re PR tree-optimization/80549 (wrong code at -O2 and -O3 in both 32-bit and 64-bit modes on x86_64-linux-gnu (executable does not terminate))

2017-05-02  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/80549
	* tree-cfgcleanup.c (mfb_keep_latches): New helper.
	(cleanup_tree_cfg_noloop): Create forwarders to known loop
	headers if they do not have a preheader.

	* gcc.dg/torture/pr80549.c: New testcase.

From-SVN: r247486