fix codegen of drops of fields of packed structs

src/test/mir-opt/packed-struct-drop-aligned.rs

@@ -0,0 +1,68 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {
+    let mut x = Packed(Aligned(Droppy(0)));
+    x.0 = Aligned(Droppy(0));
+}
+
+struct Aligned(Droppy);
+#[repr(packed)]
+struct Packed(Aligned);
+
+struct Droppy(usize);
+impl Drop for Droppy {
+    fn drop(&mut self) {}
+}
+
+// END RUST SOURCE
+// START rustc.main.EraseRegions.before.mir
+// fn main() -> () {
+//     let mut _0: ();
+//     scope 1 {
+//         let mut _1: Packed;
+//     }
+//     scope 2 {
+//     }
+//     let mut _2: Aligned;
+//     let mut _3: Droppy;
+//     let mut _4: Aligned;
+//     let mut _5: Droppy;
+//     let mut _6: Aligned;
+//
+//     bb0: {
+//         StorageLive(_1);
+//         ...
+//         _1 = Packed::{{constructor}}(_2,);
+//         ...
+//         StorageLive(_6);
+//         _6 = (_1.0: Aligned);
+//         drop(_6) -> [return: bb4, unwind: bb3];
+//     }
+//     bb1: {
+//         resume;
+//     }
+//     bb2: {
+//         StorageDead(_1);
+//         return;
+//     }
+//     bb3: {
+//         (_1.0: Aligned) = _4;
+//         drop(_1) -> bb1;
+//     }
+//     bb4: {
+//         StorageDead(_6);
+//         (_1.0: Aligned) = _4;
+//         StorageDead(_4);
+//         _0 = ();
+//         drop(_1) -> bb2;
+//     }
+// }
+// END rustc.main.EraseRegions.before.mir

src/test/run-pass/packed-struct-drop-aligned.rs

@@ -0,0 +1,42 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::cell::Cell;
+use std::mem;
+
+struct Aligned<'a> {
+    drop_count: &'a Cell<usize>
+}
+
+#[inline(never)]
+fn check_align(ptr: *const Aligned) {
+    assert_eq!(ptr as usize % mem::align_of::<Aligned>(),
+               0);
+}
+
+impl<'a> Drop for Aligned<'a> {
+    fn drop(&mut self) {
+        check_align(self);
+        self.drop_count.set(self.drop_count.get() + 1);
+    }
+}
+
+#[repr(packed)]
+struct Packed<'a>(u8, Aligned<'a>);
+
+fn main() {
+    let drop_count = &Cell::new(0);
+    {
+        let mut p = Packed(0, Aligned { drop_count });
+        p.1 = Aligned { drop_count };
+        assert_eq!(drop_count.get(), 1);
+    }
+    assert_eq!(drop_count.get(), 2);
+}