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

[Jan Beulich]

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.
Also even if it was mentioned there, compatibility considerations then
still call for there being a warning. People moving code from other
assemblers may otherwise be caught by surprise.

Jan