Rollup merge of #72998 - poliorcetics:atomic-availability-doc, r=Amanieu

Mention that some atomic operations may not be available on some platforms

fixes #54250

This simply adds a line saying the type/function/method may not be available on some platforms, depending on said platform capabilities.

I *think* I got them all.

Author: Dylan-DPC

src/libcore/sync/atomic.rs

@@ -153,6 +153,9 @@ pub fn spin_loop_hint() {
 ///
 /// This type has the same in-memory representation as a [`bool`].
 ///
+/// **Note**: This type is only available on platforms that support atomic
+/// loads and stores of `u8`.
+///
 /// [`bool`]: ../../../std/primitive.bool.html
 #[cfg(target_has_atomic_load_store = "8")]
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -178,6 +181,9 @@ unsafe impl Sync for AtomicBool {}
 /// A raw pointer type which can be safely shared between threads.
 ///
 /// This type has the same in-memory representation as a `*mut T`.
+///
+/// **Note**: This type is only available on platforms that support atomic
+/// loads and stores of pointers. Its size depends on the target pointer's size.
 #[cfg(target_has_atomic_load_store = "ptr")]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[cfg_attr(target_pointer_width = "16", repr(C, align(2)))]
@@ -447,6 +453,9 @@ impl AtomicBool {
     /// [`Acquire`] makes the store part of this operation [`Relaxed`], and
     /// using [`Release`] makes the load part [`Relaxed`].
     ///
+    /// **Note:** This method is only available on platforms that support atomic
+    /// operations on `u8`.
+    ///
     /// [`Ordering`]: enum.Ordering.html
     /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
     /// [`Release`]: enum.Ordering.html#variant.Release
@@ -481,6 +490,9 @@ impl AtomicBool {
     /// Using [`Acquire`] makes the store part of this operation [`Relaxed`] if it
     /// happens, and using [`Release`] makes the load part [`Relaxed`].
     ///
+    /// **Note:** This method is only available on platforms that support atomic
+    /// operations on `u8`.
+    ///
     /// [`Ordering`]: enum.Ordering.html
     /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
     /// [`Release`]: enum.Ordering.html#variant.Release
@@ -524,6 +536,8 @@ impl AtomicBool {
     /// [`Relaxed`]. The failure ordering can only be [`SeqCst`], [`Acquire`] or [`Relaxed`]
     /// and must be equivalent to or weaker than the success ordering.
     ///
+    /// **Note:** This method is only available on platforms that support atomic
+    /// operations on `u8`.
     ///
     /// [`bool`]: ../../../std/primitive.bool.html
     /// [`Ordering`]: enum.Ordering.html
@@ -586,6 +600,9 @@ impl AtomicBool {
     /// [`Relaxed`]. The failure ordering can only be [`SeqCst`], [`Acquire`] or [`Relaxed`]
     /// and must be equivalent to or weaker than the success ordering.
     ///
+    /// **Note:** This method is only available on platforms that support atomic
+    /// operations on `u8`.
+    ///
     /// [`bool`]: ../../../std/primitive.bool.html
     /// [`compare_exchange`]: #method.compare_exchange
     /// [`Ordering`]: enum.Ordering.html
@@ -646,6 +663,9 @@ impl AtomicBool {
     /// [`Release`]: enum.Ordering.html#variant.Release
     /// [`Acquire`]: enum.Ordering.html#variant.Acquire
     ///
+    /// **Note:** This method is only available on platforms that support atomic
+    /// operations on `u8`.
+    ///
     /// # Examples
     ///
     /// ```
@@ -683,6 +703,9 @@ impl AtomicBool {
     /// [`Acquire`] makes the store part of this operation [`Relaxed`], and
     /// using [`Release`] makes the load part [`Relaxed`].
     ///
+    /// **Note:** This method is only available on platforms that support atomic
+    /// operations on `u8`.
+    ///
     /// [`Ordering`]: enum.Ordering.html
     /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
     /// [`Release`]: enum.Ordering.html#variant.Release
@@ -737,6 +760,9 @@ impl AtomicBool {
     /// [`Acquire`] makes the store part of this operation [`Relaxed`], and
     /// using [`Release`] makes the load part [`Relaxed`].
     ///
+    /// **Note:** This method is only available on platforms that support atomic
+    /// operations on `u8`.
+    ///
     /// [`Ordering`]: enum.Ordering.html
     /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
     /// [`Release`]: enum.Ordering.html#variant.Release
@@ -779,6 +805,9 @@ impl AtomicBool {
     /// [`Acquire`] makes the store part of this operation [`Relaxed`], and
     /// using [`Release`] makes the load part [`Relaxed`].
     ///
+    /// **Note:** This method is only available on platforms that support atomic
+    /// operations on `u8`.
+    ///
     /// [`Ordering`]: enum.Ordering.html
     /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
     /// [`Release`]: enum.Ordering.html#variant.Release
@@ -981,6 +1010,9 @@ impl<T> AtomicPtr<T> {
     /// [`Acquire`] makes the store part of this operation [`Relaxed`], and
     /// using [`Release`] makes the load part [`Relaxed`].
     ///
+    /// **Note:** This method is only available on platforms that support atomic
+    /// operations on pointers.
+    ///
     /// [`Ordering`]: enum.Ordering.html
     /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
     /// [`Release`]: enum.Ordering.html#variant.Release
@@ -1017,6 +1049,9 @@ impl<T> AtomicPtr<T> {
     /// Using [`Acquire`] makes the store part of this operation [`Relaxed`] if it
     /// happens, and using [`Release`] makes the load part [`Relaxed`].
     ///
+    /// **Note:** This method is only available on platforms that support atomic
+    /// operations on pointers.
+    ///
     /// [`Ordering`]: enum.Ordering.html
     /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
     /// [`Release`]: enum.Ordering.html#variant.Release
@@ -1058,6 +1093,9 @@ impl<T> AtomicPtr<T> {
     /// [`Relaxed`]. The failure ordering can only be [`SeqCst`], [`Acquire`] or [`Relaxed`]
     /// and must be equivalent to or weaker than the success ordering.
     ///
+    /// **Note:** This method is only available on platforms that support atomic
+    /// operations on pointers.
+    ///
     /// [`Ordering`]: enum.Ordering.html
     /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
     /// [`Release`]: enum.Ordering.html#variant.Release
@@ -1118,6 +1156,9 @@ impl<T> AtomicPtr<T> {
     /// [`Relaxed`]. The failure ordering can only be [`SeqCst`], [`Acquire`] or [`Relaxed`]
     /// and must be equivalent to or weaker than the success ordering.
     ///
+    /// **Note:** This method is only available on platforms that support atomic
+    /// operations on pointers.
+    ///
     /// [`compare_exchange`]: #method.compare_exchange
     /// [`Ordering`]: enum.Ordering.html
     /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
@@ -1223,6 +1264,13 @@ macro_rules! atomic_int {
         /// non-atomic types as well as information about the portability of
         /// this type, please see the [module-level documentation].
         ///
+        /// **Note:** This type is only available on platforms that support
+        /// atomic loads and stores of [`
+        #[doc = $s_int_type]
+        /// `](
+        #[doc = $int_ref]
+        /// ).
+        ///
         /// [module-level documentation]: index.html
         #[$stable]
         #[repr(C, align($align))]
@@ -1408,6 +1456,9 @@ of this operation. All ordering modes are possible. Note that using
 [`Acquire`] makes the store part of this operation [`Relaxed`], and
 using [`Release`] makes the load part [`Relaxed`].
 
+**Note**: This method is only available on platforms that support atomic
+operations on [`", $s_int_type, "`](", $int_ref, ").
+
 [`Ordering`]: enum.Ordering.html
 [`Relaxed`]: enum.Ordering.html#variant.Relaxed
 [`Release`]: enum.Ordering.html#variant.Release
@@ -1444,6 +1495,9 @@ might fail and hence just perform an `Acquire` load, but not have `Release` sema
 Using [`Acquire`] makes the store part of this operation [`Relaxed`] if it
 happens, and using [`Release`] makes the load part [`Relaxed`].
 
+**Note**: This method is only available on platforms that support atomic
+operations on [`", $s_int_type, "`](", $int_ref, ").
+
 [`Ordering`]: enum.Ordering.html
 [`Relaxed`]: enum.Ordering.html#variant.Relaxed
 [`Release`]: enum.Ordering.html#variant.Release
@@ -1496,6 +1550,9 @@ of this operation [`Relaxed`], and using [`Release`] makes the successful load
 [`Relaxed`]. The failure ordering can only be [`SeqCst`], [`Acquire`] or [`Relaxed`]
 and must be equivalent to or weaker than the success ordering.
 
+**Note**: This method is only available on platforms that support atomic
+operations on [`", $s_int_type, "`](", $int_ref, ").
+
 [`Ordering`]: enum.Ordering.html
 [`Relaxed`]: enum.Ordering.html#variant.Relaxed
 [`Release`]: enum.Ordering.html#variant.Release
@@ -1558,6 +1615,9 @@ and must be equivalent to or weaker than the success ordering.
 [`Acquire`]: enum.Ordering.html#variant.Acquire
 [`SeqCst`]: enum.Ordering.html#variant.SeqCst
 
+**Note**: This method is only available on platforms that support atomic
+operations on [`", $s_int_type, "`](", $int_ref, ").
+
 # Examples
 
 ```
@@ -1599,6 +1659,9 @@ of this operation. All ordering modes are possible. Note that using
 [`Acquire`] makes the store part of this operation [`Relaxed`], and
 using [`Release`] makes the load part [`Relaxed`].
 
+**Note**: This method is only available on platforms that support atomic
+operations on [`", $s_int_type, "`](", $int_ref, ").
+
 [`Ordering`]: enum.Ordering.html
 [`Relaxed`]: enum.Ordering.html#variant.Relaxed
 [`Release`]: enum.Ordering.html#variant.Release
@@ -1632,6 +1695,9 @@ of this operation. All ordering modes are possible. Note that using
 [`Acquire`] makes the store part of this operation [`Relaxed`], and
 using [`Release`] makes the load part [`Relaxed`].
 
+**Note**: This method is only available on platforms that support atomic
+operations on [`", $s_int_type, "`](", $int_ref, ").
+
 [`Ordering`]: enum.Ordering.html
 [`Relaxed`]: enum.Ordering.html#variant.Relaxed
 [`Release`]: enum.Ordering.html#variant.Release
@@ -1668,6 +1734,9 @@ of this operation. All ordering modes are possible. Note that using
 [`Acquire`] makes the store part of this operation [`Relaxed`], and
 using [`Release`] makes the load part [`Relaxed`].
 
+**Note**: This method is only available on platforms that support atomic
+operations on [`", $s_int_type, "`](", $int_ref, ").
+
 [`Ordering`]: enum.Ordering.html
 [`Relaxed`]: enum.Ordering.html#variant.Relaxed
 [`Release`]: enum.Ordering.html#variant.Release
@@ -1704,6 +1773,9 @@ of this operation. All ordering modes are possible. Note that using
 [`Acquire`] makes the store part of this operation [`Relaxed`], and
 using [`Release`] makes the load part [`Relaxed`].
 
+**Note**: This method is only available on platforms that support atomic
+operations on [`", $s_int_type, "`](", $int_ref, ").
+
 [`Ordering`]: enum.Ordering.html
 [`Relaxed`]: enum.Ordering.html#variant.Relaxed
 [`Release`]: enum.Ordering.html#variant.Release
@@ -1741,6 +1813,9 @@ of this operation. All ordering modes are possible. Note that using
 [`Acquire`] makes the store part of this operation [`Relaxed`], and
 using [`Release`] makes the load part [`Relaxed`].
 
+**Note**: This method is only available on platforms that support atomic
+operations on [`", $s_int_type, "`](", $int_ref, ").
+
 [`Ordering`]: enum.Ordering.html
 [`Relaxed`]: enum.Ordering.html#variant.Relaxed
 [`Release`]: enum.Ordering.html#variant.Release
@@ -1777,6 +1852,9 @@ of this operation. All ordering modes are possible. Note that using
 [`Acquire`] makes the store part of this operation [`Relaxed`], and
 using [`Release`] makes the load part [`Relaxed`].
 
+**Note**: This method is only available on platforms that support atomic
+operations on [`", $s_int_type, "`](", $int_ref, ").
+
 [`Ordering`]: enum.Ordering.html
 [`Relaxed`]: enum.Ordering.html#variant.Relaxed
 [`Release`]: enum.Ordering.html#variant.Release
@@ -1819,6 +1897,9 @@ of this operation [`Relaxed`], and using [`Release`] makes the final successful
 [`Relaxed`]. The (failed) load ordering can only be [`SeqCst`], [`Acquire`] or [`Relaxed`]
 and must be equivalent to or weaker than the success ordering.
 
+**Note**: This method is only available on platforms that support atomic
+operations on [`", $s_int_type, "`](", $int_ref, ").
+
 [`bool`]: ../../../std/primitive.bool.html
 [`compare_exchange`]: #method.compare_exchange
 [`Ordering`]: enum.Ordering.html
@@ -1870,6 +1951,9 @@ of this operation. All ordering modes are possible. Note that using
 [`Acquire`] makes the store part of this operation [`Relaxed`], and
 using [`Release`] makes the load part [`Relaxed`].
 
+**Note**: This method is only available on platforms that support atomic
+operations on [`", $s_int_type, "`](", $int_ref, ").
+
 [`Ordering`]: enum.Ordering.html
 [`Relaxed`]: enum.Ordering.html#variant.Relaxed
 [`Release`]: enum.Ordering.html#variant.Release
@@ -1917,6 +2001,9 @@ of this operation. All ordering modes are possible. Note that using
 [`Acquire`] makes the store part of this operation [`Relaxed`], and
 using [`Release`] makes the load part [`Relaxed`].
 
+**Note**: This method is only available on platforms that support atomic
+operations on [`", $s_int_type, "`](", $int_ref, ").
+
 [`Ordering`]: enum.Ordering.html
 [`Relaxed`]: enum.Ordering.html#variant.Relaxed
 [`Release`]: enum.Ordering.html#variant.Release