poly_int: get_bit_range

poly_int: get_bit_range

This patch makes get_bit_range return the range and position as poly_ints.

2017-12-21  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* expr.h (get_bit_range): Return the bitstart and bitend as
	poly_uint64s rather than unsigned HOST_WIDE_INTs.  Return the bitpos
	as a poly_int64 rather than a HOST_WIDE_INT.
	* expr.c (get_bit_range): Likewise.
	(expand_assignment): Update call accordingly.
	* fold-const.c (optimize_bit_field_compare): Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>
From-SVN: r255912