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Diffstat (limited to 'js/src/frontend/ParseContext.h')
| -rw-r--r-- | js/src/frontend/ParseContext.h | 697 |
1 files changed, 697 insertions, 0 deletions
diff --git a/js/src/frontend/ParseContext.h b/js/src/frontend/ParseContext.h new file mode 100644 index 0000000000..8124073bf9 --- /dev/null +++ b/js/src/frontend/ParseContext.h @@ -0,0 +1,697 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- + * vim: set ts=8 sts=2 et sw=2 tw=80: + * This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#ifndef frontend_ParseContext_h +#define frontend_ParseContext_h + +#include "ds/Nestable.h" +#include "frontend/ErrorReporter.h" +#include "frontend/NameAnalysisTypes.h" // DeclaredNameInfo, FunctionBoxVector +#include "frontend/NameCollections.h" +#include "frontend/ParserAtom.h" // TaggedParserAtomIndex +#include "frontend/ScriptIndex.h" // ScriptIndex +#include "frontend/SharedContext.h" +#include "js/friend/ErrorMessages.h" // JSMSG_* +#include "vm/GeneratorAndAsyncKind.h" // js::GeneratorKind, js::FunctionAsyncKind + +namespace js { + +namespace frontend { + +class ParserBase; +class UsedNameTracker; + +struct CompilationState; + +const char* DeclarationKindString(DeclarationKind kind); + +// Returns true if the declaration is `var` or equivalent. +bool DeclarationKindIsVar(DeclarationKind kind); + +bool DeclarationKindIsParameter(DeclarationKind kind); + +/* + * The struct ParseContext stores information about the current parsing context, + * which is part of the parser state (see the field Parser::pc). The current + * parsing context is either the global context, or the function currently being + * parsed. When the parser encounters a function definition, it creates a new + * ParseContext, makes it the new current context. + */ +class ParseContext : public Nestable<ParseContext> { + public: + // The intra-function statement stack. + // + // Used for early error checking that depend on the nesting structure of + // statements, such as continue/break targets, labels, and unbraced + // lexical declarations. + class Statement : public Nestable<Statement> { + StatementKind kind_; + + public: + using Nestable<Statement>::enclosing; + using Nestable<Statement>::findNearest; + + Statement(ParseContext* pc, StatementKind kind) + : Nestable<Statement>(&pc->innermostStatement_), kind_(kind) {} + + template <typename T> + inline bool is() const; + template <typename T> + inline T& as(); + + StatementKind kind() const { return kind_; } + + void refineForKind(StatementKind newForKind) { + MOZ_ASSERT(kind_ == StatementKind::ForLoop); + MOZ_ASSERT(newForKind == StatementKind::ForInLoop || + newForKind == StatementKind::ForOfLoop); + kind_ = newForKind; + } + }; + + class LabelStatement : public Statement { + TaggedParserAtomIndex label_; + + public: + LabelStatement(ParseContext* pc, TaggedParserAtomIndex label) + : Statement(pc, StatementKind::Label), label_(label) {} + + TaggedParserAtomIndex label() const { return label_; } + }; + + struct ClassStatement : public Statement { + FunctionBox* constructorBox; + + explicit ClassStatement(ParseContext* pc) + : Statement(pc, StatementKind::Class), constructorBox(nullptr) {} + }; + + // The intra-function scope stack. + // + // Tracks declared and used names within a scope. + class Scope : public Nestable<Scope> { + // Names declared in this scope. Corresponds to the union of + // VarDeclaredNames and LexicallyDeclaredNames in the ES spec. + // + // A 'var' declared name is a member of the declared name set of every + // scope in its scope contour. + // + // A lexically declared name is a member only of the declared name set of + // the scope in which it is declared. + PooledMapPtr<DeclaredNameMap> declared_; + + // FunctionBoxes in this scope that need to be considered for Annex + // B.3.3 semantics. This is checked on Scope exit, as by then we have + // all the declared names and would know if Annex B.3.3 is applicable. + PooledVectorPtr<FunctionBoxVector> possibleAnnexBFunctionBoxes_; + + // Monotonically increasing id. + uint32_t id_; + + // Flag for determining if we can apply an optimization to store bindings in + // stack slots, which is applied in generator or async functions, or in + // async modules. + // + // This limit is a performance heuristic. Stack slots reduce allocations, + // and `Local` opcodes are a bit faster than `AliasedVar` ones; but at each + // `yield` or `await` the stack slots must be memcpy'd into a + // GeneratorObject. At some point the memcpy is too much. The limit is + // plenty for typical human-authored code. + enum class GeneratorOrAsyncScopeFlag : uint32_t { + // Scope is small enough that bindings can be stored in stack slots. + Optimizable = 0, + + // Scope is too big and all bindings should be closed over. + TooManyBindings = UINT32_MAX, + }; + + // Scope size info, relevant for scopes in generators, async functions, and + // async modules only. + static constexpr uint32_t InnerScopeSlotCountInitialValue = 0; + union { + // The estimated number of slots needed for nested scopes inside this one. + // Calculated while parsing the scope and inner scopes. + // Valid only if isOptimizableFlagCalculated_ is false. + uint32_t innerScopeSlotCount_ = InnerScopeSlotCountInitialValue; + + // Set when leaving the scope. + // Valid only if isOptimizableFlagCalculated_ is true. + GeneratorOrAsyncScopeFlag optimizableFlag_; + } generatorOrAsyncScopeInfo_; + +#ifdef DEBUG + bool isGeneratorOrAsyncScopeInfoUsed_ = false; + bool isOptimizableFlagCalculated_ = false; +#endif + + uint32_t innerScopeSlotCount() { + MOZ_ASSERT(!isOptimizableFlagCalculated_); +#ifdef DEBUG + isGeneratorOrAsyncScopeInfoUsed_ = true; +#endif + return generatorOrAsyncScopeInfo_.innerScopeSlotCount_; + } + void setInnerScopeSlotCount(uint32_t slotCount) { + MOZ_ASSERT(!isOptimizableFlagCalculated_); + generatorOrAsyncScopeInfo_.innerScopeSlotCount_ = slotCount; +#ifdef DEBUG + isGeneratorOrAsyncScopeInfoUsed_ = true; +#endif + } + void propagateInnerScopeSlotCount(uint32_t slotCount) { + if (slotCount > innerScopeSlotCount()) { + setInnerScopeSlotCount(slotCount); + } + } + + void setGeneratorOrAsyncScopeIsOptimizable() { + MOZ_ASSERT(!isOptimizableFlagCalculated_); +#ifdef DEBUG + isGeneratorOrAsyncScopeInfoUsed_ = true; + isOptimizableFlagCalculated_ = true; +#endif + generatorOrAsyncScopeInfo_.optimizableFlag_ = + GeneratorOrAsyncScopeFlag::Optimizable; + } + + void setGeneratorOrAsyncScopeHasTooManyBindings() { + MOZ_ASSERT(!isOptimizableFlagCalculated_); +#ifdef DEBUG + isGeneratorOrAsyncScopeInfoUsed_ = true; + isOptimizableFlagCalculated_ = true; +#endif + generatorOrAsyncScopeInfo_.optimizableFlag_ = + GeneratorOrAsyncScopeFlag::TooManyBindings; + } + + bool maybeReportOOM(ParseContext* pc, bool result) { + if (!result) { + ReportOutOfMemory(pc->sc()->fc_); + } + return result; + } + + public: + using DeclaredNamePtr = DeclaredNameMap::Ptr; + using AddDeclaredNamePtr = DeclaredNameMap::AddPtr; + + using Nestable<Scope>::enclosing; + + explicit inline Scope(ParserBase* parser); + explicit inline Scope(FrontendContext* fc, ParseContext* pc, + UsedNameTracker& usedNames); + + void dump(ParseContext* pc, ParserBase* parser); + + uint32_t id() const { return id_; } + + [[nodiscard]] bool init(ParseContext* pc) { + if (id_ == UINT32_MAX) { + pc->errorReporter_.errorNoOffset(JSMSG_NEED_DIET, "script"); + return false; + } + + return declared_.acquire(pc->sc()->fc_); + } + + bool isEmpty() const { return declared_->all().empty(); } + + uint32_t declaredCount() const { + size_t count = declared_->count(); + MOZ_ASSERT(count <= UINT32_MAX); + return uint32_t(count); + } + + DeclaredNamePtr lookupDeclaredName(TaggedParserAtomIndex name) { + return declared_->lookup(name); + } + + AddDeclaredNamePtr lookupDeclaredNameForAdd(TaggedParserAtomIndex name) { + return declared_->lookupForAdd(name); + } + + [[nodiscard]] bool addDeclaredName(ParseContext* pc, AddDeclaredNamePtr& p, + TaggedParserAtomIndex name, + DeclarationKind kind, uint32_t pos, + ClosedOver closedOver = ClosedOver::No) { + return maybeReportOOM( + pc, declared_->add(p, name, DeclaredNameInfo(kind, pos, closedOver))); + } + + // Add a FunctionBox as a possible candidate for Annex B.3.3 semantics. + [[nodiscard]] bool addPossibleAnnexBFunctionBox(ParseContext* pc, + FunctionBox* funbox); + + // Check if the candidate function boxes for Annex B.3.3 should in + // fact get Annex B semantics. Checked on Scope exit. + [[nodiscard]] bool propagateAndMarkAnnexBFunctionBoxes(ParseContext* pc, + ParserBase* parser); + + // Add and remove catch parameter names. Used to implement the odd + // semantics of catch bodies. + bool addCatchParameters(ParseContext* pc, Scope& catchParamScope); + void removeCatchParameters(ParseContext* pc, Scope& catchParamScope); + + void useAsVarScope(ParseContext* pc) { + MOZ_ASSERT(!pc->varScope_); + pc->varScope_ = this; + } + + // Maximum number of fixed stack slots in a generator or async function + // script. If a script would have more, we instead store some variables in + // heap EnvironmentObjects. + // + // This limit is a performance heuristic. Stack slots reduce allocations, + // and `Local` opcodes are a bit faster than `AliasedVar` ones; but at each + // `yield` or `await` the stack slots must be memcpy'd into a + // GeneratorObject. At some point the memcpy is too much. The limit is + // plenty for typical human-authored code. + // + // NOTE: This just limits the number of fixed slots, not the entire stack + // slots. `yield` and `await` can happen with more slots if there + // are many stack values, and the number of values copied to the + // generator's stack storage array can be more than the limit. + static constexpr uint32_t FixedSlotLimit = 256; + + // This is called as we leave a function, var, or lexical scope in a + // generator or async function. `ownSlotCount` is the number of `bindings_` + // that are not closed over. + void setOwnStackSlotCount(uint32_t ownSlotCount) { + uint32_t slotCount = ownSlotCount + innerScopeSlotCount(); + if (slotCount > FixedSlotLimit) { + slotCount = innerScopeSlotCount(); + setGeneratorOrAsyncScopeHasTooManyBindings(); + } else { + setGeneratorOrAsyncScopeIsOptimizable(); + } + + // Propagate total size to enclosing scope. + if (Scope* parent = enclosing()) { + parent->propagateInnerScopeSlotCount(slotCount); + } + } + + bool tooBigToOptimize() const { + // NOTE: This is called also for scopes in non-generator/non-async. + // generatorOrAsyncScopeInfo_ is used only from generator or async, + // and if it's not used, it holds the initial value, which is the + // same value as GeneratorOrAsyncScopeFlag::Optimizable. + static_assert(InnerScopeSlotCountInitialValue == + uint32_t(GeneratorOrAsyncScopeFlag::Optimizable)); + MOZ_ASSERT(!isGeneratorOrAsyncScopeInfoUsed_ || + isOptimizableFlagCalculated_); + return generatorOrAsyncScopeInfo_.optimizableFlag_ != + GeneratorOrAsyncScopeFlag::Optimizable; + } + + // An iterator for the set of names a scope binds: the set of all + // declared names for 'var' scopes, and the set of lexically declared + // names, plus synthetic names, for non-'var' scopes. + class BindingIter { + friend class Scope; + + DeclaredNameMap::Range declaredRange_; + mozilla::DebugOnly<uint32_t> count_; + bool isVarScope_; + + BindingIter(Scope& scope, bool isVarScope) + : declaredRange_(scope.declared_->all()), + count_(0), + isVarScope_(isVarScope) { + settle(); + } + + bool isLexicallyDeclared() { + return BindingKindIsLexical(kind()) || + kind() == BindingKind::Synthetic || + kind() == BindingKind::PrivateMethod; + } + + void settle() { + // Both var and lexically declared names are binding in a var + // scope. + if (isVarScope_) { + return; + } + + // Otherwise, only lexically declared names are binding. Pop the range + // until we find such a name. + while (!declaredRange_.empty()) { + if (isLexicallyDeclared()) { + break; + } + declaredRange_.popFront(); + } + } + + public: + bool done() const { return declaredRange_.empty(); } + + explicit operator bool() const { return !done(); } + + TaggedParserAtomIndex name() { + MOZ_ASSERT(!done()); + return declaredRange_.front().key(); + } + + DeclarationKind declarationKind() { + MOZ_ASSERT(!done()); + return declaredRange_.front().value()->kind(); + } + + BindingKind kind() { + return DeclarationKindToBindingKind(declarationKind()); + } + + bool closedOver() { + MOZ_ASSERT(!done()); + return declaredRange_.front().value()->closedOver(); + } + + void setClosedOver() { + MOZ_ASSERT(!done()); + return declaredRange_.front().value()->setClosedOver(); + } + + void operator++(int) { + MOZ_ASSERT(!done()); + MOZ_ASSERT(count_ != UINT32_MAX); + declaredRange_.popFront(); + settle(); + } + }; + + inline BindingIter bindings(ParseContext* pc); + }; + + class VarScope : public Scope { + public: + explicit inline VarScope(ParserBase* parser); + explicit inline VarScope(FrontendContext* fc, ParseContext* pc, + UsedNameTracker& usedNames); + }; + + private: + // Context shared between parsing and bytecode generation. + SharedContext* sc_; + + // A mechanism used for error reporting. + ErrorReporter& errorReporter_; + + // The innermost statement, i.e., top of the statement stack. + Statement* innermostStatement_; + + // The innermost scope, i.e., top of the scope stack. + // + // The outermost scope in the stack is usually varScope_. In the case of + // functions, the outermost scope is functionScope_, which may be + // varScope_. See comment above functionScope_. + Scope* innermostScope_; + + // If isFunctionBox() and the function is a named lambda, the DeclEnv + // scope for named lambdas. + mozilla::Maybe<Scope> namedLambdaScope_; + + // If isFunctionBox(), the scope for the function. If there are no + // parameter expressions, this is scope for the entire function. If there + // are parameter expressions, this holds the special function names + // ('.this', 'arguments') and the formal parameters. + mozilla::Maybe<Scope> functionScope_; + + // The body-level scope. This always exists, but not necessarily at the + // beginning of parsing the script in the case of functions with parameter + // expressions. + Scope* varScope_; + + // Simple formal parameter names, in order of appearance. Only used when + // isFunctionBox(). + PooledVectorPtr<AtomVector> positionalFormalParameterNames_; + + // Closed over binding names, in order of appearance. Null-delimited + // between scopes. Only used when syntax parsing. + PooledVectorPtr<AtomVector> closedOverBindingsForLazy_; + + public: + // All inner functions in this context. Only used when syntax parsing. + // The Functions (or FunctionCreateionDatas) are traced as part of the + // CompilationStencil function vector. + Vector<ScriptIndex, 4> innerFunctionIndexesForLazy; + + // In a function context, points to a Directive struct that can be updated + // to reflect new directives encountered in the Directive Prologue that + // require reparsing the function. In global/module/generator-tail contexts, + // we don't need to reparse when encountering a DirectivePrologue so this + // pointer may be nullptr. + Directives* newDirectives; + + // lastYieldOffset stores the offset of the last yield that was parsed. + // NoYieldOffset is its initial value. + static const uint32_t NoYieldOffset = UINT32_MAX; + uint32_t lastYieldOffset; + + // lastAwaitOffset stores the offset of the last await that was parsed. + // NoAwaitOffset is its initial value. + static const uint32_t NoAwaitOffset = UINT32_MAX; + uint32_t lastAwaitOffset; + + private: + // Monotonically increasing id. + uint32_t scriptId_; + + // Set when encountering a super.property inside a method. We need to mark + // the nearest super scope as needing a home object. + bool superScopeNeedsHomeObject_; + + public: + ParseContext(FrontendContext* fc, ParseContext*& parent, SharedContext* sc, + ErrorReporter& errorReporter, CompilationState& compilationState, + Directives* newDirectives, bool isFull); + + [[nodiscard]] bool init(); + + SharedContext* sc() { return sc_; } + + // `true` if we are in the body of a function definition. + bool isFunctionBox() const { return sc_->isFunctionBox(); } + + FunctionBox* functionBox() { return sc_->asFunctionBox(); } + + Statement* innermostStatement() { return innermostStatement_; } + + Scope* innermostScope() { + // There is always at least one scope: the 'var' scope. + MOZ_ASSERT(innermostScope_); + return innermostScope_; + } + + Scope& namedLambdaScope() { + MOZ_ASSERT(functionBox()->isNamedLambda()); + return *namedLambdaScope_; + } + + Scope& functionScope() { + MOZ_ASSERT(isFunctionBox()); + return *functionScope_; + } + + Scope& varScope() { + MOZ_ASSERT(varScope_); + return *varScope_; + } + + bool isFunctionExtraBodyVarScopeInnermost() { + return isFunctionBox() && functionBox()->hasParameterExprs && + innermostScope() == varScope_; + } + + template <typename Predicate /* (Statement*) -> bool */> + Statement* findInnermostStatement(Predicate predicate) { + return Statement::findNearest(innermostStatement_, predicate); + } + + template <typename T, typename Predicate /* (Statement*) -> bool */> + T* findInnermostStatement(Predicate predicate) { + return Statement::findNearest<T>(innermostStatement_, predicate); + } + + template <typename T> + T* findInnermostStatement() { + return Statement::findNearest<T>(innermostStatement_); + } + + AtomVector& positionalFormalParameterNames() { + return *positionalFormalParameterNames_; + } + + AtomVector& closedOverBindingsForLazy() { + return *closedOverBindingsForLazy_; + } + + enum class BreakStatementError : uint8_t { + // Unlabeled break must be inside loop or switch. + ToughBreak, + LabelNotFound, + }; + + // Return Err(true) if we have encountered at least one loop, + // Err(false) otherwise. + [[nodiscard]] inline JS::Result<Ok, BreakStatementError> checkBreakStatement( + TaggedParserAtomIndex label); + + enum class ContinueStatementError : uint8_t { + NotInALoop, + LabelNotFound, + }; + [[nodiscard]] inline JS::Result<Ok, ContinueStatementError> + checkContinueStatement(TaggedParserAtomIndex label); + + // True if we are at the topmost level of a entire script or function body. + // For example, while parsing this code we would encounter f1 and f2 at + // body level, but we would not encounter f3 or f4 at body level: + // + // function f1() { function f2() { } } + // if (cond) { function f3() { if (cond) { function f4() { } } } } + // + bool atBodyLevel() { return !innermostStatement_; } + + bool atGlobalLevel() { return atBodyLevel() && sc_->isGlobalContext(); } + + // True if we are at the topmost level of a module only. + bool atModuleLevel() { return atBodyLevel() && sc_->isModuleContext(); } + + // True if we are at the topmost level of an entire script or module. For + // example, in the comment on |atBodyLevel()| above, we would encounter |f1| + // and the outermost |if (cond)| at top level, and everything else would not + // be at top level. + bool atTopLevel() { return atBodyLevel() && sc_->isTopLevelContext(); } + + bool atModuleTopLevel() { + // True if we are at the topmost level of an entire module. + // + // For example, this is used to determine if an await statement should + // mark a module as an async module during parsing. + // + // Example module: + // import x from "y"; + // + // await x.foo(); // mark as Top level await. + // + // if (cond) { + // await x.bar(); // mark as Top level await. + // } + // + // async function z() { + // await x.baz(); // do not mark as Top level await. + // } + return sc_->isModuleContext() && sc_->isTopLevelContext(); + } + + // True if this is the outermost ParserContext for current compile. For + // delazification, this lets us identify if the lazy PrivateScriptData is for + // current parser context. + bool isOutermostOfCurrentCompile() const { + MOZ_ASSERT(!!enclosing() == !!scriptId()); + return (scriptId() == 0); + } + + void setSuperScopeNeedsHomeObject() { + MOZ_ASSERT(sc_->allowSuperProperty()); + superScopeNeedsHomeObject_ = true; + } + + bool superScopeNeedsHomeObject() const { return superScopeNeedsHomeObject_; } + + bool useAsmOrInsideUseAsm() const { + return sc_->isFunctionBox() && sc_->asFunctionBox()->useAsmOrInsideUseAsm(); + } + + // A generator is marked as a generator before its body is parsed. + GeneratorKind generatorKind() const { + return sc_->isFunctionBox() ? sc_->asFunctionBox()->generatorKind() + : GeneratorKind::NotGenerator; + } + + bool isGenerator() const { + return generatorKind() == GeneratorKind::Generator; + } + + bool isAsync() const { + return sc_->isSuspendableContext() && + sc_->asSuspendableContext()->isAsync(); + } + + bool isGeneratorOrAsync() const { return isGenerator() || isAsync(); } + + bool needsDotGeneratorName() const { return isGeneratorOrAsync(); } + + FunctionAsyncKind asyncKind() const { + return isAsync() ? FunctionAsyncKind::AsyncFunction + : FunctionAsyncKind::SyncFunction; + } + + bool isArrowFunction() const { + return sc_->isFunctionBox() && sc_->asFunctionBox()->isArrow(); + } + + bool isMethod() const { + return sc_->isFunctionBox() && sc_->asFunctionBox()->isMethod(); + } + + bool isGetterOrSetter() const { + return sc_->isFunctionBox() && (sc_->asFunctionBox()->isGetter() || + sc_->asFunctionBox()->isSetter()); + } + + bool allowReturn() const { + return sc_->isFunctionBox() && sc_->asFunctionBox()->allowReturn(); + } + + uint32_t scriptId() const { return scriptId_; } + + bool computeAnnexBAppliesToLexicalFunctionInInnermostScope( + FunctionBox* funbox, ParserBase* parser, bool* annexBApplies); + + bool tryDeclareVar(TaggedParserAtomIndex name, ParserBase* parser, + DeclarationKind kind, uint32_t beginPos, + mozilla::Maybe<DeclarationKind>* redeclaredKind, + uint32_t* prevPos); + + bool hasUsedName(const UsedNameTracker& usedNames, + TaggedParserAtomIndex name); + bool hasUsedFunctionSpecialName(const UsedNameTracker& usedNames, + TaggedParserAtomIndex name); + + bool declareFunctionThis(const UsedNameTracker& usedNames, + bool canSkipLazyClosedOverBindings); + bool declareFunctionArgumentsObject(const UsedNameTracker& usedNames, + bool canSkipLazyClosedOverBindings); + bool declareNewTarget(const UsedNameTracker& usedNames, + bool canSkipLazyClosedOverBindings); + bool declareDotGeneratorName(); + bool declareTopLevelDotGeneratorName(); + + private: + [[nodiscard]] bool isVarRedeclaredInInnermostScope( + TaggedParserAtomIndex name, ParserBase* parser, DeclarationKind kind, + mozilla::Maybe<DeclarationKind>* out); + + [[nodiscard]] bool isVarRedeclaredInEval( + TaggedParserAtomIndex name, ParserBase* parser, DeclarationKind kind, + mozilla::Maybe<DeclarationKind>* out); + + enum DryRunOption { NotDryRun, DryRunInnermostScopeOnly }; + template <DryRunOption dryRunOption> + bool tryDeclareVarHelper(TaggedParserAtomIndex name, ParserBase* parser, + DeclarationKind kind, uint32_t beginPos, + mozilla::Maybe<DeclarationKind>* redeclaredKind, + uint32_t* prevPos); +}; + +} // namespace frontend + +} // namespace js + +#endif // frontend_ParseContext_h |