Implement interleave via permutation.

Implement interleave via permutation.

        * expr.c (expand_expr_real_2) [VEC_EXTRACT_EVEN_EXPR]: Use binop.
        [VEC_EXTRACT_ODD_EXPR, VEC_INTERLEAVE_HIGH_EXPR]: Likewise.
        [VEC_INTERLEAVE_LOW_EXPR]: Likewise.
        * optabs.c (expand_binop): Implement vec_interleave_high_optab,
        vec_interleave_low_optab, vec_extract_even_optab,
        vec_extract_odd_optab with expand_vec_perm.
        (can_vec_perm_for_code_p): New.
        * optabs.h: Update.
        * tree-vect-data-refs.c (vect_strided_store_supported): Allow for
        fallback via can_vec_perm_for_code_p.
        (vect_strided_load_supported): Likewise.
        * tree-vect-generic.c (expand_vector_operations_1): Never lower
        VEC_INTERLEAVE_HIGH_EXPR, VEC_INTERLEAVE_LOW_EXPR,
        VEC_EXTRACT_EVEN_EXPR, VEC_EXTRACT_ODD_EXPR.

From-SVN: r180450