/* * Copyright (C) 2012-2019 Apple Inc. All Rights Reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #pragma once #include "UnlinkedGlobalCodeBlock.h" namespace JSC { class Decoder; class CachedModuleCodeBlock; class UnlinkedModuleProgramCodeBlock final : public UnlinkedGlobalCodeBlock { public: typedef UnlinkedGlobalCodeBlock Base; static constexpr unsigned StructureFlags = Base::StructureFlags | StructureIsImmortal; template<typename CellType, SubspaceAccess mode> static IsoSubspace* subspaceFor(VM& vm) { return vm.unlinkedModuleProgramCodeBlockSpace<mode>(); } static UnlinkedModuleProgramCodeBlock* create(VM& vm, const ExecutableInfo& info, OptionSet<CodeGenerationMode> codeGenerationMode) { UnlinkedModuleProgramCodeBlock* instance = new (NotNull, allocateCell<UnlinkedModuleProgramCodeBlock>(vm.heap)) UnlinkedModuleProgramCodeBlock(vm, vm.unlinkedModuleProgramCodeBlockStructure.get(), info, codeGenerationMode); instance->finishCreation(vm); return instance; } static void destroy(JSCell*); // This offset represents the constant register offset to the stored symbol table that represents the layout of the // module environment. This symbol table is created by the byte code generator since the module environment includes // the top-most lexical captured variables inside the module code. This means that, once the module environment is // allocated and instantiated from this symbol table, it is titely coupled with the specific unlinked module program // code block and the stored symbol table. So before executing the module code, we should not clear the unlinked module // program code block in the module executable. This requirement is met because the garbage collector only clears // unlinked code in (1) unmarked executables and (2) function executables. // // Since the function code may be executed repeatedly and the environment of each function execution is different, // the function code need to allocate and instantiate the environment in the prologue of the function code. On the // other hand, the module code is executed only once. So we can instantiate the module environment outside the module // code. At that time, we construct the module environment by using the symbol table that is held by the module executable. // The symbol table held by the executable is the cloned one from one in the unlinked code block. Instantiating the module // environment before executing and linking the module code is required to link the imported bindings between the modules. // // The unlinked module program code block only holds the pre-cloned symbol table in its constant register pool. It does // not hold the instantiated module environment. So while the module environment requires the specific unlinked module // program code block, the unlinked module code block can be used for the module environment instantiated from this // unlinked code block. There is 1:N relation between the unlinked module code block and the module environments. So the // unlinked module program code block can be cached. // // On the other hand, the linked code block for the module environment includes the resolved references to the imported // bindings. The imported binding references the other module environment, so the linked code block is titly coupled // with the specific set of the module environments. Thus, the linked code block should not be cached. int moduleEnvironmentSymbolTableConstantRegisterOffset() { return m_moduleEnvironmentSymbolTableConstantRegisterOffset; } void setModuleEnvironmentSymbolTableConstantRegisterOffset(int offset) { m_moduleEnvironmentSymbolTableConstantRegisterOffset = offset; } private: friend CachedModuleCodeBlock; UnlinkedModuleProgramCodeBlock(VM& vm, Structure* structure, const ExecutableInfo& info, OptionSet<CodeGenerationMode> codeGenerationMode) : Base(vm, structure, ModuleCode, info, codeGenerationMode) { } UnlinkedModuleProgramCodeBlock(Decoder&, const CachedModuleCodeBlock&); int m_moduleEnvironmentSymbolTableConstantRegisterOffset { 0 }; public: static Structure* createStructure(VM& vm, JSGlobalObject* globalObject, JSValue proto) { return Structure::create(vm, globalObject, proto, TypeInfo(UnlinkedModuleProgramCodeBlockType, StructureFlags), info()); } DECLARE_INFO; }; }