[turbofan] Optimize loads from the global object in JSTypeFeedbackSpecializer.

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 <sstream>
 
 #include "src/base/platform/elapsed-timer.h"
@@ skipping 501 matching lines @@
   static const char* phase_name() { return "type feedback specializing"; }
 
   void Run(PipelineData* data, Zone* temp_zone) {
     SourcePositionTable::Scope pos(data->source_positions(),
                                    SourcePosition::Unknown());
     Handle<Context> native_context(data->info()->context()->native_context());
     TypeFeedbackOracle oracle(data->isolate(), temp_zone,
                               data->info()->unoptimized_code(),
                               data->info()->feedback_vector(), native_context);
     GraphReducer graph_reducer(data->graph(), temp_zone);
-    JSTypeFeedbackSpecializer specializer(data->jsgraph(),
-                                          data->js_type_feedback(), &oracle);
+    Handle<GlobalObject> global_object = Handle<GlobalObject>::null();
+    if (data->info()->has_global_object()) {

[Michael Starzinger, 2015/04/21 12:34:01]

This is only valid if we don't share TurboFan code accross native contexts. We
are starting to add more and more assumptions like this. I think it's time to
introduce some sort of "sharing mode" that let's the pipeline (and the different
reducers) know what level of sharing is expected. WDYT?

Can we leave TODO in that regard here and introduce the "sharing mode" in a
follow-up CL?

[titzer, 2015/04/21 12:56:52]

Acknowledge, agreed. I have sketched out a specialization mode struct in another
CL and dropped in a TODO.

+      global_object =
+          Handle<GlobalObject>(data->info()->global_object(), data->isolate());
+    }
+    JSTypeFeedbackSpecializer specializer(
+        data->jsgraph(), data->js_type_feedback(), &oracle, global_object,
+        data->info()->dependencies());
     AddReducer(data, &graph_reducer, &specializer);
     graph_reducer.ReduceGraph();
   }
 };
 
 
 struct TypedLoweringPhase {
   static const char* phase_name() { return "typed lowering"; }
 
   void Run(PipelineData* data, Zone* temp_zone) {
@@ skipping 728 matching lines @@
 
   if (FLAG_trace_turbo && !data->MayHaveUnverifiableGraph()) {
     TurboCfgFile tcf(data->isolate());
     tcf << AsC1VAllocator("CodeGen", data->register_allocator());
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8