Re: [PATCH] x86: allow suffix-less sign-extending movsb, movsw, and movsl

["Jan Beulich" <JBeulich at suse dot com>]

>>> On 01.07.16 at 17:20, <jonas-devlists@watlock.be> wrote:

> Jan Beulich wrote on Fri, 01 Jul 2016:
> 
>>>>> On 01.07.16 at 16:24, <jonas-devlists@watlock.be> wrote:
>>> Referring again to the above document, it says about movsb/movsw:
>>> "movsb is not movsb{wlq}" and "movsw
>>> is not movsw{lq}" (on p. 37). Those are the only mnemonics that are
>>> singled out in this way.
>>
>> Well, the document referenced is a random one; it's way too new
>> to be a canonical reference.
> 
> I disagree that (originally) Sun documentation is a random reference  
> in the context of AT&T/System V UNIX. Yes, SVR4.2 i386 documentation  
> would be even better (if it mentions this issue), but I guess that  
> only exists as hard copy in someone's basement.
> 
>> I do not understand what inconsistency you refer to here. The
>> only inconsistency I can see is that one can't omit the suffixes
>> from these three instructions, unlike any others with GPR
>> operands.
> 
> It is not consistent that all base mnemonics (i.e., without size  
> suffix) refer to individual opcodes (or groups of opcodes) as defined  
> in Intel's architecture manuals, except for movsb/w/l.

I don't see what's wrong with this, when it's okay for the assembler
to accept all kinds on non-AT&T syntax instructions in AT&T mode.
Note how, for example, both movsx and movzx have specific AT&T
entries despite these being Intel syntax mnemonics.

Jan