src/main/java/com/android/tools/r8/ir/desugar/LambdaBridgeMethodSourceCode.java

// Copyright (c) 2017, the R8 project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

package com.android.tools.r8.ir.desugar;

import com.android.tools.r8.graph.DexMethod;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.ir.code.Invoke;
import com.android.tools.r8.ir.code.Position;
import com.android.tools.r8.ir.code.ValueType;
import com.android.tools.r8.ir.conversion.IRBuilder;
import java.util.ArrayList;
import java.util.List;

// Source code representing synthesized lambda bridge method.
final class LambdaBridgeMethodSourceCode extends SynthesizedLambdaSourceCode {

  private final DexMethod mainMethod;

  LambdaBridgeMethodSourceCode(
      LambdaClass lambda, DexMethod mainMethod, DexMethod bridgeMethod, Position callerPosition) {
    super(lambda, bridgeMethod, callerPosition);
    this.mainMethod = mainMethod;
  }

  @Override
  protected void prepareInstructions() {
    DexType[] currentParams = proto.parameters.values;
    DexType[] enforcedParams = descriptor().enforcedProto.parameters.values;

    // Prepare call arguments.
    List<ValueType> argValueTypes = new ArrayList<>();
    List<Integer> argRegisters = new ArrayList<>();

    // Always add a receiver representing 'this' of the lambda class.
    argValueTypes.add(ValueType.OBJECT);
    argRegisters.add(getReceiverRegister());

    // Prepare arguments.
    for (int i = 0; i < currentParams.length; i++) {
      DexType expectedParamType = enforcedParams[i];
      argValueTypes.add(ValueType.fromDexType(expectedParamType));
      argRegisters.add(enforceParameterType(
          getParamRegister(i), currentParams[i], expectedParamType));
    }

    // Method call to the main functional interface method.
    add(
        builder ->
            builder.addInvoke(
                Invoke.Type.VIRTUAL,
                this.mainMethod,
                this.mainMethod.proto,
                argValueTypes,
                argRegisters,
                false /* isInterface */));

    // Does the method have return value?
    if (proto.returnType == factory().voidType) {
      add(IRBuilder::addReturn);
    } else {
      ValueType valueType = ValueType.fromDexType(proto.returnType);
      int tempValue = nextRegister(valueType);
      add(builder -> builder.addMoveResult(tempValue));
      // We lack precise sub-type information, but there should not be a need to cast to object.
      if (proto.returnType != mainMethod.proto.returnType
          && proto.returnType != factory().objectType) {
        add(builder -> builder.addCheckCast(tempValue, proto.returnType));
      }
      add(builder -> builder.addReturn(tempValue));
    }
  }
}