[PATCH] D19391: transform obscured FP sign bit ops into a fabs/fneg using TLI hook

[David Majnemer via llvm-commits]

majnemer added a comment.

In http://reviews.llvm.org/D19391#447164, @spatel wrote:

> In http://reviews.llvm.org/D19391#447144, @majnemer wrote:
>
> > IIRC, I asked you to add support for `fabs` to `computeKnownBits` when you added this canonicalization.
>
>
> Yes, that was http://reviews.llvm.org/D13222 / http://reviews.llvm.org/rL249701 .
>
> > Seeing as how the canonicalization is removed, I think we should undo this aspect of `computeKnownBits`.
>
>
> What is the advantage of removing the analysis? It is still true that an llvm fabs() intrinsic clears the sign bit in all cases, right?


I'm not sure if what we were allowed to assume about the bitpattern of float/double from the middle end.
If it's fine, then this LGTM without touching ValueTracking.


http://reviews.llvm.org/D19391