[wasm] Call a runtime function for a MemorySize instruction.

src/runtime/runtime-wasm.cc

Index: src/runtime/runtime-wasm.cc
diff --git a/src/runtime/runtime-wasm.cc b/src/runtime/runtime-wasm.cc
index 4be8fa57184e71535bd8108b4dc3737c364db359..ab69046c457255e8f44974fa4798370b5b31cefd 100644
--- a/src/runtime/runtime-wasm.cc
+++ b/src/runtime/runtime-wasm.cc
@@ -18,6 +18,27 @@
 namespace v8 {
 namespace internal {
 
+RUNTIME_FUNCTION(Runtime_WasmMemorySize) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(0, args.length());
+
+  Handle<JSObject> module_instance;
+  {
+    // Get the module JSObject
+    DisallowHeapAllocation no_allocation;
+    const Address entry = Isolate::c_entry_fp(isolate->thread_local_top());
+    Address pc =
+        Memory::Address_at(entry + StandardFrameConstants::kCallerPCOffset);
+    Code* code =
+        isolate->inner_pointer_to_code_cache()->GetCacheEntry(pc)->code;
+    Object* owning_instance = wasm::GetOwningWasmInstance(code);
+    CHECK_NOT_NULL(owning_instance);
+    module_instance = handle(JSObject::cast(owning_instance), isolate);
+  }
+  return *isolate->factory()->NewNumberFromInt(
+      wasm::GetInstanceMemorySize(isolate, module_instance));
+}
+
 RUNTIME_FUNCTION(Runtime_WasmGrowMemory) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());