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Optimise av_log2 with clz when available

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10% faster flac decoding on x86 and ARM.

Originally committed as revision 21217 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Måns Rullgård
2010-01-14 19:58:12 +00:00
parent 669b558330
commit 544f5a922f
2 changed files with 49 additions and 0 deletions
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8
libavutil/common.h
View File

@@ -117,6 +117,10 @@
#endif
#endif
#ifdef HAVE_AV_CONFIG_H
# include "intmath.h"
#endif
//rounded division & shift
#define RSHIFT(a,b) ((a) > 0 ? ((a) + ((1<<(b))>>1))>>(b) : ((a) + ((1<<(b))>>1)-1)>>(b))
/* assume b>0 */
@@ -138,6 +142,7 @@ extern const uint8_t ff_log2_tab[256];
extern const uint8_t av_reverse[256];
#ifndef av_log2
static inline av_const int av_log2(unsigned int v)
{
int n = 0;
@@ -153,7 +158,9 @@ static inline av_const int av_log2(unsigned int v)
return n;
}
#endif
#ifndef av_log2_16bit
static inline av_const int av_log2_16bit(unsigned int v)
{
int n = 0;
@@ -165,6 +172,7 @@ static inline av_const int av_log2_16bit(unsigned int v)
return n;
}
#endif
/**
* Clips a signed integer value into the amin-amax range.

41
libavutil/intmath.h Normal file
View File

@@ -0,0 +1,41 @@
/*
* Copyright (c) 2010 Mans Rullgard <mans@mansr.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
*/
#ifndef AVUTIL_INTMATH_H
#define AVUTIL_INTMATH_H
#include "config.h"
#include "common.h"
#if HAVE_FAST_CLZ && AV_GCC_VERSION_AT_LEAST(3,4)
#ifndef av_log2
#define av_log2(x) (31 - __builtin_clz((x)|1))
#ifndef av_log2_16bit
#define av_log2_16bit av_log2
#endif
#endif /* av_log2 */
#endif /* AV_GCC_VERSION_AT_LEAST(3,4) */
#endif /* AVUTIL_INTMATH_H */