target/linux/at91-2.6/image/dfboot/src/_umodsi3.S

   1 /* # 1 "libgcc1.S" */
   2 @ libgcc1 routines for ARM cpu.
   3 @ Division routines, written by Richard Earnshaw, (rearnsha@armltd.co.uk)
   4 /* # 145 "libgcc1.S" */
   5 dividend        .req    r0
   6 divisor         .req    r1
   7 overdone        .req    r2
   8 curbit          .req    r3
   9 /* ip           .req    r12     */
  10 /* sp           .req    r13     */
  11 /* lr           .req    r14     */
  12 /* pc           .req    r15     */
  13         .text
  14         .globl   __umodsi3
  15         .type  __umodsi3       ,function
  16         .align 0
  17  __umodsi3      :
  18         cmp     divisor, #0
  19         beq     Ldiv0
  20         mov     curbit, #1
  21         cmp     dividend, divisor
  22         movcc   pc, lr
  23 Loop1:
  24         @ Unless the divisor is very big, shift it up in multiples of
  25         @ four bits, since this is the amount of unwinding in the main
  26         @ division loop.  Continue shifting until the divisor is
  27         @ larger than the dividend.
  28         cmp     divisor, #0x10000000
  29         cmpcc   divisor, dividend
  30         movcc   divisor, divisor, lsl #4
  31         movcc   curbit, curbit, lsl #4
  32         bcc     Loop1
  33 Lbignum:
  34         @ For very big divisors, we must shift it a bit at a time, or
  35         @ we will be in danger of overflowing.
  36         cmp     divisor, #0x80000000
  37         cmpcc   divisor, dividend
  38         movcc   divisor, divisor, lsl #1
  39         movcc   curbit, curbit, lsl #1
  40         bcc     Lbignum
  41 Loop3:
  42         @ Test for possible subtractions.  On the final pass, this may
  43         @ subtract too much from the dividend, so keep track of which
  44         @ subtractions are done, we can fix them up afterwards...
  45         mov     overdone, #0
  46         cmp     dividend, divisor
  47         subcs   dividend, dividend, divisor
  48         cmp     dividend, divisor, lsr #1
  49         subcs   dividend, dividend, divisor, lsr #1
  50         orrcs   overdone, overdone, curbit, ror #1
  51         cmp     dividend, divisor, lsr #2
  52         subcs   dividend, dividend, divisor, lsr #2
  53         orrcs   overdone, overdone, curbit, ror #2
  54         cmp     dividend, divisor, lsr #3
  55         subcs   dividend, dividend, divisor, lsr #3
  56         orrcs   overdone, overdone, curbit, ror #3
  57         mov     ip, curbit
  58         cmp     dividend, #0                    @ Early termination?
  59         movnes  curbit, curbit, lsr #4          @ No, any more bits to do?
  60         movne   divisor, divisor, lsr #4
  61         bne     Loop3
  62         @ Any subtractions that we should not have done will be recorded in
  63         @ the top three bits of "overdone".  Exactly which were not needed
  64         @ are governed by the position of the bit, stored in ip.
  65         @ If we terminated early, because dividend became zero,
  66         @ then none of the below will match, since the bit in ip will not be
  67         @ in the bottom nibble.
  68         ands    overdone, overdone, #0xe0000000
  69         moveq   pc, lr                          @ No fixups needed
  70         tst     overdone, ip, ror #3
  71         addne   dividend, dividend, divisor, lsr #3
  72         tst     overdone, ip, ror #2
  73         addne   dividend, dividend, divisor, lsr #2
  74         tst     overdone, ip, ror #1
  75         addne   dividend, dividend, divisor, lsr #1
  76         mov     pc, lr
  77 Ldiv0:
  78         str     lr, [sp, #-4]!
  79         bl       __div0       (PLT)
  80         mov     r0, #0                  @ about as wrong as it could be
  81         ldmia   sp!, {pc}
  82         .size  __umodsi3       , . -  __umodsi3
  83 /* # 320 "libgcc1.S" */
  84 /* # 421 "libgcc1.S" */
  85 /* # 433 "libgcc1.S" */
  86 /* # 456 "libgcc1.S" */
  87 /* # 500 "libgcc1.S" */
  88 /* # 580 "libgcc1.S" */