gimple-fold.c (get_base_constructor): Add VIEW_CONVERT case, handle all tcc_constant bases and valueize SSA names.

2016-07-19  Richard Biener  <rguenther@suse.de>

	* gimple-fold.c (get_base_constructor): Add VIEW_CONVERT case,
	handle all tcc_constant bases and valueize SSA names.
	* tree-ssa-sccvn.c (fully_constant_vn_reference_p): Handle
	tcc_constant bases.

	* c-c++-common/vector-subscript-6.c: New testcase.
	* c-c++-common/vector-subscript-7.c: Likewise.

From-SVN: r238475