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

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Fri, Jul 1, 2016 at 8:32 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>> On 01.07.16 at 17:23, <hjl.tools@gmail.com> wrote:
>> On Fri, Jul 1, 2016 at 8:19 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>>>> On 01.07.16 at 17:12, <hjl.tools@gmail.com> wrote:
>>>> On Fri, Jul 1, 2016 at 7:55 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>>>>>> On 01.07.16 at 16:24, <jonas-devlists@watlock.be> wrote:
>>>>>> So in the end, I guess the movzb/movzw change is fine, but this one is
>>>>>> not. It's in inherent inconsistency related to the ability of leaving
>>>>>> away the size suffixes in combination with the chosen mnemonics, it
>>>>>> seems.
>>>>>
>>>>> 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.
>>>>
>>>> This mnemonic inconsistency comes from ISA and AT&T syntax.
>>>> But there are no issues now.
>>>
>>> There is - as said, I fell into the trap seeing "movzb" in source code
>>> and assuming I then could also use "movzw" or "movsb" (etc). I
>>> can certainly open a bug if that helps you re-consider.
>>
>> It is unfortunate.  But it won't lead to wrong instructions being used.
>
> So since I see that rational arguments won't lead anywhere here
> - would you at least allow in the fix for the bug that this change
> uncovered (the one hunk changing tc-i386.c), even if that also
> doesn't seem to cause any issues right now?

Please open a bug report with a testcase.


-- 
H.J.