src/main/java/com/android/tools/r8/ir/analysis/modeling/LibraryMethodReadSetModeling.java

// Copyright (c) 2019, 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.analysis.modeling;

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.ir.analysis.fieldvalueanalysis.AbstractFieldSet;
import com.android.tools.r8.ir.analysis.fieldvalueanalysis.EmptyFieldSet;
import com.android.tools.r8.ir.analysis.fieldvalueanalysis.UnknownFieldSet;
import com.android.tools.r8.ir.code.InvokeMethod;
import java.util.function.Predicate;

/** Models if a given library method may cause a program field to be read. */
public class LibraryMethodReadSetModeling {

  public static AbstractFieldSet getModeledReadSetOrUnknown(
      InvokeMethod invoke, DexItemFactory dexItemFactory) {
    DexMethod invokedMethod = invoke.getInvokedMethod();

    // Check if it is a library method that does not have side effects. In that case it is safe to
    // assume that the method does not read any fields, since even if it did, it would not be able
    // to do anything with the values it read (since we will remove such invocations without side
    // effects).
    Predicate<InvokeMethod> noSideEffectsPredicate =
        dexItemFactory.libraryMethodsWithoutSideEffects.get(invokedMethod);
    if (noSideEffectsPredicate != null && noSideEffectsPredicate.test(invoke)) {
      return EmptyFieldSet.getInstance();
    }

    // Already handled above.
    assert !dexItemFactory.classMethods.isReflectiveNameLookup(invokedMethod);

    // Modeling of other library methods.
    DexType holder = invokedMethod.holder;
    if (holder == dexItemFactory.objectType) {
      if (invokedMethod == dexItemFactory.objectMethods.constructor) {
        return EmptyFieldSet.getInstance();
      }
    }
    return UnknownFieldSet.getInstance();
  }
}