sysdeps/unix/sysv/linux/alpha/setfpucw.c

   1 /* Set FP exception mask and rounding mode.
   2    Copyright (C) 1996, 1997 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 Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    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    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <fpu_control.h>
  21 #include <asm/fpu.h>
  22
  23
  24 extern void             __ieee_set_fp_control (unsigned long);
  25 extern unsigned long    __ieee_get_fp_control (void);
  26
  27 static inline unsigned long
  28 rdfpcr (void)
  29 {
  30   unsigned long fpcr;
  31   asm ("excb; mf_fpcr %0" : "=f"(fpcr));
  32   return fpcr;
  33 }
  34
  35
  36 static inline void
  37 wrfpcr (unsigned long fpcr)
  38 {
  39   asm volatile ("mt_fpcr %0; excb" : : "f"(fpcr));
  40 }
  41
  42
  43 void
  44 __setfpucw (unsigned short fpu_control)
  45 {
  46   unsigned long fpcr = 0, fpcw = 0;
  47
  48   if (!fpu_control)
  49     fpu_control = _FPU_DEFAULT;
  50
  51   /* first, set dynamic rounding mode: */
  52
  53   fpcr = rdfpcr();
  54   fpcr &= ~FPCR_DYN_MASK;
  55   switch (fpu_control & 0xc00)
  56     {
  57     case _FPU_RC_NEAREST:       fpcr |= FPCR_DYN_NORMAL; break;
  58     case _FPU_RC_DOWN:          fpcr |= FPCR_DYN_MINUS; break;
  59     case _FPU_RC_UP:            fpcr |= FPCR_DYN_PLUS; break;
  60     case _FPU_RC_ZERO:          fpcr |= FPCR_DYN_CHOPPED; break;
  61     }
  62   wrfpcr(fpcr);
  63
  64   /* now tell kernel about traps that we like to hear about: */
  65
  66   fpcw = __ieee_get_fp_control();
  67   fpcw &= ~IEEE_TRAP_ENABLE_MASK;
  68
  69   if (!(fpu_control & _FPU_MASK_IM)) fpcw |= IEEE_TRAP_ENABLE_INV;
  70   if (!(fpu_control & _FPU_MASK_DM)) fpcw |= IEEE_TRAP_ENABLE_UNF;
  71   if (!(fpu_control & _FPU_MASK_ZM)) fpcw |= IEEE_TRAP_ENABLE_DZE;
  72   if (!(fpu_control & _FPU_MASK_OM)) fpcw |= IEEE_TRAP_ENABLE_OVF;
  73   if (!(fpu_control & _FPU_MASK_PM)) fpcw |= IEEE_TRAP_ENABLE_INE;
  74
  75   __fpu_control = fpu_control;  /* update global copy */
  76
  77   __ieee_set_fp_control(fpcw);
  78 }