Initial real implementation of simple merge for frames. Does not yet...

src/register-allocator-ia32.h

 // Copyright 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 83 matching lines @@
   void Unuse(Register reg) { registers_.Unuse(reg); }
 
   // Initialize the register allocator for entry to a JS function.  On
   // entry, esp, ebp, esi, and edi are externally referenced (ie, outside
   // the virtual frame); and the other registers are free.
   void Initialize();
 
   // Allocate a free register if possible or fail by returning no_reg.
   Register Allocate();
 
+  // Allocate a free register without spilling any or fail and return
+  // no_reg.
+  Register AllocateWithoutSpilling();
+
  private:
   CodeGenerator* code_generator_;
   RegisterFile registers_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_REGISTER_ALLOCATOR_IA32_H_