https://llvm.org/bugs/show_bug.cgi?id=28294
Bug ID: 28294
Summary: UB in APInt::slt
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Support Libraries
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
When VAL has its MSbit set, the left shift on line 558 shifts a negative value
leftward, which is UB. Similarly for RHS.VAL on line 559:
555: bool APInt::slt(const APInt& RHS) const {
556: assert(BitWidth == RHS.BitWidth && "Bit widths must be same for
comparison");
557: if (isSingleWord()) {
558: int64_t lhsSext = (int64_t(VAL) << (64-BitWidth)) >> (64-BitWidth);
559: int64_t rhsSext = (int64_t(RHS.VAL) << (64-BitWidth)) >>
(64-BitWidth);
560: return lhsSext < rhsSext;
561: }
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