--- /dev/null	2016-05-31 09:42:47.975716356 -0700
+++ new/src/jdk.vm.compiler/share/classes/org.graalvm.compiler.replacements/src/org/graalvm/compiler/replacements/nodes/BitScanReverseNode.java	2016-12-09 00:57:08.185539865 -0800
@@ -0,0 +1,133 @@
+/*
+ * Copyright (c) 2012, 2015, 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.
+ */
+package org.graalvm.compiler.replacements.nodes;
+
+import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_3;
+import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_1;
+
+import org.graalvm.compiler.core.common.type.IntegerStamp;
+import org.graalvm.compiler.core.common.type.PrimitiveStamp;
+import org.graalvm.compiler.core.common.type.Stamp;
+import org.graalvm.compiler.core.common.type.StampFactory;
+import org.graalvm.compiler.graph.NodeClass;
+import org.graalvm.compiler.graph.spi.CanonicalizerTool;
+import org.graalvm.compiler.lir.gen.ArithmeticLIRGeneratorTool;
+import org.graalvm.compiler.nodeinfo.NodeInfo;
+import org.graalvm.compiler.nodes.ConstantNode;
+import org.graalvm.compiler.nodes.ValueNode;
+import org.graalvm.compiler.nodes.calc.UnaryNode;
+import org.graalvm.compiler.nodes.spi.ArithmeticLIRLowerable;
+import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool;
+
+import jdk.vm.ci.code.CodeUtil;
+import jdk.vm.ci.meta.JavaConstant;
+import jdk.vm.ci.meta.JavaKind;
+
+/**
+ * Determines the index of the most significant "1" bit. Note that the result is undefined if the
+ * input is zero.
+ */
+@NodeInfo(cycles = CYCLES_3, size = SIZE_1)
+public final class BitScanReverseNode extends UnaryNode implements ArithmeticLIRLowerable {
+
+    public static final NodeClass<BitScanReverseNode> TYPE = NodeClass.create(BitScanReverseNode.class);
+
+    public BitScanReverseNode(ValueNode value) {
+        super(TYPE, StampFactory.forInteger(JavaKind.Int, 0, ((PrimitiveStamp) value.stamp()).getBits()), value);
+        assert value.getStackKind() == JavaKind.Int || value.getStackKind() == JavaKind.Long;
+    }
+
+    @Override
+    public Stamp foldStamp(Stamp newStamp) {
+        assert newStamp.isCompatible(getValue().stamp());
+        IntegerStamp valueStamp = (IntegerStamp) newStamp;
+        int min;
+        int max;
+        long mask = CodeUtil.mask(valueStamp.getBits());
+        int lastAlwaysSetBit = scan(valueStamp.downMask() & mask);
+        if (lastAlwaysSetBit == -1) {
+            int firstMaybeSetBit = BitScanForwardNode.scan(valueStamp.upMask() & mask);
+            min = firstMaybeSetBit;
+        } else {
+            min = lastAlwaysSetBit;
+        }
+        int lastMaybeSetBit = scan(valueStamp.upMask() & mask);
+        max = lastMaybeSetBit;
+        return StampFactory.forInteger(JavaKind.Int, min, max);
+    }
+
+    @Override
+    public ValueNode canonical(CanonicalizerTool tool, ValueNode forValue) {
+        if (forValue.isConstant()) {
+            JavaConstant c = forValue.asJavaConstant();
+            if (c.asLong() != 0) {
+                return ConstantNode.forInt(forValue.getStackKind() == JavaKind.Int ? scan(c.asInt()) : scan(c.asLong()));
+            }
+        }
+        return this;
+    }
+
+    /**
+     * Utility method with defined return value for 0.
+     *
+     * @param v
+     * @return index of first set bit or -1 if {@code v} == 0.
+     */
+    public static int scan(long v) {
+        return 63 - Long.numberOfLeadingZeros(v);
+    }
+
+    /**
+     * Utility method with defined return value for 0.
+     *
+     * @param v
+     * @return index of first set bit or -1 if {@code v} == 0.
+     */
+    public static int scan(int v) {
+        return 31 - Integer.numberOfLeadingZeros(v);
+    }
+
+    /**
+     * Raw intrinsic for bsr instruction.
+     *
+     * @param v
+     * @return index of first set bit or an undefined value if {@code v} == 0.
+     */
+    @NodeIntrinsic
+    public static native int unsafeScan(int v);
+
+    /**
+     * Raw intrinsic for bsr instruction.
+     *
+     * @param v
+     * @return index of first set bit or an undefined value if {@code v} == 0.
+     */
+    @NodeIntrinsic
+    public static native int unsafeScan(long v);
+
+    @Override
+    public void generate(NodeLIRBuilderTool builder, ArithmeticLIRGeneratorTool gen) {
+        builder.setResult(this, gen.emitBitScanReverse(builder.operand(getValue())));
+    }
+
+}