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

[H.J. Lu]

On Mon, Jan 8, 2018 at 4:12 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>> On 08.01.18 at 12:52, <hjl.tools@gmail.com> wrote:
>> On Mon, Jan 8, 2018 at 3:39 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>>>> On 08.01.18 at 12:14, <hjl.tools@gmail.com> wrote:
>>>> On Mon, Jan 8, 2018 at 12:48 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>>> Furthermore I think that the AVX512 64-bit variant should go away
>>>>> altogether - it's register form is just a longer re-encoding of the
>>>>> AVX form, and hence redundant, and gcc (afaics) doesn't use it.
>>>>
>>>> Shouln't vmovd with upper 32 xmm registers be encoded with AVX512?
>>>
>>> No, such an instruction simply doesn't exist (as per SDM). The
>>
>> What do you mean by that?  These
>>
>> vmovd 128(%rax), %xmm19
>
> As per the SDM this one is a 32-bit operation.
>
>> vmovd %rax, %xmm19
>
> As per the SDM this one doesn't exist.
>
>> vmovd %xmm19, 128(%rax)
>
> 32-bit again.
>
>> vmovd %xmm19, %rax
>
> non-existing again.
>
>> .intel_syntax noprefix
>> vmovd xmm19, qword ptr [rax + 128]
>> vmovd xmm19, rax
>> vmovd qword ptr [rax + 128], xmm19
>> vmovd rax, xmm19
>>
>> are encoded with AVX512.
>>
>>> difference to the AVX flavor is that gcc new enough to support
>>> AVX512 is also new enough to check for the availability of the
>>> well-formed VMOVQ, and there's also no mode equivalent to
>>> SSE2AVX to take care of.
>>
>> GCC has
>>
>>     case TYPE_SSEMOV:
>>       switch (get_attr_mode (insn))
>>         {
>>         case MODE_DI:
>>           /* Handle broken assemblers that require movd instead of movq.  */
>>           if (!HAVE_AS_IX86_INTERUNIT_MOVQ
>>               && (GENERAL_REG_P (operands[0]) || GENERAL_REG_P (operands[1])))
>>             return "%vmovd\t{%1, %0|%0, %1}";
>>           return "%vmovq\t{%1, %0|%0, %1}";
>>
>> It doesn't check upper 32 xmm registers.
>
> Ah, yes you're right. See also my other reply just sent.

I just realized that all AVX512 assemblers set HAVE_AS_IX86_INTERUNIT_MOVQ.
We can remove AVX512 vmovd after all.

-- 
H.J.