[PATCH v6 2/7] x86: re-work insn/suffix recognition

[H.J. Lu]

On Mon, Nov 7, 2022 at 2:23 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 05.11.2022 00:54, H.J. Lu wrote:
> > On Fri, Nov 4, 2022 at 3:51 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>
> >> Having templates with a suffix explicitly present has always been
> >> quirky. Introduce a 2nd matching pass in case the 1st one couldn't find
> >> a suitable template _and_ didn't itself already need to trim off a
> >> suffix to find a match at all. This requires error reporting adjustments
> >> (albeit luckily fewer than I was afraid might be necessary), as errors
> >> previously reported during matching now need deferring until after the
> >> 2nd pass (because, obviously, we must not emit any error if the 2nd pass
> >> succeeds). While also related to PR gas/29524, it was requested that
> >> move-with-sign-extend be left as broken as it always was.
> >>
> >> PR gas/29525
> >> Note that with the dropped CMPSD and MOVSD Intel Syntax string insn
> >> templates taking operands, mixed IsString/non-IsString template groups
> >> (with memory operands) cannot occur anymore. With that
> >> maybe_adjust_templates() becomes unnecessary (and is hence being
> >> removed).
> >>
> >> PR gas/29526
> >> Note further that while the additions to the intel16 testcase aren't
> >> really proper Intel syntax, we've been permitting all of those except
> >> for the MOVD variant. The test therefore is to avoid re-introducing such
> >> an inconsistency.
> >> ---
> >> To limit code churn I'm using "goto" for the retry loop, but I'd be
> >> happy to make this a proper loop either right here or in a follow-on
> >> change doing just the necessary re-indentation.
> >>
> >> The "too many memory references" errors which are being deleted weren't
> >> fully consistent anyway - even the majority of IsString insns accepts
> >> only a single memory operand. If we wanted to retain that, it would need
> >> re-introducing in md_assemble(), latching the error into i.error just
> >> like match_template() does.
> >>
> >> As an unrelated observation: Why is "MOVQ $imm64, %reg64" being
> >> optimized but "MOVABS $imm64, %reg64" is not?
> >> ---
> >> v6: Re-base over dropping of Pass2 attribute.
> >> v5: Split off move-with-sign-extend changes.
> >> v4: Retain support for operand-less MOVSD and CMPSD.
> >> v3: Limit xstrdup() to just the templates where a 2nd pass actually
> >>     makes sense (new Pass2 attribute).
> >
> > I don't think we should add a second pass.
>
> So you've asked me to re-work the series several times just to _now_
> say "no" altogether? What's your alternative proposal to address the
> various shortcomings that this series is addressing? (Yes, patches 4
> and 5 can, with some effort, probably be re-based ahead, but those
> are only minor improvements found while doing the main piece of work
> here, and they aren't strictly related to the main goal of the series.)

The more I looked, the more I didn't think we needed the second pass.
The issues you raised are minor issues.  We shouldn't add the second
pass because of them.

> Plus I now really feel urged to point out that you're blocking further
> work I have pending, which I keep re-basing over all the adjustments I
> was making to address your comments (plus of course the new ISA
> extension patches which have gone in recently, all of which also
> collide with work I'm doing). This re-basing is non-trivial and hence
> is consuming a considerable amount of time as well.
>
> Jan



-- 
H.J.