1 //===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This transformation implements the well known scalar replacement of
11 // aggregates transformation. This xform breaks up alloca instructions of
12 // aggregate type (structure or array) into individual alloca instructions for
13 // each member (if possible). Then, if possible, it transforms the individual
14 // alloca instructions into nice clean scalar SSA form.
16 // This combines a simple SRoA algorithm with the Mem2Reg algorithm because
17 // often interact, especially for C++ programs. As such, iterating between
18 // SRoA, then Mem2Reg until we run out of things to promote works well.
20 //===----------------------------------------------------------------------===//
22 #define DEBUG_TYPE "scalarrepl"
23 #include "llvm/Transforms/Scalar.h"
24 #include "llvm/Constants.h"
25 #include "llvm/DerivedTypes.h"
26 #include "llvm/Function.h"
27 #include "llvm/GlobalVariable.h"
28 #include "llvm/Instructions.h"
29 #include "llvm/IntrinsicInst.h"
30 #include "llvm/LLVMContext.h"
31 #include "llvm/Module.h"
32 #include "llvm/Pass.h"
33 #include "llvm/Analysis/Dominators.h"
34 #include "llvm/Target/TargetData.h"
35 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
36 #include "llvm/Transforms/Utils/Local.h"
37 #include "llvm/Support/CallSite.h"
38 #include "llvm/Support/Debug.h"
39 #include "llvm/Support/ErrorHandling.h"
40 #include "llvm/Support/GetElementPtrTypeIterator.h"
41 #include "llvm/Support/IRBuilder.h"
42 #include "llvm/Support/MathExtras.h"
43 #include "llvm/Support/raw_ostream.h"
44 #include "llvm/ADT/SmallVector.h"
45 #include "llvm/ADT/Statistic.h"
48 STATISTIC(NumReplaced, "Number of allocas broken up");
49 STATISTIC(NumPromoted, "Number of allocas promoted");
50 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
51 STATISTIC(NumGlobals, "Number of allocas copied from constant global");
54 struct SROA : public FunctionPass {
55 static char ID; // Pass identification, replacement for typeid
56 explicit SROA(signed T = -1) : FunctionPass(ID) {
57 initializeSROAPass(*PassRegistry::getPassRegistry());
64 bool runOnFunction(Function &F);
66 bool performScalarRepl(Function &F);
67 bool performPromotion(Function &F);
69 // getAnalysisUsage - This pass does not require any passes, but we know it
70 // will not alter the CFG, so say so.
71 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
72 AU.addRequired<DominatorTree>();
73 AU.addRequired<DominanceFrontier>();
80 /// DeadInsts - Keep track of instructions we have made dead, so that
81 /// we can remove them after we are done working.
82 SmallVector<Value*, 32> DeadInsts;
84 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
85 /// information about the uses. All these fields are initialized to false
86 /// and set to true when something is learned.
88 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
91 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
94 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
98 : isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false) {}
101 unsigned SRThreshold;
103 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
105 bool isSafeAllocaToScalarRepl(AllocaInst *AI);
107 void isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
109 void isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t &Offset,
111 void isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize,
112 const Type *MemOpType, bool isStore, AllocaInfo &Info);
113 bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size);
114 uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset,
117 void DoScalarReplacement(AllocaInst *AI,
118 std::vector<AllocaInst*> &WorkList);
119 void DeleteDeadInstructions();
121 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
122 SmallVector<AllocaInst*, 32> &NewElts);
123 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
124 SmallVector<AllocaInst*, 32> &NewElts);
125 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
126 SmallVector<AllocaInst*, 32> &NewElts);
127 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
129 SmallVector<AllocaInst*, 32> &NewElts);
130 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
131 SmallVector<AllocaInst*, 32> &NewElts);
132 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
133 SmallVector<AllocaInst*, 32> &NewElts);
135 static MemTransferInst *isOnlyCopiedFromConstantGlobal(AllocaInst *AI);
140 INITIALIZE_PASS_BEGIN(SROA, "scalarrepl",
141 "Scalar Replacement of Aggregates", false, false)
142 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
143 INITIALIZE_PASS_DEPENDENCY(DominanceFrontier)
144 INITIALIZE_PASS_END(SROA, "scalarrepl",
145 "Scalar Replacement of Aggregates", false, false)
147 // Public interface to the ScalarReplAggregates pass
148 FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) {
149 return new SROA(Threshold);
153 //===----------------------------------------------------------------------===//
154 // Convert To Scalar Optimization.
155 //===----------------------------------------------------------------------===//
158 /// ConvertToScalarInfo - This class implements the "Convert To Scalar"
159 /// optimization, which scans the uses of an alloca and determines if it can
160 /// rewrite it in terms of a single new alloca that can be mem2reg'd.
161 class ConvertToScalarInfo {
162 /// AllocaSize - The size of the alloca being considered.
164 const TargetData &TD;
166 /// IsNotTrivial - This is set to true if there is some access to the object
167 /// which means that mem2reg can't promote it.
170 /// VectorTy - This tracks the type that we should promote the vector to if
171 /// it is possible to turn it into a vector. This starts out null, and if it
172 /// isn't possible to turn into a vector type, it gets set to VoidTy.
173 const Type *VectorTy;
175 /// HadAVector - True if there is at least one vector access to the alloca.
176 /// We don't want to turn random arrays into vectors and use vector element
177 /// insert/extract, but if there are element accesses to something that is
178 /// also declared as a vector, we do want to promote to a vector.
182 explicit ConvertToScalarInfo(unsigned Size, const TargetData &td)
183 : AllocaSize(Size), TD(td) {
184 IsNotTrivial = false;
189 AllocaInst *TryConvert(AllocaInst *AI);
192 bool CanConvertToScalar(Value *V, uint64_t Offset);
193 void MergeInType(const Type *In, uint64_t Offset);
194 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
196 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
197 uint64_t Offset, IRBuilder<> &Builder);
198 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
199 uint64_t Offset, IRBuilder<> &Builder);
201 } // end anonymous namespace.
204 /// IsVerbotenVectorType - Return true if this is a vector type ScalarRepl isn't
205 /// allowed to form. We do this to avoid MMX types, which is a complete hack,
206 /// but is required until the backend is fixed.
207 static bool IsVerbotenVectorType(const VectorType *VTy, const Instruction *I) {
208 StringRef Triple(I->getParent()->getParent()->getParent()->getTargetTriple());
209 if (!Triple.startswith("i386") &&
210 !Triple.startswith("x86_64"))
213 // Reject all the MMX vector types.
214 switch (VTy->getNumElements()) {
215 default: return false;
216 case 1: return VTy->getElementType()->isIntegerTy(64);
217 case 2: return VTy->getElementType()->isIntegerTy(32);
218 case 4: return VTy->getElementType()->isIntegerTy(16);
219 case 8: return VTy->getElementType()->isIntegerTy(8);
224 /// TryConvert - Analyze the specified alloca, and if it is safe to do so,
225 /// rewrite it to be a new alloca which is mem2reg'able. This returns the new
226 /// alloca if possible or null if not.
227 AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
228 // If we can't convert this scalar, or if mem2reg can trivially do it, bail
230 if (!CanConvertToScalar(AI, 0) || !IsNotTrivial)
233 // If we were able to find a vector type that can handle this with
234 // insert/extract elements, and if there was at least one use that had
235 // a vector type, promote this to a vector. We don't want to promote
236 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
237 // we just get a lot of insert/extracts. If at least one vector is
238 // involved, then we probably really do have a union of vector/array.
240 if (VectorTy && VectorTy->isVectorTy() && HadAVector &&
241 !IsVerbotenVectorType(cast<VectorType>(VectorTy), AI)) {
242 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
243 << *VectorTy << '\n');
244 NewTy = VectorTy; // Use the vector type.
246 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
247 // Create and insert the integer alloca.
248 NewTy = IntegerType::get(AI->getContext(), AllocaSize*8);
250 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
251 ConvertUsesToScalar(AI, NewAI, 0);
255 /// MergeInType - Add the 'In' type to the accumulated vector type (VectorTy)
256 /// so far at the offset specified by Offset (which is specified in bytes).
258 /// There are two cases we handle here:
259 /// 1) A union of vector types of the same size and potentially its elements.
260 /// Here we turn element accesses into insert/extract element operations.
261 /// This promotes a <4 x float> with a store of float to the third element
262 /// into a <4 x float> that uses insert element.
263 /// 2) A fully general blob of memory, which we turn into some (potentially
264 /// large) integer type with extract and insert operations where the loads
265 /// and stores would mutate the memory. We mark this by setting VectorTy
267 void ConvertToScalarInfo::MergeInType(const Type *In, uint64_t Offset) {
268 // If we already decided to turn this into a blob of integer memory, there is
269 // nothing to be done.
270 if (VectorTy && VectorTy->isVoidTy())
273 // If this could be contributing to a vector, analyze it.
275 // If the In type is a vector that is the same size as the alloca, see if it
276 // matches the existing VecTy.
277 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
278 // Remember if we saw a vector type.
281 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
282 // If we're storing/loading a vector of the right size, allow it as a
283 // vector. If this the first vector we see, remember the type so that
284 // we know the element size. If this is a subsequent access, ignore it
285 // even if it is a differing type but the same size. Worst case we can
286 // bitcast the resultant vectors.
291 } else if (In->isFloatTy() || In->isDoubleTy() ||
292 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
293 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
294 // If we're accessing something that could be an element of a vector, see
295 // if the implied vector agrees with what we already have and if Offset is
296 // compatible with it.
297 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
298 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 &&
300 cast<VectorType>(VectorTy)->getElementType()
301 ->getPrimitiveSizeInBits()/8 == EltSize)) {
303 VectorTy = VectorType::get(In, AllocaSize/EltSize);
308 // Otherwise, we have a case that we can't handle with an optimized vector
309 // form. We can still turn this into a large integer.
310 VectorTy = Type::getVoidTy(In->getContext());
313 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
314 /// its accesses to a single vector type, return true and set VecTy to
315 /// the new type. If we could convert the alloca into a single promotable
316 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
317 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
318 /// is the current offset from the base of the alloca being analyzed.
320 /// If we see at least one access to the value that is as a vector type, set the
322 bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) {
323 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
324 Instruction *User = cast<Instruction>(*UI);
326 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
327 // Don't break volatile loads.
328 if (LI->isVolatile())
330 // Don't touch MMX operations.
331 if (LI->getType()->isX86_MMXTy())
333 MergeInType(LI->getType(), Offset);
337 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
338 // Storing the pointer, not into the value?
339 if (SI->getOperand(0) == V || SI->isVolatile()) return false;
340 // Don't touch MMX operations.
341 if (SI->getOperand(0)->getType()->isX86_MMXTy())
343 MergeInType(SI->getOperand(0)->getType(), Offset);
347 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
348 IsNotTrivial = true; // Can't be mem2reg'd.
349 if (!CanConvertToScalar(BCI, Offset))
354 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
355 // If this is a GEP with a variable indices, we can't handle it.
356 if (!GEP->hasAllConstantIndices())
359 // Compute the offset that this GEP adds to the pointer.
360 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
361 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
362 &Indices[0], Indices.size());
363 // See if all uses can be converted.
364 if (!CanConvertToScalar(GEP, Offset+GEPOffset))
366 IsNotTrivial = true; // Can't be mem2reg'd.
370 // If this is a constant sized memset of a constant value (e.g. 0) we can
372 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
373 // Store of constant value and constant size.
374 if (!isa<ConstantInt>(MSI->getValue()) ||
375 !isa<ConstantInt>(MSI->getLength()))
377 IsNotTrivial = true; // Can't be mem2reg'd.
381 // If this is a memcpy or memmove into or out of the whole allocation, we
382 // can handle it like a load or store of the scalar type.
383 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
384 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
385 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0)
388 IsNotTrivial = true; // Can't be mem2reg'd.
392 // Otherwise, we cannot handle this!
399 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
400 /// directly. This happens when we are converting an "integer union" to a
401 /// single integer scalar, or when we are converting a "vector union" to a
402 /// vector with insert/extractelement instructions.
404 /// Offset is an offset from the original alloca, in bits that need to be
405 /// shifted to the right. By the end of this, there should be no uses of Ptr.
406 void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
408 while (!Ptr->use_empty()) {
409 Instruction *User = cast<Instruction>(Ptr->use_back());
411 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
412 ConvertUsesToScalar(CI, NewAI, Offset);
413 CI->eraseFromParent();
417 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
418 // Compute the offset that this GEP adds to the pointer.
419 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
420 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
421 &Indices[0], Indices.size());
422 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
423 GEP->eraseFromParent();
427 IRBuilder<> Builder(User->getParent(), User);
429 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
430 // The load is a bit extract from NewAI shifted right by Offset bits.
431 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
433 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
434 LI->replaceAllUsesWith(NewLoadVal);
435 LI->eraseFromParent();
439 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
440 assert(SI->getOperand(0) != Ptr && "Consistency error!");
441 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
442 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
444 Builder.CreateStore(New, NewAI);
445 SI->eraseFromParent();
447 // If the load we just inserted is now dead, then the inserted store
448 // overwrote the entire thing.
449 if (Old->use_empty())
450 Old->eraseFromParent();
454 // If this is a constant sized memset of a constant value (e.g. 0) we can
455 // transform it into a store of the expanded constant value.
456 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
457 assert(MSI->getRawDest() == Ptr && "Consistency error!");
458 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
460 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
462 // Compute the value replicated the right number of times.
463 APInt APVal(NumBytes*8, Val);
465 // Splat the value if non-zero.
467 for (unsigned i = 1; i != NumBytes; ++i)
470 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
471 Value *New = ConvertScalar_InsertValue(
472 ConstantInt::get(User->getContext(), APVal),
473 Old, Offset, Builder);
474 Builder.CreateStore(New, NewAI);
476 // If the load we just inserted is now dead, then the memset overwrote
478 if (Old->use_empty())
479 Old->eraseFromParent();
481 MSI->eraseFromParent();
485 // If this is a memcpy or memmove into or out of the whole allocation, we
486 // can handle it like a load or store of the scalar type.
487 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
488 assert(Offset == 0 && "must be store to start of alloca");
490 // If the source and destination are both to the same alloca, then this is
491 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
493 AllocaInst *OrigAI = cast<AllocaInst>(Ptr->getUnderlyingObject(0));
495 if (MTI->getSource()->getUnderlyingObject(0) != OrigAI) {
496 // Dest must be OrigAI, change this to be a load from the original
497 // pointer (bitcasted), then a store to our new alloca.
498 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
499 Value *SrcPtr = MTI->getSource();
500 SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType());
502 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
503 SrcVal->setAlignment(MTI->getAlignment());
504 Builder.CreateStore(SrcVal, NewAI);
505 } else if (MTI->getDest()->getUnderlyingObject(0) != OrigAI) {
506 // Src must be OrigAI, change this to be a load from NewAI then a store
507 // through the original dest pointer (bitcasted).
508 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
509 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
511 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType());
512 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
513 NewStore->setAlignment(MTI->getAlignment());
515 // Noop transfer. Src == Dst
518 MTI->eraseFromParent();
522 llvm_unreachable("Unsupported operation!");
526 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
527 /// or vector value FromVal, extracting the bits from the offset specified by
528 /// Offset. This returns the value, which is of type ToType.
530 /// This happens when we are converting an "integer union" to a single
531 /// integer scalar, or when we are converting a "vector union" to a vector with
532 /// insert/extractelement instructions.
534 /// Offset is an offset from the original alloca, in bits that need to be
535 /// shifted to the right.
536 Value *ConvertToScalarInfo::
537 ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
538 uint64_t Offset, IRBuilder<> &Builder) {
539 // If the load is of the whole new alloca, no conversion is needed.
540 if (FromVal->getType() == ToType && Offset == 0)
543 // If the result alloca is a vector type, this is either an element
544 // access or a bitcast to another vector type of the same size.
545 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
546 if (ToType->isVectorTy())
547 return Builder.CreateBitCast(FromVal, ToType, "tmp");
549 // Otherwise it must be an element access.
552 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
553 Elt = Offset/EltSize;
554 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
556 // Return the element extracted out of it.
557 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(
558 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp");
559 if (V->getType() != ToType)
560 V = Builder.CreateBitCast(V, ToType, "tmp");
564 // If ToType is a first class aggregate, extract out each of the pieces and
565 // use insertvalue's to form the FCA.
566 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
567 const StructLayout &Layout = *TD.getStructLayout(ST);
568 Value *Res = UndefValue::get(ST);
569 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
570 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
571 Offset+Layout.getElementOffsetInBits(i),
573 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
578 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
579 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
580 Value *Res = UndefValue::get(AT);
581 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
582 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
583 Offset+i*EltSize, Builder);
584 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
589 // Otherwise, this must be a union that was converted to an integer value.
590 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
592 // If this is a big-endian system and the load is narrower than the
593 // full alloca type, we need to do a shift to get the right bits.
595 if (TD.isBigEndian()) {
596 // On big-endian machines, the lowest bit is stored at the bit offset
597 // from the pointer given by getTypeStoreSizeInBits. This matters for
598 // integers with a bitwidth that is not a multiple of 8.
599 ShAmt = TD.getTypeStoreSizeInBits(NTy) -
600 TD.getTypeStoreSizeInBits(ToType) - Offset;
605 // Note: we support negative bitwidths (with shl) which are not defined.
606 // We do this to support (f.e.) loads off the end of a structure where
607 // only some bits are used.
608 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
609 FromVal = Builder.CreateLShr(FromVal,
610 ConstantInt::get(FromVal->getType(),
612 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
613 FromVal = Builder.CreateShl(FromVal,
614 ConstantInt::get(FromVal->getType(),
617 // Finally, unconditionally truncate the integer to the right width.
618 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType);
619 if (LIBitWidth < NTy->getBitWidth())
621 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
623 else if (LIBitWidth > NTy->getBitWidth())
625 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
628 // If the result is an integer, this is a trunc or bitcast.
629 if (ToType->isIntegerTy()) {
631 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
632 // Just do a bitcast, we know the sizes match up.
633 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
635 // Otherwise must be a pointer.
636 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
638 assert(FromVal->getType() == ToType && "Didn't convert right?");
642 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
643 /// or vector value "Old" at the offset specified by Offset.
645 /// This happens when we are converting an "integer union" to a
646 /// single integer scalar, or when we are converting a "vector union" to a
647 /// vector with insert/extractelement instructions.
649 /// Offset is an offset from the original alloca, in bits that need to be
650 /// shifted to the right.
651 Value *ConvertToScalarInfo::
652 ConvertScalar_InsertValue(Value *SV, Value *Old,
653 uint64_t Offset, IRBuilder<> &Builder) {
654 // Convert the stored type to the actual type, shift it left to insert
655 // then 'or' into place.
656 const Type *AllocaType = Old->getType();
657 LLVMContext &Context = Old->getContext();
659 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
660 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy);
661 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType());
663 // Changing the whole vector with memset or with an access of a different
665 if (ValSize == VecSize)
666 return Builder.CreateBitCast(SV, AllocaType, "tmp");
668 uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
670 // Must be an element insertion.
671 unsigned Elt = Offset/EltSize;
673 if (SV->getType() != VTy->getElementType())
674 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
676 SV = Builder.CreateInsertElement(Old, SV,
677 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt),
682 // If SV is a first-class aggregate value, insert each value recursively.
683 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
684 const StructLayout &Layout = *TD.getStructLayout(ST);
685 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
686 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
687 Old = ConvertScalar_InsertValue(Elt, Old,
688 Offset+Layout.getElementOffsetInBits(i),
694 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
695 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
696 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
697 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
698 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
703 // If SV is a float, convert it to the appropriate integer type.
704 // If it is a pointer, do the same.
705 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType());
706 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType);
707 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType());
708 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType);
709 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
710 SV = Builder.CreateBitCast(SV,
711 IntegerType::get(SV->getContext(),SrcWidth), "tmp");
712 else if (SV->getType()->isPointerTy())
713 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "tmp");
715 // Zero extend or truncate the value if needed.
716 if (SV->getType() != AllocaType) {
717 if (SV->getType()->getPrimitiveSizeInBits() <
718 AllocaType->getPrimitiveSizeInBits())
719 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
721 // Truncation may be needed if storing more than the alloca can hold
722 // (undefined behavior).
723 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
724 SrcWidth = DestWidth;
725 SrcStoreWidth = DestStoreWidth;
729 // If this is a big-endian system and the store is narrower than the
730 // full alloca type, we need to do a shift to get the right bits.
732 if (TD.isBigEndian()) {
733 // On big-endian machines, the lowest bit is stored at the bit offset
734 // from the pointer given by getTypeStoreSizeInBits. This matters for
735 // integers with a bitwidth that is not a multiple of 8.
736 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
741 // Note: we support negative bitwidths (with shr) which are not defined.
742 // We do this to support (f.e.) stores off the end of a structure where
743 // only some bits in the structure are set.
744 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
745 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
746 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(),
749 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
750 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(),
752 Mask = Mask.lshr(-ShAmt);
755 // Mask out the bits we are about to insert from the old value, and or
757 if (SrcWidth != DestWidth) {
758 assert(DestWidth > SrcWidth);
759 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
760 SV = Builder.CreateOr(Old, SV, "ins");
766 //===----------------------------------------------------------------------===//
768 //===----------------------------------------------------------------------===//
771 bool SROA::runOnFunction(Function &F) {
772 TD = getAnalysisIfAvailable<TargetData>();
774 bool Changed = performPromotion(F);
776 // FIXME: ScalarRepl currently depends on TargetData more than it
777 // theoretically needs to. It should be refactored in order to support
778 // target-independent IR. Until this is done, just skip the actual
779 // scalar-replacement portion of this pass.
780 if (!TD) return Changed;
783 bool LocalChange = performScalarRepl(F);
784 if (!LocalChange) break; // No need to repromote if no scalarrepl
786 LocalChange = performPromotion(F);
787 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
794 bool SROA::performPromotion(Function &F) {
795 std::vector<AllocaInst*> Allocas;
796 DominatorTree &DT = getAnalysis<DominatorTree>();
797 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
799 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
801 bool Changed = false;
806 // Find allocas that are safe to promote, by looking at all instructions in
808 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
809 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
810 if (isAllocaPromotable(AI))
811 Allocas.push_back(AI);
813 if (Allocas.empty()) break;
815 PromoteMemToReg(Allocas, DT, DF);
816 NumPromoted += Allocas.size();
824 /// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
825 /// SROA. It must be a struct or array type with a small number of elements.
826 static bool ShouldAttemptScalarRepl(AllocaInst *AI) {
827 const Type *T = AI->getAllocatedType();
828 // Do not promote any struct into more than 32 separate vars.
829 if (const StructType *ST = dyn_cast<StructType>(T))
830 return ST->getNumElements() <= 32;
831 // Arrays are much less likely to be safe for SROA; only consider
832 // them if they are very small.
833 if (const ArrayType *AT = dyn_cast<ArrayType>(T))
834 return AT->getNumElements() <= 8;
839 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
840 // which runs on all of the malloc/alloca instructions in the function, removing
841 // them if they are only used by getelementptr instructions.
843 bool SROA::performScalarRepl(Function &F) {
844 std::vector<AllocaInst*> WorkList;
846 // Scan the entry basic block, adding allocas to the worklist.
847 BasicBlock &BB = F.getEntryBlock();
848 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
849 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
850 WorkList.push_back(A);
852 // Process the worklist
853 bool Changed = false;
854 while (!WorkList.empty()) {
855 AllocaInst *AI = WorkList.back();
858 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
859 // with unused elements.
860 if (AI->use_empty()) {
861 AI->eraseFromParent();
866 // If this alloca is impossible for us to promote, reject it early.
867 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
870 // Check to see if this allocation is only modified by a memcpy/memmove from
871 // a constant global. If this is the case, we can change all users to use
872 // the constant global instead. This is commonly produced by the CFE by
873 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
874 // is only subsequently read.
875 if (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
876 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n');
877 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n');
878 Constant *TheSrc = cast<Constant>(TheCopy->getSource());
879 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
880 TheCopy->eraseFromParent(); // Don't mutate the global.
881 AI->eraseFromParent();
887 // Check to see if we can perform the core SROA transformation. We cannot
888 // transform the allocation instruction if it is an array allocation
889 // (allocations OF arrays are ok though), and an allocation of a scalar
890 // value cannot be decomposed at all.
891 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
893 // Do not promote [0 x %struct].
894 if (AllocaSize == 0) continue;
896 // Do not promote any struct whose size is too big.
897 if (AllocaSize > SRThreshold) continue;
899 // If the alloca looks like a good candidate for scalar replacement, and if
900 // all its users can be transformed, then split up the aggregate into its
901 // separate elements.
902 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
903 DoScalarReplacement(AI, WorkList);
908 // If we can turn this aggregate value (potentially with casts) into a
909 // simple scalar value that can be mem2reg'd into a register value.
910 // IsNotTrivial tracks whether this is something that mem2reg could have
911 // promoted itself. If so, we don't want to transform it needlessly. Note
912 // that we can't just check based on the type: the alloca may be of an i32
913 // but that has pointer arithmetic to set byte 3 of it or something.
914 if (AllocaInst *NewAI =
915 ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) {
917 AI->eraseFromParent();
923 // Otherwise, couldn't process this alloca.
929 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
930 /// predicate, do SROA now.
931 void SROA::DoScalarReplacement(AllocaInst *AI,
932 std::vector<AllocaInst*> &WorkList) {
933 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
934 SmallVector<AllocaInst*, 32> ElementAllocas;
935 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
936 ElementAllocas.reserve(ST->getNumContainedTypes());
937 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
938 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
940 AI->getName() + "." + Twine(i), AI);
941 ElementAllocas.push_back(NA);
942 WorkList.push_back(NA); // Add to worklist for recursive processing
945 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
946 ElementAllocas.reserve(AT->getNumElements());
947 const Type *ElTy = AT->getElementType();
948 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
949 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
950 AI->getName() + "." + Twine(i), AI);
951 ElementAllocas.push_back(NA);
952 WorkList.push_back(NA); // Add to worklist for recursive processing
956 // Now that we have created the new alloca instructions, rewrite all the
957 // uses of the old alloca.
958 RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
960 // Now erase any instructions that were made dead while rewriting the alloca.
961 DeleteDeadInstructions();
962 AI->eraseFromParent();
967 /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
968 /// recursively including all their operands that become trivially dead.
969 void SROA::DeleteDeadInstructions() {
970 while (!DeadInsts.empty()) {
971 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
973 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
974 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
975 // Zero out the operand and see if it becomes trivially dead.
976 // (But, don't add allocas to the dead instruction list -- they are
977 // already on the worklist and will be deleted separately.)
979 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
980 DeadInsts.push_back(U);
983 I->eraseFromParent();
987 /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
988 /// performing scalar replacement of alloca AI. The results are flagged in
989 /// the Info parameter. Offset indicates the position within AI that is
990 /// referenced by this instruction.
991 void SROA::isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
993 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
994 Instruction *User = cast<Instruction>(*UI);
996 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
997 isSafeForScalarRepl(BC, AI, Offset, Info);
998 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
999 uint64_t GEPOffset = Offset;
1000 isSafeGEP(GEPI, AI, GEPOffset, Info);
1002 isSafeForScalarRepl(GEPI, AI, GEPOffset, Info);
1003 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1004 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1006 isSafeMemAccess(AI, Offset, Length->getZExtValue(), 0,
1007 UI.getOperandNo() == 0, Info);
1010 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1011 if (!LI->isVolatile()) {
1012 const Type *LIType = LI->getType();
1013 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(LIType),
1014 LIType, false, Info);
1017 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1018 // Store is ok if storing INTO the pointer, not storing the pointer
1019 if (!SI->isVolatile() && SI->getOperand(0) != I) {
1020 const Type *SIType = SI->getOperand(0)->getType();
1021 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(SIType),
1022 SIType, true, Info);
1026 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n');
1029 if (Info.isUnsafe) return;
1033 /// isSafeGEP - Check if a GEP instruction can be handled for scalar
1034 /// replacement. It is safe when all the indices are constant, in-bounds
1035 /// references, and when the resulting offset corresponds to an element within
1036 /// the alloca type. The results are flagged in the Info parameter. Upon
1037 /// return, Offset is adjusted as specified by the GEP indices.
1038 void SROA::isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI,
1039 uint64_t &Offset, AllocaInfo &Info) {
1040 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
1044 // Walk through the GEP type indices, checking the types that this indexes
1046 for (; GEPIt != E; ++GEPIt) {
1047 // Ignore struct elements, no extra checking needed for these.
1048 if ((*GEPIt)->isStructTy())
1051 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
1053 return MarkUnsafe(Info);
1056 // Compute the offset due to this GEP and check if the alloca has a
1057 // component element at that offset.
1058 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1059 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1060 &Indices[0], Indices.size());
1061 if (!TypeHasComponent(AI->getAllocatedType(), Offset, 0))
1065 /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
1066 /// alloca or has an offset and size that corresponds to a component element
1067 /// within it. The offset checked here may have been formed from a GEP with a
1068 /// pointer bitcasted to a different type.
1069 void SROA::isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize,
1070 const Type *MemOpType, bool isStore,
1072 // Check if this is a load/store of the entire alloca.
1073 if (Offset == 0 && MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) {
1074 bool UsesAggregateType = (MemOpType == AI->getAllocatedType());
1075 // This is safe for MemIntrinsics (where MemOpType is 0), integer types
1076 // (which are essentially the same as the MemIntrinsics, especially with
1077 // regard to copying padding between elements), or references using the
1078 // aggregate type of the alloca.
1079 if (!MemOpType || MemOpType->isIntegerTy() || UsesAggregateType) {
1080 if (!UsesAggregateType) {
1082 Info.isMemCpyDst = true;
1084 Info.isMemCpySrc = true;
1089 // Check if the offset/size correspond to a component within the alloca type.
1090 const Type *T = AI->getAllocatedType();
1091 if (TypeHasComponent(T, Offset, MemSize))
1094 return MarkUnsafe(Info);
1097 /// TypeHasComponent - Return true if T has a component type with the
1098 /// specified offset and size. If Size is zero, do not check the size.
1099 bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) {
1102 if (const StructType *ST = dyn_cast<StructType>(T)) {
1103 const StructLayout *Layout = TD->getStructLayout(ST);
1104 unsigned EltIdx = Layout->getElementContainingOffset(Offset);
1105 EltTy = ST->getContainedType(EltIdx);
1106 EltSize = TD->getTypeAllocSize(EltTy);
1107 Offset -= Layout->getElementOffset(EltIdx);
1108 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1109 EltTy = AT->getElementType();
1110 EltSize = TD->getTypeAllocSize(EltTy);
1111 if (Offset >= AT->getNumElements() * EltSize)
1117 if (Offset == 0 && (Size == 0 || EltSize == Size))
1119 // Check if the component spans multiple elements.
1120 if (Offset + Size > EltSize)
1122 return TypeHasComponent(EltTy, Offset, Size);
1125 /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
1126 /// the instruction I, which references it, to use the separate elements.
1127 /// Offset indicates the position within AI that is referenced by this
1129 void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1130 SmallVector<AllocaInst*, 32> &NewElts) {
1131 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1132 Instruction *User = cast<Instruction>(*UI);
1134 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1135 RewriteBitCast(BC, AI, Offset, NewElts);
1136 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1137 RewriteGEP(GEPI, AI, Offset, NewElts);
1138 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1139 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1140 uint64_t MemSize = Length->getZExtValue();
1142 MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
1143 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
1144 // Otherwise the intrinsic can only touch a single element and the
1145 // address operand will be updated, so nothing else needs to be done.
1146 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1147 const Type *LIType = LI->getType();
1148 if (LIType == AI->getAllocatedType()) {
1150 // %res = load { i32, i32 }* %alloc
1152 // %load.0 = load i32* %alloc.0
1153 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
1154 // %load.1 = load i32* %alloc.1
1155 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
1156 // (Also works for arrays instead of structs)
1157 Value *Insert = UndefValue::get(LIType);
1158 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1159 Value *Load = new LoadInst(NewElts[i], "load", LI);
1160 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
1162 LI->replaceAllUsesWith(Insert);
1163 DeadInsts.push_back(LI);
1164 } else if (LIType->isIntegerTy() &&
1165 TD->getTypeAllocSize(LIType) ==
1166 TD->getTypeAllocSize(AI->getAllocatedType())) {
1167 // If this is a load of the entire alloca to an integer, rewrite it.
1168 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
1170 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1171 Value *Val = SI->getOperand(0);
1172 const Type *SIType = Val->getType();
1173 if (SIType == AI->getAllocatedType()) {
1175 // store { i32, i32 } %val, { i32, i32 }* %alloc
1177 // %val.0 = extractvalue { i32, i32 } %val, 0
1178 // store i32 %val.0, i32* %alloc.0
1179 // %val.1 = extractvalue { i32, i32 } %val, 1
1180 // store i32 %val.1, i32* %alloc.1
1181 // (Also works for arrays instead of structs)
1182 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1183 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
1184 new StoreInst(Extract, NewElts[i], SI);
1186 DeadInsts.push_back(SI);
1187 } else if (SIType->isIntegerTy() &&
1188 TD->getTypeAllocSize(SIType) ==
1189 TD->getTypeAllocSize(AI->getAllocatedType())) {
1190 // If this is a store of the entire alloca from an integer, rewrite it.
1191 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
1197 /// RewriteBitCast - Update a bitcast reference to the alloca being replaced
1198 /// and recursively continue updating all of its uses.
1199 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
1200 SmallVector<AllocaInst*, 32> &NewElts) {
1201 RewriteForScalarRepl(BC, AI, Offset, NewElts);
1202 if (BC->getOperand(0) != AI)
1205 // The bitcast references the original alloca. Replace its uses with
1206 // references to the first new element alloca.
1207 Instruction *Val = NewElts[0];
1208 if (Val->getType() != BC->getDestTy()) {
1209 Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
1212 BC->replaceAllUsesWith(Val);
1213 DeadInsts.push_back(BC);
1216 /// FindElementAndOffset - Return the index of the element containing Offset
1217 /// within the specified type, which must be either a struct or an array.
1218 /// Sets T to the type of the element and Offset to the offset within that
1219 /// element. IdxTy is set to the type of the index result to be used in a
1220 /// GEP instruction.
1221 uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset,
1222 const Type *&IdxTy) {
1224 if (const StructType *ST = dyn_cast<StructType>(T)) {
1225 const StructLayout *Layout = TD->getStructLayout(ST);
1226 Idx = Layout->getElementContainingOffset(Offset);
1227 T = ST->getContainedType(Idx);
1228 Offset -= Layout->getElementOffset(Idx);
1229 IdxTy = Type::getInt32Ty(T->getContext());
1232 const ArrayType *AT = cast<ArrayType>(T);
1233 T = AT->getElementType();
1234 uint64_t EltSize = TD->getTypeAllocSize(T);
1235 Idx = Offset / EltSize;
1236 Offset -= Idx * EltSize;
1237 IdxTy = Type::getInt64Ty(T->getContext());
1241 /// RewriteGEP - Check if this GEP instruction moves the pointer across
1242 /// elements of the alloca that are being split apart, and if so, rewrite
1243 /// the GEP to be relative to the new element.
1244 void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
1245 SmallVector<AllocaInst*, 32> &NewElts) {
1246 uint64_t OldOffset = Offset;
1247 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1248 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1249 &Indices[0], Indices.size());
1251 RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
1253 const Type *T = AI->getAllocatedType();
1255 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
1256 if (GEPI->getOperand(0) == AI)
1257 OldIdx = ~0ULL; // Force the GEP to be rewritten.
1259 T = AI->getAllocatedType();
1260 uint64_t EltOffset = Offset;
1261 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
1263 // If this GEP does not move the pointer across elements of the alloca
1264 // being split, then it does not needs to be rewritten.
1268 const Type *i32Ty = Type::getInt32Ty(AI->getContext());
1269 SmallVector<Value*, 8> NewArgs;
1270 NewArgs.push_back(Constant::getNullValue(i32Ty));
1271 while (EltOffset != 0) {
1272 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
1273 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
1275 Instruction *Val = NewElts[Idx];
1276 if (NewArgs.size() > 1) {
1277 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(),
1278 NewArgs.end(), "", GEPI);
1279 Val->takeName(GEPI);
1281 if (Val->getType() != GEPI->getType())
1282 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
1283 GEPI->replaceAllUsesWith(Val);
1284 DeadInsts.push_back(GEPI);
1287 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
1288 /// Rewrite it to copy or set the elements of the scalarized memory.
1289 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
1291 SmallVector<AllocaInst*, 32> &NewElts) {
1292 // If this is a memcpy/memmove, construct the other pointer as the
1293 // appropriate type. The "Other" pointer is the pointer that goes to memory
1294 // that doesn't have anything to do with the alloca that we are promoting. For
1295 // memset, this Value* stays null.
1296 Value *OtherPtr = 0;
1297 unsigned MemAlignment = MI->getAlignment();
1298 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
1299 if (Inst == MTI->getRawDest())
1300 OtherPtr = MTI->getRawSource();
1302 assert(Inst == MTI->getRawSource());
1303 OtherPtr = MTI->getRawDest();
1307 // If there is an other pointer, we want to convert it to the same pointer
1308 // type as AI has, so we can GEP through it safely.
1310 unsigned AddrSpace =
1311 cast<PointerType>(OtherPtr->getType())->getAddressSpace();
1313 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
1314 // optimization, but it's also required to detect the corner case where
1315 // both pointer operands are referencing the same memory, and where
1316 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
1317 // function is only called for mem intrinsics that access the whole
1318 // aggregate, so non-zero GEPs are not an issue here.)
1319 OtherPtr = OtherPtr->stripPointerCasts();
1321 // Copying the alloca to itself is a no-op: just delete it.
1322 if (OtherPtr == AI || OtherPtr == NewElts[0]) {
1323 // This code will run twice for a no-op memcpy -- once for each operand.
1324 // Put only one reference to MI on the DeadInsts list.
1325 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
1326 E = DeadInsts.end(); I != E; ++I)
1327 if (*I == MI) return;
1328 DeadInsts.push_back(MI);
1332 // If the pointer is not the right type, insert a bitcast to the right
1335 PointerType::get(AI->getType()->getElementType(), AddrSpace);
1337 if (OtherPtr->getType() != NewTy)
1338 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
1341 // Process each element of the aggregate.
1342 Value *TheFn = MI->getCalledValue();
1343 const Type *BytePtrTy = MI->getRawDest()->getType();
1344 bool SROADest = MI->getRawDest() == Inst;
1346 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
1348 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1349 // If this is a memcpy/memmove, emit a GEP of the other element address.
1350 Value *OtherElt = 0;
1351 unsigned OtherEltAlign = MemAlignment;
1354 Value *Idx[2] = { Zero,
1355 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
1356 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2,
1357 OtherPtr->getName()+"."+Twine(i),
1360 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
1361 const Type *OtherTy = OtherPtrTy->getElementType();
1362 if (const StructType *ST = dyn_cast<StructType>(OtherTy)) {
1363 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
1365 const Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
1366 EltOffset = TD->getTypeAllocSize(EltTy)*i;
1369 // The alignment of the other pointer is the guaranteed alignment of the
1370 // element, which is affected by both the known alignment of the whole
1371 // mem intrinsic and the alignment of the element. If the alignment of
1372 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
1373 // known alignment is just 4 bytes.
1374 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
1377 Value *EltPtr = NewElts[i];
1378 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
1380 // If we got down to a scalar, insert a load or store as appropriate.
1381 if (EltTy->isSingleValueType()) {
1382 if (isa<MemTransferInst>(MI)) {
1384 // From Other to Alloca.
1385 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
1386 new StoreInst(Elt, EltPtr, MI);
1388 // From Alloca to Other.
1389 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
1390 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
1394 assert(isa<MemSetInst>(MI));
1396 // If the stored element is zero (common case), just store a null
1399 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
1401 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
1403 // If EltTy is a vector type, get the element type.
1404 const Type *ValTy = EltTy->getScalarType();
1406 // Construct an integer with the right value.
1407 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
1408 APInt OneVal(EltSize, CI->getZExtValue());
1409 APInt TotalVal(OneVal);
1411 for (unsigned i = 0; 8*i < EltSize; ++i) {
1412 TotalVal = TotalVal.shl(8);
1416 // Convert the integer value to the appropriate type.
1417 StoreVal = ConstantInt::get(CI->getContext(), TotalVal);
1418 if (ValTy->isPointerTy())
1419 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
1420 else if (ValTy->isFloatingPointTy())
1421 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
1422 assert(StoreVal->getType() == ValTy && "Type mismatch!");
1424 // If the requested value was a vector constant, create it.
1425 if (EltTy != ValTy) {
1426 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
1427 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
1428 StoreVal = ConstantVector::get(&Elts[0], NumElts);
1431 new StoreInst(StoreVal, EltPtr, MI);
1434 // Otherwise, if we're storing a byte variable, use a memset call for
1438 // Cast the element pointer to BytePtrTy.
1439 if (EltPtr->getType() != BytePtrTy)
1440 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getName(), MI);
1442 // Cast the other pointer (if we have one) to BytePtrTy.
1443 if (OtherElt && OtherElt->getType() != BytePtrTy) {
1444 // Preserve address space of OtherElt
1445 const PointerType* OtherPTy = cast<PointerType>(OtherElt->getType());
1446 const PointerType* PTy = cast<PointerType>(BytePtrTy);
1447 if (OtherPTy->getElementType() != PTy->getElementType()) {
1448 Type *NewOtherPTy = PointerType::get(PTy->getElementType(),
1449 OtherPTy->getAddressSpace());
1450 OtherElt = new BitCastInst(OtherElt, NewOtherPTy,
1451 OtherElt->getName(), MI);
1455 unsigned EltSize = TD->getTypeAllocSize(EltTy);
1457 // Finally, insert the meminst for this element.
1458 if (isa<MemTransferInst>(MI)) {
1460 SROADest ? EltPtr : OtherElt, // Dest ptr
1461 SROADest ? OtherElt : EltPtr, // Src ptr
1462 ConstantInt::get(MI->getArgOperand(2)->getType(), EltSize), // Size
1464 ConstantInt::get(Type::getInt32Ty(MI->getContext()), OtherEltAlign),
1465 MI->getVolatileCst()
1467 // In case we fold the address space overloaded memcpy of A to B
1468 // with memcpy of B to C, change the function to be a memcpy of A to C.
1469 const Type *Tys[] = { Ops[0]->getType(), Ops[1]->getType(),
1470 Ops[2]->getType() };
1471 Module *M = MI->getParent()->getParent()->getParent();
1472 TheFn = Intrinsic::getDeclaration(M, MI->getIntrinsicID(), Tys, 3);
1473 CallInst::Create(TheFn, Ops, Ops + 5, "", MI);
1475 assert(isa<MemSetInst>(MI));
1477 EltPtr, MI->getArgOperand(1), // Dest, Value,
1478 ConstantInt::get(MI->getArgOperand(2)->getType(), EltSize), // Size
1480 ConstantInt::getFalse(MI->getContext()) // isVolatile
1482 const Type *Tys[] = { Ops[0]->getType(), Ops[2]->getType() };
1483 Module *M = MI->getParent()->getParent()->getParent();
1484 TheFn = Intrinsic::getDeclaration(M, Intrinsic::memset, Tys, 2);
1485 CallInst::Create(TheFn, Ops, Ops + 5, "", MI);
1488 DeadInsts.push_back(MI);
1491 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
1492 /// overwrites the entire allocation. Extract out the pieces of the stored
1493 /// integer and store them individually.
1494 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
1495 SmallVector<AllocaInst*, 32> &NewElts){
1496 // Extract each element out of the integer according to its structure offset
1497 // and store the element value to the individual alloca.
1498 Value *SrcVal = SI->getOperand(0);
1499 const Type *AllocaEltTy = AI->getAllocatedType();
1500 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1502 // Handle tail padding by extending the operand
1503 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
1504 SrcVal = new ZExtInst(SrcVal,
1505 IntegerType::get(SI->getContext(), AllocaSizeBits),
1508 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
1511 // There are two forms here: AI could be an array or struct. Both cases
1512 // have different ways to compute the element offset.
1513 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1514 const StructLayout *Layout = TD->getStructLayout(EltSTy);
1516 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1517 // Get the number of bits to shift SrcVal to get the value.
1518 const Type *FieldTy = EltSTy->getElementType(i);
1519 uint64_t Shift = Layout->getElementOffsetInBits(i);
1521 if (TD->isBigEndian())
1522 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
1524 Value *EltVal = SrcVal;
1526 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
1527 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
1528 "sroa.store.elt", SI);
1531 // Truncate down to an integer of the right size.
1532 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1534 // Ignore zero sized fields like {}, they obviously contain no data.
1535 if (FieldSizeBits == 0) continue;
1537 if (FieldSizeBits != AllocaSizeBits)
1538 EltVal = new TruncInst(EltVal,
1539 IntegerType::get(SI->getContext(), FieldSizeBits),
1541 Value *DestField = NewElts[i];
1542 if (EltVal->getType() == FieldTy) {
1543 // Storing to an integer field of this size, just do it.
1544 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
1545 // Bitcast to the right element type (for fp/vector values).
1546 EltVal = new BitCastInst(EltVal, FieldTy, "", SI);
1548 // Otherwise, bitcast the dest pointer (for aggregates).
1549 DestField = new BitCastInst(DestField,
1550 PointerType::getUnqual(EltVal->getType()),
1553 new StoreInst(EltVal, DestField, SI);
1557 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
1558 const Type *ArrayEltTy = ATy->getElementType();
1559 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1560 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
1564 if (TD->isBigEndian())
1565 Shift = AllocaSizeBits-ElementOffset;
1569 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1570 // Ignore zero sized fields like {}, they obviously contain no data.
1571 if (ElementSizeBits == 0) continue;
1573 Value *EltVal = SrcVal;
1575 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
1576 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
1577 "sroa.store.elt", SI);
1580 // Truncate down to an integer of the right size.
1581 if (ElementSizeBits != AllocaSizeBits)
1582 EltVal = new TruncInst(EltVal,
1583 IntegerType::get(SI->getContext(),
1584 ElementSizeBits),"",SI);
1585 Value *DestField = NewElts[i];
1586 if (EltVal->getType() == ArrayEltTy) {
1587 // Storing to an integer field of this size, just do it.
1588 } else if (ArrayEltTy->isFloatingPointTy() ||
1589 ArrayEltTy->isVectorTy()) {
1590 // Bitcast to the right element type (for fp/vector values).
1591 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI);
1593 // Otherwise, bitcast the dest pointer (for aggregates).
1594 DestField = new BitCastInst(DestField,
1595 PointerType::getUnqual(EltVal->getType()),
1598 new StoreInst(EltVal, DestField, SI);
1600 if (TD->isBigEndian())
1601 Shift -= ElementOffset;
1603 Shift += ElementOffset;
1607 DeadInsts.push_back(SI);
1610 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
1611 /// an integer. Load the individual pieces to form the aggregate value.
1612 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
1613 SmallVector<AllocaInst*, 32> &NewElts) {
1614 // Extract each element out of the NewElts according to its structure offset
1615 // and form the result value.
1616 const Type *AllocaEltTy = AI->getAllocatedType();
1617 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1619 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
1622 // There are two forms here: AI could be an array or struct. Both cases
1623 // have different ways to compute the element offset.
1624 const StructLayout *Layout = 0;
1625 uint64_t ArrayEltBitOffset = 0;
1626 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1627 Layout = TD->getStructLayout(EltSTy);
1629 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
1630 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1634 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
1636 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1637 // Load the value from the alloca. If the NewElt is an aggregate, cast
1638 // the pointer to an integer of the same size before doing the load.
1639 Value *SrcField = NewElts[i];
1640 const Type *FieldTy =
1641 cast<PointerType>(SrcField->getType())->getElementType();
1642 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1644 // Ignore zero sized fields like {}, they obviously contain no data.
1645 if (FieldSizeBits == 0) continue;
1647 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
1649 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
1650 !FieldTy->isVectorTy())
1651 SrcField = new BitCastInst(SrcField,
1652 PointerType::getUnqual(FieldIntTy),
1654 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
1656 // If SrcField is a fp or vector of the right size but that isn't an
1657 // integer type, bitcast to an integer so we can shift it.
1658 if (SrcField->getType() != FieldIntTy)
1659 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
1661 // Zero extend the field to be the same size as the final alloca so that
1662 // we can shift and insert it.
1663 if (SrcField->getType() != ResultVal->getType())
1664 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
1666 // Determine the number of bits to shift SrcField.
1668 if (Layout) // Struct case.
1669 Shift = Layout->getElementOffsetInBits(i);
1671 Shift = i*ArrayEltBitOffset;
1673 if (TD->isBigEndian())
1674 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
1677 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
1678 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
1681 // Don't create an 'or x, 0' on the first iteration.
1682 if (!isa<Constant>(ResultVal) ||
1683 !cast<Constant>(ResultVal)->isNullValue())
1684 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
1686 ResultVal = SrcField;
1689 // Handle tail padding by truncating the result
1690 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
1691 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
1693 LI->replaceAllUsesWith(ResultVal);
1694 DeadInsts.push_back(LI);
1697 /// HasPadding - Return true if the specified type has any structure or
1698 /// alignment padding, false otherwise.
1699 static bool HasPadding(const Type *Ty, const TargetData &TD) {
1700 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty))
1701 return HasPadding(ATy->getElementType(), TD);
1703 if (const VectorType *VTy = dyn_cast<VectorType>(Ty))
1704 return HasPadding(VTy->getElementType(), TD);
1706 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
1707 const StructLayout *SL = TD.getStructLayout(STy);
1708 unsigned PrevFieldBitOffset = 0;
1709 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1710 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
1712 // Padding in sub-elements?
1713 if (HasPadding(STy->getElementType(i), TD))
1716 // Check to see if there is any padding between this element and the
1719 unsigned PrevFieldEnd =
1720 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
1721 if (PrevFieldEnd < FieldBitOffset)
1725 PrevFieldBitOffset = FieldBitOffset;
1728 // Check for tail padding.
1729 if (unsigned EltCount = STy->getNumElements()) {
1730 unsigned PrevFieldEnd = PrevFieldBitOffset +
1731 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
1732 if (PrevFieldEnd < SL->getSizeInBits())
1737 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
1740 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
1741 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
1742 /// or 1 if safe after canonicalization has been performed.
1743 bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
1744 // Loop over the use list of the alloca. We can only transform it if all of
1745 // the users are safe to transform.
1748 isSafeForScalarRepl(AI, AI, 0, Info);
1749 if (Info.isUnsafe) {
1750 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
1754 // Okay, we know all the users are promotable. If the aggregate is a memcpy
1755 // source and destination, we have to be careful. In particular, the memcpy
1756 // could be moving around elements that live in structure padding of the LLVM
1757 // types, but may actually be used. In these cases, we refuse to promote the
1759 if (Info.isMemCpySrc && Info.isMemCpyDst &&
1760 HasPadding(AI->getAllocatedType(), *TD))
1768 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1769 /// some part of a constant global variable. This intentionally only accepts
1770 /// constant expressions because we don't can't rewrite arbitrary instructions.
1771 static bool PointsToConstantGlobal(Value *V) {
1772 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1773 return GV->isConstant();
1774 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1775 if (CE->getOpcode() == Instruction::BitCast ||
1776 CE->getOpcode() == Instruction::GetElementPtr)
1777 return PointsToConstantGlobal(CE->getOperand(0));
1781 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1782 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
1783 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
1784 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
1785 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1786 /// the alloca, and if the source pointer is a pointer to a constant global, we
1787 /// can optimize this.
1788 static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
1790 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1791 User *U = cast<Instruction>(*UI);
1793 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1794 // Ignore non-volatile loads, they are always ok.
1795 if (LI->isVolatile()) return false;
1799 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
1800 // If uses of the bitcast are ok, we are ok.
1801 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
1805 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
1806 // If the GEP has all zero indices, it doesn't offset the pointer. If it
1807 // doesn't, it does.
1808 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
1809 isOffset || !GEP->hasAllZeroIndices()))
1814 if (CallSite CS = U) {
1815 // If this is a readonly/readnone call site, then we know it is just a
1816 // load and we can ignore it.
1817 if (CS.onlyReadsMemory())
1820 // If this is the function being called then we treat it like a load and
1822 if (CS.isCallee(UI))
1825 // If this is being passed as a byval argument, the caller is making a
1826 // copy, so it is only a read of the alloca.
1827 unsigned ArgNo = CS.getArgumentNo(UI);
1828 if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal))
1832 // If this is isn't our memcpy/memmove, reject it as something we can't
1834 MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
1838 // If the transfer is using the alloca as a source of the transfer, then
1839 // ignore it since it is a load (unless the transfer is volatile).
1840 if (UI.getOperandNo() == 1) {
1841 if (MI->isVolatile()) return false;
1845 // If we already have seen a copy, reject the second one.
1846 if (TheCopy) return false;
1848 // If the pointer has been offset from the start of the alloca, we can't
1849 // safely handle this.
1850 if (isOffset) return false;
1852 // If the memintrinsic isn't using the alloca as the dest, reject it.
1853 if (UI.getOperandNo() != 0) return false;
1855 // If the source of the memcpy/move is not a constant global, reject it.
1856 if (!PointsToConstantGlobal(MI->getSource()))
1859 // Otherwise, the transform is safe. Remember the copy instruction.
1865 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
1866 /// modified by a copy from a constant global. If we can prove this, we can
1867 /// replace any uses of the alloca with uses of the global directly.
1868 MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) {
1869 MemTransferInst *TheCopy = 0;
1870 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))