[VPlan] Only retain NSW when possible in getFlagsFromIndDesc. - #226315
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getFlagsFromIndDesc is used to get the flags to use for wide inductions. Those are normalized to Adds, with the step negated if the induction binop is Sub. Only retain all flags for Add. For Sub, never retain NUW and only keep NSW if the step is known to not be signed min. Alive2 Proofs showing incorrect NUW/NSW transfer and transfer of NSW if step is != signed INT_MIN: https://alive2.llvm.org/ce/z/zGKeZg Fixes llvm#224024.
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September 24, 2026 22:27
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getFlagsFromIndDesc is used to get the flags to use for wide inductions. Those are normalized to Adds, with the step negated if the induction binop is Sub.
Only retain all flags for Add. For Sub, never retain NUW and only keep NSW if the step is known to not be signed min.
Alive2 Proofs showing incorrect NUW/NSW transfer and transfer of NSW if step is != signed INT_MIN: https://alive2.llvm.org/ce/z/zGKeZg
Fixes #224024.