From e9b28d22fb1fe343ddb03c456516973abe15afcd Mon Sep 17 00:00:00 2001
From: "Felix S. Klock II" <pnkfelix@pnkfx.org>
Date: Fri, 7 Aug 2015 15:51:25 +0200
Subject: [PATCH 1/3] Turn nonzeroing move hints back off by default.

This is a temporary workaround for the bugs that have been found in
the implementation of PR #26173.

 * pnkfelix is unavailable in the short-term (i.e. for the next week) to fix them.

 * When the bugs are fixed, we will turn this back on by default.

(If you want to play with the known-to-be-buggy optimization in the
meantime, you can opt-back in via the debugging option that this
commit is toggling.)
---
 src/librustc/session/config.rs | 4 ++--
 src/librustc/session/mod.rs    | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index f74bb9ee89ad0..c5db7cd718b8e 100644
--- a/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@ -596,8 +596,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
           "Force drop flag checks on or off"),
     trace_macros: bool = (false, parse_bool,
           "For every macro invocation, print its name and arguments"),
-    disable_nonzeroing_move_hints: bool = (false, parse_bool,
-          "Force nonzeroing move optimization off"),
+    enable_nonzeroing_move_hints: bool = (false, parse_bool,
+          "Force nonzeroing move optimization on"),
 }
 
 pub fn default_lib_output() -> CrateType {
diff --git a/src/librustc/session/mod.rs b/src/librustc/session/mod.rs
index efd46d35f56b7..99a58f07ae62b 100644
--- a/src/librustc/session/mod.rs
+++ b/src/librustc/session/mod.rs
@@ -273,7 +273,7 @@ impl Session {
         self.opts.debugging_opts.print_enum_sizes
     }
     pub fn nonzeroing_move_hints(&self) -> bool {
-        !self.opts.debugging_opts.disable_nonzeroing_move_hints
+        self.opts.debugging_opts.enable_nonzeroing_move_hints
     }
     pub fn sysroot<'a>(&'a self) -> &'a Path {
         match self.opts.maybe_sysroot {

From 61704350553060a782a6ca2fbf6f9f0a04d4a1b6 Mon Sep 17 00:00:00 2001
From: "Felix S. Klock II" <pnkfelix@pnkfx.org>
Date: Fri, 7 Aug 2015 16:21:22 +0200
Subject: [PATCH 2/3] Regression test for dropflag reinit issue.

Fix #27401.
---
 .../run-pass/issue-27401-dropflag-reinit.rs   | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 src/test/run-pass/issue-27401-dropflag-reinit.rs

diff --git a/src/test/run-pass/issue-27401-dropflag-reinit.rs b/src/test/run-pass/issue-27401-dropflag-reinit.rs
new file mode 100644
index 0000000000000..99d5e5cd536df
--- /dev/null
+++ b/src/test/run-pass/issue-27401-dropflag-reinit.rs
@@ -0,0 +1,34 @@
+// Copyright 2015 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.
+
+// Check that when a `let`-binding occurs in a loop, its associated
+// drop-flag is reinitialized (to indicate "needs-drop" at the end of
+// the owning variable's scope).
+
+struct A<'a>(&'a mut i32);
+
+impl<'a> Drop for A<'a> {
+    fn drop(&mut self) {
+        *self.0 += 1;
+    }
+}
+
+fn main() {
+    let mut cnt = 0;
+    for i in 0..2 {
+        let a = A(&mut cnt);
+        if i == 1 { // Note that
+            break;  //  both this break
+        }           //   and also
+        drop(a);    //    this move of `a`
+        // are necessary to expose the bug
+    }
+    assert_eq!(cnt, 2);
+}

From 1a68b187630f19236c8c48e813775f29e1f52114 Mon Sep 17 00:00:00 2001
From: "Felix S. Klock II" <pnkfelix@pnkfx.org>
Date: Fri, 7 Aug 2015 18:23:37 +0200
Subject: [PATCH 3/3] placate the pretty tests by ignoring my test.

---
 src/test/run-pass/issue-27401-dropflag-reinit.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/test/run-pass/issue-27401-dropflag-reinit.rs b/src/test/run-pass/issue-27401-dropflag-reinit.rs
index 99d5e5cd536df..ab8f22e78be72 100644
--- a/src/test/run-pass/issue-27401-dropflag-reinit.rs
+++ b/src/test/run-pass/issue-27401-dropflag-reinit.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-pretty #27582
+
 // Check that when a `let`-binding occurs in a loop, its associated
 // drop-flag is reinitialized (to indicate "needs-drop" at the end of
 // the owning variable's scope).