[PATCH] D121243: [InstCombine] Preserve FMF in foldLogicOfFCmps.

[Nuno Lopes via Phabricator via llvm-commits]

nlopes added a comment.

> For this transform only -- because we are guaranteed to repeat the values in each fcmp -- I was expecting that we could 'or' the relevant flags. But there's a surprising corner case with `true` and `false` fcmp predicates according to Alive2:
> https://alive2.llvm.org/ce/z/Nffn3L
>
> The behavior -- blocking poison via predicate? -- does not seem to be documented in the LangRef.

oops, that seems to be a bug in Alive2.
We convert `fcmp true` to `true`, but that is wrong as we lose the fast-math flags. Let me fix that.


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https://reviews.llvm.org/D121243