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_rx(a, w) returns a / w with infinities handled according
31 * to C99.
32 *
33 * If a and w are both finite and w is nonzero, _F_cplx_div_rx(a, 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 = (a * c)
36 * / r and y = (-a * d) / r with r = c * c + d * d. This implementa-
37 * tion computes intermediate results in double precision to avoid
38 * premature underflow or overflow.
39 *
40 * If a is neither NaN nor zero and w is zero, or if a is infinite
41 * and w is finite and nonzero, _F_cplx_div_rx delivers an infinite
42 * result. If a is finite and w is infinite, _F_cplx_div_rx delivers
43 * a zero result.
44 *
45 * If a and w are both zero or both infinite, or if either a or w is
46 * NaN, _F_cplx_div_rx 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(sparc) && !defined(__sparc)
57 #error This code is for SPARC only
58 #endif
59
60 /*
61 * Return +1 if x is +Inf, -1 if x is -Inf, and 0 otherwise
62 */
63 static int
testinff(float x)64 testinff(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
75 float _Complex
_F_cplx_div_rx(float a,float _Complex w)76 _F_cplx_div_rx(float a, float _Complex w)
77 {
78 float _Complex v;
79 union {
80 int i;
81 float f;
82 } cc, dd;
83 float c, d;
84 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 = (double)c * c + (double)d * d;
96
97 if (r == 0.0) {
98 /* w is zero; multiply a by 1/Re(w) - I * Im(w) */
99 c = 1.0f / c;
100 i = testinff(a);
101 if (i) { /* a is infinite */
102 a = i;
103 }
104 ((float *)&v)[0] = a * c;
105 ((float *)&v)[1] = (a == 0.0f)? a * c : -a * d;
106 return (v);
107 }
108
109 r = (double)a / r;
110 x = (double)c * r;
111 y = (double)-d * r;
112
113 if (x != x || y != y) {
114 /*
115 * x or y is NaN, so a 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 = (double)c * a;
127 y = (double)-d * a;
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