Improve load of global variables.

src/ia32/codegen-ia32.cc

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 // modification, are permitted provided that the following conditions are
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 //
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@@ skipping 671 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()) {
+      // Named loads require object in eax.  Named stores don't use references.
+      // Spilling eax makes it free, so LoadGlobal loads directly into eax.

[Kevin Millikin (Chromium), 2010/02/19 10:23:04]

The comment is still not quite right.  LoadIC wants receiver in eax and the
register allocator will prefer eax if free.

I think it's obvious that Spill(eax) makes it free, but not that the register
allocator prefers it.

Named stores do use reference in the case of e.x++ and ++e.x, so don't put that
comment at all since it's not true.  

+      frame_->Spill(eax);
       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 10054 matching lines @@
 
   // Call the runtime; it returns -1 (less), 0 (equal), or 1 (greater)
   // tagged as a small integer.
   __ bind(&runtime);
   __ TailCallRuntime(ExternalReference(Runtime::kStringCompare), 2, 1);
 }
 
 #undef __
 
 } }  // namespace v8::internal