1# S/390 __udiv_qrnnd
2
3#include <linux/linkage.h>
4
5# r2 : &__r
6# r3 : upper half of 64 bit word n
7# r4 : lower half of 64 bit word n
8# r5 : divisor d
9# the reminder r of the division is to be stored to &__r and
10# the quotient q is to be returned
11
12	.text
13ENTRY(__udiv_qrnnd)
14	st    %r2,24(%r15)	  # store pointer to reminder for later
15	lr    %r0,%r3		  # reload n
16	lr    %r1,%r4
17	ltr   %r2,%r5		  # reload and test divisor
18	jp    5f
19	# divisor >= 0x80000000
20	srdl  %r0,2		  # n/4
21	srl   %r2,1		  # d/2
22	slr   %r1,%r2		  # special case if last bit of d is set
23	brc   3,0f		  #  (n/4) div (n/2) can overflow by 1
24	ahi   %r0,-1		  #  trick: subtract n/2, then divide
250:	dr    %r0,%r2		  # signed division
26	ahi   %r1,1		  #  trick part 2: add 1 to the quotient
27	# now (n >> 2) = (d >> 1) * %r1 + %r0
28	lhi   %r3,1
29	nr    %r3,%r1		  # test last bit of q
30	jz    1f
31	alr   %r0,%r2		  # add (d>>1) to r
321:	srl   %r1,1		  # q >>= 1
33	# now (n >> 2) = (d&-2) * %r1 + %r0
34	lhi   %r3,1
35	nr    %r3,%r5		  # test last bit of d
36	jz    2f
37	slr   %r0,%r1		  # r -= q
38	brc   3,2f		  # borrow ?
39	alr   %r0,%r5		  # r += d
40	ahi   %r1,-1
412:	# now (n >> 2) = d * %r1 + %r0
42	alr   %r1,%r1		  # q <<= 1
43	alr   %r0,%r0		  # r <<= 1
44	brc   12,3f		  # overflow on r ?
45	slr   %r0,%r5		  # r -= d
46	ahi   %r1,1		  # q += 1
473:	lhi   %r3,2
48	nr    %r3,%r4		  # test next to last bit of n
49	jz    4f
50	ahi   %r0,1		  # r += 1
514:	clr   %r0,%r5		  # r >= d ?
52	jl    6f
53	slr   %r0,%r5		  # r -= d
54	ahi   %r1,1		  # q += 1
55	# now (n >> 1) = d * %r1 + %r0
56	j     6f
575:	# divisor < 0x80000000
58	srdl  %r0,1
59	dr    %r0,%r2		  # signed division
60	# now (n >> 1) = d * %r1 + %r0
616:	alr   %r1,%r1		  # q <<= 1
62	alr   %r0,%r0		  # r <<= 1
63	brc   12,7f		  # overflow on r ?
64	slr   %r0,%r5		  # r -= d
65	ahi   %r1,1		  # q += 1
667:	lhi   %r3,1
67	nr    %r3,%r4		  # isolate last bit of n
68	alr   %r0,%r3		  # r += (n & 1)
69	clr   %r0,%r5		  # r >= d ?
70	jl    8f
71	slr   %r0,%r5		  # r -= d
72	ahi   %r1,1		  # q += 1
738:	# now n = d * %r1 + %r0
74	l     %r2,24(%r15)
75	st    %r0,0(%r2)
76	lr    %r2,%r1
77	br    %r14
78	.end	__udiv_qrnnd
79