Pointer to integer casts that expose provenance are incorrectly removed

[tmiasko]

The pointer to integer cast has an implicit side effect of exposing the provenance, so it cannot be removed under strict provenance model.

Example of an incorrect transformation:

pub fn expose_addr<T>(a: &T) {
    a as *const T as usize;
}

-// MIR for `expose_addr` before SimplifyLocals
+// MIR for `expose_addr` after SimplifyLocals
 
 fn expose_addr(_1: &T) -> () {
     debug a => _1;                       // in scope 0 at a.rs:1:23: 1:24
     let mut _0: ();                      // return place in scope 0 at a.rs:1:30: 1:30
-    let _2: usize;                       // in scope 0 at a.rs:2:5: 2:27
-    let mut _3: *const T;                // in scope 0 at a.rs:2:5: 2:18
 
     bb0: {
-        _3 = &raw const (*_1);           // scope 0 at a.rs:2:5: 2:6
-        _2 = move _3 as usize (Misc);    // scope 0 at a.rs:2:5: 2:27
         return;                          // scope 0 at a.rs:3:2: 3:2
     }
 }

[RalfJung]

Thanks!
Indeed, this optimization can cause the miscompilation outlined in my blog post.