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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: "Jonas Maebe" <jonas-devlists at watlock dot be>
- Cc: <binutils at sourceware dot org>
- Date: Fri, 01 Jul 2016 08:01:12 -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> <57768C3F02000078000FA6B0 at prv-mh dot provo dot novell dot com> <20160701154345 dot Horde dot cBkeSkisJlFXdnORG8cFS7A at mail dot elis dot ugent dot be>
>>> On 01.07.16 at 15:43, <jonas-devlists@watlock.be> wrote:
> Jan Beulich wrote on Fri, 01 Jul 2016:
>
>> 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.
>
> I think that is a really bad idea. movsb, movsw and movsl are existing
> mnemonics for completely different opcodes (as in "rep movsb"). It
> also seems to be against the spirit of AT&T syntax, which normally
> requires you to explicitly specify all operand sizes fully with the
> mnemonic in all cases, even if the assembler could in theory deduce
> them from the operands.
Where's that written down please? As said in the movz patch
description yesterday, movz{b,w} and movs{b,w,l} really are
the odd ones - everything else gets accepted without suffixes when
they're deducible from operands. And I'm of the strong opinion
that such inconsistencies should be eliminated. (And btw., no-one's
going to be forced to omit the suffixes, if they like them.)
Jan