예제 #1
0
void fmul__(void)
{
	/* fmul st,st(i) */
	int i = FPU_rm;
	clear_C1();
	FPU_mul(&st(i), FPU_gettagi(i), 0, control_word);
}
예제 #2
0
void fadd_i(void)
{
	/* fadd st(i),st */
	int i = FPU_rm;
	clear_C1();
	FPU_add(&st(i), FPU_gettagi(i), i, control_word);
}
예제 #3
0
void faddp_(void)
{
	/* faddp st(i),st */
	int i = FPU_rm;
	clear_C1();
	if (FPU_add(&st(i), FPU_gettagi(i), i, control_word) >= 0)
		FPU_pop();
}
예제 #4
0
static int compare_u_st_st(int nr)
{
	int f = 0, c;
	FPU_REG *st_ptr;

	if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
		setcc(SW_C3 | SW_C2 | SW_C0);
		/*             */
		EXCEPTION(EX_StackUnder);
		return !(control_word & CW_Invalid);
	}

	st_ptr = &st(nr);
	c = compare(st_ptr, FPU_gettagi(nr));
	if (c & COMP_NaN) {
		setcc(SW_C3 | SW_C2 | SW_C0);
		if (c & COMP_SNaN) {	/*                                    
                                            */
			EXCEPTION(EX_Invalid);
			return !(control_word & CW_Invalid);
		}
		return 0;
	} else
		switch (c & 7) {
		case COMP_A_lt_B:
			f = SW_C0;
			break;
		case COMP_A_eq_B:
			f = SW_C3;
			break;
		case COMP_A_gt_B:
			f = 0;
			break;
		case COMP_No_Comp:
			f = SW_C3 | SW_C2 | SW_C0;
			break;
#ifdef PARANOID
		default:
			EXCEPTION(EX_INTERNAL | 0x123);
			f = SW_C3 | SW_C2 | SW_C0;
			break;
#endif /*          */
		}
	setcc(f);
	if (c & COMP_Denormal) {
		return denormal_operand() < 0;
	}
	return 0;
}
int FPU_sub(int flags, int rm, int control_w)
{
	FPU_REG const *a, *b;
	FPU_REG *dest;
	u_char taga, tagb, signa, signb, saved_sign, sign;
	int diff, tag = 0, expa, expb, deststnr;

	a = &st(0);
	taga = FPU_gettag0();

	deststnr = 0;
	if (flags & LOADED) {
		b = (FPU_REG *) rm;
		tagb = flags & 0x0f;
	} else {
		b = &st(rm);
		tagb = FPU_gettagi(rm);

		if (flags & DEST_RM)
			deststnr = rm;
	}

	signa = getsign(a);
	signb = getsign(b);

	if (flags & REV) {
		signa ^= SIGN_NEG;
		signb ^= SIGN_NEG;
	}

	dest = &st(deststnr);
	saved_sign = getsign(dest);

	if (!(taga | tagb)) {
		expa = exponent(a);
		expb = exponent(b);

	      valid_subtract:
		

		diff = expa - expb;

		if (!diff) {
			diff = a->sigh - b->sigh;	
			if (!diff) {
				diff = a->sigl > b->sigl;
				if (!diff)
					diff = -(a->sigl < b->sigl);
			}
		}

		switch ((((int)signa) * 2 + signb) / SIGN_NEG) {
		case 0:	
		case 3:	
			if (diff > 0) {
				
				tag =
				    FPU_u_sub(a, b, dest, control_w, signa,
					      expa, expb);
			} else if (diff == 0) {
				FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);

				
				setsign(dest, ((control_w & CW_RC) != RC_DOWN)
					? SIGN_POS : SIGN_NEG);
				return TAG_Zero;
			} else {
				sign = signa ^ SIGN_NEG;
				tag =
				    FPU_u_sub(b, a, dest, control_w, sign, expb,
					      expa);
			}
			break;
		case 1:	
			tag =
			    FPU_u_add(a, b, dest, control_w, SIGN_POS, expa,
				      expb);
			break;
		case 2:	
			tag =
			    FPU_u_add(a, b, dest, control_w, SIGN_NEG, expa,
				      expb);
			break;
#ifdef PARANOID
		default:
			EXCEPTION(EX_INTERNAL | 0x111);
			return -1;
#endif
		}
		if (tag < 0) {
			setsign(dest, saved_sign);
			return tag;
		}
		FPU_settagi(deststnr, tag);
		return tag;
	}

	if (taga == TAG_Special)
		taga = FPU_Special(a);
	if (tagb == TAG_Special)
		tagb = FPU_Special(b);

	if (((taga == TAG_Valid) && (tagb == TW_Denormal))
	    || ((taga == TW_Denormal) && (tagb == TAG_Valid))
	    || ((taga == TW_Denormal) && (tagb == TW_Denormal))) {
		FPU_REG x, y;

		if (denormal_operand() < 0)
			return FPU_Exception;

		FPU_to_exp16(a, &x);
		FPU_to_exp16(b, &y);
		a = &x;
		b = &y;
		expa = exponent16(a);
		expb = exponent16(b);

		goto valid_subtract;
	}

	if ((taga == TW_NaN) || (tagb == TW_NaN)) {
		FPU_REG const *d1, *d2;
		if (flags & REV) {
			d1 = b;
			d2 = a;
		} else {
			d1 = a;
			d2 = b;
		}
		if (flags & LOADED)
			return real_2op_NaN(b, tagb, deststnr, d1);
		if (flags & DEST_RM)
			return real_2op_NaN(a, taga, deststnr, d2);
		else
			return real_2op_NaN(b, tagb, deststnr, d2);
	}

	return add_sub_specials(a, taga, signa, b, tagb, signb ^ SIGN_NEG,
				dest, deststnr, control_w);
}
예제 #6
0
int FPU_load_store(u_char type, fpu_addr_modes addr_modes,
		     void __user *data_address)
{
  FPU_REG loaded_data;
  FPU_REG *st0_ptr;
  u_char st0_tag = TAG_Empty;  /* This is just to stop a gcc warning. */
  u_char loaded_tag;

  st0_ptr = NULL;    /* Initialized just to stop compiler warnings. */

  if ( addr_modes.default_mode & PROTECTED )
    {
      if ( addr_modes.default_mode == SEG32 )
	{
	  if ( access_limit < data_sizes_32[type] )
	    math_abort(FPU_info,SIGSEGV);
	}
      else if ( addr_modes.default_mode == PM16 )
	{
	  if ( access_limit < data_sizes_16[type] )
	    math_abort(FPU_info,SIGSEGV);
	}
#ifdef PARANOID
      else
	EXCEPTION(EX_INTERNAL|0x140);
#endif /* PARANOID */
    }

  switch ( type_table[type] )
    {
    case _NONE_:
      break;
    case _REG0_:
      st0_ptr = &st(0);       /* Some of these instructions pop after
				 storing */
      st0_tag = FPU_gettag0();
      break;
    case _PUSH_:
      {
	if ( FPU_gettagi(-1) != TAG_Empty )
	  { FPU_stack_overflow(); return 0; }
	top--;
	st0_ptr = &st(0);
      }
      break;
    case _null_:
      FPU_illegal();
      return 0;
#ifdef PARANOID
    default:
      EXCEPTION(EX_INTERNAL|0x141);
      return 0;
#endif /* PARANOID */
    }

  switch ( type )
    {
    case 000:       /* fld m32real */
      clear_C1();
      loaded_tag = FPU_load_single((float __user *)data_address, &loaded_data);
      if ( (loaded_tag == TAG_Special)
	   && isNaN(&loaded_data)
	   && (real_1op_NaN(&loaded_data) < 0) )
	{
	  top++;
	  break;
	}
      FPU_copy_to_reg0(&loaded_data, loaded_tag);
      break;
    case 001:      /* fild m32int */
      clear_C1();
      loaded_tag = FPU_load_int32((long __user *)data_address, &loaded_data);
      FPU_copy_to_reg0(&loaded_data, loaded_tag);
      break;
    case 002:      /* fld m64real */
      clear_C1();
      loaded_tag = FPU_load_double((double __user *)data_address, &loaded_data);
      if ( (loaded_tag == TAG_Special)
	   && isNaN(&loaded_data)
	   && (real_1op_NaN(&loaded_data) < 0) )
	{
	  top++;
	  break;
	}
      FPU_copy_to_reg0(&loaded_data, loaded_tag);
      break;
    case 003:      /* fild m16int */
      clear_C1();
      loaded_tag = FPU_load_int16((short __user *)data_address, &loaded_data);
      FPU_copy_to_reg0(&loaded_data, loaded_tag);
      break;
    case 010:      /* fst m32real */
      clear_C1();
      FPU_store_single(st0_ptr, st0_tag, (float __user *)data_address);
      break;
    case 011:      /* fist m32int */
      clear_C1();
      FPU_store_int32(st0_ptr, st0_tag, (long __user *)data_address);
      break;
    case 012:     /* fst m64real */
      clear_C1();
      FPU_store_double(st0_ptr, st0_tag, (double __user *)data_address);
      break;
    case 013:     /* fist m16int */
      clear_C1();
      FPU_store_int16(st0_ptr, st0_tag, (short __user *)data_address);
      break;
    case 014:     /* fstp m32real */
      clear_C1();
      if ( FPU_store_single(st0_ptr, st0_tag, (float __user *)data_address) )
	pop_0();  /* pop only if the number was actually stored
		     (see the 80486 manual p16-28) */
      break;
    case 015:     /* fistp m32int */
      clear_C1();
      if ( FPU_store_int32(st0_ptr, st0_tag, (long __user *)data_address) )
	pop_0();  /* pop only if the number was actually stored
		     (see the 80486 manual p16-28) */
      break;
    case 016:     /* fstp m64real */
      clear_C1();
      if ( FPU_store_double(st0_ptr, st0_tag, (double __user *)data_address) )
	pop_0();  /* pop only if the number was actually stored
		     (see the 80486 manual p16-28) */
      break;
    case 017:     /* fistp m16int */
      clear_C1();
      if ( FPU_store_int16(st0_ptr, st0_tag, (short __user *)data_address) )
	pop_0();  /* pop only if the number was actually stored
		     (see the 80486 manual p16-28) */
      break;
    case 020:     /* fldenv  m14/28byte */
      fldenv(addr_modes, (u_char __user *)data_address);
      /* Ensure that the values just loaded are not changed by
	 fix-up operations. */
      return 1;
    case 022:     /* frstor m94/108byte */
      frstor(addr_modes, (u_char __user *)data_address);
      /* Ensure that the values just loaded are not changed by
	 fix-up operations. */
      return 1;
    case 023:     /* fbld m80dec */
      clear_C1();
      loaded_tag = FPU_load_bcd((u_char __user *)data_address);
      FPU_settag0(loaded_tag);
      break;
    case 024:     /* fldcw */
      RE_ENTRANT_CHECK_OFF;
      FPU_verify_area(VERIFY_READ, data_address, 2);
      FPU_get_user(control_word, (unsigned short __user *) data_address);
      RE_ENTRANT_CHECK_ON;
      if ( partial_status & ~control_word & CW_Exceptions )
	partial_status |= (SW_Summary | SW_Backward);
      else
	partial_status &= ~(SW_Summary | SW_Backward);
#ifdef PECULIAR_486
      control_word |= 0x40;  /* An 80486 appears to always set this bit */
#endif /* PECULIAR_486 */
      return 1;
    case 025:      /* fld m80real */
      clear_C1();
      loaded_tag = FPU_load_extended((long double __user *)data_address, 0);
      FPU_settag0(loaded_tag);
      break;
    case 027:      /* fild m64int */
      clear_C1();
      loaded_tag = FPU_load_int64((long long __user *)data_address);
      FPU_settag0(loaded_tag);
      break;
    case 030:     /* fstenv  m14/28byte */
      fstenv(addr_modes, (u_char __user *)data_address);
      return 1;
    case 032:      /* fsave */
      fsave(addr_modes, (u_char __user *)data_address);
      return 1;
    case 033:      /* fbstp m80dec */
      clear_C1();
      if ( FPU_store_bcd(st0_ptr, st0_tag, (u_char __user *)data_address) )
	pop_0();  /* pop only if the number was actually stored
		     (see the 80486 manual p16-28) */
      break;
    case 034:      /* fstcw m16int */
      RE_ENTRANT_CHECK_OFF;
      FPU_verify_area(VERIFY_WRITE,data_address,2);
      FPU_put_user(control_word, (unsigned short __user *) data_address);
      RE_ENTRANT_CHECK_ON;
      return 1;
    case 035:      /* fstp m80real */
      clear_C1();
      if ( FPU_store_extended(st0_ptr, st0_tag, (long double __user *)data_address) )
	pop_0();  /* pop only if the number was actually stored
		     (see the 80486 manual p16-28) */
      break;
    case 036:      /* fstsw m2byte */
      RE_ENTRANT_CHECK_OFF;
      FPU_verify_area(VERIFY_WRITE,data_address,2);
      FPU_put_user(status_word(),(unsigned short __user *) data_address);
      RE_ENTRANT_CHECK_ON;
      return 1;
    case 037:      /* fistp m64int */
      clear_C1();
      if ( FPU_store_int64(st0_ptr, st0_tag, (long long __user *)data_address) )
	pop_0();  /* pop only if the number was actually stored
		     (see the 80486 manual p16-28) */
      break;
    }
  return 0;
}
예제 #7
0
/*
  Divide one register by another and put the result into a third register.
  */
int FPU_div(int flags, int rm, int control_w)
{
	FPU_REG x, y;
	FPU_REG const *a, *b, *st0_ptr, *st_ptr;
	FPU_REG *dest;
	u_char taga, tagb, signa, signb, sign, saved_sign;
	int tag, deststnr;

	if (flags & DEST_RM)
		deststnr = rm;
	else
		deststnr = 0;

	if (flags & REV) {
		b = &st(0);
		st0_ptr = b;
		tagb = FPU_gettag0();
		if (flags & LOADED) {
			a = (FPU_REG *) rm;
			taga = flags & 0x0f;
		} else {
			a = &st(rm);
			st_ptr = a;
			taga = FPU_gettagi(rm);
		}
	} else {
		a = &st(0);
		st0_ptr = a;
		taga = FPU_gettag0();
		if (flags & LOADED) {
			b = (FPU_REG *) rm;
			tagb = flags & 0x0f;
		} else {
			b = &st(rm);
			st_ptr = b;
			tagb = FPU_gettagi(rm);
		}
	}

	signa = getsign(a);
	signb = getsign(b);

	sign = signa ^ signb;

	dest = &st(deststnr);
	saved_sign = getsign(dest);

	if (!(taga | tagb)) {
		/* Both regs Valid, this should be the most common case. */
		reg_copy(a, &x);
		reg_copy(b, &y);
		setpositive(&x);
		setpositive(&y);
		tag = FPU_u_div(&x, &y, dest, control_w, sign);

		if (tag < 0)
			return tag;

		FPU_settagi(deststnr, tag);
		return tag;
	}

	if (taga == TAG_Special)
		taga = FPU_Special(a);
	if (tagb == TAG_Special)
		tagb = FPU_Special(b);

	if (((taga == TAG_Valid) && (tagb == TW_Denormal))
	    || ((taga == TW_Denormal) && (tagb == TAG_Valid))
	    || ((taga == TW_Denormal) && (tagb == TW_Denormal))) {
		if (denormal_operand() < 0)
			return FPU_Exception;

		FPU_to_exp16(a, &x);
		FPU_to_exp16(b, &y);
		tag = FPU_u_div(&x, &y, dest, control_w, sign);
		if (tag < 0)
			return tag;

		FPU_settagi(deststnr, tag);
		return tag;
	} else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) {
		if (tagb != TAG_Zero) {
			/* Want to find Zero/Valid */
			if (tagb == TW_Denormal) {
				if (denormal_operand() < 0)
					return FPU_Exception;
			}

			/* The result is zero. */
			FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
			setsign(dest, sign);
			return TAG_Zero;
		}
		/* We have an exception condition, either 0/0 or Valid/Zero. */
		if (taga == TAG_Zero) {
			/* 0/0 */
			return arith_invalid(deststnr);
		}
		/* Valid/Zero */
		return FPU_divide_by_zero(deststnr, sign);
	}
	/* Must have infinities, NaNs, etc */
	else if ((taga == TW_NaN) || (tagb == TW_NaN)) {
		if (flags & LOADED)
			return real_2op_NaN((FPU_REG *) rm, flags & 0x0f, 0,
					    st0_ptr);

		if (flags & DEST_RM) {
			int tag;
			tag = FPU_gettag0();
			if (tag == TAG_Special)
				tag = FPU_Special(st0_ptr);
			return real_2op_NaN(st0_ptr, tag, rm,
					    (flags & REV) ? st0_ptr : &st(rm));
		} else {
			int tag;
			tag = FPU_gettagi(rm);
			if (tag == TAG_Special)
				tag = FPU_Special(&st(rm));
			return real_2op_NaN(&st(rm), tag, 0,
					    (flags & REV) ? st0_ptr : &st(rm));
		}
	} else if (taga == TW_Infinity) {
		if (tagb == TW_Infinity) {
			/* infinity/infinity */
			return arith_invalid(deststnr);
		} else {
			/* tagb must be Valid or Zero */
			if ((tagb == TW_Denormal) && (denormal_operand() < 0))
				return FPU_Exception;

			/* Infinity divided by Zero or Valid does
			   not raise and exception, but returns Infinity */
			FPU_copy_to_regi(a, TAG_Special, deststnr);
			setsign(dest, sign);
			return taga;
		}
	} else if (tagb == TW_Infinity) {
		if ((taga == TW_Denormal) && (denormal_operand() < 0))
			return FPU_Exception;

		/* The result is zero. */
		FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
		setsign(dest, sign);
		return TAG_Zero;
	}
#ifdef PARANOID
	else {
		EXCEPTION(EX_INTERNAL | 0x102);
		return FPU_Exception;
	}
#endif /* PARANOID */

	return 0;
}
예제 #8
0
int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w)
{
	FPU_REG *a = &st(deststnr);
	FPU_REG *dest = a;
	u_char taga = FPU_gettagi(deststnr);
	u_char saved_sign = getsign(dest);
	u_char sign = (getsign(a) ^ getsign(b));
	int tag;

	if (!(taga | tagb)) {
		

		tag =
		    FPU_u_mul(a, b, dest, control_w, sign,
			      exponent(a) + exponent(b));
		if (tag < 0) {
			setsign(dest, saved_sign);
			return tag;
		}
		FPU_settagi(deststnr, tag);
		return tag;
	}

	if (taga == TAG_Special)
		taga = FPU_Special(a);
	if (tagb == TAG_Special)
		tagb = FPU_Special(b);

	if (((taga == TAG_Valid) && (tagb == TW_Denormal))
	    || ((taga == TW_Denormal) && (tagb == TAG_Valid))
	    || ((taga == TW_Denormal) && (tagb == TW_Denormal))) {
		FPU_REG x, y;
		if (denormal_operand() < 0)
			return FPU_Exception;

		FPU_to_exp16(a, &x);
		FPU_to_exp16(b, &y);
		tag = FPU_u_mul(&x, &y, dest, control_w, sign,
				exponent16(&x) + exponent16(&y));
		if (tag < 0) {
			setsign(dest, saved_sign);
			return tag;
		}
		FPU_settagi(deststnr, tag);
		return tag;
	} else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) {
		if (((tagb == TW_Denormal) || (taga == TW_Denormal))
		    && (denormal_operand() < 0))
			return FPU_Exception;

		FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
		setsign(dest, sign);
		return TAG_Zero;
	}
	
	else if ((taga == TW_NaN) || (tagb == TW_NaN)) {
		return real_2op_NaN(b, tagb, deststnr, &st(0));
	} else if (((taga == TW_Infinity) && (tagb == TAG_Zero))
		   || ((tagb == TW_Infinity) && (taga == TAG_Zero))) {
		return arith_invalid(deststnr);	
	} else if (((taga == TW_Denormal) || (tagb == TW_Denormal))
		   && (denormal_operand() < 0)) {
		return FPU_Exception;
	} else if (taga == TW_Infinity) {
		FPU_copy_to_regi(a, TAG_Special, deststnr);
		setsign(dest, sign);
		return TAG_Special;
	} else if (tagb == TW_Infinity) {
		FPU_copy_to_regi(b, TAG_Special, deststnr);
		setsign(dest, sign);
		return TAG_Special;
	}
#ifdef PARANOID
	else {
		EXCEPTION(EX_INTERNAL | 0x102);
		return FPU_Exception;
	}
#endif 

	return 0;
}
예제 #9
0
int FPU_div(int flags, int rm, int control_w)
{
	FPU_REG x, y;
	FPU_REG const *a, *b, *st0_ptr, *st_ptr;
	FPU_REG *dest;
	u_char taga, tagb, signa, signb, sign, saved_sign;
	int tag, deststnr;

	if (flags & DEST_RM)
		deststnr = rm;
	else
		deststnr = 0;

	if (flags & REV) {
		b = &st(0);
		st0_ptr = b;
		tagb = FPU_gettag0();
		if (flags & LOADED) {
			a = (FPU_REG *) rm;
			taga = flags & 0x0f;
		} else {
			a = &st(rm);
			st_ptr = a;
			taga = FPU_gettagi(rm);
		}
	} else {
		a = &st(0);
		st0_ptr = a;
		taga = FPU_gettag0();
		if (flags & LOADED) {
			b = (FPU_REG *) rm;
			tagb = flags & 0x0f;
		} else {
			b = &st(rm);
			st_ptr = b;
			tagb = FPU_gettagi(rm);
		}
	}

	signa = getsign(a);
	signb = getsign(b);

	sign = signa ^ signb;

	dest = &st(deststnr);
	saved_sign = getsign(dest);

	if (!(taga | tagb)) {
		
		reg_copy(a, &x);
		reg_copy(b, &y);
		setpositive(&x);
		setpositive(&y);
		tag = FPU_u_div(&x, &y, dest, control_w, sign);

		if (tag < 0)
			return tag;

		FPU_settagi(deststnr, tag);
		return tag;
	}

	if (taga == TAG_Special)
		taga = FPU_Special(a);
	if (tagb == TAG_Special)
		tagb = FPU_Special(b);

	if (((taga == TAG_Valid) && (tagb == TW_Denormal))
	    || ((taga == TW_Denormal) && (tagb == TAG_Valid))
	    || ((taga == TW_Denormal) && (tagb == TW_Denormal))) {
		if (denormal_operand() < 0)
			return FPU_Exception;

		FPU_to_exp16(a, &x);
		FPU_to_exp16(b, &y);
		tag = FPU_u_div(&x, &y, dest, control_w, sign);
		if (tag < 0)
			return tag;

		FPU_settagi(deststnr, tag);
		return tag;
	} else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) {
		if (tagb != TAG_Zero) {
			
			if (tagb == TW_Denormal) {
				if (denormal_operand() < 0)
					return FPU_Exception;
			}

			
			FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
			setsign(dest, sign);
			return TAG_Zero;
		}
		
		if (taga == TAG_Zero) {
			
			return arith_invalid(deststnr);
		}
		
		return FPU_divide_by_zero(deststnr, sign);
	}
	
	else if ((taga == TW_NaN) || (tagb == TW_NaN)) {
		if (flags & LOADED)
			return real_2op_NaN((FPU_REG *) rm, flags & 0x0f, 0,
					    st0_ptr);

		if (flags & DEST_RM) {
			int tag;
			tag = FPU_gettag0();
			if (tag == TAG_Special)
				tag = FPU_Special(st0_ptr);
			return real_2op_NaN(st0_ptr, tag, rm,
					    (flags & REV) ? st0_ptr : &st(rm));
		} else {
			int tag;
			tag = FPU_gettagi(rm);
			if (tag == TAG_Special)
				tag = FPU_Special(&st(rm));
			return real_2op_NaN(&st(rm), tag, 0,
					    (flags & REV) ? st0_ptr : &st(rm));
		}
	} else if (taga == TW_Infinity) {
		if (tagb == TW_Infinity) {
			
			return arith_invalid(deststnr);
		} else {
			
			if ((tagb == TW_Denormal) && (denormal_operand() < 0))
				return FPU_Exception;

			
			FPU_copy_to_regi(a, TAG_Special, deststnr);
			setsign(dest, sign);
			return taga;
		}
	} else if (tagb == TW_Infinity) {
		if ((taga == TW_Denormal) && (denormal_operand() < 0))
			return FPU_Exception;

		
		FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
		setsign(dest, sign);
		return TAG_Zero;
	}
#ifdef PARANOID
	else {
		EXCEPTION(EX_INTERNAL | 0x102);
		return FPU_Exception;
	}
#endif 

	return 0;
}