re PR tree-optimization/46590 (long compile time with -O2 and many loops)

re PR tree-optimization/46590 (long compile time with -O2 and many loops)

2012-08-22  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/46590
	* tree-ssa-alias.h (get_continuation_for_phi): Add alias query
	counter output argument.
	(walk_non_aliased_vuses): Add alias query counter argument
	to the walker callback.
	* tree-ssa-alias.c (maybe_skip_until): Add alias query counter
	output argument and count alias queries.
	(get_continuation_for_phi_1): Likewise.
	(get_continuation_for_phi): Likewise.
	(walk_non_aliased_vuses): Add alias query counter argument
	to the walker callback and allow it to abort the walk by
	returning -1.
	* tree-ssa-pre.c (translate_vuse_through_block): Adjust.
	* tree-ssa-sccvn.c (vn_reference_lookup_2): Add alias query
	counter parmeter, abort walk if that is bigger than
	--param sccvn-max-alias-queries-per-access.
	* params.def (sccvn-max-alias-queries-per-access): New param.
	* doc/invoke.texi (sccvn-max-alias-queries-per-access): Document.

From-SVN: r190594