alt Hacker NewsBit manipulation instructions are part and parcel of any curriculum that teaches CPU architecture. They are the basic building blocks for many more complex instructions.
https://five-embeddev.com/riscv-bitmanip/1.0.0/bitmanip.html
I can see quite a few items on that list that imnsho should have been included in the core and for the life of me I can't see the rationale behind leaving them out. Even the most basic 8 bit CPU had various shifts and rolls baked in.
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Yeah I don’t get it. Shifts and rolls are among the simplest of all instructions to implement because they can be done with just wires, zero gates. Hard to imagine a justification for leaving them out.
32-bit barrel shifters consume significant area and RISC-V was developed to support resource constrained low cost embedded hardware in a minimal ISA implementation.
This is the reason behind the profiles like RVA23 which include bitmanip, vector and a large number of other extensions. Real chips coming very soon will all be RVA23.