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

import com.android.tools.r8.cf.LoadStoreHelper;
import com.android.tools.r8.cf.TypeVerificationHelper;
import com.android.tools.r8.cf.code.CfConstClass;
import com.android.tools.r8.dex.Constants;
import com.android.tools.r8.graph.AppInfo;
import com.android.tools.r8.graph.DexClass;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.ir.analysis.type.TypeLatticeElement;
import com.android.tools.r8.ir.conversion.CfBuilder;
import com.android.tools.r8.ir.conversion.DexBuilder;
import com.android.tools.r8.ir.optimize.Inliner.ConstraintWithTarget;
import com.android.tools.r8.ir.optimize.InliningConstraints;

public class ConstClass extends ConstInstruction {

  private final DexType clazz;

  public ConstClass(Value dest, DexType clazz) {
    super(dest);
    dest.markNeverNull();
    this.clazz = clazz;
  }

  public static ConstClass copyOf(IRCode code, ConstClass original) {
    Value newValue =
        new Value(
            code.valueNumberGenerator.next(),
            original.outValue().getTypeLattice(),
            original.getLocalInfo());
    return copyOf(newValue, original);
  }

  public static ConstClass copyOf(Value newValue, ConstClass original) {
    return new ConstClass(newValue, original.getValue());
  }

  public Value dest() {
    return outValue;
  }

  public DexType getValue() {
    return clazz;
  }

  @Override
  public void buildDex(DexBuilder builder) {
    int dest = builder.allocatedRegister(dest(), getNumber());
    builder.add(this, new com.android.tools.r8.code.ConstClass(dest, clazz));
  }

  @Override
  public int maxInValueRegister() {
    assert false : "ConstClass has no register arguments.";
    return 0;
  }

  @Override
  public int maxOutValueRegister() {
    return Constants.U8BIT_MAX;
  }

  @Override
  public String toString() {
    return super.toString() + clazz.toSourceString();
  }

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

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

  @Override
  public boolean identicalNonValueNonPositionParts(Instruction other) {
    return other.isConstClass() && other.asConstClass().clazz == clazz;
  }

  @Override
  public boolean canBeDeadCode(AppInfo appInfo, IRCode code) {
    // A const-class instruction can be dead code only if the resulting program is known to contain
    // the class mentioned.
    DexType baseType = clazz.toBaseType(appInfo.dexItemFactory);
    if (baseType.isPrimitiveType()) {
      return true;
    }
    DexClass holder = appInfo.definitionFor(baseType);
    return holder != null && holder.isProgramClass();
  }

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

  @Override
  public ConstClass asConstClass() {
    return this;
  }

  @Override
  public ConstraintWithTarget inliningConstraint(
      InliningConstraints inliningConstraints, DexType invocationContext) {
    return inliningConstraints.forConstClass(clazz, invocationContext);
  }

  @Override
  public TypeLatticeElement evaluate(AppInfo appInfo) {
    return TypeLatticeElement.fromDexType(appInfo.dexItemFactory.classType, false, appInfo);
  }

  @Override
  public DexType computeVerificationType(TypeVerificationHelper helper) {
    return helper.getFactory().classType;
  }

  @Override
  public void insertLoadAndStores(InstructionListIterator it, LoadStoreHelper helper) {
    helper.storeOutValue(this, it);
  }

  @Override
  public void buildCf(CfBuilder builder) {
    builder.add(new CfConstClass(clazz));
  }
}