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_nothrow_flag_1): Rename to ...
	(set_nothrow_flag_1): ... this; handle interposition correctly;
	recurse on aliases and thunks.
	(cgraph_node::set_nothrow_flag): New.
	* ipa-pure-const.c (ignore_edge_for_nothrow): Ignore calls to
	functions compiled with non-call exceptions that binds to current
	def.
	(propagate_nothrow): Be safe WRT interposition.
	* cgraph.h (set_nothrow_flag): Update prototype.

	* g++.dg/ipa/nothrow-1.C: New testcase.

From-SVN: r235318