Sanjay Patel 7a2949647a [InstCombine] propagate no-wrap flag through select-of-mul fold ...

This may not be obvious, but Alive2 agrees:
https://alive2.llvm.org/ce/z/Ld9qNT

If the mul has "nsw", then -1 * INT_MIN is poison, so the
negate can also have "nsw" because 0 - INT_MIN is poison.

If the mul has "nuw", then that means the "OtherOp" can only
be 0 or 1 (anything else multiplied by 0xfff... would wrap).
So the replacement negate must be "nsw" because it is either
"0-0" or "0-1".

This is another regression noticed with a planned follow-up
to D111410.

2021-10-12 12:57:20 -04:00

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