sysdeps/mach/alpha/setfpucw.c

   1 /* Set FP exception mask and rounding mode.  Mach/Alpha version.
   2    Copyright (C) 2002 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <fpu_control.h>
  21
  22
  23 #define FPCR_DYN_SHIFT  58              /* first dynamic rounding mode bit */
  24 #define FPCR_DYN_CHOPPED (0x0UL << FPCR_DYN_SHIFT)      /* towards 0 */
  25 #define FPCR_DYN_MINUS   (0x1UL << FPCR_DYN_SHIFT)      /* towards -INF */
  26 #define FPCR_DYN_NORMAL  (0x2UL << FPCR_DYN_SHIFT)      /* towards nearest */
  27 #define FPCR_DYN_PLUS    (0x3UL << FPCR_DYN_SHIFT)      /* towards +INF */
  28 #define FPCR_DYN_MASK    (0x3UL << FPCR_DYN_SHIFT)
  29
  30 static inline unsigned long
  31 rdfpcr (void)
  32 {
  33   unsigned long fpcr;
  34   asm ("excb; mf_fpcr %0" : "=f"(fpcr));
  35   return fpcr;
  36 }
  37
  38 static inline void
  39 wrfpcr (unsigned long fpcr)
  40 {
  41   asm volatile ("mt_fpcr %0; excb" : : "f"(fpcr));
  42 }
  43
  44
  45 void
  46 __setfpucw (fpu_control_t fpu_control)
  47 {
  48   unsigned long fpcr;
  49
  50   if (!fpu_control)
  51     fpu_control = _FPU_DEFAULT;
  52
  53   /* first, set dynamic rounding mode: */
  54
  55   fpcr = rdfpcr();
  56   fpcr &= ~FPCR_DYN_MASK;
  57   switch (fpu_control & 0xc00)
  58     {
  59     case _FPU_RC_NEAREST:       fpcr |= FPCR_DYN_NORMAL; break;
  60     case _FPU_RC_DOWN:          fpcr |= FPCR_DYN_MINUS; break;
  61     case _FPU_RC_UP:            fpcr |= FPCR_DYN_PLUS; break;
  62     case _FPU_RC_ZERO:          fpcr |= FPCR_DYN_CHOPPED; break;
  63     }
  64   wrfpcr(fpcr);
  65
  66   /* XXX trap bits? */
  67
  68   __fpu_control = fpu_control;  /* update global copy */
  69 }