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 static org.graalvm.compiler.core.common.GraalOptions.DetailedAsserts;
26 import static org.graalvm.compiler.lir.LIRValueUtil.isStackSlotValue;
27 import static org.graalvm.compiler.lir.LIRValueUtil.isVariable;
28 import static org.graalvm.compiler.lir.phases.LIRPhase.Options.LIROptimization;
29 import static jdk.vm.ci.code.ValueUtil.isRegister;
30
31 import java.util.List;
32
33 import org.graalvm.compiler.core.common.cfg.AbstractBlockBase;
34 import org.graalvm.compiler.debug.Debug;
35 import org.graalvm.compiler.debug.Indent;
36 import org.graalvm.compiler.lir.LIRInsertionBuffer;
37 import org.graalvm.compiler.lir.LIRInstruction;
38 import org.graalvm.compiler.lir.StandardOp.LoadConstantOp;
39 import org.graalvm.compiler.lir.StandardOp.MoveOp;
40 import org.graalvm.compiler.lir.StandardOp.ValueMoveOp;
41 import org.graalvm.compiler.lir.alloc.lsra.Interval.SpillState;
42 import org.graalvm.compiler.lir.alloc.lsra.LinearScan.IntervalPredicate;
43 import org.graalvm.compiler.lir.gen.LIRGenerationResult;
44 import org.graalvm.compiler.lir.phases.AllocationPhase;
45 import org.graalvm.compiler.options.NestedBooleanOptionValue;
46 import org.graalvm.compiler.options.Option;
47 import org.graalvm.compiler.options.OptionType;
48 import org.graalvm.compiler.options.OptionValue;
49
50 import jdk.vm.ci.code.TargetDescription;
51 import jdk.vm.ci.meta.AllocatableValue;
52
53 public class LinearScanEliminateSpillMovePhase extends AllocationPhase {
54
55 public static class Options {
56 // @formatter:off
57 @Option(help = "Enable spill move elimination.", type = OptionType.Debug)
58 public static final OptionValue<Boolean> LIROptLSRAEliminateSpillMoves = new NestedBooleanOptionValue(LIROptimization, true);
59 // @formatter:on
60 }
61
62 private static final IntervalPredicate mustStoreAtDefinition = new LinearScan.IntervalPredicate() {
63
64 @Override
65 public boolean apply(Interval i) {
66 return i.isSplitParent() && i.spillState() == SpillState.StoreAtDefinition;
67 }
68 };
69
70 protected final LinearScan allocator;
71
72 protected LinearScanEliminateSpillMovePhase(LinearScan allocator) {
73 this.allocator = allocator;
74 }
75
76 @Override
77 protected void run(TargetDescription target, LIRGenerationResult lirGenRes, AllocationContext context) {
78 eliminateSpillMoves();
79 }
80
81 /**
82 * @return the index of the first instruction that is of interest for
83 * {@link #eliminateSpillMoves()}
84 */
85 protected int firstInstructionOfInterest() {
86 // skip the first because it is always a label
87 return 1;
88 }
89
90 // called once before assignment of register numbers
91 @SuppressWarnings("try")
92 void eliminateSpillMoves() {
93 try (Indent indent = Debug.logAndIndent("Eliminating unnecessary spill moves")) {
94
95 /*
96 * collect all intervals that must be stored after their definition. The list is sorted
97 * by Interval.spillDefinitionPos.
98 */
99 Interval interval;
100 interval = allocator.createUnhandledLists(mustStoreAtDefinition, null).first;
101 if (DetailedAsserts.getValue()) {
102 checkIntervals(interval);
103 }
104
105 LIRInsertionBuffer insertionBuffer = new LIRInsertionBuffer();
106 for (AbstractBlockBase<?> block : allocator.sortedBlocks()) {
107 try (Indent indent1 = Debug.logAndIndent("Handle %s", block)) {
108 List<LIRInstruction> instructions = allocator.getLIR().getLIRforBlock(block);
109 int numInst = instructions.size();
110
111 // iterate all instructions of the block.
112 for (int j = firstInstructionOfInterest(); j < numInst; j++) {
113 LIRInstruction op = instructions.get(j);
114 int opId = op.id();
115
116 if (opId == -1) {
117 MoveOp move = (MoveOp) op;
118 /*
119 * Remove move from register to stack if the stack slot is guaranteed to
120 * be correct. Only moves that have been inserted by LinearScan can be
121 * removed.
122 */
123 if (Options.LIROptLSRAEliminateSpillMoves.getValue() && canEliminateSpillMove(block, move)) {
124 /*
125 * Move target is a stack slot that is always correct, so eliminate
126 * instruction.
127 */
128 if (Debug.isLogEnabled()) {
129 if (move instanceof ValueMoveOp) {
130 ValueMoveOp vmove = (ValueMoveOp) move;
131 Debug.log("eliminating move from interval %d (%s) to %d (%s) in block %s", allocator.operandNumber(vmove.getInput()), vmove.getInput(),
132 allocator.operandNumber(vmove.getResult()), vmove.getResult(), block);
133 } else {
134 LoadConstantOp load = (LoadConstantOp) move;
135 Debug.log("eliminating constant load from %s to %d (%s) in block %s", load.getConstant(), allocator.operandNumber(load.getResult()), load.getResult(), block);
136 }
137 }
138
139 // null-instructions are deleted by assignRegNum
140 instructions.set(j, null);
141 }
142
143 } else {
144 /*
145 * Insert move from register to stack just after the beginning of the
146 * interval.
147 */
148 assert interval == Interval.EndMarker || interval.spillDefinitionPos() >= opId : "invalid order";
149 assert interval == Interval.EndMarker || (interval.isSplitParent() && interval.spillState() == SpillState.StoreAtDefinition) : "invalid interval";
150
151 while (interval != Interval.EndMarker && interval.spillDefinitionPos() == opId) {
152 if (!interval.canMaterialize()) {
153 if (!insertionBuffer.initialized()) {
154 /*
155 * prepare insertion buffer (appended when all instructions
156 * in the block are processed)
157 */
158 insertionBuffer.init(instructions);
159 }
160
161 AllocatableValue fromLocation = interval.location();
162 AllocatableValue toLocation = LinearScan.canonicalSpillOpr(interval);
163 if (!fromLocation.equals(toLocation)) {
164
165 assert isRegister(fromLocation) : "from operand must be a register but is: " + fromLocation + " toLocation=" + toLocation + " spillState=" +
166 interval.spillState();
167 assert isStackSlotValue(toLocation) : "to operand must be a stack slot";
168
169 LIRInstruction move = allocator.getSpillMoveFactory().createMove(toLocation, fromLocation);
170 insertionBuffer.append(j + 1, move);
171
172 if (Debug.isLogEnabled()) {
173 Debug.log("inserting move after definition of interval %d to stack slot %s at opId %d", interval.operandNumber, interval.spillSlot(), opId);
174 }
175 }
176 }
177 interval = interval.next;
178 }
179 }
180 } // end of instruction iteration
181
182 if (insertionBuffer.initialized()) {
183 insertionBuffer.finish();
184 }
185 }
186 } // end of block iteration
187
188 assert interval == Interval.EndMarker : "missed an interval";
189 }
190 }
191
192 /**
193 * @param block The block {@code move} is located in.
194 * @param move Spill move.
195 */
196 protected boolean canEliminateSpillMove(AbstractBlockBase<?> block, MoveOp move) {
197 assert isVariable(move.getResult()) : "LinearScan inserts only moves to variables: " + move;
198
199 Interval curInterval = allocator.intervalFor(move.getResult());
200
201 if (!isRegister(curInterval.location()) && curInterval.alwaysInMemory()) {
202 assert isStackSlotValue(curInterval.location()) : "Not a stack slot: " + curInterval.location();
203 return true;
204 }
205 return false;
206 }
207
208 private static void checkIntervals(Interval interval) {
209 Interval prev = null;
210 Interval temp = interval;
211 while (temp != Interval.EndMarker) {
212 assert temp.spillDefinitionPos() > 0 : "invalid spill definition pos";
213 if (prev != null) {
214 assert temp.from() >= prev.from() : "intervals not sorted";
215 assert temp.spillDefinitionPos() >= prev.spillDefinitionPos() : "when intervals are sorted by from : then they must also be sorted by spillDefinitionPos";
216 }
217
218 assert temp.spillSlot() != null || temp.canMaterialize() : "interval has no spill slot assigned";
219 assert temp.spillDefinitionPos() >= temp.from() : "invalid order";
220 assert temp.spillDefinitionPos() <= temp.from() + 2 : "only intervals defined once at their start-pos can be optimized";
221
222 if (Debug.isLogEnabled()) {
223 Debug.log("interval %d (from %d to %d) must be stored at %d", temp.operandNumber, temp.from(), temp.to(), temp.spillDefinitionPos());
224 }
225
226 prev = temp;
227 temp = temp.next;
228 }
229 }
230
231 }