xref: /freebsd/sys/i386/include/ieeefp.h (revision 52267f7411adcc76ede961420e08c0e42f42d415)
1 /*-
2  * Copyright (c) 2003 Peter Wemm.
3  * Copyright (c) 1990 Andrew Moore, Talke Studio
4  * All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  * 3. All advertising materials mentioning features or use of this software
15  *    must display the following acknowledgement:
16  *	This product includes software developed by the University of
17  *	California, Berkeley and its contributors.
18  * 4. Neither the name of the University nor the names of its contributors
19  *    may be used to endorse or promote products derived from this software
20  *    without specific prior written permission.
21  *
22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32  * SUCH DAMAGE.
33  *
34  * 	from: @(#) ieeefp.h 	1.0 (Berkeley) 9/23/93
35  * $FreeBSD$
36  */
37 
38 #ifndef _MACHINE_IEEEFP_H_
39 #define _MACHINE_IEEEFP_H_
40 
41 /*
42  * IEEE floating point type, constant and function definitions.
43  * XXX: FP*FLD and FP*OFF are undocumented pollution.
44  */
45 
46 #ifndef _SYS_CDEFS_H_
47 #error this file needs sys/cdefs.h as a prerequisite
48 #endif
49 
50 /*
51  * Rounding modes.
52  */
53 typedef enum {
54 	FP_RN=0,	/* round to nearest */
55 	FP_RM,		/* round down towards minus infinity */
56 	FP_RP,		/* round up towards plus infinity */
57 	FP_RZ		/* truncate */
58 } fp_rnd_t;
59 
60 /*
61  * Precision (i.e., rounding precision) modes.
62  */
63 typedef enum {
64 	FP_PS=0,	/* 24 bit (single-precision) */
65 	FP_PRS,		/* reserved */
66 	FP_PD,		/* 53 bit (double-precision) */
67 	FP_PE		/* 64 bit (extended-precision) */
68 } fp_prec_t;
69 
70 #define fp_except_t	int
71 
72 /*
73  * Exception bit masks.
74  */
75 #define FP_X_INV	0x01	/* invalid operation */
76 #define FP_X_DNML	0x02	/* denormal */
77 #define FP_X_DZ		0x04	/* zero divide */
78 #define FP_X_OFL	0x08	/* overflow */
79 #define FP_X_UFL	0x10	/* underflow */
80 #define FP_X_IMP	0x20	/* (im)precision */
81 #define FP_X_STK	0x40	/* stack fault */
82 
83 /*
84  * FPU control word bit-field masks.
85  */
86 #define FP_MSKS_FLD	0x3f	/* exception masks field */
87 #define FP_PRC_FLD	0x300	/* precision control field */
88 #define	FP_RND_FLD	0xc00	/* rounding control field */
89 
90 /*
91  * FPU status word bit-field masks.
92  */
93 #define FP_STKY_FLD	0x3f	/* sticky flags field */
94 
95 /*
96  * FPU control word bit-field offsets (shift counts).
97  */
98 #define FP_MSKS_OFF	0	/* exception masks offset */
99 #define FP_PRC_OFF	8	/* precision control offset */
100 #define	FP_RND_OFF	10	/* rounding control offset */
101 
102 /*
103  * FPU status word bit-field offsets (shift counts).
104  */
105 #define FP_STKY_OFF	0	/* sticky flags offset */
106 
107 #ifdef __GNUCLIKE_ASM
108 
109 #define	__fldcw(addr)	__asm __volatile("fldcw %0" : : "m" (*(addr)))
110 #define	__fldenv(addr)	__asm __volatile("fldenv %0" : : "m" (*(addr)))
111 #define	__fnclex()	__asm __volatile("fnclex")
112 #define	__fnstcw(addr)	__asm __volatile("fnstcw %0" : "=m" (*(addr)))
113 #define	__fnstenv(addr)	__asm __volatile("fnstenv %0" : "=m" (*(addr)))
114 #define	__fnstsw(addr)	__asm __volatile("fnstsw %0" : "=m" (*(addr)))
115 
116 /*
117  * Load the control word.  Be careful not to trap if there is a currently
118  * unmasked exception (ones that will become freshly unmasked are not a
119  * problem).  This case must be handled by a save/restore of the
120  * environment or even of the full x87 state.  Accessing the environment
121  * is very inefficient, so only do it when necessary.
122  */
123 static __inline void
124 __fnldcw(unsigned short _cw, unsigned short _newcw)
125 {
126 	struct {
127 		unsigned _cw;
128 		unsigned _other[6];
129 	} _env;
130 	unsigned short _sw;
131 
132 	if ((_cw & FP_MSKS_FLD) != FP_MSKS_FLD) {
133 		__fnstsw(&_sw);
134 		if (((_sw & ~_cw) & FP_STKY_FLD) != 0) {
135 			__fnstenv(&_env);
136 			_env._cw = _newcw;
137 			__fldenv(&_env);
138 			return;
139 		}
140 	}
141 	__fldcw(&_newcw);
142 }
143 
144 static __inline fp_rnd_t
145 fpgetround(void)
146 {
147 	unsigned short _cw;
148 
149 	__fnstcw(&_cw);
150 	return ((fp_rnd_t)((_cw & FP_RND_FLD) >> FP_RND_OFF));
151 }
152 
153 static __inline fp_rnd_t
154 fpsetround(fp_rnd_t _m)
155 {
156 	fp_rnd_t _p;
157 	unsigned short _cw, _newcw;
158 
159 	__fnstcw(&_cw);
160 	_p = (fp_rnd_t)((_cw & FP_RND_FLD) >> FP_RND_OFF);
161 	_newcw = _cw & ~FP_RND_FLD;
162 	_newcw |= (_m << FP_RND_OFF) & FP_RND_FLD;
163 	__fnldcw(_cw, _newcw);
164 	return (_p);
165 }
166 
167 static __inline fp_prec_t
168 fpgetprec(void)
169 {
170 	unsigned short _cw;
171 
172 	__fnstcw(&_cw);
173 	return ((fp_prec_t)((_cw & FP_PRC_FLD) >> FP_PRC_OFF));
174 }
175 
176 static __inline fp_prec_t
177 fpsetprec(fp_prec_t _m)
178 {
179 	fp_prec_t _p;
180 	unsigned short _cw, _newcw;
181 
182 	__fnstcw(&_cw);
183 	_p = (fp_prec_t)((_cw & FP_PRC_FLD) >> FP_PRC_OFF);
184 	_newcw = _cw & ~FP_PRC_FLD;
185 	_newcw |= (_m << FP_PRC_OFF) & FP_PRC_FLD;
186 	__fnldcw(_cw, _newcw);
187 	return (_p);
188 }
189 
190 /*
191  * Get or set the exception mask.
192  * Note that the x87 mask bits are inverted by the API -- a mask bit of 1
193  * means disable for x87 and SSE, but for fp*mask() it means enable.
194  */
195 
196 static __inline fp_except_t
197 fpgetmask(void)
198 {
199 	unsigned short _cw;
200 
201 	__fnstcw(&_cw);
202 	return ((~_cw & FP_MSKS_FLD) >> FP_MSKS_OFF);
203 }
204 
205 static __inline fp_except_t
206 fpsetmask(fp_except_t _m)
207 {
208 	fp_except_t _p;
209 	unsigned short _cw, _newcw;
210 
211 	__fnstcw(&_cw);
212 	_p = (~_cw & FP_MSKS_FLD) >> FP_MSKS_OFF;
213 	_newcw = _cw & ~FP_MSKS_FLD;
214 	_newcw |= (~_m << FP_MSKS_OFF) & FP_MSKS_FLD;
215 	__fnldcw(_cw, _newcw);
216 	return (_p);
217 }
218 
219 static __inline fp_except_t
220 fpgetsticky(void)
221 {
222 	unsigned _ex;
223 	unsigned short _sw;
224 
225 	__fnstsw(&_sw);
226 	_ex = (_sw & FP_STKY_FLD) >> FP_STKY_OFF;
227 	return ((fp_except_t)_ex);
228 }
229 
230 static __inline fp_except_t
231 fpresetsticky(fp_except_t _m)
232 {
233 	struct {
234 		unsigned _cw;
235 		unsigned _sw;
236 		unsigned _other[5];
237 	} _env;
238 	fp_except_t _p;
239 
240 	_m &= FP_STKY_FLD >> FP_STKY_OFF;
241 	_p = fpgetsticky();
242 	if ((_p & ~_m) == _p)
243 		return (_p);
244 	if ((_p & ~_m) == 0) {
245 		__fnclex();
246 		return (_p);
247 	}
248 	__fnstenv(&_env);
249 	_env._sw &= ~_m;
250 	__fldenv(&_env);
251 	return (_p);
252 }
253 
254 #endif /* __GNUCLIKE_ASM */
255 
256 /* Suppress prototypes in the MI header. */
257 #define	_IEEEFP_INLINED_	1
258 
259 #endif /* !_MACHINE_IEEEFP_H_ */
260