ffmpeg | branch: master | Ganesh Ajjanagadde <gajjanaga...@gmail.com> | Tue Dec 29 08:18:44 2015 -0800| [b272c3a5aabeafb37d5aeecc4524e8a8aeecf9da] | committer: Ganesh Ajjanagadde
lavc/dsd_tablegen: speed up table generation Tables are bit identical. Sample benchmark (Haswell, GNU/Linux+gcc): old: 814485 decicycles in dsd_ctables_tableinit, 512 runs, 0 skips new: 356808 decicycles in dsd_ctable_tableinit, 512 runs, 0 skips Binary size should essentially be identical, and is in fact identical on the configuration I tested on. Reviewed-by: Michael Niedermayer <mich...@niedermayer.cc> Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com> > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b272c3a5aabeafb37d5aeecc4524e8a8aeecf9da --- libavcodec/dsd_tablegen.h | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/libavcodec/dsd_tablegen.h b/libavcodec/dsd_tablegen.h index 6afb416..d4ef302 100644 --- a/libavcodec/dsd_tablegen.h +++ b/libavcodec/dsd_tablegen.h @@ -78,16 +78,17 @@ static float ctables[CTABLES][256]; static av_cold void dsd_ctables_tableinit(void) { - int t, e, m, k; - double acc; - for (t = 0; t < CTABLES; ++t) { - k = FFMIN(HTAPS - t * 8, 8); - for (e = 0; e < 256; ++e) { - acc = 0.0; - for (m = 0; m < k; ++m) - acc += (((e >> (7 - m)) & 1) * 2 - 1) * htaps[t * 8 + m]; - ctables[CTABLES - 1 - t][e] = (float)acc; + int t, e, m, sign; + double acc[CTABLES]; + for (e = 0; e < 256; ++e) { + memset(acc, 0, sizeof(acc)); + for (m = 0; m < 8; ++m) { + sign = (((e >> (7 - m)) & 1) * 2 - 1); + for (t = 0; t < CTABLES; ++t) + acc[t] += sign * htaps[t * 8 + m]; } + for (t = 0; t < CTABLES; ++t) + ctables[CTABLES - 1 - t][e] = acc[t]; } } #endif /* CONFIG_HARDCODED_TABLES */ _______________________________________________ ffmpeg-cvslog mailing list ffmpeg-cvslog@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-cvslog
