[wasm] Support asm.js modules with a single function.

src/asmjs/asm-js.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/asmjs/asm-js.h"
 
 #include "src/api-natives.h"
 #include "src/api.h"
 #include "src/asmjs/asm-typer.h"
 #include "src/asmjs/asm-wasm-builder.h"
@@ skipping 194 matching lines @@
       i::FixedArray::cast(wasm_data->get(1)));
 
   ErrorThrower thrower(isolate, "Asm.js -> WebAssembly instantiation");
 
   i::MaybeHandle<i::JSObject> maybe_module_object =
       i::wasm::WasmModule::Instantiate(isolate, module, foreign, memory);
   if (maybe_module_object.is_null()) {
     return MaybeHandle<Object>();
   }
 
-  i::Handle<i::Name> name(isolate->factory()->InternalizeOneByteString(
-      STATIC_CHAR_VECTOR("__foreign_init__")));
+  i::Handle<i::Name> init_name(isolate->factory()->InternalizeUtf8String(
+      wasm::AsmWasmBuilder::foreign_init_name));
 
   i::Handle<i::Object> module_object = maybe_module_object.ToHandleChecked();
   i::MaybeHandle<i::Object> maybe_init =
-      i::Object::GetProperty(module_object, name);
+      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()];
   for (int j = 0; j < foreign_globals->length(); j++) {
     if (!foreign.is_null()) {
       i::MaybeHandle<i::Name> name = i::Object::ToName(
           isolate, i::Handle<i::Object>(foreign_globals->get(j), isolate));
       if (!name.is_null()) {
         i::MaybeHandle<i::Object> val =
             i::Object::GetProperty(foreign, name.ToHandleChecked());
         if (!val.is_null()) {
           foreign_args_array[j] = val.ToHandleChecked();
           continue;
         }
       }
     }
     foreign_args_array[j] = undefined;
   }
   i::MaybeHandle<i::Object> retval = i::Execution::Call(
       isolate, init, undefined, foreign_globals->length(), foreign_args_array);
   delete[] foreign_args_array;
-
   DCHECK(!retval.is_null());
 
-  return maybe_module_object;
+  i::Handle<i::Name> single_function_name(
+      isolate->factory()->InternalizeUtf8String(
+          wasm::AsmWasmBuilder::single_function_name));
+  i::MaybeHandle<i::Object> single_function =
+      i::Object::GetProperty(module_object, single_function_name);
+  if (!single_function.is_null() &&
+      !single_function.ToHandleChecked()->IsUndefined(isolate)) {
+    return single_function;
+  }
+  return module_object;
 }
 
 }  // namespace internal
 }  // namespace v8