Optimize loading the global object for a named load on x64....

src/x64/codegen-x64.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5233 matching lines @@
     if (property->key()->IsPropertyName()) {
       ref->set_type(Reference::NAMED);
     } else {
       Load(property->key());
       ref->set_type(Reference::KEYED);
     }
   } else if (var != NULL) {
     // The expression is a variable proxy that does not rewrite to a
     // property.  Global variables are treated as named property references.
     if (var->is_global()) {
+      // If rax is free, the register allocator prefers it.  Thus the code
+      // generator will load the global object into rax, which is where
+      // LoadIC wants it.  Most uses of Reference call LoadIC directly
+      // after the reference is created.
+      frame_->Spill(rax);
       LoadGlobal();
       ref->set_type(Reference::NAMED);
     } else {
       ASSERT(var->slot() != NULL);
       ref->set_type(Reference::SLOT);
     }
   } else {
     // Anything else is a runtime error.
     Load(e);
     frame_->CallRuntime(Runtime::kThrowReferenceError, 1);
@@ skipping 6308 matching lines @@
   // Call the function from C++.
   return FUNCTION_CAST<ModuloFunction>(buffer);
 }
 
 #endif
 
 
 #undef __
 
 } }  // namespace v8::internal