Merge pull request #1896 from haileys/inline-never-for-rvo

Write to TaskStorage::future via never-inlined fn to encourage RVO

3 files changed, 7 insertions, 5 deletions

diff --git a/embassy-executor/src/arch/wasm.rs b/embassy-executor/src/arch/wasm.rs
index 934fd69e5..15aed867a 100644
--- a/embassy-executor/src/arch/wasm.rs
+++ b/embassy-executor/src/arch/wasm.rs
@@ -73,9 +73,10 @@ mod thread {
         pub fn start(&'static mut self, init: impl FnOnce(Spawner)) {
             unsafe {
                 let executor = &self.inner;
-                self.ctx.closure.write(Closure::new(move |_| {
+                let future = Closure::new(move |_| {
                     executor.poll();
-                }));
+                });
+                self.ctx.closure.write_in_place(|| future);
                 init(self.inner.spawner());
             }
         }
diff --git a/embassy-executor/src/raw/mod.rs b/embassy-executor/src/raw/mod.rs
index c1d82e18a..6d2c1c18a 100644
--- a/embassy-executor/src/raw/mod.rs
+++ b/embassy-executor/src/raw/mod.rs
@@ -203,7 +203,7 @@ impl<F: Future + 'static> AvailableTask<F> {
     fn initialize_impl<S>(self, future: impl FnOnce() -> F) -> SpawnToken<S> {
         unsafe {
             self.task.raw.poll_fn.set(Some(TaskStorage::<F>::poll));
-            self.task.future.write(future());
+            self.task.future.write_in_place(future);
 
             let task = TaskRef::new(self.task);
 
diff --git a/embassy-executor/src/raw/util.rs b/embassy-executor/src/raw/util.rs
index e2e8f4df8..c46085e45 100644
--- a/embassy-executor/src/raw/util.rs
+++ b/embassy-executor/src/raw/util.rs
@@ -17,8 +17,9 @@ impl<T> UninitCell<T> {
         &mut *self.as_mut_ptr()
     }
 
-    pub unsafe fn write(&self, val: T) {
-        ptr::write(self.as_mut_ptr(), val)
+    #[inline(never)]
+    pub unsafe fn write_in_place(&self, func: impl FnOnce() -> T) {
+        ptr::write(self.as_mut_ptr(), func())
     }
 
     pub unsafe fn drop_in_place(&self) {