1 files changed, 38 insertions, 0 deletions
diff --git a/sysdeps/ieee754/ldbl-128ibm/lgamma_productl.c b/sysdeps/ieee754/ldbl-128ibm/lgamma_productl.c
new file mode 100644
index 0000000000..c5fa81be8e
--- /dev/null
+++ b/sysdeps/ieee754/ldbl-128ibm/lgamma_productl.c
@@ -0,0 +1,38 @@
+/* Compute a product of 1 + (T/X), 1 + (T/(X+1)), ....
+   Copyright (C) 2015-2016 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 <float.h>
+
+/* Compute the product of 1 + (T / (X + X_EPS)), 1 + (T / (X + X_EPS +
+   1)), ..., 1 + (T / (X + X_EPS + N - 1)), minus 1.  X is such that
+   all the values X + 1, ..., X + N - 1 are exactly representable, and
+   X_EPS / X is small enough that factors quadratic in it can be
+   neglected.  */
+
+long double
+__lgamma_productl (long double t, long double x, long double x_eps, int n)
+{
+  long double x_full = x + x_eps;
+  long double ret = 0;
+  for (int i = 0; i < n; i++)
+    /* FIXME: no extra precision used.  */
+    ret += (t / (x_full + i)) * (1 + ret);
+  return ret;
+}