Crankshaft part of the 'loads and stores to global vars through property cell shortcuts' feature.

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 5541 matching lines @@
           if (field_maps == nullptr) {
             instr = New<HLoadNamedField>(cell_constant, nullptr, access);
           } else {
             instr = New<HLoadNamedField>(cell_constant, nullptr, access,
                                          field_maps, HType::HeapObject());
           }
           instr->ClearDependsOnFlag(kInobjectFields);
           instr->SetDependsOnFlag(kGlobalVars);
           return ast_context()->ReturnInstruction(instr, expr->id());
         }
+      } else if (variable->IsGlobalSlot()) {
+        DCHECK(variable->index() > 0);
+        DCHECK(variable->IsStaticGlobalObjectProperty());
+        // Each var occupies two slots in the context: for reads and writes.
+        int slot_index = variable->index();
+        int depth = scope()->ContextChainLength(variable->scope());
+
+        HLoadGlobalViaContext* instr =
+            New<HLoadGlobalViaContext>(variable->name(), depth, slot_index);
+        return ast_context()->ReturnInstruction(instr, expr->id());
+
       } else {
         HValue* global_object = Add<HLoadNamedField>(
             context(), nullptr,
             HObjectAccess::ForContextSlot(Context::GLOBAL_OBJECT_INDEX));
         HLoadGlobalGeneric* instr = New<HLoadGlobalGeneric>(
             global_object, variable->name(), ast_context()->typeof_mode());
         instr->SetVectorAndSlot(handle(current_feedback_vector(), isolate()),
                                 expr->VariableFeedbackSlot());
         return ast_context()->ReturnInstruction(instr, expr->id());
       }
@@ skipping 1201 matching lines @@
           break;
         }
       }
     }
     HInstruction* instr = Add<HStoreNamedField>(cell_constant, access, value);
     instr->ClearChangesFlag(kInobjectFields);
     instr->SetChangesFlag(kGlobalVars);
     if (instr->HasObservableSideEffects()) {
       Add<HSimulate>(ast_id, REMOVABLE_SIMULATE);
     }
+  } else if (var->IsGlobalSlot()) {
+    DCHECK(var->index() > 0);
+    DCHECK(var->IsStaticGlobalObjectProperty());
+    // Each var occupies two slots in the context: for reads and writes.
+    int slot_index = var->index() + 1;
+    int depth = scope()->ContextChainLength(var->scope());
+
+    HStoreGlobalViaContext* instr = Add<HStoreGlobalViaContext>(
+        var->name(), value, depth, slot_index, function_language_mode());
+    USE(instr);
+    DCHECK(instr->HasObservableSideEffects());
+    Add<HSimulate>(ast_id, REMOVABLE_SIMULATE);
+
   } else {
     HValue* global_object = Add<HLoadNamedField>(
         context(), nullptr,
         HObjectAccess::ForContextSlot(Context::GLOBAL_OBJECT_INDEX));
     HStoreNamedGeneric* instr =
         Add<HStoreNamedGeneric>(global_object, var->name(), value,
                                 function_language_mode(), PREMONOMORPHIC);
     USE(instr);
     DCHECK(instr->HasObservableSideEffects());
     Add<HSimulate>(ast_id, REMOVABLE_SIMULATE);
@@ skipping 6504 matching lines @@
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 }  // namespace internal
 }  // namespace v8