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_ceil.c 5.1 93/09/24
12 */
13
14#include <sys/cdefs.h>
15__RCSID("$NetBSD$");
16#if 0
17__FBSDID("$FreeBSD: head/lib/msun/src/s_ceill.c 176280 2008-02-14 15:10:34Z bde $");
18#endif
19
20/*
21 * ceill(x)
22 * Return x rounded toward -inf to integral value
23 * Method:
24 *	Bit twiddling.
25 * Exception:
26 *	Inexact flag raised if x not equal to ceill(x).
27 */
28#include "namespace.h"
29
30#include <float.h>
31#include <math.h>
32#include <stdint.h>
33#include <machine/ieee.h>
34
35#ifdef __HAVE_LONG_DOUBLE
36
37#ifdef __weak_alias
38__weak_alias(ceill, _ceill)
39#endif
40
41#ifdef LDBL_IMPLICIT_NBIT
42#define	MANH_SIZE	(EXT_FRACHBITS + 1)
43#define	INC_MANH(ux, c)	do {					\
44	uint64_t oi = ux.extu_frach;				\
45	ux.extu_frach += (c);					\
46	if (ux.extu_frach < oi)					\
47		ux.extu_exp++;					\
48} while (0)
49#else
50#define	MANH_SIZE	EXT_FRACHBITS
51#define	INC_MANH(ux, c)	do {					\
52	uint64_t oi = ux.extu_frach;				\
53	ux.extu_frach += (c);					\
54	if (ux.extu_frach < oi) {				\
55		ux.extu_exp++;					\
56		ux.extu_frach |= 1llu << (EXT_FRACHBITS - 1);	\
57	}							\
58} while (0)
59#endif
60
61static const long double huge = 1.0e300;
62
63long double
64ceill(long double x)
65{
66	union ieee_ext_u ux = { .extu_ld = x, };
67	int e = ux.extu_exp - LDBL_MAX_EXP + 1;
68
69	if (e < MANH_SIZE - 1) {
70		if (e < 0) {			/* raise inexact if x != 0 */
71			if (huge + x > 0.0)
72				if (ux.extu_exp > 0 ||
73				    (ux.extu_frach | ux.extu_fracl) != 0)
74					ux.extu_ld = ux.extu_sign ? -0.0 : 1.0;
75		} else {
76			uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1);
77			if (((ux.extu_frach & m) | ux.extu_fracl) == 0)
78				return (x);	/* x is integral */
79			if (!ux.extu_sign) {
80#ifdef LDBL_IMPLICIT_NBIT
81				if (e == 0)
82					ux.extu_exp++;
83				else
84#endif
85				INC_MANH(ux, 1llu << (MANH_SIZE - e - 1));
86			}
87			if (huge + x > 0.0) {	/* raise inexact flag */
88				ux.extu_frach &= ~m;
89				ux.extu_fracl = 0;
90			}
91		}
92	} else if (e < LDBL_MANT_DIG - 1) {
93		uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1);
94		if ((ux.extu_fracl & m) == 0)
95			return (x);	/* x is integral */
96		if (!ux.extu_sign) {
97			if (e == MANH_SIZE - 1)
98				INC_MANH(ux, 1);
99			else {
100				uint64_t o = ux.extu_fracl;
101				ux.extu_fracl += 1llu << (LDBL_MANT_DIG - e - 1);
102				if (ux.extu_fracl < o)	/* got a carry */
103					INC_MANH(ux, 1);
104			}
105		}
106		if (huge + x > 0.0)		/* raise inexact flag */
107			ux.extu_fracl &= ~m;
108	}
109	return (ux.extu_ld);
110}
111
112#endif /* __HAVE_LONG_DOUBLE */
113