Author: modocache Date: Sun Oct 7 20:08:39 2018 New Revision: 343949 URL: http://llvm.org/viewvc/llvm-project?rev=343949&view=rev Log: [coro]Pass rvalue reference for named local variable to return_value
Summary: Addressing https://bugs.llvm.org/show_bug.cgi?id=37265. Implements [class.copy]/33 of coroutines TS. When the criteria for elision of a copy/move operation are met, but not for an exception-declaration, and the object to be copied is designated by an lvalue, or when the expression in a return or co_return statement is a (possibly parenthesized) id-expression that names an object with automatic storage duration declared in the body or parameter-declaration-clause of the innermost enclosing function or lambda-expression, overload resolution to select the constructor for the copy or the return_value overload to call is first performed as if the object were designated by an rvalue. Patch by Tanoy Sinha! Reviewers: modocache, GorNishanov Reviewed By: modocache, GorNishanov Subscribers: cfe-commits Differential Revision: https://reviews.llvm.org/D51741 Added: cfe/trunk/test/SemaCXX/coroutine-rvo.cpp Modified: cfe/trunk/lib/Sema/SemaCoroutine.cpp Modified: cfe/trunk/lib/Sema/SemaCoroutine.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaCoroutine.cpp?rev=343949&r1=343948&r2=343949&view=diff ============================================================================== --- cfe/trunk/lib/Sema/SemaCoroutine.cpp (original) +++ cfe/trunk/lib/Sema/SemaCoroutine.cpp Sun Oct 7 20:08:39 2018 @@ -841,6 +841,19 @@ StmtResult Sema::BuildCoreturnStmt(Sourc E = R.get(); } + // Move the return value if we can + if (E) { + auto NRVOCandidate = this->getCopyElisionCandidate(E->getType(), E, CES_AsIfByStdMove); + if (NRVOCandidate) { + InitializedEntity Entity = + InitializedEntity::InitializeResult(Loc, E->getType(), NRVOCandidate); + ExprResult MoveResult = this->PerformMoveOrCopyInitialization( + Entity, NRVOCandidate, E->getType(), E); + if (MoveResult.get()) + E = MoveResult.get(); + } + } + // FIXME: If the operand is a reference to a variable that's about to go out // of scope, we should treat the operand as an xvalue for this overload // resolution. Added: cfe/trunk/test/SemaCXX/coroutine-rvo.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/coroutine-rvo.cpp?rev=343949&view=auto ============================================================================== --- cfe/trunk/test/SemaCXX/coroutine-rvo.cpp (added) +++ cfe/trunk/test/SemaCXX/coroutine-rvo.cpp Sun Oct 7 20:08:39 2018 @@ -0,0 +1,69 @@ +// RUN: %clang_cc1 -triple x86_64-apple-darwin9 %s -stdlib=libc++ -std=c++1z -fcoroutines-ts -fsyntax-only + +namespace std::experimental { +template <class Promise = void> struct coroutine_handle { + coroutine_handle() = default; + static coroutine_handle from_address(void *) noexcept; +}; + +template <> struct coroutine_handle<void> { + static coroutine_handle from_address(void *) noexcept; + coroutine_handle() = default; + template <class PromiseType> + coroutine_handle(coroutine_handle<PromiseType>) noexcept; +}; + +template <class... Args> +struct void_t_imp { + using type = void; +}; +template <class... Args> +using void_t = typename void_t_imp<Args...>::type; + +template <class T, class = void> +struct traits_sfinae_base {}; + +template <class T> +struct traits_sfinae_base<T, void_t<typename T::promise_type>> { + using promise_type = typename T::promise_type; +}; + +template <class Ret, class... Args> +struct coroutine_traits : public traits_sfinae_base<Ret> {}; +} + +struct suspend_never { + bool await_ready() noexcept; + void await_suspend(std::experimental::coroutine_handle<>) noexcept; + void await_resume() noexcept; +}; + +struct MoveOnly { + MoveOnly() {}; + MoveOnly(const MoveOnly&) = delete; + MoveOnly(MoveOnly&&) noexcept {}; + ~MoveOnly() {}; +}; + +template <typename T> +struct task { + struct promise_type { + auto initial_suspend() { return suspend_never{}; } + auto final_suspend() { return suspend_never{}; } + auto get_return_object() { return task{}; } + static void unhandled_exception() {} + void return_value(T&& value) {} + }; +}; + +task<MoveOnly> f() { + MoveOnly value; + co_return value; +} + +int main() { + f(); + return 0; +} + +// expected-no-diagnostics _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
