lib_arm/_divsi3.S

   1
   2 .macro ARM_DIV_BODY dividend, divisor, result, curbit
   3
   4 #if __LINUX_ARM_ARCH__ >= 5
   5
   6         clz     \curbit, \divisor
   7         clz     \result, \dividend
   8         sub     \result, \curbit, \result
   9         mov     \curbit, #1
  10         mov     \divisor, \divisor, lsl \result
  11         mov     \curbit, \curbit, lsl \result
  12         mov     \result, #0
  13
  14 #else
  15
  16         @ Initially shift the divisor left 3 bits if possible,
  17         @ set curbit accordingly.  This allows for curbit to be located
  18         @ at the left end of each 4 bit nibbles in the division loop
  19         @ to save one loop in most cases.
  20         tst     \divisor, #0xe0000000
  21         moveq   \divisor, \divisor, lsl #3
  22         moveq   \curbit, #8
  23         movne   \curbit, #1
  24
  25         @ Unless the divisor is very big, shift it up in multiples of
  26         @ four bits, since this is the amount of unwinding in the main
  27         @ division loop.  Continue shifting until the divisor is
  28         @ larger than the dividend.
  29 1:      cmp     \divisor, #0x10000000
  30         cmplo   \divisor, \dividend
  31         movlo   \divisor, \divisor, lsl #4
  32         movlo   \curbit, \curbit, lsl #4
  33         blo     1b
  34
  35         @ For very big divisors, we must shift it a bit at a time, or
  36         @ we will be in danger of overflowing.
  37 1:      cmp     \divisor, #0x80000000
  38         cmplo   \divisor, \dividend
  39         movlo   \divisor, \divisor, lsl #1
  40         movlo   \curbit, \curbit, lsl #1
  41         blo     1b
  42
  43         mov     \result, #0
  44
  45 #endif
  46
  47         @ Division loop
  48 1:      cmp     \dividend, \divisor
  49         subhs   \dividend, \dividend, \divisor
  50         orrhs   \result,   \result,   \curbit
  51         cmp     \dividend, \divisor,  lsr #1
  52         subhs   \dividend, \dividend, \divisor, lsr #1
  53         orrhs   \result,   \result,   \curbit,  lsr #1
  54         cmp     \dividend, \divisor,  lsr #2
  55         subhs   \dividend, \dividend, \divisor, lsr #2
  56         orrhs   \result,   \result,   \curbit,  lsr #2
  57         cmp     \dividend, \divisor,  lsr #3
  58         subhs   \dividend, \dividend, \divisor, lsr #3
  59         orrhs   \result,   \result,   \curbit,  lsr #3
  60         cmp     \dividend, #0                   @ Early termination?
  61         movnes  \curbit,   \curbit,  lsr #4     @ No, any more bits to do?
  62         movne   \divisor,  \divisor, lsr #4
  63         bne     1b
  64
  65 .endm
  66
  67 .macro ARM_DIV2_ORDER divisor, order
  68
  69 #if __LINUX_ARM_ARCH__ >= 5
  70
  71         clz     \order, \divisor
  72         rsb     \order, \order, #31
  73
  74 #else
  75
  76         cmp     \divisor, #(1 << 16)
  77         movhs   \divisor, \divisor, lsr #16
  78         movhs   \order, #16
  79         movlo   \order, #0
  80
  81         cmp     \divisor, #(1 << 8)
  82         movhs   \divisor, \divisor, lsr #8
  83         addhs   \order, \order, #8
  84
  85         cmp     \divisor, #(1 << 4)
  86         movhs   \divisor, \divisor, lsr #4
  87         addhs   \order, \order, #4
  88
  89         cmp     \divisor, #(1 << 2)
  90         addhi   \order, \order, #3
  91         addls   \order, \order, \divisor, lsr #1
  92
  93 #endif
  94
  95 .endm
  96
  97         .align  5
  98 .globl __divsi3
  99 __divsi3:
 100         cmp     r1, #0
 101         eor     ip, r0, r1                      @ save the sign of the result.
 102         beq     Ldiv0
 103         rsbmi   r1, r1, #0                      @ loops below use unsigned.
 104         subs    r2, r1, #1                      @ division by 1 or -1 ?
 105         beq     10f
 106         movs    r3, r0
 107         rsbmi   r3, r0, #0                      @ positive dividend value
 108         cmp     r3, r1
 109         bls     11f
 110         tst     r1, r2                          @ divisor is power of 2 ?
 111         beq     12f
 112
 113         ARM_DIV_BODY r3, r1, r0, r2
 114
 115         cmp     ip, #0
 116         rsbmi   r0, r0, #0
 117         mov     pc, lr
 118
 119 10:     teq     ip, r0                          @ same sign ?
 120         rsbmi   r0, r0, #0
 121         mov     pc, lr
 122
 123 11:     movlo   r0, #0
 124         moveq   r0, ip, asr #31
 125         orreq   r0, r0, #1
 126         mov     pc, lr
 127
 128 12:     ARM_DIV2_ORDER r1, r2
 129
 130         cmp     ip, #0
 131         mov     r0, r3, lsr r2
 132         rsbmi   r0, r0, #0
 133         mov     pc, lr
 134
 135 Ldiv0:
 136
 137         str     lr, [sp, #-4]!
 138         bl      __div0
 139         mov     r0, #0                  @ About as wrong as it could be.
 140         ldr     pc, [sp], #4