2019-02-05  Richard Biener  <rguenther@suse.de>

	PR middle-end/89150
	* bitmap.h (struct bitmap_obstack): Do not mark GTY.
	(struct bitmap_element): Drop chain_prev so we properly recurse on
	the prev member, supporting tree views.
	(struct bitmap_head): GTY skip the obstack member.

From-SVN: r268530