[PATCH] x86: Remove movsx/movzx with memory operand from AT&T syntax

["H.J. Lu" <hjl.tools@gmail.com>]

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On Tue, Feb 11, 2020 at 9:04 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Tue, Feb 11, 2020 at 8:45 AM Jan Beulich <jbeulich@suse.com> wrote:
> >
> > On 11.02.2020 14:07, H.J. Lu wrote:
> > > On Tue, Feb 11, 2020 at 5:04 AM Jan Beulich <jbeulich@suse.com> wrote:
> > >>
> > >> On 11.02.2020 14:01, H.J. Lu wrote:
> > >>> On Tue, Feb 11, 2020 at 4:58 AM Jan Beulich <jbeulich@suse.com> wrote:
> > >>>>
> > >>>> On 11.02.2020 13:19, H.J. Lu wrote:
> > >>>>> On Tue, Feb 11, 2020 at 3:55 AM Jan Beulich <jbeulich@suse.com> wrote:
> > >>>>>>
> > >>>>>> On 11.02.2020 12:42, H.J. Lu wrote:
> > >>>>>>> On Tue, Feb 11, 2020 at 2:25 AM Jan Beulich <jbeulich@suse.com> wrote:
> > >>>>>>>>
> > >>>>>>>> Some encodings are about to gain a warning - move them from test cases
> > >>>>>>>> not expecting any diagnostics to the new, dedicated ones, to allow
> > >>>>>>>> better focus on the actual changes in the subsequent patch.
> > >>>>>>>>
> > >>>>>>>> The new tests added have some wrong expectations right now, which will
> > >>>>>>>> be corrected by the next patch. The test is being added here to make
> > >>>>>>>> more visible which cases actually were wrong (and hence get changed),
> > >>>>>>>> besides demonstrating that in the vast majority of cases the subsequent
> > >>>>>>>> change doesn't alter generated code.
> > >>>>>>>>
> > >>>>>>>> gas/
> > >>>>>>>> 2020-02-XX  Jan Beulich  <jbeulich@suse.com>
> > >>>>>>>>
> > >>>>>>>>         * testsuite/gas/i386/i386.s, testsuite/gas/i386/iamcu-1.s,
> > >>>>>>>>         testsuite/gas/i386/ilp32/x86-64.s: Move ambiguous operand size
> > >>>>>>>>         tests ...
> > >>>>>>>>         * testsuite/gas/i386/noreg16.s, testsuite/gas/i386/noreg32.s,
> > >>>>>>>>         testsuite/gas/i386/noreg64.s, testsuite/gas/i386/x86_64.s: ...
> > >>>>>>>>         here.
> > >>>>>>>>         * testsuite/gas/i386/i386.d, testsuite/gas/i386/i386-intel.d
> > >>>>>>>>         testsuite/gas/i386/iamcu-1.d, testsuite/gas/i386/ilp32/x86-64.d,
> > >>>>>>>>         testsuite/gas/i386/k1om.d, testsuite/gas/i386/l1om.d,
> > >>>>>>>>         testsuite/gas/i386/noreg16.d, testsuite/gas/i386/noreg32.d,
> > >>>>>>>>         testsuite/gas/i386/noreg64.d, testsuite/gas/i386/x86_64-intel.d,
> > >>>>>>>>         testsuite/gas/i386/x86_64.d: Adjust expectations.
> > >>>>>>>>         * testsuite/gas/i386/movx16.s, testsuite/gas/i386/movx16.l,
> > >>>>>>>>         testsuite/gas/i386/movx32.s, testsuite/gas/i386/movx32.l,
> > >>>>>>>>         testsuite/gas/i386/movx64.s, testsuite/gas/i386/movx64.l: New.
> > >>>>>>>>         * testsuite/gas/i386/i386.exp: Run new tests.
> > >>>>>>>
> > >>>>>>> Please make a separate patch to address MOVSX/MOVZX.
> > >>>>>>
> > >>>>>> I don't understand what you mean here. This patch simply documents the
> > >>>>>> status quo, to make it (much) easier to see what the next patch
> > >>>>>> actually adjusts. It doesn't "address" anything. If, for the purpose
> > >>>>>> of committing, you'd like to see both patches folded - fine by me. But
> > >>>>>> only then, not any earlier.
> > >>>>>>
> > >>>>>>>  MOVSX and MOVZX
> > >>>>>>> should take no suffixes.  AT&T syntax is supported if there is no
> > >>>>>>> ambiguity.  AT&T
> > >>>>>>> syntax also supports movsXY and movzXY.
> > >>>>>>
> > >>>>>> Please could you clarify what specifically you'd like to see changed,
> > >>>>>> at the very least by pointing out one case each where you think I'm
> > >>>>>> moving in the wrong direction (presumably in the next patch really)?
> > >>>>>> I'm afraid your response isn't such that I can derive from it what
> > >>>>>> exactly you want.
> > >>>>>
> > >>>>> We support
> > >>>>>
> > >>>>> movsx %ax, %ecx
> > >>>>> movzx %ax, %ecx
> > >>>>> movswl %ax, %ecx
> > >>>>> movzwl %ax, %ecx
> > >>>>>
> > >>>>> We disallow
> > >>>>>
> > >>>>> movsxw %ax, %ecx
> > >>>>> movzxw %ax, %ecx
> > >>>>
> > >>>> We don't (as this patch demonstrates, along with pre-existing tests,
> > >>>> unless you mean once again to have an inconsistency between insns
> > >>>> with all register operands and similar ones with e memory source),
> > >>>> and if you want it to be this way, then please do so yourself, but
> > >>>
> > >>> I will do it.
> > >>>
> > >>>> please also only on top of my changes, so I won't need to re-base
> > >>>
> > >>> Which changes of yours are you referring to?
> > >>
> > >> This patch and the subsequent one.
> > >>
> > >
> > > Both changes won't be necessary after my changes.
> >
> > I'm confused. What you want to deal with is - afaict - orthogonal to
> > what the next patch in the series here does.
> >
>
> You will see what I mean when I post my patch for review.
>

AT&T syntax requires suffix to specify memory operand size.  Since
movsx and movzx can have different memory operand sizes with the same
destination register, this patch removes movsx and movzx with memory
operand from AT&T syntax.  Since AT&T syntax uses different mnemonics
for movsx and movzx, this change should have little impact on assembly
sources.  Tested with Linux kernel 5.5.3 for x86-64 and glibc 2.31 for
i686 and x86-64.

-- 
H.J.

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