================
@@ -7416,3 +7416,69 @@ that ``p->array`` must have at least ``p->count`` number
of elements available:
}];
}
+
+def CoroOnlyDestroyWhenCompleteDocs : Documentation {
+ let Category = DocCatDecl;
+ let Content = [{
+The `coro_only_destroy_when_complete` attribute should be marked on a C++
class. The coroutines
+whose return type is marked as the attribute are assumed to be destroyed only
after then coroutines
+reached to the final suspend point.
+
+This is helpful for the optimizers to perform more optimizations.
+
+For example,
+
+.. code-block:: c++
+
+ A foo() {
+ dtor d;
+ co_await something();
+ dtor d1;
+ co_await something();
+ dtor d2;
+ co_return 43;
+ }
+
+The compiler may generate the following pseudocode:
+
+.. code-block:: c++
+
+ void foo.destroy(foo.Frame *frame) {
+ switch(frame->suspend_index()) {
+ case 1:
+ frame->d.~dtor();
+ break;
+ case 2:
+ frame->d.~dtor();
+ frame->d1.~dtor();
+ break;
+ case 3:
+ frame->d.~dtor();
+ frame->d1.~dtor();
+ frame->d2.~dtor();
+ break;
+ default: // coroutine completed or haven't started
+ break;
+ }
+
+ frame->promise.~promise_type();
+ delete frame;
+ }
+
----------------
erichkeane wrote:
For the section below, how about:
```
The `foo.destroy()` function's purpose is to release all of the resources
initialized for the coroutine when it is destroyed in a suspended state.
However, if the coroutine is only ever destroyed at the final suspend state,
the rest of the conditions are superfluous. The user can use the
`coro_only_destroy_when_complete` attributo suppress generation of the other
destruction cases, optimizing the above `foo.destroy` to:
```
https://github.com/llvm/llvm-project/pull/71014
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