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 * _D_cplx_mul(z, w) returns z * w with infinities handled according
31 * to C99.
32 *
33 * If z and w are both finite, _D_cplx_mul(z, w) delivers the complex
34 * product according to the usual formula: let a = Re(z), b = Im(z),
35 * c = Re(w), and d = Im(w); then _D_cplx_mul(z, w) delivers x + I * y
36 * where x = a * c - b * d and y = a * d + b * c. Note that if both
37 * ac and bd overflow, then at least one of ad or bc must also over-
38 * flow, and vice versa, so that if one component of the product is
39 * NaN, the other is infinite. (Such a value is considered infinite
40 * according to C99.)
41 *
42 * If one of z or w is infinite and the other is either finite nonzero
43 * or infinite, _D_cplx_mul delivers an infinite result. If one factor
44 * is infinite and the other is zero, _D_cplx_mul delivers NaN + I * NaN.
45 * C99 doesn't specify the latter case.
46 *
47 * C99 also doesn't specify what should happen if either z or w is a
48 * complex NaN (i.e., neither finite nor infinite). This implementation
49 * delivers NaN + I * NaN in this case.
50 *
51 * This implementation can raise spurious underflow, overflow, invalid
52 * operation, and inexact exceptions. C99 allows this.
53 */
54
55 #if !defined(sparc) && !defined(__sparc)
56 #error This code is for SPARC only
57 #endif
58
59 static union {
60 int i[2];
61 double d;
62 } inf = {
63 0x7ff00000, 0
64 };
65
66 /*
67 * Return +1 if x is +Inf, -1 if x is -Inf, and 0 otherwise
68 */
69 static int
testinf(double x)70 testinf(double x)
71 {
72 union {
73 int i[2];
74 double d;
75 } xx;
76
77 xx.d = x;
78 return (((((xx.i[0] << 1) - 0xffe00000) | xx.i[1]) == 0)?
79 (1 | (xx.i[0] >> 31)) : 0);
80 }
81
82 double _Complex
_D_cplx_mul(double _Complex z,double _Complex w)83 _D_cplx_mul(double _Complex z, double _Complex w)
84 {
85 double _Complex v;
86 double a, b, c, d, x, y;
87 int recalc, i, j;
88
89 /*
90 * The following is equivalent to
91 *
92 * a = creal(z); b = cimag(z);
93 * c = creal(w); d = cimag(w);
94 */
95 a = ((double *)&z)[0];
96 b = ((double *)&z)[1];
97 c = ((double *)&w)[0];
98 d = ((double *)&w)[1];
99
100 x = a * c - b * d;
101 y = a * d + b * c;
102
103 if (x != x && y != y) {
104 /*
105 * Both x and y are NaN, so z and w can't both be finite.
106 * If at least one of z or w is a complex NaN, and neither
107 * is infinite, then we might as well deliver NaN + I * NaN.
108 * So the only cases to check are when one of z or w is
109 * infinite.
110 */
111 recalc = 0;
112 i = testinf(a);
113 j = testinf(b);
114 if (i | j) { /* z is infinite */
115 /* "factor out" infinity */
116 a = i;
117 b = j;
118 recalc = 1;
119 }
120 i = testinf(c);
121 j = testinf(d);
122 if (i | j) { /* w is infinite */
123 /* "factor out" infinity */
124 c = i;
125 d = j;
126 recalc = 1;
127 }
128 if (recalc) {
129 x = inf.d * (a * c - b * d);
130 y = inf.d * (a * d + b * c);
131 }
132 }
133
134 /*
135 * The following is equivalent to
136 *
137 * return x + I * y;
138 */
139 ((double *)&v)[0] = x;
140 ((double *)&v)[1] = y;
141 return (v);
142 }
143