clang/test/CodeGenCoroutines/coro-elide.cpp

   1 // This tests that the coroutine elide optimization could happen succesfully.
   2 // RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++20 -O2 -emit-llvm %s -o - | FileCheck %s
   3
   4 #include "Inputs/coroutine.h"
   5
   6 struct Task {
   7   struct promise_type {
   8     struct FinalAwaiter {
   9       bool await_ready() const noexcept { return false; }
  10       template <typename PromiseType>
  11       std::coroutine_handle<> await_suspend(std::coroutine_handle<PromiseType> h) noexcept {
  12         if (!h)
  13           return std::noop_coroutine();
  14         return h.promise().continuation;
  15       }
  16       void await_resume() noexcept {}
  17     };
  18     Task get_return_object() noexcept {
  19       return std::coroutine_handle<promise_type>::from_promise(*this);
  20     }
  21     std::suspend_always initial_suspend() noexcept { return {}; }
  22     FinalAwaiter final_suspend() noexcept { return {}; }
  23     void unhandled_exception() noexcept {}
  24     void return_value(int x) noexcept {
  25       _value = x;
  26     }
  27     std::coroutine_handle<> continuation;
  28     int _value;
  29   };
  30
  31   Task(std::coroutine_handle<promise_type> handle) : handle(handle) {}
  32   ~Task() {
  33     if (handle)
  34       handle.destroy();
  35   }
  36
  37   struct Awaiter {
  38     bool await_ready() const noexcept { return false; }
  39     void await_suspend(std::coroutine_handle<void> continuation) noexcept {}
  40     int await_resume() noexcept {
  41       return 43;
  42     }
  43   };
  44
  45   auto operator co_await() {
  46     return Awaiter{};
  47   }
  48
  49 private:
  50   std::coroutine_handle<promise_type> handle;
  51 };
  52
  53 Task task0() {
  54   co_return 43;
  55 }
  56
  57 Task task1() {
  58   co_return co_await task0();
  59 }
  60
  61 // CHECK-LABEL: define{{.*}} void @_Z5task1v.resume
  62 // CHECK-NOT: call{{.*}}_Znwm