// compile-flags: -Zmiri-ignore-leaks

// Tests operations not perfomable through C++'s atomic API
// but doable in safe (at least sound) Rust.

#![feature(atomic_from_mut)]
#![feature(core_intrinsics)]

use std::sync::atomic::Ordering::*;
use std::sync::atomic::{AtomicU16, AtomicU32};
use std::thread::spawn;

fn static_atomic_mut(val: u32) -> &'static mut AtomicU32 {
    let ret = Box::leak(Box::new(AtomicU32::new(val)));
    ret
}

fn static_atomic(val: u32) -> &'static AtomicU32 {
    let ret = Box::leak(Box::new(AtomicU32::new(val)));
    ret
}

fn split_u32(dword: &mut u32) -> &mut [u16; 2] {
    unsafe { std::mem::transmute::<&mut u32, &mut [u16; 2]>(dword) }
}

fn split_u32_ptr(dword: *const u32) -> *const [u16; 2] {
    unsafe { std::mem::transmute::<*const u32, *const [u16; 2]>(dword) }
}

fn mem_replace() {
    let mut x = AtomicU32::new(0);

    let old_x = std::mem::replace(&mut x, AtomicU32::new(42));

    assert_eq!(x.load(Relaxed), 42);
    assert_eq!(old_x.load(Relaxed), 0);
}

fn assign_to_mut() {
    let x = static_atomic_mut(0);
    x.store(1, Relaxed);

    *x = AtomicU32::new(2);

    assert_eq!(x.load(Relaxed), 2);
}

fn get_mut_write() {
    let x = static_atomic_mut(0);
    x.store(1, Relaxed);
    {
        let x_mut = x.get_mut();
        *x_mut = 2;
    }

    let j1 = spawn(move || x.load(Relaxed));

    let r1 = j1.join().unwrap();
    assert_eq!(r1, 2);
}

// This is technically doable in C++ with atomic_ref
// but little literature exists atm on its involvement
// in mixed size/atomicity accesses
fn from_mut_split() {
    let mut x: u32 = 0;

    {
        let x_atomic = AtomicU32::from_mut(&mut x);
        x_atomic.store(u32::from_be(0xabbafafa), Relaxed);
    }

    let (x_hi, x_lo) = split_u32(&mut x).split_at_mut(1);

    let x_hi_atomic = AtomicU16::from_mut(&mut x_hi[0]);
    let x_lo_atomic = AtomicU16::from_mut(&mut x_lo[0]);

    assert_eq!(x_hi_atomic.load(Relaxed), u16::from_be(0xabba));
    assert_eq!(x_lo_atomic.load(Relaxed), u16::from_be(0xfafa));
}

// Although not possible to do in safe Rust,
// we allow non-atomic and atomic reads to race
// as this should be sound
fn racing_mixed_atomicity_read() {
    let x = static_atomic(0);
    x.store(42, Relaxed);

    let j1 = spawn(move || x.load(Relaxed));

    let j2 = spawn(move || {
        let x_ptr = x as *const AtomicU32 as *const u32;
        unsafe { std::intrinsics::atomic_load_relaxed(x_ptr) }
    });

    let r1 = j1.join().unwrap();
    let r2 = j2.join().unwrap();

    assert_eq!(r1, 42);
    assert_eq!(r2, 42);
}

fn racing_mixed_size_read() {
    let x = static_atomic(0);

    let j1 = spawn(move || {
        x.load(Relaxed);
    });

    let j2 = spawn(move || {
        let x_ptr = x as *const AtomicU32 as *const u32;
        let x_split = split_u32_ptr(x_ptr);
        unsafe {
            let hi = &(*x_split)[0] as *const u16;
            std::intrinsics::atomic_load_relaxed(hi); //~ ERROR: imperfectly overlapping
        }
    });

    j1.join().unwrap();
    j2.join().unwrap();
}

fn racing_mixed_atomicity_and_size_read() {
    let x = static_atomic(u32::from_be(0xabbafafa));

    let j1 = spawn(move || {
        x.load(Relaxed);
    });

    let j2 = spawn(move || {
        let x_ptr = x as *const AtomicU32 as *const u32;
        unsafe { *x_ptr };
    });

    let j3 = spawn(move || {
        let x_ptr = x as *const AtomicU32 as *const u32;
        let x_split = split_u32_ptr(x_ptr);
        unsafe {
            let hi = &(*x_split)[0] as *const u16;
            std::intrinsics::atomic_load_relaxed(hi)
        }
    });

    j1.join().unwrap();
    j2.join().unwrap();
    let r3 = j3.join().unwrap();

    assert_eq!(r3, u16::from_be(0xabba));
}

pub fn main() {
    get_mut_write();
    from_mut_split();
    assign_to_mut();
    mem_replace();
    racing_mixed_atomicity_read();
    racing_mixed_size_read();
    racing_mixed_atomicity_and_size_read();
}