[openssl-dev] Stitched AES-NI AES-GCM code & AVX2

[Andy Polyakov]

>>> But, I think the stitched AES-NI AES-GCM code requires AVX2, not just
>>> AVX.
>>
>> No, it doesn't. It requires exactly AVX+MOVBE.
> 
> I see. I was confused because the code says:
> 
>      if ($avx>1) {{{
> 
> I had been thinking the whole time that "$avx > 1" means that AVX2 is required.

There is certain heuristics to whole thing. 'if ($avx>1)', it's used
because it *happens* to work. Look at it as "support for MOVBE was
*incidentally* added at same time as for AVX2 to *assembler*". [Well, it
still might a bug, i.e. it could have been 'if ($avx)'.]