poly_int: same_addr_size_stores_p

poly_int: same_addr_size_stores_p

This patch makes tree-ssa-alias.c:same_addr_size_stores_p handle
poly_int sizes and offsets.

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

gcc/
	* tree-ssa-alias.c (same_addr_size_stores_p): Take the offsets and
	sizes as poly_int64s rather than HOST_WIDE_INTs.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>
From-SVN: r255870