1 files changed, 121 insertions, 0 deletions
diff --git a/sysdeps/ieee754/ldbl-128/s_cbrtl.c b/sysdeps/ieee754/ldbl-128/s_cbrtl.c
new file mode 100644
index 0000000000..298754ea74
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128/s_cbrtl.c
@@ -0,0 +1,121 @@
+/*							cbrtl.c
+ *
+ *	Cube root, long double precision
+ *
+ *
+ *
+ * SYNOPSIS:
+ *
+ * long double x, y, cbrtl();
+ *
+ * y = cbrtl( x );
+ *
+ *
+ *
+ * DESCRIPTION:
+ *
+ * Returns the cube root of the argument, which may be negative.
+ *
+ * Range reduction involves determining the power of 2 of
+ * the argument.  A polynomial of degree 2 applied to the
+ * mantissa, and multiplication by the cube root of 1, 2, or 4
+ * approximates the root to within about 0.1%.  Then Newton's
+ * iteration is used three times to converge to an accurate
+ * result.
+ *
+ *
+ *
+ * ACCURACY:
+ *
+ *                      Relative error:
+ * arithmetic   domain     # trials      peak         rms
+ *    IEEE       -8,8       100000      1.3e-34     3.9e-35
+ *    IEEE    exp(+-707)    100000      1.3e-34     4.3e-35
+ *
+ */
+
+/*
+Cephes Math Library Release 2.2: January, 1991
+Copyright 1984, 1991 by Stephen L. Moshier
+Adapted for glibc October, 2001.
+*/
+
+#include "math.h"
+#include "math_private.h"
+
+static const long double CBRT2 = 1.259921049894873164767210607278228350570251L;
+static const long double CBRT4 = 1.587401051968199474751705639272308260391493L;
+static const long double CBRT2I = 0.7937005259840997373758528196361541301957467L;
+static const long double CBRT4I = 0.6299605249474365823836053036391141752851257L;
+
+
+long double
+__cbrtl (long double x)
+{
+  int e, rem, sign;
+  long double z;
+
+  if (!__finitel (x))
+    return x + x;
+
+  if (x == 0)
+    return (x);
+
+  if (x > 0)
+    sign = 1;
+  else
+    {
+      sign = -1;
+      x = -x;
+    }
+
+  z = x;
+ /* extract power of 2, leaving mantissa between 0.5 and 1  */
+  x = __frexpl (x, &e);
+
+  /* Approximate cube root of number between .5 and 1,
+     peak relative error = 1.2e-6  */
+  x = ((((1.3584464340920900529734e-1L * x
+	  - 6.3986917220457538402318e-1L) * x
+	 + 1.2875551670318751538055e0L) * x
+	- 1.4897083391357284957891e0L) * x
+       + 1.3304961236013647092521e0L) * x + 3.7568280825958912391243e-1L;
+
+  /* exponent divided by 3 */
+  if (e >= 0)
+    {
+      rem = e;
+      e /= 3;
+      rem -= 3 * e;
+      if (rem == 1)
+	x *= CBRT2;
+      else if (rem == 2)
+	x *= CBRT4;
+    }
+  else
+    {				/* argument less than 1 */
+      e = -e;
+      rem = e;
+      e /= 3;
+      rem -= 3 * e;
+      if (rem == 1)
+	x *= CBRT2I;
+      else if (rem == 2)
+	x *= CBRT4I;
+      e = -e;
+    }
+
+  /* multiply by power of 2 */
+  x = __ldexpl (x, e);
+
+  /* Newton iteration */
+  x -= (x - (z / (x * x))) * 0.3333333333333333333333333333333333333333L;
+  x -= (x - (z / (x * x))) * 0.3333333333333333333333333333333333333333L;
+  x -= (x - (z / (x * x))) * 0.3333333333333333333333333333333333333333L;
+
+  if (sign < 0)
+    x = -x;
+  return (x);
+}
+
+weak_alias (__cbrtl, cbrtl)