Want to clarify my understanding on R-type instruction

Question

I am now working on a simple risc-v processor which will be compatible with the following cmds:

If I don't understand wrongly, is it correct that all the instructions apart from the highlighted are in R-type? Since I am constructing a logical circuit to distinguish the two groups (R-type / non R-type). Many thanks!

Answer 1

The RISC-V specs say at page 22:

All branch instructions use the B-type instruction format.

So BEQ, BNE etc are not R, but B. SLLI is I type. The only R types here are ADD and SUB. If you really try to implement a RISC-V cpu, then it would be wise to get familiar with this documentation.