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;
  24 
  25 import java.util.List;
  26 
  27 import org.graalvm.compiler.core.common.alloc.Trace;
  28 import org.graalvm.compiler.core.common.alloc.TraceBuilderResult;
  29 import org.graalvm.compiler.core.common.cfg.AbstractBlockBase;
  30 import org.graalvm.compiler.lir.LIR;
  31 import org.graalvm.compiler.lir.LIRInstruction;
  32 import org.graalvm.compiler.lir.StandardOp.JumpOp;
  33 import org.graalvm.compiler.lir.StandardOp.LabelOp;
  34 
  35 import jdk.vm.ci.meta.Value;
  36 
  37 public class TraceUtil {
  38 
  39     public static AbstractBlockBase<?> getBestTraceInterPredecessor(TraceBuilderResult traceResult, AbstractBlockBase<?> block) {
  40         AbstractBlockBase<?> bestPred = null;
  41         int bestTraceId = traceResult.getTraceForBlock(block).getId();
  42         for (AbstractBlockBase<?> pred : block.getPredecessors()) {
  43             int predTraceId = traceResult.getTraceForBlock(pred).getId();
  44             if (predTraceId < bestTraceId) {
  45                 bestPred = pred;
  46                 bestTraceId = predTraceId;
  47             }
  48         }
  49         return bestPred;
  50     }
  51 
  52     public static boolean isShadowedRegisterValue(Value value) {
  53         assert value != null;
  54         return value instanceof ShadowedRegisterValue;
  55     }
  56 
  57     public static ShadowedRegisterValue asShadowedRegisterValue(Value value) {
  58         assert isShadowedRegisterValue(value);
  59         return (ShadowedRegisterValue) value;
  60     }
  61 
  62     public static boolean isTrivialTrace(LIR lir, Trace trace) {
  63         if (trace.size() != 1) {
  64             return false;
  65         }
  66         List<LIRInstruction> instructions = lir.getLIRforBlock(trace.getBlocks()[0]);
  67         if (instructions.size() != 2) {
  68             return false;
  69         }
  70         assert instructions.get(0) instanceof LabelOp : "First instruction not a LabelOp: " + instructions.get(0);
  71         if (((LabelOp) instructions.get(0)).isPhiIn()) {
  72             /*
  73              * Merge blocks are in general not trivial block because variables defined by a PHI
  74              * always need a location. If the outgoing value of the predecessor is a constant we
  75              * need to find an appropriate location (register or stack).
  76              *
  77              * Note that this case should not happen in practice since the trace containing the
  78              * merge block should also contain one of the predecessors. For non-standard trace
  79              * builders (e.g. the single block trace builder) this is not the true, though.
  80              */
  81             return false;
  82         }
  83         /*
  84          * Now we need to check if the BlockEndOp has no special operand requirements (i.e.
  85          * stack-slot, register). For now we just check for JumpOp because we know that it doesn't.
  86          */
  87         return instructions.get(1) instanceof JumpOp;
  88     }
  89 }