Creating new instructions in RISC-V

[teotro]

Hi everyone,

I am new in RISC-V and I am using Pulpissimo.
Is there somewhere a tutorial of how to create new custom instructions in RISC-V?
For instance, a "mod" instruction.
What are the steps to do it?

Thank you in advance,
Theodoros

[bluewww]

If you are asking for a full tutorial how to do this then no we don't have such a thing.

I would look into the cv32e40p core and look into the id stage (where instructions are decoded) and ex stage (where instructions are executed) to get started. Maybe try to trace/follow the signals belonging to an already implemented instruction for example "add".