properly compare unequal function pointers

Author: RalfJung

src/operator.rs

@@ -145,8 +145,8 @@ impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'a, 'mir, '
                     // Dead allocations in miri cannot overlap with live allocations, but
                     // on read hardware this can easily happen. Thus for comparisons we require
                     // both pointers to be live.
-                    self.memory().get(left.alloc_id)?.check_bounds_ptr(left)?;
-                    self.memory().get(right.alloc_id)?.check_bounds_ptr(right)?;
+                    self.memory().check_bounds_ptr(left, InboundsCheck::Live)?;
+                    self.memory().check_bounds_ptr(right, InboundsCheck::Live)?;
                     // Two in-bounds pointers, we can compare across allocations
                     left == right
                 }

tests/run-pass/function_pointers.rs

@@ -44,4 +44,5 @@ fn main() {
     let g = f as fn() -> i32;
     assert!(return_fn_ptr(g) == g);
     assert!(return_fn_ptr(g) as unsafe fn() -> i32 == g as fn() -> i32 as unsafe fn() -> i32);
+    assert!(return_fn_ptr(f) != f);
 }