| Wolfgang Denk | ba94a1b | 2006-05-30 15:56:48 +0200 | [diff] [blame] | 1 | .macro ARM_MOD_BODY dividend, divisor, order, spare |
| 2 | |
| 3 | #if __LINUX_ARM_ARCH__ >= 5 |
| 4 | |
| 5 | clz \order, \divisor |
| 6 | clz \spare, \dividend |
| 7 | sub \order, \order, \spare |
| 8 | mov \divisor, \divisor, lsl \order |
| 9 | |
| 10 | #else |
| 11 | |
| 12 | mov \order, #0 |
| 13 | |
| 14 | @ Unless the divisor is very big, shift it up in multiples of |
| 15 | @ four bits, since this is the amount of unwinding in the main |
| 16 | @ division loop. Continue shifting until the divisor is |
| 17 | @ larger than the dividend. |
| 18 | 1: cmp \divisor, #0x10000000 |
| 19 | cmplo \divisor, \dividend |
| 20 | movlo \divisor, \divisor, lsl #4 |
| 21 | addlo \order, \order, #4 |
| 22 | blo 1b |
| 23 | |
| 24 | @ For very big divisors, we must shift it a bit at a time, or |
| 25 | @ we will be in danger of overflowing. |
| 26 | 1: cmp \divisor, #0x80000000 |
| 27 | cmplo \divisor, \dividend |
| 28 | movlo \divisor, \divisor, lsl #1 |
| 29 | addlo \order, \order, #1 |
| 30 | blo 1b |
| 31 | |
| 32 | #endif |
| 33 | |
| 34 | @ Perform all needed substractions to keep only the reminder. |
| 35 | @ Do comparisons in batch of 4 first. |
| 36 | subs \order, \order, #3 @ yes, 3 is intended here |
| 37 | blt 2f |
| 38 | |
| 39 | 1: cmp \dividend, \divisor |
| 40 | subhs \dividend, \dividend, \divisor |
| 41 | cmp \dividend, \divisor, lsr #1 |
| 42 | subhs \dividend, \dividend, \divisor, lsr #1 |
| 43 | cmp \dividend, \divisor, lsr #2 |
| 44 | subhs \dividend, \dividend, \divisor, lsr #2 |
| 45 | cmp \dividend, \divisor, lsr #3 |
| 46 | subhs \dividend, \dividend, \divisor, lsr #3 |
| 47 | cmp \dividend, #1 |
| 48 | mov \divisor, \divisor, lsr #4 |
| 49 | subges \order, \order, #4 |
| 50 | bge 1b |
| 51 | |
| 52 | tst \order, #3 |
| 53 | teqne \dividend, #0 |
| 54 | beq 5f |
| 55 | |
| 56 | @ Either 1, 2 or 3 comparison/substractions are left. |
| 57 | 2: cmn \order, #2 |
| 58 | blt 4f |
| 59 | beq 3f |
| 60 | cmp \dividend, \divisor |
| 61 | subhs \dividend, \dividend, \divisor |
| 62 | mov \divisor, \divisor, lsr #1 |
| 63 | 3: cmp \dividend, \divisor |
| 64 | subhs \dividend, \dividend, \divisor |
| 65 | mov \divisor, \divisor, lsr #1 |
| 66 | 4: cmp \dividend, \divisor |
| 67 | subhs \dividend, \dividend, \divisor |
| 68 | 5: |
| 69 | .endm |
| 70 | |
| 71 | .align 5 |
| 72 | .globl __modsi3 |
| 73 | __modsi3: |
| 74 | cmp r1, #0 |
| 75 | beq Ldiv0 |
| 76 | rsbmi r1, r1, #0 @ loops below use unsigned. |
| 77 | movs ip, r0 @ preserve sign of dividend |
| 78 | rsbmi r0, r0, #0 @ if negative make positive |
| 79 | subs r2, r1, #1 @ compare divisor with 1 |
| 80 | cmpne r0, r1 @ compare dividend with divisor |
| 81 | moveq r0, #0 |
| 82 | tsthi r1, r2 @ see if divisor is power of 2 |
| 83 | andeq r0, r0, r2 |
| 84 | bls 10f |
| 85 | |
| 86 | ARM_MOD_BODY r0, r1, r2, r3 |
| 87 | |
| 88 | 10: cmp ip, #0 |
| 89 | rsbmi r0, r0, #0 |
| 90 | mov pc, lr |
| 91 | |
| 92 | |
| 93 | Ldiv0: |
| 94 | |
| 95 | str lr, [sp, #-4]! |
| 96 | bl __div0 |
| 97 | mov r0, #0 @ About as wrong as it could be. |
| 98 | ldr pc, [sp], #4 |