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/floatingpoint.h

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    1 /*-
    2  * Copyright (c) 1993 Andrew Moore, Talke Studio
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 3. All advertising materials mentioning features or use of this software
   14  *    must display the following acknowledgement:
   15  *      This product includes software developed by the University of
   16  *      California, Berkeley and its contributors.
   17  * 4. Neither the name of the University nor the names of its contributors
   18  *    may be used to endorse or promote products derived from this software
   19  *    without specific prior written permission.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31  * SUCH DAMAGE.
   32  *
   33  *      from: @(#) floatingpoint.h      1.0 (Berkeley) 9/23/93
   34  * $FreeBSD: src/sys/i386/include/floatingpoint.h,v 1.6.12.1 1999/09/05 08:11:48 peter Exp $
   35  */
   36 
   37 #ifndef _FLOATINGPOINT_H_
   38 #define _FLOATINGPOINT_H_
   39 
   40 /*
   41  * IEEE floating point structure and function definitions
   42  */
   43 
   44 /*-
   45  * XXX the following undocumented pollution is exported:
   46  *      fpsetsticky().
   47  *      FP*FLD, FP*OFF and FP*REG from <machine/ieeefp.h>
   48  */
   49 
   50 #include <sys/cdefs.h>
   51 #include <machine/ieeefp.h>
   52 
   53 #ifdef __GNUC__
   54 
   55 #define __fldenv(addr)  __asm __volatile("fldenv %0" : : "m" (*(addr)))
   56 #define __fnstenv(addr) __asm __volatile("fnstenv %0" : "=m" (*(addr)))
   57 #define __fnstcw(addr)  __asm __volatile("fnstcw %0" : "=m" (*(addr)))
   58 #define __fnstsw(addr)  __asm __volatile("fnstsw %0" : "=m" (*(addr)))
   59 
   60 /*
   61  * return the contents of a FP register
   62  */
   63 static __inline__ int
   64 __fpgetreg(int _reg)
   65 {
   66         unsigned short _mem;
   67 
   68         /*-
   69          * This is more efficient than it looks.  The switch gets optimized
   70          * away if _reg is constant.
   71          *
   72          * The default case only supports _reg == 0.  We could handle more
   73          * registers (e.g., tags) using fnstenv, but the interface doesn't
   74          * support more.
   75          */
   76         switch(_reg) {
   77         default:
   78                 __fnstcw(&_mem);
   79                 break;
   80         case FP_STKY_REG:
   81                 __fnstsw(&_mem);
   82                 break;
   83         }
   84         return _mem;
   85 }
   86 
   87 /*
   88  * set a FP mode; return previous mode
   89  */
   90 static __inline__ int
   91 __fpsetreg(int _m, int _reg, int _fld, int _off)
   92 {
   93         unsigned _env[7];
   94         unsigned _p;
   95 
   96         /*
   97          * _reg == 0 could be handled better using fnstcw/fldcw.
   98          */
   99         __fnstenv(_env);
  100         _p =  (_env[_reg] & _fld) >> _off;
  101         _env[_reg] = (_env[_reg] & ~_fld) | (_m << _off & _fld);
  102         __fldenv(_env);
  103         return _p;
  104 }
  105 
  106 #endif /* __GNUC__ */
  107 
  108 /*
  109  * SysV/386 FP control interface
  110  */
  111 #define fpgetround()    ((__fpgetreg(FP_RND_REG) & FP_RND_FLD) >> FP_RND_OFF)
  112 #define fpsetround(m)   __fpsetreg((m), FP_RND_REG, FP_RND_FLD, FP_RND_OFF)
  113 #define fpgetprec()     ((__fpgetreg(FP_PRC_REG) & FP_PRC_FLD) >> FP_PRC_OFF)
  114 #define fpsetprec(m)    __fpsetreg((m), FP_PRC_REG, FP_PRC_FLD, FP_PRC_OFF)
  115 #define fpgetmask()     ((~__fpgetreg(FP_MSKS_REG) & FP_MSKS_FLD) >> FP_MSKS_OFF)
  116 #define fpsetmask(m)    __fpsetreg(~(m), FP_MSKS_REG, FP_MSKS_FLD, FP_MSKS_OFF)
  117 #define fpgetsticky()   ((__fpgetreg(FP_STKY_REG) & FP_STKY_FLD) >> FP_STKY_OFF)
  118 #define fpresetsticky(m)        __fpsetreg(0, FP_STKY_REG, (m), FP_STKY_OFF)
  119 #define fpsetsticky(m)  fpresetsticky(m)
  120 
  121 #endif /* !_FLOATINGPOINT_H_ */

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