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/*
* Copyright (c) 2010 Broadcom Corporation
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#ifndef _BITFUNCS_H
#define _BITFUNCS_H
#include <typedefs.h>
/* local prototypes */
static inline uint32 find_msbit(uint32 x);
/*
* find_msbit: returns index of most significant set bit in x, with index
* range defined as 0-31. NOTE: returns zero if input is zero.
*/
#if defined(USE_PENTIUM_BSR) && defined(__GNUC__)
/*
* Implementation for Pentium processors and gcc. Note that this
* instruction is actually very slow on some processors (e.g., family 5,
* model 2, stepping 12, "Pentium 75 - 200"), so we use the generic
* implementation instead.
*/
static inline uint32 find_msbit(uint32 x)
{
uint msbit;
__asm__("bsrl %1,%0" : "=r"(msbit)
: "r"(x));
return msbit;
}
#else /* !USE_PENTIUM_BSR || !__GNUC__ */
/*
* Generic Implementation
*/
#define DB_POW_MASK16 0xffff0000
#define DB_POW_MASK8 0x0000ff00
#define DB_POW_MASK4 0x000000f0
#define DB_POW_MASK2 0x0000000c
#define DB_POW_MASK1 0x00000002
static inline uint32 find_msbit(uint32 x)
{
uint32 temp_x = x;
uint msbit = 0;
if (temp_x & DB_POW_MASK16) {
temp_x >>= 16;
msbit = 16;
}
if (temp_x & DB_POW_MASK8) {
temp_x >>= 8;
msbit += 8;
}
if (temp_x & DB_POW_MASK4) {
temp_x >>= 4;
msbit += 4;
}
if (temp_x & DB_POW_MASK2) {
temp_x >>= 2;
msbit += 2;
}
if (temp_x & DB_POW_MASK1) {
msbit += 1;
}
return msbit;
}
#endif /* USE_PENTIUM_BSR && __GNUC__ */
#endif /* _BITFUNCS_H */
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