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  * 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: releng/11.2/sys/i386/include/ieeefp.h 331722 2018-03-29 02:50:57Z eadler $
   36  */
   37 
   38 #ifndef _MACHINE_IEEEFP_H_
   39 #define _MACHINE_IEEEFP_H_
   40 
   41 /*
   42  * Deprecated historical FPU control interface
   43  *
   44  * IEEE floating point type, constant and function definitions.
   45  * XXX: FP*FLD and FP*OFF are undocumented pollution.
   46  */
   47 
   48 #ifndef _SYS_CDEFS_H_
   49 #error this file needs sys/cdefs.h as a prerequisite
   50 #endif
   51 
   52 /*
   53  * Rounding modes.
   54  */
   55 typedef enum {
   56         FP_RN=0,        /* round to nearest */
   57         FP_RM,          /* round down towards minus infinity */
   58         FP_RP,          /* round up towards plus infinity */
   59         FP_RZ           /* truncate */
   60 } fp_rnd_t;
   61 
   62 /*
   63  * Precision (i.e., rounding precision) modes.
   64  */
   65 typedef enum {
   66         FP_PS=0,        /* 24 bit (single-precision) */
   67         FP_PRS,         /* reserved */
   68         FP_PD,          /* 53 bit (double-precision) */
   69         FP_PE           /* 64 bit (extended-precision) */
   70 } fp_prec_t;
   71 
   72 #define fp_except_t     int
   73 
   74 /*
   75  * Exception bit masks.
   76  */
   77 #define FP_X_INV        0x01    /* invalid operation */
   78 #define FP_X_DNML       0x02    /* denormal */
   79 #define FP_X_DZ         0x04    /* zero divide */
   80 #define FP_X_OFL        0x08    /* overflow */
   81 #define FP_X_UFL        0x10    /* underflow */
   82 #define FP_X_IMP        0x20    /* (im)precision */
   83 #define FP_X_STK        0x40    /* stack fault */
   84 
   85 /*
   86  * FPU control word bit-field masks.
   87  */
   88 #define FP_MSKS_FLD     0x3f    /* exception masks field */
   89 #define FP_PRC_FLD      0x300   /* precision control field */
   90 #define FP_RND_FLD      0xc00   /* rounding control field */
   91 
   92 /*
   93  * FPU status word bit-field masks.
   94  */
   95 #define FP_STKY_FLD     0x3f    /* sticky flags field */
   96 
   97 /*
   98  * FPU control word bit-field offsets (shift counts).
   99  */
  100 #define FP_MSKS_OFF     0       /* exception masks offset */
  101 #define FP_PRC_OFF      8       /* precision control offset */
  102 #define FP_RND_OFF      10      /* rounding control offset */
  103 
  104 /*
  105  * FPU status word bit-field offsets (shift counts).
  106  */
  107 #define FP_STKY_OFF     0       /* sticky flags offset */
  108 
  109 #ifdef __GNUCLIKE_ASM
  110 
  111 #define __fldcw(addr)   __asm __volatile("fldcw %0" : : "m" (*(addr)))
  112 #define __fldenv(addr)  __asm __volatile("fldenv %0" : : "m" (*(addr)))
  113 #define __fnclex()      __asm __volatile("fnclex")
  114 #define __fnstcw(addr)  __asm __volatile("fnstcw %0" : "=m" (*(addr)))
  115 #define __fnstenv(addr) __asm __volatile("fnstenv %0" : "=m" (*(addr)))
  116 #define __fnstsw(addr)  __asm __volatile("fnstsw %0" : "=m" (*(addr)))
  117 
  118 /*
  119  * Load the control word.  Be careful not to trap if there is a currently
  120  * unmasked exception (ones that will become freshly unmasked are not a
  121  * problem).  This case must be handled by a save/restore of the
  122  * environment or even of the full x87 state.  Accessing the environment
  123  * is very inefficient, so only do it when necessary.
  124  */
  125 static __inline void
  126 __fnldcw(unsigned short _cw, unsigned short _newcw)
  127 {
  128         struct {
  129                 unsigned _cw;
  130                 unsigned _other[6];
  131         } _env;
  132         unsigned short _sw;
  133 
  134         if ((_cw & FP_MSKS_FLD) != FP_MSKS_FLD) {
  135                 __fnstsw(&_sw);
  136                 if (((_sw & ~_cw) & FP_STKY_FLD) != 0) {
  137                         __fnstenv(&_env);
  138                         _env._cw = _newcw;
  139                         __fldenv(&_env);
  140                         return;
  141                 }
  142         }
  143         __fldcw(&_newcw);
  144 }
  145 
  146 static __inline fp_rnd_t
  147 fpgetround(void)
  148 {
  149         unsigned short _cw;
  150 
  151         __fnstcw(&_cw);
  152         return ((fp_rnd_t)((_cw & FP_RND_FLD) >> FP_RND_OFF));
  153 }
  154 
  155 static __inline fp_rnd_t
  156 fpsetround(fp_rnd_t _m)
  157 {
  158         fp_rnd_t _p;
  159         unsigned short _cw, _newcw;
  160 
  161         __fnstcw(&_cw);
  162         _p = (fp_rnd_t)((_cw & FP_RND_FLD) >> FP_RND_OFF);
  163         _newcw = _cw & ~FP_RND_FLD;
  164         _newcw |= (_m << FP_RND_OFF) & FP_RND_FLD;
  165         __fnldcw(_cw, _newcw);
  166         return (_p);
  167 }
  168 
  169 static __inline fp_prec_t
  170 fpgetprec(void)
  171 {
  172         unsigned short _cw;
  173 
  174         __fnstcw(&_cw);
  175         return ((fp_prec_t)((_cw & FP_PRC_FLD) >> FP_PRC_OFF));
  176 }
  177 
  178 static __inline fp_prec_t
  179 fpsetprec(fp_prec_t _m)
  180 {
  181         fp_prec_t _p;
  182         unsigned short _cw, _newcw;
  183 
  184         __fnstcw(&_cw);
  185         _p = (fp_prec_t)((_cw & FP_PRC_FLD) >> FP_PRC_OFF);
  186         _newcw = _cw & ~FP_PRC_FLD;
  187         _newcw |= (_m << FP_PRC_OFF) & FP_PRC_FLD;
  188         __fnldcw(_cw, _newcw);
  189         return (_p);
  190 }
  191 
  192 /*
  193  * Get or set the exception mask.
  194  * Note that the x87 mask bits are inverted by the API -- a mask bit of 1
  195  * means disable for x87 and SSE, but for fp*mask() it means enable.
  196  */
  197 
  198 static __inline fp_except_t
  199 fpgetmask(void)
  200 {
  201         unsigned short _cw;
  202 
  203         __fnstcw(&_cw);
  204         return ((~_cw & FP_MSKS_FLD) >> FP_MSKS_OFF);
  205 }
  206 
  207 static __inline fp_except_t
  208 fpsetmask(fp_except_t _m)
  209 {
  210         fp_except_t _p;
  211         unsigned short _cw, _newcw;
  212 
  213         __fnstcw(&_cw);
  214         _p = (~_cw & FP_MSKS_FLD) >> FP_MSKS_OFF;
  215         _newcw = _cw & ~FP_MSKS_FLD;
  216         _newcw |= (~_m << FP_MSKS_OFF) & FP_MSKS_FLD;
  217         __fnldcw(_cw, _newcw);
  218         return (_p);
  219 }
  220 
  221 static __inline fp_except_t
  222 fpgetsticky(void)
  223 {
  224         unsigned _ex;
  225         unsigned short _sw;
  226 
  227         __fnstsw(&_sw);
  228         _ex = (_sw & FP_STKY_FLD) >> FP_STKY_OFF;
  229         return ((fp_except_t)_ex);
  230 }
  231 
  232 static __inline fp_except_t
  233 fpresetsticky(fp_except_t _m)
  234 {
  235         struct {
  236                 unsigned _cw;
  237                 unsigned _sw;
  238                 unsigned _other[5];
  239         } _env;
  240         fp_except_t _p;
  241 
  242         _m &= FP_STKY_FLD >> FP_STKY_OFF;
  243         _p = fpgetsticky();
  244         if ((_p & ~_m) == _p)
  245                 return (_p);
  246         if ((_p & ~_m) == 0) {
  247                 __fnclex();
  248                 return (_p);
  249         }
  250         __fnstenv(&_env);
  251         _env._sw &= ~_m;
  252         __fldenv(&_env);
  253         return (_p);
  254 }
  255 
  256 #endif /* __GNUCLIKE_ASM */
  257 
  258 #endif /* !_MACHINE_IEEEFP_H_ */

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