re PR rtl-optimization/85455 (ICE in verify_loop_structure, at cfgloop.c:1708 (error: basic block 3 should be marked irreducible))

2018-04-19  Richard Biener  <rguenther@suse.de>

	PR middle-end/85455
	* cfg.c (clear_bb_flags): When loop state says we have
	marked irreducible regions also preserve BB_IRREDUCIBLE_LOOP.

	* gcc.dg/pr85455.c: New testcase.

From-SVN: r259494