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/*
* bit manipulation utility functions
*
* Copyright 2005, Broadcom Corporation
* All Rights Reserved.
*
* THIS SOFTWARE IS OFFERED "AS IS", AND BROADCOM GRANTS NO WARRANTIES OF ANY
* KIND, EXPRESS OR IMPLIED, BY STATUTE, COMMUNICATION OR OTHERWISE. BROADCOM
* SPECIFICALLY DISCLAIMS ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A SPECIFIC PURPOSE OR NONINFRINGEMENT CONCERNING THIS SOFTWARE.
* $Id: bitfuncs.h,v 1.1.1.7 2005/03/07 07:31:12 kanki Exp $
*/
#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
/*
* 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
#endif /* _BITFUNCS_H */
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