For the cover letter of this patch-set, please checkout D146872.
Depends on D147731.
This is the 4th patch of the patch-set.
This patch is a proof-of-concept and will be extended to full coverage
in the future. Currently, the old non-tuple unit-stride segment store is
not removed, and only signed integer unit-strided segment store of NF=2,
EEW=32 is defined here.
Offset variable