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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.
60 lines
1.3 KiB
C++
60 lines
1.3 KiB
C++
// Test for PR59181. Tests that no conditional cleanup is created around await_suspend.
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//
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// REQUIRES: x86-registered-target
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//
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// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-llvm %s -o - -std=c++20 -disable-llvm-passes -fsanitize-address-use-after-scope | FileCheck %s
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#include "Inputs/coroutine.h"
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struct Task {
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int value_;
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struct promise_type {
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Task get_return_object() {
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return Task{0};
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}
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std::suspend_never initial_suspend() noexcept {
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return {};
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}
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std::suspend_never final_suspend() noexcept {
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return {};
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}
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void return_value(Task t) noexcept {}
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void unhandled_exception() noexcept {}
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auto await_transform(Task t) {
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struct Suspension {
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auto await_ready() noexcept { return false;}
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auto await_suspend(std::coroutine_handle<> coro) {
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coro.destroy();
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}
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auto await_resume() noexcept {
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return 0;
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}
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};
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return Suspension{};
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}
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};
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};
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Task bar(bool cond) {
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co_return cond ? Task{ co_await Task{}}: Task{};
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}
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void foo() {
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bar(true);
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}
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// CHECK: cleanup.cont:{{.*}}
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// CHECK-NEXT: load i8
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// CHECK-NEXT: trunc
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// CHECK-NEXT: store i1 false
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// CHECK: await.suspend:{{.*}}
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// CHECK-NOT: call void @llvm.lifetime
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// CHECK: call void @llvm.coro.await.suspend.void(
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// CHECK-NEXT: %{{[0-9]+}} = call i8 @llvm.coro.suspend(
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