From: Chris Lattner Date: Tue, 9 Dec 2003 23:12:55 +0000 (+0000) Subject: Do not insert one entry PHI nodes in split exit blocks! X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=010ba10032d7c5f34c209cae1a9445776f49914a;p=oota-llvm.git Do not insert one entry PHI nodes in split exit blocks! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10348 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/lib/Transforms/Utils/LoopSimplify.cpp b/lib/Transforms/Utils/LoopSimplify.cpp index 60e35d5ca92..2618b73409d 100644 --- a/lib/Transforms/Utils/LoopSimplify.cpp +++ b/lib/Transforms/Utils/LoopSimplify.cpp @@ -162,21 +162,31 @@ BasicBlock *LoopSimplify::SplitBlockPredecessors(BasicBlock *BB, // incoming edges in BB into new PHI nodes in NewBB. // if (!Preds.empty()) { // Is the loop not obviously dead? - for (BasicBlock::iterator I = BB->begin(); - PHINode *PN = dyn_cast(I); ++I) { - - // Create the new PHI node, insert it into NewBB at the end of the block - PHINode *NewPHI = new PHINode(PN->getType(), PN->getName()+".ph", BI); + if (Preds.size() == 1) { + // No need to insert one operand PHI nodes! Instead, just update the + // incoming block ID's. + for (BasicBlock::iterator I = BB->begin(); + PHINode *PN = dyn_cast(I); ++I) { + unsigned i = PN->getBasicBlockIndex(Preds[0]); + PN->setIncomingBlock(i, NewBB); + } + } else { + for (BasicBlock::iterator I = BB->begin(); + PHINode *PN = dyn_cast(I); ++I) { - // Move all of the edges from blocks outside the loop to the new PHI - for (unsigned i = 0, e = Preds.size(); i != e; ++i) { - Value *V = PN->removeIncomingValue(Preds[i]); - NewPHI->addIncoming(V, Preds[i]); + // Create the new PHI node, insert it into NewBB at the end of the block + PHINode *NewPHI = new PHINode(PN->getType(), PN->getName()+".ph", BI); + + // Move all of the edges from blocks outside the loop to the new PHI + for (unsigned i = 0, e = Preds.size(); i != e; ++i) { + Value *V = PN->removeIncomingValue(Preds[i]); + NewPHI->addIncoming(V, Preds[i]); + } + + // Add an incoming value to the PHI node in the loop for the preheader + // edge. + PN->addIncoming(NewPHI, NewBB); } - - // Add an incoming value to the PHI node in the loop for the preheader - // edge - PN->addIncoming(NewPHI, NewBB); } // Now that the PHI nodes are updated, actually move the edges from