1 files changed, 105 insertions, 0 deletions
diff --git a/sysdeps/ieee754/dbl-64/s_roundeven.c b/sysdeps/ieee754/dbl-64/s_roundeven.c
new file mode 100644
index 0000000000..1438e81d45
--- /dev/null
+++ b/sysdeps/ieee754/dbl-64/s_roundeven.c
@@ -0,0 +1,105 @@
+/* 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)