ports/sysdeps/alpha/fpu/fpu_control.h

   1 /* FPU control word bits.  Alpha-mapped-to-Intel version.
   2    Copyright (C) 1996-2014 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, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef _ALPHA_FPU_CONTROL_H
  21 #define _ALPHA_FPU_CONTROL_H
  22
  23 /*
  24  * Since many programs seem to hardcode the values passed to __setfpucw()
  25  * (rather than using the manifest constants) we emulate the x87 interface
  26  * here (at least where this makes sense).
  27  *
  28  *     15-13    12  11-10  9-8     7-6     5    4    3    2    1    0
  29  * | reserved | IC | RC  | PC | reserved | PM | UM | OM | ZM | DM | IM
  30  *
  31  * IM: Invalid operation mask
  32  * DM: Denormalized operand mask
  33  * ZM: Zero-divide mask
  34  * OM: Overflow mask
  35  * UM: Underflow mask
  36  * PM: Precision (inexact result) mask
  37  *
  38  * Mask bit is 1 means no interrupt.
  39  *
  40  * PC: Precision control
  41  * 11 - round to extended precision
  42  * 10 - round to double precision
  43  * 00 - round to single precision
  44  *
  45  * RC: Rounding control
  46  * 00 - rounding to nearest
  47  * 01 - rounding down (toward - infinity)
  48  * 10 - rounding up (toward + infinity)
  49  * 11 - rounding toward zero
  50  *
  51  * IC: Infinity control
  52  * That is for 8087 and 80287 only.
  53  *
  54  * The hardware default is 0x037f. I choose 0x1372.
  55  */
  56
  57 #include <features.h>
  58
  59 /* masking of interrupts */
  60 #define _FPU_MASK_IM  0x01
  61 #define _FPU_MASK_DM  0x02
  62 #define _FPU_MASK_ZM  0x04
  63 #define _FPU_MASK_OM  0x08
  64 #define _FPU_MASK_UM  0x10
  65 #define _FPU_MASK_PM  0x20
  66
  67 /* precision control -- without effect on Alpha */
  68 #define _FPU_EXTENDED 0x300   /* RECOMMENDED */
  69 #define _FPU_DOUBLE   0x200
  70 #define _FPU_SINGLE   0x0     /* DO NOT USE */
  71
  72 /*
  73  * rounding control---notice that on the Alpha this affects only
  74  * instructions with the dynamic rounding mode qualifier (/d).
  75  */
  76 #define _FPU_RC_NEAREST 0x000 /* RECOMMENDED */
  77 #define _FPU_RC_DOWN    0x400
  78 #define _FPU_RC_UP      0x800
  79 #define _FPU_RC_ZERO    0xC00
  80
  81 #define _FPU_RESERVED 0xF0C0  /* Reserved bits in cw */
  82
  83
  84 /* Now two recommended cw */
  85
  86 /* Linux default:
  87      - extended precision
  88      - rounding to positive infinity.  There is no /p instruction
  89        qualifier.  By setting the dynamic rounding mode to +infinity,
  90        one can use /d to get round to +infinity with no extra overhead
  91        (so long as the default isn't changed, of course...)
  92      - no exceptions enabled.  */
  93
  94 #define _FPU_DEFAULT  0x137f
  95
  96 /* IEEE:  same as above. */
  97 #define _FPU_IEEE     0x137f
  98
  99 /* Type of the control word.  */
 100 typedef unsigned int fpu_control_t;
 101
 102 /* Default control word set at startup.  */
 103 extern fpu_control_t __fpu_control;
 104
 105 #endif  /* _ALPHA_FPU_CONTROL */