1 /* $NetBSD: lrintf.c,v 1.6 2015/07/09 06:17:13 nat Exp $ */
2
3 /*-
4 * Copyright (c) 2004
5 * Matthias Drochner. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <math.h>
30 #include <sys/ieee754.h>
31 #include <machine/limits.h>
32 #include "math_private.h"
33
34 #ifndef LRINTNAME
35 #define LRINTNAME lrintf
36 #define RESTYPE long int
37 #define RESTYPE_MIN LONG_MIN
38 #define RESTYPE_MAX LONG_MAX
39 #endif
40
41 #define RESTYPE_BITS (sizeof(RESTYPE) * 8)
42
43 static const float
44 TWO23[2]={
45 8.3886080000e+06, /* 0x4b000000 */
46 -8.3886080000e+06, /* 0xcb000000 */
47 };
48
49 RESTYPE
LRINTNAME(float x)50 LRINTNAME(float x)
51 {
52 u_int32_t i0;
53 int e, s, shift;
54 RESTYPE res;
55 #ifdef __i386__ /* XXX gcc4 will omit the rounding otherwise */
56 volatile
57 #endif
58 float w;
59
60 GET_FLOAT_WORD(i0, x);
61 e = i0 >> SNG_FRACBITS;
62 s = (uint32_t)e >> SNG_EXPBITS;
63 e = (e & 0xff) - SNG_EXP_BIAS;
64
65 /* 1.0 x 2^-1 is the smallest number which can be rounded to 1 */
66 if (e < -1)
67 return (0);
68 /* 1.0 x 2^31 (or 2^63) is already too large */
69 if (e >= (int)RESTYPE_BITS - 1)
70 return (s ? RESTYPE_MIN : RESTYPE_MAX); /* ??? unspecified */
71
72 /* >= 2^23 is already an exact integer */
73 if (e < SNG_FRACBITS) {
74 /* round, using current direction */
75 w = TWO23[s] + x;
76 x = w - TWO23[s];
77 } else
78 return x;
79
80 GET_FLOAT_WORD(i0, x);
81 e = ((i0 >> SNG_FRACBITS) & 0xff) - SNG_EXP_BIAS;
82 i0 &= 0x7fffff;
83 i0 |= (1 << SNG_FRACBITS);
84
85 shift = e - SNG_FRACBITS;
86 if (shift >=0)
87 res = (shift < 32 ? (RESTYPE)i0 << shift : 0);
88 else
89 res = (shift > -32 ? i0 >> -shift : 0);
90
91 return (s ? -res : res);
92 }
93