diff options
| -rw-r--r-- | llvm/lib/Analysis/ScalarEvolution.cpp | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp index 6edd8621ab3..2ff254394a3 100644 --- a/llvm/lib/Analysis/ScalarEvolution.cpp +++ b/llvm/lib/Analysis/ScalarEvolution.cpp @@ -1327,12 +1327,12 @@ static const SCEV *getOverflowLimitForStep(const SCEV *Step, return nullptr; } -// The recurrence AR has been shown to have no signed wrap. Typically, if we can -// prove NSW for AR, then we can just as easily prove NSW for its preincrement -// or postincrement sibling. This allows normalizing a sign extended AddRec as -// such: {sext(Step + Start),+,Step} => {(Step + sext(Start),+,Step} As a -// result, the expression "Step + sext(PreIncAR)" is congruent with -// "sext(PostIncAR)" +// The recurrence AR has been shown to have no signed wrap or something close to +// it. Typically, if we can prove NSW for AR, then we can just as easily prove +// NSW for its preincrement or postincrement sibling. This allows normalizing a +// sign extended AddRec as such: {sext(Step + Start),+,Step} => {(Step + +// sext(Start),+,Step} As a result, the expression "Step + sext(PreIncAR)" is +// congruent with "sext(PostIncAR)" static const SCEV *getPreStartForSignExtend(const SCEVAddRecExpr *AR, Type *Ty, ScalarEvolution *SE) { @@ -1392,7 +1392,7 @@ static const SCEV *getPreStartForSignExtend(const SCEVAddRecExpr *AR, SE->getSignExtendExpr(Step, WideTy)); if (SE->getSignExtendExpr(Start, WideTy) == OperandExtendedStart) { // Cache knowledge of PreAR NSW. - if (PreAR) + if (PreAR && AR->getNoWrapFlags(SCEV::FlagNSW)) const_cast<SCEVAddRecExpr *>(PreAR)->setNoWrapFlags(SCEV::FlagNSW); // FIXME: this optimization needs a unit test DEBUG(dbgs() << "SCEV: untested prestart overflow check\n"); |
