This patch would like to introduce the combine of vec_dup + vssub.vv into vssub.vx on the cost value of GR2VR. The late-combine will take place if the cost of GR2VR is zero, or reject the combine if non-zero like 1, 2, 15 in test. There will be two cases for the combine:
Jeff has already pre-acked this so it's good to go. I'm seeing a few failures in the CI, though. Could you check if they're real?
-- Regards Robin
