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/Pass.h"
32 #include "llvm/Analysis/Dominators.h"
33 #include "llvm/Target/TargetData.h"
34 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
35 #include "llvm/Transforms/Utils/Local.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/Support/GetElementPtrTypeIterator.h"
38 #include "llvm/Support/IRBuilder.h"
39 #include "llvm/Support/MathExtras.h"
40 #include "llvm/Support/Compiler.h"
41 #include "llvm/ADT/SmallVector.h"
42 #include "llvm/ADT/Statistic.h"
43 #include "llvm/ADT/StringExtras.h"
46 STATISTIC(NumReplaced, "Number of allocas broken up");
47 STATISTIC(NumPromoted, "Number of allocas promoted");
48 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
49 STATISTIC(NumGlobals, "Number of allocas copied from constant global");
52 struct VISIBILITY_HIDDEN SROA : public FunctionPass {
53 static char ID; // Pass identification, replacement for typeid
54 explicit SROA(signed T = -1) : FunctionPass(&ID) {
61 bool runOnFunction(Function &F);
63 bool performScalarRepl(Function &F);
64 bool performPromotion(Function &F);
66 // getAnalysisUsage - This pass does not require any passes, but we know it
67 // will not alter the CFG, so say so.
68 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
69 AU.addRequired<DominatorTree>();
70 AU.addRequired<DominanceFrontier>();
71 AU.addRequired<TargetData>();
78 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
79 /// information about the uses. All these fields are initialized to false
80 /// and set to true when something is learned.
82 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
85 /// needsCleanup - This is set to true if there is some use of the alloca
86 /// that requires cleanup.
87 bool needsCleanup : 1;
89 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
92 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
96 : isUnsafe(false), needsCleanup(false),
97 isMemCpySrc(false), isMemCpyDst(false) {}
100 unsigned SRThreshold;
102 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
104 int isSafeAllocaToScalarRepl(AllocationInst *AI);
106 void isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
108 void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
110 void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
111 unsigned OpNo, AllocaInfo &Info);
112 void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocationInst *AI,
115 void DoScalarReplacement(AllocationInst *AI,
116 std::vector<AllocationInst*> &WorkList);
117 void CleanupGEP(GetElementPtrInst *GEP);
118 void CleanupAllocaUsers(AllocationInst *AI);
119 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base);
121 void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
122 SmallVector<AllocaInst*, 32> &NewElts);
124 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
126 SmallVector<AllocaInst*, 32> &NewElts);
127 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocationInst *AI,
128 SmallVector<AllocaInst*, 32> &NewElts);
129 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI,
130 SmallVector<AllocaInst*, 32> &NewElts);
132 bool CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
133 bool &SawVec, uint64_t Offset, unsigned AllocaSize);
134 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
135 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
136 uint64_t Offset, IRBuilder<> &Builder);
137 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
138 uint64_t Offset, IRBuilder<> &Builder);
139 static Instruction *isOnlyCopiedFromConstantGlobal(AllocationInst *AI);
144 static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates");
146 // Public interface to the ScalarReplAggregates pass
147 FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) {
148 return new SROA(Threshold);
152 bool SROA::runOnFunction(Function &F) {
153 TD = &getAnalysis<TargetData>();
155 bool Changed = performPromotion(F);
157 bool LocalChange = performScalarRepl(F);
158 if (!LocalChange) break; // No need to repromote if no scalarrepl
160 LocalChange = performPromotion(F);
161 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
168 bool SROA::performPromotion(Function &F) {
169 std::vector<AllocaInst*> Allocas;
170 DominatorTree &DT = getAnalysis<DominatorTree>();
171 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
173 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
175 bool Changed = false;
180 // Find allocas that are safe to promote, by looking at all instructions in
182 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
183 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
184 if (isAllocaPromotable(AI))
185 Allocas.push_back(AI);
187 if (Allocas.empty()) break;
189 PromoteMemToReg(Allocas, DT, DF, Context);
190 NumPromoted += Allocas.size();
197 /// getNumSAElements - Return the number of elements in the specific struct or
199 static uint64_t getNumSAElements(const Type *T) {
200 if (const StructType *ST = dyn_cast<StructType>(T))
201 return ST->getNumElements();
202 return cast<ArrayType>(T)->getNumElements();
205 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
206 // which runs on all of the malloc/alloca instructions in the function, removing
207 // them if they are only used by getelementptr instructions.
209 bool SROA::performScalarRepl(Function &F) {
210 std::vector<AllocationInst*> WorkList;
212 // Scan the entry basic block, adding any alloca's and mallocs to the worklist
213 BasicBlock &BB = F.getEntryBlock();
214 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
215 if (AllocationInst *A = dyn_cast<AllocationInst>(I))
216 WorkList.push_back(A);
218 // Process the worklist
219 bool Changed = false;
220 while (!WorkList.empty()) {
221 AllocationInst *AI = WorkList.back();
224 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
225 // with unused elements.
226 if (AI->use_empty()) {
227 AI->eraseFromParent();
231 // If this alloca is impossible for us to promote, reject it early.
232 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
235 // Check to see if this allocation is only modified by a memcpy/memmove from
236 // a constant global. If this is the case, we can change all users to use
237 // the constant global instead. This is commonly produced by the CFE by
238 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
239 // is only subsequently read.
240 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
241 DOUT << "Found alloca equal to global: " << *AI;
242 DOUT << " memcpy = " << *TheCopy;
243 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2));
244 AI->replaceAllUsesWith(
245 Context->getConstantExprBitCast(TheSrc, AI->getType()));
246 TheCopy->eraseFromParent(); // Don't mutate the global.
247 AI->eraseFromParent();
253 // Check to see if we can perform the core SROA transformation. We cannot
254 // transform the allocation instruction if it is an array allocation
255 // (allocations OF arrays are ok though), and an allocation of a scalar
256 // value cannot be decomposed at all.
257 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
259 // Do not promote any struct whose size is too big.
260 if (AllocaSize > SRThreshold) continue;
262 if ((isa<StructType>(AI->getAllocatedType()) ||
263 isa<ArrayType>(AI->getAllocatedType())) &&
264 // Do not promote any struct into more than "32" separate vars.
265 getNumSAElements(AI->getAllocatedType()) <= SRThreshold/4) {
266 // Check that all of the users of the allocation are capable of being
268 switch (isSafeAllocaToScalarRepl(AI)) {
269 default: assert(0 && "Unexpected value!");
270 case 0: // Not safe to scalar replace.
272 case 1: // Safe, but requires cleanup/canonicalizations first
273 CleanupAllocaUsers(AI);
275 case 3: // Safe to scalar replace.
276 DoScalarReplacement(AI, WorkList);
282 // If we can turn this aggregate value (potentially with casts) into a
283 // simple scalar value that can be mem2reg'd into a register value.
284 // IsNotTrivial tracks whether this is something that mem2reg could have
285 // promoted itself. If so, we don't want to transform it needlessly. Note
286 // that we can't just check based on the type: the alloca may be of an i32
287 // but that has pointer arithmetic to set byte 3 of it or something.
288 bool IsNotTrivial = false;
289 const Type *VectorTy = 0;
290 bool HadAVector = false;
291 if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector,
292 0, unsigned(AllocaSize)) && IsNotTrivial) {
294 // If we were able to find a vector type that can handle this with
295 // insert/extract elements, and if there was at least one use that had
296 // a vector type, promote this to a vector. We don't want to promote
297 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
298 // we just get a lot of insert/extracts. If at least one vector is
299 // involved, then we probably really do have a union of vector/array.
300 if (VectorTy && isa<VectorType>(VectorTy) && HadAVector) {
301 DOUT << "CONVERT TO VECTOR: " << *AI << " TYPE = " << *VectorTy <<"\n";
303 // Create and insert the vector alloca.
304 NewAI = new AllocaInst(VectorTy, 0, "", AI->getParent()->begin());
305 ConvertUsesToScalar(AI, NewAI, 0);
307 DOUT << "CONVERT TO SCALAR INTEGER: " << *AI << "\n";
309 // Create and insert the integer alloca.
310 const Type *NewTy = Context->getIntegerType(AllocaSize*8);
311 NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
312 ConvertUsesToScalar(AI, NewAI, 0);
315 AI->eraseFromParent();
321 // Otherwise, couldn't process this alloca.
327 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
328 /// predicate, do SROA now.
329 void SROA::DoScalarReplacement(AllocationInst *AI,
330 std::vector<AllocationInst*> &WorkList) {
331 DOUT << "Found inst to SROA: " << *AI;
332 SmallVector<AllocaInst*, 32> ElementAllocas;
333 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
334 ElementAllocas.reserve(ST->getNumContainedTypes());
335 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
336 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
338 AI->getName() + "." + utostr(i), AI);
339 ElementAllocas.push_back(NA);
340 WorkList.push_back(NA); // Add to worklist for recursive processing
343 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
344 ElementAllocas.reserve(AT->getNumElements());
345 const Type *ElTy = AT->getElementType();
346 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
347 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
348 AI->getName() + "." + utostr(i), AI);
349 ElementAllocas.push_back(NA);
350 WorkList.push_back(NA); // Add to worklist for recursive processing
354 // Now that we have created the alloca instructions that we want to use,
355 // expand the getelementptr instructions to use them.
357 while (!AI->use_empty()) {
358 Instruction *User = cast<Instruction>(AI->use_back());
359 if (BitCastInst *BCInst = dyn_cast<BitCastInst>(User)) {
360 RewriteBitCastUserOfAlloca(BCInst, AI, ElementAllocas);
361 BCInst->eraseFromParent();
366 // %res = load { i32, i32 }* %alloc
368 // %load.0 = load i32* %alloc.0
369 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
370 // %load.1 = load i32* %alloc.1
371 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
372 // (Also works for arrays instead of structs)
373 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
374 Value *Insert = Context->getUndef(LI->getType());
375 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
376 Value *Load = new LoadInst(ElementAllocas[i], "load", LI);
377 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
379 LI->replaceAllUsesWith(Insert);
380 LI->eraseFromParent();
385 // store { i32, i32 } %val, { i32, i32 }* %alloc
387 // %val.0 = extractvalue { i32, i32 } %val, 0
388 // store i32 %val.0, i32* %alloc.0
389 // %val.1 = extractvalue { i32, i32 } %val, 1
390 // store i32 %val.1, i32* %alloc.1
391 // (Also works for arrays instead of structs)
392 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
393 Value *Val = SI->getOperand(0);
394 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
395 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
396 new StoreInst(Extract, ElementAllocas[i], SI);
398 SI->eraseFromParent();
402 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User);
403 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst>
405 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
407 assert(Idx < ElementAllocas.size() && "Index out of range?");
408 AllocaInst *AllocaToUse = ElementAllocas[Idx];
411 if (GEPI->getNumOperands() == 3) {
412 // Do not insert a new getelementptr instruction with zero indices, only
413 // to have it optimized out later.
414 RepValue = AllocaToUse;
416 // We are indexing deeply into the structure, so we still need a
417 // getelement ptr instruction to finish the indexing. This may be
418 // expanded itself once the worklist is rerun.
420 SmallVector<Value*, 8> NewArgs;
421 NewArgs.push_back(Context->getNullValue(Type::Int32Ty));
422 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end());
423 RepValue = GetElementPtrInst::Create(AllocaToUse, NewArgs.begin(),
424 NewArgs.end(), "", GEPI);
425 RepValue->takeName(GEPI);
428 // If this GEP is to the start of the aggregate, check for memcpys.
429 if (Idx == 0 && GEPI->hasAllZeroIndices())
430 RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas);
432 // Move all of the users over to the new GEP.
433 GEPI->replaceAllUsesWith(RepValue);
434 // Delete the old GEP
435 GEPI->eraseFromParent();
438 // Finally, delete the Alloca instruction
439 AI->eraseFromParent();
444 /// isSafeElementUse - Check to see if this use is an allowed use for a
445 /// getelementptr instruction of an array aggregate allocation. isFirstElt
446 /// indicates whether Ptr is known to the start of the aggregate.
448 void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
450 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
452 Instruction *User = cast<Instruction>(*I);
453 switch (User->getOpcode()) {
454 case Instruction::Load: break;
455 case Instruction::Store:
456 // Store is ok if storing INTO the pointer, not storing the pointer
457 if (User->getOperand(0) == Ptr) return MarkUnsafe(Info);
459 case Instruction::GetElementPtr: {
460 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User);
461 bool AreAllZeroIndices = isFirstElt;
462 if (GEP->getNumOperands() > 1) {
463 if (!isa<ConstantInt>(GEP->getOperand(1)) ||
464 !cast<ConstantInt>(GEP->getOperand(1))->isZero())
465 // Using pointer arithmetic to navigate the array.
466 return MarkUnsafe(Info);
468 if (AreAllZeroIndices)
469 AreAllZeroIndices = GEP->hasAllZeroIndices();
471 isSafeElementUse(GEP, AreAllZeroIndices, AI, Info);
472 if (Info.isUnsafe) return;
475 case Instruction::BitCast:
477 isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info);
478 if (Info.isUnsafe) return;
481 DOUT << " Transformation preventing inst: " << *User;
482 return MarkUnsafe(Info);
483 case Instruction::Call:
484 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
486 isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info);
487 if (Info.isUnsafe) return;
491 DOUT << " Transformation preventing inst: " << *User;
492 return MarkUnsafe(Info);
494 DOUT << " Transformation preventing inst: " << *User;
495 return MarkUnsafe(Info);
498 return; // All users look ok :)
501 /// AllUsersAreLoads - Return true if all users of this value are loads.
502 static bool AllUsersAreLoads(Value *Ptr) {
503 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
505 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load)
510 /// isSafeUseOfAllocation - Check to see if this user is an allowed use for an
511 /// aggregate allocation.
513 void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
515 if (BitCastInst *C = dyn_cast<BitCastInst>(User))
516 return isSafeUseOfBitCastedAllocation(C, AI, Info);
518 if (LoadInst *LI = dyn_cast<LoadInst>(User))
519 if (!LI->isVolatile())
520 return;// Loads (returning a first class aggregrate) are always rewritable
522 if (StoreInst *SI = dyn_cast<StoreInst>(User))
523 if (!SI->isVolatile() && SI->getOperand(0) != AI)
524 return;// Store is ok if storing INTO the pointer, not storing the pointer
526 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User);
528 return MarkUnsafe(Info);
530 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI);
532 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>".
534 I.getOperand() != Context->getNullValue(I.getOperand()->getType())) {
535 return MarkUnsafe(Info);
539 if (I == E) return MarkUnsafe(Info); // ran out of GEP indices??
541 bool IsAllZeroIndices = true;
543 // If the first index is a non-constant index into an array, see if we can
544 // handle it as a special case.
545 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
546 if (!isa<ConstantInt>(I.getOperand())) {
547 IsAllZeroIndices = 0;
548 uint64_t NumElements = AT->getNumElements();
550 // If this is an array index and the index is not constant, we cannot
551 // promote... that is unless the array has exactly one or two elements in
552 // it, in which case we CAN promote it, but we have to canonicalize this
553 // out if this is the only problem.
554 if ((NumElements == 1 || NumElements == 2) &&
555 AllUsersAreLoads(GEPI)) {
556 Info.needsCleanup = true;
557 return; // Canonicalization required!
559 return MarkUnsafe(Info);
563 // Walk through the GEP type indices, checking the types that this indexes
565 for (; I != E; ++I) {
566 // Ignore struct elements, no extra checking needed for these.
567 if (isa<StructType>(*I))
570 ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand());
571 if (!IdxVal) return MarkUnsafe(Info);
573 // Are all indices still zero?
574 IsAllZeroIndices &= IdxVal->isZero();
576 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
577 // This GEP indexes an array. Verify that this is an in-range constant
578 // integer. Specifically, consider A[0][i]. We cannot know that the user
579 // isn't doing invalid things like allowing i to index an out-of-range
580 // subscript that accesses A[1]. Because of this, we have to reject SROA
581 // of any accesses into structs where any of the components are variables.
582 if (IdxVal->getZExtValue() >= AT->getNumElements())
583 return MarkUnsafe(Info);
584 } else if (const VectorType *VT = dyn_cast<VectorType>(*I)) {
585 if (IdxVal->getZExtValue() >= VT->getNumElements())
586 return MarkUnsafe(Info);
590 // If there are any non-simple uses of this getelementptr, make sure to reject
592 return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info);
595 /// isSafeMemIntrinsicOnAllocation - Return true if the specified memory
596 /// intrinsic can be promoted by SROA. At this point, we know that the operand
597 /// of the memintrinsic is a pointer to the beginning of the allocation.
598 void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
599 unsigned OpNo, AllocaInfo &Info) {
600 // If not constant length, give up.
601 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
602 if (!Length) return MarkUnsafe(Info);
604 // If not the whole aggregate, give up.
605 if (Length->getZExtValue() !=
606 TD->getTypeAllocSize(AI->getType()->getElementType()))
607 return MarkUnsafe(Info);
609 // We only know about memcpy/memset/memmove.
610 if (!isa<MemIntrinsic>(MI))
611 return MarkUnsafe(Info);
613 // Otherwise, we can transform it. Determine whether this is a memcpy/set
614 // into or out of the aggregate.
616 Info.isMemCpyDst = true;
619 Info.isMemCpySrc = true;
623 /// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast
625 void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI,
627 for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end();
629 if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) {
630 isSafeUseOfBitCastedAllocation(BCU, AI, Info);
631 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) {
632 isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info);
633 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
634 if (SI->isVolatile())
635 return MarkUnsafe(Info);
637 // If storing the entire alloca in one chunk through a bitcasted pointer
638 // to integer, we can transform it. This happens (for example) when you
639 // cast a {i32,i32}* to i64* and store through it. This is similar to the
640 // memcpy case and occurs in various "byval" cases and emulated memcpys.
641 if (isa<IntegerType>(SI->getOperand(0)->getType()) &&
642 TD->getTypeAllocSize(SI->getOperand(0)->getType()) ==
643 TD->getTypeAllocSize(AI->getType()->getElementType())) {
644 Info.isMemCpyDst = true;
647 return MarkUnsafe(Info);
648 } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
649 if (LI->isVolatile())
650 return MarkUnsafe(Info);
652 // If loading the entire alloca in one chunk through a bitcasted pointer
653 // to integer, we can transform it. This happens (for example) when you
654 // cast a {i32,i32}* to i64* and load through it. This is similar to the
655 // memcpy case and occurs in various "byval" cases and emulated memcpys.
656 if (isa<IntegerType>(LI->getType()) &&
657 TD->getTypeAllocSize(LI->getType()) ==
658 TD->getTypeAllocSize(AI->getType()->getElementType())) {
659 Info.isMemCpySrc = true;
662 return MarkUnsafe(Info);
663 } else if (isa<DbgInfoIntrinsic>(UI)) {
664 // If one user is DbgInfoIntrinsic then check if all users are
665 // DbgInfoIntrinsics.
666 if (OnlyUsedByDbgInfoIntrinsics(BC)) {
667 Info.needsCleanup = true;
674 return MarkUnsafe(Info);
676 if (Info.isUnsafe) return;
680 /// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes
681 /// to its first element. Transform users of the cast to use the new values
683 void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
684 SmallVector<AllocaInst*, 32> &NewElts) {
685 Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end();
687 Instruction *User = cast<Instruction>(*UI++);
688 if (BitCastInst *BCU = dyn_cast<BitCastInst>(User)) {
689 RewriteBitCastUserOfAlloca(BCU, AI, NewElts);
690 if (BCU->use_empty()) BCU->eraseFromParent();
694 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
695 // This must be memcpy/memmove/memset of the entire aggregate.
696 // Split into one per element.
697 RewriteMemIntrinUserOfAlloca(MI, BCInst, AI, NewElts);
701 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
702 // If this is a store of the entire alloca from an integer, rewrite it.
703 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
707 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
708 // If this is a load of the entire alloca to an integer, rewrite it.
709 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
713 // Otherwise it must be some other user of a gep of the first pointer. Just
714 // leave these alone.
719 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
720 /// Rewrite it to copy or set the elements of the scalarized memory.
721 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
723 SmallVector<AllocaInst*, 32> &NewElts) {
725 // If this is a memcpy/memmove, construct the other pointer as the
726 // appropriate type. The "Other" pointer is the pointer that goes to memory
727 // that doesn't have anything to do with the alloca that we are promoting. For
728 // memset, this Value* stays null.
730 unsigned MemAlignment = MI->getAlignment();
731 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
732 if (BCInst == MTI->getRawDest())
733 OtherPtr = MTI->getRawSource();
735 assert(BCInst == MTI->getRawSource());
736 OtherPtr = MTI->getRawDest();
740 // If there is an other pointer, we want to convert it to the same pointer
741 // type as AI has, so we can GEP through it safely.
743 // It is likely that OtherPtr is a bitcast, if so, remove it.
744 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr))
745 OtherPtr = BC->getOperand(0);
746 // All zero GEPs are effectively bitcasts.
747 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr))
748 if (GEP->hasAllZeroIndices())
749 OtherPtr = GEP->getOperand(0);
751 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr))
752 if (BCE->getOpcode() == Instruction::BitCast)
753 OtherPtr = BCE->getOperand(0);
755 // If the pointer is not the right type, insert a bitcast to the right
757 if (OtherPtr->getType() != AI->getType())
758 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(),
762 // Process each element of the aggregate.
763 Value *TheFn = MI->getOperand(0);
764 const Type *BytePtrTy = MI->getRawDest()->getType();
765 bool SROADest = MI->getRawDest() == BCInst;
767 Constant *Zero = Context->getNullValue(Type::Int32Ty);
769 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
770 // If this is a memcpy/memmove, emit a GEP of the other element address.
772 unsigned OtherEltAlign = MemAlignment;
775 Value *Idx[2] = { Zero, Context->getConstantInt(Type::Int32Ty, i) };
776 OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2,
777 OtherPtr->getNameStr()+"."+utostr(i),
780 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
781 if (const StructType *ST =
782 dyn_cast<StructType>(OtherPtrTy->getElementType())) {
783 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
786 cast<SequentialType>(OtherPtr->getType())->getElementType();
787 EltOffset = TD->getTypeAllocSize(EltTy)*i;
790 // The alignment of the other pointer is the guaranteed alignment of the
791 // element, which is affected by both the known alignment of the whole
792 // mem intrinsic and the alignment of the element. If the alignment of
793 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
794 // known alignment is just 4 bytes.
795 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
798 Value *EltPtr = NewElts[i];
799 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
801 // If we got down to a scalar, insert a load or store as appropriate.
802 if (EltTy->isSingleValueType()) {
803 if (isa<MemTransferInst>(MI)) {
805 // From Other to Alloca.
806 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
807 new StoreInst(Elt, EltPtr, MI);
809 // From Alloca to Other.
810 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
811 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
815 assert(isa<MemSetInst>(MI));
817 // If the stored element is zero (common case), just store a null
820 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) {
822 StoreVal = Context->getNullValue(EltTy); // 0.0, null, 0, <0,0>
824 // If EltTy is a vector type, get the element type.
825 const Type *ValTy = EltTy->getScalarType();
827 // Construct an integer with the right value.
828 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
829 APInt OneVal(EltSize, CI->getZExtValue());
830 APInt TotalVal(OneVal);
832 for (unsigned i = 0; 8*i < EltSize; ++i) {
833 TotalVal = TotalVal.shl(8);
837 // Convert the integer value to the appropriate type.
838 StoreVal = Context->getConstantInt(TotalVal);
839 if (isa<PointerType>(ValTy))
840 StoreVal = Context->getConstantExprIntToPtr(StoreVal, ValTy);
841 else if (ValTy->isFloatingPoint())
842 StoreVal = Context->getConstantExprBitCast(StoreVal, ValTy);
843 assert(StoreVal->getType() == ValTy && "Type mismatch!");
845 // If the requested value was a vector constant, create it.
846 if (EltTy != ValTy) {
847 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
848 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
849 StoreVal = Context->getConstantVector(&Elts[0], NumElts);
852 new StoreInst(StoreVal, EltPtr, MI);
855 // Otherwise, if we're storing a byte variable, use a memset call for
859 // Cast the element pointer to BytePtrTy.
860 if (EltPtr->getType() != BytePtrTy)
861 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI);
863 // Cast the other pointer (if we have one) to BytePtrTy.
864 if (OtherElt && OtherElt->getType() != BytePtrTy)
865 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(),
868 unsigned EltSize = TD->getTypeAllocSize(EltTy);
870 // Finally, insert the meminst for this element.
871 if (isa<MemTransferInst>(MI)) {
873 SROADest ? EltPtr : OtherElt, // Dest ptr
874 SROADest ? OtherElt : EltPtr, // Src ptr
875 Context->getConstantInt(MI->getOperand(3)->getType(), EltSize), // Size
876 Context->getConstantInt(Type::Int32Ty, OtherEltAlign) // Align
878 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
880 assert(isa<MemSetInst>(MI));
882 EltPtr, MI->getOperand(2), // Dest, Value,
883 Context->getConstantInt(MI->getOperand(3)->getType(), EltSize), // Size
886 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
889 MI->eraseFromParent();
892 /// RewriteStoreUserOfWholeAlloca - We found an store of an integer that
893 /// overwrites the entire allocation. Extract out the pieces of the stored
894 /// integer and store them individually.
895 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI,
897 SmallVector<AllocaInst*, 32> &NewElts){
898 // Extract each element out of the integer according to its structure offset
899 // and store the element value to the individual alloca.
900 Value *SrcVal = SI->getOperand(0);
901 const Type *AllocaEltTy = AI->getType()->getElementType();
902 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
904 // If this isn't a store of an integer to the whole alloca, it may be a store
905 // to the first element. Just ignore the store in this case and normal SROA
907 if (!isa<IntegerType>(SrcVal->getType()) ||
908 TD->getTypeAllocSizeInBits(SrcVal->getType()) != AllocaSizeBits)
910 // Handle tail padding by extending the operand
911 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
912 SrcVal = new ZExtInst(SrcVal,
913 Context->getIntegerType(AllocaSizeBits), "", SI);
915 DOUT << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << *SI;
917 // There are two forms here: AI could be an array or struct. Both cases
918 // have different ways to compute the element offset.
919 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
920 const StructLayout *Layout = TD->getStructLayout(EltSTy);
922 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
923 // Get the number of bits to shift SrcVal to get the value.
924 const Type *FieldTy = EltSTy->getElementType(i);
925 uint64_t Shift = Layout->getElementOffsetInBits(i);
927 if (TD->isBigEndian())
928 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
930 Value *EltVal = SrcVal;
932 Value *ShiftVal = Context->getConstantInt(EltVal->getType(), Shift);
933 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
934 "sroa.store.elt", SI);
937 // Truncate down to an integer of the right size.
938 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
940 // Ignore zero sized fields like {}, they obviously contain no data.
941 if (FieldSizeBits == 0) continue;
943 if (FieldSizeBits != AllocaSizeBits)
944 EltVal = new TruncInst(EltVal,
945 Context->getIntegerType(FieldSizeBits), "", SI);
946 Value *DestField = NewElts[i];
947 if (EltVal->getType() == FieldTy) {
948 // Storing to an integer field of this size, just do it.
949 } else if (FieldTy->isFloatingPoint() || isa<VectorType>(FieldTy)) {
950 // Bitcast to the right element type (for fp/vector values).
951 EltVal = new BitCastInst(EltVal, FieldTy, "", SI);
953 // Otherwise, bitcast the dest pointer (for aggregates).
954 DestField = new BitCastInst(DestField,
955 Context->getPointerTypeUnqual(EltVal->getType()),
958 new StoreInst(EltVal, DestField, SI);
962 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
963 const Type *ArrayEltTy = ATy->getElementType();
964 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
965 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
969 if (TD->isBigEndian())
970 Shift = AllocaSizeBits-ElementOffset;
974 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
975 // Ignore zero sized fields like {}, they obviously contain no data.
976 if (ElementSizeBits == 0) continue;
978 Value *EltVal = SrcVal;
980 Value *ShiftVal = Context->getConstantInt(EltVal->getType(), Shift);
981 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
982 "sroa.store.elt", SI);
985 // Truncate down to an integer of the right size.
986 if (ElementSizeBits != AllocaSizeBits)
987 EltVal = new TruncInst(EltVal,
988 Context->getIntegerType(ElementSizeBits),"",SI);
989 Value *DestField = NewElts[i];
990 if (EltVal->getType() == ArrayEltTy) {
991 // Storing to an integer field of this size, just do it.
992 } else if (ArrayEltTy->isFloatingPoint() || isa<VectorType>(ArrayEltTy)) {
993 // Bitcast to the right element type (for fp/vector values).
994 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI);
996 // Otherwise, bitcast the dest pointer (for aggregates).
997 DestField = new BitCastInst(DestField,
998 Context->getPointerTypeUnqual(EltVal->getType()),
1001 new StoreInst(EltVal, DestField, SI);
1003 if (TD->isBigEndian())
1004 Shift -= ElementOffset;
1006 Shift += ElementOffset;
1010 SI->eraseFromParent();
1013 /// RewriteLoadUserOfWholeAlloca - We found an load of the entire allocation to
1014 /// an integer. Load the individual pieces to form the aggregate value.
1015 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI,
1016 SmallVector<AllocaInst*, 32> &NewElts) {
1017 // Extract each element out of the NewElts according to its structure offset
1018 // and form the result value.
1019 const Type *AllocaEltTy = AI->getType()->getElementType();
1020 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1022 // If this isn't a load of the whole alloca to an integer, it may be a load
1023 // of the first element. Just ignore the load in this case and normal SROA
1025 if (!isa<IntegerType>(LI->getType()) ||
1026 TD->getTypeAllocSizeInBits(LI->getType()) != AllocaSizeBits)
1029 DOUT << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << *LI;
1031 // There are two forms here: AI could be an array or struct. Both cases
1032 // have different ways to compute the element offset.
1033 const StructLayout *Layout = 0;
1034 uint64_t ArrayEltBitOffset = 0;
1035 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1036 Layout = TD->getStructLayout(EltSTy);
1038 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
1039 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1043 Context->getNullValue(Context->getIntegerType(AllocaSizeBits));
1045 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1046 // Load the value from the alloca. If the NewElt is an aggregate, cast
1047 // the pointer to an integer of the same size before doing the load.
1048 Value *SrcField = NewElts[i];
1049 const Type *FieldTy =
1050 cast<PointerType>(SrcField->getType())->getElementType();
1051 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1053 // Ignore zero sized fields like {}, they obviously contain no data.
1054 if (FieldSizeBits == 0) continue;
1056 const IntegerType *FieldIntTy = Context->getIntegerType(FieldSizeBits);
1057 if (!isa<IntegerType>(FieldTy) && !FieldTy->isFloatingPoint() &&
1058 !isa<VectorType>(FieldTy))
1059 SrcField = new BitCastInst(SrcField,
1060 Context->getPointerTypeUnqual(FieldIntTy),
1062 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
1064 // If SrcField is a fp or vector of the right size but that isn't an
1065 // integer type, bitcast to an integer so we can shift it.
1066 if (SrcField->getType() != FieldIntTy)
1067 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
1069 // Zero extend the field to be the same size as the final alloca so that
1070 // we can shift and insert it.
1071 if (SrcField->getType() != ResultVal->getType())
1072 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
1074 // Determine the number of bits to shift SrcField.
1076 if (Layout) // Struct case.
1077 Shift = Layout->getElementOffsetInBits(i);
1079 Shift = i*ArrayEltBitOffset;
1081 if (TD->isBigEndian())
1082 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
1085 Value *ShiftVal = Context->getConstantInt(SrcField->getType(), Shift);
1086 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
1089 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
1092 // Handle tail padding by truncating the result
1093 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
1094 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
1096 LI->replaceAllUsesWith(ResultVal);
1097 LI->eraseFromParent();
1101 /// HasPadding - Return true if the specified type has any structure or
1102 /// alignment padding, false otherwise.
1103 static bool HasPadding(const Type *Ty, const TargetData &TD) {
1104 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
1105 const StructLayout *SL = TD.getStructLayout(STy);
1106 unsigned PrevFieldBitOffset = 0;
1107 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1108 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
1110 // Padding in sub-elements?
1111 if (HasPadding(STy->getElementType(i), TD))
1114 // Check to see if there is any padding between this element and the
1117 unsigned PrevFieldEnd =
1118 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
1119 if (PrevFieldEnd < FieldBitOffset)
1123 PrevFieldBitOffset = FieldBitOffset;
1126 // Check for tail padding.
1127 if (unsigned EltCount = STy->getNumElements()) {
1128 unsigned PrevFieldEnd = PrevFieldBitOffset +
1129 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
1130 if (PrevFieldEnd < SL->getSizeInBits())
1134 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1135 return HasPadding(ATy->getElementType(), TD);
1136 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) {
1137 return HasPadding(VTy->getElementType(), TD);
1139 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
1142 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
1143 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
1144 /// or 1 if safe after canonicalization has been performed.
1146 int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) {
1147 // Loop over the use list of the alloca. We can only transform it if all of
1148 // the users are safe to transform.
1151 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end();
1153 isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info);
1154 if (Info.isUnsafe) {
1155 DOUT << "Cannot transform: " << *AI << " due to user: " << **I;
1160 // Okay, we know all the users are promotable. If the aggregate is a memcpy
1161 // source and destination, we have to be careful. In particular, the memcpy
1162 // could be moving around elements that live in structure padding of the LLVM
1163 // types, but may actually be used. In these cases, we refuse to promote the
1165 if (Info.isMemCpySrc && Info.isMemCpyDst &&
1166 HasPadding(AI->getType()->getElementType(), *TD))
1169 // If we require cleanup, return 1, otherwise return 3.
1170 return Info.needsCleanup ? 1 : 3;
1173 /// CleanupGEP - GEP is used by an Alloca, which can be prompted after the GEP
1174 /// is canonicalized here.
1175 void SROA::CleanupGEP(GetElementPtrInst *GEPI) {
1176 gep_type_iterator I = gep_type_begin(GEPI);
1179 const ArrayType *AT = dyn_cast<ArrayType>(*I);
1183 uint64_t NumElements = AT->getNumElements();
1185 if (isa<ConstantInt>(I.getOperand()))
1188 if (NumElements == 1) {
1189 GEPI->setOperand(2, Context->getNullValue(Type::Int32Ty));
1193 assert(NumElements == 2 && "Unhandled case!");
1194 // All users of the GEP must be loads. At each use of the GEP, insert
1195 // two loads of the appropriate indexed GEP and select between them.
1196 Value *IsOne = new ICmpInst(ICmpInst::ICMP_NE, I.getOperand(),
1197 Context->getNullValue(I.getOperand()->getType()),
1199 // Insert the new GEP instructions, which are properly indexed.
1200 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end());
1201 Indices[1] = Context->getNullValue(Type::Int32Ty);
1202 Value *ZeroIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1205 GEPI->getName()+".0", GEPI);
1206 Indices[1] = Context->getConstantInt(Type::Int32Ty, 1);
1207 Value *OneIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1210 GEPI->getName()+".1", GEPI);
1211 // Replace all loads of the variable index GEP with loads from both
1212 // indexes and a select.
1213 while (!GEPI->use_empty()) {
1214 LoadInst *LI = cast<LoadInst>(GEPI->use_back());
1215 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI);
1216 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI);
1217 Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI);
1218 LI->replaceAllUsesWith(R);
1219 LI->eraseFromParent();
1221 GEPI->eraseFromParent();
1225 /// CleanupAllocaUsers - If SROA reported that it can promote the specified
1226 /// allocation, but only if cleaned up, perform the cleanups required.
1227 void SROA::CleanupAllocaUsers(AllocationInst *AI) {
1228 // At this point, we know that the end result will be SROA'd and promoted, so
1229 // we can insert ugly code if required so long as sroa+mem2reg will clean it
1231 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
1234 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U))
1237 Instruction *I = cast<Instruction>(U);
1238 SmallVector<DbgInfoIntrinsic *, 2> DbgInUses;
1239 if (!isa<StoreInst>(I) && OnlyUsedByDbgInfoIntrinsics(I, &DbgInUses)) {
1240 // Safe to remove debug info uses.
1241 while (!DbgInUses.empty()) {
1242 DbgInfoIntrinsic *DI = DbgInUses.back(); DbgInUses.pop_back();
1243 DI->eraseFromParent();
1245 I->eraseFromParent();
1251 /// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at
1252 /// the offset specified by Offset (which is specified in bytes).
1254 /// There are two cases we handle here:
1255 /// 1) A union of vector types of the same size and potentially its elements.
1256 /// Here we turn element accesses into insert/extract element operations.
1257 /// This promotes a <4 x float> with a store of float to the third element
1258 /// into a <4 x float> that uses insert element.
1259 /// 2) A fully general blob of memory, which we turn into some (potentially
1260 /// large) integer type with extract and insert operations where the loads
1261 /// and stores would mutate the memory.
1262 static void MergeInType(const Type *In, uint64_t Offset, const Type *&VecTy,
1263 unsigned AllocaSize, const TargetData &TD,
1264 LLVMContext *Context) {
1265 // If this could be contributing to a vector, analyze it.
1266 if (VecTy != Type::VoidTy) { // either null or a vector type.
1268 // If the In type is a vector that is the same size as the alloca, see if it
1269 // matches the existing VecTy.
1270 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
1271 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
1272 // If we're storing/loading a vector of the right size, allow it as a
1273 // vector. If this the first vector we see, remember the type so that
1274 // we know the element size.
1279 } else if (In == Type::FloatTy || In == Type::DoubleTy ||
1280 (isa<IntegerType>(In) && In->getPrimitiveSizeInBits() >= 8 &&
1281 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
1282 // If we're accessing something that could be an element of a vector, see
1283 // if the implied vector agrees with what we already have and if Offset is
1284 // compatible with it.
1285 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
1286 if (Offset % EltSize == 0 &&
1287 AllocaSize % EltSize == 0 &&
1289 cast<VectorType>(VecTy)->getElementType()
1290 ->getPrimitiveSizeInBits()/8 == EltSize)) {
1292 VecTy = Context->getVectorType(In, AllocaSize/EltSize);
1298 // Otherwise, we have a case that we can't handle with an optimized vector
1299 // form. We can still turn this into a large integer.
1300 VecTy = Type::VoidTy;
1303 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
1304 /// its accesses to use a to single vector type, return true, and set VecTy to
1305 /// the new type. If we could convert the alloca into a single promotable
1306 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
1307 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
1308 /// is the current offset from the base of the alloca being analyzed.
1310 /// If we see at least one access to the value that is as a vector type, set the
1313 bool SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
1314 bool &SawVec, uint64_t Offset,
1315 unsigned AllocaSize) {
1316 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1317 Instruction *User = cast<Instruction>(*UI);
1319 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1320 // Don't break volatile loads.
1321 if (LI->isVolatile())
1323 MergeInType(LI->getType(), Offset, VecTy, AllocaSize, *TD, Context);
1324 SawVec |= isa<VectorType>(LI->getType());
1328 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1329 // Storing the pointer, not into the value?
1330 if (SI->getOperand(0) == V || SI->isVolatile()) return 0;
1331 MergeInType(SI->getOperand(0)->getType(), Offset,
1332 VecTy, AllocaSize, *TD, Context);
1333 SawVec |= isa<VectorType>(SI->getOperand(0)->getType());
1337 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
1338 if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset,
1341 IsNotTrivial = true;
1345 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1346 // If this is a GEP with a variable indices, we can't handle it.
1347 if (!GEP->hasAllConstantIndices())
1350 // Compute the offset that this GEP adds to the pointer.
1351 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1352 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1353 &Indices[0], Indices.size());
1354 // See if all uses can be converted.
1355 if (!CanConvertToScalar(GEP, IsNotTrivial, VecTy, SawVec,Offset+GEPOffset,
1358 IsNotTrivial = true;
1362 // If this is a constant sized memset of a constant value (e.g. 0) we can
1364 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1365 // Store of constant value and constant size.
1366 if (isa<ConstantInt>(MSI->getValue()) &&
1367 isa<ConstantInt>(MSI->getLength())) {
1368 IsNotTrivial = true;
1373 // If this is a memcpy or memmove into or out of the whole allocation, we
1374 // can handle it like a load or store of the scalar type.
1375 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1376 if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()))
1377 if (Len->getZExtValue() == AllocaSize && Offset == 0) {
1378 IsNotTrivial = true;
1383 // Ignore dbg intrinsic.
1384 if (isa<DbgInfoIntrinsic>(User))
1387 // Otherwise, we cannot handle this!
1395 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
1396 /// directly. This happens when we are converting an "integer union" to a
1397 /// single integer scalar, or when we are converting a "vector union" to a
1398 /// vector with insert/extractelement instructions.
1400 /// Offset is an offset from the original alloca, in bits that need to be
1401 /// shifted to the right. By the end of this, there should be no uses of Ptr.
1402 void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) {
1403 while (!Ptr->use_empty()) {
1404 Instruction *User = cast<Instruction>(Ptr->use_back());
1406 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
1407 ConvertUsesToScalar(CI, NewAI, Offset);
1408 CI->eraseFromParent();
1412 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1413 // Compute the offset that this GEP adds to the pointer.
1414 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1415 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1416 &Indices[0], Indices.size());
1417 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
1418 GEP->eraseFromParent();
1422 IRBuilder<> Builder(User->getParent(), User);
1424 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1425 // The load is a bit extract from NewAI shifted right by Offset bits.
1426 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
1428 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
1429 LI->replaceAllUsesWith(NewLoadVal);
1430 LI->eraseFromParent();
1434 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1435 assert(SI->getOperand(0) != Ptr && "Consistency error!");
1436 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str());
1437 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
1439 Builder.CreateStore(New, NewAI);
1440 SI->eraseFromParent();
1444 // If this is a constant sized memset of a constant value (e.g. 0) we can
1445 // transform it into a store of the expanded constant value.
1446 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1447 assert(MSI->getRawDest() == Ptr && "Consistency error!");
1448 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
1449 if (NumBytes != 0) {
1450 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
1452 // Compute the value replicated the right number of times.
1453 APInt APVal(NumBytes*8, Val);
1455 // Splat the value if non-zero.
1457 for (unsigned i = 1; i != NumBytes; ++i)
1458 APVal |= APVal << 8;
1460 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str());
1461 Value *New = ConvertScalar_InsertValue(Context->getConstantInt(APVal),
1462 Old, Offset, Builder);
1463 Builder.CreateStore(New, NewAI);
1465 MSI->eraseFromParent();
1469 // If this is a memcpy or memmove into or out of the whole allocation, we
1470 // can handle it like a load or store of the scalar type.
1471 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1472 assert(Offset == 0 && "must be store to start of alloca");
1474 // If the source and destination are both to the same alloca, then this is
1475 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
1477 AllocaInst *OrigAI = cast<AllocaInst>(Ptr->getUnderlyingObject());
1479 if (MTI->getSource()->getUnderlyingObject() != OrigAI) {
1480 // Dest must be OrigAI, change this to be a load from the original
1481 // pointer (bitcasted), then a store to our new alloca.
1482 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
1483 Value *SrcPtr = MTI->getSource();
1484 SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType());
1486 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
1487 SrcVal->setAlignment(MTI->getAlignment());
1488 Builder.CreateStore(SrcVal, NewAI);
1489 } else if (MTI->getDest()->getUnderlyingObject() != OrigAI) {
1490 // Src must be OrigAI, change this to be a load from NewAI then a store
1491 // through the original dest pointer (bitcasted).
1492 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
1493 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
1495 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType());
1496 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
1497 NewStore->setAlignment(MTI->getAlignment());
1499 // Noop transfer. Src == Dst
1503 MTI->eraseFromParent();
1507 // If user is a dbg info intrinsic then it is safe to remove it.
1508 if (isa<DbgInfoIntrinsic>(User)) {
1509 User->eraseFromParent();
1513 assert(0 && "Unsupported operation!");
1518 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
1519 /// or vector value FromVal, extracting the bits from the offset specified by
1520 /// Offset. This returns the value, which is of type ToType.
1522 /// This happens when we are converting an "integer union" to a single
1523 /// integer scalar, or when we are converting a "vector union" to a vector with
1524 /// insert/extractelement instructions.
1526 /// Offset is an offset from the original alloca, in bits that need to be
1527 /// shifted to the right.
1528 Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
1529 uint64_t Offset, IRBuilder<> &Builder) {
1530 // If the load is of the whole new alloca, no conversion is needed.
1531 if (FromVal->getType() == ToType && Offset == 0)
1534 // If the result alloca is a vector type, this is either an element
1535 // access or a bitcast to another vector type of the same size.
1536 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
1537 if (isa<VectorType>(ToType))
1538 return Builder.CreateBitCast(FromVal, ToType, "tmp");
1540 // Otherwise it must be an element access.
1543 unsigned EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1544 Elt = Offset/EltSize;
1545 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
1547 // Return the element extracted out of it.
1548 Value *V = Builder.CreateExtractElement(FromVal,
1549 Context->getConstantInt(Type::Int32Ty,Elt),
1551 if (V->getType() != ToType)
1552 V = Builder.CreateBitCast(V, ToType, "tmp");
1556 // If ToType is a first class aggregate, extract out each of the pieces and
1557 // use insertvalue's to form the FCA.
1558 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
1559 const StructLayout &Layout = *TD->getStructLayout(ST);
1560 Value *Res = Context->getUndef(ST);
1561 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1562 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
1563 Offset+Layout.getElementOffsetInBits(i),
1565 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1570 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
1571 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1572 Value *Res = Context->getUndef(AT);
1573 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1574 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
1575 Offset+i*EltSize, Builder);
1576 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1581 // Otherwise, this must be a union that was converted to an integer value.
1582 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
1584 // If this is a big-endian system and the load is narrower than the
1585 // full alloca type, we need to do a shift to get the right bits.
1587 if (TD->isBigEndian()) {
1588 // On big-endian machines, the lowest bit is stored at the bit offset
1589 // from the pointer given by getTypeStoreSizeInBits. This matters for
1590 // integers with a bitwidth that is not a multiple of 8.
1591 ShAmt = TD->getTypeStoreSizeInBits(NTy) -
1592 TD->getTypeStoreSizeInBits(ToType) - Offset;
1597 // Note: we support negative bitwidths (with shl) which are not defined.
1598 // We do this to support (f.e.) loads off the end of a structure where
1599 // only some bits are used.
1600 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
1601 FromVal = Builder.CreateLShr(FromVal,
1602 Context->getConstantInt(FromVal->getType(),
1604 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
1605 FromVal = Builder.CreateShl(FromVal,
1606 Context->getConstantInt(FromVal->getType(),
1609 // Finally, unconditionally truncate the integer to the right width.
1610 unsigned LIBitWidth = TD->getTypeSizeInBits(ToType);
1611 if (LIBitWidth < NTy->getBitWidth())
1613 Builder.CreateTrunc(FromVal, Context->getIntegerType(LIBitWidth), "tmp");
1614 else if (LIBitWidth > NTy->getBitWidth())
1616 Builder.CreateZExt(FromVal, Context->getIntegerType(LIBitWidth), "tmp");
1618 // If the result is an integer, this is a trunc or bitcast.
1619 if (isa<IntegerType>(ToType)) {
1621 } else if (ToType->isFloatingPoint() || isa<VectorType>(ToType)) {
1622 // Just do a bitcast, we know the sizes match up.
1623 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
1625 // Otherwise must be a pointer.
1626 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
1628 assert(FromVal->getType() == ToType && "Didn't convert right?");
1633 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
1634 /// or vector value "Old" at the offset specified by Offset.
1636 /// This happens when we are converting an "integer union" to a
1637 /// single integer scalar, or when we are converting a "vector union" to a
1638 /// vector with insert/extractelement instructions.
1640 /// Offset is an offset from the original alloca, in bits that need to be
1641 /// shifted to the right.
1642 Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old,
1643 uint64_t Offset, IRBuilder<> &Builder) {
1645 // Convert the stored type to the actual type, shift it left to insert
1646 // then 'or' into place.
1647 const Type *AllocaType = Old->getType();
1649 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
1650 uint64_t VecSize = TD->getTypeAllocSizeInBits(VTy);
1651 uint64_t ValSize = TD->getTypeAllocSizeInBits(SV->getType());
1653 // Changing the whole vector with memset or with an access of a different
1655 if (ValSize == VecSize)
1656 return Builder.CreateBitCast(SV, AllocaType, "tmp");
1658 uint64_t EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1660 // Must be an element insertion.
1661 unsigned Elt = Offset/EltSize;
1663 if (SV->getType() != VTy->getElementType())
1664 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
1666 SV = Builder.CreateInsertElement(Old, SV,
1667 Context->getConstantInt(Type::Int32Ty, Elt),
1672 // If SV is a first-class aggregate value, insert each value recursively.
1673 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
1674 const StructLayout &Layout = *TD->getStructLayout(ST);
1675 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1676 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1677 Old = ConvertScalar_InsertValue(Elt, Old,
1678 Offset+Layout.getElementOffsetInBits(i),
1684 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
1685 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1686 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1687 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1688 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
1693 // If SV is a float, convert it to the appropriate integer type.
1694 // If it is a pointer, do the same.
1695 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType());
1696 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType);
1697 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType());
1698 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType);
1699 if (SV->getType()->isFloatingPoint() || isa<VectorType>(SV->getType()))
1700 SV = Builder.CreateBitCast(SV, Context->getIntegerType(SrcWidth), "tmp");
1701 else if (isa<PointerType>(SV->getType()))
1702 SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(), "tmp");
1704 // Zero extend or truncate the value if needed.
1705 if (SV->getType() != AllocaType) {
1706 if (SV->getType()->getPrimitiveSizeInBits() <
1707 AllocaType->getPrimitiveSizeInBits())
1708 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
1710 // Truncation may be needed if storing more than the alloca can hold
1711 // (undefined behavior).
1712 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
1713 SrcWidth = DestWidth;
1714 SrcStoreWidth = DestStoreWidth;
1718 // If this is a big-endian system and the store is narrower than the
1719 // full alloca type, we need to do a shift to get the right bits.
1721 if (TD->isBigEndian()) {
1722 // On big-endian machines, the lowest bit is stored at the bit offset
1723 // from the pointer given by getTypeStoreSizeInBits. This matters for
1724 // integers with a bitwidth that is not a multiple of 8.
1725 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
1730 // Note: we support negative bitwidths (with shr) which are not defined.
1731 // We do this to support (f.e.) stores off the end of a structure where
1732 // only some bits in the structure are set.
1733 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1734 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1735 SV = Builder.CreateShl(SV, Context->getConstantInt(SV->getType(),
1738 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1739 SV = Builder.CreateLShr(SV, Context->getConstantInt(SV->getType(),
1741 Mask = Mask.lshr(-ShAmt);
1744 // Mask out the bits we are about to insert from the old value, and or
1746 if (SrcWidth != DestWidth) {
1747 assert(DestWidth > SrcWidth);
1748 Old = Builder.CreateAnd(Old, Context->getConstantInt(~Mask), "mask");
1749 SV = Builder.CreateOr(Old, SV, "ins");
1756 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1757 /// some part of a constant global variable. This intentionally only accepts
1758 /// constant expressions because we don't can't rewrite arbitrary instructions.
1759 static bool PointsToConstantGlobal(Value *V) {
1760 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1761 return GV->isConstant();
1762 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1763 if (CE->getOpcode() == Instruction::BitCast ||
1764 CE->getOpcode() == Instruction::GetElementPtr)
1765 return PointsToConstantGlobal(CE->getOperand(0));
1769 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1770 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
1771 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
1772 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
1773 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1774 /// the alloca, and if the source pointer is a pointer to a constant global, we
1775 /// can optimize this.
1776 static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy,
1778 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1779 if (LoadInst *LI = dyn_cast<LoadInst>(*UI))
1780 // Ignore non-volatile loads, they are always ok.
1781 if (!LI->isVolatile())
1784 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) {
1785 // If uses of the bitcast are ok, we are ok.
1786 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
1790 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
1791 // If the GEP has all zero indices, it doesn't offset the pointer. If it
1792 // doesn't, it does.
1793 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
1794 isOffset || !GEP->hasAllZeroIndices()))
1799 // If this is isn't our memcpy/memmove, reject it as something we can't
1801 if (!isa<MemTransferInst>(*UI))
1804 // If we already have seen a copy, reject the second one.
1805 if (TheCopy) return false;
1807 // If the pointer has been offset from the start of the alloca, we can't
1808 // safely handle this.
1809 if (isOffset) return false;
1811 // If the memintrinsic isn't using the alloca as the dest, reject it.
1812 if (UI.getOperandNo() != 1) return false;
1814 MemIntrinsic *MI = cast<MemIntrinsic>(*UI);
1816 // If the source of the memcpy/move is not a constant global, reject it.
1817 if (!PointsToConstantGlobal(MI->getOperand(2)))
1820 // Otherwise, the transform is safe. Remember the copy instruction.
1826 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
1827 /// modified by a copy from a constant global. If we can prove this, we can
1828 /// replace any uses of the alloca with uses of the global directly.
1829 Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocationInst *AI) {
1830 Instruction *TheCopy = 0;
1831 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))