Unify the handling of comparinsons against null and undefined.

src/full-codegen.h

 // Copyright 2011 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 373 matching lines @@
     VisitInCurrentContext(expr);
   }
 
   void VisitDeclarations(ZoneList<Declaration*>* declarations);
   void DeclareGlobals(Handle<FixedArray> pairs);
   int DeclareGlobalsFlags();
 
   // Try to perform a comparison as a fast inlined literal compare if
   // the operands allow it.  Returns true if the compare operations
   // has been matched and all code generated; false otherwise.
-  bool TryLiteralCompare(CompareOperation* compare,
-                         Label* if_true,
-                         Label* if_false,
-                         Label* fall_through);
+  bool TryLiteralCompare(CompareOperation* compare);
 
   // Platform-specific code for comparing the type of a value with
   // a given literal string.
-  void EmitLiteralCompareTypeof(Expression* expr,
-                                Handle<String> check,
-                                Label* if_true,
-                                Label* if_false,
-                                Label* fall_through);
+  void EmitLiteralCompareTypeof(Expression* expr, Handle<String> check);
 
-  // Platform-specific code for strict equality comparison with
-  // the undefined value.
-  void EmitLiteralCompareUndefined(Expression* expr,
-                                   Label* if_true,
-                                   Label* if_false,
-                                   Label* fall_through);
+  // Platform-specific code for equality comparison with a nil-like value.
+  void EmitLiteralCompareNil(CompareOperation* expr,
+                             Expression* sub_expr,
+                             NilValue nil);
 
-  // Platform-specific code for equality comparison with the null value.
-  void EmitLiteralCompareNull(Expression* expr,
-                              bool is_strict,
-                              Label* if_true,
-                              Label* if_false,
-                              Label* fall_through);
   // Bailout support.
   void PrepareForBailout(Expression* node, State state);
   void PrepareForBailoutForId(int id, State state);
 
   // Record a call's return site offset, used to rebuild the frame if the
   // called function was inlined at the site.
   void RecordJSReturnSite(Call* call);
 
   // Prepare for bailout before a test (or compare) and branch.  If
   // should_normalize, then the following comparison will not handle the
@@ skipping 409 matching lines @@
 
   friend class NestedStatement;
 
   DISALLOW_COPY_AND_ASSIGN(FullCodeGenerator);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_FULL_CODEGEN_H_