[compiler][modules] Constant-fold the loads of module cells.

src/compiler/pipeline.cc

Index: src/compiler/pipeline.cc
diff --git a/src/compiler/pipeline.cc b/src/compiler/pipeline.cc
index 585923fa69d36c63e016846be502018fea6b65be..f274d00afbf6a58de3eda9aef47a5bc9e8fee541 100644
--- a/src/compiler/pipeline.cc
+++ b/src/compiler/pipeline.cc
@@ -781,6 +781,31 @@ struct GraphBuilderPhase {
   }
 };
 
+namespace {
+
+Maybe<OuterContext> GetModuleContext(Handle<JSFunction> closure) {
+  Context* current = closure->context();
+  size_t distance = 0;
+  while (current != nullptr && !current->IsNativeContext() &&
+         !current->IsModuleContext()) {
+    current = current->previous();
+    distance++;
+  }
+  if (current != nullptr && current->IsModuleContext()) {

[Michael Starzinger, 2017/05/03 17:28:16]

question: Can we ever hit the {nullptr} case here? There should always be a
native context on any context chain AFAICT. What am I missing?

[neis, 2017/05/04 10:36:21]

As discussed, I removed this condition.

+    return Just(OuterContext(handle(current), distance));
+  }
+  return Nothing<OuterContext>();
+}
+
+Maybe<OuterContext> ChooseSpecializationContext(CompilationInfo* info) {
+  if (info->is_function_context_specializing()) {
+    DCHECK(info->has_context());
+    return Just(OuterContext(handle(info->context()), 0));
+  }
+  return GetModuleContext(info->closure());
+}
+
+}  // anonymous namespace
 
 struct InliningPhase {
   static const char* phase_name() { return "inlining"; }
@@ -797,9 +822,7 @@ struct InliningPhase {
                                data->info()->dependencies());
     JSContextSpecialization context_specialization(
         &graph_reducer, data->jsgraph(),
-        data->info()->is_function_context_specializing()
-            ? handle(data->info()->context())
-            : MaybeHandle<Context>(),
+        ChooseSpecializationContext(data->info()),
         data->info()->is_function_context_specializing()
             ? data->info()->closure()
             : MaybeHandle<JSFunction>());