arch/arm/lib/findbit.S

   1 /*
   2  *  linux/arch/arm/lib/findbit.S
   3  *
   4  *  Copyright (C) 1995-2000 Russell King
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * 16th March 2001 - John Ripley <jripley@sonicblue.com>
  11  *   Fixed so that "size" is an exclusive not an inclusive quantity.
  12  *   All users of these functions expect exclusive sizes, and may
  13  *   also call with zero size.
  14  * Reworked by rmk.
  15  */
  16 #include <linux/linkage.h>
  17 #include <asm/assembler.h>
  18                 .text
  19
  20 /*
  21  * Purpose  : Find a 'zero' bit
  22  * Prototype: int find_first_zero_bit(void *addr, unsigned int maxbit);
  23  */
  24 ENTRY(_find_first_zero_bit_le)
  25                 teq     r1, #0
  26                 beq     3f
  27                 mov     r2, #0
  28 1:              ldrb    r3, [r0, r2, lsr #3]
  29                 eors    r3, r3, #0xff           @ invert bits
  30                 bne     .L_found                @ any now set - found zero bit
  31                 add     r2, r2, #8              @ next bit pointer
  32 2:              cmp     r2, r1                  @ any more?
  33                 blo     1b
  34 3:              mov     r0, r1                  @ no free bits
  35                 mov     pc, lr
  36 ENDPROC(_find_first_zero_bit_le)
  37
  38 /*
  39  * Purpose  : Find next 'zero' bit
  40  * Prototype: int find_next_zero_bit(void *addr, unsigned int maxbit, int offset)
  41  */
  42 ENTRY(_find_next_zero_bit_le)
  43                 teq     r1, #0
  44                 beq     3b
  45                 ands    ip, r2, #7
  46                 beq     1b                      @ If new byte, goto old routine
  47                 ldrb    r3, [r0, r2, lsr #3]
  48                 eor     r3, r3, #0xff           @ now looking for a 1 bit
  49                 movs    r3, r3, lsr ip          @ shift off unused bits
  50                 bne     .L_found
  51                 orr     r2, r2, #7              @ if zero, then no bits here
  52                 add     r2, r2, #1              @ align bit pointer
  53                 b       2b                      @ loop for next bit
  54 ENDPROC(_find_next_zero_bit_le)
  55
  56 /*
  57  * Purpose  : Find a 'one' bit
  58  * Prototype: int find_first_bit(const unsigned long *addr, unsigned int maxbit);
  59  */
  60 ENTRY(_find_first_bit_le)
  61                 teq     r1, #0
  62                 beq     3f
  63                 mov     r2, #0
  64 1:              ldrb    r3, [r0, r2, lsr #3]
  65                 movs    r3, r3
  66                 bne     .L_found                @ any now set - found zero bit
  67                 add     r2, r2, #8              @ next bit pointer
  68 2:              cmp     r2, r1                  @ any more?
  69                 blo     1b
  70 3:              mov     r0, r1                  @ no free bits
  71                 mov     pc, lr
  72 ENDPROC(_find_first_bit_le)
  73
  74 /*
  75  * Purpose  : Find next 'one' bit
  76  * Prototype: int find_next_zero_bit(void *addr, unsigned int maxbit, int offset)
  77  */
  78 ENTRY(_find_next_bit_le)
  79                 teq     r1, #0
  80                 beq     3b
  81                 ands    ip, r2, #7
  82                 beq     1b                      @ If new byte, goto old routine
  83                 ldrb    r3, [r0, r2, lsr #3]
  84                 movs    r3, r3, lsr ip          @ shift off unused bits
  85                 bne     .L_found
  86                 orr     r2, r2, #7              @ if zero, then no bits here
  87                 add     r2, r2, #1              @ align bit pointer
  88                 b       2b                      @ loop for next bit
  89 ENDPROC(_find_next_bit_le)
  90
  91 #ifdef __ARMEB__
  92
  93 ENTRY(_find_first_zero_bit_be)
  94                 teq     r1, #0
  95                 beq     3f
  96                 mov     r2, #0
  97 1:              eor     r3, r2, #0x18           @ big endian byte ordering
  98                 ldrb    r3, [r0, r3, lsr #3]
  99                 eors    r3, r3, #0xff           @ invert bits
 100                 bne     .L_found                @ any now set - found zero bit
 101                 add     r2, r2, #8              @ next bit pointer
 102 2:              cmp     r2, r1                  @ any more?
 103                 blo     1b
 104 3:              mov     r0, r1                  @ no free bits
 105                 mov     pc, lr
 106 ENDPROC(_find_first_zero_bit_be)
 107
 108 ENTRY(_find_next_zero_bit_be)
 109                 teq     r1, #0
 110                 beq     3b
 111                 ands    ip, r2, #7
 112                 beq     1b                      @ If new byte, goto old routine
 113                 eor     r3, r2, #0x18           @ big endian byte ordering
 114                 ldrb    r3, [r0, r3, lsr #3]
 115                 eor     r3, r3, #0xff           @ now looking for a 1 bit
 116                 movs    r3, r3, lsr ip          @ shift off unused bits
 117                 bne     .L_found
 118                 orr     r2, r2, #7              @ if zero, then no bits here
 119                 add     r2, r2, #1              @ align bit pointer
 120                 b       2b                      @ loop for next bit
 121 ENDPROC(_find_next_zero_bit_be)
 122
 123 ENTRY(_find_first_bit_be)
 124                 teq     r1, #0
 125                 beq     3f
 126                 mov     r2, #0
 127 1:              eor     r3, r2, #0x18           @ big endian byte ordering
 128                 ldrb    r3, [r0, r3, lsr #3]
 129                 movs    r3, r3
 130                 bne     .L_found                @ any now set - found zero bit
 131                 add     r2, r2, #8              @ next bit pointer
 132 2:              cmp     r2, r1                  @ any more?
 133                 blo     1b
 134 3:              mov     r0, r1                  @ no free bits
 135                 mov     pc, lr
 136 ENDPROC(_find_first_bit_be)
 137
 138 ENTRY(_find_next_bit_be)
 139                 teq     r1, #0
 140                 beq     3b
 141                 ands    ip, r2, #7
 142                 beq     1b                      @ If new byte, goto old routine
 143                 eor     r3, r2, #0x18           @ big endian byte ordering
 144                 ldrb    r3, [r0, r3, lsr #3]
 145                 movs    r3, r3, lsr ip          @ shift off unused bits
 146                 bne     .L_found
 147                 orr     r2, r2, #7              @ if zero, then no bits here
 148                 add     r2, r2, #1              @ align bit pointer
 149                 b       2b                      @ loop for next bit
 150 ENDPROC(_find_next_bit_be)
 151
 152 #endif
 153
 154 /*
 155  * One or more bits in the LSB of r3 are assumed to be set.
 156  */
 157 .L_found:
 158 #if __LINUX_ARM_ARCH__ >= 5
 159                 rsb     r1, r3, #0
 160                 and     r3, r3, r1
 161                 clz     r3, r3
 162                 rsb     r3, r3, #31
 163                 add     r0, r2, r3
 164 #else
 165                 tst     r3, #0x0f
 166                 addeq   r2, r2, #4
 167                 movne   r3, r3, lsl #4
 168                 tst     r3, #0x30
 169                 addeq   r2, r2, #2
 170                 movne   r3, r3, lsl #2
 171                 tst     r3, #0x40
 172                 addeq   r2, r2, #1
 173                 mov     r0, r2
 174 #endif
 175                 mov     pc, lr
 176