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 org.jikesrvm.compilers.opt.DefUse;
016    import org.jikesrvm.compilers.opt.OptOptions;
017    import org.jikesrvm.compilers.opt.driver.CompilerPhase;
018    import org.jikesrvm.compilers.opt.ir.IR;
019    
020    /**
021     * The driver that creates an annotated {@link AnnotatedLSTGraph}.
022     *
023     * @see AnnotatedLSTGraph
024     */
025    public class LoopAnalysis extends CompilerPhase {
026      /**
027       * Return a string name for this phase.
028       * @return "Loop Analysis"
029       */
030      @Override
031      public final String getName() {
032        return "Loop Analysis";
033      }
034    
035      /**
036       * This phase is disabled by default.
037       * <p>
038       * It will run only on O3 but O2 is the default maximum optimization level.
039       */
040      @Override
041      public boolean shouldPerform(OptOptions options) {
042        return options.getOptLevel() >= 3;
043      }
044    
045      @Override
046      public final void perform(IR ir) {
047        if (!ir.hasReachableExceptionHandlers()) {
048          // Build LST tree and dominator info
049          new DominatorsPhase(false).perform(ir);
050          DefUse.computeDU(ir);
051          // Build annotated version
052          ir.HIRInfo.loopStructureTree = new AnnotatedLSTGraph(ir, ir.HIRInfo.loopStructureTree);
053        }
054      }
055    }