C++ SymbolTableEntry::scopeOffset方法代码示例

inline bool JSLexicalEnvironment::symbolTableGet(PropertyName propertyName, PropertySlot& slot)
{
    SymbolTableEntry entry = symbolTable()->inlineGet(propertyName.uid());
    if (entry.isNull())
        return false;

    ScopeOffset offset = entry.scopeOffset();

    // Defend against the inspector asking for a var after it has been optimized out.
    if (!isValid(offset))
        return false;

    slot.setValue(this, DontEnum, variableAt(offset).get());
    return true;
}

// Returns true if we found enough information to terminate optimization.
static inline bool abstractAccess(ExecState* exec, JSScope* scope, const Identifier& ident, GetOrPut getOrPut, size_t depth, bool& needsVarInjectionChecks, ResolveOp& op, InitializationMode initializationMode)
{
    if (scope->isJSLexicalEnvironment()) {
        JSLexicalEnvironment* lexicalEnvironment = jsCast<JSLexicalEnvironment*>(scope);
        if (ident == exec->propertyNames().arguments) {
            // We know the property will be at this lexical environment scope, but we don't know how to cache it.
            op = ResolveOp(Dynamic, 0, 0, 0, 0, 0);
            return true;
        }

        SymbolTableEntry entry = lexicalEnvironment->symbolTable()->get(ident.impl());
        if (entry.isReadOnly() && getOrPut == Put) {
            // We know the property will be at this lexical environment scope, but we don't know how to cache it.
            op = ResolveOp(Dynamic, 0, 0, 0, 0, 0);
            return true;
        }

        if (!entry.isNull()) {
            op = ResolveOp(makeType(ClosureVar, needsVarInjectionChecks), depth, 0, lexicalEnvironment, entry.watchpointSet(), entry.scopeOffset().offset());
            return true;
        }

        if (scope->type() == ModuleEnvironmentType) {
            JSModuleEnvironment* moduleEnvironment = jsCast<JSModuleEnvironment*>(scope);
            JSModuleRecord* moduleRecord = moduleEnvironment->moduleRecord();
            JSModuleRecord::Resolution resolution = moduleRecord->resolveImport(exec, ident);
            if (resolution.type == JSModuleRecord::Resolution::Type::Resolved) {
                JSModuleRecord* importedRecord = resolution.moduleRecord;
                JSModuleEnvironment* importedEnvironment = importedRecord->moduleEnvironment();
                SymbolTableEntry entry = importedEnvironment->symbolTable()->get(resolution.localName.impl());
                ASSERT(!entry.isNull());
                op = ResolveOp(makeType(ModuleVar, needsVarInjectionChecks), depth, 0, importedEnvironment, entry.watchpointSet(), entry.scopeOffset().offset(), resolution.localName.impl());
                return true;
            }
        }

        if (lexicalEnvironment->symbolTable()->usesNonStrictEval())
            needsVarInjectionChecks = true;
        return false;
    }

    if (scope->isGlobalLexicalEnvironment()) {
        JSGlobalLexicalEnvironment* globalLexicalEnvironment = jsCast<JSGlobalLexicalEnvironment*>(scope);
        SymbolTableEntry entry = globalLexicalEnvironment->symbolTable()->get(ident.impl());
        if (!entry.isNull()) {
            if (getOrPut == Put && entry.isReadOnly() && initializationMode != Initialization) {
                // We know the property will be at global lexical environment, but we don't know how to cache it.
                op = ResolveOp(Dynamic, 0, 0, 0, 0, 0);
                return true;
            }

            // We can try to force const Initialization to always go down the fast path. It is provably impossible to construct
            // a program that needs a var injection check here. You can convince yourself of this as follows:
            // Any other let/const/class would be a duplicate of this in the global scope, so we would never get here in that situation.
            // Also, if we had an eval in the global scope that defined a const, it would also be a duplicate of this const, and so it would
            // also throw an error. Therefore, we're *the only* thing that can assign to this "const" slot for the first (and only) time. Also, 
            // we will never have a Dynamic ResolveType here because if we were inside a "with" statement, that would mean the "const" definition 
            // isn't a global, it would be a local to the "with" block. 
            // We still need to make the slow path correct for when we need to fire a watchpoint.
            ResolveType resolveType = initializationMode == Initialization ? GlobalLexicalVar : makeType(GlobalLexicalVar, needsVarInjectionChecks);
            op = ResolveOp(
                resolveType, depth, 0, 0, entry.watchpointSet(),
                reinterpret_cast<uintptr_t>(globalLexicalEnvironment->variableAt(entry.scopeOffset()).slot()));
            return true;
        }

        return false;
    }

    if (scope->isGlobalObject()) {
        JSGlobalObject* globalObject = jsCast<JSGlobalObject*>(scope);
        SymbolTableEntry entry = globalObject->symbolTable()->get(ident.impl());
        if (!entry.isNull()) {
            if (getOrPut == Put && entry.isReadOnly()) {
                // We know the property will be at global scope, but we don't know how to cache it.
                op = ResolveOp(Dynamic, 0, 0, 0, 0, 0);
                return true;
            }

            op = ResolveOp(
                makeType(GlobalVar, needsVarInjectionChecks), depth, 0, 0, entry.watchpointSet(),
                reinterpret_cast<uintptr_t>(globalObject->variableAt(entry.scopeOffset()).slot()));
            return true;
        }

        PropertySlot slot(globalObject, PropertySlot::InternalMethodType::VMInquiry);
        bool hasOwnProperty = globalObject->getOwnPropertySlot(globalObject, exec, ident, slot);
        if (!hasOwnProperty) {
            op = ResolveOp(makeType(UnresolvedProperty, needsVarInjectionChecks), 0, 0, 0, 0, 0);
            return true;
        }

        if (!slot.isCacheableValue()
            || !globalObject->structure()->propertyAccessesAreCacheable()
            || (globalObject->structure()->hasReadOnlyOrGetterSetterPropertiesExcludingProto() && getOrPut == Put)) {
            // We know the property will be at global scope, but we don't know how to cache it.
            ASSERT(!scope->next());
            op = ResolveOp(makeType(GlobalProperty, needsVarInjectionChecks), 0, 0, 0, 0, 0);
            return true;
//.........这里部分代码省略.........