[PATCH] x86: Extract extended states from instruction template

[H.J. Lu]

On Fri, Jul 10, 2020 at 12:02 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 09.07.2020 18:22, H.J. Lu wrote:
> > On Thu, Jul 9, 2020 at 9:17 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >> On Thu, Jul 9, 2020 at 9:13 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>> On 09.07.2020 17:44, H.J. Lu wrote:
> >>>> Should we add a field to i386 opcode table for this?
> >>>
> >>> I was wanting to try without, to see how much logic would be needed.
> >>> If it gets too much, doing so may be the better choice.
> >>
> >> I am checking in this patch.
> >
> > Here is the right patch.
>
> Well, this is certainly an improvement. But it doesn't come close to
> what's needed. Again - imo the concept of i.has_reg* isn't helpful
> at all. It's not the registers an insn _actually_ accesses, but the
> ones the template says it might access. Think of vfpclass* with a
> memory operand, for example. Or see some of the extra checks of
> certain opcodes when setting the MMX bit, which could be avoided by
> using such an alternative model.
>
> I'm leaving aside here special cases where the templates don't carry
> enough information. I'm also leaving aside the need to e.g. record
> mask register use in some form (maybe translating to ZMM use if you
> want to avoid introducing a separate tracking bit), as well as
> various other issues I had spotted without looking very closely yet.

Here is a patch to extract extended states from operand types in
instruction template and set xstate_zmm for master register move.

> I believe a fundamental issue here is the very scarce testing: While
> it may be avoidable to add an attribute to the insn templates, there
> should be full testing coverage of _all_ insns with _all_ possible
> operand type combinations, if the resulting notes are to be
> dependable. If such (presumably table based) testing was there (and
> of course if the table reflected the real needs rather than what
> gas currently happens to produce), you'd easily notice the issues
> I've spotted (and likely more).

This is just a starting point.  I will fix any issues discovered.

Thanks.

-- 
H.J.
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