2017-08-04  Richard Biener  <rguenther@suse.de>

	PR middle-end/81705
	* fold-const.c (fold_binary_loc): Properly restrict
	minus_var0 && minus_var1 case when associating undefined overflow
	entities.

	* c-c++-common/ubsan/pr81705.c: New testcase.

From-SVN: r250866