src/main/java/com/android/tools/r8/optimize/argumentpropagation/utils/WideningUtils.java

// Copyright (c) 2021, 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.argumentpropagation.utils;

import com.android.tools.r8.graph.AppView;
import com.android.tools.r8.graph.DexClass;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.graph.ObjectAllocationInfoCollection;
import com.android.tools.r8.graph.ProgramMethod;
import com.android.tools.r8.ir.analysis.type.ClassTypeElement;
import com.android.tools.r8.ir.analysis.type.DynamicType;
import com.android.tools.r8.ir.analysis.type.Nullability;
import com.android.tools.r8.shaking.AppInfoWithLiveness;

public class WideningUtils {

  public static DynamicType widenDynamicReceiverType(
      AppView<AppInfoWithLiveness> appView,
      ProgramMethod resolvedMethod,
      DynamicType dynamicReceiverType) {
    return shouldWidenDynamicType(
            appView,
            dynamicReceiverType,
            resolvedMethod.getHolderType(),
            Nullability.definitelyNotNull())
        ? DynamicType.unknown()
        : dynamicReceiverType;
  }

  public static DynamicType widenDynamicNonReceiverType(
      AppView<AppInfoWithLiveness> appView, DynamicType dynamicType, DexType staticType) {
    return widenDynamicNonReceiverType(appView, dynamicType, staticType, Nullability.maybeNull());
  }

  public static DynamicType widenDynamicNonReceiverType(
      AppView<AppInfoWithLiveness> appView,
      DynamicType dynamicType,
      DexType staticType,
      Nullability staticNullability) {
    return shouldWidenDynamicType(appView, dynamicType, staticType, staticNullability)
        ? DynamicType.unknown()
        : dynamicType;
  }

  private static boolean shouldWidenDynamicType(
      AppView<AppInfoWithLiveness> appView,
      DynamicType dynamicType,
      DexType staticType,
      Nullability staticNullability) {
    assert staticType.isClassType();
    if (dynamicType.isUnknown()) {
      return true;
    }
    if (dynamicType.isBottom()
        || dynamicType.isNullType()
        || dynamicType.getNullability().strictlyLessThan(staticNullability)) {
      return false;
    }
    ClassTypeElement staticTypeElement =
        staticType.toTypeElement(appView).asClassType().getOrCreateVariant(staticNullability);
    if (!dynamicType.getDynamicUpperBoundType().equals(staticTypeElement)) {
      return false;
    }
    if (!dynamicType.hasDynamicLowerBoundType()) {
      return true;
    }

    DexClass staticTypeClass = appView.definitionFor(staticType);
    if (staticTypeClass == null || !staticTypeClass.isProgramClass()) {
      // TODO(b/190154391): If this is a library class with no program subtypes, then we might as
      //  well widen to 'unknown'.
      return false;
    }

    // If the static type does not have any program subtypes, then widen the dynamic type to
    // unknown.
    //
    // Note that if the static type is pinned, it could have subtypes outside the set of program
    // classes, but in this case it is still unlikely that we can use the dynamic lower bound type
    // information for anything, so we intentionally also widen to 'unknown' in this case.
    ObjectAllocationInfoCollection objectAllocationInfoCollection =
        appView.appInfo().getObjectAllocationInfoCollection();
    return !objectAllocationInfoCollection.hasInstantiatedStrictSubtype(
        staticTypeClass.asProgramClass());
  }
}