modsi3.c

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/*
 *  modsi3.c
 *
 *  32-bit signed modulo: r0r1 %= r2r3
 *
 *  Calls the ROM version of divsi3, which leaves the absolute value of the
 *  remainder in r3r4.
 *
 *  The contents of this file are subject to the Mozilla Public License
 *  Version 1.0 (the "License"); you may not use this file except in
 *  compliance with the License. You may obtain a copy of the License at
 *  http://www.mozilla.org/MPL/
 *
 *  Software distributed under the License is distributed on an "AS IS"
 *  basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
 *  License for the specific language governing rights and limitations
 *  under the License.
 *
 *  The Original Code is Rcxlib code, released January 20, 1999.
 *
 *  The Initial Developer of the Original Code is Kekoa Proudfoot.
 *  Portions created by Kekoa Proudfoot are Copyright (C) 1999
 *  Kekoa Proudfoot. All Rights Reserved.
 *
 *  Contributor(s): Kekoa Proudfoot <kekoa@graphics.stanford.edu>
 */

__asm__ (
    ".section .text\n\t"
    ".global ___modsi3\n"
    "___modsi3:\n\t"
    "push r4\n\t"
    "push r5\n\t"
    "push r6\n\t"
    "push r0\n\t"
    "mov.w r1,r6\n\t"
    "mov.w r0,r5\n\t"
    "mov.w r3,r4\n\t"
    "mov.w r2,r3\n\t"
    "jsr @@88\n\t"
    "mov.w r4,r1\n\t"
    "mov.w r3,r0\n\t"
    "# negate remainder if numerator was less than zero\n\t"
    "btst #0x7,@r7\n\t"
    "beq skipnegate\n\t"
    "not.b r0l\n\t"
    "not.b r0h\n\t"
    "not.b r1l\n\t"
    "not.b r1h\n\t"
    "add.b #0x1,r1l\n\t"
    "addx #0x0,r1h\n\t"
    "addx #0x0,r0l\n\t"
    "addx #0x0,r0h\n"
    "skipnegate:\n\t"
    "adds #0x2,r7\n\t"
    "pop r6\n\t"
    "pop r5\n\t"
    "pop r4\n\t"
    "rts"
);

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