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
12 /*
13 * ceill(x)
14 * Return x rounded toward -inf to integral value
15 * Method:
16 * Bit twiddling.
17 * Exception:
18 * Inexact flag raised if x not equal to ceill(x).
19 */
20
21 #include <float.h>
22 #include <math.h>
23 #include <stdint.h>
24
25 #include "fpmath.h"
26
27 #ifdef LDBL_IMPLICIT_NBIT
28 #define MANH_SIZE (LDBL_MANH_SIZE + 1)
29 #define INC_MANH(u, c) do { \
30 uint64_t o = u.bits.manh; \
31 u.bits.manh += (c); \
32 if (u.bits.manh < o) \
33 u.bits.exp++; \
34 } while (0)
35 #else
36 #define MANH_SIZE LDBL_MANH_SIZE
37 #define INC_MANH(u, c) do { \
38 uint64_t o = u.bits.manh; \
39 u.bits.manh += (c); \
40 if (u.bits.manh < o) { \
41 u.bits.exp++; \
42 u.bits.manh |= 1llu << (LDBL_MANH_SIZE - 1); \
43 } \
44 } while (0)
45 #endif
46
47 static const long double huge = 1.0e300;
48
49 long double
ceill(long double x)50 ceill(long double x)
51 {
52 union IEEEl2bits u = { .e = x };
53 int e = u.bits.exp - LDBL_MAX_EXP + 1;
54
55 if (e < MANH_SIZE - 1) {
56 if (e < 0) { /* raise inexact if x != 0 */
57 if (huge + x > 0.0)
58 if (u.bits.exp > 0 ||
59 (u.bits.manh | u.bits.manl) != 0)
60 u.e = u.bits.sign ? -0.0 : 1.0;
61 } else {
62 uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
63 if (((u.bits.manh & m) | u.bits.manl) == 0)
64 return (x); /* x is integral */
65 if (!u.bits.sign) {
66 #ifdef LDBL_IMPLICIT_NBIT
67 if (e == 0)
68 u.bits.exp++;
69 else
70 #endif
71 INC_MANH(u, 1llu << (MANH_SIZE - e - 1));
72 }
73 if (huge + x > 0.0) { /* raise inexact flag */
74 u.bits.manh &= ~m;
75 u.bits.manl = 0;
76 }
77 }
78 } else if (e < LDBL_MANT_DIG - 1) {
79 uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
80 if ((u.bits.manl & m) == 0)
81 return (x); /* x is integral */
82 if (!u.bits.sign) {
83 if (e == MANH_SIZE - 1)
84 INC_MANH(u, 1);
85 else {
86 uint64_t o = u.bits.manl;
87 u.bits.manl += 1llu << (LDBL_MANT_DIG - e - 1);
88 if (u.bits.manl < o) /* got a carry */
89 INC_MANH(u, 1);
90 }
91 }
92 if (huge + x > 0.0) /* raise inexact flag */
93 u.bits.manl &= ~m;
94 }
95 return (u.e);
96 }
97