1  /* FPU control word bits.  Alpha-mapped-to-Intel version.
       2     Copyright (C) 1996-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library.  If not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #ifndef _ALPHA_FPU_CONTROL_H
      20  #define _ALPHA_FPU_CONTROL_H
      21  
      22  /*
      23   * Since many programs seem to hardcode the values passed to __setfpucw()
      24   * (rather than using the manifest constants) we emulate the x87 interface
      25   * here (at least where this makes sense).
      26   *
      27   *     15-13    12  11-10  9-8     7-6     5    4    3    2    1    0
      28   * | reserved | IC | RC  | PC | reserved | PM | UM | OM | ZM | DM | IM
      29   *
      30   * IM: Invalid operation mask
      31   * DM: Denormalized operand mask
      32   * ZM: Zero-divide mask
      33   * OM: Overflow mask
      34   * UM: Underflow mask
      35   * PM: Precision (inexact result) mask
      36   *
      37   * Mask bit is 1 means no interrupt.
      38   *
      39   * PC: Precision control
      40   * 11 - round to extended precision
      41   * 10 - round to double precision
      42   * 00 - round to single precision
      43   *
      44   * RC: Rounding control
      45   * 00 - rounding to nearest
      46   * 01 - rounding down (toward - infinity)
      47   * 10 - rounding up (toward + infinity)
      48   * 11 - rounding toward zero
      49   *
      50   * IC: Infinity control
      51   * That is for 8087 and 80287 only.
      52   *
      53   * The hardware default is 0x037f. I choose 0x1372.
      54   */
      55  
      56  #include <features.h>
      57  
      58  /* masking of interrupts */
      59  #define _FPU_MASK_IM  0x01
      60  #define _FPU_MASK_DM  0x02
      61  #define _FPU_MASK_ZM  0x04
      62  #define _FPU_MASK_OM  0x08
      63  #define _FPU_MASK_UM  0x10
      64  #define _FPU_MASK_PM  0x20
      65  
      66  /* precision control -- without effect on Alpha */
      67  #define _FPU_EXTENDED 0x300   /* RECOMMENDED */
      68  #define _FPU_DOUBLE   0x200
      69  #define _FPU_SINGLE   0x0     /* DO NOT USE */
      70  
      71  /*
      72   * rounding control---notice that on the Alpha this affects only
      73   * instructions with the dynamic rounding mode qualifier (/d).
      74   */
      75  #define _FPU_RC_NEAREST 0x000 /* RECOMMENDED */
      76  #define _FPU_RC_DOWN    0x400
      77  #define _FPU_RC_UP      0x800
      78  #define _FPU_RC_ZERO    0xC00
      79  
      80  #define _FPU_RESERVED 0xF0C0  /* Reserved bits in cw */
      81  
      82  
      83  /* Now two recommended cw */
      84  
      85  /* Linux default:
      86       - extended precision
      87       - rounding to positive infinity.  There is no /p instruction
      88         qualifier.  By setting the dynamic rounding mode to +infinity,
      89         one can use /d to get round to +infinity with no extra overhead
      90         (so long as the default isn't changed, of course...)
      91       - no exceptions enabled.  */
      92  
      93  #define _FPU_DEFAULT  0x137f
      94  
      95  /* IEEE:  same as above. */
      96  #define _FPU_IEEE     0x137f
      97  
      98  /* Type of the control word.  */
      99  typedef unsigned int fpu_control_t;
     100  
     101  /* Default control word set at startup.  */
     102  extern fpu_control_t __fpu_control;
     103  
     104  #endif	/* _ALPHA_FPU_CONTROL */