From ca2d2fa28391fec6e022cede26b400c85afb8c0c Mon Sep 17 00:00:00 2001
From: The8472 <git@infinite-source.de>
Date: Fri, 17 Sep 2021 00:24:36 +0200
Subject: [PATCH] Don't inline OnceCell initialization closures

---
 library/core/src/lazy.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/library/core/src/lazy.rs b/library/core/src/lazy.rs
index 2c517371c2c..e6bea462fa9 100644
--- a/library/core/src/lazy.rs
+++ b/library/core/src/lazy.rs
@@ -214,7 +214,16 @@ pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&T, E>
         if let Some(val) = self.get() {
             return Ok(val);
         }
-        let val = f()?;
+        /// Avoid inlining the initialization closure into the common path that fetches
+        /// the already initialized value
+        #[cold]
+        fn outlined_call<F, T, E>(f: F) -> Result<T, E>
+        where
+            F: FnOnce() -> Result<T, E>,
+        {
+            f()
+        }
+        let val = outlined_call(f)?;
         // Note that *some* forms of reentrant initialization might lead to
         // UB (see `reentrant_init` test). I believe that just removing this
         // `assert`, while keeping `set/get` would be sound, but it seems