#### /arch/powerpc/boot/div64.S

http://github.com/mirrors/linux
Assembly | 107 lines | 103 code | 4 blank | 0 comment | 3 complexity | 87d3f9e0f0ff4dd049d47dea414a8962 MD5 | raw file
```  1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 * Divide a 64-bit unsigned number by a 32-bit unsigned number.
4 * This routine assumes that the top 32 bits of the dividend are
6 * On entry, r3 points to the dividend, which get overwritten with
7 * the 64-bit quotient, and r4 contains the divisor.
8 * On exit, r3 contains the remainder.
9 *
10 * Copyright (C) 2002 Paul Mackerras, IBM Corp.
11 */
12#include "ppc_asm.h"
13
14	.globl __div64_32
15__div64_32:
16	lwz	r5,0(r3)	# get the dividend into r5/r6
17	lwz	r6,4(r3)
18	cmplw	r5,r4
19	li	r7,0
20	li	r8,0
21	blt	1f
22	divwu	r7,r5,r4	# if dividend.hi >= divisor,
23	mullw	r0,r7,r4	# quotient.hi = dividend.hi / divisor
24	subf.	r5,r0,r5	# dividend.hi %= divisor
25	beq	3f
261:	mr	r11,r5		# here dividend.hi != 0
27	andis.	r0,r5,0xc000
28	bne	2f
29	cntlzw	r0,r5		# we are shifting the dividend right
30	li	r10,-1		# to make it < 2^32, and shifting
31	srw	r10,r10,r0	# the divisor right the same amount,
32	addc	r9,r4,r10	# rounding up (so the estimate cannot
33	andc	r11,r6,r10	# ever be too large, only too small)
34	andc	r9,r9,r10
36	or	r11,r5,r11
37	rotlw	r9,r9,r0
38	rotlw	r11,r11,r0
39	divwu	r11,r11,r9	# then we divide the shifted quantities
402:	mullw	r10,r11,r4	# to get an estimate of the quotient,
41	mulhwu	r9,r11,r4	# multiply the estimate by the divisor,
42	subfc	r6,r10,r6	# take the product from the divisor,
43	add	r8,r8,r11	# and add the estimate to the accumulated
44	subfe.	r5,r9,r5	# quotient
45	bne	1b
463:	cmplw	r6,r4
47	blt	4f
48	divwu	r0,r6,r4	# perform the remaining 32-bit division
49	mullw	r10,r0,r4	# and get the remainder
51	subf	r6,r10,r6
524:	stw	r7,0(r3)	# return the quotient in *r3
53	stw	r8,4(r3)
54	mr	r3,r6		# return the remainder in r3
55	blr
56
57/*
58 * Extended precision shifts.
59 *
60 * Updated to be valid for shift counts from 0 to 63 inclusive.
61 * -- Gabriel
62 *
63 * R3/R4 has 64 bit value
64 * R5    has shift count
65 * result in R3/R4
66 *
67 *  ashrdi3: arithmetic right shift (sign propagation)
68 *  lshrdi3: logical right shift
69 *  ashldi3: left shift
70 */
71	.globl __ashrdi3
72__ashrdi3:
73	subfic	r6,r5,32
74	srw	r4,r4,r5	# LSW = count > 31 ? 0 : LSW >> count
75	addi	r7,r5,32	# could be xori, or addi with -32
76	slw	r6,r3,r6	# t1 = count > 31 ? 0 : MSW << (32-count)
77	rlwinm	r8,r7,0,32	# t3 = (count < 32) ? 32 : 0
78	sraw	r7,r3,r7	# t2 = MSW >> (count-32)
79	or	r4,r4,r6	# LSW |= t1
80	slw	r7,r7,r8	# t2 = (count < 32) ? 0 : t2
81	sraw	r3,r3,r5	# MSW = MSW >> count
82	or	r4,r4,r7	# LSW |= t2
83	blr
84
85	.globl __ashldi3
86__ashldi3:
87	subfic	r6,r5,32
88	slw	r3,r3,r5	# MSW = count > 31 ? 0 : MSW << count
89	addi	r7,r5,32	# could be xori, or addi with -32
90	srw	r6,r4,r6	# t1 = count > 31 ? 0 : LSW >> (32-count)
91	slw	r7,r4,r7	# t2 = count < 32 ? 0 : LSW << (count-32)
92	or	r3,r3,r6	# MSW |= t1
93	slw	r4,r4,r5	# LSW = LSW << count
94	or	r3,r3,r7	# MSW |= t2
95	blr
96
97	.globl __lshrdi3
98__lshrdi3:
99	subfic	r6,r5,32
100	srw	r4,r4,r5	# LSW = count > 31 ? 0 : LSW >> count
101	addi	r7,r5,32	# could be xori, or addi with -32
102	slw	r6,r3,r6	# t1 = count > 31 ? 0 : MSW << (32-count)
103	srw	r7,r3,r7	# t2 = count < 32 ? 0 : MSW >> (count-32)
104	or	r4,r4,r6	# LSW |= t1
105	srw	r3,r3,r5	# MSW = MSW >> count
106	or	r4,r4,r7	# LSW |= t2
107	blr
```