add.rs

//! Add example.
//!
//! Jit compile a function at runtime (generate native host code) which calls a function defined in
//! the example based on the SystemV abi to demonstrate the [`juicebox_asm`] crate.

#[cfg(not(any(target_arch = "x86_64", target_os = "linux")))]
compile_error!("Only supported on x86_64 with SystemV abi");

use juicebox_asm::insn::*;
use juicebox_asm::Runtime;
use juicebox_asm::{Asm, Imm64, Reg64::*};

extern "C" fn add(a: u32, b: u32) -> u32 {
    a + b
}

fn main() {
    let mut asm = Asm::new();

    // SystemV abi:
    //   rdi -> first argument
    //   rsi -> second argument
    //   rax -> return value

    asm.mov(rsi, Imm64::from(42));
    asm.mov(rax, Imm64::from(add as usize));
    asm.call(rax);
    asm.ret();

    let code = asm.into_code();
    std::fs::write("jit.asm", &code).unwrap();

    let mut rt = Runtime::new();
    let add42 = unsafe { rt.add_code::<extern "C" fn(u32) -> u32>(code) };

    let res = add42(5);
    assert_eq!(res, 47);
}