#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Constant.h"
#include "llvm/Type.h"
#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/MemoryDependenceAnalysis.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/ValueHandle.h"
#include <algorithm>
using namespace llvm;
+/// DeleteDeadBlock - Delete the specified block, which must have no
+/// predecessors.
+void llvm::DeleteDeadBlock(BasicBlock *BB) {
+ assert((pred_begin(BB) == pred_end(BB) ||
+ // Can delete self loop.
+ BB->getSinglePredecessor() == BB) && "Block is not dead!");
+ TerminatorInst *BBTerm = BB->getTerminator();
+
+ // Loop through all of our successors and make sure they know that one
+ // of their predecessors is going away.
+ for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i)
+ BBTerm->getSuccessor(i)->removePredecessor(BB);
+
+ // Zap all the instructions in the block.
+ while (!BB->empty()) {
+ Instruction &I = BB->back();
+ // If this instruction is used, replace uses with an arbitrary value.
+ // Because control flow can't get here, we don't care what we replace the
+ // value with. Note that since this block is unreachable, and all values
+ // contained within it must dominate their uses, that all uses will
+ // eventually be removed (they are themselves dead).
+ if (!I.use_empty())
+ I.replaceAllUsesWith(UndefValue::get(I.getType()));
+ BB->getInstList().pop_back();
+ }
+
+ // Zap the block!
+ BB->eraseFromParent();
+}
+
+/// FoldSingleEntryPHINodes - We know that BB has one predecessor. If there are
+/// any single-entry PHI nodes in it, fold them away. This handles the case
+/// when all entries to the PHI nodes in a block are guaranteed equal, such as
+/// when the block has exactly one predecessor.
+void llvm::FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P) {
+ if (!isa<PHINode>(BB->begin())) return;
+
+ AliasAnalysis *AA = 0;
+ MemoryDependenceAnalysis *MemDep = 0;
+ if (P) {
+ AA = P->getAnalysisIfAvailable<AliasAnalysis>();
+ MemDep = P->getAnalysisIfAvailable<MemoryDependenceAnalysis>();
+ }
+
+ while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
+ if (PN->getIncomingValue(0) != PN)
+ PN->replaceAllUsesWith(PN->getIncomingValue(0));
+ else
+ PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
+
+ if (MemDep)
+ MemDep->removeInstruction(PN); // Memdep updates AA itself.
+ else if (AA && isa<PointerType>(PN->getType()))
+ AA->deleteValue(PN);
+
+ PN->eraseFromParent();
+ }
+}
+
+
+/// DeleteDeadPHIs - Examine each PHI in the given block and delete it if it
+/// is dead. Also recursively delete any operands that become dead as
+/// a result. This includes tracing the def-use list from the PHI to see if
+/// it is ultimately unused or if it reaches an unused cycle.
+bool llvm::DeleteDeadPHIs(BasicBlock *BB) {
+ // Recursively deleting a PHI may cause multiple PHIs to be deleted
+ // or RAUW'd undef, so use an array of WeakVH for the PHIs to delete.
+ SmallVector<WeakVH, 8> PHIs;
+ for (BasicBlock::iterator I = BB->begin();
+ PHINode *PN = dyn_cast<PHINode>(I); ++I)
+ PHIs.push_back(PN);
+
+ bool Changed = false;
+ for (unsigned i = 0, e = PHIs.size(); i != e; ++i)
+ if (PHINode *PN = dyn_cast_or_null<PHINode>(PHIs[i].operator Value*()))
+ Changed |= RecursivelyDeleteDeadPHINode(PN);
+
+ return Changed;
+}
+
+/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
+/// if possible. The return value indicates success or failure.
+bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P) {
+ // Don't merge away blocks who have their address taken.
+ if (BB->hasAddressTaken()) return false;
+
+ // Can't merge if there are multiple predecessors, or no predecessors.
+ BasicBlock *PredBB = BB->getUniquePredecessor();
+ if (!PredBB) return false;
+
+ // Don't break self-loops.
+ if (PredBB == BB) return false;
+ // Don't break invokes.
+ if (isa<InvokeInst>(PredBB->getTerminator())) return false;
+
+ succ_iterator SI(succ_begin(PredBB)), SE(succ_end(PredBB));
+ BasicBlock *OnlySucc = BB;
+ for (; SI != SE; ++SI)
+ if (*SI != OnlySucc) {
+ OnlySucc = 0; // There are multiple distinct successors!
+ break;
+ }
+
+ // Can't merge if there are multiple successors.
+ if (!OnlySucc) return false;
+
+ // Can't merge if there is PHI loop.
+ for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI) {
+ if (PHINode *PN = dyn_cast<PHINode>(BI)) {
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) == PN)
+ return false;
+ } else
+ break;
+ }
+
+ // Begin by getting rid of unneeded PHIs.
+ if (isa<PHINode>(BB->front()))
+ FoldSingleEntryPHINodes(BB, P);
+
+ // Delete the unconditional branch from the predecessor...
+ PredBB->getInstList().pop_back();
+
+ // Make all PHI nodes that referred to BB now refer to Pred as their
+ // source...
+ BB->replaceAllUsesWith(PredBB);
+
+ // Move all definitions in the successor to the predecessor...
+ PredBB->getInstList().splice(PredBB->end(), BB->getInstList());
+
+ // Inherit predecessors name if it exists.
+ if (!PredBB->hasName())
+ PredBB->takeName(BB);
+
+ // Finally, erase the old block and update dominator info.
+ if (P) {
+ if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>()) {
+ if (DomTreeNode *DTN = DT->getNode(BB)) {
+ DomTreeNode *PredDTN = DT->getNode(PredBB);
+ SmallVector<DomTreeNode*, 8> Children(DTN->begin(), DTN->end());
+ for (SmallVector<DomTreeNode*, 8>::iterator DI = Children.begin(),
+ DE = Children.end(); DI != DE; ++DI)
+ DT->changeImmediateDominator(*DI, PredDTN);
+
+ DT->eraseNode(BB);
+ }
+
+ if (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>())
+ LI->removeBlock(BB);
+
+ if (MemoryDependenceAnalysis *MD =
+ P->getAnalysisIfAvailable<MemoryDependenceAnalysis>())
+ MD->invalidateCachedPredecessors();
+ }
+ }
+
+ BB->eraseFromParent();
+ return true;
+}
+
/// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
/// with a value, then remove and delete the original instruction.
///
ReplaceInstWithInst(From->getParent()->getInstList(), BI, To);
}
-/// RemoveSuccessor - Change the specified terminator instruction such that its
-/// successor SuccNum no longer exists. Because this reduces the outgoing
-/// degree of the current basic block, the actual terminator instruction itself
-/// may have to be changed. In the case where the last successor of the block
-/// is deleted, a return instruction is inserted in its place which can cause a
-/// surprising change in program behavior if it is not expected.
-///
-void llvm::RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) {
- assert(SuccNum < TI->getNumSuccessors() &&
- "Trying to remove a nonexistant successor!");
-
- // If our old successor block contains any PHI nodes, remove the entry in the
- // PHI nodes that comes from this branch...
- //
- BasicBlock *BB = TI->getParent();
- TI->getSuccessor(SuccNum)->removePredecessor(BB);
-
- TerminatorInst *NewTI = 0;
- switch (TI->getOpcode()) {
- case Instruction::Br:
- // If this is a conditional branch... convert to unconditional branch.
- if (TI->getNumSuccessors() == 2) {
- cast<BranchInst>(TI)->setUnconditionalDest(TI->getSuccessor(1-SuccNum));
- } else { // Otherwise convert to a return instruction...
- Value *RetVal = 0;
-
- // Create a value to return... if the function doesn't return null...
- if (BB->getParent()->getReturnType() != Type::VoidTy)
- RetVal = Constant::getNullValue(BB->getParent()->getReturnType());
-
- // Create the return...
- NewTI = ReturnInst::Create(RetVal);
- }
- break;
-
- case Instruction::Invoke: // Should convert to call
- case Instruction::Switch: // Should remove entry
- default:
- case Instruction::Ret: // Cannot happen, has no successors!
- assert(0 && "Unhandled terminator instruction type in RemoveSuccessor!");
- abort();
+/// GetSuccessorNumber - Search for the specified successor of basic block BB
+/// and return its position in the terminator instruction's list of
+/// successors. It is an error to call this with a block that is not a
+/// successor.
+unsigned llvm::GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ) {
+ TerminatorInst *Term = BB->getTerminator();
+#ifndef NDEBUG
+ unsigned e = Term->getNumSuccessors();
+#endif
+ for (unsigned i = 0; ; ++i) {
+ assert(i != e && "Didn't find edge?");
+ if (Term->getSuccessor(i) == Succ)
+ return i;
}
-
- if (NewTI) // If it's a different instruction, replace.
- ReplaceInstWithInst(TI, NewTI);
+ return 0;
}
/// SplitEdge - Split the edge connecting specified block. Pass P must
/// not be NULL.
BasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) {
- TerminatorInst *LatchTerm = BB->getTerminator();
- unsigned SuccNum = 0;
- for (unsigned i = 0, e = LatchTerm->getNumSuccessors(); ; ++i) {
- assert(i != e && "Didn't find edge?");
- if (LatchTerm->getSuccessor(i) == Succ) {
- SuccNum = i;
- break;
- }
- }
+ unsigned SuccNum = GetSuccessorNumber(BB, Succ);
// If this is a critical edge, let SplitCriticalEdge do it.
- if (SplitCriticalEdge(BB->getTerminator(), SuccNum, P))
+ TerminatorInst *LatchTerm = BB->getTerminator();
+ if (SplitCriticalEdge(LatchTerm, SuccNum, P))
return LatchTerm->getSuccessor(SuccNum);
// If the edge isn't critical, then BB has a single successor or Succ has a
// If the successor only has a single pred, split the top of the successor
// block.
assert(SP == BB && "CFG broken");
+ SP = NULL;
return SplitBlock(Succ, Succ->begin(), P);
- } else {
- // Otherwise, if BB has a single successor, split it at the bottom of the
- // block.
- assert(BB->getTerminator()->getNumSuccessors() == 1 &&
- "Should have a single succ!");
- return SplitBlock(BB, BB->getTerminator(), P);
}
+
+ // Otherwise, if BB has a single successor, split it at the bottom of the
+ // block.
+ assert(BB->getTerminator()->getNumSuccessors() == 1 &&
+ "Should have a single succ!");
+ return SplitBlock(BB, BB->getTerminator(), P);
}
/// SplitBlock - Split the specified block at the specified instruction - every
/// the loop info is updated.
///
BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) {
-
- LoopInfo &LI = P->getAnalysis<LoopInfo>();
BasicBlock::iterator SplitIt = SplitPt;
while (isa<PHINode>(SplitIt))
++SplitIt;
BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
- // The new block lives in whichever loop the old one did.
- if (Loop *L = LI.getLoopFor(Old))
- L->addBasicBlockToLoop(New, LI.getBase());
-
- if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>())
- {
- // Old dominates New. New node domiantes all other nodes dominated by Old.
- DomTreeNode *OldNode = DT->getNode(Old);
- std::vector<DomTreeNode *> Children;
- for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end();
- I != E; ++I)
- Children.push_back(*I);
+ // The new block lives in whichever loop the old one did. This preserves
+ // LCSSA as well, because we force the split point to be after any PHI nodes.
+ if (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>())
+ if (Loop *L = LI->getLoopFor(Old))
+ L->addBasicBlockToLoop(New, LI->getBase());
- DomTreeNode *NewNode = DT->addNewBlock(New,Old);
+ if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>()) {
+ // Old dominates New. New node dominates all other nodes dominated by Old.
+ DomTreeNode *OldNode = DT->getNode(Old);
+ std::vector<DomTreeNode *> Children;
+ for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end();
+ I != E; ++I)
+ Children.push_back(*I);
+ DomTreeNode *NewNode = DT->addNewBlock(New,Old);
for (std::vector<DomTreeNode *>::iterator I = Children.begin(),
E = Children.end(); I != E; ++I)
DT->changeImmediateDominator(*I, NewNode);
- }
+ }
- if (DominanceFrontier *DF = P->getAnalysisToUpdate<DominanceFrontier>())
- DF->splitBlock(Old);
-
return New;
}
/// Preds array, which has NumPreds elements in it. The new block is given a
/// suffix of 'Suffix'.
///
-/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree and
-/// DominanceFrontier, but no other analyses.
+/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
+/// LoopInfo, and LCCSA but no other analyses. In particular, it does not
+/// preserve LoopSimplify (because it's complicated to handle the case where one
+/// of the edges being split is an exit of a loop with other exits).
+///
BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
BasicBlock *const *Preds,
unsigned NumPreds, const char *Suffix,
Pass *P) {
// Create new basic block, insert right before the original block.
- BasicBlock *NewBB =
- BasicBlock::Create(BB->getName()+Suffix, BB->getParent(), BB);
+ BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), BB->getName()+Suffix,
+ BB->getParent(), BB);
// The new block unconditionally branches to the old block.
BranchInst *BI = BranchInst::Create(BB, NewBB);
+ LoopInfo *LI = P ? P->getAnalysisIfAvailable<LoopInfo>() : 0;
+ Loop *L = LI ? LI->getLoopFor(BB) : 0;
+ bool PreserveLCSSA = P->mustPreserveAnalysisID(LCSSAID);
+
// Move the edges from Preds to point to NewBB instead of BB.
- for (unsigned i = 0; i != NumPreds; ++i)
+ // While here, if we need to preserve loop analyses, collect
+ // some information about how this split will affect loops.
+ bool HasLoopExit = false;
+ bool IsLoopEntry = !!L;
+ bool SplitMakesNewLoopHeader = false;
+ for (unsigned i = 0; i != NumPreds; ++i) {
+ // This is slightly more strict than necessary; the minimum requirement
+ // is that there be no more than one indirectbr branching to BB. And
+ // all BlockAddress uses would need to be updated.
+ assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
+ "Cannot split an edge from an IndirectBrInst");
+
Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
-
- // Update dominator tree and dominator frontier if available.
- DominatorTree *DT = P ? P->getAnalysisToUpdate<DominatorTree>() : 0;
+
+ if (LI) {
+ // If we need to preserve LCSSA, determine if any of
+ // the preds is a loop exit.
+ if (PreserveLCSSA)
+ if (Loop *PL = LI->getLoopFor(Preds[i]))
+ if (!PL->contains(BB))
+ HasLoopExit = true;
+ // If we need to preserve LoopInfo, note whether any of the
+ // preds crosses an interesting loop boundary.
+ if (L) {
+ if (L->contains(Preds[i]))
+ IsLoopEntry = false;
+ else
+ SplitMakesNewLoopHeader = true;
+ }
+ }
+ }
+
+ // Update dominator tree if available.
+ DominatorTree *DT = P ? P->getAnalysisIfAvailable<DominatorTree>() : 0;
if (DT)
DT->splitBlock(NewBB);
- if (DominanceFrontier *DF = P ? P->getAnalysisToUpdate<DominanceFrontier>():0)
- DF->splitBlock(NewBB);
- AliasAnalysis *AA = P ? P->getAnalysisToUpdate<AliasAnalysis>() : 0;
-
-
+
// Insert a new PHI node into NewBB for every PHI node in BB and that new PHI
// node becomes an incoming value for BB's phi node. However, if the Preds
// list is empty, we need to insert dummy entries into the PHI nodes in BB to
cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
return NewBB;
}
+
+ AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
+
+ if (L) {
+ if (IsLoopEntry) {
+ // Add the new block to the nearest enclosing loop (and not an
+ // adjacent loop). To find this, examine each of the predecessors and
+ // determine which loops enclose them, and select the most-nested loop
+ // which contains the loop containing the block being split.
+ Loop *InnermostPredLoop = 0;
+ for (unsigned i = 0; i != NumPreds; ++i)
+ if (Loop *PredLoop = LI->getLoopFor(Preds[i])) {
+ // Seek a loop which actually contains the block being split (to
+ // avoid adjacent loops).
+ while (PredLoop && !PredLoop->contains(BB))
+ PredLoop = PredLoop->getParentLoop();
+ // Select the most-nested of these loops which contains the block.
+ if (PredLoop &&
+ PredLoop->contains(BB) &&
+ (!InnermostPredLoop ||
+ InnermostPredLoop->getLoopDepth() < PredLoop->getLoopDepth()))
+ InnermostPredLoop = PredLoop;
+ }
+ if (InnermostPredLoop)
+ InnermostPredLoop->addBasicBlockToLoop(NewBB, LI->getBase());
+ } else {
+ L->addBasicBlockToLoop(NewBB, LI->getBase());
+ if (SplitMakesNewLoopHeader)
+ L->moveToHeader(NewBB);
+ }
+ }
// Otherwise, create a new PHI node in NewBB for each PHI node in BB.
for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ) {
PHINode *PN = cast<PHINode>(I++);
// Check to see if all of the values coming in are the same. If so, we
- // don't need to create a new PHI node.
- Value *InVal = PN->getIncomingValueForBlock(Preds[0]);
- for (unsigned i = 1; i != NumPreds; ++i)
- if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
- InVal = 0;
- break;
- }
-
+ // don't need to create a new PHI node, unless it's needed for LCSSA.
+ Value *InVal = 0;
+ if (!HasLoopExit) {
+ InVal = PN->getIncomingValueForBlock(Preds[0]);
+ for (unsigned i = 1; i != NumPreds; ++i)
+ if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
+ InVal = 0;
+ break;
+ }
+ }
+
if (InVal) {
// If all incoming values for the new PHI would be the same, just don't
// make a new PHI. Instead, just remove the incoming values from the old
// If the values coming into the block are not the same, we need a PHI.
// Create the new PHI node, insert it into NewBB at the end of the block
PHINode *NewPHI =
- PHINode::Create(PN->getType(), PN->getName()+".ph", BI);
+ PHINode::Create(PN->getType(), NumPreds, PN->getName()+".ph", BI);
if (AA) AA->copyValue(PN, NewPHI);
// Move all of the PHI values for 'Preds' to the new PHI.
// Add an incoming value to the PHI node in the loop for the preheader
// edge.
PN->addIncoming(InVal, NewBB);
-
- // Check to see if we can eliminate this phi node.
- if (Value *V = PN->hasConstantValue(DT != 0)) {
- Instruction *I = dyn_cast<Instruction>(V);
- if (!I || DT == 0 || DT->dominates(I, PN)) {
- PN->replaceAllUsesWith(V);
- if (AA) AA->deleteValue(PN);
- PN->eraseFromParent();
- }
- }
}
return NewBB;
}
+
+/// FindFunctionBackedges - Analyze the specified function to find all of the
+/// loop backedges in the function and return them. This is a relatively cheap
+/// (compared to computing dominators and loop info) analysis.
+///
+/// The output is added to Result, as pairs of <from,to> edge info.
+void llvm::FindFunctionBackedges(const Function &F,
+ SmallVectorImpl<std::pair<const BasicBlock*,const BasicBlock*> > &Result) {
+ const BasicBlock *BB = &F.getEntryBlock();
+ if (succ_begin(BB) == succ_end(BB))
+ return;
+
+ SmallPtrSet<const BasicBlock*, 8> Visited;
+ SmallVector<std::pair<const BasicBlock*, succ_const_iterator>, 8> VisitStack;
+ SmallPtrSet<const BasicBlock*, 8> InStack;
+
+ Visited.insert(BB);
+ VisitStack.push_back(std::make_pair(BB, succ_begin(BB)));
+ InStack.insert(BB);
+ do {
+ std::pair<const BasicBlock*, succ_const_iterator> &Top = VisitStack.back();
+ const BasicBlock *ParentBB = Top.first;
+ succ_const_iterator &I = Top.second;
+
+ bool FoundNew = false;
+ while (I != succ_end(ParentBB)) {
+ BB = *I++;
+ if (Visited.insert(BB)) {
+ FoundNew = true;
+ break;
+ }
+ // Successor is in VisitStack, it's a back edge.
+ if (InStack.count(BB))
+ Result.push_back(std::make_pair(ParentBB, BB));
+ }
+
+ if (FoundNew) {
+ // Go down one level if there is a unvisited successor.
+ InStack.insert(BB);
+ VisitStack.push_back(std::make_pair(BB, succ_begin(BB)));
+ } else {
+ // Go up one level.
+ InStack.erase(VisitStack.pop_back_val().first);
+ }
+ } while (!VisitStack.empty());
+}
+
+/// FoldReturnIntoUncondBranch - This method duplicates the specified return
+/// instruction into a predecessor which ends in an unconditional branch. If
+/// the return instruction returns a value defined by a PHI, propagate the
+/// right value into the return. It returns the new return instruction in the
+/// predecessor.
+ReturnInst *llvm::FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB,
+ BasicBlock *Pred) {
+ Instruction *UncondBranch = Pred->getTerminator();
+ // Clone the return and add it to the end of the predecessor.
+ Instruction *NewRet = RI->clone();
+ Pred->getInstList().push_back(NewRet);
+
+ // If the return instruction returns a value, and if the value was a
+ // PHI node in "BB", propagate the right value into the return.
+ for (User::op_iterator i = NewRet->op_begin(), e = NewRet->op_end();
+ i != e; ++i)
+ if (PHINode *PN = dyn_cast<PHINode>(*i))
+ if (PN->getParent() == BB)
+ *i = PN->getIncomingValueForBlock(Pred);
+
+ // Update any PHI nodes in the returning block to realize that we no
+ // longer branch to them.
+ BB->removePredecessor(Pred);
+ UncondBranch->eraseFromParent();
+ return cast<ReturnInst>(NewRet);
+}
+
+/// GetFirstDebugLocInBasicBlock - Return first valid DebugLoc entry in a
+/// given basic block.
+DebugLoc llvm::GetFirstDebugLocInBasicBlock(const BasicBlock *BB) {
+ if (const Instruction *I = BB->getFirstNonPHI())
+ return I->getDebugLoc();
+ // Scanning entire block may be too expensive, if the first instruction
+ // does not have valid location info.
+ return DebugLoc();
+}
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