/*
* Copyright 2013 Alexey Andreev.
*
* 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 org.teavm.optimization;
import org.teavm.common.IntegerStack;
import org.teavm.model.BasicBlock;
import org.teavm.model.Program;
import org.teavm.model.TryCatchBlock;
import org.teavm.model.util.InstructionTransitionExtractor;
/**
*
* @author Alexey Andreev
*/
public class UnreachableBasicBlockEliminator {
public void optimize(Program program) {
if (program.basicBlockCount() == 0) {
return;
}
InstructionTransitionExtractor transitionExtractor = new InstructionTransitionExtractor();
boolean[] reachable = new boolean[program.basicBlockCount()];
IntegerStack stack = new IntegerStack(program.basicBlockCount());
stack.push(0);
while (!stack.isEmpty()) {
int i = stack.pop();
if (reachable[i]) {
continue;
}
reachable[i] = true;
BasicBlock block = program.basicBlockAt(i);
block.getLastInstruction().acceptVisitor(transitionExtractor);
for (BasicBlock successor : transitionExtractor.getTargets()) {
if (!reachable[successor.getIndex()]) {
stack.push(successor.getIndex());
}
}
for (TryCatchBlock tryCatch : block.getTryCatchBlocks()) {
stack.push(tryCatch.getHandler().getIndex());
}
}
for (int i = 0; i < reachable.length; ++i) {
if (!reachable[i]) {
program.deleteBasicBlock(i);
}
}
program.pack();
}
}