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 "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