From 8385146ffaddd90d79dff28d7924140ba079adfa Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sat, 8 Aug 2020 10:36:16 +0200
Subject: [PATCH] make black_box a NOP in Miri

---
 library/core/src/hint.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/library/core/src/hint.rs b/library/core/src/hint.rs
index 3116815f5d655..3dc0ee2b55530 100644
--- a/library/core/src/hint.rs
+++ b/library/core/src/hint.rs
@@ -119,9 +119,11 @@ pub fn black_box<T>(dummy: T) -> T {
     // box. This isn't the greatest implementation since it probably deoptimizes
     // more than we want, but it's so far good enough.
 
+    #[cfg(not(miri))] // This is just a hint, so it is fine to skip in Miri.
     // SAFETY: the inline assembly is a no-op.
     unsafe {
         llvm_asm!("" : : "r"(&dummy));
-        dummy
     }
+
+    dummy
 }