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/ErrorHandling.h"
38 #include "llvm/Support/GetElementPtrTypeIterator.h"
39 #include "llvm/Support/IRBuilder.h"
40 #include "llvm/Support/MathExtras.h"
41 #include "llvm/Support/raw_ostream.h"
42 #include "llvm/ADT/SmallVector.h"
43 #include "llvm/ADT/Statistic.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 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>();
77 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
78 /// information about the uses. All these fields are initialized to false
79 /// and set to true when something is learned.
81 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
84 /// needsCleanup - This is set to true if there is some use of the alloca
85 /// that requires cleanup.
86 bool needsCleanup : 1;
88 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
91 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
95 : isUnsafe(false), needsCleanup(false),
96 isMemCpySrc(false), isMemCpyDst(false) {}
101 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
103 int isSafeAllocaToScalarRepl(AllocaInst *AI);
105 void isSafeUseOfAllocation(Instruction *User, AllocaInst *AI,
107 void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocaInst *AI,
109 void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocaInst *AI,
110 unsigned OpNo, AllocaInfo &Info);
111 void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocaInst *AI,
114 void DoScalarReplacement(AllocaInst *AI,
115 std::vector<AllocaInst*> &WorkList);
116 void CleanupGEP(GetElementPtrInst *GEP);
117 void CleanupAllocaUsers(AllocaInst *AI);
118 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocaInst *Base);
120 void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocaInst *AI,
121 SmallVector<AllocaInst*, 32> &NewElts);
123 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
125 SmallVector<AllocaInst*, 32> &NewElts);
126 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
127 SmallVector<AllocaInst*, 32> &NewElts);
128 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
129 SmallVector<AllocaInst*, 32> &NewElts);
131 bool CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
132 bool &SawVec, uint64_t Offset, unsigned AllocaSize);
133 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
134 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
135 uint64_t Offset, IRBuilder<> &Builder);
136 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
137 uint64_t Offset, IRBuilder<> &Builder);
138 static Instruction *isOnlyCopiedFromConstantGlobal(AllocaInst *AI);
143 static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates");
145 // Public interface to the ScalarReplAggregates pass
146 FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) {
147 return new SROA(Threshold);
151 bool SROA::runOnFunction(Function &F) {
152 TD = getAnalysisIfAvailable<TargetData>();
154 bool Changed = performPromotion(F);
156 // FIXME: ScalarRepl currently depends on TargetData more than it
157 // theoretically needs to. It should be refactored in order to support
158 // target-independent IR. Until this is done, just skip the actual
159 // scalar-replacement portion of this pass.
160 if (!TD) return Changed;
163 bool LocalChange = performScalarRepl(F);
164 if (!LocalChange) break; // No need to repromote if no scalarrepl
166 LocalChange = performPromotion(F);
167 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
174 bool SROA::performPromotion(Function &F) {
175 std::vector<AllocaInst*> Allocas;
176 DominatorTree &DT = getAnalysis<DominatorTree>();
177 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
179 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
181 bool Changed = false;
186 // Find allocas that are safe to promote, by looking at all instructions in
188 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
189 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
190 if (isAllocaPromotable(AI))
191 Allocas.push_back(AI);
193 if (Allocas.empty()) break;
195 PromoteMemToReg(Allocas, DT, DF);
196 NumPromoted += Allocas.size();
203 /// getNumSAElements - Return the number of elements in the specific struct or
205 static uint64_t getNumSAElements(const Type *T) {
206 if (const StructType *ST = dyn_cast<StructType>(T))
207 return ST->getNumElements();
208 return cast<ArrayType>(T)->getNumElements();
211 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
212 // which runs on all of the malloc/alloca instructions in the function, removing
213 // them if they are only used by getelementptr instructions.
215 bool SROA::performScalarRepl(Function &F) {
216 std::vector<AllocaInst*> WorkList;
218 // Scan the entry basic block, adding any alloca's and mallocs to the worklist
219 BasicBlock &BB = F.getEntryBlock();
220 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
221 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
222 WorkList.push_back(A);
224 // Process the worklist
225 bool Changed = false;
226 while (!WorkList.empty()) {
227 AllocaInst *AI = WorkList.back();
230 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
231 // with unused elements.
232 if (AI->use_empty()) {
233 AI->eraseFromParent();
237 // If this alloca is impossible for us to promote, reject it early.
238 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
241 // Check to see if this allocation is only modified by a memcpy/memmove from
242 // a constant global. If this is the case, we can change all users to use
243 // the constant global instead. This is commonly produced by the CFE by
244 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
245 // is only subsequently read.
246 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
247 DEBUG(errs() << "Found alloca equal to global: " << *AI << '\n');
248 DEBUG(errs() << " memcpy = " << *TheCopy << '\n');
249 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2));
250 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
251 TheCopy->eraseFromParent(); // Don't mutate the global.
252 AI->eraseFromParent();
258 // Check to see if we can perform the core SROA transformation. We cannot
259 // transform the allocation instruction if it is an array allocation
260 // (allocations OF arrays are ok though), and an allocation of a scalar
261 // value cannot be decomposed at all.
262 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
264 // Do not promote [0 x %struct].
265 if (AllocaSize == 0) continue;
267 // Do not promote any struct whose size is too big.
268 if (AllocaSize > SRThreshold) continue;
270 if ((isa<StructType>(AI->getAllocatedType()) ||
271 isa<ArrayType>(AI->getAllocatedType())) &&
272 // Do not promote any struct into more than "32" separate vars.
273 getNumSAElements(AI->getAllocatedType()) <= SRThreshold/4) {
274 // Check that all of the users of the allocation are capable of being
276 switch (isSafeAllocaToScalarRepl(AI)) {
277 default: llvm_unreachable("Unexpected value!");
278 case 0: // Not safe to scalar replace.
280 case 1: // Safe, but requires cleanup/canonicalizations first
281 CleanupAllocaUsers(AI);
283 case 3: // Safe to scalar replace.
284 DoScalarReplacement(AI, WorkList);
290 // If we can turn this aggregate value (potentially with casts) into a
291 // simple scalar value that can be mem2reg'd into a register value.
292 // IsNotTrivial tracks whether this is something that mem2reg could have
293 // promoted itself. If so, we don't want to transform it needlessly. Note
294 // that we can't just check based on the type: the alloca may be of an i32
295 // but that has pointer arithmetic to set byte 3 of it or something.
296 bool IsNotTrivial = false;
297 const Type *VectorTy = 0;
298 bool HadAVector = false;
299 if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector,
300 0, unsigned(AllocaSize)) && IsNotTrivial) {
302 // If we were able to find a vector type that can handle this with
303 // insert/extract elements, and if there was at least one use that had
304 // a vector type, promote this to a vector. We don't want to promote
305 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
306 // we just get a lot of insert/extracts. If at least one vector is
307 // involved, then we probably really do have a union of vector/array.
308 if (VectorTy && isa<VectorType>(VectorTy) && HadAVector) {
309 DEBUG(errs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
310 << *VectorTy << '\n');
312 // Create and insert the vector alloca.
313 NewAI = new AllocaInst(VectorTy, 0, "", AI->getParent()->begin());
314 ConvertUsesToScalar(AI, NewAI, 0);
316 DEBUG(errs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
318 // Create and insert the integer alloca.
319 const Type *NewTy = IntegerType::get(AI->getContext(), AllocaSize*8);
320 NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
321 ConvertUsesToScalar(AI, NewAI, 0);
324 AI->eraseFromParent();
330 // Otherwise, couldn't process this alloca.
336 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
337 /// predicate, do SROA now.
338 void SROA::DoScalarReplacement(AllocaInst *AI,
339 std::vector<AllocaInst*> &WorkList) {
340 DEBUG(errs() << "Found inst to SROA: " << *AI << '\n');
341 SmallVector<AllocaInst*, 32> ElementAllocas;
342 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
343 ElementAllocas.reserve(ST->getNumContainedTypes());
344 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
345 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
347 AI->getName() + "." + Twine(i), AI);
348 ElementAllocas.push_back(NA);
349 WorkList.push_back(NA); // Add to worklist for recursive processing
352 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
353 ElementAllocas.reserve(AT->getNumElements());
354 const Type *ElTy = AT->getElementType();
355 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
356 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
357 AI->getName() + "." + Twine(i), AI);
358 ElementAllocas.push_back(NA);
359 WorkList.push_back(NA); // Add to worklist for recursive processing
363 // Now that we have created the alloca instructions that we want to use,
364 // expand the getelementptr instructions to use them.
366 while (!AI->use_empty()) {
367 Instruction *User = cast<Instruction>(AI->use_back());
368 if (BitCastInst *BCInst = dyn_cast<BitCastInst>(User)) {
369 RewriteBitCastUserOfAlloca(BCInst, AI, ElementAllocas);
370 BCInst->eraseFromParent();
375 // %res = load { i32, i32 }* %alloc
377 // %load.0 = load i32* %alloc.0
378 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
379 // %load.1 = load i32* %alloc.1
380 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
381 // (Also works for arrays instead of structs)
382 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
383 Value *Insert = UndefValue::get(LI->getType());
384 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
385 Value *Load = new LoadInst(ElementAllocas[i], "load", LI);
386 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
388 LI->replaceAllUsesWith(Insert);
389 LI->eraseFromParent();
394 // store { i32, i32 } %val, { i32, i32 }* %alloc
396 // %val.0 = extractvalue { i32, i32 } %val, 0
397 // store i32 %val.0, i32* %alloc.0
398 // %val.1 = extractvalue { i32, i32 } %val, 1
399 // store i32 %val.1, i32* %alloc.1
400 // (Also works for arrays instead of structs)
401 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
402 Value *Val = SI->getOperand(0);
403 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
404 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
405 new StoreInst(Extract, ElementAllocas[i], SI);
407 SI->eraseFromParent();
411 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User);
412 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst>
414 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
416 assert(Idx < ElementAllocas.size() && "Index out of range?");
417 AllocaInst *AllocaToUse = ElementAllocas[Idx];
420 if (GEPI->getNumOperands() == 3) {
421 // Do not insert a new getelementptr instruction with zero indices, only
422 // to have it optimized out later.
423 RepValue = AllocaToUse;
425 // We are indexing deeply into the structure, so we still need a
426 // getelement ptr instruction to finish the indexing. This may be
427 // expanded itself once the worklist is rerun.
429 SmallVector<Value*, 8> NewArgs;
430 NewArgs.push_back(Constant::getNullValue(
431 Type::getInt32Ty(AI->getContext())));
432 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end());
433 RepValue = GetElementPtrInst::Create(AllocaToUse, NewArgs.begin(),
434 NewArgs.end(), "", GEPI);
435 RepValue->takeName(GEPI);
438 // If this GEP is to the start of the aggregate, check for memcpys.
439 if (Idx == 0 && GEPI->hasAllZeroIndices())
440 RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas);
442 // Move all of the users over to the new GEP.
443 GEPI->replaceAllUsesWith(RepValue);
444 // Delete the old GEP
445 GEPI->eraseFromParent();
448 // Finally, delete the Alloca instruction
449 AI->eraseFromParent();
454 /// isSafeElementUse - Check to see if this use is an allowed use for a
455 /// getelementptr instruction of an array aggregate allocation. isFirstElt
456 /// indicates whether Ptr is known to the start of the aggregate.
458 void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocaInst *AI,
460 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
462 Instruction *User = cast<Instruction>(*I);
463 switch (User->getOpcode()) {
464 case Instruction::Load: break;
465 case Instruction::Store:
466 // Store is ok if storing INTO the pointer, not storing the pointer
467 if (User->getOperand(0) == Ptr) return MarkUnsafe(Info);
469 case Instruction::GetElementPtr: {
470 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User);
471 bool AreAllZeroIndices = isFirstElt;
472 if (GEP->getNumOperands() > 1 &&
473 (!isa<ConstantInt>(GEP->getOperand(1)) ||
474 !cast<ConstantInt>(GEP->getOperand(1))->isZero()))
475 // Using pointer arithmetic to navigate the array.
476 return MarkUnsafe(Info);
478 // Verify that any array subscripts are in range.
479 for (gep_type_iterator GEPIt = gep_type_begin(GEP),
480 E = gep_type_end(GEP); GEPIt != E; ++GEPIt) {
481 // Ignore struct elements, no extra checking needed for these.
482 if (isa<StructType>(*GEPIt))
485 // This GEP indexes an array. Verify that this is an in-range
486 // constant integer. Specifically, consider A[0][i]. We cannot know that
487 // the user isn't doing invalid things like allowing i to index an
488 // out-of-range subscript that accesses A[1]. Because of this, we have
489 // to reject SROA of any accesses into structs where any of the
490 // components are variables.
491 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
492 if (!IdxVal) return MarkUnsafe(Info);
494 // Are all indices still zero?
495 AreAllZeroIndices &= IdxVal->isZero();
497 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPIt)) {
498 if (IdxVal->getZExtValue() >= AT->getNumElements())
499 return MarkUnsafe(Info);
500 } else if (const VectorType *VT = dyn_cast<VectorType>(*GEPIt)) {
501 if (IdxVal->getZExtValue() >= VT->getNumElements())
502 return MarkUnsafe(Info);
507 isSafeElementUse(GEP, AreAllZeroIndices, AI, Info);
508 if (Info.isUnsafe) return;
511 case Instruction::BitCast:
513 isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info);
514 if (Info.isUnsafe) return;
517 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n');
518 return MarkUnsafe(Info);
519 case Instruction::Call:
520 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
522 isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info);
523 if (Info.isUnsafe) return;
527 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n');
528 return MarkUnsafe(Info);
530 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n');
531 return MarkUnsafe(Info);
534 return; // All users look ok :)
537 /// AllUsersAreLoads - Return true if all users of this value are loads.
538 static bool AllUsersAreLoads(Value *Ptr) {
539 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
541 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load)
546 /// isSafeUseOfAllocation - Check to see if this user is an allowed use for an
547 /// aggregate allocation.
549 void SROA::isSafeUseOfAllocation(Instruction *User, AllocaInst *AI,
551 if (BitCastInst *C = dyn_cast<BitCastInst>(User))
552 return isSafeUseOfBitCastedAllocation(C, AI, Info);
554 if (LoadInst *LI = dyn_cast<LoadInst>(User))
555 if (!LI->isVolatile())
556 return;// Loads (returning a first class aggregrate) are always rewritable
558 if (StoreInst *SI = dyn_cast<StoreInst>(User))
559 if (!SI->isVolatile() && SI->getOperand(0) != AI)
560 return;// Store is ok if storing INTO the pointer, not storing the pointer
562 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User);
564 return MarkUnsafe(Info);
566 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI);
568 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>".
570 I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) {
571 return MarkUnsafe(Info);
575 if (I == E) return MarkUnsafe(Info); // ran out of GEP indices??
577 bool IsAllZeroIndices = true;
579 // If the first index is a non-constant index into an array, see if we can
580 // handle it as a special case.
581 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
582 if (!isa<ConstantInt>(I.getOperand())) {
583 IsAllZeroIndices = 0;
584 uint64_t NumElements = AT->getNumElements();
586 // If this is an array index and the index is not constant, we cannot
587 // promote... that is unless the array has exactly one or two elements in
588 // it, in which case we CAN promote it, but we have to canonicalize this
589 // out if this is the only problem.
590 if ((NumElements == 1 || NumElements == 2) &&
591 AllUsersAreLoads(GEPI)) {
592 Info.needsCleanup = true;
593 return; // Canonicalization required!
595 return MarkUnsafe(Info);
599 // Walk through the GEP type indices, checking the types that this indexes
601 for (; I != E; ++I) {
602 // Ignore struct elements, no extra checking needed for these.
603 if (isa<StructType>(*I))
606 ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand());
607 if (!IdxVal) return MarkUnsafe(Info);
609 // Are all indices still zero?
610 IsAllZeroIndices &= IdxVal->isZero();
612 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
613 // This GEP indexes an array. Verify that this is an in-range constant
614 // integer. Specifically, consider A[0][i]. We cannot know that the user
615 // isn't doing invalid things like allowing i to index an out-of-range
616 // subscript that accesses A[1]. Because of this, we have to reject SROA
617 // of any accesses into structs where any of the components are variables.
618 if (IdxVal->getZExtValue() >= AT->getNumElements())
619 return MarkUnsafe(Info);
620 } else if (const VectorType *VT = dyn_cast<VectorType>(*I)) {
621 if (IdxVal->getZExtValue() >= VT->getNumElements())
622 return MarkUnsafe(Info);
626 // If there are any non-simple uses of this getelementptr, make sure to reject
628 return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info);
631 /// isSafeMemIntrinsicOnAllocation - Return true if the specified memory
632 /// intrinsic can be promoted by SROA. At this point, we know that the operand
633 /// of the memintrinsic is a pointer to the beginning of the allocation.
634 void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocaInst *AI,
635 unsigned OpNo, AllocaInfo &Info) {
636 // If not constant length, give up.
637 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
638 if (!Length) return MarkUnsafe(Info);
640 // If not the whole aggregate, give up.
641 if (Length->getZExtValue() !=
642 TD->getTypeAllocSize(AI->getType()->getElementType()))
643 return MarkUnsafe(Info);
645 // We only know about memcpy/memset/memmove.
646 if (!isa<MemIntrinsic>(MI))
647 return MarkUnsafe(Info);
649 // Otherwise, we can transform it. Determine whether this is a memcpy/set
650 // into or out of the aggregate.
652 Info.isMemCpyDst = true;
655 Info.isMemCpySrc = true;
659 /// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast
661 void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocaInst *AI,
663 for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end();
665 if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) {
666 isSafeUseOfBitCastedAllocation(BCU, AI, Info);
667 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) {
668 isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info);
669 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
670 if (SI->isVolatile())
671 return MarkUnsafe(Info);
673 // If storing the entire alloca in one chunk through a bitcasted pointer
674 // to integer, we can transform it. This happens (for example) when you
675 // cast a {i32,i32}* to i64* and store through it. This is similar to the
676 // memcpy case and occurs in various "byval" cases and emulated memcpys.
677 if (isa<IntegerType>(SI->getOperand(0)->getType()) &&
678 TD->getTypeAllocSize(SI->getOperand(0)->getType()) ==
679 TD->getTypeAllocSize(AI->getType()->getElementType())) {
680 Info.isMemCpyDst = true;
683 return MarkUnsafe(Info);
684 } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
685 if (LI->isVolatile())
686 return MarkUnsafe(Info);
688 // If loading the entire alloca in one chunk through a bitcasted pointer
689 // to integer, we can transform it. This happens (for example) when you
690 // cast a {i32,i32}* to i64* and load through it. This is similar to the
691 // memcpy case and occurs in various "byval" cases and emulated memcpys.
692 if (isa<IntegerType>(LI->getType()) &&
693 TD->getTypeAllocSize(LI->getType()) ==
694 TD->getTypeAllocSize(AI->getType()->getElementType())) {
695 Info.isMemCpySrc = true;
698 return MarkUnsafe(Info);
699 } else if (isa<DbgInfoIntrinsic>(UI)) {
700 // If one user is DbgInfoIntrinsic then check if all users are
701 // DbgInfoIntrinsics.
702 if (OnlyUsedByDbgInfoIntrinsics(BC)) {
703 Info.needsCleanup = true;
710 return MarkUnsafe(Info);
712 if (Info.isUnsafe) return;
716 /// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes
717 /// to its first element. Transform users of the cast to use the new values
719 void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocaInst *AI,
720 SmallVector<AllocaInst*, 32> &NewElts) {
721 Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end();
723 Instruction *User = cast<Instruction>(*UI++);
724 if (BitCastInst *BCU = dyn_cast<BitCastInst>(User)) {
725 RewriteBitCastUserOfAlloca(BCU, AI, NewElts);
726 if (BCU->use_empty()) BCU->eraseFromParent();
730 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
731 // This must be memcpy/memmove/memset of the entire aggregate.
732 // Split into one per element.
733 RewriteMemIntrinUserOfAlloca(MI, BCInst, AI, NewElts);
737 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
738 // If this is a store of the entire alloca from an integer, rewrite it.
739 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
743 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
744 // If this is a load of the entire alloca to an integer, rewrite it.
745 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
749 // Otherwise it must be some other user of a gep of the first pointer. Just
750 // leave these alone.
755 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
756 /// Rewrite it to copy or set the elements of the scalarized memory.
757 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
759 SmallVector<AllocaInst*, 32> &NewElts) {
761 // If this is a memcpy/memmove, construct the other pointer as the
762 // appropriate type. The "Other" pointer is the pointer that goes to memory
763 // that doesn't have anything to do with the alloca that we are promoting. For
764 // memset, this Value* stays null.
766 LLVMContext &Context = MI->getContext();
767 unsigned MemAlignment = MI->getAlignment();
768 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
769 if (BCInst == MTI->getRawDest())
770 OtherPtr = MTI->getRawSource();
772 assert(BCInst == MTI->getRawSource());
773 OtherPtr = MTI->getRawDest();
777 // If there is an other pointer, we want to convert it to the same pointer
778 // type as AI has, so we can GEP through it safely.
780 // It is likely that OtherPtr is a bitcast, if so, remove it.
781 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr))
782 OtherPtr = BC->getOperand(0);
783 // All zero GEPs are effectively bitcasts.
784 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr))
785 if (GEP->hasAllZeroIndices())
786 OtherPtr = GEP->getOperand(0);
788 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr))
789 if (BCE->getOpcode() == Instruction::BitCast)
790 OtherPtr = BCE->getOperand(0);
792 // If the pointer is not the right type, insert a bitcast to the right
794 if (OtherPtr->getType() != AI->getType())
795 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(),
799 // Process each element of the aggregate.
800 Value *TheFn = MI->getOperand(0);
801 const Type *BytePtrTy = MI->getRawDest()->getType();
802 bool SROADest = MI->getRawDest() == BCInst;
804 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
806 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
807 // If this is a memcpy/memmove, emit a GEP of the other element address.
809 unsigned OtherEltAlign = MemAlignment;
812 Value *Idx[2] = { Zero,
813 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
814 OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2,
815 OtherPtr->getNameStr()+"."+Twine(i),
818 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
819 if (const StructType *ST =
820 dyn_cast<StructType>(OtherPtrTy->getElementType())) {
821 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
824 cast<SequentialType>(OtherPtr->getType())->getElementType();
825 EltOffset = TD->getTypeAllocSize(EltTy)*i;
828 // The alignment of the other pointer is the guaranteed alignment of the
829 // element, which is affected by both the known alignment of the whole
830 // mem intrinsic and the alignment of the element. If the alignment of
831 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
832 // known alignment is just 4 bytes.
833 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
836 Value *EltPtr = NewElts[i];
837 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
839 // If we got down to a scalar, insert a load or store as appropriate.
840 if (EltTy->isSingleValueType()) {
841 if (isa<MemTransferInst>(MI)) {
843 // From Other to Alloca.
844 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
845 new StoreInst(Elt, EltPtr, MI);
847 // From Alloca to Other.
848 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
849 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
853 assert(isa<MemSetInst>(MI));
855 // If the stored element is zero (common case), just store a null
858 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) {
860 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
862 // If EltTy is a vector type, get the element type.
863 const Type *ValTy = EltTy->getScalarType();
865 // Construct an integer with the right value.
866 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
867 APInt OneVal(EltSize, CI->getZExtValue());
868 APInt TotalVal(OneVal);
870 for (unsigned i = 0; 8*i < EltSize; ++i) {
871 TotalVal = TotalVal.shl(8);
875 // Convert the integer value to the appropriate type.
876 StoreVal = ConstantInt::get(Context, TotalVal);
877 if (isa<PointerType>(ValTy))
878 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
879 else if (ValTy->isFloatingPoint())
880 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
881 assert(StoreVal->getType() == ValTy && "Type mismatch!");
883 // If the requested value was a vector constant, create it.
884 if (EltTy != ValTy) {
885 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
886 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
887 StoreVal = ConstantVector::get(&Elts[0], NumElts);
890 new StoreInst(StoreVal, EltPtr, MI);
893 // Otherwise, if we're storing a byte variable, use a memset call for
897 // Cast the element pointer to BytePtrTy.
898 if (EltPtr->getType() != BytePtrTy)
899 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI);
901 // Cast the other pointer (if we have one) to BytePtrTy.
902 if (OtherElt && OtherElt->getType() != BytePtrTy)
903 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(),
906 unsigned EltSize = TD->getTypeAllocSize(EltTy);
908 // Finally, insert the meminst for this element.
909 if (isa<MemTransferInst>(MI)) {
911 SROADest ? EltPtr : OtherElt, // Dest ptr
912 SROADest ? OtherElt : EltPtr, // Src ptr
913 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
915 ConstantInt::get(Type::getInt32Ty(MI->getContext()), OtherEltAlign)
917 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
919 assert(isa<MemSetInst>(MI));
921 EltPtr, MI->getOperand(2), // Dest, Value,
922 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
925 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
928 MI->eraseFromParent();
931 /// RewriteStoreUserOfWholeAlloca - We found an store of an integer that
932 /// overwrites the entire allocation. Extract out the pieces of the stored
933 /// integer and store them individually.
934 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
935 SmallVector<AllocaInst*, 32> &NewElts){
936 // Extract each element out of the integer according to its structure offset
937 // and store the element value to the individual alloca.
938 Value *SrcVal = SI->getOperand(0);
939 const Type *AllocaEltTy = AI->getType()->getElementType();
940 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
942 // If this isn't a store of an integer to the whole alloca, it may be a store
943 // to the first element. Just ignore the store in this case and normal SROA
945 if (!isa<IntegerType>(SrcVal->getType()) ||
946 TD->getTypeAllocSizeInBits(SrcVal->getType()) != AllocaSizeBits)
948 // Handle tail padding by extending the operand
949 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
950 SrcVal = new ZExtInst(SrcVal,
951 IntegerType::get(SI->getContext(), AllocaSizeBits),
954 DEBUG(errs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
957 // There are two forms here: AI could be an array or struct. Both cases
958 // have different ways to compute the element offset.
959 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
960 const StructLayout *Layout = TD->getStructLayout(EltSTy);
962 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
963 // Get the number of bits to shift SrcVal to get the value.
964 const Type *FieldTy = EltSTy->getElementType(i);
965 uint64_t Shift = Layout->getElementOffsetInBits(i);
967 if (TD->isBigEndian())
968 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
970 Value *EltVal = SrcVal;
972 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
973 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
974 "sroa.store.elt", SI);
977 // Truncate down to an integer of the right size.
978 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
980 // Ignore zero sized fields like {}, they obviously contain no data.
981 if (FieldSizeBits == 0) continue;
983 if (FieldSizeBits != AllocaSizeBits)
984 EltVal = new TruncInst(EltVal,
985 IntegerType::get(SI->getContext(), FieldSizeBits),
987 Value *DestField = NewElts[i];
988 if (EltVal->getType() == FieldTy) {
989 // Storing to an integer field of this size, just do it.
990 } else if (FieldTy->isFloatingPoint() || isa<VectorType>(FieldTy)) {
991 // Bitcast to the right element type (for fp/vector values).
992 EltVal = new BitCastInst(EltVal, FieldTy, "", SI);
994 // Otherwise, bitcast the dest pointer (for aggregates).
995 DestField = new BitCastInst(DestField,
996 PointerType::getUnqual(EltVal->getType()),
999 new StoreInst(EltVal, DestField, SI);
1003 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
1004 const Type *ArrayEltTy = ATy->getElementType();
1005 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1006 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
1010 if (TD->isBigEndian())
1011 Shift = AllocaSizeBits-ElementOffset;
1015 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1016 // Ignore zero sized fields like {}, they obviously contain no data.
1017 if (ElementSizeBits == 0) continue;
1019 Value *EltVal = SrcVal;
1021 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
1022 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
1023 "sroa.store.elt", SI);
1026 // Truncate down to an integer of the right size.
1027 if (ElementSizeBits != AllocaSizeBits)
1028 EltVal = new TruncInst(EltVal,
1029 IntegerType::get(SI->getContext(),
1030 ElementSizeBits),"",SI);
1031 Value *DestField = NewElts[i];
1032 if (EltVal->getType() == ArrayEltTy) {
1033 // Storing to an integer field of this size, just do it.
1034 } else if (ArrayEltTy->isFloatingPoint() || isa<VectorType>(ArrayEltTy)) {
1035 // Bitcast to the right element type (for fp/vector values).
1036 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI);
1038 // Otherwise, bitcast the dest pointer (for aggregates).
1039 DestField = new BitCastInst(DestField,
1040 PointerType::getUnqual(EltVal->getType()),
1043 new StoreInst(EltVal, DestField, SI);
1045 if (TD->isBigEndian())
1046 Shift -= ElementOffset;
1048 Shift += ElementOffset;
1052 SI->eraseFromParent();
1055 /// RewriteLoadUserOfWholeAlloca - We found an load of the entire allocation to
1056 /// an integer. Load the individual pieces to form the aggregate value.
1057 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
1058 SmallVector<AllocaInst*, 32> &NewElts) {
1059 // Extract each element out of the NewElts according to its structure offset
1060 // and form the result value.
1061 const Type *AllocaEltTy = AI->getType()->getElementType();
1062 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1064 // If this isn't a load of the whole alloca to an integer, it may be a load
1065 // of the first element. Just ignore the load in this case and normal SROA
1067 if (!isa<IntegerType>(LI->getType()) ||
1068 TD->getTypeAllocSizeInBits(LI->getType()) != AllocaSizeBits)
1071 DEBUG(errs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
1074 // There are two forms here: AI could be an array or struct. Both cases
1075 // have different ways to compute the element offset.
1076 const StructLayout *Layout = 0;
1077 uint64_t ArrayEltBitOffset = 0;
1078 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1079 Layout = TD->getStructLayout(EltSTy);
1081 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
1082 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1086 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
1088 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1089 // Load the value from the alloca. If the NewElt is an aggregate, cast
1090 // the pointer to an integer of the same size before doing the load.
1091 Value *SrcField = NewElts[i];
1092 const Type *FieldTy =
1093 cast<PointerType>(SrcField->getType())->getElementType();
1094 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1096 // Ignore zero sized fields like {}, they obviously contain no data.
1097 if (FieldSizeBits == 0) continue;
1099 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
1101 if (!isa<IntegerType>(FieldTy) && !FieldTy->isFloatingPoint() &&
1102 !isa<VectorType>(FieldTy))
1103 SrcField = new BitCastInst(SrcField,
1104 PointerType::getUnqual(FieldIntTy),
1106 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
1108 // If SrcField is a fp or vector of the right size but that isn't an
1109 // integer type, bitcast to an integer so we can shift it.
1110 if (SrcField->getType() != FieldIntTy)
1111 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
1113 // Zero extend the field to be the same size as the final alloca so that
1114 // we can shift and insert it.
1115 if (SrcField->getType() != ResultVal->getType())
1116 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
1118 // Determine the number of bits to shift SrcField.
1120 if (Layout) // Struct case.
1121 Shift = Layout->getElementOffsetInBits(i);
1123 Shift = i*ArrayEltBitOffset;
1125 if (TD->isBigEndian())
1126 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
1129 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
1130 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
1133 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
1136 // Handle tail padding by truncating the result
1137 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
1138 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
1140 LI->replaceAllUsesWith(ResultVal);
1141 LI->eraseFromParent();
1145 /// HasPadding - Return true if the specified type has any structure or
1146 /// alignment padding, false otherwise.
1147 static bool HasPadding(const Type *Ty, const TargetData &TD) {
1148 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
1149 const StructLayout *SL = TD.getStructLayout(STy);
1150 unsigned PrevFieldBitOffset = 0;
1151 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1152 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
1154 // Padding in sub-elements?
1155 if (HasPadding(STy->getElementType(i), TD))
1158 // Check to see if there is any padding between this element and the
1161 unsigned PrevFieldEnd =
1162 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
1163 if (PrevFieldEnd < FieldBitOffset)
1167 PrevFieldBitOffset = FieldBitOffset;
1170 // Check for tail padding.
1171 if (unsigned EltCount = STy->getNumElements()) {
1172 unsigned PrevFieldEnd = PrevFieldBitOffset +
1173 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
1174 if (PrevFieldEnd < SL->getSizeInBits())
1178 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1179 return HasPadding(ATy->getElementType(), TD);
1180 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) {
1181 return HasPadding(VTy->getElementType(), TD);
1183 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
1186 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
1187 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
1188 /// or 1 if safe after canonicalization has been performed.
1190 int SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
1191 // Loop over the use list of the alloca. We can only transform it if all of
1192 // the users are safe to transform.
1195 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end();
1197 isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info);
1198 if (Info.isUnsafe) {
1199 DEBUG(errs() << "Cannot transform: " << *AI << "\n due to user: "
1205 // Okay, we know all the users are promotable. If the aggregate is a memcpy
1206 // source and destination, we have to be careful. In particular, the memcpy
1207 // could be moving around elements that live in structure padding of the LLVM
1208 // types, but may actually be used. In these cases, we refuse to promote the
1210 if (Info.isMemCpySrc && Info.isMemCpyDst &&
1211 HasPadding(AI->getType()->getElementType(), *TD))
1214 // If we require cleanup, return 1, otherwise return 3.
1215 return Info.needsCleanup ? 1 : 3;
1218 /// CleanupGEP - GEP is used by an Alloca, which can be prompted after the GEP
1219 /// is canonicalized here.
1220 void SROA::CleanupGEP(GetElementPtrInst *GEPI) {
1221 gep_type_iterator I = gep_type_begin(GEPI);
1224 const ArrayType *AT = dyn_cast<ArrayType>(*I);
1228 uint64_t NumElements = AT->getNumElements();
1230 if (isa<ConstantInt>(I.getOperand()))
1233 if (NumElements == 1) {
1235 Constant::getNullValue(Type::getInt32Ty(GEPI->getContext())));
1239 assert(NumElements == 2 && "Unhandled case!");
1240 // All users of the GEP must be loads. At each use of the GEP, insert
1241 // two loads of the appropriate indexed GEP and select between them.
1242 Value *IsOne = new ICmpInst(GEPI, ICmpInst::ICMP_NE, I.getOperand(),
1243 Constant::getNullValue(I.getOperand()->getType()),
1245 // Insert the new GEP instructions, which are properly indexed.
1246 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end());
1247 Indices[1] = Constant::getNullValue(Type::getInt32Ty(GEPI->getContext()));
1248 Value *ZeroIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1251 GEPI->getName()+".0", GEPI);
1252 Indices[1] = ConstantInt::get(Type::getInt32Ty(GEPI->getContext()), 1);
1253 Value *OneIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1256 GEPI->getName()+".1", GEPI);
1257 // Replace all loads of the variable index GEP with loads from both
1258 // indexes and a select.
1259 while (!GEPI->use_empty()) {
1260 LoadInst *LI = cast<LoadInst>(GEPI->use_back());
1261 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI);
1262 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI);
1263 Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI);
1264 LI->replaceAllUsesWith(R);
1265 LI->eraseFromParent();
1267 GEPI->eraseFromParent();
1271 /// CleanupAllocaUsers - If SROA reported that it can promote the specified
1272 /// allocation, but only if cleaned up, perform the cleanups required.
1273 void SROA::CleanupAllocaUsers(AllocaInst *AI) {
1274 // At this point, we know that the end result will be SROA'd and promoted, so
1275 // we can insert ugly code if required so long as sroa+mem2reg will clean it
1277 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
1280 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U))
1283 Instruction *I = cast<Instruction>(U);
1284 SmallVector<DbgInfoIntrinsic *, 2> DbgInUses;
1285 if (!isa<StoreInst>(I) && OnlyUsedByDbgInfoIntrinsics(I, &DbgInUses)) {
1286 // Safe to remove debug info uses.
1287 while (!DbgInUses.empty()) {
1288 DbgInfoIntrinsic *DI = DbgInUses.back(); DbgInUses.pop_back();
1289 DI->eraseFromParent();
1291 I->eraseFromParent();
1297 /// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at
1298 /// the offset specified by Offset (which is specified in bytes).
1300 /// There are two cases we handle here:
1301 /// 1) A union of vector types of the same size and potentially its elements.
1302 /// Here we turn element accesses into insert/extract element operations.
1303 /// This promotes a <4 x float> with a store of float to the third element
1304 /// into a <4 x float> that uses insert element.
1305 /// 2) A fully general blob of memory, which we turn into some (potentially
1306 /// large) integer type with extract and insert operations where the loads
1307 /// and stores would mutate the memory.
1308 static void MergeInType(const Type *In, uint64_t Offset, const Type *&VecTy,
1309 unsigned AllocaSize, const TargetData &TD,
1310 LLVMContext &Context) {
1311 // If this could be contributing to a vector, analyze it.
1312 if (VecTy != Type::getVoidTy(Context)) { // either null or a vector type.
1314 // If the In type is a vector that is the same size as the alloca, see if it
1315 // matches the existing VecTy.
1316 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
1317 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
1318 // If we're storing/loading a vector of the right size, allow it as a
1319 // vector. If this the first vector we see, remember the type so that
1320 // we know the element size.
1325 } else if (In->isFloatTy() || In->isDoubleTy() ||
1326 (isa<IntegerType>(In) && In->getPrimitiveSizeInBits() >= 8 &&
1327 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
1328 // If we're accessing something that could be an element of a vector, see
1329 // if the implied vector agrees with what we already have and if Offset is
1330 // compatible with it.
1331 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
1332 if (Offset % EltSize == 0 &&
1333 AllocaSize % EltSize == 0 &&
1335 cast<VectorType>(VecTy)->getElementType()
1336 ->getPrimitiveSizeInBits()/8 == EltSize)) {
1338 VecTy = VectorType::get(In, AllocaSize/EltSize);
1344 // Otherwise, we have a case that we can't handle with an optimized vector
1345 // form. We can still turn this into a large integer.
1346 VecTy = Type::getVoidTy(Context);
1349 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
1350 /// its accesses to use a to single vector type, return true, and set VecTy to
1351 /// the new type. If we could convert the alloca into a single promotable
1352 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
1353 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
1354 /// is the current offset from the base of the alloca being analyzed.
1356 /// If we see at least one access to the value that is as a vector type, set the
1359 bool SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
1360 bool &SawVec, uint64_t Offset,
1361 unsigned AllocaSize) {
1362 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1363 Instruction *User = cast<Instruction>(*UI);
1365 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1366 // Don't break volatile loads.
1367 if (LI->isVolatile())
1369 MergeInType(LI->getType(), Offset, VecTy,
1370 AllocaSize, *TD, V->getContext());
1371 SawVec |= isa<VectorType>(LI->getType());
1375 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1376 // Storing the pointer, not into the value?
1377 if (SI->getOperand(0) == V || SI->isVolatile()) return 0;
1378 MergeInType(SI->getOperand(0)->getType(), Offset,
1379 VecTy, AllocaSize, *TD, V->getContext());
1380 SawVec |= isa<VectorType>(SI->getOperand(0)->getType());
1384 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
1385 if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset,
1388 IsNotTrivial = true;
1392 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1393 // If this is a GEP with a variable indices, we can't handle it.
1394 if (!GEP->hasAllConstantIndices())
1397 // Compute the offset that this GEP adds to the pointer.
1398 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1399 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1400 &Indices[0], Indices.size());
1401 // See if all uses can be converted.
1402 if (!CanConvertToScalar(GEP, IsNotTrivial, VecTy, SawVec,Offset+GEPOffset,
1405 IsNotTrivial = true;
1409 // If this is a constant sized memset of a constant value (e.g. 0) we can
1411 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1412 // Store of constant value and constant size.
1413 if (isa<ConstantInt>(MSI->getValue()) &&
1414 isa<ConstantInt>(MSI->getLength())) {
1415 IsNotTrivial = true;
1420 // If this is a memcpy or memmove into or out of the whole allocation, we
1421 // can handle it like a load or store of the scalar type.
1422 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1423 if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()))
1424 if (Len->getZExtValue() == AllocaSize && Offset == 0) {
1425 IsNotTrivial = true;
1430 // Ignore dbg intrinsic.
1431 if (isa<DbgInfoIntrinsic>(User))
1434 // Otherwise, we cannot handle this!
1442 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
1443 /// directly. This happens when we are converting an "integer union" to a
1444 /// single integer scalar, or when we are converting a "vector union" to a
1445 /// vector with insert/extractelement instructions.
1447 /// Offset is an offset from the original alloca, in bits that need to be
1448 /// shifted to the right. By the end of this, there should be no uses of Ptr.
1449 void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) {
1450 while (!Ptr->use_empty()) {
1451 Instruction *User = cast<Instruction>(Ptr->use_back());
1453 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
1454 ConvertUsesToScalar(CI, NewAI, Offset);
1455 CI->eraseFromParent();
1459 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1460 // Compute the offset that this GEP adds to the pointer.
1461 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1462 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1463 &Indices[0], Indices.size());
1464 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
1465 GEP->eraseFromParent();
1469 IRBuilder<> Builder(User->getParent(), User);
1471 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1472 // The load is a bit extract from NewAI shifted right by Offset bits.
1473 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
1475 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
1476 LI->replaceAllUsesWith(NewLoadVal);
1477 LI->eraseFromParent();
1481 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1482 assert(SI->getOperand(0) != Ptr && "Consistency error!");
1483 // FIXME: Remove once builder has Twine API.
1484 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").str().c_str());
1485 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
1487 Builder.CreateStore(New, NewAI);
1488 SI->eraseFromParent();
1492 // If this is a constant sized memset of a constant value (e.g. 0) we can
1493 // transform it into a store of the expanded constant value.
1494 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1495 assert(MSI->getRawDest() == Ptr && "Consistency error!");
1496 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
1497 if (NumBytes != 0) {
1498 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
1500 // Compute the value replicated the right number of times.
1501 APInt APVal(NumBytes*8, Val);
1503 // Splat the value if non-zero.
1505 for (unsigned i = 1; i != NumBytes; ++i)
1506 APVal |= APVal << 8;
1508 // FIXME: Remove once builder has Twine API.
1509 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").str().c_str());
1510 Value *New = ConvertScalar_InsertValue(
1511 ConstantInt::get(User->getContext(), APVal),
1512 Old, Offset, Builder);
1513 Builder.CreateStore(New, NewAI);
1515 MSI->eraseFromParent();
1519 // If this is a memcpy or memmove into or out of the whole allocation, we
1520 // can handle it like a load or store of the scalar type.
1521 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1522 assert(Offset == 0 && "must be store to start of alloca");
1524 // If the source and destination are both to the same alloca, then this is
1525 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
1527 AllocaInst *OrigAI = cast<AllocaInst>(Ptr->getUnderlyingObject());
1529 if (MTI->getSource()->getUnderlyingObject() != OrigAI) {
1530 // Dest must be OrigAI, change this to be a load from the original
1531 // pointer (bitcasted), then a store to our new alloca.
1532 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
1533 Value *SrcPtr = MTI->getSource();
1534 SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType());
1536 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
1537 SrcVal->setAlignment(MTI->getAlignment());
1538 Builder.CreateStore(SrcVal, NewAI);
1539 } else if (MTI->getDest()->getUnderlyingObject() != OrigAI) {
1540 // Src must be OrigAI, change this to be a load from NewAI then a store
1541 // through the original dest pointer (bitcasted).
1542 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
1543 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
1545 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType());
1546 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
1547 NewStore->setAlignment(MTI->getAlignment());
1549 // Noop transfer. Src == Dst
1553 MTI->eraseFromParent();
1557 // If user is a dbg info intrinsic then it is safe to remove it.
1558 if (isa<DbgInfoIntrinsic>(User)) {
1559 User->eraseFromParent();
1563 llvm_unreachable("Unsupported operation!");
1567 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
1568 /// or vector value FromVal, extracting the bits from the offset specified by
1569 /// Offset. This returns the value, which is of type ToType.
1571 /// This happens when we are converting an "integer union" to a single
1572 /// integer scalar, or when we are converting a "vector union" to a vector with
1573 /// insert/extractelement instructions.
1575 /// Offset is an offset from the original alloca, in bits that need to be
1576 /// shifted to the right.
1577 Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
1578 uint64_t Offset, IRBuilder<> &Builder) {
1579 // If the load is of the whole new alloca, no conversion is needed.
1580 if (FromVal->getType() == ToType && Offset == 0)
1583 // If the result alloca is a vector type, this is either an element
1584 // access or a bitcast to another vector type of the same size.
1585 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
1586 if (isa<VectorType>(ToType))
1587 return Builder.CreateBitCast(FromVal, ToType, "tmp");
1589 // Otherwise it must be an element access.
1592 unsigned EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1593 Elt = Offset/EltSize;
1594 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
1596 // Return the element extracted out of it.
1597 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(
1598 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp");
1599 if (V->getType() != ToType)
1600 V = Builder.CreateBitCast(V, ToType, "tmp");
1604 // If ToType is a first class aggregate, extract out each of the pieces and
1605 // use insertvalue's to form the FCA.
1606 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
1607 const StructLayout &Layout = *TD->getStructLayout(ST);
1608 Value *Res = UndefValue::get(ST);
1609 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1610 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
1611 Offset+Layout.getElementOffsetInBits(i),
1613 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1618 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
1619 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1620 Value *Res = UndefValue::get(AT);
1621 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1622 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
1623 Offset+i*EltSize, Builder);
1624 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1629 // Otherwise, this must be a union that was converted to an integer value.
1630 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
1632 // If this is a big-endian system and the load is narrower than the
1633 // full alloca type, we need to do a shift to get the right bits.
1635 if (TD->isBigEndian()) {
1636 // On big-endian machines, the lowest bit is stored at the bit offset
1637 // from the pointer given by getTypeStoreSizeInBits. This matters for
1638 // integers with a bitwidth that is not a multiple of 8.
1639 ShAmt = TD->getTypeStoreSizeInBits(NTy) -
1640 TD->getTypeStoreSizeInBits(ToType) - Offset;
1645 // Note: we support negative bitwidths (with shl) which are not defined.
1646 // We do this to support (f.e.) loads off the end of a structure where
1647 // only some bits are used.
1648 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
1649 FromVal = Builder.CreateLShr(FromVal,
1650 ConstantInt::get(FromVal->getType(),
1652 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
1653 FromVal = Builder.CreateShl(FromVal,
1654 ConstantInt::get(FromVal->getType(),
1657 // Finally, unconditionally truncate the integer to the right width.
1658 unsigned LIBitWidth = TD->getTypeSizeInBits(ToType);
1659 if (LIBitWidth < NTy->getBitWidth())
1661 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
1662 LIBitWidth), "tmp");
1663 else if (LIBitWidth > NTy->getBitWidth())
1665 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
1666 LIBitWidth), "tmp");
1668 // If the result is an integer, this is a trunc or bitcast.
1669 if (isa<IntegerType>(ToType)) {
1671 } else if (ToType->isFloatingPoint() || isa<VectorType>(ToType)) {
1672 // Just do a bitcast, we know the sizes match up.
1673 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
1675 // Otherwise must be a pointer.
1676 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
1678 assert(FromVal->getType() == ToType && "Didn't convert right?");
1683 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
1684 /// or vector value "Old" at the offset specified by Offset.
1686 /// This happens when we are converting an "integer union" to a
1687 /// single integer scalar, or when we are converting a "vector union" to a
1688 /// vector with insert/extractelement instructions.
1690 /// Offset is an offset from the original alloca, in bits that need to be
1691 /// shifted to the right.
1692 Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old,
1693 uint64_t Offset, IRBuilder<> &Builder) {
1695 // Convert the stored type to the actual type, shift it left to insert
1696 // then 'or' into place.
1697 const Type *AllocaType = Old->getType();
1698 LLVMContext &Context = Old->getContext();
1700 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
1701 uint64_t VecSize = TD->getTypeAllocSizeInBits(VTy);
1702 uint64_t ValSize = TD->getTypeAllocSizeInBits(SV->getType());
1704 // Changing the whole vector with memset or with an access of a different
1706 if (ValSize == VecSize)
1707 return Builder.CreateBitCast(SV, AllocaType, "tmp");
1709 uint64_t EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1711 // Must be an element insertion.
1712 unsigned Elt = Offset/EltSize;
1714 if (SV->getType() != VTy->getElementType())
1715 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
1717 SV = Builder.CreateInsertElement(Old, SV,
1718 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt),
1723 // If SV is a first-class aggregate value, insert each value recursively.
1724 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
1725 const StructLayout &Layout = *TD->getStructLayout(ST);
1726 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1727 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1728 Old = ConvertScalar_InsertValue(Elt, Old,
1729 Offset+Layout.getElementOffsetInBits(i),
1735 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
1736 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1737 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1738 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1739 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
1744 // If SV is a float, convert it to the appropriate integer type.
1745 // If it is a pointer, do the same.
1746 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType());
1747 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType);
1748 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType());
1749 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType);
1750 if (SV->getType()->isFloatingPoint() || isa<VectorType>(SV->getType()))
1751 SV = Builder.CreateBitCast(SV,
1752 IntegerType::get(SV->getContext(),SrcWidth), "tmp");
1753 else if (isa<PointerType>(SV->getType()))
1754 SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(SV->getContext()), "tmp");
1756 // Zero extend or truncate the value if needed.
1757 if (SV->getType() != AllocaType) {
1758 if (SV->getType()->getPrimitiveSizeInBits() <
1759 AllocaType->getPrimitiveSizeInBits())
1760 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
1762 // Truncation may be needed if storing more than the alloca can hold
1763 // (undefined behavior).
1764 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
1765 SrcWidth = DestWidth;
1766 SrcStoreWidth = DestStoreWidth;
1770 // If this is a big-endian system and the store is narrower than the
1771 // full alloca type, we need to do a shift to get the right bits.
1773 if (TD->isBigEndian()) {
1774 // On big-endian machines, the lowest bit is stored at the bit offset
1775 // from the pointer given by getTypeStoreSizeInBits. This matters for
1776 // integers with a bitwidth that is not a multiple of 8.
1777 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
1782 // Note: we support negative bitwidths (with shr) which are not defined.
1783 // We do this to support (f.e.) stores off the end of a structure where
1784 // only some bits in the structure are set.
1785 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1786 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1787 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(),
1790 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1791 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(),
1793 Mask = Mask.lshr(-ShAmt);
1796 // Mask out the bits we are about to insert from the old value, and or
1798 if (SrcWidth != DestWidth) {
1799 assert(DestWidth > SrcWidth);
1800 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
1801 SV = Builder.CreateOr(Old, SV, "ins");
1808 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1809 /// some part of a constant global variable. This intentionally only accepts
1810 /// constant expressions because we don't can't rewrite arbitrary instructions.
1811 static bool PointsToConstantGlobal(Value *V) {
1812 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1813 return GV->isConstant();
1814 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1815 if (CE->getOpcode() == Instruction::BitCast ||
1816 CE->getOpcode() == Instruction::GetElementPtr)
1817 return PointsToConstantGlobal(CE->getOperand(0));
1821 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1822 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
1823 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
1824 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
1825 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1826 /// the alloca, and if the source pointer is a pointer to a constant global, we
1827 /// can optimize this.
1828 static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy,
1830 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1831 if (LoadInst *LI = dyn_cast<LoadInst>(*UI))
1832 // Ignore non-volatile loads, they are always ok.
1833 if (!LI->isVolatile())
1836 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) {
1837 // If uses of the bitcast are ok, we are ok.
1838 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
1842 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
1843 // If the GEP has all zero indices, it doesn't offset the pointer. If it
1844 // doesn't, it does.
1845 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
1846 isOffset || !GEP->hasAllZeroIndices()))
1851 // If this is isn't our memcpy/memmove, reject it as something we can't
1853 if (!isa<MemTransferInst>(*UI))
1856 // If we already have seen a copy, reject the second one.
1857 if (TheCopy) return false;
1859 // If the pointer has been offset from the start of the alloca, we can't
1860 // safely handle this.
1861 if (isOffset) return false;
1863 // If the memintrinsic isn't using the alloca as the dest, reject it.
1864 if (UI.getOperandNo() != 1) return false;
1866 MemIntrinsic *MI = cast<MemIntrinsic>(*UI);
1868 // If the source of the memcpy/move is not a constant global, reject it.
1869 if (!PointsToConstantGlobal(MI->getOperand(2)))
1872 // Otherwise, the transform is safe. Remember the copy instruction.
1878 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
1879 /// modified by a copy from a constant global. If we can prove this, we can
1880 /// replace any uses of the alloca with uses of the global directly.
1881 Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) {
1882 Instruction *TheCopy = 0;
1883 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))