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

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

>>> 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.

> 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?

Jan