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/DebugInfo.h"
34 #include "llvm/Analysis/DIBuilder.h"
35 #include "llvm/Analysis/Dominators.h"
36 #include "llvm/Analysis/Loads.h"
37 #include "llvm/Analysis/ValueTracking.h"
38 #include "llvm/Target/TargetData.h"
39 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
40 #include "llvm/Transforms/Utils/Local.h"
41 #include "llvm/Transforms/Utils/SSAUpdater.h"
42 #include "llvm/Support/CallSite.h"
43 #include "llvm/Support/Debug.h"
44 #include "llvm/Support/ErrorHandling.h"
45 #include "llvm/Support/GetElementPtrTypeIterator.h"
46 #include "llvm/Support/IRBuilder.h"
47 #include "llvm/Support/MathExtras.h"
48 #include "llvm/Support/raw_ostream.h"
49 #include "llvm/ADT/SetVector.h"
50 #include "llvm/ADT/SmallVector.h"
51 #include "llvm/ADT/Statistic.h"
54 STATISTIC(NumReplaced, "Number of allocas broken up");
55 STATISTIC(NumPromoted, "Number of allocas promoted");
56 STATISTIC(NumAdjusted, "Number of scalar allocas adjusted to allow promotion");
57 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
58 STATISTIC(NumGlobals, "Number of allocas copied from constant global");
61 struct SROA : public FunctionPass {
62 SROA(int T, bool hasDT, char &ID)
63 : FunctionPass(ID), HasDomTree(hasDT) {
70 bool runOnFunction(Function &F);
72 bool performScalarRepl(Function &F);
73 bool performPromotion(Function &F);
79 /// DeadInsts - Keep track of instructions we have made dead, so that
80 /// we can remove them after we are done working.
81 SmallVector<Value*, 32> DeadInsts;
83 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
84 /// information about the uses. All these fields are initialized to false
85 /// and set to true when something is learned.
87 /// The alloca to promote.
90 /// CheckedPHIs - This is a set of verified PHI nodes, to prevent infinite
91 /// looping and avoid redundant work.
92 SmallPtrSet<PHINode*, 8> CheckedPHIs;
94 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
97 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
100 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
101 bool isMemCpyDst : 1;
103 /// hasSubelementAccess - This is true if a subelement of the alloca is
104 /// ever accessed, or false if the alloca is only accessed with mem
105 /// intrinsics or load/store that only access the entire alloca at once.
106 bool hasSubelementAccess : 1;
108 /// hasALoadOrStore - This is true if there are any loads or stores to it.
109 /// The alloca may just be accessed with memcpy, for example, which would
111 bool hasALoadOrStore : 1;
113 explicit AllocaInfo(AllocaInst *ai)
114 : AI(ai), isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false),
115 hasSubelementAccess(false), hasALoadOrStore(false) {}
118 unsigned SRThreshold;
120 void MarkUnsafe(AllocaInfo &I, Instruction *User) {
122 DEBUG(dbgs() << " Transformation preventing inst: " << *User << '\n');
125 bool isSafeAllocaToScalarRepl(AllocaInst *AI);
127 void isSafeForScalarRepl(Instruction *I, uint64_t Offset, AllocaInfo &Info);
128 void isSafePHISelectUseForScalarRepl(Instruction *User, uint64_t Offset,
130 void isSafeGEP(GetElementPtrInst *GEPI, uint64_t &Offset, AllocaInfo &Info);
131 void isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
132 Type *MemOpType, bool isStore, AllocaInfo &Info,
133 Instruction *TheAccess, bool AllowWholeAccess);
134 bool TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size);
135 uint64_t FindElementAndOffset(Type *&T, uint64_t &Offset,
138 void DoScalarReplacement(AllocaInst *AI,
139 std::vector<AllocaInst*> &WorkList);
140 void DeleteDeadInstructions();
142 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
143 SmallVector<AllocaInst*, 32> &NewElts);
144 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
145 SmallVector<AllocaInst*, 32> &NewElts);
146 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
147 SmallVector<AllocaInst*, 32> &NewElts);
148 void RewriteLifetimeIntrinsic(IntrinsicInst *II, AllocaInst *AI,
150 SmallVector<AllocaInst*, 32> &NewElts);
151 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
153 SmallVector<AllocaInst*, 32> &NewElts);
154 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
155 SmallVector<AllocaInst*, 32> &NewElts);
156 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
157 SmallVector<AllocaInst*, 32> &NewElts);
159 static MemTransferInst *isOnlyCopiedFromConstantGlobal(
160 AllocaInst *AI, SmallVector<Instruction*, 4> &ToDelete);
163 // SROA_DT - SROA that uses DominatorTree.
164 struct SROA_DT : public SROA {
167 SROA_DT(int T = -1) : SROA(T, true, ID) {
168 initializeSROA_DTPass(*PassRegistry::getPassRegistry());
171 // getAnalysisUsage - This pass does not require any passes, but we know it
172 // will not alter the CFG, so say so.
173 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
174 AU.addRequired<DominatorTree>();
175 AU.setPreservesCFG();
179 // SROA_SSAUp - SROA that uses SSAUpdater.
180 struct SROA_SSAUp : public SROA {
183 SROA_SSAUp(int T = -1) : SROA(T, false, ID) {
184 initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry());
187 // getAnalysisUsage - This pass does not require any passes, but we know it
188 // will not alter the CFG, so say so.
189 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
190 AU.setPreservesCFG();
196 char SROA_DT::ID = 0;
197 char SROA_SSAUp::ID = 0;
199 INITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl",
200 "Scalar Replacement of Aggregates (DT)", false, false)
201 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
202 INITIALIZE_PASS_END(SROA_DT, "scalarrepl",
203 "Scalar Replacement of Aggregates (DT)", false, false)
205 INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa",
206 "Scalar Replacement of Aggregates (SSAUp)", false, false)
207 INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa",
208 "Scalar Replacement of Aggregates (SSAUp)", false, false)
210 // Public interface to the ScalarReplAggregates pass
211 FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold,
214 return new SROA_DT(Threshold);
215 return new SROA_SSAUp(Threshold);
219 //===----------------------------------------------------------------------===//
220 // Convert To Scalar Optimization.
221 //===----------------------------------------------------------------------===//
224 /// ConvertToScalarInfo - This class implements the "Convert To Scalar"
225 /// optimization, which scans the uses of an alloca and determines if it can
226 /// rewrite it in terms of a single new alloca that can be mem2reg'd.
227 class ConvertToScalarInfo {
228 /// AllocaSize - The size of the alloca being considered in bytes.
230 const TargetData &TD;
232 /// IsNotTrivial - This is set to true if there is some access to the object
233 /// which means that mem2reg can't promote it.
236 /// ScalarKind - Tracks the kind of alloca being considered for promotion,
237 /// computed based on the uses of the alloca rather than the LLVM type system.
241 // Accesses via GEPs that are consistent with element access of a vector
242 // type. This will not be converted into a vector unless there is a later
243 // access using an actual vector type.
246 // Accesses via vector operations and GEPs that are consistent with the
247 // layout of a vector type.
250 // An integer bag-of-bits with bitwise operations for insertion and
251 // extraction. Any combination of types can be converted into this kind
256 /// VectorTy - This tracks the type that we should promote the vector to if
257 /// it is possible to turn it into a vector. This starts out null, and if it
258 /// isn't possible to turn into a vector type, it gets set to VoidTy.
259 VectorType *VectorTy;
261 /// HadNonMemTransferAccess - True if there is at least one access to the
262 /// alloca that is not a MemTransferInst. We don't want to turn structs into
263 /// large integers unless there is some potential for optimization.
264 bool HadNonMemTransferAccess;
267 explicit ConvertToScalarInfo(unsigned Size, const TargetData &td)
268 : AllocaSize(Size), TD(td), IsNotTrivial(false), ScalarKind(Unknown),
269 VectorTy(0), HadNonMemTransferAccess(false) { }
271 AllocaInst *TryConvert(AllocaInst *AI);
274 bool CanConvertToScalar(Value *V, uint64_t Offset);
275 void MergeInTypeForLoadOrStore(Type *In, uint64_t Offset);
276 bool MergeInVectorType(VectorType *VInTy, uint64_t Offset);
277 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
279 Value *ConvertScalar_ExtractValue(Value *NV, Type *ToType,
280 uint64_t Offset, IRBuilder<> &Builder);
281 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
282 uint64_t Offset, IRBuilder<> &Builder);
284 } // end anonymous namespace.
287 /// TryConvert - Analyze the specified alloca, and if it is safe to do so,
288 /// rewrite it to be a new alloca which is mem2reg'able. This returns the new
289 /// alloca if possible or null if not.
290 AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
291 // If we can't convert this scalar, or if mem2reg can trivially do it, bail
293 if (!CanConvertToScalar(AI, 0) || !IsNotTrivial)
296 // If an alloca has only memset / memcpy uses, it may still have an Unknown
297 // ScalarKind. Treat it as an Integer below.
298 if (ScalarKind == Unknown)
299 ScalarKind = Integer;
301 if (ScalarKind == Vector && VectorTy->getBitWidth() != AllocaSize * 8)
302 ScalarKind = Integer;
304 // If we were able to find a vector type that can handle this with
305 // insert/extract elements, and if there was at least one use that had
306 // a vector type, promote this to a vector. We don't want to promote
307 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
308 // we just get a lot of insert/extracts. If at least one vector is
309 // involved, then we probably really do have a union of vector/array.
311 if (ScalarKind == Vector) {
312 assert(VectorTy && "Missing type for vector scalar.");
313 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
314 << *VectorTy << '\n');
315 NewTy = VectorTy; // Use the vector type.
317 unsigned BitWidth = AllocaSize * 8;
318 if ((ScalarKind == ImplicitVector || ScalarKind == Integer) &&
319 !HadNonMemTransferAccess && !TD.fitsInLegalInteger(BitWidth))
322 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
323 // Create and insert the integer alloca.
324 NewTy = IntegerType::get(AI->getContext(), BitWidth);
326 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
327 ConvertUsesToScalar(AI, NewAI, 0);
331 /// MergeInTypeForLoadOrStore - Add the 'In' type to the accumulated vector type
332 /// (VectorTy) so far at the offset specified by Offset (which is specified in
335 /// There are two cases we handle here:
336 /// 1) A union of vector types of the same size and potentially its elements.
337 /// Here we turn element accesses into insert/extract element operations.
338 /// This promotes a <4 x float> with a store of float to the third element
339 /// into a <4 x float> that uses insert element.
340 /// 2) A fully general blob of memory, which we turn into some (potentially
341 /// large) integer type with extract and insert operations where the loads
342 /// and stores would mutate the memory. We mark this by setting VectorTy
344 void ConvertToScalarInfo::MergeInTypeForLoadOrStore(Type *In,
346 // If we already decided to turn this into a blob of integer memory, there is
347 // nothing to be done.
348 if (ScalarKind == Integer)
351 // If this could be contributing to a vector, analyze it.
353 // If the In type is a vector that is the same size as the alloca, see if it
354 // matches the existing VecTy.
355 if (VectorType *VInTy = dyn_cast<VectorType>(In)) {
356 if (MergeInVectorType(VInTy, Offset))
358 } else if (In->isFloatTy() || In->isDoubleTy() ||
359 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
360 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
361 // Full width accesses can be ignored, because they can always be turned
363 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
364 if (EltSize == AllocaSize)
367 // If we're accessing something that could be an element of a vector, see
368 // if the implied vector agrees with what we already have and if Offset is
369 // compatible with it.
370 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 &&
371 (!VectorTy || EltSize == VectorTy->getElementType()
372 ->getPrimitiveSizeInBits()/8)) {
374 ScalarKind = ImplicitVector;
375 VectorTy = VectorType::get(In, AllocaSize/EltSize);
381 // Otherwise, we have a case that we can't handle with an optimized vector
382 // form. We can still turn this into a large integer.
383 ScalarKind = Integer;
386 /// MergeInVectorType - Handles the vector case of MergeInTypeForLoadOrStore,
387 /// returning true if the type was successfully merged and false otherwise.
388 bool ConvertToScalarInfo::MergeInVectorType(VectorType *VInTy,
390 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
391 // If we're storing/loading a vector of the right size, allow it as a
392 // vector. If this the first vector we see, remember the type so that
393 // we know the element size. If this is a subsequent access, ignore it
394 // even if it is a differing type but the same size. Worst case we can
395 // bitcast the resultant vectors.
405 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
406 /// its accesses to a single vector type, return true and set VecTy to
407 /// the new type. If we could convert the alloca into a single promotable
408 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
409 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
410 /// is the current offset from the base of the alloca being analyzed.
412 /// If we see at least one access to the value that is as a vector type, set the
414 bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) {
415 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
416 Instruction *User = cast<Instruction>(*UI);
418 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
419 // Don't break volatile loads.
422 // Don't touch MMX operations.
423 if (LI->getType()->isX86_MMXTy())
425 HadNonMemTransferAccess = true;
426 MergeInTypeForLoadOrStore(LI->getType(), Offset);
430 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
431 // Storing the pointer, not into the value?
432 if (SI->getOperand(0) == V || !SI->isSimple()) return false;
433 // Don't touch MMX operations.
434 if (SI->getOperand(0)->getType()->isX86_MMXTy())
436 HadNonMemTransferAccess = true;
437 MergeInTypeForLoadOrStore(SI->getOperand(0)->getType(), Offset);
441 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
442 if (!onlyUsedByLifetimeMarkers(BCI))
443 IsNotTrivial = true; // Can't be mem2reg'd.
444 if (!CanConvertToScalar(BCI, Offset))
449 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
450 // If this is a GEP with a variable indices, we can't handle it.
451 if (!GEP->hasAllConstantIndices())
454 // Compute the offset that this GEP adds to the pointer.
455 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
456 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
458 // See if all uses can be converted.
459 if (!CanConvertToScalar(GEP, Offset+GEPOffset))
461 IsNotTrivial = true; // Can't be mem2reg'd.
462 HadNonMemTransferAccess = true;
466 // If this is a constant sized memset of a constant value (e.g. 0) we can
468 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
469 // Store of constant value.
470 if (!isa<ConstantInt>(MSI->getValue()))
473 // Store of constant size.
474 ConstantInt *Len = dyn_cast<ConstantInt>(MSI->getLength());
478 // If the size differs from the alloca, we can only convert the alloca to
479 // an integer bag-of-bits.
480 // FIXME: This should handle all of the cases that are currently accepted
481 // as vector element insertions.
482 if (Len->getZExtValue() != AllocaSize || Offset != 0)
483 ScalarKind = Integer;
485 IsNotTrivial = true; // Can't be mem2reg'd.
486 HadNonMemTransferAccess = true;
490 // If this is a memcpy or memmove into or out of the whole allocation, we
491 // can handle it like a load or store of the scalar type.
492 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
493 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
494 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0)
497 IsNotTrivial = true; // Can't be mem2reg'd.
501 // If this is a lifetime intrinsic, we can handle it.
502 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
503 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
504 II->getIntrinsicID() == Intrinsic::lifetime_end) {
509 // Otherwise, we cannot handle this!
516 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
517 /// directly. This happens when we are converting an "integer union" to a
518 /// single integer scalar, or when we are converting a "vector union" to a
519 /// vector with insert/extractelement instructions.
521 /// Offset is an offset from the original alloca, in bits that need to be
522 /// shifted to the right. By the end of this, there should be no uses of Ptr.
523 void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
525 while (!Ptr->use_empty()) {
526 Instruction *User = cast<Instruction>(Ptr->use_back());
528 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
529 ConvertUsesToScalar(CI, NewAI, Offset);
530 CI->eraseFromParent();
534 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
535 // Compute the offset that this GEP adds to the pointer.
536 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
537 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
539 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
540 GEP->eraseFromParent();
544 IRBuilder<> Builder(User);
546 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
547 // The load is a bit extract from NewAI shifted right by Offset bits.
548 Value *LoadedVal = Builder.CreateLoad(NewAI);
550 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
551 LI->replaceAllUsesWith(NewLoadVal);
552 LI->eraseFromParent();
556 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
557 assert(SI->getOperand(0) != Ptr && "Consistency error!");
558 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
559 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
561 Builder.CreateStore(New, NewAI);
562 SI->eraseFromParent();
564 // If the load we just inserted is now dead, then the inserted store
565 // overwrote the entire thing.
566 if (Old->use_empty())
567 Old->eraseFromParent();
571 // If this is a constant sized memset of a constant value (e.g. 0) we can
572 // transform it into a store of the expanded constant value.
573 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
574 assert(MSI->getRawDest() == Ptr && "Consistency error!");
575 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
577 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
579 // Compute the value replicated the right number of times.
580 APInt APVal(NumBytes*8, Val);
582 // Splat the value if non-zero.
584 for (unsigned i = 1; i != NumBytes; ++i)
587 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
588 Value *New = ConvertScalar_InsertValue(
589 ConstantInt::get(User->getContext(), APVal),
590 Old, Offset, Builder);
591 Builder.CreateStore(New, NewAI);
593 // If the load we just inserted is now dead, then the memset overwrote
595 if (Old->use_empty())
596 Old->eraseFromParent();
598 MSI->eraseFromParent();
602 // If this is a memcpy or memmove into or out of the whole allocation, we
603 // can handle it like a load or store of the scalar type.
604 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
605 assert(Offset == 0 && "must be store to start of alloca");
607 // If the source and destination are both to the same alloca, then this is
608 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
610 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, &TD, 0));
612 if (GetUnderlyingObject(MTI->getSource(), &TD, 0) != OrigAI) {
613 // Dest must be OrigAI, change this to be a load from the original
614 // pointer (bitcasted), then a store to our new alloca.
615 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
616 Value *SrcPtr = MTI->getSource();
617 PointerType* SPTy = cast<PointerType>(SrcPtr->getType());
618 PointerType* AIPTy = cast<PointerType>(NewAI->getType());
619 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
620 AIPTy = PointerType::get(AIPTy->getElementType(),
621 SPTy->getAddressSpace());
623 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy);
625 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
626 SrcVal->setAlignment(MTI->getAlignment());
627 Builder.CreateStore(SrcVal, NewAI);
628 } else if (GetUnderlyingObject(MTI->getDest(), &TD, 0) != OrigAI) {
629 // Src must be OrigAI, change this to be a load from NewAI then a store
630 // through the original dest pointer (bitcasted).
631 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
632 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
634 PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType());
635 PointerType* AIPTy = cast<PointerType>(NewAI->getType());
636 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
637 AIPTy = PointerType::get(AIPTy->getElementType(),
638 DPTy->getAddressSpace());
640 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy);
642 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
643 NewStore->setAlignment(MTI->getAlignment());
645 // Noop transfer. Src == Dst
648 MTI->eraseFromParent();
652 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
653 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
654 II->getIntrinsicID() == Intrinsic::lifetime_end) {
655 // There's no need to preserve these, as the resulting alloca will be
656 // converted to a register anyways.
657 II->eraseFromParent();
662 llvm_unreachable("Unsupported operation!");
666 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
667 /// or vector value FromVal, extracting the bits from the offset specified by
668 /// Offset. This returns the value, which is of type ToType.
670 /// This happens when we are converting an "integer union" to a single
671 /// integer scalar, or when we are converting a "vector union" to a vector with
672 /// insert/extractelement instructions.
674 /// Offset is an offset from the original alloca, in bits that need to be
675 /// shifted to the right.
676 Value *ConvertToScalarInfo::
677 ConvertScalar_ExtractValue(Value *FromVal, Type *ToType,
678 uint64_t Offset, IRBuilder<> &Builder) {
679 // If the load is of the whole new alloca, no conversion is needed.
680 Type *FromType = FromVal->getType();
681 if (FromType == ToType && Offset == 0)
684 // If the result alloca is a vector type, this is either an element
685 // access or a bitcast to another vector type of the same size.
686 if (VectorType *VTy = dyn_cast<VectorType>(FromType)) {
687 unsigned FromTypeSize = TD.getTypeAllocSize(FromType);
688 unsigned ToTypeSize = TD.getTypeAllocSize(ToType);
689 if (FromTypeSize == ToTypeSize)
690 return Builder.CreateBitCast(FromVal, ToType);
692 // Otherwise it must be an element access.
695 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
696 Elt = Offset/EltSize;
697 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
699 // Return the element extracted out of it.
700 Value *V = Builder.CreateExtractElement(FromVal, Builder.getInt32(Elt));
701 if (V->getType() != ToType)
702 V = Builder.CreateBitCast(V, ToType);
706 // If ToType is a first class aggregate, extract out each of the pieces and
707 // use insertvalue's to form the FCA.
708 if (StructType *ST = dyn_cast<StructType>(ToType)) {
709 const StructLayout &Layout = *TD.getStructLayout(ST);
710 Value *Res = UndefValue::get(ST);
711 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
712 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
713 Offset+Layout.getElementOffsetInBits(i),
715 Res = Builder.CreateInsertValue(Res, Elt, i);
720 if (ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
721 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
722 Value *Res = UndefValue::get(AT);
723 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
724 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
725 Offset+i*EltSize, Builder);
726 Res = Builder.CreateInsertValue(Res, Elt, i);
731 // Otherwise, this must be a union that was converted to an integer value.
732 IntegerType *NTy = cast<IntegerType>(FromVal->getType());
734 // If this is a big-endian system and the load is narrower than the
735 // full alloca type, we need to do a shift to get the right bits.
737 if (TD.isBigEndian()) {
738 // On big-endian machines, the lowest bit is stored at the bit offset
739 // from the pointer given by getTypeStoreSizeInBits. This matters for
740 // integers with a bitwidth that is not a multiple of 8.
741 ShAmt = TD.getTypeStoreSizeInBits(NTy) -
742 TD.getTypeStoreSizeInBits(ToType) - Offset;
747 // Note: we support negative bitwidths (with shl) which are not defined.
748 // We do this to support (f.e.) loads off the end of a structure where
749 // only some bits are used.
750 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
751 FromVal = Builder.CreateLShr(FromVal,
752 ConstantInt::get(FromVal->getType(), ShAmt));
753 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
754 FromVal = Builder.CreateShl(FromVal,
755 ConstantInt::get(FromVal->getType(), -ShAmt));
757 // Finally, unconditionally truncate the integer to the right width.
758 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType);
759 if (LIBitWidth < NTy->getBitWidth())
761 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
763 else if (LIBitWidth > NTy->getBitWidth())
765 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
768 // If the result is an integer, this is a trunc or bitcast.
769 if (ToType->isIntegerTy()) {
771 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
772 // Just do a bitcast, we know the sizes match up.
773 FromVal = Builder.CreateBitCast(FromVal, ToType);
775 // Otherwise must be a pointer.
776 FromVal = Builder.CreateIntToPtr(FromVal, ToType);
778 assert(FromVal->getType() == ToType && "Didn't convert right?");
782 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
783 /// or vector value "Old" at the offset specified by Offset.
785 /// This happens when we are converting an "integer union" to a
786 /// single integer scalar, or when we are converting a "vector union" to a
787 /// vector with insert/extractelement instructions.
789 /// Offset is an offset from the original alloca, in bits that need to be
790 /// shifted to the right.
791 Value *ConvertToScalarInfo::
792 ConvertScalar_InsertValue(Value *SV, Value *Old,
793 uint64_t Offset, IRBuilder<> &Builder) {
794 // Convert the stored type to the actual type, shift it left to insert
795 // then 'or' into place.
796 Type *AllocaType = Old->getType();
797 LLVMContext &Context = Old->getContext();
799 if (VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
800 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy);
801 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType());
803 // Changing the whole vector with memset or with an access of a different
805 if (ValSize == VecSize)
806 return Builder.CreateBitCast(SV, AllocaType);
808 // Must be an element insertion.
809 assert(SV->getType() == VTy->getElementType());
810 uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
811 unsigned Elt = Offset/EltSize;
812 return Builder.CreateInsertElement(Old, SV, Builder.getInt32(Elt));
815 // If SV is a first-class aggregate value, insert each value recursively.
816 if (StructType *ST = dyn_cast<StructType>(SV->getType())) {
817 const StructLayout &Layout = *TD.getStructLayout(ST);
818 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
819 Value *Elt = Builder.CreateExtractValue(SV, i);
820 Old = ConvertScalar_InsertValue(Elt, Old,
821 Offset+Layout.getElementOffsetInBits(i),
827 if (ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
828 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
829 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
830 Value *Elt = Builder.CreateExtractValue(SV, i);
831 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
836 // If SV is a float, convert it to the appropriate integer type.
837 // If it is a pointer, do the same.
838 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType());
839 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType);
840 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType());
841 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType);
842 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
843 SV = Builder.CreateBitCast(SV, IntegerType::get(SV->getContext(),SrcWidth));
844 else if (SV->getType()->isPointerTy())
845 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()));
847 // Zero extend or truncate the value if needed.
848 if (SV->getType() != AllocaType) {
849 if (SV->getType()->getPrimitiveSizeInBits() <
850 AllocaType->getPrimitiveSizeInBits())
851 SV = Builder.CreateZExt(SV, AllocaType);
853 // Truncation may be needed if storing more than the alloca can hold
854 // (undefined behavior).
855 SV = Builder.CreateTrunc(SV, AllocaType);
856 SrcWidth = DestWidth;
857 SrcStoreWidth = DestStoreWidth;
861 // If this is a big-endian system and the store is narrower than the
862 // full alloca type, we need to do a shift to get the right bits.
864 if (TD.isBigEndian()) {
865 // On big-endian machines, the lowest bit is stored at the bit offset
866 // from the pointer given by getTypeStoreSizeInBits. This matters for
867 // integers with a bitwidth that is not a multiple of 8.
868 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
873 // Note: we support negative bitwidths (with shr) which are not defined.
874 // We do this to support (f.e.) stores off the end of a structure where
875 // only some bits in the structure are set.
876 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
877 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
878 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), ShAmt));
880 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
881 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), -ShAmt));
882 Mask = Mask.lshr(-ShAmt);
885 // Mask out the bits we are about to insert from the old value, and or
887 if (SrcWidth != DestWidth) {
888 assert(DestWidth > SrcWidth);
889 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
890 SV = Builder.CreateOr(Old, SV, "ins");
896 //===----------------------------------------------------------------------===//
898 //===----------------------------------------------------------------------===//
901 bool SROA::runOnFunction(Function &F) {
902 TD = getAnalysisIfAvailable<TargetData>();
904 bool Changed = performPromotion(F);
906 // FIXME: ScalarRepl currently depends on TargetData more than it
907 // theoretically needs to. It should be refactored in order to support
908 // target-independent IR. Until this is done, just skip the actual
909 // scalar-replacement portion of this pass.
910 if (!TD) return Changed;
913 bool LocalChange = performScalarRepl(F);
914 if (!LocalChange) break; // No need to repromote if no scalarrepl
916 LocalChange = performPromotion(F);
917 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
924 class AllocaPromoter : public LoadAndStorePromoter {
927 SmallVector<DbgDeclareInst *, 4> DDIs;
928 SmallVector<DbgValueInst *, 4> DVIs;
930 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S,
932 : LoadAndStorePromoter(Insts, S), AI(0), DIB(DB) {}
934 void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) {
935 // Remember which alloca we're promoting (for isInstInList).
937 if (MDNode *DebugNode = MDNode::getIfExists(AI->getContext(), AI))
938 for (Value::use_iterator UI = DebugNode->use_begin(),
939 E = DebugNode->use_end(); UI != E; ++UI)
940 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(*UI))
942 else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(*UI))
945 LoadAndStorePromoter::run(Insts);
946 AI->eraseFromParent();
947 for (SmallVector<DbgDeclareInst *, 4>::iterator I = DDIs.begin(),
948 E = DDIs.end(); I != E; ++I) {
949 DbgDeclareInst *DDI = *I;
950 DDI->eraseFromParent();
952 for (SmallVector<DbgValueInst *, 4>::iterator I = DVIs.begin(),
953 E = DVIs.end(); I != E; ++I) {
954 DbgValueInst *DVI = *I;
955 DVI->eraseFromParent();
959 virtual bool isInstInList(Instruction *I,
960 const SmallVectorImpl<Instruction*> &Insts) const {
961 if (LoadInst *LI = dyn_cast<LoadInst>(I))
962 return LI->getOperand(0) == AI;
963 return cast<StoreInst>(I)->getPointerOperand() == AI;
966 virtual void updateDebugInfo(Instruction *Inst) const {
967 for (SmallVector<DbgDeclareInst *, 4>::const_iterator I = DDIs.begin(),
968 E = DDIs.end(); I != E; ++I) {
969 DbgDeclareInst *DDI = *I;
970 if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
971 ConvertDebugDeclareToDebugValue(DDI, SI, *DIB);
972 else if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
973 ConvertDebugDeclareToDebugValue(DDI, LI, *DIB);
975 for (SmallVector<DbgValueInst *, 4>::const_iterator I = DVIs.begin(),
976 E = DVIs.end(); I != E; ++I) {
977 DbgValueInst *DVI = *I;
978 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
979 Instruction *DbgVal = NULL;
980 // If an argument is zero extended then use argument directly. The ZExt
981 // may be zapped by an optimization pass in future.
982 Argument *ExtendedArg = NULL;
983 if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
984 ExtendedArg = dyn_cast<Argument>(ZExt->getOperand(0));
985 if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
986 ExtendedArg = dyn_cast<Argument>(SExt->getOperand(0));
988 DbgVal = DIB->insertDbgValueIntrinsic(ExtendedArg, 0,
989 DIVariable(DVI->getVariable()),
992 DbgVal = DIB->insertDbgValueIntrinsic(SI->getOperand(0), 0,
993 DIVariable(DVI->getVariable()),
995 DbgVal->setDebugLoc(DVI->getDebugLoc());
996 } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
997 Instruction *DbgVal =
998 DIB->insertDbgValueIntrinsic(LI->getOperand(0), 0,
999 DIVariable(DVI->getVariable()), LI);
1000 DbgVal->setDebugLoc(DVI->getDebugLoc());
1005 } // end anon namespace
1007 /// isSafeSelectToSpeculate - Select instructions that use an alloca and are
1008 /// subsequently loaded can be rewritten to load both input pointers and then
1009 /// select between the result, allowing the load of the alloca to be promoted.
1011 /// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
1012 /// %V = load i32* %P2
1014 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1015 /// %V2 = load i32* %Other
1016 /// %V = select i1 %cond, i32 %V1, i32 %V2
1018 /// We can do this to a select if its only uses are loads and if the operand to
1019 /// the select can be loaded unconditionally.
1020 static bool isSafeSelectToSpeculate(SelectInst *SI, const TargetData *TD) {
1021 bool TDerefable = SI->getTrueValue()->isDereferenceablePointer();
1022 bool FDerefable = SI->getFalseValue()->isDereferenceablePointer();
1024 for (Value::use_iterator UI = SI->use_begin(), UE = SI->use_end();
1026 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1027 if (LI == 0 || !LI->isSimple()) return false;
1029 // Both operands to the select need to be dereferencable, either absolutely
1030 // (e.g. allocas) or at this point because we can see other accesses to it.
1031 if (!TDerefable && !isSafeToLoadUnconditionally(SI->getTrueValue(), LI,
1032 LI->getAlignment(), TD))
1034 if (!FDerefable && !isSafeToLoadUnconditionally(SI->getFalseValue(), LI,
1035 LI->getAlignment(), TD))
1042 /// isSafePHIToSpeculate - PHI instructions that use an alloca and are
1043 /// subsequently loaded can be rewritten to load both input pointers in the pred
1044 /// blocks and then PHI the results, allowing the load of the alloca to be
1047 /// %P2 = phi [i32* %Alloca, i32* %Other]
1048 /// %V = load i32* %P2
1050 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1052 /// %V2 = load i32* %Other
1054 /// %V = phi [i32 %V1, i32 %V2]
1056 /// We can do this to a select if its only uses are loads and if the operand to
1057 /// the select can be loaded unconditionally.
1058 static bool isSafePHIToSpeculate(PHINode *PN, const TargetData *TD) {
1059 // For now, we can only do this promotion if the load is in the same block as
1060 // the PHI, and if there are no stores between the phi and load.
1061 // TODO: Allow recursive phi users.
1062 // TODO: Allow stores.
1063 BasicBlock *BB = PN->getParent();
1064 unsigned MaxAlign = 0;
1065 for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end();
1067 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1068 if (LI == 0 || !LI->isSimple()) return false;
1070 // For now we only allow loads in the same block as the PHI. This is a
1071 // common case that happens when instcombine merges two loads through a PHI.
1072 if (LI->getParent() != BB) return false;
1074 // Ensure that there are no instructions between the PHI and the load that
1076 for (BasicBlock::iterator BBI = PN; &*BBI != LI; ++BBI)
1077 if (BBI->mayWriteToMemory())
1080 MaxAlign = std::max(MaxAlign, LI->getAlignment());
1083 // Okay, we know that we have one or more loads in the same block as the PHI.
1084 // We can transform this if it is safe to push the loads into the predecessor
1085 // blocks. The only thing to watch out for is that we can't put a possibly
1086 // trapping load in the predecessor if it is a critical edge.
1087 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1088 BasicBlock *Pred = PN->getIncomingBlock(i);
1089 Value *InVal = PN->getIncomingValue(i);
1091 // If the terminator of the predecessor has side-effects (an invoke),
1092 // there is no safe place to put a load in the predecessor.
1093 if (Pred->getTerminator()->mayHaveSideEffects())
1096 // If the value is produced by the terminator of the predecessor
1097 // (an invoke), there is no valid place to put a load in the predecessor.
1098 if (Pred->getTerminator() == InVal)
1101 // If the predecessor has a single successor, then the edge isn't critical.
1102 if (Pred->getTerminator()->getNumSuccessors() == 1)
1105 // If this pointer is always safe to load, or if we can prove that there is
1106 // already a load in the block, then we can move the load to the pred block.
1107 if (InVal->isDereferenceablePointer() ||
1108 isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign, TD))
1118 /// tryToMakeAllocaBePromotable - This returns true if the alloca only has
1119 /// direct (non-volatile) loads and stores to it. If the alloca is close but
1120 /// not quite there, this will transform the code to allow promotion. As such,
1121 /// it is a non-pure predicate.
1122 static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const TargetData *TD) {
1123 SetVector<Instruction*, SmallVector<Instruction*, 4>,
1124 SmallPtrSet<Instruction*, 4> > InstsToRewrite;
1126 for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end();
1129 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1130 if (!LI->isSimple())
1135 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1136 if (SI->getOperand(0) == AI || !SI->isSimple())
1137 return false; // Don't allow a store OF the AI, only INTO the AI.
1141 if (SelectInst *SI = dyn_cast<SelectInst>(U)) {
1142 // If the condition being selected on is a constant, fold the select, yes
1143 // this does (rarely) happen early on.
1144 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) {
1145 Value *Result = SI->getOperand(1+CI->isZero());
1146 SI->replaceAllUsesWith(Result);
1147 SI->eraseFromParent();
1149 // This is very rare and we just scrambled the use list of AI, start
1151 return tryToMakeAllocaBePromotable(AI, TD);
1154 // If it is safe to turn "load (select c, AI, ptr)" into a select of two
1155 // loads, then we can transform this by rewriting the select.
1156 if (!isSafeSelectToSpeculate(SI, TD))
1159 InstsToRewrite.insert(SI);
1163 if (PHINode *PN = dyn_cast<PHINode>(U)) {
1164 if (PN->use_empty()) { // Dead PHIs can be stripped.
1165 InstsToRewrite.insert(PN);
1169 // If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads
1170 // in the pred blocks, then we can transform this by rewriting the PHI.
1171 if (!isSafePHIToSpeculate(PN, TD))
1174 InstsToRewrite.insert(PN);
1178 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
1179 if (onlyUsedByLifetimeMarkers(BCI)) {
1180 InstsToRewrite.insert(BCI);
1188 // If there are no instructions to rewrite, then all uses are load/stores and
1190 if (InstsToRewrite.empty())
1193 // If we have instructions that need to be rewritten for this to be promotable
1194 // take care of it now.
1195 for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) {
1196 if (BitCastInst *BCI = dyn_cast<BitCastInst>(InstsToRewrite[i])) {
1197 // This could only be a bitcast used by nothing but lifetime intrinsics.
1198 for (BitCastInst::use_iterator I = BCI->use_begin(), E = BCI->use_end();
1200 Use &U = I.getUse();
1202 cast<Instruction>(U.getUser())->eraseFromParent();
1204 BCI->eraseFromParent();
1208 if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) {
1209 // Selects in InstsToRewrite only have load uses. Rewrite each as two
1210 // loads with a new select.
1211 while (!SI->use_empty()) {
1212 LoadInst *LI = cast<LoadInst>(SI->use_back());
1214 IRBuilder<> Builder(LI);
1215 LoadInst *TrueLoad =
1216 Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t");
1217 LoadInst *FalseLoad =
1218 Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".f");
1220 // Transfer alignment and TBAA info if present.
1221 TrueLoad->setAlignment(LI->getAlignment());
1222 FalseLoad->setAlignment(LI->getAlignment());
1223 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) {
1224 TrueLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1225 FalseLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1228 Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad);
1230 LI->replaceAllUsesWith(V);
1231 LI->eraseFromParent();
1234 // Now that all the loads are gone, the select is gone too.
1235 SI->eraseFromParent();
1239 // Otherwise, we have a PHI node which allows us to push the loads into the
1241 PHINode *PN = cast<PHINode>(InstsToRewrite[i]);
1242 if (PN->use_empty()) {
1243 PN->eraseFromParent();
1247 Type *LoadTy = cast<PointerType>(PN->getType())->getElementType();
1248 PHINode *NewPN = PHINode::Create(LoadTy, PN->getNumIncomingValues(),
1249 PN->getName()+".ld", PN);
1251 // Get the TBAA tag and alignment to use from one of the loads. It doesn't
1252 // matter which one we get and if any differ, it doesn't matter.
1253 LoadInst *SomeLoad = cast<LoadInst>(PN->use_back());
1254 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa);
1255 unsigned Align = SomeLoad->getAlignment();
1257 // Rewrite all loads of the PN to use the new PHI.
1258 while (!PN->use_empty()) {
1259 LoadInst *LI = cast<LoadInst>(PN->use_back());
1260 LI->replaceAllUsesWith(NewPN);
1261 LI->eraseFromParent();
1264 // Inject loads into all of the pred blocks. Keep track of which blocks we
1265 // insert them into in case we have multiple edges from the same block.
1266 DenseMap<BasicBlock*, LoadInst*> InsertedLoads;
1268 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1269 BasicBlock *Pred = PN->getIncomingBlock(i);
1270 LoadInst *&Load = InsertedLoads[Pred];
1272 Load = new LoadInst(PN->getIncomingValue(i),
1273 PN->getName() + "." + Pred->getName(),
1274 Pred->getTerminator());
1275 Load->setAlignment(Align);
1276 if (TBAATag) Load->setMetadata(LLVMContext::MD_tbaa, TBAATag);
1279 NewPN->addIncoming(Load, Pred);
1282 PN->eraseFromParent();
1289 bool SROA::performPromotion(Function &F) {
1290 std::vector<AllocaInst*> Allocas;
1291 DominatorTree *DT = 0;
1293 DT = &getAnalysis<DominatorTree>();
1295 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
1296 DIBuilder DIB(*F.getParent());
1297 bool Changed = false;
1298 SmallVector<Instruction*, 64> Insts;
1302 // Find allocas that are safe to promote, by looking at all instructions in
1304 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
1305 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
1306 if (tryToMakeAllocaBePromotable(AI, TD))
1307 Allocas.push_back(AI);
1309 if (Allocas.empty()) break;
1312 PromoteMemToReg(Allocas, *DT);
1315 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
1316 AllocaInst *AI = Allocas[i];
1318 // Build list of instructions to promote.
1319 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
1321 Insts.push_back(cast<Instruction>(*UI));
1322 AllocaPromoter(Insts, SSA, &DIB).run(AI, Insts);
1326 NumPromoted += Allocas.size();
1334 /// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
1335 /// SROA. It must be a struct or array type with a small number of elements.
1336 static bool ShouldAttemptScalarRepl(AllocaInst *AI) {
1337 Type *T = AI->getAllocatedType();
1338 // Do not promote any struct into more than 32 separate vars.
1339 if (StructType *ST = dyn_cast<StructType>(T))
1340 return ST->getNumElements() <= 32;
1341 // Arrays are much less likely to be safe for SROA; only consider
1342 // them if they are very small.
1343 if (ArrayType *AT = dyn_cast<ArrayType>(T))
1344 return AT->getNumElements() <= 8;
1349 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
1350 // which runs on all of the alloca instructions in the function, removing them
1351 // if they are only used by getelementptr instructions.
1353 bool SROA::performScalarRepl(Function &F) {
1354 std::vector<AllocaInst*> WorkList;
1356 // Scan the entry basic block, adding allocas to the worklist.
1357 BasicBlock &BB = F.getEntryBlock();
1358 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
1359 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
1360 WorkList.push_back(A);
1362 // Process the worklist
1363 bool Changed = false;
1364 while (!WorkList.empty()) {
1365 AllocaInst *AI = WorkList.back();
1366 WorkList.pop_back();
1368 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
1369 // with unused elements.
1370 if (AI->use_empty()) {
1371 AI->eraseFromParent();
1376 // If this alloca is impossible for us to promote, reject it early.
1377 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
1380 // Check to see if this allocation is only modified by a memcpy/memmove from
1381 // a constant global. If this is the case, we can change all users to use
1382 // the constant global instead. This is commonly produced by the CFE by
1383 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
1384 // is only subsequently read.
1385 SmallVector<Instruction *, 4> ToDelete;
1386 if (MemTransferInst *Copy = isOnlyCopiedFromConstantGlobal(AI, ToDelete)) {
1387 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n');
1388 DEBUG(dbgs() << " memcpy = " << *Copy << '\n');
1389 for (unsigned i = 0, e = ToDelete.size(); i != e; ++i)
1390 ToDelete[i]->eraseFromParent();
1391 Constant *TheSrc = cast<Constant>(Copy->getSource());
1392 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
1393 Copy->eraseFromParent(); // Don't mutate the global.
1394 AI->eraseFromParent();
1400 // Check to see if we can perform the core SROA transformation. We cannot
1401 // transform the allocation instruction if it is an array allocation
1402 // (allocations OF arrays are ok though), and an allocation of a scalar
1403 // value cannot be decomposed at all.
1404 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
1406 // Do not promote [0 x %struct].
1407 if (AllocaSize == 0) continue;
1409 // Do not promote any struct whose size is too big.
1410 if (AllocaSize > SRThreshold) continue;
1412 // If the alloca looks like a good candidate for scalar replacement, and if
1413 // all its users can be transformed, then split up the aggregate into its
1414 // separate elements.
1415 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
1416 DoScalarReplacement(AI, WorkList);
1421 // If we can turn this aggregate value (potentially with casts) into a
1422 // simple scalar value that can be mem2reg'd into a register value.
1423 // IsNotTrivial tracks whether this is something that mem2reg could have
1424 // promoted itself. If so, we don't want to transform it needlessly. Note
1425 // that we can't just check based on the type: the alloca may be of an i32
1426 // but that has pointer arithmetic to set byte 3 of it or something.
1427 if (AllocaInst *NewAI =
1428 ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) {
1429 NewAI->takeName(AI);
1430 AI->eraseFromParent();
1436 // Otherwise, couldn't process this alloca.
1442 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
1443 /// predicate, do SROA now.
1444 void SROA::DoScalarReplacement(AllocaInst *AI,
1445 std::vector<AllocaInst*> &WorkList) {
1446 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
1447 SmallVector<AllocaInst*, 32> ElementAllocas;
1448 if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
1449 ElementAllocas.reserve(ST->getNumContainedTypes());
1450 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
1451 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
1453 AI->getName() + "." + Twine(i), AI);
1454 ElementAllocas.push_back(NA);
1455 WorkList.push_back(NA); // Add to worklist for recursive processing
1458 ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
1459 ElementAllocas.reserve(AT->getNumElements());
1460 Type *ElTy = AT->getElementType();
1461 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1462 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
1463 AI->getName() + "." + Twine(i), AI);
1464 ElementAllocas.push_back(NA);
1465 WorkList.push_back(NA); // Add to worklist for recursive processing
1469 // Now that we have created the new alloca instructions, rewrite all the
1470 // uses of the old alloca.
1471 RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
1473 // Now erase any instructions that were made dead while rewriting the alloca.
1474 DeleteDeadInstructions();
1475 AI->eraseFromParent();
1480 /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
1481 /// recursively including all their operands that become trivially dead.
1482 void SROA::DeleteDeadInstructions() {
1483 while (!DeadInsts.empty()) {
1484 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
1486 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
1487 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
1488 // Zero out the operand and see if it becomes trivially dead.
1489 // (But, don't add allocas to the dead instruction list -- they are
1490 // already on the worklist and will be deleted separately.)
1492 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
1493 DeadInsts.push_back(U);
1496 I->eraseFromParent();
1500 /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
1501 /// performing scalar replacement of alloca AI. The results are flagged in
1502 /// the Info parameter. Offset indicates the position within AI that is
1503 /// referenced by this instruction.
1504 void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset,
1506 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1507 Instruction *User = cast<Instruction>(*UI);
1509 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1510 isSafeForScalarRepl(BC, Offset, Info);
1511 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1512 uint64_t GEPOffset = Offset;
1513 isSafeGEP(GEPI, GEPOffset, Info);
1515 isSafeForScalarRepl(GEPI, GEPOffset, Info);
1516 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1517 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1519 return MarkUnsafe(Info, User);
1520 isSafeMemAccess(Offset, Length->getZExtValue(), 0,
1521 UI.getOperandNo() == 0, Info, MI,
1522 true /*AllowWholeAccess*/);
1523 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1524 if (!LI->isSimple())
1525 return MarkUnsafe(Info, User);
1526 Type *LIType = LI->getType();
1527 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
1528 LIType, false, Info, LI, true /*AllowWholeAccess*/);
1529 Info.hasALoadOrStore = true;
1531 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1532 // Store is ok if storing INTO the pointer, not storing the pointer
1533 if (!SI->isSimple() || SI->getOperand(0) == I)
1534 return MarkUnsafe(Info, User);
1536 Type *SIType = SI->getOperand(0)->getType();
1537 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
1538 SIType, true, Info, SI, true /*AllowWholeAccess*/);
1539 Info.hasALoadOrStore = true;
1540 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
1541 if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
1542 II->getIntrinsicID() != Intrinsic::lifetime_end)
1543 return MarkUnsafe(Info, User);
1544 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
1545 isSafePHISelectUseForScalarRepl(User, Offset, Info);
1547 return MarkUnsafe(Info, User);
1549 if (Info.isUnsafe) return;
1554 /// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer
1555 /// derived from the alloca, we can often still split the alloca into elements.
1556 /// This is useful if we have a large alloca where one element is phi'd
1557 /// together somewhere: we can SRoA and promote all the other elements even if
1558 /// we end up not being able to promote this one.
1560 /// All we require is that the uses of the PHI do not index into other parts of
1561 /// the alloca. The most important use case for this is single load and stores
1562 /// that are PHI'd together, which can happen due to code sinking.
1563 void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset,
1565 // If we've already checked this PHI, don't do it again.
1566 if (PHINode *PN = dyn_cast<PHINode>(I))
1567 if (!Info.CheckedPHIs.insert(PN))
1570 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1571 Instruction *User = cast<Instruction>(*UI);
1573 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1574 isSafePHISelectUseForScalarRepl(BC, Offset, Info);
1575 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1576 // Only allow "bitcast" GEPs for simplicity. We could generalize this,
1577 // but would have to prove that we're staying inside of an element being
1579 if (!GEPI->hasAllZeroIndices())
1580 return MarkUnsafe(Info, User);
1581 isSafePHISelectUseForScalarRepl(GEPI, Offset, Info);
1582 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1583 if (!LI->isSimple())
1584 return MarkUnsafe(Info, User);
1585 Type *LIType = LI->getType();
1586 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
1587 LIType, false, Info, LI, false /*AllowWholeAccess*/);
1588 Info.hasALoadOrStore = true;
1590 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1591 // Store is ok if storing INTO the pointer, not storing the pointer
1592 if (!SI->isSimple() || SI->getOperand(0) == I)
1593 return MarkUnsafe(Info, User);
1595 Type *SIType = SI->getOperand(0)->getType();
1596 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
1597 SIType, true, Info, SI, false /*AllowWholeAccess*/);
1598 Info.hasALoadOrStore = true;
1599 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
1600 isSafePHISelectUseForScalarRepl(User, Offset, Info);
1602 return MarkUnsafe(Info, User);
1604 if (Info.isUnsafe) return;
1608 /// isSafeGEP - Check if a GEP instruction can be handled for scalar
1609 /// replacement. It is safe when all the indices are constant, in-bounds
1610 /// references, and when the resulting offset corresponds to an element within
1611 /// the alloca type. The results are flagged in the Info parameter. Upon
1612 /// return, Offset is adjusted as specified by the GEP indices.
1613 void SROA::isSafeGEP(GetElementPtrInst *GEPI,
1614 uint64_t &Offset, AllocaInfo &Info) {
1615 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
1619 // Walk through the GEP type indices, checking the types that this indexes
1621 for (; GEPIt != E; ++GEPIt) {
1622 // Ignore struct elements, no extra checking needed for these.
1623 if ((*GEPIt)->isStructTy())
1626 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
1628 return MarkUnsafe(Info, GEPI);
1631 // Compute the offset due to this GEP and check if the alloca has a
1632 // component element at that offset.
1633 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1634 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), Indices);
1635 if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset, 0))
1636 MarkUnsafe(Info, GEPI);
1639 /// isHomogeneousAggregate - Check if type T is a struct or array containing
1640 /// elements of the same type (which is always true for arrays). If so,
1641 /// return true with NumElts and EltTy set to the number of elements and the
1642 /// element type, respectively.
1643 static bool isHomogeneousAggregate(Type *T, unsigned &NumElts,
1645 if (ArrayType *AT = dyn_cast<ArrayType>(T)) {
1646 NumElts = AT->getNumElements();
1647 EltTy = (NumElts == 0 ? 0 : AT->getElementType());
1650 if (StructType *ST = dyn_cast<StructType>(T)) {
1651 NumElts = ST->getNumContainedTypes();
1652 EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0));
1653 for (unsigned n = 1; n < NumElts; ++n) {
1654 if (ST->getContainedType(n) != EltTy)
1662 /// isCompatibleAggregate - Check if T1 and T2 are either the same type or are
1663 /// "homogeneous" aggregates with the same element type and number of elements.
1664 static bool isCompatibleAggregate(Type *T1, Type *T2) {
1668 unsigned NumElts1, NumElts2;
1669 Type *EltTy1, *EltTy2;
1670 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) &&
1671 isHomogeneousAggregate(T2, NumElts2, EltTy2) &&
1672 NumElts1 == NumElts2 &&
1679 /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
1680 /// alloca or has an offset and size that corresponds to a component element
1681 /// within it. The offset checked here may have been formed from a GEP with a
1682 /// pointer bitcasted to a different type.
1684 /// If AllowWholeAccess is true, then this allows uses of the entire alloca as a
1685 /// unit. If false, it only allows accesses known to be in a single element.
1686 void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
1687 Type *MemOpType, bool isStore,
1688 AllocaInfo &Info, Instruction *TheAccess,
1689 bool AllowWholeAccess) {
1690 // Check if this is a load/store of the entire alloca.
1691 if (Offset == 0 && AllowWholeAccess &&
1692 MemSize == TD->getTypeAllocSize(Info.AI->getAllocatedType())) {
1693 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer
1694 // loads/stores (which are essentially the same as the MemIntrinsics with
1695 // regard to copying padding between elements). But, if an alloca is
1696 // flagged as both a source and destination of such operations, we'll need
1697 // to check later for padding between elements.
1698 if (!MemOpType || MemOpType->isIntegerTy()) {
1700 Info.isMemCpyDst = true;
1702 Info.isMemCpySrc = true;
1705 // This is also safe for references using a type that is compatible with
1706 // the type of the alloca, so that loads/stores can be rewritten using
1707 // insertvalue/extractvalue.
1708 if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) {
1709 Info.hasSubelementAccess = true;
1713 // Check if the offset/size correspond to a component within the alloca type.
1714 Type *T = Info.AI->getAllocatedType();
1715 if (TypeHasComponent(T, Offset, MemSize)) {
1716 Info.hasSubelementAccess = true;
1720 return MarkUnsafe(Info, TheAccess);
1723 /// TypeHasComponent - Return true if T has a component type with the
1724 /// specified offset and size. If Size is zero, do not check the size.
1725 bool SROA::TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size) {
1728 if (StructType *ST = dyn_cast<StructType>(T)) {
1729 const StructLayout *Layout = TD->getStructLayout(ST);
1730 unsigned EltIdx = Layout->getElementContainingOffset(Offset);
1731 EltTy = ST->getContainedType(EltIdx);
1732 EltSize = TD->getTypeAllocSize(EltTy);
1733 Offset -= Layout->getElementOffset(EltIdx);
1734 } else if (ArrayType *AT = dyn_cast<ArrayType>(T)) {
1735 EltTy = AT->getElementType();
1736 EltSize = TD->getTypeAllocSize(EltTy);
1737 if (Offset >= AT->getNumElements() * EltSize)
1743 if (Offset == 0 && (Size == 0 || EltSize == Size))
1745 // Check if the component spans multiple elements.
1746 if (Offset + Size > EltSize)
1748 return TypeHasComponent(EltTy, Offset, Size);
1751 /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
1752 /// the instruction I, which references it, to use the separate elements.
1753 /// Offset indicates the position within AI that is referenced by this
1755 void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1756 SmallVector<AllocaInst*, 32> &NewElts) {
1757 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) {
1758 Use &TheUse = UI.getUse();
1759 Instruction *User = cast<Instruction>(*UI++);
1761 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1762 RewriteBitCast(BC, AI, Offset, NewElts);
1766 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1767 RewriteGEP(GEPI, AI, Offset, NewElts);
1771 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1772 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1773 uint64_t MemSize = Length->getZExtValue();
1775 MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
1776 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
1777 // Otherwise the intrinsic can only touch a single element and the
1778 // address operand will be updated, so nothing else needs to be done.
1782 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
1783 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
1784 II->getIntrinsicID() == Intrinsic::lifetime_end) {
1785 RewriteLifetimeIntrinsic(II, AI, Offset, NewElts);
1790 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1791 Type *LIType = LI->getType();
1793 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) {
1795 // %res = load { i32, i32 }* %alloc
1797 // %load.0 = load i32* %alloc.0
1798 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
1799 // %load.1 = load i32* %alloc.1
1800 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
1801 // (Also works for arrays instead of structs)
1802 Value *Insert = UndefValue::get(LIType);
1803 IRBuilder<> Builder(LI);
1804 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1805 Value *Load = Builder.CreateLoad(NewElts[i], "load");
1806 Insert = Builder.CreateInsertValue(Insert, Load, i, "insert");
1808 LI->replaceAllUsesWith(Insert);
1809 DeadInsts.push_back(LI);
1810 } else if (LIType->isIntegerTy() &&
1811 TD->getTypeAllocSize(LIType) ==
1812 TD->getTypeAllocSize(AI->getAllocatedType())) {
1813 // If this is a load of the entire alloca to an integer, rewrite it.
1814 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
1819 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1820 Value *Val = SI->getOperand(0);
1821 Type *SIType = Val->getType();
1822 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) {
1824 // store { i32, i32 } %val, { i32, i32 }* %alloc
1826 // %val.0 = extractvalue { i32, i32 } %val, 0
1827 // store i32 %val.0, i32* %alloc.0
1828 // %val.1 = extractvalue { i32, i32 } %val, 1
1829 // store i32 %val.1, i32* %alloc.1
1830 // (Also works for arrays instead of structs)
1831 IRBuilder<> Builder(SI);
1832 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1833 Value *Extract = Builder.CreateExtractValue(Val, i, Val->getName());
1834 Builder.CreateStore(Extract, NewElts[i]);
1836 DeadInsts.push_back(SI);
1837 } else if (SIType->isIntegerTy() &&
1838 TD->getTypeAllocSize(SIType) ==
1839 TD->getTypeAllocSize(AI->getAllocatedType())) {
1840 // If this is a store of the entire alloca from an integer, rewrite it.
1841 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
1846 if (isa<SelectInst>(User) || isa<PHINode>(User)) {
1847 // If we have a PHI user of the alloca itself (as opposed to a GEP or
1848 // bitcast) we have to rewrite it. GEP and bitcast uses will be RAUW'd to
1850 if (!isa<AllocaInst>(I)) continue;
1852 assert(Offset == 0 && NewElts[0] &&
1853 "Direct alloca use should have a zero offset");
1855 // If we have a use of the alloca, we know the derived uses will be
1856 // utilizing just the first element of the scalarized result. Insert a
1857 // bitcast of the first alloca before the user as required.
1858 AllocaInst *NewAI = NewElts[0];
1859 BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI);
1860 NewAI->moveBefore(BCI);
1867 /// RewriteBitCast - Update a bitcast reference to the alloca being replaced
1868 /// and recursively continue updating all of its uses.
1869 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
1870 SmallVector<AllocaInst*, 32> &NewElts) {
1871 RewriteForScalarRepl(BC, AI, Offset, NewElts);
1872 if (BC->getOperand(0) != AI)
1875 // The bitcast references the original alloca. Replace its uses with
1876 // references to the first new element alloca.
1877 Instruction *Val = NewElts[0];
1878 if (Val->getType() != BC->getDestTy()) {
1879 Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
1882 BC->replaceAllUsesWith(Val);
1883 DeadInsts.push_back(BC);
1886 /// FindElementAndOffset - Return the index of the element containing Offset
1887 /// within the specified type, which must be either a struct or an array.
1888 /// Sets T to the type of the element and Offset to the offset within that
1889 /// element. IdxTy is set to the type of the index result to be used in a
1890 /// GEP instruction.
1891 uint64_t SROA::FindElementAndOffset(Type *&T, uint64_t &Offset,
1894 if (StructType *ST = dyn_cast<StructType>(T)) {
1895 const StructLayout *Layout = TD->getStructLayout(ST);
1896 Idx = Layout->getElementContainingOffset(Offset);
1897 T = ST->getContainedType(Idx);
1898 Offset -= Layout->getElementOffset(Idx);
1899 IdxTy = Type::getInt32Ty(T->getContext());
1902 ArrayType *AT = cast<ArrayType>(T);
1903 T = AT->getElementType();
1904 uint64_t EltSize = TD->getTypeAllocSize(T);
1905 Idx = Offset / EltSize;
1906 Offset -= Idx * EltSize;
1907 IdxTy = Type::getInt64Ty(T->getContext());
1911 /// RewriteGEP - Check if this GEP instruction moves the pointer across
1912 /// elements of the alloca that are being split apart, and if so, rewrite
1913 /// the GEP to be relative to the new element.
1914 void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
1915 SmallVector<AllocaInst*, 32> &NewElts) {
1916 uint64_t OldOffset = Offset;
1917 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1918 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), Indices);
1920 RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
1922 Type *T = AI->getAllocatedType();
1924 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
1925 if (GEPI->getOperand(0) == AI)
1926 OldIdx = ~0ULL; // Force the GEP to be rewritten.
1928 T = AI->getAllocatedType();
1929 uint64_t EltOffset = Offset;
1930 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
1932 // If this GEP does not move the pointer across elements of the alloca
1933 // being split, then it does not needs to be rewritten.
1937 Type *i32Ty = Type::getInt32Ty(AI->getContext());
1938 SmallVector<Value*, 8> NewArgs;
1939 NewArgs.push_back(Constant::getNullValue(i32Ty));
1940 while (EltOffset != 0) {
1941 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
1942 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
1944 Instruction *Val = NewElts[Idx];
1945 if (NewArgs.size() > 1) {
1946 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs, "", GEPI);
1947 Val->takeName(GEPI);
1949 if (Val->getType() != GEPI->getType())
1950 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
1951 GEPI->replaceAllUsesWith(Val);
1952 DeadInsts.push_back(GEPI);
1955 /// RewriteLifetimeIntrinsic - II is a lifetime.start/lifetime.end. Rewrite it
1956 /// to mark the lifetime of the scalarized memory.
1957 void SROA::RewriteLifetimeIntrinsic(IntrinsicInst *II, AllocaInst *AI,
1959 SmallVector<AllocaInst*, 32> &NewElts) {
1960 ConstantInt *OldSize = cast<ConstantInt>(II->getArgOperand(0));
1961 // Put matching lifetime markers on everything from Offset up to
1963 Type *AIType = AI->getAllocatedType();
1964 uint64_t NewOffset = Offset;
1966 uint64_t Idx = FindElementAndOffset(AIType, NewOffset, IdxTy);
1968 IRBuilder<> Builder(II);
1969 uint64_t Size = OldSize->getLimitedValue();
1972 // Splice the first element and index 'NewOffset' bytes in. SROA will
1973 // split the alloca again later.
1974 Value *V = Builder.CreateBitCast(NewElts[Idx], Builder.getInt8PtrTy());
1975 V = Builder.CreateGEP(V, Builder.getInt64(NewOffset));
1977 IdxTy = NewElts[Idx]->getAllocatedType();
1978 uint64_t EltSize = TD->getTypeAllocSize(IdxTy) - NewOffset;
1979 if (EltSize > Size) {
1985 if (II->getIntrinsicID() == Intrinsic::lifetime_start)
1986 Builder.CreateLifetimeStart(V, Builder.getInt64(EltSize));
1988 Builder.CreateLifetimeEnd(V, Builder.getInt64(EltSize));
1992 for (; Idx != NewElts.size() && Size; ++Idx) {
1993 IdxTy = NewElts[Idx]->getAllocatedType();
1994 uint64_t EltSize = TD->getTypeAllocSize(IdxTy);
1995 if (EltSize > Size) {
2001 if (II->getIntrinsicID() == Intrinsic::lifetime_start)
2002 Builder.CreateLifetimeStart(NewElts[Idx],
2003 Builder.getInt64(EltSize));
2005 Builder.CreateLifetimeEnd(NewElts[Idx],
2006 Builder.getInt64(EltSize));
2008 DeadInsts.push_back(II);
2011 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
2012 /// Rewrite it to copy or set the elements of the scalarized memory.
2013 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
2015 SmallVector<AllocaInst*, 32> &NewElts) {
2016 // If this is a memcpy/memmove, construct the other pointer as the
2017 // appropriate type. The "Other" pointer is the pointer that goes to memory
2018 // that doesn't have anything to do with the alloca that we are promoting. For
2019 // memset, this Value* stays null.
2020 Value *OtherPtr = 0;
2021 unsigned MemAlignment = MI->getAlignment();
2022 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
2023 if (Inst == MTI->getRawDest())
2024 OtherPtr = MTI->getRawSource();
2026 assert(Inst == MTI->getRawSource());
2027 OtherPtr = MTI->getRawDest();
2031 // If there is an other pointer, we want to convert it to the same pointer
2032 // type as AI has, so we can GEP through it safely.
2034 unsigned AddrSpace =
2035 cast<PointerType>(OtherPtr->getType())->getAddressSpace();
2037 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
2038 // optimization, but it's also required to detect the corner case where
2039 // both pointer operands are referencing the same memory, and where
2040 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
2041 // function is only called for mem intrinsics that access the whole
2042 // aggregate, so non-zero GEPs are not an issue here.)
2043 OtherPtr = OtherPtr->stripPointerCasts();
2045 // Copying the alloca to itself is a no-op: just delete it.
2046 if (OtherPtr == AI || OtherPtr == NewElts[0]) {
2047 // This code will run twice for a no-op memcpy -- once for each operand.
2048 // Put only one reference to MI on the DeadInsts list.
2049 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
2050 E = DeadInsts.end(); I != E; ++I)
2051 if (*I == MI) return;
2052 DeadInsts.push_back(MI);
2056 // If the pointer is not the right type, insert a bitcast to the right
2059 PointerType::get(AI->getType()->getElementType(), AddrSpace);
2061 if (OtherPtr->getType() != NewTy)
2062 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
2065 // Process each element of the aggregate.
2066 bool SROADest = MI->getRawDest() == Inst;
2068 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
2070 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2071 // If this is a memcpy/memmove, emit a GEP of the other element address.
2072 Value *OtherElt = 0;
2073 unsigned OtherEltAlign = MemAlignment;
2076 Value *Idx[2] = { Zero,
2077 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
2078 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx,
2079 OtherPtr->getName()+"."+Twine(i),
2082 PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
2083 Type *OtherTy = OtherPtrTy->getElementType();
2084 if (StructType *ST = dyn_cast<StructType>(OtherTy)) {
2085 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
2087 Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
2088 EltOffset = TD->getTypeAllocSize(EltTy)*i;
2091 // The alignment of the other pointer is the guaranteed alignment of the
2092 // element, which is affected by both the known alignment of the whole
2093 // mem intrinsic and the alignment of the element. If the alignment of
2094 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
2095 // known alignment is just 4 bytes.
2096 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
2099 Value *EltPtr = NewElts[i];
2100 Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
2102 // If we got down to a scalar, insert a load or store as appropriate.
2103 if (EltTy->isSingleValueType()) {
2104 if (isa<MemTransferInst>(MI)) {
2106 // From Other to Alloca.
2107 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
2108 new StoreInst(Elt, EltPtr, MI);
2110 // From Alloca to Other.
2111 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
2112 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
2116 assert(isa<MemSetInst>(MI));
2118 // If the stored element is zero (common case), just store a null
2121 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
2123 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
2125 // If EltTy is a vector type, get the element type.
2126 Type *ValTy = EltTy->getScalarType();
2128 // Construct an integer with the right value.
2129 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
2130 APInt OneVal(EltSize, CI->getZExtValue());
2131 APInt TotalVal(OneVal);
2133 for (unsigned i = 0; 8*i < EltSize; ++i) {
2134 TotalVal = TotalVal.shl(8);
2138 // Convert the integer value to the appropriate type.
2139 StoreVal = ConstantInt::get(CI->getContext(), TotalVal);
2140 if (ValTy->isPointerTy())
2141 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
2142 else if (ValTy->isFloatingPointTy())
2143 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
2144 assert(StoreVal->getType() == ValTy && "Type mismatch!");
2146 // If the requested value was a vector constant, create it.
2147 if (EltTy->isVectorTy()) {
2148 unsigned NumElts = cast<VectorType>(EltTy)->getNumElements();
2149 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
2150 StoreVal = ConstantVector::get(Elts);
2153 new StoreInst(StoreVal, EltPtr, MI);
2156 // Otherwise, if we're storing a byte variable, use a memset call for
2160 unsigned EltSize = TD->getTypeAllocSize(EltTy);
2162 IRBuilder<> Builder(MI);
2164 // Finally, insert the meminst for this element.
2165 if (isa<MemSetInst>(MI)) {
2166 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize,
2169 assert(isa<MemTransferInst>(MI));
2170 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr
2171 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr
2173 if (isa<MemCpyInst>(MI))
2174 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile());
2176 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile());
2179 DeadInsts.push_back(MI);
2182 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
2183 /// overwrites the entire allocation. Extract out the pieces of the stored
2184 /// integer and store them individually.
2185 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
2186 SmallVector<AllocaInst*, 32> &NewElts){
2187 // Extract each element out of the integer according to its structure offset
2188 // and store the element value to the individual alloca.
2189 Value *SrcVal = SI->getOperand(0);
2190 Type *AllocaEltTy = AI->getAllocatedType();
2191 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
2193 IRBuilder<> Builder(SI);
2195 // Handle tail padding by extending the operand
2196 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
2197 SrcVal = Builder.CreateZExt(SrcVal,
2198 IntegerType::get(SI->getContext(), AllocaSizeBits));
2200 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
2203 // There are two forms here: AI could be an array or struct. Both cases
2204 // have different ways to compute the element offset.
2205 if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2206 const StructLayout *Layout = TD->getStructLayout(EltSTy);
2208 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2209 // Get the number of bits to shift SrcVal to get the value.
2210 Type *FieldTy = EltSTy->getElementType(i);
2211 uint64_t Shift = Layout->getElementOffsetInBits(i);
2213 if (TD->isBigEndian())
2214 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
2216 Value *EltVal = SrcVal;
2218 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2219 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2222 // Truncate down to an integer of the right size.
2223 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
2225 // Ignore zero sized fields like {}, they obviously contain no data.
2226 if (FieldSizeBits == 0) continue;
2228 if (FieldSizeBits != AllocaSizeBits)
2229 EltVal = Builder.CreateTrunc(EltVal,
2230 IntegerType::get(SI->getContext(), FieldSizeBits));
2231 Value *DestField = NewElts[i];
2232 if (EltVal->getType() == FieldTy) {
2233 // Storing to an integer field of this size, just do it.
2234 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
2235 // Bitcast to the right element type (for fp/vector values).
2236 EltVal = Builder.CreateBitCast(EltVal, FieldTy);
2238 // Otherwise, bitcast the dest pointer (for aggregates).
2239 DestField = Builder.CreateBitCast(DestField,
2240 PointerType::getUnqual(EltVal->getType()));
2242 new StoreInst(EltVal, DestField, SI);
2246 ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
2247 Type *ArrayEltTy = ATy->getElementType();
2248 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
2249 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
2253 if (TD->isBigEndian())
2254 Shift = AllocaSizeBits-ElementOffset;
2258 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2259 // Ignore zero sized fields like {}, they obviously contain no data.
2260 if (ElementSizeBits == 0) continue;
2262 Value *EltVal = SrcVal;
2264 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2265 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2268 // Truncate down to an integer of the right size.
2269 if (ElementSizeBits != AllocaSizeBits)
2270 EltVal = Builder.CreateTrunc(EltVal,
2271 IntegerType::get(SI->getContext(),
2273 Value *DestField = NewElts[i];
2274 if (EltVal->getType() == ArrayEltTy) {
2275 // Storing to an integer field of this size, just do it.
2276 } else if (ArrayEltTy->isFloatingPointTy() ||
2277 ArrayEltTy->isVectorTy()) {
2278 // Bitcast to the right element type (for fp/vector values).
2279 EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy);
2281 // Otherwise, bitcast the dest pointer (for aggregates).
2282 DestField = Builder.CreateBitCast(DestField,
2283 PointerType::getUnqual(EltVal->getType()));
2285 new StoreInst(EltVal, DestField, SI);
2287 if (TD->isBigEndian())
2288 Shift -= ElementOffset;
2290 Shift += ElementOffset;
2294 DeadInsts.push_back(SI);
2297 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
2298 /// an integer. Load the individual pieces to form the aggregate value.
2299 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
2300 SmallVector<AllocaInst*, 32> &NewElts) {
2301 // Extract each element out of the NewElts according to its structure offset
2302 // and form the result value.
2303 Type *AllocaEltTy = AI->getAllocatedType();
2304 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
2306 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
2309 // There are two forms here: AI could be an array or struct. Both cases
2310 // have different ways to compute the element offset.
2311 const StructLayout *Layout = 0;
2312 uint64_t ArrayEltBitOffset = 0;
2313 if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2314 Layout = TD->getStructLayout(EltSTy);
2316 Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
2317 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
2321 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
2323 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2324 // Load the value from the alloca. If the NewElt is an aggregate, cast
2325 // the pointer to an integer of the same size before doing the load.
2326 Value *SrcField = NewElts[i];
2328 cast<PointerType>(SrcField->getType())->getElementType();
2329 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
2331 // Ignore zero sized fields like {}, they obviously contain no data.
2332 if (FieldSizeBits == 0) continue;
2334 IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
2336 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
2337 !FieldTy->isVectorTy())
2338 SrcField = new BitCastInst(SrcField,
2339 PointerType::getUnqual(FieldIntTy),
2341 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
2343 // If SrcField is a fp or vector of the right size but that isn't an
2344 // integer type, bitcast to an integer so we can shift it.
2345 if (SrcField->getType() != FieldIntTy)
2346 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
2348 // Zero extend the field to be the same size as the final alloca so that
2349 // we can shift and insert it.
2350 if (SrcField->getType() != ResultVal->getType())
2351 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
2353 // Determine the number of bits to shift SrcField.
2355 if (Layout) // Struct case.
2356 Shift = Layout->getElementOffsetInBits(i);
2358 Shift = i*ArrayEltBitOffset;
2360 if (TD->isBigEndian())
2361 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
2364 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
2365 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
2368 // Don't create an 'or x, 0' on the first iteration.
2369 if (!isa<Constant>(ResultVal) ||
2370 !cast<Constant>(ResultVal)->isNullValue())
2371 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
2373 ResultVal = SrcField;
2376 // Handle tail padding by truncating the result
2377 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
2378 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
2380 LI->replaceAllUsesWith(ResultVal);
2381 DeadInsts.push_back(LI);
2384 /// HasPadding - Return true if the specified type has any structure or
2385 /// alignment padding in between the elements that would be split apart
2386 /// by SROA; return false otherwise.
2387 static bool HasPadding(Type *Ty, const TargetData &TD) {
2388 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
2389 Ty = ATy->getElementType();
2390 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
2393 // SROA currently handles only Arrays and Structs.
2394 StructType *STy = cast<StructType>(Ty);
2395 const StructLayout *SL = TD.getStructLayout(STy);
2396 unsigned PrevFieldBitOffset = 0;
2397 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
2398 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
2400 // Check to see if there is any padding between this element and the
2403 unsigned PrevFieldEnd =
2404 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
2405 if (PrevFieldEnd < FieldBitOffset)
2408 PrevFieldBitOffset = FieldBitOffset;
2410 // Check for tail padding.
2411 if (unsigned EltCount = STy->getNumElements()) {
2412 unsigned PrevFieldEnd = PrevFieldBitOffset +
2413 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
2414 if (PrevFieldEnd < SL->getSizeInBits())
2420 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
2421 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
2422 /// or 1 if safe after canonicalization has been performed.
2423 bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
2424 // Loop over the use list of the alloca. We can only transform it if all of
2425 // the users are safe to transform.
2426 AllocaInfo Info(AI);
2428 isSafeForScalarRepl(AI, 0, Info);
2429 if (Info.isUnsafe) {
2430 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
2434 // Okay, we know all the users are promotable. If the aggregate is a memcpy
2435 // source and destination, we have to be careful. In particular, the memcpy
2436 // could be moving around elements that live in structure padding of the LLVM
2437 // types, but may actually be used. In these cases, we refuse to promote the
2439 if (Info.isMemCpySrc && Info.isMemCpyDst &&
2440 HasPadding(AI->getAllocatedType(), *TD))
2443 // If the alloca never has an access to just *part* of it, but is accessed
2444 // via loads and stores, then we should use ConvertToScalarInfo to promote
2445 // the alloca instead of promoting each piece at a time and inserting fission
2447 if (!Info.hasSubelementAccess && Info.hasALoadOrStore) {
2448 // If the struct/array just has one element, use basic SRoA.
2449 if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
2450 if (ST->getNumElements() > 1) return false;
2452 if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1)
2462 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
2463 /// some part of a constant global variable. This intentionally only accepts
2464 /// constant expressions because we don't can't rewrite arbitrary instructions.
2465 static bool PointsToConstantGlobal(Value *V) {
2466 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
2467 return GV->isConstant();
2468 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
2469 if (CE->getOpcode() == Instruction::BitCast ||
2470 CE->getOpcode() == Instruction::GetElementPtr)
2471 return PointsToConstantGlobal(CE->getOperand(0));
2475 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
2476 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
2477 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
2478 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
2479 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
2480 /// the alloca, and if the source pointer is a pointer to a constant global, we
2481 /// can optimize this.
2483 isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
2485 SmallVector<Instruction *, 4> &LifetimeMarkers) {
2486 // We track lifetime intrinsics as we encounter them. If we decide to go
2487 // ahead and replace the value with the global, this lets the caller quickly
2488 // eliminate the markers.
2490 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
2491 User *U = cast<Instruction>(*UI);
2493 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
2494 // Ignore non-volatile loads, they are always ok.
2495 if (!LI->isSimple()) return false;
2499 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
2500 // If uses of the bitcast are ok, we are ok.
2501 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset,
2506 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
2507 // If the GEP has all zero indices, it doesn't offset the pointer. If it
2508 // doesn't, it does.
2509 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
2510 isOffset || !GEP->hasAllZeroIndices(),
2516 if (CallSite CS = U) {
2517 // If this is the function being called then we treat it like a load and
2519 if (CS.isCallee(UI))
2522 // If this is a readonly/readnone call site, then we know it is just a
2523 // load (but one that potentially returns the value itself), so we can
2524 // ignore it if we know that the value isn't captured.
2525 unsigned ArgNo = CS.getArgumentNo(UI);
2526 if (CS.onlyReadsMemory() &&
2527 (CS.getInstruction()->use_empty() ||
2528 CS.paramHasAttr(ArgNo+1, Attribute::NoCapture)))
2531 // If this is being passed as a byval argument, the caller is making a
2532 // copy, so it is only a read of the alloca.
2533 if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal))
2537 // Lifetime intrinsics can be handled by the caller.
2538 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) {
2539 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
2540 II->getIntrinsicID() == Intrinsic::lifetime_end) {
2541 assert(II->use_empty() && "Lifetime markers have no result to use!");
2542 LifetimeMarkers.push_back(II);
2547 // If this is isn't our memcpy/memmove, reject it as something we can't
2549 MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
2553 // If the transfer is using the alloca as a source of the transfer, then
2554 // ignore it since it is a load (unless the transfer is volatile).
2555 if (UI.getOperandNo() == 1) {
2556 if (MI->isVolatile()) return false;
2560 // If we already have seen a copy, reject the second one.
2561 if (TheCopy) return false;
2563 // If the pointer has been offset from the start of the alloca, we can't
2564 // safely handle this.
2565 if (isOffset) return false;
2567 // If the memintrinsic isn't using the alloca as the dest, reject it.
2568 if (UI.getOperandNo() != 0) return false;
2570 // If the source of the memcpy/move is not a constant global, reject it.
2571 if (!PointsToConstantGlobal(MI->getSource()))
2574 // Otherwise, the transform is safe. Remember the copy instruction.
2580 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
2581 /// modified by a copy from a constant global. If we can prove this, we can
2582 /// replace any uses of the alloca with uses of the global directly.
2584 SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI,
2585 SmallVector<Instruction*, 4> &ToDelete) {
2586 MemTransferInst *TheCopy = 0;
2587 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false, ToDelete))