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/*
* Copyright (c) 2016, 2017, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package com.oracle.graal.pointsto.flow.context;
import java.util.Arrays;
import java.util.concurrent.ConcurrentHashMap;
import com.oracle.graal.pointsto.BigBang;
import com.oracle.graal.pointsto.flow.MethodTypeFlow;
import com.oracle.graal.pointsto.flow.context.AnalysisContext.AnalysisContextKey;
import com.oracle.graal.pointsto.flow.context.object.AnalysisObject;
/** Provides logic for analysis context transitions. */
public abstract class AnalysisContextPolicy {
private final ContextFactory factory;
private final C emptyContext;
public AnalysisContextPolicy(C emptyContext) {
this.factory = new ContextFactory();
this.emptyContext = factory.lookupContext(emptyContext);
}
/** Returns the empty context, i.e., the outer most context. */
public final C emptyContext() {
return emptyContext;
}
public final boolean isEmpty(C context) {
return context == emptyContext;
}
/**
* Given the receiver object, caller context and callee this method returns the callee context
* for a virtual or special invoke.
*/
public abstract C calleeContext(BigBang bb, AnalysisObject receiverObject, C callerContext, MethodTypeFlow callee);
/**
* Given the invocation location, caller context and callee this method returns the callee
* context for a static invoke.
*/
public abstract C staticCalleeContext(BigBang bb, BytecodeLocation invokeLocation, C callerContext, MethodTypeFlow callee);
/**
* Given the allocator method context this method returns the allocation context for a heap
* allocated object.
*/
public abstract C allocationContext(C allocatorContext, int maxHeapContextDepth);
/**
* Peels off the least recent labels from the current context, down to {@code maxDepth} depth.
* Only the most recent labels are kept in the context, preserving the temporal order.
*/
public abstract C peel(C context, int maxDepth);
/**
* Extends the input label list with a context label. The depth of the context chain is bounded
* by {@code maxDepth}. Only the most recent context labels are kept in the chain, in the order
* that they appeared in the call chain.
*/
public static BytecodeLocation[] extend(BytecodeLocation[] labelList, BytecodeLocation add, int maxDepth) {
int resultingContextDepth = labelList.length == maxDepth ? maxDepth : labelList.length + 1;
BytecodeLocation[] resultingLabelList = new BytecodeLocation[resultingContextDepth];
for (int i = resultingContextDepth - 2, j = labelList.length - 1; i >= 0 && j >= 0; i--, j--) {
// get only the last 'resultingContextDepth - 1' contexts from the initial chain
resultingLabelList[i] = labelList[j];
}
// append the new label at the end of the chain
if (resultingContextDepth > 0) {
resultingLabelList[resultingContextDepth - 1] = add;
}
return resultingLabelList;
}
/** Extends the input label list with a context label. */
public static BytecodeLocation[] extend(BytecodeLocation[] labelList, BytecodeLocation add) {
BytecodeLocation[] result = Arrays.copyOf(labelList, labelList.length + 1);
result[result.length - 1] = add;
return result;
}
/** Prepends the context label to the input label list. */
public static BytecodeLocation[] prepend(BytecodeLocation add, BytecodeLocation[] labelList) {
BytecodeLocation[] result = new BytecodeLocation[labelList.length + 1];
result[0] = add;
System.arraycopy(labelList, 0, result, 1, labelList.length);
return result;
}
public static BytecodeLocation[] peel(BytecodeLocation[] labelList, int maxDepth) {
assert maxDepth >= 0;
assert labelList.length > maxDepth;
BytecodeLocation[] resultingLabelList = new BytecodeLocation[maxDepth];
for (int i = maxDepth - 1, j = labelList.length - 1; i >= 0 && j >= 0; i--, j--) {
// get only the last 'maxDepth' contexts from the initial chain
resultingLabelList[i] = labelList[j];
}
return resultingLabelList;
}
public AnalysisContext lookupContext(C context) {
return factory.lookupContext(context);
}
private class ContextFactory {
private final ConcurrentHashMap allContexts;
protected ContextFactory() {
this.allContexts = new ConcurrentHashMap<>();
}
protected C lookupContext(C newContext) {
/* The key implements context value equality, instead of the identity equality. */
AnalysisContextKey key = newContext.asKey();
/* Look for an existing context with the same key. */
C oldContext = allContexts.get(key);
if (oldContext == null) {
/* If no existing context was found, add it. */
oldContext = allContexts.putIfAbsent(key, newContext);
/* Check if another thread added the new context in the meantime. */
oldContext = oldContext != null ? oldContext : newContext;
}
return oldContext;
}
}
}