rs6000: Handle print_operand_address for unexpected RTL (PR87598)

As the PR shows, the user can force this to be called on at least some
RTL that is not a valid address.  Most targets treat this as if the
user knows best; let's do the same.


	PR target/87598
	* config/rs6000/rs6000.c (print_operand_address): For unexpected RTL
	call output_addr_const and hope for the best.

From-SVN: r265392

gcc/ChangeLog

+2018-10-22  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR target/87598
+	* config/rs6000/rs6000.c (print_operand_address): For unexpected RTL
+	call output_addr_const and hope for the best.
+
 2018-10-22  Richard Biener  <rguenther@suse.de>
 
 	* gimple-ssa-evrp-analyze.c

gcc/config/rs6000/rs6000.c

@@ -21273,7 +21273,7 @@ print_operand_address (FILE *file, rtx x)
 	fprintf (file, "(%s)", reg_names[REGNO (XVECEXP (tocrel_base_oac, 0, 1))]);
     }
   else
-    gcc_unreachable ();
+    output_addr_const (file, x);
 }
 
 /* Implement TARGET_ASM_OUTPUT_ADDR_CONST_EXTRA.  */