[x264-devel] question in pixel_avg2_w20_sse2

[chen]

At 2014-07-29 03:20:42,BugMaster BugMaster at narod.ru> wrote:
>On Tue, 29 Jul 2014 02:40:00 +0800 (CST), chen wrote:
>> In pixel_avg2_w20_sse2, it mixed use XMM0-XMM4 and MM4-MM5, so MM4-MM5 was not save and restore.
>> I check ABI document, it just said Microsoft Compiler didn't use MM0-MM7
>> Is it a bug?
>>  
>> btw: I know the MM_ is double faster then XMM_ in old cpu, but in
>> latest CPU, it is same speed or slower.
>>  
>> Min
>>   
>Hi. I not fully understand what was your real question and what you
>see as bug here. Yes, this function use mix of SSE2/MMX
>instructions/registers because we don't need full length XMM register
>for this width (16+4) and we need unaligned memory access here. As for
>calling ABI all MMX regs (mm0-mm7) are volatile and must be considered
>destroyed on function calls.
>>

in here, we didn't call EMMS before return, after this function, the ST(*) or MM* in non-determeric status.