From: Michael Niedermayer <michael@niedermayer.cc>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH v2 3/5] libswscale: Avx2 hscale can process inputs of any size.
Date: Fri, 22 Apr 2022 19:42:40 +0200
Message-ID: <20220422174240.GV2829255@pb2> (raw)
In-Reply-To: <20220217100404.1112755-1-alankelly@google.com>
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On Thu, Feb 17, 2022 at 11:04:04AM +0100, Alan Kelly wrote:
> The main loop processes blocks of 16 pixels. The tail processes blocks
> of size 4.
> ---
> libswscale/x86/scale_avx2.asm | 48 +++++++++++++++++++++++++++++++++--
> 1 file changed, 46 insertions(+), 2 deletions(-)
>
> diff --git a/libswscale/x86/scale_avx2.asm b/libswscale/x86/scale_avx2.asm
> index 20acdbd633..dc42abb100 100644
> --- a/libswscale/x86/scale_avx2.asm
> +++ b/libswscale/x86/scale_avx2.asm
> @@ -53,6 +53,9 @@ cglobal hscale8to15_%1, 7, 9, 16, pos0, dst, w, srcmem, filter, fltpos, fltsize,
> mova m14, [four]
> shr fltsized, 2
> %endif
> + cmp wq, 16
> + jl .tail_loop
> + mov countq, 0x10
> .loop:
> movu m1, [fltposq]
> movu m2, [fltposq+32]
> @@ -97,11 +100,52 @@ cglobal hscale8to15_%1, 7, 9, 16, pos0, dst, w, srcmem, filter, fltpos, fltsize,
> vpsrad m6, 7
> vpackssdw m5, m5, m6
> vpermd m5, m15, m5
> - vmovdqu [dstq + countq * 2], m5
> + vmovdqu [dstq], m5
> + add dstq, 0x20
> add fltposq, 0x40
> add countq, 0x10
> cmp countq, wq
> - jl .loop
> + jle .loop
> +
> + sub countq, 0x10
> + cmp countq, wq
> + jge .end
> +
> +.tail_loop:
> + movu xm1, [fltposq]
> +%ifidn %1, X4
> + pxor xm9, xm9
> + pxor xm10, xm10
> + xor innerq, innerq
> +.tail_innerloop:
> +%endif
> + vpcmpeqd xm13, xm13
> + vpgatherdd xm3,[srcmemq + xm1], xm13
> + vpunpcklbw xm5, xm3, xm0
> + vpunpckhbw xm6, xm3, xm0
> + vpmaddwd xm5, xm5, [filterq]
> + vpmaddwd xm6, xm6, [filterq + 16]
> + add filterq, 0x20
> +%ifidn %1, X4
> + paddd xm9, xm5
> + paddd xm10, xm6
> + paddd xm1, xm14
> + add innerq, 1
> + cmp innerq, fltsizeq
> + jl .tail_innerloop
> + vphaddd xm5, xm9, xm10
> +%else
> + vphaddd xm5, xm5, xm6
> +%endif
> + vpsrad xm5, 7
> + vpackssdw xm5, xm5, xm5
> + vmovq [dstq], xm5
> + add dstq, 0x8
> + add fltposq, 0x10
> + add countq, 0x4
> + cmp countq, wq
> + jl .tail_loop
> +.end:
> REP_RET
> %endmacro
countq is only used as counter after this
If you count against 0 this reduces the instructions in the loop from
add/cmp to just add.
similarly the previously used [dstq + countq * 2] avoids a add
can you comment on the performance impact of these changes ?
On previous generations of CPUs this would have been generally slower
I havnt really optimized ASM for current CPUs so these comments might
not apply today but noone else seems reviewing this
thx
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
The worst form of inequality is to try to make unequal things equal.
-- Aristotle
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next prev parent reply other threads:[~2022-04-22 17:42 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-17 10:04 Alan Kelly
2022-02-17 16:21 ` Michael Niedermayer
2022-03-07 15:27 ` Alan Kelly
2022-04-22 8:02 ` Alan Kelly
2022-04-22 14:53 ` Paul B Mahol
2022-04-22 17:42 ` Michael Niedermayer [this message]
2022-04-26 7:45 ` Alan Kelly
2022-04-26 8:00 ` Alan Kelly
2022-07-13 8:04 ` Alan Kelly
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