xref: /freebsd/sys/i386/include/ieeefp.h (revision 190cef3d52236565eb22e18b33e9e865ec634aa3)
1 /*-
2  * SPDX-License-Identifier: BSD-4-Clause
3  *
4  * Copyright (c) 2003 Peter Wemm.
5  * Copyright (c) 1990 Andrew Moore, Talke Studio
6  * All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  * 3. All advertising materials mentioning features or use of this software
17  *    must display the following acknowledgement:
18  *	This product includes software developed by the University of
19  *	California, Berkeley and its contributors.
20  * 4. Neither the name of the University nor the names of its contributors
21  *    may be used to endorse or promote products derived from this software
22  *    without specific prior written permission.
23  *
24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34  * SUCH DAMAGE.
35  *
36  * 	from: @(#) ieeefp.h 	1.0 (Berkeley) 9/23/93
37  * $FreeBSD$
38  */
39 
40 #ifndef _MACHINE_IEEEFP_H_
41 #define _MACHINE_IEEEFP_H_
42 
43 /*
44  * Deprecated historical FPU control interface
45  *
46  * IEEE floating point type, constant and function definitions.
47  * XXX: FP*FLD and FP*OFF are undocumented pollution.
48  */
49 
50 #ifndef _SYS_CDEFS_H_
51 #error this file needs sys/cdefs.h as a prerequisite
52 #endif
53 
54 /*
55  * Rounding modes.
56  */
57 typedef enum {
58 	FP_RN=0,	/* round to nearest */
59 	FP_RM,		/* round down towards minus infinity */
60 	FP_RP,		/* round up towards plus infinity */
61 	FP_RZ		/* truncate */
62 } fp_rnd_t;
63 
64 /*
65  * Precision (i.e., rounding precision) modes.
66  */
67 typedef enum {
68 	FP_PS=0,	/* 24 bit (single-precision) */
69 	FP_PRS,		/* reserved */
70 	FP_PD,		/* 53 bit (double-precision) */
71 	FP_PE		/* 64 bit (extended-precision) */
72 } fp_prec_t;
73 
74 #define fp_except_t	int
75 
76 /*
77  * Exception bit masks.
78  */
79 #define FP_X_INV	0x01	/* invalid operation */
80 #define FP_X_DNML	0x02	/* denormal */
81 #define FP_X_DZ		0x04	/* zero divide */
82 #define FP_X_OFL	0x08	/* overflow */
83 #define FP_X_UFL	0x10	/* underflow */
84 #define FP_X_IMP	0x20	/* (im)precision */
85 #define FP_X_STK	0x40	/* stack fault */
86 
87 /*
88  * FPU control word bit-field masks.
89  */
90 #define FP_MSKS_FLD	0x3f	/* exception masks field */
91 #define FP_PRC_FLD	0x300	/* precision control field */
92 #define	FP_RND_FLD	0xc00	/* rounding control field */
93 
94 /*
95  * FPU status word bit-field masks.
96  */
97 #define FP_STKY_FLD	0x3f	/* sticky flags field */
98 
99 /*
100  * FPU control word bit-field offsets (shift counts).
101  */
102 #define FP_MSKS_OFF	0	/* exception masks offset */
103 #define FP_PRC_OFF	8	/* precision control offset */
104 #define	FP_RND_OFF	10	/* rounding control offset */
105 
106 /*
107  * FPU status word bit-field offsets (shift counts).
108  */
109 #define FP_STKY_OFF	0	/* sticky flags offset */
110 
111 #ifdef __GNUCLIKE_ASM
112 
113 #define	__fldcw(addr)	__asm __volatile("fldcw %0" : : "m" (*(addr)))
114 #define	__fldenv(addr)	__asm __volatile("fldenv %0" : : "m" (*(addr)))
115 #define	__fnclex()	__asm __volatile("fnclex")
116 #define	__fnstcw(addr)	__asm __volatile("fnstcw %0" : "=m" (*(addr)))
117 #define	__fnstenv(addr)	__asm __volatile("fnstenv %0" : "=m" (*(addr)))
118 #define	__fnstsw(addr)	__asm __volatile("fnstsw %0" : "=m" (*(addr)))
119 #define	__ldmxcsr(addr)	__asm __volatile("ldmxcsr %0" : : "m" (*(addr)))
120 #define	__stmxcsr(addr)	__asm __volatile("stmxcsr %0" : "=m" (*(addr)))
121 
122 /*
123  * Load the control word.  Be careful not to trap if there is a currently
124  * unmasked exception (ones that will become freshly unmasked are not a
125  * problem).  This case must be handled by a save/restore of the
126  * environment or even of the full x87 state.  Accessing the environment
127  * is very inefficient, so only do it when necessary.
128  */
129 static __inline void
130 __fnldcw(unsigned short _cw, unsigned short _newcw)
131 {
132 	struct {
133 		unsigned _cw;
134 		unsigned _other[6];
135 	} _env;
136 	unsigned short _sw;
137 
138 	if ((_cw & FP_MSKS_FLD) != FP_MSKS_FLD) {
139 		__fnstsw(&_sw);
140 		if (((_sw & ~_cw) & FP_STKY_FLD) != 0) {
141 			__fnstenv(&_env);
142 			_env._cw = _newcw;
143 			__fldenv(&_env);
144 			return;
145 		}
146 	}
147 	__fldcw(&_newcw);
148 }
149 
150 static __inline fp_rnd_t
151 fpgetround(void)
152 {
153 	unsigned short _cw;
154 
155 	__fnstcw(&_cw);
156 	return ((fp_rnd_t)((_cw & FP_RND_FLD) >> FP_RND_OFF));
157 }
158 
159 static __inline fp_rnd_t
160 fpsetround(fp_rnd_t _m)
161 {
162 	fp_rnd_t _p;
163 	unsigned short _cw, _newcw;
164 
165 	__fnstcw(&_cw);
166 	_p = (fp_rnd_t)((_cw & FP_RND_FLD) >> FP_RND_OFF);
167 	_newcw = _cw & ~FP_RND_FLD;
168 	_newcw |= (_m << FP_RND_OFF) & FP_RND_FLD;
169 	__fnldcw(_cw, _newcw);
170 	return (_p);
171 }
172 
173 static __inline fp_prec_t
174 fpgetprec(void)
175 {
176 	unsigned short _cw;
177 
178 	__fnstcw(&_cw);
179 	return ((fp_prec_t)((_cw & FP_PRC_FLD) >> FP_PRC_OFF));
180 }
181 
182 static __inline fp_prec_t
183 fpsetprec(fp_prec_t _m)
184 {
185 	fp_prec_t _p;
186 	unsigned short _cw, _newcw;
187 
188 	__fnstcw(&_cw);
189 	_p = (fp_prec_t)((_cw & FP_PRC_FLD) >> FP_PRC_OFF);
190 	_newcw = _cw & ~FP_PRC_FLD;
191 	_newcw |= (_m << FP_PRC_OFF) & FP_PRC_FLD;
192 	__fnldcw(_cw, _newcw);
193 	return (_p);
194 }
195 
196 /*
197  * Get or set the exception mask.
198  * Note that the x87 mask bits are inverted by the API -- a mask bit of 1
199  * means disable for x87 and SSE, but for fp*mask() it means enable.
200  */
201 
202 static __inline fp_except_t
203 fpgetmask(void)
204 {
205 	unsigned short _cw;
206 
207 	__fnstcw(&_cw);
208 	return ((~_cw & FP_MSKS_FLD) >> FP_MSKS_OFF);
209 }
210 
211 static __inline fp_except_t
212 fpsetmask(fp_except_t _m)
213 {
214 	fp_except_t _p;
215 	unsigned short _cw, _newcw;
216 
217 	__fnstcw(&_cw);
218 	_p = (~_cw & FP_MSKS_FLD) >> FP_MSKS_OFF;
219 	_newcw = _cw & ~FP_MSKS_FLD;
220 	_newcw |= (~_m << FP_MSKS_OFF) & FP_MSKS_FLD;
221 	__fnldcw(_cw, _newcw);
222 	return (_p);
223 }
224 
225 static __inline fp_except_t
226 fpgetsticky(void)
227 {
228 	unsigned _ex;
229 	unsigned short _sw;
230 
231 	__fnstsw(&_sw);
232 	_ex = (_sw & FP_STKY_FLD) >> FP_STKY_OFF;
233 	return ((fp_except_t)_ex);
234 }
235 
236 static __inline fp_except_t
237 fpresetsticky(fp_except_t _m)
238 {
239 	struct {
240 		unsigned _cw;
241 		unsigned _sw;
242 		unsigned _other[5];
243 	} _env;
244 	fp_except_t _p;
245 
246 	_m &= FP_STKY_FLD >> FP_STKY_OFF;
247 	_p = fpgetsticky();
248 	if ((_p & ~_m) == _p)
249 		return (_p);
250 	if ((_p & ~_m) == 0) {
251 		__fnclex();
252 		return (_p);
253 	}
254 	__fnstenv(&_env);
255 	_env._sw &= ~_m;
256 	__fldenv(&_env);
257 	return (_p);
258 }
259 
260 #endif /* __GNUCLIKE_ASM */
261 
262 #endif /* !_MACHINE_IEEEFP_H_ */
263