re PR bootstrap/79069 (Bootstrap failure on s390x-linux while building libgo)

	PR bootstrap/79069
	* cfgrtl.c (rtl_tidy_fallthru_edge): For any_uncondjump_p that can't
	be removed due to side-effects, don't remove following barrier nor
	turn the successor edge into fallthru edge.

From-SVN: r244383

gcc/ChangeLog

+2017-01-12  Jakub Jelinek  <jakub@redhat.com>
+
+	PR bootstrap/79069
+	* cfgrtl.c (rtl_tidy_fallthru_edge): For any_uncondjump_p that can't
+	be removed due to side-effects, don't remove following barrier nor
+	turn the successor edge into fallthru edge.
+
 2017-01-12  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>
 
 	PR target/79044

gcc/cfgrtl.c

@@ -1794,6 +1794,10 @@ rtl_tidy_fallthru_edge (edge e)
 
       q = PREV_INSN (q);
     }
+  /* Unconditional jumps with side-effects (i.e. which we can't just delete
+     together with the barrier) should never have a fallthru edge.  */
+  else if (JUMP_P (q) && any_uncondjump_p (q))
+    return;
 
   /* Selectively unlink the sequence.  */
   if (q != PREV_INSN (BB_HEAD (c)))