This patch makes RTL DSE use poly_int for offsets and sizes.
The local phase can optimise them normally but the global phase
treats them as wild accesses.

2017-12-20  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* dse.c (store_info): Change offset and width from HOST_WIDE_INT
	to poly_int64.  Update commentary for positions_needed.large.
	(read_info_type): Change offset and width from HOST_WIDE_INT
	to poly_int64.
	(set_usage_bits): Likewise.
	(canon_address): Return the offset as a poly_int64 rather than
	a HOST_WIDE_INT.  Use strip_offset_and_add.
	(set_all_positions_unneeded, any_positions_needed_p): Use
	positions_needed.large to track stores with non-constant widths.
	(all_positions_needed_p): Likewise.  Take the offset and width
	as poly_int64s rather than ints.  Assert that rhs is nonnull.
	(record_store): Cope with non-constant offsets and widths.
	Nullify the rhs of an earlier store if we can't tell which bytes
	of it are needed.
	(find_shift_sequence): Take the access_size and shift as poly_int64s
	rather than ints.
	(get_stored_val): Take the read_offset and read_width as poly_int64s
	rather than HOST_WIDE_INTs.
	(check_mem_read_rtx, scan_stores, scan_reads, dse_step5): Handle
	non-constant offsets and widths.

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

From-SVN: r255873