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

[Jan Beulich]

>>> On 01.07.16 at 14:38, <hjl.tools@gmail.com> wrote:
> On Fri, Jul 1, 2016 at 2:36 AM, Jan Beulich <JBeulich@suse.com> wrote:
>> ... just like has been made the case recently for movzb and movzw.
>>
>> Note that this exposed a bug in check_qword_reg(): A missing 'r' (or
>> wrong 'e') register prefix needs to be complained about if the template
>> allows for a 64-bit register, not a 32-bit one. I assume this was a
>> copy-and-paste type of mistake (from check_long_reg()).
>>
> 
> We don't support
> 
>        movsl  %eax,%rax
>        movsl   (%rax),%rax
> 
> today.

Nor do we support (prior to this patch) the respective movsb and
movsw. Adding support for them (and then consistently, i.e.
including movsl) is the purpose of this patch.

>  Remind me why we changed to support
> 
>        movzl   %eax,%rax
>        movzl   (%rax),%rax
> 
> There is no code outer there which uses this mnemonic.  Maybe it
> was a mistake to allow it.

Where did you see this getting added?

Jan