1 files changed, 76 insertions, 0 deletions
diff --git a/sysdeps/ieee754/dbl-64/s_cbrt.c b/sysdeps/ieee754/dbl-64/s_cbrt.c
new file mode 100644
index 0000000000..753049d375
--- /dev/null
+++ b/sysdeps/ieee754/dbl-64/s_cbrt.c
@@ -0,0 +1,76 @@
+/* Compute cubic root of double value.
+   Copyright (C) 1997 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Dirk Alboth <dirka@uni-paderborn.de> and
+   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 Library General Public License as
+   published by the Free Software Foundation; either version 2 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  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"
+
+
+#define CBRT2 1.2599210498948731648		/* 2^(1/3) */
+#define SQR_CBRT2 1.5874010519681994748		/* 2^(2/3) */
+
+static const double factor[5] =
+{
+  1.0 / SQR_CBRT2,
+  1.0 / CBRT2,
+  1.0,
+  CBRT2,
+  SQR_CBRT2
+};
+
+
+double
+__cbrt (double x)
+{
+  double xm, ym, u, t2;
+  int xe;
+
+  /* Reduce X.  XM now is an range 1.0 to 0.5.  */
+  xm = __frexp (fabs (x), &xe);
+
+  /* If X is not finite or is null return it (with raising exceptions
+     if necessary.
+     Note: *Our* version of `frexp' sets XE to zero if the argument is
+     Inf or NaN.  This is not portable but faster.  */
+  if (xe == 0 && fpclassify (x) <= FP_ZERO)
+    return x + x;
+
+ u = (0.354895765043919860
+      + ((1.50819193781584896
+	 + ((-2.11499494167371287
+	    + ((2.44693122563534430
+	       + ((-1.83469277483613086
+		  + (0.784932344976639262 - 0.145263899385486377 * xm) * xm)
+		  * xm))
+	       * xm))
+	    * xm))
+	 * xm));
+
+  t2 = u * u * u;
+
+  ym = u * (t2 + 2.0 * xm) / (2.0 * t2 + xm) * factor[2 + xe % 3];
+
+  return __ldexp (x > 0.0 ? ym : -ym, xe / 3);
+}
+weak_alias (__cbrt, cbrt)
+#ifdef NO_LONG_DOUBLE
+strong_alias (__cbrt, __cbrtl)
+weak_alias (__cbrt, cbrtl)
+#endif