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 #define DEBUG_TYPE "scalarrepl"
23 #include "llvm/Transforms/Scalar.h"
24 #include "llvm/ADT/SetVector.h"
25 #include "llvm/ADT/SmallVector.h"
26 #include "llvm/ADT/Statistic.h"
27 #include "llvm/Analysis/Loads.h"
28 #include "llvm/Analysis/ValueTracking.h"
29 #include "llvm/IR/CallSite.h"
30 #include "llvm/IR/Constants.h"
31 #include "llvm/IR/DIBuilder.h"
32 #include "llvm/IR/DataLayout.h"
33 #include "llvm/IR/DebugInfo.h"
34 #include "llvm/IR/DerivedTypes.h"
35 #include "llvm/IR/Dominators.h"
36 #include "llvm/IR/Function.h"
37 #include "llvm/IR/GetElementPtrTypeIterator.h"
38 #include "llvm/IR/GlobalVariable.h"
39 #include "llvm/IR/IRBuilder.h"
40 #include "llvm/IR/Instructions.h"
41 #include "llvm/IR/IntrinsicInst.h"
42 #include "llvm/IR/LLVMContext.h"
43 #include "llvm/IR/Module.h"
44 #include "llvm/IR/Operator.h"
45 #include "llvm/Pass.h"
46 #include "llvm/Support/Debug.h"
47 #include "llvm/Support/ErrorHandling.h"
48 #include "llvm/Support/MathExtras.h"
49 #include "llvm/Support/raw_ostream.h"
50 #include "llvm/Transforms/Utils/Local.h"
51 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
52 #include "llvm/Transforms/Utils/SSAUpdater.h"
55 STATISTIC(NumReplaced, "Number of allocas broken up");
56 STATISTIC(NumPromoted, "Number of allocas promoted");
57 STATISTIC(NumAdjusted, "Number of scalar allocas adjusted to allow promotion");
58 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
61 struct SROA : public FunctionPass {
62 SROA(int T, bool hasDT, char &ID, int ST, int AT, int SLT)
63 : FunctionPass(ID), HasDomTree(hasDT) {
69 StructMemberThreshold = 32;
71 StructMemberThreshold = ST;
73 ArrayElementThreshold = 8;
75 ArrayElementThreshold = AT;
77 // Do not limit the scalar integer load size if no threshold is given.
78 ScalarLoadThreshold = -1;
80 ScalarLoadThreshold = SLT;
83 bool runOnFunction(Function &F) override;
85 bool performScalarRepl(Function &F);
86 bool performPromotion(Function &F);
92 /// DeadInsts - Keep track of instructions we have made dead, so that
93 /// we can remove them after we are done working.
94 SmallVector<Value*, 32> DeadInsts;
96 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
97 /// information about the uses. All these fields are initialized to false
98 /// and set to true when something is learned.
100 /// The alloca to promote.
103 /// CheckedPHIs - This is a set of verified PHI nodes, to prevent infinite
104 /// looping and avoid redundant work.
105 SmallPtrSet<PHINode*, 8> CheckedPHIs;
107 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
110 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
111 bool isMemCpySrc : 1;
113 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
114 bool isMemCpyDst : 1;
116 /// hasSubelementAccess - This is true if a subelement of the alloca is
117 /// ever accessed, or false if the alloca is only accessed with mem
118 /// intrinsics or load/store that only access the entire alloca at once.
119 bool hasSubelementAccess : 1;
121 /// hasALoadOrStore - This is true if there are any loads or stores to it.
122 /// The alloca may just be accessed with memcpy, for example, which would
124 bool hasALoadOrStore : 1;
126 explicit AllocaInfo(AllocaInst *ai)
127 : AI(ai), isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false),
128 hasSubelementAccess(false), hasALoadOrStore(false) {}
131 /// SRThreshold - The maximum alloca size to considered for SROA.
132 unsigned SRThreshold;
134 /// StructMemberThreshold - The maximum number of members a struct can
135 /// contain to be considered for SROA.
136 unsigned StructMemberThreshold;
138 /// ArrayElementThreshold - The maximum number of elements an array can
139 /// have to be considered for SROA.
140 unsigned ArrayElementThreshold;
142 /// ScalarLoadThreshold - The maximum size in bits of scalars to load when
143 /// converting to scalar
144 unsigned ScalarLoadThreshold;
146 void MarkUnsafe(AllocaInfo &I, Instruction *User) {
148 DEBUG(dbgs() << " Transformation preventing inst: " << *User << '\n');
151 bool isSafeAllocaToScalarRepl(AllocaInst *AI);
153 void isSafeForScalarRepl(Instruction *I, uint64_t Offset, AllocaInfo &Info);
154 void isSafePHISelectUseForScalarRepl(Instruction *User, uint64_t Offset,
156 void isSafeGEP(GetElementPtrInst *GEPI, uint64_t &Offset, AllocaInfo &Info);
157 void isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
158 Type *MemOpType, bool isStore, AllocaInfo &Info,
159 Instruction *TheAccess, bool AllowWholeAccess);
160 bool TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size);
161 uint64_t FindElementAndOffset(Type *&T, uint64_t &Offset,
164 void DoScalarReplacement(AllocaInst *AI,
165 std::vector<AllocaInst*> &WorkList);
166 void DeleteDeadInstructions();
168 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
169 SmallVectorImpl<AllocaInst *> &NewElts);
170 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
171 SmallVectorImpl<AllocaInst *> &NewElts);
172 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
173 SmallVectorImpl<AllocaInst *> &NewElts);
174 void RewriteLifetimeIntrinsic(IntrinsicInst *II, AllocaInst *AI,
176 SmallVectorImpl<AllocaInst *> &NewElts);
177 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
179 SmallVectorImpl<AllocaInst *> &NewElts);
180 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
181 SmallVectorImpl<AllocaInst *> &NewElts);
182 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
183 SmallVectorImpl<AllocaInst *> &NewElts);
184 bool ShouldAttemptScalarRepl(AllocaInst *AI);
187 // SROA_DT - SROA that uses DominatorTree.
188 struct SROA_DT : public SROA {
191 SROA_DT(int T = -1, int ST = -1, int AT = -1, int SLT = -1) :
192 SROA(T, true, ID, ST, AT, SLT) {
193 initializeSROA_DTPass(*PassRegistry::getPassRegistry());
196 // getAnalysisUsage - This pass does not require any passes, but we know it
197 // will not alter the CFG, so say so.
198 void getAnalysisUsage(AnalysisUsage &AU) const override {
199 AU.addRequired<DominatorTreeWrapperPass>();
200 AU.setPreservesCFG();
204 // SROA_SSAUp - SROA that uses SSAUpdater.
205 struct SROA_SSAUp : public SROA {
208 SROA_SSAUp(int T = -1, int ST = -1, int AT = -1, int SLT = -1) :
209 SROA(T, false, ID, ST, AT, SLT) {
210 initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry());
213 // getAnalysisUsage - This pass does not require any passes, but we know it
214 // will not alter the CFG, so say so.
215 void getAnalysisUsage(AnalysisUsage &AU) const override {
216 AU.setPreservesCFG();
222 char SROA_DT::ID = 0;
223 char SROA_SSAUp::ID = 0;
225 INITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl",
226 "Scalar Replacement of Aggregates (DT)", false, false)
227 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
228 INITIALIZE_PASS_END(SROA_DT, "scalarrepl",
229 "Scalar Replacement of Aggregates (DT)", false, false)
231 INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa",
232 "Scalar Replacement of Aggregates (SSAUp)", false, false)
233 INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa",
234 "Scalar Replacement of Aggregates (SSAUp)", false, false)
236 // Public interface to the ScalarReplAggregates pass
237 FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold,
239 int StructMemberThreshold,
240 int ArrayElementThreshold,
241 int ScalarLoadThreshold) {
243 return new SROA_DT(Threshold, StructMemberThreshold, ArrayElementThreshold,
244 ScalarLoadThreshold);
245 return new SROA_SSAUp(Threshold, StructMemberThreshold,
246 ArrayElementThreshold, ScalarLoadThreshold);
250 //===----------------------------------------------------------------------===//
251 // Convert To Scalar Optimization.
252 //===----------------------------------------------------------------------===//
255 /// ConvertToScalarInfo - This class implements the "Convert To Scalar"
256 /// optimization, which scans the uses of an alloca and determines if it can
257 /// rewrite it in terms of a single new alloca that can be mem2reg'd.
258 class ConvertToScalarInfo {
259 /// AllocaSize - The size of the alloca being considered in bytes.
261 const DataLayout &DL;
262 unsigned ScalarLoadThreshold;
264 /// IsNotTrivial - This is set to true if there is some access to the object
265 /// which means that mem2reg can't promote it.
268 /// ScalarKind - Tracks the kind of alloca being considered for promotion,
269 /// computed based on the uses of the alloca rather than the LLVM type system.
273 // Accesses via GEPs that are consistent with element access of a vector
274 // type. This will not be converted into a vector unless there is a later
275 // access using an actual vector type.
278 // Accesses via vector operations and GEPs that are consistent with the
279 // layout of a vector type.
282 // An integer bag-of-bits with bitwise operations for insertion and
283 // extraction. Any combination of types can be converted into this kind
288 /// VectorTy - This tracks the type that we should promote the vector to if
289 /// it is possible to turn it into a vector. This starts out null, and if it
290 /// isn't possible to turn into a vector type, it gets set to VoidTy.
291 VectorType *VectorTy;
293 /// HadNonMemTransferAccess - True if there is at least one access to the
294 /// alloca that is not a MemTransferInst. We don't want to turn structs into
295 /// large integers unless there is some potential for optimization.
296 bool HadNonMemTransferAccess;
298 /// HadDynamicAccess - True if some element of this alloca was dynamic.
299 /// We don't yet have support for turning a dynamic access into a large
301 bool HadDynamicAccess;
304 explicit ConvertToScalarInfo(unsigned Size, const DataLayout &DL,
306 : AllocaSize(Size), DL(DL), ScalarLoadThreshold(SLT), IsNotTrivial(false),
307 ScalarKind(Unknown), VectorTy(0), HadNonMemTransferAccess(false),
308 HadDynamicAccess(false) { }
310 AllocaInst *TryConvert(AllocaInst *AI);
313 bool CanConvertToScalar(Value *V, uint64_t Offset, Value* NonConstantIdx);
314 void MergeInTypeForLoadOrStore(Type *In, uint64_t Offset);
315 bool MergeInVectorType(VectorType *VInTy, uint64_t Offset);
316 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset,
317 Value *NonConstantIdx);
319 Value *ConvertScalar_ExtractValue(Value *NV, Type *ToType,
320 uint64_t Offset, Value* NonConstantIdx,
321 IRBuilder<> &Builder);
322 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
323 uint64_t Offset, Value* NonConstantIdx,
324 IRBuilder<> &Builder);
326 } // end anonymous namespace.
329 /// TryConvert - Analyze the specified alloca, and if it is safe to do so,
330 /// rewrite it to be a new alloca which is mem2reg'able. This returns the new
331 /// alloca if possible or null if not.
332 AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
333 // If we can't convert this scalar, or if mem2reg can trivially do it, bail
335 if (!CanConvertToScalar(AI, 0, 0) || !IsNotTrivial)
338 // If an alloca has only memset / memcpy uses, it may still have an Unknown
339 // ScalarKind. Treat it as an Integer below.
340 if (ScalarKind == Unknown)
341 ScalarKind = Integer;
343 if (ScalarKind == Vector && VectorTy->getBitWidth() != AllocaSize * 8)
344 ScalarKind = Integer;
346 // If we were able to find a vector type that can handle this with
347 // insert/extract elements, and if there was at least one use that had
348 // a vector type, promote this to a vector. We don't want to promote
349 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
350 // we just get a lot of insert/extracts. If at least one vector is
351 // involved, then we probably really do have a union of vector/array.
353 if (ScalarKind == Vector) {
354 assert(VectorTy && "Missing type for vector scalar.");
355 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
356 << *VectorTy << '\n');
357 NewTy = VectorTy; // Use the vector type.
359 unsigned BitWidth = AllocaSize * 8;
361 // Do not convert to scalar integer if the alloca size exceeds the
362 // scalar load threshold.
363 if (BitWidth > ScalarLoadThreshold)
366 if ((ScalarKind == ImplicitVector || ScalarKind == Integer) &&
367 !HadNonMemTransferAccess && !DL.fitsInLegalInteger(BitWidth))
369 // Dynamic accesses on integers aren't yet supported. They need us to shift
370 // by a dynamic amount which could be difficult to work out as we might not
371 // know whether to use a left or right shift.
372 if (ScalarKind == Integer && HadDynamicAccess)
375 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
376 // Create and insert the integer alloca.
377 NewTy = IntegerType::get(AI->getContext(), BitWidth);
379 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
380 ConvertUsesToScalar(AI, NewAI, 0, 0);
384 /// MergeInTypeForLoadOrStore - Add the 'In' type to the accumulated vector type
385 /// (VectorTy) so far at the offset specified by Offset (which is specified in
388 /// There are two cases we handle here:
389 /// 1) A union of vector types of the same size and potentially its elements.
390 /// Here we turn element accesses into insert/extract element operations.
391 /// This promotes a <4 x float> with a store of float to the third element
392 /// into a <4 x float> that uses insert element.
393 /// 2) A fully general blob of memory, which we turn into some (potentially
394 /// large) integer type with extract and insert operations where the loads
395 /// and stores would mutate the memory. We mark this by setting VectorTy
397 void ConvertToScalarInfo::MergeInTypeForLoadOrStore(Type *In,
399 // If we already decided to turn this into a blob of integer memory, there is
400 // nothing to be done.
401 if (ScalarKind == Integer)
404 // If this could be contributing to a vector, analyze it.
406 // If the In type is a vector that is the same size as the alloca, see if it
407 // matches the existing VecTy.
408 if (VectorType *VInTy = dyn_cast<VectorType>(In)) {
409 if (MergeInVectorType(VInTy, Offset))
411 } else if (In->isFloatTy() || In->isDoubleTy() ||
412 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
413 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
414 // Full width accesses can be ignored, because they can always be turned
416 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
417 if (EltSize == AllocaSize)
420 // If we're accessing something that could be an element of a vector, see
421 // if the implied vector agrees with what we already have and if Offset is
422 // compatible with it.
423 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 &&
424 (!VectorTy || EltSize == VectorTy->getElementType()
425 ->getPrimitiveSizeInBits()/8)) {
427 ScalarKind = ImplicitVector;
428 VectorTy = VectorType::get(In, AllocaSize/EltSize);
434 // Otherwise, we have a case that we can't handle with an optimized vector
435 // form. We can still turn this into a large integer.
436 ScalarKind = Integer;
439 /// MergeInVectorType - Handles the vector case of MergeInTypeForLoadOrStore,
440 /// returning true if the type was successfully merged and false otherwise.
441 bool ConvertToScalarInfo::MergeInVectorType(VectorType *VInTy,
443 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
444 // If we're storing/loading a vector of the right size, allow it as a
445 // vector. If this the first vector we see, remember the type so that
446 // we know the element size. If this is a subsequent access, ignore it
447 // even if it is a differing type but the same size. Worst case we can
448 // bitcast the resultant vectors.
458 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
459 /// its accesses to a single vector type, return true and set VecTy to
460 /// the new type. If we could convert the alloca into a single promotable
461 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
462 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
463 /// is the current offset from the base of the alloca being analyzed.
465 /// If we see at least one access to the value that is as a vector type, set the
467 bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset,
468 Value* NonConstantIdx) {
469 for (User *U : V->users()) {
470 Instruction *UI = cast<Instruction>(U);
472 if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
473 // Don't break volatile loads.
476 // Don't touch MMX operations.
477 if (LI->getType()->isX86_MMXTy())
479 HadNonMemTransferAccess = true;
480 MergeInTypeForLoadOrStore(LI->getType(), Offset);
484 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
485 // Storing the pointer, not into the value?
486 if (SI->getOperand(0) == V || !SI->isSimple()) return false;
487 // Don't touch MMX operations.
488 if (SI->getOperand(0)->getType()->isX86_MMXTy())
490 HadNonMemTransferAccess = true;
491 MergeInTypeForLoadOrStore(SI->getOperand(0)->getType(), Offset);
495 if (BitCastInst *BCI = dyn_cast<BitCastInst>(UI)) {
496 if (!onlyUsedByLifetimeMarkers(BCI))
497 IsNotTrivial = true; // Can't be mem2reg'd.
498 if (!CanConvertToScalar(BCI, Offset, NonConstantIdx))
503 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(UI)) {
504 // If this is a GEP with a variable indices, we can't handle it.
505 PointerType* PtrTy = dyn_cast<PointerType>(GEP->getPointerOperandType());
509 // Compute the offset that this GEP adds to the pointer.
510 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
511 Value *GEPNonConstantIdx = 0;
512 if (!GEP->hasAllConstantIndices()) {
513 if (!isa<VectorType>(PtrTy->getElementType()))
517 GEPNonConstantIdx = Indices.pop_back_val();
518 if (!GEPNonConstantIdx->getType()->isIntegerTy(32))
520 HadDynamicAccess = true;
522 GEPNonConstantIdx = NonConstantIdx;
523 uint64_t GEPOffset = DL.getIndexedOffset(PtrTy,
525 // See if all uses can be converted.
526 if (!CanConvertToScalar(GEP, Offset+GEPOffset, GEPNonConstantIdx))
528 IsNotTrivial = true; // Can't be mem2reg'd.
529 HadNonMemTransferAccess = true;
533 // If this is a constant sized memset of a constant value (e.g. 0) we can
535 if (MemSetInst *MSI = dyn_cast<MemSetInst>(UI)) {
536 // Store to dynamic index.
539 // Store of constant value.
540 if (!isa<ConstantInt>(MSI->getValue()))
543 // Store of constant size.
544 ConstantInt *Len = dyn_cast<ConstantInt>(MSI->getLength());
548 // If the size differs from the alloca, we can only convert the alloca to
549 // an integer bag-of-bits.
550 // FIXME: This should handle all of the cases that are currently accepted
551 // as vector element insertions.
552 if (Len->getZExtValue() != AllocaSize || Offset != 0)
553 ScalarKind = Integer;
555 IsNotTrivial = true; // Can't be mem2reg'd.
556 HadNonMemTransferAccess = true;
560 // If this is a memcpy or memmove into or out of the whole allocation, we
561 // can handle it like a load or store of the scalar type.
562 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(UI)) {
563 // Store to dynamic index.
566 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
567 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0)
570 IsNotTrivial = true; // Can't be mem2reg'd.
574 // If this is a lifetime intrinsic, we can handle it.
575 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(UI)) {
576 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
577 II->getIntrinsicID() == Intrinsic::lifetime_end) {
582 // Otherwise, we cannot handle this!
589 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
590 /// directly. This happens when we are converting an "integer union" to a
591 /// single integer scalar, or when we are converting a "vector union" to a
592 /// vector with insert/extractelement instructions.
594 /// Offset is an offset from the original alloca, in bits that need to be
595 /// shifted to the right. By the end of this, there should be no uses of Ptr.
596 void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
598 Value* NonConstantIdx) {
599 while (!Ptr->use_empty()) {
600 Instruction *User = cast<Instruction>(Ptr->user_back());
602 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
603 ConvertUsesToScalar(CI, NewAI, Offset, NonConstantIdx);
604 CI->eraseFromParent();
608 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
609 // Compute the offset that this GEP adds to the pointer.
610 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
611 Value* GEPNonConstantIdx = 0;
612 if (!GEP->hasAllConstantIndices()) {
613 assert(!NonConstantIdx &&
614 "Dynamic GEP reading from dynamic GEP unsupported");
615 GEPNonConstantIdx = Indices.pop_back_val();
617 GEPNonConstantIdx = NonConstantIdx;
618 uint64_t GEPOffset = DL.getIndexedOffset(GEP->getPointerOperandType(),
620 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8, GEPNonConstantIdx);
621 GEP->eraseFromParent();
625 IRBuilder<> Builder(User);
627 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
628 // The load is a bit extract from NewAI shifted right by Offset bits.
629 Value *LoadedVal = Builder.CreateLoad(NewAI);
631 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset,
632 NonConstantIdx, Builder);
633 LI->replaceAllUsesWith(NewLoadVal);
634 LI->eraseFromParent();
638 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
639 assert(SI->getOperand(0) != Ptr && "Consistency error!");
640 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
641 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
642 NonConstantIdx, Builder);
643 Builder.CreateStore(New, NewAI);
644 SI->eraseFromParent();
646 // If the load we just inserted is now dead, then the inserted store
647 // overwrote the entire thing.
648 if (Old->use_empty())
649 Old->eraseFromParent();
653 // If this is a constant sized memset of a constant value (e.g. 0) we can
654 // transform it into a store of the expanded constant value.
655 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
656 assert(MSI->getRawDest() == Ptr && "Consistency error!");
657 assert(!NonConstantIdx && "Cannot replace dynamic memset with insert");
658 int64_t SNumBytes = cast<ConstantInt>(MSI->getLength())->getSExtValue();
659 if (SNumBytes > 0 && (SNumBytes >> 32) == 0) {
660 unsigned NumBytes = static_cast<unsigned>(SNumBytes);
661 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
663 // Compute the value replicated the right number of times.
664 APInt APVal(NumBytes*8, Val);
666 // Splat the value if non-zero.
668 for (unsigned i = 1; i != NumBytes; ++i)
671 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
672 Value *New = ConvertScalar_InsertValue(
673 ConstantInt::get(User->getContext(), APVal),
674 Old, Offset, 0, Builder);
675 Builder.CreateStore(New, NewAI);
677 // If the load we just inserted is now dead, then the memset overwrote
679 if (Old->use_empty())
680 Old->eraseFromParent();
682 MSI->eraseFromParent();
686 // If this is a memcpy or memmove into or out of the whole allocation, we
687 // can handle it like a load or store of the scalar type.
688 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
689 assert(Offset == 0 && "must be store to start of alloca");
690 assert(!NonConstantIdx && "Cannot replace dynamic transfer with insert");
692 // If the source and destination are both to the same alloca, then this is
693 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
695 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, &DL, 0));
697 if (GetUnderlyingObject(MTI->getSource(), &DL, 0) != OrigAI) {
698 // Dest must be OrigAI, change this to be a load from the original
699 // pointer (bitcasted), then a store to our new alloca.
700 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
701 Value *SrcPtr = MTI->getSource();
702 PointerType* SPTy = cast<PointerType>(SrcPtr->getType());
703 PointerType* AIPTy = cast<PointerType>(NewAI->getType());
704 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
705 AIPTy = PointerType::get(AIPTy->getElementType(),
706 SPTy->getAddressSpace());
708 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy);
710 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
711 SrcVal->setAlignment(MTI->getAlignment());
712 Builder.CreateStore(SrcVal, NewAI);
713 } else if (GetUnderlyingObject(MTI->getDest(), &DL, 0) != OrigAI) {
714 // Src must be OrigAI, change this to be a load from NewAI then a store
715 // through the original dest pointer (bitcasted).
716 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
717 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
719 PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType());
720 PointerType* AIPTy = cast<PointerType>(NewAI->getType());
721 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
722 AIPTy = PointerType::get(AIPTy->getElementType(),
723 DPTy->getAddressSpace());
725 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy);
727 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
728 NewStore->setAlignment(MTI->getAlignment());
730 // Noop transfer. Src == Dst
733 MTI->eraseFromParent();
737 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
738 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
739 II->getIntrinsicID() == Intrinsic::lifetime_end) {
740 // There's no need to preserve these, as the resulting alloca will be
741 // converted to a register anyways.
742 II->eraseFromParent();
747 llvm_unreachable("Unsupported operation!");
751 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
752 /// or vector value FromVal, extracting the bits from the offset specified by
753 /// Offset. This returns the value, which is of type ToType.
755 /// This happens when we are converting an "integer union" to a single
756 /// integer scalar, or when we are converting a "vector union" to a vector with
757 /// insert/extractelement instructions.
759 /// Offset is an offset from the original alloca, in bits that need to be
760 /// shifted to the right.
761 Value *ConvertToScalarInfo::
762 ConvertScalar_ExtractValue(Value *FromVal, Type *ToType,
763 uint64_t Offset, Value* NonConstantIdx,
764 IRBuilder<> &Builder) {
765 // If the load is of the whole new alloca, no conversion is needed.
766 Type *FromType = FromVal->getType();
767 if (FromType == ToType && Offset == 0)
770 // If the result alloca is a vector type, this is either an element
771 // access or a bitcast to another vector type of the same size.
772 if (VectorType *VTy = dyn_cast<VectorType>(FromType)) {
773 unsigned FromTypeSize = DL.getTypeAllocSize(FromType);
774 unsigned ToTypeSize = DL.getTypeAllocSize(ToType);
775 if (FromTypeSize == ToTypeSize)
776 return Builder.CreateBitCast(FromVal, ToType);
778 // Otherwise it must be an element access.
781 unsigned EltSize = DL.getTypeAllocSizeInBits(VTy->getElementType());
782 Elt = Offset/EltSize;
783 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
785 // Return the element extracted out of it.
787 if (NonConstantIdx) {
789 Idx = Builder.CreateAdd(NonConstantIdx,
790 Builder.getInt32(Elt),
793 Idx = NonConstantIdx;
795 Idx = Builder.getInt32(Elt);
796 Value *V = Builder.CreateExtractElement(FromVal, Idx);
797 if (V->getType() != ToType)
798 V = Builder.CreateBitCast(V, ToType);
802 // If ToType is a first class aggregate, extract out each of the pieces and
803 // use insertvalue's to form the FCA.
804 if (StructType *ST = dyn_cast<StructType>(ToType)) {
805 assert(!NonConstantIdx &&
806 "Dynamic indexing into struct types not supported");
807 const StructLayout &Layout = *DL.getStructLayout(ST);
808 Value *Res = UndefValue::get(ST);
809 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
810 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
811 Offset+Layout.getElementOffsetInBits(i),
813 Res = Builder.CreateInsertValue(Res, Elt, i);
818 if (ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
819 assert(!NonConstantIdx &&
820 "Dynamic indexing into array types not supported");
821 uint64_t EltSize = DL.getTypeAllocSizeInBits(AT->getElementType());
822 Value *Res = UndefValue::get(AT);
823 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
824 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
825 Offset+i*EltSize, 0, Builder);
826 Res = Builder.CreateInsertValue(Res, Elt, i);
831 // Otherwise, this must be a union that was converted to an integer value.
832 IntegerType *NTy = cast<IntegerType>(FromVal->getType());
834 // If this is a big-endian system and the load is narrower than the
835 // full alloca type, we need to do a shift to get the right bits.
837 if (DL.isBigEndian()) {
838 // On big-endian machines, the lowest bit is stored at the bit offset
839 // from the pointer given by getTypeStoreSizeInBits. This matters for
840 // integers with a bitwidth that is not a multiple of 8.
841 ShAmt = DL.getTypeStoreSizeInBits(NTy) -
842 DL.getTypeStoreSizeInBits(ToType) - Offset;
847 // Note: we support negative bitwidths (with shl) which are not defined.
848 // We do this to support (f.e.) loads off the end of a structure where
849 // only some bits are used.
850 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
851 FromVal = Builder.CreateLShr(FromVal,
852 ConstantInt::get(FromVal->getType(), ShAmt));
853 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
854 FromVal = Builder.CreateShl(FromVal,
855 ConstantInt::get(FromVal->getType(), -ShAmt));
857 // Finally, unconditionally truncate the integer to the right width.
858 unsigned LIBitWidth = DL.getTypeSizeInBits(ToType);
859 if (LIBitWidth < NTy->getBitWidth())
861 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
863 else if (LIBitWidth > NTy->getBitWidth())
865 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
868 // If the result is an integer, this is a trunc or bitcast.
869 if (ToType->isIntegerTy()) {
871 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
872 // Just do a bitcast, we know the sizes match up.
873 FromVal = Builder.CreateBitCast(FromVal, ToType);
875 // Otherwise must be a pointer.
876 FromVal = Builder.CreateIntToPtr(FromVal, ToType);
878 assert(FromVal->getType() == ToType && "Didn't convert right?");
882 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
883 /// or vector value "Old" at the offset specified by Offset.
885 /// This happens when we are converting an "integer union" to a
886 /// single integer scalar, or when we are converting a "vector union" to a
887 /// vector with insert/extractelement instructions.
889 /// Offset is an offset from the original alloca, in bits that need to be
890 /// shifted to the right.
892 /// NonConstantIdx is an index value if there was a GEP with a non-constant
893 /// index value. If this is 0 then all GEPs used to find this insert address
895 Value *ConvertToScalarInfo::
896 ConvertScalar_InsertValue(Value *SV, Value *Old,
897 uint64_t Offset, Value* NonConstantIdx,
898 IRBuilder<> &Builder) {
899 // Convert the stored type to the actual type, shift it left to insert
900 // then 'or' into place.
901 Type *AllocaType = Old->getType();
902 LLVMContext &Context = Old->getContext();
904 if (VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
905 uint64_t VecSize = DL.getTypeAllocSizeInBits(VTy);
906 uint64_t ValSize = DL.getTypeAllocSizeInBits(SV->getType());
908 // Changing the whole vector with memset or with an access of a different
910 if (ValSize == VecSize)
911 return Builder.CreateBitCast(SV, AllocaType);
913 // Must be an element insertion.
914 Type *EltTy = VTy->getElementType();
915 if (SV->getType() != EltTy)
916 SV = Builder.CreateBitCast(SV, EltTy);
917 uint64_t EltSize = DL.getTypeAllocSizeInBits(EltTy);
918 unsigned Elt = Offset/EltSize;
920 if (NonConstantIdx) {
922 Idx = Builder.CreateAdd(NonConstantIdx,
923 Builder.getInt32(Elt),
926 Idx = NonConstantIdx;
928 Idx = Builder.getInt32(Elt);
929 return Builder.CreateInsertElement(Old, SV, Idx);
932 // If SV is a first-class aggregate value, insert each value recursively.
933 if (StructType *ST = dyn_cast<StructType>(SV->getType())) {
934 assert(!NonConstantIdx &&
935 "Dynamic indexing into struct types not supported");
936 const StructLayout &Layout = *DL.getStructLayout(ST);
937 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
938 Value *Elt = Builder.CreateExtractValue(SV, i);
939 Old = ConvertScalar_InsertValue(Elt, Old,
940 Offset+Layout.getElementOffsetInBits(i),
946 if (ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
947 assert(!NonConstantIdx &&
948 "Dynamic indexing into array types not supported");
949 uint64_t EltSize = DL.getTypeAllocSizeInBits(AT->getElementType());
950 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
951 Value *Elt = Builder.CreateExtractValue(SV, i);
952 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, 0, Builder);
957 // If SV is a float, convert it to the appropriate integer type.
958 // If it is a pointer, do the same.
959 unsigned SrcWidth = DL.getTypeSizeInBits(SV->getType());
960 unsigned DestWidth = DL.getTypeSizeInBits(AllocaType);
961 unsigned SrcStoreWidth = DL.getTypeStoreSizeInBits(SV->getType());
962 unsigned DestStoreWidth = DL.getTypeStoreSizeInBits(AllocaType);
963 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
964 SV = Builder.CreateBitCast(SV, IntegerType::get(SV->getContext(),SrcWidth));
965 else if (SV->getType()->isPointerTy())
966 SV = Builder.CreatePtrToInt(SV, DL.getIntPtrType(SV->getType()));
968 // Zero extend or truncate the value if needed.
969 if (SV->getType() != AllocaType) {
970 if (SV->getType()->getPrimitiveSizeInBits() <
971 AllocaType->getPrimitiveSizeInBits())
972 SV = Builder.CreateZExt(SV, AllocaType);
974 // Truncation may be needed if storing more than the alloca can hold
975 // (undefined behavior).
976 SV = Builder.CreateTrunc(SV, AllocaType);
977 SrcWidth = DestWidth;
978 SrcStoreWidth = DestStoreWidth;
982 // If this is a big-endian system and the store is narrower than the
983 // full alloca type, we need to do a shift to get the right bits.
985 if (DL.isBigEndian()) {
986 // On big-endian machines, the lowest bit is stored at the bit offset
987 // from the pointer given by getTypeStoreSizeInBits. This matters for
988 // integers with a bitwidth that is not a multiple of 8.
989 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
994 // Note: we support negative bitwidths (with shr) which are not defined.
995 // We do this to support (f.e.) stores off the end of a structure where
996 // only some bits in the structure are set.
997 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
998 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
999 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), ShAmt));
1001 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1002 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), -ShAmt));
1003 Mask = Mask.lshr(-ShAmt);
1006 // Mask out the bits we are about to insert from the old value, and or
1008 if (SrcWidth != DestWidth) {
1009 assert(DestWidth > SrcWidth);
1010 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
1011 SV = Builder.CreateOr(Old, SV, "ins");
1017 //===----------------------------------------------------------------------===//
1019 //===----------------------------------------------------------------------===//
1022 bool SROA::runOnFunction(Function &F) {
1023 if (skipOptnoneFunction(F))
1026 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
1027 DL = DLP ? &DLP->getDataLayout() : 0;
1029 bool Changed = performPromotion(F);
1031 // FIXME: ScalarRepl currently depends on DataLayout more than it
1032 // theoretically needs to. It should be refactored in order to support
1033 // target-independent IR. Until this is done, just skip the actual
1034 // scalar-replacement portion of this pass.
1035 if (!DL) return Changed;
1038 bool LocalChange = performScalarRepl(F);
1039 if (!LocalChange) break; // No need to repromote if no scalarrepl
1041 LocalChange = performPromotion(F);
1042 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
1049 class AllocaPromoter : public LoadAndStorePromoter {
1052 SmallVector<DbgDeclareInst *, 4> DDIs;
1053 SmallVector<DbgValueInst *, 4> DVIs;
1055 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S,
1057 : LoadAndStorePromoter(Insts, S), AI(0), DIB(DB) {}
1059 void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) {
1060 // Remember which alloca we're promoting (for isInstInList).
1062 if (MDNode *DebugNode = MDNode::getIfExists(AI->getContext(), AI)) {
1063 for (User *U : DebugNode->users())
1064 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(U))
1065 DDIs.push_back(DDI);
1066 else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(U))
1067 DVIs.push_back(DVI);
1070 LoadAndStorePromoter::run(Insts);
1071 AI->eraseFromParent();
1072 for (SmallVectorImpl<DbgDeclareInst *>::iterator I = DDIs.begin(),
1073 E = DDIs.end(); I != E; ++I) {
1074 DbgDeclareInst *DDI = *I;
1075 DDI->eraseFromParent();
1077 for (SmallVectorImpl<DbgValueInst *>::iterator I = DVIs.begin(),
1078 E = DVIs.end(); I != E; ++I) {
1079 DbgValueInst *DVI = *I;
1080 DVI->eraseFromParent();
1084 bool isInstInList(Instruction *I,
1085 const SmallVectorImpl<Instruction*> &Insts) const override {
1086 if (LoadInst *LI = dyn_cast<LoadInst>(I))
1087 return LI->getOperand(0) == AI;
1088 return cast<StoreInst>(I)->getPointerOperand() == AI;
1091 void updateDebugInfo(Instruction *Inst) const override {
1092 for (SmallVectorImpl<DbgDeclareInst *>::const_iterator I = DDIs.begin(),
1093 E = DDIs.end(); I != E; ++I) {
1094 DbgDeclareInst *DDI = *I;
1095 if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
1096 ConvertDebugDeclareToDebugValue(DDI, SI, *DIB);
1097 else if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
1098 ConvertDebugDeclareToDebugValue(DDI, LI, *DIB);
1100 for (SmallVectorImpl<DbgValueInst *>::const_iterator I = DVIs.begin(),
1101 E = DVIs.end(); I != E; ++I) {
1102 DbgValueInst *DVI = *I;
1104 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
1105 // If an argument is zero extended then use argument directly. The ZExt
1106 // may be zapped by an optimization pass in future.
1107 if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
1108 Arg = dyn_cast<Argument>(ZExt->getOperand(0));
1109 if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
1110 Arg = dyn_cast<Argument>(SExt->getOperand(0));
1112 Arg = SI->getOperand(0);
1113 } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
1114 Arg = LI->getOperand(0);
1118 Instruction *DbgVal =
1119 DIB->insertDbgValueIntrinsic(Arg, 0, DIVariable(DVI->getVariable()),
1121 DbgVal->setDebugLoc(DVI->getDebugLoc());
1125 } // end anon namespace
1127 /// isSafeSelectToSpeculate - Select instructions that use an alloca and are
1128 /// subsequently loaded can be rewritten to load both input pointers and then
1129 /// select between the result, allowing the load of the alloca to be promoted.
1131 /// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
1132 /// %V = load i32* %P2
1134 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1135 /// %V2 = load i32* %Other
1136 /// %V = select i1 %cond, i32 %V1, i32 %V2
1138 /// We can do this to a select if its only uses are loads and if the operand to
1139 /// the select can be loaded unconditionally.
1140 static bool isSafeSelectToSpeculate(SelectInst *SI, const DataLayout *DL) {
1141 bool TDerefable = SI->getTrueValue()->isDereferenceablePointer();
1142 bool FDerefable = SI->getFalseValue()->isDereferenceablePointer();
1144 for (User *U : SI->users()) {
1145 LoadInst *LI = dyn_cast<LoadInst>(U);
1146 if (LI == 0 || !LI->isSimple()) return false;
1148 // Both operands to the select need to be dereferencable, either absolutely
1149 // (e.g. allocas) or at this point because we can see other accesses to it.
1150 if (!TDerefable && !isSafeToLoadUnconditionally(SI->getTrueValue(), LI,
1151 LI->getAlignment(), DL))
1153 if (!FDerefable && !isSafeToLoadUnconditionally(SI->getFalseValue(), LI,
1154 LI->getAlignment(), DL))
1161 /// isSafePHIToSpeculate - PHI instructions that use an alloca and are
1162 /// subsequently loaded can be rewritten to load both input pointers in the pred
1163 /// blocks and then PHI the results, allowing the load of the alloca to be
1166 /// %P2 = phi [i32* %Alloca, i32* %Other]
1167 /// %V = load i32* %P2
1169 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1171 /// %V2 = load i32* %Other
1173 /// %V = phi [i32 %V1, i32 %V2]
1175 /// We can do this to a select if its only uses are loads and if the operand to
1176 /// the select can be loaded unconditionally.
1177 static bool isSafePHIToSpeculate(PHINode *PN, const DataLayout *DL) {
1178 // For now, we can only do this promotion if the load is in the same block as
1179 // the PHI, and if there are no stores between the phi and load.
1180 // TODO: Allow recursive phi users.
1181 // TODO: Allow stores.
1182 BasicBlock *BB = PN->getParent();
1183 unsigned MaxAlign = 0;
1184 for (User *U : PN->users()) {
1185 LoadInst *LI = dyn_cast<LoadInst>(U);
1186 if (LI == 0 || !LI->isSimple()) return false;
1188 // For now we only allow loads in the same block as the PHI. This is a
1189 // common case that happens when instcombine merges two loads through a PHI.
1190 if (LI->getParent() != BB) return false;
1192 // Ensure that there are no instructions between the PHI and the load that
1194 for (BasicBlock::iterator BBI = PN; &*BBI != LI; ++BBI)
1195 if (BBI->mayWriteToMemory())
1198 MaxAlign = std::max(MaxAlign, LI->getAlignment());
1201 // Okay, we know that we have one or more loads in the same block as the PHI.
1202 // We can transform this if it is safe to push the loads into the predecessor
1203 // blocks. The only thing to watch out for is that we can't put a possibly
1204 // trapping load in the predecessor if it is a critical edge.
1205 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1206 BasicBlock *Pred = PN->getIncomingBlock(i);
1207 Value *InVal = PN->getIncomingValue(i);
1209 // If the terminator of the predecessor has side-effects (an invoke),
1210 // there is no safe place to put a load in the predecessor.
1211 if (Pred->getTerminator()->mayHaveSideEffects())
1214 // If the value is produced by the terminator of the predecessor
1215 // (an invoke), there is no valid place to put a load in the predecessor.
1216 if (Pred->getTerminator() == InVal)
1219 // If the predecessor has a single successor, then the edge isn't critical.
1220 if (Pred->getTerminator()->getNumSuccessors() == 1)
1223 // If this pointer is always safe to load, or if we can prove that there is
1224 // already a load in the block, then we can move the load to the pred block.
1225 if (InVal->isDereferenceablePointer() ||
1226 isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign, DL))
1236 /// tryToMakeAllocaBePromotable - This returns true if the alloca only has
1237 /// direct (non-volatile) loads and stores to it. If the alloca is close but
1238 /// not quite there, this will transform the code to allow promotion. As such,
1239 /// it is a non-pure predicate.
1240 static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const DataLayout *DL) {
1241 SetVector<Instruction*, SmallVector<Instruction*, 4>,
1242 SmallPtrSet<Instruction*, 4> > InstsToRewrite;
1243 for (User *U : AI->users()) {
1244 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1245 if (!LI->isSimple())
1250 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1251 if (SI->getOperand(0) == AI || !SI->isSimple())
1252 return false; // Don't allow a store OF the AI, only INTO the AI.
1256 if (SelectInst *SI = dyn_cast<SelectInst>(U)) {
1257 // If the condition being selected on is a constant, fold the select, yes
1258 // this does (rarely) happen early on.
1259 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) {
1260 Value *Result = SI->getOperand(1+CI->isZero());
1261 SI->replaceAllUsesWith(Result);
1262 SI->eraseFromParent();
1264 // This is very rare and we just scrambled the use list of AI, start
1266 return tryToMakeAllocaBePromotable(AI, DL);
1269 // If it is safe to turn "load (select c, AI, ptr)" into a select of two
1270 // loads, then we can transform this by rewriting the select.
1271 if (!isSafeSelectToSpeculate(SI, DL))
1274 InstsToRewrite.insert(SI);
1278 if (PHINode *PN = dyn_cast<PHINode>(U)) {
1279 if (PN->use_empty()) { // Dead PHIs can be stripped.
1280 InstsToRewrite.insert(PN);
1284 // If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads
1285 // in the pred blocks, then we can transform this by rewriting the PHI.
1286 if (!isSafePHIToSpeculate(PN, DL))
1289 InstsToRewrite.insert(PN);
1293 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
1294 if (onlyUsedByLifetimeMarkers(BCI)) {
1295 InstsToRewrite.insert(BCI);
1303 // If there are no instructions to rewrite, then all uses are load/stores and
1305 if (InstsToRewrite.empty())
1308 // If we have instructions that need to be rewritten for this to be promotable
1309 // take care of it now.
1310 for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) {
1311 if (BitCastInst *BCI = dyn_cast<BitCastInst>(InstsToRewrite[i])) {
1312 // This could only be a bitcast used by nothing but lifetime intrinsics.
1313 for (BitCastInst::user_iterator I = BCI->user_begin(), E = BCI->user_end();
1315 cast<Instruction>(*I++)->eraseFromParent();
1316 BCI->eraseFromParent();
1320 if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) {
1321 // Selects in InstsToRewrite only have load uses. Rewrite each as two
1322 // loads with a new select.
1323 while (!SI->use_empty()) {
1324 LoadInst *LI = cast<LoadInst>(SI->user_back());
1326 IRBuilder<> Builder(LI);
1327 LoadInst *TrueLoad =
1328 Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t");
1329 LoadInst *FalseLoad =
1330 Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".f");
1332 // Transfer alignment and TBAA info if present.
1333 TrueLoad->setAlignment(LI->getAlignment());
1334 FalseLoad->setAlignment(LI->getAlignment());
1335 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) {
1336 TrueLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1337 FalseLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1340 Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad);
1342 LI->replaceAllUsesWith(V);
1343 LI->eraseFromParent();
1346 // Now that all the loads are gone, the select is gone too.
1347 SI->eraseFromParent();
1351 // Otherwise, we have a PHI node which allows us to push the loads into the
1353 PHINode *PN = cast<PHINode>(InstsToRewrite[i]);
1354 if (PN->use_empty()) {
1355 PN->eraseFromParent();
1359 Type *LoadTy = cast<PointerType>(PN->getType())->getElementType();
1360 PHINode *NewPN = PHINode::Create(LoadTy, PN->getNumIncomingValues(),
1361 PN->getName()+".ld", PN);
1363 // Get the TBAA tag and alignment to use from one of the loads. It doesn't
1364 // matter which one we get and if any differ, it doesn't matter.
1365 LoadInst *SomeLoad = cast<LoadInst>(PN->user_back());
1366 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa);
1367 unsigned Align = SomeLoad->getAlignment();
1369 // Rewrite all loads of the PN to use the new PHI.
1370 while (!PN->use_empty()) {
1371 LoadInst *LI = cast<LoadInst>(PN->user_back());
1372 LI->replaceAllUsesWith(NewPN);
1373 LI->eraseFromParent();
1376 // Inject loads into all of the pred blocks. Keep track of which blocks we
1377 // insert them into in case we have multiple edges from the same block.
1378 DenseMap<BasicBlock*, LoadInst*> InsertedLoads;
1380 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1381 BasicBlock *Pred = PN->getIncomingBlock(i);
1382 LoadInst *&Load = InsertedLoads[Pred];
1384 Load = new LoadInst(PN->getIncomingValue(i),
1385 PN->getName() + "." + Pred->getName(),
1386 Pred->getTerminator());
1387 Load->setAlignment(Align);
1388 if (TBAATag) Load->setMetadata(LLVMContext::MD_tbaa, TBAATag);
1391 NewPN->addIncoming(Load, Pred);
1394 PN->eraseFromParent();
1401 bool SROA::performPromotion(Function &F) {
1402 std::vector<AllocaInst*> Allocas;
1403 DominatorTree *DT = 0;
1405 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
1407 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
1408 DIBuilder DIB(*F.getParent());
1409 bool Changed = false;
1410 SmallVector<Instruction*, 64> Insts;
1414 // Find allocas that are safe to promote, by looking at all instructions in
1416 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
1417 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
1418 if (tryToMakeAllocaBePromotable(AI, DL))
1419 Allocas.push_back(AI);
1421 if (Allocas.empty()) break;
1424 PromoteMemToReg(Allocas, *DT);
1427 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
1428 AllocaInst *AI = Allocas[i];
1430 // Build list of instructions to promote.
1431 for (User *U : AI->users())
1432 Insts.push_back(cast<Instruction>(U));
1433 AllocaPromoter(Insts, SSA, &DIB).run(AI, Insts);
1437 NumPromoted += Allocas.size();
1445 /// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
1446 /// SROA. It must be a struct or array type with a small number of elements.
1447 bool SROA::ShouldAttemptScalarRepl(AllocaInst *AI) {
1448 Type *T = AI->getAllocatedType();
1449 // Do not promote any struct that has too many members.
1450 if (StructType *ST = dyn_cast<StructType>(T))
1451 return ST->getNumElements() <= StructMemberThreshold;
1452 // Do not promote any array that has too many elements.
1453 if (ArrayType *AT = dyn_cast<ArrayType>(T))
1454 return AT->getNumElements() <= ArrayElementThreshold;
1458 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
1459 // which runs on all of the alloca instructions in the entry block, removing
1460 // them if they are only used by getelementptr instructions.
1462 bool SROA::performScalarRepl(Function &F) {
1463 std::vector<AllocaInst*> WorkList;
1465 // Scan the entry basic block, adding allocas to the worklist.
1466 BasicBlock &BB = F.getEntryBlock();
1467 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
1468 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
1469 WorkList.push_back(A);
1471 // Process the worklist
1472 bool Changed = false;
1473 while (!WorkList.empty()) {
1474 AllocaInst *AI = WorkList.back();
1475 WorkList.pop_back();
1477 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
1478 // with unused elements.
1479 if (AI->use_empty()) {
1480 AI->eraseFromParent();
1485 // If this alloca is impossible for us to promote, reject it early.
1486 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
1489 // Check to see if we can perform the core SROA transformation. We cannot
1490 // transform the allocation instruction if it is an array allocation
1491 // (allocations OF arrays are ok though), and an allocation of a scalar
1492 // value cannot be decomposed at all.
1493 uint64_t AllocaSize = DL->getTypeAllocSize(AI->getAllocatedType());
1495 // Do not promote [0 x %struct].
1496 if (AllocaSize == 0) continue;
1498 // Do not promote any struct whose size is too big.
1499 if (AllocaSize > SRThreshold) continue;
1501 // If the alloca looks like a good candidate for scalar replacement, and if
1502 // all its users can be transformed, then split up the aggregate into its
1503 // separate elements.
1504 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
1505 DoScalarReplacement(AI, WorkList);
1510 // If we can turn this aggregate value (potentially with casts) into a
1511 // simple scalar value that can be mem2reg'd into a register value.
1512 // IsNotTrivial tracks whether this is something that mem2reg could have
1513 // promoted itself. If so, we don't want to transform it needlessly. Note
1514 // that we can't just check based on the type: the alloca may be of an i32
1515 // but that has pointer arithmetic to set byte 3 of it or something.
1516 if (AllocaInst *NewAI = ConvertToScalarInfo(
1517 (unsigned)AllocaSize, *DL, ScalarLoadThreshold).TryConvert(AI)) {
1518 NewAI->takeName(AI);
1519 AI->eraseFromParent();
1525 // Otherwise, couldn't process this alloca.
1531 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
1532 /// predicate, do SROA now.
1533 void SROA::DoScalarReplacement(AllocaInst *AI,
1534 std::vector<AllocaInst*> &WorkList) {
1535 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
1536 SmallVector<AllocaInst*, 32> ElementAllocas;
1537 if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
1538 ElementAllocas.reserve(ST->getNumContainedTypes());
1539 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
1540 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
1542 AI->getName() + "." + Twine(i), AI);
1543 ElementAllocas.push_back(NA);
1544 WorkList.push_back(NA); // Add to worklist for recursive processing
1547 ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
1548 ElementAllocas.reserve(AT->getNumElements());
1549 Type *ElTy = AT->getElementType();
1550 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1551 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
1552 AI->getName() + "." + Twine(i), AI);
1553 ElementAllocas.push_back(NA);
1554 WorkList.push_back(NA); // Add to worklist for recursive processing
1558 // Now that we have created the new alloca instructions, rewrite all the
1559 // uses of the old alloca.
1560 RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
1562 // Now erase any instructions that were made dead while rewriting the alloca.
1563 DeleteDeadInstructions();
1564 AI->eraseFromParent();
1569 /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
1570 /// recursively including all their operands that become trivially dead.
1571 void SROA::DeleteDeadInstructions() {
1572 while (!DeadInsts.empty()) {
1573 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
1575 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
1576 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
1577 // Zero out the operand and see if it becomes trivially dead.
1578 // (But, don't add allocas to the dead instruction list -- they are
1579 // already on the worklist and will be deleted separately.)
1581 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
1582 DeadInsts.push_back(U);
1585 I->eraseFromParent();
1589 /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
1590 /// performing scalar replacement of alloca AI. The results are flagged in
1591 /// the Info parameter. Offset indicates the position within AI that is
1592 /// referenced by this instruction.
1593 void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset,
1595 for (Use &U : I->uses()) {
1596 Instruction *User = cast<Instruction>(U.getUser());
1598 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1599 isSafeForScalarRepl(BC, Offset, Info);
1600 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1601 uint64_t GEPOffset = Offset;
1602 isSafeGEP(GEPI, GEPOffset, Info);
1604 isSafeForScalarRepl(GEPI, GEPOffset, Info);
1605 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1606 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1608 return MarkUnsafe(Info, User);
1609 if (Length->isNegative())
1610 return MarkUnsafe(Info, User);
1612 isSafeMemAccess(Offset, Length->getZExtValue(), 0,
1613 U.getOperandNo() == 0, Info, MI,
1614 true /*AllowWholeAccess*/);
1615 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1616 if (!LI->isSimple())
1617 return MarkUnsafe(Info, User);
1618 Type *LIType = LI->getType();
1619 isSafeMemAccess(Offset, DL->getTypeAllocSize(LIType),
1620 LIType, false, Info, LI, true /*AllowWholeAccess*/);
1621 Info.hasALoadOrStore = true;
1623 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1624 // Store is ok if storing INTO the pointer, not storing the pointer
1625 if (!SI->isSimple() || SI->getOperand(0) == I)
1626 return MarkUnsafe(Info, User);
1628 Type *SIType = SI->getOperand(0)->getType();
1629 isSafeMemAccess(Offset, DL->getTypeAllocSize(SIType),
1630 SIType, true, Info, SI, true /*AllowWholeAccess*/);
1631 Info.hasALoadOrStore = true;
1632 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
1633 if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
1634 II->getIntrinsicID() != Intrinsic::lifetime_end)
1635 return MarkUnsafe(Info, User);
1636 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
1637 isSafePHISelectUseForScalarRepl(User, Offset, Info);
1639 return MarkUnsafe(Info, User);
1641 if (Info.isUnsafe) return;
1646 /// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer
1647 /// derived from the alloca, we can often still split the alloca into elements.
1648 /// This is useful if we have a large alloca where one element is phi'd
1649 /// together somewhere: we can SRoA and promote all the other elements even if
1650 /// we end up not being able to promote this one.
1652 /// All we require is that the uses of the PHI do not index into other parts of
1653 /// the alloca. The most important use case for this is single load and stores
1654 /// that are PHI'd together, which can happen due to code sinking.
1655 void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset,
1657 // If we've already checked this PHI, don't do it again.
1658 if (PHINode *PN = dyn_cast<PHINode>(I))
1659 if (!Info.CheckedPHIs.insert(PN))
1662 for (User *U : I->users()) {
1663 Instruction *UI = cast<Instruction>(U);
1665 if (BitCastInst *BC = dyn_cast<BitCastInst>(UI)) {
1666 isSafePHISelectUseForScalarRepl(BC, Offset, Info);
1667 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(UI)) {
1668 // Only allow "bitcast" GEPs for simplicity. We could generalize this,
1669 // but would have to prove that we're staying inside of an element being
1671 if (!GEPI->hasAllZeroIndices())
1672 return MarkUnsafe(Info, UI);
1673 isSafePHISelectUseForScalarRepl(GEPI, Offset, Info);
1674 } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
1675 if (!LI->isSimple())
1676 return MarkUnsafe(Info, UI);
1677 Type *LIType = LI->getType();
1678 isSafeMemAccess(Offset, DL->getTypeAllocSize(LIType),
1679 LIType, false, Info, LI, false /*AllowWholeAccess*/);
1680 Info.hasALoadOrStore = true;
1682 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1683 // Store is ok if storing INTO the pointer, not storing the pointer
1684 if (!SI->isSimple() || SI->getOperand(0) == I)
1685 return MarkUnsafe(Info, UI);
1687 Type *SIType = SI->getOperand(0)->getType();
1688 isSafeMemAccess(Offset, DL->getTypeAllocSize(SIType),
1689 SIType, true, Info, SI, false /*AllowWholeAccess*/);
1690 Info.hasALoadOrStore = true;
1691 } else if (isa<PHINode>(UI) || isa<SelectInst>(UI)) {
1692 isSafePHISelectUseForScalarRepl(UI, Offset, Info);
1694 return MarkUnsafe(Info, UI);
1696 if (Info.isUnsafe) return;
1700 /// isSafeGEP - Check if a GEP instruction can be handled for scalar
1701 /// replacement. It is safe when all the indices are constant, in-bounds
1702 /// references, and when the resulting offset corresponds to an element within
1703 /// the alloca type. The results are flagged in the Info parameter. Upon
1704 /// return, Offset is adjusted as specified by the GEP indices.
1705 void SROA::isSafeGEP(GetElementPtrInst *GEPI,
1706 uint64_t &Offset, AllocaInfo &Info) {
1707 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
1710 bool NonConstant = false;
1711 unsigned NonConstantIdxSize = 0;
1713 // Walk through the GEP type indices, checking the types that this indexes
1715 for (; GEPIt != E; ++GEPIt) {
1716 // Ignore struct elements, no extra checking needed for these.
1717 if ((*GEPIt)->isStructTy())
1720 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
1722 return MarkUnsafe(Info, GEPI);
1725 // Compute the offset due to this GEP and check if the alloca has a
1726 // component element at that offset.
1727 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1728 // If this GEP is non-constant then the last operand must have been a
1729 // dynamic index into a vector. Pop this now as it has no impact on the
1730 // constant part of the offset.
1733 Offset += DL->getIndexedOffset(GEPI->getPointerOperandType(), Indices);
1734 if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset,
1735 NonConstantIdxSize))
1736 MarkUnsafe(Info, GEPI);
1739 /// isHomogeneousAggregate - Check if type T is a struct or array containing
1740 /// elements of the same type (which is always true for arrays). If so,
1741 /// return true with NumElts and EltTy set to the number of elements and the
1742 /// element type, respectively.
1743 static bool isHomogeneousAggregate(Type *T, unsigned &NumElts,
1745 if (ArrayType *AT = dyn_cast<ArrayType>(T)) {
1746 NumElts = AT->getNumElements();
1747 EltTy = (NumElts == 0 ? 0 : AT->getElementType());
1750 if (StructType *ST = dyn_cast<StructType>(T)) {
1751 NumElts = ST->getNumContainedTypes();
1752 EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0));
1753 for (unsigned n = 1; n < NumElts; ++n) {
1754 if (ST->getContainedType(n) != EltTy)
1762 /// isCompatibleAggregate - Check if T1 and T2 are either the same type or are
1763 /// "homogeneous" aggregates with the same element type and number of elements.
1764 static bool isCompatibleAggregate(Type *T1, Type *T2) {
1768 unsigned NumElts1, NumElts2;
1769 Type *EltTy1, *EltTy2;
1770 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) &&
1771 isHomogeneousAggregate(T2, NumElts2, EltTy2) &&
1772 NumElts1 == NumElts2 &&
1779 /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
1780 /// alloca or has an offset and size that corresponds to a component element
1781 /// within it. The offset checked here may have been formed from a GEP with a
1782 /// pointer bitcasted to a different type.
1784 /// If AllowWholeAccess is true, then this allows uses of the entire alloca as a
1785 /// unit. If false, it only allows accesses known to be in a single element.
1786 void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
1787 Type *MemOpType, bool isStore,
1788 AllocaInfo &Info, Instruction *TheAccess,
1789 bool AllowWholeAccess) {
1790 // Check if this is a load/store of the entire alloca.
1791 if (Offset == 0 && AllowWholeAccess &&
1792 MemSize == DL->getTypeAllocSize(Info.AI->getAllocatedType())) {
1793 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer
1794 // loads/stores (which are essentially the same as the MemIntrinsics with
1795 // regard to copying padding between elements). But, if an alloca is
1796 // flagged as both a source and destination of such operations, we'll need
1797 // to check later for padding between elements.
1798 if (!MemOpType || MemOpType->isIntegerTy()) {
1800 Info.isMemCpyDst = true;
1802 Info.isMemCpySrc = true;
1805 // This is also safe for references using a type that is compatible with
1806 // the type of the alloca, so that loads/stores can be rewritten using
1807 // insertvalue/extractvalue.
1808 if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) {
1809 Info.hasSubelementAccess = true;
1813 // Check if the offset/size correspond to a component within the alloca type.
1814 Type *T = Info.AI->getAllocatedType();
1815 if (TypeHasComponent(T, Offset, MemSize)) {
1816 Info.hasSubelementAccess = true;
1820 return MarkUnsafe(Info, TheAccess);
1823 /// TypeHasComponent - Return true if T has a component type with the
1824 /// specified offset and size. If Size is zero, do not check the size.
1825 bool SROA::TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size) {
1828 if (StructType *ST = dyn_cast<StructType>(T)) {
1829 const StructLayout *Layout = DL->getStructLayout(ST);
1830 unsigned EltIdx = Layout->getElementContainingOffset(Offset);
1831 EltTy = ST->getContainedType(EltIdx);
1832 EltSize = DL->getTypeAllocSize(EltTy);
1833 Offset -= Layout->getElementOffset(EltIdx);
1834 } else if (ArrayType *AT = dyn_cast<ArrayType>(T)) {
1835 EltTy = AT->getElementType();
1836 EltSize = DL->getTypeAllocSize(EltTy);
1837 if (Offset >= AT->getNumElements() * EltSize)
1840 } else if (VectorType *VT = dyn_cast<VectorType>(T)) {
1841 EltTy = VT->getElementType();
1842 EltSize = DL->getTypeAllocSize(EltTy);
1843 if (Offset >= VT->getNumElements() * EltSize)
1849 if (Offset == 0 && (Size == 0 || EltSize == Size))
1851 // Check if the component spans multiple elements.
1852 if (Offset + Size > EltSize)
1854 return TypeHasComponent(EltTy, Offset, Size);
1857 /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
1858 /// the instruction I, which references it, to use the separate elements.
1859 /// Offset indicates the position within AI that is referenced by this
1861 void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1862 SmallVectorImpl<AllocaInst *> &NewElts) {
1863 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) {
1864 Use &TheUse = *UI++;
1865 Instruction *User = cast<Instruction>(TheUse.getUser());
1867 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1868 RewriteBitCast(BC, AI, Offset, NewElts);
1872 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1873 RewriteGEP(GEPI, AI, Offset, NewElts);
1877 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1878 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1879 uint64_t MemSize = Length->getZExtValue();
1881 MemSize == DL->getTypeAllocSize(AI->getAllocatedType()))
1882 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
1883 // Otherwise the intrinsic can only touch a single element and the
1884 // address operand will be updated, so nothing else needs to be done.
1888 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
1889 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
1890 II->getIntrinsicID() == Intrinsic::lifetime_end) {
1891 RewriteLifetimeIntrinsic(II, AI, Offset, NewElts);
1896 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1897 Type *LIType = LI->getType();
1899 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) {
1901 // %res = load { i32, i32 }* %alloc
1903 // %load.0 = load i32* %alloc.0
1904 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
1905 // %load.1 = load i32* %alloc.1
1906 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
1907 // (Also works for arrays instead of structs)
1908 Value *Insert = UndefValue::get(LIType);
1909 IRBuilder<> Builder(LI);
1910 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1911 Value *Load = Builder.CreateLoad(NewElts[i], "load");
1912 Insert = Builder.CreateInsertValue(Insert, Load, i, "insert");
1914 LI->replaceAllUsesWith(Insert);
1915 DeadInsts.push_back(LI);
1916 } else if (LIType->isIntegerTy() &&
1917 DL->getTypeAllocSize(LIType) ==
1918 DL->getTypeAllocSize(AI->getAllocatedType())) {
1919 // If this is a load of the entire alloca to an integer, rewrite it.
1920 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
1925 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1926 Value *Val = SI->getOperand(0);
1927 Type *SIType = Val->getType();
1928 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) {
1930 // store { i32, i32 } %val, { i32, i32 }* %alloc
1932 // %val.0 = extractvalue { i32, i32 } %val, 0
1933 // store i32 %val.0, i32* %alloc.0
1934 // %val.1 = extractvalue { i32, i32 } %val, 1
1935 // store i32 %val.1, i32* %alloc.1
1936 // (Also works for arrays instead of structs)
1937 IRBuilder<> Builder(SI);
1938 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1939 Value *Extract = Builder.CreateExtractValue(Val, i, Val->getName());
1940 Builder.CreateStore(Extract, NewElts[i]);
1942 DeadInsts.push_back(SI);
1943 } else if (SIType->isIntegerTy() &&
1944 DL->getTypeAllocSize(SIType) ==
1945 DL->getTypeAllocSize(AI->getAllocatedType())) {
1946 // If this is a store of the entire alloca from an integer, rewrite it.
1947 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
1952 if (isa<SelectInst>(User) || isa<PHINode>(User)) {
1953 // If we have a PHI user of the alloca itself (as opposed to a GEP or
1954 // bitcast) we have to rewrite it. GEP and bitcast uses will be RAUW'd to
1956 if (!isa<AllocaInst>(I)) continue;
1958 assert(Offset == 0 && NewElts[0] &&
1959 "Direct alloca use should have a zero offset");
1961 // If we have a use of the alloca, we know the derived uses will be
1962 // utilizing just the first element of the scalarized result. Insert a
1963 // bitcast of the first alloca before the user as required.
1964 AllocaInst *NewAI = NewElts[0];
1965 BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI);
1966 NewAI->moveBefore(BCI);
1973 /// RewriteBitCast - Update a bitcast reference to the alloca being replaced
1974 /// and recursively continue updating all of its uses.
1975 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
1976 SmallVectorImpl<AllocaInst *> &NewElts) {
1977 RewriteForScalarRepl(BC, AI, Offset, NewElts);
1978 if (BC->getOperand(0) != AI)
1981 // The bitcast references the original alloca. Replace its uses with
1982 // references to the alloca containing offset zero (which is normally at
1983 // index zero, but might not be in cases involving structs with elements
1985 Type *T = AI->getAllocatedType();
1986 uint64_t EltOffset = 0;
1988 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
1989 Instruction *Val = NewElts[Idx];
1990 if (Val->getType() != BC->getDestTy()) {
1991 Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
1994 BC->replaceAllUsesWith(Val);
1995 DeadInsts.push_back(BC);
1998 /// FindElementAndOffset - Return the index of the element containing Offset
1999 /// within the specified type, which must be either a struct or an array.
2000 /// Sets T to the type of the element and Offset to the offset within that
2001 /// element. IdxTy is set to the type of the index result to be used in a
2002 /// GEP instruction.
2003 uint64_t SROA::FindElementAndOffset(Type *&T, uint64_t &Offset,
2006 if (StructType *ST = dyn_cast<StructType>(T)) {
2007 const StructLayout *Layout = DL->getStructLayout(ST);
2008 Idx = Layout->getElementContainingOffset(Offset);
2009 T = ST->getContainedType(Idx);
2010 Offset -= Layout->getElementOffset(Idx);
2011 IdxTy = Type::getInt32Ty(T->getContext());
2013 } else if (ArrayType *AT = dyn_cast<ArrayType>(T)) {
2014 T = AT->getElementType();
2015 uint64_t EltSize = DL->getTypeAllocSize(T);
2016 Idx = Offset / EltSize;
2017 Offset -= Idx * EltSize;
2018 IdxTy = Type::getInt64Ty(T->getContext());
2021 VectorType *VT = cast<VectorType>(T);
2022 T = VT->getElementType();
2023 uint64_t EltSize = DL->getTypeAllocSize(T);
2024 Idx = Offset / EltSize;
2025 Offset -= Idx * EltSize;
2026 IdxTy = Type::getInt64Ty(T->getContext());
2030 /// RewriteGEP - Check if this GEP instruction moves the pointer across
2031 /// elements of the alloca that are being split apart, and if so, rewrite
2032 /// the GEP to be relative to the new element.
2033 void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
2034 SmallVectorImpl<AllocaInst *> &NewElts) {
2035 uint64_t OldOffset = Offset;
2036 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
2037 // If the GEP was dynamic then it must have been a dynamic vector lookup.
2038 // In this case, it must be the last GEP operand which is dynamic so keep that
2039 // aside until we've found the constant GEP offset then add it back in at the
2041 Value* NonConstantIdx = 0;
2042 if (!GEPI->hasAllConstantIndices())
2043 NonConstantIdx = Indices.pop_back_val();
2044 Offset += DL->getIndexedOffset(GEPI->getPointerOperandType(), Indices);
2046 RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
2048 Type *T = AI->getAllocatedType();
2050 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
2051 if (GEPI->getOperand(0) == AI)
2052 OldIdx = ~0ULL; // Force the GEP to be rewritten.
2054 T = AI->getAllocatedType();
2055 uint64_t EltOffset = Offset;
2056 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
2058 // If this GEP does not move the pointer across elements of the alloca
2059 // being split, then it does not needs to be rewritten.
2063 Type *i32Ty = Type::getInt32Ty(AI->getContext());
2064 SmallVector<Value*, 8> NewArgs;
2065 NewArgs.push_back(Constant::getNullValue(i32Ty));
2066 while (EltOffset != 0) {
2067 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
2068 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
2070 if (NonConstantIdx) {
2072 // This GEP has a dynamic index. We need to add "i32 0" to index through
2073 // any structs or arrays in the original type until we get to the vector
2075 while (!isa<VectorType>(GepTy)) {
2076 NewArgs.push_back(Constant::getNullValue(i32Ty));
2077 GepTy = cast<CompositeType>(GepTy)->getTypeAtIndex(0U);
2079 NewArgs.push_back(NonConstantIdx);
2081 Instruction *Val = NewElts[Idx];
2082 if (NewArgs.size() > 1) {
2083 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs, "", GEPI);
2084 Val->takeName(GEPI);
2086 if (Val->getType() != GEPI->getType())
2087 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
2088 GEPI->replaceAllUsesWith(Val);
2089 DeadInsts.push_back(GEPI);
2092 /// RewriteLifetimeIntrinsic - II is a lifetime.start/lifetime.end. Rewrite it
2093 /// to mark the lifetime of the scalarized memory.
2094 void SROA::RewriteLifetimeIntrinsic(IntrinsicInst *II, AllocaInst *AI,
2096 SmallVectorImpl<AllocaInst *> &NewElts) {
2097 ConstantInt *OldSize = cast<ConstantInt>(II->getArgOperand(0));
2098 // Put matching lifetime markers on everything from Offset up to
2100 Type *AIType = AI->getAllocatedType();
2101 uint64_t NewOffset = Offset;
2103 uint64_t Idx = FindElementAndOffset(AIType, NewOffset, IdxTy);
2105 IRBuilder<> Builder(II);
2106 uint64_t Size = OldSize->getLimitedValue();
2109 // Splice the first element and index 'NewOffset' bytes in. SROA will
2110 // split the alloca again later.
2111 Value *V = Builder.CreateBitCast(NewElts[Idx], Builder.getInt8PtrTy());
2112 V = Builder.CreateGEP(V, Builder.getInt64(NewOffset));
2114 IdxTy = NewElts[Idx]->getAllocatedType();
2115 uint64_t EltSize = DL->getTypeAllocSize(IdxTy) - NewOffset;
2116 if (EltSize > Size) {
2122 if (II->getIntrinsicID() == Intrinsic::lifetime_start)
2123 Builder.CreateLifetimeStart(V, Builder.getInt64(EltSize));
2125 Builder.CreateLifetimeEnd(V, Builder.getInt64(EltSize));
2129 for (; Idx != NewElts.size() && Size; ++Idx) {
2130 IdxTy = NewElts[Idx]->getAllocatedType();
2131 uint64_t EltSize = DL->getTypeAllocSize(IdxTy);
2132 if (EltSize > Size) {
2138 if (II->getIntrinsicID() == Intrinsic::lifetime_start)
2139 Builder.CreateLifetimeStart(NewElts[Idx],
2140 Builder.getInt64(EltSize));
2142 Builder.CreateLifetimeEnd(NewElts[Idx],
2143 Builder.getInt64(EltSize));
2145 DeadInsts.push_back(II);
2148 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
2149 /// Rewrite it to copy or set the elements of the scalarized memory.
2151 SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
2153 SmallVectorImpl<AllocaInst *> &NewElts) {
2154 // If this is a memcpy/memmove, construct the other pointer as the
2155 // appropriate type. The "Other" pointer is the pointer that goes to memory
2156 // that doesn't have anything to do with the alloca that we are promoting. For
2157 // memset, this Value* stays null.
2158 Value *OtherPtr = 0;
2159 unsigned MemAlignment = MI->getAlignment();
2160 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
2161 if (Inst == MTI->getRawDest())
2162 OtherPtr = MTI->getRawSource();
2164 assert(Inst == MTI->getRawSource());
2165 OtherPtr = MTI->getRawDest();
2169 // If there is an other pointer, we want to convert it to the same pointer
2170 // type as AI has, so we can GEP through it safely.
2172 unsigned AddrSpace =
2173 cast<PointerType>(OtherPtr->getType())->getAddressSpace();
2175 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
2176 // optimization, but it's also required to detect the corner case where
2177 // both pointer operands are referencing the same memory, and where
2178 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
2179 // function is only called for mem intrinsics that access the whole
2180 // aggregate, so non-zero GEPs are not an issue here.)
2181 OtherPtr = OtherPtr->stripPointerCasts();
2183 // Copying the alloca to itself is a no-op: just delete it.
2184 if (OtherPtr == AI || OtherPtr == NewElts[0]) {
2185 // This code will run twice for a no-op memcpy -- once for each operand.
2186 // Put only one reference to MI on the DeadInsts list.
2187 for (SmallVectorImpl<Value *>::const_iterator I = DeadInsts.begin(),
2188 E = DeadInsts.end(); I != E; ++I)
2189 if (*I == MI) return;
2190 DeadInsts.push_back(MI);
2194 // If the pointer is not the right type, insert a bitcast to the right
2197 PointerType::get(AI->getType()->getElementType(), AddrSpace);
2199 if (OtherPtr->getType() != NewTy)
2200 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
2203 // Process each element of the aggregate.
2204 bool SROADest = MI->getRawDest() == Inst;
2206 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
2208 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2209 // If this is a memcpy/memmove, emit a GEP of the other element address.
2210 Value *OtherElt = 0;
2211 unsigned OtherEltAlign = MemAlignment;
2214 Value *Idx[2] = { Zero,
2215 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
2216 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx,
2217 OtherPtr->getName()+"."+Twine(i),
2220 PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
2221 Type *OtherTy = OtherPtrTy->getElementType();
2222 if (StructType *ST = dyn_cast<StructType>(OtherTy)) {
2223 EltOffset = DL->getStructLayout(ST)->getElementOffset(i);
2225 Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
2226 EltOffset = DL->getTypeAllocSize(EltTy)*i;
2229 // The alignment of the other pointer is the guaranteed alignment of the
2230 // element, which is affected by both the known alignment of the whole
2231 // mem intrinsic and the alignment of the element. If the alignment of
2232 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
2233 // known alignment is just 4 bytes.
2234 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
2237 Value *EltPtr = NewElts[i];
2238 Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
2240 // If we got down to a scalar, insert a load or store as appropriate.
2241 if (EltTy->isSingleValueType()) {
2242 if (isa<MemTransferInst>(MI)) {
2244 // From Other to Alloca.
2245 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
2246 new StoreInst(Elt, EltPtr, MI);
2248 // From Alloca to Other.
2249 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
2250 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
2254 assert(isa<MemSetInst>(MI));
2256 // If the stored element is zero (common case), just store a null
2259 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
2261 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
2263 // If EltTy is a vector type, get the element type.
2264 Type *ValTy = EltTy->getScalarType();
2266 // Construct an integer with the right value.
2267 unsigned EltSize = DL->getTypeSizeInBits(ValTy);
2268 APInt OneVal(EltSize, CI->getZExtValue());
2269 APInt TotalVal(OneVal);
2271 for (unsigned i = 0; 8*i < EltSize; ++i) {
2272 TotalVal = TotalVal.shl(8);
2276 // Convert the integer value to the appropriate type.
2277 StoreVal = ConstantInt::get(CI->getContext(), TotalVal);
2278 if (ValTy->isPointerTy())
2279 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
2280 else if (ValTy->isFloatingPointTy())
2281 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
2282 assert(StoreVal->getType() == ValTy && "Type mismatch!");
2284 // If the requested value was a vector constant, create it.
2285 if (EltTy->isVectorTy()) {
2286 unsigned NumElts = cast<VectorType>(EltTy)->getNumElements();
2287 StoreVal = ConstantVector::getSplat(NumElts, StoreVal);
2290 new StoreInst(StoreVal, EltPtr, MI);
2293 // Otherwise, if we're storing a byte variable, use a memset call for
2297 unsigned EltSize = DL->getTypeAllocSize(EltTy);
2301 IRBuilder<> Builder(MI);
2303 // Finally, insert the meminst for this element.
2304 if (isa<MemSetInst>(MI)) {
2305 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize,
2308 assert(isa<MemTransferInst>(MI));
2309 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr
2310 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr
2312 if (isa<MemCpyInst>(MI))
2313 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile());
2315 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile());
2318 DeadInsts.push_back(MI);
2321 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
2322 /// overwrites the entire allocation. Extract out the pieces of the stored
2323 /// integer and store them individually.
2325 SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
2326 SmallVectorImpl<AllocaInst *> &NewElts) {
2327 // Extract each element out of the integer according to its structure offset
2328 // and store the element value to the individual alloca.
2329 Value *SrcVal = SI->getOperand(0);
2330 Type *AllocaEltTy = AI->getAllocatedType();
2331 uint64_t AllocaSizeBits = DL->getTypeAllocSizeInBits(AllocaEltTy);
2333 IRBuilder<> Builder(SI);
2335 // Handle tail padding by extending the operand
2336 if (DL->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
2337 SrcVal = Builder.CreateZExt(SrcVal,
2338 IntegerType::get(SI->getContext(), AllocaSizeBits));
2340 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
2343 // There are two forms here: AI could be an array or struct. Both cases
2344 // have different ways to compute the element offset.
2345 if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2346 const StructLayout *Layout = DL->getStructLayout(EltSTy);
2348 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2349 // Get the number of bits to shift SrcVal to get the value.
2350 Type *FieldTy = EltSTy->getElementType(i);
2351 uint64_t Shift = Layout->getElementOffsetInBits(i);
2353 if (DL->isBigEndian())
2354 Shift = AllocaSizeBits-Shift-DL->getTypeAllocSizeInBits(FieldTy);
2356 Value *EltVal = SrcVal;
2358 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2359 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2362 // Truncate down to an integer of the right size.
2363 uint64_t FieldSizeBits = DL->getTypeSizeInBits(FieldTy);
2365 // Ignore zero sized fields like {}, they obviously contain no data.
2366 if (FieldSizeBits == 0) continue;
2368 if (FieldSizeBits != AllocaSizeBits)
2369 EltVal = Builder.CreateTrunc(EltVal,
2370 IntegerType::get(SI->getContext(), FieldSizeBits));
2371 Value *DestField = NewElts[i];
2372 if (EltVal->getType() == FieldTy) {
2373 // Storing to an integer field of this size, just do it.
2374 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
2375 // Bitcast to the right element type (for fp/vector values).
2376 EltVal = Builder.CreateBitCast(EltVal, FieldTy);
2378 // Otherwise, bitcast the dest pointer (for aggregates).
2379 DestField = Builder.CreateBitCast(DestField,
2380 PointerType::getUnqual(EltVal->getType()));
2382 new StoreInst(EltVal, DestField, SI);
2386 ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
2387 Type *ArrayEltTy = ATy->getElementType();
2388 uint64_t ElementOffset = DL->getTypeAllocSizeInBits(ArrayEltTy);
2389 uint64_t ElementSizeBits = DL->getTypeSizeInBits(ArrayEltTy);
2393 if (DL->isBigEndian())
2394 Shift = AllocaSizeBits-ElementOffset;
2398 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2399 // Ignore zero sized fields like {}, they obviously contain no data.
2400 if (ElementSizeBits == 0) continue;
2402 Value *EltVal = SrcVal;
2404 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2405 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2408 // Truncate down to an integer of the right size.
2409 if (ElementSizeBits != AllocaSizeBits)
2410 EltVal = Builder.CreateTrunc(EltVal,
2411 IntegerType::get(SI->getContext(),
2413 Value *DestField = NewElts[i];
2414 if (EltVal->getType() == ArrayEltTy) {
2415 // Storing to an integer field of this size, just do it.
2416 } else if (ArrayEltTy->isFloatingPointTy() ||
2417 ArrayEltTy->isVectorTy()) {
2418 // Bitcast to the right element type (for fp/vector values).
2419 EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy);
2421 // Otherwise, bitcast the dest pointer (for aggregates).
2422 DestField = Builder.CreateBitCast(DestField,
2423 PointerType::getUnqual(EltVal->getType()));
2425 new StoreInst(EltVal, DestField, SI);
2427 if (DL->isBigEndian())
2428 Shift -= ElementOffset;
2430 Shift += ElementOffset;
2434 DeadInsts.push_back(SI);
2437 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
2438 /// an integer. Load the individual pieces to form the aggregate value.
2440 SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
2441 SmallVectorImpl<AllocaInst *> &NewElts) {
2442 // Extract each element out of the NewElts according to its structure offset
2443 // and form the result value.
2444 Type *AllocaEltTy = AI->getAllocatedType();
2445 uint64_t AllocaSizeBits = DL->getTypeAllocSizeInBits(AllocaEltTy);
2447 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
2450 // There are two forms here: AI could be an array or struct. Both cases
2451 // have different ways to compute the element offset.
2452 const StructLayout *Layout = 0;
2453 uint64_t ArrayEltBitOffset = 0;
2454 if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2455 Layout = DL->getStructLayout(EltSTy);
2457 Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
2458 ArrayEltBitOffset = DL->getTypeAllocSizeInBits(ArrayEltTy);
2462 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
2464 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2465 // Load the value from the alloca. If the NewElt is an aggregate, cast
2466 // the pointer to an integer of the same size before doing the load.
2467 Value *SrcField = NewElts[i];
2469 cast<PointerType>(SrcField->getType())->getElementType();
2470 uint64_t FieldSizeBits = DL->getTypeSizeInBits(FieldTy);
2472 // Ignore zero sized fields like {}, they obviously contain no data.
2473 if (FieldSizeBits == 0) continue;
2475 IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
2477 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
2478 !FieldTy->isVectorTy())
2479 SrcField = new BitCastInst(SrcField,
2480 PointerType::getUnqual(FieldIntTy),
2482 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
2484 // If SrcField is a fp or vector of the right size but that isn't an
2485 // integer type, bitcast to an integer so we can shift it.
2486 if (SrcField->getType() != FieldIntTy)
2487 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
2489 // Zero extend the field to be the same size as the final alloca so that
2490 // we can shift and insert it.
2491 if (SrcField->getType() != ResultVal->getType())
2492 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
2494 // Determine the number of bits to shift SrcField.
2496 if (Layout) // Struct case.
2497 Shift = Layout->getElementOffsetInBits(i);
2499 Shift = i*ArrayEltBitOffset;
2501 if (DL->isBigEndian())
2502 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
2505 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
2506 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
2509 // Don't create an 'or x, 0' on the first iteration.
2510 if (!isa<Constant>(ResultVal) ||
2511 !cast<Constant>(ResultVal)->isNullValue())
2512 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
2514 ResultVal = SrcField;
2517 // Handle tail padding by truncating the result
2518 if (DL->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
2519 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
2521 LI->replaceAllUsesWith(ResultVal);
2522 DeadInsts.push_back(LI);
2525 /// HasPadding - Return true if the specified type has any structure or
2526 /// alignment padding in between the elements that would be split apart
2527 /// by SROA; return false otherwise.
2528 static bool HasPadding(Type *Ty, const DataLayout &DL) {
2529 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
2530 Ty = ATy->getElementType();
2531 return DL.getTypeSizeInBits(Ty) != DL.getTypeAllocSizeInBits(Ty);
2534 // SROA currently handles only Arrays and Structs.
2535 StructType *STy = cast<StructType>(Ty);
2536 const StructLayout *SL = DL.getStructLayout(STy);
2537 unsigned PrevFieldBitOffset = 0;
2538 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
2539 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
2541 // Check to see if there is any padding between this element and the
2544 unsigned PrevFieldEnd =
2545 PrevFieldBitOffset+DL.getTypeSizeInBits(STy->getElementType(i-1));
2546 if (PrevFieldEnd < FieldBitOffset)
2549 PrevFieldBitOffset = FieldBitOffset;
2551 // Check for tail padding.
2552 if (unsigned EltCount = STy->getNumElements()) {
2553 unsigned PrevFieldEnd = PrevFieldBitOffset +
2554 DL.getTypeSizeInBits(STy->getElementType(EltCount-1));
2555 if (PrevFieldEnd < SL->getSizeInBits())
2561 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
2562 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
2563 /// or 1 if safe after canonicalization has been performed.
2564 bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
2565 // Loop over the use list of the alloca. We can only transform it if all of
2566 // the users are safe to transform.
2567 AllocaInfo Info(AI);
2569 isSafeForScalarRepl(AI, 0, Info);
2570 if (Info.isUnsafe) {
2571 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
2575 // Okay, we know all the users are promotable. If the aggregate is a memcpy
2576 // source and destination, we have to be careful. In particular, the memcpy
2577 // could be moving around elements that live in structure padding of the LLVM
2578 // types, but may actually be used. In these cases, we refuse to promote the
2580 if (Info.isMemCpySrc && Info.isMemCpyDst &&
2581 HasPadding(AI->getAllocatedType(), *DL))
2584 // If the alloca never has an access to just *part* of it, but is accessed
2585 // via loads and stores, then we should use ConvertToScalarInfo to promote
2586 // the alloca instead of promoting each piece at a time and inserting fission
2588 if (!Info.hasSubelementAccess && Info.hasALoadOrStore) {
2589 // If the struct/array just has one element, use basic SRoA.
2590 if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
2591 if (ST->getNumElements() > 1) return false;
2593 if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1)