// 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.
// 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);
}