poly_int: vector_builder element count

This patch changes the number of elements in a vector being built
by a vector_builder from unsigned int to poly_uint64.  The case
in which it isn't a constant is the one that motivated adding
the vector encoding in the first place.

2018-01-03  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* vector-builder.h (vector_builder::m_full_nelts): Change from
	unsigned int to poly_uint64.
	(vector_builder::full_nelts): Update prototype accordingly.
	(vector_builder::new_vector): Likewise.
	(vector_builder::encoded_full_vector_p): Handle polynomial full_nelts.
	(vector_builder::operator ==): Likewise.
	(vector_builder::finalize): Likewise.
	* int-vector-builder.h (int_vector_builder::int_vector_builder):
	Take the number of elements as a poly_uint64 rather than an
	unsigned int.
	* vec-perm-indices.h (vec_perm_indices::m_nelts_per_input): Change
	from unsigned int to poly_uint64.
	(vec_perm_indices::vec_perm_indices): Update prototype accordingly.
	(vec_perm_indices::new_vector): Likewise.
	(vec_perm_indices::length): Likewise.
	(vec_perm_indices::nelts_per_input): Likewise.
	(vec_perm_indices::input_nelts): Likewise.
	* vec-perm-indices.c (vec_perm_indices::new_vector): Take the
	number of elements per input as a poly_uint64 rather than an
	unsigned int.  Use the original encoding for variable-length
	vectors, rather than clamping each individual element.
	For the second and subsequent elements in each pattern,
	clamp the step and base before clamping their sum.
	(vec_perm_indices::series_p): Handle polynomial element counts.
	(vec_perm_indices::all_in_range_p): Likewise.
	(vec_perm_indices_to_tree): Likewise.
	(vec_perm_indices_to_rtx): Likewise.
	* tree-vect-stmts.c (vect_gen_perm_mask_any): Likewise.
	* tree-vector-builder.c (tree_vector_builder::new_unary_operation)
	(tree_vector_builder::new_binary_operation): Handle polynomial
	element counts.  Return false if we need to know the number
	of elements at compile time.
	* fold-const.c (fold_vec_perm): Punt if the number of elements
	isn't known at compile time.

From-SVN: r256165