* tree.c (build_zero_cst): New.
	* tree.h (build_zero_cst): Declare.
	* tree-ssa-ccp.c (get_constant_value): Accept general operands.
	(get_base_constructor): Break out from ...
	(fold_const_aggregate_ref): Here; handle empty constructors.

	* gcc.dg/torture/pr23821.c: Drop static keyword.
	* gcc.dg/tree-ssa/loop-19.c: Likewise.
	* gcc.dg/tree-ssa/foldconst-4.c: New.

From-SVN: r164250