1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22/*
23 * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
24 */
25/*
26 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
27 * Use is subject to license terms.
28 */
29
30#pragma weak nearbyintf = __nearbyintf
31
32#include "libm.h"
33#include <fenv.h>
34
35float
36__nearbyintf(float x) {
37	union {
38		unsigned i;
39		float f;
40	} xx;
41	unsigned hx, sx, i, frac;
42	int rm;
43
44	xx.f = x;
45	sx = xx.i & 0x80000000;
46	hx = xx.i & ~0x80000000;
47
48	/* handle trivial cases */
49	if (hx >= 0x4b000000) {	/* x is nan, inf, or already integral */
50		if (hx > 0x7f800000)	/* x is nan */
51			return (x * x);		/* + -> * for Cheetah */
52		return (x);
53	} else if (hx == 0)		/* x is zero */
54		return (x);
55
56	/* get the rounding mode */
57	rm = fegetround();
58
59	/* flip the sense of directed roundings if x is negative */
60	if (sx && (rm == FE_UPWARD || rm == FE_DOWNWARD))
61		rm = (FE_UPWARD + FE_DOWNWARD) - rm;
62
63	/* handle |x| < 1 */
64	if (hx < 0x3f800000) {
65		if (rm == FE_UPWARD || (rm == FE_TONEAREST && hx > 0x3f000000))
66			xx.i = sx | 0x3f800000;
67		else
68			xx.i = sx;
69		return (xx.f);
70	}
71
72	/* round x at the integer bit */
73	i = 1 << (0x96 - (hx >> 23));
74	frac = hx & (i - 1);
75	if (!frac)
76		return (x);
77
78	hx &= ~(i - 1);
79	if (rm == FE_UPWARD || (rm == FE_TONEAREST && (frac > (i >> 1) ||
80		((frac == (i >> 1)) && (hx & i)))))
81		xx.i = sx | (hx + i);
82	else
83		xx.i = sx | hx;
84	return (xx.f);
85}
86
87#if 0
88
89/*
90 * Alternate implementations for SPARC, x86, using fp ops.  These may
91 * be faster depending on how expensive saving and restoring the fp
92 * modes and status flags is.
93 */
94
95#include "libm.h"
96#include "fma.h"
97
98#if defined(__sparc)
99
100float
101__nearbyintf(float x) {
102	union {
103		unsigned i;
104		float f;
105	} xx, yy;
106	float z;
107	unsigned hx, sx, fsr, oldfsr;
108	int rm;
109
110	xx.f = x;
111	sx = xx.i & 0x80000000;
112	hx = xx.i & ~0x80000000;
113
114	/* handle trivial cases */
115	if (hx >= 0x4b000000)	/* x is nan, inf, or already integral */
116		return (x + 0.0f);
117	else if (hx == 0)	/* x is zero */
118		return (x);
119
120	/* save the fsr */
121	__fenv_getfsr(&oldfsr);
122
123	/* handle |x| < 1 */
124	if (hx < 0x3f800000) {
125		/* flip the sense of directed roundings if x is negative */
126		rm = oldfsr >> 30;
127		if (sx)
128			rm ^= rm >> 1;
129		if (rm == FSR_RP || (rm == FSR_RN && hx > 0x3f000000))
130			xx.i = sx | 0x3f800000;
131		else
132			xx.i = sx;
133		return (xx.f);
134	}
135
136	/* clear the inexact trap */
137	fsr = oldfsr & ~FSR_NXM;
138	__fenv_setfsr(&fsr);
139
140	/* round x at the integer bit */
141	yy.i = sx | 0x4b000000;
142	z = (x + yy.f) - yy.f;
143
144	/* restore the old fsr */
145	__fenv_setfsr(&oldfsr);
146
147	return (z);
148}
149
150#elif defined(__x86)
151
152/* inline template */
153extern long double frndint(long double);
154
155float
156__nearbyintf(float x) {
157	long double z;
158	unsigned oldcwsw, cwsw;
159
160	/* save the control and status words, mask the inexact exception */
161	__fenv_getcwsw(&oldcwsw);
162	cwsw = oldcwsw | 0x00200000;
163	__fenv_setcwsw(&cwsw);
164
165	z = frndint((long double) x);
166
167	/*
168	 * restore the control and status words, preserving all but the
169	 * inexact flag
170	 */
171	__fenv_getcwsw(&cwsw);
172	oldcwsw |= (cwsw & 0x1f);
173	__fenv_setcwsw(&oldcwsw);
174
175	/* note: the value of z is representable in single precision */
176	return (z);
177}
178
179#else
180#error Unknown architecture
181#endif
182
183#endif
184