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 /*
16 * floorl(x)
17 * Return x rounded toward -inf to integral value
18 * Method:
19 * Bit twiddling.
20 * Exception:
21 * Inexact flag raised if x not equal to floorl(x).
22 */
23
24 #include <float.h>
25 #include <math.h>
26 #include <stdint.h>
27
28 #include "fpmath.h"
29
30 #ifdef LDBL_IMPLICIT_NBIT
31 #define MANH_SIZE (LDBL_MANH_SIZE + 1)
32 #define INC_MANH(u, c) do { \
33 uint64_t o = u.bits.manh; \
34 u.bits.manh += (c); \
35 if (u.bits.manh < o) \
36 u.bits.exp++; \
37 } while (0)
38 #else
39 #define MANH_SIZE LDBL_MANH_SIZE
40 #define INC_MANH(u, c) do { \
41 uint64_t o = u.bits.manh; \
42 u.bits.manh += (c); \
43 if (u.bits.manh < o) { \
44 u.bits.exp++; \
45 u.bits.manh |= 1llu << (LDBL_MANH_SIZE - 1); \
46 } \
47 } while (0)
48 #endif
49
50 static const long double huge = 1.0e300;
51
52 long double
floorl(long double x)53 floorl(long double x)
54 {
55 union IEEEl2bits u = { .e = x };
56 int e = u.bits.exp - LDBL_MAX_EXP + 1;
57
58 if (e < MANH_SIZE - 1) {
59 if (e < 0) { /* raise inexact if x != 0 */
60 if (huge + x > 0.0)
61 if (u.bits.exp > 0 ||
62 (u.bits.manh | u.bits.manl) != 0)
63 u.e = u.bits.sign ? -1.0 : 0.0;
64 } else {
65 uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
66 if (((u.bits.manh & m) | u.bits.manl) == 0)
67 return (x); /* x is integral */
68 if (u.bits.sign) {
69 #ifdef LDBL_IMPLICIT_NBIT
70 if (e == 0)
71 u.bits.exp++;
72 else
73 #endif
74 INC_MANH(u, 1llu << (MANH_SIZE - e - 1));
75 }
76 if (huge + x > 0.0) { /* raise inexact flag */
77 u.bits.manh &= ~m;
78 u.bits.manl = 0;
79 }
80 }
81 } else if (e < LDBL_MANT_DIG - 1) {
82 uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
83 if ((u.bits.manl & m) == 0)
84 return (x); /* x is integral */
85 if (u.bits.sign) {
86 if (e == MANH_SIZE - 1)
87 INC_MANH(u, 1);
88 else {
89 uint64_t o = u.bits.manl;
90 u.bits.manl += 1llu << (LDBL_MANT_DIG - e - 1);
91 if (u.bits.manl < o) /* got a carry */
92 INC_MANH(u, 1);
93 }
94 }
95 if (huge + x > 0.0) /* raise inexact flag */
96 u.bits.manl &= ~m;
97 }
98 return (u.e);
99 }
100