src/main/java/com/android/tools/r8/ir/code/ArrayAccess.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.code;

import com.android.tools.r8.graph.AppView;
import com.android.tools.r8.graph.ProgramMethod;
import java.util.List;

public abstract class ArrayAccess extends Instruction implements ImpreciseMemberTypeInstruction {

  // Input values are ordered according to the stack order of the Java bytecodes.
  private static final int ARRAY_INDEX = 0;
  private static final int INDEX_INDEX = 1;

  ArrayAccess(Value outValue, List<? extends Value> inValues) {
    super(outValue, inValues);
  }

  public Value array() {
    return inValues.get(ARRAY_INDEX);
  }

  public Value index() {
    return inValues.get(INDEX_INDEX);
  }

  public int indexOrDefault(int defaultValue) {
    int ret = indexIfConstAndInBounds(Integer.MAX_VALUE);
    return ret == -1 ? defaultValue : ret;
  }

  public int indexIfConstAndInBounds(int size) {
    int ret = index().getConstIntValueIfNonNegative();
    return ret < size ? ret : -1;
  }

  public int arraySizeIfConst() {
    Value arrayRoot = array().getAliasedValue();
    if (arrayRoot.isDefinedByInstructionSatisfying(Instruction::isNewArrayEmptyOrNewArrayFilled)) {
      Instruction definition = arrayRoot.getDefinition();
      if (definition.isNewArrayEmpty()) {
        Value newArraySizeValue = definition.asNewArrayEmpty().size();
        return newArraySizeValue.getConstIntValueIfNonNegative();
      }
      return definition.asNewArrayFilled().size();
    }
    return -1;
  }

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

  @Override
  public ArrayAccess asArrayAccess() {
    return this;
  }

  public abstract ArrayAccess withMemberType(MemberType newMemberType);

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

  @Override
  public boolean instructionInstanceCanThrow(
      AppView<?> appView,
      ProgramMethod context,
      AbstractValueSupplier abstractValueSupplier,
      SideEffectAssumption assumption) {
    // TODO(b/203731608): Add parameters to the method and use abstract value in R8.
    int arraySize = arraySizeIfConst();
    return arraySize < 0 || indexIfConstAndInBounds(arraySize) < 0;
  }
}