[wasm] Avoid double-serializing the wire bytes

src/snapshot/code-serializer.cc

Index: src/snapshot/code-serializer.cc
diff --git a/src/snapshot/code-serializer.cc b/src/snapshot/code-serializer.cc
index 74ccf5f26064b04617df74f59577126dcdc2b3fe..10ea5ddde741499f38785b3476d139938198abe4 100644
--- a/src/snapshot/code-serializer.cc
+++ b/src/snapshot/code-serializer.cc
@@ -223,12 +223,15 @@ std::unique_ptr<ScriptData> WasmCompiledModuleSerializer::SerializeWasmModule(
       Handle<wasm::WasmCompiledModule>::cast(input);
   WasmCompiledModuleSerializer wasm_cs(isolate, 0);
   wasm_cs.reference_map()->AddAttachedReference(*isolate->native_context());
+  Handle<SeqOneByteString> wire_bytes = compiled_module->module_bytes();

[Yang, 2016/10/20 06:46:17]

Another way to do this is to use attached references. You would register this
string as attached reference so that the serializer recognizes this object. The
deserializer then restores it. This is what we do for the source string in
CodeSerializer.

This way, if there are other references to wire bytes in the object graph, the
serializer would find them. Which may not be the case now, but maybe sometime in
the future?

[Mircea Trofin, 2016/10/20 07:22:30]

Oh... yes. Yes, makes sense :) Thanks!

+  compiled_module->reset_module_bytes();
   ScriptData* data = wasm_cs.Serialize(compiled_module);
+  compiled_module->set_module_bytes(wire_bytes);
   return std::unique_ptr<ScriptData>(data);
 }
 
 MaybeHandle<FixedArray> WasmCompiledModuleSerializer::DeserializeWasmModule(
-    Isolate* isolate, ScriptData* data) {
+    Isolate* isolate, ScriptData* data, Vector<const byte> wire_bytes) {
   SerializedCodeData::SanityCheckResult sanity_check_result =
       SerializedCodeData::CHECK_SUCCESS;
   MaybeHandle<FixedArray> nothing;
@@ -250,8 +253,16 @@ MaybeHandle<FixedArray> WasmCompiledModuleSerializer::DeserializeWasmModule(
 
   MaybeHandle<HeapObject> obj = deserializer.DeserializeObject(isolate);
   if (obj.is_null() || !obj.ToHandleChecked()->IsFixedArray()) return nothing;
-  Handle<FixedArray> compiled_module =
-      Handle<FixedArray>::cast(obj.ToHandleChecked());
+  Handle<wasm::WasmCompiledModule> compiled_module =
+      Handle<wasm::WasmCompiledModule>::cast(obj.ToHandleChecked());
+  MaybeHandle<String> maybe_wire_bytes_as_string =
+      isolate->factory()->NewStringFromOneByte(wire_bytes, TENURED);
+  Handle<String> wire_bytes_as_string;
+  if (!maybe_wire_bytes_as_string.ToHandle(&wire_bytes_as_string))
+    return nothing;
+
+  compiled_module->set_module_bytes(
+      handle(SeqOneByteString::cast(*wire_bytes_as_string)));
   wasm::WasmCompiledModule::RecreateModuleWrapper(isolate, compiled_module);
   return compiled_module;
 }