On 11/14/2022 10:54 AM, Wang, Bin wrote:
-----Original Message-----
From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of James
Almer
Sent: Monday, November 14, 2022 9:36 PM
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH v7] libavfilter/x86/vf_convolution: add
sobel filter optimization and unit test with intel AVX512 VNNI
On 11/14/2022 10:30 AM, Wang, Bin wrote:
By using xmm# you're not taking into account any x86inc SWAPing, so
this is using xmm0 and xmm1 where the single scalar float input
arguments reside (at least on unix64), instead of xm0 and xm1 (xmm16
and xmm17) where the broadcasted scalars were stored.
This, again, only worked by chance on unix64 because you're using
scalar fmadd, and shouldn't work at all on win64.
Also, all these as is are being encoded as VEX, not EVEX, but it
should be fine leaving them untouched instead of using xm#, since
they will be shorter (five bytes instead of six for some) by using the lower,
non callee-saved regs.
Thanks for the help. I'm not familiar with WIN64 asm. So what I need to do is
change the WIN64 swap from:
SWAP xmm0, xmm2
SWAP xmm1, xmm3
To:
VBROADCASTSS m0, xmm2
VBROADCASTSS m1, xmm3
Is that correct?
Yes, that will ultimately broadcast the two scalars in xmm2 and xmm3 to
zmm16 and zmm17.
After that what you need to do is either change the fmaddss instruction to use
xm0 and xm1 macros instead of xmm0 and xmm1 (so xmm16 and xmm17 with
EVEX encoding is used), or much like the broadcast above use xmm2 and xmm3
explicitly on win64, so it remains VEX encoded.
So, to fix the issue, does this 2 changes looks good for you?
First change the WIN64 swap from:
SWAP xmm0, xmm2
SWAP xmm1, xmm3
To:
VBROADCASTSS m0, xmm2
VBROADCASTSS m1, xmm3
Second change the fmaddss from:
fmaddss xmm4, xmm4, xmm0, xmm1
To:
fmaddss xmm4, xmm4, xm0, xm1
Yes.
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