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

src/compiler/pipeline.cc

 // Copyright 2014 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/compiler/pipeline.h"
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <memory>
 #include <sstream>
 
@@ skipping 763 matching lines @@
           data->loop_assignment(), data->source_positions());
       succeeded = graph_builder.CreateGraph();
     }
 
     if (!succeeded) {
       data->set_compilation_failed();
     }
   }
 };
 
+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"; }
 
   void Run(PipelineData* data, Zone* temp_zone) {
     JSGraphReducer graph_reducer(data->jsgraph(), temp_zone);
     DeadCodeElimination dead_code_elimination(&graph_reducer, data->graph(),
                                               data->common());
     CheckpointElimination checkpoint_elimination(&graph_reducer);
     CommonOperatorReducer common_reducer(&graph_reducer, data->graph(),
                                          data->common(), data->machine());
     JSCallReducer call_reducer(&graph_reducer, data->jsgraph(),
                                data->native_context(),
                                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>());
     JSFrameSpecialization frame_specialization(
         &graph_reducer, data->info()->osr_frame(), data->jsgraph());
     JSNativeContextSpecialization::Flags flags =
         JSNativeContextSpecialization::kNoFlags;
     if (data->info()->is_accessor_inlining_enabled()) {
       flags |= JSNativeContextSpecialization::kAccessorInliningEnabled;
     }
@@ skipping 1214 matching lines @@
   data->DeleteRegisterAllocationZone();
 }
 
 CompilationInfo* PipelineImpl::info() const { return data_->info(); }
 
 Isolate* PipelineImpl::isolate() const { return info()->isolate(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8