refactor LIM a bit

refactor LIM a bit

This refactors LIM to eschew alloc_aux_for_edges and re-uses the RPO
order of the move_computations walk for invariantness computation as well.
It also removes one unnecessary sorting (but retaining it as checking
code because we bsearch the vector) and moves edge insert commit code
to the place where it doesn't have to scan all the functions edges.

This was all done when investigating whether LIM can be refactored
to work on a specific loop for on-demand processing (but we're not
there yet).

2020-08-05  Richard Biener  <rguenther@suse.de>

	* tree-ssa-loop-im.c (invariantness_dom_walker): Remove.
	(invariantness_dom_walker::before_dom_children): Move to ...
	(compute_invariantness): ... this function.
	(move_computations): Inline ...
	(tree_ssa_lim): ... here, share RPO order and avoid some
	cfun references.
	(analyze_memory_references): Remove sorting of location
	lists, instead assert they are sorted already when checking.
	(prev_flag_edges): Remove.
	(execute_sm_if_changed): Pass down and adjust prev edge state.
	(execute_sm_exit): Likewise.
	(hoist_memory_references): Likewise.  Commit edge insertions
	of each processed exit.
	(store_motion_loop): Do not commit edge insertions on all
	edges in the function.
	(tree_ssa_lim_initialize): Do not call alloc_aux_for_edges.
	(tree_ssa_lim_finalize): Do not call free_aux_for_edges.