From 1673b15da2d908e0ea9fd2d64f61d6d226cfe16e Mon Sep 17 00:00:00 2001 From: Duncan Sands Date: Sat, 15 Oct 2011 11:13:42 +0000 Subject: [PATCH] Don't replace all dominated uses if there is only one use, since that use can't be dominated, saving one domtree lookup. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142066 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/GVN.cpp | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp index cbfdbcddaec..a51cbb631ba 100644 --- a/lib/Transforms/Scalar/GVN.cpp +++ b/lib/Transforms/Scalar/GVN.cpp @@ -1935,10 +1935,15 @@ bool GVN::propagateEquality(Value *LHS, Value *RHS, BasicBlock *Root) { // to 'LHS' then ensure it will be turned into 'RHS'. addToLeaderTable(VN.lookup_or_add(LHS), RHS, Root); - // Replace all occurrences of 'LHS' with 'RHS' everywhere in the scope. - unsigned NumReplacements = replaceAllDominatedUsesWith(LHS, RHS, Root); - bool Changed = NumReplacements > 0; - NumGVNEqProp += NumReplacements; + // Replace all occurrences of 'LHS' with 'RHS' everywhere in the scope. As + // LHS always has at least one use that is not dominated by Root, this will + // never do anything if LHS has only one use. + bool Changed = false; + if (!LHS->hasOneUse()) { + unsigned NumReplacements = replaceAllDominatedUsesWith(LHS, RHS, Root); + Changed |= NumReplacements > 0; + NumGVNEqProp += NumReplacements; + } // Now try to deduce additional equalities from this one. For example, if the // known equality was "(A != B)" == "false" then it follows that A and B are -- 2.34.1