re PR c++/70018 (Possible issue around IPO and C++ comdats discovered as pure/const)

re PR c++/70018 (Possible issue around IPO and C++ comdats discovered as pure/const)

	PR ipa/70018
	* cgraph.c (cgraph_set_const_flag_1): Only set as pure if
	function does not bind to current def.
	* ipa-pure-const.c (worse_state): Add FROM and TO parameters;
	handle conservatively calls to functions that does not need to bind
	to current def.
	(check_call): Update call of worse_state.
	(ignore_edge_for_nothrow): Update.
	(ignore_edge_for_pure_const): Likewise.
	(propagate_pure_const): Update calls to worse_state.
	(skip_function_for_local_pure_const): Reformat comments.

	* g++.dg/ipa/pure-const-1.C: New testcase.
	* g++.dg/ipa/pure-const-2.C: New testcase.
	* g++.dg/ipa/pure-const-3.C: New testcase.

From-SVN: r235065