src/main/java/com/android/tools/r8/ir/optimize/info/field/InstanceFieldArgumentInitializationInfo.java

// Copyright (c) 2020, 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.optimize.info.field;

import com.android.tools.r8.graph.AppView;
import com.android.tools.r8.graph.GraphLens;
import com.android.tools.r8.graph.RewrittenPrototypeDescription.ArgumentInfo;
import com.android.tools.r8.graph.RewrittenPrototypeDescription.ArgumentInfoCollection;
import com.android.tools.r8.graph.RewrittenPrototypeDescription.RemovedArgumentInfo;
import com.android.tools.r8.shaking.AppInfoWithLiveness;

/**
 * Used to represent that a constructor initializes an instance field on the newly created instance
 * with argument number {@link #argumentIndex} from the constructor's argument list.
 */
public class InstanceFieldArgumentInitializationInfo implements InstanceFieldInitializationInfo {

  private final int argumentIndex;

  /** Intentionally package private, use {@link InstanceFieldInitializationInfoFactory} instead. */
  InstanceFieldArgumentInitializationInfo(int argumentIndex) {
    this.argumentIndex = argumentIndex;
  }

  public int getArgumentIndex() {
    return argumentIndex;
  }

  @Override
  public boolean isArgumentInitializationInfo() {
    return true;
  }

  @Override
  public InstanceFieldArgumentInitializationInfo asArgumentInitializationInfo() {
    return this;
  }

  @Override
  public InstanceFieldInitializationInfo fixupAfterParametersChanged(
      ArgumentInfoCollection argumentInfoCollection) {
    ArgumentInfo argumentInfo = argumentInfoCollection.getArgumentInfo(argumentIndex);
    if (argumentInfo.isRemovedArgumentInfo()) {
      RemovedArgumentInfo removedArgumentInfo = argumentInfo.asRemovedArgumentInfo();
      if (!removedArgumentInfo.hasSingleValue()) {
        // This should only happen if the argument is unused, but here the argument is used to
        // initialize an instance field on the enclosing class.
        assert false;
        return UnknownInstanceFieldInitializationInfo.getInstance();
      }
      // Now the constant is used to initialize the field instead of the argument.
      return removedArgumentInfo.getSingleValue();
    }

    int newArgumentIndex = argumentInfoCollection.getNewArgumentIndex(argumentIndex);
    return newArgumentIndex != argumentIndex
        ? new InstanceFieldArgumentInitializationInfo(newArgumentIndex)
        : this;
  }

  @Override
  public InstanceFieldInitializationInfo rewrittenWithLens(
      AppView<AppInfoWithLiveness> appView, GraphLens lens) {
    // We don't have the context here to determine what should happen. It is the responsibility of
    // optimizations that change the proto of instance initializers to update the argument
    // initialization info.
    return this;
  }

  @Override
  public String toString() {
    return "InstanceFieldArgumentInitializationInfo(argumentIndex=" + argumentIndex + ")";
  }
}