1 .\" Copyright (c) 1993 Andrew Moore, Talke Studio
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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 $
43 .Nd IEEE floating point interface
50 FP_RN, /* round to nearest */
51 FP_RM, /* round down to minus infinity */
52 FP_RP, /* round up to plus infinity */
59 .Fn fpsetround "fp_rnd_t direction"
62 FP_PS, /* 24 bit (single-precision) */
63 FP_PRS, /* reserved */
64 FP_PD, /* 53 bit (double-precision) */
65 FP_PE /* 64 bit (extended-precision) */
71 .Fn fpsetprec "fp_prec_t precision"
73 #define fp_except_t int
74 #define FP_X_INV 0x01 /* invalid operation */
75 #define FP_X_DNML 0x02 /* denormal */
76 #define FP_X_DZ 0x04 /* zero divide */
77 #define FP_X_OFL 0x08 /* overflow */
78 #define FP_X_UFL 0x10 /* underflow */
79 #define FP_X_IMP 0x20 /* (im)precision */
80 #define FP_X_STK 0x40 /* stack fault */
85 .Fn fpsetmask "fp_except_t mask"
89 .Fn fpresetsticky "fp_except_t sticky"
91 The routines described herein are deprecated.
92 New code should use the functionality provided by
95 When a floating point exception is detected, the exception sticky flag is
96 set and the exception mask is tested.
97 If the mask is set, then a trap occurs.
98 These routines allow both setting the floating point exception
99 masks, and resetting the exception sticky flags after an exception is
101 In addition, they allow setting the floating point rounding mode
107 returns the current floating point rounding mode.
112 sets the floating point rounding mode and returns
118 returns the current floating point precision.
123 sets the floating point precision and returns
124 the previous precision.
129 returns the current floating point exception masks.
134 sets the floating point exception masks and returns the
140 returns the current floating point sticky flags.
145 clears the floating point sticky flags and returns
148 Sample code which prevents a trap on divide-by-zero:
149 .Bd -literal -offset indent
154 fpresetsticky(FP_X_DZ);
157 .Sh IMPLEMENTATION NOTES
162 functions provide functionality unavailable on many platforms.
163 At present, they are implemented only on the x86_64 platform.
164 Changing precision is not a supported feature:
165 it may be ineffective when code is compiled to take advantage of SSE,
166 and many library functions and compiler optimizations depend upon the
167 default precision for correct behavior.
172 These routines are based on SysV/386 routines of the same name.
174 After a floating point exception and before a mask is set, the sticky
176 If another exception occurs before the sticky
177 flags are reset, then a wrong exception type may be signaled.