001 /*
002 * This file is part of the Jikes RVM project (http://jikesrvm.org).
003 *
004 * This file is licensed to You under the Eclipse Public License (EPL);
005 * You may not use this file except in compliance with the License. You
006 * may obtain a copy of the License at
007 *
008 * http://www.opensource.org/licenses/eclipse-1.0.php
009 *
010 * See the COPYRIGHT.txt file distributed with this work for information
011 * regarding copyright ownership.
012 */
013 package org.jikesrvm.compilers.opt.controlflow;
014
015 import static org.jikesrvm.compilers.opt.driver.OptConstants.INSTRUMENTATION_BCI;
016 import static org.jikesrvm.compilers.opt.ir.Operators.IR_PROLOGUE_opcode;
017 import static org.jikesrvm.compilers.opt.ir.Operators.YIELDPOINT_BACKEDGE;
018 import static org.jikesrvm.compilers.opt.ir.Operators.YIELDPOINT_EPILOGUE;
019 import static org.jikesrvm.compilers.opt.ir.Operators.YIELDPOINT_PROLOGUE;
020
021 import java.util.Enumeration;
022
023 import org.jikesrvm.VM;
024 import org.jikesrvm.compilers.opt.driver.CompilerPhase;
025 import org.jikesrvm.compilers.opt.inlining.InlineSequence;
026 import org.jikesrvm.compilers.opt.ir.BasicBlock;
027 import org.jikesrvm.compilers.opt.ir.Empty;
028 import org.jikesrvm.compilers.opt.ir.IR;
029 import org.jikesrvm.compilers.opt.ir.Instruction;
030 import org.jikesrvm.compilers.opt.ir.Operator;
031
032 /**
033 * This class inserts yield points in
034 * <ul>
035 * <li>1) a method's prologue
036 * <li>2) loop headers
037 * <li>3) (optionally) method exits (epilogue, athrow)
038 * </ul>
039 */
040 public class YieldPoints extends CompilerPhase {
041
042 /**
043 * Return the name of this phase
044 * @return "Yield Point Insertion"
045 */
046 @Override
047 public final String getName() {
048 return "Yield Point Insertion";
049 }
050
051 /**
052 * This phase contains no per-compilation instance fields.
053 */
054 @Override
055 public final CompilerPhase newExecution(IR ir) {
056 return this;
057 }
058
059 /**
060 * Insert yield points in method prologues, loop heads, and method exits
061 *
062 */
063 @Override
064 public final void perform(IR ir) {
065 if (!ir.method.isInterruptible()) {
066 return; // don't insert yieldpoints in Uninterruptible code.
067 }
068
069 // (1) Insert prologue yieldpoint unconditionally.
070 // As part of prologue/epilogue insertion we'll remove
071 // the yieldpoints in trivial methods that otherwise wouldn't need
072 // a stackframe.
073 prependYield(ir.cfg.entry(), YIELDPOINT_PROLOGUE, 0, ir.gc.inlineSequence);
074
075 // (2) If using epilogue yieldpoints scan basic blocks, looking for returns or throws
076 if (VM.UseEpilogueYieldPoints) {
077 for (Enumeration<BasicBlock> e = ir.getBasicBlocks(); e.hasMoreElements();) {
078 BasicBlock block = e.nextElement();
079 if (block.hasReturn() || block.hasAthrowInst()) {
080 prependYield(block, YIELDPOINT_EPILOGUE, INSTRUMENTATION_BCI, ir.gc.inlineSequence);
081 }
082 }
083 }
084
085 // (3) Insert yieldpoints in loop heads based on the LST.
086 LSTGraph lst = ir.HIRInfo.loopStructureTree;
087 if (lst != null) {
088 for (java.util.Enumeration<LSTNode> e = lst.getRoot().getChildren(); e.hasMoreElements();) {
089 processLoopNest(e.nextElement());
090 }
091 }
092 }
093
094 /**
095 * Process all loop heads in a loop nest by inserting a backedge yieldpoint in each of them.
096 */
097 private void processLoopNest(LSTNode n) {
098 for (java.util.Enumeration<LSTNode> e = n.getChildren(); e.hasMoreElements();) {
099 processLoopNest(e.nextElement());
100 }
101 Instruction dest = n.header.firstInstruction();
102 if (dest.position.getMethod().isInterruptible()) {
103 prependYield(n.header, YIELDPOINT_BACKEDGE, dest.bcIndex, dest.position);
104 }
105 }
106
107 /**
108 * Add a YIELD instruction to the appropriate place for the basic
109 * block passed.
110 *
111 * @param bb the basic block
112 * @param yp the yieldpoint operator to insert
113 * @param bcIndex the bcIndex of the yieldpoint
114 * @param position the source position of the yieldpoint
115 */
116 private void prependYield(BasicBlock bb, Operator yp, int bcIndex, InlineSequence position) {
117 Instruction insertionPoint = null;
118
119 if (bb.isEmpty()) {
120 insertionPoint = bb.lastInstruction();
121 } else {
122 insertionPoint = bb.firstRealInstruction();
123 }
124
125 if (yp == YIELDPOINT_PROLOGUE) {
126 if (VM.VerifyAssertions) {
127 VM._assert((insertionPoint != null) && (insertionPoint.getOpcode() == IR_PROLOGUE_opcode));
128 }
129 // put it after the prologue
130 insertionPoint = insertionPoint.nextInstructionInCodeOrder();
131 } else if (VM.UseEpilogueYieldPoints && yp == YIELDPOINT_EPILOGUE) {
132 // epilogues go before the return or athrow (at end of block)
133 insertionPoint = bb.lastRealInstruction();
134 }
135
136 Instruction s = Empty.create(yp);
137 insertionPoint.insertBefore(s);
138 s.position = position;
139 s.bcIndex = bcIndex;
140 }
141 }
142
143
144
145