tree-core.h: Document use of deprecated_flag in SSA_NAME.

tree-core.h: Document use of deprecated_flag in SSA_NAME.

2018-08-29  Richard Biener  <rguenther@suse.de>

	* tree-core.h: Document use of deprecated_flag in SSA_NAME.
	* tree.h (SSA_NAME_POINTS_TO_READONLY_MEMORY): Define.
	* tree-into-ssa.c (pass_build_ssa::execute): Initialize
	function parameters SSA_NAME_POINTS_TO_READONLY_MEMORY from fnspec.
	* tree-ssa-sccvn.c (const_parms, init_const_parms): Remove.
	(vn_reference_lookup_3): Remove use of const_parms.
	(free_rpo_vn): Do not free const_parms.
	(do_rpo_vn): Do not call init_const_parms.
	* tree-ssa-alias.c (refs_may_alias_p_1): Honor
	SSA_NAME_POINTS_TO_READONLY_MEMORY.
	(call_may_clobber_ref_p_1): Likewise.

From-SVN: r263958