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author | Duncan Sands <baldrick@free.fr> | 2011-10-15 11:13:42 +0000 |
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committer | Duncan Sands <baldrick@free.fr> | 2011-10-15 11:13:42 +0000 |
commit | 1673b15da2d908e0ea9fd2d64f61d6d226cfe16e (patch) | |
tree | 9007d5fb98a8a2af011af018194a873ef1291c3d /lib/Transforms | |
parent | 6e6a558ebce556476d8fd659b419a2760f2ab154 (diff) | |
download | llvm-1673b15da2d908e0ea9fd2d64f61d6d226cfe16e.tar.gz llvm-1673b15da2d908e0ea9fd2d64f61d6d226cfe16e.tar.bz2 llvm-1673b15da2d908e0ea9fd2d64f61d6d226cfe16e.tar.xz |
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
Diffstat (limited to 'lib/Transforms')
-rw-r--r-- | lib/Transforms/Scalar/GVN.cpp | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp index cbfdbcddae..a51cbb631b 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 |