1 /*
2 * Copyright (c) 2013, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24 package org.graalvm.compiler.hotspot.phases;
25
26 import java.util.Iterator;
27
28 import org.graalvm.compiler.debug.GraalError;
29 import org.graalvm.compiler.graph.Node;
30 import org.graalvm.compiler.graph.NodeFlood;
31 import org.graalvm.compiler.hotspot.GraalHotSpotVMConfig;
32 import org.graalvm.compiler.hotspot.nodes.ArrayRangeWriteBarrier;
33 import org.graalvm.compiler.hotspot.nodes.G1PostWriteBarrier;
34 import org.graalvm.compiler.hotspot.nodes.ObjectWriteBarrier;
35 import org.graalvm.compiler.hotspot.nodes.SerialWriteBarrier;
36 import org.graalvm.compiler.nodes.DeoptimizingNode;
37 import org.graalvm.compiler.nodes.FixedWithNextNode;
38 import org.graalvm.compiler.nodes.LoopBeginNode;
39 import org.graalvm.compiler.nodes.StructuredGraph;
40 import org.graalvm.compiler.nodes.ValueNode;
41 import org.graalvm.compiler.nodes.extended.ArrayRangeWriteNode;
42 import org.graalvm.compiler.nodes.java.LoweredAtomicReadAndWriteNode;
43 import org.graalvm.compiler.nodes.java.LoweredCompareAndSwapNode;
44 import org.graalvm.compiler.nodes.memory.FixedAccessNode;
45 import org.graalvm.compiler.nodes.memory.HeapAccess;
46 import org.graalvm.compiler.nodes.memory.HeapAccess.BarrierType;
47 import org.graalvm.compiler.nodes.memory.ReadNode;
48 import org.graalvm.compiler.nodes.memory.WriteNode;
49 import org.graalvm.compiler.nodes.memory.address.OffsetAddressNode;
50 import org.graalvm.compiler.nodes.type.StampTool;
51 import org.graalvm.compiler.phases.Phase;
52
53 /**
54 * Verification phase that checks if, for every write, at least one write barrier is present at all
55 * paths leading to the previous safepoint. For every write, necessitating a write barrier, a
56 * bottom-up traversal of the graph is performed up to the previous safepoints via all possible
57 * paths. If, for a certain path, no write barrier satisfying the processed write is found, an
58 * assertion is generated.
59 */
60 public class WriteBarrierVerificationPhase extends Phase {
61
62 private final GraalHotSpotVMConfig config;
63
64 public WriteBarrierVerificationPhase(GraalHotSpotVMConfig config) {
65 this.config = config;
66 }
67
68 @Override
69 protected void run(StructuredGraph graph) {
70 processWrites(graph);
71 }
72
73 private void processWrites(StructuredGraph graph) {
74 for (Node node : graph.getNodes()) {
75 if (isObjectWrite(node) || isObjectArrayRangeWrite(node)) {
76 validateWrite(node);
77 }
78 }
79 }
80
81 private void validateWrite(Node write) {
82 /*
83 * The currently validated write is checked in order to discover if it has an appropriate
84 * attached write barrier.
85 */
86 if (hasAttachedBarrier((FixedWithNextNode) write)) {
87 return;
88 }
89 NodeFlood frontier = write.graph().createNodeFlood();
90 expandFrontier(frontier, write);
91 Iterator<Node> iterator = frontier.iterator();
92 while (iterator.hasNext()) {
93 Node currentNode = iterator.next();
94 if (isSafepoint(currentNode)) {
95 throw new AssertionError("Write barrier must be present " + write);
96 }
97 if (useG1GC()) {
98 if (!(currentNode instanceof G1PostWriteBarrier) || (!validateBarrier((FixedAccessNode) write, (ObjectWriteBarrier) currentNode))) {
99 expandFrontier(frontier, currentNode);
100 }
101 } else {
102 if (!(currentNode instanceof SerialWriteBarrier) || (!validateBarrier((FixedAccessNode) write, (ObjectWriteBarrier) currentNode)) ||
103 ((currentNode instanceof SerialWriteBarrier) && !validateBarrier((FixedAccessNode) write, (ObjectWriteBarrier) currentNode))) {
104 expandFrontier(frontier, currentNode);
105 }
106 }
107 }
108 }
109
110 private boolean useG1GC() {
111 return config.useG1GC;
112 }
113
114 private boolean hasAttachedBarrier(FixedWithNextNode node) {
115 final Node next = node.next();
116 final Node previous = node.predecessor();
117 final boolean validatePreBarrier = useG1GC() && (isObjectWrite(node) || !((ArrayRangeWriteNode) node).isInitialization());
118 if (isObjectWrite(node)) {
119 return (isObjectBarrier(node, next) || StampTool.isPointerAlwaysNull(getValueWritten(node))) && (!validatePreBarrier || isObjectBarrier(node, previous));
120 } else if (isObjectArrayRangeWrite(node)) {
121 return (isArrayBarrier(node, next) || StampTool.isPointerAlwaysNull(getValueWritten(node))) && (!validatePreBarrier || isArrayBarrier(node, previous));
122 } else {
123 return true;
124 }
125 }
126
127 private static boolean isObjectBarrier(FixedWithNextNode node, final Node next) {
128 return next instanceof ObjectWriteBarrier && validateBarrier((FixedAccessNode) node, (ObjectWriteBarrier) next);
129 }
130
131 private static boolean isArrayBarrier(FixedWithNextNode node, final Node next) {
132 return (next instanceof ArrayRangeWriteBarrier) && ((ArrayRangeWriteNode) node).getArray() == ((ArrayRangeWriteBarrier) next).getObject();
133 }
134
135 private static boolean isObjectWrite(Node node) {
136 // Read nodes with barrier attached (G1 Ref field) are not validated yet.
137 return node instanceof FixedAccessNode && ((HeapAccess) node).getBarrierType() != BarrierType.NONE && !(node instanceof ReadNode);
138 }
139
140 private static boolean isObjectArrayRangeWrite(Node node) {
141 return node instanceof ArrayRangeWriteNode && ((ArrayRangeWriteNode) node).isObjectArray();
142 }
143
144 private static void expandFrontier(NodeFlood frontier, Node node) {
145 for (Node previousNode : node.cfgPredecessors()) {
146 if (previousNode != null) {
147 frontier.add(previousNode);
148 }
149 }
150 }
151
152 private static boolean isSafepoint(Node node) {
153 /*
154 * LoopBegin nodes are also treated as safepoints since a bottom-up analysis is performed
155 * and loop safepoints are placed before LoopEnd nodes. Possible elimination of write
156 * barriers inside loops, derived from writes outside loops, can not be permitted.
157 */
158 return ((node instanceof DeoptimizingNode) && ((DeoptimizingNode) node).canDeoptimize()) || (node instanceof LoopBeginNode);
159 }
160
161 private static ValueNode getValueWritten(FixedWithNextNode write) {
162 if (write instanceof WriteNode) {
163 return ((WriteNode) write).value();
164 } else if (write instanceof LoweredCompareAndSwapNode) {
165 return ((LoweredCompareAndSwapNode) write).getNewValue();
166 } else if (write instanceof LoweredAtomicReadAndWriteNode) {
167 return ((LoweredAtomicReadAndWriteNode) write).getNewValue();
168 } else {
169 throw GraalError.shouldNotReachHere(String.format("unexpected write node %s", write));
170 }
171 }
172
173 private static boolean validateBarrier(FixedAccessNode write, ObjectWriteBarrier barrier) {
174 assert write instanceof WriteNode || write instanceof LoweredCompareAndSwapNode || write instanceof LoweredAtomicReadAndWriteNode : "Node must be of type requiring a write barrier " + write;
175 if (!barrier.usePrecise()) {
176 if (barrier.getAddress() instanceof OffsetAddressNode && write.getAddress() instanceof OffsetAddressNode) {
177 return ((OffsetAddressNode) barrier.getAddress()).getBase() == ((OffsetAddressNode) write.getAddress()).getBase();
178 }
179 }
180 return barrier.getAddress() == write.getAddress();
181 }
182 }