Remove UBSAN in dwarf2out.c (PR tree-optimization/82491).

2018-04-03  Martin Liska  <mliska@suse.cz>

	PR tree-optimization/82491
	* rtl.h (strip_offset_and_add): Replace += suboffset with
	poly_uint64 () + suboffset.

From-SVN: r259030

gcc/ChangeLog

+2018-04-03  Martin Liska  <mliska@suse.cz>
+
+	PR tree-optimization/82491
+	* rtl.h (strip_offset_and_add): Replace += suboffset with
+	poly_uint64 () + suboffset.
+
 2018-03-29  Martin Liska  <mliska@suse.cz>
 	    Martin Jambor  <mjambor@suse.cz>
 

gcc/rtl.h

@@ -4339,7 +4339,7 @@ strip_offset_and_add (rtx x, poly_int64_pod *offset)
     {
       poly_int64 suboffset;
       x = strip_offset (x, &suboffset);
-      *offset += suboffset;
+      *offset = poly_uint64 (*offset) + suboffset;
     }
   return x;
 }