Enable more WITH_SIZE_EXPR processing

Enable more WITH_SIZE_EXPR processing

This enables the alias machinery for WITH_SIZE_EXPR which can appear
in call LHS and arguments.  In particular this drops the NULL
return from get_base_address and it adjusts get_ref_base_and_extent
and friends to use the size information in WITH_SIZE_EXPR and
look through it for further processing.

2021-05-19  Richard Biener  <rguenther@suse.de>

	* builtins.c (get_object_alignment_1): Strip outer
	WITH_SIZE_EXPR.
	* tree-dfa.c (get_ref_base_and_extent): Handle outer
	WITH_SIZE_EXPR for size processing and process the
	containing ref.
	* tree-ssa-alias.c (ao_ref_base_alias_set): Strip
	outer WITH_SIZE_EXPR.
	(ao_ref_base_alias_ptr_type): Likewise.
	(refs_may_alias_p_2): Allow WITH_SIZE_EXPR in ref->ref
	and handle that accordingly, stripping it for the
	core alias workers.
	* tree.c (get_base_address): Handle WITH_SIZE_EXPR by
	looking through it instead of returning NULL.