Extended Description

I am not sure if it is OK to mark this with a bug. It is like a feature more to me. I mark this with bugzilla since I found this: #44911 , which tells an optimization instead of a bug.

The motivation example comes from: https://godbolt.org/z/c4zx9fE88.

The key codes is:

cppcoro::task<int> simple() noexcept {
    // 552 byte coroutine frame
    char dummy[500];
    for (int i = 0;i < 500; i++)
        dummy[i] = rand()%8;
    consume(dummy[rand()%500]);
    co_await std::experimental::suspend_always{};
    co_return 10;
}

Here we can find that the dummy isn't used across suspend point. So the dummy could show as a stack variable. If compilers could optimize this, we could get a smaller coroutine frame.