The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/i386/include/ieeefp.h

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    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_ */

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