text: /* FPU control word bits.  Alpha-mapped-to-Intel version.
     Copyright (C) 1996-2020 Free Software Foundation, Inc.
     This file is part of the GNU C Library.
     Contributed by Olaf Flebbe.
  
     The GNU C Library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Lesser General Public
     License as published by the Free Software Foundation; either
     version 2.1 of the License, or (at your option) any later version.
  
     The GNU C Library is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Lesser General Public License for more details.
  
     You should have received a copy of the GNU Lesser General Public
     License along with the GNU C Library.  If not, see
     <https://www.gnu.org/licenses/>.  */
  
  #ifndef _ALPHA_FPU_CONTROL_H
  #define _ALPHA_FPU_CONTROL_H
  
  /*
   * Since many programs seem to hardcode the values passed to __setfpucw()
   * (rather than using the manifest constants) we emulate the x87 interface
   * here (at least where this makes sense).
   *
   *     15-13    12  11-10  9-8     7-6     5    4    3    2    1    0
   * | reserved | IC | RC  | PC | reserved | PM | UM | OM | ZM | DM | IM
   *
   * IM: Invalid operation mask
   * DM: Denormalized operand mask
   * ZM: Zero-divide mask
   * OM: Overflow mask
   * UM: Underflow mask
   * PM: Precision (inexact result) mask
   *
   * Mask bit is 1 means no interrupt.
   *
   * PC: Precision control
   * 11 - round to extended precision
   * 10 - round to double precision
   * 00 - round to single precision
   *
   * RC: Rounding control
   * 00 - rounding to nearest
   * 01 - rounding down (toward - infinity)
   * 10 - rounding up (toward + infinity)
   * 11 - rounding toward zero
   *
   * IC: Infinity control
   * That is for 8087 and 80287 only.
   *
   * The hardware default is 0x037f. I choose 0x1372.
   */
  
  #include <features.h>
  
  /* masking of interrupts */
  #define _FPU_MASK_IM  0x01
  #define _FPU_MASK_DM  0x02
  #define _FPU_MASK_ZM  0x04
  #define _FPU_MASK_OM  0x08
  #define _FPU_MASK_UM  0x10
  #define _FPU_MASK_PM  0x20
  
  /* precision control -- without effect on Alpha */
  #define _FPU_EXTENDED 0x300   /* RECOMMENDED */
  #define _FPU_DOUBLE   0x200
  #define _FPU_SINGLE   0x0     /* DO NOT USE */
  
  /*
   * rounding control---notice that on the Alpha this affects only
   * instructions with the dynamic rounding mode qualifier (/d).
   */
  #define _FPU_RC_NEAREST 0x000 /* RECOMMENDED */
  #define _FPU_RC_DOWN    0x400
  #define _FPU_RC_UP      0x800
  #define _FPU_RC_ZERO    0xC00
  
  #define _FPU_RESERVED 0xF0C0  /* Reserved bits in cw */
  
  
  /* Now two recommended cw */
  
  /* Linux default:
       - extended precision
       - rounding to positive infinity.  There is no /p instruction
         qualifier.  By setting the dynamic rounding mode to +infinity,
         one can use /d to get round to +infinity with no extra overhead
         (so long as the default isn't changed, of course...)
       - no exceptions enabled.  */
  
  #define _FPU_DEFAULT  0x137f
  
  /* IEEE:  same as above. */
  #define _FPU_IEEE     0x137f
  
  /* Type of the control word.  */
  typedef unsigned int fpu_control_t;
  
  /* Default control word set at startup.  */
  extern fpu_control_t __fpu_control;
  
  #endif	/* _ALPHA_FPU_CONTROL */
  