sparc/fp/_Q_cplx_div_rx.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2003 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 * On SPARC V8, _Q_cplx_div_rx(v, a, w) sets *v = *a / *w with in-
 * finities handling according to C99.
 *
 * On SPARC V9, _Q_cplx_div_rx(a, w) returns *a / *w with infinities
 * handled according to C99.
 *
 * If a and w are both finite and w is nonzero, _Q_cplx_div_rx de-
 * livers the complex quotient q according to the usual formula: let
 * c = Re(w), and d = Im(w); then q = x + I * y where x = (a * c) / r
 * and y = (-a * d) / r with r = c * c + d * d.  This implementation
 * scales to avoid premature underflow or overflow.
 *
 * If a is neither NaN nor zero and w is zero, or if a is infinite
 * and w is finite and nonzero, _Q_cplx_div_rx delivers an infinite
 * result.  If a is finite and w is infinite, _Q_cplx_div_rx delivers
 * a zero result.
 *
 * If a and w are both zero or both infinite, or if either a or w is
 * NaN, _Q_cplx_div_rx delivers NaN + I * NaN.  C99 doesn't specify
 * these cases.
 *
 * This implementation can raise spurious underflow, overflow, in-
 * valid operation, inexact, and division-by-zero exceptions.  C99
 * allows this.
 */

#if !defined(sparc) && !defined(__sparc)
#error This code is for SPARC only
#endif

extern void _Q_scl(long double *, int);
extern void _Q_scle(long double *, int);

/*
 * Return +1 if x is +Inf, -1 if x is -Inf, and 0 otherwise
 */
static int
testinfl(long double x)
{
    union {
        int     i[4];
        long double q;
    } xx;

    xx.q = x;
    return (((((xx.i[0] << 1) - 0xfffe0000) | xx.i[1] | xx.i[2] | xx.i[3])
        == 0)? (1 | (xx.i[0] >> 31)) : 0);
}

#ifdef __sparcv9
long double _Complex
_Q_cplx_div_rx(const long double *pa, const long double _Complex *w)
{
    long double _Complex    v;
#else
void
_Q_cplx_div_rx(long double _Complex *v, const long double *pa,
    const long double _Complex *w)
{
#endif
    union {
        int     i[4];
        long double q;
    } aa, cc, dd;
    long double a, c, d, sc, sd, r;
    int     ha, hc, hd, hw, i, j;

    a = *pa;

    /*
     * The following is equivalent to
     *
     *  c = creall(*w); d = cimagl(*w);
     */
    c = ((long double *)w)[0];
    d = ((long double *)w)[1];

    /* extract high-order words to estimate |a| and |w| */
    aa.q = a;
    ha = aa.i[0] & ~0x80000000;

    cc.q = c;
    dd.q = d;
    hc = cc.i[0] & ~0x80000000;
    hd = dd.i[0] & ~0x80000000;
    hw = (hc > hd)? hc : hd;

    /* check for special cases */
    if (hw >= 0x7fff0000) { /* w is inf or nan */
        i = testinfl(c);
        j = testinfl(d);
        if (i | j) { /* w is infinite */
            c = (cc.i[0] < 0)? -0.0l : 0.0l;
            d = (dd.i[0] < 0)? -0.0l : 0.0l;
        } else /* w is nan */
            a += c + d;
        c *= a;
        d *= -a;
        goto done;
    }

    if (hw == 0 && (cc.i[1] | cc.i[2] | cc.i[3] |
        dd.i[1] | dd.i[2] | dd.i[3]) == 0) {
        /* w is zero; multiply a by 1/Re(w) - I * Im(w) */
        c = 1.0l / c;
        i = testinfl(a);
        if (i) { /* a is infinite */
            a = i;
        }
        c *= a;
        d = (a == 0.0l)? c : -a * d;
        goto done;
    }

    if (ha >= 0x7fff0000) { /* a is inf or nan */
        c *= a;
        d *= -a;
        goto done;
    }

    /*
     * Compute the real and imaginary parts of the quotient,
     * scaling to avoid overflow or underflow.
     */
    hw = (hw - 0x3fff0000) >> 16;
    sc = c;
    sd = d;
    _Q_scl(&sc, -hw);
    _Q_scl(&sd, -hw);
    r = sc * sc + sd * sd;

    ha = (ha - 0x3fff0000) >> 16;
    _Q_scl(&a, -ha);
    a /= r;
    ha -= (hw + hw);

    hc = (hc - 0x3fff0000) >> 16;
    _Q_scl(&c, -hc);
    c *= a;
    hc += ha;

    hd = (hd - 0x3fff0000) >> 16;
    _Q_scl(&d, -hd);
    d *= -a;
    hd += ha;

    /* compensate for scaling */
    _Q_scle(&c, hc);
    _Q_scle(&d, hd);

done:
#ifdef __sparcv9
    ((long double *)&v)[0] = c;
    ((long double *)&v)[1] = d;
    return (v);
#else
    ((long double *)v)[0] = c;
    ((long double *)v)[1] = d;
#endif
}