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.cfg.AbstractControlFlowGraph.commonDominator;
26 import static org.graalvm.compiler.core.common.cfg.AbstractControlFlowGraph.dominates;
27 import static org.graalvm.compiler.lir.LIRValueUtil.isStackSlotValue;
28
29 import java.util.Iterator;
30
31 import org.graalvm.compiler.core.common.cfg.AbstractBlockBase;
32 import org.graalvm.compiler.debug.CounterKey;
33 import org.graalvm.compiler.debug.DebugContext;
34 import org.graalvm.compiler.debug.Indent;
35 import org.graalvm.compiler.lir.LIRInsertionBuffer;
36 import org.graalvm.compiler.lir.LIRInstruction;
37 import org.graalvm.compiler.lir.LIRInstruction.OperandMode;
38 import org.graalvm.compiler.lir.alloc.lsra.Interval.SpillState;
39 import org.graalvm.compiler.lir.gen.LIRGenerationResult;
40 import org.graalvm.compiler.lir.phases.AllocationPhase.AllocationContext;
41
42 import jdk.vm.ci.code.TargetDescription;
43 import jdk.vm.ci.meta.AllocatableValue;
44
45 public final class LinearScanOptimizeSpillPositionPhase extends LinearScanAllocationPhase {
46
47 private static final CounterKey betterSpillPos = DebugContext.counter("BetterSpillPosition");
48 private static final CounterKey betterSpillPosWithLowerProbability = DebugContext.counter("BetterSpillPositionWithLowerProbability");
49
50 private final LinearScan allocator;
51 private DebugContext debug;
52
53 LinearScanOptimizeSpillPositionPhase(LinearScan allocator) {
54 this.allocator = allocator;
55 this.debug = allocator.getDebug();
56 }
57
58 @Override
59 protected void run(TargetDescription target, LIRGenerationResult lirGenRes, AllocationContext context) {
60 optimizeSpillPosition(lirGenRes);
61 allocator.printIntervals("After optimize spill position");
62 }
63
64 @SuppressWarnings("try")
65 private void optimizeSpillPosition(LIRGenerationResult res) {
66 try (Indent indent0 = debug.logAndIndent("OptimizeSpillPositions")) {
67 LIRInsertionBuffer[] insertionBuffers = new LIRInsertionBuffer[allocator.getLIR().linearScanOrder().length];
68 for (Interval interval : allocator.intervals()) {
69 optimizeInterval(insertionBuffers, interval, res);
70 }
71 for (LIRInsertionBuffer insertionBuffer : insertionBuffers) {
72 if (insertionBuffer != null) {
73 assert insertionBuffer.initialized() : "Insertion buffer is nonnull but not initialized!";
74 insertionBuffer.finish();
75 }
76 }
77 }
78 }
79
80 @SuppressWarnings("try")
81 private void optimizeInterval(LIRInsertionBuffer[] insertionBuffers, Interval interval, LIRGenerationResult res) {
82 if (interval == null || !interval.isSplitParent() || interval.spillState() != SpillState.SpillInDominator) {
83 return;
84 }
85 AbstractBlockBase<?> defBlock = allocator.blockForId(interval.spillDefinitionPos());
86 AbstractBlockBase<?> spillBlock = null;
87 Interval firstSpillChild = null;
88 try (Indent indent = debug.logAndIndent("interval %s (%s)", interval, defBlock)) {
89 for (Interval splitChild : interval.getSplitChildren()) {
90 if (isStackSlotValue(splitChild.location())) {
91 if (firstSpillChild == null || splitChild.from() < firstSpillChild.from()) {
92 firstSpillChild = splitChild;
93 } else {
94 assert firstSpillChild.from() < splitChild.from();
95 }
96 // iterate all blocks where the interval has use positions
97 for (AbstractBlockBase<?> splitBlock : blocksForInterval(splitChild)) {
98 if (dominates(defBlock, splitBlock)) {
99 debug.log("Split interval %s, block %s", splitChild, splitBlock);
100 if (spillBlock == null) {
101 spillBlock = splitBlock;
102 } else {
103 spillBlock = commonDominator(spillBlock, splitBlock);
104 assert spillBlock != null;
105 }
106 }
107 }
108 }
109 }
110 if (spillBlock == null) {
111 debug.log("not spill interval found");
112 // no spill interval
113 interval.setSpillState(SpillState.StoreAtDefinition);
114 return;
115 }
116 debug.log(DebugContext.VERBOSE_LEVEL, "Spill block candidate (initial): %s", spillBlock);
117 // move out of loops
118 if (defBlock.getLoopDepth() < spillBlock.getLoopDepth()) {
119 spillBlock = moveSpillOutOfLoop(defBlock, spillBlock);
120 }
121 debug.log(DebugContext.VERBOSE_LEVEL, "Spill block candidate (after loop optimizaton): %s", spillBlock);
122
123 /*
124 * The spill block is the begin of the first split child (aka the value is on the
125 * stack).
126 *
127 * The problem is that if spill block has more than one predecessor, the values at the
128 * end of the predecessors might differ. Therefore, we would need a spill move in all
129 * predecessors. To avoid this we spill in the dominator.
130 */
131 assert firstSpillChild != null;
132 if (!defBlock.equals(spillBlock) && spillBlock.equals(allocator.blockForId(firstSpillChild.from()))) {
133 AbstractBlockBase<?> dom = spillBlock.getDominator();
134 if (debug.isLogEnabled()) {
135 debug.log("Spill block (%s) is the beginning of a spill child -> use dominator (%s)", spillBlock, dom);
136 }
137 spillBlock = dom;
138 }
139 if (defBlock.equals(spillBlock)) {
140 debug.log(DebugContext.VERBOSE_LEVEL, "Definition is the best choice: %s", defBlock);
141 // definition is the best choice
142 interval.setSpillState(SpillState.StoreAtDefinition);
143 return;
144 }
145 assert dominates(defBlock, spillBlock);
146 betterSpillPos.increment(debug);
147 if (debug.isLogEnabled()) {
148 debug.log("Better spill position found (Block %s)", spillBlock);
149 }
150
151 if (defBlock.probability() <= spillBlock.probability()) {
152 debug.log(DebugContext.VERBOSE_LEVEL, "Definition has lower probability %s (%f) is lower than spill block %s (%f)", defBlock, defBlock.probability(), spillBlock,
153 spillBlock.probability());
154 // better spill block has the same probability -> do nothing
155 interval.setSpillState(SpillState.StoreAtDefinition);
156 return;
157 }
158
159 LIRInsertionBuffer insertionBuffer = insertionBuffers[spillBlock.getId()];
160 if (insertionBuffer == null) {
161 insertionBuffer = new LIRInsertionBuffer();
162 insertionBuffers[spillBlock.getId()] = insertionBuffer;
163 insertionBuffer.init(allocator.getLIR().getLIRforBlock(spillBlock));
164 }
165 int spillOpId = allocator.getFirstLirInstructionId(spillBlock);
166 // insert spill move
167 AllocatableValue fromLocation = interval.getSplitChildAtOpId(spillOpId, OperandMode.DEF, allocator).location();
168 AllocatableValue toLocation = LinearScan.canonicalSpillOpr(interval);
169 LIRInstruction move = allocator.getSpillMoveFactory().createMove(toLocation, fromLocation);
170 move.setComment(res, "LSRAOptimizeSpillPos: optimize spill pos");
171 debug.log(DebugContext.VERBOSE_LEVEL, "Insert spill move %s", move);
172 move.setId(LinearScan.DOMINATOR_SPILL_MOVE_ID);
173 /*
174 * We can use the insertion buffer directly because we always insert at position 1.
175 */
176 insertionBuffer.append(1, move);
177
178 betterSpillPosWithLowerProbability.increment(debug);
179 interval.setSpillDefinitionPos(spillOpId);
180 }
181 }
182
183 /**
184 * Iterate over all {@link AbstractBlockBase blocks} of an interval.
185 */
186 private class IntervalBlockIterator implements Iterator<AbstractBlockBase<?>> {
187
188 Range range;
189 AbstractBlockBase<?> block;
190
191 IntervalBlockIterator(Interval interval) {
192 range = interval.first();
193 block = allocator.blockForId(range.from);
194 }
195
196 @Override
197 public AbstractBlockBase<?> next() {
198 AbstractBlockBase<?> currentBlock = block;
199 int nextBlockIndex = block.getLinearScanNumber() + 1;
200 if (nextBlockIndex < allocator.sortedBlocks().length) {
201 block = allocator.sortedBlocks()[nextBlockIndex];
202 if (range.to <= allocator.getFirstLirInstructionId(block)) {
203 range = range.next;
204 if (range.isEndMarker()) {
205 block = null;
206 } else {
207 block = allocator.blockForId(range.from);
208 }
209 }
210 } else {
211 block = null;
212 }
213 return currentBlock;
214 }
215
216 @Override
217 public boolean hasNext() {
218 return block != null;
219 }
220 }
221
222 private Iterable<AbstractBlockBase<?>> blocksForInterval(Interval interval) {
223 return new Iterable<AbstractBlockBase<?>>() {
224 @Override
225 public Iterator<AbstractBlockBase<?>> iterator() {
226 return new IntervalBlockIterator(interval);
227 }
228 };
229 }
230
231 private static AbstractBlockBase<?> moveSpillOutOfLoop(AbstractBlockBase<?> defBlock, AbstractBlockBase<?> spillBlock) {
232 int defLoopDepth = defBlock.getLoopDepth();
233 for (AbstractBlockBase<?> block = spillBlock.getDominator(); !defBlock.equals(block); block = block.getDominator()) {
234 assert block != null : "spill block not dominated by definition block?";
235 if (block.getLoopDepth() <= defLoopDepth) {
236 assert block.getLoopDepth() == defLoopDepth : "Cannot spill an interval outside of the loop where it is defined!";
237 return block;
238 }
239 }
240 return defBlock;
241 }
242 }