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