.ref-BSD-4_3_Net_2/usr/src/sys/tahoe/math/Kldexpf.s

/*-
 * Copyright (c) 1985 The 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.
 *
 *      @(#)Kldexpf.s   7.1 (Berkeley) 12/6/90
 */

#include "../tahoe/SYS.h"
#include "../math/fp.h"
#include "../math/Kfp.h"

/* @(*)Kldexpf.s        4.2 (Berkeley) 12/21/80
 *      Tahoe           2/2/83
 *
 * float Kldexpf (op_most, op_least, exp, hfs)
 *
 * 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,
 * the external int "errno" is set to ERANGE.  Note that errno is
 * not modified if no error occurs, so if you intend to test it
 * after you use Kldexpf, you had better set it to something
 * other than ERANGE first (zero is a reasonable value to use).
 */

        .text
ENTRY(Kldexpf, R2)
        movl    4(fp),r0        /* Fetch "value" */
        movl    8(fp),r1

        andl3   $EXPMASK,r0,r2  /* r2 := shifted biased exponent */
        jeql    ld1             /* If it's zero, we're done */
        shar    $EXPSHIFT,r2,r2 /* shift to get value of exponent  */

        addl2   12(fp),r2       /* r2 := new biased exponent */
        jleq    under           /* if it's <= 0, we have an underflow */
        cmpl    r2,$256         /* Otherwise check if it's too big */
        jgeq    over            /* jump if overflow */
/*
 *      Construct the result and return
 */
        andl2   $0!EXPMASK,r0   /* clear old exponent */
        shal    $EXPSHIFT,r2,r2 /* Put the exponent back in the result */
        orl2    r2,r0
ld1:    ret
/*
 *      Underflow
 */
under:  clrl    r0              /* Result is zero */
        clrl    r1
        orl2    $HFS_UNDF,*16(fp)
        jmp     err             /* Join general error code */
/*
 *      Overflow
 */
over:   movl    huge0,r0        /* Largest possible floating magnitude */
        movl    huge1,r1
        orl2    $HFS_OVF,*16(fp)
        orl2    $SIGNBIT,r0     /* If arg < 0, make result negative */

err:    orl2    $HFS_RANGE,*16(fp)      /* Indicate range error */
        ret

        .data
huge0:  .long   0x7fffffff
huge1:  .long   0xffffffff