[PATCH] D52997: [x86] allow single source horizontal op matching (PR39195)

Tue Oct 9 05:35:24 PDT 2018

andreadb added a comment.

In https://reviews.llvm.org/D52997#1258720, @RKSimon wrote:

> In https://reviews.llvm.org/D52997#1258717, @spatel wrote:
>
> > So 2 options for moving forward:
> >
> > 1. Allow this transform as shown here because it is mostly just restoring the behavior of last week. Follow that up with a subtarget feature to prevent the transform (not ideal, but the alternative 'undo' is much harder).
> > 2. Limit this transform to 'optsize' right now because it's a size win in all cases.
>
>
> I'd vote for (1) for this patch - optsize + HasFastHorinzontalOp might be necessary depending on how soon we can agree on a scheduler model driven mechanism that re-expands HADD later on (per Andrea's suggestion - but hopefully we can discuss that at the devmtg)

Same.
I am okay with (1) for now.

https://reviews.llvm.org/D52997