From 0af922b40490c1997ab365c4cd9f2f8adce28ae6 Mon Sep 17 00:00:00 2001
From: Ben Kimock <kimockb@gmail.com>
Date: Wed, 7 Dec 2022 19:38:25 -0500
Subject: [PATCH] Use const_eval_select in ptr::is_null

---
 library/core/src/ptr/const_ptr.rs | 20 ++++++++++++++++----
 library/core/src/ptr/mut_ptr.rs   | 20 ++++++++++++++++----
 2 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/library/core/src/ptr/const_ptr.rs b/library/core/src/ptr/const_ptr.rs
index b6373beac5f76..327b8a8762c50 100644
--- a/library/core/src/ptr/const_ptr.rs
+++ b/library/core/src/ptr/const_ptr.rs
@@ -34,12 +34,24 @@ impl<T: ?Sized> *const T {
     #[rustc_const_unstable(feature = "const_ptr_is_null", issue = "74939")]
     #[inline]
     pub const fn is_null(self) -> bool {
+        #[inline]
+        const fn ct(ptr: *const u8) -> bool {
+            match (ptr).guaranteed_eq(null()) {
+                None => false,
+                Some(res) => res,
+            }
+        }
+
+        #[inline]
+        fn rt(ptr: *const u8) -> bool {
+            ptr.addr() == 0
+        }
+
         // Compare via a cast to a thin pointer, so fat pointers are only
         // considering their "data" part for null-ness.
-        match (self as *const u8).guaranteed_eq(null()) {
-            None => false,
-            Some(res) => res,
-        }
+
+        // SAFETY: NOYET
+        unsafe { intrinsics::const_eval_select((self as *const u8,), ct, rt) }
     }
 
     /// Casts to a pointer of another type.
diff --git a/library/core/src/ptr/mut_ptr.rs b/library/core/src/ptr/mut_ptr.rs
index 7a5d9a7059459..16beb1f77fe0a 100644
--- a/library/core/src/ptr/mut_ptr.rs
+++ b/library/core/src/ptr/mut_ptr.rs
@@ -33,12 +33,24 @@ impl<T: ?Sized> *mut T {
     #[rustc_const_unstable(feature = "const_ptr_is_null", issue = "74939")]
     #[inline]
     pub const fn is_null(self) -> bool {
+        #[inline]
+        const fn ct(ptr: *mut u8) -> bool {
+            match (ptr).guaranteed_eq(null_mut()) {
+                None => false,
+                Some(res) => res,
+            }
+        }
+
+        #[inline]
+        fn rt(ptr: *mut u8) -> bool {
+            ptr.addr() == 0
+        }
+
         // Compare via a cast to a thin pointer, so fat pointers are only
         // considering their "data" part for null-ness.
-        match (self as *mut u8).guaranteed_eq(null_mut()) {
-            None => false,
-            Some(res) => res,
-        }
+
+        // SAFETY: NOYET
+        unsafe { intrinsics::const_eval_select((self as *mut u8,), ct, rt) }
     }
 
     /// Casts to a pointer of another type.