third-party-mirror / u-boot / refs/tags/astro/4.20210608.1.1146075 / . / arch / arm / lib / _umodsi3.S

/* # 1 "libgcc1.S" */ | |

@ libgcc1 routines for ARM cpu. | |

@ Division routines, written by Richard Earnshaw, (rearnsha@armltd.co.uk) | |

/* # 145 "libgcc1.S" */ | |

dividend .req r0 | |

divisor .req r1 | |

overdone .req r2 | |

curbit .req r3 | |

/* ip .req r12 */ | |

/* sp .req r13 */ | |

/* lr .req r14 */ | |

/* pc .req r15 */ | |

.text | |

.globl __umodsi3 | |

.type __umodsi3 ,function | |

.align 0 | |

__umodsi3 : | |

cmp divisor, #0 | |

beq Ldiv0 | |

mov curbit, #1 | |

cmp dividend, divisor | |

movcc pc, lr | |

Loop1: | |

@ Unless the divisor is very big, shift it up in multiples of | |

@ four bits, since this is the amount of unwinding in the main | |

@ division loop. Continue shifting until the divisor is | |

@ larger than the dividend. | |

cmp divisor, #0x10000000 | |

cmpcc divisor, dividend | |

movcc divisor, divisor, lsl #4 | |

movcc curbit, curbit, lsl #4 | |

bcc Loop1 | |

Lbignum: | |

@ For very big divisors, we must shift it a bit at a time, or | |

@ we will be in danger of overflowing. | |

cmp divisor, #0x80000000 | |

cmpcc divisor, dividend | |

movcc divisor, divisor, lsl #1 | |

movcc curbit, curbit, lsl #1 | |

bcc Lbignum | |

Loop3: | |

@ Test for possible subtractions. On the final pass, this may | |

@ subtract too much from the dividend, so keep track of which | |

@ subtractions are done, we can fix them up afterwards... | |

mov overdone, #0 | |

cmp dividend, divisor | |

subcs dividend, dividend, divisor | |

cmp dividend, divisor, lsr #1 | |

subcs dividend, dividend, divisor, lsr #1 | |

orrcs overdone, overdone, curbit, ror #1 | |

cmp dividend, divisor, lsr #2 | |

subcs dividend, dividend, divisor, lsr #2 | |

orrcs overdone, overdone, curbit, ror #2 | |

cmp dividend, divisor, lsr #3 | |

subcs dividend, dividend, divisor, lsr #3 | |

orrcs overdone, overdone, curbit, ror #3 | |

mov ip, curbit | |

cmp dividend, #0 @ Early termination? | |

movnes curbit, curbit, lsr #4 @ No, any more bits to do? | |

movne divisor, divisor, lsr #4 | |

bne Loop3 | |

@ Any subtractions that we should not have done will be recorded in | |

@ the top three bits of "overdone". Exactly which were not needed | |

@ are governed by the position of the bit, stored in ip. | |

@ If we terminated early, because dividend became zero, | |

@ then none of the below will match, since the bit in ip will not be | |

@ in the bottom nibble. | |

ands overdone, overdone, #0xe0000000 | |

moveq pc, lr @ No fixups needed | |

tst overdone, ip, ror #3 | |

addne dividend, dividend, divisor, lsr #3 | |

tst overdone, ip, ror #2 | |

addne dividend, dividend, divisor, lsr #2 | |

tst overdone, ip, ror #1 | |

addne dividend, dividend, divisor, lsr #1 | |

mov pc, lr | |

Ldiv0: | |

str lr, [sp, #-4]! | |

bl __div0 (PLT) | |

mov r0, #0 @ about as wrong as it could be | |

ldmia sp!, {pc} | |

.size __umodsi3 , . - __umodsi3 | |

/* # 320 "libgcc1.S" */ | |

/* # 421 "libgcc1.S" */ | |

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/* # 580 "libgcc1.S" */ |