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