[otbn,dv] Add a handy wrapper to run lots of Verilated tests

[rswarbrick]

This is a "pre-dv-only" thing, but it's a darn sight faster than
running VCS. Example usage:

hw/ip/otbn/dv/verilator/run-some.py --size=1500 --count=10 XXX

[sriyerg]

FYI, DVSim already supports Verilator. Here's the hjson config file for the chip level:
https://github.com/lowRISC/opentitan/blob/master/hw/top_earlgrey/dv/verilator/verilator_sim_cfg.hjson

[rswarbrick]

That would probably work well if someone improves the dvsim scheduler to be able to run a job in less than a second. As it is, I suspect running ninja (or make) directly is massively quicker for examples like this where each job takes a very short time.

When dvsim is faster, I'd be very happy to revisit this! Until then, getting this working took half an hour and has already saved me time. I think we should merge this as a stop-gap.

[sriyerg]

That would probably work well if someone improves the dvsim scheduler to be able to run a job in less than a second. As it is, I suspect running ninja (or make) directly is massively quicker for examples like this where each job takes a very short time.

When dvsim is faster, I'd be very happy to revisit this! Until then, getting this working took half an hour and has already saved me time. I think we should merge this as a stop-gap.

I agree quite a few parts of DVSim are still inefficient. However, it will be great to see quantitative data showing how slow DVSim really is, rather than make assumptions. Would you please add a short README explaining what / how are tests run? I would like to take a stab at porting this over to DVSim (later, when I have the time). For now, feel free to proceed with this.