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 addc 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 addze r9,r9 40 or r11,r5,r11 41 rotlw r9,r9,r0 42 rotlw r11,r11,r0 43 divwu r11,r11,r9 # then we divide the shifted quantities 442: mullw r10,r11,r4 # to get an estimate of the quotient, 45 mulhwu r9,r11,r4 # multiply the estimate by the divisor, 46 subfc r6,r10,r6 # take the product from the divisor, 47 add r8,r8,r11 # and add the estimate to the accumulated 48 subfe. r5,r9,r5 # quotient 49 bne 1b 503: cmplw r6,r4 51 blt 4f 52 divwu r0,r6,r4 # perform the remaining 32-bit division 53 mullw r10,r0,r4 # and get the remainder 54 add r8,r8,r0 55 subf r6,r10,r6 564: stw r7,0(r3) # return the quotient in *r3 57 stw r8,4(r3) 58 mr r3,r6 # return the remainder in r3 59 blr 60