Optimized remquo for 64-bit platforms

2 files changed, 114 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index b867e4f..3b99f69 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,7 @@
 2011-10-23  Ulrich Drepper  <drepper@gmail.com>
 
+	* sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c: New file.
+
 	* sysdeps/ieee754/dbl-64/e_fmod.c (__ieee754_fmod): Add some branch
 	prediction.
 	* sysdeps/ieee754/dbl-64/wordsize-64/e_fmod.c: New file.
diff --git a/sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c b/sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c
new file mode 100644
index 0000000..011401e
--- /dev/null
+++ b/sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c
@@ -0,0 +1,112 @@
+/* Compute remainder and a congruent to the quotient.
+   Copyright (C) 1997, 2011 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
+
+   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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <math.h>
+
+#include "math_private.h"
+
+
+static const double zero = 0.0;
+
+
+double
+__remquo (double x, double y, int *quo)
+{
+  int64_t hx, hy;
+  uint64_t sx, qs;
+  int cquo;
+
+  EXTRACT_WORDS64 (hx, x);
+  EXTRACT_WORDS64 (hy, y);
+  sx = hx & UINT64_C(0x8000000000000000);
+  qs = sx ^ (hy & UINT64_C(0x8000000000000000));
+  hy &= UINT64_C(0x7fffffffffffffff);
+  hx &= UINT64_C(0x7fffffffffffffff);
+
+  /* Purge off exception values.  */
+  if (__builtin_expect (hy == 0, 0))
+    return (x * y) / (x * y);			/* y = 0 */
+  if (__builtin_expect (hx >= UINT64_C(0x7ff0000000000000) /* x not finite */
+			|| hy > UINT64_C(0x7ff0000000000000), 0))/* y is NaN */
+    return (x * y) / (x * y);
+
+  if (hy <= UINT64_C(0x7fbfffffffffffff))
+    x = __ieee754_fmod (x, 8 * y);		/* now x < 8y */
+
+  if (__builtin_expect (hx == hy, 0))
+    {
+      *quo = qs ? -1 : 1;
+      return zero * x;
+    }
+
+  INSERT_WORDS64 (x, hx);
+  INSERT_WORDS64 (y, hy);
+  cquo = 0;
+
+  if (x >= 4 * y)
+    {
+      x -= 4 * y;
+      cquo += 4;
+    }
+  if (x >= 2 * y)
+    {
+      x -= 2 * y;
+      cquo += 2;
+    }
+
+  if (hy < UINT64_C(0x0020000000000000))
+    {
+      if (x + x > y)
+	{
+	  x -= y;
+	  ++cquo;
+	  if (x + x >= y)
+	    {
+	      x -= y;
+	      ++cquo;
+	    }
+	}
+    }
+  else
+    {
+      double y_half = 0.5 * y;
+      if (x > y_half)
+	{
+	  x -= y;
+	  ++cquo;
+	  if (x >= y_half)
+	    {
+	      x -= y;
+	      ++cquo;
+	    }
+	}
+    }
+
+  *quo = qs ? -cquo : cquo;
+
+  if (sx)
+    x = -x;
+  return x;
+}
+weak_alias (__remquo, remquo)
+#ifdef NO_LONG_DOUBLE
+strong_alias (__remquo, __remquol)
+weak_alias (__remquo, remquol)
+#endif