re PR rtl-optimization/64081 (r217828 prevents RTL loop unroll)

re PR rtl-optimization/64081 (r217828 prevents RTL loop unroll)

gcc/

	PR rtl-optimization/64081
	* loop-iv.c (def_pred_latch_p): New function.
	(latch_dominating_def): Allow specific cases with non-single
	definitions.
	(iv_get_reaching_def): Likewise.
	(check_complex_exit_p): New function.
	(check_simple_exit): Use check_complex_exit_p to allow certain cases
	with exits not executing on any iteration.

gcc/testsuite/

	PR rtl-optimization/64081
	* gcc.dg/pr64081.c: New test.

From-SVN: r219842