re PR libstdc++/85116 (std::min_element does not optimize well with inlined predicate)

re PR libstdc++/85116 (std::min_element does not optimize well with inlined predicate)

2018-04-26  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/85116
	* tree-ssa-loop-ch.c (do_while_loop_p): A do-while loop should
	have a loop exit from the single latch predecessor.  Remove
	case of header with just condition.
	(ch_base::copy_headers): Exclude infinite loops from any
	processing.
	(pass_ch::execute): Record exits.

	* gcc.dg/tree-ssa/copy-headers-2.c: New testcase.
	* gcc.dg/tree-ssa/copy-headers-3.c: Likewise.
	* gcc.dg/tree-ssa/copy-headers-4.c: Likewise.
	* gcc.dg/tree-ssa/loadpre6.c: Adjust.

From-SVN: r259672