Re: [PATCH v8 2/2] x86/AT&T: don't default to byte source for ambiguous for MOVSX/MOVZX

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

On Fri, Feb 14, 2020 at 8:35 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 14.02.2020 17:26, H.J. Lu wrote:
> > On Fri, Feb 14, 2020 at 7:52 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>
> >> On 14.02.2020 15:37, H.J. Lu wrote:
> >>> On Fri, Feb 14, 2020 at 6:32 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>>>
> >>>> On 14.02.2020 15:25, H.J. Lu wrote:
> >>>>> On Fri, Feb 14, 2020 at 6:23 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>>>>>
> >>>>>> On 14.02.2020 15:16, H.J. Lu wrote:
> >>>>>>> On Fri, Feb 14, 2020 at 5:54 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>>>>>>>
> >>>>>>>> On 14.02.2020 13:28, H.J. Lu wrote:
> >>>>>>>>> On Fri, Feb 14, 2020 at 4:26 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>>>>>>>>>
> >>>>>>>>>> As pointed out in "x86: replace adhoc (partly wrong) ambiguous operand
> >>>>>>>>>> checking for MOVSX/MOVZX" silently guessing what the programmer may have
> >>>>>>>>>> meant is not helpful, the more that we don't do so elsewhere anymore
> >>>>>>>>>> (except in cases where it is overwhelmingly likely that the other case
> >>>>>>>>>> isn't meant, like here for it meant to be a "sign/zero extension" from
> >>>>>>>>>> 16 bits to 16 bits).
> >>>>>>>>>>
> >>>>>>>>>> gas/
> >>>>>>>>>> 2020-02-XX  Jan Beulich  <jbeulich@suse.com>
> >>>>>>>>>>
> >>>>>>>>>>         PR gas/25438
> >>>>>>>>>>         * config/tc-i386.c (process_suffix): Default movsx/movzx to byte
> >>>>>>>>>>         suffix only when destination is a word reg.
> >>>>>>>>>>         testsuite/gas/i386/noreg16.l, testsuite/gas/i386/noreg32.l,
> >>>>>>>>>>         testsuite/gas/i386/noreg64.l: Adjust expectations.
> >>>>>>>>>
> >>>>>>>>> No need for this since this is documented behavior of AT&T syntax.
> >>>>>>>>
> >>>>>>>> I've just looked at the documentation again: As said in the
> >>>>>>>> other reply to your doc change, these mnemonics aren't
> >>>>>>>> mentioned as legal in Solaris'es AT&T spec. And I also
> >>>>>>>> can't find gas doc saying so. Would you please point me at
> >>>>>>>> where this is being documented?
> >>>>>>>
> >>>>>>> Solaris spec doesn't mention movsx[bwl] nor movsx.
> >>>>>>
> >>>>>> Right, so where did you take from that "this is documented behavior"?
> >>>>>>
> >>>>>
> >>>>> Documented in gas manual.
> >>>>
> >>>> Where? As said, I did look there without finding anything to this effect.
> >>>
> >>> It is there now.
> >>
> >> Hmm, even worse: It's not there. Neither of the two doc changes of
> >> yours today say anything like this. Did you forget to both post a
> >> patch _and_ push it, or am I blind, or are you simply lying to me?
> >> I'm sorry for being blunt, but I'm getting really annoyed.
> >>
> >
> > info as.info on master branch shows
> >
> >
> >  The Intel-syntax extension instructions
> >
> >    * 'movsx' -- sign-extend 'reg8/mem8' to 'reg16'.
> >
> >    * 'movsx' -- sign-extend 'reg8/mem8' to 'reg32'.
> >
> >    * 'movsx' -- sign-extend 'reg8/mem8' to 'reg64' (x86-64 only).
> >
> >    * 'movsx' -- sign-extend 'reg16/mem16' to 'reg32'
> >
> >    * 'movsx' -- sign-extend 'reg16/mem16' to 'reg64' (x86-64 only).
> >
> >    * 'movsxd' -- sign-extend 'reg32/mem32' to 'reg64' (x86-64 only).
> >
> >    * 'movzx' -- zero-extend 'reg8/mem8' to 'reg16'.
> >
> >    * 'movzx' -- zero-extend 'reg8/mem8' to 'reg32'.
> >
> >    * 'movzx' -- zero-extend 'reg8/mem8' to 'reg64' (x86-64 only).
> >
> >    * 'movzx' -- zero-extend 'reg16/mem16' to 'reg32'
> >
> >    * 'movzx' -- zero-extend 'reg16/mem16' to 'reg64' (x86-64 only).
> >
> > are called 'movsbw/movsxb/movsx', 'movsbl/movsxb/movsx',
> > 'movsbq/movsb/movsx', 'movswl/movsxw', 'movswq/movsxw', 'movslq/movsxl',
> > 'movzbw/movzxb/movzx', 'movzbl/movzxb/movzx', 'movzbq/movzxb/movzx',
> > 'movzwl/movzxw' and 'movzwq/movzxw' in AT&T syntax.
>
> Which doesn't say anywhere that with a memory operand but
> without suffix both default to a byte source. Yet that's the
> whole point of the discussion we're having.
>

Does 'movsbw/movsxb/movsx' cover it?


-- 
H.J.