[PATCH] D71064: [InstCombine] Invert `add A, sext(B) --> sub A, zext(B)` canonicalization (to `sub A, zext B -> add A, sext B`)

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D71064#1771082 <https://reviews.llvm.org/D71064#1771082>, @spatel wrote:

> In D71064#1771063 <https://reviews.llvm.org/D71064#1771063>, @lebedev.ri wrote:
>
> > In D71064#1771030 <https://reviews.llvm.org/D71064#1771030>, @spatel wrote:
> >
> > > Scalar looks same all-around. Vector shows some potential diffs:
> > >  https://godbolt.org/z/y3E-mb
> > >
> > > If I'm seeing it correctly, we always do better on the typical case where the bool vector is produced by a compare, but we might do worse if we don't have that cmp and don't have AssertSext knowledge.
> >
> >
> > So the comment is that the undo fold needs to be adjusted first, to fire for non-cmp i1 vectors on aarch64 and powerpc64le?
>
>
> I don't think that's necessary as a preliminary step because we're improving what should be the common patterns (the examples that include the cmp).
>  LGTM.


Ah, okay, good point :)
Thank you for the review.


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