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.
9 * Copyright (C) 2002 Paul Mackerras, IBM Corp.
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.
16 #include <asm/ppc_asm.h>
17 #include <asm/processor.h>
20 lwz r5,0(r3) # get the dividend into r5/r6
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
30 1: mr r11,r5 # here dividend.hi != 0
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)
42 divwu r11,r11,r9 # then we divide the shifted quantities
43 2: 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
51 divwu r0,r6,r4 # perform the remaining 32-bit division
52 mullw r10,r0,r4 # and get the remainder
55 4: stw r7,0(r3) # return the quotient in *r3
57 mr r3,r6 # return the remainder in r3