FreeBSD/Linux Kernel Cross Reference
sys/x86/include/x86_ieeefp.h

     /*-
      * SPDX-License-Identifier: BSD-4-Clause
      *
      * Copyright (c) 2003 Peter Wemm.
      * Copyright (c) 1990 Andrew Moore, Talke Studio
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      from: @(#) ieeefp.h     1.0 (Berkeley) 9/23/93
     * $FreeBSD$
     */
    
    #ifndef _X86_X86_IEEEFP_H_
    #define _X86_X86_IEEEFP_H_
    
    /* Deprecated historical FPU control interface */
    
    /*
     * IEEE floating point type, constant and function definitions.
     * XXX: {FP,SSE}*FLD and {FP,SSE}*OFF are undocumented pollution.
     */
    
    /*
     * Rounding modes.
     */
    typedef enum {
            FP_RN=0,        /* round to nearest */
            FP_RM,          /* round down towards minus infinity */
            FP_RP,          /* round up towards plus infinity */
            FP_RZ           /* truncate */
    } fp_rnd_t;
    
    /*
     * Precision (i.e., rounding precision) modes.
     */
    typedef enum {
            FP_PS=0,        /* 24 bit (single-precision) */
            FP_PRS,         /* reserved */
            FP_PD,          /* 53 bit (double-precision) */
            FP_PE           /* 64 bit (extended-precision) */
    } fp_prec_t;
    
    #define fp_except_t     int
    
    /*
     * Exception bit masks.
     */
    #define FP_X_INV        0x01    /* invalid operation */
    #define FP_X_DNML       0x02    /* denormal */
    #define FP_X_DZ         0x04    /* zero divide */
    #define FP_X_OFL        0x08    /* overflow */
    #define FP_X_UFL        0x10    /* underflow */
    #define FP_X_IMP        0x20    /* (im)precision */
    #define FP_X_STK        0x40    /* stack fault */
    
    /*
     * FPU control word bit-field masks.
     */
    #define FP_MSKS_FLD     0x3f    /* exception masks field */
    #define FP_PRC_FLD      0x300   /* precision control field */
    #define FP_RND_FLD      0xc00   /* rounding control field */
    
    /*
     * FPU status word bit-field masks.
     */
    #define FP_STKY_FLD     0x3f    /* sticky flags field */
    
    /*
     * FPU control word bit-field offsets (shift counts).
     */
    #define FP_MSKS_OFF     0       /* exception masks offset */
    #define FP_PRC_OFF      8       /* precision control offset */
   #define FP_RND_OFF      10      /* rounding control offset */
   
   /*
    * FPU status word bit-field offsets (shift counts).
    */
   #define FP_STKY_OFF     0       /* sticky flags offset */
   
   #define __fldcw(addr)   __asm __volatile("fldcw %0" : : "m" (*(addr)))
   #define __fldenv(addr)  __asm __volatile("fldenv %0" : : "m" (*(addr)))
   #define __fnclex()      __asm __volatile("fnclex")
   #define __fnstcw(addr)  __asm __volatile("fnstcw %0" : "=m" (*(addr)))
   #define __fnstenv(addr) __asm __volatile("fnstenv %0" : "=m" (*(addr)))
   #define __fnstsw(addr)  __asm __volatile("fnstsw %0" : "=m" (*(addr)))
   #define __ldmxcsr(addr) __asm __volatile("ldmxcsr %0" : : "m" (*(addr)))
   #define __stmxcsr(addr) __asm __volatile("stmxcsr %0" : "=m" (*(addr)))
   
   /*
    * Load the control word.  Be careful not to trap if there is a currently
    * unmasked exception (ones that will become freshly unmasked are not a
    * problem).  This case must be handled by a save/restore of the
    * environment or even of the full x87 state.  Accessing the environment
    * is very inefficient, so only do it when necessary.
    */
   static __inline void
   __fnldcw(unsigned short _cw, unsigned short _newcw)
   {
           struct {
                   unsigned _cw;
                   unsigned _other[6];
           } _env;
           unsigned short _sw;
   
           if ((_cw & FP_MSKS_FLD) != FP_MSKS_FLD) {
                   __fnstsw(&_sw);
                   if (((_sw & ~_cw) & FP_STKY_FLD) != 0) {
                           __fnstenv(&_env);
                           _env._cw = _newcw;
                           __fldenv(&_env);
                           return;
                   }
           }
           __fldcw(&_newcw);
   }
   
   #endif/* _X86_X86_IEEEFP_H_ */

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