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/*
* Copyright 2000-2014 JetBrains s.r.o.
*
* 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 com.intellij.codeInspection.bytecodeAnalysis.asm;
import gnu.trove.TIntArrayList;
import org.jetbrains.annotations.Nullable;
import org.jetbrains.org.objectweb.asm.Opcodes;
import org.jetbrains.org.objectweb.asm.tree.AbstractInsnNode;
import org.jetbrains.org.objectweb.asm.tree.InsnList;
import org.jetbrains.org.objectweb.asm.tree.analysis.*;
import java.util.HashSet;
import java.util.LinkedList;
/**
* @author lambdamix
*/
public class OriginsAnalysis {
private static SourceInterpreter ourInterpreter = new SourceInterpreter() {
@Override
public SourceValue copyOperation(AbstractInsnNode insn, SourceValue value) {
return value;
}
};
private static class PreValue extends SourceValue {
final boolean local;
final int slot;
public PreValue(boolean local, int slot, int size) {
super(size);
this.local = local;
this.slot = slot;
}
}
private static class Location {
final boolean local;
final int slot;
Location(boolean local, int slot) {
this.local = local;
this.slot = slot;
}
}
private static class InsnLocation extends Location {
final int insnIndex;
private InsnLocation(boolean local, int insnIndex, int slot) {
super(local, slot);
this.insnIndex = insnIndex;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null) return false;
InsnLocation insnLocation = (InsnLocation)o;
if (local != insnLocation.local) return false;
if (insnIndex != insnLocation.insnIndex) return false;
if (slot != insnLocation.slot) return false;
return true;
}
@Override
public int hashCode() {
// +1 is to avoid collisions
int result = 31 * insnIndex + slot + 1;
return local ? result : -result;
}
}
/**
*
* @param frames fixpoint of frames
* @param instructions method instructions
* @param graph method control flow graph
* @return array, array[i] == true means that the result of a method execution may originate at an i-th instruction
* @throws AnalyzerException
*/
public static boolean[] resultOrigins(Frame<Value>[] frames, InsnList instructions, ControlFlowGraph graph) throws AnalyzerException {
TIntArrayList[] backTransitions = new TIntArrayList[instructions.size()];
for (int i = 0; i < backTransitions.length; i++) {
backTransitions[i] = new TIntArrayList();
}
LinkedList<InsnLocation> queue = new LinkedList<InsnLocation>();
HashSet<InsnLocation> queued = new HashSet<InsnLocation>();
for (int from = 0; from < instructions.size(); from++) {
for (int to : graph.transitions[from]) {
TIntArrayList froms = backTransitions[to];
froms.add(from);
int opcode = instructions.get(to).getOpcode();
if (opcode >= Opcodes.IRETURN && opcode <= Opcodes.ARETURN) {
InsnLocation sourceLoc = new InsnLocation(false, from, frames[to].getStackSize() - 1);
if (queued.add(sourceLoc)) {
queue.push(sourceLoc);
}
}
}
}
boolean[] result = new boolean[instructions.size()];
while (!queue.isEmpty()) {
InsnLocation resultLocation = queue.pop();
int insnIndex = resultLocation.insnIndex;
AbstractInsnNode insn = instructions.get(insnIndex);
int opcode = insn.getOpcode();
Location preLocation = previousLocation(frames[insnIndex], resultLocation, insn);
if (preLocation == null) {
if (opcode != Opcodes.INVOKEINTERFACE && opcode != Opcodes.GETFIELD && !(opcode >= Opcodes.IALOAD && opcode <= Opcodes.SALOAD)) {
result[insnIndex] = true;
}
} else {
TIntArrayList froms = backTransitions[insnIndex];
for (int i = 0; i < froms.size(); i++) {
InsnLocation preILoc = new InsnLocation(preLocation.local, froms.getQuick(i), preLocation.slot);
if (queued.add(preILoc)) {
queue.push(preILoc);
}
}
}
}
return result;
}
/**
*
* @param frame a start frame with an interesting value
* @param location location of an interesting value *after* execution of an instruction
* @param insn an executed instruction
* @return location of an interesting value *before* execution of an instruction (in the past) or null if it is not traceable
* @throws AnalyzerException
*/
@Nullable
private static Location previousLocation(Frame<Value> frame, Location location, AbstractInsnNode insn) throws AnalyzerException {
int insnType = insn.getType();
if (insnType == AbstractInsnNode.LABEL || insnType == AbstractInsnNode.LINE || insnType == AbstractInsnNode.FRAME) {
return location;
}
int opCode = insn.getOpcode();
if (location.local && !((opCode >= Opcodes.ISTORE && opCode <= Opcodes.ASTORE) || opCode == Opcodes.IINC)) {
return location;
}
Frame<SourceValue> preFrame = makePreFrame(frame);
preFrame.execute(insn, ourInterpreter);
if (location.local) {
SourceValue preVal = preFrame.getLocal(location.slot);
if (preVal instanceof PreValue) {
PreValue val = (PreValue)preVal;
return new Location(val.local, val.slot);
}
} else {
SourceValue preVal = preFrame.getStack(location.slot);
if (preVal instanceof PreValue) {
PreValue val = (PreValue)preVal;
return new Location(val.local, val.slot);
}
}
return null;
}
private static Frame<SourceValue> makePreFrame(Frame<Value> frame) {
Frame<SourceValue> preFrame = new Frame<SourceValue>(frame.getLocals(), frame.getMaxStackSize());
for (int i = 0; i < frame.getLocals(); i++) {
preFrame.setLocal(i, new PreValue(true, i, frame.getLocal(i).getSize()));
}
for (int i = 0; i < frame.getStackSize(); i++) {
preFrame.push(new PreValue(false, i, frame.getStack(i).getSize()));
}
return preFrame;
}
}
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