[Libre-soc-isa] [Bug 535] setvl/setvli encoding & future reg file expansion

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Tue Dec 1 14:14:01 GMT 2020


--- Comment #2 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
i took another look at RVV setvl/i and some example loops: a critical aspect of
setvl/i is that there is an RT and an RA.

* RA is the "number of times that we would *like* to run the hw-loop"
* RT contains a copy of VL that is set to the *actual* hw-loop quantity
* at the end of the loop, the actual amount can be subtracted.

    vsetvli a3, a0   #  update a3 with vl (# of elements this iteration)
    sub a0, a0, a3   # Decrement count by vl
    bnez a0, loop    # Any more?

if we do not have both RT and RA the "lack" of the same will require an
additional mr (register copy) instruction.

You are receiving this mail because:
You are on the CC list for the bug.

More information about the Libre-SOC-ISA mailing list