mirror of
https://github.com/asterisk/asterisk.git
synced 2025-10-31 10:47:18 +00:00
75 lines
1.4 KiB
C
75 lines
1.4 KiB
C
/*! \file
|
|
* \brief log2comp.h - various base 2 log computation versions
|
|
*
|
|
* Asterisk -- An open source telephony toolkit.
|
|
*
|
|
* \author Alex Volkov <codepro@usa.net>
|
|
*
|
|
* Copyright (c) 2004 - 2005, Digium Inc.
|
|
*
|
|
* This program is free software, distributed under the terms of
|
|
* the GNU General Public License
|
|
*
|
|
* Define WANT_ASM before including this file to use assembly
|
|
* whenever possible
|
|
*/
|
|
|
|
#if defined(_MSC_VER)
|
|
# define inline __inline
|
|
#elif defined(__GNUC__)
|
|
# define inline __inline__
|
|
#else
|
|
# define inline
|
|
#endif
|
|
|
|
#if defined(WANT_ASM) && defined(_MSC_VER) && defined(_M_IX86)
|
|
/* MS C Inline Asm */
|
|
# pragma warning( disable : 4035 )
|
|
static inline int ilog2(int val) { __asm
|
|
{
|
|
xor eax, eax
|
|
dec eax
|
|
bsr eax, val
|
|
}}
|
|
# pragma warning( default : 4035 )
|
|
#elif defined(WANT_ASM) && defined(__GNUC__) && (defined(__i386__) || defined(i386))
|
|
/* GNU Inline Asm */
|
|
static inline int ilog2(int val)
|
|
{
|
|
int a;
|
|
__asm__
|
|
("\
|
|
xorl %0, %0 ;\
|
|
decl %0 ;\
|
|
bsrl %1, %0 ;\
|
|
"
|
|
: "=&r" (a)
|
|
: "mr" (val)
|
|
: "cc"
|
|
);
|
|
return a;
|
|
}
|
|
#elif defined(WANT_ASM) && defined(__GNUC__) && defined(__powerpc__)
|
|
static inline int ilog2(int val)
|
|
{
|
|
int a;
|
|
__asm__ ("cntlzw %0,%1"
|
|
: "=r" (a)
|
|
: "r" (val)
|
|
);
|
|
return 31-a;
|
|
}
|
|
#else
|
|
/* no ASM for this compiler and/or platform */
|
|
/* rather slow base 2 log computation
|
|
* Using looped shift.
|
|
*/
|
|
static inline int ilog2(int val)
|
|
{
|
|
int i;
|
|
for (i = -1; val; ++i, val >>= 1)
|
|
;
|
|
return (i);
|
|
}
|
|
#endif
|