1 //===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This transformation implements the well known scalar replacement of
11 // aggregates transformation. This xform breaks up alloca instructions of
12 // aggregate type (structure or array) into individual alloca instructions for
13 // each member (if possible). Then, if possible, it transforms the individual
14 // alloca instructions into nice clean scalar SSA form.
16 // This combines a simple SRoA algorithm with the Mem2Reg algorithm because
17 // often interact, especially for C++ programs. As such, iterating between
18 // SRoA, then Mem2Reg until we run out of things to promote works well.
20 //===----------------------------------------------------------------------===//
22 #define DEBUG_TYPE "scalarrepl"
23 #include "llvm/Transforms/Scalar.h"
24 #include "llvm/Constants.h"
25 #include "llvm/DerivedTypes.h"
26 #include "llvm/Function.h"
27 #include "llvm/GlobalVariable.h"
28 #include "llvm/Instructions.h"
29 #include "llvm/IntrinsicInst.h"
30 #include "llvm/LLVMContext.h"
31 #include "llvm/Module.h"
32 #include "llvm/Pass.h"
33 #include "llvm/Analysis/DIBuilder.h"
34 #include "llvm/Analysis/Dominators.h"
35 #include "llvm/Analysis/Loads.h"
36 #include "llvm/Analysis/ValueTracking.h"
37 #include "llvm/Target/TargetData.h"
38 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
39 #include "llvm/Transforms/Utils/Local.h"
40 #include "llvm/Transforms/Utils/SSAUpdater.h"
41 #include "llvm/Support/CallSite.h"
42 #include "llvm/Support/Debug.h"
43 #include "llvm/Support/ErrorHandling.h"
44 #include "llvm/Support/GetElementPtrTypeIterator.h"
45 #include "llvm/Support/IRBuilder.h"
46 #include "llvm/Support/MathExtras.h"
47 #include "llvm/Support/raw_ostream.h"
48 #include "llvm/ADT/SetVector.h"
49 #include "llvm/ADT/SmallVector.h"
50 #include "llvm/ADT/Statistic.h"
53 STATISTIC(NumReplaced, "Number of allocas broken up");
54 STATISTIC(NumPromoted, "Number of allocas promoted");
55 STATISTIC(NumAdjusted, "Number of scalar allocas adjusted to allow promotion");
56 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
57 STATISTIC(NumGlobals, "Number of allocas copied from constant global");
60 struct SROA : public FunctionPass {
61 SROA(int T, bool hasDT, char &ID)
62 : FunctionPass(ID), HasDomTree(hasDT) {
69 bool runOnFunction(Function &F);
71 bool performScalarRepl(Function &F);
72 bool performPromotion(Function &F);
78 /// DeadInsts - Keep track of instructions we have made dead, so that
79 /// we can remove them after we are done working.
80 SmallVector<Value*, 32> DeadInsts;
82 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
83 /// information about the uses. All these fields are initialized to false
84 /// and set to true when something is learned.
86 /// The alloca to promote.
89 /// CheckedPHIs - This is a set of verified PHI nodes, to prevent infinite
90 /// looping and avoid redundant work.
91 SmallPtrSet<PHINode*, 8> CheckedPHIs;
93 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
96 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
99 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
100 bool isMemCpyDst : 1;
102 /// hasSubelementAccess - This is true if a subelement of the alloca is
103 /// ever accessed, or false if the alloca is only accessed with mem
104 /// intrinsics or load/store that only access the entire alloca at once.
105 bool hasSubelementAccess : 1;
107 /// hasALoadOrStore - This is true if there are any loads or stores to it.
108 /// The alloca may just be accessed with memcpy, for example, which would
110 bool hasALoadOrStore : 1;
112 explicit AllocaInfo(AllocaInst *ai)
113 : AI(ai), isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false),
114 hasSubelementAccess(false), hasALoadOrStore(false) {}
117 unsigned SRThreshold;
119 void MarkUnsafe(AllocaInfo &I, Instruction *User) {
121 DEBUG(dbgs() << " Transformation preventing inst: " << *User << '\n');
124 bool isSafeAllocaToScalarRepl(AllocaInst *AI);
126 void isSafeForScalarRepl(Instruction *I, uint64_t Offset, AllocaInfo &Info);
127 void isSafePHISelectUseForScalarRepl(Instruction *User, uint64_t Offset,
129 void isSafeGEP(GetElementPtrInst *GEPI, uint64_t &Offset, AllocaInfo &Info);
130 void isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
131 const Type *MemOpType, bool isStore, AllocaInfo &Info,
132 Instruction *TheAccess, bool AllowWholeAccess);
133 bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size);
134 uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset,
137 void DoScalarReplacement(AllocaInst *AI,
138 std::vector<AllocaInst*> &WorkList);
139 void DeleteDeadInstructions();
141 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
142 SmallVector<AllocaInst*, 32> &NewElts);
143 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
144 SmallVector<AllocaInst*, 32> &NewElts);
145 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
146 SmallVector<AllocaInst*, 32> &NewElts);
147 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
149 SmallVector<AllocaInst*, 32> &NewElts);
150 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
151 SmallVector<AllocaInst*, 32> &NewElts);
152 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
153 SmallVector<AllocaInst*, 32> &NewElts);
155 static MemTransferInst *isOnlyCopiedFromConstantGlobal(AllocaInst *AI);
158 // SROA_DT - SROA that uses DominatorTree.
159 struct SROA_DT : public SROA {
162 SROA_DT(int T = -1) : SROA(T, true, ID) {
163 initializeSROA_DTPass(*PassRegistry::getPassRegistry());
166 // getAnalysisUsage - This pass does not require any passes, but we know it
167 // will not alter the CFG, so say so.
168 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
169 AU.addRequired<DominatorTree>();
170 AU.setPreservesCFG();
174 // SROA_SSAUp - SROA that uses SSAUpdater.
175 struct SROA_SSAUp : public SROA {
178 SROA_SSAUp(int T = -1) : SROA(T, false, ID) {
179 initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry());
182 // getAnalysisUsage - This pass does not require any passes, but we know it
183 // will not alter the CFG, so say so.
184 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
185 AU.setPreservesCFG();
191 char SROA_DT::ID = 0;
192 char SROA_SSAUp::ID = 0;
194 INITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl",
195 "Scalar Replacement of Aggregates (DT)", false, false)
196 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
197 INITIALIZE_PASS_END(SROA_DT, "scalarrepl",
198 "Scalar Replacement of Aggregates (DT)", false, false)
200 INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa",
201 "Scalar Replacement of Aggregates (SSAUp)", false, false)
202 INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa",
203 "Scalar Replacement of Aggregates (SSAUp)", false, false)
205 // Public interface to the ScalarReplAggregates pass
206 FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold,
209 return new SROA_DT(Threshold);
210 return new SROA_SSAUp(Threshold);
214 //===----------------------------------------------------------------------===//
215 // Convert To Scalar Optimization.
216 //===----------------------------------------------------------------------===//
219 /// ConvertToScalarInfo - This class implements the "Convert To Scalar"
220 /// optimization, which scans the uses of an alloca and determines if it can
221 /// rewrite it in terms of a single new alloca that can be mem2reg'd.
222 class ConvertToScalarInfo {
223 /// AllocaSize - The size of the alloca being considered in bytes.
225 const TargetData &TD;
227 /// IsNotTrivial - This is set to true if there is some access to the object
228 /// which means that mem2reg can't promote it.
231 /// ScalarKind - Tracks the kind of alloca being considered for promotion,
232 /// computed based on the uses of the alloca rather than the LLVM type system.
236 // Accesses via GEPs that are consistent with element access of a vector
237 // type. This will not be converted into a vector unless there is a later
238 // access using an actual vector type.
241 // Accesses via vector operations and GEPs that are consistent with the
242 // layout of a vector type.
245 // An integer bag-of-bits with bitwise operations for insertion and
246 // extraction. Any combination of types can be converted into this kind
251 /// VectorTy - This tracks the type that we should promote the vector to if
252 /// it is possible to turn it into a vector. This starts out null, and if it
253 /// isn't possible to turn into a vector type, it gets set to VoidTy.
254 const VectorType *VectorTy;
256 /// HadNonMemTransferAccess - True if there is at least one access to the
257 /// alloca that is not a MemTransferInst. We don't want to turn structs into
258 /// large integers unless there is some potential for optimization.
259 bool HadNonMemTransferAccess;
262 explicit ConvertToScalarInfo(unsigned Size, const TargetData &td)
263 : AllocaSize(Size), TD(td), IsNotTrivial(false), ScalarKind(Unknown),
264 VectorTy(0), HadNonMemTransferAccess(false) { }
266 AllocaInst *TryConvert(AllocaInst *AI);
269 bool CanConvertToScalar(Value *V, uint64_t Offset);
270 void MergeInTypeForLoadOrStore(const Type *In, uint64_t Offset);
271 bool MergeInVectorType(const VectorType *VInTy, uint64_t Offset);
272 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
274 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
275 uint64_t Offset, IRBuilder<> &Builder);
276 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
277 uint64_t Offset, IRBuilder<> &Builder);
279 } // end anonymous namespace.
282 /// TryConvert - Analyze the specified alloca, and if it is safe to do so,
283 /// rewrite it to be a new alloca which is mem2reg'able. This returns the new
284 /// alloca if possible or null if not.
285 AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
286 // If we can't convert this scalar, or if mem2reg can trivially do it, bail
288 if (!CanConvertToScalar(AI, 0) || !IsNotTrivial)
291 // If an alloca has only memset / memcpy uses, it may still have an Unknown
292 // ScalarKind. Treat it as an Integer below.
293 if (ScalarKind == Unknown)
294 ScalarKind = Integer;
296 // If we were able to find a vector type that can handle this with
297 // insert/extract elements, and if there was at least one use that had
298 // a vector type, promote this to a vector. We don't want to promote
299 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
300 // we just get a lot of insert/extracts. If at least one vector is
301 // involved, then we probably really do have a union of vector/array.
303 if (VectorTy && ScalarKind != ImplicitVector) {
304 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
305 << *VectorTy << '\n');
306 NewTy = VectorTy; // Use the vector type.
308 unsigned BitWidth = AllocaSize * 8;
309 if ((ScalarKind == ImplicitVector || ScalarKind == Integer) &&
310 !HadNonMemTransferAccess && !TD.fitsInLegalInteger(BitWidth))
313 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
314 // Create and insert the integer alloca.
315 NewTy = IntegerType::get(AI->getContext(), BitWidth);
317 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
318 ConvertUsesToScalar(AI, NewAI, 0);
322 /// MergeInTypeForLoadOrStore - Add the 'In' type to the accumulated vector type
323 /// (VectorTy) so far at the offset specified by Offset (which is specified in
326 /// There are three cases we handle here:
327 /// 1) A union of vector types of the same size and potentially its elements.
328 /// Here we turn element accesses into insert/extract element operations.
329 /// This promotes a <4 x float> with a store of float to the third element
330 /// into a <4 x float> that uses insert element.
331 /// 2) A union of vector types with power-of-2 size differences, e.g. a float,
332 /// <2 x float> and <4 x float>. Here we turn element accesses into insert
333 /// and extract element operations, and <2 x float> accesses into a cast to
334 /// <2 x double>, an extract, and a cast back to <2 x float>.
335 /// 3) A fully general blob of memory, which we turn into some (potentially
336 /// large) integer type with extract and insert operations where the loads
337 /// and stores would mutate the memory. We mark this by setting VectorTy
339 void ConvertToScalarInfo::MergeInTypeForLoadOrStore(const Type *In,
341 // If we already decided to turn this into a blob of integer memory, there is
342 // nothing to be done.
343 if (ScalarKind == Integer)
346 // If this could be contributing to a vector, analyze it.
348 // If the In type is a vector that is the same size as the alloca, see if it
349 // matches the existing VecTy.
350 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
351 if (MergeInVectorType(VInTy, Offset))
353 } else if (In->isFloatTy() || In->isDoubleTy() ||
354 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
355 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
356 // Full width accesses can be ignored, because they can always be turned
358 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
359 if (EltSize == AllocaSize)
362 // If we're accessing something that could be an element of a vector, see
363 // if the implied vector agrees with what we already have and if Offset is
364 // compatible with it.
365 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 &&
366 (!VectorTy || Offset * 8 < VectorTy->getPrimitiveSizeInBits())) {
368 ScalarKind = ImplicitVector;
369 VectorTy = VectorType::get(In, AllocaSize/EltSize);
373 unsigned CurrentEltSize = VectorTy->getElementType()
374 ->getPrimitiveSizeInBits()/8;
375 if (EltSize == CurrentEltSize)
378 if (In->isIntegerTy() && isPowerOf2_32(AllocaSize / EltSize))
383 // Otherwise, we have a case that we can't handle with an optimized vector
384 // form. We can still turn this into a large integer.
385 ScalarKind = Integer;
389 /// MergeInVectorType - Handles the vector case of MergeInTypeForLoadOrStore,
390 /// returning true if the type was successfully merged and false otherwise.
391 bool ConvertToScalarInfo::MergeInVectorType(const VectorType *VInTy,
393 // TODO: Support nonzero offsets?
397 // Only allow vectors that are a power-of-2 away from the size of the alloca.
398 if (!isPowerOf2_64(AllocaSize / (VInTy->getBitWidth() / 8)))
401 // If this the first vector we see, remember the type so that we know the
409 unsigned BitWidth = VectorTy->getBitWidth();
410 unsigned InBitWidth = VInTy->getBitWidth();
412 // Vectors of the same size can be converted using a simple bitcast.
413 if (InBitWidth == BitWidth && AllocaSize == (InBitWidth / 8)) {
418 const Type *ElementTy = VectorTy->getElementType();
419 const Type *InElementTy = VInTy->getElementType();
421 // Do not allow mixed integer and floating-point accesses from vectors of
423 if (ElementTy->isFloatingPointTy() != InElementTy->isFloatingPointTy())
426 if (ElementTy->isFloatingPointTy()) {
427 // Only allow floating-point vectors of different sizes if they have the
428 // same element type.
429 // TODO: This could be loosened a bit, but would anything benefit?
430 if (ElementTy != InElementTy)
433 // There are no arbitrary-precision floating-point types, which limits the
434 // number of legal vector types with larger element types that we can form
435 // to bitcast and extract a subvector.
436 // TODO: We could support some more cases with mixed fp128 and double here.
437 if (!(BitWidth == 64 || BitWidth == 128) ||
438 !(InBitWidth == 64 || InBitWidth == 128))
441 assert(ElementTy->isIntegerTy() && "Vector elements must be either integer "
442 "or floating-point.");
443 unsigned BitWidth = ElementTy->getPrimitiveSizeInBits();
444 unsigned InBitWidth = InElementTy->getPrimitiveSizeInBits();
446 // Do not allow integer types smaller than a byte or types whose widths are
447 // not a multiple of a byte.
448 if (BitWidth < 8 || InBitWidth < 8 ||
449 BitWidth % 8 != 0 || InBitWidth % 8 != 0)
453 // Pick the largest of the two vector types.
455 if (InBitWidth > BitWidth)
461 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
462 /// its accesses to a single vector type, return true and set VecTy to
463 /// the new type. If we could convert the alloca into a single promotable
464 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
465 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
466 /// is the current offset from the base of the alloca being analyzed.
468 /// If we see at least one access to the value that is as a vector type, set the
470 bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) {
471 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
472 Instruction *User = cast<Instruction>(*UI);
474 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
475 // Don't break volatile loads.
476 if (LI->isVolatile())
478 // Don't touch MMX operations.
479 if (LI->getType()->isX86_MMXTy())
481 HadNonMemTransferAccess = true;
482 MergeInTypeForLoadOrStore(LI->getType(), Offset);
486 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
487 // Storing the pointer, not into the value?
488 if (SI->getOperand(0) == V || SI->isVolatile()) return false;
489 // Don't touch MMX operations.
490 if (SI->getOperand(0)->getType()->isX86_MMXTy())
492 HadNonMemTransferAccess = true;
493 MergeInTypeForLoadOrStore(SI->getOperand(0)->getType(), Offset);
497 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
498 IsNotTrivial = true; // Can't be mem2reg'd.
499 if (!CanConvertToScalar(BCI, Offset))
504 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
505 // If this is a GEP with a variable indices, we can't handle it.
506 if (!GEP->hasAllConstantIndices())
509 // Compute the offset that this GEP adds to the pointer.
510 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
511 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
512 &Indices[0], Indices.size());
513 // See if all uses can be converted.
514 if (!CanConvertToScalar(GEP, Offset+GEPOffset))
516 IsNotTrivial = true; // Can't be mem2reg'd.
517 HadNonMemTransferAccess = true;
521 // If this is a constant sized memset of a constant value (e.g. 0) we can
523 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
524 // Store of constant value and constant size.
525 if (!isa<ConstantInt>(MSI->getValue()) ||
526 !isa<ConstantInt>(MSI->getLength()))
528 IsNotTrivial = true; // Can't be mem2reg'd.
529 HadNonMemTransferAccess = true;
533 // If this is a memcpy or memmove into or out of the whole allocation, we
534 // can handle it like a load or store of the scalar type.
535 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
536 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
537 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0)
540 IsNotTrivial = true; // Can't be mem2reg'd.
544 // Otherwise, we cannot handle this!
551 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
552 /// directly. This happens when we are converting an "integer union" to a
553 /// single integer scalar, or when we are converting a "vector union" to a
554 /// vector with insert/extractelement instructions.
556 /// Offset is an offset from the original alloca, in bits that need to be
557 /// shifted to the right. By the end of this, there should be no uses of Ptr.
558 void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
560 while (!Ptr->use_empty()) {
561 Instruction *User = cast<Instruction>(Ptr->use_back());
563 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
564 ConvertUsesToScalar(CI, NewAI, Offset);
565 CI->eraseFromParent();
569 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
570 // Compute the offset that this GEP adds to the pointer.
571 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
572 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
573 &Indices[0], Indices.size());
574 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
575 GEP->eraseFromParent();
579 IRBuilder<> Builder(User);
581 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
582 // The load is a bit extract from NewAI shifted right by Offset bits.
583 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
585 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
586 LI->replaceAllUsesWith(NewLoadVal);
587 LI->eraseFromParent();
591 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
592 assert(SI->getOperand(0) != Ptr && "Consistency error!");
593 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
594 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
596 Builder.CreateStore(New, NewAI);
597 SI->eraseFromParent();
599 // If the load we just inserted is now dead, then the inserted store
600 // overwrote the entire thing.
601 if (Old->use_empty())
602 Old->eraseFromParent();
606 // If this is a constant sized memset of a constant value (e.g. 0) we can
607 // transform it into a store of the expanded constant value.
608 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
609 assert(MSI->getRawDest() == Ptr && "Consistency error!");
610 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
612 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
614 // Compute the value replicated the right number of times.
615 APInt APVal(NumBytes*8, Val);
617 // Splat the value if non-zero.
619 for (unsigned i = 1; i != NumBytes; ++i)
622 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
623 Value *New = ConvertScalar_InsertValue(
624 ConstantInt::get(User->getContext(), APVal),
625 Old, Offset, Builder);
626 Builder.CreateStore(New, NewAI);
628 // If the load we just inserted is now dead, then the memset overwrote
630 if (Old->use_empty())
631 Old->eraseFromParent();
633 MSI->eraseFromParent();
637 // If this is a memcpy or memmove into or out of the whole allocation, we
638 // can handle it like a load or store of the scalar type.
639 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
640 assert(Offset == 0 && "must be store to start of alloca");
642 // If the source and destination are both to the same alloca, then this is
643 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
645 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, &TD, 0));
647 if (GetUnderlyingObject(MTI->getSource(), &TD, 0) != OrigAI) {
648 // Dest must be OrigAI, change this to be a load from the original
649 // pointer (bitcasted), then a store to our new alloca.
650 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
651 Value *SrcPtr = MTI->getSource();
652 const PointerType* SPTy = cast<PointerType>(SrcPtr->getType());
653 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
654 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
655 AIPTy = PointerType::get(AIPTy->getElementType(),
656 SPTy->getAddressSpace());
658 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy);
660 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
661 SrcVal->setAlignment(MTI->getAlignment());
662 Builder.CreateStore(SrcVal, NewAI);
663 } else if (GetUnderlyingObject(MTI->getDest(), &TD, 0) != OrigAI) {
664 // Src must be OrigAI, change this to be a load from NewAI then a store
665 // through the original dest pointer (bitcasted).
666 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
667 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
669 const PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType());
670 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
671 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
672 AIPTy = PointerType::get(AIPTy->getElementType(),
673 DPTy->getAddressSpace());
675 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy);
677 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
678 NewStore->setAlignment(MTI->getAlignment());
680 // Noop transfer. Src == Dst
683 MTI->eraseFromParent();
687 llvm_unreachable("Unsupported operation!");
691 /// getScaledElementType - Gets a scaled element type for a partial vector
692 /// access of an alloca. The input types must be integer or floating-point
693 /// scalar or vector types, and the resulting type is an integer, float or
695 static const Type *getScaledElementType(const Type *Ty1, const Type *Ty2,
696 unsigned NewBitWidth) {
697 bool IsFP1 = Ty1->isFloatingPointTy() ||
698 (Ty1->isVectorTy() &&
699 cast<VectorType>(Ty1)->getElementType()->isFloatingPointTy());
700 bool IsFP2 = Ty2->isFloatingPointTy() ||
701 (Ty2->isVectorTy() &&
702 cast<VectorType>(Ty2)->getElementType()->isFloatingPointTy());
704 LLVMContext &Context = Ty1->getContext();
706 // Prefer floating-point types over integer types, as integer types may have
707 // been created by earlier scalar replacement.
708 if (IsFP1 || IsFP2) {
709 if (NewBitWidth == 32)
710 return Type::getFloatTy(Context);
711 if (NewBitWidth == 64)
712 return Type::getDoubleTy(Context);
715 return Type::getIntNTy(Context, NewBitWidth);
718 /// CreateShuffleVectorCast - Creates a shuffle vector to convert one vector
719 /// to another vector of the same element type which has the same allocation
720 /// size but different primitive sizes (e.g. <3 x i32> and <4 x i32>).
721 static Value *CreateShuffleVectorCast(Value *FromVal, const Type *ToType,
722 IRBuilder<> &Builder) {
723 const Type *FromType = FromVal->getType();
724 const VectorType *FromVTy = cast<VectorType>(FromType);
725 const VectorType *ToVTy = cast<VectorType>(ToType);
726 assert((ToVTy->getElementType() == FromVTy->getElementType()) &&
727 "Vectors must have the same element type");
728 Value *UnV = UndefValue::get(FromType);
729 unsigned numEltsFrom = FromVTy->getNumElements();
730 unsigned numEltsTo = ToVTy->getNumElements();
732 SmallVector<Constant*, 3> Args;
733 const Type* Int32Ty = Builder.getInt32Ty();
734 unsigned minNumElts = std::min(numEltsFrom, numEltsTo);
736 for (i=0; i != minNumElts; ++i)
737 Args.push_back(ConstantInt::get(Int32Ty, i));
740 Constant* UnC = UndefValue::get(Int32Ty);
741 for (; i != numEltsTo; ++i)
744 Constant *Mask = ConstantVector::get(Args);
745 return Builder.CreateShuffleVector(FromVal, UnV, Mask, "tmpV");
748 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
749 /// or vector value FromVal, extracting the bits from the offset specified by
750 /// Offset. This returns the value, which is of type ToType.
752 /// This happens when we are converting an "integer union" to a single
753 /// integer scalar, or when we are converting a "vector union" to a vector with
754 /// insert/extractelement instructions.
756 /// Offset is an offset from the original alloca, in bits that need to be
757 /// shifted to the right.
758 Value *ConvertToScalarInfo::
759 ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
760 uint64_t Offset, IRBuilder<> &Builder) {
761 // If the load is of the whole new alloca, no conversion is needed.
762 const Type *FromType = FromVal->getType();
763 if (FromType == ToType && Offset == 0)
766 // If the result alloca is a vector type, this is either an element
767 // access or a bitcast to another vector type of the same size.
768 if (const VectorType *VTy = dyn_cast<VectorType>(FromType)) {
769 unsigned FromTypeSize = TD.getTypeAllocSize(FromType);
770 unsigned ToTypeSize = TD.getTypeAllocSize(ToType);
771 if (FromTypeSize == ToTypeSize) {
772 // If the two types have the same primitive size, use a bit cast.
773 // Otherwise, it is two vectors with the same element type that has
774 // the same allocation size but different number of elements so use
776 if (FromType->getPrimitiveSizeInBits() ==
777 ToType->getPrimitiveSizeInBits())
778 return Builder.CreateBitCast(FromVal, ToType, "tmp");
780 return CreateShuffleVectorCast(FromVal, ToType, Builder);
783 if (isPowerOf2_64(FromTypeSize / ToTypeSize)) {
784 assert(!(ToType->isVectorTy() && Offset != 0) && "Can't extract a value "
785 "of a smaller vector type at a nonzero offset.");
787 const Type *CastElementTy = getScaledElementType(FromType, ToType,
789 unsigned NumCastVectorElements = FromTypeSize / ToTypeSize;
791 LLVMContext &Context = FromVal->getContext();
792 const Type *CastTy = VectorType::get(CastElementTy,
793 NumCastVectorElements);
794 Value *Cast = Builder.CreateBitCast(FromVal, CastTy, "tmp");
796 unsigned EltSize = TD.getTypeAllocSizeInBits(CastElementTy);
797 unsigned Elt = Offset/EltSize;
798 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
799 Value *Extract = Builder.CreateExtractElement(Cast, ConstantInt::get(
800 Type::getInt32Ty(Context), Elt), "tmp");
801 return Builder.CreateBitCast(Extract, ToType, "tmp");
804 // Otherwise it must be an element access.
807 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
808 Elt = Offset/EltSize;
809 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
811 // Return the element extracted out of it.
812 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(
813 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp");
814 if (V->getType() != ToType)
815 V = Builder.CreateBitCast(V, ToType, "tmp");
819 // If ToType is a first class aggregate, extract out each of the pieces and
820 // use insertvalue's to form the FCA.
821 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
822 const StructLayout &Layout = *TD.getStructLayout(ST);
823 Value *Res = UndefValue::get(ST);
824 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
825 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
826 Offset+Layout.getElementOffsetInBits(i),
828 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
833 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
834 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
835 Value *Res = UndefValue::get(AT);
836 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
837 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
838 Offset+i*EltSize, Builder);
839 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
844 // Otherwise, this must be a union that was converted to an integer value.
845 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
847 // If this is a big-endian system and the load is narrower than the
848 // full alloca type, we need to do a shift to get the right bits.
850 if (TD.isBigEndian()) {
851 // On big-endian machines, the lowest bit is stored at the bit offset
852 // from the pointer given by getTypeStoreSizeInBits. This matters for
853 // integers with a bitwidth that is not a multiple of 8.
854 ShAmt = TD.getTypeStoreSizeInBits(NTy) -
855 TD.getTypeStoreSizeInBits(ToType) - Offset;
860 // Note: we support negative bitwidths (with shl) which are not defined.
861 // We do this to support (f.e.) loads off the end of a structure where
862 // only some bits are used.
863 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
864 FromVal = Builder.CreateLShr(FromVal,
865 ConstantInt::get(FromVal->getType(),
867 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
868 FromVal = Builder.CreateShl(FromVal,
869 ConstantInt::get(FromVal->getType(),
872 // Finally, unconditionally truncate the integer to the right width.
873 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType);
874 if (LIBitWidth < NTy->getBitWidth())
876 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
878 else if (LIBitWidth > NTy->getBitWidth())
880 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
883 // If the result is an integer, this is a trunc or bitcast.
884 if (ToType->isIntegerTy()) {
886 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
887 // Just do a bitcast, we know the sizes match up.
888 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
890 // Otherwise must be a pointer.
891 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
893 assert(FromVal->getType() == ToType && "Didn't convert right?");
897 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
898 /// or vector value "Old" at the offset specified by Offset.
900 /// This happens when we are converting an "integer union" to a
901 /// single integer scalar, or when we are converting a "vector union" to a
902 /// vector with insert/extractelement instructions.
904 /// Offset is an offset from the original alloca, in bits that need to be
905 /// shifted to the right.
906 Value *ConvertToScalarInfo::
907 ConvertScalar_InsertValue(Value *SV, Value *Old,
908 uint64_t Offset, IRBuilder<> &Builder) {
909 // Convert the stored type to the actual type, shift it left to insert
910 // then 'or' into place.
911 const Type *AllocaType = Old->getType();
912 LLVMContext &Context = Old->getContext();
914 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
915 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy);
916 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType());
918 // Changing the whole vector with memset or with an access of a different
920 if (ValSize == VecSize) {
921 // If the two types have the same primitive size, use a bit cast.
922 // Otherwise, it is two vectors with the same element type that has
923 // the same allocation size but different number of elements so use
925 if (VTy->getPrimitiveSizeInBits() ==
926 SV->getType()->getPrimitiveSizeInBits())
927 return Builder.CreateBitCast(SV, AllocaType, "tmp");
929 return CreateShuffleVectorCast(SV, VTy, Builder);
932 if (isPowerOf2_64(VecSize / ValSize)) {
933 assert(!(SV->getType()->isVectorTy() && Offset != 0) && "Can't insert a "
934 "value of a smaller vector type at a nonzero offset.");
936 const Type *CastElementTy = getScaledElementType(VTy, SV->getType(),
938 unsigned NumCastVectorElements = VecSize / ValSize;
940 LLVMContext &Context = SV->getContext();
941 const Type *OldCastTy = VectorType::get(CastElementTy,
942 NumCastVectorElements);
943 Value *OldCast = Builder.CreateBitCast(Old, OldCastTy, "tmp");
945 Value *SVCast = Builder.CreateBitCast(SV, CastElementTy, "tmp");
947 unsigned EltSize = TD.getTypeAllocSizeInBits(CastElementTy);
948 unsigned Elt = Offset/EltSize;
949 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
951 Builder.CreateInsertElement(OldCast, SVCast, ConstantInt::get(
952 Type::getInt32Ty(Context), Elt), "tmp");
953 return Builder.CreateBitCast(Insert, AllocaType, "tmp");
956 // Must be an element insertion.
957 assert(SV->getType() == VTy->getElementType());
958 uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
959 unsigned Elt = Offset/EltSize;
960 return Builder.CreateInsertElement(Old, SV,
961 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt),
965 // If SV is a first-class aggregate value, insert each value recursively.
966 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
967 const StructLayout &Layout = *TD.getStructLayout(ST);
968 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
969 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
970 Old = ConvertScalar_InsertValue(Elt, Old,
971 Offset+Layout.getElementOffsetInBits(i),
977 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
978 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
979 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
980 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
981 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
986 // If SV is a float, convert it to the appropriate integer type.
987 // If it is a pointer, do the same.
988 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType());
989 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType);
990 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType());
991 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType);
992 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
993 SV = Builder.CreateBitCast(SV,
994 IntegerType::get(SV->getContext(),SrcWidth), "tmp");
995 else if (SV->getType()->isPointerTy())
996 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "tmp");
998 // Zero extend or truncate the value if needed.
999 if (SV->getType() != AllocaType) {
1000 if (SV->getType()->getPrimitiveSizeInBits() <
1001 AllocaType->getPrimitiveSizeInBits())
1002 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
1004 // Truncation may be needed if storing more than the alloca can hold
1005 // (undefined behavior).
1006 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
1007 SrcWidth = DestWidth;
1008 SrcStoreWidth = DestStoreWidth;
1012 // If this is a big-endian system and the store is narrower than the
1013 // full alloca type, we need to do a shift to get the right bits.
1015 if (TD.isBigEndian()) {
1016 // On big-endian machines, the lowest bit is stored at the bit offset
1017 // from the pointer given by getTypeStoreSizeInBits. This matters for
1018 // integers with a bitwidth that is not a multiple of 8.
1019 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
1024 // Note: we support negative bitwidths (with shr) which are not defined.
1025 // We do this to support (f.e.) stores off the end of a structure where
1026 // only some bits in the structure are set.
1027 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1028 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1029 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(),
1032 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1033 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(),
1035 Mask = Mask.lshr(-ShAmt);
1038 // Mask out the bits we are about to insert from the old value, and or
1040 if (SrcWidth != DestWidth) {
1041 assert(DestWidth > SrcWidth);
1042 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
1043 SV = Builder.CreateOr(Old, SV, "ins");
1049 //===----------------------------------------------------------------------===//
1051 //===----------------------------------------------------------------------===//
1054 bool SROA::runOnFunction(Function &F) {
1055 TD = getAnalysisIfAvailable<TargetData>();
1057 bool Changed = performPromotion(F);
1059 // FIXME: ScalarRepl currently depends on TargetData more than it
1060 // theoretically needs to. It should be refactored in order to support
1061 // target-independent IR. Until this is done, just skip the actual
1062 // scalar-replacement portion of this pass.
1063 if (!TD) return Changed;
1066 bool LocalChange = performScalarRepl(F);
1067 if (!LocalChange) break; // No need to repromote if no scalarrepl
1069 LocalChange = performPromotion(F);
1070 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
1077 class AllocaPromoter : public LoadAndStorePromoter {
1080 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S,
1081 DbgDeclareInst *DD, DIBuilder *&DB)
1082 : LoadAndStorePromoter(Insts, S, DD, DB), AI(0) {}
1084 void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) {
1085 // Remember which alloca we're promoting (for isInstInList).
1087 LoadAndStorePromoter::run(Insts);
1088 AI->eraseFromParent();
1091 virtual bool isInstInList(Instruction *I,
1092 const SmallVectorImpl<Instruction*> &Insts) const {
1093 if (LoadInst *LI = dyn_cast<LoadInst>(I))
1094 return LI->getOperand(0) == AI;
1095 return cast<StoreInst>(I)->getPointerOperand() == AI;
1098 } // end anon namespace
1100 /// isSafeSelectToSpeculate - Select instructions that use an alloca and are
1101 /// subsequently loaded can be rewritten to load both input pointers and then
1102 /// select between the result, allowing the load of the alloca to be promoted.
1104 /// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
1105 /// %V = load i32* %P2
1107 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1108 /// %V2 = load i32* %Other
1109 /// %V = select i1 %cond, i32 %V1, i32 %V2
1111 /// We can do this to a select if its only uses are loads and if the operand to
1112 /// the select can be loaded unconditionally.
1113 static bool isSafeSelectToSpeculate(SelectInst *SI, const TargetData *TD) {
1114 bool TDerefable = SI->getTrueValue()->isDereferenceablePointer();
1115 bool FDerefable = SI->getFalseValue()->isDereferenceablePointer();
1117 for (Value::use_iterator UI = SI->use_begin(), UE = SI->use_end();
1119 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1120 if (LI == 0 || LI->isVolatile()) return false;
1122 // Both operands to the select need to be dereferencable, either absolutely
1123 // (e.g. allocas) or at this point because we can see other accesses to it.
1124 if (!TDerefable && !isSafeToLoadUnconditionally(SI->getTrueValue(), LI,
1125 LI->getAlignment(), TD))
1127 if (!FDerefable && !isSafeToLoadUnconditionally(SI->getFalseValue(), LI,
1128 LI->getAlignment(), TD))
1135 /// isSafePHIToSpeculate - PHI instructions that use an alloca and are
1136 /// subsequently loaded can be rewritten to load both input pointers in the pred
1137 /// blocks and then PHI the results, allowing the load of the alloca to be
1140 /// %P2 = phi [i32* %Alloca, i32* %Other]
1141 /// %V = load i32* %P2
1143 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1145 /// %V2 = load i32* %Other
1147 /// %V = phi [i32 %V1, i32 %V2]
1149 /// We can do this to a select if its only uses are loads and if the operand to
1150 /// the select can be loaded unconditionally.
1151 static bool isSafePHIToSpeculate(PHINode *PN, const TargetData *TD) {
1152 // For now, we can only do this promotion if the load is in the same block as
1153 // the PHI, and if there are no stores between the phi and load.
1154 // TODO: Allow recursive phi users.
1155 // TODO: Allow stores.
1156 BasicBlock *BB = PN->getParent();
1157 unsigned MaxAlign = 0;
1158 for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end();
1160 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1161 if (LI == 0 || LI->isVolatile()) return false;
1163 // For now we only allow loads in the same block as the PHI. This is a
1164 // common case that happens when instcombine merges two loads through a PHI.
1165 if (LI->getParent() != BB) return false;
1167 // Ensure that there are no instructions between the PHI and the load that
1169 for (BasicBlock::iterator BBI = PN; &*BBI != LI; ++BBI)
1170 if (BBI->mayWriteToMemory())
1173 MaxAlign = std::max(MaxAlign, LI->getAlignment());
1176 // Okay, we know that we have one or more loads in the same block as the PHI.
1177 // We can transform this if it is safe to push the loads into the predecessor
1178 // blocks. The only thing to watch out for is that we can't put a possibly
1179 // trapping load in the predecessor if it is a critical edge.
1180 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1181 BasicBlock *Pred = PN->getIncomingBlock(i);
1183 // If the predecessor has a single successor, then the edge isn't critical.
1184 if (Pred->getTerminator()->getNumSuccessors() == 1)
1187 Value *InVal = PN->getIncomingValue(i);
1189 // If the InVal is an invoke in the pred, we can't put a load on the edge.
1190 if (InvokeInst *II = dyn_cast<InvokeInst>(InVal))
1191 if (II->getParent() == Pred)
1194 // If this pointer is always safe to load, or if we can prove that there is
1195 // already a load in the block, then we can move the load to the pred block.
1196 if (InVal->isDereferenceablePointer() ||
1197 isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign, TD))
1207 /// tryToMakeAllocaBePromotable - This returns true if the alloca only has
1208 /// direct (non-volatile) loads and stores to it. If the alloca is close but
1209 /// not quite there, this will transform the code to allow promotion. As such,
1210 /// it is a non-pure predicate.
1211 static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const TargetData *TD) {
1212 SetVector<Instruction*, SmallVector<Instruction*, 4>,
1213 SmallPtrSet<Instruction*, 4> > InstsToRewrite;
1215 for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end();
1218 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1219 if (LI->isVolatile())
1224 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1225 if (SI->getOperand(0) == AI || SI->isVolatile())
1226 return false; // Don't allow a store OF the AI, only INTO the AI.
1230 if (SelectInst *SI = dyn_cast<SelectInst>(U)) {
1231 // If the condition being selected on is a constant, fold the select, yes
1232 // this does (rarely) happen early on.
1233 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) {
1234 Value *Result = SI->getOperand(1+CI->isZero());
1235 SI->replaceAllUsesWith(Result);
1236 SI->eraseFromParent();
1238 // This is very rare and we just scrambled the use list of AI, start
1240 return tryToMakeAllocaBePromotable(AI, TD);
1243 // If it is safe to turn "load (select c, AI, ptr)" into a select of two
1244 // loads, then we can transform this by rewriting the select.
1245 if (!isSafeSelectToSpeculate(SI, TD))
1248 InstsToRewrite.insert(SI);
1252 if (PHINode *PN = dyn_cast<PHINode>(U)) {
1253 if (PN->use_empty()) { // Dead PHIs can be stripped.
1254 InstsToRewrite.insert(PN);
1258 // If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads
1259 // in the pred blocks, then we can transform this by rewriting the PHI.
1260 if (!isSafePHIToSpeculate(PN, TD))
1263 InstsToRewrite.insert(PN);
1270 // If there are no instructions to rewrite, then all uses are load/stores and
1272 if (InstsToRewrite.empty())
1275 // If we have instructions that need to be rewritten for this to be promotable
1276 // take care of it now.
1277 for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) {
1278 if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) {
1279 // Selects in InstsToRewrite only have load uses. Rewrite each as two
1280 // loads with a new select.
1281 while (!SI->use_empty()) {
1282 LoadInst *LI = cast<LoadInst>(SI->use_back());
1284 IRBuilder<> Builder(LI);
1285 LoadInst *TrueLoad =
1286 Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t");
1287 LoadInst *FalseLoad =
1288 Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".t");
1290 // Transfer alignment and TBAA info if present.
1291 TrueLoad->setAlignment(LI->getAlignment());
1292 FalseLoad->setAlignment(LI->getAlignment());
1293 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) {
1294 TrueLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1295 FalseLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1298 Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad);
1300 LI->replaceAllUsesWith(V);
1301 LI->eraseFromParent();
1304 // Now that all the loads are gone, the select is gone too.
1305 SI->eraseFromParent();
1309 // Otherwise, we have a PHI node which allows us to push the loads into the
1311 PHINode *PN = cast<PHINode>(InstsToRewrite[i]);
1312 if (PN->use_empty()) {
1313 PN->eraseFromParent();
1317 const Type *LoadTy = cast<PointerType>(PN->getType())->getElementType();
1318 PHINode *NewPN = PHINode::Create(LoadTy, PN->getNumIncomingValues(),
1319 PN->getName()+".ld", PN);
1321 // Get the TBAA tag and alignment to use from one of the loads. It doesn't
1322 // matter which one we get and if any differ, it doesn't matter.
1323 LoadInst *SomeLoad = cast<LoadInst>(PN->use_back());
1324 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa);
1325 unsigned Align = SomeLoad->getAlignment();
1327 // Rewrite all loads of the PN to use the new PHI.
1328 while (!PN->use_empty()) {
1329 LoadInst *LI = cast<LoadInst>(PN->use_back());
1330 LI->replaceAllUsesWith(NewPN);
1331 LI->eraseFromParent();
1334 // Inject loads into all of the pred blocks. Keep track of which blocks we
1335 // insert them into in case we have multiple edges from the same block.
1336 DenseMap<BasicBlock*, LoadInst*> InsertedLoads;
1338 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1339 BasicBlock *Pred = PN->getIncomingBlock(i);
1340 LoadInst *&Load = InsertedLoads[Pred];
1342 Load = new LoadInst(PN->getIncomingValue(i),
1343 PN->getName() + "." + Pred->getName(),
1344 Pred->getTerminator());
1345 Load->setAlignment(Align);
1346 if (TBAATag) Load->setMetadata(LLVMContext::MD_tbaa, TBAATag);
1349 NewPN->addIncoming(Load, Pred);
1352 PN->eraseFromParent();
1359 bool SROA::performPromotion(Function &F) {
1360 std::vector<AllocaInst*> Allocas;
1361 DominatorTree *DT = 0;
1363 DT = &getAnalysis<DominatorTree>();
1365 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
1367 bool Changed = false;
1368 SmallVector<Instruction*, 64> Insts;
1373 // Find allocas that are safe to promote, by looking at all instructions in
1375 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
1376 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
1377 if (tryToMakeAllocaBePromotable(AI, TD))
1378 Allocas.push_back(AI);
1380 if (Allocas.empty()) break;
1383 PromoteMemToReg(Allocas, *DT);
1386 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
1387 AllocaInst *AI = Allocas[i];
1389 // Build list of instructions to promote.
1390 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
1392 Insts.push_back(cast<Instruction>(*UI));
1394 DbgDeclareInst *DDI = FindAllocaDbgDeclare(AI);
1396 DIB = new DIBuilder(*AI->getParent()->getParent()->getParent());
1397 AllocaPromoter(Insts, SSA, DDI, DIB).run(AI, Insts);
1401 NumPromoted += Allocas.size();
1405 // FIXME: Is there a better way to handle the lazy initialization of DIB
1406 // so that there doesn't need to be an explicit delete?
1413 /// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
1414 /// SROA. It must be a struct or array type with a small number of elements.
1415 static bool ShouldAttemptScalarRepl(AllocaInst *AI) {
1416 const Type *T = AI->getAllocatedType();
1417 // Do not promote any struct into more than 32 separate vars.
1418 if (const StructType *ST = dyn_cast<StructType>(T))
1419 return ST->getNumElements() <= 32;
1420 // Arrays are much less likely to be safe for SROA; only consider
1421 // them if they are very small.
1422 if (const ArrayType *AT = dyn_cast<ArrayType>(T))
1423 return AT->getNumElements() <= 8;
1428 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
1429 // which runs on all of the malloc/alloca instructions in the function, removing
1430 // them if they are only used by getelementptr instructions.
1432 bool SROA::performScalarRepl(Function &F) {
1433 std::vector<AllocaInst*> WorkList;
1435 // Scan the entry basic block, adding allocas to the worklist.
1436 BasicBlock &BB = F.getEntryBlock();
1437 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
1438 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
1439 WorkList.push_back(A);
1441 // Process the worklist
1442 bool Changed = false;
1443 while (!WorkList.empty()) {
1444 AllocaInst *AI = WorkList.back();
1445 WorkList.pop_back();
1447 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
1448 // with unused elements.
1449 if (AI->use_empty()) {
1450 AI->eraseFromParent();
1455 // If this alloca is impossible for us to promote, reject it early.
1456 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
1459 // Check to see if this allocation is only modified by a memcpy/memmove from
1460 // a constant global. If this is the case, we can change all users to use
1461 // the constant global instead. This is commonly produced by the CFE by
1462 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
1463 // is only subsequently read.
1464 if (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
1465 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n');
1466 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n');
1467 Constant *TheSrc = cast<Constant>(TheCopy->getSource());
1468 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
1469 TheCopy->eraseFromParent(); // Don't mutate the global.
1470 AI->eraseFromParent();
1476 // Check to see if we can perform the core SROA transformation. We cannot
1477 // transform the allocation instruction if it is an array allocation
1478 // (allocations OF arrays are ok though), and an allocation of a scalar
1479 // value cannot be decomposed at all.
1480 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
1482 // Do not promote [0 x %struct].
1483 if (AllocaSize == 0) continue;
1485 // Do not promote any struct whose size is too big.
1486 if (AllocaSize > SRThreshold) continue;
1488 // If the alloca looks like a good candidate for scalar replacement, and if
1489 // all its users can be transformed, then split up the aggregate into its
1490 // separate elements.
1491 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
1492 DoScalarReplacement(AI, WorkList);
1497 // If we can turn this aggregate value (potentially with casts) into a
1498 // simple scalar value that can be mem2reg'd into a register value.
1499 // IsNotTrivial tracks whether this is something that mem2reg could have
1500 // promoted itself. If so, we don't want to transform it needlessly. Note
1501 // that we can't just check based on the type: the alloca may be of an i32
1502 // but that has pointer arithmetic to set byte 3 of it or something.
1503 if (AllocaInst *NewAI =
1504 ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) {
1505 NewAI->takeName(AI);
1506 AI->eraseFromParent();
1512 // Otherwise, couldn't process this alloca.
1518 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
1519 /// predicate, do SROA now.
1520 void SROA::DoScalarReplacement(AllocaInst *AI,
1521 std::vector<AllocaInst*> &WorkList) {
1522 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
1523 SmallVector<AllocaInst*, 32> ElementAllocas;
1524 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
1525 ElementAllocas.reserve(ST->getNumContainedTypes());
1526 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
1527 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
1529 AI->getName() + "." + Twine(i), AI);
1530 ElementAllocas.push_back(NA);
1531 WorkList.push_back(NA); // Add to worklist for recursive processing
1534 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
1535 ElementAllocas.reserve(AT->getNumElements());
1536 const Type *ElTy = AT->getElementType();
1537 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1538 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
1539 AI->getName() + "." + Twine(i), AI);
1540 ElementAllocas.push_back(NA);
1541 WorkList.push_back(NA); // Add to worklist for recursive processing
1545 // Now that we have created the new alloca instructions, rewrite all the
1546 // uses of the old alloca.
1547 RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
1549 // Now erase any instructions that were made dead while rewriting the alloca.
1550 DeleteDeadInstructions();
1551 AI->eraseFromParent();
1556 /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
1557 /// recursively including all their operands that become trivially dead.
1558 void SROA::DeleteDeadInstructions() {
1559 while (!DeadInsts.empty()) {
1560 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
1562 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
1563 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
1564 // Zero out the operand and see if it becomes trivially dead.
1565 // (But, don't add allocas to the dead instruction list -- they are
1566 // already on the worklist and will be deleted separately.)
1568 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
1569 DeadInsts.push_back(U);
1572 I->eraseFromParent();
1576 /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
1577 /// performing scalar replacement of alloca AI. The results are flagged in
1578 /// the Info parameter. Offset indicates the position within AI that is
1579 /// referenced by this instruction.
1580 void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset,
1582 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1583 Instruction *User = cast<Instruction>(*UI);
1585 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1586 isSafeForScalarRepl(BC, Offset, Info);
1587 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1588 uint64_t GEPOffset = Offset;
1589 isSafeGEP(GEPI, GEPOffset, Info);
1591 isSafeForScalarRepl(GEPI, GEPOffset, Info);
1592 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1593 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1595 return MarkUnsafe(Info, User);
1596 isSafeMemAccess(Offset, Length->getZExtValue(), 0,
1597 UI.getOperandNo() == 0, Info, MI,
1598 true /*AllowWholeAccess*/);
1599 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1600 if (LI->isVolatile())
1601 return MarkUnsafe(Info, User);
1602 const Type *LIType = LI->getType();
1603 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
1604 LIType, false, Info, LI, true /*AllowWholeAccess*/);
1605 Info.hasALoadOrStore = true;
1607 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1608 // Store is ok if storing INTO the pointer, not storing the pointer
1609 if (SI->isVolatile() || SI->getOperand(0) == I)
1610 return MarkUnsafe(Info, User);
1612 const Type *SIType = SI->getOperand(0)->getType();
1613 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
1614 SIType, true, Info, SI, true /*AllowWholeAccess*/);
1615 Info.hasALoadOrStore = true;
1616 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
1617 isSafePHISelectUseForScalarRepl(User, Offset, Info);
1619 return MarkUnsafe(Info, User);
1621 if (Info.isUnsafe) return;
1626 /// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer
1627 /// derived from the alloca, we can often still split the alloca into elements.
1628 /// This is useful if we have a large alloca where one element is phi'd
1629 /// together somewhere: we can SRoA and promote all the other elements even if
1630 /// we end up not being able to promote this one.
1632 /// All we require is that the uses of the PHI do not index into other parts of
1633 /// the alloca. The most important use case for this is single load and stores
1634 /// that are PHI'd together, which can happen due to code sinking.
1635 void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset,
1637 // If we've already checked this PHI, don't do it again.
1638 if (PHINode *PN = dyn_cast<PHINode>(I))
1639 if (!Info.CheckedPHIs.insert(PN))
1642 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1643 Instruction *User = cast<Instruction>(*UI);
1645 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1646 isSafePHISelectUseForScalarRepl(BC, Offset, Info);
1647 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1648 // Only allow "bitcast" GEPs for simplicity. We could generalize this,
1649 // but would have to prove that we're staying inside of an element being
1651 if (!GEPI->hasAllZeroIndices())
1652 return MarkUnsafe(Info, User);
1653 isSafePHISelectUseForScalarRepl(GEPI, Offset, Info);
1654 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1655 if (LI->isVolatile())
1656 return MarkUnsafe(Info, User);
1657 const Type *LIType = LI->getType();
1658 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
1659 LIType, false, Info, LI, false /*AllowWholeAccess*/);
1660 Info.hasALoadOrStore = true;
1662 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1663 // Store is ok if storing INTO the pointer, not storing the pointer
1664 if (SI->isVolatile() || SI->getOperand(0) == I)
1665 return MarkUnsafe(Info, User);
1667 const Type *SIType = SI->getOperand(0)->getType();
1668 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
1669 SIType, true, Info, SI, false /*AllowWholeAccess*/);
1670 Info.hasALoadOrStore = true;
1671 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
1672 isSafePHISelectUseForScalarRepl(User, Offset, Info);
1674 return MarkUnsafe(Info, User);
1676 if (Info.isUnsafe) return;
1680 /// isSafeGEP - Check if a GEP instruction can be handled for scalar
1681 /// replacement. It is safe when all the indices are constant, in-bounds
1682 /// references, and when the resulting offset corresponds to an element within
1683 /// the alloca type. The results are flagged in the Info parameter. Upon
1684 /// return, Offset is adjusted as specified by the GEP indices.
1685 void SROA::isSafeGEP(GetElementPtrInst *GEPI,
1686 uint64_t &Offset, AllocaInfo &Info) {
1687 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
1691 // Walk through the GEP type indices, checking the types that this indexes
1693 for (; GEPIt != E; ++GEPIt) {
1694 // Ignore struct elements, no extra checking needed for these.
1695 if ((*GEPIt)->isStructTy())
1698 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
1700 return MarkUnsafe(Info, GEPI);
1703 // Compute the offset due to this GEP and check if the alloca has a
1704 // component element at that offset.
1705 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1706 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1707 &Indices[0], Indices.size());
1708 if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset, 0))
1709 MarkUnsafe(Info, GEPI);
1712 /// isHomogeneousAggregate - Check if type T is a struct or array containing
1713 /// elements of the same type (which is always true for arrays). If so,
1714 /// return true with NumElts and EltTy set to the number of elements and the
1715 /// element type, respectively.
1716 static bool isHomogeneousAggregate(const Type *T, unsigned &NumElts,
1717 const Type *&EltTy) {
1718 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1719 NumElts = AT->getNumElements();
1720 EltTy = (NumElts == 0 ? 0 : AT->getElementType());
1723 if (const StructType *ST = dyn_cast<StructType>(T)) {
1724 NumElts = ST->getNumContainedTypes();
1725 EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0));
1726 for (unsigned n = 1; n < NumElts; ++n) {
1727 if (ST->getContainedType(n) != EltTy)
1735 /// isCompatibleAggregate - Check if T1 and T2 are either the same type or are
1736 /// "homogeneous" aggregates with the same element type and number of elements.
1737 static bool isCompatibleAggregate(const Type *T1, const Type *T2) {
1741 unsigned NumElts1, NumElts2;
1742 const Type *EltTy1, *EltTy2;
1743 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) &&
1744 isHomogeneousAggregate(T2, NumElts2, EltTy2) &&
1745 NumElts1 == NumElts2 &&
1752 /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
1753 /// alloca or has an offset and size that corresponds to a component element
1754 /// within it. The offset checked here may have been formed from a GEP with a
1755 /// pointer bitcasted to a different type.
1757 /// If AllowWholeAccess is true, then this allows uses of the entire alloca as a
1758 /// unit. If false, it only allows accesses known to be in a single element.
1759 void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
1760 const Type *MemOpType, bool isStore,
1761 AllocaInfo &Info, Instruction *TheAccess,
1762 bool AllowWholeAccess) {
1763 // Check if this is a load/store of the entire alloca.
1764 if (Offset == 0 && AllowWholeAccess &&
1765 MemSize == TD->getTypeAllocSize(Info.AI->getAllocatedType())) {
1766 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer
1767 // loads/stores (which are essentially the same as the MemIntrinsics with
1768 // regard to copying padding between elements). But, if an alloca is
1769 // flagged as both a source and destination of such operations, we'll need
1770 // to check later for padding between elements.
1771 if (!MemOpType || MemOpType->isIntegerTy()) {
1773 Info.isMemCpyDst = true;
1775 Info.isMemCpySrc = true;
1778 // This is also safe for references using a type that is compatible with
1779 // the type of the alloca, so that loads/stores can be rewritten using
1780 // insertvalue/extractvalue.
1781 if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) {
1782 Info.hasSubelementAccess = true;
1786 // Check if the offset/size correspond to a component within the alloca type.
1787 const Type *T = Info.AI->getAllocatedType();
1788 if (TypeHasComponent(T, Offset, MemSize)) {
1789 Info.hasSubelementAccess = true;
1793 return MarkUnsafe(Info, TheAccess);
1796 /// TypeHasComponent - Return true if T has a component type with the
1797 /// specified offset and size. If Size is zero, do not check the size.
1798 bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) {
1801 if (const StructType *ST = dyn_cast<StructType>(T)) {
1802 const StructLayout *Layout = TD->getStructLayout(ST);
1803 unsigned EltIdx = Layout->getElementContainingOffset(Offset);
1804 EltTy = ST->getContainedType(EltIdx);
1805 EltSize = TD->getTypeAllocSize(EltTy);
1806 Offset -= Layout->getElementOffset(EltIdx);
1807 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1808 EltTy = AT->getElementType();
1809 EltSize = TD->getTypeAllocSize(EltTy);
1810 if (Offset >= AT->getNumElements() * EltSize)
1816 if (Offset == 0 && (Size == 0 || EltSize == Size))
1818 // Check if the component spans multiple elements.
1819 if (Offset + Size > EltSize)
1821 return TypeHasComponent(EltTy, Offset, Size);
1824 /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
1825 /// the instruction I, which references it, to use the separate elements.
1826 /// Offset indicates the position within AI that is referenced by this
1828 void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1829 SmallVector<AllocaInst*, 32> &NewElts) {
1830 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) {
1831 Use &TheUse = UI.getUse();
1832 Instruction *User = cast<Instruction>(*UI++);
1834 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1835 RewriteBitCast(BC, AI, Offset, NewElts);
1839 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1840 RewriteGEP(GEPI, AI, Offset, NewElts);
1844 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1845 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1846 uint64_t MemSize = Length->getZExtValue();
1848 MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
1849 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
1850 // Otherwise the intrinsic can only touch a single element and the
1851 // address operand will be updated, so nothing else needs to be done.
1855 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1856 const Type *LIType = LI->getType();
1858 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) {
1860 // %res = load { i32, i32 }* %alloc
1862 // %load.0 = load i32* %alloc.0
1863 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
1864 // %load.1 = load i32* %alloc.1
1865 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
1866 // (Also works for arrays instead of structs)
1867 Value *Insert = UndefValue::get(LIType);
1868 IRBuilder<> Builder(LI);
1869 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1870 Value *Load = Builder.CreateLoad(NewElts[i], "load");
1871 Insert = Builder.CreateInsertValue(Insert, Load, i, "insert");
1873 LI->replaceAllUsesWith(Insert);
1874 DeadInsts.push_back(LI);
1875 } else if (LIType->isIntegerTy() &&
1876 TD->getTypeAllocSize(LIType) ==
1877 TD->getTypeAllocSize(AI->getAllocatedType())) {
1878 // If this is a load of the entire alloca to an integer, rewrite it.
1879 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
1884 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1885 Value *Val = SI->getOperand(0);
1886 const Type *SIType = Val->getType();
1887 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) {
1889 // store { i32, i32 } %val, { i32, i32 }* %alloc
1891 // %val.0 = extractvalue { i32, i32 } %val, 0
1892 // store i32 %val.0, i32* %alloc.0
1893 // %val.1 = extractvalue { i32, i32 } %val, 1
1894 // store i32 %val.1, i32* %alloc.1
1895 // (Also works for arrays instead of structs)
1896 IRBuilder<> Builder(SI);
1897 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1898 Value *Extract = Builder.CreateExtractValue(Val, i, Val->getName());
1899 Builder.CreateStore(Extract, NewElts[i]);
1901 DeadInsts.push_back(SI);
1902 } else if (SIType->isIntegerTy() &&
1903 TD->getTypeAllocSize(SIType) ==
1904 TD->getTypeAllocSize(AI->getAllocatedType())) {
1905 // If this is a store of the entire alloca from an integer, rewrite it.
1906 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
1911 if (isa<SelectInst>(User) || isa<PHINode>(User)) {
1912 // If we have a PHI user of the alloca itself (as opposed to a GEP or
1913 // bitcast) we have to rewrite it. GEP and bitcast uses will be RAUW'd to
1915 if (!isa<AllocaInst>(I)) continue;
1917 assert(Offset == 0 && NewElts[0] &&
1918 "Direct alloca use should have a zero offset");
1920 // If we have a use of the alloca, we know the derived uses will be
1921 // utilizing just the first element of the scalarized result. Insert a
1922 // bitcast of the first alloca before the user as required.
1923 AllocaInst *NewAI = NewElts[0];
1924 BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI);
1925 NewAI->moveBefore(BCI);
1932 /// RewriteBitCast - Update a bitcast reference to the alloca being replaced
1933 /// and recursively continue updating all of its uses.
1934 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
1935 SmallVector<AllocaInst*, 32> &NewElts) {
1936 RewriteForScalarRepl(BC, AI, Offset, NewElts);
1937 if (BC->getOperand(0) != AI)
1940 // The bitcast references the original alloca. Replace its uses with
1941 // references to the first new element alloca.
1942 Instruction *Val = NewElts[0];
1943 if (Val->getType() != BC->getDestTy()) {
1944 Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
1947 BC->replaceAllUsesWith(Val);
1948 DeadInsts.push_back(BC);
1951 /// FindElementAndOffset - Return the index of the element containing Offset
1952 /// within the specified type, which must be either a struct or an array.
1953 /// Sets T to the type of the element and Offset to the offset within that
1954 /// element. IdxTy is set to the type of the index result to be used in a
1955 /// GEP instruction.
1956 uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset,
1957 const Type *&IdxTy) {
1959 if (const StructType *ST = dyn_cast<StructType>(T)) {
1960 const StructLayout *Layout = TD->getStructLayout(ST);
1961 Idx = Layout->getElementContainingOffset(Offset);
1962 T = ST->getContainedType(Idx);
1963 Offset -= Layout->getElementOffset(Idx);
1964 IdxTy = Type::getInt32Ty(T->getContext());
1967 const ArrayType *AT = cast<ArrayType>(T);
1968 T = AT->getElementType();
1969 uint64_t EltSize = TD->getTypeAllocSize(T);
1970 Idx = Offset / EltSize;
1971 Offset -= Idx * EltSize;
1972 IdxTy = Type::getInt64Ty(T->getContext());
1976 /// RewriteGEP - Check if this GEP instruction moves the pointer across
1977 /// elements of the alloca that are being split apart, and if so, rewrite
1978 /// the GEP to be relative to the new element.
1979 void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
1980 SmallVector<AllocaInst*, 32> &NewElts) {
1981 uint64_t OldOffset = Offset;
1982 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1983 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1984 &Indices[0], Indices.size());
1986 RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
1988 const Type *T = AI->getAllocatedType();
1990 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
1991 if (GEPI->getOperand(0) == AI)
1992 OldIdx = ~0ULL; // Force the GEP to be rewritten.
1994 T = AI->getAllocatedType();
1995 uint64_t EltOffset = Offset;
1996 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
1998 // If this GEP does not move the pointer across elements of the alloca
1999 // being split, then it does not needs to be rewritten.
2003 const Type *i32Ty = Type::getInt32Ty(AI->getContext());
2004 SmallVector<Value*, 8> NewArgs;
2005 NewArgs.push_back(Constant::getNullValue(i32Ty));
2006 while (EltOffset != 0) {
2007 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
2008 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
2010 Instruction *Val = NewElts[Idx];
2011 if (NewArgs.size() > 1) {
2012 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(),
2013 NewArgs.end(), "", GEPI);
2014 Val->takeName(GEPI);
2016 if (Val->getType() != GEPI->getType())
2017 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
2018 GEPI->replaceAllUsesWith(Val);
2019 DeadInsts.push_back(GEPI);
2022 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
2023 /// Rewrite it to copy or set the elements of the scalarized memory.
2024 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
2026 SmallVector<AllocaInst*, 32> &NewElts) {
2027 // If this is a memcpy/memmove, construct the other pointer as the
2028 // appropriate type. The "Other" pointer is the pointer that goes to memory
2029 // that doesn't have anything to do with the alloca that we are promoting. For
2030 // memset, this Value* stays null.
2031 Value *OtherPtr = 0;
2032 unsigned MemAlignment = MI->getAlignment();
2033 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
2034 if (Inst == MTI->getRawDest())
2035 OtherPtr = MTI->getRawSource();
2037 assert(Inst == MTI->getRawSource());
2038 OtherPtr = MTI->getRawDest();
2042 // If there is an other pointer, we want to convert it to the same pointer
2043 // type as AI has, so we can GEP through it safely.
2045 unsigned AddrSpace =
2046 cast<PointerType>(OtherPtr->getType())->getAddressSpace();
2048 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
2049 // optimization, but it's also required to detect the corner case where
2050 // both pointer operands are referencing the same memory, and where
2051 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
2052 // function is only called for mem intrinsics that access the whole
2053 // aggregate, so non-zero GEPs are not an issue here.)
2054 OtherPtr = OtherPtr->stripPointerCasts();
2056 // Copying the alloca to itself is a no-op: just delete it.
2057 if (OtherPtr == AI || OtherPtr == NewElts[0]) {
2058 // This code will run twice for a no-op memcpy -- once for each operand.
2059 // Put only one reference to MI on the DeadInsts list.
2060 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
2061 E = DeadInsts.end(); I != E; ++I)
2062 if (*I == MI) return;
2063 DeadInsts.push_back(MI);
2067 // If the pointer is not the right type, insert a bitcast to the right
2070 PointerType::get(AI->getType()->getElementType(), AddrSpace);
2072 if (OtherPtr->getType() != NewTy)
2073 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
2076 // Process each element of the aggregate.
2077 bool SROADest = MI->getRawDest() == Inst;
2079 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
2081 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2082 // If this is a memcpy/memmove, emit a GEP of the other element address.
2083 Value *OtherElt = 0;
2084 unsigned OtherEltAlign = MemAlignment;
2087 Value *Idx[2] = { Zero,
2088 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
2089 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2,
2090 OtherPtr->getName()+"."+Twine(i),
2093 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
2094 const Type *OtherTy = OtherPtrTy->getElementType();
2095 if (const StructType *ST = dyn_cast<StructType>(OtherTy)) {
2096 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
2098 const Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
2099 EltOffset = TD->getTypeAllocSize(EltTy)*i;
2102 // The alignment of the other pointer is the guaranteed alignment of the
2103 // element, which is affected by both the known alignment of the whole
2104 // mem intrinsic and the alignment of the element. If the alignment of
2105 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
2106 // known alignment is just 4 bytes.
2107 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
2110 Value *EltPtr = NewElts[i];
2111 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
2113 // If we got down to a scalar, insert a load or store as appropriate.
2114 if (EltTy->isSingleValueType()) {
2115 if (isa<MemTransferInst>(MI)) {
2117 // From Other to Alloca.
2118 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
2119 new StoreInst(Elt, EltPtr, MI);
2121 // From Alloca to Other.
2122 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
2123 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
2127 assert(isa<MemSetInst>(MI));
2129 // If the stored element is zero (common case), just store a null
2132 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
2134 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
2136 // If EltTy is a vector type, get the element type.
2137 const Type *ValTy = EltTy->getScalarType();
2139 // Construct an integer with the right value.
2140 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
2141 APInt OneVal(EltSize, CI->getZExtValue());
2142 APInt TotalVal(OneVal);
2144 for (unsigned i = 0; 8*i < EltSize; ++i) {
2145 TotalVal = TotalVal.shl(8);
2149 // Convert the integer value to the appropriate type.
2150 StoreVal = ConstantInt::get(CI->getContext(), TotalVal);
2151 if (ValTy->isPointerTy())
2152 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
2153 else if (ValTy->isFloatingPointTy())
2154 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
2155 assert(StoreVal->getType() == ValTy && "Type mismatch!");
2157 // If the requested value was a vector constant, create it.
2158 if (EltTy != ValTy) {
2159 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
2160 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
2161 StoreVal = ConstantVector::get(Elts);
2164 new StoreInst(StoreVal, EltPtr, MI);
2167 // Otherwise, if we're storing a byte variable, use a memset call for
2171 unsigned EltSize = TD->getTypeAllocSize(EltTy);
2173 IRBuilder<> Builder(MI);
2175 // Finally, insert the meminst for this element.
2176 if (isa<MemSetInst>(MI)) {
2177 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize,
2180 assert(isa<MemTransferInst>(MI));
2181 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr
2182 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr
2184 if (isa<MemCpyInst>(MI))
2185 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile());
2187 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile());
2190 DeadInsts.push_back(MI);
2193 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
2194 /// overwrites the entire allocation. Extract out the pieces of the stored
2195 /// integer and store them individually.
2196 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
2197 SmallVector<AllocaInst*, 32> &NewElts){
2198 // Extract each element out of the integer according to its structure offset
2199 // and store the element value to the individual alloca.
2200 Value *SrcVal = SI->getOperand(0);
2201 const Type *AllocaEltTy = AI->getAllocatedType();
2202 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
2204 IRBuilder<> Builder(SI);
2206 // Handle tail padding by extending the operand
2207 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
2208 SrcVal = Builder.CreateZExt(SrcVal,
2209 IntegerType::get(SI->getContext(), AllocaSizeBits));
2211 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
2214 // There are two forms here: AI could be an array or struct. Both cases
2215 // have different ways to compute the element offset.
2216 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2217 const StructLayout *Layout = TD->getStructLayout(EltSTy);
2219 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2220 // Get the number of bits to shift SrcVal to get the value.
2221 const Type *FieldTy = EltSTy->getElementType(i);
2222 uint64_t Shift = Layout->getElementOffsetInBits(i);
2224 if (TD->isBigEndian())
2225 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
2227 Value *EltVal = SrcVal;
2229 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2230 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2233 // Truncate down to an integer of the right size.
2234 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
2236 // Ignore zero sized fields like {}, they obviously contain no data.
2237 if (FieldSizeBits == 0) continue;
2239 if (FieldSizeBits != AllocaSizeBits)
2240 EltVal = Builder.CreateTrunc(EltVal,
2241 IntegerType::get(SI->getContext(), FieldSizeBits));
2242 Value *DestField = NewElts[i];
2243 if (EltVal->getType() == FieldTy) {
2244 // Storing to an integer field of this size, just do it.
2245 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
2246 // Bitcast to the right element type (for fp/vector values).
2247 EltVal = Builder.CreateBitCast(EltVal, FieldTy);
2249 // Otherwise, bitcast the dest pointer (for aggregates).
2250 DestField = Builder.CreateBitCast(DestField,
2251 PointerType::getUnqual(EltVal->getType()));
2253 new StoreInst(EltVal, DestField, SI);
2257 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
2258 const Type *ArrayEltTy = ATy->getElementType();
2259 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
2260 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
2264 if (TD->isBigEndian())
2265 Shift = AllocaSizeBits-ElementOffset;
2269 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2270 // Ignore zero sized fields like {}, they obviously contain no data.
2271 if (ElementSizeBits == 0) continue;
2273 Value *EltVal = SrcVal;
2275 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2276 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2279 // Truncate down to an integer of the right size.
2280 if (ElementSizeBits != AllocaSizeBits)
2281 EltVal = Builder.CreateTrunc(EltVal,
2282 IntegerType::get(SI->getContext(),
2284 Value *DestField = NewElts[i];
2285 if (EltVal->getType() == ArrayEltTy) {
2286 // Storing to an integer field of this size, just do it.
2287 } else if (ArrayEltTy->isFloatingPointTy() ||
2288 ArrayEltTy->isVectorTy()) {
2289 // Bitcast to the right element type (for fp/vector values).
2290 EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy);
2292 // Otherwise, bitcast the dest pointer (for aggregates).
2293 DestField = Builder.CreateBitCast(DestField,
2294 PointerType::getUnqual(EltVal->getType()));
2296 new StoreInst(EltVal, DestField, SI);
2298 if (TD->isBigEndian())
2299 Shift -= ElementOffset;
2301 Shift += ElementOffset;
2305 DeadInsts.push_back(SI);
2308 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
2309 /// an integer. Load the individual pieces to form the aggregate value.
2310 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
2311 SmallVector<AllocaInst*, 32> &NewElts) {
2312 // Extract each element out of the NewElts according to its structure offset
2313 // and form the result value.
2314 const Type *AllocaEltTy = AI->getAllocatedType();
2315 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
2317 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
2320 // There are two forms here: AI could be an array or struct. Both cases
2321 // have different ways to compute the element offset.
2322 const StructLayout *Layout = 0;
2323 uint64_t ArrayEltBitOffset = 0;
2324 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2325 Layout = TD->getStructLayout(EltSTy);
2327 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
2328 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
2332 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
2334 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2335 // Load the value from the alloca. If the NewElt is an aggregate, cast
2336 // the pointer to an integer of the same size before doing the load.
2337 Value *SrcField = NewElts[i];
2338 const Type *FieldTy =
2339 cast<PointerType>(SrcField->getType())->getElementType();
2340 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
2342 // Ignore zero sized fields like {}, they obviously contain no data.
2343 if (FieldSizeBits == 0) continue;
2345 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
2347 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
2348 !FieldTy->isVectorTy())
2349 SrcField = new BitCastInst(SrcField,
2350 PointerType::getUnqual(FieldIntTy),
2352 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
2354 // If SrcField is a fp or vector of the right size but that isn't an
2355 // integer type, bitcast to an integer so we can shift it.
2356 if (SrcField->getType() != FieldIntTy)
2357 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
2359 // Zero extend the field to be the same size as the final alloca so that
2360 // we can shift and insert it.
2361 if (SrcField->getType() != ResultVal->getType())
2362 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
2364 // Determine the number of bits to shift SrcField.
2366 if (Layout) // Struct case.
2367 Shift = Layout->getElementOffsetInBits(i);
2369 Shift = i*ArrayEltBitOffset;
2371 if (TD->isBigEndian())
2372 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
2375 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
2376 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
2379 // Don't create an 'or x, 0' on the first iteration.
2380 if (!isa<Constant>(ResultVal) ||
2381 !cast<Constant>(ResultVal)->isNullValue())
2382 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
2384 ResultVal = SrcField;
2387 // Handle tail padding by truncating the result
2388 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
2389 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
2391 LI->replaceAllUsesWith(ResultVal);
2392 DeadInsts.push_back(LI);
2395 /// HasPadding - Return true if the specified type has any structure or
2396 /// alignment padding in between the elements that would be split apart
2397 /// by SROA; return false otherwise.
2398 static bool HasPadding(const Type *Ty, const TargetData &TD) {
2399 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
2400 Ty = ATy->getElementType();
2401 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
2404 // SROA currently handles only Arrays and Structs.
2405 const StructType *STy = cast<StructType>(Ty);
2406 const StructLayout *SL = TD.getStructLayout(STy);
2407 unsigned PrevFieldBitOffset = 0;
2408 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
2409 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
2411 // Check to see if there is any padding between this element and the
2414 unsigned PrevFieldEnd =
2415 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
2416 if (PrevFieldEnd < FieldBitOffset)
2419 PrevFieldBitOffset = FieldBitOffset;
2421 // Check for tail padding.
2422 if (unsigned EltCount = STy->getNumElements()) {
2423 unsigned PrevFieldEnd = PrevFieldBitOffset +
2424 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
2425 if (PrevFieldEnd < SL->getSizeInBits())
2431 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
2432 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
2433 /// or 1 if safe after canonicalization has been performed.
2434 bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
2435 // Loop over the use list of the alloca. We can only transform it if all of
2436 // the users are safe to transform.
2437 AllocaInfo Info(AI);
2439 isSafeForScalarRepl(AI, 0, Info);
2440 if (Info.isUnsafe) {
2441 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
2445 // Okay, we know all the users are promotable. If the aggregate is a memcpy
2446 // source and destination, we have to be careful. In particular, the memcpy
2447 // could be moving around elements that live in structure padding of the LLVM
2448 // types, but may actually be used. In these cases, we refuse to promote the
2450 if (Info.isMemCpySrc && Info.isMemCpyDst &&
2451 HasPadding(AI->getAllocatedType(), *TD))
2454 // If the alloca never has an access to just *part* of it, but is accessed
2455 // via loads and stores, then we should use ConvertToScalarInfo to promote
2456 // the alloca instead of promoting each piece at a time and inserting fission
2458 if (!Info.hasSubelementAccess && Info.hasALoadOrStore) {
2459 // If the struct/array just has one element, use basic SRoA.
2460 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
2461 if (ST->getNumElements() > 1) return false;
2463 if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1)
2473 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
2474 /// some part of a constant global variable. This intentionally only accepts
2475 /// constant expressions because we don't can't rewrite arbitrary instructions.
2476 static bool PointsToConstantGlobal(Value *V) {
2477 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
2478 return GV->isConstant();
2479 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
2480 if (CE->getOpcode() == Instruction::BitCast ||
2481 CE->getOpcode() == Instruction::GetElementPtr)
2482 return PointsToConstantGlobal(CE->getOperand(0));
2486 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
2487 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
2488 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
2489 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
2490 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
2491 /// the alloca, and if the source pointer is a pointer to a constant global, we
2492 /// can optimize this.
2493 static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
2495 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
2496 User *U = cast<Instruction>(*UI);
2498 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
2499 // Ignore non-volatile loads, they are always ok.
2500 if (LI->isVolatile()) return false;
2504 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
2505 // If uses of the bitcast are ok, we are ok.
2506 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
2510 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
2511 // If the GEP has all zero indices, it doesn't offset the pointer. If it
2512 // doesn't, it does.
2513 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
2514 isOffset || !GEP->hasAllZeroIndices()))
2519 if (CallSite CS = U) {
2520 // If this is the function being called then we treat it like a load and
2522 if (CS.isCallee(UI))
2525 // If this is a readonly/readnone call site, then we know it is just a
2526 // load (but one that potentially returns the value itself), so we can
2527 // ignore it if we know that the value isn't captured.
2528 unsigned ArgNo = CS.getArgumentNo(UI);
2529 if (CS.onlyReadsMemory() &&
2530 (CS.getInstruction()->use_empty() ||
2531 CS.paramHasAttr(ArgNo+1, Attribute::NoCapture)))
2534 // If this is being passed as a byval argument, the caller is making a
2535 // copy, so it is only a read of the alloca.
2536 if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal))
2540 // If this is isn't our memcpy/memmove, reject it as something we can't
2542 MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
2546 // If the transfer is using the alloca as a source of the transfer, then
2547 // ignore it since it is a load (unless the transfer is volatile).
2548 if (UI.getOperandNo() == 1) {
2549 if (MI->isVolatile()) return false;
2553 // If we already have seen a copy, reject the second one.
2554 if (TheCopy) return false;
2556 // If the pointer has been offset from the start of the alloca, we can't
2557 // safely handle this.
2558 if (isOffset) return false;
2560 // If the memintrinsic isn't using the alloca as the dest, reject it.
2561 if (UI.getOperandNo() != 0) return false;
2563 // If the source of the memcpy/move is not a constant global, reject it.
2564 if (!PointsToConstantGlobal(MI->getSource()))
2567 // Otherwise, the transform is safe. Remember the copy instruction.
2573 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
2574 /// modified by a copy from a constant global. If we can prove this, we can
2575 /// replace any uses of the alloca with uses of the global directly.
2576 MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) {
2577 MemTransferInst *TheCopy = 0;
2578 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))