usr/src/lib/libc/tahoe/gen/modf.s

/*
 * Copyright (c) 1988 Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Computer Consoles Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
        .asciz "@(#)modf.s      5.1 (Berkeley) 1/30/91"
#endif /* LIBC_SCCS and not lint */

/*
 * double modf (value, iptr)
 * double value, *iptr;
 *
 * Modf returns the fractional part of "value",
 * and stores the integer part indirectly through "iptr".
 *
 * This version uses floating point (look in ../fpe for
 * a much slower integer version).
 */

#include "DEFS.h"

ENTRY(modf, 0)
        ldd     4(fp)           # value
        cvdl    r2              # integerize
        bvs     1f              # did integer part overflow?
        cvld    r2              # integer part
        std     r0
        std     *12(fp)         # *iptr = r2
        ldd     4(fp)
        subd    r0              # value-(int)value
        std     r0              # return fraction
        ret
1:
        /*
         * If the integer portion overflowed, mask out the fractional
         * bits in the double word instead of cvdl-ing.
         */
        ldd     4(fp)
        std     r0              # (r0,r1) = value
        shrl    $23,r0,r2       # extract sign,exponent of value
        andl2   $255,r2         # exponent
        subl2   $152,r2         # e-152
        /*
         * If it overflowed then value>=2^31 and e>=160
         * so we mask only r1 (low bits of fraction), not r0
         */
        mnegl   $1,r3
        shrl    r2,r3,r3        # -1>>(e-152) is neg mask to clear fraction
        mcoml   r3,r3           # complement mask
        andl2   r3,r1           # mask off truly fractional bits from fraction
        ldd     r0              # now (r0,r1) = integerized value
        std     *12(fp)         # *iptr = integerized
        ldd     4(fp)
        subd    r0
        std     r0              # return fraction
        ret