Minor cleanup of CompareIC state

src/ic.h

 // Copyright 2012 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 734 matching lines @@
   void patch(Code* code);
 
   static const char* GetName(TypeInfo type_info);
 
   static State ToState(TypeInfo type_info);
 };
 
 
 class CompareIC: public IC {
  public:
+  // The type/state lattice is defined by the following inequations:
+  //   UNINITIALIZED < ...
+  //   ... < GENERIC
+  //   SMI < NUMBER
+  //   SYMBOL < STRING
+  //   KNOWN_OBJECT < OBJECT
   enum State {
     UNINITIALIZED,
     SMI,
-    HEAP_NUMBER,
+    NUMBER,

[Jakob Kummerow, 2013/02/15 09:12:53]

I don't think this renaming is an improvement, for two reasons:
(1) All ICs call this state HEAP_NUMBER, so renaming it for CompareICs
introduces inconsistency.
(2) The previous name does make sense, as generally a stub's type name indicates
the most generic type it can handle. The "SMI < [HEAP_]NUMBER" inequation above
implies that the HEAP_NUMBER stub can handle Smis.
That said, if you insist on this change, I don't feel strongly enough about it
to argue.

[rossberg, 2013/02/19 11:32:13]

Good point, I fixed it for Unary and Binary ops as well. :)
As discussed offline, your very argument is why I changed it. HEAP_NUMBER names
a specific representation type, but a stub in the respective state can also
handle SMI representations, so NUMBER is the actual type it handles, in
accordance to our type hierarchy.

     SYMBOL,
     STRING,
-    OBJECT,
-    KNOWN_OBJECTS,
+    OBJECT,         // JSObject
+    KNOWN_OBJECT,   // JSObject with specific map (faster check)
     GENERIC
   };
 
   CompareIC(Isolate* isolate, Token::Value op)
       : IC(EXTRA_CALL_FRAME, isolate), op_(op) { }
 
   // Update the inline cache for the given operands.
   void UpdateCaches(Handle<Object> x, Handle<Object> y);
 
 
@@ skipping 39 matching lines @@
 // Helper for BinaryOpIC and CompareIC.
 enum InlinedSmiCheck { ENABLE_INLINED_SMI_CHECK, DISABLE_INLINED_SMI_CHECK };
 void PatchInlinedSmiCode(Address address, InlinedSmiCheck check);
 
 DECLARE_RUNTIME_FUNCTION(MaybeObject*, KeyedLoadIC_Miss);
 DECLARE_RUNTIME_FUNCTION(MaybeObject*, KeyedLoadIC_MissFromStubFailure);
 
 } }  // namespace v8::internal
 
 #endif  // V8_IC_H_