2011-08-26  Zdenek Dvorak  <ook@ucw.cz>
	    Tom de Vries  <tom@codesourcery.com>

	* tree-ssa-loop-ivopts.c (struct cost_pair): Add comp field.
	(struct ivopts_data): Add loop_single_exit_p field.
	(niter_for_exit): Change parameter desc_p into return value.  Return
	desc if	desc->may_be_zero.  Free desc if unused.
	(niter_for_single_dom_exit): Change return type.
	(find_induction_variables): Handle changed return type of
	niter_for_single_dom_exit.  Dump may_be_zero.
	(add_candidate_1): Keep original base and step type for IP_ORIGINAL.
	(set_use_iv_cost): Add and handle comp parameter.
	(determine_use_iv_cost_generic, determine_use_iv_cost_address): Add
	comp argument to set_use_iv_cost.
	(strip_wrap_conserving_type_conversions, expr_equal_p)
	(difference_cannot_overflow_p, iv_elimination_compare_lt): New function.
	(may_eliminate_iv): Add comp parameter.  Handle new return type of
	niter_for_exit.  Use loop_single_exit_p.  Use iv_elimination_compare_lt.
	(determine_use_iv_cost_condition): Add comp argument to set_use_iv_cost
	and may_eliminate_iv.
	(rewrite_use_compare): Move call to iv_elimination_compare to ...
	(may_eliminate_iv): Here.
	(tree_ssa_iv_optimize_loop): Initialize loop_single_exit_p.

Co-Authored-By: Tom de Vries <tom@codesourcery.com>

From-SVN: r178104