Add new parameter to vec_perm_const hook for specifying operand mode.

Add new parameter to vec_perm_const hook for specifying operand mode.

The rationale of the patch is to support vec_perm_expr of the form:
lhs = vec_perm_expr<rhs, mask>
where lhs and rhs are vector types with different lengths but have
same element type. For example, lhs is SVE vector and rhs
is corresponding AdvSIMD vector.

It would also allow to express extract even/odd and interleave operations
with a VEC_PERM_EXPR.  The interleave currently has the issue that we have
to artificially widen the inputs with "dont-care" elements.

gcc/ChangeLog:

	* target.def (vec_perm_const): Define new parameter op_mode and
	update doc.
	* doc/tm.texi: Regenerate.
	* config/aarch64/aarch64.cc (aarch64_vectorize_vec_perm_const): Adjust
	vec_perm_const hook to add new parameter op_mode and return false
	if result and operand modes do not match.
	* config/arm/arm.cc (arm_vectorize_vec_perm_const): Likewise.
	* config/gcn/gcn.cc (gcn_vectorize_vec_perm_const): Likewise.
	* config/ia64/ia64.cc (ia64_vectorize_vec_perm_const): Likewise.
	* config/mips/mips.cc (mips_vectorize_vec_perm_const): Likewise.
	* config/rs6000/rs6000.cc (rs6000_vectorize_vec_perm_const): Likewise
	* config/s390/s390.cc (s390_vectorize_vec_perm_const): Likewise.
	* config/sparc/sparc.cc (sparc_vectorize_vec_perm_const): Likewise.
	* config/i386/i386-expand.cc (ix86_vectorize_vec_perm_const): Likewise.
	* config/i386/i386-expand.h (ix86_vectorize_vec_perm_const): Adjust
	prototype.
	* config/i386/sse.md (ashrv4di3): Adjust call to vec_perm_const hook.
	(ashrv2di3): Likewise.
	* optabs.cc (expand_vec_perm_const): Likewise.
	* optabs-query.h (can_vec_perm_const_p): Adjust prototype.
	* optabs-query.cc (can_vec_perm_const_p): Define new parameter
	op_mode and pass it to vec_perm_const hook.
	(can_mult_highpart_p): Adjust call to can_vec_perm_const_p.
	* match.pd (vec_perm X Y CST): Likewise.
	* tree-ssa-forwprop.cc (simplify_vector_constructor): Likewise.
	* tree-vect-data-refs.cc (vect_grouped_store_supported): Likewise.
	(vect_grouped_load_supported): Likewise.
	(vect_shift_permute_load_chain): Likewise.
	* tree-vect-generic.cc (lower_vec_perm): Likewise.
	* tree-vect-loop-manip.cc (interleave_supported_p): Likewise.
	* tree-vect-loop.cc (have_whole_vector_shift): Likewise.
	* tree-vect-patterns.cc (vect_recog_rotate_pattern): Likewise.
	* tree-vect-slp.cc (can_duplicate_and_interleave_p): Likewise.
	(vect_transform_slp_perm_load): Likewise.
	(vectorizable_slp_permutation): Likewise.
	* tree-vect-stmts.cc (perm_mask_for_reverse): Likewise.
	(vectorizable_bswap): Likewise.
	(scan_store_can_perm_p): Likewise.
	(vect_gen_perm_mask_checked): Likewise.