[P0] Overwrite and overuse the same register in xbar

[tancheng]

s.send_rdy_vector[i] @= s.send_rdy_towards_other_tiles or s.send_accepted_towards_other_tiles from #281 (comment)

[yyan7223]

Should be discussed during tomorrow's meeting.

[tancheng]

Hi @yyan7223, any progress on this issue? Thanks~!

[yyan7223]

Sorry, I was busy in the past weeks, but I will try to fix this before May 18.