[Bug c++/120243] [15/16 Regression] Exception rethrown from coroutine promise type unhandled_exception not caught under -O1

[rs2740 at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120243

--- Comment #1 from TC <rs2740 at gmail dot com> ---
A similar example but with an initially suspended coroutine terminates at -O2
or highter.

#include <coroutine>

struct coro {
     struct promise_type {
        promise_type() = default;

        std::suspend_always initial_suspend() const noexcept { return {}; }
        std::suspend_always final_suspend() const noexcept { return {}; }

        void unhandled_exception() { throw; }

        coro get_return_object() { return
{std::coroutine_handle<promise_type>::from_promise(*this)}; }
        void return_void() {}
    };

    std::coroutine_handle<promise_type> h;
};

int main() {
    auto c = []() -> coro {
        throw "hello";
        __builtin_abort();
        co_return;
    };
    try {
        c().h.resume();
    }
    catch(...) {
        __builtin_printf("Caught!\n");
    }
}