diff options
Diffstat (limited to 'lib/Transforms/Utils/BreakCriticalEdges.cpp')
| -rw-r--r-- | lib/Transforms/Utils/BreakCriticalEdges.cpp | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/lib/Transforms/Utils/BreakCriticalEdges.cpp b/lib/Transforms/Utils/BreakCriticalEdges.cpp index eb3e3b2ff3..dac60131c3 100644 --- a/lib/Transforms/Utils/BreakCriticalEdges.cpp +++ b/lib/Transforms/Utils/BreakCriticalEdges.cpp @@ -179,7 +179,7 @@ BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, // Create a new basic block, linking it into the CFG. BasicBlock *NewBB = BasicBlock::Create(TI->getContext(), TIBB->getName() + "." + DestBB->getName() + "_crit_edge"); - // Create our unconditional branch... + // Create our unconditional branch. BranchInst::Create(DestBB, NewBB); // Branch to the new block, breaking the edge. @@ -193,12 +193,19 @@ BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, // If there are any PHI nodes in DestBB, we need to update them so that they // merge incoming values from NewBB instead of from TIBB. // + unsigned BBIdx = 0; for (BasicBlock::iterator I = DestBB->begin(); isa<PHINode>(I); ++I) { - PHINode *PN = cast<PHINode>(I); // We no longer enter through TIBB, now we come in through NewBB. Revector // exactly one entry in the PHI node that used to come from TIBB to come // from NewBB. - int BBIdx = PN->getBasicBlockIndex(TIBB); + PHINode *PN = cast<PHINode>(I); + + // Reuse the previous value of BBIdx if it lines up. In cases where we have + // multiple phi nodes with *lots* of predecessors, this is a speed win + // because we don't have to scan the PHI looking for TIBB. This happens + // because the BB list of PHI nodes are usually in the same order. + if (PN->getIncomingBlock(BBIdx) != TIBB) + BBIdx = PN->getBasicBlockIndex(TIBB); PN->setIncomingBlock(BBIdx, NewBB); } |