Speed up compares with characters ie single-character strings....

src/codegen.h

 // Copyright 2006-2008 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 299 matching lines @@
   int MinorKey() {
     return OpField::encode(op_) | OverwriteField::encode(overwrite_);
   }
 
   void Generate(MacroAssembler* masm);
 
   const char* GetName();
 };
 
 
+enum NaNInformation { BothCouldBeNaN, CantBothBeNaN };
+
+
 class CompareStub: public CodeStub {
  public:
-  CompareStub(Condition cc, bool strict) : cc_(cc), strict_(strict) { }
+  CompareStub(Condition cc,
+              bool strict,
+              NaNInformation nan_info = BothCouldBeNaN) :
+      cc_(cc), strict_(strict), never_nan_nan_(nan_info == CantBothBeNaN) { }
 
   void Generate(MacroAssembler* masm);
 
  private:
   Condition cc_;
   bool strict_;
+  // Only used for 'equal' comparisons.  Tells the stub that we already know
+  // that at least one side of the comparison is not NaN.  This allows the
+  // stub to use object identity in the positive case.  We ignore it when
+  // generating the minor key for other comparisons to avoid creating more
+  // stubs.
+  bool never_nan_nan_;
 
   Major MajorKey() { return Compare; }
 
   int MinorKey();
 
   // Branch to the label if the given object isn't a symbol.
   void BranchIfNonSymbol(MacroAssembler* masm,
                          Label* label,
                          Register object,
                          Register scratch);
 
+  // Unfortunately you have to run without snapshots to see most of these
+  // names in the profile since most compare stubs end up in the snapshot.
+  const char* GetName();
 #ifdef DEBUG
   void Print() {
     PrintF("CompareStub (cc %d), (strict %s)\n",
            static_cast<int>(cc_),
            strict_ ? "true" : "false");
   }
 #endif
 };
 
 
@@ skipping 145 matching lines @@
     PrintF("RegExpExecStub\n");
   }
 #endif
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CODEGEN_H_