rust/tests/mir-opt/dataflow-const-prop/sibling_ptr.rs

// EMIT_MIR_FOR_EACH_PANIC_STRATEGY
// This attempts to modify `x.1` via a pointer derived from `addr_of_mut!(x.0)`.
// According to Miri, that is UB. However, T-opsem has not finalized that
// decision and as such we cannot rely on it in optimizations. Consequently,
// DataflowConstProp must treat the `addr_of_mut!(x.0)` as potentially being
// used to modify `x.1` - if it did not, then it might incorrectly assume that it
// can infer the value of `x.1` at the end of this function.

//@ test-mir-pass: DataflowConstProp

// EMIT_MIR sibling_ptr.main.DataflowConstProp.diff

// CHECK-LABEL: fn main(
fn main() {
    // CHECK: debug x1 => [[x1:_.*]];

    let mut x: (u8, u8) = (0, 0);
    unsafe {
        let p = std::ptr::addr_of_mut!(x.0);
        *p.add(1) = 1;
    }

    // CHECK: [[x1]] = copy ({{_.*}}.1: u8);
    let x1 = x.1; // should not be propagated
}