c++: Pseudo-destructor ends object lifetime.

c++: Pseudo-destructor ends object lifetime.

P0593R6 is mostly about a new object model whereby malloc and the like are
treated as implicitly starting the lifetime of whatever trivial types are
necessary to give the program well-defined semantics; that seems only
relevant to TBAA, and is not implemented here.

The paper also specifies that a pseudo-destructor call (a destructor call
for a non-class type) ends the lifetime of the object like a destructor call
for an object of class type, even though it doesn't call a destructor; this
patch implements that change.

The paper was voted as a DR, so I'm applying this change to all standard
levels.  Like class end-of-life clobbers, it is controlled by
-flifetime-dse.

gcc/cp/ChangeLog:

	* pt.c (type_dependent_expression_p): A pseudo-dtor can be
	dependent.
	* semantics.c (finish_call_expr): Use build_trivial_dtor_call for
	pseudo-destructor.
	(finish_pseudo_destructor_expr): Leave type NULL for dependent arg.

gcc/testsuite/ChangeLog:

	* g++.dg/opt/flifetime-dse7.C: New test.