FreeBSD/Linux Kernel Cross Reference
sys/amd64/include/ieeefp.h

     /*-
      * 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: releng/9.0/sys/amd64/include/ieeefp.h 175231 2008-01-11 17:11:32Z bde $
     */
    
    #ifndef _MACHINE_IEEEFP_H_
    #define _MACHINE_IEEEFP_H_
    
    /*
     * IEEE floating point type, constant and function definitions.
     * XXX: {FP,SSE}*FLD and {FP,SSE}*OFF are undocumented pollution.
     */
    
    #ifndef _SYS_CDEFS_H_
    #error this file needs sys/cdefs.h as a prerequisite
    #endif
    
    /*
     * 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 */
    
    /*
     * SSE mxcsr register bit-field masks.
     */
    #define SSE_STKY_FLD    0x3f    /* exception flags */
    #define SSE_DAZ_FLD     0x40    /* Denormals are zero */
   #define SSE_MSKS_FLD    0x1f80  /* exception masks field */
   #define SSE_RND_FLD     0x6000  /* rounding control */
   #define SSE_FZ_FLD      0x8000  /* flush to zero on underflow */
   
   /*
    * 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 */
   
   /*
    * SSE mxcsr register bit-field offsets (shift counts).
    */
   #define SSE_STKY_OFF    0       /* exception flags offset */
   #define SSE_DAZ_OFF     6       /* DAZ exception mask offset */
   #define SSE_MSKS_OFF    7       /* other exception masks offset */
   #define SSE_RND_OFF     13      /* rounding control offset */
   #define SSE_FZ_OFF      15      /* flush to zero offset */
   
   #ifdef __GNUCLIKE_ASM
   
   #define __fldcw(addr)   __asm __volatile("fldcw %0" : : "m" (*(addr)))
   #define __fldenv(addr)  __asm __volatile("fldenv %0" : : "m" (*(addr)))
   #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);
   }
   
   /*
    * General notes about conflicting SSE vs FP status bits.
    * This code assumes that software will not fiddle with the control
    * bits of the SSE and x87 in such a way to get them out of sync and
    * still expect this to work.  Break this at your peril.
    * Because I based this on the i386 port, the x87 state is used for
    * the fpget*() functions, and is shadowed into the SSE state for
    * the fpset*() functions.  For dual source fpget*() functions, I
    * merge the two together.  I think.
    */
   
   static __inline fp_rnd_t
   __fpgetround(void)
   {
           unsigned short _cw;
   
           __fnstcw(&_cw);
           return ((fp_rnd_t)((_cw & FP_RND_FLD) >> FP_RND_OFF));
   }
   
   static __inline fp_rnd_t
   __fpsetround(fp_rnd_t _m)
   {
           fp_rnd_t _p;
           unsigned _mxcsr;
           unsigned short _cw, _newcw;
   
           __fnstcw(&_cw);
           _p = (fp_rnd_t)((_cw & FP_RND_FLD) >> FP_RND_OFF);
           _newcw = _cw & ~FP_RND_FLD;
           _newcw |= (_m << FP_RND_OFF) & FP_RND_FLD;
           __fnldcw(_cw, _newcw);
           __stmxcsr(&_mxcsr);
           _mxcsr &= ~SSE_RND_FLD;
           _mxcsr |= (_m << SSE_RND_OFF) & SSE_RND_FLD;
           __ldmxcsr(&_mxcsr);
           return (_p);
   }
   
   /*
    * Get or set the rounding precision for x87 arithmetic operations.
    * There is no equivalent SSE mode or control.
    */
   
   static __inline fp_prec_t
   __fpgetprec(void)
   {
           unsigned short _cw;
   
           __fnstcw(&_cw);
           return ((fp_prec_t)((_cw & FP_PRC_FLD) >> FP_PRC_OFF));
   }
   
   static __inline fp_prec_t
   __fpsetprec(fp_prec_t _m)
   {
           fp_prec_t _p;
           unsigned short _cw, _newcw;
   
           __fnstcw(&_cw);
           _p = (fp_prec_t)((_cw & FP_PRC_FLD) >> FP_PRC_OFF);
           _newcw = _cw & ~FP_PRC_FLD;
           _newcw |= (_m << FP_PRC_OFF) & FP_PRC_FLD;
           __fnldcw(_cw, _newcw);
           return (_p);
   }
   
   /*
    * Get or set the exception mask.
    * Note that the x87 mask bits are inverted by the API -- a mask bit of 1
    * means disable for x87 and SSE, but for fp*mask() it means enable.
    */
   
   static __inline fp_except_t
   __fpgetmask(void)
   {
           unsigned short _cw;
   
           __fnstcw(&_cw);
           return ((~_cw & FP_MSKS_FLD) >> FP_MSKS_OFF);
   }
   
   static __inline fp_except_t
   __fpsetmask(fp_except_t _m)
   {
           fp_except_t _p;
           unsigned _mxcsr;
           unsigned short _cw, _newcw;
   
           __fnstcw(&_cw);
           _p = (~_cw & FP_MSKS_FLD) >> FP_MSKS_OFF;
           _newcw = _cw & ~FP_MSKS_FLD;
           _newcw |= (~_m << FP_MSKS_OFF) & FP_MSKS_FLD;
           __fnldcw(_cw, _newcw);
           __stmxcsr(&_mxcsr);
           /* XXX should we clear non-ieee SSE_DAZ_FLD and SSE_FZ_FLD ? */
           _mxcsr &= ~SSE_MSKS_FLD;
           _mxcsr |= (~_m << SSE_MSKS_OFF) & SSE_MSKS_FLD;
           __ldmxcsr(&_mxcsr);
           return (_p);
   }
   
   static __inline fp_except_t
   __fpgetsticky(void)
   {
           unsigned _ex, _mxcsr;
           unsigned short _sw;
   
           __fnstsw(&_sw);
           _ex = (_sw & FP_STKY_FLD) >> FP_STKY_OFF;
           __stmxcsr(&_mxcsr);
           _ex |= (_mxcsr & SSE_STKY_FLD) >> SSE_STKY_OFF;
           return ((fp_except_t)_ex);
   }
   
   #endif /* __GNUCLIKE_ASM */
   
   #if !defined(__IEEEFP_NOINLINES__) && defined(__GNUCLIKE_ASM)
   
   #define fpgetmask()     __fpgetmask()
   #define fpgetprec()     __fpgetprec()
   #define fpgetround()    __fpgetround()
   #define fpgetsticky()   __fpgetsticky()
   #define fpsetmask(m)    __fpsetmask(m)
   #define fpsetprec(m)    __fpsetprec(m)
   #define fpsetround(m)   __fpsetround(m)
   
   /* Suppress prototypes in the MI header. */
   #define _IEEEFP_INLINED_        1
   
   #else /* !(!__IEEEFP_NOINLINES__ && __GNUCLIKE_ASM) */
   
   /* Augment the userland declarations. */
   __BEGIN_DECLS
   fp_prec_t       fpgetprec(void);
   fp_prec_t       fpsetprec(fp_prec_t);
   __END_DECLS
   
   #endif /* !__IEEEFP_NOINLINES__ && __GNUCLIKE_ASM */
   
   #endif /* !_MACHINE_IEEEFP_H_ */

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