Bitmap management for ARM-7

I haven't found any suitable log-like assembly instruction... so I've wrote this. Are you up to you to make it better? Maybe it could be improved by reading...


.code 32
.text
.align 0

  .global dw_bmp_msb_pos
dw_bmp_msb_pos:
  movs r1, r0
  moveq r0, #0
  bxeq lr
  mov r0, #33
getmsb_cycle:
  sub r0, r0, #1
  movs r1, r1, lsl #1
  bxcs lr
  b getmsb_cycle

  .global dw_bmp_set
dw_bmp_set:
  ldr r2, [r0, #0]
  mov r3, #1
  mov r3, r3, lsl r1
  orr r2, r2, r3
  str r2, [r0, #0]
  bx lr

  .global dw_bmp_reset
dw_bmp_reset:
  ldr r2, [r0, #0]
  mov r3, #1
  mov r3, r3, lsl r1
  bic r2, r2, r3
  str r2, [r0, #0]
  bx lr

>>10
Architecture version
Version 5 and above.¹
Surpisingly, ARM7 is architecture version 3².

¹ http://www.arm.com/miscPDFs/14128.pdf
² http://en.wikipedia.org/wiki/ARM_architecture#ARM_cores