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/*
 * Copyright 2010-2015 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.kotlin.codegen.optimization;

import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import org.jetbrains.kotlin.codegen.inline.InlineCodegenUtil;
import org.jetbrains.kotlin.codegen.optimization.boxing.RedundantBoxingMethodTransformer;
import org.jetbrains.kotlin.codegen.optimization.boxing.RedundantNullCheckMethodTransformer;
import org.jetbrains.kotlin.codegen.optimization.common.UtilKt;
import org.jetbrains.kotlin.codegen.optimization.transformer.MethodTransformer;
import org.jetbrains.org.objectweb.asm.MethodVisitor;
import org.jetbrains.org.objectweb.asm.Opcodes;
import org.jetbrains.org.objectweb.asm.tree.LocalVariableNode;
import org.jetbrains.org.objectweb.asm.tree.MethodNode;
import org.jetbrains.org.objectweb.asm.util.Textifier;
import org.jetbrains.org.objectweb.asm.util.TraceMethodVisitor;

import java.util.ArrayList;
import java.util.List;

public class OptimizationMethodVisitor extends MethodVisitor {
    private static final int MEMORY_LIMIT_BY_METHOD_MB = 50;

    private static final MethodTransformer MANDATORY_METHOD_TRANSFORMER = new MandatoryMethodTransformer();

    private static final MethodTransformer[] OPTIMIZATION_TRANSFORMERS = new MethodTransformer[] {
            new RedundantNullCheckMethodTransformer(),
            new RedundantBoxingMethodTransformer(),
            new DeadCodeEliminationMethodTransformer(),
            new RedundantGotoMethodTransformer()
    };

    private final MethodNode methodNode;
    private final MethodVisitor delegate;
    private final boolean disableOptimization;

    public OptimizationMethodVisitor(
            @NotNull MethodVisitor delegate,
            boolean disableOptimization,
            int access,
            @NotNull String name,
            @NotNull String desc,
            @Nullable String signature,
            @Nullable String[] exceptions
    ) {
        super(Opcodes.ASM5);
        this.delegate = delegate;
        this.methodNode = new MethodNode(access, name, desc, signature, exceptions);
        this.methodNode.localVariables = new ArrayList(5);
        this.mv = InlineCodegenUtil.wrapWithMaxLocalCalc(methodNode);
        this.disableOptimization = disableOptimization;
    }

    @Override
    public void visitEnd() {
        // force mv to calculate maxStack/maxLocals in case it didn't yet done
        if (methodNode.maxLocals <= 0 || methodNode.maxStack <= 0) {
            mv.visitMaxs(-1, -1);
        }

        super.visitEnd();

        if (shouldBeTransformed(methodNode)) {
            MANDATORY_METHOD_TRANSFORMER.transform("fake", methodNode);
            if (canBeOptimized(methodNode) && !disableOptimization) {
                for (MethodTransformer transformer : OPTIMIZATION_TRANSFORMERS) {
                    transformer.transform("fake", methodNode);
                }
            }
            UtilKt.prepareForEmitting(methodNode);
        }

        methodNode.accept(new EndIgnoringMethodVisitorDecorator(Opcodes.ASM5, delegate));


        // In case of empty instructions list MethodNode.accept doesn't call visitLocalVariables of delegate
        // So we just do it here
        if (methodNode.instructions.size() == 0) {
            List localVariables = methodNode.localVariables;
            // visits local variables
            int n = localVariables == null ? 0 : localVariables.size();
            for (int i = 0; i < n; ++i) {
                localVariables.get(i).accept(delegate);
            }
        }

        delegate.visitEnd();
    }

    /**
     * You can use it when you need to ignore visit end
     */
    private static class EndIgnoringMethodVisitorDecorator extends MethodVisitor {
        public EndIgnoringMethodVisitorDecorator(int api, @NotNull MethodVisitor mv) {
            super(api, mv);
        }

        @Override
        public void visitEnd() {

        }
    }

    @Nullable
    public TraceMethodVisitor getTraceMethodVisitorIfPossible() {
        TraceMethodVisitor traceMethodVisitor = new TraceMethodVisitor(new Textifier());
        try {
            methodNode.accept(traceMethodVisitor);
        }
        catch (Throwable e) {
            return null;
        }

        return traceMethodVisitor;
    }

    private static boolean shouldBeTransformed(@NotNull MethodNode node) {
        return node.instructions.size() > 0;
    }

    private static boolean canBeOptimized(@NotNull MethodNode node) {
        int totalFramesSizeMb = node.instructions.size() * (node.maxLocals + node.maxStack) / (1024 * 1024);
        return totalFramesSizeMb < MEMORY_LIMIT_BY_METHOD_MB;
    }
}