1 /*
   2  * Copyright (c) 2011, 2019, 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 
  24 
  25 package org.graalvm.compiler.loop.phases;
  26 
  27 import org.graalvm.compiler.loop.LoopEx;
  28 import org.graalvm.compiler.loop.LoopsData;
  29 import org.graalvm.compiler.nodes.FixedNode;
  30 import org.graalvm.compiler.nodes.Invoke;
  31 import org.graalvm.compiler.nodes.LoopEndNode;
  32 import org.graalvm.compiler.nodes.StructuredGraph;
  33 import org.graalvm.compiler.nodes.cfg.Block;
  34 import org.graalvm.compiler.nodes.extended.ForeignCallNode;
  35 import org.graalvm.compiler.phases.BasePhase;
  36 import org.graalvm.compiler.phases.tiers.MidTierContext;
  37 
  38 public class LoopSafepointEliminationPhase extends BasePhase<MidTierContext> {
  39 
  40     @Override
  41     protected void run(StructuredGraph graph, MidTierContext context) {
  42         LoopsData loops = new LoopsData(graph);
  43         loops.detectedCountedLoops();
  44         for (LoopEx loop : loops.countedLoops()) {
  45             if (loop.loop().getChildren().isEmpty() && loop.counted().getStamp().getBits() <= 32) {
  46                 boolean hasSafepoint = false;
  47                 for (LoopEndNode loopEnd : loop.loopBegin().loopEnds()) {
  48                     hasSafepoint |= loopEnd.canSafepoint();
  49                 }
  50                 if (hasSafepoint) {
  51                     if (!loop.counted().counterNeverOverflows()) {
  52                         // Counter can overflow, need to create a guard.
  53                         if (context.getOptimisticOptimizations().useLoopLimitChecks(graph.getOptions()) && graph.getGuardsStage().allowsFloatingGuards()) {
  54                             loop.counted().createOverFlowGuard();
  55                         } else {
  56                             // Cannot disable this safepoint, because the loop could overflow.
  57                             continue;
  58                         }
  59                     }
  60                     loop.loopBegin().disableSafepoint();
  61                 }
  62             }
  63         }
  64         for (LoopEx loop : loops.loops()) {
  65             for (LoopEndNode loopEnd : loop.loopBegin().loopEnds()) {
  66                 Block b = loops.getCFG().blockFor(loopEnd);
  67                 blocks: while (b != loop.loop().getHeader()) {
  68                     assert b != null;
  69                     for (FixedNode node : b.getNodes()) {
  70                         if (node instanceof Invoke || (node instanceof ForeignCallNode && ((ForeignCallNode) node).isGuaranteedSafepoint())) {
  71                             loopEnd.disableSafepoint();
  72                             break blocks;
  73                         }
  74                     }
  75                     b = b.getDominator();
  76                 }
  77             }
  78         }
  79         loops.deleteUnusedNodes();
  80     }
  81 }