poly_int: build_ref_for_offset

poly_int: build_ref_for_offset

This patch changes the offset parameter to build_ref_for_offset
from HOST_WIDE_INT to poly_int64.

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

gcc/
	* ipa-prop.h (build_ref_for_offset): Take the offset as a poly_int64
	rather than a HOST_WIDE_INT.
	* tree-sra.c (build_ref_for_offset): Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>
From-SVN: r255931