[PATCH] D41587: [AArch64] Change order of candidate FMLS patterns

[Matthew Simpson via Phabricator via llvm-commits]

mssimpso added a comment.

In https://reviews.llvm.org/D41587#964226, @fhahn wrote:

> Thanks for spotting this!
>  The reordering looks good to me, give the current behavior of the MachineCombiner it makes sense to move up the more profitable patterns.
>
> > However, the order in which we add the patterns to the list of candidates determines the transformation that takes place, since only the first pattern that matches will be used.
>
> This behavior is not ideal though, especially as some order of patterns might be good for one micro architecture, whereas a different order is better for a different micro architecture.
>
> I'll try to look into this. Maybe it's worth to change the MachineCombiner to try all available patterns.


Thanks Florian! Yes, I agree with your comment. There's actually a note about the limitations of the current behavior in `MachineCombiner::combineInstructions`.


https://reviews.llvm.org/D41587