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 2004 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_ix(b, w) returns (I * b) / w with infinities handled
31 * according to C99.
32 *
33 * If b and w are both finite and w is nonzero, _F_cplx_div_ix(b, w)
34 * delivers the complex quotient q according to the usual formula:
35 * let c = Re(w), and d = Im(w); then q = x + I * y where x = (b * d)
36 * / r and y = (b * c) / r with r = c * c + d * d.  This implementa-
37 * tion computes intermediate results in extended precision to avoid
38 * premature underflow or overflow.
39 *
40 * If b is neither NaN nor zero and w is zero, or if b is infinite
41 * and w is finite and nonzero, _F_cplx_div_ix delivers an infinite
42 * result.  If b is finite and w is infinite, _F_cplx_div_ix delivers
43 * a zero result.
44 *
45 * If b and w are both zero or both infinite, or if either b or w is
46 * NaN, _F_cplx_div_ix delivers NaN + I * NaN.  C99 doesn't specify
47 * these cases.
48 *
49 * This implementation can raise spurious invalid operation, inexact,
50 * and division-by-zero exceptions.  C99 allows this.
51 *
52 * Warning: Do not attempt to "optimize" this code by removing multi-
53 * plications by zero.
54 */
55
56#if !defined(i386) && !defined(__i386) && !defined(__amd64)
57#error This code is for x86 only
58#endif
59
60/*
61 * Return +1 if x is +Inf, -1 if x is -Inf, and 0 otherwise
62 */
63static int
64testinff(float x)
65{
66	union {
67		int	i;
68		float	f;
69	} xx;
70
71	xx.f = x;
72	return ((((xx.i << 1) - 0xff000000) == 0)? (1 | (xx.i >> 31)) : 0);
73}
74
75float _Complex
76_F_cplx_div_ix(float b, float _Complex w)
77{
78	float _Complex	v;
79	union {
80		int	i;
81		float	f;
82	} cc, dd;
83	float		c, d;
84	long double	r, x, y;
85	int		i, j;
86
87	/*
88	 * The following is equivalent to
89	 *
90	 *  c = crealf(w); d = cimagf(w);
91	 */
92	c = ((float *)&w)[0];
93	d = ((float *)&w)[1];
94
95	r = (long double)c * c + (long double)d * d;
96
97	if (r == 0.0f) {
98		/* w is zero; multiply b by 1/Re(w) - I * Im(w) */
99		c = 1.0f / c;
100		j = testinff(b);
101		if (j) { /* b is infinite */
102			b = j;
103		}
104		((float *)&v)[0] = (b == 0.0f)? b * c : b * d;
105		((float *)&v)[1] = b * c;
106		return (v);
107	}
108
109	r = (long double)b / r;
110	x = (long double)d * r;
111	y = (long double)c * r;
112
113	if (x != x || y != y) {
114		/*
115		 * x or y is NaN, so b and w can't both be finite and
116		 * nonzero.  Since we handled the case w = 0 above, the
117		 * only case to check here is when w is infinite.
118		 */
119		i = testinff(c);
120		j = testinff(d);
121		if (i | j) { /* w is infinite */
122			cc.f = c;
123			dd.f = d;
124			c = (cc.i < 0)? -0.0f : 0.0f;
125			d = (dd.i < 0)? -0.0f : 0.0f;
126			x = (long double)d * b;
127			y = (long double)c * b;
128		}
129	}
130
131	/*
132	 * The following is equivalent to
133	 *
134	 *  return x + I * y;
135	 */
136	((float *)&v)[0] = (float)x;
137	((float *)&v)[1] = (float)y;
138	return (v);
139}
140