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transformer.dart
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transformer.dart
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// Copyright (c) 2017, the Dart 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.
/// Transformations based on type flow analysis.
library vm.transformations.type_flow.transformer;
import 'dart:core' hide Type;
import 'package:kernel/target/targets.dart';
import 'package:kernel/ast.dart' hide Statement, StatementVisitor;
import 'package:kernel/core_types.dart' show CoreTypes;
import 'package:kernel/class_hierarchy.dart' show ClassHierarchy;
import 'package:kernel/library_index.dart' show LibraryIndex;
import 'package:kernel/type_environment.dart';
import 'analysis.dart';
import 'calls.dart';
import 'summary_collector.dart';
import 'types.dart';
import 'utils.dart';
import '../pragma.dart';
import '../devirtualization.dart' show Devirtualization;
import '../../metadata/direct_call.dart';
import '../../metadata/inferred_type.dart';
import '../../metadata/procedure_attributes.dart';
import '../../metadata/unreachable.dart';
const bool kDumpAllSummaries =
const bool.fromEnvironment('global.type.flow.dump.all.summaries');
const bool kDumpClassHierarchy =
const bool.fromEnvironment('global.type.flow.dump.class.hierarchy');
/// Whole-program type flow analysis and transformation.
/// Assumes strong mode and closed world.
Component transformComponent(
Target target, CoreTypes coreTypes, Component component,
[PragmaAnnotationParser matcher]) {
void ignoreAmbiguousSupertypes(Class cls, Supertype a, Supertype b) {}
final hierarchy = new ClassHierarchy(component,
onAmbiguousSupertypes: ignoreAmbiguousSupertypes);
final types = new TypeEnvironment(coreTypes, hierarchy);
final libraryIndex = new LibraryIndex.all(component);
final genericInterfacesInfo = new GenericInterfacesInfoImpl(hierarchy);
if (kDumpAllSummaries) {
Statistics.reset();
new CreateAllSummariesVisitor(target, types, genericInterfacesInfo)
.visitComponent(component);
Statistics.print("All summaries statistics");
}
Statistics.reset();
final analysisStopWatch = new Stopwatch()..start();
final typeFlowAnalysis = new TypeFlowAnalysis(target, component, coreTypes,
hierarchy, genericInterfacesInfo, types, libraryIndex,
matcher: matcher);
Procedure main = component.mainMethod;
final Selector mainSelector = new DirectSelector(main);
typeFlowAnalysis.addRawCall(mainSelector);
typeFlowAnalysis.process();
analysisStopWatch.stop();
if (kDumpClassHierarchy) {
debugPrint(typeFlowAnalysis.hierarchyCache);
}
final transformsStopWatch = new Stopwatch()..start();
new TreeShaker(component, typeFlowAnalysis).transformComponent(component);
new TFADevirtualization(component, typeFlowAnalysis)
.visitComponent(component);
new AnnotateKernel(component, typeFlowAnalysis).visitComponent(component);
transformsStopWatch.stop();
statPrint("TF analysis took ${analysisStopWatch.elapsedMilliseconds}ms");
statPrint("TF transforms took ${transformsStopWatch.elapsedMilliseconds}ms");
Statistics.print("TFA statistics");
return component;
}
/// Devirtualization based on results of type flow analysis.
class TFADevirtualization extends Devirtualization {
final TypeFlowAnalysis _typeFlowAnalysis;
TFADevirtualization(Component component, this._typeFlowAnalysis)
: super(_typeFlowAnalysis.environment.coreTypes, component,
_typeFlowAnalysis.environment.hierarchy);
@override
DirectCallMetadata getDirectCall(TreeNode node, Member interfaceTarget,
{bool setter = false}) {
final callSite = _typeFlowAnalysis.callSite(node);
if (callSite != null) {
final Member singleTarget = callSite.monomorphicTarget;
if (singleTarget != null) {
return new DirectCallMetadata(
singleTarget, callSite.isNullableReceiver);
}
}
return null;
}
}
/// Annotates kernel AST with metadata using results of type flow analysis.
class AnnotateKernel extends RecursiveVisitor<Null> {
final TypeFlowAnalysis _typeFlowAnalysis;
final InferredTypeMetadataRepository _inferredTypeMetadata;
final UnreachableNodeMetadataRepository _unreachableNodeMetadata;
final ProcedureAttributesMetadataRepository _procedureAttributesMetadata;
final DartType _intType;
AnnotateKernel(Component component, this._typeFlowAnalysis)
: _inferredTypeMetadata = new InferredTypeMetadataRepository(),
_unreachableNodeMetadata = new UnreachableNodeMetadataRepository(),
_procedureAttributesMetadata =
new ProcedureAttributesMetadataRepository(),
_intType = _typeFlowAnalysis.environment.intType {
component.addMetadataRepository(_inferredTypeMetadata);
component.addMetadataRepository(_unreachableNodeMetadata);
component.addMetadataRepository(_procedureAttributesMetadata);
}
InferredType _convertType(Type type, {bool skipCheck: false}) {
assertx(type != null);
Class concreteClass;
bool isInt = false;
final nullable = type is NullableType;
if (nullable) {
type = (type as NullableType).baseType;
}
if (nullable && type == const EmptyType()) {
concreteClass = _typeFlowAnalysis.environment.coreTypes.nullClass;
} else {
concreteClass = type.getConcreteClass(_typeFlowAnalysis.hierarchyCache);
if (concreteClass == null) {
isInt = type.isSubtypeOf(_typeFlowAnalysis.hierarchyCache, _intType);
}
}
List<DartType> typeArgs;
if (type is ConcreteType && type.typeArgs != null) {
typeArgs = type.typeArgs
.take(type.numImmediateTypeArgs)
.map((t) => t is AnyType ? null : (t as RuntimeType).representedType)
.toList();
}
if ((concreteClass != null) || !nullable || isInt || skipCheck) {
return new InferredType(concreteClass, nullable, isInt,
exactTypeArguments: typeArgs, skipCheck: skipCheck);
}
return null;
}
void _setInferredType(TreeNode node, Type type, {bool skipCheck: false}) {
final inferredType = _convertType(type, skipCheck: skipCheck);
if (inferredType != null) {
_inferredTypeMetadata.mapping[node] = inferredType;
}
}
void _setUnreachable(TreeNode node) {
_unreachableNodeMetadata.mapping[node] = const UnreachableNode();
}
void _annotateCallSite(TreeNode node) {
final callSite = _typeFlowAnalysis.callSite(node);
if (callSite != null) {
if (callSite.isReachable) {
bool markSkipCheck = !callSite.useCheckedEntry &&
(node is MethodInvocation || node is PropertySet);
if (callSite.isResultUsed) {
_setInferredType(node, callSite.resultType, skipCheck: markSkipCheck);
} else if (markSkipCheck) {
// If the call is not marked as 'isResultUsed', the 'resultType' will
// not be observed (i.e., it will always be EmptyType). This is the
// case even if the result acutally might be used but is not used by
// the summary, e.g. if the result is an argument to a closure call.
// Therefore, we need to pass in 'NullableType(AnyType)' as the
// inferred result type here (since we don't know what it actually
// is).
_setInferredType(node, NullableType(const AnyType()),
skipCheck: true);
}
} else {
_setUnreachable(node);
}
}
}
void _annotateMember(Member member) {
if (_typeFlowAnalysis.isMemberUsed(member)) {
if (member is Field) {
_setInferredType(member, _typeFlowAnalysis.fieldType(member));
} else {
Args<Type> argTypes = _typeFlowAnalysis.argumentTypes(member);
assertx(argTypes != null);
final int firstParamIndex =
numTypeParams(member) + (hasReceiverArg(member) ? 1 : 0);
final positionalParams = member.function.positionalParameters;
assertx(argTypes.positionalCount ==
firstParamIndex + positionalParams.length);
for (int i = 0; i < positionalParams.length; i++) {
_setInferredType(
positionalParams[i], argTypes.values[firstParamIndex + i]);
}
// TODO(dartbug.com/32292): make sure parameters are sorted in kernel
// AST and iterate parameters in parallel, without lookup.
final names = argTypes.names;
for (int i = 0; i < names.length; i++) {
final param = findNamedParameter(member.function, names[i]);
assertx(param != null);
_setInferredType(param,
argTypes.values[firstParamIndex + positionalParams.length + i]);
}
// TODO(alexmarkov): figure out how to pass receiver type.
}
if (member.isInstanceMember &&
!(member is Procedure && member.isGetter)) {
final attrs = new ProcedureAttributesMetadata(
hasDynamicUses: _typeFlowAnalysis.isCalledDynamically(member),
hasThisUses: _typeFlowAnalysis.isCalledViaThis(member),
hasNonThisUses: _typeFlowAnalysis.isCalledNotViaThis(member),
hasTearOffUses: _typeFlowAnalysis.isTearOffTaken(member));
_procedureAttributesMetadata.mapping[member] = attrs;
}
} else if (!member.isAbstract) {
_setUnreachable(member);
}
}
@override
visitConstructor(Constructor node) {
_annotateMember(node);
super.visitConstructor(node);
}
@override
visitProcedure(Procedure node) {
_annotateMember(node);
super.visitProcedure(node);
}
@override
visitField(Field node) {
_annotateMember(node);
super.visitField(node);
}
@override
visitMethodInvocation(MethodInvocation node) {
_annotateCallSite(node);
super.visitMethodInvocation(node);
}
@override
visitPropertyGet(PropertyGet node) {
_annotateCallSite(node);
super.visitPropertyGet(node);
}
@override
visitDirectMethodInvocation(DirectMethodInvocation node) {
_annotateCallSite(node);
super.visitDirectMethodInvocation(node);
}
@override
visitDirectPropertyGet(DirectPropertyGet node) {
_annotateCallSite(node);
super.visitDirectPropertyGet(node);
}
@override
visitSuperMethodInvocation(SuperMethodInvocation node) {
_annotateCallSite(node);
super.visitSuperMethodInvocation(node);
}
@override
visitSuperPropertyGet(SuperPropertyGet node) {
_annotateCallSite(node);
super.visitSuperPropertyGet(node);
}
@override
visitStaticInvocation(StaticInvocation node) {
_annotateCallSite(node);
super.visitStaticInvocation(node);
}
@override
visitStaticGet(StaticGet node) {
_annotateCallSite(node);
super.visitStaticGet(node);
}
}
/// Tree shaking based on results of type flow analysis (TFA).
///
/// TFA provides information about allocated classes and reachable member
/// bodies. However, it is not enough to perform tree shaking in one pass:
/// we need to figure out which classes, members and typedefs are used
/// in types, interface targets and annotations.
///
/// So, tree shaking is performed in 2 passes:
///
/// * Pass 1 visits declarations of classes and members, and dives deep into
/// bodies of reachable members. It collects sets of used classes, members
/// and typedefs. Also, while visiting bodies of reachable members, it
/// transforms unreachable calls into 'throw' expressions.
///
/// * Pass 2 removes unused classes and members, and replaces bodies of
/// used but unreachable members.
///
class TreeShaker {
final TypeFlowAnalysis typeFlowAnalysis;
final Set<Class> _usedClasses = new Set<Class>();
final Set<Class> _classesUsedInType = new Set<Class>();
final Set<Member> _usedMembers = new Set<Member>();
final Set<Typedef> _usedTypedefs = new Set<Typedef>();
_TreeShakerTypeVisitor typeVisitor;
_TreeShakerConstantVisitor constantVisitor;
_TreeShakerPass1 _pass1;
_TreeShakerPass2 _pass2;
TreeShaker(Component component, this.typeFlowAnalysis) {
typeVisitor = new _TreeShakerTypeVisitor(this);
constantVisitor = new _TreeShakerConstantVisitor(this, typeVisitor);
_pass1 = new _TreeShakerPass1(this);
_pass2 = new _TreeShakerPass2(this);
}
transformComponent(Component component) {
_pass1.transform(component);
_pass2.transform(component);
}
bool isClassUsed(Class c) => _usedClasses.contains(c);
bool isClassUsedInType(Class c) => _classesUsedInType.contains(c);
bool isClassAllocated(Class c) => typeFlowAnalysis.isClassAllocated(c);
bool isMemberUsed(Member m) => _usedMembers.contains(m);
bool isMemberBodyReachable(Member m) => typeFlowAnalysis.isMemberUsed(m);
bool isMemberReferencedFromNativeCode(Member m) =>
typeFlowAnalysis.nativeCodeOracle.isMemberReferencedFromNativeCode(m);
bool isTypedefUsed(Typedef t) => _usedTypedefs.contains(t);
void addClassUsedInType(Class c) {
if (_classesUsedInType.add(c)) {
if (kPrintDebug) {
debugPrint('Class ${c.name} used in type');
}
_usedClasses.add(c);
visitIterable(c.supers, typeVisitor);
transformList(c.typeParameters, _pass1, c);
transformList(c.annotations, _pass1, c);
// Preserve NSM forwarders. They are overlooked by TFA / tree shaker
// as they are abstract and don't have a body.
for (Procedure p in c.procedures) {
if (p.isAbstract && p.isNoSuchMethodForwarder) {
addUsedMember(p);
}
}
}
}
void addUsedMember(Member m) {
if (_usedMembers.add(m)) {
final enclosingClass = m.enclosingClass;
if (enclosingClass != null) {
if (kPrintDebug) {
debugPrint('Member $m from class ${enclosingClass.name} is used');
}
_usedClasses.add(enclosingClass);
}
FunctionNode func = null;
if (m is Field) {
m.type.accept(typeVisitor);
} else if (m is Procedure) {
func = m.function;
if (m.forwardingStubSuperTarget != null) {
addUsedMember(m.forwardingStubSuperTarget);
}
if (m.forwardingStubInterfaceTarget != null) {
addUsedMember(m.forwardingStubInterfaceTarget);
}
} else if (m is Constructor) {
func = m.function;
} else {
throw 'Unexpected member ${m.runtimeType}: $m';
}
if (func != null) {
transformList(func.typeParameters, _pass1, func);
transformList(func.positionalParameters, _pass1, func);
transformList(func.namedParameters, _pass1, func);
func.returnType.accept(typeVisitor);
}
transformList(m.annotations, _pass1, m);
}
}
void addUsedTypedef(Typedef typedef) {
if (_usedTypedefs.add(typedef)) {
transformList(typedef.annotations, _pass1, typedef);
transformList(typedef.typeParameters, _pass1, typedef);
transformList(typedef.typeParametersOfFunctionType, _pass1, typedef);
transformList(typedef.positionalParameters, _pass1, typedef);
transformList(typedef.namedParameters, _pass1, typedef);
typedef.type?.accept(typeVisitor);
}
}
}
/// Visits Dart types and collects all classes and typedefs used in types.
/// This visitor is used during pass 1 of tree shaking. It is a separate
/// visitor because [Transformer] does not provide a way to traverse types.
class _TreeShakerTypeVisitor extends RecursiveVisitor<Null> {
final TreeShaker shaker;
_TreeShakerTypeVisitor(this.shaker);
@override
visitInterfaceType(InterfaceType node) {
shaker.addClassUsedInType(node.classNode);
node.visitChildren(this);
}
@override
visitSupertype(Supertype node) {
shaker.addClassUsedInType(node.classNode);
node.visitChildren(this);
}
@override
visitTypedefType(TypedefType node) {
shaker.addUsedTypedef(node.typedefNode);
node.visitChildren(this);
}
@override
visitFunctionType(FunctionType node) {
node.visitChildren(this);
final typedef = node.typedef;
if (typedef != null) {
shaker.addUsedTypedef(typedef);
}
}
@override
visitTypeParameterType(TypeParameterType node) {
final parent = node.parameter.parent;
if (parent is Class) {
shaker.addClassUsedInType(parent);
}
}
}
/// The first pass of [TreeShaker].
/// Visits all classes, members and bodies of reachable members.
/// Collects all used classes, members and types, and
/// transforms unreachable calls into 'throw' expressions.
class _TreeShakerPass1 extends Transformer {
final TreeShaker shaker;
_TreeShakerPass1(this.shaker);
void transform(Component component) {
component.transformChildren(this);
}
bool _isUnreachable(TreeNode node) {
final callSite = shaker.typeFlowAnalysis.callSite(node);
return (callSite != null) && !callSite.isReachable;
}
List<Expression> _flattenArguments(Arguments arguments,
{Expression receiver}) {
final args = <Expression>[];
if (receiver != null) {
args.add(receiver);
}
args.addAll(arguments.positional);
args.addAll(arguments.named.map((a) => a.value));
return args;
}
bool _isThrowExpression(Expression expr) {
while (expr is Let) {
expr = (expr as Let).body;
}
return expr is Throw;
}
TreeNode _makeUnreachableCall(List<Expression> args) {
TreeNode node;
final int last = args.indexWhere(_isThrowExpression);
if (last >= 0) {
// One of the arguments is a Throw expression.
// Ignore the rest of the arguments.
node = args[last];
args = args.sublist(0, last);
Statistics.throwExpressionsPruned++;
} else {
node = new Throw(new StringLiteral(
'Attempt to execute code removed by Dart AOT compiler (TFA)'));
}
for (var arg in args.reversed) {
node = new Let(new VariableDeclaration(null, initializer: arg), node);
}
Statistics.callsDropped++;
return node;
}
TreeNode _makeUnreachableInitializer(List<Expression> args) {
return new LocalInitializer(
new VariableDeclaration(null, initializer: _makeUnreachableCall(args)));
}
TreeNode _visitAssertNode(TreeNode node) {
if (kRemoveAsserts) {
return null;
} else {
node.transformChildren(this);
return node;
}
}
@override
DartType visitDartType(DartType node) {
node.accept(shaker.typeVisitor);
return node;
}
@override
Supertype visitSupertype(Supertype node) {
node.accept(shaker.typeVisitor);
return node;
}
@override
TreeNode visitTypedef(Typedef node) {
return node; // Do not go deeper.
}
@override
TreeNode visitClass(Class node) {
if (shaker.isClassAllocated(node)) {
shaker.addClassUsedInType(node);
}
transformList(node.constructors, this, node);
transformList(node.procedures, this, node);
transformList(node.fields, this, node);
transformList(node.redirectingFactoryConstructors, this, node);
return node;
}
@override
TreeNode defaultMember(Member node) {
if (shaker.isMemberBodyReachable(node)) {
if (kPrintTrace) {
tracePrint("Visiting $node");
}
shaker.addUsedMember(node);
node.transformChildren(this);
} else if (shaker.isMemberReferencedFromNativeCode(node)) {
// Preserve members referenced from native code to satisfy lookups, even
// if they are not reachable. An instance member could be added via
// native code entry point but still unreachable if no instances of
// its enclosing class are allocated.
shaker.addUsedMember(node);
}
return node;
}
@override
TreeNode visitMethodInvocation(MethodInvocation node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableCall(
_flattenArguments(node.arguments, receiver: node.receiver));
} else {
if (node.interfaceTarget != null) {
shaker.addUsedMember(node.interfaceTarget);
}
return node;
}
}
@override
TreeNode visitPropertyGet(PropertyGet node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableCall([node.receiver]);
} else {
if (node.interfaceTarget != null) {
shaker.addUsedMember(node.interfaceTarget);
}
return node;
}
}
@override
TreeNode visitPropertySet(PropertySet node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableCall([node.receiver, node.value]);
} else {
if (node.interfaceTarget != null) {
shaker.addUsedMember(node.interfaceTarget);
}
return node;
}
}
@override
TreeNode visitSuperMethodInvocation(SuperMethodInvocation node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableCall(_flattenArguments(node.arguments));
} else {
if (node.interfaceTarget != null) {
shaker.addUsedMember(node.interfaceTarget);
}
return node;
}
}
@override
TreeNode visitSuperPropertyGet(SuperPropertyGet node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableCall([]);
} else {
if (node.interfaceTarget != null) {
shaker.addUsedMember(node.interfaceTarget);
}
return node;
}
}
@override
TreeNode visitSuperPropertySet(SuperPropertySet node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableCall([node.value]);
} else {
if (node.interfaceTarget != null) {
shaker.addUsedMember(node.interfaceTarget);
}
return node;
}
}
@override
TreeNode visitStaticInvocation(StaticInvocation node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableCall(_flattenArguments(node.arguments));
} else {
assertx(shaker.isMemberBodyReachable(node.target), details: node.target);
return node;
}
}
@override
TreeNode visitStaticGet(StaticGet node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableCall([]);
} else {
if (!shaker.isMemberBodyReachable(node.target)) {
// Annotations could contain references to constant fields.
assertx((node.target is Field) && (node.target as Field).isConst);
shaker.addUsedMember(node.target);
}
return node;
}
}
@override
TreeNode visitConstantExpression(ConstantExpression node) {
shaker.constantVisitor.analyzeConstant(node.constant);
return node;
}
@override
TreeNode visitStaticSet(StaticSet node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableCall([node.value]);
} else {
assertx(shaker.isMemberBodyReachable(node.target), details: node.target);
return node;
}
}
@override
TreeNode visitDirectMethodInvocation(DirectMethodInvocation node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableCall(
_flattenArguments(node.arguments, receiver: node.receiver));
} else {
assertx(shaker.isMemberBodyReachable(node.target), details: node.target);
return node;
}
}
@override
TreeNode visitDirectPropertyGet(DirectPropertyGet node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableCall([node.receiver]);
} else {
assertx(shaker.isMemberBodyReachable(node.target), details: node.target);
return node;
}
}
@override
TreeNode visitDirectPropertySet(DirectPropertySet node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableCall([node.receiver, node.value]);
} else {
assertx(shaker.isMemberBodyReachable(node.target), details: node.target);
return node;
}
}
@override
TreeNode visitConstructorInvocation(ConstructorInvocation node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableCall(_flattenArguments(node.arguments));
} else {
if (!shaker.isMemberBodyReachable(node.target)) {
// Annotations could contain references to const constructors.
assertx(node.isConst);
shaker.addUsedMember(node.target);
}
return node;
}
}
@override
TreeNode visitRedirectingInitializer(RedirectingInitializer node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableInitializer(_flattenArguments(node.arguments));
} else {
assertx(shaker.isMemberBodyReachable(node.target), details: node.target);
return node;
}
}
@override
TreeNode visitSuperInitializer(SuperInitializer node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableInitializer(_flattenArguments(node.arguments));
} else {
// Can't assert that node.target is used due to partial mixin resolution.
return node;
}
}
@override
visitFieldInitializer(FieldInitializer node) {
node.transformChildren(this);
if (_isUnreachable(node)) {
return _makeUnreachableInitializer([node.value]);
} else {
assertx(shaker.isMemberBodyReachable(node.field), details: node.field);
return node;
}
}
@override
TreeNode visitAssertStatement(AssertStatement node) {
return _visitAssertNode(node);
}
@override
TreeNode visitAssertBlock(AssertBlock node) {
return _visitAssertNode(node);
}
@override
TreeNode visitAssertInitializer(AssertInitializer node) {
return _visitAssertNode(node);
}
}
/// The second pass of [TreeShaker]. It is called after set of used
/// classes, members and typedefs is determined during the first pass.
/// This pass visits classes and members and removes unused classes and member.
/// Bodies of unreachable but used members are replaced with 'throw'
/// expressions. This pass does not dive deeper than member level.
class _TreeShakerPass2 extends Transformer {
final TreeShaker shaker;
_TreeShakerPass2(this.shaker);
void transform(Component component) {
component.transformChildren(this);
}
@override
TreeNode visitLibrary(Library node) {
node.transformChildren(this);
// The transformer API does not iterate over `Library.additionalExports`,
// so we manually delete the references to shaken nodes.
node.additionalExports.removeWhere((Reference reference) {
final node = reference.node;
if (node is Class) {
return !shaker.isClassUsed(node);
} else if (node is Typedef) {
return !shaker.isTypedefUsed(node);
} else {
return !shaker.isMemberUsed(node as Member);
}
});
return node;
}
@override
Typedef visitTypedef(Typedef node) {
return shaker.isTypedefUsed(node) ? node : null;
}
@override
Class visitClass(Class node) {
if (!shaker.isClassUsed(node)) {
debugPrint('Dropped class ${node.name}');
node.canonicalName?.unbind();
Statistics.classesDropped++;
return null; // Remove the class.
}
if (!shaker.isClassUsedInType(node)) {
debugPrint('Dropped supers from class ${node.name}');
// The class is only a namespace for static members. Remove its
// hierarchy information. This is mandatory, since these references
// might otherwise become dangling.
node.supertype = shaker
.typeFlowAnalysis.environment.coreTypes.objectClass.asRawSupertype;
node.implementedTypes.clear();
node.typeParameters.clear();
node.isAbstract = true;
// Mixin applications cannot have static members.
assertx(node.mixedInType == null);
node.annotations = const <Expression>[];
}
if (!shaker.isClassAllocated(node)) {
debugPrint('Class ${node.name} converted to abstract');
node.isAbstract = true;
}
node.transformChildren(this);
return node;
}
/// Preserve instance fields of enums as VM relies on their existence.
bool _preserveSpecialMember(Member node) =>
node is Field &&
!node.isStatic &&
node.enclosingClass != null &&
node.enclosingClass.isEnum;
@override
Member defaultMember(Member node) {
if (!shaker.isMemberUsed(node) && !_preserveSpecialMember(node)) {
node.canonicalName?.unbind();
Statistics.membersDropped++;
return null;
}
if (!shaker.isMemberBodyReachable(node)) {
if (node is Procedure) {
// Remove body of unused member.
if (!node.isStatic && node.enclosingClass.isAbstract) {
node.isAbstract = true;
node.function.body = null;
} else {
// If the enclosing class is not abstract, the method should still
// have a body even if it can never be called.
_makeUnreachableBody(node.function);
}
node.function.asyncMarker = AsyncMarker.Sync;
node.forwardingStubSuperTargetReference = null;
node.forwardingStubInterfaceTargetReference = null;
Statistics.methodBodiesDropped++;
} else if (node is Field) {
node.initializer = null;
Statistics.fieldInitializersDropped++;
} else if (node is Constructor) {
_makeUnreachableBody(node.function);
node.initializers = const <Initializer>[];
Statistics.constructorBodiesDropped++;
} else {
throw 'Unexpected member ${node.runtimeType}: $node';
}
}
return node;
}
void _makeUnreachableBody(FunctionNode function) {
if (function.body != null) {
function.body = new ExpressionStatement(new Throw(new StringLiteral(
"Attempt to execute method removed by Dart AOT compiler (TFA)")))
..parent = function;
}
}
@override
TreeNode defaultTreeNode(TreeNode node) {
return node; // Do not traverse into other nodes.
}
}
class _TreeShakerConstantVisitor extends ConstantVisitor<Null> {
final TreeShaker shaker;
final _TreeShakerTypeVisitor typeVisitor;
final Set<Constant> constants = new Set<Constant>();
final Set<InstanceConstant> instanceConstants = new Set<InstanceConstant>();
_TreeShakerConstantVisitor(this.shaker, this.typeVisitor);
analyzeConstant(Constant constant) {
if (constants.add(constant)) {
constant.accept(this);
}
}
@override
defaultConstant(Constant constant) {
throw 'There is no support for constant "$constant" in TFA yet!';
}
@override
visitNullConstant(NullConstant constant) {}
@override
visitBoolConstant(BoolConstant constant) {}
@override
visitIntConstant(IntConstant constant) {}
@override
visitDoubleConstant(DoubleConstant constant) {}
@override
visitStringConstant(StringConstant constant) {}
@override
visitSymbolConstant(SymbolConstant constant) {
// The Symbol class and it's _name field are always retained.
}
@override
visitMapConstant(MapConstant node) {
throw 'The kernel2kernel constants transformation desugars const maps!';
}
@override
visitListConstant(ListConstant constant) {
for (final Constant entry in constant.entries) {
analyzeConstant(entry);
}
}
@override
visitInstanceConstant(InstanceConstant constant) {