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

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 56980266af249194862def6a90b425c7364003b7..7c5d7df04366d65053a554cbd0f554c4729685d7 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -5559,6 +5559,17 @@ void HOptimizedGraphBuilder::VisitVariableProxy(VariableProxy* expr) {
           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,
@@ -6780,6 +6791,19 @@ void HOptimizedGraphBuilder::HandleGlobalVariableAssignment(
     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,