fpu_etc.c

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/*---------------------------------------------------------------------------+
 |  fpu_etc.c                                                                |
 |                                                                           |
 | Implement a few FPU instructions.                                         |
 |                                                                           |
 | Copyright (C) 1992,1993,1994,1997                                         |
 |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
 |                       Australia.  E-mail   [e-mail]             |
 |                                                                           |
 |                                                                           |
 +---------------------------------------------------------------------------*/

#include "fpu_system.h"
#include "exception.h"
#include "fpu_emu.h"
#include "status_w.h"
#include "reg_constant.h"


static void fchs(FPU_REG *st0_ptr, u_char st0tag)
{
  if ( st0tag ^ TAG_Empty )
    {
      signbyte(st0_ptr) ^= SIGN_NEG;
      clear_C1();
    }
  else
    FPU_stack_underflow();
}


static void fabs(FPU_REG *st0_ptr, u_char st0tag)
{
  if ( st0tag ^ TAG_Empty )
    {
      setpositive(st0_ptr);
      clear_C1();
    }
  else
    FPU_stack_underflow();
}


static void ftst_(FPU_REG *st0_ptr, u_char st0tag)
{
  switch (st0tag)
    {
    case TAG_Zero:
      setcc(SW_C3);
      break;
    case TAG_Valid:
      if (getsign(st0_ptr) == SIGN_POS)
        setcc(0);
      else
        setcc(SW_C0);
      break;
    case TAG_Special:
      switch ( FPU_Special(st0_ptr) )
	{
	case TW_Denormal:
	  if (getsign(st0_ptr) == SIGN_POS)
	    setcc(0);
	  else
	    setcc(SW_C0);
	  if ( denormal_operand() < 0 )
	    {
#ifdef PECULIAR_486
	      /* This is weird! */
	      if (getsign(st0_ptr) == SIGN_POS)
		setcc(SW_C3);
#endif PECULIAR_486
	      return;
	    }
	  break;
	case TW_NaN:
	  setcc(SW_C0|SW_C2|SW_C3);   /* Operand is not comparable */ 
	  EXCEPTION(EX_Invalid);
	  break;
	case TW_Infinity:
	  if (getsign(st0_ptr) == SIGN_POS)
	    setcc(0);
	  else
	    setcc(SW_C0);
	  break;
	default:
	  setcc(SW_C0|SW_C2|SW_C3);   /* Operand is not comparable */ 
	  EXCEPTION(EX_INTERNAL|0x14);
	  break;
	}
      break;
    case TAG_Empty:
      setcc(SW_C0|SW_C2|SW_C3);
      EXCEPTION(EX_StackUnder);
      break;
    }
}


static void fxam(FPU_REG *st0_ptr, u_char st0tag)
{
  int c = 0;
  switch (st0tag)
    {
    case TAG_Empty:
      c = SW_C3|SW_C0;
      break;
    case TAG_Zero:
      c = SW_C3;
      break;
    case TAG_Valid:
      c = SW_C2;
      break;
    case TAG_Special:
      switch ( FPU_Special(st0_ptr) )
	{
	case TW_Denormal:
	  c = SW_C2|SW_C3;  /* Denormal */
	  break;
	case TW_NaN:
	  /* We also use NaN for unsupported types. */
	  if ( (st0_ptr->sigh & 0x80000000) && (exponent(st0_ptr) == EXP_OVER) )
	    c = SW_C0;
	  break;
	case TW_Infinity:
	  c = SW_C2|SW_C0;
	  break;
	}
    }
  if ( getsign(st0_ptr) == SIGN_NEG )
    c |= SW_C1;
  setcc(c);
}


static FUNC_ST0 const fp_etc_table[] = {
  fchs, fabs, (FUNC_ST0)FPU_illegal, (FUNC_ST0)FPU_illegal,
  ftst_, fxam, (FUNC_ST0)FPU_illegal, (FUNC_ST0)FPU_illegal
};

void FPU_etc()
{
  (fp_etc_table[FPU_rm])(&st(0), FPU_gettag0());
}