1 /* ieee-utils/fp-tru64.c
2 *
3 * Copyright (C) 1996, 1997, 1998, 1999, 2000 Tim Mooney
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 3 of the License, or (at
8 * your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
18 */
19
20
21 /*
22 * Under Compaq's Unix with the silly name, read the man pages for read_rnd,
23 * write_rnd, and ieee(3) for more information on the functions used here.
24 *
25 * Note that enabling control of dynamic rounding mode (via write_rnd) requires
26 * that you pass a special flag to your C compiler. For Compaq's C compiler
27 * the flag is `-fprm d', for gcc it's `-mfp-rounding-mode=d'.
28 *
29 * Enabling the trap control (via ieee_set_fp_control) also requires a
30 * flag be passed to the C compiler. The flag for Compaq's C compiler
31 * is `-ieee' and for gcc it's `-mieee'.
32
33 * We have not implemented the `inexact' case, since it is rarely used
34 * and requires the library being built with an additional compiler
35 * flag that can degrade performance for everything else. If you need
36 * to add support for `inexact' the relevant flag for Compaq's
37 * compiler is `-ieee_with_inexact', and the flag for gcc is
38 * `-mieee-with-inexact'.
39 *
40 * Problem have been reported with the "fixed" float.h installed with
41 * gcc-2.95 lacking some of the definitions in the system float.h (the
42 * symptoms are errors like: `FP_RND_RN' undeclared). To work around
43 * this we can include the system float.h before the gcc version, e.g.
44 *
45 * #include "/usr/include/float.h"
46 * #include <float.h>
47 */
48
49 #include <float.h>
50
51 #ifndef FP_RND_RN
52 # undef _FLOAT_H_
53 # include "/usr/include/float.h"
54 # undef _FLOAT_H_
55 # include <float.h>
56 #endif
57
58 #include <machine/fpu.h>
59 #include <stdio.h>
60 #include <gsl/gsl_ieee_utils.h>
61 #include <gsl/gsl_errno.h>
62
63 int
gsl_ieee_set_mode(int precision,int rounding,int exception_mask)64 gsl_ieee_set_mode (int precision, int rounding, int exception_mask)
65 {
66 unsigned long int mode = 0 ;
67 unsigned int rnd = 0 ;
68
69 /* I'm actually not completely sure that the alpha only supports default
70 * precisions rounding, but I couldn't find any information regarding this, so
71 * it seems safe to assume this for now until it's proven otherwise.
72 */
73
74 switch (precision)
75 {
76 case GSL_IEEE_SINGLE_PRECISION:
77 GSL_ERROR ("Tru64 Unix on the alpha only supports default precision rounding",
78 GSL_EUNSUP) ;
79 break ;
80 case GSL_IEEE_DOUBLE_PRECISION:
81 GSL_ERROR ("Tru64 Unix on the alpha only supports default precision rounding",
82 GSL_EUNSUP) ;
83 break ;
84 case GSL_IEEE_EXTENDED_PRECISION:
85 GSL_ERROR ("Tru64 Unix on the alpha only supports default precision rounding",
86 GSL_EUNSUP) ;
87 break ;
88 }
89
90
91 switch (rounding)
92 {
93 case GSL_IEEE_ROUND_TO_NEAREST:
94 rnd = FP_RND_RN ;
95 write_rnd (rnd) ;
96 break ;
97 case GSL_IEEE_ROUND_DOWN:
98 rnd = FP_RND_RM ;
99 write_rnd (rnd) ;
100 break ;
101 case GSL_IEEE_ROUND_UP:
102 rnd = FP_RND_RP ;
103 write_rnd (rnd) ;
104 break ;
105 case GSL_IEEE_ROUND_TO_ZERO:
106 rnd = FP_RND_RZ ;
107 write_rnd (rnd) ;
108 break ;
109 default:
110 rnd = FP_RND_RN ;
111 write_rnd (rnd) ;
112 }
113
114 /* Turn on all the exceptions apart from 'inexact' */
115
116 /* from the ieee(3) man page:
117 * IEEE_TRAP_ENABLE_INV -> Invalid operation
118 * IEEE_TRAP_ENABLE_DZE -> Divide by 0
119 * IEEE_TRAP_ENABLE_OVF -> Overflow
120 * IEEE_TRAP_ENABLE_UNF -> Underflow
121 * IEEE_TRAP_ENABLE_INE -> Inexact (requires special option to C compiler)
122 * IEEE_TRAP_ENABLE_DNO -> denormal operand
123 * Note: IEEE_TRAP_ENABLE_DNO is not supported on OSF 3.x or Digital Unix
124 * 4.0 - 4.0d(?).
125 * IEEE_TRAP_ENABLE_MASK -> mask of all the trap enables
126 * IEEE_MAP_DMZ -> map denormal inputs to zero
127 * IEEE_MAP_UMZ -> map underflow results to zero
128 */
129
130 mode = IEEE_TRAP_ENABLE_INV | IEEE_TRAP_ENABLE_DZE | IEEE_TRAP_ENABLE_OVF
131 | IEEE_TRAP_ENABLE_UNF ;
132
133 if (exception_mask & GSL_IEEE_MASK_INVALID)
134 mode &= ~ IEEE_TRAP_ENABLE_INV ;
135
136 if (exception_mask & GSL_IEEE_MASK_DENORMALIZED)
137 {
138 #ifdef IEEE_TRAP_ENABLE_DNO
139 mode &= ~ IEEE_TRAP_ENABLE_DNO ;
140 #else
141 GSL_ERROR ("Sorry, this version of Digital Unix does not support denormalized operands", GSL_EUNSUP) ;
142 #endif
143 }
144
145 if (exception_mask & GSL_IEEE_MASK_DIVISION_BY_ZERO)
146 mode &= ~ IEEE_TRAP_ENABLE_DZE ;
147
148 if (exception_mask & GSL_IEEE_MASK_OVERFLOW)
149 mode &= ~ IEEE_TRAP_ENABLE_OVF ;
150
151 if (exception_mask & GSL_IEEE_MASK_UNDERFLOW)
152 mode &= ~ IEEE_TRAP_ENABLE_UNF ;
153
154 if (exception_mask & GSL_IEEE_TRAP_INEXACT)
155 {
156 /* To implement this would require a special flag to the C
157 compiler which can cause degraded performance */
158
159 GSL_ERROR ("Sorry, GSL does not implement trap-inexact for Tru64 Unix on the alpha - see fp-tru64.c for details", GSL_EUNSUP) ;
160
161 /* In case you need to add it, the appropriate line would be
162 *
163 * mode |= IEEE_TRAP_ENABLE_INE ;
164 *
165 */
166
167 }
168 else
169 {
170 mode &= ~ IEEE_TRAP_ENABLE_INE ;
171 }
172
173 ieee_set_fp_control (mode) ;
174
175 return GSL_SUCCESS ;
176 }
177