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PHINode::getBasicBlockIndex is O(n) in the number of inputs
to a PHI, avoid it in the common case where the BB occurs in the same index for multiple phis. This speeds up CGP on an insane testcase from 8.35 to 3.58s. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96080 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -179,7 +179,7 @@ BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
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// Create a new basic block, linking it into the CFG.
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BasicBlock *NewBB = BasicBlock::Create(TI->getContext(),
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TIBB->getName() + "." + DestBB->getName() + "_crit_edge");
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// Create our unconditional branch...
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// Create our unconditional branch.
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BranchInst::Create(DestBB, NewBB);
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// Branch to the new block, breaking the edge.
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@ -193,12 +193,19 @@ BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
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// If there are any PHI nodes in DestBB, we need to update them so that they
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// merge incoming values from NewBB instead of from TIBB.
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//
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unsigned BBIdx = 0;
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for (BasicBlock::iterator I = DestBB->begin(); isa<PHINode>(I); ++I) {
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PHINode *PN = cast<PHINode>(I);
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// We no longer enter through TIBB, now we come in through NewBB. Revector
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// exactly one entry in the PHI node that used to come from TIBB to come
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// from NewBB.
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int BBIdx = PN->getBasicBlockIndex(TIBB);
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PHINode *PN = cast<PHINode>(I);
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// Reuse the previous value of BBIdx if it lines up. In cases where we have
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// multiple phi nodes with *lots* of predecessors, this is a speed win
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// because we don't have to scan the PHI looking for TIBB. This happens
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// because the BB list of PHI nodes are usually in the same order.
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if (PN->getIncomingBlock(BBIdx) != TIBB)
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BBIdx = PN->getBasicBlockIndex(TIBB);
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PN->setIncomingBlock(BBIdx, NewBB);
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}
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