* gcc.dg/tree-ssa/foldconst-2.c: New testcase.
	* gcc.dg/tree-ssa/foldconst-3.c: New testcase.

	* gimple-fold.c (maybe_fold_reference): Use fold_const_aggregate_ref.
	* tree-ssa-ccp.c (fold_const_aggregate_ref): Use
	fold_read_from_constant_string.

	* gimple.h (canonicalize_constructor_val): Declare.
	* gimple-fold.c (canonicalize_constructor_val): New function.
	(get_symbol_constant_value):Use it.
	* tree-ssa-ccp.c (fold_const_aggregate_ref): Likewise.

From-SVN: r163861