O3: Don't try to scoreboard misc registers.

I'm not positive this is the correct fix, but it's working right now.
Either we need to do something like this, prevent the misc reg from being renamed at all,
or there something else going on. We need to find the root cause as to why
this is only a problem sometimes.

src/cpu/o3/rename_impl.hh

@@ -1,4 +1,16 @@
 /*
+ * Copyright (c) 2010 ARM Limited
+ * All rights reserved.
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
  * Copyright (c) 2004-2006 The Regents of The University of Michigan
  * All rights reserved.
  *
@@ -1044,7 +1056,8 @@ DefaultRename<Impl>::renameDestRegs(DynInstPtr &inst, ThreadID tid)
         rename_result = renameMap[tid]->rename(flat_dest_reg);
 
         //Mark Scoreboard entry as not ready
-        scoreboard->unsetReg(rename_result.first);
+        if (dest_reg < TheISA::Ctrl_Base_DepTag)
+            scoreboard->unsetReg(rename_result.first);
 
         DPRINTF(Rename, "[tid:%u]: Renaming arch reg %i to physical "
                 "reg %i.\n", tid, (int)flat_dest_reg,