Re: [PATCH v4] xtensa: Eliminate the use of callee-saved register that saves and restores only once

[Max Filippov <jcmvbkbc@gmail.com>]

On Fri, Jan 20, 2023 at 8:39 PM Takayuki 'January June' Suwa
<jjsuwa_sys3175@yahoo.co.jp> wrote:
> On 2023/01/21 0:14, Max Filippov wrote:
> > After having this many attempts and getting to the issues that are
> > really hard to detect I wonder if the target backend is the right place
> > for this optimization?
> >
> I guess they are not hard to detect

I mean, on the testing side. check-gcc testsuite passed without new
regressions with this change, linux kernel smoke test passed, I was
almost convinced that it's ok to commit.

> but just issues I didn't anticipate (and I just need a little more work).

Looking at other peephole2 patterns I see that their code transformations
are much more compact and they don't need to track additional properties
of unrelated instructions.

> And where else should it be done?  What about implementing a
> target-specific pass just for one-point optimization?

I don't even understand what's target-specific in this optimization?
It looks very generic to me.

-- 
Thanks.
-- Max