diff options
Diffstat (limited to 'llvm/lib/Analysis')
| -rw-r--r-- | llvm/lib/Analysis/ScalarEvolution.cpp | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp index 649c6e0d575..9aefe8c33f7 100644 --- a/llvm/lib/Analysis/ScalarEvolution.cpp +++ b/llvm/lib/Analysis/ScalarEvolution.cpp @@ -1550,8 +1550,16 @@ const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op, getMulExpr(WideMaxBECount, getZeroExtendExpr(Step, WideTy))); if (SAdd == OperandExtendedAdd) { - // Cache knowledge of AR NSW, which is propagated to this AddRec. - const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW); + // If AR wraps around then + // + // abs(Step) * MaxBECount > unsigned-max(AR->getType()) + // => SAdd != OperandExtendedAdd + // + // Thus (AR is not NW => SAdd != OperandExtendedAdd) <=> + // (SAdd == OperandExtendedAdd => AR is NW) + + const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW); + // Return the expression with the addrec on the outside. return getAddRecExpr(getSignExtendAddRecStart(AR, Ty, this), getZeroExtendExpr(Step, Ty), |
