org.jetbrains.jet.codegen.optimization.boxing.RedundantNullCheckMethodTransformer Maven / Gradle / Ivy
/*
* Copyright 2010-2014 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 org.jetbrains.jet.codegen.optimization.boxing;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.jet.codegen.optimization.transformer.MethodTransformer;
import org.jetbrains.org.objectweb.asm.Opcodes;
import org.jetbrains.org.objectweb.asm.tree.*;
import org.jetbrains.org.objectweb.asm.tree.analysis.Analyzer;
import org.jetbrains.org.objectweb.asm.tree.analysis.BasicValue;
import org.jetbrains.org.objectweb.asm.tree.analysis.Frame;
import java.util.ArrayList;
import java.util.List;
public class RedundantNullCheckMethodTransformer extends MethodTransformer {
public RedundantNullCheckMethodTransformer(MethodTransformer methodTransformer) {
super(methodTransformer);
}
@Override
public void transform(@NotNull String internalClassName, @NotNull MethodNode methodNode) {
while (removeRedundantNullCheckPass(internalClassName, methodNode)) {
//do nothing
}
super.transform(internalClassName, methodNode);
}
private static boolean removeRedundantNullCheckPass(@NotNull String internalClassName, @NotNull MethodNode methodNode) {
InsnList insnList = methodNode.instructions;
Frame[] frames = analyze(
internalClassName, methodNode,
new BoxingInterpreter(insnList)
);
List insnsToOptimize = new ArrayList();
for (int i = 0; i < insnList.size(); i++) {
Frame frame = frames[i];
AbstractInsnNode insn = insnList.get(i);
if ((insn.getOpcode() == Opcodes.IFNULL || insn.getOpcode() == Opcodes.IFNONNULL) &&
frame != null && frame.getStack(frame.getStackSize() - 1) instanceof BoxedBasicValue) {
insnsToOptimize.add(insn);
}
}
for (AbstractInsnNode insn : insnsToOptimize) {
if (insn.getPrevious() != null && insn.getPrevious().getOpcode() == Opcodes.DUP) {
insnList.remove(insn.getPrevious());
}
else {
insnList.insertBefore(insn, new InsnNode(Opcodes.POP));
}
assert insn.getOpcode() == Opcodes.IFNULL
|| insn.getOpcode() == Opcodes.IFNONNULL : "only IFNULL/IFNONNULL are supported";
if (insn.getOpcode() == Opcodes.IFNULL) {
insnList.remove(insn);
}
else {
insnList.set(
insn,
new JumpInsnNode(Opcodes.GOTO, ((JumpInsnNode) insn).label)
);
}
}
return insnsToOptimize.size() > 0;
}
}