re PR target/92669 (ICE in pre_and_rev_post_order_compute_fn at gcc/cfganal.c:1034 since r278666)

2019-11-26  Richard Biener  <rguenther@suse.de>

	PR middle-end/92669
	* cfganal.c (pre_and_rev_post_order_compute_fn): Deal with
	NULL pre_order.

From-SVN: r278723

gcc/ChangeLog

+2019-11-26  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/92669
+	* cfganal.c (pre_and_rev_post_order_compute_fn): Deal with
+	NULL pre_order.
+
 2019-11-26  Robin Dapp  <rdapp@linux.ibm.com>
 
 	* config/s390/linux.h: Add undef for MUSL_DYNAMIC_LINKERxx.

gcc/cfganal.c

@@ -1030,6 +1030,8 @@ pre_and_rev_post_order_compute_fn (struct function *fn,
     }
 
   /* Clear the temporarily allocated flag.  */
+  if (!rev_post_order)
+    rev_post_order = pre_order;
   for (int i = 0; i < pre_order_num; ++i)
     BASIC_BLOCK_FOR_FN (fn, rev_post_order[i])->flags &= ~visited;