tree-optimization/95045 - fix SM with exit exiting multiple loops

Since we apply SM to an edge which exits multiple loops we have
to make sure to commit insertions on it immediately since otherwise
store order is not preserved.

2020-05-12  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/95045
	* dbgcnt.def (lim): Add debug-counter.
	* tree-ssa-loop-im.c: Include dbgcnt.h.
	(find_refs_for_sm): Use lim debug counter for store motion
	candidates.
	(do_store_motion): Rename form store_motion.  Commit edge
	insertions...
	(store_motion_loop): ... here.
	(tree_ssa_lim): Adjust.