Use const-TLS for the WorkerThread pointer (MSRV 1.59)

cuviper · cuviper · commit 733e93b53cb3 · 2023-02-26T16:58:46.000-08:00
This enables more efficient code -- stabilized in rust-lang/rust#91355.
diff --git a/rayon-core/src/registry.rs b/rayon-core/src/registry.rs
@@ -686,7 +686,7 @@ pub(super) struct WorkerThread {
 // worker is fully unwound. Using an unsafe pointer avoids the need
 // for a RefCell<T> etc.
 thread_local! {
-    static WORKER_THREAD_STATE: Cell<*const WorkerThread> = Cell::new(ptr::null());
+    static WORKER_THREAD_STATE: Cell<*const WorkerThread> = const { Cell::new(ptr::null()) };
 }
 
 impl From<ThreadBuilder> for WorkerThread {

Original file line number	Diff line number	Diff line change
`@@ -686,7 +686,7 @@ pub(super) struct WorkerThread {`
`686`	`686`	`// worker is fully unwound. Using an unsafe pointer avoids the need`
`687`	`687`	`// for a RefCell<T> etc.`
`688`	`688`	`thread_local! {`
`689`		`- static WORKER_THREAD_STATE: Cell<*const WorkerThread> = Cell::new(ptr::null());`
	`689`	`+ static WORKER_THREAD_STATE: Cell<*const WorkerThread> = const { Cell::new(ptr::null()) };`
`690`	`690`	`}`
`691`	`691`
`692`	`692`	`impl From<ThreadBuilder> for WorkerThread {`