Remove backup implementation of likely/unlikely that didn't work

src/raw/mod.rs

@@ -44,32 +44,12 @@ use self::imp::Group;
 
 // Branch prediction hint. This is currently only available on nightly but it
 // consistently improves performance by 10-15%.
-#[cfg(feature = "nightly")]
-use core::intrinsics::{likely, unlikely};
-
-// On stable we can use #[cold] to get a equivalent effect: this attributes
-// suggests that the function is unlikely to be called
 #[cfg(not(feature = "nightly"))]
-#[inline]
-#[cold]
-fn cold() {}
-
-#[cfg(not(feature = "nightly"))]
-#[inline]
-fn likely(b: bool) -> bool {
-    if !b {
-        cold();
-    }
-    b
-}
+use core::convert::identity as likely;
 #[cfg(not(feature = "nightly"))]
-#[inline]
-fn unlikely(b: bool) -> bool {
-    if b {
-        cold();
-    }
-    b
-}
+use core::convert::identity as unlikely;
+#[cfg(feature = "nightly")]
+use core::intrinsics::{likely, unlikely};
 
 // Use strict provenance functions if available.
 #[cfg(feature = "nightly")]