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.trace.lsra;
24
25 import static jdk.vm.ci.code.ValueUtil.isRegister;
26 import static org.graalvm.compiler.core.common.GraalOptions.DetailedAsserts;
27 import static org.graalvm.compiler.lir.LIRValueUtil.isStackSlotValue;
28 import static org.graalvm.compiler.lir.LIRValueUtil.isVariable;
29
30 import java.util.ArrayList;
31
32 import org.graalvm.compiler.core.common.alloc.Trace;
33 import org.graalvm.compiler.core.common.alloc.TraceBuilderResult;
34 import org.graalvm.compiler.core.common.cfg.AbstractBlockBase;
35 import org.graalvm.compiler.debug.Debug;
36 import org.graalvm.compiler.debug.Indent;
37 import org.graalvm.compiler.lir.LIRInsertionBuffer;
38 import org.graalvm.compiler.lir.LIRInstruction;
39 import org.graalvm.compiler.lir.LIRInstruction.OperandMode;
40 import org.graalvm.compiler.lir.StandardOp.LoadConstantOp;
41 import org.graalvm.compiler.lir.StandardOp.MoveOp;
42 import org.graalvm.compiler.lir.StandardOp.ValueMoveOp;
43 import org.graalvm.compiler.lir.alloc.trace.lsra.TraceInterval.SpillState;
44 import org.graalvm.compiler.lir.alloc.trace.lsra.TraceLinearScanPhase.IntervalPredicate;
45 import org.graalvm.compiler.lir.alloc.trace.lsra.TraceLinearScanPhase.TraceLinearScan;
46 import org.graalvm.compiler.lir.gen.LIRGenerationResult;
47
48 import jdk.vm.ci.code.TargetDescription;
49 import jdk.vm.ci.meta.AllocatableValue;
50
51 final class TraceLinearScanEliminateSpillMovePhase extends TraceLinearScanAllocationPhase {
52
53 private static final IntervalPredicate spilledIntervals = new TraceLinearScanPhase.IntervalPredicate() {
54
55 @Override
56 public boolean apply(TraceInterval i) {
57 return i.isSplitParent() && SpillState.IN_MEMORY.contains(i.spillState());
58 }
59 };
60
61 @Override
62 protected void run(TargetDescription target, LIRGenerationResult lirGenRes, Trace trace, TraceLinearScanAllocationContext context) {
63 TraceBuilderResult traceBuilderResult = context.resultTraces;
64 TraceLinearScan allocator = context.allocator;
65 boolean shouldEliminateSpillMoves = shouldEliminateSpillMoves(traceBuilderResult, allocator);
66 eliminateSpillMoves(allocator, shouldEliminateSpillMoves, traceBuilderResult);
67 }
68
69 private static boolean shouldEliminateSpillMoves(TraceBuilderResult traceBuilderResult, TraceLinearScan allocator) {
70 return !traceBuilderResult.incomingSideEdges(traceBuilderResult.getTraceForBlock(allocator.blockAt(0)));
71 }
72
73 // called once before assignment of register numbers
74 @SuppressWarnings("try")
75 private static void eliminateSpillMoves(TraceLinearScan allocator, boolean shouldEliminateSpillMoves, TraceBuilderResult traceBuilderResult) {
76 try (Indent indent = Debug.logAndIndent("Eliminating unnecessary spill moves: Trace%d", traceBuilderResult.getTraceForBlock(allocator.blockAt(0)).getId())) {
77 allocator.sortIntervalsBySpillPos();
78
79 /*
80 * collect all intervals that must be stored after their definition. The list is sorted
81 * by Interval.spillDefinitionPos.
82 */
83 TraceInterval interval = allocator.createUnhandledListBySpillPos(spilledIntervals);
84 if (DetailedAsserts.getValue(allocator.getOptions())) {
85 checkIntervals(interval);
86 }
87 if (Debug.isLogEnabled()) {
88 try (Indent indent2 = Debug.logAndIndent("Sorted intervals")) {
89 for (TraceInterval i = interval; i != null; i = i.next) {
90 Debug.log("%5d: %s", i.spillDefinitionPos(), i);
91 }
92 }
93 }
94
95 LIRInsertionBuffer insertionBuffer = new LIRInsertionBuffer();
96 for (AbstractBlockBase<?> block : allocator.sortedBlocks()) {
97 try (Indent indent1 = Debug.logAndIndent("Handle %s", block)) {
98 ArrayList<LIRInstruction> instructions = allocator.getLIR().getLIRforBlock(block);
99 int numInst = instructions.size();
100
101 int lastOpId = -1;
102 // iterate all instructions of the block.
103 for (int j = 0; j < numInst; j++) {
104 LIRInstruction op = instructions.get(j);
105 int opId = op.id();
106 try (Indent indent2 = Debug.logAndIndent("%5d %s", opId, op)) {
107
108 if (opId == -1) {
109 MoveOp move = (MoveOp) op;
110 /*
111 * Remove move from register to stack if the stack slot is
112 * guaranteed to be correct. Only moves that have been inserted by
113 * LinearScan can be removed.
114 */
115 if (shouldEliminateSpillMoves && canEliminateSpillMove(allocator, block, move, lastOpId)) {
116 /*
117 * Move target is a stack slot that is always correct, so
118 * eliminate instruction.
119 */
120 if (Debug.isLogEnabled()) {
121 if (move instanceof ValueMoveOp) {
122 ValueMoveOp vmove = (ValueMoveOp) move;
123 Debug.log("eliminating move from interval %d (%s) to %d (%s) in block %s", allocator.operandNumber(vmove.getInput()), vmove.getInput(),
124 allocator.operandNumber(vmove.getResult()), vmove.getResult(), block);
125 } else {
126 LoadConstantOp load = (LoadConstantOp) move;
127 Debug.log("eliminating constant load from %s to %d (%s) in block %s", load.getConstant(), allocator.operandNumber(load.getResult()), load.getResult(),
128 block);
129 }
130 }
131
132 // null-instructions are deleted by assignRegNum
133 instructions.set(j, null);
134 }
135
136 } else {
137 lastOpId = opId;
138 /*
139 * Insert move from register to stack just after the beginning of
140 * the interval.
141 */
142 // assert interval == TraceInterval.EndMarker ||
143 // interval.spillDefinitionPos() >= opId : "invalid order";
144 assert interval == TraceInterval.EndMarker || (interval.isSplitParent() && SpillState.IN_MEMORY.contains(interval.spillState())) : "invalid interval";
145
146 while (interval != TraceInterval.EndMarker && interval.spillDefinitionPos() == opId) {
147 Debug.log("handle %s", interval);
148 if (!interval.canMaterialize() && interval.spillState() != SpillState.StartInMemory) {
149
150 AllocatableValue fromLocation = interval.getSplitChildAtOpId(opId, OperandMode.DEF).location();
151 AllocatableValue toLocation = allocator.canonicalSpillOpr(interval);
152 if (!fromLocation.equals(toLocation)) {
153
154 if (!insertionBuffer.initialized()) {
155 /*
156 * prepare insertion buffer (appended when all
157 * instructions in the block are processed)
158 */
159 insertionBuffer.init(instructions);
160 }
161
162 assert isRegister(fromLocation) : "from operand must be a register but is: " + fromLocation + " toLocation=" + toLocation + " spillState=" +
163 interval.spillState();
164 assert isStackSlotValue(toLocation) : "to operand must be a stack slot";
165
166 LIRInstruction move = allocator.getSpillMoveFactory().createMove(toLocation, fromLocation);
167 insertionBuffer.append(j + 1, move);
168
169 if (Debug.isLogEnabled()) {
170 Debug.log("inserting move after definition of interval %d to stack slot %s at opId %d", interval.operandNumber, interval.spillSlot(), opId);
171 }
172 }
173 }
174 interval = interval.next;
175 }
176 }
177 }
178 } // end of instruction iteration
179
180 if (insertionBuffer.initialized()) {
181 insertionBuffer.finish();
182 }
183 }
184 } // end of block iteration
185
186 assert interval == TraceInterval.EndMarker : "missed an interval";
187 }
188 }
189
190 /**
191 * @param allocator
192 * @param block The block {@code move} is located in.
193 * @param move Spill move.
194 * @param lastOpId The id of last "normal" instruction before the spill move. (Spill moves have
195 * no valid opId but -1.)
196 */
197 private static boolean canEliminateSpillMove(TraceLinearScan allocator, AbstractBlockBase<?> block, MoveOp move, int lastOpId) {
198 assert ((LIRInstruction) move).id() == -1 : "Not a spill move: " + move;
199 assert isVariable(move.getResult()) : "LinearScan inserts only moves to variables: " + move;
200 assert lastOpId >= 0 : "Invalid lastOpId: " + lastOpId;
201
202 TraceInterval curInterval = allocator.intervalFor(move.getResult());
203
204 if (!isRegister(curInterval.location()) && curInterval.inMemoryAt(lastOpId) && !isPhiResolutionMove(allocator, move)) {
205 /* Phi resolution moves cannot be removed because they define the value. */
206 // TODO (je) check if the comment is still valid!
207 assert isStackSlotValue(curInterval.location()) : "Not a stack slot: " + curInterval.location();
208 return true;
209 }
210 return false;
211 }
212
213 /**
214 * Checks if a (spill or split) move is a Phi resolution move.
215 *
216 * A spill or split move connects a split parent or a split child with another split child.
217 * Therefore the destination of the move is always a split child. Phi resolution moves look like
218 * spill moves (i.e. {@link LIRInstruction#id() id} is {@code 0}, but they define a new
219 * variable. As a result the destination interval is a split parent.
220 */
221 private static boolean isPhiResolutionMove(TraceLinearScan allocator, MoveOp move) {
222 assert ((LIRInstruction) move).id() == -1 : "Not a spill move: " + move;
223 TraceInterval curInterval = allocator.intervalFor(move.getResult());
224 return curInterval.isSplitParent();
225 }
226
227 private static void checkIntervals(TraceInterval interval) {
228 TraceInterval prev = null;
229 TraceInterval temp = interval;
230 while (temp != TraceInterval.EndMarker) {
231 assert temp.spillDefinitionPos() >= 0 : "invalid spill definition pos " + temp;
232 if (prev != null) {
233 // assert temp.from() >= prev.from() : "intervals not sorted";
234 assert temp.spillDefinitionPos() >= prev.spillDefinitionPos() : "when intervals are sorted by from : then they must also be sorted by spillDefinitionPos";
235 }
236
237 assert temp.spillSlot() != null || temp.canMaterialize() : "interval has no spill slot assigned";
238 assert temp.spillDefinitionPos() >= temp.from() : "invalid order";
239 // assert temp.spillDefinitionPos() <= temp.from() + 2 :
240 // "only intervals defined once at their start-pos can be optimized";
241
242 if (Debug.isLogEnabled()) {
243 Debug.log("interval %d (from %d to %d) must be stored at %d", temp.operandNumber, temp.from(), temp.to(), temp.spillDefinitionPos());
244 }
245
246 prev = temp;
247 temp = temp.next;
248 }
249 }
250
251 }