src/main/java/com/android/tools/r8/optimize/FieldRebindingIdentityLens.java

// Copyright (c) 2018, 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.optimize;

import com.android.tools.r8.graph.DexField;
import com.android.tools.r8.graph.DexItemFactory;
import com.android.tools.r8.graph.DexMethod;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.graph.GraphLens;
import com.android.tools.r8.graph.GraphLens.NonIdentityGraphLens;
import com.android.tools.r8.graph.proto.RewrittenPrototypeDescription;
import java.util.IdentityHashMap;
import java.util.Map;

/**
 * This lens is used to populate the rebound field reference during lookup, such that both the
 * non-rebound and rebound field references are available to all descendants of this lens.
 *
 * <p>TODO(b/157616970): All uses of this should be replaced by {@link MemberRebindingIdentityLens}.
 */
public class FieldRebindingIdentityLens extends NonIdentityGraphLens {

  private final Map<DexField, DexField> nonReboundFieldReferenceToDefinitionMap;

  private FieldRebindingIdentityLens(
      Map<DexField, DexField> nonReboundFieldReferenceToDefinitionMap,
      DexItemFactory dexItemFactory,
      GraphLens previousLens) {
    super(dexItemFactory, previousLens);
    this.nonReboundFieldReferenceToDefinitionMap = nonReboundFieldReferenceToDefinitionMap;
  }

  public static Builder builder() {
    return new Builder();
  }

  @Override
  public boolean hasCodeRewritings() {
    return false;
  }

  @Override
  protected FieldLookupResult internalDescribeLookupField(FieldLookupResult previous) {
    assert !previous.hasReadCastType();
    assert !previous.hasReboundReference();
    return FieldLookupResult.builder(this)
        .setReference(previous.getReference())
        .setReboundReference(getReboundFieldReference(previous.getReference()))
        .build();
  }

  private DexField getReboundFieldReference(DexField field) {
    return nonReboundFieldReferenceToDefinitionMap.getOrDefault(field, field);
  }

  @Override
  public DexType getOriginalType(DexType type) {
    return getPrevious().getOriginalType(type);
  }

  @Override
  public Iterable<DexType> getOriginalTypes(DexType type) {
    return getPrevious().getOriginalTypes(type);
  }

  @Override
  public DexField getOriginalFieldSignature(DexField field) {
    return getPrevious().getOriginalFieldSignature(field);
  }

  @Override
  public DexField getRenamedFieldSignature(DexField originalField, GraphLens codeLens) {
    if (this == codeLens) {
      return originalField;
    }
    return getPrevious().getRenamedFieldSignature(originalField);
  }

  @Override
  public DexMethod getRenamedMethodSignature(DexMethod originalMethod, GraphLens applied) {
    return getPrevious().getRenamedMethodSignature(originalMethod, applied);
  }

  @Override
  public final DexType internalDescribeLookupClassType(DexType previous) {
    return previous;
  }

  @Override
  public MethodLookupResult internalDescribeLookupMethod(
      MethodLookupResult previous, DexMethod context) {
    return previous;
  }

  @Override
  public DexMethod getPreviousMethodSignature(DexMethod method) {
    return method;
  }

  @Override
  public DexMethod getNextMethodSignature(DexMethod method) {
    return method;
  }

  @Override
  public RewrittenPrototypeDescription lookupPrototypeChangesForMethodDefinition(
      DexMethod method, GraphLens codeLens) {
    if (this == codeLens) {
      return getIdentityLens().lookupPrototypeChangesForMethodDefinition(method, codeLens);
    }
    return getPrevious().lookupPrototypeChangesForMethodDefinition(method, codeLens);
  }

  @Override
  public boolean isContextFreeForMethods() {
    return getPrevious().isContextFreeForMethods();
  }

  public static class Builder {

    private final Map<DexField, DexField> nonReboundFieldReferenceToDefinitionMap =
        new IdentityHashMap<>();

    private Builder() {}

    void recordDefinitionForNonReboundFieldReference(
        DexField nonReboundFieldReference, DexField reboundFieldReference) {
      nonReboundFieldReferenceToDefinitionMap.put(nonReboundFieldReference, reboundFieldReference);
    }

    FieldRebindingIdentityLens build(DexItemFactory dexItemFactory) {
      // This intentionally does not return null when the map is empty. In this case there are no
      // non-rebound field references, but the member rebinding lens is still needed to populate the
      // rebound reference during field lookup.
      return new FieldRebindingIdentityLens(
          nonReboundFieldReferenceToDefinitionMap, dexItemFactory, GraphLens.getIdentityLens());
    }
  }
}