[libre-riscv-dev] microwatt feature request: "switch off all optimisations" mode

Luke Kenneth Casson Leighton lkcl at lkcl.net
Sat Aug 1 14:55:27 BST 2020

On Friday, July 31, 2020, Luke Kenneth Casson Leighton <lkcl at lkcl.net>

> what would you suggest here? how can we "single-step" microwatt?  clearly
> performance is not important: cycle-accurate comparisons is the goal.

i since realised that the DMI interface serves this purpose, and
investigated core_debug.vhdl

with a little bit (or a lot) of futzing about with a FSM i should be able
to run a single instruction then cycle through all of the GPRs, PC and MSR,
dumping them out.

by implementing the same interface in libresoc i can do a cycle by cycle
comparison and find the discrepancies.

it would be particularly useful to be able to get at the SPRs and the CR as
well, this way.

is there a standard for DMI address bus locations?


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