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