x86_64 inline assembly that adds two numbers in rust

Here's an example of x86_64 inline assembly in Rust that adds two numbers using the add instruction:

main.rs
fn add_numbers(a: i32, b: i32) -> i32 {
    let result: i32;
    unsafe {
        asm!(
            "add {0}, {1}",
            in(reg) a,
            in(reg) b,
            out("eax") result,
        );
    }
    result
}

fn main() {
    let a = 5;
    let b = 3;
    let sum = add_numbers(a, b);
    println!("{} + {} = {}", a, b, sum);
}
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In the code above, we define the add_numbers function that takes two i32 arguments, adds them using the x86_64 add instruction, and returns the result.

To use inline assembly in Rust, we need to define the assembly code as a string and use the asm! macro to embed it in our Rust function. The macro takes a string of assembly code as its first argument, and a set of input and output operands as subsequent arguments. In this example, we use the reg constraint to specify that the a and b arguments should be loaded into general-purpose registers (%eax and %ebx, respectively), and use the eax constraint to specify that the result should be stored in %eax.

Note that using inline assembly is generally not recommended in Rust, as it can be difficult to ensure that the assembly code is safe and doesn't violate any of Rust's memory-safety guarantees. However, in cases where performance is critical and Rust's compiler optimization isn't sufficient, inline assembly can be a useful tool.