/* Round to nearest integer value, rounding halfway cases to even.

   dbl-64 version.

   Copyright (C) 2016-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <math.h>

#include <math_private.h>

#include <libm-alias-double.h>

#include <stdint.h>

#define BIAS 0x3ff

#define MANT_DIG 53

#define MAX_EXP (2 * BIAS + 1)

double

__roundeven (double x)

{

  uint32_t hx, lx, uhx;

  EXTRACT_WORDS (hx, lx, x);

  uhx = hx & 0x7fffffff;

  int exponent = uhx >> (MANT_DIG - 1 - 32);

  if (exponent >= BIAS + MANT_DIG - 1)

    {

      /* Integer, infinity or NaN.  */

      if (exponent == MAX_EXP)

	/* Infinity or NaN; quiet signaling NaNs.  */

	return x + x;

      else

	return x;

    }

  else if (exponent >= BIAS + MANT_DIG - 32)

    {

      /* Not necessarily an integer; integer bit is in low word.

	 Locate the bits with exponents 0 and -1.  */

      int int_pos = (BIAS + MANT_DIG - 1) - exponent;

      int half_pos = int_pos - 1;

      uint32_t half_bit = 1U << half_pos;

      uint32_t int_bit = 1U << int_pos;

      if ((lx & (int_bit | (half_bit - 1))) != 0)

	{

	  /* Carry into the exponent works correctly.  No need to test

	     whether HALF_BIT is set.  */

	  lx += half_bit;

	  hx += lx < half_bit;

	}

      lx &= ~(int_bit - 1);

    }

  else if (exponent == BIAS + MANT_DIG - 33)

    {

      /* Not necessarily an integer; integer bit is bottom of high

	 word, half bit is top of low word.  */

      if (((hx & 1) | (lx & 0x7fffffff)) != 0)

	{

	  lx += 0x80000000;

	  hx += lx < 0x80000000;

	}

      lx = 0;

    }

  else if (exponent >= BIAS)

    {

      /* At least 1; not necessarily an integer, integer bit and half

	 bit are in the high word.  Locate the bits with exponents 0

	 and -1 (when the unbiased exponent is 0, the bit with

	 exponent 0 is implicit, but as the bias is odd it is OK to

	 take it from the low bit of the exponent).  */

      int int_pos = (BIAS + MANT_DIG - 33) - exponent;

      int half_pos = int_pos - 1;

      uint32_t half_bit = 1U << half_pos;

      uint32_t int_bit = 1U << int_pos;

      if (((hx & (int_bit | (half_bit - 1))) | lx) != 0)

	hx += half_bit;

      hx &= ~(int_bit - 1);

      lx = 0;

    }

  else if (exponent == BIAS - 1 && (uhx > 0x3fe00000 || lx != 0))

    {

      /* Interval (0.5, 1).  */

      hx = (hx & 0x80000000) | 0x3ff00000;

      lx = 0;

    }

  else

    {

      /* Rounds to 0.  */

      hx &= 0x80000000;

      lx = 0;

    }

  INSERT_WORDS (x, hx, lx);

  return x;

}

hidden_def (__roundeven)

libm_alias_double (__roundeven, roundeven)