[rustc.git] / tests / mir-opt / dataflow-const-prop / sibling_ptr.rs

// 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.

// unit-test: DataflowConstProp

// EMIT_MIR sibling_ptr.main.DataflowConstProp.diff
fn main() {
    let mut x: (u8, u8) = (0, 0);
    unsafe {
        let p = std::ptr::addr_of_mut!(x.0);
        *p.add(1) = 1;
    }
    let x1 = x.1; // should not be propagated
}
Commit	Line	Data
9ffffee4 FG	1	// This attempts to modify `x.1` via a pointer derived from `addr_of_mut!(x.0)`.
	2	// According to Miri, that is UB. However, T-opsem has not finalized that
	3	// decision and as such we cannot rely on it in optimizations. Consequently,
	4	// DataflowConstProp must treat the `addr_of_mut!(x.0)` as potentially being
	5	// used to modify `x.1` - if it did not, then it might incorrectly assume that it
	6	// can infer the value of `x.1` at the end of this function.
	7
487cf647 FG	8	// unit-test: DataflowConstProp
	9
	10	// EMIT_MIR sibling_ptr.main.DataflowConstProp.diff
	11	fn main() {
	12	let mut x: (u8, u8) = (0, 0);
	13	unsafe {
	14	let p = std::ptr::addr_of_mut!(x.0);
	15	*p.add(1) = 1;
	16	}
9ffffee4	17	let x1 = x.1; // should not be propagated
487cf647	18	}