i965/fs: half exec_size when dealing with 64 bits attributes

The HW has a restriction that only vertical stride may cross register
boundaries. Until now this was only handled on VGRFs at
rw_reg_from_fs_reg, but it is also needed for attributes.

v2:
 * Remove reference to commit id on commit message (Juan Suarez)
 * Simplify code that compute final exec_size (Ian Romanick)
 * Use REG_SIZE on that same code (Kenneth Graunke)

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
1 file changed