[FFmpeg-devel] [PATCH] Altivec split-radix FFT

[Guillaume POIRIER]

Hello,

On Mon, Aug 24, 2009 at 6:09 AM, Loren Merritt<lorenm at u.washington.edu> wrote:
> 1.6x faster than altivec radix-2 as measured by fft-test on a G4.
> 2.0x as measured by gprof.

Outstanding!

> I failed to get oprofile or POWERPC_PERF to measure anything.

Don't use that, it doesn't work.


> This is my first time writing ppc asm, so any optimization hints are
> appreciated.

I'll try to do my best.


> I used raw asm rather than intrinsics because gcc adds a ginormous overhead
> to each function call. Is there anything I need to do to make it work on
> ppc64, if it doesn't already?

I'll look into this. I think all you need to do is avoid refering to
the general purpose registers' name explicitely.

You patch doesn't apply cleanly here:
patch -p1 --dry-run < ../fft_altivec.diff
patching file libavcodec/Makefile
Hunk #1 FAILED at 523.
1 out of 1 hunk FAILED -- saving rejects to file libavcodec/Makefile.rej
patching file libavcodec/fft.c
Hunk #1 FAILED at 110.
1 out of 1 hunk FAILED -- saving rejects to file libavcodec/fft.c.rej
patching file libavcodec/ppc/fft_altivec.c
Hunk #1 FAILED at 1.
Hunk #2 FAILED at 22.
Hunk #3 FAILED at 30.
3 out of 3 hunks FAILED -- saving rejects to file
libavcodec/ppc/fft_altivec.c.rej
patching file libavcodec/ppc/fft_altivec_s.S
patching file libavcodec/ppc/types_altivec.h
Hunk #1 FAILED at 30.
1 out of 1 hunk FAILED -- saving rejects to file
libavcodec/ppc/types_altivec.h.rej


patch -p1 --dry-run < ../cleanup.diff
patching file libavcodec/dsputil.h
Hunk #1 FAILED at 691.
1 out of 1 hunk FAILED -- saving rejects to file libavcodec/dsputil.h.rej
patching file libavcodec/fft.c
Hunk #1 FAILED at 60.
Hunk #2 FAILED at 68.
Hunk #3 FAILED at 107.
3 out of 3 hunks FAILED -- saving rejects to file libavcodec/fft.c.rej


Did I miss something?

Guillaume
-- 
Only a very small fraction of our DNA does anything; the rest is all
comments and ifdefs.

Mike Ditka  - "If God had wanted man to play soccer, he wouldn't have
given us arms." -
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