Rollup merge of #52391 - Amanieu:volatile_unaligned, r=alexcrichton

Add unaligned volatile intrinsics

Surprisingly enough, it turns out that unaligned volatile loads are actually useful for certain (very niche) types of lock-free code. I included unaligned volatile stores for completeness, but I currently do not know of any use cases for them.

These are only exposed as intrinsics for now. If they turn out to be useful in practice, we can work towards stabilizing them.

r? @alexcrichton

1 files changed, 9 insertions, 0 deletions

diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs
index 89fe2d941a3..854cb5f4e3b 100644
--- a/src/libcore/intrinsics.rs
+++ b/src/libcore/intrinsics.rs
@@ -1085,6 +1085,15 @@ extern "rust-intrinsic" {
     /// [`std::ptr::write_volatile`](../../std/ptr/fn.write_volatile.html).
     pub fn volatile_store<T>(dst: *mut T, val: T);
 
+    /// Perform a volatile load from the `src` pointer
+    /// The pointer is not required to be aligned.
+    #[cfg(not(stage0))]
+    pub fn unaligned_volatile_load<T>(src: *const T) -> T;
+    /// Perform a volatile store to the `dst` pointer.
+    /// The pointer is not required to be aligned.
+    #[cfg(not(stage0))]
+    pub fn unaligned_volatile_store<T>(dst: *mut T, val: T);
+
     /// Returns the square root of an `f32`
     pub fn sqrtf32(x: f32) -> f32;
     /// Returns the square root of an `f64`