--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/utilities/population_count.hpp	Wed Jan 23 10:01:21 2019 +0100
@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code 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 General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_UTILITIES_POPULATION_COUNT_HPP
+#define SHARE_UTILITIES_POPULATION_COUNT_HPP
+
+#include "utilities/debug.hpp"
+#include "utilities/globalDefinitions.hpp"
+
+// Returns the population count of x, i.e., the number of bits set in x.
+//
+// Adapted from Hacker's Delight, 2nd Edition, Figure 5-2.
+//
+// Ideally this should be dispatched per platform to use optimized
+// instructions when available, such as POPCNT on modern x86/AMD. Our builds
+// still target and support older architectures that might lack support for
+// these, however. For example, with current build configurations,
+// __builtin_popcount(x) would generate a call to a similar but slower 64-bit
+// version of this 32-bit implementation.
+static uint32_t population_count(uint32_t x) {
+  x -= ((x >> 1) & 0x55555555);
+  x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
+  return (((x + (x >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24;
+}
+
+#endif // SHARE_UTILITIES_POPULATION_COUNT_HPP