/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.flink.api.java.sca;
import org.apache.flink.annotation.Internal;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.JumpInsnNode;
import org.objectweb.asm.tree.analysis.Analyzer;
import org.objectweb.asm.tree.analysis.Frame;
import org.objectweb.asm.tree.analysis.Interpreter;
import java.lang.reflect.Field;
/**
* Modified version of ASMs Analyzer. It defines a custom ASM Frame
* and allows jump modification which is necessary for UDFs with
* one iterable input e.g. GroupReduce.
* (see also UdfAnalyzer's field "iteratorTrueAssumptionApplied")
*/
@Internal
public class ModifiedASMAnalyzer extends Analyzer {
private NestedMethodAnalyzer interpreter;
public ModifiedASMAnalyzer(Interpreter interpreter) {
super(interpreter);
this.interpreter = (NestedMethodAnalyzer) interpreter;
}
protected Frame newFrame(int nLocals, int nStack) {
return new ModifiedASMFrame(nLocals, nStack);
}
protected Frame newFrame(Frame src) {
return new ModifiedASMFrame(src);
}
// type of jump modification
private int jumpModification = NO_MOD;
private static final int NO_MOD = -1;
private static final int IFEQ_MOD = 0;
private static final int IFNE_MOD = 1;
private int eventInsn;
// current state of modification
private int jumpModificationState = DO_NOTHING;
private static final int DO_NOTHING = -1;
private static final int PRE_STATE = 0;
private static final int MOD_STATE = 1;
private static final int WAIT_FOR_INSN_STATE = 2;
public void requestIFEQLoopModification() {
if (jumpModificationState != DO_NOTHING) {
throw new CodeAnalyzerException("Unable to do jump modifications (unsupported nested jumping).");
}
jumpModification = IFEQ_MOD;
jumpModificationState = PRE_STATE;
}
public void requestIFNELoopModification() {
if (jumpModificationState != DO_NOTHING) {
throw new CodeAnalyzerException("Unable to do jump modifications (unsupported nested jumping).");
}
jumpModification = IFNE_MOD;
jumpModificationState = PRE_STATE;
}
@Override
protected void newControlFlowEdge(int insn, int successor) {
try {
if (jumpModificationState == PRE_STATE) {
jumpModificationState = MOD_STATE;
}
else if (jumpModificationState == MOD_STATE) {
// this modification swaps the top 2 values on the queue stack
// it ensures that the "TRUE" path will be executed first, which is important
// for a later merge
if (jumpModification == IFEQ_MOD) {
final int top = accessField(Analyzer.class, "top").getInt(this);
final int[] queue = (int[]) accessField(Analyzer.class, "queue").get(this);
final int tmp = queue[top - 2];
queue[top - 2] = queue[top - 1];
queue[top - 1] = tmp;
eventInsn = queue[top - 2] - 1;
final InsnList insns = (InsnList) accessField(Analyzer.class, "insns").get(this);
// check if instruction is a goto instruction
// if yes this is loop structure
if (insns.get(eventInsn) instanceof JumpInsnNode) {
jumpModificationState = WAIT_FOR_INSN_STATE;
}
// no loop -> end of modification
else {
jumpModificationState = DO_NOTHING;
}
}
// this modification changes the merge priority of certain frames (the expression part of the IF)
else if (jumpModification == IFNE_MOD) {
final Frame[] frames = (Frame[]) accessField(Analyzer.class, "frames").get(this);
final Field indexField = accessField(AbstractInsnNode.class, "index");
final InsnList insns = (InsnList) accessField(Analyzer.class, "insns").get(this);
final AbstractInsnNode gotoInsnn = insns.get(successor - 1);
// check for a loop
if (gotoInsnn instanceof JumpInsnNode) {
jumpModificationState = WAIT_FOR_INSN_STATE;
// sets a merge priority for all instructions (the expression of the IF)
// from the label the goto instruction points to until the evaluation with IFEQ
final int idx = indexField.getInt(accessField(JumpInsnNode.class, "label").get(gotoInsnn));
for (int i=idx; i <= insn; i++) {
((ModifiedASMFrame) frames[i]).mergePriority = true;
}
eventInsn = idx - 2;
}
else {
jumpModificationState = DO_NOTHING;
}
}
}
// wait for the goto instruction
else if (jumpModificationState == WAIT_FOR_INSN_STATE && insn == eventInsn) {
jumpModificationState = DO_NOTHING;
final Frame[] frames = (Frame[]) accessField(Analyzer.class, "frames").get(this);
// merge the goto instruction frame with the frame that follows
// this ensures that local variables are kept
if (jumpModification == IFEQ_MOD) {
interpreter.rightMergePriority = true;
final Field top = accessField(Frame.class, "top");
top.setInt(frames[eventInsn], top.getInt(frames[eventInsn + 1]));
frames[eventInsn + 1].merge(frames[eventInsn], interpreter);
}
// finally set a merge priority for the last instruction of the loop (before the IF expression)
else if (jumpModification == IFNE_MOD) {
((ModifiedASMFrame) frames[eventInsn + 1]).mergePriority = true;
}
}
}
catch (Exception e) {
throw new CodeAnalyzerException("Unable to do jump modifications.", e);
}
}
private Field accessField(Class<?> clazz, String name) {
for (Field f : clazz.getDeclaredFields()) {
if (f.getName().equals(name)) {
f.setAccessible(true);
return f;
}
}
return null;
}
}