[PATCH] D54882: [AMDGPU] Add sdwa support for ADD|SUB U64 decomposed Pseudos

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

rampitec added a comment.

In D54882#1309639 <https://reviews.llvm.org/D54882#1309639>, @ronlieb wrote:

> In D54882#1309605 <https://reviews.llvm.org/D54882#1309605>, @rampitec wrote:
>
> > In D54882#1309588 <https://reviews.llvm.org/D54882#1309588>, @rampitec wrote:
> >
> > > In D54882#1309583 <https://reviews.llvm.org/D54882#1309583>, @ronlieb wrote:
> > >
> > > > In D54882#1308240 <https://reviews.llvm.org/D54882#1308240>, @rampitec wrote:
> > > >
> > > > > Essentially this is a limited version of shrinking. So I have several questions:
> > > > >
> > > > > 1. Why not to run shrink pass before sdwa instead?
> > > >
> > > >
> > > > I tried adding Shrink pass before PeepholeSDWA and observed 88 lit test failures.
> > > >  i tried moving Shrink pass before Peephole SDWA and observed 25 lit test failures
> > >
> > >
> > > Which may be a good thing if these failures are progressions (as I suspect) and not regressions. Are they progressions?
> > >  That is the point of other comments too, this patch is limited to handle just two instructions while there is a clear possibility to do it for almost any VOP3.
> >
> >
> > I would also assume many of these failures are just commute which is attempted by shrink pass. That is normal and would only need to change the tests.
>
>
> i tried an experiment of simply invoking the Shrink pass a 2nd time.
>
>   addPass(createSIShrinkInstructionsPass());
>   addPass(createSIShrinkInstructionsPass());
>
> which resulted in 74 failures, and they do seem to be commute changes primarily (did not look at them all)
>  So then, i added a 3rd invocation and zero failures (i'm still laughing at this one).


So it must be commute. I guess you just need to add a new shrink pass before sdwa. Does it help to deal with these two instructions, e.g. does it help you lit test?

If yes there are two options, either:

1. Revert the commute in shrink pass if it did not help.
2. Just update tests.


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