| // skip-filecheck |
| //@ test-mir-pass: CopyProp |
| // |
| // This attempts to mutate `a` via a pointer derived from `addr_of!(a)`. That is UB |
| // according to Miri. However, the decision to make this UB - and to allow |
| // rustc to rely on that fact for the purpose of optimizations - has not been |
| // finalized. |
| // |
| // As such, we include this test to ensure that copy prop does not rely on that |
| // fact. Specifically, if `addr_of!(a)` could not be used to modify a, it would |
| // be correct for CopyProp to replace all occurrences of `a` with `c` - but that |
| // would cause `f(true)` to output `false` instead of `true`. |
| |
| #![feature(custom_mir, core_intrinsics)] |
| #![allow(unused_assignments)] |
| extern crate core; |
| use core::intrinsics::mir::*; |
| |
| #[custom_mir(dialect = "analysis", phase = "post-cleanup")] |
| fn f(c: bool) -> bool { |
| mir!({ |
| let a = c; |
| let p = core::ptr::addr_of!(a); |
| let p2 = core::ptr::addr_of_mut!(*p); |
| *p2 = false; |
| RET = c; |
| Return() |
| }) |
| } |
| |
| fn main() { |
| assert_eq!(true, f(true)); |
| } |
| |
| // EMIT_MIR mutate_through_pointer.f.CopyProp.diff |
