middle-end/112830 - avoid gimplifying non-default addr-space assign to memcpy

middle-end/112830 - avoid gimplifying non-default addr-space assign to memcpy

The following avoids turning aggregate copy involving non-default
address-spaces to memcpy since that is not prepared for that.

GIMPLE verification no longer accepts WITH_SIZE_EXPR in aggregate
copies, the following re-allows that for the RHS.  I also needed
to adjust one assert in DCE.

get_memory_address is used for string builtin expansion, so instead
of fixing that up for non-generic address-spaces I've put an assert
there.

I'll note that the same issue exists for initialization from an
empty CTOR which we gimplify to a memset call but since we are
not prepared to handle RTL expansion of the original VLA init and
I failed to provide test coverage (without extending the GNU C
extension for VLA structs) and the Ada frontend (or other frontends)
to not have address-space support the patch instead asserts we only
see generic address-spaces there.

	PR middle-end/112830
	* gimplify.cc (gimplify_modify_expr): Avoid turning aggregate
	copy of non-generic address-spaces to memcpy.
	(gimplify_modify_expr_to_memcpy): Assert we are dealing with
	a copy inside the generic address-space.
	(gimplify_modify_expr_to_memset): Likewise.
	* tree-cfg.cc (verify_gimple_assign_single): Allow
	WITH_SIZE_EXPR as part of the RHS of an assignment.
	* builtins.cc (get_memory_address): Assert we are dealing
	with the generic address-space.
	* tree-ssa-dce.cc (ref_may_be_aliased): Handle WITH_SIZE_EXPR.

	* gcc.target/avr/pr112830.c: New testcase.
	* gcc.target/i386/pr112830.c: Likewise.