From f02c46834a2494f1318d9fbccc1fc7c7299360ee Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Tue, 20 Aug 2002 15:35:35 +0000 Subject: [PATCH] - implemented instcombine of phi (X, X, X) -> X git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3397 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/InstructionCombining.cpp | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 088a758c7f5..71c2cc6e3f5 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -594,10 +594,21 @@ Instruction *InstCombiner::visitCastInst(CastInst &CI) { // Instruction *InstCombiner::visitPHINode(PHINode &PN) { // If the PHI node only has one incoming value, eliminate the PHI node... + if (PN.getNumIncomingValues() == 0) + return ReplaceInstUsesWith(PN, Constant::getNullValue(PN.getType())); if (PN.getNumIncomingValues() == 1) return ReplaceInstUsesWith(PN, PN.getIncomingValue(0)); + + // 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. - return 0; + // All of the incoming values are the same, replace the PHI node now. + return ReplaceInstUsesWith(PN, InVal); } -- 2.34.1