1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License, Version 1.0 only
6 * (the "License").  You may not use this file except in compliance
7 * with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://www.opensolaris.org/os/licensing.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22/*
23 * Copyright 2003 Sun Microsystems, Inc.  All rights reserved.
24 * Use is subject to license terms.
25 */
26
27#pragma ident	"%Z%%M%	%I%	%E% SMI"
28
29/*
30 * _F_cplx_div(z, w) returns z / w with infinities handled according
31 * to C99.
32 *
33 * If z and w are both finite and w is nonzero, _F_cplx_div(z, w)
34 * delivers the complex quotient q according to the usual formula:
35 * let a = Re(z), b = Im(z), c = Re(w), and d = Im(w); then q = x +
36 * I * y where x = (a * c + b * d) / r and y = (b * c - a * d) / r
37 * with r = c * c + d * d.  This implementation computes intermediate
38 * results in double precision to avoid premature underflow or over-
39 * flow.
40 *
41 * If z is neither NaN nor zero and w is zero, or if z is infinite
42 * and w is finite and nonzero, _F_cplx_div delivers an infinite
43 * result.  If z is finite and w is infinite, _F_cplx_div delivers
44 * a zero result.
45 *
46 * If z and w are both zero or both infinite, or if either z or w is
47 * a complex NaN, _F_cplx_div delivers NaN + I * NaN.  C99 doesn't
48 * specify these cases.
49 *
50 * This implementation can raise spurious invalid operation, inexact,
51 * and division-by-zero exceptions.  C99 allows this.
52 *
53 * Warning: Do not attempt to "optimize" this code by removing multi-
54 * plications by zero.
55 */
56
57#if !defined(sparc) && !defined(__sparc)
58#error This code is for SPARC only
59#endif
60
61static union {
62	int	i[2];
63	double	d;
64} inf = {
65	0x7ff00000, 0
66};
67
68/*
69 * Return +1 if x is +Inf, -1 if x is -Inf, and 0 otherwise
70 */
71static int
72testinff(float x)
73{
74	union {
75		int	i;
76		float	f;
77	} xx;
78
79	xx.f = x;
80	return ((((xx.i << 1) - 0xff000000) == 0)? (1 | (xx.i >> 31)) : 0);
81}
82
83float _Complex
84_F_cplx_div(float _Complex z, float _Complex w)
85{
86	float _Complex	v;
87	union {
88		int	i;
89		float	f;
90	} cc, dd;
91	float		a, b, c, d;
92	double		r, x, y;
93	int		i, j, recalc;
94
95	/*
96	 * The following is equivalent to
97	 *
98	 *  a = crealf(z); b = cimagf(z);
99	 *  c = crealf(w); d = cimagf(w);
100	 */
101	a = ((float *)&z)[0];
102	b = ((float *)&z)[1];
103	c = ((float *)&w)[0];
104	d = ((float *)&w)[1];
105
106	r = (double)c * c + (double)d * d;
107
108	if (r == 0.0) {
109		/* w is zero; multiply z by 1/Re(w) - I * Im(w) */
110		c = 1.0f / c;
111		i = testinff(a);
112		j = testinff(b);
113		if (i | j) { /* z is infinite */
114			a = i;
115			b = j;
116		}
117		((float *)&v)[0] = a * c + b * d;
118		((float *)&v)[1] = b * c - a * d;
119		return (v);
120	}
121
122	r = 1.0 / r;
123	x = ((double)a * c + (double)b * d) * r;
124	y = ((double)b * c - (double)a * d) * r;
125
126	if (x != x && y != y) {
127		/*
128		 * Both x and y are NaN, so z and w can't both be finite
129		 * and nonzero.  Since we handled the case w = 0 above,
130		 * the only cases to check here are when one of z or w
131		 * is infinite.
132		 */
133		r = 1.0;
134		recalc = 0;
135		i = testinff(a);
136		j = testinff(b);
137		if (i | j) { /* z is infinite */
138			/* "factor out" infinity */
139			a = i;
140			b = j;
141			r = inf.d;
142			recalc = 1;
143		}
144		i = testinff(c);
145		j = testinff(d);
146		if (i | j) { /* w is infinite */
147			/*
148			 * "factor out" infinity, being careful to preserve
149			 * signs of finite values
150			 */
151			cc.f = c;
152			dd.f = d;
153			c = i? i : ((cc.i < 0)? -0.0f : 0.0f);
154			d = j? j : ((dd.i < 0)? -0.0f : 0.0f);
155			r *= 0.0;
156			recalc = 1;
157		}
158		if (recalc) {
159			x = ((double)a * c + (double)b * d) * r;
160			y = ((double)b * c - (double)a * d) * r;
161		}
162	}
163
164	/*
165	 * The following is equivalent to
166	 *
167	 *  return x + I * y;
168	 */
169	((float *)&v)[0] = (float)x;
170	((float *)&v)[1] = (float)y;
171	return (v);
172}
173