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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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