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Optimisation of Java Bytecode via EOLANG
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/*
* The MIT License (MIT)
*
* Copyright (c) 2016-2024 Objectionary.com
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package org.eolang.jeo.representation.bytecode;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.HashMap;
import java.util.List;
import java.util.Optional;
import java.util.function.Function;
import java.util.stream.Collectors;
/**
* Data-flow analysis.
* This class knows how to compute the maximum value of a reducible element based
* on the instruction flow.
* @param Type of the reducible element.
* @since 0.6
*/
public final class InstructionsFlow> {
/**
* Method instructions.
*/
private final List instructions;
/**
* Try-catch blocks.
*/
private final List blocks;
/**
* Constructor.
* @param instr Instructions.
* @param catches Try-catch blocks.
*/
InstructionsFlow(
final List instr, final List catches
) {
this.instructions = instr;
this.blocks = new ArrayList<>(catches);
}
/**
* Compute the maximum value for stack or variables.
* @param initial Initial value.
* @param generator Function to generate the reducible element from the instruction.
* @return Maximum value.
*/
public Optional max(final T initial, final Function generator) {
final MaxValueMap visited = new MaxValueMap<>();
final Deque> worklist = new ArrayDeque<>(0);
worklist.push(new Entry<>(0, initial));
final int total = this.instructions.size();
T current;
while (!worklist.isEmpty()) {
final Entry starting = worklist.pop();
int index = starting.index();
current = starting.value();
if (visited.isGreaterThan(index, current)) {
continue;
}
while (index < total) {
final BytecodeEntry instruction = this.instructions.get(index);
final T updated = current.add(generator.apply(instruction));
if (instruction.isSwitch()) {
instruction.jumps().stream().map(this::index)
.forEach(ind -> worklist.push(new Entry<>(ind, updated)));
visited.putIfGreater(index, updated);
break;
} else if (instruction.isIf()) {
final BytecodeLabel label = instruction.jumps().get(0);
final int jump = this.index(label);
worklist.push(new Entry<>(jump, updated));
final int next = index + 1;
worklist.push(new Entry<>(next, updated));
visited.putIfGreater(index, updated);
break;
} else if (instruction.isJump()) {
final BytecodeLabel label = instruction.jumps().get(0);
final int jump = this.index(label);
worklist.push(new Entry<>(jump, updated));
visited.putIfGreater(index, updated);
break;
} else if (instruction.isReturn() || instruction.isThrow()) {
visited.putIfGreater(index, updated);
break;
}
this.suitableBlocks(index)
.forEach(ind -> worklist.push(new Entry<>(ind, updated.enterBlock())));
visited.putIfGreater(index, updated);
current = updated;
++index;
}
}
return visited.values().stream().max(T::compareTo);
}
/**
* Which try-catch-blocks cover the instruction.
* @param instruction Instruction index.
* @return List of block indexes.
*/
private List suitableBlocks(final int instruction) {
return this.blocks.stream()
.map(BytecodeTryCatchBlock.class::cast)
.filter(block -> this.index(block.startLabel()) <= instruction)
.filter(block -> this.index(block.endLabel()) >= instruction)
.map(block -> this.index(block.handlerLabel()))
.collect(Collectors.toList());
}
/**
* Index of the label.
* @param label Label.
* @return Index.
*/
private int index(final BytecodeLabel label) {
for (int index = 0; index < this.instructions.size(); ++index) {
if (this.instructions.get(index).equals(label)) {
return index;
}
}
throw new IllegalStateException(String.format("Label %s not found", label));
}
/**
* Map with maximum values.
* @param Key type.
* @param Value type.
* @since 0.6
* @checkstyle IllegalTypeCheck (5 lines)
*/
private static class MaxValueMap> extends HashMap {
/**
* Serial version UID.
*/
private static final long serialVersionUID = 6517835829882158842L;
/**
* Constructor.
*/
MaxValueMap() {
super(0);
}
/**
* Is the value greater than the current one?
* @param key Key.
* @param value Value.
* @return True if it is.
*/
boolean isGreaterThan(final K key, final V value) {
return this.get(key) != null && this.get(key).compareTo(value) >= 0;
}
/**
* Put the value if it is greater.
* @param key Key.
* @param value Value.
*/
void putIfGreater(final K key, final V value) {
this.merge(key, value, MaxValueMap::max);
}
/**
* Max of two reducible elements.
* @param first First element.
* @param second Second element.
* @param Type of the element.
* @return Max element.
*/
private static > T max(
final T first, final T second
) {
final T result;
if (first.compareTo(second) > 0) {
result = first;
} else {
result = second;
}
return result;
}
}
/**
* Entry in the worklist.
* @param Type of the element.
* @since 0.6
*/
private static class Entry {
/**
* Bytecode instruction index.
*/
private final int indx;
/**
* Value.
*/
private final T evalue;
/**
* Constructor.
* @param index Index.
* @param value Value.
*/
Entry(final int index, final T value) {
this.indx = index;
this.evalue = value;
}
/**
* Index.
* @return Index.
*/
int index() {
return this.indx;
}
/**
* Value.
* @return Value.
*/
T value() {
return this.evalue;
}
}
/**
* Reducible element in the data-flow analysis.
* @param Type of the element.
* @since 0.6
*/
interface Reducible extends Comparable {
T add(T other);
T enterBlock();
}
}
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