sysdeps/alpha/fpu/fpu_control.h

   1 /* FPU control word bits.  Alpha-mapped-to-Intel version.
   2    Copyright (C) 1996, 1998, 2000, 2002 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Olaf Flebbe.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #ifndef _ALPHA_FPU_CONTROL_H
  22 #define _ALPHA_FPU_CONTROL_H
  23
  24 /*
  25  * Since many programs seem to hardcode the values passed to __setfpucw()
  26  * (rather than using the manifest constants) we emulate the x87 interface
  27  * here (at least where this makes sense).
  28  *
  29  *     15-13    12  11-10  9-8     7-6     5    4    3    2    1    0
  30  * | reserved | IC | RC  | PC | reserved | PM | UM | OM | ZM | DM | IM
  31  *
  32  * IM: Invalid operation mask
  33  * DM: Denormalized operand mask
  34  * ZM: Zero-divide mask
  35  * OM: Overflow mask
  36  * UM: Underflow mask
  37  * PM: Precision (inexact result) mask
  38  *
  39  * Mask bit is 1 means no interrupt.
  40  *
  41  * PC: Precision control
  42  * 11 - round to extended precision
  43  * 10 - round to double precision
  44  * 00 - round to single precision
  45  *
  46  * RC: Rounding control
  47  * 00 - rounding to nearest
  48  * 01 - rounding down (toward - infinity)
  49  * 10 - rounding up (toward + infinity)
  50  * 11 - rounding toward zero
  51  *
  52  * IC: Infinity control
  53  * That is for 8087 and 80287 only.
  54  *
  55  * The hardware default is 0x037f. I choose 0x1372.
  56  */
  57
  58 #include <features.h>
  59
  60 /* masking of interrupts */
  61 #define _FPU_MASK_IM  0x01
  62 #define _FPU_MASK_DM  0x02
  63 #define _FPU_MASK_ZM  0x04
  64 #define _FPU_MASK_OM  0x08
  65 #define _FPU_MASK_UM  0x10
  66 #define _FPU_MASK_PM  0x20
  67
  68 /* precision control -- without effect on Alpha */
  69 #define _FPU_EXTENDED 0x300   /* RECOMMENDED */
  70 #define _FPU_DOUBLE   0x200
  71 #define _FPU_SINGLE   0x0     /* DO NOT USE */
  72
  73 /*
  74  * rounding control---notice that on the Alpha this affects only
  75  * instructions with the dynamic rounding mode qualifier (/d).
  76  */
  77 #define _FPU_RC_NEAREST 0x000 /* RECOMMENDED */
  78 #define _FPU_RC_DOWN    0x400
  79 #define _FPU_RC_UP      0x800
  80 #define _FPU_RC_ZERO    0xC00
  81
  82 #define _FPU_RESERVED 0xF0C0  /* Reserved bits in cw */
  83
  84
  85 /* Now two recommended cw */
  86
  87 /* Linux default:
  88      - extended precision
  89      - rounding to positive infinity.  There is no /p instruction
  90        qualifier.  By setting the dynamic rounding mode to +infinity,
  91        one can use /d to get round to +infinity with no extra overhead
  92        (so long as the default isn't changed, of course...)
  93      - no exceptions enabled.  */
  94
  95 #define _FPU_DEFAULT  0x137f
  96
  97 /* IEEE:  same as above. */
  98 #define _FPU_IEEE     0x137f
  99
 100 /* Type of the control word.  */
 101 typedef unsigned int fpu_control_t;
 102
 103 /* Default control word set at startup.  */
 104 extern fpu_control_t __fpu_control;
 105
 106 #endif  /* _ALPHA_FPU_CONTROL */