This patch makes pass_store_merging track polynomial sizes
and offsets.  store_immediate_info remains restricted to stores
with a constant offset and size.

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

gcc/
	* poly-int-types.h (round_down_to_byte_boundary): New macro.
	(round_up_to_byte_boundary): Likewise.
	* expr.h (get_bit_range): Add temporary shim.
	* gimple-ssa-store-merging.c (store_operand_info): Change the
	bitsize, bitpos, bitregion_start and bitregion_end fields from
	unsigned HOST_WIDE_INT to poly_uint64.
	(merged_store_group): Likewise load_align_base.
	(compatible_load_p, compatible_load_p): Update accordingly.
	(imm_store_chain_info::coalesce_immediate_stores): Likewise.
	(split_group, imm_store_chain_info::output_merged_store): Likewise.
	(mem_valid_for_store_merging): Return the bitsize, bitpos,
	bitregion_start and bitregion_end as poly_uint64s rather than
	unsigned HOST_WIDE_INTs.  Track polynomial offsets internally.
	(handled_load): Take the bitsize, bitpos,
	bitregion_start and bitregion_end as poly_uint64s rather than
	unsigned HOST_WIDE_INTs.
	(pass_store_merging::process_store): Update call to
	mem_valid_for_store_merging.

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

From-SVN: r255894