Re: [PATCH] x86: Properly encode vmovd with 64-bit memeory

["Jan Beulich" <JBeulich at suse dot com>]

>>> On 08.01.18 at 12:48, <hjl.tools@gmail.com> wrote:
> On Mon, Jan 8, 2018 at 3:35 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>>> On 08.01.18 at 12:22, <hjl.tools@gmail.com> wrote:
>>> On Mon, Jan 8, 2018 at 3:14 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>>> On Mon, Jan 8, 2018 at 12:48 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>>>>>> On 08.01.18 at 02:18, <hongjiu.lu@intel.com> wrote:
>>>>>> For historical reason, we allow movd/vmovd with 64-bit register and
>>>>>> memeory operands.  But for vmovd, we failed to handle 64-bit memeory
>>>>>> operand.  This has been gone unnoticed since AT&T syntax always treats
>>>>>> memory operand as 32-bit memory.  This patch properly encodes vmovd
>>>>>> with 64-bit memeory operands.
>>>>>
>>>>> Interesting coincidence - just over the weekend I've run into this
>>>>> issue too. My intended solution is quite different, though: Since
>>>>> VMOVD (other than MOVD) doesn't have a 64-bit operand variant
>>>>> in either Intel's SDM nor AMD's PM, I'd rather remove memory
>>>>> operand support from it:
>>>>> - generate code was wrong so far, so anyone having used it would
>>>>>   have run buggy code anyway,
>>>>> - old gcc only ever uses the 64-bit variants with register operands.
>>>>
>>>> Works for me.  Can you submit a patch?
>>
>> Hopefully later this week.
>>
>>> If we do that, should we also remove MOVD with 64-bit memory?
>>
>> We can't, as even up-to-date AMD PM still specifies this name
>> instead of MOVQ.
> 
> I consider it is a defect in AMD manual.
> 
>>> Otherwise, -msse2avx won't work on MOVD with 64-bit memory.
>>
>> Hmm, good point - perhaps the SSE2AVX pattern then needs the
>> change that you've been doing, while the plain one could have its
>> memory alternative removed?
> 
> If we can't remove MOVD with 64-bit memory, I will go with my patch.

Fine with me for the AVX variant, but please consider dropping
the AVX512 one.

Jan