Add optimized 64-bit frexp

2 files changed, 69 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 081b4142ef..c47826c0f9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,7 @@
 2011-10-17  Ulrich Drepper  <drepper@gmail.com>
 
+	* sysdeps/ieee754/dbl-64/wordsize-64/s_frexp.c: New file.
+
 	* sysdeps/x86_64/fpu/math_private.h: Relax asm requirements for
 	recently added interfaces.
 	* sysdeps/x86_64/fpu/bits/mathinline.h: Likewise.
diff --git a/sysdeps/ieee754/dbl-64/wordsize-64/s_frexp.c b/sysdeps/ieee754/dbl-64/wordsize-64/s_frexp.c
new file mode 100644
index 0000000000..76f7610804
--- /dev/null
+++ b/sysdeps/ieee754/dbl-64/wordsize-64/s_frexp.c
@@ -0,0 +1,67 @@
+/* Copyright (C) 2011 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
+
+   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 <inttypes.h>
+#include "math.h"
+#include "math_private.h"
+
+/*
+ * for non-zero, finite x
+ *	x = frexp(arg,&exp);
+ * return a double fp quantity x such that 0.5 <= |x| <1.0
+ * and the corresponding binary exponent "exp". That is
+ *	arg = x*2^exp.
+ * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
+ * with *exp=0.
+ */
+
+
+double
+__frexp (double x, int *eptr)
+{
+  int64_t ix;
+  EXTRACT_WORDS64 (ix, x);
+  int32_t ex = 0x7ff & (ix >> 52);
+  int e = 0;
+
+  if (__builtin_expect (ex != 0x7ff && x != 0.0, 1))
+    {
+      /* Not zero and finite.  */
+      e = ex - 1022;
+      if (__builtin_expect (ex == 0, 0))
+	{
+	  /* Subnormal.  */
+	  x *= 0x1p54;
+	  EXTRACT_WORDS64 (ix, x);
+	  ex = 0x7ff & (ix >> 52);
+	  e = ex - 1022 - 54;
+	}
+
+      ix = (ix & INT64_C (0x800fffffffffffff)) | INT64_C (0x3fe0000000000000);
+      INSERT_WORDS64 (x, ix);
+    }
+
+  *eptr = e;
+  return x;
+}
+weak_alias (__frexp, frexp)
+#ifdef NO_LONG_DOUBLE
+strong_alias (__frexp, __frexpl)
+weak_alias (__frexp, frexpl)
+#endif