usr/src/lib/libc/vax/gen/ldexp.s

/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.
 *
 * 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 "@(#)ldexp.s     5.6 (Berkeley) 6/1/90"
#endif /* LIBC_SCCS and not lint */

/*
 * double ldexp (value, exp)
 * double value;
 * int exp;
 *
 * Ldexp returns value*2**exp, if that result is in range.
 * If underflow occurs, it returns zero.  If overflow occurs,
 * it returns a value of appropriate sign and largest
 * possible magnitude.  In case of either overflow or underflow,
 * errno is set to ERANGE.  Note that errno is not modified if
 * no error occurs.
 */

#include "DEFS.h"

/*
 * don't include errno.h, ANSI C says it defines errno.
 *
 * #include <errno.h>
 */
#define ERANGE  34

        .globl  _errno

ENTRY(ldexp, 0)
        movd    4(ap),r0        /* fetch "value" */
        extzv   $7,$8,r0,r2     /* r2 := biased exponent */
        jeql    1f              /* if zero, done */

        addl2   12(ap),r2       /* r2 := new biased exponent */
        jleq    2f              /* if <= 0, underflow */
        cmpl    r2,$256         /* otherwise check if too big */
        jgeq    3f              /* jump if overflow */
        insv    r2,$7,$8,r0     /* put exponent back in result */
1:
        ret
2:
        clrd    r0
        jbr     1f
3:
        movd    huge,r0         /* largest possible floating magnitude */
        jbc     $15,4(ap),1f    /* jump if argument was positive */
        mnegd   r0,r0           /* if arg < 0, make result negative */
1:
        movl    $ERANGE,_errno
        ret

        .data
huge:   .word   0x7fff          /* the largest number that can */
        .word   0xffff          /*   be represented in a long floating */
        .word   0xffff          /*   number.  This is given in hex in order */
        .word   0xffff          /*   to avoid floating conversions */