1 files changed, 30 insertions, 5 deletions

diff --git a/library/core/src/intrinsics.rs b/library/core/src/intrinsics.rs
index 79bd0bbb0c1..23ded42fa66 100644
--- a/library/core/src/intrinsics.rs
+++ b/library/core/src/intrinsics.rs
@@ -1187,7 +1187,7 @@ extern "rust-intrinsic" {
     /// Below are common applications of `transmute` which can be replaced with safer
     /// constructs.
     ///
-    /// Turning raw bytes (`&[u8]`) into `u32`, `f64`, etc.:
+    /// Turning raw bytes (`[u8; SZ]`) into `u32`, `f64`, etc.:
     ///
     /// ```
     /// let raw_bytes = [0x78, 0x56, 0x34, 0x12];
@@ -2257,12 +2257,23 @@ extern "rust-intrinsic" {
     /// This is an implementation detail of [`crate::ptr::read`] and should
     /// not be used anywhere else.  See its comments for why this exists.
     ///
-    /// This intrinsic can *only* be called where the argument is a local without
-    /// projections (`read_via_copy(p)`, not `read_via_copy(*p)`) so that it
+    /// This intrinsic can *only* be called where the pointer is a local without
+    /// projections (`read_via_copy(ptr)`, not `read_via_copy(*ptr)`) so that it
     /// trivially obeys runtime-MIR rules about derefs in operands.
-    #[rustc_const_unstable(feature = "const_ptr_read", issue = "80377")]
+    #[rustc_const_stable(feature = "const_ptr_read", since = "CURRENT_RUSTC_VERSION")]
     #[rustc_nounwind]
-    pub fn read_via_copy<T>(p: *const T) -> T;
+    pub fn read_via_copy<T>(ptr: *const T) -> T;
+
+    /// This is an implementation detail of [`crate::ptr::write`] and should
+    /// not be used anywhere else.  See its comments for why this exists.
+    ///
+    /// This intrinsic can *only* be called where the pointer is a local without
+    /// projections (`write_via_move(ptr, x)`, not `write_via_move(*ptr, x)`) so
+    /// that it trivially obeys runtime-MIR rules about derefs in operands.
+    #[cfg(not(bootstrap))]
+    #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
+    #[rustc_nounwind]
+    pub fn write_via_move<T>(ptr: *mut T, value: T);
 
     /// Returns the value of the discriminant for the variant in 'v';
     /// if `T` has no discriminant, returns `0`.
@@ -2512,6 +2523,7 @@ macro_rules! assert_unsafe_precondition {
                 }
             }
             #[allow(non_snake_case)]
+            #[inline]
             const fn comptime$(<$($tt)*>)?($(_:$ty),*) {}
 
             ::core::intrinsics::const_eval_select(($($i,)*), comptime, runtime);
@@ -2828,3 +2840,16 @@ pub const unsafe fn transmute_unchecked<Src, Dst>(src: Src) -> Dst {
     // SAFETY: It's a transmute -- the caller promised it's fine.
     unsafe { transmute_copy(&ManuallyDrop::new(src)) }
 }
+
+/// Polyfill for bootstrap
+#[cfg(bootstrap)]
+pub const unsafe fn write_via_move<T>(ptr: *mut T, value: T) {
+    use crate::mem::*;
+    // SAFETY: the caller must guarantee that `dst` is valid for writes.
+    // `dst` cannot overlap `src` because the caller has mutable access
+    // to `dst` while `src` is owned by this function.
+    unsafe {
+        copy_nonoverlapping::<T>(&value, ptr, 1);
+        forget(value);
+    }
+}