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 package org.graalvm.compiler.phases.common;
24
25 import org.graalvm.compiler.core.common.cfg.Loop;
26 import org.graalvm.compiler.debug.DebugCloseable;
27 import org.graalvm.compiler.debug.DebugContext;
28 import org.graalvm.compiler.graph.Node;
29 import org.graalvm.compiler.nodes.AbstractBeginNode;
30 import org.graalvm.compiler.nodes.BeginNode;
31 import org.graalvm.compiler.nodes.DeoptimizeNode;
32 import org.graalvm.compiler.nodes.FixedWithNextNode;
33 import org.graalvm.compiler.nodes.GuardNode;
34 import org.graalvm.compiler.nodes.IfNode;
35 import org.graalvm.compiler.nodes.LoopBeginNode;
36 import org.graalvm.compiler.nodes.LoopExitNode;
37 import org.graalvm.compiler.nodes.StructuredGraph;
38 import org.graalvm.compiler.nodes.StructuredGraph.GuardsStage;
39 import org.graalvm.compiler.nodes.StructuredGraph.ScheduleResult;
40 import org.graalvm.compiler.nodes.cfg.Block;
41 import org.graalvm.compiler.phases.BasePhase;
42 import org.graalvm.compiler.phases.graph.ScheduledNodeIterator;
43 import org.graalvm.compiler.phases.schedule.SchedulePhase;
44 import org.graalvm.compiler.phases.schedule.SchedulePhase.SchedulingStrategy;
45 import org.graalvm.compiler.phases.tiers.MidTierContext;
46
47 /**
48 * This phase lowers {@link GuardNode GuardNodes} into corresponding control-flow structure and
49 * {@link DeoptimizeNode DeoptimizeNodes}.
50 *
51 * This allow to enter the {@link GuardsStage#FIXED_DEOPTS FIXED_DEOPTS} stage of the graph where
52 * all node that may cause deoptimization are fixed.
53 * <p>
54 * It first makes a schedule in order to know where the control flow should be placed. Then, for
55 * each block, it applies two passes. The first one tries to replace null-check guards with implicit
56 * null checks performed by access to the objects that need to be null checked. The second phase
57 * does the actual control-flow expansion of the remaining {@link GuardNode GuardNodes}.
58 */
59 public class GuardLoweringPhase extends BasePhase<MidTierContext> {
60
61 private static class LowerGuards extends ScheduledNodeIterator {
62
63 private final Block block;
64 private boolean useGuardIdAsDebugId;
65
66 LowerGuards(Block block, boolean useGuardIdAsDebugId) {
67 this.block = block;
68 this.useGuardIdAsDebugId = useGuardIdAsDebugId;
69 }
70
71 @Override
72 protected void processNode(Node node) {
73 if (node instanceof GuardNode) {
74 GuardNode guard = (GuardNode) node;
75 FixedWithNextNode lowered = guard.lowerGuard();
76 if (lowered != null) {
77 replaceCurrent(lowered);
78 } else {
79 lowerToIf(guard);
80 }
81 }
82 }
83
84 @SuppressWarnings("try")
85 private void lowerToIf(GuardNode guard) {
86 try (DebugCloseable position = guard.withNodeSourcePosition()) {
87 StructuredGraph graph = guard.graph();
88 AbstractBeginNode fastPath = graph.add(new BeginNode());
89 @SuppressWarnings("deprecation")
90 int debugId = useGuardIdAsDebugId ? guard.getId() : DeoptimizeNode.DEFAULT_DEBUG_ID;
91 DeoptimizeNode deopt = graph.add(new DeoptimizeNode(guard.getAction(), guard.getReason(), debugId, guard.getSpeculation(), null));
92 AbstractBeginNode deoptBranch = BeginNode.begin(deopt);
93 AbstractBeginNode trueSuccessor;
94 AbstractBeginNode falseSuccessor;
95 insertLoopExits(deopt);
96 if (guard.isNegated()) {
97 trueSuccessor = deoptBranch;
98 falseSuccessor = fastPath;
99 } else {
100 trueSuccessor = fastPath;
101 falseSuccessor = deoptBranch;
102 }
103 IfNode ifNode = graph.add(new IfNode(guard.getCondition(), trueSuccessor, falseSuccessor, trueSuccessor == fastPath ? 1 : 0));
104 guard.replaceAndDelete(fastPath);
105 insert(ifNode, fastPath);
106 }
107 }
108
109 private void insertLoopExits(DeoptimizeNode deopt) {
110 Loop<Block> loop = block.getLoop();
111 StructuredGraph graph = deopt.graph();
112 while (loop != null) {
113 LoopExitNode exit = graph.add(new LoopExitNode((LoopBeginNode) loop.getHeader().getBeginNode()));
114 graph.addBeforeFixed(deopt, exit);
115 loop = loop.getParent();
116 }
117 }
118 }
119
120 @Override
121 protected void run(StructuredGraph graph, MidTierContext context) {
122 if (graph.getGuardsStage().allowsFloatingGuards()) {
123 SchedulePhase schedulePhase = new SchedulePhase(SchedulingStrategy.EARLIEST);
124 schedulePhase.apply(graph);
125 ScheduleResult schedule = graph.getLastSchedule();
126
127 for (Block block : schedule.getCFG().getBlocks()) {
128 processBlock(block, schedule);
129 }
130 graph.setGuardsStage(GuardsStage.FIXED_DEOPTS);
131 }
132
133 assert assertNoGuardsLeft(graph);
134 }
135
136 private static boolean assertNoGuardsLeft(StructuredGraph graph) {
137 assert graph.getNodes().filter(GuardNode.class).isEmpty();
138 return true;
139 }
140
141 private static void processBlock(Block block, ScheduleResult schedule) {
142 DebugContext debug = block.getBeginNode().getDebug();
143 new LowerGuards(block, debug.isDumpEnabledForMethod() || debug.isLogEnabledForMethod()).processNodes(block, schedule);
144 }
145 }