/*
 * 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.
 */

/*
 * _D_cplx_div_ix(b, w) returns (I * b) / w with infinities handled
 * according to C99.
 *
 * If b and w are both finite and w is nonzero, _D_cplx_div_ix(b, w)
 * delivers the complex quotient q according to the usual formula:
 * let c = Re(w), and d = Im(w); then q = x + I * y where x = (b * d)
 * / r and y = (b * c) / r with r = c * c + d * d.  This implementa-
 * tion scales to avoid premature underflow or overflow.
 *
 * If b is neither NaN nor zero and w is zero, or if b is infinite
 * and w is finite and nonzero, _D_cplx_div_ix delivers an infinite
 * result.  If b is finite and w is infinite, _D_cplx_div_ix delivers
 * a zero result.
 *
 * If b and w are both zero or both infinite, or if either b or w is
 * NaN, _D_cplx_div_ix 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.
 *
 * Warning: Do not attempt to "optimize" this code by removing multi-
 * plications by zero.
 */

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

/*
 * scl[i].d = 2^(250*(4-i)) for i = 0, ..., 9
 */
static const union {
        int     i[2];
        double  d;
} scl[9] = {
        { 0x7e700000, 0 },
        { 0x6ed00000, 0 },
        { 0x5f300000, 0 },
        { 0x4f900000, 0 },
        { 0x3ff00000, 0 },
        { 0x30500000, 0 },
        { 0x20b00000, 0 },
        { 0x11100000, 0 },
        { 0x01700000, 0 }
};

/*
 * Return +1 if x is +Inf, -1 if x is -Inf, and 0 otherwise
 */
static int
testinf(double x)
{
        union {
                int     i[2];
                double  d;
        } xx;

        xx.d = x;
        return (((((xx.i[0] << 1) - 0xffe00000) | xx.i[1]) == 0)?
                (1 | (xx.i[0] >> 31)) : 0);
}

double _Complex
_D_cplx_div_ix(double b, double _Complex w)
{
        double _Complex v;
        union {
                int     i[2];
                double  d;
        } bb, cc, dd;
        double          c, d, sc, sd, r;
        int             hb, hc, hd, hw, i, j;

        /*
         * The following is equivalent to
         *
         *  c = creal(w); d = cimag(w);
         */
        c = ((double *)&w)[0];
        d = ((double *)&w)[1];

        /* extract high-order words to estimate |b| and |w| */
        bb.d = b;
        hb = bb.i[0] & ~0x80000000;

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

        /* check for special cases */
        if (hw >= 0x7ff00000) { /* w is inf or nan */
                i = testinf(c);
                j = testinf(d);
                if (i | j) { /* w is infinite */
                        c = (cc.i[0] < 0)? -0.0 : 0.0;
                        d = (dd.i[0] < 0)? -0.0 : 0.0;
                } else /* w is nan */
                        b *= c * d;
                ((double *)&v)[0] = b * d;
                ((double *)&v)[1] = b * c;
                return (v);
        }

        if (hw < 0x00100000) {
                /*
                 * This nonsense is needed to work around some SPARC
                 * implementations of nonstandard mode; if both parts
                 * of w are subnormal, multiply them by one to force
                 * them to be flushed to zero when nonstandard mode
                 * is enabled.  Sheesh.
                 */
                cc.d = c = c * 1.0;
                dd.d = d = d * 1.0;
                hc = cc.i[0] & ~0x80000000;
                hd = dd.i[0] & ~0x80000000;
                hw = (hc > hd)? hc : hd;
        }

        if (hw == 0 && (cc.i[1] | dd.i[1]) == 0) {
                /* w is zero; multiply b by 1/Re(w) - I * Im(w) */
                c = 1.0 / c;
                j = testinf(b);
                if (j) { /* b is infinite */
                        b = j;
                }
                ((double *)&v)[0] = (b == 0.0)? b * c : b * d;
                ((double *)&v)[1] = b * c;
                return (v);
        }

        if (hb >= 0x7ff00000) { /* a is inf or nan */
                ((double *)&v)[0] = b * d;
                ((double *)&v)[1] = b * c;
                return (v);
        }

        /*
         * Compute the real and imaginary parts of the quotient,
         * scaling to avoid overflow or underflow.
         */
        hw = (hw - 0x38000000) >> 28;
        sc = c * scl[hw + 4].d;
        sd = d * scl[hw + 4].d;
        r = sc * sc + sd * sd;

        hb = (hb - 0x38000000) >> 28;
        b = (b * scl[hb + 4].d) / r;
        hb -= (hw + hw);

        hc = (hc - 0x38000000) >> 28;
        c = (c * scl[hc + 4].d) * b;
        hc += hb;

        hd = (hd - 0x38000000) >> 28;
        d = (d * scl[hd + 4].d) * b;
        hd += hb;

        /* compensate for scaling */
        sc = scl[3].d; /* 2^250 */
        if (hc < 0) {
                hc = -hc;
                sc = scl[5].d; /* 2^-250 */
        }
        while (hc--)
                c *= sc;

        sd = scl[3].d;
        if (hd < 0) {
                hd = -hd;
                sd = scl[5].d;
        }
        while (hd--)
                d *= sd;

        ((double *)&v)[0] = d;
        ((double *)&v)[1] = c;
        return (v);
}