reasm

ReASM

Wiki

A RISC-V IMFD + Zbb/Zbs compatible assembler/disassembler to Luau.

175+ supported instructions & directives!

[!NOTE] Some programs, will not work! Create an issue if you find an assembly file which is compiling invalid.

Example:

void printf(const char *, ...); /* manually define printf if we are not using stdlib.h */

int fib(int n) {
    if (n <= 1)
        return n;
    return fib(n-1) + fib(n-2);
}

int main() {
    for (int i = 0; i < 10; i++){
        printf("%d ", fib(i));
    }
    return 0;
}

clang -S -target riscv32 -march=rv32im main.c -o main.s
reasm main.s -o main.luau # where the magic happens
luau main.luau

Usage:

reasm main.S -o main.luau --mode {module|main|bench} --trace --comments --accurate

Input file can either be a .S assembly file, or a .elf file which is linked (experimental).

Options

• --comments: This will place comments all around the generated code with details such as the instruction's purpose, operands, and any relevant debug information.
• --trace: Everytime a jump happens it will log to output, this is a more extreme option and should only be used for debug.
• --accurate: Enables more accurate ISA modeling. This turns on 32-bit overflow wrapping and float32 instruction rounding behavior. Much slower, but gives more accurate mathematics.
• --memory: Sets generated RAM buffer size in bytes (default: 524288000 / 500MB).
• --mode:
  • module will automatically expose memory, API to inject functions, and registers to whoever imports.
  • main will generate a simple Luau file which runs on its own.
  • bench will generate a module prepared for benchmarking with Scriptbench or Benchmarker.

Resources:

Super helpful resources in development below:

• https://www.cs.sfu.ca/~ashriram/Courses/CS295/assets/notebooks/RISCV/RISCV_CARD.pdf
• https://msyksphinz-self.github.io/riscv-isadoc/
• https://godbolt.org/
• https://projectf.io/posts/riscv-cheat-sheet/
• https://en.wikipedia.org/wiki/RISC-V_instruction_listings (IMB)

TODO:

• Vector extension
• Work on support for ELF files. (or decide to remove it)