Auto merge of #54639 - nagisa:lets-alias-for-now, r=eddyb

Do not put noalias annotations by default

This will be re-enabled sooner or later depending on results of further
investigation.

Fixes #54462

Beta backport is: #54640

r? @nikomatsakis

1 files changed, 33 insertions, 0 deletions

diff --git a/src/test/run-pass/issue-54462-mutable-noalias-correctness.rs b/src/test/run-pass/issue-54462-mutable-noalias-correctness.rs
new file mode 100644
index 00000000000..f0e52b29287
--- /dev/null
+++ b/src/test/run-pass/issue-54462-mutable-noalias-correctness.rs
@@ -0,0 +1,33 @@
+// Copyright 2018 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.
+//
+// compile-flags: -Ccodegen-units=1 -O
+
+fn linidx(row: usize, col: usize) -> usize {
+    row * 1 + col * 3
+}
+
+fn main() {
+    let mut mat = [1.0f32, 5.0, 9.0, 2.0, 6.0, 10.0, 3.0, 7.0, 11.0, 4.0, 8.0, 12.0];
+
+    for i in 0..2 {
+        for j in i+1..3 {
+            if mat[linidx(j, 3)] > mat[linidx(i, 3)] {
+                    for k in 0..4 {
+                            let (x, rest) = mat.split_at_mut(linidx(i, k) + 1);
+                            let a = x.last_mut().unwrap();
+                            let b = rest.get_mut(linidx(j, k) - linidx(i, k) - 1).unwrap();
+                            ::std::mem::swap(a, b);
+                    }
+            }
+        }
+    }
+    assert_eq!([9.0, 5.0, 1.0, 10.0, 6.0, 2.0, 11.0, 7.0, 3.0, 12.0, 8.0, 4.0], mat);
+}