Fix UBSAN errors in dse.c (PR rtl-optimization/82044).

2017-11-21  Martin Liska  <mliska@suse.cz>

	PR rtl-optimization/82044
	PR tree-optimization/82042
	* dse.c (check_mem_read_rtx): Check for overflow.

From-SVN: r255001

gcc/ChangeLog

+2017-11-21  Martin Liska  <mliska@suse.cz>
+
+	PR rtl-optimization/82044
+	PR tree-optimization/82042
+	* dse.c (check_mem_read_rtx): Check for overflow.
+
 2017-11-21  Aldy Hernandez  <aldyh@redhat.com>
 
 	* tree-ssa-threadbackward.c (find_jump_threads_backwards): Fix

gcc/dse.c

@@ -1981,6 +1981,12 @@ check_mem_read_rtx (rtx *loc, bb_info_t bb_info)
   else
     width = GET_MODE_SIZE (GET_MODE (mem));
 
+  if (offset > HOST_WIDE_INT_MAX - width)
+    {
+      clear_rhs_from_active_local_stores ();
+      return;
+    }
+
   read_info = read_info_type_pool.allocate ();
   read_info->group_id = group_id;
   read_info->mem = mem;