src/main/java/com/android/tools/r8/graph/DexEncodedField.java

// Copyright (c) 2016, 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.graph;

import static com.android.tools.r8.ir.analysis.type.Nullability.maybeNull;

import com.android.tools.r8.dex.IndexedItemCollection;
import com.android.tools.r8.dex.MixedSectionCollection;
import com.android.tools.r8.ir.analysis.type.TypeLatticeElement;
import com.android.tools.r8.ir.analysis.value.AbstractValue;
import com.android.tools.r8.ir.analysis.value.SingleValue;
import com.android.tools.r8.ir.code.IRCode;
import com.android.tools.r8.ir.code.Instruction;
import com.android.tools.r8.ir.code.TypeAndLocalInfoSupplier;
import com.android.tools.r8.ir.optimize.info.DefaultFieldOptimizationInfo;
import com.android.tools.r8.ir.optimize.info.FieldOptimizationInfo;
import com.android.tools.r8.ir.optimize.info.MutableFieldOptimizationInfo;
import com.android.tools.r8.shaking.AppInfoWithLiveness;
import com.google.common.collect.Sets;

public class DexEncodedField extends KeyedDexItem<DexField> {
  public static final DexEncodedField[] EMPTY_ARRAY = {};

  public final DexField field;
  public final FieldAccessFlags accessFlags;
  public DexAnnotationSet annotations;
  private DexValue staticValue;

  private FieldOptimizationInfo optimizationInfo = DefaultFieldOptimizationInfo.getInstance();

  public DexEncodedField(
      DexField field,
      FieldAccessFlags accessFlags,
      DexAnnotationSet annotations,
      DexValue staticValue) {
    this.field = field;
    this.accessFlags = accessFlags;
    this.annotations = annotations;
    this.staticValue = staticValue;
  }

  public boolean isProgramField(DexDefinitionSupplier definitions) {
    if (field.holder.isClassType()) {
      DexClass clazz = definitions.definitionFor(field.holder);
      return clazz != null && clazz.isProgramClass();
    }
    return false;
  }

  public FieldOptimizationInfo getOptimizationInfo() {
    return optimizationInfo;
  }

  public synchronized MutableFieldOptimizationInfo getMutableOptimizationInfo() {
    if (optimizationInfo.isDefaultFieldOptimizationInfo()) {
      MutableFieldOptimizationInfo mutableOptimizationInfo = new MutableFieldOptimizationInfo();
      optimizationInfo = mutableOptimizationInfo;
      return mutableOptimizationInfo;
    }
    assert optimizationInfo.isMutableFieldOptimizationInfo();
    return optimizationInfo.asMutableFieldOptimizationInfo();
  }

  public void setOptimizationInfo(MutableFieldOptimizationInfo info) {
    optimizationInfo = info;
  }

  @Override
  public void collectIndexedItems(
      IndexedItemCollection indexedItems, DexMethod method, int instructionOffset) {
    field.collectIndexedItems(indexedItems, method, instructionOffset);
    annotations.collectIndexedItems(indexedItems, method, instructionOffset);
    if (accessFlags.isStatic()) {
      getStaticValue().collectIndexedItems(indexedItems, method, instructionOffset);
    }
  }

  @Override
  void collectMixedSectionItems(MixedSectionCollection mixedItems) {
    annotations.collectMixedSectionItems(mixedItems);
  }

  @Override
  public String toString() {
    return "Encoded field " + field;
  }

  @Override
  public String toSmaliString() {
    return field.toSmaliString();
  }

  @Override
  public String toSourceString() {
    return field.toSourceString();
  }

  @Override
  public DexField getKey() {
    return field;
  }

  @Override
  public DexReference toReference() {
    return field;
  }

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

  @Override
  public DexEncodedField asDexEncodedField() {
    return this;
  }

  public boolean isFinal() {
    return accessFlags.isFinal();
  }

  @Override
  public boolean isStatic() {
    return accessFlags.isStatic();
  }

  public boolean isPrivate() {
    return accessFlags.isPrivate();
  }

  @Override
  public boolean isStaticMember() {
    return isStatic();
  }

  public boolean hasAnnotation() {
    return !annotations.isEmpty();
  }

  public boolean hasExplicitStaticValue() {
    assert accessFlags.isStatic();
    return staticValue != null;
  }

  public void setStaticValue(DexValue staticValue) {
    assert accessFlags.isStatic();
    assert staticValue != null;
    this.staticValue = staticValue;
  }

  public DexValue getStaticValue() {
    assert accessFlags.isStatic();
    return staticValue == null ? DexValue.defaultForType(field.type) : staticValue;
  }

  /**
   * Returns a const instructions if this field is a compile time final const.
   *
   * <p>NOTE: It is the responsibility of the caller to check if this field is pinned or not.
   */
  public Instruction valueAsConstInstruction(
      IRCode code, DebugLocalInfo local, AppView<AppInfoWithLiveness> appView) {
    boolean isWritten = appView.appInfo().isFieldWrittenByFieldPutInstruction(this);
    if (!isWritten) {
      // Since the field is not written, we can simply return the default value for the type.
      DexValue value = isStatic() ? getStaticValue() : DexValue.defaultForType(field.type);
      return value.asConstInstruction(appView, code, local);
    }

    // Check if we have a single value for the field according to the field optimization info.
    AbstractValue abstractValue = getOptimizationInfo().getAbstractValue();
    if (abstractValue.isSingleValue()) {
      SingleValue singleValue = abstractValue.asSingleValue();
      if (singleValue.isMaterializableInContext(appView, code.method.method.holder)) {
        TypeLatticeElement type = TypeLatticeElement.fromDexType(field.type, maybeNull(), appView);
        return singleValue.createMaterializingInstruction(
            appView, code, TypeAndLocalInfoSupplier.create(type, local));
      }
    }

    // The only way to figure out whether the static value contains the final value is ensure the
    // value is not the default or check that <clinit> is not present.
    if (accessFlags.isFinal() && isStatic()) {
      DexClass clazz = appView.definitionFor(field.holder);
      if (clazz == null || clazz.hasClassInitializer()) {
        return null;
      }
      DexValue staticValue = getStaticValue();
      if (!staticValue.isDefault(field.type)) {
        return staticValue.asConstInstruction(appView, code, local);
      }
    }

    return null;
  }

  public boolean mayTriggerClassInitializationSideEffects(
      AppView<AppInfoWithLiveness> appView, DexType context) {
    // Only static field matters when it comes to class initialization side effects.
    if (!isStatic()) {
      return false;
    }
    DexClass clazz = appView.definitionFor(field.holder);
    if (clazz == null) {
      return true;
    }
    if (clazz.classInitializationMayHaveSideEffects(
        appView,
        // Types that are a super type of the current context are guaranteed to be initialized
        // already.
        type -> appView.isSubtype(context, type).isTrue(),
        Sets.newIdentityHashSet())) {
      // Ignore class initialization side-effects for dead proto extension fields to ensure that
      // we force replace these field reads by null.
      boolean ignore =
          appView.withGeneratedExtensionRegistryShrinker(
              shrinker -> shrinker.isDeadProtoExtensionField(field), false);
      return !ignore;
    }
    return false;
  }

  public DexEncodedField toTypeSubstitutedField(DexField field) {
    if (this.field == field) {
      return this;
    }
    DexEncodedField result = new DexEncodedField(field, accessFlags, annotations, staticValue);
    result.optimizationInfo =
        optimizationInfo.isMutableFieldOptimizationInfo()
            ? optimizationInfo.asMutableFieldOptimizationInfo().mutableCopy()
            : DefaultFieldOptimizationInfo.getInstance();
    return result;
  }
}