Assert dbx_reg_number doesn't return INVALID_REGNUM

	PR debug/52857
	* dwarf2out.c (dbx_reg_number): Assert return value !=
	INVALID_REGNUM.

From-SVN: r186837

gcc/ChangeLog

+2012-04-25  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR debug/52857
+	* dwarf2out.c (dbx_reg_number): Assert return value !=
+	INVALID_REGNUM.
+
 2012-04-25  Jakub Jelinek  <jakub@redhat.com>
 
 	* common.opt (flag_debug_types_section): Default to 0.

gcc/dwarf2out.c

@@ -10167,7 +10167,9 @@ dbx_reg_number (const_rtx rtl)
     }
 #endif
 
-  return DBX_REGISTER_NUMBER (regno);
+  regno = DBX_REGISTER_NUMBER (regno);
+  gcc_assert (regno != INVALID_REGNUM);
+  return regno;
 }
 
 /* Optionally add a DW_OP_piece term to a location description expression.