1 /*-
2 * Copyright (c) 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 */
26
27 //__FBSDID("$FreeBSD: src/lib/msun/src/s_rintl.c,v 1.5 2008/02/22 11:59:05 bde Exp $");
28
29
30 #if LDBL_MAX_EXP != 0x4000
31 /* We also require the usual bias, min exp and expsign packing. */
32 #error "Unsupported long double format"
33 #endif
34
35 #define BIAS (LDBL_MAX_EXP - 1)
36
37 static const float
38 shift[2] = {
39 #if LDBL_MANT_DIG == 64
40 0x1.0p63, -0x1.0p63
41 #elif LDBL_MANT_DIG == 113
42 0x1.0p112, -0x1.0p112
43 #else
44 #error "Unsupported long double format"
45 #endif
46 };
47 static const float zero[2] = { 0.0, -0.0 };
48
49 long double
rintl(long double x)50 rintl(long double x)
51 {
52 union IEEEl2bits u;
53 u_int32_t expsign;
54 int ex, sign;
55
56 u.e = x;
57 expsign = u.xbits.expsign;
58 ex = expsign & 0x7fff;
59
60 if (ex >= BIAS + LDBL_MANT_DIG - 1) {
61 if (ex == BIAS + LDBL_MAX_EXP)
62 return (x + x); /* Inf, NaN, or unsupported format */
63 return (x); /* finite and already an integer */
64 }
65 sign = expsign >> 15;
66
67 /*
68 * The following code assumes that intermediate results are
69 * evaluated in long double precision. If they are evaluated in
70 * greater precision, double rounding may occur, and if they are
71 * evaluated in less precision (as on i386), results will be
72 * wildly incorrect.
73 */
74 x += (long double)shift[sign];
75 x -= (long double)shift[sign];
76
77 /*
78 * If the result is +-0, then it must have the same sign as x, but
79 * the above calculation doesn't always give this. Fix up the sign.
80 */
81 if (ex < BIAS && x == 0.0L)
82 return ((long double)zero[sign]);
83
84 return (x);
85 }
86
87 /*
88 * We save and restore the floating-point environment to avoid raising
89 * an inexact exception. We can get away with using fesetenv()
90 * instead of feclearexcept()/feupdateenv() to restore the environment
91 * because the only exception defined for rint() is overflow, and
92 * rounding can't overflow as long as emax >= p.
93 */
94 long double
nearbyintl(long double x)95 nearbyintl(long double x)
96 {
97 long double ret;
98
99 if (isnan(x))
100 return x + x;
101 #if defined(FE_INEXACT) && !defined(PICOLIBC_DOUBLE_NOEXECPT)
102 fenv_t env;
103 fegetenv(&env);
104 #endif
105 ret = rintl(x);
106 #if defined(FE_INEXACT) && !defined(PICOLIBC_DOUBLE_NOEXECPT)
107 fesetenv(&env);
108 #endif
109 return (ret);
110 }
111
