diff options
Diffstat (limited to 'lib/Analysis/ScalarEvolution.cpp')
| -rw-r--r-- | lib/Analysis/ScalarEvolution.cpp | 15 |
1 files changed, 7 insertions, 8 deletions
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index 86852d634ff23..ee42737705556 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -3154,8 +3154,9 @@ const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS, if (LHS == RHS) return getConstant(LHS->getType(), 0); - // X - Y --> X + -Y - return getAddExpr(LHS, getNegativeSCEV(RHS), Flags); + // X - Y --> X + -Y. + // X -(nsw || nuw) Y --> X + -Y. + return getAddExpr(LHS, getNegativeSCEV(RHS)); } /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion of the @@ -3461,12 +3462,10 @@ const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) { if (isKnownPositive(getMinusSCEV(getSCEV(GEP), Ptr))) Flags = setFlags(Flags, SCEV::FlagNUW); } - } else if (const SubOperator *OBO = - dyn_cast<SubOperator>(BEValueV)) { - if (OBO->hasNoUnsignedWrap()) - Flags = setFlags(Flags, SCEV::FlagNUW); - if (OBO->hasNoSignedWrap()) - Flags = setFlags(Flags, SCEV::FlagNSW); + + // We cannot transfer nuw and nsw flags from subtraction + // operations -- sub nuw X, Y is not the same as add nuw X, -Y + // for instance. } const SCEV *StartVal = getSCEV(StartValueV); |