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Re: [PATCH] x86: allow suffix-less sign-extending movsb, movsw, and movsl
- From: "Jan Beulich" <JBeulich at suse dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: "Binutils" <binutils at sourceware dot org>
- Date: Fri, 01 Jul 2016 07:29:03 -0600
- Subject: Re: [PATCH] x86: allow suffix-less sign-extending movsb, movsw, and movsl
- Authentication-results: sourceware.org; auth=none
- References: <577655C002000078000FA593 at prv-mh dot provo dot novell dot com> <CAMe9rOodb0Grq+soDSJq4aZfneTEkmJy8_M-quUBn6FJyK_=6w at mail dot gmail dot com>
>>> 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