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Add a fast path for x - x.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108855 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-07-20 16:53:00 +00:00
parent 08993c03ab
commit eb4152c192
1 changed files with 4 additions and 0 deletions
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4
lib/Analysis/ScalarEvolution.cpp
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@ -2442,6 +2442,10 @@ const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
///
const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS,
const SCEV *RHS) {
// Fast path: X - X --> 0.
if (LHS == RHS)
return getConstant(LHS->getType(), 0);
// X - Y --> X + -Y
return getAddExpr(LHS, getNegativeSCEV(RHS));
}