diff options
| -rw-r--r-- | llvm/lib/Analysis/ValueTracking.cpp | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index e31ddf0d646..4c2e7f253be 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -4146,19 +4146,21 @@ static OverflowResult computeOverflowForSignedAdd(const Value *LHS, return OverflowResult::MayOverflow; // If the sign of Add is the same as at least one of the operands, this add - // CANNOT overflow. This is particularly useful when the sum is - // @llvm.assume'ed non-negative rather than proved so from analyzing its - // operands. + // CANNOT overflow. If this can be determined from the known bits of the + // operands the above signedAddMayOverflow() check will have already done so. + // The only other way to improve on the known bits is from an assumption, so + // call computeKnownBitsFromAssume() directly. bool LHSOrRHSKnownNonNegative = (LHSKnown.isNonNegative() || RHSKnown.isNonNegative()); bool LHSOrRHSKnownNegative = (LHSKnown.isNegative() || RHSKnown.isNegative()); if (LHSOrRHSKnownNonNegative || LHSOrRHSKnownNegative) { - KnownBits AddKnown = computeKnownBits(Add, DL, /*Depth=*/0, AC, CxtI, DT); + KnownBits AddKnown(LHSKnown.getBitWidth()); + computeKnownBitsFromAssume( + Add, AddKnown, /*Depth=*/0, Query(DL, AC, CxtI, DT, true)); if ((AddKnown.isNonNegative() && LHSOrRHSKnownNonNegative) || - (AddKnown.isNegative() && LHSOrRHSKnownNegative)) { + (AddKnown.isNegative() && LHSOrRHSKnownNegative)) return OverflowResult::NeverOverflows; - } } return OverflowResult::MayOverflow; |
