Mercurial > hg > Members > kono > jpf-core
view src/main/gov/nasa/jpf/jvm/bytecode/GetHelper.java @ 0:61d41facf527
initial v8 import (history reset)
author | Peter Mehlitz <Peter.C.Mehlitz@nasa.gov> |
---|---|
date | Fri, 23 Jan 2015 10:14:01 -0800 |
parents | |
children |
line wrap: on
line source
/* * Copyright (C) 2014, United States Government, as represented by the * Administrator of the National Aeronautics and Space Administration. * All rights reserved. * * The Java Pathfinder core (jpf-core) platform is licensed under the * Apache License, Version 2.0 (the "License"); you may not use this file except * in compliance with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0. * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package gov.nasa.jpf.jvm.bytecode; import gov.nasa.jpf.vm.Instruction; import gov.nasa.jpf.vm.MethodInfo; /** * helper class to factor out common GET code * * <2do> This is going to be moved into a Java 8 interface with default methods */ public class GetHelper { /** * do a little bytecode pattern analysis on the fly, to find out if a * GETFIELD or GETSTATIC is just part of a "..synchronized (obj) {..} .." * pattern, which usually translates into the following pattern: * ... * getfield / getstatic * dup * [astore] * monitorenter * ... * * If it does, there is no need to break the transition since the object * reference is not used for anything that can cause violations between * the get and the monitorenter. * * <2do> We might want to extend this in the future to also cover sync on * local vars, like "Object o = myField; synchronized(o){..}..", but then * the check becomes more expensive since we get interspersed aload/astore * insns, and some of the locals could be used outside the sync block. Not * sure if it buys much on the bottom line * * <2do> this relies on javac code patterns. The dup/astore could * lead to subsequent use of the object reference w/o corresponding get/putfield * insns (if it's not a volatile), but this access would be either a call * or a get/putfield on a share object, i.e. would be checked separately */ protected static boolean isMonitorEnterPrologue(MethodInfo mi, int insnIndex){ Instruction[] code = mi.getInstructions(); int off = insnIndex+1; if (off < code.length-3) { // we don't reach out further than 3 instructions if (code[off] instanceof DUP) { off++; if (code[off] instanceof ASTORE) { off++; } if (code[off] instanceof MONITORENTER) { return true; } } } return false; // if in doubt, we assume it is not part of a monitorenter code pattern } }