gcc/
	* tree-vect-data-refs.c (vect_grouped_store_supported): New
	check for stores group of length 3.
	(vect_permute_store_chain): New permutations for stores group of
	length 3.
	* tree-vect-stmts.c (vect_model_store_cost): Change cost
	of vec_perm_shuffle for the new permutations.

gcc/testsuite/
	PR tree-optimization/52252
	* gcc.dg/vect/pr52252-st.c: Test on stores group of size 3.

From-SVN: r211439