[26/46] Make more use of dyn_cast in tree-vect*

[26/46] Make more use of dyn_cast in tree-vect*

If we use stmt_vec_infos to represent statements in the vectoriser,
it's then more natural to use dyn_cast when processing the statement
as an assignment, call, etc.  This patch does that in a few more places.

2018-07-31  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-vect-data-refs.c (vect_check_gather_scatter): Pass the
	gcall rather than the generic gimple stmt to gimple_call_internal_fn.
	(vect_get_smallest_scalar_type, can_group_stmts_p): Use dyn_cast
	to get gassigns and gcalls, rather than operating on generc gimple
	stmts.
	* tree-vect-stmts.c (exist_non_indexing_operands_for_use_p)
	(vect_mark_stmts_to_be_vectorized, vectorizable_store)
	(vectorizable_load, vect_analyze_stmt): Likewise.
	* tree-vect-loop.c (vectorizable_reduction): Likewise gphi.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@263141 138bc75d-0d04-0410-961f-82ee72b054a4