Implement DSE of dead functions calls storing memory.

Implement DSE of dead functions calls storing memory.

gcc/ChangeLog:

2021-11-13  Jan Hubicka  <hubicka@ucw.cz>

	* ipa-modref.c (modref_summary::modref_summary): Clear new flags.
	(modref_summary::dump): Dump try_dse.
	(modref_summary::finalize): Add FUN attribute; compute try-dse.
	(analyze_function): Update.
	(read_section): Update.
	(update_signature): Update.
	(pass_ipa_modref::execute): Update.
	* ipa-modref.h (struct modref_summary):
	* tree-ssa-alias.c (ao_ref_init_from_ptr_and_range): Export.
	* tree-ssa-alias.h (ao_ref_init_from_ptr_and_range): Declare.
	* tree-ssa-dse.c (dse_optimize_call): New function.
	(dse_optimize_stmt): Use it.

gcc/testsuite/ChangeLog:

2021-11-13  Jan Hubicka  <hubicka@ucw.cz>

	* g++.dg/cpp1z/inh-ctor23.C: Fix template
	* g++.dg/ipa/ipa-icf-4.C: Fix template
	* gcc.dg/tree-ssa/modref-dse-1.c: New test.
	* gcc.dg/tree-ssa/modref-dse-2.c: New test.