loops: Invoke lim after successful loop interchange

This patch makes the entry point to loop invariant motion public, so
that it can be called after loop interchange when that pass has
swapped loops.  This avoids the non-LTO -Ofast run-time regressions of
410.bwaves and 503.bwaves_r (which are 19% and 15% faster than current
master on an AMD zen2 machine) while not introducing a full LIM pass
into the pass pipeline.

The patch also adds a parameter which allows not to perform any store
motion so that it is not done after an interchange.

gcc/ChangeLog:

2020-11-12  Martin Jambor  <mjambor@suse.cz>

	PR tree-optimization/94406
	* tree-ssa-loop-im.c (tree_ssa_lim): Renamed to
	loop_invariant_motion_in_fun, added a parameter to control store
	motion.
	(pass_lim::execute): Adjust call to tree_ssa_lim, now
	loop_invariant_motion_in_fun.
	* tree-ssa-loop-manip.h (loop_invariant_motion_in_fun): Declare.
	* gimple-loop-interchange.cc (pass_linterchange::execute): Call
	loop_invariant_motion_in_fun if any interchange has been done.