sra: Avoid totally scalarizing overallping field_decls (PR 93667)

sra: Avoid totally scalarizing overallping field_decls (PR 93667)

[[no_unique_address]] C++ attribute can cause two fields of a
RECORD_TYPE overlap, which currently confuses the totally scalarizing
code into creating invalid access tree.  For GCC 10, I'd like to
simply disable total scalarization of types where this happens.

For GCC 11 I'll write down a TODO item to enable total scalarization
of cases like this where the problematic fields are basically empty -
despite having a non-zero size - i.e. when they are just RECORD_TYPEs
without any data fields.

2020-02-19  Martin Jambor  <mjambor@suse.cz>

	gcc/

	PR tree-optimization/93667
	* tree-sra.c (scalarizable_type_p): Return false if record fields
	do not follow wach other.

	gcc/testsuite/

	PR tree-optimization/93667
	* g++.dg/tree-ssa/pr93667.C: New test.