2016-05-11  Richard Biener  <rguenther@suse.de>

	PR middle-end/71002
	* alias.c (reference_alias_ptr_type): Preserve alias-set zero
	if the langhook insists on it.
	* fold-const.c (make_bit_field_ref): Add arg for the original
	reference and preserve its alias-set.
	(decode_field_reference): Take exp by reference and adjust it
	to the original memory reference.
	(optimize_bit_field_compare): Adjust callers.
	(fold_truth_andor_1): Likewise.
	* gimplify.c (gimplify_expr): Adjust in-SSA form test.

	* g++.dg/torture/pr71002.C: New testcase.

From-SVN: r236117