1 //===-- BasicBlockUtils.cpp - BasicBlock Utilities -------------------------==//
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 family of functions perform manipulations on basic blocks, and
11 // instructions contained within basic blocks.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
16 #include "llvm/Function.h"
17 #include "llvm/Instructions.h"
18 #include "llvm/IntrinsicInst.h"
19 #include "llvm/LLVMContext.h"
20 #include "llvm/Constant.h"
21 #include "llvm/Type.h"
22 #include "llvm/Analysis/AliasAnalysis.h"
23 #include "llvm/Analysis/LoopInfo.h"
24 #include "llvm/Analysis/Dominators.h"
25 #include "llvm/Target/TargetData.h"
26 #include "llvm/Transforms/Utils/Local.h"
27 #include "llvm/Transforms/Scalar.h"
28 #include "llvm/Support/ErrorHandling.h"
29 #include "llvm/Support/ValueHandle.h"
33 /// DeleteDeadBlock - Delete the specified block, which must have no
35 void llvm::DeleteDeadBlock(BasicBlock *BB) {
36 assert((pred_begin(BB) == pred_end(BB) ||
37 // Can delete self loop.
38 BB->getSinglePredecessor() == BB) && "Block is not dead!");
39 TerminatorInst *BBTerm = BB->getTerminator();
41 // Loop through all of our successors and make sure they know that one
42 // of their predecessors is going away.
43 for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i)
44 BBTerm->getSuccessor(i)->removePredecessor(BB);
46 // Zap all the instructions in the block.
47 while (!BB->empty()) {
48 Instruction &I = BB->back();
49 // If this instruction is used, replace uses with an arbitrary value.
50 // Because control flow can't get here, we don't care what we replace the
51 // value with. Note that since this block is unreachable, and all values
52 // contained within it must dominate their uses, that all uses will
53 // eventually be removed (they are themselves dead).
55 I.replaceAllUsesWith(UndefValue::get(I.getType()));
56 BB->getInstList().pop_back();
60 BB->eraseFromParent();
63 /// FoldSingleEntryPHINodes - We know that BB has one predecessor. If there are
64 /// any single-entry PHI nodes in it, fold them away. This handles the case
65 /// when all entries to the PHI nodes in a block are guaranteed equal, such as
66 /// when the block has exactly one predecessor.
67 void llvm::FoldSingleEntryPHINodes(BasicBlock *BB) {
68 while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
69 if (PN->getIncomingValue(0) != PN)
70 PN->replaceAllUsesWith(PN->getIncomingValue(0));
72 PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
73 PN->eraseFromParent();
78 /// DeleteDeadPHIs - Examine each PHI in the given block and delete it if it
79 /// is dead. Also recursively delete any operands that become dead as
80 /// a result. This includes tracing the def-use list from the PHI to see if
81 /// it is ultimately unused or if it reaches an unused cycle.
82 void llvm::DeleteDeadPHIs(BasicBlock *BB) {
83 // Recursively deleting a PHI may cause multiple PHIs to be deleted
84 // or RAUW'd undef, so use an array of WeakVH for the PHIs to delete.
85 SmallVector<WeakVH, 8> PHIs;
86 for (BasicBlock::iterator I = BB->begin();
87 PHINode *PN = dyn_cast<PHINode>(I); ++I)
90 for (unsigned i = 0, e = PHIs.size(); i != e; ++i)
91 if (PHINode *PN = dyn_cast_or_null<PHINode>(PHIs[i].operator Value*()))
92 RecursivelyDeleteDeadPHINode(PN);
95 /// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
96 /// if possible. The return value indicates success or failure.
97 bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P) {
98 pred_iterator PI(pred_begin(BB)), PE(pred_end(BB));
99 // Can't merge the entry block. Don't merge away blocks who have their
100 // address taken: this is a bug if the predecessor block is the entry node
101 // (because we'd end up taking the address of the entry) and undesirable in
103 if (pred_begin(BB) == pred_end(BB) ||
104 BB->hasAddressTaken()) return false;
106 BasicBlock *PredBB = *PI++;
107 for (; PI != PE; ++PI) // Search all predecessors, see if they are all same
109 PredBB = 0; // There are multiple different predecessors...
113 // Can't merge if there are multiple predecessors.
114 if (!PredBB) return false;
115 // Don't break self-loops.
116 if (PredBB == BB) return false;
117 // Don't break invokes.
118 if (isa<InvokeInst>(PredBB->getTerminator())) return false;
120 succ_iterator SI(succ_begin(PredBB)), SE(succ_end(PredBB));
121 BasicBlock* OnlySucc = BB;
122 for (; SI != SE; ++SI)
123 if (*SI != OnlySucc) {
124 OnlySucc = 0; // There are multiple distinct successors!
128 // Can't merge if there are multiple successors.
129 if (!OnlySucc) return false;
131 // Can't merge if there is PHI loop.
132 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI) {
133 if (PHINode *PN = dyn_cast<PHINode>(BI)) {
134 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
135 if (PN->getIncomingValue(i) == PN)
141 // Begin by getting rid of unneeded PHIs.
142 while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
143 PN->replaceAllUsesWith(PN->getIncomingValue(0));
144 BB->getInstList().pop_front(); // Delete the phi node...
147 // Delete the unconditional branch from the predecessor...
148 PredBB->getInstList().pop_back();
150 // Move all definitions in the successor to the predecessor...
151 PredBB->getInstList().splice(PredBB->end(), BB->getInstList());
153 // Make all PHI nodes that referred to BB now refer to Pred as their
155 BB->replaceAllUsesWith(PredBB);
157 // Inherit predecessors name if it exists.
158 if (!PredBB->hasName())
159 PredBB->takeName(BB);
161 // Finally, erase the old block and update dominator info.
163 if (DominatorTree* DT = P->getAnalysisIfAvailable<DominatorTree>()) {
164 DomTreeNode* DTN = DT->getNode(BB);
165 DomTreeNode* PredDTN = DT->getNode(PredBB);
168 SmallPtrSet<DomTreeNode*, 8> Children(DTN->begin(), DTN->end());
169 for (SmallPtrSet<DomTreeNode*, 8>::iterator DI = Children.begin(),
170 DE = Children.end(); DI != DE; ++DI)
171 DT->changeImmediateDominator(*DI, PredDTN);
178 BB->eraseFromParent();
184 /// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
185 /// with a value, then remove and delete the original instruction.
187 void llvm::ReplaceInstWithValue(BasicBlock::InstListType &BIL,
188 BasicBlock::iterator &BI, Value *V) {
189 Instruction &I = *BI;
190 // Replaces all of the uses of the instruction with uses of the value
191 I.replaceAllUsesWith(V);
193 // Make sure to propagate a name if there is one already.
194 if (I.hasName() && !V->hasName())
197 // Delete the unnecessary instruction now...
202 /// ReplaceInstWithInst - Replace the instruction specified by BI with the
203 /// instruction specified by I. The original instruction is deleted and BI is
204 /// updated to point to the new instruction.
206 void llvm::ReplaceInstWithInst(BasicBlock::InstListType &BIL,
207 BasicBlock::iterator &BI, Instruction *I) {
208 assert(I->getParent() == 0 &&
209 "ReplaceInstWithInst: Instruction already inserted into basic block!");
211 // Insert the new instruction into the basic block...
212 BasicBlock::iterator New = BIL.insert(BI, I);
214 // Replace all uses of the old instruction, and delete it.
215 ReplaceInstWithValue(BIL, BI, I);
217 // Move BI back to point to the newly inserted instruction
221 /// ReplaceInstWithInst - Replace the instruction specified by From with the
222 /// instruction specified by To.
224 void llvm::ReplaceInstWithInst(Instruction *From, Instruction *To) {
225 BasicBlock::iterator BI(From);
226 ReplaceInstWithInst(From->getParent()->getInstList(), BI, To);
229 /// RemoveSuccessor - Change the specified terminator instruction such that its
230 /// successor SuccNum no longer exists. Because this reduces the outgoing
231 /// degree of the current basic block, the actual terminator instruction itself
232 /// may have to be changed. In the case where the last successor of the block
233 /// is deleted, a return instruction is inserted in its place which can cause a
234 /// surprising change in program behavior if it is not expected.
236 void llvm::RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) {
237 assert(SuccNum < TI->getNumSuccessors() &&
238 "Trying to remove a nonexistant successor!");
240 // If our old successor block contains any PHI nodes, remove the entry in the
241 // PHI nodes that comes from this branch...
243 BasicBlock *BB = TI->getParent();
244 TI->getSuccessor(SuccNum)->removePredecessor(BB);
246 TerminatorInst *NewTI = 0;
247 switch (TI->getOpcode()) {
248 case Instruction::Br:
249 // If this is a conditional branch... convert to unconditional branch.
250 if (TI->getNumSuccessors() == 2) {
251 cast<BranchInst>(TI)->setUnconditionalDest(TI->getSuccessor(1-SuccNum));
252 } else { // Otherwise convert to a return instruction...
255 // Create a value to return... if the function doesn't return null...
256 if (BB->getParent()->getReturnType() != Type::getVoidTy(TI->getContext()))
257 RetVal = Constant::getNullValue(BB->getParent()->getReturnType());
259 // Create the return...
260 NewTI = ReturnInst::Create(TI->getContext(), RetVal);
264 case Instruction::Invoke: // Should convert to call
265 case Instruction::Switch: // Should remove entry
267 case Instruction::Ret: // Cannot happen, has no successors!
268 llvm_unreachable("Unhandled terminator instruction type in RemoveSuccessor!");
271 if (NewTI) // If it's a different instruction, replace.
272 ReplaceInstWithInst(TI, NewTI);
275 /// SplitEdge - Split the edge connecting specified block. Pass P must
277 BasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) {
278 assert(!isa<IndirectBrInst>(BB->getTerminator()) &&
279 "Cannot split an edge from an IndirectBrInst");
280 TerminatorInst *LatchTerm = BB->getTerminator();
281 unsigned SuccNum = 0;
283 unsigned e = LatchTerm->getNumSuccessors();
285 for (unsigned i = 0; ; ++i) {
286 assert(i != e && "Didn't find edge?");
287 if (LatchTerm->getSuccessor(i) == Succ) {
293 // If this is a critical edge, let SplitCriticalEdge do it.
294 if (SplitCriticalEdge(BB->getTerminator(), SuccNum, P))
295 return LatchTerm->getSuccessor(SuccNum);
297 // If the edge isn't critical, then BB has a single successor or Succ has a
298 // single pred. Split the block.
299 BasicBlock::iterator SplitPoint;
300 if (BasicBlock *SP = Succ->getSinglePredecessor()) {
301 // If the successor only has a single pred, split the top of the successor
303 assert(SP == BB && "CFG broken");
305 return SplitBlock(Succ, Succ->begin(), P);
307 // Otherwise, if BB has a single successor, split it at the bottom of the
309 assert(BB->getTerminator()->getNumSuccessors() == 1 &&
310 "Should have a single succ!");
311 return SplitBlock(BB, BB->getTerminator(), P);
315 /// SplitBlock - Split the specified block at the specified instruction - every
316 /// thing before SplitPt stays in Old and everything starting with SplitPt moves
317 /// to a new block. The two blocks are joined by an unconditional branch and
318 /// the loop info is updated.
320 BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) {
321 BasicBlock::iterator SplitIt = SplitPt;
322 while (isa<PHINode>(SplitIt))
324 BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
326 // The new block lives in whichever loop the old one did. This preserves
327 // LCSSA as well, because we force the split point to be after any PHI nodes.
328 if (LoopInfo* LI = P->getAnalysisIfAvailable<LoopInfo>())
329 if (Loop *L = LI->getLoopFor(Old))
330 L->addBasicBlockToLoop(New, LI->getBase());
332 if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>())
334 // Old dominates New. New node domiantes all other nodes dominated by Old.
335 DomTreeNode *OldNode = DT->getNode(Old);
336 std::vector<DomTreeNode *> Children;
337 for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end();
339 Children.push_back(*I);
341 DomTreeNode *NewNode = DT->addNewBlock(New,Old);
343 for (std::vector<DomTreeNode *>::iterator I = Children.begin(),
344 E = Children.end(); I != E; ++I)
345 DT->changeImmediateDominator(*I, NewNode);
348 if (DominanceFrontier *DF = P->getAnalysisIfAvailable<DominanceFrontier>())
355 /// SplitBlockPredecessors - This method transforms BB by introducing a new
356 /// basic block into the function, and moving some of the predecessors of BB to
357 /// be predecessors of the new block. The new predecessors are indicated by the
358 /// Preds array, which has NumPreds elements in it. The new block is given a
359 /// suffix of 'Suffix'.
361 /// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
362 /// DominanceFrontier, LoopInfo, and LCCSA but no other analyses.
363 /// In particular, it does not preserve LoopSimplify (because it's
364 /// complicated to handle the case where one of the edges being split
365 /// is an exit of a loop with other exits).
367 BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
368 BasicBlock *const *Preds,
369 unsigned NumPreds, const char *Suffix,
371 // Create new basic block, insert right before the original block.
372 BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), BB->getName()+Suffix,
373 BB->getParent(), BB);
375 // The new block unconditionally branches to the old block.
376 BranchInst *BI = BranchInst::Create(BB, NewBB);
378 LoopInfo *LI = P ? P->getAnalysisIfAvailable<LoopInfo>() : 0;
379 Loop *L = LI ? LI->getLoopFor(BB) : 0;
380 bool PreserveLCSSA = P->mustPreserveAnalysisID(LCSSAID);
382 // Move the edges from Preds to point to NewBB instead of BB.
383 // While here, if we need to preserve loop analyses, collect
384 // some information about how this split will affect loops.
385 bool HasLoopExit = false;
386 bool IsLoopEntry = !!L;
387 bool SplitMakesNewLoopHeader = false;
388 for (unsigned i = 0; i != NumPreds; ++i) {
389 Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
392 // If we need to preserve LCSSA, determine if any of
393 // the preds is a loop exit.
395 if (Loop *PL = LI->getLoopFor(Preds[i]))
396 if (!PL->contains(BB))
398 // If we need to preserve LoopInfo, note whether any of the
399 // preds crosses an interesting loop boundary.
401 if (L->contains(Preds[i]))
404 SplitMakesNewLoopHeader = true;
409 // Update dominator tree and dominator frontier if available.
410 DominatorTree *DT = P ? P->getAnalysisIfAvailable<DominatorTree>() : 0;
412 DT->splitBlock(NewBB);
413 if (DominanceFrontier *DF = P ? P->getAnalysisIfAvailable<DominanceFrontier>():0)
414 DF->splitBlock(NewBB);
416 // Insert a new PHI node into NewBB for every PHI node in BB and that new PHI
417 // node becomes an incoming value for BB's phi node. However, if the Preds
418 // list is empty, we need to insert dummy entries into the PHI nodes in BB to
419 // account for the newly created predecessor.
421 // Insert dummy values as the incoming value.
422 for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I)
423 cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
427 AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
431 // Add the new block to the nearest enclosing loop (and not an
432 // adjacent loop). To find this, examine each of the predecessors and
433 // determine which loops enclose them, and select the most-nested loop
434 // which contains the loop containing the block being split.
435 Loop *InnermostPredLoop = 0;
436 for (unsigned i = 0; i != NumPreds; ++i)
437 if (Loop *PredLoop = LI->getLoopFor(Preds[i])) {
438 // Seek a loop which actually contains the block being split (to
439 // avoid adjacent loops).
440 while (PredLoop && !PredLoop->contains(BB))
441 PredLoop = PredLoop->getParentLoop();
442 // Select the most-nested of these loops which contains the block.
444 PredLoop->contains(BB) &&
445 (!InnermostPredLoop ||
446 InnermostPredLoop->getLoopDepth() < PredLoop->getLoopDepth()))
447 InnermostPredLoop = PredLoop;
449 if (InnermostPredLoop)
450 InnermostPredLoop->addBasicBlockToLoop(NewBB, LI->getBase());
452 L->addBasicBlockToLoop(NewBB, LI->getBase());
453 if (SplitMakesNewLoopHeader)
454 L->moveToHeader(NewBB);
458 // Otherwise, create a new PHI node in NewBB for each PHI node in BB.
459 for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ) {
460 PHINode *PN = cast<PHINode>(I++);
462 // Check to see if all of the values coming in are the same. If so, we
463 // don't need to create a new PHI node, unless it's needed for LCSSA.
466 InVal = PN->getIncomingValueForBlock(Preds[0]);
467 for (unsigned i = 1; i != NumPreds; ++i)
468 if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
475 // If all incoming values for the new PHI would be the same, just don't
476 // make a new PHI. Instead, just remove the incoming values from the old
478 for (unsigned i = 0; i != NumPreds; ++i)
479 PN->removeIncomingValue(Preds[i], false);
481 // If the values coming into the block are not the same, we need a PHI.
482 // Create the new PHI node, insert it into NewBB at the end of the block
484 PHINode::Create(PN->getType(), PN->getName()+".ph", BI);
485 if (AA) AA->copyValue(PN, NewPHI);
487 // Move all of the PHI values for 'Preds' to the new PHI.
488 for (unsigned i = 0; i != NumPreds; ++i) {
489 Value *V = PN->removeIncomingValue(Preds[i], false);
490 NewPHI->addIncoming(V, Preds[i]);
495 // Add an incoming value to the PHI node in the loop for the preheader
497 PN->addIncoming(InVal, NewBB);
503 /// FindFunctionBackedges - Analyze the specified function to find all of the
504 /// loop backedges in the function and return them. This is a relatively cheap
505 /// (compared to computing dominators and loop info) analysis.
507 /// The output is added to Result, as pairs of <from,to> edge info.
508 void llvm::FindFunctionBackedges(const Function &F,
509 SmallVectorImpl<std::pair<const BasicBlock*,const BasicBlock*> > &Result) {
510 const BasicBlock *BB = &F.getEntryBlock();
511 if (succ_begin(BB) == succ_end(BB))
514 SmallPtrSet<const BasicBlock*, 8> Visited;
515 SmallVector<std::pair<const BasicBlock*, succ_const_iterator>, 8> VisitStack;
516 SmallPtrSet<const BasicBlock*, 8> InStack;
519 VisitStack.push_back(std::make_pair(BB, succ_begin(BB)));
522 std::pair<const BasicBlock*, succ_const_iterator> &Top = VisitStack.back();
523 const BasicBlock *ParentBB = Top.first;
524 succ_const_iterator &I = Top.second;
526 bool FoundNew = false;
527 while (I != succ_end(ParentBB)) {
529 if (Visited.insert(BB)) {
533 // Successor is in VisitStack, it's a back edge.
534 if (InStack.count(BB))
535 Result.push_back(std::make_pair(ParentBB, BB));
539 // Go down one level if there is a unvisited successor.
541 VisitStack.push_back(std::make_pair(BB, succ_begin(BB)));
544 InStack.erase(VisitStack.pop_back_val().first);
546 } while (!VisitStack.empty());
553 /// AreEquivalentAddressValues - Test if A and B will obviously have the same
554 /// value. This includes recognizing that %t0 and %t1 will have the same
555 /// value in code like this:
556 /// %t0 = getelementptr \@a, 0, 3
557 /// store i32 0, i32* %t0
558 /// %t1 = getelementptr \@a, 0, 3
559 /// %t2 = load i32* %t1
561 static bool AreEquivalentAddressValues(const Value *A, const Value *B) {
562 // Test if the values are trivially equivalent.
563 if (A == B) return true;
565 // Test if the values come from identical arithmetic instructions.
566 // Use isIdenticalToWhenDefined instead of isIdenticalTo because
567 // this function is only used when one address use dominates the
568 // other, which means that they'll always either have the same
569 // value or one of them will have an undefined value.
570 if (isa<BinaryOperator>(A) || isa<CastInst>(A) ||
571 isa<PHINode>(A) || isa<GetElementPtrInst>(A))
572 if (const Instruction *BI = dyn_cast<Instruction>(B))
573 if (cast<Instruction>(A)->isIdenticalToWhenDefined(BI))
576 // Otherwise they may not be equivalent.
580 /// FindAvailableLoadedValue - Scan the ScanBB block backwards (starting at the
581 /// instruction before ScanFrom) checking to see if we have the value at the
582 /// memory address *Ptr locally available within a small number of instructions.
583 /// If the value is available, return it.
585 /// If not, return the iterator for the last validated instruction that the
586 /// value would be live through. If we scanned the entire block and didn't find
587 /// something that invalidates *Ptr or provides it, ScanFrom would be left at
588 /// begin() and this returns null. ScanFrom could also be left
590 /// MaxInstsToScan specifies the maximum instructions to scan in the block. If
591 /// it is set to 0, it will scan the whole block. You can also optionally
592 /// specify an alias analysis implementation, which makes this more precise.
593 Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
594 BasicBlock::iterator &ScanFrom,
595 unsigned MaxInstsToScan,
597 if (MaxInstsToScan == 0) MaxInstsToScan = ~0U;
599 // If we're using alias analysis to disambiguate get the size of *Ptr.
600 unsigned AccessSize = 0;
602 const Type *AccessTy = cast<PointerType>(Ptr->getType())->getElementType();
603 AccessSize = AA->getTypeStoreSize(AccessTy);
606 while (ScanFrom != ScanBB->begin()) {
607 // We must ignore debug info directives when counting (otherwise they
608 // would affect codegen).
609 Instruction *Inst = --ScanFrom;
610 if (isa<DbgInfoIntrinsic>(Inst))
612 // We skip pointer-to-pointer bitcasts, which are NOPs.
613 // It is necessary for correctness to skip those that feed into a
614 // llvm.dbg.declare, as these are not present when debugging is off.
615 if (isa<BitCastInst>(Inst) && isa<PointerType>(Inst->getType()))
618 // Restore ScanFrom to expected value in case next test succeeds
621 // Don't scan huge blocks.
622 if (MaxInstsToScan-- == 0) return 0;
625 // If this is a load of Ptr, the loaded value is available.
626 if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
627 if (AreEquivalentAddressValues(LI->getOperand(0), Ptr))
630 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
631 // If this is a store through Ptr, the value is available!
632 if (AreEquivalentAddressValues(SI->getOperand(1), Ptr))
633 return SI->getOperand(0);
635 // If Ptr is an alloca and this is a store to a different alloca, ignore
636 // the store. This is a trivial form of alias analysis that is important
637 // for reg2mem'd code.
638 if ((isa<AllocaInst>(Ptr) || isa<GlobalVariable>(Ptr)) &&
639 (isa<AllocaInst>(SI->getOperand(1)) ||
640 isa<GlobalVariable>(SI->getOperand(1))))
643 // If we have alias analysis and it says the store won't modify the loaded
644 // value, ignore the store.
646 (AA->getModRefInfo(SI, Ptr, AccessSize) & AliasAnalysis::Mod) == 0)
649 // Otherwise the store that may or may not alias the pointer, bail out.
654 // If this is some other instruction that may clobber Ptr, bail out.
655 if (Inst->mayWriteToMemory()) {
656 // If alias analysis claims that it really won't modify the load,
659 (AA->getModRefInfo(Inst, Ptr, AccessSize) & AliasAnalysis::Mod) == 0)
662 // May modify the pointer, bail out.
668 // Got to the start of the block, we didn't find it, but are done for this
673 /// CopyPrecedingStopPoint - If I is immediately preceded by a StopPoint,
674 /// make a copy of the stoppoint before InsertPos (presumably before copying
676 void llvm::CopyPrecedingStopPoint(Instruction *I,
677 BasicBlock::iterator InsertPos) {
678 if (I != I->getParent()->begin()) {
679 BasicBlock::iterator BBI = I; --BBI;
680 if (DbgStopPointInst *DSPI = dyn_cast<DbgStopPointInst>(BBI)) {
681 CallInst *newDSPI = cast<CallInst>(DSPI->clone());
682 newDSPI->insertBefore(InsertPos);