xfb_decl_assign_location() assumes that arrays are going to be packed. But some conditions might prevent packing (e.g: explicit location or smooth interpolation mode). Instead of assuming that packing will happen, this commit adds a check to determine if it'll happen and use the result to compute the proper location. Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/2214 Acked-by: Marek Olšák <marek.olsak@amd.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18175>