[hydrogen] optimize switch with string clauses

src/hydrogen.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 631 matching lines @@
   // return blocks.  NULL in all other cases.
   TestContext* test_context_;
 
   FunctionState* outer_;
 };
 
 
 class HGraphBuilder: public AstVisitor {
  public:
   enum BreakType { BREAK, CONTINUE };
+  enum SwitchType { UNKNOWN_SWITCH, SMI_SWITCH, STRING_SWITCH };
 
   // A class encapsulating (lazily-allocated) break and continue blocks for
   // a breakable statement.  Separated from BreakAndContinueScope so that it
   // can have a separate lifetime.
   class BreakAndContinueInfo BASE_EMBEDDED {
    public:
     explicit BreakAndContinueInfo(BreakableStatement* target)
       : target_(target), break_block_(NULL), continue_block_(NULL) {
     }
 
@@ skipping 578 matching lines @@
   const char* filename_;
   HeapStringAllocator string_allocator_;
   StringStream trace_;
   int indent_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_H_