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:
  29  ARM(           ldrb    r3, [r0, r2, lsr #3]    )
  30  THUMB(         lsr     r3, r2, #3              )
  31  THUMB(         ldrb    r3, [r0, r3]            )
  32                 eors    r3, r3, #0xff           @ invert bits
  33                 bne     .L_found                @ any now set - found zero bit
  34                 add     r2, r2, #8              @ next bit pointer
  35 2:              cmp     r2, r1                  @ any more?
  36                 blo     1b
  37 3:              mov     r0, r1                  @ no free bits
  38                 ret     lr
  39 ENDPROC(_find_first_zero_bit_le)
  40
  41 /*
  42  * Purpose  : Find next 'zero' bit
  43  * Prototype: int find_next_zero_bit(void *addr, unsigned int maxbit, int offset)
  44  */
  45 ENTRY(_find_next_zero_bit_le)
  46                 teq     r1, #0
  47                 beq     3b
  48                 ands    ip, r2, #7
  49                 beq     1b                      @ If new byte, goto old routine
  50  ARM(           ldrb    r3, [r0, r2, lsr #3]    )
  51  THUMB(         lsr     r3, r2, #3              )
  52  THUMB(         ldrb    r3, [r0, r3]            )
  53                 eor     r3, r3, #0xff           @ now looking for a 1 bit
  54                 movs    r3, r3, lsr ip          @ shift off unused bits
  55                 bne     .L_found
  56                 orr     r2, r2, #7              @ if zero, then no bits here
  57                 add     r2, r2, #1              @ align bit pointer
  58                 b       2b                      @ loop for next bit
  59 ENDPROC(_find_next_zero_bit_le)
  60
  61 /*
  62  * Purpose  : Find a 'one' bit
  63  * Prototype: int find_first_bit(const unsigned long *addr, unsigned int maxbit);
  64  */
  65 ENTRY(_find_first_bit_le)
  66                 teq     r1, #0
  67                 beq     3f
  68                 mov     r2, #0
  69 1:
  70  ARM(           ldrb    r3, [r0, r2, lsr #3]    )
  71  THUMB(         lsr     r3, r2, #3              )
  72  THUMB(         ldrb    r3, [r0, r3]            )
  73                 movs    r3, r3
  74                 bne     .L_found                @ any now set - found zero bit
  75                 add     r2, r2, #8              @ next bit pointer
  76 2:              cmp     r2, r1                  @ any more?
  77                 blo     1b
  78 3:              mov     r0, r1                  @ no free bits
  79                 ret     lr
  80 ENDPROC(_find_first_bit_le)
  81
  82 /*
  83  * Purpose  : Find next 'one' bit
  84  * Prototype: int find_next_zero_bit(void *addr, unsigned int maxbit, int offset)
  85  */
  86 ENTRY(_find_next_bit_le)
  87                 teq     r1, #0
  88                 beq     3b
  89                 ands    ip, r2, #7
  90                 beq     1b                      @ If new byte, goto old routine
  91  ARM(           ldrb    r3, [r0, r2, lsr #3]    )
  92  THUMB(         lsr     r3, r2, #3              )
  93  THUMB(         ldrb    r3, [r0, r3]            )
  94                 movs    r3, r3, lsr ip          @ shift off unused bits
  95                 bne     .L_found
  96                 orr     r2, r2, #7              @ if zero, then no bits here
  97                 add     r2, r2, #1              @ align bit pointer
  98                 b       2b                      @ loop for next bit
  99 ENDPROC(_find_next_bit_le)
 100
 101 #ifdef __ARMEB__
 102
 103 ENTRY(_find_first_zero_bit_be)
 104                 teq     r1, #0
 105                 beq     3f
 106                 mov     r2, #0
 107 1:              eor     r3, r2, #0x18           @ big endian byte ordering
 108  ARM(           ldrb    r3, [r0, r3, lsr #3]    )
 109  THUMB(         lsr     r3, #3                  )
 110  THUMB(         ldrb    r3, [r0, r3]            )
 111                 eors    r3, r3, #0xff           @ invert bits
 112                 bne     .L_found                @ any now set - found zero bit
 113                 add     r2, r2, #8              @ next bit pointer
 114 2:              cmp     r2, r1                  @ any more?
 115                 blo     1b
 116 3:              mov     r0, r1                  @ no free bits
 117                 ret     lr
 118 ENDPROC(_find_first_zero_bit_be)
 119
 120 ENTRY(_find_next_zero_bit_be)
 121                 teq     r1, #0
 122                 beq     3b
 123                 ands    ip, r2, #7
 124                 beq     1b                      @ If new byte, goto old routine
 125                 eor     r3, r2, #0x18           @ big endian byte ordering
 126  ARM(           ldrb    r3, [r0, r3, lsr #3]    )
 127  THUMB(         lsr     r3, #3                  )
 128  THUMB(         ldrb    r3, [r0, r3]            )
 129                 eor     r3, r3, #0xff           @ now looking for a 1 bit
 130                 movs    r3, r3, lsr ip          @ shift off unused bits
 131                 bne     .L_found
 132                 orr     r2, r2, #7              @ if zero, then no bits here
 133                 add     r2, r2, #1              @ align bit pointer
 134                 b       2b                      @ loop for next bit
 135 ENDPROC(_find_next_zero_bit_be)
 136
 137 ENTRY(_find_first_bit_be)
 138                 teq     r1, #0
 139                 beq     3f
 140                 mov     r2, #0
 141 1:              eor     r3, r2, #0x18           @ big endian byte ordering
 142  ARM(           ldrb    r3, [r0, r3, lsr #3]    )
 143  THUMB(         lsr     r3, #3                  )
 144  THUMB(         ldrb    r3, [r0, r3]            )
 145                 movs    r3, r3
 146                 bne     .L_found                @ any now set - found zero bit
 147                 add     r2, r2, #8              @ next bit pointer
 148 2:              cmp     r2, r1                  @ any more?
 149                 blo     1b
 150 3:              mov     r0, r1                  @ no free bits
 151                 ret     lr
 152 ENDPROC(_find_first_bit_be)
 153
 154 ENTRY(_find_next_bit_be)
 155                 teq     r1, #0
 156                 beq     3b
 157                 ands    ip, r2, #7
 158                 beq     1b                      @ If new byte, goto old routine
 159                 eor     r3, r2, #0x18           @ big endian byte ordering
 160  ARM(           ldrb    r3, [r0, r3, lsr #3]    )
 161  THUMB(         lsr     r3, #3                  )
 162  THUMB(         ldrb    r3, [r0, r3]            )
 163                 movs    r3, r3, lsr ip          @ shift off unused bits
 164                 bne     .L_found
 165                 orr     r2, r2, #7              @ if zero, then no bits here
 166                 add     r2, r2, #1              @ align bit pointer
 167                 b       2b                      @ loop for next bit
 168 ENDPROC(_find_next_bit_be)
 169
 170 #endif
 171
 172 /*
 173  * One or more bits in the LSB of r3 are assumed to be set.
 174  */
 175 .L_found:
 176 #if __LINUX_ARM_ARCH__ >= 5
 177                 rsb     r0, r3, #0
 178                 and     r3, r3, r0
 179                 clz     r3, r3
 180                 rsb     r3, r3, #31
 181                 add     r0, r2, r3
 182 #else
 183                 tst     r3, #0x0f
 184                 addeq   r2, r2, #4
 185                 movne   r3, r3, lsl #4
 186                 tst     r3, #0x30
 187                 addeq   r2, r2, #2
 188                 movne   r3, r3, lsl #2
 189                 tst     r3, #0x40
 190                 addeq   r2, r2, #1
 191                 mov     r0, r2
 192 #endif
 193                 cmp     r1, r0                  @ Clamp to maxbit
 194                 movlo   r0, r1
 195                 ret     lr
 196