->isIntegerTy());
1513 LTy = SplitIntTy;
1514 }
1515 if (!canConvertValue(DL, SliceTy, LTy))
1516 return false;
1517 } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
1518 if (SI->isVolatile())
1519 return false;
1520 Type *STy = SI->getValueOperand()->getType();
1521 if (SliceBeginOffset > I->beginOffset() ||
1522 SliceEndOffset < I->endOffset()) {
1523 assert(STy->isIntegerTy());
1524 STy = SplitIntTy;
1525 }
1526 if (!canConvertValue(DL, STy, SliceTy))
1527 return false;
1528 } else {
1529 return false;
1530 }
1532 return true;
1533 }
1535 /// \brief Test whether the given alloca partitioning and range of slices can be
1536 /// promoted to a vector.
1537 ///
1538 /// This is a quick test to check whether we can rewrite a particular alloca
1539 /// partition (and its newly formed alloca) into a vector alloca with only
1540 /// whole-vector loads and stores such that it could be promoted to a vector
1541 /// SSA value. We only can ensure this for a limited set of operations, and we
1542 /// don't want to do the rewrites unless we are confident that the result will
1543 /// be promotable, so we have an early test here.
1544 static bool
1545 isVectorPromotionViable(const DataLayout &DL, Type *AllocaTy, AllocaSlices &S,
1546 uint64_t SliceBeginOffset, uint64_t SliceEndOffset,
1547 AllocaSlices::const_iterator I,
1548 AllocaSlices::const_iterator E,
1549 ArrayRef<AllocaSlices::iterator> SplitUses) {
1550 VectorType *Ty = dyn_cast<VectorType>(AllocaTy);
1551 if (!Ty)
1552 return false;
1554 uint64_t ElementSize = DL.getTypeSizeInBits(Ty->getScalarType());
1556 // While the definition of LLVM vectors is bitpacked, we don't support sizes
1557 // that aren't byte sized.
1558 if (ElementSize % 8)
1559 return false;
1560 assert((DL.getTypeSizeInBits(Ty) % 8) == 0 &&
1561 "vector size not a multiple of element size?");
1562 ElementSize /= 8;
1564 for (; I != E; ++I)
1565 if (!isVectorPromotionViableForSlice(DL, S, SliceBeginOffset,
1566 SliceEndOffset, Ty, ElementSize, I))
1567 return false;
1569 for (ArrayRef<AllocaSlices::iterator>::const_iterator SUI = SplitUses.begin(),
1570 SUE = SplitUses.end();
1571 SUI != SUE; ++SUI)
1572 if (!isVectorPromotionViableForSlice(DL, S, SliceBeginOffset,
1573 SliceEndOffset, Ty, ElementSize, *SUI))
1574 return false;
1576 return true;
1577 }
1579 /// \brief Test whether a slice of an alloca is valid for integer widening.
1580 ///
1581 /// This implements the necessary checking for the \c isIntegerWideningViable
1582 /// test below on a single slice of the alloca.
1583 static bool isIntegerWideningViableForSlice(const DataLayout &DL,
1584 Type *AllocaTy,
1585 uint64_t AllocBeginOffset,
1586 uint64_t Size, AllocaSlices &S,
1587 AllocaSlices::const_iterator I,
1588 bool &WholeAllocaOp) {
1589 uint64_t RelBegin = I->beginOffset() - AllocBeginOffset;
1590 uint64_t RelEnd = I->endOffset() - AllocBeginOffset;
1592 // We can't reasonably handle cases where the load or store extends past
1593 // the end of the aloca's type and into its padding.
1594 if (RelEnd > Size)
1595 return false;
1597 Use *U = I->getUse();
1599 if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) {
1600 if (LI->isVolatile())
1601 return false;
1602 if (RelBegin == 0 && RelEnd == Size)
1603 WholeAllocaOp = true;
1604 if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType())) {
1605 if (ITy->getBitWidth() < DL.getTypeStoreSizeInBits(ITy))
1606 return false;
1607 } else if (RelBegin != 0 || RelEnd != Size ||
1608 !canConvertValue(DL, AllocaTy, LI->getType())) {
1609 // Non-integer loads need to be convertible from the alloca type so that
1610 // they are promotable.
1611 return false;
1612 }
1613 } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) {
1614 Type *ValueTy = SI->getValueOperand()->getType();
1615 if (SI->isVolatile())
1616 return false;
1617 if (RelBegin == 0 && RelEnd == Size)
1618 WholeAllocaOp = true;
1619 if (IntegerType *ITy = dyn_cast<IntegerType>(ValueTy)) {
1620 if (ITy->getBitWidth() < DL.getTypeStoreSizeInBits(ITy))
1621 return false;
1622 } else if (RelBegin != 0 || RelEnd != Size ||
1623 !canConvertValue(DL, ValueTy, AllocaTy)) {
1624 // Non-integer stores need to be convertible to the alloca type so that
1625 // they are promotable.
1626 return false;
1627 }
1628 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) {
1629 if (MI->isVolatile() || !isa<Constant>(MI->getLength()))
1630 return false;
1631 if (!I->isSplittable())
1632 return false; // Skip any unsplittable intrinsics.
1633 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U->getUser())) {
1634 if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
1635 II->getIntrinsicID() != Intrinsic::lifetime_end)
1636 return false;
1637 } else {
1638 return false;
1639 }
1641 return true;
1642 }
1644 /// \brief Test whether the given alloca partition's integer operations can be
1645 /// widened to promotable ones.
1646 ///
1647 /// This is a quick test to check whether we can rewrite the integer loads and
1648 /// stores to a particular alloca into wider loads and stores and be able to
1649 /// promote the resulting alloca.
1650 static bool
1651 isIntegerWideningViable(const DataLayout &DL, Type *AllocaTy,
1652 uint64_t AllocBeginOffset, AllocaSlices &S,
1653 AllocaSlices::const_iterator I,
1654 AllocaSlices::const_iterator E,
1655 ArrayRef<AllocaSlices::iterator> SplitUses) {
1656 uint64_t SizeInBits = DL.getTypeSizeInBits(AllocaTy);
1657 // Don't create integer types larger than the maximum bitwidth.
1658 if (SizeInBits > IntegerType::MAX_INT_BITS)
1659 return false;
1661 // Don't try to handle allocas with bit-padding.
1662 if (SizeInBits != DL.getTypeStoreSizeInBits(AllocaTy))
1663 return false;
1665 // We need to ensure that an integer type with the appropriate bitwidth can
1666 // be converted to the alloca type, whatever that is. We don't want to force
1667 // the alloca itself to have an integer type if there is a more suitable one.
1668 Type *IntTy = Type::getIntNTy(AllocaTy->getContext(), SizeInBits);
1669 if (!canConvertValue(DL, AllocaTy, IntTy) ||
1670 !canConvertValue(DL, IntTy, AllocaTy))
1671 return false;
1673 uint64_t Size = DL.getTypeStoreSize(AllocaTy);
1675 // While examining uses, we ensure that the alloca has a covering load or
1676 // store. We don't want to widen the integer operations only to fail to
1677 // promote due to some other unsplittable entry (which we may make splittable
1678 // later). However, if there are only splittable uses, go ahead and assume
1679 // that we cover the alloca.
1680 bool WholeAllocaOp = (I != E) ? false : DL.isLegalInteger(SizeInBits);
1682 for (; I != E; ++I)
1683 if (!isIntegerWideningViableForSlice(DL, AllocaTy, AllocBeginOffset, Size,
1684 S, I, WholeAllocaOp))
1685 return false;
1687 for (ArrayRef<AllocaSlices::iterator>::const_iterator SUI = SplitUses.begin(),
1688 SUE = SplitUses.end();
1689 SUI != SUE; ++SUI)
1690 if (!isIntegerWideningViableForSlice(DL, AllocaTy, AllocBeginOffset, Size,
1691 S, *SUI, WholeAllocaOp))
1692 return false;
1694 return WholeAllocaOp;
1695 }
1697 static Value *extractInteger(const DataLayout &DL, IRBuilderTy &IRB, Value *V,
1698 IntegerType *Ty, uint64_t Offset,
1699 const Twine &Name) {
1700 DEBUG(dbgs() << " start: " << *V << "\n");
1701 IntegerType *IntTy = cast<IntegerType>(V->getType());
1702 assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) &&
1703 "Element extends past full value");
1704 uint64_t ShAmt = 8*Offset;
1705 if (DL.isBigEndian())
1706 ShAmt = 8*(DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset);
1707 if (ShAmt) {
1708 V = IRB.CreateLShr(V, ShAmt, Name + ".shift");
1709 DEBUG(dbgs() << " shifted: " << *V << "\n");
1710 }
1711 assert(Ty->getBitWidth() <= IntTy->getBitWidth() &&
1712 "Cannot extract to a larger integer!");
1713 if (Ty != IntTy) {
1714 V = IRB.CreateTrunc(V, Ty, Name + ".trunc");
1715 DEBUG(dbgs() << " trunced: " << *V << "\n");
1716 }
1717 return V;
1718 }
1720 static Value *insertInteger(const DataLayout &DL, IRBuilderTy &IRB, Value *Old,
1721 Value *V, uint64_t Offset, const Twine &Name) {
1722 IntegerType *IntTy = cast<IntegerType>(Old->getType());
1723 IntegerType *Ty = cast<IntegerType>(V->getType());
1724 assert(Ty->getBitWidth() <= IntTy->getBitWidth() &&
1725 "Cannot insert a larger integer!");
1726 DEBUG(dbgs() << " start: " << *V << "\n");
1727 if (Ty != IntTy) {
1728 V = IRB.CreateZExt(V, IntTy, Name + ".ext");
1729 DEBUG(dbgs() << " extended: " << *V << "\n");
1730 }
1731 assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) &&
1732 "Element store outside of alloca store");
1733 uint64_t ShAmt = 8*Offset;
1734 if (DL.isBigEndian())
1735 ShAmt = 8*(DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset);
1736 if (ShAmt) {
1737 V = IRB.CreateShl(V, ShAmt, Name + ".shift");
1738 DEBUG(dbgs() << " shifted: " << *V << "\n");
1739 }
1741 if (ShAmt || Ty->getBitWidth() < IntTy->getBitWidth()) {
1742 APInt Mask = ~Ty->getMask().zext(IntTy->getBitWidth()).shl(ShAmt);
1743 Old = IRB.CreateAnd(Old, Mask, Name + ".mask");
1744 DEBUG(dbgs() << " masked: " << *Old << "\n");
1745 V = IRB.CreateOr(Old, V, Name + ".insert");
1746 DEBUG(dbgs() << " inserted: " << *V << "\n");
1747 }
1748 return V;
1749 }
1751 static Value *extractVector(IRBuilderTy &IRB, Value *V,
1752 unsigned BeginIndex, unsigned EndIndex,
1753 const Twine &Name) {
1754 VectorType *VecTy = cast<VectorType>(V->getType());
1755 unsigned NumElements = EndIndex - BeginIndex;
1756 assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
1758 if (NumElements == VecTy->getNumElements())
1759 return V;
1761 if (NumElements == 1) {
1762 V = IRB.CreateExtractElement(V, IRB.getInt32(BeginIndex),
1763 Name + ".extract");
1764 DEBUG(dbgs() << " extract: " << *V << "\n");
1765 return V;
1766 }
1768 SmallVector<Constant*, 8> Mask;
1769 Mask.reserve(NumElements);
1770 for (unsigned i = BeginIndex; i != EndIndex; ++i)
1771 Mask.push_back(IRB.getInt32(i));
1772 V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()),
1773 ConstantVector::get(Mask),
1774 Name + ".extract");
1775 DEBUG(dbgs() << " shuffle: " << *V << "\n");
1776 return V;
1777 }
1779 static Value *insertVector(IRBuilderTy &IRB, Value *Old, Value *V,
1780 unsigned BeginIndex, const Twine &Name) {
1781 VectorType *VecTy = cast<VectorType>(Old->getType());
1782 assert(VecTy && "Can only insert a vector into a vector");
1784 VectorType *Ty = dyn_cast<VectorType>(V->getType());
1785 if (!Ty) {
1786 // Single element to insert.
1787 V = IRB.CreateInsertElement(Old, V, IRB.getInt32(BeginIndex),
1788 Name + ".insert");
1789 DEBUG(dbgs() << " insert: " << *V << "\n");
1790 return V;
1791 }
1793 assert(Ty->getNumElements() <= VecTy->getNumElements() &&
1794 "Too many elements!");
1795 if (Ty->getNumElements() == VecTy->getNumElements()) {
1796 assert(V->getType() == VecTy && "Vector type mismatch");
1797 return V;
1798 }
1799 unsigned EndIndex = BeginIndex + Ty->getNumElements();
1801 // When inserting a smaller vector into the larger to store, we first
1802 // use a shuffle vector to widen it with undef elements, and then
1803 // a second shuffle vector to select between the loaded vector and the
1804 // incoming vector.
1805 SmallVector<Constant*, 8> Mask;
1806 Mask.reserve(VecTy->getNumElements());
1807 for (unsigned i = 0; i != VecTy->getNumElements(); ++i)
1808 if (i >= BeginIndex && i < EndIndex)
1809 Mask.push_back(IRB.getInt32(i - BeginIndex));
1810 else
1811 Mask.push_back(UndefValue::get(IRB.getInt32Ty()));
1812 V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()),
1813 ConstantVector::get(Mask),
1814 Name + ".expand");
1815 DEBUG(dbgs() << " shuffle: " << *V << "\n");
1817 Mask.clear();
1818 for (unsigned i = 0; i != VecTy->getNumElements(); ++i)
1819 Mask.push_back(IRB.getInt1(i >= BeginIndex && i < EndIndex));
1821 V = IRB.CreateSelect(ConstantVector::get(Mask), V, Old, Name + "blend");
1823 DEBUG(dbgs() << " blend: " << *V << "\n");
1824 return V;
1825 }
1827 namespace {
1828 /// \brief Visitor to rewrite instructions using p particular slice of an alloca
1829 /// to use a new alloca.
1830 ///
1831 /// Also implements the rewriting to vector-based accesses when the partition
1832 /// passes the isVectorPromotionViable predicate. Most of the rewriting logic
1833 /// lives here.
1834 class AllocaSliceRewriter : public InstVisitor<AllocaSliceRewriter, bool> {
1835 // Befriend the base class so it can delegate to private visit methods.
1836 friend class llvm::InstVisitor<AllocaSliceRewriter, bool>;
1837 typedef llvm::InstVisitor<AllocaSliceRewriter, bool> Base;
1839 const DataLayout &DL;
1840 AllocaSlices &S;
1841 SROA &Pass;
1842 AllocaInst &OldAI, &NewAI;
1843 const uint64_t NewAllocaBeginOffset, NewAllocaEndOffset;
1844 Type *NewAllocaTy;
1846 // If we are rewriting an alloca partition which can be written as pure
1847 // vector operations, we stash extra information here. When VecTy is
1848 // non-null, we have some strict guarantees about the rewritten alloca:
1849 // - The new alloca is exactly the size of the vector type here.
1850 // - The accesses all either map to the entire vector or to a single
1851 // element.
1852 // - The set of accessing instructions is only one of those handled above
1853 // in isVectorPromotionViable. Generally these are the same access kinds
1854 // which are promotable via mem2reg.
1855 VectorType *VecTy;
1856 Type *ElementTy;
1857 uint64_t ElementSize;
1859 // This is a convenience and flag variable that will be null unless the new
1860 // alloca's integer operations should be widened to this integer type due to
1861 // passing isIntegerWideningViable above. If it is non-null, the desired
1862 // integer type will be stored here for easy access during rewriting.
1863 IntegerType *IntTy;
1865 // The offset of the slice currently being rewritten.
1866 uint64_t BeginOffset, EndOffset;
1867 bool IsSplittable;
1868 bool IsSplit;
1869 Use *OldUse;
1870 Instruction *OldPtr;
1872 // Output members carrying state about the result of visiting and rewriting
1873 // the slice of the alloca.
1874 bool IsUsedByRewrittenSpeculatableInstructions;
1876 // Utility IR builder, whose name prefix is setup for each visited use, and
1877 // the insertion point is set to point to the user.
1878 IRBuilderTy IRB;
1880 public:
1881 AllocaSliceRewriter(const DataLayout &DL, AllocaSlices &S, SROA &Pass,
1882 AllocaInst &OldAI, AllocaInst &NewAI,
1883 uint64_t NewBeginOffset, uint64_t NewEndOffset,
1884 bool IsVectorPromotable = false,
1885 bool IsIntegerPromotable = false)
1886 : DL(DL), S(S), Pass(Pass), OldAI(OldAI), NewAI(NewAI),
1887 NewAllocaBeginOffset(NewBeginOffset), NewAllocaEndOffset(NewEndOffset),
1888 NewAllocaTy(NewAI.getAllocatedType()),
1889 VecTy(IsVectorPromotable ? cast<VectorType>(NewAllocaTy) : 0),
1890 ElementTy(VecTy ? VecTy->getElementType() : 0),
1891 ElementSize(VecTy ? DL.getTypeSizeInBits(ElementTy) / 8 : 0),
1892 IntTy(IsIntegerPromotable
1893 ? Type::getIntNTy(
1894 NewAI.getContext(),
1895 DL.getTypeSizeInBits(NewAI.getAllocatedType()))
1896 : 0),
1897 BeginOffset(), EndOffset(), IsSplittable(), IsSplit(), OldUse(),
1898 OldPtr(), IsUsedByRewrittenSpeculatableInstructions(false),
1899 IRB(NewAI.getContext(), ConstantFolder()) {
1900 if (VecTy) {
1901 assert((DL.getTypeSizeInBits(ElementTy) % 8) == 0 &&
1902 "Only multiple-of-8 sized vector elements are viable");
1903 ++NumVectorized;
1904 }
1905 assert((!IsVectorPromotable && !IsIntegerPromotable) ||
1906 IsVectorPromotable != IsIntegerPromotable);
1907 }
1909 bool visit(AllocaSlices::const_iterator I) {
1910 bool CanSROA = true;
1911 BeginOffset = I->beginOffset();
1912 EndOffset = I->endOffset();
1913 IsSplittable = I->isSplittable();
1914 IsSplit =
1915 BeginOffset < NewAllocaBeginOffset || EndOffset > NewAllocaEndOffset;
1917 OldUse = I->getUse();
1918 OldPtr = cast<Instruction>(OldUse->get());
1920 Instruction *OldUserI = cast<Instruction>(OldUse->getUser());
1921 IRB.SetInsertPoint(OldUserI);
1922 IRB.SetCurrentDebugLocation(OldUserI->getDebugLoc());
1923 IRB.SetNamePrefix(Twine(NewAI.getName()) + "." + Twine(BeginOffset) + ".");
1925 CanSROA &= visit(cast<Instruction>(OldUse->getUser()));
1926 if (VecTy || IntTy)
1927 assert(CanSROA);
1928 return CanSROA;
1929 }
1931 /// \brief Query whether this slice is used by speculatable instructions after
1932 /// rewriting.
1933 ///
1934 /// These instructions (PHIs and Selects currently) require the alloca slice
1935 /// to run back through the rewriter. Thus, they are promotable, but not on
1936 /// this iteration. This is distinct from a slice which is unpromotable for
1937 /// some other reason, in which case we don't even want to perform the
1938 /// speculation. This can be querried at any time and reflects whether (at
1939 /// that point) a visit call has rewritten a speculatable instruction on the
1940 /// current slice.
1941 bool isUsedByRewrittenSpeculatableInstructions() const {
1942 return IsUsedByRewrittenSpeculatableInstructions;
1943 }
1945 private:
1946 // Make sure the other visit overloads are visible.
1947 using Base::visit;
1949 // Every instruction which can end up as a user must have a rewrite rule.
1950 bool visitInstruction(Instruction &I) {
1951 DEBUG(dbgs() << " !!!! Cannot rewrite: " << I << "\n");
1952 llvm_unreachable("No rewrite rule for this instruction!");
1953 }
1955 Value *getAdjustedAllocaPtr(IRBuilderTy &IRB, uint64_t Offset,
1956 Type *PointerTy) {
1957 assert(Offset >= NewAllocaBeginOffset);
1958 return getAdjustedPtr(IRB, DL, &NewAI, APInt(DL.getPointerSizeInBits(),
1959 Offset - NewAllocaBeginOffset),
1960 PointerTy);
1961 }
1963 /// \brief Compute suitable alignment to access an offset into the new alloca.
1964 unsigned getOffsetAlign(uint64_t Offset) {
1965 unsigned NewAIAlign = NewAI.getAlignment();
1966 if (!NewAIAlign)
1967 NewAIAlign = DL.getABITypeAlignment(NewAI.getAllocatedType());
1968 return MinAlign(NewAIAlign, Offset);
1969 }
1971 /// \brief Compute suitable alignment to access a type at an offset of the
1972 /// new alloca.
1973 ///
1974 /// \returns zero if the type's ABI alignment is a suitable alignment,
1975 /// otherwise returns the maximal suitable alignment.
1976 unsigned getOffsetTypeAlign(Type *Ty, uint64_t Offset) {
1977 unsigned Align = getOffsetAlign(Offset);
1978 return Align == DL.getABITypeAlignment(Ty) ? 0 : Align;
1979 }
1981 unsigned getIndex(uint64_t Offset) {
1982 assert(VecTy && "Can only call getIndex when rewriting a vector");
1983 uint64_t RelOffset = Offset - NewAllocaBeginOffset;
1984 assert(RelOffset / ElementSize < UINT32_MAX && "Index out of bounds");
1985 uint32_t Index = RelOffset / ElementSize;
1986 assert(Index * ElementSize == RelOffset);
1987 return Index;
1988 }
1990 void deleteIfTriviallyDead(Value *V) {
1991 Instruction *I = cast<Instruction>(V);
1992 if (isInstructionTriviallyDead(I))
1993 Pass.DeadInsts.insert(I);
1994 }
1996 Value *rewriteVectorizedLoadInst(uint64_t NewBeginOffset,
1997 uint64_t NewEndOffset) {
1998 unsigned BeginIndex = getIndex(NewBeginOffset);
1999 unsigned EndIndex = getIndex(NewEndOffset);
2000 assert(EndIndex > BeginIndex && "Empty vector!");
2002 Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2003 "load");
2004 return extractVector(IRB, V, BeginIndex, EndIndex, "vec");
2005 }
2007 Value *rewriteIntegerLoad(LoadInst &LI, uint64_t NewBeginOffset,
2008 uint64_t NewEndOffset) {
2009 assert(IntTy && "We cannot insert an integer to the alloca");
2010 assert(!LI.isVolatile());
2011 Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2012 "load");
2013 V = convertValue(DL, IRB, V, IntTy);
2014 assert(NewBeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2015 uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
2016 if (Offset > 0 || NewEndOffset < NewAllocaEndOffset)
2017 V = extractInteger(DL, IRB, V, cast<IntegerType>(LI.getType()), Offset,
2018 "extract");
2019 return V;
2020 }
2022 bool visitLoadInst(LoadInst &LI) {
2023 DEBUG(dbgs() << " original: " << LI << "\n");
2024 Value *OldOp = LI.getOperand(0);
2025 assert(OldOp == OldPtr);
2027 // Compute the intersecting offset range.
2028 assert(BeginOffset < NewAllocaEndOffset);
2029 assert(EndOffset > NewAllocaBeginOffset);
2030 uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset);
2031 uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset);
2033 uint64_t Size = NewEndOffset - NewBeginOffset;
2035 Type *TargetTy = IsSplit ? Type::getIntNTy(LI.getContext(), Size * 8)
2036 : LI.getType();
2037 bool IsPtrAdjusted = false;
2038 Value *V;
2039 if (VecTy) {
2040 V = rewriteVectorizedLoadInst(NewBeginOffset, NewEndOffset);
2041 } else if (IntTy && LI.getType()->isIntegerTy()) {
2042 V = rewriteIntegerLoad(LI, NewBeginOffset, NewEndOffset);
2043 } else if (NewBeginOffset == NewAllocaBeginOffset &&
2044 canConvertValue(DL, NewAllocaTy, LI.getType())) {
2045 V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2046 LI.isVolatile(), "load");
2047 } else {
2048 Type *LTy = TargetTy->getPointerTo();
2049 V = IRB.CreateAlignedLoad(
2050 getAdjustedAllocaPtr(IRB, NewBeginOffset, LTy),
2051 getOffsetTypeAlign(TargetTy, NewBeginOffset - NewAllocaBeginOffset),
2052 LI.isVolatile(), "load");
2053 IsPtrAdjusted = true;
2054 }
2055 V = convertValue(DL, IRB, V, TargetTy);
2057 if (IsSplit) {
2058 assert(!LI.isVolatile());
2059 assert(LI.getType()->isIntegerTy() &&
2060 "Only integer type loads and stores are split");
2061 assert(Size < DL.getTypeStoreSize(LI.getType()) &&
2062 "Split load isn't smaller than original load");
2063 assert(LI.getType()->getIntegerBitWidth() ==
2064 DL.getTypeStoreSizeInBits(LI.getType()) &&
2065 "Non-byte-multiple bit width");
2066 // Move the insertion point just past the load so that we can refer to it.
2067 IRB.SetInsertPoint(llvm::next(BasicBlock::iterator(&LI)));
2068 // Create a placeholder value with the same type as LI to use as the
2069 // basis for the new value. This allows us to replace the uses of LI with
2070 // the computed value, and then replace the placeholder with LI, leaving
2071 // LI only used for this computation.
2072 Value *Placeholder
2073 = new LoadInst(UndefValue::get(LI.getType()->getPointerTo()));
2074 V = insertInteger(DL, IRB, Placeholder, V, NewBeginOffset,
2075 "insert");
2076 LI.replaceAllUsesWith(V);
2077 Placeholder->replaceAllUsesWith(&LI);
2078 delete Placeholder;
2079 } else {
2080 LI.replaceAllUsesWith(V);
2081 }
2083 Pass.DeadInsts.insert(&LI);
2084 deleteIfTriviallyDead(OldOp);
2085 DEBUG(dbgs() << " to: " << *V << "\n");
2086 return !LI.isVolatile() && !IsPtrAdjusted;
2087 }
2089 bool rewriteVectorizedStoreInst(Value *V, StoreInst &SI, Value *OldOp,
2090 uint64_t NewBeginOffset,
2091 uint64_t NewEndOffset) {
2092 if (V->getType() != VecTy) {
2093 unsigned BeginIndex = getIndex(NewBeginOffset);
2094 unsigned EndIndex = getIndex(NewEndOffset);
2095 assert(EndIndex > BeginIndex && "Empty vector!");
2096 unsigned NumElements = EndIndex - BeginIndex;
2097 assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
2098 Type *SliceTy =
2099 (NumElements == 1) ? ElementTy
2100 : VectorType::get(ElementTy, NumElements);
2101 if (V->getType() != SliceTy)
2102 V = convertValue(DL, IRB, V, SliceTy);
2104 // Mix in the existing elements.
2105 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2106 "load");
2107 V = insertVector(IRB, Old, V, BeginIndex, "vec");
2108 }
2109 StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment());
2110 Pass.DeadInsts.insert(&SI);
2112 (void)Store;
2113 DEBUG(dbgs() << " to: " << *Store << "\n");
2114 return true;
2115 }
2117 bool rewriteIntegerStore(Value *V, StoreInst &SI,
2118 uint64_t NewBeginOffset, uint64_t NewEndOffset) {
2119 assert(IntTy && "We cannot extract an integer from the alloca");
2120 assert(!SI.isVolatile());
2121 if (DL.getTypeSizeInBits(V->getType()) != IntTy->getBitWidth()) {
2122 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2123 "oldload");
2124 Old = convertValue(DL, IRB, Old, IntTy);
2125 assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset");
2126 uint64_t Offset = BeginOffset - NewAllocaBeginOffset;
2127 V = insertInteger(DL, IRB, Old, SI.getValueOperand(), Offset,
2128 "insert");
2129 }
2130 V = convertValue(DL, IRB, V, NewAllocaTy);
2131 StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment());
2132 Pass.DeadInsts.insert(&SI);
2133 (void)Store;
2134 DEBUG(dbgs() << " to: " << *Store << "\n");
2135 return true;
2136 }
2138 bool visitStoreInst(StoreInst &SI) {
2139 DEBUG(dbgs() << " original: " << SI << "\n");
2140 Value *OldOp = SI.getOperand(1);
2141 assert(OldOp == OldPtr);
2143 Value *V = SI.getValueOperand();
2145 // Strip all inbounds GEPs and pointer casts to try to dig out any root
2146 // alloca that should be re-examined after promoting this alloca.
2147 if (V->getType()->isPointerTy())
2148 if (AllocaInst *AI = dyn_cast<AllocaInst>(V->stripInBoundsOffsets()))
2149 Pass.PostPromotionWorklist.insert(AI);
2151 // Compute the intersecting offset range.
2152 assert(BeginOffset < NewAllocaEndOffset);
2153 assert(EndOffset > NewAllocaBeginOffset);
2154 uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset);
2155 uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset);
2157 uint64_t Size = NewEndOffset - NewBeginOffset;
2158 if (Size < DL.getTypeStoreSize(V->getType())) {
2159 assert(!SI.isVolatile());
2160 assert(V->getType()->isIntegerTy() &&
2161 "Only integer type loads and stores are split");
2162 assert(V->getType()->getIntegerBitWidth() ==
2163 DL.getTypeStoreSizeInBits(V->getType()) &&
2164 "Non-byte-multiple bit width");
2165 IntegerType *NarrowTy = Type::getIntNTy(SI.getContext(), Size * 8);
2166 V = extractInteger(DL, IRB, V, NarrowTy, NewBeginOffset,
2167 "extract");
2168 }
2170 if (VecTy)
2171 return rewriteVectorizedStoreInst(V, SI, OldOp, NewBeginOffset,
2172 NewEndOffset);
2173 if (IntTy && V->getType()->isIntegerTy())
2174 return rewriteIntegerStore(V, SI, NewBeginOffset, NewEndOffset);
2176 StoreInst *NewSI;
2177 if (NewBeginOffset == NewAllocaBeginOffset &&
2178 NewEndOffset == NewAllocaEndOffset &&
2179 canConvertValue(DL, V->getType(), NewAllocaTy)) {
2180 V = convertValue(DL, IRB, V, NewAllocaTy);
2181 NewSI = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(),
2182 SI.isVolatile());
2183 } else {
2184 Value *NewPtr = getAdjustedAllocaPtr(IRB, NewBeginOffset,
2185 V->getType()->getPointerTo());
2186 NewSI = IRB.CreateAlignedStore(
2187 V, NewPtr, getOffsetTypeAlign(
2188 V->getType(), NewBeginOffset - NewAllocaBeginOffset),
2189 SI.isVolatile());
2190 }
2191 (void)NewSI;
2192 Pass.DeadInsts.insert(&SI);
2193 deleteIfTriviallyDead(OldOp);
2195 DEBUG(dbgs() << " to: " << *NewSI << "\n");
2196 return NewSI->getPointerOperand() == &NewAI && !SI.isVolatile();
2197 }
2199 /// \brief Compute an integer value from splatting an i8 across the given
2200 /// number of bytes.
2201 ///
2202 /// Note that this routine assumes an i8 is a byte. If that isn't true, don't
2203 /// call this routine.
2204 /// FIXME: Heed the advice above.
2205 ///
2206 /// \param V The i8 value to splat.
2207 /// \param Size The number of bytes in the output (assuming i8 is one byte)
2208 Value *getIntegerSplat(Value *V, unsigned Size) {
2209 assert(Size > 0 && "Expected a positive number of bytes.");
2210 IntegerType *VTy = cast<IntegerType>(V->getType());
2211 assert(VTy->getBitWidth() == 8 && "Expected an i8 value for the byte");
2212 if (Size == 1)
2213 return V;
2215 Type *SplatIntTy = Type::getIntNTy(VTy->getContext(), Size*8);
2216 V = IRB.CreateMul(IRB.CreateZExt(V, SplatIntTy, "zext"),
2217 ConstantExpr::getUDiv(
2218 Constant::getAllOnesValue(SplatIntTy),
2219 ConstantExpr::getZExt(
2220 Constant::getAllOnesValue(V->getType()),
2221 SplatIntTy)),
2222 "isplat");
2223 return V;
2224 }
2226 /// \brief Compute a vector splat for a given element value.
2227 Value *getVectorSplat(Value *V, unsigned NumElements) {
2228 V = IRB.CreateVectorSplat(NumElements, V, "vsplat");
2229 DEBUG(dbgs() << " splat: " << *V << "\n");
2230 return V;
2231 }
2233 bool visitMemSetInst(MemSetInst &II) {
2234 DEBUG(dbgs() << " original: " << II << "\n");
2235 assert(II.getRawDest() == OldPtr);
2237 // If the memset has a variable size, it cannot be split, just adjust the
2238 // pointer to the new alloca.
2239 if (!isa<Constant>(II.getLength())) {
2240 assert(!IsSplit);
2241 assert(BeginOffset >= NewAllocaBeginOffset);
2242 II.setDest(
2243 getAdjustedAllocaPtr(IRB, BeginOffset, II.getRawDest()->getType()));
2244 Type *CstTy = II.getAlignmentCst()->getType();
2245 II.setAlignment(ConstantInt::get(CstTy, getOffsetAlign(BeginOffset)));
2247 deleteIfTriviallyDead(OldPtr);
2248 return false;
2249 }
2251 // Record this instruction for deletion.
2252 Pass.DeadInsts.insert(&II);
2254 Type *AllocaTy = NewAI.getAllocatedType();
2255 Type *ScalarTy = AllocaTy->getScalarType();
2257 // Compute the intersecting offset range.
2258 assert(BeginOffset < NewAllocaEndOffset);
2259 assert(EndOffset > NewAllocaBeginOffset);
2260 uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset);
2261 uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset);
2262 uint64_t SliceOffset = NewBeginOffset - NewAllocaBeginOffset;
2264 // If this doesn't map cleanly onto the alloca type, and that type isn't
2265 // a single value type, just emit a memset.
2266 if (!VecTy && !IntTy &&
2267 (BeginOffset > NewAllocaBeginOffset ||
2268 EndOffset < NewAllocaEndOffset ||
2269 !AllocaTy->isSingleValueType() ||
2270 !DL.isLegalInteger(DL.getTypeSizeInBits(ScalarTy)) ||
2271 DL.getTypeSizeInBits(ScalarTy)%8 != 0)) {
2272 Type *SizeTy = II.getLength()->getType();
2273 Constant *Size = ConstantInt::get(SizeTy, NewEndOffset - NewBeginOffset);
2274 CallInst *New = IRB.CreateMemSet(
2275 getAdjustedAllocaPtr(IRB, NewBeginOffset, II.getRawDest()->getType()),
2276 II.getValue(), Size, getOffsetAlign(SliceOffset), II.isVolatile());
2277 (void)New;
2278 DEBUG(dbgs() << " to: " << *New << "\n");
2279 return false;
2280 }
2282 // If we can represent this as a simple value, we have to build the actual
2283 // value to store, which requires expanding the byte present in memset to
2284 // a sensible representation for the alloca type. This is essentially
2285 // splatting the byte to a sufficiently wide integer, splatting it across
2286 // any desired vector width, and bitcasting to the final type.
2287 Value *V;
2289 if (VecTy) {
2290 // If this is a memset of a vectorized alloca, insert it.
2291 assert(ElementTy == ScalarTy);
2293 unsigned BeginIndex = getIndex(NewBeginOffset);
2294 unsigned EndIndex = getIndex(NewEndOffset);
2295 assert(EndIndex > BeginIndex && "Empty vector!");
2296 unsigned NumElements = EndIndex - BeginIndex;
2297 assert(NumElements <= VecTy->getNumElements() && "Too many elements!");
2299 Value *Splat =
2300 getIntegerSplat(II.getValue(), DL.getTypeSizeInBits(ElementTy) / 8);
2301 Splat = convertValue(DL, IRB, Splat, ElementTy);
2302 if (NumElements > 1)
2303 Splat = getVectorSplat(Splat, NumElements);
2305 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2306 "oldload");
2307 V = insertVector(IRB, Old, Splat, BeginIndex, "vec");
2308 } else if (IntTy) {
2309 // If this is a memset on an alloca where we can widen stores, insert the
2310 // set integer.
2311 assert(!II.isVolatile());
2313 uint64_t Size = NewEndOffset - NewBeginOffset;
2314 V = getIntegerSplat(II.getValue(), Size);
2316 if (IntTy && (BeginOffset != NewAllocaBeginOffset ||
2317 EndOffset != NewAllocaBeginOffset)) {
2318 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2319 "oldload");
2320 Old = convertValue(DL, IRB, Old, IntTy);
2321 uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
2322 V = insertInteger(DL, IRB, Old, V, Offset, "insert");
2323 } else {
2324 assert(V->getType() == IntTy &&
2325 "Wrong type for an alloca wide integer!");
2326 }
2327 V = convertValue(DL, IRB, V, AllocaTy);
2328 } else {
2329 // Established these invariants above.
2330 assert(NewBeginOffset == NewAllocaBeginOffset);
2331 assert(NewEndOffset == NewAllocaEndOffset);
2333 V = getIntegerSplat(II.getValue(), DL.getTypeSizeInBits(ScalarTy) / 8);
2334 if (VectorType *AllocaVecTy = dyn_cast<VectorType>(AllocaTy))
2335 V = getVectorSplat(V, AllocaVecTy->getNumElements());
2337 V = convertValue(DL, IRB, V, AllocaTy);
2338 }
2340 Value *New = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(),
2341 II.isVolatile());
2342 (void)New;
2343 DEBUG(dbgs() << " to: " << *New << "\n");
2344 return !II.isVolatile();
2345 }
2347 bool visitMemTransferInst(MemTransferInst &II) {
2348 // Rewriting of memory transfer instructions can be a bit tricky. We break
2349 // them into two categories: split intrinsics and unsplit intrinsics.
2351 DEBUG(dbgs() << " original: " << II << "\n");
2353 // Compute the intersecting offset range.
2354 assert(BeginOffset < NewAllocaEndOffset);
2355 assert(EndOffset > NewAllocaBeginOffset);
2356 uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset);
2357 uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset);
2359 assert(II.getRawSource() == OldPtr || II.getRawDest() == OldPtr);
2360 bool IsDest = II.getRawDest() == OldPtr;
2362 // Compute the relative offset within the transfer.
2363 unsigned IntPtrWidth = DL.getPointerSizeInBits();
2364 APInt RelOffset(IntPtrWidth, NewBeginOffset - BeginOffset);
2366 unsigned Align = II.getAlignment();
2367 uint64_t SliceOffset = NewBeginOffset - NewAllocaBeginOffset;
2368 if (Align > 1)
2369 Align =
2370 MinAlign(RelOffset.zextOrTrunc(64).getZExtValue(),
2371 MinAlign(II.getAlignment(), getOffsetAlign(SliceOffset)));
2373 // For unsplit intrinsics, we simply modify the source and destination
2374 // pointers in place. This isn't just an optimization, it is a matter of
2375 // correctness. With unsplit intrinsics we may be dealing with transfers
2376 // within a single alloca before SROA ran, or with transfers that have
2377 // a variable length. We may also be dealing with memmove instead of
2378 // memcpy, and so simply updating the pointers is the necessary for us to
2379 // update both source and dest of a single call.
2380 if (!IsSplittable) {
2381 Value *OldOp = IsDest ? II.getRawDest() : II.getRawSource();
2382 if (IsDest)
2383 II.setDest(
2384 getAdjustedAllocaPtr(IRB, BeginOffset, II.getRawDest()->getType()));
2385 else
2386 II.setSource(getAdjustedAllocaPtr(IRB, BeginOffset,
2387 II.getRawSource()->getType()));
2389 Type *CstTy = II.getAlignmentCst()->getType();
2390 II.setAlignment(ConstantInt::get(CstTy, Align));
2392 DEBUG(dbgs() << " to: " << II << "\n");
2393 deleteIfTriviallyDead(OldOp);
2394 return false;
2395 }
2396 // For split transfer intrinsics we have an incredibly useful assurance:
2397 // the source and destination do not reside within the same alloca, and at
2398 // least one of them does not escape. This means that we can replace
2399 // memmove with memcpy, and we don't need to worry about all manner of
2400 // downsides to splitting and transforming the operations.
2402 // If this doesn't map cleanly onto the alloca type, and that type isn't
2403 // a single value type, just emit a memcpy.
2404 bool EmitMemCpy
2405 = !VecTy && !IntTy && (BeginOffset > NewAllocaBeginOffset ||
2406 EndOffset < NewAllocaEndOffset ||
2407 !NewAI.getAllocatedType()->isSingleValueType());
2409 // If we're just going to emit a memcpy, the alloca hasn't changed, and the
2410 // size hasn't been shrunk based on analysis of the viable range, this is
2411 // a no-op.
2412 if (EmitMemCpy && &OldAI == &NewAI) {
2413 // Ensure the start lines up.
2414 assert(NewBeginOffset == BeginOffset);
2416 // Rewrite the size as needed.
2417 if (NewEndOffset != EndOffset)
2418 II.setLength(ConstantInt::get(II.getLength()->getType(),
2419 NewEndOffset - NewBeginOffset));
2420 return false;
2421 }
2422 // Record this instruction for deletion.
2423 Pass.DeadInsts.insert(&II);
2425 // Strip all inbounds GEPs and pointer casts to try to dig out any root
2426 // alloca that should be re-examined after rewriting this instruction.
2427 Value *OtherPtr = IsDest ? II.getRawSource() : II.getRawDest();
2428 if (AllocaInst *AI
2429 = dyn_cast<AllocaInst>(OtherPtr->stripInBoundsOffsets()))
2430 Pass.Worklist.insert(AI);
2432 if (EmitMemCpy) {
2433 Type *OtherPtrTy = IsDest ? II.getRawSource()->getType()
2434 : II.getRawDest()->getType();
2436 // Compute the other pointer, folding as much as possible to produce
2437 // a single, simple GEP in most cases.
2438 OtherPtr = getAdjustedPtr(IRB, DL, OtherPtr, RelOffset, OtherPtrTy);
2440 Value *OurPtr = getAdjustedAllocaPtr(
2441 IRB, NewBeginOffset,
2442 IsDest ? II.getRawDest()->getType() : II.getRawSource()->getType());
2443 Type *SizeTy = II.getLength()->getType();
2444 Constant *Size = ConstantInt::get(SizeTy, NewEndOffset - NewBeginOffset);
2446 CallInst *New = IRB.CreateMemCpy(IsDest ? OurPtr : OtherPtr,
2447 IsDest ? OtherPtr : OurPtr,
2448 Size, Align, II.isVolatile());
2449 (void)New;
2450 DEBUG(dbgs() << " to: " << *New << "\n");
2451 return false;
2452 }
2454 // Note that we clamp the alignment to 1 here as a 0 alignment for a memcpy
2455 // is equivalent to 1, but that isn't true if we end up rewriting this as
2456 // a load or store.
2457 if (!Align)
2458 Align = 1;
2460 bool IsWholeAlloca = NewBeginOffset == NewAllocaBeginOffset &&
2461 NewEndOffset == NewAllocaEndOffset;
2462 uint64_t Size = NewEndOffset - NewBeginOffset;
2463 unsigned BeginIndex = VecTy ? getIndex(NewBeginOffset) : 0;
2464 unsigned EndIndex = VecTy ? getIndex(NewEndOffset) : 0;
2465 unsigned NumElements = EndIndex - BeginIndex;
2466 IntegerType *SubIntTy
2467 = IntTy ? Type::getIntNTy(IntTy->getContext(), Size*8) : 0;
2469 Type *OtherPtrTy = NewAI.getType();
2470 if (VecTy && !IsWholeAlloca) {
2471 if (NumElements == 1)
2472 OtherPtrTy = VecTy->getElementType();
2473 else
2474 OtherPtrTy = VectorType::get(VecTy->getElementType(), NumElements);
2476 OtherPtrTy = OtherPtrTy->getPointerTo();
2477 } else if (IntTy && !IsWholeAlloca) {
2478 OtherPtrTy = SubIntTy->getPointerTo();
2479 }
2481 Value *SrcPtr = getAdjustedPtr(IRB, DL, OtherPtr, RelOffset, OtherPtrTy);
2482 Value *DstPtr = &NewAI;
2483 if (!IsDest)
2484 std::swap(SrcPtr, DstPtr);
2486 Value *Src;
2487 if (VecTy && !IsWholeAlloca && !IsDest) {
2488 Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2489 "load");
2490 Src = extractVector(IRB, Src, BeginIndex, EndIndex, "vec");
2491 } else if (IntTy && !IsWholeAlloca && !IsDest) {
2492 Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2493 "load");
2494 Src = convertValue(DL, IRB, Src, IntTy);
2495 uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
2496 Src = extractInteger(DL, IRB, Src, SubIntTy, Offset, "extract");
2497 } else {
2498 Src = IRB.CreateAlignedLoad(SrcPtr, Align, II.isVolatile(),
2499 "copyload");
2500 }
2502 if (VecTy && !IsWholeAlloca && IsDest) {
2503 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2504 "oldload");
2505 Src = insertVector(IRB, Old, Src, BeginIndex, "vec");
2506 } else if (IntTy && !IsWholeAlloca && IsDest) {
2507 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(),
2508 "oldload");
2509 Old = convertValue(DL, IRB, Old, IntTy);
2510 uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset;
2511 Src = insertInteger(DL, IRB, Old, Src, Offset, "insert");
2512 Src = convertValue(DL, IRB, Src, NewAllocaTy);
2513 }
2515 StoreInst *Store = cast<StoreInst>(
2516 IRB.CreateAlignedStore(Src, DstPtr, Align, II.isVolatile()));
2517 (void)Store;
2518 DEBUG(dbgs() << " to: " << *Store << "\n");
2519 return !II.isVolatile();
2520 }
2522 bool visitIntrinsicInst(IntrinsicInst &II) {
2523 assert(II.getIntrinsicID() == Intrinsic::lifetime_start ||
2524 II.getIntrinsicID() == Intrinsic::lifetime_end);
2525 DEBUG(dbgs() << " original: " << II << "\n");
2526 assert(II.getArgOperand(1) == OldPtr);
2528 // Compute the intersecting offset range.
2529 assert(BeginOffset < NewAllocaEndOffset);
2530 assert(EndOffset > NewAllocaBeginOffset);
2531 uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset);
2532 uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset);
2534 // Record this instruction for deletion.
2535 Pass.DeadInsts.insert(&II);
2537 ConstantInt *Size
2538 = ConstantInt::get(cast<IntegerType>(II.getArgOperand(0)->getType()),
2539 NewEndOffset - NewBeginOffset);
2540 Value *Ptr =
2541 getAdjustedAllocaPtr(IRB, NewBeginOffset, II.getArgOperand(1)->getType());
2542 Value *New;
2543 if (II.getIntrinsicID() == Intrinsic::lifetime_start)
2544 New = IRB.CreateLifetimeStart(Ptr, Size);
2545 else
2546 New = IRB.CreateLifetimeEnd(Ptr, Size);
2548 (void)New;
2549 DEBUG(dbgs() << " to: " << *New << "\n");
2550 return true;
2551 }
2553 bool visitPHINode(PHINode &PN) {
2554 DEBUG(dbgs() << " original: " << PN << "\n");
2555 assert(BeginOffset >= NewAllocaBeginOffset && "PHIs are unsplittable");
2556 assert(EndOffset <= NewAllocaEndOffset && "PHIs are unsplittable");
2558 // We would like to compute a new pointer in only one place, but have it be
2559 // as local as possible to the PHI. To do that, we re-use the location of
2560 // the old pointer, which necessarily must be in the right position to
2561 // dominate the PHI.
2562 IRBuilderTy PtrBuilder(OldPtr);
2563 PtrBuilder.SetNamePrefix(Twine(NewAI.getName()) + "." + Twine(BeginOffset) +
2564 ".");
2566 Value *NewPtr =
2567 getAdjustedAllocaPtr(PtrBuilder, BeginOffset, OldPtr->getType());
2568 // Replace the operands which were using the old pointer.
2569 std::replace(PN.op_begin(), PN.op_end(), cast<Value>(OldPtr), NewPtr);
2571 DEBUG(dbgs() << " to: " << PN << "\n");
2572 deleteIfTriviallyDead(OldPtr);
2574 // Check whether we can speculate this PHI node, and if so remember that
2575 // fact and queue it up for another iteration after the speculation
2576 // occurs.
2577 if (isSafePHIToSpeculate(PN, &DL)) {
2578 Pass.SpeculatablePHIs.insert(&PN);
2579 IsUsedByRewrittenSpeculatableInstructions = true;
2580 return true;
2581 }
2583 return false; // PHIs can't be promoted on their own.
2584 }
2586 bool visitSelectInst(SelectInst &SI) {
2587 DEBUG(dbgs() << " original: " << SI << "\n");
2588 assert((SI.getTrueValue() == OldPtr || SI.getFalseValue() == OldPtr) &&
2589 "Pointer isn't an operand!");
2590 assert(BeginOffset >= NewAllocaBeginOffset && "Selects are unsplittable");
2591 assert(EndOffset <= NewAllocaEndOffset && "Selects are unsplittable");
2593 Value *NewPtr = getAdjustedAllocaPtr(IRB, BeginOffset, OldPtr->getType());
2594 // Replace the operands which were using the old pointer.
2595 if (SI.getOperand(1) == OldPtr)
2596 SI.setOperand(1, NewPtr);
2597 if (SI.getOperand(2) == OldPtr)
2598 SI.setOperand(2, NewPtr);
2600 DEBUG(dbgs() << " to: " << SI << "\n");
2601 deleteIfTriviallyDead(OldPtr);
2603 // Check whether we can speculate this select instruction, and if so
2604 // remember that fact and queue it up for another iteration after the
2605 // speculation occurs.
2606 if (isSafeSelectToSpeculate(SI, &DL)) {
2607 Pass.SpeculatableSelects.insert(&SI);
2608 IsUsedByRewrittenSpeculatableInstructions = true;
2609 return true;
2610 }
2612 return false; // Selects can't be promoted on their own.
2613 }
2615 };
2616 }
2618 namespace {
2619 /// \brief Visitor to rewrite aggregate loads and stores as scalar.
2620 ///
2621 /// This pass aggressively rewrites all aggregate loads and stores on
2622 /// a particular pointer (or any pointer derived from it which we can identify)
2623 /// with scalar loads and stores.
2624 class AggLoadStoreRewriter : public InstVisitor<AggLoadStoreRewriter, bool> {
2625 // Befriend the base class so it can delegate to private visit methods.
2626 friend class llvm::InstVisitor<AggLoadStoreRewriter, bool>;
2628 const DataLayout &DL;
2630 /// Queue of pointer uses to analyze and potentially rewrite.
2631 SmallVector<Use *, 8> Queue;
2633 /// Set to prevent us from cycling with phi nodes and loops.
2634 SmallPtrSet<User *, 8> Visited;
2636 /// The current pointer use being rewritten. This is used to dig up the used
2637 /// value (as opposed to the user).
2638 Use *U;
2640 public:
2641 AggLoadStoreRewriter(const DataLayout &DL) : DL(DL) {}
2643 /// Rewrite loads and stores through a pointer and all pointers derived from
2644 /// it.
2645 bool rewrite(Instruction &I) {
2646 DEBUG(dbgs() << " Rewriting FCA loads and stores...\n");
2647 enqueueUsers(I);
2648 bool Changed = false;
2649 while (!Queue.empty()) {
2650 U = Queue.pop_back_val();
2651 Changed |= visit(cast<Instruction>(U->getUser()));
2652 }
2653 return Changed;
2654 }
2656 private:
2657 /// Enqueue all the users of the given instruction for further processing.
2658 /// This uses a set to de-duplicate users.
2659 void enqueueUsers(Instruction &I) {
2660 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE;
2661 ++UI)
2662 if (Visited.insert(*UI))
2663 Queue.push_back(&UI.getUse());
2664 }
2666 // Conservative default is to not rewrite anything.
2667 bool visitInstruction(Instruction &I) { return false; }
2669 /// \brief Generic recursive split emission class.
2670 template <typename Derived>
2671 class OpSplitter {
2672 protected:
2673 /// The builder used to form new instructions.
2674 IRBuilderTy IRB;
2675 /// The indices which to be used with insert- or extractvalue to select the
2676 /// appropriate value within the aggregate.
2677 SmallVector<unsigned, 4> Indices;
2678 /// The indices to a GEP instruction which will move Ptr to the correct slot
2679 /// within the aggregate.
2680 SmallVector<Value *, 4> GEPIndices;
2681 /// The base pointer of the original op, used as a base for GEPing the
2682 /// split operations.
2683 Value *Ptr;
2685 /// Initialize the splitter with an insertion point, Ptr and start with a
2686 /// single zero GEP index.
2687 OpSplitter(Instruction *InsertionPoint, Value *Ptr)
2688 : IRB(InsertionPoint), GEPIndices(1, IRB.getInt32(0)), Ptr(Ptr) {}
2690 public:
2691 /// \brief Generic recursive split emission routine.
2692 ///
2693 /// This method recursively splits an aggregate op (load or store) into
2694 /// scalar or vector ops. It splits recursively until it hits a single value
2695 /// and emits that single value operation via the template argument.
2696 ///
2697 /// The logic of this routine relies on GEPs and insertvalue and
2698 /// extractvalue all operating with the same fundamental index list, merely
2699 /// formatted differently (GEPs need actual values).
2700 ///
2701 /// \param Ty The type being split recursively into smaller ops.
2702 /// \param Agg The aggregate value being built up or stored, depending on
2703 /// whether this is splitting a load or a store respectively.
2704 void emitSplitOps(Type *Ty, Value *&Agg, const Twine &Name) {
2705 if (Ty->isSingleValueType())
2706 return static_cast<Derived *>(this)->emitFunc(Ty, Agg, Name);
2708 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
2709 unsigned OldSize = Indices.size();
2710 (void)OldSize;
2711 for (unsigned Idx = 0, Size = ATy->getNumElements(); Idx != Size;
2712 ++Idx) {
2713 assert(Indices.size() == OldSize && "Did not return to the old size");
2714 Indices.push_back(Idx);
2715 GEPIndices.push_back(IRB.getInt32(Idx));
2716 emitSplitOps(ATy->getElementType(), Agg, Name + "." + Twine(Idx));
2717 GEPIndices.pop_back();
2718 Indices.pop_back();
2719 }
2720 return;
2721 }
2723 if (StructType *STy = dyn_cast<StructType>(Ty)) {
2724 unsigned OldSize = Indices.size();
2725 (void)OldSize;
2726 for (unsigned Idx = 0, Size = STy->getNumElements(); Idx != Size;
2727 ++Idx) {
2728 assert(Indices.size() == OldSize && "Did not return to the old size");
2729 Indices.push_back(Idx);
2730 GEPIndices.push_back(IRB.getInt32(Idx));
2731 emitSplitOps(STy->getElementType(Idx), Agg, Name + "." + Twine(Idx));
2732 GEPIndices.pop_back();
2733 Indices.pop_back();
2734 }
2735 return;
2736 }
2738 llvm_unreachable("Only arrays and structs are aggregate loadable types");
2739 }
2740 };
2742 struct LoadOpSplitter : public OpSplitter<LoadOpSplitter> {
2743 LoadOpSplitter(Instruction *InsertionPoint, Value *Ptr)
2744 : OpSplitter<LoadOpSplitter>(InsertionPoint, Ptr) {}
2746 /// Emit a leaf load of a single value. This is called at the leaves of the
2747 /// recursive emission to actually load values.
2748 void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) {
2749 assert(Ty->isSingleValueType());
2750 // Load the single value and insert it using the indices.
2751 Value *GEP = IRB.CreateInBoundsGEP(Ptr, GEPIndices, Name + ".gep");
2752 Value *Load = IRB.CreateLoad(GEP, Name + ".load");
2753 Agg = IRB.CreateInsertValue(Agg, Load, Indices, Name + ".insert");
2754 DEBUG(dbgs() << " to: " << *Load << "\n");
2755 }
2756 };
2758 bool visitLoadInst(LoadInst &LI) {
2759 assert(LI.getPointerOperand() == *U);
2760 if (!LI.isSimple() || LI.getType()->isSingleValueType())
2761 return false;
2763 // We have an aggregate being loaded, split it apart.
2764 DEBUG(dbgs() << " original: " << LI << "\n");
2765 LoadOpSplitter Splitter(&LI, *U);
2766 Value *V = UndefValue::get(LI.getType());
2767 Splitter.emitSplitOps(LI.getType(), V, LI.getName() + ".fca");
2768 LI.replaceAllUsesWith(V);
2769 LI.eraseFromParent();
2770 return true;
2771 }
2773 struct StoreOpSplitter : public OpSplitter<StoreOpSplitter> {
2774 StoreOpSplitter(Instruction *InsertionPoint, Value *Ptr)
2775 : OpSplitter<StoreOpSplitter>(InsertionPoint, Ptr) {}
2777 /// Emit a leaf store of a single value. This is called at the leaves of the
2778 /// recursive emission to actually produce stores.
2779 void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) {
2780 assert(Ty->isSingleValueType());
2781 // Extract the single value and store it using the indices.
2782 Value *Store = IRB.CreateStore(
2783 IRB.CreateExtractValue(Agg, Indices, Name + ".extract"),
2784 IRB.CreateInBoundsGEP(Ptr, GEPIndices, Name + ".gep"));
2785 (void)Store;
2786 DEBUG(dbgs() << " to: " << *Store << "\n");
2787 }
2788 };
2790 bool visitStoreInst(StoreInst &SI) {
2791 if (!SI.isSimple() || SI.getPointerOperand() != *U)
2792 return false;
2793 Value *V = SI.getValueOperand();
2794 if (V->getType()->isSingleValueType())
2795 return false;
2797 // We have an aggregate being stored, split it apart.
2798 DEBUG(dbgs() << " original: " << SI << "\n");
2799 StoreOpSplitter Splitter(&SI, *U);
2800 Splitter.emitSplitOps(V->getType(), V, V->getName() + ".fca");
2801 SI.eraseFromParent();
2802 return true;
2803 }
2805 bool visitBitCastInst(BitCastInst &BC) {
2806 enqueueUsers(BC);
2807 return false;
2808 }
2810 bool visitGetElementPtrInst(GetElementPtrInst &GEPI) {
2811 enqueueUsers(GEPI);
2812 return false;
2813 }
2815 bool visitPHINode(PHINode &PN) {
2816 enqueueUsers(PN);
2817 return false;
2818 }
2820 bool visitSelectInst(SelectInst &SI) {
2821 enqueueUsers(SI);
2822 return false;
2823 }
2824 };
2825 }
2827 /// \brief Strip aggregate type wrapping.
2828 ///
2829 /// This removes no-op aggregate types wrapping an underlying type. It will
2830 /// strip as many layers of types as it can without changing either the type
2831 /// size or the allocated size.
2832 static Type *stripAggregateTypeWrapping(const DataLayout &DL, Type *Ty) {
2833 if (Ty->isSingleValueType())
2834 return Ty;
2836 uint64_t AllocSize = DL.getTypeAllocSize(Ty);
2837 uint64_t TypeSize = DL.getTypeSizeInBits(Ty);
2839 Type *InnerTy;
2840 if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) {
2841 InnerTy = ArrTy->getElementType();
2842 } else if (StructType *STy = dyn_cast<StructType>(Ty)) {
2843 const StructLayout *SL = DL.getStructLayout(STy);
2844 unsigned Index = SL->getElementContainingOffset(0);
2845 InnerTy = STy->getElementType(Index);
2846 } else {
2847 return Ty;
2848 }
2850 if (AllocSize > DL.getTypeAllocSize(InnerTy) ||
2851 TypeSize > DL.getTypeSizeInBits(InnerTy))
2852 return Ty;
2854 return stripAggregateTypeWrapping(DL, InnerTy);
2855 }
2857 /// \brief Try to find a partition of the aggregate type passed in for a given
2858 /// offset and size.
2859 ///
2860 /// This recurses through the aggregate type and tries to compute a subtype
2861 /// based on the offset and size. When the offset and size span a sub-section
2862 /// of an array, it will even compute a new array type for that sub-section,
2863 /// and the same for structs.
2864 ///
2865 /// Note that this routine is very strict and tries to find a partition of the
2866 /// type which produces the *exact* right offset and size. It is not forgiving
2867 /// when the size or offset cause either end of type-based partition to be off.
2868 /// Also, this is a best-effort routine. It is reasonable to give up and not
2869 /// return a type if necessary.
2870 static Type *getTypePartition(const DataLayout &DL, Type *Ty,
2871 uint64_t Offset, uint64_t Size) {
2872 if (Offset == 0 && DL.getTypeAllocSize(Ty) == Size)
2873 return stripAggregateTypeWrapping(DL, Ty);
2874 if (Offset > DL.getTypeAllocSize(Ty) ||
2875 (DL.getTypeAllocSize(Ty) - Offset) < Size)
2876 return 0;
2878 if (SequentialType *SeqTy = dyn_cast<SequentialType>(Ty)) {
2879 // We can't partition pointers...
2880 if (SeqTy->isPointerTy())
2881 return 0;
2883 Type *ElementTy = SeqTy->getElementType();
2884 uint64_t ElementSize = DL.getTypeAllocSize(ElementTy);
2885 uint64_t NumSkippedElements = Offset / ElementSize;
2886 if (ArrayType *ArrTy = dyn_cast<ArrayType>(SeqTy)) {
2887 if (NumSkippedElements >= ArrTy->getNumElements())
2888 return 0;
2889 } else if (VectorType *VecTy = dyn_cast<VectorType>(SeqTy)) {
2890 if (NumSkippedElements >= VecTy->getNumElements())
2891 return 0;
2892 }
2893 Offset -= NumSkippedElements * ElementSize;
2895 // First check if we need to recurse.
2896 if (Offset > 0 || Size < ElementSize) {
2897 // Bail if the partition ends in a different array element.
2898 if ((Offset + Size) > ElementSize)
2899 return 0;
2900 // Recurse through the element type trying to peel off offset bytes.
2901 return getTypePartition(DL, ElementTy, Offset, Size);
2902 }
2903 assert(Offset == 0);
2905 if (Size == ElementSize)
2906 return stripAggregateTypeWrapping(DL, ElementTy);
2907 assert(Size > ElementSize);
2908 uint64_t NumElements = Size / ElementSize;
2909 if (NumElements * ElementSize != Size)
2910 return 0;
2911 return ArrayType::get(ElementTy, NumElements);
2912 }
2914 StructType *STy = dyn_cast<StructType>(Ty);
2915 if (!STy)
2916 return 0;
2918 const StructLayout *SL = DL.getStructLayout(STy);
2919 if (Offset >= SL->getSizeInBytes())
2920 return 0;
2921 uint64_t EndOffset = Offset + Size;
2922 if (EndOffset > SL->getSizeInBytes())
2923 return 0;
2925 unsigned Index = SL->getElementContainingOffset(Offset);
2926 Offset -= SL->getElementOffset(Index);
2928 Type *ElementTy = STy->getElementType(Index);
2929 uint64_t ElementSize = DL.getTypeAllocSize(ElementTy);
2930 if (Offset >= ElementSize)
2931 return 0; // The offset points into alignment padding.
2933 // See if any partition must be contained by the element.
2934 if (Offset > 0 || Size < ElementSize) {
2935 if ((Offset + Size) > ElementSize)
2936 return 0;
2937 return getTypePartition(DL, ElementTy, Offset, Size);
2938 }
2939 assert(Offset == 0);
2941 if (Size == ElementSize)
2942 return stripAggregateTypeWrapping(DL, ElementTy);
2944 StructType::element_iterator EI = STy->element_begin() + Index,
2945 EE = STy->element_end();
2946 if (EndOffset < SL->getSizeInBytes()) {
2947 unsigned EndIndex = SL->getElementContainingOffset(EndOffset);
2948 if (Index == EndIndex)
2949 return 0; // Within a single element and its padding.
2951 // Don't try to form "natural" types if the elements don't line up with the
2952 // expected size.
2953 // FIXME: We could potentially recurse down through the last element in the
2954 // sub-struct to find a natural end point.
2955 if (SL->getElementOffset(EndIndex) != EndOffset)
2956 return 0;
2958 assert(Index < EndIndex);
2959 EE = STy->element_begin() + EndIndex;
2960 }
2962 // Try to build up a sub-structure.
2963 StructType *SubTy = StructType::get(STy->getContext(), makeArrayRef(EI, EE),
2964 STy->isPacked());
2965 const StructLayout *SubSL = DL.getStructLayout(SubTy);
2966 if (Size != SubSL->getSizeInBytes())
2967 return 0; // The sub-struct doesn't have quite the size needed.
2969 return SubTy;
2970 }
2972 /// \brief Rewrite an alloca partition's users.
2973 ///
2974 /// This routine drives both of the rewriting goals of the SROA pass. It tries
2975 /// to rewrite uses of an alloca partition to be conducive for SSA value
2976 /// promotion. If the partition needs a new, more refined alloca, this will
2977 /// build that new alloca, preserving as much type information as possible, and
2978 /// rewrite the uses of the old alloca to point at the new one and have the
2979 /// appropriate new offsets. It also evaluates how successful the rewrite was
2980 /// at enabling promotion and if it was successful queues the alloca to be
2981 /// promoted.
2982 bool SROA::rewritePartition(AllocaInst &AI, AllocaSlices &S,
2983 AllocaSlices::iterator B, AllocaSlices::iterator E,
2984 int64_t BeginOffset, int64_t EndOffset,
2985 ArrayRef<AllocaSlices::iterator> SplitUses) {
2986 assert(BeginOffset < EndOffset);
2987 uint64_t SliceSize = EndOffset - BeginOffset;
2989 // Try to compute a friendly type for this partition of the alloca. This
2990 // won't always succeed, in which case we fall back to a legal integer type
2991 // or an i8 array of an appropriate size.
2992 Type *SliceTy = 0;
2993 if (Type *CommonUseTy = findCommonType(B, E, EndOffset))
2994 if (DL->getTypeAllocSize(CommonUseTy) >= SliceSize)
2995 SliceTy = CommonUseTy;
2996 if (!SliceTy)
2997 if (Type *TypePartitionTy = getTypePartition(*DL, AI.getAllocatedType(),
2998 BeginOffset, SliceSize))
2999 SliceTy = TypePartitionTy;
3000 if ((!SliceTy || (SliceTy->isArrayTy() &&
3001 SliceTy->getArrayElementType()->isIntegerTy())) &&
3002 DL->isLegalInteger(SliceSize * 8))
3003 SliceTy = Type::getIntNTy(*C, SliceSize * 8);
3004 if (!SliceTy)
3005 SliceTy = ArrayType::get(Type::getInt8Ty(*C), SliceSize);
3006 assert(DL->getTypeAllocSize(SliceTy) >= SliceSize);
3008 bool IsVectorPromotable = isVectorPromotionViable(
3009 *DL, SliceTy, S, BeginOffset, EndOffset, B, E, SplitUses);
3011 bool IsIntegerPromotable =
3012 !IsVectorPromotable &&
3013 isIntegerWideningViable(*DL, SliceTy, BeginOffset, S, B, E, SplitUses);
3015 // Check for the case where we're going to rewrite to a new alloca of the
3016 // exact same type as the original, and with the same access offsets. In that
3017 // case, re-use the existing alloca, but still run through the rewriter to
3018 // perform phi and select speculation.
3019 AllocaInst *NewAI;
3020 if (SliceTy == AI.getAllocatedType()) {
3021 assert(BeginOffset == 0 &&
3022 "Non-zero begin offset but same alloca type");
3023 NewAI = &AI;
3024 // FIXME: We should be able to bail at this point with "nothing changed".
3025 // FIXME: We might want to defer PHI speculation until after here.
3026 } else {
3027 unsigned Alignment = AI.getAlignment();
3028 if (!Alignment) {
3029 // The minimum alignment which users can rely on when the explicit
3030 // alignment is omitted or zero is that required by the ABI for this
3031 // type.
3032 Alignment = DL->getABITypeAlignment(AI.getAllocatedType());
3033 }
3034 Alignment = MinAlign(Alignment, BeginOffset);
3035 // If we will get at least this much alignment from the type alone, leave
3036 // the alloca's alignment unconstrained.
3037 if (Alignment <= DL->getABITypeAlignment(SliceTy))
3038 Alignment = 0;
3039 NewAI = new AllocaInst(SliceTy, 0, Alignment,
3040 AI.getName() + ".sroa." + Twine(B - S.begin()), &AI);
3041 ++NumNewAllocas;
3042 }
3044 DEBUG(dbgs() << "Rewriting alloca partition "
3045 << "[" << BeginOffset << "," << EndOffset << ") to: " << *NewAI
3046 << "\n");
3048 // Track the high watermark on several worklists that are only relevant for
3049 // promoted allocas. We will reset it to this point if the alloca is not in
3050 // fact scheduled for promotion.
3051 unsigned PPWOldSize = PostPromotionWorklist.size();
3052 unsigned SPOldSize = SpeculatablePHIs.size();
3053 unsigned SSOldSize = SpeculatableSelects.size();
3055 #if !defined(NDEBUG) || defined(LLVM_ENABLE_STATS)
3056 unsigned NumUses = 0;
3057 #endif
3059 AllocaSliceRewriter Rewriter(*DL, S, *this, AI, *NewAI, BeginOffset,
3060 EndOffset, IsVectorPromotable,
3061 IsIntegerPromotable);
3062 bool Promotable = true;
3063 for (ArrayRef<AllocaSlices::iterator>::const_iterator SUI = SplitUses.begin(),
3064 SUE = SplitUses.end();
3065 SUI != SUE; ++SUI) {
3066 DEBUG(dbgs() << " rewriting split ");
3067 DEBUG(S.printSlice(dbgs(), *SUI, ""));
3068 Promotable &= Rewriter.visit(*SUI);
3069 #if !defined(NDEBUG) || defined(LLVM_ENABLE_STATS)
3070 ++NumUses;
3071 #endif
3072 }
3073 for (AllocaSlices::iterator I = B; I != E; ++I) {
3074 DEBUG(dbgs() << " rewriting ");
3075 DEBUG(S.printSlice(dbgs(), I, ""));
3076 Promotable &= Rewriter.visit(I);
3077 #if !defined(NDEBUG) || defined(LLVM_ENABLE_STATS)
3078 ++NumUses;
3079 #endif
3080 }
3082 #if !defined(NDEBUG) || defined(LLVM_ENABLE_STATS)
3083 NumAllocaPartitionUses += NumUses;
3084 MaxUsesPerAllocaPartition =
3085 std::max<unsigned>(NumUses, MaxUsesPerAllocaPartition);
3086 #endif
3088 if (Promotable && !Rewriter.isUsedByRewrittenSpeculatableInstructions()) {
3089 DEBUG(dbgs() << " and queuing for promotion\n");
3090 PromotableAllocas.push_back(NewAI);
3091 } else if (NewAI != &AI ||
3092 (Promotable &&
3093 Rewriter.isUsedByRewrittenSpeculatableInstructions())) {
3094 // If we can't promote the alloca, iterate on it to check for new
3095 // refinements exposed by splitting the current alloca. Don't iterate on an
3096 // alloca which didn't actually change and didn't get promoted.
3097 //
3098 // Alternatively, if we could promote the alloca but have speculatable
3099 // instructions then we will speculate them after finishing our processing
3100 // of the original alloca. Mark the new one for re-visiting in the next
3101 // iteration so the speculated operations can be rewritten.
3102 //
3103 // FIXME: We should actually track whether the rewriter changed anything.
3104 Worklist.insert(NewAI);
3105 }
3107 // Drop any post-promotion work items if promotion didn't happen.
3108 if (!Promotable) {
3109 while (PostPromotionWorklist.size() > PPWOldSize)
3110 PostPromotionWorklist.pop_back();
3111 while (SpeculatablePHIs.size() > SPOldSize)
3112 SpeculatablePHIs.pop_back();
3113 while (SpeculatableSelects.size() > SSOldSize)
3114 SpeculatableSelects.pop_back();
3115 }
3117 return true;
3118 }
3120 namespace {
3121 struct IsSliceEndLessOrEqualTo {
3122 uint64_t UpperBound;
3124 IsSliceEndLessOrEqualTo(uint64_t UpperBound) : UpperBound(UpperBound) {}
3126 bool operator()(const AllocaSlices::iterator &I) {
3127 return I->endOffset() <= UpperBound;
3128 }
3129 };
3130 }
3132 static void
3133 removeFinishedSplitUses(SmallVectorImpl<AllocaSlices::iterator> &SplitUses,
3134 uint64_t &MaxSplitUseEndOffset, uint64_t Offset) {
3135 if (Offset >= MaxSplitUseEndOffset) {
3136 SplitUses.clear();
3137 MaxSplitUseEndOffset = 0;
3138 return;
3139 }
3141 size_t SplitUsesOldSize = SplitUses.size();
3142 SplitUses.erase(std::remove_if(SplitUses.begin(), SplitUses.end(),
3143 IsSliceEndLessOrEqualTo(Offset)),
3144 SplitUses.end());
3145 if (SplitUsesOldSize == SplitUses.size())
3146 return;
3148 // Recompute the max. While this is linear, so is remove_if.
3149 MaxSplitUseEndOffset = 0;
3150 for (SmallVectorImpl<AllocaSlices::iterator>::iterator
3151 SUI = SplitUses.begin(),
3152 SUE = SplitUses.end();
3153 SUI != SUE; ++SUI)
3154 MaxSplitUseEndOffset = std::max((*SUI)->endOffset(), MaxSplitUseEndOffset);
3155 }
3157 /// \brief Walks the slices of an alloca and form partitions based on them,
3158 /// rewriting each of their uses.
3159 bool SROA::splitAlloca(AllocaInst &AI, AllocaSlices &S) {
3160 if (S.begin() == S.end())
3161 return false;
3163 #if !defined(NDEBUG) || defined(LLVM_ENABLE_STATS)
3164 unsigned NumPartitions = 0;
3165 #endif
3167 bool Changed = false;
3168 SmallVector<AllocaSlices::iterator, 4> SplitUses;
3169 uint64_t MaxSplitUseEndOffset = 0;
3171 uint64_t BeginOffset = S.begin()->beginOffset();
3173 for (AllocaSlices::iterator SI = S.begin(), SJ = llvm::next(SI), SE = S.end();
3174 SI != SE; SI = SJ) {
3175 uint64_t MaxEndOffset = SI->endOffset();
3177 if (!SI->isSplittable()) {
3178 // When we're forming an unsplittable region, it must always start at the
3179 // first slice and will extend through its end.
3180 assert(BeginOffset == SI->beginOffset());
3182 // Form a partition including all of the overlapping slices with this
3183 // unsplittable slice.
3184 while (SJ != SE && SJ->beginOffset() < MaxEndOffset) {
3185 if (!SJ->isSplittable())
3186 MaxEndOffset = std::max(MaxEndOffset, SJ->endOffset());
3187 ++SJ;
3188 }
3189 } else {
3190 assert(SI->isSplittable()); // Established above.
3192 // Collect all of the overlapping splittable slices.
3193 while (SJ != SE && SJ->beginOffset() < MaxEndOffset &&
3194 SJ->isSplittable()) {
3195 MaxEndOffset = std::max(MaxEndOffset, SJ->endOffset());
3196 ++SJ;
3197 }
3199 // Back up MaxEndOffset and SJ if we ended the span early when
3200 // encountering an unsplittable slice.
3201 if (SJ != SE && SJ->beginOffset() < MaxEndOffset) {
3202 assert(!SJ->isSplittable());
3203 MaxEndOffset = SJ->beginOffset();
3204 }
3205 }
3207 // Check if we have managed to move the end offset forward yet. If so,
3208 // we'll have to rewrite uses and erase old split uses.
3209 if (BeginOffset < MaxEndOffset) {
3210 // Rewrite a sequence of overlapping slices.
3211 Changed |=
3212 rewritePartition(AI, S, SI, SJ, BeginOffset, MaxEndOffset, SplitUses);
3213 #if !defined(NDEBUG) || defined(LLVM_ENABLE_STATS)
3214 ++NumPartitions;
3215 #endif
3217 removeFinishedSplitUses(SplitUses, MaxSplitUseEndOffset, MaxEndOffset);
3218 }
3220 // Accumulate all the splittable slices from the [SI,SJ) region which
3221 // overlap going forward.
3222 for (AllocaSlices::iterator SK = SI; SK != SJ; ++SK)
3223 if (SK->isSplittable() && SK->endOffset() > MaxEndOffset) {
3224 SplitUses.push_back(SK);
3225 MaxSplitUseEndOffset = std::max(SK->endOffset(), MaxSplitUseEndOffset);
3226 }
3228 // If we're already at the end and we have no split uses, we're done.
3229 if (SJ == SE && SplitUses.empty())
3230 break;
3232 // If we have no split uses or no gap in offsets, we're ready to move to
3233 // the next slice.
3234 if (SplitUses.empty() || (SJ != SE && MaxEndOffset == SJ->beginOffset())) {
3235 BeginOffset = SJ->beginOffset();
3236 continue;
3237 }
3239 // Even if we have split slices, if the next slice is splittable and the
3240 // split slices reach it, we can simply set up the beginning offset of the
3241 // next iteration to bridge between them.
3242 if (SJ != SE && SJ->isSplittable() &&
3243 MaxSplitUseEndOffset > SJ->beginOffset()) {
3244 BeginOffset = MaxEndOffset;
3245 continue;
3246 }
3248 // Otherwise, we have a tail of split slices. Rewrite them with an empty
3249 // range of slices.
3250 uint64_t PostSplitEndOffset =
3251 SJ == SE ? MaxSplitUseEndOffset : SJ->beginOffset();
3253 Changed |= rewritePartition(AI, S, SJ, SJ, MaxEndOffset, PostSplitEndOffset,
3254 SplitUses);
3255 #if !defined(NDEBUG) || defined(LLVM_ENABLE_STATS)
3256 ++NumPartitions;
3257 #endif
3259 if (SJ == SE)
3260 break; // Skip the rest, we don't need to do any cleanup.
3262 removeFinishedSplitUses(SplitUses, MaxSplitUseEndOffset,
3263 PostSplitEndOffset);
3265 // Now just reset the begin offset for the next iteration.
3266 BeginOffset = SJ->beginOffset();
3267 }
3269 #if !defined(NDEBUG) || defined(LLVM_ENABLE_STATS)
3270 NumAllocaPartitions += NumPartitions;
3271 MaxPartitionsPerAlloca =
3272 std::max<unsigned>(NumPartitions, MaxPartitionsPerAlloca);
3273 #endif
3275 return Changed;
3276 }
3278 /// \brief Analyze an alloca for SROA.
3279 ///
3280 /// This analyzes the alloca to ensure we can reason about it, builds
3281 /// the slices of the alloca, and then hands it off to be split and
3282 /// rewritten as needed.
3283 bool SROA::runOnAlloca(AllocaInst &AI) {
3284 DEBUG(dbgs() << "SROA alloca: " << AI << "\n");
3285 ++NumAllocasAnalyzed;
3287 // Special case dead allocas, as they're trivial.
3288 if (AI.use_empty()) {
3289 AI.eraseFromParent();
3290 return true;
3291 }
3293 // Skip alloca forms that this analysis can't handle.
3294 if (AI.isArrayAllocation() || !AI.getAllocatedType()->isSized() ||
3295 DL->getTypeAllocSize(AI.getAllocatedType()) == 0)
3296 return false;
3298 bool Changed = false;
3300 // First, split any FCA loads and stores touching this alloca to promote
3301 // better splitting and promotion opportunities.
3302 AggLoadStoreRewriter AggRewriter(*DL);
3303 Changed |= AggRewriter.rewrite(AI);
3305 // Build the slices using a recursive instruction-visiting builder.
3306 AllocaSlices S(*DL, AI);
3307 DEBUG(S.print(dbgs()));
3308 if (S.isEscaped())
3309 return Changed;
3311 // Delete all the dead users of this alloca before splitting and rewriting it.
3312 for (AllocaSlices::dead_user_iterator DI = S.dead_user_begin(),
3313 DE = S.dead_user_end();
3314 DI != DE; ++DI) {
3315 Changed = true;
3316 (*DI)->replaceAllUsesWith(UndefValue::get((*DI)->getType()));
3317 DeadInsts.insert(*DI);
3318 }
3319 for (AllocaSlices::dead_op_iterator DO = S.dead_op_begin(),
3320 DE = S.dead_op_end();
3321 DO != DE; ++DO) {
3322 Value *OldV = **DO;
3323 // Clobber the use with an undef value.
3324 **DO = UndefValue::get(OldV->getType());
3325 if (Instruction *OldI = dyn_cast<Instruction>(OldV))
3326 if (isInstructionTriviallyDead(OldI)) {
3327 Changed = true;
3328 DeadInsts.insert(OldI);
3329 }
3330 }
3332 // No slices to split. Leave the dead alloca for a later pass to clean up.
3333 if (S.begin() == S.end())
3334 return Changed;
3336 Changed |= splitAlloca(AI, S);
3338 DEBUG(dbgs() << " Speculating PHIs\n");
3339 while (!SpeculatablePHIs.empty())
3340 speculatePHINodeLoads(*SpeculatablePHIs.pop_back_val());
3342 DEBUG(dbgs() << " Speculating Selects\n");
3343 while (!SpeculatableSelects.empty())
3344 speculateSelectInstLoads(*SpeculatableSelects.pop_back_val());
3346 return Changed;
3347 }
3349 /// \brief Delete the dead instructions accumulated in this run.
3350 ///
3351 /// Recursively deletes the dead instructions we've accumulated. This is done
3352 /// at the very end to maximize locality of the recursive delete and to
3353 /// minimize the problems of invalidated instruction pointers as such pointers
3354 /// are used heavily in the intermediate stages of the algorithm.
3355 ///
3356 /// We also record the alloca instructions deleted here so that they aren't
3357 /// subsequently handed to mem2reg to promote.
3358 void SROA::deleteDeadInstructions(SmallPtrSet<AllocaInst*, 4> &DeletedAllocas) {
3359 while (!DeadInsts.empty()) {
3360 Instruction *I = DeadInsts.pop_back_val();
3361 DEBUG(dbgs() << "Deleting dead instruction: " << *I << "\n");
3363 I->replaceAllUsesWith(UndefValue::get(I->getType()));
3365 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
3366 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
3367 // Zero out the operand and see if it becomes trivially dead.
3368 *OI = 0;
3369 if (isInstructionTriviallyDead(U))
3370 DeadInsts.insert(U);
3371 }
3373 if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
3374 DeletedAllocas.insert(AI);
3376 ++NumDeleted;
3377 I->eraseFromParent();
3378 }
3379 }
3381 /// \brief Promote the allocas, using the best available technique.
3382 ///
3383 /// This attempts to promote whatever allocas have been identified as viable in
3384 /// the PromotableAllocas list. If that list is empty, there is nothing to do.
3385 /// If there is a domtree available, we attempt to promote using the full power
3386 /// of mem2reg. Otherwise, we build and use the AllocaPromoter above which is
3387 /// based on the SSAUpdater utilities. This function returns whether any
3388 /// promotion occurred.
3389 bool SROA::promoteAllocas(Function &F) {
3390 if (PromotableAllocas.empty())
3391 return false;
3393 NumPromoted += PromotableAllocas.size();
3395 if (DT && !ForceSSAUpdater) {
3396 DEBUG(dbgs() << "Promoting allocas with mem2reg...\n");
3397 PromoteMemToReg(PromotableAllocas, *DT);
3398 PromotableAllocas.clear();
3399 return true;
3400 }
3402 DEBUG(dbgs() << "Promoting allocas with SSAUpdater...\n");
3403 SSAUpdater SSA;
3404 DIBuilder DIB(*F.getParent());
3405 SmallVector<Instruction*, 64> Insts;
3407 for (unsigned Idx = 0, Size = PromotableAllocas.size(); Idx != Size; ++Idx) {
3408 AllocaInst *AI = PromotableAllocas[Idx];
3409 for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end();
3410 UI != UE;) {
3411 Instruction *I = cast<Instruction>(*UI++);
3412 // FIXME: Currently the SSAUpdater infrastructure doesn't reason about
3413 // lifetime intrinsics and so we strip them (and the bitcasts+GEPs
3414 // leading to them) here. Eventually it should use them to optimize the
3415 // scalar values produced.
3416 if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) {
3417 assert(onlyUsedByLifetimeMarkers(I) &&
3418 "Found a bitcast used outside of a lifetime marker.");
3419 while (!I->use_empty())
3420 cast<Instruction>(*I->use_begin())->eraseFromParent();
3421 I->eraseFromParent();
3422 continue;
3423 }
3424 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
3425 assert(II->getIntrinsicID() == Intrinsic::lifetime_start ||
3426 II->getIntrinsicID() == Intrinsic::lifetime_end);
3427 II->eraseFromParent();
3428 continue;
3429 }
3431 Insts.push_back(I);
3432 }
3433 AllocaPromoter(Insts, SSA, *AI, DIB).run(Insts);
3434 Insts.clear();
3435 }
3437 PromotableAllocas.clear();
3438 return true;
3439 }
3441 namespace {
3442 /// \brief A predicate to test whether an alloca belongs to a set.
3443 class IsAllocaInSet {
3444 typedef SmallPtrSet<AllocaInst *, 4> SetType;
3445 const SetType &Set;
3447 public:
3448 typedef AllocaInst *argument_type;
3450 IsAllocaInSet(const SetType &Set) : Set(Set) {}
3451 bool operator()(AllocaInst *AI) const { return Set.count(AI); }
3452 };
3453 }
3455 bool SROA::runOnFunction(Function &F) {
3456 DEBUG(dbgs() << "SROA function: " << F.getName() << "\n");
3457 C = &F.getContext();
3458 DL = getAnalysisIfAvailable<DataLayout>();
3459 if (!DL) {
3460 DEBUG(dbgs() << " Skipping SROA -- no target data!\n");
3461 return false;
3462 }
3463 DT = getAnalysisIfAvailable<DominatorTree>();
3465 BasicBlock &EntryBB = F.getEntryBlock();
3466 for (BasicBlock::iterator I = EntryBB.begin(), E = llvm::prior(EntryBB.end());
3467 I != E; ++I)
3468 if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
3469 Worklist.insert(AI);
3471 bool Changed = false;
3472 // A set of deleted alloca instruction pointers which should be removed from
3473 // the list of promotable allocas.
3474 SmallPtrSet<AllocaInst *, 4> DeletedAllocas;
3476 do {
3477 while (!Worklist.empty()) {
3478 Changed |= runOnAlloca(*Worklist.pop_back_val());
3479 deleteDeadInstructions(DeletedAllocas);
3481 // Remove the deleted allocas from various lists so that we don't try to
3482 // continue processing them.
3483 if (!DeletedAllocas.empty()) {
3484 Worklist.remove_if(IsAllocaInSet(DeletedAllocas));
3485 PostPromotionWorklist.remove_if(IsAllocaInSet(DeletedAllocas));
3486 PromotableAllocas.erase(std::remove_if(PromotableAllocas.begin(),
3487 PromotableAllocas.end(),
3488 IsAllocaInSet(DeletedAllocas)),
3489 PromotableAllocas.end());
3490 DeletedAllocas.clear();
3491 }
3492 }
3494 Changed |= promoteAllocas(F);
3496 Worklist = PostPromotionWorklist;
3497 PostPromotionWorklist.clear();
3498 } while (!Worklist.empty());
3500 return Changed;
3501 }
3503 void SROA::getAnalysisUsage(AnalysisUsage &AU) const {
3504 if (RequiresDomTree)
3505 AU.addRequired<DominatorTree>();
3506 AU.setPreservesCFG();
3507 }