2015-10-29  Richard Biener  <rguenther@suse.de>

	PR middle-end/56956
	* fold-const.c (fold_cond_expr_with_comparison): Do not fold
	unsigned conditonal negation to ABS_EXPR.

	* c-c++-common/ubsan/pr56956.c: New testcase.

From-SVN: r229517