src/main/java/com/android/tools/r8/ir/code/UnusedArgument.java

// Copyright (c) 2022, 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.errors.Unreachable;
import com.android.tools.r8.graph.AppView;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.graph.ProgramMethod;
import com.android.tools.r8.ir.analysis.type.TypeElement;
import com.android.tools.r8.ir.conversion.CfBuilder;
import com.android.tools.r8.ir.conversion.DexBuilder;
import com.android.tools.r8.ir.optimize.DeadCodeRemover.DeadInstructionResult;
import com.android.tools.r8.ir.optimize.Inliner.ConstraintWithTarget;
import com.android.tools.r8.ir.optimize.InliningConstraints;

/**
 * A special instruction to load the value of an argument that has been removed as a result of code
 * optimizations. Only used in R8 between the point of building IR and lens code rewriting.
 */
public class UnusedArgument extends Instruction {

  public UnusedArgument(Value outValue) {
    super(outValue);
  }

  @Override
  public <T> T accept(InstructionVisitor<T> visitor) {
    return visitor.visit(this);
  }

  @Override
  public void buildCf(CfBuilder builder) {
    throw new Unreachable();
  }

  @Override
  public void buildDex(DexBuilder builder) {
    throw new Unreachable();
  }

  @Override
  public DeadInstructionResult canBeDeadCode(AppView<?> appview, IRCode code) {
    return DeadInstructionResult.deadIfOutValueIsDead();
  }

  @Override
  public DexType computeVerificationType(AppView<?> appView, TypeVerificationHelper helper) {
    throw new Unreachable();
  }

  @Override
  public TypeElement evaluate(AppView<?> appView) {
    return outValue.getType();
  }

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

  @Override
  public boolean identicalNonValueNonPositionParts(Instruction other) {
    throw new Unreachable();
  }

  @Override
  public ConstraintWithTarget inliningConstraint(
      InliningConstraints inliningConstraints, ProgramMethod context) {
    throw new Unreachable();
  }

  @Override
  public boolean instructionMayTriggerMethodInvocation(AppView<?> appView, ProgramMethod context) {
    throw new Unreachable();
  }

  @Override
  public void insertLoadAndStores(InstructionListIterator it, LoadStoreHelper helper) {
    throw new Unreachable();
  }

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

  @Override
  public UnusedArgument asUnusedArgument() {
    return this;
  }

  @Override
  public int maxInValueRegister() {
    throw new Unreachable();
  }

  @Override
  public int maxOutValueRegister() {
    throw new Unreachable();
  }

  @Override
  public int opcode() {
    return Opcodes.UNUSED_ARGUMENT;
  }
}