From 242f2e3c7588574eb5f399dc4cde8f75d7e3e294 Mon Sep 17 00:00:00 2001
From: bjorn3 <bjorn3@users.noreply.github.com>
Date: Sat, 25 Jan 2020 16:24:15 +0100
Subject: [PATCH] Fix correctness of optimization

---
 src/abi/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/abi/mod.rs b/src/abi/mod.rs
index 813a436ddf2..6d254abb2bf 100644
--- a/src/abi/mod.rs
+++ b/src/abi/mod.rs
@@ -363,7 +363,7 @@ pub fn codegen_fn_prelude(fx: &mut FunctionCx<'_, '_, impl Backend>, start_ebb:
                         ParamEnv::reveal_all(),
                         local_decl.source_info.span,
                     );
-                    if local_decl.mutability == mir::Mutability::Not && internally_mutable {
+                    if local_decl.mutability == mir::Mutability::Not && !internally_mutable {
                         // We wont mutate this argument, so it is fine to borrow the backing storage
                         // of this argument, to prevent a copy.