Auto merge of #68778 - RalfJung:raw-addr-of, r=eddyb

add raw-addr-of variant to mir_raw_fat_ptr

As suggested at https://github.com/rust-lang/rust/pull/48300#discussion_r372520388

r? @eddyb

src/test/ui/mir/mir_raw_fat_ptr.rs

@@ -1,6 +1,7 @@
 // run-pass
 // check raw fat pointer ops in mir
 // FIXME: please improve this when we get monomorphization support
+#![feature(raw_ref_op)]
 
 use std::mem;
 
@@ -104,7 +105,7 @@ impl<T> Foo for T {
 
 struct S<T:?Sized>(u32, T);
 
-fn main() {
+fn main_ref() {
     let array = [0,1,2,3,4];
     let array2 = [5,6,7,8,9];
 
@@ -156,3 +157,59 @@ fn main() {
     assert!(simple_eq(&0u8 as *const _, &0u8 as *const _));
     assert!(!simple_eq(&0u8 as *const _, &1u8 as *const _));
 }
+
+// similar to above, but using &raw
+fn main_raw() {
+    let array = [0,1,2,3,4];
+    let array2 = [5,6,7,8,9];
+
+    // fat ptr comparison: addr then extra
+
+    // check ordering for arrays
+    let mut ptrs: Vec<*const [u8]> = vec![
+        &raw const array[0..0], &raw const array[0..1], &raw const array, &raw const array[1..]
+    ];
+
+    let array_addr = &raw const array as *const u8 as usize;
+    let array2_addr = &raw const array2 as *const u8 as usize;
+    if array2_addr < array_addr {
+        ptrs.insert(0, &raw const array2);
+    } else {
+        ptrs.push(&raw const array2);
+    }
+    assert_inorder(&ptrs, compare_au8);
+
+    let u8_ = (0u8, 1u8);
+    let u32_ = (4u32, 5u32);
+
+    // check ordering for ptrs
+    let buf: &mut [*const dyn Foo] = &mut [
+        &raw const u8_, &raw const u8_.0,
+        &raw const u32_, &raw const u32_.0,
+    ];
+    buf.sort_by(|u,v| {
+        let u : [*const (); 2] = unsafe { mem::transmute(*u) };
+        let v : [*const (); 2] = unsafe { mem::transmute(*v) };
+        u.cmp(&v)
+    });
+    assert_inorder(buf, compare_foo);
+
+    // check ordering for structs containing arrays
+    let ss: (S<[u8; 2]>,
+             S<[u8; 3]>,
+             S<[u8; 2]>) = (
+        S(7, [8, 9]),
+        S(10, [11, 12, 13]),
+        S(4, [5, 6])
+    );
+    assert_inorder(&[
+        &raw const ss.0 as *const S<[u8]>,
+        &raw const ss.1 as *const S<[u8]>,
+        &raw const ss.2 as *const S<[u8]>
+            ], compare_su8);
+}
+
+fn main() {
+    main_ref();
+    main_raw();
+}