зеркало из https://github.com/mozilla/gecko-dev.git
129 строки
6.1 KiB
C
129 строки
6.1 KiB
C
/********************************************************************
|
|
* *
|
|
* THIS FILE IS PART OF THE OggTheora SOFTWARE CODEC SOURCE CODE. *
|
|
* USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS *
|
|
* GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
|
|
* IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. *
|
|
* *
|
|
* THE Theora SOURCE CODE IS COPYRIGHT (C) 2002-2009 *
|
|
* by the Xiph.Org Foundation and contributors http://www.xiph.org/ *
|
|
* *
|
|
********************************************************************
|
|
|
|
function:
|
|
last mod: $Id: ocintrin.h 16503 2009-08-22 18:14:02Z giles $
|
|
|
|
********************************************************************/
|
|
|
|
/*Some common macros for potential platform-specific optimization.*/
|
|
#include <math.h>
|
|
#if !defined(_ocintrin_H)
|
|
# define _ocintrin_H (1)
|
|
|
|
/*Some specific platforms may have optimized intrinsic or inline assembly
|
|
versions of these functions which can substantially improve performance.
|
|
We define macros for them to allow easy incorporation of these non-ANSI
|
|
features.*/
|
|
|
|
/*Note that we do not provide a macro for abs(), because it is provided as a
|
|
library function, which we assume is translated into an intrinsic to avoid
|
|
the function call overhead and then implemented in the smartest way for the
|
|
target platform.
|
|
With modern gcc (4.x), this is true: it uses cmov instructions if the
|
|
architecture supports it and branchless bit-twiddling if it does not (the
|
|
speed difference between the two approaches is not measurable).
|
|
Interestingly, the bit-twiddling method was patented in 2000 (US 6,073,150)
|
|
by Sun Microsystems, despite prior art dating back to at least 1996:
|
|
http://web.archive.org/web/19961201174141/www.x86.org/ftp/articles/pentopt/PENTOPT.TXT
|
|
On gcc 3.x, however, our assumption is not true, as abs() is translated to a
|
|
conditional jump, which is horrible on deeply piplined architectures (e.g.,
|
|
all consumer architectures for the past decade or more).
|
|
Also be warned that -C*abs(x) where C is a constant is mis-optimized as
|
|
abs(C*x) on every gcc release before 4.2.3.
|
|
See bug http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34130 */
|
|
|
|
/*Modern gcc (4.x) can compile the naive versions of min and max with cmov if
|
|
given an appropriate architecture, but the branchless bit-twiddling versions
|
|
are just as fast, and do not require any special target architecture.
|
|
Earlier gcc versions (3.x) compiled both code to the same assembly
|
|
instructions, because of the way they represented ((_b)>(_a)) internally.*/
|
|
#define OC_MAXI(_a,_b) ((_a)-((_a)-(_b)&-((_b)>(_a))))
|
|
#define OC_MINI(_a,_b) ((_a)+((_b)-(_a)&-((_b)<(_a))))
|
|
/*Clamps an integer into the given range.
|
|
If _a>_c, then the lower bound _a is respected over the upper bound _c (this
|
|
behavior is required to meet our documented API behavior).
|
|
_a: The lower bound.
|
|
_b: The value to clamp.
|
|
_c: The upper boud.*/
|
|
#define OC_CLAMPI(_a,_b,_c) (OC_MAXI(_a,OC_MINI(_b,_c)))
|
|
#define OC_CLAMP255(_x) ((unsigned char)((((_x)<0)-1)&((_x)|-((_x)>255))))
|
|
/*This has a chance of compiling branchless, and is just as fast as the
|
|
bit-twiddling method, which is slightly less portable, since it relies on a
|
|
sign-extended rightshift, which is not guaranteed by ANSI (but present on
|
|
every relevant platform).*/
|
|
#define OC_SIGNI(_a) (((_a)>0)-((_a)<0))
|
|
/*Slightly more portable than relying on a sign-extended right-shift (which is
|
|
not guaranteed by ANSI), and just as fast, since gcc (3.x and 4.x both)
|
|
compile it into the right-shift anyway.*/
|
|
#define OC_SIGNMASK(_a) (-((_a)<0))
|
|
/*Divides an integer by a power of two, truncating towards 0.
|
|
_dividend: The integer to divide.
|
|
_shift: The non-negative power of two to divide by.
|
|
_rmask: (1<<_shift)-1*/
|
|
#define OC_DIV_POW2(_dividend,_shift,_rmask)\
|
|
((_dividend)+(OC_SIGNMASK(_dividend)&(_rmask))>>(_shift))
|
|
/*Divides _x by 65536, truncating towards 0.*/
|
|
#define OC_DIV2_16(_x) OC_DIV_POW2(_x,16,0xFFFF)
|
|
/*Divides _x by 2, truncating towards 0.*/
|
|
#define OC_DIV2(_x) OC_DIV_POW2(_x,1,0x1)
|
|
/*Divides _x by 8, truncating towards 0.*/
|
|
#define OC_DIV8(_x) OC_DIV_POW2(_x,3,0x7)
|
|
/*Divides _x by 16, truncating towards 0.*/
|
|
#define OC_DIV16(_x) OC_DIV_POW2(_x,4,0xF)
|
|
/*Right shifts _dividend by _shift, adding _rval, and subtracting one for
|
|
negative dividends first.
|
|
When _rval is (1<<_shift-1), this is equivalent to division with rounding
|
|
ties away from zero.*/
|
|
#define OC_DIV_ROUND_POW2(_dividend,_shift,_rval)\
|
|
((_dividend)+OC_SIGNMASK(_dividend)+(_rval)>>(_shift))
|
|
/*Divides a _x by 2, rounding towards even numbers.*/
|
|
#define OC_DIV2_RE(_x) ((_x)+((_x)>>1&1)>>1)
|
|
/*Divides a _x by (1<<(_shift)), rounding towards even numbers.*/
|
|
#define OC_DIV_POW2_RE(_x,_shift) \
|
|
((_x)+((_x)>>(_shift)&1)+((1<<(_shift))-1>>1)>>(_shift))
|
|
/*Swaps two integers _a and _b if _a>_b.*/
|
|
#define OC_SORT2I(_a,_b) \
|
|
do{ \
|
|
int t__; \
|
|
t__=((_a)^(_b))&-((_b)<(_a)); \
|
|
(_a)^=t__; \
|
|
(_b)^=t__; \
|
|
} \
|
|
while(0)
|
|
|
|
/*Accesses one of four (signed) bytes given an index.
|
|
This can be used to avoid small lookup tables.*/
|
|
#define OC_BYTE_TABLE32(_a,_b,_c,_d,_i) \
|
|
((signed char) \
|
|
(((_a)&0xFF|((_b)&0xFF)<<8|((_c)&0xFF)<<16|((_d)&0xFF)<<24)>>(_i)*8))
|
|
/*Accesses one of eight (unsigned) nibbles given an index.
|
|
This can be used to avoid small lookup tables.*/
|
|
#define OC_UNIBBLE_TABLE32(_a,_b,_c,_d,_e,_f,_g,_h,_i) \
|
|
((((_a)&0xF|((_b)&0xF)<<4|((_c)&0xF)<<8|((_d)&0xF)<<12| \
|
|
((_e)&0xF)<<16|((_f)&0xF)<<20|((_g)&0xF)<<24|((_h)&0xF)<<28)>>(_i)*4)&0xF)
|
|
|
|
|
|
|
|
/*All of these macros should expect floats as arguments.*/
|
|
#define OC_MAXF(_a,_b) ((_a)<(_b)?(_b):(_a))
|
|
#define OC_MINF(_a,_b) ((_a)>(_b)?(_b):(_a))
|
|
#define OC_CLAMPF(_a,_b,_c) (OC_MINF(_a,OC_MAXF(_b,_c)))
|
|
#define OC_FABSF(_f) ((float)fabs(_f))
|
|
#define OC_SQRTF(_f) ((float)sqrt(_f))
|
|
#define OC_POWF(_b,_e) ((float)pow(_b,_e))
|
|
#define OC_LOGF(_f) ((float)log(_f))
|
|
#define OC_IFLOORF(_f) ((int)floor(_f))
|
|
#define OC_ICEILF(_f) ((int)ceil(_f))
|
|
|
|
#endif
|