---

yaml
---
r: 141241
b: refs/heads/try2
c: 1f8c4b0
h: refs/heads/master
i:
  141239: 0613fc8
v: v3

Author: bors

[refs]

@@ -5,7 +5,7 @@ refs/heads/snap-stage3: 78a7676898d9f80ab540c6df5d4c9ce35bb50463
 refs/heads/try: 519addf6277dbafccbb4159db4b710c37eaa2ec5
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/heads/ndm: f3868061cd7988080c30d6d5bf352a5a5fe2460b
-refs/heads/try2: d89a6ceb1b36e7460afece5b3392c8f24f7ef6ce
+refs/heads/try2: 1f8c4b096da8d7c6436038730fa4a862e1ac91f5
 refs/heads/dist-snap: ba4081a5a8573875fed17545846f6f6902c8ba8d
 refs/tags/release-0.2: c870d2dffb391e14efb05aa27898f1f6333a9596
 refs/tags/release-0.3: b5f0d0f648d9a6153664837026ba1be43d3e2503

branches/try2/src/librustc/middle/trans/base.rs

@@ -1694,7 +1694,20 @@ pub fn create_llargs_for_fn_args(cx: fn_ctxt,
     vec::from_fn(args.len(), |i| {
         unsafe {
             let arg_n = first_real_arg + i;
-            llvm::LLVMGetParam(cx.llfn, arg_n as c_uint)
+            let arg = &args[i];
+            let llarg = llvm::LLVMGetParam(cx.llfn, arg_n as c_uint);
+
+            // Mark `&mut T` as no-alias, as the borrowck pass ensures it's true
+            match arg.ty.node {
+                ast::ty_rptr(_, mt) => {
+                    if mt.mutbl == ast::m_mutbl  {
+                        llvm::LLVMAddAttribute(llarg, lib::llvm::NoAliasAttribute as c_uint);
+                    }
+                }
+                _ => {}
+            }
+
+            llarg
         }
     })
 }