Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

/*
 * 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 <asm/ppc_asm.h>
#include <asm/processor.h>

_GLOBAL(__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,
        addc    r9,r4,r10       # rounding up (so the estimate cannot
        andc    r11,r6,r10      # ever be too large, only too small)
        andc    r9,r9,r10
        addze   r9,r9
        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