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 getIndexOrDefault(int defaultValue) {
    return index().isConstant()
        ? index().getConstInstruction().asConstInstruction().asConstNumber().getIntValue()
        : defaultValue;
  }

  @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;
    Value arrayRoot = array().getAliasedValue();
    if (arrayRoot.isDefinedByInstructionSatisfying(Instruction::isNewArrayEmptyOrNewArrayFilled)) {
      Instruction definition = arrayRoot.getDefinition();
      if (definition.isNewArrayEmpty()) {
        Value newArraySizeValue = definition.asNewArrayEmpty().size();
        if (newArraySizeValue.isConstant()) {
          arraySize = newArraySizeValue.getConstInstruction().asConstNumber().getIntValue();
        } else {
          return true;
        }
      } else {
        arraySize = definition.asNewArrayFilled().size();
      }
    } else {
      return true;
    }

    int index;
    if (index().isConstant()) {
      index = index().getConstInstruction().asConstNumber().getIntValue();
    } else {
      return true;
    }

    return arraySize <= 0 || index < 0 || arraySize <= index;
  }
}