PR tree-optimization/27283

	PR tree-optimization/27283
	* tree-ssa-loop-ivopts.c (struct nfe_cache_elt): Store just trees,
	not whole # of iteration descriptions.
	(niter_for_exit): Return just # of iterations.  Fail if # of iterations
	uses abnormal ssa name.
	(niter_for_single_dom_exit): Ditto.
	(find_induction_variables, may_eliminate_iv): Expect niter_for_exit to
	return just the number of iterations.

	* g++.dg/tree-ssa/pr27283.C: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@113427 138bc75d-0d04-0410-961f-82ee72b054a4