Scheme utility procedures for the RISC-V instruction set architecture.

The feature set of provided procedures is centered around easing the development of utilities for RISC-V (especially instruction set simulators). Currently the following features are provided:

• decode.scm: Decoding of RISC-V instructions.
• encode.scm: Encoding of RISC-V instructions.
• convert.scm: Conversion from/to different representations.
• opcodes.scm: Constants for instruction opcodes (currently rv32i only).

The code is supposed to be used from a Scheme REPL, no binaries are provided. The Scheme files in the riscv/ directory are mostly(?) R7RS compatible. It should be possible to use them with any standard compliant Scheme implementation which provides an SRFI-151 module. Just load the files you want to use using (load "riscv/<file>.scm") from your Scheme REPL.

If your favorite Scheme implementation is CHICKEN, read on.

The API is intentionally very low-level. Nonetheless, many fun things can be done with it. The following example takes an existing JAL instruction (e.g. as extracted from a riscv32-unknown-elf-objdump -d output) and modifies it to jump somewhere else.

$ csi
> (import riscv)
> (set! jal #x0100056f)
> (instr-j-imm jal)
16
> (j-type (instr-opcode jal) (instr-rd jal) 32)
33555823

The value 33555823 (0x200056f) is RISC-V machine code for a JAL instruction holing the value 32 (instead of 16) as a J-immediate. This can be easily verified using:

> (set! jal-new 33555823)
> (instr->hex jal-new)
"#x200056f"
> (instr-j-imm jal-new)
32

In addition to standard compliant(?) Scheme source code, this repository also contains the required files for using the code as a CHICKEN Scheme egg. However, since the code is still in very early stages of development I haven't published it as an egg yet. Nonetheless, an egg can be built locally using:

$ chicken-install -test

If installation is not desired, build as follows:

$ export CHICKEN_REPOSITORY_PATH="$(pwd):${CHICKEN_REPOSITORY_PATH}"
$ chicken-install -n -test

Afterwards simply run (import riscv) in csi(1) as usual.

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.