1 //===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source 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/Pass.h"
31 #include "llvm/Analysis/Dominators.h"
32 #include "llvm/Target/TargetData.h"
33 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
34 #include "llvm/Support/Debug.h"
35 #include "llvm/Support/GetElementPtrTypeIterator.h"
36 #include "llvm/Support/MathExtras.h"
37 #include "llvm/Support/Compiler.h"
38 #include "llvm/ADT/SmallVector.h"
39 #include "llvm/ADT/Statistic.h"
40 #include "llvm/ADT/StringExtras.h"
43 STATISTIC(NumReplaced, "Number of allocas broken up");
44 STATISTIC(NumPromoted, "Number of allocas promoted");
45 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
46 STATISTIC(NumGlobals, "Number of allocas copied from constant global");
49 struct VISIBILITY_HIDDEN SROA : public FunctionPass {
50 static char ID; // Pass identification, replacement for typeid
51 SROA(signed T = -1) : FunctionPass((intptr_t)&ID) {
58 bool runOnFunction(Function &F);
60 bool performScalarRepl(Function &F);
61 bool performPromotion(Function &F);
63 // getAnalysisUsage - This pass does not require any passes, but we know it
64 // will not alter the CFG, so say so.
65 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
66 AU.addRequired<DominatorTree>();
67 AU.addRequired<DominanceFrontier>();
68 AU.addRequired<TargetData>();
73 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
74 /// information about the uses. All these fields are initialized to false
75 /// and set to true when something is learned.
77 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
80 /// needsCanon - This is set to true if there is some use of the alloca
81 /// that requires canonicalization.
84 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
87 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
91 : isUnsafe(false), needsCanon(false),
92 isMemCpySrc(false), isMemCpyDst(false) {}
97 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
99 int isSafeAllocaToScalarRepl(AllocationInst *AI);
101 void isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
103 void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
105 void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
106 unsigned OpNo, AllocaInfo &Info);
107 void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocationInst *AI,
110 void DoScalarReplacement(AllocationInst *AI,
111 std::vector<AllocationInst*> &WorkList);
112 void CanonicalizeAllocaUsers(AllocationInst *AI);
113 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base);
115 void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
116 SmallVector<AllocaInst*, 32> &NewElts);
118 const Type *CanConvertToScalar(Value *V, bool &IsNotTrivial);
119 void ConvertToScalar(AllocationInst *AI, const Type *Ty);
120 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset);
121 static Instruction *isOnlyCopiedFromConstantGlobal(AllocationInst *AI);
125 RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates");
128 // Public interface to the ScalarReplAggregates pass
129 FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) {
130 return new SROA(Threshold);
134 bool SROA::runOnFunction(Function &F) {
135 bool Changed = performPromotion(F);
137 bool LocalChange = performScalarRepl(F);
138 if (!LocalChange) break; // No need to repromote if no scalarrepl
140 LocalChange = performPromotion(F);
141 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
148 bool SROA::performPromotion(Function &F) {
149 std::vector<AllocaInst*> Allocas;
150 DominatorTree &DT = getAnalysis<DominatorTree>();
151 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
153 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
155 bool Changed = false;
160 // Find allocas that are safe to promote, by looking at all instructions in
162 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
163 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
164 if (isAllocaPromotable(AI))
165 Allocas.push_back(AI);
167 if (Allocas.empty()) break;
169 PromoteMemToReg(Allocas, DT, DF);
170 NumPromoted += Allocas.size();
177 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
178 // which runs on all of the malloc/alloca instructions in the function, removing
179 // them if they are only used by getelementptr instructions.
181 bool SROA::performScalarRepl(Function &F) {
182 std::vector<AllocationInst*> WorkList;
184 // Scan the entry basic block, adding any alloca's and mallocs to the worklist
185 BasicBlock &BB = F.getEntryBlock();
186 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
187 if (AllocationInst *A = dyn_cast<AllocationInst>(I))
188 WorkList.push_back(A);
190 const TargetData &TD = getAnalysis<TargetData>();
192 // Process the worklist
193 bool Changed = false;
194 while (!WorkList.empty()) {
195 AllocationInst *AI = WorkList.back();
198 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
199 // with unused elements.
200 if (AI->use_empty()) {
201 AI->eraseFromParent();
205 // If we can turn this aggregate value (potentially with casts) into a
206 // simple scalar value that can be mem2reg'd into a register value.
207 bool IsNotTrivial = false;
208 if (const Type *ActualType = CanConvertToScalar(AI, IsNotTrivial))
209 if (IsNotTrivial && ActualType != Type::VoidTy) {
210 ConvertToScalar(AI, ActualType);
215 // Check to see if we can perform the core SROA transformation. We cannot
216 // transform the allocation instruction if it is an array allocation
217 // (allocations OF arrays are ok though), and an allocation of a scalar
218 // value cannot be decomposed at all.
219 if (!AI->isArrayAllocation() &&
220 (isa<StructType>(AI->getAllocatedType()) ||
221 isa<ArrayType>(AI->getAllocatedType())) &&
222 AI->getAllocatedType()->isSized() &&
223 TD.getTypeSize(AI->getAllocatedType()) < SRThreshold) {
224 // Check that all of the users of the allocation are capable of being
226 switch (isSafeAllocaToScalarRepl(AI)) {
227 default: assert(0 && "Unexpected value!");
228 case 0: // Not safe to scalar replace.
230 case 1: // Safe, but requires cleanup/canonicalizations first
231 CanonicalizeAllocaUsers(AI);
233 case 3: // Safe to scalar replace.
234 DoScalarReplacement(AI, WorkList);
240 // Check to see if this allocation is only modified by a memcpy/memmove from
241 // a constant global. If this is the case, we can change all users to use
242 // the constant global instead. This is commonly produced by the CFE by
243 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
244 // is only subsequently read.
245 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
246 DOUT << "Found alloca equal to global: " << *AI;
247 DOUT << " memcpy = " << *TheCopy;
248 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2));
249 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
250 TheCopy->eraseFromParent(); // Don't mutate the global.
251 AI->eraseFromParent();
257 // Otherwise, couldn't process this.
263 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
264 /// predicate, do SROA now.
265 void SROA::DoScalarReplacement(AllocationInst *AI,
266 std::vector<AllocationInst*> &WorkList) {
267 DOUT << "Found inst to SROA: " << *AI;
268 SmallVector<AllocaInst*, 32> ElementAllocas;
269 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
270 ElementAllocas.reserve(ST->getNumContainedTypes());
271 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
272 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
274 AI->getName() + "." + utostr(i), AI);
275 ElementAllocas.push_back(NA);
276 WorkList.push_back(NA); // Add to worklist for recursive processing
279 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
280 ElementAllocas.reserve(AT->getNumElements());
281 const Type *ElTy = AT->getElementType();
282 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
283 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
284 AI->getName() + "." + utostr(i), AI);
285 ElementAllocas.push_back(NA);
286 WorkList.push_back(NA); // Add to worklist for recursive processing
290 // Now that we have created the alloca instructions that we want to use,
291 // expand the getelementptr instructions to use them.
293 while (!AI->use_empty()) {
294 Instruction *User = cast<Instruction>(AI->use_back());
295 if (BitCastInst *BCInst = dyn_cast<BitCastInst>(User)) {
296 RewriteBitCastUserOfAlloca(BCInst, AI, ElementAllocas);
297 BCInst->eraseFromParent();
301 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User);
302 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst>
304 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
306 assert(Idx < ElementAllocas.size() && "Index out of range?");
307 AllocaInst *AllocaToUse = ElementAllocas[Idx];
310 if (GEPI->getNumOperands() == 3) {
311 // Do not insert a new getelementptr instruction with zero indices, only
312 // to have it optimized out later.
313 RepValue = AllocaToUse;
315 // We are indexing deeply into the structure, so we still need a
316 // getelement ptr instruction to finish the indexing. This may be
317 // expanded itself once the worklist is rerun.
319 SmallVector<Value*, 8> NewArgs;
320 NewArgs.push_back(Constant::getNullValue(Type::Int32Ty));
321 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end());
322 RepValue = new GetElementPtrInst(AllocaToUse, &NewArgs[0],
323 NewArgs.size(), "", GEPI);
324 RepValue->takeName(GEPI);
327 // If this GEP is to the start of the aggregate, check for memcpys.
329 bool IsStartOfAggregateGEP = true;
330 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i) {
331 if (!isa<ConstantInt>(GEPI->getOperand(i))) {
332 IsStartOfAggregateGEP = false;
335 if (!cast<ConstantInt>(GEPI->getOperand(i))->isZero()) {
336 IsStartOfAggregateGEP = false;
341 if (IsStartOfAggregateGEP)
342 RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas);
346 // Move all of the users over to the new GEP.
347 GEPI->replaceAllUsesWith(RepValue);
348 // Delete the old GEP
349 GEPI->eraseFromParent();
352 // Finally, delete the Alloca instruction
353 AI->eraseFromParent();
358 /// isSafeElementUse - Check to see if this use is an allowed use for a
359 /// getelementptr instruction of an array aggregate allocation. isFirstElt
360 /// indicates whether Ptr is known to the start of the aggregate.
362 void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
364 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
366 Instruction *User = cast<Instruction>(*I);
367 switch (User->getOpcode()) {
368 case Instruction::Load: break;
369 case Instruction::Store:
370 // Store is ok if storing INTO the pointer, not storing the pointer
371 if (User->getOperand(0) == Ptr) return MarkUnsafe(Info);
373 case Instruction::GetElementPtr: {
374 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User);
375 bool AreAllZeroIndices = isFirstElt;
376 if (GEP->getNumOperands() > 1) {
377 if (!isa<ConstantInt>(GEP->getOperand(1)) ||
378 !cast<ConstantInt>(GEP->getOperand(1))->isZero())
379 // Using pointer arithmetic to navigate the array.
380 return MarkUnsafe(Info);
382 if (AreAllZeroIndices) {
383 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i) {
384 if (!isa<ConstantInt>(GEP->getOperand(i)) ||
385 !cast<ConstantInt>(GEP->getOperand(i))->isZero()) {
386 AreAllZeroIndices = false;
392 isSafeElementUse(GEP, AreAllZeroIndices, AI, Info);
393 if (Info.isUnsafe) return;
396 case Instruction::BitCast:
398 isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info);
399 if (Info.isUnsafe) return;
402 DOUT << " Transformation preventing inst: " << *User;
403 return MarkUnsafe(Info);
404 case Instruction::Call:
405 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
407 isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info);
408 if (Info.isUnsafe) return;
412 DOUT << " Transformation preventing inst: " << *User;
413 return MarkUnsafe(Info);
415 DOUT << " Transformation preventing inst: " << *User;
416 return MarkUnsafe(Info);
419 return; // All users look ok :)
422 /// AllUsersAreLoads - Return true if all users of this value are loads.
423 static bool AllUsersAreLoads(Value *Ptr) {
424 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
426 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load)
431 /// isSafeUseOfAllocation - Check to see if this user is an allowed use for an
432 /// aggregate allocation.
434 void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
436 if (BitCastInst *C = dyn_cast<BitCastInst>(User))
437 return isSafeUseOfBitCastedAllocation(C, AI, Info);
439 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User);
441 return MarkUnsafe(Info);
443 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI);
445 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>".
447 I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) {
448 return MarkUnsafe(Info);
452 if (I == E) return MarkUnsafe(Info); // ran out of GEP indices??
454 bool IsAllZeroIndices = true;
456 // If this is a use of an array allocation, do a bit more checking for sanity.
457 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
458 uint64_t NumElements = AT->getNumElements();
460 if (ConstantInt *Idx = dyn_cast<ConstantInt>(I.getOperand())) {
461 IsAllZeroIndices &= Idx->isZero();
463 // Check to make sure that index falls within the array. If not,
464 // something funny is going on, so we won't do the optimization.
466 if (Idx->getZExtValue() >= NumElements)
467 return MarkUnsafe(Info);
469 // We cannot scalar repl this level of the array unless any array
470 // sub-indices are in-range constants. In particular, consider:
471 // A[0][i]. We cannot know that the user isn't doing invalid things like
472 // allowing i to index an out-of-range subscript that accesses A[1].
474 // Scalar replacing *just* the outer index of the array is probably not
475 // going to be a win anyway, so just give up.
476 for (++I; I != E && (isa<ArrayType>(*I) || isa<VectorType>(*I)); ++I) {
477 uint64_t NumElements;
478 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*I))
479 NumElements = SubArrayTy->getNumElements();
481 NumElements = cast<VectorType>(*I)->getNumElements();
483 ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand());
484 if (!IdxVal) return MarkUnsafe(Info);
485 if (IdxVal->getZExtValue() >= NumElements)
486 return MarkUnsafe(Info);
487 IsAllZeroIndices &= IdxVal->isZero();
491 IsAllZeroIndices = 0;
493 // If this is an array index and the index is not constant, we cannot
494 // promote... that is unless the array has exactly one or two elements in
495 // it, in which case we CAN promote it, but we have to canonicalize this
496 // out if this is the only problem.
497 if ((NumElements == 1 || NumElements == 2) &&
498 AllUsersAreLoads(GEPI)) {
499 Info.needsCanon = true;
500 return; // Canonicalization required!
502 return MarkUnsafe(Info);
506 // If there are any non-simple uses of this getelementptr, make sure to reject
508 return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info);
511 /// isSafeMemIntrinsicOnAllocation - Return true if the specified memory
512 /// intrinsic can be promoted by SROA. At this point, we know that the operand
513 /// of the memintrinsic is a pointer to the beginning of the allocation.
514 void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
515 unsigned OpNo, AllocaInfo &Info) {
516 // If not constant length, give up.
517 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
518 if (!Length) return MarkUnsafe(Info);
520 // If not the whole aggregate, give up.
521 const TargetData &TD = getAnalysis<TargetData>();
522 if (Length->getZExtValue() != TD.getTypeSize(AI->getType()->getElementType()))
523 return MarkUnsafe(Info);
525 // We only know about memcpy/memset/memmove.
526 if (!isa<MemCpyInst>(MI) && !isa<MemSetInst>(MI) && !isa<MemMoveInst>(MI))
527 return MarkUnsafe(Info);
529 // Otherwise, we can transform it. Determine whether this is a memcpy/set
530 // into or out of the aggregate.
532 Info.isMemCpyDst = true;
535 Info.isMemCpySrc = true;
539 /// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast
541 void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI,
543 for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end();
545 if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) {
546 isSafeUseOfBitCastedAllocation(BCU, AI, Info);
547 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) {
548 isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info);
550 return MarkUnsafe(Info);
552 if (Info.isUnsafe) return;
556 /// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes
557 /// to its first element. Transform users of the cast to use the new values
559 void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
560 SmallVector<AllocaInst*, 32> &NewElts) {
561 Constant *Zero = Constant::getNullValue(Type::Int32Ty);
562 const TargetData &TD = getAnalysis<TargetData>();
564 Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end();
566 if (BitCastInst *BCU = dyn_cast<BitCastInst>(*UI)) {
567 RewriteBitCastUserOfAlloca(BCU, AI, NewElts);
569 BCU->eraseFromParent();
573 // Otherwise, must be memcpy/memmove/memset of the entire aggregate. Split
574 // into one per element.
575 MemIntrinsic *MI = dyn_cast<MemIntrinsic>(*UI);
577 // If it's not a mem intrinsic, it must be some other user of a gep of the
578 // first pointer. Just leave these alone.
584 // If this is a memcpy/memmove, construct the other pointer as the
587 if (MemCpyInst *MCI = dyn_cast<MemCpyInst>(MI)) {
588 if (BCInst == MCI->getRawDest())
589 OtherPtr = MCI->getRawSource();
591 assert(BCInst == MCI->getRawSource());
592 OtherPtr = MCI->getRawDest();
594 } else if (MemMoveInst *MMI = dyn_cast<MemMoveInst>(MI)) {
595 if (BCInst == MMI->getRawDest())
596 OtherPtr = MMI->getRawSource();
598 assert(BCInst == MMI->getRawSource());
599 OtherPtr = MMI->getRawDest();
603 // If there is an other pointer, we want to convert it to the same pointer
604 // type as AI has, so we can GEP through it.
606 // It is likely that OtherPtr is a bitcast, if so, remove it.
607 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr))
608 OtherPtr = BC->getOperand(0);
609 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr))
610 if (BCE->getOpcode() == Instruction::BitCast)
611 OtherPtr = BCE->getOperand(0);
613 // If the pointer is not the right type, insert a bitcast to the right
615 if (OtherPtr->getType() != AI->getType())
616 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(),
620 // Process each element of the aggregate.
621 Value *TheFn = MI->getOperand(0);
622 const Type *BytePtrTy = MI->getRawDest()->getType();
623 bool SROADest = MI->getRawDest() == BCInst;
625 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
626 // If this is a memcpy/memmove, emit a GEP of the other element address.
629 OtherElt = new GetElementPtrInst(OtherPtr, Zero,
630 ConstantInt::get(Type::Int32Ty, i),
631 OtherPtr->getNameStr()+"."+utostr(i),
635 Value *EltPtr = NewElts[i];
636 const Type *EltTy =cast<PointerType>(EltPtr->getType())->getElementType();
638 // If we got down to a scalar, insert a load or store as appropriate.
639 if (EltTy->isFirstClassType()) {
640 if (isa<MemCpyInst>(MI) || isa<MemMoveInst>(MI)) {
641 Value *Elt = new LoadInst(SROADest ? OtherElt : EltPtr, "tmp",
643 new StoreInst(Elt, SROADest ? EltPtr : OtherElt, MI);
646 assert(isa<MemSetInst>(MI));
648 // If the stored element is zero (common case), just store a null
651 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) {
653 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
655 // If EltTy is a vector type, get the element type.
656 const Type *ValTy = EltTy;
657 if (const VectorType *VTy = dyn_cast<VectorType>(ValTy))
658 ValTy = VTy->getElementType();
660 // Construct an integer with the right value.
661 unsigned EltSize = TD.getTypeSize(ValTy);
662 APInt OneVal(EltSize*8, CI->getZExtValue());
663 APInt TotalVal(OneVal);
665 for (unsigned i = 0; i != EltSize-1; ++i) {
666 TotalVal = TotalVal.shl(8);
670 // Convert the integer value to the appropriate type.
671 StoreVal = ConstantInt::get(TotalVal);
672 if (isa<PointerType>(ValTy))
673 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
674 else if (ValTy->isFloatingPoint())
675 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
676 assert(StoreVal->getType() == ValTy && "Type mismatch!");
678 // If the requested value was a vector constant, create it.
679 if (EltTy != ValTy) {
680 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
681 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
682 StoreVal = ConstantVector::get(&Elts[0], NumElts);
685 new StoreInst(StoreVal, EltPtr, MI);
688 // Otherwise, if we're storing a byte variable, use a memset call for
693 // Cast the element pointer to BytePtrTy.
694 if (EltPtr->getType() != BytePtrTy)
695 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI);
697 // Cast the other pointer (if we have one) to BytePtrTy.
698 if (OtherElt && OtherElt->getType() != BytePtrTy)
699 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(),
702 unsigned EltSize = TD.getTypeSize(EltTy);
704 // Finally, insert the meminst for this element.
705 if (isa<MemCpyInst>(MI) || isa<MemMoveInst>(MI)) {
707 SROADest ? EltPtr : OtherElt, // Dest ptr
708 SROADest ? OtherElt : EltPtr, // Src ptr
709 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
712 new CallInst(TheFn, Ops, 4, "", MI);
714 assert(isa<MemSetInst>(MI));
716 EltPtr, MI->getOperand(2), // Dest, Value,
717 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
720 new CallInst(TheFn, Ops, 4, "", MI);
724 // Finally, MI is now dead, as we've modified its actions to occur on all of
725 // the elements of the aggregate.
727 MI->eraseFromParent();
731 /// HasStructPadding - Return true if the specified type has any structure
732 /// padding, false otherwise.
733 static bool HasStructPadding(const Type *Ty, const TargetData &TD) {
734 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
735 const StructLayout *SL = TD.getStructLayout(STy);
736 unsigned PrevFieldBitOffset = 0;
737 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
738 unsigned FieldBitOffset = SL->getElementOffset(i)*8;
740 // Padding in sub-elements?
741 if (HasStructPadding(STy->getElementType(i), TD))
744 // Check to see if there is any padding between this element and the
747 unsigned PrevFieldEnd =
748 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
749 if (PrevFieldEnd < FieldBitOffset)
753 PrevFieldBitOffset = FieldBitOffset;
756 // Check for tail padding.
757 if (unsigned EltCount = STy->getNumElements()) {
758 unsigned PrevFieldEnd = PrevFieldBitOffset +
759 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
760 if (PrevFieldEnd < SL->getSizeInBytes()*8)
764 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
765 return HasStructPadding(ATy->getElementType(), TD);
770 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
771 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
772 /// or 1 if safe after canonicalization has been performed.
774 int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) {
775 // Loop over the use list of the alloca. We can only transform it if all of
776 // the users are safe to transform.
779 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end();
781 isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info);
783 DOUT << "Cannot transform: " << *AI << " due to user: " << **I;
788 // Okay, we know all the users are promotable. If the aggregate is a memcpy
789 // source and destination, we have to be careful. In particular, the memcpy
790 // could be moving around elements that live in structure padding of the LLVM
791 // types, but may actually be used. In these cases, we refuse to promote the
793 if (Info.isMemCpySrc && Info.isMemCpyDst &&
794 HasStructPadding(AI->getType()->getElementType(),
795 getAnalysis<TargetData>()))
798 // If we require cleanup, return 1, otherwise return 3.
799 return Info.needsCanon ? 1 : 3;
802 /// CanonicalizeAllocaUsers - If SROA reported that it can promote the specified
803 /// allocation, but only if cleaned up, perform the cleanups required.
804 void SROA::CanonicalizeAllocaUsers(AllocationInst *AI) {
805 // At this point, we know that the end result will be SROA'd and promoted, so
806 // we can insert ugly code if required so long as sroa+mem2reg will clean it
808 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
810 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI++);
812 gep_type_iterator I = gep_type_begin(GEPI);
815 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
816 uint64_t NumElements = AT->getNumElements();
818 if (!isa<ConstantInt>(I.getOperand())) {
819 if (NumElements == 1) {
820 GEPI->setOperand(2, Constant::getNullValue(Type::Int32Ty));
822 assert(NumElements == 2 && "Unhandled case!");
823 // All users of the GEP must be loads. At each use of the GEP, insert
824 // two loads of the appropriate indexed GEP and select between them.
825 Value *IsOne = new ICmpInst(ICmpInst::ICMP_NE, I.getOperand(),
826 Constant::getNullValue(I.getOperand()->getType()),
828 // Insert the new GEP instructions, which are properly indexed.
829 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end());
830 Indices[1] = Constant::getNullValue(Type::Int32Ty);
831 Value *ZeroIdx = new GetElementPtrInst(GEPI->getOperand(0),
832 &Indices[0], Indices.size(),
833 GEPI->getName()+".0", GEPI);
834 Indices[1] = ConstantInt::get(Type::Int32Ty, 1);
835 Value *OneIdx = new GetElementPtrInst(GEPI->getOperand(0),
836 &Indices[0], Indices.size(),
837 GEPI->getName()+".1", GEPI);
838 // Replace all loads of the variable index GEP with loads from both
839 // indexes and a select.
840 while (!GEPI->use_empty()) {
841 LoadInst *LI = cast<LoadInst>(GEPI->use_back());
842 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI);
843 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI);
844 Value *R = new SelectInst(IsOne, One, Zero, LI->getName(), LI);
845 LI->replaceAllUsesWith(R);
846 LI->eraseFromParent();
848 GEPI->eraseFromParent();
855 /// MergeInType - Add the 'In' type to the accumulated type so far. If the
856 /// types are incompatible, return true, otherwise update Accum and return
859 /// There are three cases we handle here:
860 /// 1) An effectively-integer union, where the pieces are stored into as
861 /// smaller integers (common with byte swap and other idioms).
862 /// 2) A union of vector types of the same size and potentially its elements.
863 /// Here we turn element accesses into insert/extract element operations.
864 /// 3) A union of scalar types, such as int/float or int/pointer. Here we
865 /// merge together into integers, allowing the xform to work with #1 as
867 static bool MergeInType(const Type *In, const Type *&Accum,
868 const TargetData &TD) {
869 // If this is our first type, just use it.
870 const VectorType *PTy;
871 if (Accum == Type::VoidTy || In == Accum) {
873 } else if (In == Type::VoidTy) {
875 } else if (In->isInteger() && Accum->isInteger()) { // integer union.
876 // Otherwise pick whichever type is larger.
877 if (cast<IntegerType>(In)->getBitWidth() >
878 cast<IntegerType>(Accum)->getBitWidth())
880 } else if (isa<PointerType>(In) && isa<PointerType>(Accum)) {
881 // Pointer unions just stay as one of the pointers.
882 } else if (isa<VectorType>(In) || isa<VectorType>(Accum)) {
883 if ((PTy = dyn_cast<VectorType>(Accum)) &&
884 PTy->getElementType() == In) {
885 // Accum is a vector, and we are accessing an element: ok.
886 } else if ((PTy = dyn_cast<VectorType>(In)) &&
887 PTy->getElementType() == Accum) {
888 // In is a vector, and accum is an element: ok, remember In.
890 } else if ((PTy = dyn_cast<VectorType>(In)) && isa<VectorType>(Accum) &&
891 PTy->getBitWidth() == cast<VectorType>(Accum)->getBitWidth()) {
892 // Two vectors of the same size: keep Accum.
894 // Cannot insert an short into a <4 x int> or handle
895 // <2 x int> -> <4 x int>
899 // Pointer/FP/Integer unions merge together as integers.
900 switch (Accum->getTypeID()) {
901 case Type::PointerTyID: Accum = TD.getIntPtrType(); break;
902 case Type::FloatTyID: Accum = Type::Int32Ty; break;
903 case Type::DoubleTyID: Accum = Type::Int64Ty; break;
905 assert(Accum->isInteger() && "Unknown FP type!");
909 switch (In->getTypeID()) {
910 case Type::PointerTyID: In = TD.getIntPtrType(); break;
911 case Type::FloatTyID: In = Type::Int32Ty; break;
912 case Type::DoubleTyID: In = Type::Int64Ty; break;
914 assert(In->isInteger() && "Unknown FP type!");
917 return MergeInType(In, Accum, TD);
922 /// getUIntAtLeastAsBitAs - Return an unsigned integer type that is at least
923 /// as big as the specified type. If there is no suitable type, this returns
925 const Type *getUIntAtLeastAsBitAs(unsigned NumBits) {
926 if (NumBits > 64) return 0;
927 if (NumBits > 32) return Type::Int64Ty;
928 if (NumBits > 16) return Type::Int32Ty;
929 if (NumBits > 8) return Type::Int16Ty;
933 /// CanConvertToScalar - V is a pointer. If we can convert the pointee to a
934 /// single scalar integer type, return that type. Further, if the use is not
935 /// a completely trivial use that mem2reg could promote, set IsNotTrivial. If
936 /// there are no uses of this pointer, return Type::VoidTy to differentiate from
939 const Type *SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial) {
940 const Type *UsedType = Type::VoidTy; // No uses, no forced type.
941 const TargetData &TD = getAnalysis<TargetData>();
942 const PointerType *PTy = cast<PointerType>(V->getType());
944 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
945 Instruction *User = cast<Instruction>(*UI);
947 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
948 if (MergeInType(LI->getType(), UsedType, TD))
951 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
952 // Storing the pointer, not into the value?
953 if (SI->getOperand(0) == V) return 0;
955 // NOTE: We could handle storing of FP imms into integers here!
957 if (MergeInType(SI->getOperand(0)->getType(), UsedType, TD))
959 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
961 const Type *SubTy = CanConvertToScalar(CI, IsNotTrivial);
962 if (!SubTy || MergeInType(SubTy, UsedType, TD)) return 0;
963 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
964 // Check to see if this is stepping over an element: GEP Ptr, int C
965 if (GEP->getNumOperands() == 2 && isa<ConstantInt>(GEP->getOperand(1))) {
966 unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getZExtValue();
967 unsigned ElSize = TD.getTypeSize(PTy->getElementType());
968 unsigned BitOffset = Idx*ElSize*8;
969 if (BitOffset > 64 || !isPowerOf2_32(ElSize)) return 0;
972 const Type *SubElt = CanConvertToScalar(GEP, IsNotTrivial);
973 if (SubElt == 0) return 0;
974 if (SubElt != Type::VoidTy && SubElt->isInteger()) {
976 getUIntAtLeastAsBitAs(TD.getTypeSize(SubElt)*8+BitOffset);
977 if (NewTy == 0 || MergeInType(NewTy, UsedType, TD)) return 0;
980 } else if (GEP->getNumOperands() == 3 &&
981 isa<ConstantInt>(GEP->getOperand(1)) &&
982 isa<ConstantInt>(GEP->getOperand(2)) &&
983 cast<ConstantInt>(GEP->getOperand(1))->isZero()) {
984 // We are stepping into an element, e.g. a structure or an array:
985 // GEP Ptr, int 0, uint C
986 const Type *AggTy = PTy->getElementType();
987 unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
989 if (const ArrayType *ATy = dyn_cast<ArrayType>(AggTy)) {
990 if (Idx >= ATy->getNumElements()) return 0; // Out of range.
991 } else if (const VectorType *VectorTy = dyn_cast<VectorType>(AggTy)) {
992 // Getting an element of the vector.
993 if (Idx >= VectorTy->getNumElements()) return 0; // Out of range.
995 // Merge in the vector type.
996 if (MergeInType(VectorTy, UsedType, TD)) return 0;
998 const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial);
999 if (SubTy == 0) return 0;
1001 if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, TD))
1004 // We'll need to change this to an insert/extract element operation.
1005 IsNotTrivial = true;
1006 continue; // Everything looks ok
1008 } else if (isa<StructType>(AggTy)) {
1009 // Structs are always ok.
1013 const Type *NTy = getUIntAtLeastAsBitAs(TD.getTypeSize(AggTy)*8);
1014 if (NTy == 0 || MergeInType(NTy, UsedType, TD)) return 0;
1015 const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial);
1016 if (SubTy == 0) return 0;
1017 if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, TD))
1019 continue; // Everything looks ok
1023 // Cannot handle this!
1031 /// ConvertToScalar - The specified alloca passes the CanConvertToScalar
1032 /// predicate and is non-trivial. Convert it to something that can be trivially
1033 /// promoted into a register by mem2reg.
1034 void SROA::ConvertToScalar(AllocationInst *AI, const Type *ActualTy) {
1035 DOUT << "CONVERT TO SCALAR: " << *AI << " TYPE = "
1036 << *ActualTy << "\n";
1039 BasicBlock *EntryBlock = AI->getParent();
1040 assert(EntryBlock == &EntryBlock->getParent()->getEntryBlock() &&
1041 "Not in the entry block!");
1042 EntryBlock->getInstList().remove(AI); // Take the alloca out of the program.
1044 // Create and insert the alloca.
1045 AllocaInst *NewAI = new AllocaInst(ActualTy, 0, AI->getName(),
1046 EntryBlock->begin());
1047 ConvertUsesToScalar(AI, NewAI, 0);
1052 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
1053 /// directly. This happens when we are converting an "integer union" to a
1054 /// single integer scalar, or when we are converting a "vector union" to a
1055 /// vector with insert/extractelement instructions.
1057 /// Offset is an offset from the original alloca, in bits that need to be
1058 /// shifted to the right. By the end of this, there should be no uses of Ptr.
1059 void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset) {
1060 const TargetData &TD = getAnalysis<TargetData>();
1061 while (!Ptr->use_empty()) {
1062 Instruction *User = cast<Instruction>(Ptr->use_back());
1064 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1065 // The load is a bit extract from NewAI shifted right by Offset bits.
1066 Value *NV = new LoadInst(NewAI, LI->getName(), LI);
1067 if (NV->getType() == LI->getType()) {
1068 // We win, no conversion needed.
1069 } else if (const VectorType *PTy = dyn_cast<VectorType>(NV->getType())) {
1070 // If the result alloca is a vector type, this is either an element
1071 // access or a bitcast to another vector type.
1072 if (isa<VectorType>(LI->getType())) {
1073 NV = new BitCastInst(NV, LI->getType(), LI->getName(), LI);
1075 // Must be an element access.
1076 unsigned Elt = Offset/(TD.getTypeSize(PTy->getElementType())*8);
1077 NV = new ExtractElementInst(
1078 NV, ConstantInt::get(Type::Int32Ty, Elt), "tmp", LI);
1080 } else if (isa<PointerType>(NV->getType())) {
1081 assert(isa<PointerType>(LI->getType()));
1082 // Must be ptr->ptr cast. Anything else would result in NV being
1084 NV = new BitCastInst(NV, LI->getType(), LI->getName(), LI);
1086 const IntegerType *NTy = cast<IntegerType>(NV->getType());
1087 unsigned LIBitWidth = TD.getTypeSizeInBits(LI->getType());
1089 // If this is a big-endian system and the load is narrower than the
1090 // full alloca type, we need to do a shift to get the right bits.
1092 if (TD.isBigEndian()) {
1093 ShAmt = NTy->getBitWidth()-LIBitWidth-Offset;
1098 // Note: we support negative bitwidths (with shl) which are not defined.
1099 // We do this to support (f.e.) loads off the end of a structure where
1100 // only some bits are used.
1101 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
1102 NV = BinaryOperator::createLShr(NV,
1103 ConstantInt::get(NV->getType(),ShAmt),
1105 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
1106 NV = BinaryOperator::createShl(NV,
1107 ConstantInt::get(NV->getType(),-ShAmt),
1110 // Finally, unconditionally truncate the integer to the right width.
1111 if (LIBitWidth < NTy->getBitWidth())
1112 NV = new TruncInst(NV, IntegerType::get(LIBitWidth),
1115 // If the result is an integer, this is a trunc or bitcast.
1116 if (isa<IntegerType>(LI->getType())) {
1117 assert(NV->getType() == LI->getType() && "Truncate wasn't enough?");
1118 } else if (LI->getType()->isFloatingPoint()) {
1119 // Just do a bitcast, we know the sizes match up.
1120 NV = new BitCastInst(NV, LI->getType(), LI->getName(), LI);
1122 // Otherwise must be a pointer.
1123 NV = new IntToPtrInst(NV, LI->getType(), LI->getName(), LI);
1126 LI->replaceAllUsesWith(NV);
1127 LI->eraseFromParent();
1128 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1129 assert(SI->getOperand(0) != Ptr && "Consistency error!");
1131 // Convert the stored type to the actual type, shift it left to insert
1132 // then 'or' into place.
1133 Value *SV = SI->getOperand(0);
1134 const Type *AllocaType = NewAI->getType()->getElementType();
1135 if (SV->getType() == AllocaType) {
1137 } else if (const VectorType *PTy = dyn_cast<VectorType>(AllocaType)) {
1138 Value *Old = new LoadInst(NewAI, NewAI->getName()+".in", SI);
1140 // If the result alloca is a vector type, this is either an element
1141 // access or a bitcast to another vector type.
1142 if (isa<VectorType>(SV->getType())) {
1143 SV = new BitCastInst(SV, AllocaType, SV->getName(), SI);
1145 // Must be an element insertion.
1146 unsigned Elt = Offset/(TD.getTypeSize(PTy->getElementType())*8);
1147 SV = new InsertElementInst(Old, SV,
1148 ConstantInt::get(Type::Int32Ty, Elt),
1151 } else if (isa<PointerType>(AllocaType)) {
1152 // If the alloca type is a pointer, then all the elements must be
1154 if (SV->getType() != AllocaType)
1155 SV = new BitCastInst(SV, AllocaType, SV->getName(), SI);
1157 Value *Old = new LoadInst(NewAI, NewAI->getName()+".in", SI);
1159 // If SV is a float, convert it to the appropriate integer type.
1160 // If it is a pointer, do the same, and also handle ptr->ptr casts
1162 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType());
1163 unsigned DestWidth = AllocaType->getPrimitiveSizeInBits();
1164 if (SV->getType()->isFloatingPoint())
1165 SV = new BitCastInst(SV, IntegerType::get(SrcWidth),
1167 else if (isa<PointerType>(SV->getType()))
1168 SV = new PtrToIntInst(SV, TD.getIntPtrType(), SV->getName(), SI);
1170 // Always zero extend the value if needed.
1171 if (SV->getType() != AllocaType)
1172 SV = new ZExtInst(SV, AllocaType, SV->getName(), SI);
1174 // If this is a big-endian system and the store is narrower than the
1175 // full alloca type, we need to do a shift to get the right bits.
1177 if (TD.isBigEndian()) {
1178 ShAmt = DestWidth-SrcWidth-Offset;
1183 // Note: we support negative bitwidths (with shr) which are not defined.
1184 // We do this to support (f.e.) stores off the end of a structure where
1185 // only some bits in the structure are set.
1186 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1187 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1188 SV = BinaryOperator::createShl(SV,
1189 ConstantInt::get(SV->getType(), ShAmt),
1192 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1193 SV = BinaryOperator::createLShr(SV,
1194 ConstantInt::get(SV->getType(),-ShAmt),
1196 Mask = Mask.lshr(ShAmt);
1199 // Mask out the bits we are about to insert from the old value, and or
1201 if (SrcWidth != DestWidth) {
1202 assert(DestWidth > SrcWidth);
1203 Old = BinaryOperator::createAnd(Old, ConstantInt::get(~Mask),
1204 Old->getName()+".mask", SI);
1205 SV = BinaryOperator::createOr(Old, SV, SV->getName()+".ins", SI);
1208 new StoreInst(SV, NewAI, SI);
1209 SI->eraseFromParent();
1211 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
1212 ConvertUsesToScalar(CI, NewAI, Offset);
1213 CI->eraseFromParent();
1214 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1215 const PointerType *AggPtrTy =
1216 cast<PointerType>(GEP->getOperand(0)->getType());
1217 const TargetData &TD = getAnalysis<TargetData>();
1218 unsigned AggSizeInBits = TD.getTypeSize(AggPtrTy->getElementType())*8;
1220 // Check to see if this is stepping over an element: GEP Ptr, int C
1221 unsigned NewOffset = Offset;
1222 if (GEP->getNumOperands() == 2) {
1223 unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getZExtValue();
1224 unsigned BitOffset = Idx*AggSizeInBits;
1226 NewOffset += BitOffset;
1227 } else if (GEP->getNumOperands() == 3) {
1228 // We know that operand #2 is zero.
1229 unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
1230 const Type *AggTy = AggPtrTy->getElementType();
1231 if (const SequentialType *SeqTy = dyn_cast<SequentialType>(AggTy)) {
1232 unsigned ElSizeBits = TD.getTypeSize(SeqTy->getElementType())*8;
1234 NewOffset += ElSizeBits*Idx;
1235 } else if (const StructType *STy = dyn_cast<StructType>(AggTy)) {
1236 unsigned EltBitOffset =
1237 TD.getStructLayout(STy)->getElementOffset(Idx)*8;
1239 NewOffset += EltBitOffset;
1241 assert(0 && "Unsupported operation!");
1245 assert(0 && "Unsupported operation!");
1248 ConvertUsesToScalar(GEP, NewAI, NewOffset);
1249 GEP->eraseFromParent();
1251 assert(0 && "Unsupported operation!");
1258 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1259 /// some part of a constant global variable. This intentionally only accepts
1260 /// constant expressions because we don't can't rewrite arbitrary instructions.
1261 static bool PointsToConstantGlobal(Value *V) {
1262 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1263 return GV->isConstant();
1264 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1265 if (CE->getOpcode() == Instruction::BitCast ||
1266 CE->getOpcode() == Instruction::GetElementPtr)
1267 return PointsToConstantGlobal(CE->getOperand(0));
1271 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1272 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
1273 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
1274 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
1275 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1276 /// the alloca, and if the source pointer is a pointer to a constant global, we
1277 /// can optimize this.
1278 static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy,
1280 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1281 if (isa<LoadInst>(*UI)) {
1282 // Ignore loads, they are always ok.
1285 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) {
1286 // If uses of the bitcast are ok, we are ok.
1287 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
1291 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
1292 // If the GEP has all zero indices, it doesn't offset the pointer. If it
1293 // doesn't, it does.
1294 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
1295 isOffset || !GEP->hasAllZeroIndices()))
1300 // If this is isn't our memcpy/memmove, reject it as something we can't
1302 if (!isa<MemCpyInst>(*UI) && !isa<MemMoveInst>(*UI))
1305 // If we already have seen a copy, reject the second one.
1306 if (TheCopy) return false;
1308 // If the pointer has been offset from the start of the alloca, we can't
1309 // safely handle this.
1310 if (isOffset) return false;
1312 // If the memintrinsic isn't using the alloca as the dest, reject it.
1313 if (UI.getOperandNo() != 1) return false;
1315 MemIntrinsic *MI = cast<MemIntrinsic>(*UI);
1317 // If the source of the memcpy/move is not a constant global, reject it.
1318 if (!PointsToConstantGlobal(MI->getOperand(2)))
1321 // Otherwise, the transform is safe. Remember the copy instruction.
1327 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
1328 /// modified by a copy from a constant global. If we can prove this, we can
1329 /// replace any uses of the alloca with uses of the global directly.
1330 Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocationInst *AI) {
1331 Instruction *TheCopy = 0;
1332 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))