Re: [PATCH 5/7] x86: re-work insn/suffix recognition

[Jan Beulich <jbeulich@suse.com>]

On 17.08.2022 22:29, H.J. Lu wrote:
> On Tue, Aug 16, 2022 at 12:32 AM Jan Beulich <jbeulich@suse.com> wrote:
>>
>> x86: re-work insn/suffix recognition
>>
>> Having templates with a suffix explicitly present has always been
>> quirky. Introduce a 2nd matching pass in case the 1st one couldn't find
> 
> I don't like the second pass.   What problem does it solve?

It addresses the reasons we have various pretty odd (and confusing by
their mere presence) insn templates which better would never have been
there. If you have a better suggestion to eliminate those, I'm all ears.

You can also easily see the issues this solves by looking at the
testsuite changes. Among other things this once again is a matter of
providing consistent and hence predictable behavior.

Further this sets the stage for the subsequent two changes, which I
don't think are easily possible without this 2nd pass.

And finally you've likely spotted that this is actually a reduction in
code size, first and foremost because the odd maybe_adjust_templates()
can now go away. Plus I think you realize that the 2nd pass wouldn't
be engaged in many cases - it requires a template match failure in the
1st pass, after all, which isn't going to happen very often.

Jan