Mercurial > hg > Members > kono > jpf-core

annotate src/main/gov/nasa/jpf/jvm/bytecode/GetHelper.java @ 0:61d41facf527

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initial v8 import (history reset)
author Peter Mehlitz <Peter.C.Mehlitz@nasa.gov>
date Fri, 23 Jan 2015 10:14:01 -0800
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Peter Mehlitz <Peter.C.Mehlitz@nasa.gov>
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1 /*
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2 * Copyright (C) 2014, United States Government, as represented by the
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Peter Mehlitz <Peter.C.Mehlitz@nasa.gov>
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3 * Administrator of the National Aeronautics and Space Administration.
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4 * All rights reserved.
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5 *
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6 * The Java Pathfinder core (jpf-core) platform is licensed under the
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7 * Apache License, Version 2.0 (the "License"); you may not use this file except
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8 * in compliance with the License. You may obtain a copy of the License at
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9 *
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10 * http://www.apache.org/licenses/LICENSE-2.0.
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11 *
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12 * Unless required by applicable law or agreed to in writing, software
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Peter Mehlitz <Peter.C.Mehlitz@nasa.gov>
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13 * distributed under the License is distributed on an "AS IS" BASIS,
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14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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15 * See the License for the specific language governing permissions and
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16 * limitations under the License.
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17 */
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18
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19 package gov.nasa.jpf.jvm.bytecode;
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20
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21 import gov.nasa.jpf.vm.Instruction;
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22 import gov.nasa.jpf.vm.MethodInfo;
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23
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24 /**
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25 * helper class to factor out common GET code
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26 *
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27 * <2do> This is going to be moved into a Java 8 interface with default methods
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28 */
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29 public class GetHelper {
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30
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31 /**
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32 * do a little bytecode pattern analysis on the fly, to find out if a
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33 * GETFIELD or GETSTATIC is just part of a "..synchronized (obj) {..} .."
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34 * pattern, which usually translates into the following pattern:
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35 * ...
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36 * getfield / getstatic
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37 * dup
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38 * [astore]
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39 * monitorenter
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40 * ...
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41 *
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42 * If it does, there is no need to break the transition since the object
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43 * reference is not used for anything that can cause violations between
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44 * the get and the monitorenter.
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45 *
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46 * <2do> We might want to extend this in the future to also cover sync on
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47 * local vars, like "Object o = myField; synchronized(o){..}..", but then
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48 * the check becomes more expensive since we get interspersed aload/astore
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49 * insns, and some of the locals could be used outside the sync block. Not
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50 * sure if it buys much on the bottom line
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51 *
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52 * <2do> this relies on javac code patterns. The dup/astore could
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53 * lead to subsequent use of the object reference w/o corresponding get/putfield
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54 * insns (if it's not a volatile), but this access would be either a call
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55 * or a get/putfield on a share object, i.e. would be checked separately
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56 */
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57 protected static boolean isMonitorEnterPrologue(MethodInfo mi, int insnIndex){
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58 Instruction[] code = mi.getInstructions();
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59 int off = insnIndex+1;
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60
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61 if (off < code.length-3) {
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62 // we don't reach out further than 3 instructions
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63 if (code[off] instanceof DUP) {
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64 off++;
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65
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66 if (code[off] instanceof ASTORE) {
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67 off++;
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68 }
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69
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70 if (code[off] instanceof MONITORENTER) {
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71 return true;
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72 }
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73 }
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74 }
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75
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76 return false; // if in doubt, we assume it is not part of a monitorenter code pattern
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77 }
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78 }