harmony-scoping: Implement LoadIC handler for loads from global contexts.

src/hydrogen.cc

 // Copyright 2013 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/hydrogen.h"
 
 #include <sstream>
 
 #include "src/v8.h"
 
@@ skipping 5358 matching lines @@
       // Handle known global constants like 'undefined' specially to avoid a
       // load from a global cell for them.
       Handle<Object> constant_value =
           isolate()->factory()->GlobalConstantFor(variable->name());
       if (!constant_value.is_null()) {
         HConstant* instr = New<HConstant>(constant_value);
         return ast_context()->ReturnInstruction(instr, expr->id());
       }
 
       Handle<GlobalObject> global(current_info()->global_object());
+
+      if (FLAG_harmony_scoping) {
+        Handle<GlobalContextTable> global_contexts(
+            global->native_context()->global_context_table());
+        GlobalContextTable::LookupResult lookup;
+        if (GlobalContextTable::Lookup(global_contexts, variable->name(),
+                                       &lookup)) {
+          Handle<Context> global_context = GlobalContextTable::GetContext(
+              global_contexts, lookup.context_index);
+          HInstruction* result = New<HLoadNamedField>(
+              Add<HConstant>(global_context), static_cast<HValue*>(NULL),
+              HObjectAccess::ForContextSlot(lookup.slot_index));
+          return ast_context()->ReturnInstruction(result, expr->id());
+        }
+      }
+
       LookupIterator it(global, variable->name(),
                         LookupIterator::OWN_SKIP_INTERCEPTOR);
       GlobalPropertyAccess type = LookupGlobalProperty(variable, &it, LOAD);
 
       if (type == kUseCell) {
         Handle<PropertyCell> cell = it.GetPropertyCell();
         if (cell->type()->IsConstant()) {
           PropertyCell::AddDependentCompilationInfo(cell, top_info());
           Handle<Object> constant_object = cell->type()->AsConstant()->Value();
           if (constant_object->IsConsString()) {
@@ skipping 7296 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal