Make SRA less strict with memcpy performing MEM_REFs

Make SRA less strict with memcpy performing MEM_REFs

2019-03-10  Martin Jambor  <mjambor@suse.cz>

	PR tree-optimization/85762
	PR tree-optimization/87008
	PR tree-optimization/85459
	* tree-sra.c (contains_vce_or_bfcref_p): New parameter, set the bool
	it points to if there is a type changing MEM_REF.  Adjust all callers.
	(build_accesses_from_assign): Disable total scalarization if
	contains_vce_or_bfcref_p returns true through the new parameter, for
	both rhs and lhs.

	testsuite/
	* g++.dg/tree-ssa/pr87008.C: New test.
	* gcc.dg/guality/pr54970.c: Xfail tests querying a[0] everywhere.

From-SVN: r269556