From c20e24524f6dcfb423b9c6d9d223ec11f13d3c84 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Thu, 22 Aug 2002 20:22:01 +0000 Subject: [PATCH] Instcombine PHI's of the form %PN = phi PN, X into X and %PN = phi PN, PN, PN into 0 (because the phi must not be reachable) git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3470 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/InstructionCombining.cpp | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 30e143dec46..0f8ae0c6bdb 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -610,10 +610,19 @@ Instruction *InstCombiner::visitPHINode(PHINode &PN) { // Otherwise if all of the incoming values are the same for the PHI, replace // the PHI node with the incoming value. // - Value *InVal = PN.getIncomingValue(0); - for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) - if (PN.getIncomingValue(i) != InVal) - return 0; // Not the same, bail out. + Value *InVal = 0; + for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) + if (PN.getIncomingValue(i) != &PN) // Not the PHI node itself... + if (InVal && PN.getIncomingValue(i) != InVal) + return 0; // Not the same, bail out. + else + InVal = PN.getIncomingValue(i); + + // The only case that could cause InVal to be null is if we have a PHI node + // that only has entries for itself. In this case, there is no entry into the + // loop, so kill the PHI. + // + if (InVal == 0) InVal = Constant::getNullValue(PN.getType()); // All of the incoming values are the same, replace the PHI node now. return ReplaceInstUsesWith(PN, InVal); -- 2.34.1