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Don't replace all dominated uses if there is only one use, since that

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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
This commit is contained in:
Duncan Sands 2011-10-15 11:13:42 +00:00
parent 6e6a558ebc
commit 1673b15da2
1 changed files with 9 additions and 4 deletions
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13
lib/Transforms/Scalar/GVN.cpp
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@ -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