[wasm] Merge function table and signature table

Both tables are always updated together and are always accessed
together. Thus merge them, reducing code complexity, but also code
space and overhead for accessing them during runtime. Instead of two
weak global handles, we only need one, which also means one less load
for each indirect call.
Merging them also improves cache locality, since signature and code
address are not stored next to each other in memory, so they will very
likely end up in the same cache line.

R=titzer@chromium.org

Change-Id: I862df7de93a98aa602a3895796610c2c520d6f21
Reviewed-on: https://chromium-review.googlesource.com/866868
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50623}

src/compiler/wasm-compiler.cc

@@ -88,9 +88,7 @@ WasmGraphBuilder::WasmGraphBuilder(
       jsgraph_(jsgraph),
       centry_stub_node_(jsgraph_->HeapConstant(centry_stub)),
       env_(env),
-      signature_tables_(zone),
       function_tables_(zone),
-      function_table_sizes_(zone),
       cur_buffer_(def_buffer_),
       cur_bufsize_(kDefaultBufferSize),
       has_simd_(ContainsSimd(sig)),
@@ -2425,45 +2423,39 @@ Node* WasmGraphBuilder::CallIndirect(uint32_t sig_index, Node** args,
   Node* key = args[0];
 
   // Bounds check against the table size.
-  Node* size = function_table_sizes_[table_index];
+  Node* size = function_tables_[table_index].size;
   Node* in_bounds = graph()->NewNode(machine->Uint32LessThan(), key, size);
   TrapIfFalse(wasm::kTrapFuncInvalid, in_bounds, position);
-  Node* table_address = function_tables_[table_index];
+  Node* table_address = function_tables_[table_index].table_addr;
   Node* table = graph()->NewNode(
       jsgraph()->machine()->Load(MachineType::AnyTagged()), table_address,
       jsgraph()->IntPtrConstant(0), *effect_, *control_);
-  Node* signatures_address = signature_tables_[table_index];
-  Node* signatures = graph()->NewNode(
-      jsgraph()->machine()->Load(MachineType::AnyTagged()), signatures_address,
-      jsgraph()->IntPtrConstant(0), *effect_, *control_);
   // Load signature from the table and check.
   // The table is a FixedArray; signatures are encoded as SMIs.
-  // [sig1, sig2, sig3, ...., code1, code2, code3 ...]
+  // [sig1, code1, sig2, code2, sig3, code3, ...]
+  static_assert(compiler::kFunctionTableEntrySize == 2, "consistency");
+  static_assert(compiler::kFunctionTableSignatureOffset == 0, "consistency");
+  static_assert(compiler::kFunctionTableCodeOffset == 1, "consistency");
   ElementAccess access = AccessBuilder::ForFixedArrayElement();
   const int fixed_offset = access.header_size - access.tag();
-  {
-    Node* load_sig = graph()->NewNode(
-        machine->Load(MachineType::AnyTagged()), signatures,
-        graph()->NewNode(machine->Int32Add(),
-                         graph()->NewNode(machine->Word32Shl(), key,
-                                          Int32Constant(kPointerSizeLog2)),
+  Node* key_offset = graph()->NewNode(machine->Word32Shl(), key,
+                                      Int32Constant(kPointerSizeLog2 + 1));
+  Node* load_sig =
+      graph()->NewNode(machine->Load(MachineType::AnyTagged()), table,
+                       graph()->NewNode(machine->Int32Add(), key_offset,
                                         Int32Constant(fixed_offset)),
                        *effect_, *control_);
   int32_t canonical_sig_num = env_->module->signature_ids[sig_index];
   CHECK_GE(sig_index, 0);
-    Node* sig_match =
-        graph()->NewNode(machine->WordEqual(), load_sig,
+  Node* sig_match = graph()->NewNode(machine->WordEqual(), load_sig,
                                      jsgraph()->SmiConstant(canonical_sig_num));
   TrapIfFalse(wasm::kTrapFuncSigMismatch, sig_match, position);
-  }
 
   // Load code object from the table. It is held by a Foreign.
   Node* entry = graph()->NewNode(
       machine->Load(MachineType::AnyTagged()), table,
-      graph()->NewNode(machine->Int32Add(),
-                       graph()->NewNode(machine->Word32Shl(), key,
-                                        Int32Constant(kPointerSizeLog2)),
-                       Uint32Constant(fixed_offset)),
+      graph()->NewNode(machine->Int32Add(), key_offset,
+                       Uint32Constant(fixed_offset + kPointerSize)),
       *effect_, *control_);
   if (FLAG_wasm_jit_to_native) {
     Node* address = graph()->NewNode(
@@ -3426,18 +3418,14 @@ void WasmGraphBuilder::EnsureFunctionTableNodes() {
   for (size_t i = 0; i < tables_size; ++i) {
     wasm::GlobalHandleAddress function_handle_address =
         env_->function_tables[i];
-    wasm::GlobalHandleAddress signature_handle_address =
-        env_->signature_tables[i];
-    function_tables_.push_back(jsgraph()->RelocatableIntPtrConstant(
+    Node* table_addr = jsgraph()->RelocatableIntPtrConstant(
         reinterpret_cast<intptr_t>(function_handle_address),
-        RelocInfo::WASM_GLOBAL_HANDLE));
-    signature_tables_.push_back(jsgraph()->RelocatableIntPtrConstant(
-        reinterpret_cast<intptr_t>(signature_handle_address),
-        RelocInfo::WASM_GLOBAL_HANDLE));
+        RelocInfo::WASM_GLOBAL_HANDLE);
     uint32_t table_size = env_->module->function_tables[i].initial_size;
-    function_table_sizes_.push_back(jsgraph()->RelocatableInt32Constant(
+    Node* size = jsgraph()->RelocatableInt32Constant(
         static_cast<uint32_t>(table_size),
-        RelocInfo::WASM_FUNCTION_TABLE_SIZE_REFERENCE));
+        RelocInfo::WASM_FUNCTION_TABLE_SIZE_REFERENCE);
+    function_tables_.push_back({table_addr, size});
   }
 }
 
@@ -4451,14 +4439,11 @@ Handle<Code> CompileJSToWasmWrapper(Isolate* isolate, wasm::WasmModule* module,
   Node* effect = nullptr;
 
   // TODO(titzer): compile JS to WASM wrappers without a {ModuleEnv}.
-  ModuleEnv env = {module,
-                   std::vector<Address>(),  // function_tables
-                   std::vector<Address>(),  // signature_tables
-                   // TODO(mtrofin): remove these 2 lines when we don't need
+  ModuleEnv env(module,
+                // TODO(mtrofin): remove the Illegal builtin when we don't need
                 // FLAG_wasm_jit_to_native
-                   std::vector<Handle<Code>>(),     // function_code
                 BUILTIN_CODE(isolate, Illegal),  // default_function_code
-                   use_trap_handler};
+                use_trap_handler);
 
   WasmGraphBuilder builder(&env, &zone, &jsgraph,
                            CEntryStub(isolate, 1).GetCode(), func->sig);
@@ -4571,12 +4556,7 @@ Handle<Code> CompileWasmToJSWrapper(
       origin == wasm::kAsmJsOrigin ? new (&zone) SourcePositionTable(&graph)
                                    : nullptr;
 
-  ModuleEnv env = {nullptr,
-                   std::vector<Address>(),
-                   std::vector<Address>(),
-                   std::vector<Handle<Code>>(),
-                   Handle<Code>(),
-                   use_trap_handler};
+  ModuleEnv env(nullptr, Handle<Code>::null(), use_trap_handler);
   WasmGraphBuilder builder(&env, &zone, &jsgraph,
                            CEntryStub(isolate, 1).GetCode(), sig,
                            source_position_table);
@@ -4663,13 +4643,9 @@ Handle<Code> CompileWasmToWasmWrapper(Isolate* isolate, WasmCodeWrapper target,
   Node* control = nullptr;
   Node* effect = nullptr;
 
-  ModuleEnv env = {
-      nullptr,
-      std::vector<Address>(),
-      std::vector<Address>(),
-      std::vector<Handle<Code>>(),
-      Handle<Code>(),
-      !target.IsCodeObject() && target.GetWasmCode()->HasTrapHandlerIndex()};
+  ModuleEnv env(
+      nullptr, Handle<Code>::null(),
+      !target.IsCodeObject() && target.GetWasmCode()->HasTrapHandlerIndex());
   WasmGraphBuilder builder(&env, &zone, &jsgraph, Handle<Code>(), sig);
   builder.set_control_ptr(&control);
   builder.set_effect_ptr(&effect);
@@ -4856,13 +4832,6 @@ Handle<Code> CompileCWasmEntry(Isolate* isolate, wasm::FunctionSig* sig,
 
 SourcePositionTable* WasmCompilationUnit::BuildGraphForWasmFunction(
     double* decode_ms) {
-#if DEBUG
-  if (env_) {
-    size_t tables_size = env_->module->function_tables.size();
-    DCHECK_EQ(tables_size, env_->function_tables.size());
-    DCHECK_EQ(tables_size, env_->signature_tables.size());
-  }
-#endif
 
   base::ElapsedTimer decode_timer;
   if (FLAG_trace_wasm_decode_time) {

src/compiler/wasm-compiler.h

@@ -43,25 +43,34 @@ class WasmCode;
 
 namespace compiler {
 
+// Indirect function tables contain a <smi(sig), code> pair for each entry.
+enum FunctionTableEntries : int {
+  kFunctionTableSignatureOffset = 0,
+  kFunctionTableCodeOffset = 1,
+  kFunctionTableEntrySize = 2
+};
+constexpr inline int FunctionTableSigOffset(int i) {
+  return kFunctionTableEntrySize * i + kFunctionTableSignatureOffset;
+}
+constexpr inline int FunctionTableCodeOffset(int i) {
+  return kFunctionTableEntrySize * i + kFunctionTableCodeOffset;
+}
+
 // The {ModuleEnv} encapsulates the module data that is used by the
 // {WasmGraphBuilder} during graph building. It represents the parameters to
 // which the  compiled code should be specialized, including which code to call
 // for direct calls {function_code}, which tables to use for indirect calls
 // {function_tables}, memory start address and size {mem_start, mem_size},
-// as well as signature maps {signature_maps} and the module itself {module}.
+// as well as the module itself {module}.
 // ModuleEnvs are shareable across multiple compilations.
 struct ModuleEnv {
   // A pointer to the decoded module's static representation.
   const wasm::WasmModule* module;
-  // The function tables are FixedArrays of code used to dispatch indirect
-  // calls. (the same length as module.function_tables). We use the address
-  // to a global handle to the FixedArray.
+  // The function tables are FixedArrays of <smi, code> pairs used to signature
+  // check and dispatch indirect calls. It has the same length as
+  // module.function_tables. We use the address to a global handle to the
+  // FixedArray.
   const std::vector<Address> function_tables;
-  // The signatures tables are FixedArrays of SMIs used to check signatures
-  // match at runtime.
-  // (the same length as module.function_tables)
-  //  We use the address to a global handle to the FixedArray.
-  const std::vector<Address> signature_tables;
 
   // TODO(mtrofin): remove these 2 once we don't need FLAG_wasm_jit_to_native
   // Contains the code objects to call for each direct call.
@@ -72,6 +81,22 @@ struct ModuleEnv {
   // True if trap handling should be used in compiled code, rather than
   // compiling in bounds checks for each memory access.
   const bool use_trap_handler;
+
+  ModuleEnv(const wasm::WasmModule* module, Handle<Code> default_function_code,
+            bool use_trap_handler)
+      : module(module),
+        default_function_code(default_function_code),
+        use_trap_handler(use_trap_handler) {}
+
+  ModuleEnv(const wasm::WasmModule* module,
+            std::vector<Address> function_tables,
+            std::vector<Handle<Code>> function_code,
+            Handle<Code> default_function_code, bool use_trap_handler)
+      : module(module),
+        function_tables(std::move(function_tables)),
+        function_code(std::move(function_code)),
+        default_function_code(default_function_code),
+        use_trap_handler(use_trap_handler) {}
 };
 
 enum RuntimeExceptionSupport : bool {
@@ -432,9 +457,11 @@ class WasmGraphBuilder {
   // wrappers or interpreter stubs.
   ModuleEnv* const env_ = nullptr;
   SetOncePointer<Node> wasm_context_;
-  NodeVector signature_tables_;
-  NodeVector function_tables_;
-  NodeVector function_table_sizes_;
+  struct FunctionTableNodes {
+    Node* table_addr;
+    Node* size;
+  };
+  ZoneVector<FunctionTableNodes> function_tables_;
   Node** control_ = nullptr;
   Node** effect_ = nullptr;
   WasmContextCacheNodes* context_cache_ = nullptr;

src/wasm/wasm-code-manager.h

@@ -248,16 +248,10 @@ class V8_EXPORT_PRIVATE NativeModule final {
   std::vector<wasm::GlobalHandleAddress>& function_tables() {
     return specialization_data_.function_tables;
   }
-  std::vector<wasm::GlobalHandleAddress>& signature_tables() {
-    return specialization_data_.signature_tables;
-  }
 
   std::vector<wasm::GlobalHandleAddress>& empty_function_tables() {
     return specialization_data_.empty_function_tables;
   }
-  std::vector<wasm::GlobalHandleAddress>& empty_signature_tables() {
-    return specialization_data_.empty_signature_tables;
-  }
 
   uint32_t num_imported_functions() const { return num_imported_functions_; }
   size_t num_function_tables() const {
@@ -337,9 +331,7 @@ class V8_EXPORT_PRIVATE NativeModule final {
   // elements a 1 line copy.
   struct {
     std::vector<wasm::GlobalHandleAddress> function_tables;
-    std::vector<wasm::GlobalHandleAddress> signature_tables;
     std::vector<wasm::GlobalHandleAddress> empty_function_tables;
-    std::vector<wasm::GlobalHandleAddress> empty_signature_tables;
   } specialization_data_;
 };
 

src/wasm/wasm-interpreter.cc

@@ -2558,63 +2558,57 @@ class ThreadImpl {
 
       if (!FLAG_wasm_jit_to_native) {
         // Check signature.
-        FixedArray* sig_tables = compiled_module->signature_tables();
-        if (table_index >= static_cast<uint32_t>(sig_tables->length())) {
+        FixedArray* fun_tables = compiled_module->function_tables();
+        if (table_index >= static_cast<uint32_t>(fun_tables->length())) {
           return {ExternalCallResult::INVALID_FUNC};
         }
-        // Reconstitute the global handle to sig_table, and, further below,
-        // to the function table, from the address stored in the
-        // respective table of tables.
+        // Reconstitute the global handle to the function table, from the
+        // address stored in the respective table of tables.
         int table_index_as_int = static_cast<int>(table_index);
-        Handle<FixedArray> sig_table(reinterpret_cast<FixedArray**>(
-            WasmCompiledModule::GetTableValue(sig_tables, table_index_as_int)));
-        if (entry_index >= static_cast<uint32_t>(sig_table->length())) {
+        FixedArray* fun_table = *reinterpret_cast<FixedArray**>(
+            WasmCompiledModule::GetTableValue(fun_tables, table_index_as_int));
+        // Function tables store <smi, code> pairs.
+        int num_funcs_in_table =
+            fun_table->length() / compiler::kFunctionTableEntrySize;
+        if (entry_index >= static_cast<uint32_t>(num_funcs_in_table)) {
           return {ExternalCallResult::INVALID_FUNC};
         }
-        int found_sig =
-            Smi::ToInt(sig_table->get(static_cast<int>(entry_index)));
+        int found_sig = Smi::ToInt(fun_table->get(
+            compiler::FunctionTableSigOffset(static_cast<int>(entry_index))));
         if (static_cast<uint32_t>(found_sig) != canonical_sig_index) {
           return {ExternalCallResult::SIGNATURE_MISMATCH};
         }
 
         // Get code object.
-        FixedArray* fun_tables = compiled_module->function_tables();
-        DCHECK_EQ(sig_tables->length(), fun_tables->length());
-        Handle<FixedArray> fun_table(reinterpret_cast<FixedArray**>(
-            WasmCompiledModule::GetTableValue(fun_tables, table_index_as_int)));
-        DCHECK_EQ(sig_table->length(), fun_table->length());
-        target_gc = Code::cast(fun_table->get(static_cast<int>(entry_index)));
+        target_gc = Code::cast(fun_table->get(
+            compiler::FunctionTableCodeOffset(static_cast<int>(entry_index))));
       } else {
         // Check signature.
-        std::vector<GlobalHandleAddress>& sig_tables =
-            compiled_module->GetNativeModule()->signature_tables();
-        if (table_index >= sig_tables.size()) {
+        std::vector<GlobalHandleAddress>& fun_tables =
+            compiled_module->GetNativeModule()->function_tables();
+        if (table_index >= fun_tables.size()) {
           return {ExternalCallResult::INVALID_FUNC};
         }
-        // Reconstitute the global handle to sig_table, and, further below,
-        // to the function table, from the address stored in the
-        // respective table of tables.
-        int table_index_as_int = static_cast<int>(table_index);
-        Handle<FixedArray> sig_table(
-            reinterpret_cast<FixedArray**>(sig_tables[table_index_as_int]));
-        if (entry_index >= static_cast<uint32_t>(sig_table->length())) {
+        // Reconstitute the global handle to the function table, from the
+        // address stored in the respective table of tables.
+        FixedArray* fun_table =
+            *reinterpret_cast<FixedArray**>(fun_tables[table_index]);
+        // Function tables store <smi, code> pairs.
+        int num_funcs_in_table =
+            fun_table->length() / compiler::kFunctionTableEntrySize;
+        if (entry_index >= static_cast<uint32_t>(num_funcs_in_table)) {
           return {ExternalCallResult::INVALID_FUNC};
         }
-        int found_sig =
-            Smi::ToInt(sig_table->get(static_cast<int>(entry_index)));
+        int found_sig = Smi::ToInt(fun_table->get(
+            compiler::FunctionTableSigOffset(static_cast<int>(entry_index))));
         if (static_cast<uint32_t>(found_sig) != canonical_sig_index) {
           return {ExternalCallResult::SIGNATURE_MISMATCH};
         }
 
         // Get code object.
-        std::vector<GlobalHandleAddress>& fun_tables =
-            compiled_module->GetNativeModule()->function_tables();
-        DCHECK_EQ(sig_tables.size(), fun_tables.size());
-        Handle<FixedArray> fun_table(
-            reinterpret_cast<FixedArray**>(fun_tables[table_index_as_int]));
-        DCHECK_EQ(sig_table->length(), fun_table->length());
         Address first_instr =
-            Foreign::cast(fun_table->get(static_cast<int>(entry_index)))
+            Foreign::cast(fun_table->get(compiler::FunctionTableCodeOffset(
+                              static_cast<int>(entry_index))))
                 ->foreign_address();
         target =
             isolate->wasm_engine()->code_manager()->GetCodeFromStartAddress(

src/wasm/wasm-objects-inl.h

@@ -56,8 +56,6 @@ OPTIONAL_ACCESSORS(WasmInstanceObject, table_object, WasmTableObject,
                    kTableObjectOffset)
 OPTIONAL_ACCESSORS(WasmInstanceObject, function_tables, FixedArray,
                    kFunctionTablesOffset)
-OPTIONAL_ACCESSORS(WasmInstanceObject, signature_tables, FixedArray,
-                   kSignatureTablesOffset)
 ACCESSORS(WasmInstanceObject, directly_called_instances, FixedArray,
           kDirectlyCalledInstancesOffset)
 ACCESSORS(WasmInstanceObject, js_imports_table, FixedArray,

src/wasm/wasm-objects.h

@@ -132,14 +132,12 @@ class WasmTableObject : public JSObject {
   static void AddDispatchTable(Isolate* isolate, Handle<WasmTableObject> table,
                                Handle<WasmInstanceObject> instance,
                                int table_index,
-                               Handle<FixedArray> function_table,
-                               Handle<FixedArray> signature_table);
+                               Handle<FixedArray> function_table);
 
   static void Set(Isolate* isolate, Handle<WasmTableObject> table,
                   int32_t index, Handle<JSFunction> function);
 
-  static void UpdateDispatchTables(Isolate* isolate,
-                                   Handle<WasmTableObject> table, int index,
+  static void UpdateDispatchTables(Handle<WasmTableObject> table, int index,
                                    wasm::FunctionSig* sig,
                                    Handle<Object> code_or_foreign);
 };
@@ -196,7 +194,6 @@ class WasmInstanceObject : public JSObject {
   DECL_OPTIONAL_ACCESSORS(debug_info, WasmDebugInfo)
   DECL_OPTIONAL_ACCESSORS(table_object, WasmTableObject)
   DECL_OPTIONAL_ACCESSORS(function_tables, FixedArray)
-  DECL_OPTIONAL_ACCESSORS(signature_tables, FixedArray)
 
   // FixedArray of all instances whose code was imported
   DECL_OPTIONAL_ACCESSORS(directly_called_instances, FixedArray)
@@ -211,7 +208,6 @@ class WasmInstanceObject : public JSObject {
     kDebugInfoIndex,
     kTableObjectIndex,
     kFunctionTablesIndex,
-    kSignatureTablesIndex,
     kDirectlyCalledInstancesIndex,
     kJsImportsTableIndex,
     kFieldCount
@@ -226,7 +222,6 @@ class WasmInstanceObject : public JSObject {
   DEF_OFFSET(DebugInfo)
   DEF_OFFSET(TableObject)
   DEF_OFFSET(FunctionTables)
-  DEF_OFFSET(SignatureTables)
   DEF_OFFSET(DirectlyCalledInstances)
   DEF_OFFSET(JsImportsTable)
 
@@ -519,7 +514,6 @@ class WasmCompiledModule : public FixedArray {
       Isolate* isolate, wasm::WasmModule* module, Handle<FixedArray> code_table,
       Handle<FixedArray> export_wrappers,
       const std::vector<wasm::GlobalHandleAddress>& function_tables,
-      const std::vector<wasm::GlobalHandleAddress>& signature_tables,
       bool use_trap_hander);
 
   static Handle<WasmCompiledModule> Clone(Isolate* isolate,

src/wasm/wasm-serialization.cc

@@ -213,8 +213,8 @@ size_t NativeModuleSerializer::MeasureHeader() const {
          sizeof(
              uint32_t) +  // imported fcts - i.e. index of first wasm function
          sizeof(uint32_t) +  // table count
-         native_module_->specialization_data_.function_tables.size() *
-             2  // 2 same-sized tables, containing pointers
+         native_module_->specialization_data_.function_tables.size()
+             // function table, containing pointers
              * sizeof(GlobalHandleAddress);
 }
 
@@ -231,7 +231,6 @@ void NativeModuleSerializer::BufferHeader() {
               e = native_module_->specialization_data_.function_tables.size();
        i < e; ++i) {
     writer.Write(native_module_->specialization_data_.function_tables[i]);
-    writer.Write(native_module_->specialization_data_.signature_tables[i]);
   }
 }
 
@@ -558,18 +557,14 @@ bool NativeModuleDeserializer::ReadHeader() {
   if (!ok) return false;
   size_t table_count = reader.Read<uint32_t>();
 
-  std::vector<GlobalHandleAddress> sigs(table_count);
   std::vector<GlobalHandleAddress> funcs(table_count);
   for (size_t i = 0; i < table_count; ++i) {
     funcs[i] = reader.Read<GlobalHandleAddress>();
-    sigs[i] = reader.Read<GlobalHandleAddress>();
   }
-  native_module_->signature_tables() = sigs;
   native_module_->function_tables() = funcs;
   // resize, so that from here on the native module can be
   // asked about num_function_tables().
   native_module_->empty_function_tables().resize(table_count);
-  native_module_->empty_signature_tables().resize(table_count);
 
   unread_ = unread_ + (start_size - reader.current_buffer().size());
   return true;
@@ -739,9 +734,8 @@ MaybeHandle<WasmCompiledModule> DeserializeNativeModule(
       static_cast<int>(export_wrappers_size), TENURED);
 
   Handle<WasmCompiledModule> compiled_module = WasmCompiledModule::New(
-      isolate, shared->module(), isolate->factory()->NewFixedArray(0, TENURED),
+      isolate, shared->module(), isolate->factory()->empty_fixed_array(),
       export_wrappers, std::vector<wasm::GlobalHandleAddress>(),
-      std::vector<wasm::GlobalHandleAddress>(),
       trap_handler::IsTrapHandlerEnabled());
   compiled_module->OnWasmModuleDecodingComplete(shared);
   NativeModuleDeserializer deserializer(isolate,

test/cctest/wasm/wasm-run-utils.cc

@@ -144,8 +144,8 @@ Handle<JSFunction> TestingModuleBuilder::WrapCode(uint32_t index) {
   return ret;
 }
 
-void TestingModuleBuilder::AddIndirectFunctionTable(uint16_t* function_indexes,
-                                                    uint32_t table_size) {
+void TestingModuleBuilder::AddIndirectFunctionTable(
+    const uint16_t* function_indexes, uint32_t table_size) {
   test_module_.function_tables.emplace_back();
   WasmIndirectFunctionTable& table = test_module_.function_tables.back();
   table.initial_size = table_size;
@@ -155,14 +155,10 @@ void TestingModuleBuilder::AddIndirectFunctionTable(uint16_t* function_indexes,
     table.values.push_back(function_indexes[i]);
   }
 
+  FixedArray* func_table = *isolate_->factory()->NewFixedArray(
+      table_size * compiler::kFunctionTableEntrySize);
   function_tables_.push_back(
-      isolate_->global_handles()
-          ->Create(*isolate_->factory()->NewFixedArray(table_size))
-          .address());
-  signature_tables_.push_back(
-      isolate_->global_handles()
-          ->Create(*isolate_->factory()->NewFixedArray(table_size))
-          .address());
+      isolate_->global_handles()->Create(func_table).address());
 }
 
 void TestingModuleBuilder::PopulateIndirectFunctionTable() {
@@ -172,22 +168,23 @@ void TestingModuleBuilder::PopulateIndirectFunctionTable() {
     WasmIndirectFunctionTable& table = test_module_.function_tables[i];
     Handle<FixedArray> function_table(
         reinterpret_cast<FixedArray**>(function_tables_[i]));
-    Handle<FixedArray> signature_table(
-        reinterpret_cast<FixedArray**>(signature_tables_[i]));
     int table_size = static_cast<int>(table.values.size());
     for (int j = 0; j < table_size; j++) {
       WasmFunction& function = test_module_.functions[table.values[j]];
-      signature_table->set(
-          j, Smi::FromInt(test_module_.signature_map.Find(function.sig)));
+      function_table->set(
+          compiler::FunctionTableSigOffset(j),
+          Smi::FromInt(test_module_.signature_map.Find(function.sig)));
       if (FLAG_wasm_jit_to_native) {
         Handle<Foreign> foreign_holder = isolate_->factory()->NewForeign(
             native_module_->GetCode(function.func_index)
                 ->instructions()
                 .start(),
             TENURED);
-        function_table->set(j, *foreign_holder);
+        function_table->set(compiler::FunctionTableCodeOffset(j),
+                            *foreign_holder);
       } else {
-        function_table->set(j, *function_code_[function.func_index]);
+        function_table->set(compiler::FunctionTableCodeOffset(j),
+                            *function_code_[function.func_index]);
       }
     }
   }
@@ -211,9 +208,8 @@ uint32_t TestingModuleBuilder::AddBytes(Vector<const byte> bytes) {
 }
 
 compiler::ModuleEnv TestingModuleBuilder::CreateModuleEnv() {
-  return {&test_module_,        function_tables_,
-          signature_tables_,    function_code_,
-          Handle<Code>::null(), trap_handler::IsTrapHandlerEnabled()};
+  return {&test_module_, function_tables_, function_code_, Handle<Code>::null(),
+          trap_handler::IsTrapHandlerEnabled()};
 }
 
 const WasmGlobal* TestingModuleBuilder::AddGlobal(ValueType type) {
@@ -244,7 +240,7 @@ Handle<WasmInstanceObject> TestingModuleBuilder::InitInstanceObject() {
   Handle<FixedArray> export_wrappers = isolate_->factory()->NewFixedArray(0);
   Handle<WasmCompiledModule> compiled_module = WasmCompiledModule::New(
       isolate_, test_module_ptr_, code_table, export_wrappers, function_tables_,
-      signature_tables_, trap_handler::IsTrapHandlerEnabled());
+      trap_handler::IsTrapHandlerEnabled());
   compiled_module->OnWasmModuleDecodingComplete(shared_module_data);
   // This method is called when we initialize TestEnvironment. We don't
   // have a memory yet, so we won't create it here. We'll update the

test/cctest/wasm/wasm-run-utils.h

@@ -191,7 +191,7 @@ class TestingModuleBuilder {
     function_code_[index] = code;
   }
 
-  void AddIndirectFunctionTable(uint16_t* function_indexes,
+  void AddIndirectFunctionTable(const uint16_t* function_indexes,
                                 uint32_t table_size);
 
   void PopulateIndirectFunctionTable();
@@ -244,7 +244,6 @@ class TestingModuleBuilder {
   uint32_t mem_size_;
   std::vector<Handle<Code>> function_code_;
   std::vector<GlobalHandleAddress> function_tables_;
-  std::vector<GlobalHandleAddress> signature_tables_;
   V8_ALIGNED(16) byte globals_data_[kMaxGlobalsSize];
   WasmInterpreter* interpreter_;
   WasmExecutionMode execution_mode_;