ipiq: Add simple IPI latency measure sysctls (2)
[dragonfly.git] / lib / libm / src / s_csqrtl.c
CommitLineData
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1/*-
2 * Copyright (c) 2007-2008 David Schultz <das@FreeBSD.ORG>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
6ff43c94 26 * $FreeBSD: head/lib/msun/src/s_csqrtl.c 181402 2008-08-08 00:15:16Z das $
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27 */
28
29#include <complex.h>
30#include <float.h>
31#include <math.h>
32
6ff43c94 33#include "math_private.h"
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34
35/*
36 * gcc doesn't implement complex multiplication or division correctly,
37 * so we need to handle infinities specially. We turn on this pragma to
38 * notify conforming c99 compilers that the fast-but-incorrect code that
39 * gcc generates is acceptable, since the special cases have already been
40 * handled.
1a3b704c 41 */
6ff43c94 42#pragma STDC CX_LIMITED_RANGE ON
1a3b704c 43
d8c83a86
SW
44/*
45 * XXX: gcc47 really shouldn't warn here on i386, exclude from -Werror for now
46 */
47#if defined(__i386__) && __GNUC_PREREQ__(4, 7)
48#pragma GCC diagnostic warning "-Woverflow"
49#endif
50
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51/* We risk spurious overflow for components >= LDBL_MAX / (1 + sqrt(2)). */
52#define THRESH (LDBL_MAX / 2.414213562373095048801688724209698L)
53
54long double complex
55csqrtl(long double complex z)
56{
57 long double complex result;
58 long double a, b;
59 long double t;
60 int scale;
61
62 a = creall(z);
63 b = cimagl(z);
64
65 /* Handle special cases. */
66 if (z == 0)
67 return (cpackl(0, b));
68 if (isinf(b))
69 return (cpackl(INFINITY, b));
70 if (isnan(a)) {
71 t = (b - b) / (b - b); /* raise invalid if b is not a NaN */
72 return (cpackl(a, t)); /* return NaN + NaN i */
73 }
74 if (isinf(a)) {
75 /*
76 * csqrt(inf + NaN i) = inf + NaN i
77 * csqrt(inf + y i) = inf + 0 i
78 * csqrt(-inf + NaN i) = NaN +- inf i
79 * csqrt(-inf + y i) = 0 + inf i
80 */
81 if (signbit(a))
82 return (cpackl(fabsl(b - b), copysignl(a, b)));
83 else
84 return (cpackl(a, copysignl(b - b, b)));
85 }
86 /*
87 * The remaining special case (b is NaN) is handled just fine by
88 * the normal code path below.
89 */
90
91 /* Scale to avoid overflow. */
92 if (fabsl(a) >= THRESH || fabsl(b) >= THRESH) {
93 a *= 0.25;
94 b *= 0.25;
95 scale = 1;
96 } else {
97 scale = 0;
98 }
99
100 /* Algorithm 312, CACM vol 10, Oct 1967. */
101 if (a >= 0) {
102 t = sqrtl((a + hypotl(a, b)) * 0.5);
103 result = cpackl(t, b / (2 * t));
104 } else {
105 t = sqrtl((-a + hypotl(a, b)) * 0.5);
106 result = cpackl(fabsl(b) / (2 * t), copysignl(t, b));
107 }
108
109 /* Rescale. */
110 if (scale)
111 return (result * 2);
112 else
113 return (result);
114}