/*
 * 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 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * _F_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, _F_cplx_div_rx(a, 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 = (a * c)
 * / r and y = (-a * d) / r with r = c * c + d * d.  This implementa-
 * tion computes intermediate results in extended precision 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, _F_cplx_div_rx delivers an infinite
 * result.  If a is finite and w is infinite, _F_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, _F_cplx_div_rx delivers NaN + I * NaN.  C99 doesn't specify
 * these cases.
 *
 * This implementation can raise spurious invalid 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(i386) && !defined(__i386) && !defined(__amd64)
#error This code is for x86 only
#endif

/*
 * Return +1 if x is +Inf, -1 if x is -Inf, and 0 otherwise
 */
static int
testinff(float x)
{
        union {
                int     i;
                float   f;
        } xx;

        xx.f = x;
        return ((((xx.i << 1) - 0xff000000) == 0)? (1 | (xx.i >> 31)) : 0);
}

float _Complex
_F_cplx_div_rx(float a, float _Complex w)
{
        float _Complex  v;
        union {
                int     i;
                float   f;
        } cc, dd;
        float           c, d;
        long double     r, x, y;
        int             i, j;

        /*
         * The following is equivalent to
         *
         *  c = crealf(w); d = cimagf(w);
         */
        c = ((float *)&w)[0];
        d = ((float *)&w)[1];

        r = (long double)c * c + (long double)d * d;

        if (r == 0.0f) {
                /* w is zero; multiply a by 1/Re(w) - I * Im(w) */
                c = 1.0f / c;
                i = testinff(a);
                if (i) { /* a is infinite */
                        a = i;
                }
                ((float *)&v)[0] = a * c;
                ((float *)&v)[1] = (a == 0.0f)? a * c : -a * d;
                return (v);
        }

        r = (long double)a / r;
        x = (long double)c * r;
        y = (long double)-d * r;

        if (x != x || y != y) {
                /*
                 * x or y is NaN, so a and w can't both be finite and
                 * nonzero.  Since we handled the case w = 0 above, the
                 * only case to check here is when w is infinite.
                 */
                i = testinff(c);
                j = testinff(d);
                if (i | j) { /* w is infinite */
                        cc.f = c;
                        dd.f = d;
                        c = (cc.i < 0)? -0.0f : 0.0f;
                        d = (dd.i < 0)? -0.0f : 0.0f;
                        x = (long double)c * a;
                        y = (long double)-d * a;
                }
        }

        /*
         * The following is equivalent to
         *
         *  return x + I * y;
         */
        ((float *)&v)[0] = (float)x;
        ((float *)&v)[1] = (float)y;
        return (v);
}