/ SCCSID: @(#)uldiv.s 3.0 4/22/86 / ////////////////////////////////////////////////////////////////////// / Copyright (c) Digital Equipment Corporation 1984, 1985, 1986. / / All Rights Reserved. / / Reference "/usr/src/COPYRIGHT" for applicable restrictions. / ////////////////////////////////////////////////////////////////////// / / Unsigned long quotient / / Based on: (System V) uldiv.s 1.3 .globl uldiv .globl csv, cret uldiv: jsr r5,csv tst 8.(r5) bne hardldiv mov 10.(r5),r3 bmi hardldiv mov 6.(r5),r2 mov 4.(r5),r1 bmi hardest clr r0 div r3,r0 mov r0,-(sp) /high quotient mov r1,r0 mov r2,r1 mov r0,r4 div r3,r0 bvc 1f mov r4,r0 mov r2,r1 sub r3,r0 / this is the clever part div r3,r0 tst r1 sxt r1 add r1,r0 / cannot overflow! 1: mov r0,r1 mov (sp)+,r0 jmp cret / The divisor is known to be >= 2^15 so only 16 cycles are needed. hardldiv: mov 6.(r5),r2 mov 4.(r5),r1 clr r0 mov 8.(r5),r3 mov $16.,r4 1: clc rol r2 rol r1 rol r0 cmp r3,r0 bhi 3f blo 2f cmp 10.(r5),r1 blos 2f 3: sob r4,1b br 1f 2: sub 10.(r5),r1 sbc r0 sub r3,r0 inc r2 sob r4,1b 1: clr r0 mov r2,r1 jmp cret / The dividend is known to be >= 2^31 so 32 cycles are needed. hardest: mov 6.(r5),r3 mov 4.(r5),r2 clr r1 clr r0 mov $32.,r4 1: clc rol r3 rol r2 rol r1 rol r0 cmp 8.(r5),r0 bhi 3f blo 2f cmp 10.(r5),r1 blos 2f 3: sob r4,1b br 1f 2: sub 10.(r5),r1 sbc r0 sub 8.(r5),r0 inc r3 sob r4,1b 1: mov r2,r0 mov r3,r1 jmp cret