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/arch/ppc/boot/lib/div64.S

https://bitbucket.org/evzijst/gittest
Assembly | 58 lines | 57 code | 1 blank | 0 comment | 2 complexity | d3fa198374d7ee07927063ca034178c0 MD5 | raw file
 1/*
 2 * Divide a 64-bit unsigned number by a 32-bit unsigned number.
 3 * This routine assumes that the top 32 bits of the dividend are
 4 * non-zero to start with.
 5 * On entry, r3 points to the dividend, which get overwritten with
 6 * the 64-bit quotient, and r4 contains the divisor.
 7 * On exit, r3 contains the remainder.
 8 *
 9 * Copyright (C) 2002 Paul Mackerras, IBM Corp.
10 *
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License
13 * as published by the Free Software Foundation; either version
14 * 2 of the License, or (at your option) any later version.
15 */
16#include <asm/ppc_asm.h>
17#include <asm/processor.h>
18
19_GLOBAL(__div64_32)
20	lwz	r5,0(r3)	# get the dividend into r5/r6
21	lwz	r6,4(r3)
22	cmplw	r5,r4
23	li	r7,0
24	li	r8,0
25	blt	1f
26	divwu	r7,r5,r4	# if dividend.hi >= divisor,
27	mullw	r0,r7,r4	# quotient.hi = dividend.hi / divisor
28	subf.	r5,r0,r5	# dividend.hi %= divisor
29	beq	3f
301:	mr	r11,r5		# here dividend.hi != 0
31	andis.	r0,r5,0xc000
32	bne	2f
33	cntlzw	r0,r5		# we are shifting the dividend right
34	li	r10,-1		# to make it < 2^32, and shifting
35	srw	r10,r10,r0	# the divisor right the same amount,
36	add	r9,r4,r10	# rounding up (so the estimate cannot
37	andc	r11,r6,r10	# ever be too large, only too small)
38	andc	r9,r9,r10
39	or	r11,r5,r11
40	rotlw	r9,r9,r0
41	rotlw	r11,r11,r0
42	divwu	r11,r11,r9	# then we divide the shifted quantities
432:	mullw	r10,r11,r4	# to get an estimate of the quotient,
44	mulhwu	r9,r11,r4	# multiply the estimate by the divisor,
45	subfc	r6,r10,r6	# take the product from the divisor,
46	add	r8,r8,r11	# and add the estimate to the accumulated
47	subfe.	r5,r9,r5	# quotient
48	bne	1b
493:	cmplw	r6,r4
50	blt	4f
51	divwu	r0,r6,r4	# perform the remaining 32-bit division
52	mullw	r10,r0,r4	# and get the remainder
53	add	r8,r8,r0
54	subf	r6,r10,r6
554:	stw	r7,0(r3)	# return the quotient in *r3
56	stw	r8,4(r3)
57	mr	r3,r6		# return the remainder in r3
58	blr