usr/src/lib/libc/tahoe/fpe/cvtuf.s

/*
 * Copyright (c) 1986 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(SYSLIBC_SCCS) && !defined(lint)
        .asciz "@(#)cvtuf.s     1.3 (Berkeley) 6/1/90"
#endif /* SYSLIBC_SCCS and not lint */

#include <tahoemath/fp.h>
#include "DEFS.h"

XENTRY(cvtuf, R2|R3|R4|R5)
 #
 #      Some initializations:
 #
        clrl    r1
        clrl    r2              # r2 - exponent.
        movl    4(fp),r0        # fetch operand.
        jeql    retzero         # return zero.
 #
 #      Compute exponent:
 #
positive:
        ffs     r0,r1
        incl    r1
        addl2   r1,r2
        shrl    r1,r0,r0
        jneq    positive        # look for more set bits.
 #
 # we have the exponent in r2.
 #
        movl    4(fp),r0        # r0 will hold the resulting f.p. number.
 #
 #      Shift the fraction part to its proper place:
 #
        subl3   r2,$HID_POS,r3
        jlss    shiftr          # if less then zero we have to shift right.
        shll    r3,r0,r0        # else we shift left.
        jmp     shifted
shiftr:
        mnegl   r3,r3
        shrl    r3,r0,r0
shifted:
        andl2   $CLEARHID,r0    # clear the hidden bit.
        shal    $EXPSHIFT,r2,r2 # shift the exponent to its proper place.
        orl2    $EXPSIGN,r2     # set the exponent sign bit(to bias it).
        orl2    r2,r0           # combine exponent & fraction.
sign_ok:
        ret

retzero:
        clrl    r0
        ret