C++ JSGlobalObject::getOwnPropertySlot方法代码示例

//.........这里部分代码省略.........
                ASSERT(!entry.isNull());
                op = ResolveOp(makeType(ModuleVar, needsVarInjectionChecks), depth, 0, importedEnvironment, entry.watchpointSet(), entry.scopeOffset().offset(), resolution.localName.impl());
                return true;
            }
        }

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

    if (scope->isGlobalLexicalEnvironment()) {
        JSGlobalLexicalEnvironment* globalLexicalEnvironment = jsCast<JSGlobalLexicalEnvironment*>(scope);
        SymbolTable* symbolTable = globalLexicalEnvironment->symbolTable();
        ConcurrentJSLocker locker(symbolTable->m_lock);
        auto iter = symbolTable->find(locker, ident.impl());
        if (iter != symbolTable->end(locker)) {
            SymbolTableEntry& entry = iter->value;
            ASSERT(!entry.isNull());
            if (getOrPut == Put && entry.isReadOnly() && !isInitialization(initializationMode)) {
                // 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 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 == InitializationMode::ConstInitialization ? 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);
        {
            SymbolTable* symbolTable = globalObject->symbolTable();
            ConcurrentJSLocker locker(symbolTable->m_lock);
            auto iter = symbolTable->find(locker, ident.impl());
            if (iter != symbolTable->end(locker)) {
                SymbolTableEntry& entry = iter->value;
                ASSERT(!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;
        }

        
        WatchpointState state = globalObject->structure()->ensurePropertyReplacementWatchpointSet(exec->vm(), slot.cachedOffset())->state();
        if (state == IsWatched && getOrPut == Put) {
            // The field exists, but because the replacement watchpoint is still intact. This is
            // kind of dangerous. We have two options:
            // 1) Invalidate the watchpoint set. That would work, but it's possible that this code
            //    path never executes - in which case this would be unwise.
            // 2) Have the invalidation happen at run-time. All we have to do is leave the code
            //    uncached. The only downside is slightly more work when this does execute.
            // We go with option (2) here because it seems less evil.
            op = ResolveOp(makeType(GlobalProperty, needsVarInjectionChecks), depth, 0, 0, 0, 0);
        } else
            op = ResolveOp(makeType(GlobalProperty, needsVarInjectionChecks), depth, globalObject->structure(), 0, 0, slot.cachedOffset());
        return true;
    }

    op = ResolveOp(Dynamic, 0, 0, 0, 0, 0);
    return true;
}