src/main/java/com/android/tools/r8/graph/lens/GraphLens.java

// Copyright (c) 2017, 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.graph.lens;

import static com.android.tools.r8.graph.DexProgramClass.asProgramClassOrNull;

import com.android.tools.r8.graph.AppView;
import com.android.tools.r8.graph.DexApplication;
import com.android.tools.r8.graph.DexCallSite;
import com.android.tools.r8.graph.DexClass;
import com.android.tools.r8.graph.DexDefinition;
import com.android.tools.r8.graph.DexDefinitionSupplier;
import com.android.tools.r8.graph.DexEncodedField;
import com.android.tools.r8.graph.DexEncodedMethod;
import com.android.tools.r8.graph.DexField;
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.DexReference;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.graph.ProgramMethod;
import com.android.tools.r8.graph.proto.RewrittenPrototypeDescription;
import com.android.tools.r8.ir.code.InvokeType;
import com.android.tools.r8.ir.conversion.LensCodeRewriterUtils;
import com.android.tools.r8.ir.optimize.enums.EnumUnboxingLens;
import com.android.tools.r8.optimize.MemberRebindingIdentityLens;
import com.android.tools.r8.optimize.MemberRebindingLens;
import com.android.tools.r8.shaking.KeepInfoCollection;
import com.android.tools.r8.utils.InternalOptions;
import com.android.tools.r8.utils.ListUtils;
import com.android.tools.r8.utils.SetUtils;
import com.android.tools.r8.utils.collections.BidirectionalManyToOneRepresentativeHashMap;
import com.android.tools.r8.utils.collections.MutableBidirectionalManyToOneRepresentativeMap;
import com.android.tools.r8.utils.collections.ProgramMethodSet;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Sets;
import it.unimi.dsi.fastutil.objects.Object2BooleanArrayMap;
import it.unimi.dsi.fastutil.objects.Object2BooleanMap;
import java.util.ArrayList;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.BiFunction;

/**
 * A GraphLens implements a virtual view on top of the graph, used to delay global rewrites until
 * later IR processing stages.
 *
 * <p>Valid remappings are limited to the following operations:
 *
 * <ul>
 *   <li>Mapping a classes type to one of the super/subtypes.
 *   <li>Renaming private methods/fields.
 *   <li>Moving methods/fields to a super/subclass.
 *   <li>Replacing method/field references by the same method/field on a super/subtype
 *   <li>Moved methods might require changed invocation type at the call site
 * </ul>
 *
 * Note that the latter two have to take visibility into account.
 */
public abstract class GraphLens {

  public abstract static class Builder {

    protected final MutableBidirectionalManyToOneRepresentativeMap<DexField, DexField> fieldMap =
        BidirectionalManyToOneRepresentativeHashMap.newIdentityHashMap();
    protected final MutableBidirectionalManyToOneRepresentativeMap<DexMethod, DexMethod> methodMap =
        BidirectionalManyToOneRepresentativeHashMap.newIdentityHashMap();
    protected final Map<DexType, DexType> typeMap = new IdentityHashMap<>();

    protected Builder() {}

    public void map(DexType from, DexType to) {
      if (from == to) {
        return;
      }
      typeMap.put(from, to);
    }

    public void move(DexMethod from, DexMethod to) {
      if (from == to) {
        return;
      }
      methodMap.put(from, to);
    }

    public void move(DexField from, DexField to) {
      if (from == to) {
        return;
      }
      fieldMap.put(from, to);
    }

    public abstract GraphLens build(AppView<?> appView);
  }

  /**
   * Intentionally package private. All graph lenses except for {@link IdentityGraphLens} should
   * inherit from {@link NonIdentityGraphLens}.
   */
  GraphLens() {}

  public boolean isSyntheticFinalizationGraphLens() {
    return false;
  }

  public abstract DexType getOriginalType(DexType type);

  public abstract Iterable<DexType> getOriginalTypes(DexType type);

  public abstract DexField getOriginalFieldSignature(DexField field);

  public final DexMember<?, ?> getOriginalMemberSignature(DexMember<?, ?> member) {
    return member.apply(this::getOriginalFieldSignature, this::getOriginalMethodSignature);
  }

  public final DexMethod getOriginalMethodSignature(DexMethod method) {
    return getOriginalMethodSignature(method, null);
  }

  public final DexMethod getOriginalMethodSignature(DexMethod method, GraphLens atGraphLens) {
    GraphLens current = this;
    DexMethod original = method;
    while (current.isNonIdentityLens() && current != atGraphLens) {
      NonIdentityGraphLens nonIdentityLens = current.asNonIdentityLens();
      original = nonIdentityLens.getPreviousMethodSignature(original);
      current = nonIdentityLens.getPrevious();
    }
    assert atGraphLens == null ? current.isIdentityLens() : (current == atGraphLens);
    return original;
  }

  public final DexMethod getOriginalMethodSignatureForMapping(DexMethod method) {
    GraphLens current = this;
    DexMethod original = method;
    while (current.isNonIdentityLens()) {
      NonIdentityGraphLens nonIdentityLens = current.asNonIdentityLens();
      original = nonIdentityLens.getPreviousMethodSignatureForMapping(original);
      current = nonIdentityLens.getPrevious();
    }
    assert current.isIdentityLens();
    return original;
  }

  public final DexField getRenamedFieldSignature(DexField originalField) {
    return getRenamedFieldSignature(originalField, null);
  }

  public abstract DexField getRenamedFieldSignature(DexField originalField, GraphLens codeLens);

  public final DexMember<?, ?> getRenamedMemberSignature(DexMember<?, ?> originalMember) {
    return originalMember.isDexField()
        ? getRenamedFieldSignature(originalMember.asDexField())
        : getRenamedMethodSignature(originalMember.asDexMethod());
  }

  public final DexMethod getRenamedMethodSignature(DexMethod originalMethod) {
    return getRenamedMethodSignature(originalMethod, null);
  }

  public abstract DexMethod getRenamedMethodSignature(DexMethod originalMethod, GraphLens applied);

  public DexEncodedMethod mapDexEncodedMethod(
      DexEncodedMethod originalEncodedMethod, DexDefinitionSupplier definitions) {
    return mapDexEncodedMethod(originalEncodedMethod, definitions, null);
  }

  public DexEncodedMethod mapDexEncodedMethod(
      DexEncodedMethod originalEncodedMethod,
      DexDefinitionSupplier definitions,
      GraphLens applied) {
    assert originalEncodedMethod != DexEncodedMethod.SENTINEL;
    DexMethod newMethod = getRenamedMethodSignature(originalEncodedMethod.getReference(), applied);
    // Note that:
    // * Even if `newMethod` is the same as `originalEncodedMethod.method`, we still need to look it
    //   up, since `originalEncodedMethod` may be obsolete.
    // * We can't directly use AppInfo#definitionFor(DexMethod) since definitions may not be
    //   updated either yet.
    DexClass newHolder = definitions.definitionFor(newMethod.holder);
    assert newHolder != null;
    DexEncodedMethod newEncodedMethod = newHolder.lookupMethod(newMethod);
    assert newEncodedMethod != null;
    return newEncodedMethod;
  }

  public ProgramMethod mapProgramMethod(
      ProgramMethod oldMethod, DexDefinitionSupplier definitions) {
    DexMethod newMethod = getRenamedMethodSignature(oldMethod.getReference());
    DexProgramClass holder = asProgramClassOrNull(definitions.definitionForHolder(newMethod));
    return newMethod.lookupOnProgramClass(holder);
  }

  // Predicate indicating if a rewritten reference is a simple renaming, meaning the move from one
  // reference to another is simply either just a renaming or/also renaming of the references. In
  // other words, the content of the definition, including the definition of all of its members is
  // the same modulo the renaming.
  public <T extends DexReference> boolean isSimpleRenaming(T from, T to) {
    assert from != to;
    return false;
  }

  // Predicate to see if a method definition is only changed by repackaging or synthetic
  // finalization indicating that it is a simple renaming.
  public final boolean isSimpleRenaming(DexMethod method) {
    DexMethod methodToCompareAgainst = method;
    DexMethod original = method;
    GraphLens current = this;
    while (current.isNonIdentityLens()) {
      NonIdentityGraphLens nonIdentityLens = current.asNonIdentityLens();
      original = nonIdentityLens.getPreviousMethodSignature(original);
      if (current.isSimpleRenamingLens()) {
        methodToCompareAgainst = original;
      } else if (methodToCompareAgainst != original) {
        return false;
      }
      assert nonIdentityLens.getPrevious() != null;
      current = nonIdentityLens.getPrevious();
    }
    return true;
  }

  public abstract String lookupPackageName(String pkg);

  public DexType lookupClassType(DexType type) {
    return lookupClassType(type, getIdentityLens());
  }

  public abstract DexType lookupClassType(DexType type, GraphLens applied);

  public DexType lookupType(DexType type) {
    return lookupType(type, getIdentityLens());
  }

  public abstract DexType lookupType(DexType type, GraphLens applied);

  @Deprecated
  public final DexMethod lookupMethod(DexMethod method) {
    assert verifyIsContextFreeForMethod(method);
    return lookupMethod(method, null, null).getReference();
  }

  public final MethodLookupResult lookupInvokeDirect(DexMethod method, ProgramMethod context) {
    return lookupMethod(method, context.getReference(), InvokeType.DIRECT);
  }

  public final MethodLookupResult lookupInvokeDirect(
      DexMethod method, ProgramMethod context, GraphLens codeLens) {
    return lookupMethod(method, context.getReference(), InvokeType.DIRECT, codeLens);
  }

  public final MethodLookupResult lookupInvokeInterface(DexMethod method, ProgramMethod context) {
    return lookupMethod(method, context.getReference(), InvokeType.INTERFACE);
  }

  public final MethodLookupResult lookupInvokeInterface(
      DexMethod method, ProgramMethod context, GraphLens codeLens) {
    return lookupMethod(method, context.getReference(), InvokeType.INTERFACE, codeLens);
  }

  public final MethodLookupResult lookupInvokeStatic(DexMethod method, ProgramMethod context) {
    return lookupMethod(method, context.getReference(), InvokeType.STATIC);
  }

  public final MethodLookupResult lookupInvokeStatic(
      DexMethod method, ProgramMethod context, GraphLens codeLens) {
    return lookupMethod(method, context.getReference(), InvokeType.STATIC, codeLens);
  }

  public final MethodLookupResult lookupInvokeSuper(DexMethod method, ProgramMethod context) {
    return lookupMethod(method, context.getReference(), InvokeType.SUPER);
  }

  public final MethodLookupResult lookupInvokeSuper(
      DexMethod method, ProgramMethod context, GraphLens codeLens) {
    return lookupMethod(method, context.getReference(), InvokeType.SUPER, codeLens);
  }

  public final MethodLookupResult lookupInvokeVirtual(DexMethod method, ProgramMethod context) {
    return lookupMethod(method, context.getReference(), InvokeType.VIRTUAL);
  }

  public final MethodLookupResult lookupInvokeVirtual(
      DexMethod method, ProgramMethod context, GraphLens codeLens) {
    return lookupMethod(method, context.getReference(), InvokeType.VIRTUAL, codeLens);
  }

  public final MethodLookupResult lookupMethod(
      DexMethod method, DexMethod context, InvokeType type) {
    return lookupMethod(method, context, type, null);
  }

  /**
   * Lookup a rebound or non-rebound method reference using the current graph lens.
   *
   * @param codeLens Specifies the graph lens which has already been applied to the code object. The
   *     lookup procedure will not recurse beyond this graph lens to ensure that each mapping is
   *     applied at most once.
   *     <p>Note: since the compiler currently inserts {@link ClearCodeRewritingGraphLens} it is
   *     generally valid to pass null for the {@param codeLens}. The removal of {@link
   *     ClearCodeRewritingGraphLens} is tracked by b/202368283. After this is removed, the compiler
   *     should generally use the result of calling {@link AppView#codeLens()}.
   */
  public abstract MethodLookupResult lookupMethod(
      DexMethod method, DexMethod context, InvokeType type, GraphLens codeLens);

  protected abstract MethodLookupResult internalLookupMethod(
      DexMethod reference,
      DexMethod context,
      InvokeType type,
      GraphLens codeLens,
      LookupMethodContinuation continuation);

  interface LookupMethodContinuation {

    MethodLookupResult lookupMethod(MethodLookupResult previous);
  }

  public final RewrittenPrototypeDescription lookupPrototypeChangesForMethodDefinition(
      DexMethod method) {
    return lookupPrototypeChangesForMethodDefinition(method, null);
  }

  public abstract RewrittenPrototypeDescription lookupPrototypeChangesForMethodDefinition(
      DexMethod method, GraphLens codeLens);

  public final DexField lookupField(DexField field) {
    return lookupField(field, null);
  }

  /** Lookup a rebound or non-rebound field reference using the current graph lens. */
  public DexField lookupField(DexField field, GraphLens codeLens) {
    // Lookup the field using the graph lens and return the (non-rebound) reference from the lookup
    // result.
    return lookupFieldResult(field, codeLens).getReference();
  }

  /** Lookup a rebound or non-rebound field reference using the current graph lens. */
  public final FieldLookupResult lookupFieldResult(DexField field) {
    // Lookup the field using the graph lens and return the lookup result.
    return lookupFieldResult(field, null);
  }

  /** Lookup a rebound or non-rebound field reference using the current graph lens. */
  public final FieldLookupResult lookupFieldResult(DexField field, GraphLens codeLens) {
    // Lookup the field using the graph lens and return the lookup result.
    return internalLookupField(field, codeLens, x -> x);
  }

  protected abstract FieldLookupResult internalLookupField(
      DexField reference, GraphLens codeLens, LookupFieldContinuation continuation);

  interface LookupFieldContinuation {

    FieldLookupResult lookupField(FieldLookupResult previous);
  }

  public DexReference lookupReference(DexReference reference) {
    return reference.apply(this::lookupType, this::lookupField, this::lookupMethod);
  }

  // The method lookupMethod() maps a pair INVOKE=(method signature, invoke type) to a new pair
  // INVOKE'=(method signature', invoke type'). This mapping can be context sensitive, meaning that
  // the result INVOKE' depends on where the invocation INVOKE is in the program. This is, for
  // example, used by the vertical class merger to translate invoke-super instructions that hit
  // a method in the direct super class to invoke-direct instructions after class merging.
  //
  // This method can be used to determine if a graph lens is context sensitive. If a graph lens
  // is context insensitive, it is safe to invoke lookupMethod() without a context (or to pass null
  // as context). Trying to invoke a context sensitive graph lens without a context will lead to
  // an assertion error.
  public abstract boolean isContextFreeForMethods();

  public boolean verifyIsContextFreeForMethod(DexMethod method) {
    return isContextFreeForMethods();
  }

  public static GraphLens getIdentityLens() {
    return IdentityGraphLens.getInstance();
  }

  public boolean hasCodeRewritings() {
    return true;
  }

  public boolean hasCustomCodeRewritings() {
    return false;
  }

  public boolean isAppliedLens() {
    return false;
  }

  public boolean isArgumentPropagatorGraphLens() {
    return false;
  }

  public boolean isClearCodeRewritingLens() {
    return false;
  }

  public boolean isEnumUnboxerLens() {
    return false;
  }

  public EnumUnboxingLens asEnumUnboxerLens() {
    return null;
  }

  public boolean isHorizontalClassMergerGraphLens() {
    return false;
  }

  public boolean isSimpleRenamingLens() {
    return false;
  }

  public abstract boolean isIdentityLens();

  public boolean isMemberRebindingLens() {
    return false;
  }

  public MemberRebindingLens asMemberRebindingLens() {
    return null;
  }

  public boolean isMemberRebindingIdentityLens() {
    return false;
  }

  public MemberRebindingIdentityLens asMemberRebindingIdentityLens() {
    return null;
  }

  public abstract boolean isNonIdentityLens();

  public NonIdentityGraphLens asNonIdentityLens() {
    return null;
  }

  public boolean isVerticalClassMergerLens() {
    return false;
  }

  public GraphLens withCodeRewritingsApplied(DexItemFactory dexItemFactory) {
    if (hasCodeRewritings()) {
      return new ClearCodeRewritingGraphLens(dexItemFactory, this);
    }
    return this;
  }

  public <T extends DexDefinition> boolean assertDefinitionsNotModified(Iterable<T> definitions) {
    for (DexDefinition definition : definitions) {
      DexReference reference = definition.getReference();
      // We allow changes to bridge methods as these get retargeted even if they are kept.
      boolean isBridge =
          definition.isDexEncodedMethod() && definition.asDexEncodedMethod().accessFlags.isBridge();
      assert isBridge || lookupReference(reference) == reference;
    }
    return true;
  }

  public <T extends DexReference> boolean assertPinnedNotModified(
      KeepInfoCollection keepInfo, InternalOptions options) {
    List<DexReference> pinnedItems = new ArrayList<>();
    keepInfo.forEachPinnedType(pinnedItems::add, options);
    keepInfo.forEachPinnedMethod(pinnedItems::add, options);
    keepInfo.forEachPinnedField(pinnedItems::add, options);
    return assertReferencesNotModified(pinnedItems);
  }

  public <T extends DexReference> boolean assertReferencesNotModified(Iterable<T> references) {
    for (DexReference reference : references) {
      if (reference.isDexField()) {
        DexField field = reference.asDexField();
        assert getRenamedFieldSignature(field) == field;
      } else if (reference.isDexMethod()) {
        DexMethod method = reference.asDexMethod();
        assert getRenamedMethodSignature(method) == method;
      } else {
        assert reference.isDexType();
        DexType type = reference.asDexType();
        assert lookupType(type) == type;
      }
    }
    return true;
  }

  public Map<DexCallSite, ProgramMethodSet> rewriteCallSites(
      Map<DexCallSite, ProgramMethodSet> callSites, DexDefinitionSupplier definitions) {
    Map<DexCallSite, ProgramMethodSet> result = new IdentityHashMap<>();
    LensCodeRewriterUtils rewriter = new LensCodeRewriterUtils(definitions, this, null);
    callSites.forEach(
        (callSite, contexts) -> {
          for (ProgramMethod context : contexts.rewrittenWithLens(definitions, this)) {
            DexCallSite rewrittenCallSite = rewriter.rewriteCallSite(callSite, context);
            result
                .computeIfAbsent(rewrittenCallSite, ignore -> ProgramMethodSet.create())
                .add(context);
          }
        });
    return result;
  }

  @SuppressWarnings("unchecked")
  public <T extends DexReference> T rewriteReference(T reference) {
    return rewriteReference(reference, null);
  }

  @SuppressWarnings("unchecked")
  public <T extends DexReference> T rewriteReference(T reference, GraphLens codeLens) {
    return (T)
        reference.apply(
            type -> lookupType(type, codeLens),
            field -> getRenamedFieldSignature(field, codeLens),
            method -> getRenamedMethodSignature(method, codeLens));
  }

  public <T extends DexReference> Set<T> rewriteReferences(Set<T> references) {
    Set<T> result = SetUtils.newIdentityHashSet(references.size());
    for (T reference : references) {
      result.add(rewriteReference(reference));
    }
    return result;
  }

  public <R extends DexReference, T> Map<R, T> rewriteReferenceKeys(
      Map<R, T> map, BiFunction<R, List<T>, T> merge) {
    Map<R, T> result = new IdentityHashMap<>();
    Map<R, List<T>> needsMerge = new IdentityHashMap<>();
    map.forEach(
        (reference, value) -> {
          R rewrittenReference = rewriteReference(reference);
          List<T> unmergedValues = needsMerge.get(rewrittenReference);
          if (unmergedValues != null) {
            unmergedValues.add(value);
          } else {
            T existingValue = result.put(rewrittenReference, value);
            if (existingValue != null) {
              // Remove this for now and let the merge function decide when all colliding values are
              // known.
              needsMerge.put(rewrittenReference, ListUtils.newArrayList(existingValue, value));
              result.remove(rewrittenReference);
            }
          }
        });
    needsMerge.forEach(
        (rewrittenReference, unmergedValues) -> {
          T mergedValue = merge.apply(rewrittenReference, unmergedValues);
          if (mergedValue != null) {
            result.put(rewrittenReference, mergedValue);
          }
        });
    return result;
  }

  public <T extends DexReference> Object2BooleanMap<T> rewriteReferenceKeys(
      Object2BooleanMap<T> map) {
    Object2BooleanMap<T> result = new Object2BooleanArrayMap<>();
    for (Object2BooleanMap.Entry<T> entry : map.object2BooleanEntrySet()) {
      result.put(rewriteReference(entry.getKey()), entry.getBooleanValue());
    }
    return result;
  }

  public <T> ImmutableMap<DexField, T> rewriteFieldKeys(Map<DexField, T> map) {
    ImmutableMap.Builder<DexField, T> builder = ImmutableMap.builder();
    map.forEach((field, value) -> builder.put(getRenamedFieldSignature(field), value));
    return builder.build();
  }

  public ImmutableSet<DexType> rewriteTypes(Set<DexType> types) {
    ImmutableSet.Builder<DexType> builder = new ImmutableSet.Builder<>();
    for (DexType type : types) {
      builder.add(lookupType(type));
    }
    return builder.build();
  }

  public <T> Map<DexType, T> rewriteTypeKeys(Map<DexType, T> map, BiFunction<T, T, T> merge) {
    Map<DexType, T> newMap = new IdentityHashMap<>();
    map.forEach(
        (type, value) -> {
          DexType rewrittenType = lookupType(type);
          T previousValue = newMap.get(rewrittenType);
          newMap.put(
              rewrittenType, previousValue != null ? merge.apply(value, previousValue) : value);
        });
    return newMap;
  }

  public boolean verifyMappingToOriginalProgram(
      AppView<?> appView, DexApplication originalApplication) {
    Iterable<DexProgramClass> classes = appView.appInfo().classesWithDeterministicOrder();
    // Collect all original fields and methods for efficient querying.
    Set<DexField> originalFields = Sets.newIdentityHashSet();
    Set<DexMethod> originalMethods = Sets.newIdentityHashSet();
    for (DexProgramClass clazz : originalApplication.classes()) {
      for (DexEncodedField field : clazz.fields()) {
        originalFields.add(field.getReference());
      }
      for (DexEncodedMethod method : clazz.methods()) {
        originalMethods.add(method.getReference());
      }
    }

    // Check that all fields and methods in the generated program can be mapped back to one of the
    // original fields or methods.
    for (DexProgramClass clazz : classes) {
      if (appView.appInfo().getSyntheticItems().isSyntheticClass(clazz)) {
        continue;
      }
      for (DexEncodedField field : clazz.fields()) {
        if (field.isD8R8Synthesized()) {
          // Fields synthesized by D8/R8 may not be mapped.
          continue;
        }
        DexField originalField = getOriginalFieldSignature(field.getReference());
        assert originalFields.contains(originalField)
            : "Unable to map field `"
                + field.getReference().toSourceString()
                + "` back to original program";
      }
      for (DexEncodedMethod method : clazz.methods()) {
        if (method.isD8R8Synthesized()) {
          // Methods synthesized by D8/R8 may not be mapped.
          continue;
        }
        DexMethod originalMethod = getOriginalMethodSignature(method.getReference());
        assert originalMethods.contains(originalMethod)
            : "Method could not be mapped back: "
                + method.toSourceString()
                + ", originalMethod: "
                + originalMethod.toSourceString();
      }
    }

    return true;
  }

}