1# S/390 __udiv_qrnnd
2
3# r2 : &__r
4# r3 : upper half of 64 bit word n
5# r4 : lower half of 64 bit word n
6# r5 : divisor d
7# the reminder r of the division is to be stored to &__r and
8# the quotient q is to be returned
9
10        .text
11        .globl __udiv_qrnnd
12__udiv_qrnnd:
13        st    %r2,24(%r15)        # store pointer to reminder for later
14        lr    %r0,%r3             # reload n
15	lr    %r1,%r4
16	ltr   %r2,%r5             # reload and test divisor
17        jp    5f
18        # divisor >= 0x80000000
19	srdl  %r0,2               # n/4
20        srl   %r2,1               # d/2
21        slr   %r1,%r2             # special case if last bit of d is set
22        brc   3,0f                #  (n/4) div (n/2) can overflow by 1
23        ahi   %r0,-1              #  trick: subtract n/2, then divide
240:      dr    %r0,%r2             # signed division
25        ahi   %r1,1               #  trick part 2: add 1 to the quotient
26        # now (n >> 2) = (d >> 1) * %r1 + %r0
27	lhi   %r3,1
28        nr    %r3,%r1             # test last bit of q
29        jz    1f
30        alr   %r0,%r2             # add (d>>1) to r
311:      srl   %r1,1               # q >>= 1
32        # now (n >> 2) = (d&-2) * %r1 + %r0
33        lhi   %r3,1
34        nr    %r3,%r5             # test last bit of d
35        jz    2f
36        slr   %r0,%r1             # r -= q
37	brc   3,2f                # borrow ?
38	alr   %r0,%r5             # r += d
39	ahi   %r1,-1
402:      # now (n >> 2) = d * %r1 + %r0
41        alr   %r1,%r1             # q <<= 1
42        alr   %r0,%r0             # r <<= 1
43        brc   12,3f               # overflow on r ?
44        slr   %r0,%r5             # r -= d
45        ahi   %r1,1               # q += 1
463:      lhi   %r3,2
47        nr    %r3,%r4             # test next to last bit of n
48        jz    4f
49        ahi   %r0,1               # r += 1
504:      clr   %r0,%r5             # r >= d ?
51        jl    6f
52        slr   %r0,%r5             # r -= d
53        ahi   %r1,1               # q += 1
54        # now (n >> 1) = d * %r1 + %r0
55        j     6f
565:      # divisor < 0x80000000
57	srdl  %r0,1
58        dr    %r0,%r2             # signed division
59        # now (n >> 1) = d * %r1 + %r0
606:      alr   %r1,%r1             # q <<= 1
61        alr   %r0,%r0             # r <<= 1
62        brc   12,7f               # overflow on r ?
63        slr   %r0,%r5             # r -= d
64        ahi   %r1,1               # q += 1
657:      lhi   %r3,1
66        nr    %r3,%r4             # isolate last bit of n
67        alr   %r0,%r3             # r += (n & 1)
68        clr   %r0,%r5             # r >= d ?
69        jl    8f
70        slr   %r0,%r5             # r -= d
71        ahi   %r1,1               # q += 1
728:      # now n = d * %r1 + %r0
73	l     %r2,24(%r15)
74        st    %r0,0(%r2)
75        lr    %r2,%r1
76        br    %r14
77	.end	__udiv_qrnnd
78