src/main/java/com/android/tools/r8/ir/desugar/nest/NestBasedAccessDesugaring.java

// Copyright (c) 2021, 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.desugar.nest;

import com.android.tools.r8.cf.code.CfConstNull;
import com.android.tools.r8.cf.code.CfFieldInstruction;
import com.android.tools.r8.cf.code.CfInstruction;
import com.android.tools.r8.cf.code.CfInvoke;
import com.android.tools.r8.dex.Constants;
import com.android.tools.r8.errors.Unreachable;
import com.android.tools.r8.graph.AppView;
import com.android.tools.r8.graph.CfCode;
import com.android.tools.r8.graph.ClassAccessFlags;
import com.android.tools.r8.graph.Code;
import com.android.tools.r8.graph.DexAnnotationSet;
import com.android.tools.r8.graph.DexClass;
import com.android.tools.r8.graph.DexClassAndField;
import com.android.tools.r8.graph.DexClassAndMember;
import com.android.tools.r8.graph.DexClassAndMethod;
import com.android.tools.r8.graph.DexEncodedField;
import com.android.tools.r8.graph.DexEncodedMethod;
import com.android.tools.r8.graph.DexItemFactory;
import com.android.tools.r8.graph.DexMember;
import com.android.tools.r8.graph.DexMethod;
import com.android.tools.r8.graph.DexProgramClass;
import com.android.tools.r8.graph.DexProto;
import com.android.tools.r8.graph.DexString;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.graph.DexTypeList;
import com.android.tools.r8.graph.GenericSignature.ClassSignature;
import com.android.tools.r8.graph.LibraryMember;
import com.android.tools.r8.graph.ProgramField;
import com.android.tools.r8.graph.ProgramMethod;
import com.android.tools.r8.origin.SynthesizedOrigin;
import com.android.tools.r8.utils.BooleanUtils;
import com.android.tools.r8.utils.ListUtils;
import com.android.tools.r8.utils.StringDiagnostic;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.Sets;
import java.util.Collections;
import java.util.List;
import java.util.Set;
import java.util.function.Consumer;
import org.objectweb.asm.Opcodes;

// NestBasedAccessDesugaring contains common code between the two subclasses
// which are specialized for d8 and r8
public class NestBasedAccessDesugaring {

  // Short names to avoid creating long strings
  public static final String NEST_ACCESS_NAME_PREFIX = "-$$Nest$";
  private static final String NEST_ACCESS_METHOD_NAME_PREFIX = NEST_ACCESS_NAME_PREFIX + "m";
  private static final String NEST_ACCESS_STATIC_METHOD_NAME_PREFIX =
      NEST_ACCESS_NAME_PREFIX + "sm";
  private static final String NEST_ACCESS_FIELD_GET_NAME_PREFIX = NEST_ACCESS_NAME_PREFIX + "fget";
  private static final String NEST_ACCESS_STATIC_GET_FIELD_NAME_PREFIX =
      NEST_ACCESS_NAME_PREFIX + "sfget";
  private static final String NEST_ACCESS_FIELD_PUT_NAME_PREFIX = NEST_ACCESS_NAME_PREFIX + "fput";
  private static final String NEST_ACCESS_STATIC_PUT_FIELD_NAME_PREFIX =
      NEST_ACCESS_NAME_PREFIX + "sfput";
  public static final String NEST_CONSTRUCTOR_NAME = NEST_ACCESS_NAME_PREFIX + "Constructor";

  protected final AppView<?> appView;
  private final DexItemFactory dexItemFactory;

  // Common single empty class for nest based private constructors
  private DexProgramClass nestConstructor;
  private boolean nestConstructorUsed;

  public NestBasedAccessDesugaring(AppView<?> appView) {
    this.appView = appView;
    this.dexItemFactory = appView.dexItemFactory();
  }

  void forEachNest(Consumer<Nest> consumer) {
    Set<DexType> seenNestHosts = Sets.newIdentityHashSet();
    for (DexProgramClass clazz : appView.appInfo().classes()) {
      if (!clazz.isInANest() || !seenNestHosts.add(clazz.getNestHost())) {
        continue;
      }

      Nest nest = Nest.create(appView, clazz);
      if (nest != null) {
        consumer.accept(nest);
      }
    }
  }

  public boolean needsDesugaring(ProgramMethod method) {
    if (!method.getHolder().isInANest() || !method.getDefinition().hasCode()) {
      return false;
    }

    Code code = method.getDefinition().getCode();
    if (code.isDexCode()) {
      assert appView.testing().allowDexInputForTesting;
      return false;
    }

    if (!code.isCfCode()) {
      throw new Unreachable("Unexpected attempt to determine if non-CF code needs desugaring");
    }

    return Iterables.any(
        code.asCfCode().getInstructions(), instruction -> needsDesugaring(instruction, method));
  }

  private boolean needsDesugaring(CfInstruction instruction, ProgramMethod context) {
    if (instruction.isFieldInstruction()) {
      return needsDesugaring(instruction.asFieldInstruction().getField(), context);
    }
    if (instruction.isInvoke()) {
      return needsDesugaring(instruction.asInvoke().getMethod(), context);
    }
    return false;
  }

  public boolean needsDesugaring(DexMember<?, ?> memberReference, ProgramMethod context) {
    if (!context.getHolder().isInANest() || !memberReference.getHolderType().isClassType()) {
      return false;
    }
    DexClass holder = appView.definitionForHolder(memberReference, context);
    DexClassAndMember<?, ?> member = memberReference.lookupMemberOnClass(holder);
    return member != null && needsDesugaring(member, context);
  }

  public boolean needsDesugaring(DexClassAndMember<?, ?> member, DexClassAndMethod context) {
    return member.getAccessFlags().isPrivate()
        && member.getHolderType() != context.getHolderType()
        && member.getHolder().isInANest()
        && member.getHolder().getNestHost() == context.getHolder().getNestHost();
  }

  public boolean desugar(ProgramMethod method) {
    return desugar(method, null);
  }

  public boolean desugar(ProgramMethod method, NestBridgeConsumer bridgeConsumer) {
    if (!method.getHolder().isInANest()) {
      return false;
    }

    Code code = method.getDefinition().getCode();
    if (!code.isCfCode()) {
      appView
          .options()
          .reporter
          .error(
              new StringDiagnostic(
                  "Unsupported attempt to desugar non-CF code",
                  method.getOrigin(),
                  method.getPosition()));
      return false;
    }

    CfCode cfCode = code.asCfCode();
    List<CfInstruction> desugaredInstructions =
        ListUtils.flatMap(
            cfCode.getInstructions(),
            instruction -> desugarInstruction(instruction, method, bridgeConsumer),
            null);
    if (desugaredInstructions != null) {
      cfCode.setInstructions(desugaredInstructions);
      return true;
    }
    return false;
  }

  public List<CfInstruction> desugarInstruction(
      CfInstruction instruction, ProgramMethod context, NestBridgeConsumer bridgeConsumer) {
    if (instruction.isFieldInstruction()) {
      return desugarFieldInstruction(instruction.asFieldInstruction(), context, bridgeConsumer);
    }
    if (instruction.isInvoke()) {
      return desugarInvokeInstruction(instruction.asInvoke(), context, bridgeConsumer);
    }
    return null;
  }

  private List<CfInstruction> desugarFieldInstruction(
      CfFieldInstruction instruction, ProgramMethod context, NestBridgeConsumer bridgeConsumer) {
    // Since we only need to desugar accesses to private fields, and all accesses to private
    // fields must be accessing the private field directly on its holder, we can lookup the
    // field on the holder instead of resolving the field.
    DexClass holder = appView.definitionForHolder(instruction.getField(), context);
    DexClassAndField field = instruction.getField().lookupMemberOnClass(holder);
    if (field == null || !needsDesugaring(field, context)) {
      return null;
    }

    DexMethod bridge = ensureFieldAccessBridge(field, instruction.isFieldGet(), bridgeConsumer);
    return ImmutableList.of(
        new CfInvoke(Opcodes.INVOKESTATIC, bridge, field.getHolder().isInterface()));
  }

  private List<CfInstruction> desugarInvokeInstruction(
      CfInvoke invoke, ProgramMethod context, NestBridgeConsumer bridgeConsumer) {
    DexMethod invokedMethod = invoke.getMethod();
    if (!invokedMethod.getHolderType().isClassType()) {
      return null;
    }

    // Since we only need to desugar accesses to private methods, and all accesses to private
    // methods must be accessing the private method directly on its holder, we can lookup the
    // method on the holder instead of resolving the method.
    DexClass holder = appView.definitionForHolder(invokedMethod, context);
    DexClassAndMethod target = invokedMethod.lookupMemberOnClass(holder);
    if (target == null || !needsDesugaring(target, context)) {
      return null;
    }

    DexMethod bridge = ensureMethodBridge(target, bridgeConsumer);
    if (target.getDefinition().isInstanceInitializer()) {
      assert !invoke.isInterface();
      return ImmutableList.of(
          new CfConstNull(), new CfInvoke(Opcodes.INVOKESPECIAL, bridge, false));
    }

    return ImmutableList.of(new CfInvoke(Opcodes.INVOKESTATIC, bridge, invoke.isInterface()));
  }

  private RuntimeException reportIncompleteNest(LibraryMember<?, ?> member) {
    Nest nest = Nest.create(appView, member.getHolder());
    assert nest != null : "Should be a compilation error if missing nest host on library class.";
    throw appView.options().errorMissingClassIncompleteNest(nest);
  }

  private DexProgramClass createNestAccessConstructor() {
    // TODO(b/176900254): ensure hygienic synthetic class.
    return new DexProgramClass(
        dexItemFactory.nestConstructorType,
        null,
        new SynthesizedOrigin("Nest based access desugaring", getClass()),
        // Make the synthesized class public since shared in the whole program.
        ClassAccessFlags.fromDexAccessFlags(
            Constants.ACC_FINAL | Constants.ACC_SYNTHETIC | Constants.ACC_PUBLIC),
        dexItemFactory.objectType,
        DexTypeList.empty(),
        dexItemFactory.createString("nest"),
        null,
        Collections.emptyList(),
        null,
        Collections.emptyList(),
        ClassSignature.noSignature(),
        DexAnnotationSet.empty(),
        DexEncodedField.EMPTY_ARRAY,
        DexEncodedField.EMPTY_ARRAY,
        DexEncodedMethod.EMPTY_ARRAY,
        DexEncodedMethod.EMPTY_ARRAY,
        dexItemFactory.getSkipNameValidationForTesting(),
        DexProgramClass::checksumFromType);
  }

  public DexProgramClass synthesizeNestConstructor() {
    if (nestConstructorUsed && nestConstructor == null) {
      nestConstructor = createNestAccessConstructor();
      return nestConstructor;
    }
    return null;
  }

  DexMethod ensureFieldAccessBridge(
      DexClassAndField field, boolean isGet, NestBridgeConsumer bridgeConsumer) {
    if (field.isProgramField()) {
      return ensureFieldAccessBridge(field.asProgramField(), isGet, bridgeConsumer);
    }
    if (field.isClasspathField()) {
      return getFieldAccessBridgeReference(field, isGet);
    }
    assert field.isLibraryField();
    throw reportIncompleteNest(field.asLibraryField());
  }

  private DexMethod ensureFieldAccessBridge(
      ProgramField field, boolean isGet, NestBridgeConsumer bridgeConsumer) {
    DexMethod bridgeReference = getFieldAccessBridgeReference(field, isGet);
    synchronized (field.getHolder().getMethodCollection()) {
      ProgramMethod bridge = field.getHolder().lookupProgramMethod(bridgeReference);
      if (bridge == null) {
        bridge = DexEncodedMethod.createFieldAccessorBridge(field, isGet, bridgeReference);
        bridge.getHolder().addDirectMethod(bridge.getDefinition());
        if (bridgeConsumer != null) {
          bridgeConsumer.acceptFieldBridge(field, bridge, isGet);
        }
      }
      return bridge.getReference();
    }
  }

  private DexMethod getFieldAccessBridgeReference(DexClassAndField field, boolean isGet) {
    int bridgeParameterCount =
        BooleanUtils.intValue(!field.getAccessFlags().isStatic()) + BooleanUtils.intValue(!isGet);
    DexType[] parameters = new DexType[bridgeParameterCount];
    if (!isGet) {
      parameters[parameters.length - 1] = field.getType();
    }
    if (!field.getAccessFlags().isStatic()) {
      parameters[0] = field.getHolderType();
    }
    DexType returnType = isGet ? field.getType() : dexItemFactory.voidType;
    DexProto proto = dexItemFactory.createProto(returnType, parameters);
    return dexItemFactory.createMethod(
        field.getHolderType(), proto, getFieldAccessBridgeName(field, isGet));
  }

  private DexString getFieldAccessBridgeName(DexClassAndField field, boolean isGet) {
    String prefix;
    if (isGet && !field.getAccessFlags().isStatic()) {
      prefix = NEST_ACCESS_FIELD_GET_NAME_PREFIX;
    } else if (isGet) {
      prefix = NEST_ACCESS_STATIC_GET_FIELD_NAME_PREFIX;
    } else if (!field.getAccessFlags().isStatic()) {
      prefix = NEST_ACCESS_FIELD_PUT_NAME_PREFIX;
    } else {
      prefix = NEST_ACCESS_STATIC_PUT_FIELD_NAME_PREFIX;
    }
    return dexItemFactory.createString(prefix + field.getName().toString());
  }

  DexMethod ensureMethodBridge(DexClassAndMethod method, NestBridgeConsumer bridgeConsumer) {
    if (method.isProgramMethod()) {
      return ensureMethodBridge(method.asProgramMethod(), bridgeConsumer);
    }
    if (method.isClasspathMethod()) {
      return getMethodBridgeReference(method);
    }
    assert method.isLibraryMethod();
    throw reportIncompleteNest(method.asLibraryMethod());
  }

  private DexMethod ensureMethodBridge(ProgramMethod method, NestBridgeConsumer bridgeConsumer) {
    DexMethod bridgeReference = getMethodBridgeReference(method);
    synchronized (method.getHolder().getMethodCollection()) {
      ProgramMethod bridge = method.getHolder().lookupProgramMethod(bridgeReference);
      if (bridge == null) {
        DexEncodedMethod definition = method.getDefinition();
        bridge =
            definition.isInstanceInitializer()
                ? definition.toInitializerForwardingBridge(
                    method.getHolder(), bridgeReference, dexItemFactory)
                : definition.toStaticForwardingBridge(
                    method.getHolder(), bridgeReference, dexItemFactory);
        bridge.getHolder().addDirectMethod(bridge.getDefinition());
        if (bridgeConsumer != null) {
          bridgeConsumer.acceptMethodBridge(method, bridge);
        }
      }
    }
    return bridgeReference;
  }

  private DexMethod getMethodBridgeReference(DexClassAndMethod method) {
    if (method.getDefinition().isInstanceInitializer()) {
      DexProto newProto =
          dexItemFactory.appendTypeToProto(method.getProto(), dexItemFactory.nestConstructorType);
      nestConstructorUsed = true;
      return method.getReference().withProto(newProto, dexItemFactory);
    }
    DexProto proto =
        method.getAccessFlags().isStatic()
            ? method.getProto()
            : dexItemFactory.prependHolderToProto(method.getReference());
    return dexItemFactory.createMethod(method.getHolderType(), proto, getMethodBridgeName(method));
  }

  private DexString getMethodBridgeName(DexClassAndMethod method) {
    String prefix =
        method.getAccessFlags().isStatic()
            ? NEST_ACCESS_STATIC_METHOD_NAME_PREFIX
            : NEST_ACCESS_METHOD_NAME_PREFIX;
    return dexItemFactory.createString(prefix + method.getName().toString());
  }
}