[wasm] remove faux code objects

src/wasm/wasm-module.cc

Index: src/wasm/wasm-module.cc
diff --git a/src/wasm/wasm-module.cc b/src/wasm/wasm-module.cc
index df63dce97c85dcb3f68cfcd7199419b70ea5a845..a1fa430f2710c96e1e1ccb1495a6601fc4b91ce7 100644
--- a/src/wasm/wasm-module.cc
+++ b/src/wasm/wasm-module.cc
@@ -22,8 +22,6 @@ namespace v8 {
 namespace internal {
 namespace wasm {
 
-static const int kPlaceholderMarker = 1000000000;
-
 static const char* wasmSections[] = {
 #define F(enumerator, order, string) string,
     FOR_EACH_WASM_SECTION_TYPE(F)
@@ -111,98 +109,6 @@ std::ostream& operator<<(std::ostream& os, const WasmFunctionName& pair) {
   return os;
 }
 
-// A helper class for compiling multiple wasm functions that offers
-// placeholder code objects for calling functions that are not yet compiled.
-class WasmLinker {
- public:
-  WasmLinker(Isolate* isolate, std::vector<Handle<Code>>* functions)
-      : isolate_(isolate),
-        placeholder_code_(functions->size()),
-        function_code_(functions) {
-    for (uint32_t i = 0; i < placeholder_code_.size(); ++i) {
-      CreatePlaceholder(i);
-    }
-  }
-
-  Handle<Code> GetPlaceholderCode(uint32_t index) const {
-    return placeholder_code_[index];
-  }
-
-  void Finish(uint32_t index, Handle<Code> code) {
-    DCHECK(index < function_code().size());
-    function_code()[index] = code;
-  }
-
-  void Link(Handle<FixedArray> function_table,
-            const std::vector<uint16_t>& functions) {
-    for (size_t i = 0; i < function_code().size(); i++) {
-      LinkFunction(function_code()[i]);
-    }
-    if (!function_table.is_null()) {
-      int table_size = static_cast<int>(functions.size());
-      DCHECK_EQ(function_table->length(), table_size * 2);
-      for (int i = 0; i < table_size; i++) {
-        function_table->set(i + table_size, *function_code()[functions[i]]);
-      }
-    }
-  }
-
- private:
-  std::vector<Handle<Code>>& function_code() { return *function_code_; }
-
-  void CreatePlaceholder(uint32_t index) {
-    DCHECK(index < function_code().size());
-    DCHECK(function_code()[index].is_null());
-    // Create a placeholder code object and encode the corresponding index in
-    // the {constant_pool_offset} field of the code object.
-    // TODO(titzer): placeholder code objects are somewhat dangerous.
-    byte buffer[] = {0, 0, 0, 0, 0, 0, 0, 0};  // fake instructions.
-    CodeDesc desc = {buffer, 8, 8, 0, 0, nullptr};
-    Handle<Code> code = isolate_->factory()->NewCode(
-        desc, Code::KindField::encode(Code::WASM_FUNCTION),
-        Handle<Object>::null());
-    code->set_constant_pool_offset(static_cast<int>(index) +
-                                   kPlaceholderMarker);
-    placeholder_code_[index] = code;
-    function_code()[index] = code;
-  }
-
-  Isolate* isolate_;
-  std::vector<Handle<Code>> placeholder_code_;
-  std::vector<Handle<Code>>* function_code_;
-
-  void LinkFunction(Handle<Code> code) {
-    bool modified = false;
-    int mode_mask = RelocInfo::kCodeTargetMask;
-    AllowDeferredHandleDereference embedding_raw_address;
-    for (RelocIterator it(*code, mode_mask); !it.done(); it.next()) {
-      RelocInfo::Mode mode = it.rinfo()->rmode();
-      if (RelocInfo::IsCodeTarget(mode)) {
-        Code* target =
-            Code::GetCodeFromTargetAddress(it.rinfo()->target_address());
-        if (target->kind() == Code::WASM_FUNCTION &&
-            target->constant_pool_offset() >= kPlaceholderMarker) {
-          // Patch direct calls to placeholder code objects.
-          uint32_t index = target->constant_pool_offset() - kPlaceholderMarker;
-          CHECK(index < function_code().size());
-          Handle<Code> new_target = function_code()[index];
-          if (target != *new_target) {
-            CHECK_EQ(*placeholder_code_[index], target);
-            it.rinfo()->set_target_address(new_target->instruction_start(),
-                                           SKIP_WRITE_BARRIER,
-                                           SKIP_ICACHE_FLUSH);
-            modified = true;
-          }
-        }
-      }
-    }
-    if (modified) {
-      Assembler::FlushICache(isolate_, code->instruction_start(),
-                             code->instruction_size());
-    }
-  }
-};
-
 namespace {
 // Internal constants for the layout of the module object.
 const int kWasmModuleInternalFieldCount = 5;
@@ -735,11 +641,9 @@ MaybeHandle<JSObject> WasmModule::Instantiate(
       isolate->counters()->wasm_compile_module_time());
 
   instance.function_table = BuildFunctionTable(isolate, this);
-  WasmLinker linker(isolate, &instance.function_code);
   ModuleEnv module_env;
   module_env.module = this;
   module_env.instance = &instance;
-  module_env.linker = &linker;
   module_env.origin = origin;
 
   //-------------------------------------------------------------------------
@@ -778,7 +682,10 @@ MaybeHandle<JSObject> WasmModule::Instantiate(
     }
 
     // Patch all direct call sites.
-    linker.Link(instance.function_table, this->function_table);
+    compiler::Link(isolate, instance.function_code);
+
+    instance.PopulateExportTable(instance.function_code, function_table);
+
     instance.js_object->SetInternalField(kWasmModuleFunctionTable,
                                          Smi::FromInt(0));
 
@@ -865,11 +772,16 @@ MaybeHandle<JSObject> WasmModule::Instantiate(
   return instance.js_object;
 }
 
-Handle<Code> ModuleEnv::GetCodeOrPlaceholder(uint32_t index) const {
-  DCHECK(IsValidFunction(index));
-  if (linker != nullptr) return linker->GetPlaceholderCode(index);
-  DCHECK_NOT_NULL(instance);
-  return instance->function_code[index];
+void WasmModuleInstance::PopulateExportTable(
+    const std::vector<Handle<Code>>& compiled_functions,
+    const std::vector<uint16_t>& functions) {
+  if (!function_table.is_null()) {
+    int table_size = static_cast<int>(functions.size());
+    DCHECK_EQ(function_table->length(), table_size * 2);
+    for (int i = 0; i < table_size; i++) {
+      function_table->set(i + table_size, *(compiled_functions[functions[i]]));
+    }
+  }
 }
 
 Handle<Code> ModuleEnv::GetImportCode(uint32_t index) {
@@ -931,11 +843,9 @@ int32_t CompileAndRunWasmModule(Isolate* isolate, const WasmModule* module) {
   instance.function_table = BuildFunctionTable(isolate, module);
 
   // Create module environment.
-  WasmLinker linker(isolate, &instance.function_code);
   ModuleEnv module_env;
   module_env.module = module;
   module_env.instance = &instance;
-  module_env.linker = &linker;
   module_env.origin = module->origin;
 
   if (module->export_table.size() == 0) {
@@ -948,11 +858,13 @@ int32_t CompileAndRunWasmModule(Isolate* isolate, const WasmModule* module) {
     // Compile the function and install it in the linker.
     Handle<Code> code = compiler::WasmCompilationUnit::CompileWasmFunction(
         &thrower, isolate, &module_env, &func);
-    if (!code.is_null()) linker.Finish(func.func_index, code);
+    if (!code.is_null()) instance.function_code[func.func_index] = code;
     if (thrower.error()) return -1;
   }
 
-  linker.Link(instance.function_table, instance.module->function_table);
+  compiler::Link(isolate, instance.function_code);
+  instance.PopulateExportTable(instance.function_code,
+                               instance.module->function_table);
 
   // Wrap the main code so it can be called as a JS function.
   uint32_t main_index = module->export_table.back().func_index;