OSDev.org

Code: Select all

static void fsqrt_(FPU_REG *st0_ptr)
{
  char st0_tag = st0_ptr->tag;

  clear_C1();
  if ( !(st0_tag ^ TW_Valid) )
    {
      int expon;
      
      if (st0_ptr->sign == SIGN_NEG)
	{
	  arith_invalid(st0_ptr);  /* sqrt(negative) is invalid */
	  return;
	}

#ifdef DENORM_OPERAND
      if ( (st0_ptr->exp <= EXP_UNDER) && (denormal_operand()) )
	return;
#endif DENORM_OPERAND

      expon = st0_ptr->exp - EXP_BIAS;
      st0_ptr->exp = EXP_BIAS + (expon & 1);  /* make st(0) in  [1.0 .. 4.0) */
      
      wm_sqrt(st0_ptr, control_word);	/* Do the computation */
      
      st0_ptr->exp += expon >> 1;
      st0_ptr->sign = SIGN_POS;
    }
  else if ( st0_tag == TW_Zero )
    return;
  else if ( st0_tag == TW_Infinity )
    {
      if ( st0_ptr->sign == SIGN_NEG )
	arith_invalid(st0_ptr);  /* sqrt(-Infinity) is invalid */
      return;
    }
  else
    { single_arg_error(st0_ptr); return; }

}

Code: Select all

double sqrt (double x)
{
  double res;
  asm ("fsqrt" : "=t" (res) : "0" (x));
  return res;
}