--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.phases/src/org/graalvm/compiler/phases/schedule/MemoryScheduleVerification.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,162 @@
+/*
+ * Copyright (c) 2015, 2016, 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.phases.schedule;
+
+import java.util.List;
+
+import org.graalvm.compiler.core.common.cfg.BlockMap;
+import org.graalvm.compiler.core.common.cfg.Loop;
+import org.graalvm.compiler.debug.DebugContext;
+import org.graalvm.compiler.graph.Node;
+import org.graalvm.compiler.nodes.AbstractBeginNode;
+import org.graalvm.compiler.nodes.AbstractMergeNode;
+import org.graalvm.compiler.nodes.LoopBeginNode;
+import org.graalvm.compiler.nodes.PhiNode;
+import org.graalvm.compiler.nodes.cfg.Block;
+import org.graalvm.compiler.nodes.cfg.HIRLoop;
+import org.graalvm.compiler.nodes.memory.FloatingReadNode;
+import org.graalvm.compiler.nodes.memory.MemoryCheckpoint;
+import org.graalvm.compiler.nodes.memory.MemoryNode;
+import org.graalvm.compiler.nodes.memory.MemoryPhiNode;
+import org.graalvm.compiler.phases.graph.ReentrantBlockIterator;
+import org.graalvm.compiler.phases.graph.ReentrantBlockIterator.BlockIteratorClosure;
+import org.graalvm.util.EconomicSet;
+import org.graalvm.util.Equivalence;
+import org.graalvm.word.LocationIdentity;
+
+public final class MemoryScheduleVerification extends BlockIteratorClosure<EconomicSet<FloatingReadNode>> {
+
+    private final BlockMap<List<Node>> blockToNodesMap;
+
+    public static boolean check(Block startBlock, BlockMap<List<Node>> blockToNodesMap) {
+        ReentrantBlockIterator.apply(new MemoryScheduleVerification(blockToNodesMap), startBlock);
+        return true;
+    }
+
+    private MemoryScheduleVerification(BlockMap<List<Node>> blockToNodesMap) {
+        this.blockToNodesMap = blockToNodesMap;
+    }
+
+    @Override
+    protected EconomicSet<FloatingReadNode> getInitialState() {
+        return EconomicSet.create(Equivalence.IDENTITY);
+    }
+
+    @Override
+    protected EconomicSet<FloatingReadNode> processBlock(Block block, EconomicSet<FloatingReadNode> currentState) {
+        AbstractBeginNode beginNode = block.getBeginNode();
+        if (beginNode instanceof AbstractMergeNode) {
+            AbstractMergeNode abstractMergeNode = (AbstractMergeNode) beginNode;
+            for (PhiNode phi : abstractMergeNode.phis()) {
+                if (phi instanceof MemoryPhiNode) {
+                    MemoryPhiNode memoryPhiNode = (MemoryPhiNode) phi;
+                    addFloatingReadUsages(currentState, memoryPhiNode);
+                }
+            }
+        }
+        for (Node n : blockToNodesMap.get(block)) {
+            if (n instanceof MemoryCheckpoint) {
+                if (n instanceof MemoryCheckpoint.Single) {
+                    MemoryCheckpoint.Single single = (MemoryCheckpoint.Single) n;
+                    processLocation(n, single.getLocationIdentity(), currentState);
+                } else if (n instanceof MemoryCheckpoint.Multi) {
+                    MemoryCheckpoint.Multi multi = (MemoryCheckpoint.Multi) n;
+                    for (LocationIdentity location : multi.getLocationIdentities()) {
+                        processLocation(n, location, currentState);
+                    }
+                }
+
+                addFloatingReadUsages(currentState, n);
+            } else if (n instanceof MemoryNode) {
+                addFloatingReadUsages(currentState, n);
+            } else if (n instanceof FloatingReadNode) {
+                FloatingReadNode floatingReadNode = (FloatingReadNode) n;
+                if (floatingReadNode.getLastLocationAccess() != null && floatingReadNode.getLocationIdentity().isMutable()) {
+                    if (currentState.contains(floatingReadNode)) {
+                        // Floating read was found in the state.
+                        currentState.remove(floatingReadNode);
+                    } else {
+                        throw new RuntimeException("Floating read node " + n + " was not found in the state, i.e., it was killed by a memory check point before its place in the schedule. Block=" +
+                                        block + ", block begin: " + block.getBeginNode() + " block loop: " + block.getLoop() + ", " + blockToNodesMap.get(block).get(0));
+                    }
+                }
+
+            }
+        }
+        return currentState;
+    }
+
+    private static void addFloatingReadUsages(EconomicSet<FloatingReadNode> currentState, Node n) {
+        for (FloatingReadNode read : n.usages().filter(FloatingReadNode.class)) {
+            if (read.getLastLocationAccess() == n && read.getLocationIdentity().isMutable()) {
+                currentState.add(read);
+            }
+        }
+    }
+
+    private void processLocation(Node n, LocationIdentity location, EconomicSet<FloatingReadNode> currentState) {
+        assert n != null;
+        if (location.isImmutable()) {
+            return;
+        }
+
+        for (FloatingReadNode r : cloneState(currentState)) {
+            if (r.getLocationIdentity().overlaps(location)) {
+                // This read is killed by this location.
+                r.getDebug().log(DebugContext.VERBOSE_LEVEL, "%s removing %s from state", n, r);
+                currentState.remove(r);
+            }
+        }
+    }
+
+    @Override
+    protected EconomicSet<FloatingReadNode> merge(Block merge, List<EconomicSet<FloatingReadNode>> states) {
+        EconomicSet<FloatingReadNode> result = states.get(0);
+        for (int i = 1; i < states.size(); ++i) {
+            result.retainAll(states.get(i));
+        }
+        return result;
+    }
+
+    @Override
+    protected EconomicSet<FloatingReadNode> cloneState(EconomicSet<FloatingReadNode> oldState) {
+        EconomicSet<FloatingReadNode> result = EconomicSet.create(Equivalence.IDENTITY);
+        if (oldState != null) {
+            result.addAll(oldState);
+        }
+        return result;
+    }
+
+    @Override
+    protected List<EconomicSet<FloatingReadNode>> processLoop(Loop<Block> loop, EconomicSet<FloatingReadNode> initialState) {
+        HIRLoop l = (HIRLoop) loop;
+        for (MemoryPhiNode memoryPhi : ((LoopBeginNode) l.getHeader().getBeginNode()).memoryPhis()) {
+            for (FloatingReadNode r : cloneState(initialState)) {
+                if (r.getLocationIdentity().overlaps(memoryPhi.getLocationIdentity())) {
+                    initialState.remove(r);
+                }
+            }
+        }
+        return ReentrantBlockIterator.processLoop(this, loop, initialState).exitStates;
+    }
+}