1 files changed, 30 insertions, 11 deletions
diff --git a/erts/emulator/beam/erl_math.c b/erts/emulator/beam/erl_math.c
index 16d4fdc09c..fc0aaed18a 100644
--- a/erts/emulator/beam/erl_math.c
+++ b/erts/emulator/beam/erl_math.c
@@ -1,18 +1,19 @@
 /*
  * %CopyrightBegin%
  * 
- * Copyright Ericsson AB 1997-2009. All Rights Reserved.
+ * Copyright Ericsson AB 1997-2016. All Rights Reserved.
  * 
- * The contents of this file are subject to the Erlang Public License,
- * Version 1.1, (the "License"); you may not use this file except in
- * compliance with the License. You should have received a copy of the
- * Erlang Public License along with this software. If not, it can be
- * retrieved online at http://www.erlang.org/.
- * 
- * Software distributed under the License is distributed on an "AS IS"
- * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
- * the License for the specific language governing rights and limitations
- * under the License.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
  * 
  * %CopyrightEnd%
  */
@@ -207,6 +208,24 @@ BIF_RETTYPE math_log_1(BIF_ALIST_1)
     return math_call_1(BIF_P, log, BIF_ARG_1);
 }
 
+#ifdef HAVE_LOG2
+static double
+log2_wrapper(double x)
+{
+    return log2(x);
+}
+#else
+static double
+log2_wrapper(double x)
+{
+    return log(x) / 0.6931471805599453; /* log(2.0); */
+}
+#endif
+
+BIF_RETTYPE math_log2_1(BIF_ALIST_1)
+{
+    return math_call_1(BIF_P, log2_wrapper, BIF_ARG_1);
+}
 
 BIF_RETTYPE math_log10_1(BIF_ALIST_1)
 {