1 /*
2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 *
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
8 * is preserved.
9 * ====================================================
10 *
11 * From: @(#)s_floor.c 5.1 93/09/24
12 */
13
14 #include <sys/cdefs.h>
15 __FBSDID("$FreeBSD$");
16
17 /*
18 * floorl(x)
19 * Return x rounded toward -inf to integral value
20 * Method:
21 * Bit twiddling.
22 * Exception:
23 * Inexact flag raised if x not equal to floorl(x).
24 */
25
26 #include <float.h>
27 #include <math.h>
28 #include <stdint.h>
29
30 #include "fpmath.h"
31
32 #ifdef LDBL_IMPLICIT_NBIT
33 #define MANH_SIZE (LDBL_MANH_SIZE + 1)
34 #define INC_MANH(u, c) do { \
35 uint64_t o = u.bits.manh; \
36 u.bits.manh += (c); \
37 if (u.bits.manh < o) \
38 u.bits.exp++; \
39 } while (0)
40 #else
41 #define MANH_SIZE LDBL_MANH_SIZE
42 #define INC_MANH(u, c) do { \
43 uint64_t o = u.bits.manh; \
44 u.bits.manh += (c); \
45 if (u.bits.manh < o) { \
46 u.bits.exp++; \
47 u.bits.manh |= 1llu << (LDBL_MANH_SIZE - 1); \
48 } \
49 } while (0)
50 #endif
51
52 static const long double huge = 1.0e300;
53
54 long double
floorl(long double x)55 floorl(long double x)
56 {
57 union IEEEl2bits u = { .e = x };
58 int e = u.bits.exp - LDBL_MAX_EXP + 1;
59
60 if (e < MANH_SIZE - 1) {
61 if (e < 0) { /* raise inexact if x != 0 */
62 if (huge + x > 0.0)
63 if (u.bits.exp > 0 ||
64 (u.bits.manh | u.bits.manl) != 0)
65 u.e = u.bits.sign ? -1.0 : 0.0;
66 } else {
67 uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
68 if (((u.bits.manh & m) | u.bits.manl) == 0)
69 return (x); /* x is integral */
70 if (u.bits.sign) {
71 #ifdef LDBL_IMPLICIT_NBIT
72 if (e == 0)
73 u.bits.exp++;
74 else
75 #endif
76 INC_MANH(u, 1llu << (MANH_SIZE - e - 1));
77 }
78 if (huge + x > 0.0) { /* raise inexact flag */
79 u.bits.manh &= ~m;
80 u.bits.manl = 0;
81 }
82 }
83 } else if (e < LDBL_MANT_DIG - 1) {
84 uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
85 if ((u.bits.manl & m) == 0)
86 return (x); /* x is integral */
87 if (u.bits.sign) {
88 if (e == MANH_SIZE - 1)
89 INC_MANH(u, 1);
90 else {
91 uint64_t o = u.bits.manl;
92 u.bits.manl += 1llu << (LDBL_MANT_DIG - e - 1);
93 if (u.bits.manl < o) /* got a carry */
94 INC_MANH(u, 1);
95 }
96 }
97 if (huge + x > 0.0) /* raise inexact flag */
98 u.bits.manl &= ~m;
99 }
100 return (u.e);
101 }
102