[wasm] Deduplicate continuation-resuming callback

For stack-switching, we create a callable object from the
WasmResume builtin and pass that as the onFulfilled argument
of Promise#then. We don't need to create this callable object each time
we suspend. Instead, create it when we initialize the Suspender object
and store it there.

R=jkummerow@chromium.org
CC=fgm@chromium.org

Bug: v8:12191
Change-Id: If8495493a71794cddc81b21a17a821fed8f4ede7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3579162
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79930}

src/runtime/runtime-wasm.cc

@@ -791,20 +791,7 @@ RUNTIME_FUNCTION(Runtime_WasmCreateResumePromise) {
   Handle<Object> promise = args.at(0);
   Handle<WasmSuspenderObject> suspender = args.at<WasmSuspenderObject>(1);
 
-  // Instantiate onFulfilled callback.
-  Handle<WasmOnFulfilledData> function_data =
-      isolate->factory()->NewWasmOnFulfilledData(suspender);
-  Handle<SharedFunctionInfo> shared =
-      isolate->factory()->NewSharedFunctionInfoForWasmOnFulfilled(
-          function_data);
-  Handle<Context> context(isolate->native_context());
-  Handle<Map> function_map = isolate->strict_function_map();
-  Handle<JSObject> on_fulfilled =
-      Factory::JSFunctionBuilder{isolate, shared, context}
-          .set_map(function_map)
-          .Build();
-
-  i::Handle<i::Object> argv[] = {on_fulfilled};
+  i::Handle<i::Object> argv[] = {handle(suspender->resume(), isolate)};
   i::Handle<i::Object> result;
   bool has_pending_exception =
       !i::Execution::CallBuiltin(isolate, isolate->promise_then(), promise,

src/wasm/wasm-objects.cc

@@ -1810,6 +1810,17 @@ Handle<WasmSuspenderObject> WasmSuspenderObject::New(Isolate* isolate) {
   suspender->set_continuation(ReadOnlyRoots(isolate).undefined_value());
   suspender->set_parent(ReadOnlyRoots(isolate).undefined_value());
   suspender->set_state(Inactive);
+  // Instantiate the callable object which resumes this Suspender. This will be
+  // used implicitly as the onFulfilled callback of the returned JS promise.
+  Handle<WasmOnFulfilledData> function_data =
+      isolate->factory()->NewWasmOnFulfilledData(suspender);
+  Handle<SharedFunctionInfo> shared =
+      isolate->factory()->NewSharedFunctionInfoForWasmOnFulfilled(
+          function_data);
+  Handle<Context> context(isolate->native_context());
+  Handle<JSObject> resume =
+      Factory::JSFunctionBuilder{isolate, shared, context}.Build();
+  suspender->set_resume(*resume);
   return suspender;
 }
 

src/wasm/wasm-objects.tq

@@ -103,6 +103,7 @@ extern class WasmContinuationObject extends Struct {
 extern class WasmSuspenderObject extends JSObject {
   continuation: WasmContinuationObject|Undefined;
   parent: WasmSuspenderObject|Undefined;
+  resume: JSObject;
   state: Smi;  // 0: Inactive, 1: Active, 2: Suspended.
 }