release/src-rt/include/bitfuncs.h

   1 /*
   2  * bit manipulation utility functions
   3  *
   4  * Copyright (C) 2010, Broadcom Corporation. All Rights Reserved.
   5  *
   6  * Permission to use, copy, modify, and/or distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
  13  * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
  15  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  16  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  * $Id: bitfuncs.h,v 13.4 2005-09-13 23:15:40 Exp $
  18  */
  19
  20 #ifndef _BITFUNCS_H
  21 #define _BITFUNCS_H
  22
  23 #include <typedefs.h>
  24
  25 /* local prototypes */
  26 static INLINE uint32 find_msbit(uint32 x);
  27
  28
  29 /*
  30  * find_msbit: returns index of most significant set bit in x, with index
  31  *   range defined as 0-31.  NOTE: returns zero if input is zero.
  32  */
  33
  34 #if defined(USE_PENTIUM_BSR) && defined(__GNUC__)
  35
  36 /*
  37  * Implementation for Pentium processors and gcc.  Note that this
  38  * instruction is actually very slow on some processors (e.g., family 5,
  39  * model 2, stepping 12, "Pentium 75 - 200"), so we use the generic
  40  * implementation instead.
  41  */
  42 static INLINE uint32 find_msbit(uint32 x)
  43 {
  44         uint msbit;
  45         __asm__("bsrl %1,%0"
  46                 :"=r" (msbit)
  47                 :"r" (x));
  48         return msbit;
  49 }
  50
  51 #else   /* !USE_PENTIUM_BSR || !__GNUC__ */
  52
  53 /*
  54  * Generic Implementation
  55  */
  56
  57 #define DB_POW_MASK16   0xffff0000
  58 #define DB_POW_MASK8    0x0000ff00
  59 #define DB_POW_MASK4    0x000000f0
  60 #define DB_POW_MASK2    0x0000000c
  61 #define DB_POW_MASK1    0x00000002
  62
  63 static INLINE uint32 find_msbit(uint32 x)
  64 {
  65         uint32 temp_x = x;
  66         uint msbit = 0;
  67         if (temp_x & DB_POW_MASK16) {
  68                 temp_x >>= 16;
  69                 msbit = 16;
  70         }
  71         if (temp_x & DB_POW_MASK8) {
  72                 temp_x >>= 8;
  73                 msbit += 8;
  74         }
  75         if (temp_x & DB_POW_MASK4) {
  76                 temp_x >>= 4;
  77                 msbit += 4;
  78         }
  79         if (temp_x & DB_POW_MASK2) {
  80                 temp_x >>= 2;
  81                 msbit += 2;
  82         }
  83         if (temp_x & DB_POW_MASK1) {
  84                 msbit += 1;
  85         }
  86         return (msbit);
  87 }
  88
  89 #endif  /* USE_PENTIUM_BSR && __GNUC__ */
  90
  91 #endif /* _BITFUNCS_H */