xref: /dragonfly/share/man/man3/fpgetround.3 (revision 0600465e) 
1.\" Copyright (c) 1993 Andrew Moore, Talke Studio
2.\" All rights reserved.
3.\"
4.\" Redistribution and use in source and binary forms, with or without
5.\" modification, are permitted provided that the following conditions
6.\" are met:
7.\" 1. Redistributions of source code must retain the above copyright
8.\"    notice, this list of conditions and the following disclaimer.
9.\" 2. Redistributions in binary form must reproduce the above copyright
10.\"    notice, this list of conditions and the following disclaimer in the
11.\"    documentation and/or other materials provided with the distribution.
12.\" 3. Neither the name of the University nor the names of its contributors
13.\"    may be used to endorse or promote products derived from this software
14.\"    without specific prior written permission.
15.\"
16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26.\" SUCH DAMAGE.
27.\"
28.\"     @(#)fpgetround.3	1.0 (Berkeley) 9/23/93
29.\" $FreeBSD: src/share/man/man3/fpgetround.3,v 1.20 2013/04/12 00:37:30 svnexp Exp $
30.\"
31.Dd August 9, 2018
32.Dt FPGETROUND 3
33.Os
34.Sh NAME
35.Nm fpgetround ,
36.Nm fpsetround ,
37.Nm fpsetprec ,
38.Nm fpgetprec ,
39.Nm fpgetmask ,
40.Nm fpsetmask ,
41.Nm fpgetsticky
42.Nd IEEE floating point interface
43.Sh LIBRARY
44.Lb libc
45.Sh SYNOPSIS
46.In ieeefp.h
47.Bd -literal
48typedef enum {
49	FP_RN,		/* round to nearest */
50	FP_RM,		/* round down to minus infinity */
51	FP_RP,		/* round up to plus infinity */
52	FP_RZ		/* truncate */
53} fp_rnd_t;
54.Ed
55.Ft fp_rnd_t
56.Fn fpgetround void
57.Ft fp_rnd_t
58.Fn fpsetround "fp_rnd_t direction"
59.Bd -literal
60typedef enum {
61	FP_PS,		/* 24 bit (single-precision) */
62	FP_PRS,		/* reserved */
63	FP_PD,		/* 53 bit (double-precision) */
64	FP_PE		/* 64 bit (extended-precision) */
65} fp_prec_t;
66.Ed
67.Ft fp_prec_t
68.Fn fpgetprec void
69.Ft fp_prec_t
70.Fn fpsetprec "fp_prec_t precision"
71.Bd -literal
72#define fp_except_t	int
73#define FP_X_INV	0x01	/* invalid operation */
74#define FP_X_DNML	0x02	/* denormal */
75#define FP_X_DZ		0x04	/* zero divide */
76#define FP_X_OFL	0x08	/* overflow */
77#define FP_X_UFL	0x10	/* underflow */
78#define FP_X_IMP	0x20	/* (im)precision */
79#define FP_X_STK	0x40	/* stack fault */
80.Ed
81.Ft fp_except_t
82.Fn fpgetmask void
83.Ft fp_except_t
84.Fn fpsetmask "fp_except_t mask"
85.Ft fp_except_t
86.Fn fpgetsticky void
87.Sh DESCRIPTION
88The routines described herein are deprecated.
89New code should use the functionality provided by
90.Fn fe*
91functions in the
92.Lb libm .
93.Pp
94When a floating point exception is detected, the exception sticky flag is
95set and the exception mask is tested.
96If the mask is set, then a trap occurs.
97These routines allow both setting the floating point exception
98masks, and resetting the exception sticky flags after an exception is
99detected.
100In addition, they allow setting the floating point rounding mode
101and precision.
102.Pp
103The
104.Fn fpgetround
105function
106returns the current floating point rounding mode.
107.Pp
108The
109.Fn fpsetround
110function
111sets the floating point rounding mode and returns
112the previous mode.
113.Pp
114The
115.Fn fpgetprec
116function
117returns the current floating point precision.
118.Pp
119The
120.Fn fpsetprec
121function
122sets the floating point precision and returns
123the previous precision.
124.Pp
125The
126.Fn fpgetmask
127function
128returns the current floating point exception masks.
129.Pp
130The
131.Fn fpsetmask
132function
133sets the floating point exception masks and returns the
134previous masks.
135.Pp
136The
137.Fn fpgetsticky
138function
139returns the current floating point sticky flags.
140.Sh IMPLEMENTATION NOTES
141The
142.Fn fpgetprec
143and
144.Fn fpsetprec
145functions provide functionality unavailable on many platforms.
146At present, they are implemented only on the x86_64 platform.
147Changing precision is not a supported feature:
148it may be ineffective when code is compiled to take advantage of SSE,
149and many library functions and compiler optimizations depend upon the
150default precision for correct behavior.
151.Sh SEE ALSO
152.Xr feclearexcept 3 ,
153.Xr feenableexcept 3 ,
154.Xr fegetenv 3 ,
155.Xr fegetround 3 ,
156.Xr isnan 3
157.Sh HISTORY
158These routines are based on SysV/386 routines of the same name.
159.Sh CAVEATS
160After a floating point exception and before a mask is set, the sticky
161flags must be reset.
162If another exception occurs before the sticky
163flags are reset, then a wrong exception type may be signaled.
164