[wasm][asm.js] Make asm.js->wasm return a regular object.

Return a regular JSObject in the asm.js -> wasm case.

BUG=v8:5877
R=mtrofin@chromium.org,aseemgarg@chromium.org,titzer@chromium.org

Review-Url: https://codereview.chromium.org/2664493002
Cr-Commit-Position: refs/heads/master@{#42757}

src/asmjs/asm-js.cc

@@ -273,22 +273,19 @@ MaybeHandle<Object> AsmJs::InstantiateAsmWasm(i::Isolate* isolate,
                           foreign, NONE);
   }
 
-  i::MaybeHandle<i::JSObject> maybe_module_object =
+  i::MaybeHandle<i::Object> maybe_module_object =
       i::wasm::WasmModule::Instantiate(isolate, &thrower, module, ffi_object,
                                        memory);
   if (maybe_module_object.is_null()) {
     return MaybeHandle<Object>();
   }
+  i::Handle<i::Object> module_object = maybe_module_object.ToHandleChecked();
 
   i::Handle<i::Name> init_name(isolate->factory()->InternalizeUtf8String(
       wasm::AsmWasmBuilder::foreign_init_name));
+  i::Handle<i::Object> init =
+      i::Object::GetProperty(module_object, init_name).ToHandleChecked();
 
-  i::Handle<i::Object> module_object = maybe_module_object.ToHandleChecked();
-  i::MaybeHandle<i::Object> maybe_init =
-      i::Object::GetProperty(module_object, init_name);
-  DCHECK(!maybe_init.is_null());
-
-  i::Handle<i::Object> init = maybe_init.ToHandleChecked();
   i::Handle<i::Object> undefined(isolate->heap()->undefined_value(), isolate);
   i::Handle<i::Object>* foreign_args_array =
       new i::Handle<i::Object>[foreign_globals->length()];
@@ -347,7 +344,9 @@ MaybeHandle<Object> AsmJs::InstantiateAsmWasm(i::Isolate* isolate,
     MessageHandler::ReportMessage(isolate, &location, message);
   }
 
-  return module_object;
+  Handle<String> exports_name =
+      isolate->factory()->InternalizeUtf8String("exports");
+  return i::Object::GetProperty(module_object, exports_name);
 }
 
 }  // namespace internal

src/wasm/wasm-module.cc

@@ -16,6 +16,7 @@
 #include "src/snapshot/snapshot.h"
 #include "src/v8.h"
 
+#include "src/asmjs/asm-wasm-builder.h"
 #include "src/wasm/function-body-decoder.h"
 #include "src/wasm/module-decoder.h"
 #include "src/wasm/wasm-js.h"
@@ -1918,17 +1919,30 @@ class WasmInstanceBuilder {
                           Handle<JSFunction>::null());
     }
 
-    Handle<JSObject> exports_object = instance;
+    Handle<JSObject> exports_object;
     if (module_->origin == kWasmOrigin) {
       // Create the "exports" object.
       exports_object = isolate_->factory()->NewJSObjectWithNullProto();
-      Handle<String> exports_name =
-          isolate_->factory()->InternalizeUtf8String("exports");
-      JSObject::AddProperty(instance, exports_name, exports_object, NONE);
+    } else if (module_->origin == kAsmJsOrigin) {
+      Handle<JSFunction> object_function = Handle<JSFunction>(
+          isolate_->native_context()->object_function(), isolate_);
+      exports_object = isolate_->factory()->NewJSObject(object_function);
+    } else {
+      UNREACHABLE();
     }
+    Handle<String> exports_name =
+        isolate_->factory()->InternalizeUtf8String("exports");
+    JSObject::AddProperty(instance, exports_name, exports_object, NONE);
+
+    Handle<String> foreign_init_name =
+        isolate_->factory()->InternalizeUtf8String(
+            wasm::AsmWasmBuilder::foreign_init_name);
+    Handle<String> single_function_name =
+        isolate_->factory()->InternalizeUtf8String(
+            wasm::AsmWasmBuilder::single_function_name);
 
     PropertyDescriptor desc;
-    desc.set_writable(false);
+    desc.set_writable(module_->origin == kAsmJsOrigin);
     desc.set_enumerable(true);
 
     // Count up export indexes.
@@ -1957,6 +1971,15 @@ class WasmInstanceBuilder {
           WasmCompiledModule::ExtractUtf8StringFromModuleBytes(
               isolate_, compiled_module_, exp.name_offset, exp.name_length)
               .ToHandleChecked();
+      Handle<JSObject> export_to;
+      if (module_->origin == kAsmJsOrigin && exp.kind == kExternalFunction &&
+          (String::Equals(name, foreign_init_name) ||
+           String::Equals(name, single_function_name))) {
+        export_to = instance;
+      } else {
+        export_to = exports_object;
+      }
+
       switch (exp.kind) {
         case kExternalFunction: {
           // Wrap and export the code as a JSFunction.
@@ -2053,14 +2076,13 @@ class WasmInstanceBuilder {
 
       // Skip duplicates for asm.js.
       if (module_->origin == kAsmJsOrigin) {
-        v8::Maybe<bool> status =
-            JSReceiver::HasOwnProperty(exports_object, name);
+        v8::Maybe<bool> status = JSReceiver::HasOwnProperty(export_to, name);
         if (status.FromMaybe(false)) {
           continue;
         }
       }
       v8::Maybe<bool> status = JSReceiver::DefineOwnProperty(
-          isolate_, exports_object, name, &desc, Object::THROW_ON_ERROR);
+          isolate_, export_to, name, &desc, Object::THROW_ON_ERROR);
       if (!status.IsJust()) {
         thrower_->LinkError("export of %.*s failed.", name->length(),
                             name->ToCString().get());

test/mjsunit/asm/asm-validation.js

@@ -476,3 +476,23 @@ function assertValidAsm(func) {
   Module();
   assertFalse(% IsAsmWasmCode(Module));
 })();
+
+(function TestAsmIsRegular() {
+  function Module() {
+    'use asm';
+    var g = 123;
+    function foo() {
+      return g | 0;
+    }
+    return {x: foo};
+  }
+  var o = Module();
+  assertValidAsm(Module);
+  assertFalse(o instanceof WebAssembly.Instance);
+  assertTrue(o instanceof Object);
+  assertTrue(o.__proto__ === Object.prototype);
+  o.x = 5;
+  assertTrue(typeof o.x === 'number');
+  assertTrue(o.__single_function__ === undefined);
+  assertTrue(o.__foreign_init__ === undefined);
+})();