[Libre-soc-dev] [RFC] SVP64 Branches (contd)

[lkcl]

On August 26, 2021 3:48:06 PM UTC, lkcl <luke.leighton at gmail.com> wrote:
>https://libre-soc.org/openpower/sv/branches/
>
>after realising that CTR can be used to save instructions in tight
>Vector loops by not needing an explicit GPR subtraction, comparison,
>and etc etc, i also realised that there are even more possible modes
>that might be useful.

again we are running out of bits, or have to start overloading even more fields from the 24 bit RM.

question:

does it make sense for CTR to *always* be decremented "per element"?

this would kinda match with the whole Sub-PC thing: CTR counts elements not SVP64 instructions.

are there any circumstances where you would want to count *batches*? i.e. the number of SVP64 Branch Instructions

and, if so, is it sufficient to simply pre-multiply CTR by VL, such that, again, CTR may be decremented by "number of elements", not "number of times sv.bc is called"?

l.