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f786881340
Implement `llvm.coro.await.suspend` intrinsics, to deal with performance regression after prohibiting `.await_suspend` inlining, as suggested in #64945. Actually, there are three new intrinsics, which directly correspond to each of three forms of `await_suspend`: ``` void llvm.coro.await.suspend.void(ptr %awaiter, ptr %frame, ptr @wrapperFunction) i1 llvm.coro.await.suspend.bool(ptr %awaiter, ptr %frame, ptr @wrapperFunction) ptr llvm.coro.await.suspend.handle(ptr %awaiter, ptr %frame, ptr @wrapperFunction) ``` There are three different versions instead of one, because in `bool` case it's result is used for resuming via a branch, and in `coroutine_handle` case exceptions from `await_suspend` are handled in the coroutine, and exceptions from the subsequent `.resume()` are propagated to the caller. Await-suspend block is simplified down to intrinsic calls only, for example for symmetric transfer: ``` %id = call token @llvm.coro.save(ptr null) %handle = call ptr @llvm.coro.await.suspend.handle(ptr %awaiter, ptr %frame, ptr @wrapperFunction) call void @llvm.coro.resume(%handle) %result = call i8 @llvm.coro.suspend(token %id, i1 false) switch i8 %result, ... ``` All await-suspend logic is moved out into a wrapper function, generated for each suspension point. The signature of the function is `<type> wrapperFunction(ptr %awaiter, ptr %frame)` where `<type>` is one of `void` `i1` or `ptr`, depending on the return type of `await_suspend`. Intrinsic calls are lowered during `CoroSplit` pass, right after the split. Because I'm new to LLVM, I'm not sure if the helper function generation, calls to them and lowering are implemented in the right way, especially with regard to various metadata and attributes, i. e. for TBAA. All things that seemed questionable are marked with `FIXME` comments. There is another detail: in case of symmetric transfer raw pointer to the frame of coroutine, that should be resumed, is returned from the helper function and a direct call to `@llvm.coro.resume` is generated. C++ standard demands, that `.resume()` method is evaluated. Not sure how important is this, because code has been generated in the same way before, sans helper function.
51 lines
1.3 KiB
C++
51 lines
1.3 KiB
C++
// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-llvm -std=c++20 \
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// RUN: -O0 %s -o - | FileCheck %s
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// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-llvm -std=c++20 \
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// RUN: -fno-inline -O0 %s -o - | FileCheck %s
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namespace std {
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struct handle {};
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struct awaitable {
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bool await_ready() noexcept { return true; }
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// CHECK-NOT: await_suspend
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inline void __attribute__((__always_inline__)) await_suspend(handle) noexcept {}
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bool await_resume() noexcept { return true; }
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};
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template <typename T>
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struct coroutine_handle {
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static handle from_address(void *address) noexcept { return {}; }
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};
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template <typename T = void>
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struct coroutine_traits {
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struct promise_type {
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awaitable initial_suspend() { return {}; }
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awaitable final_suspend() noexcept { return {}; }
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void return_void() {}
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T get_return_object() { return T(); }
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void unhandled_exception() {}
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};
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};
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} // namespace std
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// CHECK-LABEL: @_Z3foov
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// CHECK-LABEL: entry:
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// CHECK: %ref.tmp.reload.addr = getelementptr
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// CHECK: %ref.tmp3.reload.addr = getelementptr
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void foo() { co_return; }
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// Check that bar is not inlined even it's marked as always_inline.
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// CHECK-LABEL: define {{.*}} void @_Z3bazv()
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// CHECK: call void @_Z3barv(
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__attribute__((__always_inline__)) void bar() {
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co_return;
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}
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void baz() {
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bar();
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co_return;
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}
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