re PR tree-optimization/90316 (large compile time increase in opt / alias stmt walking for Go example)

2019-05-07  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/90316
	* tree-ssa-alias.h (get_continuation_for_phi): Take walking
	limit by reference.
	(walk_non_aliased_vuses): Take walking limit argument.
	* tree-ssa-alias.c (maybe_skip_until): Take limit and abort
	walking if it is reached instead of just counting.
	(get_continuation_for_phi): Likewise.
	(walk_non_aliased_vuses): Likewise, instead of leaving counter
	limiting to the callback.
	* tree-ssa-sccvn.c (vn_reference_lookup_2): Adjust.
	(vn_reference_lookup_3): Likewise.
	(vn_reference_lookup_pieces): Likewise.
	(vn_reference_lookup): Likewise.
	* tree-ssa-pre.c (translate_vuse_through_block): Limit walking.
	* tree-ssa-scopedtables.c (vuse_eq): Adjust.
	(avail_exprs_stack::lookup_avail_expr): Likewise.

From-SVN: r270940