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

src/wasm/wasm-module.cc

Index: src/wasm/wasm-module.cc
diff --git a/src/wasm/wasm-module.cc b/src/wasm/wasm-module.cc
index e4188da72a3bf1b0545c5a712c18c218ff5da8ba..ed915b10460f23381f9305b0fa4a8fa226aa4160 100644
--- a/src/wasm/wasm-module.cc
+++ b/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 &&

[titzer, 2017/01/31 00:08:13]

Can you leave a TODO here? We're adding to string comparisons here, but maybe
we'll want to just remember the foreign init and single function indices (e.g.
either by numbering convention or by another asm.js-specific section) so we
don't have to compare each time.

+          (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());