Detect atomic support using target_has_atomic

Note that `cfg(target_has_atomic = ...)` was only added in Rust 1.60.
However, we do not add a version detection feature for this since,
prior to 1.60, these cfgs are not present, so none of the atomics will
be supported. This is identical to the behavior if we were to add
version detection, so there is no point in doing so.

This is adapted from @josephlr's similar implementation in #1091.

Fixes #1086

Co-authored-by: Joe Richey <[email protected]>

Author: joshlf

.github/workflows/ci.yml

@@ -57,6 +57,7 @@ jobs:
           "riscv64gc-unknown-linux-gnu",
           "s390x-unknown-linux-gnu",
           "x86_64-pc-windows-msvc",
+          "thumbv6m-none-eabi",
           "wasm32-wasi"
         ]
         features: [ "--no-default-features", "", "--features __internal_use_only_features_that_work_on_stable", "--all-features" ]
@@ -109,6 +110,8 @@ jobs:
             event_name: "pull_request"
           - target: "s390x-unknown-linux-gnu"
             event_name: "pull_request"
+          - target: "thumbv6m-none-eabi"
+            event_name: "pull_request"
           - target: "wasm32-wasi"
             event_name: "pull_request"
 

src/impls.rs

@@ -451,15 +451,33 @@ macro_rules! impl_traits_for_atomics {
     };
 }
 
-#[rustfmt::skip]
-impl_traits_for_atomics!(
-    AtomicI16, AtomicI32, AtomicI8, AtomicIsize,
-    AtomicU16, AtomicU32, AtomicU8, AtomicUsize,
-);
-
-impl_for_transparent_wrapper!(=> TryFromBytes for AtomicBool);
-impl_for_transparent_wrapper!(=> FromZeros for AtomicBool);
-impl_for_transparent_wrapper!(=> IntoBytes for AtomicBool);
+#[cfg(target_has_atomic = "8")]
+#[cfg_attr(doc_cfg, doc(cfg(target_has_atomic = "8")))]
+mod atomic_8 {
+    use super::*;
+
+    impl_traits_for_atomics!(AtomicU8, AtomicI8);
+
+    impl_for_transparent_wrapper!(=> TryFromBytes for AtomicBool);
+    impl_for_transparent_wrapper!(=> FromZeros for AtomicBool);
+    impl_for_transparent_wrapper!(=> IntoBytes for AtomicBool);
+}
+
+#[cfg(target_has_atomic = "16")]
+#[cfg_attr(doc_cfg, doc(cfg(target_has_atomic = "16")))]
+impl_traits_for_atomics!(AtomicU16, AtomicI16);
+
+#[cfg(target_has_atomic = "32")]
+#[cfg_attr(doc_cfg, doc(cfg(target_has_atomic = "32")))]
+impl_traits_for_atomics!(AtomicU32, AtomicI32);
+
+#[cfg(target_has_atomic = "64")]
+#[cfg_attr(doc_cfg, doc(cfg(target_has_atomic = "64")))]
+impl_traits_for_atomics!(AtomicU64, AtomicI64);
+
+#[cfg(target_has_atomic = "ptr")]
+#[cfg_attr(doc_cfg, doc(cfg(target_has_atomic = "ptr")))]
+impl_traits_for_atomics!(AtomicUsize, AtomicIsize);
 
 safety_comment! {
     /// SAFETY:

src/lib.rs

@@ -338,8 +338,8 @@ use core::{
     ptr::{self, NonNull},
     slice,
     sync::atomic::{
-        AtomicBool, AtomicI16, AtomicI32, AtomicI8, AtomicIsize, AtomicPtr, AtomicU16, AtomicU32,
-        AtomicU8, AtomicUsize,
+        AtomicBool, AtomicI16, AtomicI32, AtomicI64, AtomicI8, AtomicIsize, AtomicPtr, AtomicU16,
+        AtomicU32, AtomicU64, AtomicU8, AtomicUsize,
     },
 };
 
@@ -820,8 +820,9 @@ impl_known_layout!(
     bool, char,
     NonZeroU8, NonZeroI8, NonZeroU16, NonZeroI16, NonZeroU32, NonZeroI32,
     NonZeroU64, NonZeroI64, NonZeroU128, NonZeroI128, NonZeroUsize, NonZeroIsize,
-    AtomicBool, AtomicI16, AtomicI32, AtomicI8, AtomicIsize, AtomicU16, AtomicU32,
-    AtomicU8, AtomicUsize
+    AtomicBool,
+    AtomicU8, AtomicU16, AtomicU32, AtomicU64, AtomicUsize,
+    AtomicI8, AtomicI16, AtomicI32, AtomicI64, AtomicIsize
 );
 #[rustfmt::skip]
 impl_known_layout!(