2017-06-14  Richard Biener  <rguenther@suse.de>

	PR middle-end/81088
	* fold-const.c (split_tree): Drop TREE_OVERFLOW flag from
	literal constants.
	(fold_binary_loc): When associating do not treat pre-existing
	TREE_OVERFLOW on literal constants as a reason to allow
	TREE_OVERFLOW on associated literal constants.

	* c-c++-common/ubsan/pr81088.c: New testcase.

From-SVN: r249192