[PATCH] D69563: [LV] Strip wrap flags from vectorized reductions

[Hideki Saito via Phabricator via llvm-commits]

hsaito added a comment.

Are we essentially saying that any reassociation can't preserve NSW/NUW flags?

Say, X = MAX_INT, Y = -1, and Z = 1. "t1 = X + Y; t2 = t1 + Z" does not cause signed wrap. "t1 = X + Z; t2 = t1 + Y" does, right?

If we agree on that, since vector reduction is a form of reassociation transformation. we need to drop NSW/NUW flags. We need to look at all other reassociation as well. Are we heading to that direction?


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https://reviews.llvm.org/D69563