PR81747, ICE in operator[]

	PR rtl-optimization/81747
	* cse.c (cse_extended_basic_block): Don't attempt to record
	equivalences for degenerate conditional branches that branch
	to their fall-through.

From-SVN: r251349

gcc/ChangeLog

+2017-08-25  Alan Modra  <amodra@gmail.com>
+
+	PR rtl-optimization/81747
+	* cse.c (cse_extended_basic_block): Don't attempt to record
+	equivalences for degenerate conditional branches that branch
+	to their fall-through.
+
 2017-08-24  Martin Sebor  <msebor@redhat.com>
 
 	PR middle-end/81908

gcc/cse.c

@@ -6640,6 +6640,7 @@ cse_extended_basic_block (struct cse_basic_block_data *ebb_data)
 	 equivalences due to the condition being tested.  */
       insn = BB_END (bb);
       if (path_entry < path_size - 1
+	  && EDGE_COUNT (bb->succs) == 2
 	  && JUMP_P (insn)
 	  && single_set (insn)
 	  && any_condjump_p (insn))