diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Analysis/ScalarEvolution.cpp | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index ca959ab..227f1de 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -3088,15 +3088,20 @@ const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) { Flags = setFlags(Flags, SCEV::FlagNUW); if (OBO->hasNoSignedWrap()) Flags = setFlags(Flags, SCEV::FlagNSW); - } else if (const GEPOperator *GEP = - dyn_cast<GEPOperator>(BEValueV)) { + } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(BEValueV)) { // If the increment is an inbounds GEP, then we know the address // space cannot be wrapped around. We cannot make any guarantee // about signed or unsigned overflow because pointers are // unsigned but we may have a negative index from the base - // pointer. - if (GEP->isInBounds()) + // pointer. We can guarantee that no unsigned wrap occurs if the + // indices form a positive value. + if (GEP->isInBounds()) { Flags = setFlags(Flags, SCEV::FlagNW); + + const SCEV *Ptr = getSCEV(GEP->getPointerOperand()); + if (isKnownPositive(getMinusSCEV(getSCEV(GEP), Ptr))) + Flags = setFlags(Flags, SCEV::FlagNUW); + } } const SCEV *StartVal = getSCEV(StartValueV); |