PR tree-optimization/18316
	PR tree-optimization/19126
	* tree.c (build_int_cst_type): Avoid shift by size of type.
	* tree-scalar-evolution.c (simple_iv): Add allow_nonconstant_step
	argument.
	* tree-scalar-evolution.h (simple_iv): Declaration changed.
	* tree-ssa-loop-ivopts.c (struct iv_cand): Add depends_on
	field.
	(dump_cand): Dump depends_on information.
	(determine_biv_step): Add argument to simple_iv call.
	(contains_abnormal_ssa_name_p): Handle case expr == NULL.
	(find_bivs, find_givs_in_stmt_scev): Do not require step to be a
	constant.
	(add_candidate_1): Record depends_on for candidates.
	(tree_int_cst_sign_bit, constant_multiple_of): New functions.
	(get_computation_at, get_computation_cost_at, may_eliminate_iv):
	Handle ivs with nonconstant step.
	(iv_ca_set_remove_invariants, iv_ca_set_add_invariants): New functions.
	(iv_ca_set_no_cp, iv_ca_set_cp): Handle cand->depends_on.
	(create_new_iv): Unshare the step before passing it to create_iv.
	(free_loop_data): Free cand->depends_on.
	(build_addr_strip_iref): New function.
	(find_interesting_uses_address): Use build_addr_strip_iref.
	(strip_offset_1): Split the recursive part from strip_offset.
	Strip constant offset component_refs and array_refs.
	(strip_offset): Split the recursive part to strip_offset_1.
	(add_address_candidates): Removed.
	(add_derived_ivs_candidates): Do not use add_address_candidates.
	(add_iv_value_candidates): Add candidates with stripped constant
	offset.  Consider all candidates with initial value 0 important.
	(struct affine_tree_combination): New.
	(aff_combination_const, aff_combination_elt, aff_combination_scale,
	aff_combination_add_elt, aff_combination_add,
	tree_to_aff_combination, add_elt_to_tree, aff_combination_to_tree,
	fold_affine_sum): New functions.
	(get_computation_at): Use fold_affine_sum.
	* tree-ssa-loop-manip.c (create_iv): Handle ivs with nonconstant step.
	* tree-ssa-loop-niter.c (number_of_iterations_exit): Add argument
	to simple_iv call.

	* gcc.dg/tree-ssa/loop-8.c: New test.

From-SVN: r99059