1 /*
2 * Copyright (c) 2015, 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.lir.alloc.lsra;
24
25 import java.util.ArrayList;
26 import java.util.BitSet;
27
28 import org.graalvm.compiler.core.common.cfg.AbstractBlockBase;
29 import org.graalvm.compiler.debug.Debug;
30 import org.graalvm.compiler.debug.Indent;
31 import org.graalvm.compiler.lir.LIRInstruction;
32 import org.graalvm.compiler.lir.StandardOp;
33 import org.graalvm.compiler.lir.gen.LIRGenerationResult;
34 import org.graalvm.compiler.lir.phases.AllocationPhase;
35
36 import jdk.vm.ci.code.TargetDescription;
37
38 /**
39 * Phase 6: resolve data flow
40 *
41 * Insert moves at edges between blocks if intervals have been split.
42 */
43 public class LinearScanResolveDataFlowPhase extends AllocationPhase {
44
45 protected final LinearScan allocator;
46
47 protected LinearScanResolveDataFlowPhase(LinearScan allocator) {
48 this.allocator = allocator;
49 }
50
51 @Override
52 protected void run(TargetDescription target, LIRGenerationResult lirGenRes, AllocationContext context) {
53 resolveDataFlow();
54 allocator.printIntervals("After resolve data flow");
55 }
56
57 protected void resolveCollectMappings(AbstractBlockBase<?> fromBlock, AbstractBlockBase<?> toBlock, AbstractBlockBase<?> midBlock, MoveResolver moveResolver) {
58 assert moveResolver.checkEmpty();
59 assert midBlock == null ||
60 (midBlock.getPredecessorCount() == 1 && midBlock.getSuccessorCount() == 1 && midBlock.getPredecessors()[0].equals(fromBlock) && midBlock.getSuccessors()[0].equals(
61 toBlock));
62
63 int toBlockFirstInstructionId = allocator.getFirstLirInstructionId(toBlock);
64 int fromBlockLastInstructionId = allocator.getLastLirInstructionId(fromBlock) + 1;
65 int numOperands = allocator.operandSize();
66 BitSet liveAtEdge = allocator.getBlockData(toBlock).liveIn;
67
68 // visit all variables for which the liveAtEdge bit is set
69 for (int operandNum = liveAtEdge.nextSetBit(0); operandNum >= 0; operandNum = liveAtEdge.nextSetBit(operandNum + 1)) {
70 assert operandNum < numOperands : "live information set for not exisiting interval";
71 assert allocator.getBlockData(fromBlock).liveOut.get(operandNum) && allocator.getBlockData(toBlock).liveIn.get(operandNum) : "interval not live at this edge";
72
73 Interval fromInterval = allocator.splitChildAtOpId(allocator.intervalFor(operandNum), fromBlockLastInstructionId, LIRInstruction.OperandMode.DEF);
74 Interval toInterval = allocator.splitChildAtOpId(allocator.intervalFor(operandNum), toBlockFirstInstructionId, LIRInstruction.OperandMode.DEF);
75
76 if (fromInterval != toInterval && !fromInterval.location().equals(toInterval.location())) {
77 // need to insert move instruction
78 moveResolver.addMapping(fromInterval, toInterval);
79 }
80 }
81 }
82
83 void resolveFindInsertPos(AbstractBlockBase<?> fromBlock, AbstractBlockBase<?> toBlock, MoveResolver moveResolver) {
84 if (fromBlock.getSuccessorCount() <= 1) {
85 if (Debug.isLogEnabled()) {
86 Debug.log("inserting moves at end of fromBlock B%d", fromBlock.getId());
87 }
88
89 ArrayList<LIRInstruction> instructions = allocator.getLIR().getLIRforBlock(fromBlock);
90 LIRInstruction instr = instructions.get(instructions.size() - 1);
91 if (instr instanceof StandardOp.JumpOp) {
92 // insert moves before branch
93 moveResolver.setInsertPosition(instructions, instructions.size() - 1);
94 } else {
95 moveResolver.setInsertPosition(instructions, instructions.size());
96 }
97
98 } else {
99 if (Debug.isLogEnabled()) {
100 Debug.log("inserting moves at beginning of toBlock B%d", toBlock.getId());
101 }
102
103 if (allocator.detailedAsserts) {
104 assert allocator.getLIR().getLIRforBlock(fromBlock).get(0) instanceof StandardOp.LabelOp : "block does not start with a label";
105
106 /*
107 * Because the number of predecessor edges matches the number of successor edges,
108 * blocks which are reached by switch statements may have be more than one
109 * predecessor but it will be guaranteed that all predecessors will be the same.
110 */
111 for (AbstractBlockBase<?> predecessor : toBlock.getPredecessors()) {
112 assert fromBlock == predecessor : "all critical edges must be broken";
113 }
114 }
115
116 moveResolver.setInsertPosition(allocator.getLIR().getLIRforBlock(toBlock), 1);
117 }
118 }
119
120 /**
121 * Inserts necessary moves (spilling or reloading) at edges between blocks for intervals that
122 * have been split.
123 */
124 @SuppressWarnings("try")
125 protected void resolveDataFlow() {
126 try (Indent indent = Debug.logAndIndent("resolve data flow")) {
127
128 MoveResolver moveResolver = allocator.createMoveResolver();
129 BitSet blockCompleted = new BitSet(allocator.blockCount());
130
131 optimizeEmptyBlocks(moveResolver, blockCompleted);
132
133 resolveDataFlow0(moveResolver, blockCompleted);
134
135 }
136 }
137
138 protected void optimizeEmptyBlocks(MoveResolver moveResolver, BitSet blockCompleted) {
139 for (AbstractBlockBase<?> block : allocator.sortedBlocks()) {
140
141 // check if block has only one predecessor and only one successor
142 if (block.getPredecessorCount() == 1 && block.getSuccessorCount() == 1) {
143 ArrayList<LIRInstruction> instructions = allocator.getLIR().getLIRforBlock(block);
144 assert instructions.get(0) instanceof StandardOp.LabelOp : "block must start with label";
145 assert instructions.get(instructions.size() - 1) instanceof StandardOp.JumpOp : "block with successor must end with unconditional jump";
146
147 // check if block is empty (only label and branch)
148 if (instructions.size() == 2) {
149 AbstractBlockBase<?> pred = block.getPredecessors()[0];
150 AbstractBlockBase<?> sux = block.getSuccessors()[0];
151
152 // prevent optimization of two consecutive blocks
153 if (!blockCompleted.get(pred.getLinearScanNumber()) && !blockCompleted.get(sux.getLinearScanNumber())) {
154 if (Debug.isLogEnabled()) {
155 Debug.log(" optimizing empty block B%d (pred: B%d, sux: B%d)", block.getId(), pred.getId(), sux.getId());
156 }
157
158 blockCompleted.set(block.getLinearScanNumber());
159
160 /*
161 * Directly resolve between pred and sux (without looking at the empty block
162 * between).
163 */
164 resolveCollectMappings(pred, sux, block, moveResolver);
165 if (moveResolver.hasMappings()) {
166 moveResolver.setInsertPosition(instructions, 1);
167 moveResolver.resolveAndAppendMoves();
168 }
169 }
170 }
171 }
172 }
173 }
174
175 protected void resolveDataFlow0(MoveResolver moveResolver, BitSet blockCompleted) {
176 BitSet alreadyResolved = new BitSet(allocator.blockCount());
177 for (AbstractBlockBase<?> fromBlock : allocator.sortedBlocks()) {
178 if (!blockCompleted.get(fromBlock.getLinearScanNumber())) {
179 alreadyResolved.clear();
180 alreadyResolved.or(blockCompleted);
181
182 for (AbstractBlockBase<?> toBlock : fromBlock.getSuccessors()) {
183
184 /*
185 * Check for duplicate edges between the same blocks (can happen with switch
186 * blocks).
187 */
188 if (!alreadyResolved.get(toBlock.getLinearScanNumber())) {
189 if (Debug.isLogEnabled()) {
190 Debug.log("processing edge between B%d and B%d", fromBlock.getId(), toBlock.getId());
191 }
192
193 alreadyResolved.set(toBlock.getLinearScanNumber());
194
195 // collect all intervals that have been split between
196 // fromBlock and toBlock
197 resolveCollectMappings(fromBlock, toBlock, null, moveResolver);
198 if (moveResolver.hasMappings()) {
199 resolveFindInsertPos(fromBlock, toBlock, moveResolver);
200 moveResolver.resolveAndAppendMoves();
201 }
202 }
203 }
204 }
205 }
206 }
207
208 }