[FFmpeg-devel] [PATCH] PPC64: Add IBM POWER8 SIMD Implementation
Dan Parrot
dan.parrot at mail.com
Wed Jun 22 05:45:35 CEST 2016
On Tue, 2016-06-21 at 00:04 -0500, Dan Parrot wrote:
> On Tue, 2016-06-21 at 02:22 +0200, Michael Niedermayer wrote:
> > On Mon, Jun 20, 2016 at 06:38:18PM -0500, Dan Parrot wrote:
> > > On Tue, 2016-06-21 at 01:06 +0200, Michael Niedermayer wrote:
> > > > On Mon, Jun 20, 2016 at 05:55:47PM -0500, Dan Parrot wrote:
> > > > > On Tue, 2016-06-21 at 00:45 +0200, Michael Niedermayer wrote:
> > > > > > On Sun, Jun 19, 2016 at 09:57:42PM +0000, Dan Parrot wrote:
> > > > > > > First commit addressing Trac ticket #5570. Functions defined in libswscale/input.c
> > > > > > > have corresponding SIMD definitions in libswscale/ppc/input_vsx.c
> > > > > > > ---
> > > > > > > libswscale/ppc/Makefile | 1 +
> > > > > > > libswscale/ppc/input_vsx.c | 1070 +++++++++++++++++++++++++++++++++++++++++
> > > > > > > libswscale/swscale.c | 3 +
> > > > > > > libswscale/swscale_internal.h | 1 +
> > > > > > > 4 files changed, 1075 insertions(+)
> > > > > > > create mode 100644 libswscale/ppc/input_vsx.c
> > > > > > >
> > > > > > > diff --git a/libswscale/ppc/Makefile b/libswscale/ppc/Makefile
> > > > > > > index d1b596e..2482893 100644
> > > > > > > --- a/libswscale/ppc/Makefile
> > > > > > > +++ b/libswscale/ppc/Makefile
> > > > > > > @@ -1,3 +1,4 @@
> > > > > > > OBJS += ppc/swscale_altivec.o \
> > > > > > > + ppc/input_vsx.o \
> > > > > > > ppc/yuv2rgb_altivec.o \
> > > > > > > ppc/yuv2yuv_altivec.o \
> > > > > > > diff --git a/libswscale/ppc/input_vsx.c b/libswscale/ppc/input_vsx.c
> > > > > > > new file mode 100644
> > > > > > > index 0000000..adb0e38
> > > > > > > --- /dev/null
> > > > > > > +++ b/libswscale/ppc/input_vsx.c
> > > > > > > @@ -0,0 +1,1070 @@
> > > > > > > +/*
> > > > > > > + * Copyright (C) 2016 Dan Parrot <dan.parrot at mail.com>
> > > > > > > + *
> > > > > > > + * This file is part of FFmpeg.
> > > > > > > + *
> > > > > > > + * FFmpeg is free software; you can redistribute it and/or
> > > > > > > + * modify it under the terms of the GNU Lesser General Public
> > > > > > > + * License as published by the Free Software Foundation; either
> > > > > > > + * version 2.1 of the License, or (at your option) any later version.
> > > > > > > + *
> > > > > > > + * FFmpeg is distributed in the hope that it will be useful,
> > > > > > > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > > > > > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> > > > > > > + * Lesser General Public License for more details.
> > > > > > > + *
> > > > > > > + * You should have received a copy of the GNU Lesser General Public
> > > > > > > + * License along with FFmpeg; if not, write to the Free Software
> > > > > > > + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> > > > > > > + */
> > > > > > > +
> > > > > > > +#include <math.h>
> > > > > > > +#include <stdint.h>
> > > > > > > +#include <stdio.h>
> > > > > > > +#include <string.h>
> > > > > > > +
> > > > > > > +#include "libavutil/avutil.h"
> > > > > > > +#include "libavutil/bswap.h"
> > > > > > > +#include "libavutil/cpu.h"
> > > > > > > +#include "libavutil/intreadwrite.h"
> > > > > > > +#include "libavutil/mathematics.h"
> > > > > > > +#include "libavutil/pixdesc.h"
> > > > > > > +#include "libavutil/avassert.h"
> > > > > > > +#include "config.h"
> > > > > > > +#include "libswscale/rgb2rgb.h"
> > > > > > > +#include "libswscale/swscale.h"
> > > > > > > +#include "libswscale/swscale_internal.h"
> > > > > > > +
> > > > > > > +#define input_pixel(pos) (isBE(origin) ? AV_RB16(pos) : AV_RL16(pos))
> > > > > > > +
> > > > > > > +#define r ((origin == AV_PIX_FMT_BGR48BE || origin == AV_PIX_FMT_BGR48LE || origin == AV_PIX_FMT_BGRA64BE || origin == AV_PIX_FMT_BGRA64LE) ? b_r : r_b)
> > > > > > > +#define b ((origin == AV_PIX_FMT_BGR48BE || origin == AV_PIX_FMT_BGR48LE || origin == AV_PIX_FMT_BGRA64BE || origin == AV_PIX_FMT_BGRA64LE) ? r_b : b_r)
> > > > > > > +
> > > > > > > +#if HAVE_VSX
> > > > > > > +
> > > > > > > +// This is a SIMD version for IBM POWER8 of function rgb64ToY_c_template
> > > > > > > +// in file libswscale/input.c
> > > > > > > +static av_always_inline void
> > > > > > > +rgb64ToY_c_template_vsx(uint16_t *dst, const uint16_t *src, int width,
> > > > > > > + enum AVPixelFormat origin, int32_t *rgb2yuv)
> > > > > > > +{
> > > > > > > + int32_t ry = rgb2yuv[RY_IDX], gy = rgb2yuv[GY_IDX], by = rgb2yuv[BY_IDX];
> > > > > > > + int i, j;
> > > > > > > + int num_vec, frag;
> > > > > > > +
> > > > > > > + num_vec = width / 8;
> > > > > > > + frag = width % 8;
> > > > > > > +
> > > > > > > + vector int v_ry = vec_splats((int)ry);
> > > > > > > + vector int v_gy = vec_splats((int)gy);
> > > > > > > + vector int v_by = vec_splats((int)by);
> > > > > > > +
> > > > > > > + int s_opr2;
> > > > > > > + s_opr2 = (int)(0x2001 << (RGB2YUV_SHIFT-1));
> > > > > > > +
> > > > > > > + vector int v_opr1 = vec_splats((int)RGB2YUV_SHIFT);
> > > > > > > + vector int v_opr2 = vec_splats((int)s_opr2);
> > > > > > > +
> > > > > > > + vector int v_r, v_g, v_b, v_tmp;
> > > > > > > + vector short v_tmpi, v_dst;
> > > > > > > +
> > > > > > > + for (i = 0; i < num_vec; i++) {
> > > > > > > + for (j = 7; j >= 0 ; j--) {
> > > > > > > + int r_b = input_pixel(&src[(i*8+j)*4+0]);
> > > > > > > + int g = input_pixel(&src[(i*8+j)*4+1]);
> > > > > > > + int b_r = input_pixel(&src[(i*8+j)*4+2]);
> > > > > > > +
> > > > > > > + v_r[j % 4] = r;
> > > > > > > + v_g[j % 4] = g;
> > > > > > > + v_b[j % 4] = b;
> > > > > > > +
> > > > > > > + if (!(j % 4)) {
> > > > > > ^
> > > > > >
> > > > > > > + v_tmp = v_ry * v_r;
> > > > > > > + v_tmp = v_tmp + v_gy * v_g;
> > > > > > > + v_tmp = v_tmp + v_by * v_b;
> > > > > > > + v_tmp = v_tmp + v_opr2;
> > > > > > > + v_tmp = vec_sr(v_tmp, (vector unsigned int)v_opr1);
> > > > > > > +
> > > > > > > + v_tmpi = (vector short)v_tmp;
> > > > > > > + v_dst[(j / 4) * 4 + 3] = v_tmpi[6];
> > > > > > ^
> > > > > > what is the speed of a division and modulo on PPC compared to a
> > > > > > bitwise and ?
> > > > > >
> > > > > > its also not trivial for the compiler to optimize then out as it
> > > > > > has to proof the varables are never negative
> > > > > >
> > > > > >
> > > > > > [...]
> > > > > > _______________________________________________
> > > > > > ffmpeg-devel mailing list
> > > > > > ffmpeg-devel at ffmpeg.org
> > > > > > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> > > > >
> > > > > I don't know the answer to those questions. But, I see your point.
> > > > > Bitwise operations should be faster than multiplications and divisions.
> > > > > So, I shall change the code to use bitwise ops and compare the execution
> > > > > time against its present value (well, average value over multiple runs)
> > > >
> > > > it might not make a difference if the compiler does optmize them out
> > > > but you should know the approximate speed of the instructions
> > > > that your code is likely/potentially going to use. I mean this is
> > > > code optimized for PPC.
> > > >
> > > > [...]
> > > > _______________________________________________
> > > > ffmpeg-devel mailing list
> > > > ffmpeg-devel at ffmpeg.org
> > > > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> > >
> > > I take exception to the tone in that last sentence and I shall respond
> > > in the same spirit.
> > >
> > > 1. I could spend time obtaining the detailed POWER8 micro architecture
> > > description and compare the execution time of each machine instruction.
> > > 2. Study gcc source to find out exactly which machine instructions it
> > > generates for each C language operator
> > > 3. Use 1 and 2 above to determine which C operators to use here.
> > >
> > > OR
> > >
> > > I could go ahead and run 2 simulations and compare their average
> > > execution times.
> > >
> > > Seems to me pretty clear which is a better use of time.
> >
> > Knowing the execution times of instructions is quite usefull
> > it certainly takes alot more time to search and read that than to
> > benchmark once but once you know the timings approximatly you can
> > roughly guess how fast/slow some code is by just looking.
> > If knowing that doesnt interrest you then please ignore my comment
> > to me these things always feel interresting and it was to me certainly
> > quite usefull when optmizing code to know this kind of stuff for x86
> >
> > also what are you testing on ?
> >
> > [...]
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel at ffmpeg.org
> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> Changing the operations to use bitwise operators instead of
> multiplications, divisions and modulo arithmetic did not appreciably
> change execution times. The execution times of the two versions were
> within 1.5 seconds of each other in all of worst, best and average times
> reported by command "/usr/bin/time -p make -j 4 fate
> SAMPLES=fate-suite/"
> Worst case real components clustered around 310s. Best case times
> clustered about 296s.
>
> Do you want me to submit a patch using the bitwise operators to replace
> the previous patch?
>
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
ffmpeg compiled with the SIMD patch is faster than that built using the
non-SIMD version currently in the repository. Averaging over 10 runs
each of the full FATE regression suite shows the SIMD version faster by
about 3.5 seconds. The output of "cat /proc/cpuinfo" on the machine
gives:
==============
processor : 0
cpu : POWER8E (raw), altivec supported
clock : 3425.000000MHz
revision : 2.1 (pvr 004b 0201)
processor : 1
cpu : POWER8E (raw), altivec supported
clock : 3425.000000MHz
revision : 2.1 (pvr 004b 0201)
processor : 2
cpu : POWER8E (raw), altivec supported
clock : 3425.000000MHz
revision : 2.1 (pvr 004b 0201)
processor : 3
cpu : POWER8E (raw), altivec supported
clock : 3425.000000MHz
revision : 2.1 (pvr 004b 0201)
timebase : 512000000
platform : pSeries
model : IBM pSeries (emulated by qemu)
machine : CHRP IBM pSeries (emulated by qemu)
==============
Do you need more information before you can accept and apply the patch?
I would like to move on and code up SIMD versions for the rest of the
functions in libswscale/input.c.
Thanks.
More information about the ffmpeg-devel
mailing list