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 * _D_cplx_mul(z, w) returns z * w with infinities handled according
29 * to C99.
30 *
31 * If z and w are both finite, _D_cplx_mul(z, w) delivers the complex
32 * product according to the usual formula: let a = Re(z), b = Im(z),
33 * c = Re(w), and d = Im(w); then _D_cplx_mul(z, w) delivers x + I * y
34 * where x = a * c - b * d and y = a * d + b * c. Note that if both
35 * ac and bd overflow, then at least one of ad or bc must also over-
36 * flow, and vice versa, so that if one component of the product is
37 * NaN, the other is infinite. (Such a value is considered infinite
38 * according to C99.)
39 *
40 * If one of z or w is infinite and the other is either finite nonzero
41 * or infinite, _D_cplx_mul delivers an infinite result. If one factor
42 * is infinite and the other is zero, _D_cplx_mul delivers NaN + I * NaN.
43 * C99 doesn't specify the latter case.
44 *
45 * C99 also doesn't specify what should happen if either z or w is a
46 * complex NaN (i.e., neither finite nor infinite). This implementation
47 * delivers NaN + I * NaN in this case.
48 *
49 * This implementation can raise spurious underflow, overflow, invalid
50 * operation, and inexact exceptions. C99 allows this.
51 */
52
53 #if !defined(sparc) && !defined(__sparc)
54 #error This code is for SPARC only
55 #endif
56
57 static union {
58 int i[2];
59 double d;
60 } inf = {
61 0x7ff00000, 0
62 };
63
64 /*
65 * Return +1 if x is +Inf, -1 if x is -Inf, and 0 otherwise
66 */
67 static int
testinf(double x)68 testinf(double x)
69 {
70 union {
71 int i[2];
72 double d;
73 } xx;
74
75 xx.d = x;
76 return (((((xx.i[0] << 1) - 0xffe00000) | xx.i[1]) == 0)?
77 (1 | (xx.i[0] >> 31)) : 0);
78 }
79
80 double _Complex
_D_cplx_mul(double _Complex z,double _Complex w)81 _D_cplx_mul(double _Complex z, double _Complex w)
82 {
83 double _Complex v = 0;
84 double a, b, c, d, x, y;
85 int recalc, i, j;
86
87 /*
88 * The following is equivalent to
89 *
90 * a = creal(z); b = cimag(z);
91 * c = creal(w); d = cimag(w);
92 */
93 a = ((double *)&z)[0];
94 b = ((double *)&z)[1];
95 c = ((double *)&w)[0];
96 d = ((double *)&w)[1];
97
98 x = a * c - b * d;
99 y = a * d + b * c;
100
101 if (x != x && y != y) {
102 /*
103 * Both x and y are NaN, so z and w can't both be finite.
104 * If at least one of z or w is a complex NaN, and neither
105 * is infinite, then we might as well deliver NaN + I * NaN.
106 * So the only cases to check are when one of z or w is
107 * infinite.
108 */
109 recalc = 0;
110 i = testinf(a);
111 j = testinf(b);
112 if (i | j) { /* z is infinite */
113 /* "factor out" infinity */
114 a = i;
115 b = j;
116 recalc = 1;
117 }
118 i = testinf(c);
119 j = testinf(d);
120 if (i | j) { /* w is infinite */
121 /* "factor out" infinity */
122 c = i;
123 d = j;
124 recalc = 1;
125 }
126 if (recalc) {
127 x = inf.d * (a * c - b * d);
128 y = inf.d * (a * d + b * c);
129 }
130 }
131
132 /*
133 * The following is equivalent to
134 *
135 * return x + I * y;
136 */
137 ((double *)&v)[0] = x;
138 ((double *)&v)[1] = y;
139 return (v);
140 }
141