Stabilize WebAssembly atomic intrinsics

This commit stabilizes the wasm atomic intrinsics now that the threads
proposal has advanced to Stage 4, and is shipping in browsers.
Unfortunately these intrinsics still aren't available through the
precompiled versions of the standard library because atomics are no

Author: alexcrichton

crates/core_arch/src/wasm32/atomic.rs

@@ -51,6 +51,7 @@ extern "C" {
 /// [instr]: https://webassembly.github.io/threads/syntax/instructions.html#syntax-instr-atomic-memory
 #[inline]
 #[cfg_attr(test, assert_instr("i32.atomic.wait"))]
+#[stable(feature = "wasm_atomics", since = "1.50.0")]
 pub unsafe fn memory_atomic_wait32(ptr: *mut i32, expression: i32, timeout_ns: i64) -> i32 {
     llvm_atomic_wait_i32(ptr, expression, timeout_ns)
 }
@@ -86,6 +87,7 @@ pub unsafe fn memory_atomic_wait32(ptr: *mut i32, expression: i32, timeout_ns: i
 /// [instr]: https://webassembly.github.io/threads/syntax/instructions.html#syntax-instr-atomic-memory
 #[inline]
 #[cfg_attr(test, assert_instr("i64.atomic.wait"))]
+#[stable(feature = "wasm_atomics", since = "1.50.0")]
 pub unsafe fn memory_atomic_wait64(ptr: *mut i64, expression: i64, timeout_ns: i64) -> i32 {
     llvm_atomic_wait_i64(ptr, expression, timeout_ns)
 }
@@ -113,6 +115,7 @@ pub unsafe fn memory_atomic_wait64(ptr: *mut i64, expression: i64, timeout_ns: i
 /// [instr]: https://webassembly.github.io/threads/syntax/instructions.html#syntax-instr-atomic-memory
 #[inline]
 #[cfg_attr(test, assert_instr("atomic.wake"))]
+#[stable(feature = "wasm_atomics", since = "1.50.0")]
 pub unsafe fn memory_atomic_notify(ptr: *mut i32, waiters: u32) -> u32 {
     llvm_atomic_notify(ptr, waiters as i32) as u32
 }