[Libre-soc-dev] SVP64 auto-generated table for microwatt decoding

[Luke Kenneth Casson Leighton]

On Saturday, February 27, 2021, Luke Kenneth Casson Leighton <lkcl at lkcl.net>
wrote:

> the columns are:
> * Twin/Single Predication
> * EXTRA2/3
> * in1/2/3/out

drat!

i just realised / remembered, we shifted RS from in3 to in1 in the CSV
files.

this because by doing so, because we have separate pipelines for ALU
Logical ShiftRot etc they can all be 2-operand not 3-operand and we reduce
wires and Muxes as a result.

Microwatt drops everything through one path (execute1.vhdl) which then
manually routes to sub-processor modules (logical.vhdl) so it is less of a
priority, although Muxes would be reduced.

i *believe* last time i looked at this that the move of RS from in3 to in1
was 100% consistent, meaning that it can be spotted and moved with a
post-processing function.

the corresponding sv_in1/3 columns would then also shift automatically.

l.



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