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

[H.J. Lu]

On Fri, Jul 1, 2016 at 9:12 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>> On 01.07.16 at 18:07, <hjl.tools@gmail.com> wrote:
>> 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.
>
> You're kidding? As said, the issue got uncovered only with the
> other adjustments here; I'm not aware of a case where this
> would cause a problem without the other changes, and I'm not
> going to spend a whole lot of time trying to figure a broken case.

So there is no issue with the current code base?

-- 
H.J.