/*
* Copyright (C) 2009-2010 Mathias Doenitz
*
* 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.parboiled.transform;
import com.google.common.base.Preconditions;
import org.jetbrains.annotations.NotNull;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.JumpInsnNode;
import org.objectweb.asm.tree.LabelNode;
import static org.objectweb.asm.Opcodes.ARETURN;
import static org.objectweb.asm.Opcodes.GOTO;
/**
* Replaces all "non-last" return instructions with goto instructions to the last return instruction.
* If a method contains only one return instruction the transformer does nothing.
*/
class ReturnInstructionUnifier implements RuleMethodProcessor {
public boolean appliesTo(@NotNull ParserClassNode classNode, @NotNull RuleMethod method) {
return true;
}
public void process(@NotNull ParserClassNode classNode, @NotNull RuleMethod method) throws Exception {
if (method.getNumberOfReturns() == 1) return;
Preconditions.checkState(method.getNumberOfReturns() > 1);
AbstractInsnNode current = method.instructions.getLast();
// find last return
while (current.getOpcode() != ARETURN) {
current = current.getPrevious();
}
LabelNode lastReturnLabel = new LabelNode();
method.instructions.insertBefore(current, lastReturnLabel);
// iterate backwards up to first instructions
while ((current = current.getPrevious()) != null) {
// replace returns with gotos
if (current.getOpcode() == ARETURN) {
JumpInsnNode gotoInstruction = new JumpInsnNode(GOTO, lastReturnLabel);
method.instructions.set(current, gotoInstruction);
current = gotoInstruction;
}
}
}
}