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 they
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 #include "llvm/Transforms/Scalar.h"
23 #include "llvm/ADT/SetVector.h"
24 #include "llvm/ADT/SmallVector.h"
25 #include "llvm/ADT/Statistic.h"
26 #include "llvm/Analysis/Loads.h"
27 #include "llvm/Analysis/ValueTracking.h"
28 #include "llvm/IR/CallSite.h"
29 #include "llvm/IR/Constants.h"
30 #include "llvm/IR/DIBuilder.h"
31 #include "llvm/IR/DataLayout.h"
32 #include "llvm/IR/DebugInfo.h"
33 #include "llvm/IR/DerivedTypes.h"
34 #include "llvm/IR/Dominators.h"
35 #include "llvm/IR/Function.h"
36 #include "llvm/IR/GetElementPtrTypeIterator.h"
37 #include "llvm/IR/GlobalVariable.h"
38 #include "llvm/IR/IRBuilder.h"
39 #include "llvm/IR/Instructions.h"
40 #include "llvm/IR/IntrinsicInst.h"
41 #include "llvm/IR/LLVMContext.h"
42 #include "llvm/IR/Module.h"
43 #include "llvm/IR/Operator.h"
44 #include "llvm/Pass.h"
45 #include "llvm/Support/Debug.h"
46 #include "llvm/Support/ErrorHandling.h"
47 #include "llvm/Support/MathExtras.h"
48 #include "llvm/Support/raw_ostream.h"
49 #include "llvm/Transforms/Utils/Local.h"
50 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
51 #include "llvm/Transforms/Utils/SSAUpdater.h"
54 #define DEBUG_TYPE "scalarrepl"
56 STATISTIC(NumReplaced, "Number of allocas broken up");
57 STATISTIC(NumPromoted, "Number of allocas promoted");
58 STATISTIC(NumAdjusted, "Number of scalar allocas adjusted to allow promotion");
59 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
62 struct SROA : public FunctionPass {
63 SROA(int T, bool hasDT, char &ID, int ST, int AT, int SLT)
64 : FunctionPass(ID), HasDomTree(hasDT) {
70 StructMemberThreshold = 32;
72 StructMemberThreshold = ST;
74 ArrayElementThreshold = 8;
76 ArrayElementThreshold = AT;
78 // Do not limit the scalar integer load size if no threshold is given.
79 ScalarLoadThreshold = -1;
81 ScalarLoadThreshold = SLT;
84 bool runOnFunction(Function &F) override;
86 bool performScalarRepl(Function &F);
87 bool performPromotion(Function &F);
93 /// DeadInsts - Keep track of instructions we have made dead, so that
94 /// we can remove them after we are done working.
95 SmallVector<Value*, 32> DeadInsts;
97 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
98 /// information about the uses. All these fields are initialized to false
99 /// and set to true when something is learned.
101 /// The alloca to promote.
104 /// CheckedPHIs - This is a set of verified PHI nodes, to prevent infinite
105 /// looping and avoid redundant work.
106 SmallPtrSet<PHINode*, 8> CheckedPHIs;
108 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
111 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
112 bool isMemCpySrc : 1;
114 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
115 bool isMemCpyDst : 1;
117 /// hasSubelementAccess - This is true if a subelement of the alloca is
118 /// ever accessed, or false if the alloca is only accessed with mem
119 /// intrinsics or load/store that only access the entire alloca at once.
120 bool hasSubelementAccess : 1;
122 /// hasALoadOrStore - This is true if there are any loads or stores to it.
123 /// The alloca may just be accessed with memcpy, for example, which would
125 bool hasALoadOrStore : 1;
127 explicit AllocaInfo(AllocaInst *ai)
128 : AI(ai), isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false),
129 hasSubelementAccess(false), hasALoadOrStore(false) {}
132 /// SRThreshold - The maximum alloca size to considered for SROA.
133 unsigned SRThreshold;
135 /// StructMemberThreshold - The maximum number of members a struct can
136 /// contain to be considered for SROA.
137 unsigned StructMemberThreshold;
139 /// ArrayElementThreshold - The maximum number of elements an array can
140 /// have to be considered for SROA.
141 unsigned ArrayElementThreshold;
143 /// ScalarLoadThreshold - The maximum size in bits of scalars to load when
144 /// converting to scalar
145 unsigned ScalarLoadThreshold;
147 void MarkUnsafe(AllocaInfo &I, Instruction *User) {
149 DEBUG(dbgs() << " Transformation preventing inst: " << *User << '\n');
152 bool isSafeAllocaToScalarRepl(AllocaInst *AI);
154 void isSafeForScalarRepl(Instruction *I, uint64_t Offset, AllocaInfo &Info);
155 void isSafePHISelectUseForScalarRepl(Instruction *User, uint64_t Offset,
157 void isSafeGEP(GetElementPtrInst *GEPI, uint64_t &Offset, AllocaInfo &Info);
158 void isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
159 Type *MemOpType, bool isStore, AllocaInfo &Info,
160 Instruction *TheAccess, bool AllowWholeAccess);
161 bool TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size);
162 uint64_t FindElementAndOffset(Type *&T, uint64_t &Offset,
165 void DoScalarReplacement(AllocaInst *AI,
166 std::vector<AllocaInst*> &WorkList);
167 void DeleteDeadInstructions();
169 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
170 SmallVectorImpl<AllocaInst *> &NewElts);
171 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
172 SmallVectorImpl<AllocaInst *> &NewElts);
173 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
174 SmallVectorImpl<AllocaInst *> &NewElts);
175 void RewriteLifetimeIntrinsic(IntrinsicInst *II, AllocaInst *AI,
177 SmallVectorImpl<AllocaInst *> &NewElts);
178 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
180 SmallVectorImpl<AllocaInst *> &NewElts);
181 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
182 SmallVectorImpl<AllocaInst *> &NewElts);
183 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
184 SmallVectorImpl<AllocaInst *> &NewElts);
185 bool ShouldAttemptScalarRepl(AllocaInst *AI);
188 // SROA_DT - SROA that uses DominatorTree.
189 struct SROA_DT : public SROA {
192 SROA_DT(int T = -1, int ST = -1, int AT = -1, int SLT = -1) :
193 SROA(T, true, ID, ST, AT, SLT) {
194 initializeSROA_DTPass(*PassRegistry::getPassRegistry());
197 // getAnalysisUsage - This pass does not require any passes, but we know it
198 // will not alter the CFG, so say so.
199 void getAnalysisUsage(AnalysisUsage &AU) const override {
200 AU.addRequired<DominatorTreeWrapperPass>();
201 AU.setPreservesCFG();
205 // SROA_SSAUp - SROA that uses SSAUpdater.
206 struct SROA_SSAUp : public SROA {
209 SROA_SSAUp(int T = -1, int ST = -1, int AT = -1, int SLT = -1) :
210 SROA(T, false, ID, ST, AT, SLT) {
211 initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry());
214 // getAnalysisUsage - This pass does not require any passes, but we know it
215 // will not alter the CFG, so say so.
216 void getAnalysisUsage(AnalysisUsage &AU) const override {
217 AU.setPreservesCFG();
223 char SROA_DT::ID = 0;
224 char SROA_SSAUp::ID = 0;
226 INITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl",
227 "Scalar Replacement of Aggregates (DT)", false, false)
228 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
229 INITIALIZE_PASS_END(SROA_DT, "scalarrepl",
230 "Scalar Replacement of Aggregates (DT)", false, false)
232 INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa",
233 "Scalar Replacement of Aggregates (SSAUp)", false, false)
234 INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa",
235 "Scalar Replacement of Aggregates (SSAUp)", false, false)
237 // Public interface to the ScalarReplAggregates pass
238 FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold,
240 int StructMemberThreshold,
241 int ArrayElementThreshold,
242 int ScalarLoadThreshold) {
244 return new SROA_DT(Threshold, StructMemberThreshold, ArrayElementThreshold,
245 ScalarLoadThreshold);
246 return new SROA_SSAUp(Threshold, StructMemberThreshold,
247 ArrayElementThreshold, ScalarLoadThreshold);
251 //===----------------------------------------------------------------------===//
252 // Convert To Scalar Optimization.
253 //===----------------------------------------------------------------------===//
256 /// ConvertToScalarInfo - This class implements the "Convert To Scalar"
257 /// optimization, which scans the uses of an alloca and determines if it can
258 /// rewrite it in terms of a single new alloca that can be mem2reg'd.
259 class ConvertToScalarInfo {
260 /// AllocaSize - The size of the alloca being considered in bytes.
262 const DataLayout &DL;
263 unsigned ScalarLoadThreshold;
265 /// IsNotTrivial - This is set to true if there is some access to the object
266 /// which means that mem2reg can't promote it.
269 /// ScalarKind - Tracks the kind of alloca being considered for promotion,
270 /// computed based on the uses of the alloca rather than the LLVM type system.
274 // Accesses via GEPs that are consistent with element access of a vector
275 // type. This will not be converted into a vector unless there is a later
276 // access using an actual vector type.
279 // Accesses via vector operations and GEPs that are consistent with the
280 // layout of a vector type.
283 // An integer bag-of-bits with bitwise operations for insertion and
284 // extraction. Any combination of types can be converted into this kind
289 /// VectorTy - This tracks the type that we should promote the vector to if
290 /// it is possible to turn it into a vector. This starts out null, and if it
291 /// isn't possible to turn into a vector type, it gets set to VoidTy.
292 VectorType *VectorTy;
294 /// HadNonMemTransferAccess - True if there is at least one access to the
295 /// alloca that is not a MemTransferInst. We don't want to turn structs into
296 /// large integers unless there is some potential for optimization.
297 bool HadNonMemTransferAccess;
299 /// HadDynamicAccess - True if some element of this alloca was dynamic.
300 /// We don't yet have support for turning a dynamic access into a large
302 bool HadDynamicAccess;
305 explicit ConvertToScalarInfo(unsigned Size, const DataLayout &DL,
307 : AllocaSize(Size), DL(DL), ScalarLoadThreshold(SLT), IsNotTrivial(false),
308 ScalarKind(Unknown), VectorTy(nullptr), HadNonMemTransferAccess(false),
309 HadDynamicAccess(false) { }
311 AllocaInst *TryConvert(AllocaInst *AI);
314 bool CanConvertToScalar(Value *V, uint64_t Offset, Value* NonConstantIdx);
315 void MergeInTypeForLoadOrStore(Type *In, uint64_t Offset);
316 bool MergeInVectorType(VectorType *VInTy, uint64_t Offset);
317 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset,
318 Value *NonConstantIdx);
320 Value *ConvertScalar_ExtractValue(Value *NV, Type *ToType,
321 uint64_t Offset, Value* NonConstantIdx,
322 IRBuilder<> &Builder);
323 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
324 uint64_t Offset, Value* NonConstantIdx,
325 IRBuilder<> &Builder);
327 } // end anonymous namespace.
330 /// TryConvert - Analyze the specified alloca, and if it is safe to do so,
331 /// rewrite it to be a new alloca which is mem2reg'able. This returns the new
332 /// alloca if possible or null if not.
333 AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
334 // If we can't convert this scalar, or if mem2reg can trivially do it, bail
336 if (!CanConvertToScalar(AI, 0, nullptr) || !IsNotTrivial)
339 // If an alloca has only memset / memcpy uses, it may still have an Unknown
340 // ScalarKind. Treat it as an Integer below.
341 if (ScalarKind == Unknown)
342 ScalarKind = Integer;
344 if (ScalarKind == Vector && VectorTy->getBitWidth() != AllocaSize * 8)
345 ScalarKind = Integer;
347 // If we were able to find a vector type that can handle this with
348 // insert/extract elements, and if there was at least one use that had
349 // a vector type, promote this to a vector. We don't want to promote
350 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
351 // we just get a lot of insert/extracts. If at least one vector is
352 // involved, then we probably really do have a union of vector/array.
354 if (ScalarKind == Vector) {
355 assert(VectorTy && "Missing type for vector scalar.");
356 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
357 << *VectorTy << '\n');
358 NewTy = VectorTy; // Use the vector type.
360 unsigned BitWidth = AllocaSize * 8;
362 // Do not convert to scalar integer if the alloca size exceeds the
363 // scalar load threshold.
364 if (BitWidth > ScalarLoadThreshold)
367 if ((ScalarKind == ImplicitVector || ScalarKind == Integer) &&
368 !HadNonMemTransferAccess && !DL.fitsInLegalInteger(BitWidth))
370 // Dynamic accesses on integers aren't yet supported. They need us to shift
371 // by a dynamic amount which could be difficult to work out as we might not
372 // know whether to use a left or right shift.
373 if (ScalarKind == Integer && HadDynamicAccess)
376 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
377 // Create and insert the integer alloca.
378 NewTy = IntegerType::get(AI->getContext(), BitWidth);
380 AllocaInst *NewAI = new AllocaInst(NewTy, nullptr, "",
381 AI->getParent()->begin());
382 ConvertUsesToScalar(AI, NewAI, 0, nullptr);
386 /// MergeInTypeForLoadOrStore - Add the 'In' type to the accumulated vector type
387 /// (VectorTy) so far at the offset specified by Offset (which is specified in
390 /// There are two cases we handle here:
391 /// 1) A union of vector types of the same size and potentially its elements.
392 /// Here we turn element accesses into insert/extract element operations.
393 /// This promotes a <4 x float> with a store of float to the third element
394 /// into a <4 x float> that uses insert element.
395 /// 2) A fully general blob of memory, which we turn into some (potentially
396 /// large) integer type with extract and insert operations where the loads
397 /// and stores would mutate the memory. We mark this by setting VectorTy
399 void ConvertToScalarInfo::MergeInTypeForLoadOrStore(Type *In,
401 // If we already decided to turn this into a blob of integer memory, there is
402 // nothing to be done.
403 if (ScalarKind == Integer)
406 // If this could be contributing to a vector, analyze it.
408 // If the In type is a vector that is the same size as the alloca, see if it
409 // matches the existing VecTy.
410 if (VectorType *VInTy = dyn_cast<VectorType>(In)) {
411 if (MergeInVectorType(VInTy, Offset))
413 } else if (In->isFloatTy() || In->isDoubleTy() ||
414 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
415 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
416 // Full width accesses can be ignored, because they can always be turned
418 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
419 if (EltSize == AllocaSize)
422 // If we're accessing something that could be an element of a vector, see
423 // if the implied vector agrees with what we already have and if Offset is
424 // compatible with it.
425 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 &&
426 (!VectorTy || EltSize == VectorTy->getElementType()
427 ->getPrimitiveSizeInBits()/8)) {
429 ScalarKind = ImplicitVector;
430 VectorTy = VectorType::get(In, AllocaSize/EltSize);
436 // Otherwise, we have a case that we can't handle with an optimized vector
437 // form. We can still turn this into a large integer.
438 ScalarKind = Integer;
441 /// MergeInVectorType - Handles the vector case of MergeInTypeForLoadOrStore,
442 /// returning true if the type was successfully merged and false otherwise.
443 bool ConvertToScalarInfo::MergeInVectorType(VectorType *VInTy,
445 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
446 // If we're storing/loading a vector of the right size, allow it as a
447 // vector. If this the first vector we see, remember the type so that
448 // we know the element size. If this is a subsequent access, ignore it
449 // even if it is a differing type but the same size. Worst case we can
450 // bitcast the resultant vectors.
460 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
461 /// its accesses to a single vector type, return true and set VecTy to
462 /// the new type. If we could convert the alloca into a single promotable
463 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
464 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
465 /// is the current offset from the base of the alloca being analyzed.
467 /// If we see at least one access to the value that is as a vector type, set the
469 bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset,
470 Value* NonConstantIdx) {
471 for (User *U : V->users()) {
472 Instruction *UI = cast<Instruction>(U);
474 if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
475 // Don't break volatile loads.
478 // Don't touch MMX operations.
479 if (LI->getType()->isX86_MMXTy())
481 HadNonMemTransferAccess = true;
482 MergeInTypeForLoadOrStore(LI->getType(), Offset);
486 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
487 // Storing the pointer, not into the value?
488 if (SI->getOperand(0) == V || !SI->isSimple()) return false;
489 // Don't touch MMX operations.
490 if (SI->getOperand(0)->getType()->isX86_MMXTy())
492 HadNonMemTransferAccess = true;
493 MergeInTypeForLoadOrStore(SI->getOperand(0)->getType(), Offset);
497 if (BitCastInst *BCI = dyn_cast<BitCastInst>(UI)) {
498 if (!onlyUsedByLifetimeMarkers(BCI))
499 IsNotTrivial = true; // Can't be mem2reg'd.
500 if (!CanConvertToScalar(BCI, Offset, NonConstantIdx))
505 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(UI)) {
506 // If this is a GEP with a variable indices, we can't handle it.
507 PointerType* PtrTy = dyn_cast<PointerType>(GEP->getPointerOperandType());
511 // Compute the offset that this GEP adds to the pointer.
512 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
513 Value *GEPNonConstantIdx = nullptr;
514 if (!GEP->hasAllConstantIndices()) {
515 if (!isa<VectorType>(PtrTy->getElementType()))
519 GEPNonConstantIdx = Indices.pop_back_val();
520 if (!GEPNonConstantIdx->getType()->isIntegerTy(32))
522 HadDynamicAccess = true;
524 GEPNonConstantIdx = NonConstantIdx;
525 uint64_t GEPOffset = DL.getIndexedOffset(PtrTy,
527 // See if all uses can be converted.
528 if (!CanConvertToScalar(GEP, Offset+GEPOffset, GEPNonConstantIdx))
530 IsNotTrivial = true; // Can't be mem2reg'd.
531 HadNonMemTransferAccess = true;
535 // If this is a constant sized memset of a constant value (e.g. 0) we can
537 if (MemSetInst *MSI = dyn_cast<MemSetInst>(UI)) {
538 // Store to dynamic index.
541 // Store of constant value.
542 if (!isa<ConstantInt>(MSI->getValue()))
545 // Store of constant size.
546 ConstantInt *Len = dyn_cast<ConstantInt>(MSI->getLength());
550 // If the size differs from the alloca, we can only convert the alloca to
551 // an integer bag-of-bits.
552 // FIXME: This should handle all of the cases that are currently accepted
553 // as vector element insertions.
554 if (Len->getZExtValue() != AllocaSize || Offset != 0)
555 ScalarKind = Integer;
557 IsNotTrivial = true; // Can't be mem2reg'd.
558 HadNonMemTransferAccess = true;
562 // If this is a memcpy or memmove into or out of the whole allocation, we
563 // can handle it like a load or store of the scalar type.
564 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(UI)) {
565 // Store to dynamic index.
568 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
569 if (!Len || Len->getZExtValue() != AllocaSize || Offset != 0)
572 IsNotTrivial = true; // Can't be mem2reg'd.
576 // If this is a lifetime intrinsic, we can handle it.
577 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(UI)) {
578 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
579 II->getIntrinsicID() == Intrinsic::lifetime_end) {
584 // Otherwise, we cannot handle this!
591 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
592 /// directly. This happens when we are converting an "integer union" to a
593 /// single integer scalar, or when we are converting a "vector union" to a
594 /// vector with insert/extractelement instructions.
596 /// Offset is an offset from the original alloca, in bits that need to be
597 /// shifted to the right. By the end of this, there should be no uses of Ptr.
598 void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
600 Value* NonConstantIdx) {
601 while (!Ptr->use_empty()) {
602 Instruction *User = cast<Instruction>(Ptr->user_back());
604 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
605 ConvertUsesToScalar(CI, NewAI, Offset, NonConstantIdx);
606 CI->eraseFromParent();
610 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
611 // Compute the offset that this GEP adds to the pointer.
612 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
613 Value* GEPNonConstantIdx = nullptr;
614 if (!GEP->hasAllConstantIndices()) {
615 assert(!NonConstantIdx &&
616 "Dynamic GEP reading from dynamic GEP unsupported");
617 GEPNonConstantIdx = Indices.pop_back_val();
619 GEPNonConstantIdx = NonConstantIdx;
620 uint64_t GEPOffset = DL.getIndexedOffset(GEP->getPointerOperandType(),
622 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8, GEPNonConstantIdx);
623 GEP->eraseFromParent();
627 IRBuilder<> Builder(User);
629 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
630 // The load is a bit extract from NewAI shifted right by Offset bits.
631 Value *LoadedVal = Builder.CreateLoad(NewAI);
633 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset,
634 NonConstantIdx, Builder);
635 LI->replaceAllUsesWith(NewLoadVal);
636 LI->eraseFromParent();
640 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
641 assert(SI->getOperand(0) != Ptr && "Consistency error!");
642 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
643 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
644 NonConstantIdx, Builder);
645 Builder.CreateStore(New, NewAI);
646 SI->eraseFromParent();
648 // If the load we just inserted is now dead, then the inserted store
649 // overwrote the entire thing.
650 if (Old->use_empty())
651 Old->eraseFromParent();
655 // If this is a constant sized memset of a constant value (e.g. 0) we can
656 // transform it into a store of the expanded constant value.
657 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
658 assert(MSI->getRawDest() == Ptr && "Consistency error!");
659 assert(!NonConstantIdx && "Cannot replace dynamic memset with insert");
660 int64_t SNumBytes = cast<ConstantInt>(MSI->getLength())->getSExtValue();
661 if (SNumBytes > 0 && (SNumBytes >> 32) == 0) {
662 unsigned NumBytes = static_cast<unsigned>(SNumBytes);
663 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
665 // Compute the value replicated the right number of times.
666 APInt APVal(NumBytes*8, Val);
668 // Splat the value if non-zero.
670 for (unsigned i = 1; i != NumBytes; ++i)
673 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
674 Value *New = ConvertScalar_InsertValue(
675 ConstantInt::get(User->getContext(), APVal),
676 Old, Offset, nullptr, Builder);
677 Builder.CreateStore(New, NewAI);
679 // If the load we just inserted is now dead, then the memset overwrote
681 if (Old->use_empty())
682 Old->eraseFromParent();
684 MSI->eraseFromParent();
688 // If this is a memcpy or memmove into or out of the whole allocation, we
689 // can handle it like a load or store of the scalar type.
690 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
691 assert(Offset == 0 && "must be store to start of alloca");
692 assert(!NonConstantIdx && "Cannot replace dynamic transfer with insert");
694 // If the source and destination are both to the same alloca, then this is
695 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
697 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, &DL, 0));
699 if (GetUnderlyingObject(MTI->getSource(), &DL, 0) != OrigAI) {
700 // Dest must be OrigAI, change this to be a load from the original
701 // pointer (bitcasted), then a store to our new alloca.
702 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
703 Value *SrcPtr = MTI->getSource();
704 PointerType* SPTy = cast<PointerType>(SrcPtr->getType());
705 PointerType* AIPTy = cast<PointerType>(NewAI->getType());
706 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
707 AIPTy = PointerType::get(AIPTy->getElementType(),
708 SPTy->getAddressSpace());
710 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy);
712 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
713 SrcVal->setAlignment(MTI->getAlignment());
714 Builder.CreateStore(SrcVal, NewAI);
715 } else if (GetUnderlyingObject(MTI->getDest(), &DL, 0) != OrigAI) {
716 // Src must be OrigAI, change this to be a load from NewAI then a store
717 // through the original dest pointer (bitcasted).
718 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
719 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
721 PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType());
722 PointerType* AIPTy = cast<PointerType>(NewAI->getType());
723 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
724 AIPTy = PointerType::get(AIPTy->getElementType(),
725 DPTy->getAddressSpace());
727 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy);
729 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
730 NewStore->setAlignment(MTI->getAlignment());
732 // Noop transfer. Src == Dst
735 MTI->eraseFromParent();
739 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
740 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
741 II->getIntrinsicID() == Intrinsic::lifetime_end) {
742 // There's no need to preserve these, as the resulting alloca will be
743 // converted to a register anyways.
744 II->eraseFromParent();
749 llvm_unreachable("Unsupported operation!");
753 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
754 /// or vector value FromVal, extracting the bits from the offset specified by
755 /// Offset. This returns the value, which is of type ToType.
757 /// This happens when we are converting an "integer union" to a single
758 /// integer scalar, or when we are converting a "vector union" to a vector with
759 /// insert/extractelement instructions.
761 /// Offset is an offset from the original alloca, in bits that need to be
762 /// shifted to the right.
763 Value *ConvertToScalarInfo::
764 ConvertScalar_ExtractValue(Value *FromVal, Type *ToType,
765 uint64_t Offset, Value* NonConstantIdx,
766 IRBuilder<> &Builder) {
767 // If the load is of the whole new alloca, no conversion is needed.
768 Type *FromType = FromVal->getType();
769 if (FromType == ToType && Offset == 0)
772 // If the result alloca is a vector type, this is either an element
773 // access or a bitcast to another vector type of the same size.
774 if (VectorType *VTy = dyn_cast<VectorType>(FromType)) {
775 unsigned FromTypeSize = DL.getTypeAllocSize(FromType);
776 unsigned ToTypeSize = DL.getTypeAllocSize(ToType);
777 if (FromTypeSize == ToTypeSize)
778 return Builder.CreateBitCast(FromVal, ToType);
780 // Otherwise it must be an element access.
783 unsigned EltSize = DL.getTypeAllocSizeInBits(VTy->getElementType());
784 Elt = Offset/EltSize;
785 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
787 // Return the element extracted out of it.
789 if (NonConstantIdx) {
791 Idx = Builder.CreateAdd(NonConstantIdx,
792 Builder.getInt32(Elt),
795 Idx = NonConstantIdx;
797 Idx = Builder.getInt32(Elt);
798 Value *V = Builder.CreateExtractElement(FromVal, Idx);
799 if (V->getType() != ToType)
800 V = Builder.CreateBitCast(V, ToType);
804 // If ToType is a first class aggregate, extract out each of the pieces and
805 // use insertvalue's to form the FCA.
806 if (StructType *ST = dyn_cast<StructType>(ToType)) {
807 assert(!NonConstantIdx &&
808 "Dynamic indexing into struct types not supported");
809 const StructLayout &Layout = *DL.getStructLayout(ST);
810 Value *Res = UndefValue::get(ST);
811 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
812 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
813 Offset+Layout.getElementOffsetInBits(i),
815 Res = Builder.CreateInsertValue(Res, Elt, i);
820 if (ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
821 assert(!NonConstantIdx &&
822 "Dynamic indexing into array types not supported");
823 uint64_t EltSize = DL.getTypeAllocSizeInBits(AT->getElementType());
824 Value *Res = UndefValue::get(AT);
825 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
826 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
827 Offset+i*EltSize, nullptr,
829 Res = Builder.CreateInsertValue(Res, Elt, i);
834 // Otherwise, this must be a union that was converted to an integer value.
835 IntegerType *NTy = cast<IntegerType>(FromVal->getType());
837 // If this is a big-endian system and the load is narrower than the
838 // full alloca type, we need to do a shift to get the right bits.
840 if (DL.isBigEndian()) {
841 // On big-endian machines, the lowest bit is stored at the bit offset
842 // from the pointer given by getTypeStoreSizeInBits. This matters for
843 // integers with a bitwidth that is not a multiple of 8.
844 ShAmt = DL.getTypeStoreSizeInBits(NTy) -
845 DL.getTypeStoreSizeInBits(ToType) - Offset;
850 // Note: we support negative bitwidths (with shl) which are not defined.
851 // We do this to support (f.e.) loads off the end of a structure where
852 // only some bits are used.
853 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
854 FromVal = Builder.CreateLShr(FromVal,
855 ConstantInt::get(FromVal->getType(), ShAmt));
856 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
857 FromVal = Builder.CreateShl(FromVal,
858 ConstantInt::get(FromVal->getType(), -ShAmt));
860 // Finally, unconditionally truncate the integer to the right width.
861 unsigned LIBitWidth = DL.getTypeSizeInBits(ToType);
862 if (LIBitWidth < NTy->getBitWidth())
864 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
866 else if (LIBitWidth > NTy->getBitWidth())
868 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
871 // If the result is an integer, this is a trunc or bitcast.
872 if (ToType->isIntegerTy()) {
874 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
875 // Just do a bitcast, we know the sizes match up.
876 FromVal = Builder.CreateBitCast(FromVal, ToType);
878 // Otherwise must be a pointer.
879 FromVal = Builder.CreateIntToPtr(FromVal, ToType);
881 assert(FromVal->getType() == ToType && "Didn't convert right?");
885 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
886 /// or vector value "Old" at the offset specified by Offset.
888 /// This happens when we are converting an "integer union" to a
889 /// single integer scalar, or when we are converting a "vector union" to a
890 /// vector with insert/extractelement instructions.
892 /// Offset is an offset from the original alloca, in bits that need to be
893 /// shifted to the right.
895 /// NonConstantIdx is an index value if there was a GEP with a non-constant
896 /// index value. If this is 0 then all GEPs used to find this insert address
898 Value *ConvertToScalarInfo::
899 ConvertScalar_InsertValue(Value *SV, Value *Old,
900 uint64_t Offset, Value* NonConstantIdx,
901 IRBuilder<> &Builder) {
902 // Convert the stored type to the actual type, shift it left to insert
903 // then 'or' into place.
904 Type *AllocaType = Old->getType();
905 LLVMContext &Context = Old->getContext();
907 if (VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
908 uint64_t VecSize = DL.getTypeAllocSizeInBits(VTy);
909 uint64_t ValSize = DL.getTypeAllocSizeInBits(SV->getType());
911 // Changing the whole vector with memset or with an access of a different
913 if (ValSize == VecSize)
914 return Builder.CreateBitCast(SV, AllocaType);
916 // Must be an element insertion.
917 Type *EltTy = VTy->getElementType();
918 if (SV->getType() != EltTy)
919 SV = Builder.CreateBitCast(SV, EltTy);
920 uint64_t EltSize = DL.getTypeAllocSizeInBits(EltTy);
921 unsigned Elt = Offset/EltSize;
923 if (NonConstantIdx) {
925 Idx = Builder.CreateAdd(NonConstantIdx,
926 Builder.getInt32(Elt),
929 Idx = NonConstantIdx;
931 Idx = Builder.getInt32(Elt);
932 return Builder.CreateInsertElement(Old, SV, Idx);
935 // If SV is a first-class aggregate value, insert each value recursively.
936 if (StructType *ST = dyn_cast<StructType>(SV->getType())) {
937 assert(!NonConstantIdx &&
938 "Dynamic indexing into struct types not supported");
939 const StructLayout &Layout = *DL.getStructLayout(ST);
940 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
941 Value *Elt = Builder.CreateExtractValue(SV, i);
942 Old = ConvertScalar_InsertValue(Elt, Old,
943 Offset+Layout.getElementOffsetInBits(i),
949 if (ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
950 assert(!NonConstantIdx &&
951 "Dynamic indexing into array types not supported");
952 uint64_t EltSize = DL.getTypeAllocSizeInBits(AT->getElementType());
953 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
954 Value *Elt = Builder.CreateExtractValue(SV, i);
955 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, nullptr,
961 // If SV is a float, convert it to the appropriate integer type.
962 // If it is a pointer, do the same.
963 unsigned SrcWidth = DL.getTypeSizeInBits(SV->getType());
964 unsigned DestWidth = DL.getTypeSizeInBits(AllocaType);
965 unsigned SrcStoreWidth = DL.getTypeStoreSizeInBits(SV->getType());
966 unsigned DestStoreWidth = DL.getTypeStoreSizeInBits(AllocaType);
967 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
968 SV = Builder.CreateBitCast(SV, IntegerType::get(SV->getContext(),SrcWidth));
969 else if (SV->getType()->isPointerTy())
970 SV = Builder.CreatePtrToInt(SV, DL.getIntPtrType(SV->getType()));
972 // Zero extend or truncate the value if needed.
973 if (SV->getType() != AllocaType) {
974 if (SV->getType()->getPrimitiveSizeInBits() <
975 AllocaType->getPrimitiveSizeInBits())
976 SV = Builder.CreateZExt(SV, AllocaType);
978 // Truncation may be needed if storing more than the alloca can hold
979 // (undefined behavior).
980 SV = Builder.CreateTrunc(SV, AllocaType);
981 SrcWidth = DestWidth;
982 SrcStoreWidth = DestStoreWidth;
986 // If this is a big-endian system and the store is narrower than the
987 // full alloca type, we need to do a shift to get the right bits.
989 if (DL.isBigEndian()) {
990 // On big-endian machines, the lowest bit is stored at the bit offset
991 // from the pointer given by getTypeStoreSizeInBits. This matters for
992 // integers with a bitwidth that is not a multiple of 8.
993 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
998 // Note: we support negative bitwidths (with shr) which are not defined.
999 // We do this to support (f.e.) stores off the end of a structure where
1000 // only some bits in the structure are set.
1001 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1002 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1003 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), ShAmt));
1005 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1006 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), -ShAmt));
1007 Mask = Mask.lshr(-ShAmt);
1010 // Mask out the bits we are about to insert from the old value, and or
1012 if (SrcWidth != DestWidth) {
1013 assert(DestWidth > SrcWidth);
1014 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
1015 SV = Builder.CreateOr(Old, SV, "ins");
1021 //===----------------------------------------------------------------------===//
1023 //===----------------------------------------------------------------------===//
1026 bool SROA::runOnFunction(Function &F) {
1027 if (skipOptnoneFunction(F))
1030 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
1031 DL = DLP ? &DLP->getDataLayout() : nullptr;
1033 bool Changed = performPromotion(F);
1035 // FIXME: ScalarRepl currently depends on DataLayout more than it
1036 // theoretically needs to. It should be refactored in order to support
1037 // target-independent IR. Until this is done, just skip the actual
1038 // scalar-replacement portion of this pass.
1039 if (!DL) return Changed;
1042 bool LocalChange = performScalarRepl(F);
1043 if (!LocalChange) break; // No need to repromote if no scalarrepl
1045 LocalChange = performPromotion(F);
1046 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
1053 class AllocaPromoter : public LoadAndStorePromoter {
1056 SmallVector<DbgDeclareInst *, 4> DDIs;
1057 SmallVector<DbgValueInst *, 4> DVIs;
1059 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S,
1061 : LoadAndStorePromoter(Insts, S), AI(nullptr), DIB(DB) {}
1063 void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) {
1064 // Remember which alloca we're promoting (for isInstInList).
1066 if (MDNode *DebugNode = MDNode::getIfExists(AI->getContext(), AI)) {
1067 for (User *U : DebugNode->users())
1068 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(U))
1069 DDIs.push_back(DDI);
1070 else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(U))
1071 DVIs.push_back(DVI);
1074 LoadAndStorePromoter::run(Insts);
1075 AI->eraseFromParent();
1076 for (SmallVectorImpl<DbgDeclareInst *>::iterator I = DDIs.begin(),
1077 E = DDIs.end(); I != E; ++I) {
1078 DbgDeclareInst *DDI = *I;
1079 DDI->eraseFromParent();
1081 for (SmallVectorImpl<DbgValueInst *>::iterator I = DVIs.begin(),
1082 E = DVIs.end(); I != E; ++I) {
1083 DbgValueInst *DVI = *I;
1084 DVI->eraseFromParent();
1088 bool isInstInList(Instruction *I,
1089 const SmallVectorImpl<Instruction*> &Insts) const override {
1090 if (LoadInst *LI = dyn_cast<LoadInst>(I))
1091 return LI->getOperand(0) == AI;
1092 return cast<StoreInst>(I)->getPointerOperand() == AI;
1095 void updateDebugInfo(Instruction *Inst) const override {
1096 for (SmallVectorImpl<DbgDeclareInst *>::const_iterator I = DDIs.begin(),
1097 E = DDIs.end(); I != E; ++I) {
1098 DbgDeclareInst *DDI = *I;
1099 if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
1100 ConvertDebugDeclareToDebugValue(DDI, SI, *DIB);
1101 else if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
1102 ConvertDebugDeclareToDebugValue(DDI, LI, *DIB);
1104 for (SmallVectorImpl<DbgValueInst *>::const_iterator I = DVIs.begin(),
1105 E = DVIs.end(); I != E; ++I) {
1106 DbgValueInst *DVI = *I;
1107 Value *Arg = nullptr;
1108 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
1109 // If an argument is zero extended then use argument directly. The ZExt
1110 // may be zapped by an optimization pass in future.
1111 if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
1112 Arg = dyn_cast<Argument>(ZExt->getOperand(0));
1113 if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
1114 Arg = dyn_cast<Argument>(SExt->getOperand(0));
1116 Arg = SI->getOperand(0);
1117 } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
1118 Arg = LI->getOperand(0);
1122 Instruction *DbgVal =
1123 DIB->insertDbgValueIntrinsic(Arg, 0, DIVariable(DVI->getVariable()),
1125 DbgVal->setDebugLoc(DVI->getDebugLoc());
1129 } // end anon namespace
1131 /// isSafeSelectToSpeculate - Select instructions that use an alloca and are
1132 /// subsequently loaded can be rewritten to load both input pointers and then
1133 /// select between the result, allowing the load of the alloca to be promoted.
1135 /// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
1136 /// %V = load i32* %P2
1138 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1139 /// %V2 = load i32* %Other
1140 /// %V = select i1 %cond, i32 %V1, i32 %V2
1142 /// We can do this to a select if its only uses are loads and if the operand to
1143 /// the select can be loaded unconditionally.
1144 static bool isSafeSelectToSpeculate(SelectInst *SI, const DataLayout *DL) {
1145 bool TDerefable = SI->getTrueValue()->isDereferenceablePointer(DL);
1146 bool FDerefable = SI->getFalseValue()->isDereferenceablePointer(DL);
1148 for (User *U : SI->users()) {
1149 LoadInst *LI = dyn_cast<LoadInst>(U);
1150 if (!LI || !LI->isSimple()) return false;
1152 // Both operands to the select need to be dereferencable, either absolutely
1153 // (e.g. allocas) or at this point because we can see other accesses to it.
1154 if (!TDerefable && !isSafeToLoadUnconditionally(SI->getTrueValue(), LI,
1155 LI->getAlignment(), DL))
1157 if (!FDerefable && !isSafeToLoadUnconditionally(SI->getFalseValue(), LI,
1158 LI->getAlignment(), DL))
1165 /// isSafePHIToSpeculate - PHI instructions that use an alloca and are
1166 /// subsequently loaded can be rewritten to load both input pointers in the pred
1167 /// blocks and then PHI the results, allowing the load of the alloca to be
1170 /// %P2 = phi [i32* %Alloca, i32* %Other]
1171 /// %V = load i32* %P2
1173 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1175 /// %V2 = load i32* %Other
1177 /// %V = phi [i32 %V1, i32 %V2]
1179 /// We can do this to a select if its only uses are loads and if the operand to
1180 /// the select can be loaded unconditionally.
1181 static bool isSafePHIToSpeculate(PHINode *PN, const DataLayout *DL) {
1182 // For now, we can only do this promotion if the load is in the same block as
1183 // the PHI, and if there are no stores between the phi and load.
1184 // TODO: Allow recursive phi users.
1185 // TODO: Allow stores.
1186 BasicBlock *BB = PN->getParent();
1187 unsigned MaxAlign = 0;
1188 for (User *U : PN->users()) {
1189 LoadInst *LI = dyn_cast<LoadInst>(U);
1190 if (!LI || !LI->isSimple()) return false;
1192 // For now we only allow loads in the same block as the PHI. This is a
1193 // common case that happens when instcombine merges two loads through a PHI.
1194 if (LI->getParent() != BB) return false;
1196 // Ensure that there are no instructions between the PHI and the load that
1198 for (BasicBlock::iterator BBI = PN; &*BBI != LI; ++BBI)
1199 if (BBI->mayWriteToMemory())
1202 MaxAlign = std::max(MaxAlign, LI->getAlignment());
1205 // Okay, we know that we have one or more loads in the same block as the PHI.
1206 // We can transform this if it is safe to push the loads into the predecessor
1207 // blocks. The only thing to watch out for is that we can't put a possibly
1208 // trapping load in the predecessor if it is a critical edge.
1209 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1210 BasicBlock *Pred = PN->getIncomingBlock(i);
1211 Value *InVal = PN->getIncomingValue(i);
1213 // If the terminator of the predecessor has side-effects (an invoke),
1214 // there is no safe place to put a load in the predecessor.
1215 if (Pred->getTerminator()->mayHaveSideEffects())
1218 // If the value is produced by the terminator of the predecessor
1219 // (an invoke), there is no valid place to put a load in the predecessor.
1220 if (Pred->getTerminator() == InVal)
1223 // If the predecessor has a single successor, then the edge isn't critical.
1224 if (Pred->getTerminator()->getNumSuccessors() == 1)
1227 // If this pointer is always safe to load, or if we can prove that there is
1228 // already a load in the block, then we can move the load to the pred block.
1229 if (InVal->isDereferenceablePointer(DL) ||
1230 isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign, DL))
1240 /// tryToMakeAllocaBePromotable - This returns true if the alloca only has
1241 /// direct (non-volatile) loads and stores to it. If the alloca is close but
1242 /// not quite there, this will transform the code to allow promotion. As such,
1243 /// it is a non-pure predicate.
1244 static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const DataLayout *DL) {
1245 SetVector<Instruction*, SmallVector<Instruction*, 4>,
1246 SmallPtrSet<Instruction*, 4> > InstsToRewrite;
1247 for (User *U : AI->users()) {
1248 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1249 if (!LI->isSimple())
1254 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1255 if (SI->getOperand(0) == AI || !SI->isSimple())
1256 return false; // Don't allow a store OF the AI, only INTO the AI.
1260 if (SelectInst *SI = dyn_cast<SelectInst>(U)) {
1261 // If the condition being selected on is a constant, fold the select, yes
1262 // this does (rarely) happen early on.
1263 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) {
1264 Value *Result = SI->getOperand(1+CI->isZero());
1265 SI->replaceAllUsesWith(Result);
1266 SI->eraseFromParent();
1268 // This is very rare and we just scrambled the use list of AI, start
1270 return tryToMakeAllocaBePromotable(AI, DL);
1273 // If it is safe to turn "load (select c, AI, ptr)" into a select of two
1274 // loads, then we can transform this by rewriting the select.
1275 if (!isSafeSelectToSpeculate(SI, DL))
1278 InstsToRewrite.insert(SI);
1282 if (PHINode *PN = dyn_cast<PHINode>(U)) {
1283 if (PN->use_empty()) { // Dead PHIs can be stripped.
1284 InstsToRewrite.insert(PN);
1288 // If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads
1289 // in the pred blocks, then we can transform this by rewriting the PHI.
1290 if (!isSafePHIToSpeculate(PN, DL))
1293 InstsToRewrite.insert(PN);
1297 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
1298 if (onlyUsedByLifetimeMarkers(BCI)) {
1299 InstsToRewrite.insert(BCI);
1307 // If there are no instructions to rewrite, then all uses are load/stores and
1309 if (InstsToRewrite.empty())
1312 // If we have instructions that need to be rewritten for this to be promotable
1313 // take care of it now.
1314 for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) {
1315 if (BitCastInst *BCI = dyn_cast<BitCastInst>(InstsToRewrite[i])) {
1316 // This could only be a bitcast used by nothing but lifetime intrinsics.
1317 for (BitCastInst::user_iterator I = BCI->user_begin(), E = BCI->user_end();
1319 cast<Instruction>(*I++)->eraseFromParent();
1320 BCI->eraseFromParent();
1324 if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) {
1325 // Selects in InstsToRewrite only have load uses. Rewrite each as two
1326 // loads with a new select.
1327 while (!SI->use_empty()) {
1328 LoadInst *LI = cast<LoadInst>(SI->user_back());
1330 IRBuilder<> Builder(LI);
1331 LoadInst *TrueLoad =
1332 Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t");
1333 LoadInst *FalseLoad =
1334 Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".f");
1336 // Transfer alignment and TBAA info if present.
1337 TrueLoad->setAlignment(LI->getAlignment());
1338 FalseLoad->setAlignment(LI->getAlignment());
1339 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) {
1340 TrueLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1341 FalseLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1344 Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad);
1346 LI->replaceAllUsesWith(V);
1347 LI->eraseFromParent();
1350 // Now that all the loads are gone, the select is gone too.
1351 SI->eraseFromParent();
1355 // Otherwise, we have a PHI node which allows us to push the loads into the
1357 PHINode *PN = cast<PHINode>(InstsToRewrite[i]);
1358 if (PN->use_empty()) {
1359 PN->eraseFromParent();
1363 Type *LoadTy = cast<PointerType>(PN->getType())->getElementType();
1364 PHINode *NewPN = PHINode::Create(LoadTy, PN->getNumIncomingValues(),
1365 PN->getName()+".ld", PN);
1367 // Get the TBAA tag and alignment to use from one of the loads. It doesn't
1368 // matter which one we get and if any differ, it doesn't matter.
1369 LoadInst *SomeLoad = cast<LoadInst>(PN->user_back());
1370 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa);
1371 unsigned Align = SomeLoad->getAlignment();
1373 // Rewrite all loads of the PN to use the new PHI.
1374 while (!PN->use_empty()) {
1375 LoadInst *LI = cast<LoadInst>(PN->user_back());
1376 LI->replaceAllUsesWith(NewPN);
1377 LI->eraseFromParent();
1380 // Inject loads into all of the pred blocks. Keep track of which blocks we
1381 // insert them into in case we have multiple edges from the same block.
1382 DenseMap<BasicBlock*, LoadInst*> InsertedLoads;
1384 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1385 BasicBlock *Pred = PN->getIncomingBlock(i);
1386 LoadInst *&Load = InsertedLoads[Pred];
1388 Load = new LoadInst(PN->getIncomingValue(i),
1389 PN->getName() + "." + Pred->getName(),
1390 Pred->getTerminator());
1391 Load->setAlignment(Align);
1392 if (TBAATag) Load->setMetadata(LLVMContext::MD_tbaa, TBAATag);
1395 NewPN->addIncoming(Load, Pred);
1398 PN->eraseFromParent();
1405 bool SROA::performPromotion(Function &F) {
1406 std::vector<AllocaInst*> Allocas;
1407 DominatorTree *DT = nullptr;
1409 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
1411 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
1412 DIBuilder DIB(*F.getParent());
1413 bool Changed = false;
1414 SmallVector<Instruction*, 64> Insts;
1418 // Find allocas that are safe to promote, by looking at all instructions in
1420 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
1421 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
1422 if (tryToMakeAllocaBePromotable(AI, DL))
1423 Allocas.push_back(AI);
1425 if (Allocas.empty()) break;
1428 PromoteMemToReg(Allocas, *DT);
1431 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
1432 AllocaInst *AI = Allocas[i];
1434 // Build list of instructions to promote.
1435 for (User *U : AI->users())
1436 Insts.push_back(cast<Instruction>(U));
1437 AllocaPromoter(Insts, SSA, &DIB).run(AI, Insts);
1441 NumPromoted += Allocas.size();
1449 /// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
1450 /// SROA. It must be a struct or array type with a small number of elements.
1451 bool SROA::ShouldAttemptScalarRepl(AllocaInst *AI) {
1452 Type *T = AI->getAllocatedType();
1453 // Do not promote any struct that has too many members.
1454 if (StructType *ST = dyn_cast<StructType>(T))
1455 return ST->getNumElements() <= StructMemberThreshold;
1456 // Do not promote any array that has too many elements.
1457 if (ArrayType *AT = dyn_cast<ArrayType>(T))
1458 return AT->getNumElements() <= ArrayElementThreshold;
1462 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
1463 // which runs on all of the alloca instructions in the entry block, removing
1464 // them if they are only used by getelementptr instructions.
1466 bool SROA::performScalarRepl(Function &F) {
1467 std::vector<AllocaInst*> WorkList;
1469 // Scan the entry basic block, adding allocas to the worklist.
1470 BasicBlock &BB = F.getEntryBlock();
1471 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
1472 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
1473 WorkList.push_back(A);
1475 // Process the worklist
1476 bool Changed = false;
1477 while (!WorkList.empty()) {
1478 AllocaInst *AI = WorkList.back();
1479 WorkList.pop_back();
1481 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
1482 // with unused elements.
1483 if (AI->use_empty()) {
1484 AI->eraseFromParent();
1489 // If this alloca is impossible for us to promote, reject it early.
1490 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
1493 // Check to see if we can perform the core SROA transformation. We cannot
1494 // transform the allocation instruction if it is an array allocation
1495 // (allocations OF arrays are ok though), and an allocation of a scalar
1496 // value cannot be decomposed at all.
1497 uint64_t AllocaSize = DL->getTypeAllocSize(AI->getAllocatedType());
1499 // Do not promote [0 x %struct].
1500 if (AllocaSize == 0) continue;
1502 // Do not promote any struct whose size is too big.
1503 if (AllocaSize > SRThreshold) continue;
1505 // If the alloca looks like a good candidate for scalar replacement, and if
1506 // all its users can be transformed, then split up the aggregate into its
1507 // separate elements.
1508 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
1509 DoScalarReplacement(AI, WorkList);
1514 // If we can turn this aggregate value (potentially with casts) into a
1515 // simple scalar value that can be mem2reg'd into a register value.
1516 // IsNotTrivial tracks whether this is something that mem2reg could have
1517 // promoted itself. If so, we don't want to transform it needlessly. Note
1518 // that we can't just check based on the type: the alloca may be of an i32
1519 // but that has pointer arithmetic to set byte 3 of it or something.
1520 if (AllocaInst *NewAI = ConvertToScalarInfo(
1521 (unsigned)AllocaSize, *DL, ScalarLoadThreshold).TryConvert(AI)) {
1522 NewAI->takeName(AI);
1523 AI->eraseFromParent();
1529 // Otherwise, couldn't process this alloca.
1535 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
1536 /// predicate, do SROA now.
1537 void SROA::DoScalarReplacement(AllocaInst *AI,
1538 std::vector<AllocaInst*> &WorkList) {
1539 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
1540 SmallVector<AllocaInst*, 32> ElementAllocas;
1541 if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
1542 ElementAllocas.reserve(ST->getNumContainedTypes());
1543 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
1544 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), nullptr,
1546 AI->getName() + "." + Twine(i), AI);
1547 ElementAllocas.push_back(NA);
1548 WorkList.push_back(NA); // Add to worklist for recursive processing
1551 ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
1552 ElementAllocas.reserve(AT->getNumElements());
1553 Type *ElTy = AT->getElementType();
1554 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1555 AllocaInst *NA = new AllocaInst(ElTy, nullptr, AI->getAlignment(),
1556 AI->getName() + "." + Twine(i), AI);
1557 ElementAllocas.push_back(NA);
1558 WorkList.push_back(NA); // Add to worklist for recursive processing
1562 // Now that we have created the new alloca instructions, rewrite all the
1563 // uses of the old alloca.
1564 RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
1566 // Now erase any instructions that were made dead while rewriting the alloca.
1567 DeleteDeadInstructions();
1568 AI->eraseFromParent();
1573 /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
1574 /// recursively including all their operands that become trivially dead.
1575 void SROA::DeleteDeadInstructions() {
1576 while (!DeadInsts.empty()) {
1577 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
1579 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
1580 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
1581 // Zero out the operand and see if it becomes trivially dead.
1582 // (But, don't add allocas to the dead instruction list -- they are
1583 // already on the worklist and will be deleted separately.)
1585 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
1586 DeadInsts.push_back(U);
1589 I->eraseFromParent();
1593 /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
1594 /// performing scalar replacement of alloca AI. The results are flagged in
1595 /// the Info parameter. Offset indicates the position within AI that is
1596 /// referenced by this instruction.
1597 void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset,
1599 for (Use &U : I->uses()) {
1600 Instruction *User = cast<Instruction>(U.getUser());
1602 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1603 isSafeForScalarRepl(BC, Offset, Info);
1604 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1605 uint64_t GEPOffset = Offset;
1606 isSafeGEP(GEPI, GEPOffset, Info);
1608 isSafeForScalarRepl(GEPI, GEPOffset, Info);
1609 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1610 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1611 if (!Length || Length->isNegative())
1612 return MarkUnsafe(Info, User);
1614 isSafeMemAccess(Offset, Length->getZExtValue(), nullptr,
1615 U.getOperandNo() == 0, Info, MI,
1616 true /*AllowWholeAccess*/);
1617 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1618 if (!LI->isSimple())
1619 return MarkUnsafe(Info, User);
1620 Type *LIType = LI->getType();
1621 isSafeMemAccess(Offset, DL->getTypeAllocSize(LIType),
1622 LIType, false, Info, LI, true /*AllowWholeAccess*/);
1623 Info.hasALoadOrStore = true;
1625 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1626 // Store is ok if storing INTO the pointer, not storing the pointer
1627 if (!SI->isSimple() || SI->getOperand(0) == I)
1628 return MarkUnsafe(Info, User);
1630 Type *SIType = SI->getOperand(0)->getType();
1631 isSafeMemAccess(Offset, DL->getTypeAllocSize(SIType),
1632 SIType, true, Info, SI, true /*AllowWholeAccess*/);
1633 Info.hasALoadOrStore = true;
1634 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
1635 if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
1636 II->getIntrinsicID() != Intrinsic::lifetime_end)
1637 return MarkUnsafe(Info, User);
1638 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
1639 isSafePHISelectUseForScalarRepl(User, Offset, Info);
1641 return MarkUnsafe(Info, User);
1643 if (Info.isUnsafe) return;
1648 /// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer
1649 /// derived from the alloca, we can often still split the alloca into elements.
1650 /// This is useful if we have a large alloca where one element is phi'd
1651 /// together somewhere: we can SRoA and promote all the other elements even if
1652 /// we end up not being able to promote this one.
1654 /// All we require is that the uses of the PHI do not index into other parts of
1655 /// the alloca. The most important use case for this is single load and stores
1656 /// that are PHI'd together, which can happen due to code sinking.
1657 void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset,
1659 // If we've already checked this PHI, don't do it again.
1660 if (PHINode *PN = dyn_cast<PHINode>(I))
1661 if (!Info.CheckedPHIs.insert(PN))
1664 for (User *U : I->users()) {
1665 Instruction *UI = cast<Instruction>(U);
1667 if (BitCastInst *BC = dyn_cast<BitCastInst>(UI)) {
1668 isSafePHISelectUseForScalarRepl(BC, Offset, Info);
1669 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(UI)) {
1670 // Only allow "bitcast" GEPs for simplicity. We could generalize this,
1671 // but would have to prove that we're staying inside of an element being
1673 if (!GEPI->hasAllZeroIndices())
1674 return MarkUnsafe(Info, UI);
1675 isSafePHISelectUseForScalarRepl(GEPI, Offset, Info);
1676 } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
1677 if (!LI->isSimple())
1678 return MarkUnsafe(Info, UI);
1679 Type *LIType = LI->getType();
1680 isSafeMemAccess(Offset, DL->getTypeAllocSize(LIType),
1681 LIType, false, Info, LI, false /*AllowWholeAccess*/);
1682 Info.hasALoadOrStore = true;
1684 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1685 // Store is ok if storing INTO the pointer, not storing the pointer
1686 if (!SI->isSimple() || SI->getOperand(0) == I)
1687 return MarkUnsafe(Info, UI);
1689 Type *SIType = SI->getOperand(0)->getType();
1690 isSafeMemAccess(Offset, DL->getTypeAllocSize(SIType),
1691 SIType, true, Info, SI, false /*AllowWholeAccess*/);
1692 Info.hasALoadOrStore = true;
1693 } else if (isa<PHINode>(UI) || isa<SelectInst>(UI)) {
1694 isSafePHISelectUseForScalarRepl(UI, Offset, Info);
1696 return MarkUnsafe(Info, UI);
1698 if (Info.isUnsafe) return;
1702 /// isSafeGEP - Check if a GEP instruction can be handled for scalar
1703 /// replacement. It is safe when all the indices are constant, in-bounds
1704 /// references, and when the resulting offset corresponds to an element within
1705 /// the alloca type. The results are flagged in the Info parameter. Upon
1706 /// return, Offset is adjusted as specified by the GEP indices.
1707 void SROA::isSafeGEP(GetElementPtrInst *GEPI,
1708 uint64_t &Offset, AllocaInfo &Info) {
1709 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
1712 bool NonConstant = false;
1713 unsigned NonConstantIdxSize = 0;
1715 // Walk through the GEP type indices, checking the types that this indexes
1717 for (; GEPIt != E; ++GEPIt) {
1718 // Ignore struct elements, no extra checking needed for these.
1719 if ((*GEPIt)->isStructTy())
1722 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
1724 return MarkUnsafe(Info, GEPI);
1727 // Compute the offset due to this GEP and check if the alloca has a
1728 // component element at that offset.
1729 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1730 // If this GEP is non-constant then the last operand must have been a
1731 // dynamic index into a vector. Pop this now as it has no impact on the
1732 // constant part of the offset.
1735 Offset += DL->getIndexedOffset(GEPI->getPointerOperandType(), Indices);
1736 if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset,
1737 NonConstantIdxSize))
1738 MarkUnsafe(Info, GEPI);
1741 /// isHomogeneousAggregate - Check if type T is a struct or array containing
1742 /// elements of the same type (which is always true for arrays). If so,
1743 /// return true with NumElts and EltTy set to the number of elements and the
1744 /// element type, respectively.
1745 static bool isHomogeneousAggregate(Type *T, unsigned &NumElts,
1747 if (ArrayType *AT = dyn_cast<ArrayType>(T)) {
1748 NumElts = AT->getNumElements();
1749 EltTy = (NumElts == 0 ? nullptr : AT->getElementType());
1752 if (StructType *ST = dyn_cast<StructType>(T)) {
1753 NumElts = ST->getNumContainedTypes();
1754 EltTy = (NumElts == 0 ? nullptr : ST->getContainedType(0));
1755 for (unsigned n = 1; n < NumElts; ++n) {
1756 if (ST->getContainedType(n) != EltTy)
1764 /// isCompatibleAggregate - Check if T1 and T2 are either the same type or are
1765 /// "homogeneous" aggregates with the same element type and number of elements.
1766 static bool isCompatibleAggregate(Type *T1, Type *T2) {
1770 unsigned NumElts1, NumElts2;
1771 Type *EltTy1, *EltTy2;
1772 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) &&
1773 isHomogeneousAggregate(T2, NumElts2, EltTy2) &&
1774 NumElts1 == NumElts2 &&
1781 /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
1782 /// alloca or has an offset and size that corresponds to a component element
1783 /// within it. The offset checked here may have been formed from a GEP with a
1784 /// pointer bitcasted to a different type.
1786 /// If AllowWholeAccess is true, then this allows uses of the entire alloca as a
1787 /// unit. If false, it only allows accesses known to be in a single element.
1788 void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
1789 Type *MemOpType, bool isStore,
1790 AllocaInfo &Info, Instruction *TheAccess,
1791 bool AllowWholeAccess) {
1792 // Check if this is a load/store of the entire alloca.
1793 if (Offset == 0 && AllowWholeAccess &&
1794 MemSize == DL->getTypeAllocSize(Info.AI->getAllocatedType())) {
1795 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer
1796 // loads/stores (which are essentially the same as the MemIntrinsics with
1797 // regard to copying padding between elements). But, if an alloca is
1798 // flagged as both a source and destination of such operations, we'll need
1799 // to check later for padding between elements.
1800 if (!MemOpType || MemOpType->isIntegerTy()) {
1802 Info.isMemCpyDst = true;
1804 Info.isMemCpySrc = true;
1807 // This is also safe for references using a type that is compatible with
1808 // the type of the alloca, so that loads/stores can be rewritten using
1809 // insertvalue/extractvalue.
1810 if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) {
1811 Info.hasSubelementAccess = true;
1815 // Check if the offset/size correspond to a component within the alloca type.
1816 Type *T = Info.AI->getAllocatedType();
1817 if (TypeHasComponent(T, Offset, MemSize)) {
1818 Info.hasSubelementAccess = true;
1822 return MarkUnsafe(Info, TheAccess);
1825 /// TypeHasComponent - Return true if T has a component type with the
1826 /// specified offset and size. If Size is zero, do not check the size.
1827 bool SROA::TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size) {
1830 if (StructType *ST = dyn_cast<StructType>(T)) {
1831 const StructLayout *Layout = DL->getStructLayout(ST);
1832 unsigned EltIdx = Layout->getElementContainingOffset(Offset);
1833 EltTy = ST->getContainedType(EltIdx);
1834 EltSize = DL->getTypeAllocSize(EltTy);
1835 Offset -= Layout->getElementOffset(EltIdx);
1836 } else if (ArrayType *AT = dyn_cast<ArrayType>(T)) {
1837 EltTy = AT->getElementType();
1838 EltSize = DL->getTypeAllocSize(EltTy);
1839 if (Offset >= AT->getNumElements() * EltSize)
1842 } else if (VectorType *VT = dyn_cast<VectorType>(T)) {
1843 EltTy = VT->getElementType();
1844 EltSize = DL->getTypeAllocSize(EltTy);
1845 if (Offset >= VT->getNumElements() * EltSize)
1851 if (Offset == 0 && (Size == 0 || EltSize == Size))
1853 // Check if the component spans multiple elements.
1854 if (Offset + Size > EltSize)
1856 return TypeHasComponent(EltTy, Offset, Size);
1859 /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
1860 /// the instruction I, which references it, to use the separate elements.
1861 /// Offset indicates the position within AI that is referenced by this
1863 void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1864 SmallVectorImpl<AllocaInst *> &NewElts) {
1865 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) {
1866 Use &TheUse = *UI++;
1867 Instruction *User = cast<Instruction>(TheUse.getUser());
1869 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1870 RewriteBitCast(BC, AI, Offset, NewElts);
1874 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1875 RewriteGEP(GEPI, AI, Offset, NewElts);
1879 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1880 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1881 uint64_t MemSize = Length->getZExtValue();
1883 MemSize == DL->getTypeAllocSize(AI->getAllocatedType()))
1884 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
1885 // Otherwise the intrinsic can only touch a single element and the
1886 // address operand will be updated, so nothing else needs to be done.
1890 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
1891 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
1892 II->getIntrinsicID() == Intrinsic::lifetime_end) {
1893 RewriteLifetimeIntrinsic(II, AI, Offset, NewElts);
1898 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1899 Type *LIType = LI->getType();
1901 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) {
1903 // %res = load { i32, i32 }* %alloc
1905 // %load.0 = load i32* %alloc.0
1906 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
1907 // %load.1 = load i32* %alloc.1
1908 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
1909 // (Also works for arrays instead of structs)
1910 Value *Insert = UndefValue::get(LIType);
1911 IRBuilder<> Builder(LI);
1912 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1913 Value *Load = Builder.CreateLoad(NewElts[i], "load");
1914 Insert = Builder.CreateInsertValue(Insert, Load, i, "insert");
1916 LI->replaceAllUsesWith(Insert);
1917 DeadInsts.push_back(LI);
1918 } else if (LIType->isIntegerTy() &&
1919 DL->getTypeAllocSize(LIType) ==
1920 DL->getTypeAllocSize(AI->getAllocatedType())) {
1921 // If this is a load of the entire alloca to an integer, rewrite it.
1922 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
1927 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1928 Value *Val = SI->getOperand(0);
1929 Type *SIType = Val->getType();
1930 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) {
1932 // store { i32, i32 } %val, { i32, i32 }* %alloc
1934 // %val.0 = extractvalue { i32, i32 } %val, 0
1935 // store i32 %val.0, i32* %alloc.0
1936 // %val.1 = extractvalue { i32, i32 } %val, 1
1937 // store i32 %val.1, i32* %alloc.1
1938 // (Also works for arrays instead of structs)
1939 IRBuilder<> Builder(SI);
1940 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1941 Value *Extract = Builder.CreateExtractValue(Val, i, Val->getName());
1942 Builder.CreateStore(Extract, NewElts[i]);
1944 DeadInsts.push_back(SI);
1945 } else if (SIType->isIntegerTy() &&
1946 DL->getTypeAllocSize(SIType) ==
1947 DL->getTypeAllocSize(AI->getAllocatedType())) {
1948 // If this is a store of the entire alloca from an integer, rewrite it.
1949 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
1954 if (isa<SelectInst>(User) || isa<PHINode>(User)) {
1955 // If we have a PHI user of the alloca itself (as opposed to a GEP or
1956 // bitcast) we have to rewrite it. GEP and bitcast uses will be RAUW'd to
1958 if (!isa<AllocaInst>(I)) continue;
1960 assert(Offset == 0 && NewElts[0] &&
1961 "Direct alloca use should have a zero offset");
1963 // If we have a use of the alloca, we know the derived uses will be
1964 // utilizing just the first element of the scalarized result. Insert a
1965 // bitcast of the first alloca before the user as required.
1966 AllocaInst *NewAI = NewElts[0];
1967 BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI);
1968 NewAI->moveBefore(BCI);
1975 /// RewriteBitCast - Update a bitcast reference to the alloca being replaced
1976 /// and recursively continue updating all of its uses.
1977 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
1978 SmallVectorImpl<AllocaInst *> &NewElts) {
1979 RewriteForScalarRepl(BC, AI, Offset, NewElts);
1980 if (BC->getOperand(0) != AI)
1983 // The bitcast references the original alloca. Replace its uses with
1984 // references to the alloca containing offset zero (which is normally at
1985 // index zero, but might not be in cases involving structs with elements
1987 Type *T = AI->getAllocatedType();
1988 uint64_t EltOffset = 0;
1990 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
1991 Instruction *Val = NewElts[Idx];
1992 if (Val->getType() != BC->getDestTy()) {
1993 Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
1996 BC->replaceAllUsesWith(Val);
1997 DeadInsts.push_back(BC);
2000 /// FindElementAndOffset - Return the index of the element containing Offset
2001 /// within the specified type, which must be either a struct or an array.
2002 /// Sets T to the type of the element and Offset to the offset within that
2003 /// element. IdxTy is set to the type of the index result to be used in a
2004 /// GEP instruction.
2005 uint64_t SROA::FindElementAndOffset(Type *&T, uint64_t &Offset,
2008 if (StructType *ST = dyn_cast<StructType>(T)) {
2009 const StructLayout *Layout = DL->getStructLayout(ST);
2010 Idx = Layout->getElementContainingOffset(Offset);
2011 T = ST->getContainedType(Idx);
2012 Offset -= Layout->getElementOffset(Idx);
2013 IdxTy = Type::getInt32Ty(T->getContext());
2015 } else if (ArrayType *AT = dyn_cast<ArrayType>(T)) {
2016 T = AT->getElementType();
2017 uint64_t EltSize = DL->getTypeAllocSize(T);
2018 Idx = Offset / EltSize;
2019 Offset -= Idx * EltSize;
2020 IdxTy = Type::getInt64Ty(T->getContext());
2023 VectorType *VT = cast<VectorType>(T);
2024 T = VT->getElementType();
2025 uint64_t EltSize = DL->getTypeAllocSize(T);
2026 Idx = Offset / EltSize;
2027 Offset -= Idx * EltSize;
2028 IdxTy = Type::getInt64Ty(T->getContext());
2032 /// RewriteGEP - Check if this GEP instruction moves the pointer across
2033 /// elements of the alloca that are being split apart, and if so, rewrite
2034 /// the GEP to be relative to the new element.
2035 void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
2036 SmallVectorImpl<AllocaInst *> &NewElts) {
2037 uint64_t OldOffset = Offset;
2038 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
2039 // If the GEP was dynamic then it must have been a dynamic vector lookup.
2040 // In this case, it must be the last GEP operand which is dynamic so keep that
2041 // aside until we've found the constant GEP offset then add it back in at the
2043 Value* NonConstantIdx = nullptr;
2044 if (!GEPI->hasAllConstantIndices())
2045 NonConstantIdx = Indices.pop_back_val();
2046 Offset += DL->getIndexedOffset(GEPI->getPointerOperandType(), Indices);
2048 RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
2050 Type *T = AI->getAllocatedType();
2052 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
2053 if (GEPI->getOperand(0) == AI)
2054 OldIdx = ~0ULL; // Force the GEP to be rewritten.
2056 T = AI->getAllocatedType();
2057 uint64_t EltOffset = Offset;
2058 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
2060 // If this GEP does not move the pointer across elements of the alloca
2061 // being split, then it does not needs to be rewritten.
2065 Type *i32Ty = Type::getInt32Ty(AI->getContext());
2066 SmallVector<Value*, 8> NewArgs;
2067 NewArgs.push_back(Constant::getNullValue(i32Ty));
2068 while (EltOffset != 0) {
2069 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
2070 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
2072 if (NonConstantIdx) {
2074 // This GEP has a dynamic index. We need to add "i32 0" to index through
2075 // any structs or arrays in the original type until we get to the vector
2077 while (!isa<VectorType>(GepTy)) {
2078 NewArgs.push_back(Constant::getNullValue(i32Ty));
2079 GepTy = cast<CompositeType>(GepTy)->getTypeAtIndex(0U);
2081 NewArgs.push_back(NonConstantIdx);
2083 Instruction *Val = NewElts[Idx];
2084 if (NewArgs.size() > 1) {
2085 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs, "", GEPI);
2086 Val->takeName(GEPI);
2088 if (Val->getType() != GEPI->getType())
2089 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
2090 GEPI->replaceAllUsesWith(Val);
2091 DeadInsts.push_back(GEPI);
2094 /// RewriteLifetimeIntrinsic - II is a lifetime.start/lifetime.end. Rewrite it
2095 /// to mark the lifetime of the scalarized memory.
2096 void SROA::RewriteLifetimeIntrinsic(IntrinsicInst *II, AllocaInst *AI,
2098 SmallVectorImpl<AllocaInst *> &NewElts) {
2099 ConstantInt *OldSize = cast<ConstantInt>(II->getArgOperand(0));
2100 // Put matching lifetime markers on everything from Offset up to
2102 Type *AIType = AI->getAllocatedType();
2103 uint64_t NewOffset = Offset;
2105 uint64_t Idx = FindElementAndOffset(AIType, NewOffset, IdxTy);
2107 IRBuilder<> Builder(II);
2108 uint64_t Size = OldSize->getLimitedValue();
2111 // Splice the first element and index 'NewOffset' bytes in. SROA will
2112 // split the alloca again later.
2113 unsigned AS = AI->getType()->getAddressSpace();
2114 Value *V = Builder.CreateBitCast(NewElts[Idx], Builder.getInt8PtrTy(AS));
2115 V = Builder.CreateGEP(V, Builder.getInt64(NewOffset));
2117 IdxTy = NewElts[Idx]->getAllocatedType();
2118 uint64_t EltSize = DL->getTypeAllocSize(IdxTy) - NewOffset;
2119 if (EltSize > Size) {
2125 if (II->getIntrinsicID() == Intrinsic::lifetime_start)
2126 Builder.CreateLifetimeStart(V, Builder.getInt64(EltSize));
2128 Builder.CreateLifetimeEnd(V, Builder.getInt64(EltSize));
2132 for (; Idx != NewElts.size() && Size; ++Idx) {
2133 IdxTy = NewElts[Idx]->getAllocatedType();
2134 uint64_t EltSize = DL->getTypeAllocSize(IdxTy);
2135 if (EltSize > Size) {
2141 if (II->getIntrinsicID() == Intrinsic::lifetime_start)
2142 Builder.CreateLifetimeStart(NewElts[Idx],
2143 Builder.getInt64(EltSize));
2145 Builder.CreateLifetimeEnd(NewElts[Idx],
2146 Builder.getInt64(EltSize));
2148 DeadInsts.push_back(II);
2151 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
2152 /// Rewrite it to copy or set the elements of the scalarized memory.
2154 SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
2156 SmallVectorImpl<AllocaInst *> &NewElts) {
2157 // If this is a memcpy/memmove, construct the other pointer as the
2158 // appropriate type. The "Other" pointer is the pointer that goes to memory
2159 // that doesn't have anything to do with the alloca that we are promoting. For
2160 // memset, this Value* stays null.
2161 Value *OtherPtr = nullptr;
2162 unsigned MemAlignment = MI->getAlignment();
2163 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
2164 if (Inst == MTI->getRawDest())
2165 OtherPtr = MTI->getRawSource();
2167 assert(Inst == MTI->getRawSource());
2168 OtherPtr = MTI->getRawDest();
2172 // If there is an other pointer, we want to convert it to the same pointer
2173 // type as AI has, so we can GEP through it safely.
2175 unsigned AddrSpace =
2176 cast<PointerType>(OtherPtr->getType())->getAddressSpace();
2178 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
2179 // optimization, but it's also required to detect the corner case where
2180 // both pointer operands are referencing the same memory, and where
2181 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
2182 // function is only called for mem intrinsics that access the whole
2183 // aggregate, so non-zero GEPs are not an issue here.)
2184 OtherPtr = OtherPtr->stripPointerCasts();
2186 // Copying the alloca to itself is a no-op: just delete it.
2187 if (OtherPtr == AI || OtherPtr == NewElts[0]) {
2188 // This code will run twice for a no-op memcpy -- once for each operand.
2189 // Put only one reference to MI on the DeadInsts list.
2190 for (SmallVectorImpl<Value *>::const_iterator I = DeadInsts.begin(),
2191 E = DeadInsts.end(); I != E; ++I)
2192 if (*I == MI) return;
2193 DeadInsts.push_back(MI);
2197 // If the pointer is not the right type, insert a bitcast to the right
2200 PointerType::get(AI->getType()->getElementType(), AddrSpace);
2202 if (OtherPtr->getType() != NewTy)
2203 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
2206 // Process each element of the aggregate.
2207 bool SROADest = MI->getRawDest() == Inst;
2209 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
2211 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2212 // If this is a memcpy/memmove, emit a GEP of the other element address.
2213 Value *OtherElt = nullptr;
2214 unsigned OtherEltAlign = MemAlignment;
2217 Value *Idx[2] = { Zero,
2218 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
2219 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx,
2220 OtherPtr->getName()+"."+Twine(i),
2223 PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
2224 Type *OtherTy = OtherPtrTy->getElementType();
2225 if (StructType *ST = dyn_cast<StructType>(OtherTy)) {
2226 EltOffset = DL->getStructLayout(ST)->getElementOffset(i);
2228 Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
2229 EltOffset = DL->getTypeAllocSize(EltTy)*i;
2232 // The alignment of the other pointer is the guaranteed alignment of the
2233 // element, which is affected by both the known alignment of the whole
2234 // mem intrinsic and the alignment of the element. If the alignment of
2235 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
2236 // known alignment is just 4 bytes.
2237 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
2240 Value *EltPtr = NewElts[i];
2241 Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
2243 // If we got down to a scalar, insert a load or store as appropriate.
2244 if (EltTy->isSingleValueType()) {
2245 if (isa<MemTransferInst>(MI)) {
2247 // From Other to Alloca.
2248 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
2249 new StoreInst(Elt, EltPtr, MI);
2251 // From Alloca to Other.
2252 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
2253 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
2257 assert(isa<MemSetInst>(MI));
2259 // If the stored element is zero (common case), just store a null
2262 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
2264 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
2266 // If EltTy is a vector type, get the element type.
2267 Type *ValTy = EltTy->getScalarType();
2269 // Construct an integer with the right value.
2270 unsigned EltSize = DL->getTypeSizeInBits(ValTy);
2271 APInt OneVal(EltSize, CI->getZExtValue());
2272 APInt TotalVal(OneVal);
2274 for (unsigned i = 0; 8*i < EltSize; ++i) {
2275 TotalVal = TotalVal.shl(8);
2279 // Convert the integer value to the appropriate type.
2280 StoreVal = ConstantInt::get(CI->getContext(), TotalVal);
2281 if (ValTy->isPointerTy())
2282 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
2283 else if (ValTy->isFloatingPointTy())
2284 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
2285 assert(StoreVal->getType() == ValTy && "Type mismatch!");
2287 // If the requested value was a vector constant, create it.
2288 if (EltTy->isVectorTy()) {
2289 unsigned NumElts = cast<VectorType>(EltTy)->getNumElements();
2290 StoreVal = ConstantVector::getSplat(NumElts, StoreVal);
2293 new StoreInst(StoreVal, EltPtr, MI);
2296 // Otherwise, if we're storing a byte variable, use a memset call for
2300 unsigned EltSize = DL->getTypeAllocSize(EltTy);
2304 IRBuilder<> Builder(MI);
2306 // Finally, insert the meminst for this element.
2307 if (isa<MemSetInst>(MI)) {
2308 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize,
2311 assert(isa<MemTransferInst>(MI));
2312 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr
2313 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr
2315 if (isa<MemCpyInst>(MI))
2316 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile());
2318 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile());
2321 DeadInsts.push_back(MI);
2324 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
2325 /// overwrites the entire allocation. Extract out the pieces of the stored
2326 /// integer and store them individually.
2328 SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
2329 SmallVectorImpl<AllocaInst *> &NewElts) {
2330 // Extract each element out of the integer according to its structure offset
2331 // and store the element value to the individual alloca.
2332 Value *SrcVal = SI->getOperand(0);
2333 Type *AllocaEltTy = AI->getAllocatedType();
2334 uint64_t AllocaSizeBits = DL->getTypeAllocSizeInBits(AllocaEltTy);
2336 IRBuilder<> Builder(SI);
2338 // Handle tail padding by extending the operand
2339 if (DL->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
2340 SrcVal = Builder.CreateZExt(SrcVal,
2341 IntegerType::get(SI->getContext(), AllocaSizeBits));
2343 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
2346 // There are two forms here: AI could be an array or struct. Both cases
2347 // have different ways to compute the element offset.
2348 if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2349 const StructLayout *Layout = DL->getStructLayout(EltSTy);
2351 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2352 // Get the number of bits to shift SrcVal to get the value.
2353 Type *FieldTy = EltSTy->getElementType(i);
2354 uint64_t Shift = Layout->getElementOffsetInBits(i);
2356 if (DL->isBigEndian())
2357 Shift = AllocaSizeBits-Shift-DL->getTypeAllocSizeInBits(FieldTy);
2359 Value *EltVal = SrcVal;
2361 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2362 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2365 // Truncate down to an integer of the right size.
2366 uint64_t FieldSizeBits = DL->getTypeSizeInBits(FieldTy);
2368 // Ignore zero sized fields like {}, they obviously contain no data.
2369 if (FieldSizeBits == 0) continue;
2371 if (FieldSizeBits != AllocaSizeBits)
2372 EltVal = Builder.CreateTrunc(EltVal,
2373 IntegerType::get(SI->getContext(), FieldSizeBits));
2374 Value *DestField = NewElts[i];
2375 if (EltVal->getType() == FieldTy) {
2376 // Storing to an integer field of this size, just do it.
2377 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
2378 // Bitcast to the right element type (for fp/vector values).
2379 EltVal = Builder.CreateBitCast(EltVal, FieldTy);
2381 // Otherwise, bitcast the dest pointer (for aggregates).
2382 DestField = Builder.CreateBitCast(DestField,
2383 PointerType::getUnqual(EltVal->getType()));
2385 new StoreInst(EltVal, DestField, SI);
2389 ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
2390 Type *ArrayEltTy = ATy->getElementType();
2391 uint64_t ElementOffset = DL->getTypeAllocSizeInBits(ArrayEltTy);
2392 uint64_t ElementSizeBits = DL->getTypeSizeInBits(ArrayEltTy);
2396 if (DL->isBigEndian())
2397 Shift = AllocaSizeBits-ElementOffset;
2401 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2402 // Ignore zero sized fields like {}, they obviously contain no data.
2403 if (ElementSizeBits == 0) continue;
2405 Value *EltVal = SrcVal;
2407 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2408 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2411 // Truncate down to an integer of the right size.
2412 if (ElementSizeBits != AllocaSizeBits)
2413 EltVal = Builder.CreateTrunc(EltVal,
2414 IntegerType::get(SI->getContext(),
2416 Value *DestField = NewElts[i];
2417 if (EltVal->getType() == ArrayEltTy) {
2418 // Storing to an integer field of this size, just do it.
2419 } else if (ArrayEltTy->isFloatingPointTy() ||
2420 ArrayEltTy->isVectorTy()) {
2421 // Bitcast to the right element type (for fp/vector values).
2422 EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy);
2424 // Otherwise, bitcast the dest pointer (for aggregates).
2425 DestField = Builder.CreateBitCast(DestField,
2426 PointerType::getUnqual(EltVal->getType()));
2428 new StoreInst(EltVal, DestField, SI);
2430 if (DL->isBigEndian())
2431 Shift -= ElementOffset;
2433 Shift += ElementOffset;
2437 DeadInsts.push_back(SI);
2440 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
2441 /// an integer. Load the individual pieces to form the aggregate value.
2443 SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
2444 SmallVectorImpl<AllocaInst *> &NewElts) {
2445 // Extract each element out of the NewElts according to its structure offset
2446 // and form the result value.
2447 Type *AllocaEltTy = AI->getAllocatedType();
2448 uint64_t AllocaSizeBits = DL->getTypeAllocSizeInBits(AllocaEltTy);
2450 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
2453 // There are two forms here: AI could be an array or struct. Both cases
2454 // have different ways to compute the element offset.
2455 const StructLayout *Layout = nullptr;
2456 uint64_t ArrayEltBitOffset = 0;
2457 if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2458 Layout = DL->getStructLayout(EltSTy);
2460 Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
2461 ArrayEltBitOffset = DL->getTypeAllocSizeInBits(ArrayEltTy);
2465 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
2467 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2468 // Load the value from the alloca. If the NewElt is an aggregate, cast
2469 // the pointer to an integer of the same size before doing the load.
2470 Value *SrcField = NewElts[i];
2472 cast<PointerType>(SrcField->getType())->getElementType();
2473 uint64_t FieldSizeBits = DL->getTypeSizeInBits(FieldTy);
2475 // Ignore zero sized fields like {}, they obviously contain no data.
2476 if (FieldSizeBits == 0) continue;
2478 IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
2480 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
2481 !FieldTy->isVectorTy())
2482 SrcField = new BitCastInst(SrcField,
2483 PointerType::getUnqual(FieldIntTy),
2485 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
2487 // If SrcField is a fp or vector of the right size but that isn't an
2488 // integer type, bitcast to an integer so we can shift it.
2489 if (SrcField->getType() != FieldIntTy)
2490 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
2492 // Zero extend the field to be the same size as the final alloca so that
2493 // we can shift and insert it.
2494 if (SrcField->getType() != ResultVal->getType())
2495 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
2497 // Determine the number of bits to shift SrcField.
2499 if (Layout) // Struct case.
2500 Shift = Layout->getElementOffsetInBits(i);
2502 Shift = i*ArrayEltBitOffset;
2504 if (DL->isBigEndian())
2505 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
2508 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
2509 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
2512 // Don't create an 'or x, 0' on the first iteration.
2513 if (!isa<Constant>(ResultVal) ||
2514 !cast<Constant>(ResultVal)->isNullValue())
2515 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
2517 ResultVal = SrcField;
2520 // Handle tail padding by truncating the result
2521 if (DL->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
2522 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
2524 LI->replaceAllUsesWith(ResultVal);
2525 DeadInsts.push_back(LI);
2528 /// HasPadding - Return true if the specified type has any structure or
2529 /// alignment padding in between the elements that would be split apart
2530 /// by SROA; return false otherwise.
2531 static bool HasPadding(Type *Ty, const DataLayout &DL) {
2532 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
2533 Ty = ATy->getElementType();
2534 return DL.getTypeSizeInBits(Ty) != DL.getTypeAllocSizeInBits(Ty);
2537 // SROA currently handles only Arrays and Structs.
2538 StructType *STy = cast<StructType>(Ty);
2539 const StructLayout *SL = DL.getStructLayout(STy);
2540 unsigned PrevFieldBitOffset = 0;
2541 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
2542 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
2544 // Check to see if there is any padding between this element and the
2547 unsigned PrevFieldEnd =
2548 PrevFieldBitOffset+DL.getTypeSizeInBits(STy->getElementType(i-1));
2549 if (PrevFieldEnd < FieldBitOffset)
2552 PrevFieldBitOffset = FieldBitOffset;
2554 // Check for tail padding.
2555 if (unsigned EltCount = STy->getNumElements()) {
2556 unsigned PrevFieldEnd = PrevFieldBitOffset +
2557 DL.getTypeSizeInBits(STy->getElementType(EltCount-1));
2558 if (PrevFieldEnd < SL->getSizeInBits())
2564 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
2565 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
2566 /// or 1 if safe after canonicalization has been performed.
2567 bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
2568 // Loop over the use list of the alloca. We can only transform it if all of
2569 // the users are safe to transform.
2570 AllocaInfo Info(AI);
2572 isSafeForScalarRepl(AI, 0, Info);
2573 if (Info.isUnsafe) {
2574 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
2578 // Okay, we know all the users are promotable. If the aggregate is a memcpy
2579 // source and destination, we have to be careful. In particular, the memcpy
2580 // could be moving around elements that live in structure padding of the LLVM
2581 // types, but may actually be used. In these cases, we refuse to promote the
2583 if (Info.isMemCpySrc && Info.isMemCpyDst &&
2584 HasPadding(AI->getAllocatedType(), *DL))
2587 // If the alloca never has an access to just *part* of it, but is accessed
2588 // via loads and stores, then we should use ConvertToScalarInfo to promote
2589 // the alloca instead of promoting each piece at a time and inserting fission
2591 if (!Info.hasSubelementAccess && Info.hasALoadOrStore) {
2592 // If the struct/array just has one element, use basic SRoA.
2593 if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
2594 if (ST->getNumElements() > 1) return false;
2596 if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1)