From 3122db7d038734ab4b0d92d799763ce1ac43580d Mon Sep 17 00:00:00 2001
From: Scott McMurray <scottmcm@users.noreply.github.com>
Date: Tue, 17 Jan 2023 22:44:16 -0800
Subject: [PATCH 1/2] Implement `SpecOptionPartialEq` for `cmp::Ordering`

---
 library/core/src/option.rs         | 10 +++++++++-
 tests/codegen/option-nonzero-eq.rs | 10 ++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index 7cc00e3f8d1b7..4aeb707fa6788 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -551,7 +551,7 @@ use crate::marker::Destruct;
 use crate::panicking::{panic, panic_str};
 use crate::pin::Pin;
 use crate::{
-    convert, hint, mem,
+    cmp, convert, hint, mem,
     ops::{self, ControlFlow, Deref, DerefMut},
 };
 
@@ -2146,6 +2146,14 @@ impl<T> SpecOptionPartialEq for crate::ptr::NonNull<T> {
     }
 }
 
+#[stable(feature = "rust1", since = "1.0.0")]
+impl SpecOptionPartialEq for cmp::Ordering {
+    #[inline]
+    fn eq(l: &Option<Self>, r: &Option<Self>) -> bool {
+        l.map_or(2, |x| x as i8) == r.map_or(2, |x| x as i8)
+    }
+}
+
 /////////////////////////////////////////////////////////////////////////////
 // The Option Iterators
 /////////////////////////////////////////////////////////////////////////////
diff --git a/tests/codegen/option-nonzero-eq.rs b/tests/codegen/option-nonzero-eq.rs
index 598dcc19b491b..835decd3e5f5e 100644
--- a/tests/codegen/option-nonzero-eq.rs
+++ b/tests/codegen/option-nonzero-eq.rs
@@ -3,6 +3,7 @@
 #![crate_type = "lib"]
 
 extern crate core;
+use core::cmp::Ordering;
 use core::num::{NonZeroU32, NonZeroI64};
 use core::ptr::NonNull;
 
@@ -32,3 +33,12 @@ pub fn non_null_eq(l: Option<NonNull<u8>>, r: Option<NonNull<u8>>) -> bool {
     // CHECK-NEXT: ret i1
     l == r
 }
+
+// CHECK-lABEL: @ordering_eq
+#[no_mangle]
+pub fn ordering_eq(l: Option<Ordering>, r: Option<Ordering>) -> bool {
+    // CHECK: start:
+    // CHECK-NEXT: icmp eq i8
+    // CHECK-NEXT: ret i1
+    l == r
+}

From 3e9d1e40cb2a4dc1e1d303e9d9fa382c34106277 Mon Sep 17 00:00:00 2001
From: Scott McMurray <scottmcm@users.noreply.github.com>
Date: Fri, 27 Jan 2023 19:09:52 -0800
Subject: [PATCH 2/2] Link to the LLVM issue from a comment on
 `SpecOptionPartialEq`

---
 library/core/src/option.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index 4aeb707fa6788..c43b728022d2f 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -2090,6 +2090,12 @@ impl<T: PartialEq> PartialEq for Option<T> {
     }
 }
 
+/// This specialization trait is a workaround for LLVM not currently (2023-01)
+/// being able to optimize this itself, even though Alive confirms that it would
+/// be legal to do so: <https://github.com/llvm/llvm-project/issues/52622>
+///
+/// Once that's fixed, `Option` should go back to deriving `PartialEq`, as
+/// it used to do before <https://github.com/rust-lang/rust/pull/103556>.
 #[unstable(feature = "spec_option_partial_eq", issue = "none", reason = "exposed only for rustc")]
 #[doc(hidden)]
 pub trait SpecOptionPartialEq: Sized {