[wasm] Transferrable modules

src/value-serializer.h

Index: src/value-serializer.h
diff --git a/src/value-serializer.h b/src/value-serializer.h
index 7961b2ea0b6a78375b8975945fa740cc3de8b06d..47f8a84ef80c6551839004e8a1fab20703fa5727 100644
--- a/src/value-serializer.h
+++ b/src/value-serializer.h
@@ -31,6 +31,7 @@ class JSValue;
 class Object;
 class Oddball;
 class Smi;
+class WasmModuleObject;
 
 enum class SerializationTag : uint8_t;
 
@@ -211,6 +212,13 @@ class ValueDeserializer {
                            Handle<JSArrayBuffer> array_buffer);
 
   /*
+   * Accepts the WasmModuleObject corresponding to the one having transfer_id
+   * produced by v8::ValueSerializer::GetWasmCompiledModuleId().
+   * See issue v8:6106.
+   */
+  void TransferWasmModule(uint32_t transfer_id,
+                          Handle<WasmModuleObject> module);
+  /*
    * Publicly exposed wire format writing methods.
    * These are intended for use within the delegate's WriteHostObject method.
    */
@@ -218,6 +226,9 @@ class ValueDeserializer {
   bool ReadUint64(uint64_t* value) WARN_UNUSED_RESULT;
   bool ReadDouble(double* value) WARN_UNUSED_RESULT;
   bool ReadRawBytes(size_t length, const void** data) WARN_UNUSED_RESULT;
+  void set_allow_inline_wasm(bool allow_inline_wasm) {
+    allow_inline_wasm_ = allow_inline_wasm;
+  }
 
  private:
   // Reading the wire format.
@@ -230,6 +241,7 @@ class ValueDeserializer {
   Maybe<T> ReadZigZag() WARN_UNUSED_RESULT;
   Maybe<double> ReadDouble() WARN_UNUSED_RESULT;
   Maybe<Vector<const uint8_t>> ReadRawBytes(int size) WARN_UNUSED_RESULT;
+  bool allow_inline_wasm() const { return allow_inline_wasm_; }
 
   // Reads a string if it matches the one provided.
   // Returns true if this was the case. Otherwise, nothing is consumed.
@@ -263,6 +275,7 @@ class ValueDeserializer {
   MaybeHandle<JSArrayBufferView> ReadJSArrayBufferView(
       Handle<JSArrayBuffer> buffer) WARN_UNUSED_RESULT;
   MaybeHandle<JSObject> ReadWasmModule() WARN_UNUSED_RESULT;
+  MaybeHandle<JSObject> ReadWasmModuleTransfer() WARN_UNUSED_RESULT;
   MaybeHandle<JSObject> ReadHostObject() WARN_UNUSED_RESULT;
 
   /*
@@ -285,10 +298,12 @@ class ValueDeserializer {
   PretenureFlag pretenure_;
   uint32_t version_ = 0;
   uint32_t next_id_ = 0;
+  bool allow_inline_wasm_ = false;
 
   // Always global handles.
   Handle<FixedArray> id_map_;
   MaybeHandle<SeededNumberDictionary> array_buffer_transfer_map_;
+  std::vector<Handle<WasmModuleObject>> transferred_wasm_modules_;

[jbroman, 2017/03/17 14:44:37]

Hmm. This seems to require that the handles remain valid long after they are
passed in, which depends on HandleScope lifetime. The way
|array_buffer_transfer_map_| (and, for that matter, |id_map_|) works is that the
(optional) lookup table is held as a heap object by one global handle, and the
map then holds the objects.

Put another way, as a user I'd have expected this to be a legitimate use of the
API:

{
  v8::HandleScope handleScope(isolate);
  v8::Local<v8::WasmCompiledModule> module = ...;
  deserializer.TransferWasmCompiledModule(0, module);
}
deserializer.ReadValue(...);

[Mircea Trofin, 2017/03/17 16:55:31]

As discussed offline - this alternative appears to introduce more complexity
than the previous solution, even considering the difference with SABs. We agreed
to go back to the delegate-based mechanism, and address quickly thereafter
v8:6106.

 
   DISALLOW_COPY_AND_ASSIGN(ValueDeserializer);
 };