sysdeps/alpha/fpu/fpu_control.h

   1 /* FPU control word bits.  Alpha-mapped-to-Intel version.
   2    Copyright (C) 1996-2024 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 */