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 - Folds a basic block into its predecessor if it
96 /// only has one predecessor, and that predecessor only has one successor.
97 /// If a Pass is given, the LoopInfo and DominatorTree analyses will be kept
98 /// current. Returns the combined block, or null if no merging was performed.
99 BasicBlock *llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) {
100 // Don't merge if the block has multiple predecessors.
101 BasicBlock *PredBB = BB->getSinglePredecessor();
102 if (!PredBB) return 0;
103 // Don't merge if the predecessor has multiple successors.
104 if (PredBB->getTerminator()->getNumSuccessors() != 1) return 0;
105 // Don't break self-loops.
106 if (PredBB == BB) return 0;
107 // Don't break invokes.
108 if (isa<InvokeInst>(PredBB->getTerminator())) return 0;
110 // Resolve any PHI nodes at the start of the block. They are all
111 // guaranteed to have exactly one entry if they exist, unless there are
112 // multiple duplicate (but guaranteed to be equal) entries for the
113 // incoming edges. This occurs when there are multiple edges from
115 FoldSingleEntryPHINodes(BB);
117 // Delete the unconditional branch from the predecessor...
118 PredBB->getInstList().pop_back();
120 // Move all definitions in the successor to the predecessor...
121 PredBB->getInstList().splice(PredBB->end(), BB->getInstList());
123 // Make all PHI nodes that referred to BB now refer to Pred as their
125 BB->replaceAllUsesWith(PredBB);
127 // If the predecessor doesn't have a name, take the successor's name.
128 if (!PredBB->hasName())
129 PredBB->takeName(BB);
131 // Finally, erase the old block and update dominator info.
133 if (DominatorTree* DT = P->getAnalysisIfAvailable<DominatorTree>()) {
134 DomTreeNode* DTN = DT->getNode(BB);
135 DomTreeNode* PredDTN = DT->getNode(PredBB);
138 SmallPtrSet<DomTreeNode*, 8> Children(DTN->begin(), DTN->end());
139 for (SmallPtrSet<DomTreeNode*, 8>::iterator DI = Children.begin(),
140 DE = Children.end(); DI != DE; ++DI)
141 DT->changeImmediateDominator(*DI, PredDTN);
146 // Notify LoopInfo that the block is removed.
147 if (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>())
151 BB->eraseFromParent();
156 /// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
157 /// with a value, then remove and delete the original instruction.
159 void llvm::ReplaceInstWithValue(BasicBlock::InstListType &BIL,
160 BasicBlock::iterator &BI, Value *V) {
161 Instruction &I = *BI;
162 // Replaces all of the uses of the instruction with uses of the value
163 I.replaceAllUsesWith(V);
165 // Make sure to propagate a name if there is one already.
166 if (I.hasName() && !V->hasName())
169 // Delete the unnecessary instruction now...
174 /// ReplaceInstWithInst - Replace the instruction specified by BI with the
175 /// instruction specified by I. The original instruction is deleted and BI is
176 /// updated to point to the new instruction.
178 void llvm::ReplaceInstWithInst(BasicBlock::InstListType &BIL,
179 BasicBlock::iterator &BI, Instruction *I) {
180 assert(I->getParent() == 0 &&
181 "ReplaceInstWithInst: Instruction already inserted into basic block!");
183 // Insert the new instruction into the basic block...
184 BasicBlock::iterator New = BIL.insert(BI, I);
186 // Replace all uses of the old instruction, and delete it.
187 ReplaceInstWithValue(BIL, BI, I);
189 // Move BI back to point to the newly inserted instruction
193 /// ReplaceInstWithInst - Replace the instruction specified by From with the
194 /// instruction specified by To.
196 void llvm::ReplaceInstWithInst(Instruction *From, Instruction *To) {
197 BasicBlock::iterator BI(From);
198 ReplaceInstWithInst(From->getParent()->getInstList(), BI, To);
201 /// RemoveSuccessor - Change the specified terminator instruction such that its
202 /// successor SuccNum no longer exists. Because this reduces the outgoing
203 /// degree of the current basic block, the actual terminator instruction itself
204 /// may have to be changed. In the case where the last successor of the block
205 /// is deleted, a return instruction is inserted in its place which can cause a
206 /// surprising change in program behavior if it is not expected.
208 void llvm::RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) {
209 assert(SuccNum < TI->getNumSuccessors() &&
210 "Trying to remove a nonexistant successor!");
212 // If our old successor block contains any PHI nodes, remove the entry in the
213 // PHI nodes that comes from this branch...
215 BasicBlock *BB = TI->getParent();
216 TI->getSuccessor(SuccNum)->removePredecessor(BB);
218 TerminatorInst *NewTI = 0;
219 switch (TI->getOpcode()) {
220 case Instruction::Br:
221 // If this is a conditional branch... convert to unconditional branch.
222 if (TI->getNumSuccessors() == 2) {
223 cast<BranchInst>(TI)->setUnconditionalDest(TI->getSuccessor(1-SuccNum));
224 } else { // Otherwise convert to a return instruction...
227 // Create a value to return... if the function doesn't return null...
228 if (BB->getParent()->getReturnType() != Type::getVoidTy(TI->getContext()))
229 RetVal = Constant::getNullValue(BB->getParent()->getReturnType());
231 // Create the return...
232 NewTI = ReturnInst::Create(TI->getContext(), RetVal);
236 case Instruction::Invoke: // Should convert to call
237 case Instruction::Switch: // Should remove entry
239 case Instruction::Ret: // Cannot happen, has no successors!
240 llvm_unreachable("Unhandled terminator instruction type in RemoveSuccessor!");
243 if (NewTI) // If it's a different instruction, replace.
244 ReplaceInstWithInst(TI, NewTI);
247 /// SplitEdge - Split the edge connecting specified block. Pass P must
249 BasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) {
250 TerminatorInst *LatchTerm = BB->getTerminator();
251 unsigned SuccNum = 0;
253 unsigned e = LatchTerm->getNumSuccessors();
255 for (unsigned i = 0; ; ++i) {
256 assert(i != e && "Didn't find edge?");
257 if (LatchTerm->getSuccessor(i) == Succ) {
263 // If this is a critical edge, let SplitCriticalEdge do it.
264 if (SplitCriticalEdge(BB->getTerminator(), SuccNum, P))
265 return LatchTerm->getSuccessor(SuccNum);
267 // If the edge isn't critical, then BB has a single successor or Succ has a
268 // single pred. Split the block.
269 BasicBlock::iterator SplitPoint;
270 if (BasicBlock *SP = Succ->getSinglePredecessor()) {
271 // If the successor only has a single pred, split the top of the successor
273 assert(SP == BB && "CFG broken");
275 return SplitBlock(Succ, Succ->begin(), P);
277 // Otherwise, if BB has a single successor, split it at the bottom of the
279 assert(BB->getTerminator()->getNumSuccessors() == 1 &&
280 "Should have a single succ!");
281 return SplitBlock(BB, BB->getTerminator(), P);
285 /// SplitBlock - Split the specified block at the specified instruction - every
286 /// thing before SplitPt stays in Old and everything starting with SplitPt moves
287 /// to a new block. The two blocks are joined by an unconditional branch and
288 /// the loop info is updated.
290 BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) {
291 BasicBlock::iterator SplitIt = SplitPt;
292 while (isa<PHINode>(SplitIt))
294 BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
296 // The new block lives in whichever loop the old one did. This preserves
297 // LCSSA as well, because we force the split point to be after any PHI nodes.
298 if (LoopInfo* LI = P->getAnalysisIfAvailable<LoopInfo>())
299 if (Loop *L = LI->getLoopFor(Old))
300 L->addBasicBlockToLoop(New, LI->getBase());
302 if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>())
304 // Old dominates New. New node domiantes all other nodes dominated by Old.
305 DomTreeNode *OldNode = DT->getNode(Old);
306 std::vector<DomTreeNode *> Children;
307 for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end();
309 Children.push_back(*I);
311 DomTreeNode *NewNode = DT->addNewBlock(New,Old);
313 for (std::vector<DomTreeNode *>::iterator I = Children.begin(),
314 E = Children.end(); I != E; ++I)
315 DT->changeImmediateDominator(*I, NewNode);
318 if (DominanceFrontier *DF = P->getAnalysisIfAvailable<DominanceFrontier>())
325 /// SplitBlockPredecessors - This method transforms BB by introducing a new
326 /// basic block into the function, and moving some of the predecessors of BB to
327 /// be predecessors of the new block. The new predecessors are indicated by the
328 /// Preds array, which has NumPreds elements in it. The new block is given a
329 /// suffix of 'Suffix'.
331 /// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
332 /// DominanceFrontier, LoopInfo, and LCCSA but no other analyses.
333 /// In particular, it does not preserve LoopSimplify (because it's
334 /// complicated to handle the case where one of the edges being split
335 /// is an exit of a loop with other exits).
337 BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
338 BasicBlock *const *Preds,
339 unsigned NumPreds, const char *Suffix,
341 // Create new basic block, insert right before the original block.
342 BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), BB->getName()+Suffix,
343 BB->getParent(), BB);
345 // The new block unconditionally branches to the old block.
346 BranchInst *BI = BranchInst::Create(BB, NewBB);
348 LoopInfo *LI = P ? P->getAnalysisIfAvailable<LoopInfo>() : 0;
349 Loop *L = LI ? LI->getLoopFor(BB) : 0;
350 bool PreserveLCSSA = P->mustPreserveAnalysisID(LCSSAID);
352 // Move the edges from Preds to point to NewBB instead of BB.
353 // While here, if we need to preserve loop analyses, collect
354 // some information about how this split will affect loops.
355 bool HasLoopExit = false;
356 bool IsLoopEntry = !!L;
357 bool SplitMakesNewLoopHeader = false;
358 for (unsigned i = 0; i != NumPreds; ++i) {
359 Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
362 // If we need to preserve LCSSA, determine if any of
363 // the preds is a loop exit.
365 if (Loop *PL = LI->getLoopFor(Preds[i]))
366 if (!PL->contains(BB))
368 // If we need to preserve LoopInfo, note whether any of the
369 // preds crosses an interesting loop boundary.
371 if (L->contains(Preds[i]))
374 SplitMakesNewLoopHeader = true;
379 // Update dominator tree and dominator frontier if available.
380 DominatorTree *DT = P ? P->getAnalysisIfAvailable<DominatorTree>() : 0;
382 DT->splitBlock(NewBB);
383 if (DominanceFrontier *DF = P ? P->getAnalysisIfAvailable<DominanceFrontier>():0)
384 DF->splitBlock(NewBB);
386 // Insert a new PHI node into NewBB for every PHI node in BB and that new PHI
387 // node becomes an incoming value for BB's phi node. However, if the Preds
388 // list is empty, we need to insert dummy entries into the PHI nodes in BB to
389 // account for the newly created predecessor.
391 // Insert dummy values as the incoming value.
392 for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I)
393 cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
397 AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
401 // Add the new block to the nearest enclosing loop (and not an
402 // adjacent loop). To find this, examine each of the predecessors and
403 // determine which loops enclose them, and select the most-nested loop
404 // which contains the loop containing the block being split.
405 Loop *InnermostPredLoop = 0;
406 for (unsigned i = 0; i != NumPreds; ++i)
407 if (Loop *PredLoop = LI->getLoopFor(Preds[i])) {
408 // Seek a loop which actually contains the block being split (to
409 // avoid adjacent loops).
410 while (PredLoop && !PredLoop->contains(BB))
411 PredLoop = PredLoop->getParentLoop();
412 // Select the most-nested of these loops which contains the block.
414 PredLoop->contains(BB) &&
415 (!InnermostPredLoop ||
416 InnermostPredLoop->getLoopDepth() < PredLoop->getLoopDepth()))
417 InnermostPredLoop = PredLoop;
419 if (InnermostPredLoop)
420 InnermostPredLoop->addBasicBlockToLoop(NewBB, LI->getBase());
422 L->addBasicBlockToLoop(NewBB, LI->getBase());
423 if (SplitMakesNewLoopHeader)
424 L->moveToHeader(NewBB);
428 // Otherwise, create a new PHI node in NewBB for each PHI node in BB.
429 for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ) {
430 PHINode *PN = cast<PHINode>(I++);
432 // Check to see if all of the values coming in are the same. If so, we
433 // don't need to create a new PHI node, unless it's needed for LCSSA.
436 InVal = PN->getIncomingValueForBlock(Preds[0]);
437 for (unsigned i = 1; i != NumPreds; ++i)
438 if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
445 // If all incoming values for the new PHI would be the same, just don't
446 // make a new PHI. Instead, just remove the incoming values from the old
448 for (unsigned i = 0; i != NumPreds; ++i)
449 PN->removeIncomingValue(Preds[i], false);
451 // If the values coming into the block are not the same, we need a PHI.
452 // Create the new PHI node, insert it into NewBB at the end of the block
454 PHINode::Create(PN->getType(), PN->getName()+".ph", BI);
455 if (AA) AA->copyValue(PN, NewPHI);
457 // Move all of the PHI values for 'Preds' to the new PHI.
458 for (unsigned i = 0; i != NumPreds; ++i) {
459 Value *V = PN->removeIncomingValue(Preds[i], false);
460 NewPHI->addIncoming(V, Preds[i]);
465 // Add an incoming value to the PHI node in the loop for the preheader
467 PN->addIncoming(InVal, NewBB);
473 /// FindFunctionBackedges - Analyze the specified function to find all of the
474 /// loop backedges in the function and return them. This is a relatively cheap
475 /// (compared to computing dominators and loop info) analysis.
477 /// The output is added to Result, as pairs of <from,to> edge info.
478 void llvm::FindFunctionBackedges(const Function &F,
479 SmallVectorImpl<std::pair<const BasicBlock*,const BasicBlock*> > &Result) {
480 const BasicBlock *BB = &F.getEntryBlock();
481 if (succ_begin(BB) == succ_end(BB))
484 SmallPtrSet<const BasicBlock*, 8> Visited;
485 SmallVector<std::pair<const BasicBlock*, succ_const_iterator>, 8> VisitStack;
486 SmallPtrSet<const BasicBlock*, 8> InStack;
489 VisitStack.push_back(std::make_pair(BB, succ_begin(BB)));
492 std::pair<const BasicBlock*, succ_const_iterator> &Top = VisitStack.back();
493 const BasicBlock *ParentBB = Top.first;
494 succ_const_iterator &I = Top.second;
496 bool FoundNew = false;
497 while (I != succ_end(ParentBB)) {
499 if (Visited.insert(BB)) {
503 // Successor is in VisitStack, it's a back edge.
504 if (InStack.count(BB))
505 Result.push_back(std::make_pair(ParentBB, BB));
509 // Go down one level if there is a unvisited successor.
511 VisitStack.push_back(std::make_pair(BB, succ_begin(BB)));
514 InStack.erase(VisitStack.pop_back_val().first);
516 } while (!VisitStack.empty());
523 /// AreEquivalentAddressValues - Test if A and B will obviously have the same
524 /// value. This includes recognizing that %t0 and %t1 will have the same
525 /// value in code like this:
526 /// %t0 = getelementptr \@a, 0, 3
527 /// store i32 0, i32* %t0
528 /// %t1 = getelementptr \@a, 0, 3
529 /// %t2 = load i32* %t1
531 static bool AreEquivalentAddressValues(const Value *A, const Value *B) {
532 // Test if the values are trivially equivalent.
533 if (A == B) return true;
535 // Test if the values come from identical arithmetic instructions.
536 // Use isIdenticalToWhenDefined instead of isIdenticalTo because
537 // this function is only used when one address use dominates the
538 // other, which means that they'll always either have the same
539 // value or one of them will have an undefined value.
540 if (isa<BinaryOperator>(A) || isa<CastInst>(A) ||
541 isa<PHINode>(A) || isa<GetElementPtrInst>(A))
542 if (const Instruction *BI = dyn_cast<Instruction>(B))
543 if (cast<Instruction>(A)->isIdenticalToWhenDefined(BI))
546 // Otherwise they may not be equivalent.
550 /// FindAvailableLoadedValue - Scan the ScanBB block backwards (starting at the
551 /// instruction before ScanFrom) checking to see if we have the value at the
552 /// memory address *Ptr locally available within a small number of instructions.
553 /// If the value is available, return it.
555 /// If not, return the iterator for the last validated instruction that the
556 /// value would be live through. If we scanned the entire block and didn't find
557 /// something that invalidates *Ptr or provides it, ScanFrom would be left at
558 /// begin() and this returns null. ScanFrom could also be left
560 /// MaxInstsToScan specifies the maximum instructions to scan in the block. If
561 /// it is set to 0, it will scan the whole block. You can also optionally
562 /// specify an alias analysis implementation, which makes this more precise.
563 Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
564 BasicBlock::iterator &ScanFrom,
565 unsigned MaxInstsToScan,
567 if (MaxInstsToScan == 0) MaxInstsToScan = ~0U;
569 // If we're using alias analysis to disambiguate get the size of *Ptr.
570 unsigned AccessSize = 0;
572 const Type *AccessTy = cast<PointerType>(Ptr->getType())->getElementType();
573 AccessSize = AA->getTypeStoreSize(AccessTy);
576 while (ScanFrom != ScanBB->begin()) {
577 // We must ignore debug info directives when counting (otherwise they
578 // would affect codegen).
579 Instruction *Inst = --ScanFrom;
580 if (isa<DbgInfoIntrinsic>(Inst))
582 // We skip pointer-to-pointer bitcasts, which are NOPs.
583 // It is necessary for correctness to skip those that feed into a
584 // llvm.dbg.declare, as these are not present when debugging is off.
585 if (isa<BitCastInst>(Inst) && isa<PointerType>(Inst->getType()))
588 // Restore ScanFrom to expected value in case next test succeeds
591 // Don't scan huge blocks.
592 if (MaxInstsToScan-- == 0) return 0;
595 // If this is a load of Ptr, the loaded value is available.
596 if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
597 if (AreEquivalentAddressValues(LI->getOperand(0), Ptr))
600 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
601 // If this is a store through Ptr, the value is available!
602 if (AreEquivalentAddressValues(SI->getOperand(1), Ptr))
603 return SI->getOperand(0);
605 // If Ptr is an alloca and this is a store to a different alloca, ignore
606 // the store. This is a trivial form of alias analysis that is important
607 // for reg2mem'd code.
608 if ((isa<AllocaInst>(Ptr) || isa<GlobalVariable>(Ptr)) &&
609 (isa<AllocaInst>(SI->getOperand(1)) ||
610 isa<GlobalVariable>(SI->getOperand(1))))
613 // If we have alias analysis and it says the store won't modify the loaded
614 // value, ignore the store.
616 (AA->getModRefInfo(SI, Ptr, AccessSize) & AliasAnalysis::Mod) == 0)
619 // Otherwise the store that may or may not alias the pointer, bail out.
624 // If this is some other instruction that may clobber Ptr, bail out.
625 if (Inst->mayWriteToMemory()) {
626 // If alias analysis claims that it really won't modify the load,
629 (AA->getModRefInfo(Inst, Ptr, AccessSize) & AliasAnalysis::Mod) == 0)
632 // May modify the pointer, bail out.
638 // Got to the start of the block, we didn't find it, but are done for this
643 /// CopyPrecedingStopPoint - If I is immediately preceded by a StopPoint,
644 /// make a copy of the stoppoint before InsertPos (presumably before copying
646 void llvm::CopyPrecedingStopPoint(Instruction *I,
647 BasicBlock::iterator InsertPos) {
648 if (I != I->getParent()->begin()) {
649 BasicBlock::iterator BBI = I; --BBI;
650 if (DbgStopPointInst *DSPI = dyn_cast<DbgStopPointInst>(BBI)) {
651 CallInst *newDSPI = cast<CallInst>(DSPI->clone());
652 newDSPI->insertBefore(InsertPos);