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 /*
28 * _F_cplx_div_rx(a, w) returns a / w with infinities handled according
29 * to C99.
30 *
31 * If a and w are both finite and w is nonzero, _F_cplx_div_rx(a, w)
32 * delivers the complex quotient q according to the usual formula:
33 * let c = Re(w), and d = Im(w); then q = x + I * y where x = (a * c)
34 * / r and y = (-a * d) / r with r = c * c + d * d. This implementa-
35 * tion computes intermediate results in double precision to avoid
36 * premature underflow or overflow.
37 *
38 * If a is neither NaN nor zero and w is zero, or if a is infinite
39 * and w is finite and nonzero, _F_cplx_div_rx delivers an infinite
40 * result. If a is finite and w is infinite, _F_cplx_div_rx delivers
41 * a zero result.
42 *
43 * If a and w are both zero or both infinite, or if either a or w is
44 * NaN, _F_cplx_div_rx delivers NaN + I * NaN. C99 doesn't specify
45 * these cases.
46 *
47 * This implementation can raise spurious invalid operation, inexact,
48 * and division-by-zero exceptions. C99 allows this.
49 *
50 * Warning: Do not attempt to "optimize" this code by removing multi-
51 * plications by zero.
52 */
53
54 #if !defined(sparc) && !defined(__sparc)
55 #error This code is for SPARC only
56 #endif
57
58 /*
59 * Return +1 if x is +Inf, -1 if x is -Inf, and 0 otherwise
60 */
61 static int
testinff(float x)62 testinff(float x)
63 {
64 union {
65 int i;
66 float f;
67 } xx;
68
69 xx.f = x;
70 return ((((xx.i << 1) - 0xff000000) == 0)? (1 | (xx.i >> 31)) : 0);
71 }
72
73 float _Complex
_F_cplx_div_rx(float a,float _Complex w)74 _F_cplx_div_rx(float a, float _Complex w)
75 {
76 float _Complex v;
77 union {
78 int i;
79 float f;
80 } cc, dd;
81 float c, d;
82 double r, x, y;
83 int i, j;
84
85 /*
86 * The following is equivalent to
87 *
88 * c = crealf(w); d = cimagf(w);
89 */
90 c = ((float *)&w)[0];
91 d = ((float *)&w)[1];
92
93 r = (double)c * c + (double)d * d;
94
95 if (r == 0.0) {
96 /* w is zero; multiply a by 1/Re(w) - I * Im(w) */
97 c = 1.0f / c;
98 i = testinff(a);
99 if (i) { /* a is infinite */
100 a = i;
101 }
102 ((float *)&v)[0] = a * c;
103 ((float *)&v)[1] = (a == 0.0f)? a * c : -a * d;
104 return (v);
105 }
106
107 r = (double)a / r;
108 x = (double)c * r;
109 y = (double)-d * r;
110
111 if (x != x || y != y) {
112 /*
113 * x or y is NaN, so a and w can't both be finite and
114 * nonzero. Since we handled the case w = 0 above, the
115 * only case to check here is when w is infinite.
116 */
117 i = testinff(c);
118 j = testinff(d);
119 if (i | j) { /* w is infinite */
120 cc.f = c;
121 dd.f = d;
122 c = (cc.i < 0)? -0.0f : 0.0f;
123 d = (dd.i < 0)? -0.0f : 0.0f;
124 x = (double)c * a;
125 y = (double)-d * a;
126 }
127 }
128
129 /*
130 * The following is equivalent to
131 *
132 * return x + I * y;
133 */
134 ((float *)&v)[0] = (float)x;
135 ((float *)&v)[1] = (float)y;
136 return (v);
137 }
138