A RISCV frontend for powdr is already available.

How to run the Rust-RISCV example

# Install the riscv target for the rust compiler
rustup target add riscv32imac-unknown-none-elf
# Run the powdr-rs compiler. It will generate files in ./output/
powdr-rs compile riscv/tests/riscv_data/sum -o output
# Run powdr to compile powdr-asm to powdr-PIL and generate the witness
# -i specifies the prover witness input (see below)
powdr pil output/sum.asm -o output -f -i 10,2,4,6

The example Rust code verifies that a supplied list of integers sums up to a specified value.

{{#include ../../../riscv/tests/riscv_data/sum/src/lib.rs}}

The function get_prover_input reads a number from the list supplied with -i.

This is just a first mechanism to provide access to the outside world. The plan is to be able to call arbitrary user-defined ffi functions that will translate to prover queries, and can then ask for e.g. the value of a storage slot at a certain address or the root hash of a Merkle tree.