Improve handling of memory operands in ipa-icf 3/4

this patch is based on Maritn's patch
https://gcc.gnu.org/legacy-ml/gcc-patches/2019-11/msg02633.html
however based on new code that track and compare memory accesses
so it can be implemented correctly.

As shown here
https://gcc.gnu.org/pipermail/gcc-patches/2020-November/558773.html
the most common reason for function body being streamed in but merging to fail
is the mismatch in base alias set.

This patch collect base and ref types ao_alias_ptr types, stream them to WPA
and at WPA time hash is produced. Now we can use alias_sets since these these
are assumed to be same as ltrans time alias sets. This is currently not always
true - but that is pre-existing issue.  I will try to produce a testcase and
make followup patch on this (that will stream out ODR types with TYPE_CANONICAL
that is !ODR as !ODR type). However for this patch this is not a problem since
the real alias sets are finer but definitly not coarser.

We may make it possible to use canonical type hash and save some streaming, but
I think it would be better to wait for next stage1 since it is not completely
trivial WRT ODR types: either we hash ODR type names and then hash values would
be too coarse for cases we got conflict betwen C and C++ type or we do not
stream and will again get into trouble with hash values being too weak. Tried
that - we get a lot of types that are struturally same but distinguished by
ODR names (from template instantiations).

As followup I will add code for merging with mismatched base alias sets.  This
makes the aforementioned problem about ODR names less pronounced but it is
still present on pointer loads/stores which requires REF alias set mismatches.

2020-11-13  Jan Hubicka  <hubicka@ucw.cz>
	    Martin Liska  <mliska@suse.cz>

	* ipa-icf.c: Include data-streamer.h and alias.h.
	(sem_function::sem_function): Initialize memory_access_types
	and m_alias_sets_hash.
	(sem_function::hash_stmt): For memory accesses and when going to
	do lto streaming add base and ref types into memory_access_types.
	(sem_item_optimizer::write_summary): Stream memory access types.
	(sem_item_optimizer::read_section): Likewise and also iniitalize
	m_alias_sets_hash.
	(sem_item_optimizer::execute): Call
	sem_item_optimizer::update_hash_by_memory_access_type.
	(sem_item_optimizer::update_hash_by_memory_access_type): Updat.
	* ipa-icf.h (sem_function): Add memory_access_types and
	m_alias_sets_hash.

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