re PR fortran/67170 (PRE can't hoist out a readonly argument)

re PR fortran/67170 (PRE can't hoist out a readonly argument)

2015-09-29  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/67170
	* tree-ssa-alias.h (get_continuation_for_phi): Adjust
	the translate function pointer parameter to get the
	bool whether to disambiguate only by reference.
	(walk_non_aliased_vuses): Likewise.
	* tree-ssa-alias.c (maybe_skip_until): Adjust.
	(get_continuation_for_phi_1): Likewise.
	(get_continuation_for_phi): Likewise.
	(walk_non_aliased_vuses): Likewise.
	* tree-ssa-sccvn.c (const_parms): New bitmap.
	(vn_reference_lookup_3): Adjust for interface change.
	Disambiguate parameters pointing to readonly memory.
	(free_scc_vn): Free const_parms.
	(run_scc_vn): Initialize const_parms from a fn spec attribute.

	* gfortran.dg/pr67170.f90: New testcase.

From-SVN: r228244