blob: 722f360a32a9e905b2edf6f3cdb90b9ef9e5d588 [file] [log] [blame]
 /* * Divide a 64-bit unsigned number by a 32-bit unsigned number. * This routine assumes that the top 32 bits of the dividend are * non-zero to start with. * On entry, r3 points to the dividend, which get overwritten with * the 64-bit quotient, and r4 contains the divisor. * On exit, r3 contains the remainder. * * Copyright (C) 2002 Paul Mackerras, IBM Corp. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include "ppc_asm.h" .globl __div64_32 __div64_32: lwz r5,0(r3) # get the dividend into r5/r6 lwz r6,4(r3) cmplw r5,r4 li r7,0 li r8,0 blt 1f divwu r7,r5,r4 # if dividend.hi >= divisor, mullw r0,r7,r4 # quotient.hi = dividend.hi / divisor subf. r5,r0,r5 # dividend.hi %= divisor beq 3f 1: mr r11,r5 # here dividend.hi != 0 andis. r0,r5,0xc000 bne 2f cntlzw r0,r5 # we are shifting the dividend right li r10,-1 # to make it < 2^32, and shifting srw r10,r10,r0 # the divisor right the same amount, add r9,r4,r10 # rounding up (so the estimate cannot andc r11,r6,r10 # ever be too large, only too small) andc r9,r9,r10 or r11,r5,r11 rotlw r9,r9,r0 rotlw r11,r11,r0 divwu r11,r11,r9 # then we divide the shifted quantities 2: mullw r10,r11,r4 # to get an estimate of the quotient, mulhwu r9,r11,r4 # multiply the estimate by the divisor, subfc r6,r10,r6 # take the product from the divisor, add r8,r8,r11 # and add the estimate to the accumulated subfe. r5,r9,r5 # quotient bne 1b 3: cmplw r6,r4 blt 4f divwu r0,r6,r4 # perform the remaining 32-bit division mullw r10,r0,r4 # and get the remainder add r8,r8,r0 subf r6,r10,r6 4: stw r7,0(r3) # return the quotient in *r3 stw r8,4(r3) mr r3,r6 # return the remainder in r3 blr