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

   1 #include <fpu_control.h>
   2
   3 #include <asm/fpu.h>
   4
   5 extern void             __ieee_set_fp_control (unsigned long);
   6 extern unsigned long    __ieee_get_fp_control (void);
   7
   8
   9 static inline unsigned long
  10 rdfpcr (void)
  11 {
  12     unsigned long fpcr;
  13
  14     asm ("trapb; mf_fpcr $f0; trapb; stt $f0,%0" : "m="(fpcr));
  15     return fpcr;
  16 }
  17
  18
  19 static inline void
  20 wrfpcr (unsigned long fpcr)
  21 {
  22     asm volatile ("ldt $f0,%0; trapb; mt_fpcr $f0; trapb" :: "m"(fpcr));
  23 }
  24
  25
  26 void
  27 __setfpucw (unsigned short fpu_control)
  28 {
  29     unsigned long fpcr = 0, fpcw = 0;
  30
  31     if (!fpu_control)
  32         fpu_control = _FPU_DEFAULT;
  33
  34     /* first, set dynamic rounding mode: */
  35
  36     fpcr = rdfpcr();
  37     fpcr &= ~FPCR_DYN_MASK;
  38     switch (fpu_control & 0xc00) {
  39       case _FPU_RC_NEAREST:     fpcr |= FPCR_DYN_NORMAL; break;
  40       case _FPU_RC_DOWN:        fpcr |= FPCR_DYN_MINUS; break;
  41       case _FPU_RC_UP:          fpcr |= FPCR_DYN_PLUS; break;
  42       case _FPU_RC_ZERO:        fpcr |= FPCR_DYN_CHOPPED; break;
  43     }
  44     wrfpcr(fpcr);
  45
  46     /* now tell kernel about traps that we like to hear about: */
  47
  48     fpcw = __ieee_get_fp_control();
  49     fpcw &= ~IEEE_TRAP_ENABLE_MASK;
  50
  51     if (!(fpu_control & _FPU_MASK_IM))
  52         fpcw |= IEEE_TRAP_ENABLE_INV;
  53     if (!(fpu_control & _FPU_MASK_DM))
  54         fpcw |= IEEE_TRAP_ENABLE_UNF;
  55     if (!(fpu_control & _FPU_MASK_ZM))
  56         fpcw |= IEEE_TRAP_ENABLE_DZE;
  57     if (!(fpu_control & _FPU_MASK_OM))
  58         fpcw |= IEEE_TRAP_ENABLE_OVF;
  59     if (!(fpu_control & _FPU_MASK_PM))
  60         fpcw |= IEEE_TRAP_ENABLE_INE;
  61
  62     __ieee_set_fp_control(fpcw);
  63
  64     __fpu_control = fpu_control;        /* update global copy */
  65 }