errors.c

linux 内核源代码

/* Real operation attempted on a NaN. */
/* Returns < 0 if the exception is unmasked */
int real_1op_NaN(FPU_REG *a)
{
  int signalling, isNaN;

  isNaN = (exponent(a) == EXP_OVER) && (a->sigh & 0x80000000);

  /* The default result for the case of two "equal" NaNs (signs may
     differ) is chosen to reproduce 80486 behaviour */
  signalling = isNaN && !(a->sigh & 0x40000000);

  if ( !signalling )
    {
      if ( !isNaN )  /* pseudo-NaN, or other unsupported? */
	{
	  if ( control_word & CW_Invalid )
	    {
	      /* Masked response */
	      reg_copy(&CONST_QNaN, a);
	    }
	  EXCEPTION(EX_Invalid);
	  return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Special;
	}
      return TAG_Special;
    }

  if ( control_word & CW_Invalid )
    {
      /* The masked response */
      if ( !(a->sigh & 0x80000000) )  /* pseudo-NaN ? */
	{
	  reg_copy(&CONST_QNaN, a);
	}
      /* ensure a Quiet NaN */
      a->sigh |= 0x40000000;
    }

  EXCEPTION(EX_Invalid);

  return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Special;
}


/* Real operation attempted on two operands, one a NaN. */
/* Returns < 0 if the exception is unmasked */
int real_2op_NaN(FPU_REG const *b, u_char tagb,
		 int deststnr,
		 FPU_REG const *defaultNaN)
{
  FPU_REG *dest = &st(deststnr);
  FPU_REG const *a = dest;
  u_char taga = FPU_gettagi(deststnr);
  FPU_REG const *x;
  int signalling, unsupported;

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

  /* TW_NaN is also used for unsupported data types. */
  unsupported = ((taga == TW_NaN)
		 && !((exponent(a) == EXP_OVER) && (a->sigh & 0x80000000)))
    || ((tagb == TW_NaN)
	&& !((exponent(b) == EXP_OVER) && (b->sigh & 0x80000000)));
  if ( unsupported )
    {
      if ( control_word & CW_Invalid )
	{
	  /* Masked response */
	  FPU_copy_to_regi(&CONST_QNaN, TAG_Special, deststnr);
	}
      EXCEPTION(EX_Invalid);
      return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Special;
    }

  if (taga == TW_NaN)
    {
      x = a;
      if (tagb == TW_NaN)
	{
	  signalling = !(a->sigh & b->sigh & 0x40000000);
	  if ( significand(b) > significand(a) )
	    x = b;
	  else if ( significand(b) == significand(a) )
	    {
	      /* The default result for the case of two "equal" NaNs (signs may
		 differ) is chosen to reproduce 80486 behaviour */
	      x = defaultNaN;
	    }
	}
      else
	{
	  /* return the quiet version of the NaN in a */
	  signalling = !(a->sigh & 0x40000000);
	}
    }
  else
#ifdef PARANOID
    if (tagb == TW_NaN)
#endif /* PARANOID */
    {
      signalling = !(b->sigh & 0x40000000);
      x = b;
    }
#ifdef PARANOID
  else
    {
      signalling = 0;
      EXCEPTION(EX_INTERNAL|0x113);
      x = &CONST_QNaN;
    }
#endif /* PARANOID */

  if ( (!signalling) || (control_word & CW_Invalid) )
    {
      if ( ! x )
	x = b;

      if ( !(x->sigh & 0x80000000) )  /* pseudo-NaN ? */
	x = &CONST_QNaN;

      FPU_copy_to_regi(x, TAG_Special, deststnr);

      if ( !signalling )
	return TAG_Special;

      /* ensure a Quiet NaN */
      dest->sigh |= 0x40000000;
    }

  EXCEPTION(EX_Invalid);

  return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Special;
}


/* Invalid arith operation on Valid registers */
/* Returns < 0 if the exception is unmasked */
asmlinkage int arith_invalid(int deststnr)
{

  EXCEPTION(EX_Invalid);
  
  if ( control_word & CW_Invalid )
    {
      /* The masked response */
      FPU_copy_to_regi(&CONST_QNaN, TAG_Special, deststnr);
    }
  
  return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Valid;

}


/* Divide a finite number by zero */
asmlinkage int FPU_divide_by_zero(int deststnr, u_char sign)
{
  FPU_REG *dest = &st(deststnr);
  int tag = TAG_Valid;

  if ( control_word & CW_ZeroDiv )
    {
      /* The masked response */
      FPU_copy_to_regi(&CONST_INF, TAG_Special, deststnr);
      setsign(dest, sign);
      tag = TAG_Special;
    }
 
  EXCEPTION(EX_ZeroDiv);

  return (!(control_word & CW_ZeroDiv) ? FPU_Exception : 0) | tag;

}


/* This may be called often, so keep it lean */
int set_precision_flag(int flags)
{
  if ( control_word & CW_Precision )
    {
      partial_status &= ~(SW_C1 & flags);
      partial_status |= flags;   /* The masked response */
      return 0;
    }
  else
    {
      EXCEPTION(flags);
      return 1;
    }
}


/* This may be called often, so keep it lean */
asmlinkage void set_precision_flag_up(void)
{
  if ( control_word & CW_Precision )
    partial_status |= (SW_Precision | SW_C1);   /* The masked response */
  else
    EXCEPTION(EX_Precision | SW_C1);
}


/* This may be called often, so keep it lean */
asmlinkage void set_precision_flag_down(void)
{
  if ( control_word & CW_Precision )
    {   /* The masked response */
      partial_status &= ~SW_C1;
      partial_status |= SW_Precision;
    }
  else
    EXCEPTION(EX_Precision);
}


asmlinkage int denormal_operand(void)
{
  if ( control_word & CW_Denormal )
    {   /* The masked response */
      partial_status |= SW_Denorm_Op;
      return TAG_Special;
    }
  else
    {
      EXCEPTION(EX_Denormal);
      return TAG_Special | FPU_Exception;
    }
}


asmlinkage int arith_overflow(FPU_REG *dest)
{
  int tag = TAG_Valid;

  if ( control_word & CW_Overflow )
    {
      /* The masked response */
/* ###### The response here depends upon the rounding mode */
      reg_copy(&CONST_INF, dest);
      tag = TAG_Special;
    }
  else
    {
      /* Subtract the magic number from the exponent */
      addexponent(dest, (-3 * (1 << 13)));
    }

  EXCEPTION(EX_Overflow);
  if ( control_word & CW_Overflow )
    {
      /* The overflow exception is masked. */
      /* By definition, precision is lost.
	 The roundup bit (C1) is also set because we have
	 "rounded" upwards to Infinity. */
      EXCEPTION(EX_Precision | SW_C1);
      return tag;
    }

  return tag;

}


asmlinkage int arith_underflow(FPU_REG *dest)
{
  int tag = TAG_Valid;

  if ( control_word & CW_Underflow )
    {
      /* The masked response */
      if ( exponent16(dest) <= EXP_UNDER - 63 )
	{
	  reg_copy(&CONST_Z, dest);
	  partial_status &= ~SW_C1;       /* Round down. */
	  tag = TAG_Zero;
	}
      else
	{
	  stdexp(dest);
	}
    }
  else
    {
      /* Add the magic number to the exponent. */
      addexponent(dest, (3 * (1 << 13)) + EXTENDED_Ebias);
    }

  EXCEPTION(EX_Underflow);
  if ( control_word & CW_Underflow )
    {
      /* The underflow exception is masked. */
      EXCEPTION(EX_Precision);
      return tag;
    }

  return tag;

}


void FPU_stack_overflow(void)
{

 if ( control_word & CW_Invalid )
    {
      /* The masked response */
      top--;
      FPU_copy_to_reg0(&CONST_QNaN, TAG_Special);
    }

  EXCEPTION(EX_StackOver);

  return;

}


void FPU_stack_underflow(void)
{

 if ( control_word & CW_Invalid )
    {
      /* The masked response */
      FPU_copy_to_reg0(&CONST_QNaN, TAG_Special);
    }

  EXCEPTION(EX_StackUnder);

  return;

}


void FPU_stack_underflow_i(int i)
{

 if ( control_word & CW_Invalid )
    {
      /* The masked response */
      FPU_copy_to_regi(&CONST_QNaN, TAG_Special, i);
    }

  EXCEPTION(EX_StackUnder);

  return;

}


void FPU_stack_underflow_pop(int i)
{

 if ( control_word & CW_Invalid )
    {
      /* The masked response */
      FPU_copy_to_regi(&CONST_QNaN, TAG_Special, i);
      FPU_pop();
    }

  EXCEPTION(EX_StackUnder);

  return;

}