[FFmpeg-devel] [PATCHv2] lavu/x86/lls: add fma3 optimizations for update_lls

[Ganesh Ajjanagadde]

On Thu, Jan 14, 2016 at 6:54 PM, Ganesh Ajjanagadde <gajjanag at mit.edu> wrote:
> On Thu, Jan 14, 2016 at 6:42 PM, James Almer <jamrial at gmail.com> wrote:
>> On 1/14/2016 7:46 PM, Ganesh Ajjanagadde wrote:
>>> This improves accuracy (very slightly) and speed for processors having
>>> fma3.
>>>
>>> Sample benchmark (fate flac-16-lpc-cholesky, Haswell):
>>> old:
>>> 5993610 decicycles in ff_lpc_calc_coefs,      64 runs,      0 skips
>>> 5951528 decicycles in ff_lpc_calc_coefs,     128 runs,      0 skips
>>>
>>> new:
>>> 5252410 decicycles in ff_lpc_calc_coefs,      64 runs,      0 skips
>>> 5232869 decicycles in ff_lpc_calc_coefs,     128 runs,      0 skips
>>>
>>> Tested with FATE and --disable-fma3, also examined contents of
>>> lavu/lls-test.
>>>
>>> Reviewed-by: James Almer <jamrial at gmail.com>
>>> Reviewed-by: Henrik Gramner <henrik at gramner.com>
>>> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
>>> ---
>>>  libavutil/x86/lls.asm    | 61 ++++++++++++++++++++++++++++++++++++++++++++++--
>>>  libavutil/x86/lls_init.c |  4 ++++
>>>  2 files changed, 63 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/libavutil/x86/lls.asm b/libavutil/x86/lls.asm
>>> index 769befb..925cbdb 100644
>>> --- a/libavutil/x86/lls.asm
>>> +++ b/libavutil/x86/lls.asm
>>> @@ -125,8 +125,7 @@ cglobal update_lls, 2,5,8, ctx, var, i, j, covar2
>>>  .ret:
>>>      REP_RET
>>>
>>> -%if HAVE_AVX_EXTERNAL
>>> -INIT_YMM avx
>>> +%macro UPDATE_LLS 0
>>>  cglobal update_lls, 3,6,8, ctx, var, count, i, j, count2
>>>      %define covarq ctxq
>>>      mov  countd, [ctxq + LLSModel.indep_count]
>>> @@ -140,6 +139,18 @@ cglobal update_lls, 3,6,8, ctx, var, count, i, j, count2
>>>      vbroadcastsd ymm6, [varq + iq*8 + 16]
>>>      vbroadcastsd ymm7, [varq + iq*8 + 24]
>>>      vextractf128 xmm3, ymm1, 1
>>> +%if cpuflag(fma3)
>>> +    mova ymm0, COVAR(iq  ,0)
>>> +    mova xmm2, COVAR(iq+2,2)
>>> +    fmaddpd ymm0, ymm1, ymm4, ymm0
>>> +    fmaddpd xmm2, xmm3, xmm6, xmm2
>>> +    fmaddpd ymm1, ymm5, ymm1, COVAR(iq  ,1)
>>> +    fmaddpd xmm3, xmm7, xmm3, COVAR(iq+2,3)
>>> +    mova COVAR(iq  ,0), ymm0
>>> +    mova COVAR(iq  ,1), ymm1
>>> +    mova COVAR(iq+2,2), xmm2
>>> +    mova COVAR(iq+2,3), xmm3
>>> +%else
>>>      vmulpd  ymm0, ymm1, ymm4
>>>      vmulpd  ymm1, ymm1, ymm5
>>>      vmulpd  xmm2, xmm3, xmm6
>>> @@ -148,12 +159,27 @@ cglobal update_lls, 3,6,8, ctx, var, count, i, j, count2
>>>      ADDPD_MEM COVAR(iq  ,1), ymm1
>>>      ADDPD_MEM COVAR(iq+2,2), xmm2
>>>      ADDPD_MEM COVAR(iq+2,3), xmm3
>>> +%endif ; cpuflag(fma3)
>>>      lea     jd, [iq + 4]
>>>      cmp     jd, count2d
>>>      jg .skip4x4
>>>  .loop4x4:
>>>      ; Compute all 16 pairwise products of a 4x4 block
>>>      mova    ymm3, [varq + jq*8]
>>> +%if cpuflag(fma3)
>>> +    mova ymm0, COVAR(jq, 0)
>>> +    mova ymm1, COVAR(jq, 1)
>>> +    mova ymm2, COVAR(jq, 2)
>>> +    mova ymm3, COVAR(jq, 3)
>>
>> This is wrong. You're overwriting the contents of ymm3. libavutil/lls-test didn't reflect
>> this at all?
>>
>>> +    fmaddpd ymm0, ymm3, ymm4, ymm0
>>> +    fmaddpd ymm1, ymm3, ymm5, ymm1
>>> +    fmaddpd ymm2, ymm3, ymm6, ymm2
>>> +    fmaddpd ymm3, ymm3, ymm7, ymm3
>>> +    mova COVAR(jq, 0), ymm0
>>> +    mova COVAR(jq, 1), ymm1
>>> +    mova COVAR(jq, 2), ymm2
>>> +    mova COVAR(jq, 3), ymm3
>>> +%else
>>>      vmulpd  ymm0, ymm3, ymm4
>>>      vmulpd  ymm1, ymm3, ymm5
>>>      vmulpd  ymm2, ymm3, ymm6
>>> @@ -162,6 +188,7 @@ cglobal update_lls, 3,6,8, ctx, var, count, i, j, count2
>>>      ADDPD_MEM COVAR(jq,1), ymm1
>>>      ADDPD_MEM COVAR(jq,2), ymm2
>>>      ADDPD_MEM COVAR(jq,3), ymm3
>>> +%endif ; cpuflag(fma3)
>>>      add     jd, 4
>>>      cmp     jd, count2d
>>>      jle .loop4x4
>>> @@ -169,6 +196,20 @@ cglobal update_lls, 3,6,8, ctx, var, count, i, j, count2
>>>      cmp     jd, countd
>>>      jg .skip2x4
>>>      mova    xmm3, [varq + jq*8]
>>> +%if cpuflag(fma3)
>>> +    mova xmm0, COVAR(jq, 0)
>>> +    mova xmm1, COVAR(jq, 1)
>>> +    mova xmm2, COVAR(jq, 2)
>>> +    mova xmm3, COVAR(jq, 3)
>>
>> Same here.
>
> Diff /tmp/lls.old /tmp/lls.new:
> < real:-0.326534 order:0 pred:-0.588792 var:0.272632 coeffs:1.427836
> -0.385559  0.000000
> < real:-0.326534 order:1 pred:-0.326534 var:-nan coeffs:3.274787
> -1.436430  0.000000
> < real:-0.326534 order:2 pred:-0.326534 var:0.000000 coeffs:3.274787
> -1.436430  0.000000
> ---
>> real:-0.326534 order:0 pred:-0.588792 var:0.272632 coeffs:1.427836 -0.385559 -0.000000
>> real:-0.326534 order:1 pred:-0.326534 var:0.000000 coeffs:3.274787 -1.436430  0.000000
>> real:-0.326534 order:2 pred:-0.326534 var:-nan coeffs:3.274787 -1.436430 -0.000000
>
> You are definitely right, though. Removed 2 lines:
> mova ymm3, COVAR(jq,3)
> and
> mova xmm3, COVAR(jq,2)

Still buggy. Will calmly examine this some time.

>
>>
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