middle-end: skip checking loop exits if loop malformed [PR111878]

middle-end: skip checking loop exits if loop malformed [PR111878]

Before my refactoring if the loop->latch was incorrect then find_loop_location
skipped checking the edges and would eventually return a dummy location.

It turns out that a loop can have
loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS) but also not have a latch
in which case get_loop_exit_edges traps.

This restores the old behavior.

gcc/ChangeLog:

	PR tree-optimization/111878
	* tree-vect-loop-manip.cc (find_loop_location): Skip edges check if
	latch incorrect.

gcc/testsuite/ChangeLog:

	PR tree-optimization/111878
	* gcc.dg/graphite/pr111878.c: New test.