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[[dcl.fct.def.coroutine]/p14](https://eel.is/c++draft/dcl.fct.def.coroutine#14)
says:
> If the evaluation of the expression promise.unhandled_exception() exits via
> an exception, the coroutine is considered suspended at the final suspend
> point.
However, this is not implemented in clang. We could observe this from:
https://godbolt.org/z/Edr59d5Y6.
This patch tries to implement [dcl.fct.def.coroutine]/p14 by rewrite the call
to `promise.unhandled_exception()` into:
C++
try {
promise.unhandled_exception();
} catch(...) {
__builtin_coro_mark_done();
throw;
}
And this patch introduces another coroutine intrinsic: `llvm.coro.mark.done()`.
This would mark the coroutine done (suspended at the final suspend).
Previously, this is done by the call to `llvm.coro.suspend(frame,
/*IsFinal=*/true)`. There are two reasons why I choose to create a new
intrinsic:
- The semantic isn't correct if we try to use `llvm.coro.suspend(,
/*IsFinal=*/true)`. First, there is nothing to suspend. Second,
`llvm.coro.suspend` has more semantics than `llvm.coro.mark.done`. So it seems
inappropriate to reuse `llvm.coro.suspend`.
- The implementation would be more simple and robust if we use new intrinsics.
There are codes treating `llvm.coro.suspend` specially. It is necessary to
construct the structure of the coroutine. And it would be complicated if we
reuse `llvm.coro.suspend(, /*IsFinal*/true)` in an inappropriate place.
After this patch, the behavior of this example would be the same with GCC:
https://godbolt.org/z/rh86xKf85.
Test Plan: check-all, https://godbolt.org/z/rh86xKf85 and an internal
coroutine library
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D115219
Files:
clang/docs/LanguageExtensions.rst
clang/include/clang/Basic/Builtins.def
clang/lib/CodeGen/CGBuiltin.cpp
clang/lib/Sema/SemaCoroutine.cpp
clang/test/CodeGenCoroutines/coro-await-resume-eh-exp-namespace.cpp
clang/test/CodeGenCoroutines/coro-await-resume-eh.cpp
clang/test/CodeGenCoroutines/coro-throw-from-unhandled_exception.cpp
llvm/docs/Coroutines.rst
llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
llvm/include/llvm/IR/Intrinsics.td
llvm/lib/Transforms/Coroutines/CoroInstr.h
llvm/lib/Transforms/Coroutines/CoroInternal.h
llvm/lib/Transforms/Coroutines/CoroSplit.cpp
llvm/lib/Transforms/Coroutines/Coroutines.cpp
llvm/test/Transforms/Coroutines/coro-mark-done.ll
Index: llvm/test/Transforms/Coroutines/coro-mark-done.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/Coroutines/coro-mark-done.ll
@@ -0,0 +1,68 @@
+; Check that the @llvm.coro.mark.done could be lowered correctly
+; RUN: opt < %s -passes='cgscc(coro-split),simplifycfg,early-cse' -S | FileCheck %s
+
+define i8* @f(i1 %val) "coroutine.presplit"="1" personality i32 3 {
+entry:
+ %id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
+ %hdl = call i8* @llvm.coro.begin(token %id, i8* null)
+ call void @print(i32 0)
+ br i1 %val, label %resume, label %susp
+
+susp:
+ %0 = call i8 @llvm.coro.suspend(token none, i1 false)
+ switch i8 %0, label %suspend [i8 0, label %resume
+ i8 1, label %suspend]
+resume:
+ invoke void @print(i32 1) to label %suspend unwind label %lpad
+
+suspend:
+ call i1 @llvm.coro.end(i8* %hdl, i1 false)
+ ret i8* %hdl
+
+lpad:
+ %lpval = landingpad { i8*, i32 }
+ cleanup
+
+ call void @llvm.coro.mark.done()
+ %need.resume = call i1 @llvm.coro.end(i8* null, i1 true)
+ resume { i8*, i32 } %lpval
+}
+; CHECK-LABEL: define i8* @f(
+; CHECK: lpad:
+; CHECK: store void (%f.Frame*)* null, void (%f.Frame*)** %resume.addr, align 8
+; CHECK-NEXT: resume { i8*, i32 } %lpval
+
+; CHECK-LABEL: define internal fastcc void @f.resume
+; CHECK: lpad:
+; CHECK: %ResumeFn.addr = getelementptr inbounds %f.Frame, %f.Frame* %FramePtr, i32 0, i32 0
+; CHECK-NEXT: store void (%f.Frame*)* null, void (%f.Frame*)** %ResumeFn.addr, align 8
+; CHECK-NEXT: resume { i8*, i32 } %lpval
+
+; CHECK-LABEL: define internal fastcc void @f.destroy
+; CHECK: lpad:
+; CHECK: %ResumeFn.addr = getelementptr inbounds %f.Frame, %f.Frame* %FramePtr, i32 0, i32 0
+; CHECK-NEXT: store void (%f.Frame*)* null, void (%f.Frame*)** %ResumeFn.addr, align 8
+; CHECK-NEXT: resume { i8*, i32 } %lpval
+
+; CHECK-LABEL: define internal fastcc void @f.cleanup
+; CHECK: lpad:
+; CHECK: %ResumeFn.addr = getelementptr inbounds %f.Frame, %f.Frame* %FramePtr, i32 0, i32 0
+; CHECK-NEXT: store void (%f.Frame*)* null, void (%f.Frame*)** %ResumeFn.addr, align 8
+; CHECK-NEXT: resume { i8*, i32 } %lpval
+
+declare i8* @llvm.coro.free(token, i8*)
+declare i32 @llvm.coro.size.i32()
+declare i8 @llvm.coro.suspend(token, i1)
+declare void @llvm.coro.resume(i8*)
+declare void @llvm.coro.destroy(i8*)
+declare void @llvm.coro.mark.done()
+
+declare token @llvm.coro.id(i32, i8*, i8*, i8*)
+declare i8* @llvm.coro.alloc(token)
+declare i8* @llvm.coro.begin(token, i8*)
+declare i1 @llvm.coro.end(i8*, i1)
+
+declare noalias i8* @malloc(i32)
+declare void @print(i32)
+declare void @free(i8*)
+
\ No newline at end of file
Index: llvm/lib/Transforms/Coroutines/Coroutines.cpp
===================================================================
--- llvm/lib/Transforms/Coroutines/Coroutines.cpp
+++ llvm/lib/Transforms/Coroutines/Coroutines.cpp
@@ -301,6 +301,9 @@
}
break;
}
+ case Intrinsic::coro_mark_done:
+ CoroMarkDones.push_back(cast<CoroMarkDoneInst>(II));
+ break;
case Intrinsic::coro_begin: {
auto CB = cast<CoroBeginInst>(II);
Index: llvm/lib/Transforms/Coroutines/CoroSplit.cpp
===================================================================
--- llvm/lib/Transforms/Coroutines/CoroSplit.cpp
+++ llvm/lib/Transforms/Coroutines/CoroSplit.cpp
@@ -1480,10 +1480,28 @@
S.resize(N);
}
+static void handleCoroMarkDone(Function &F, coro::Shape &Shape) {
+ IRBuilder<> Builder(F.getContext());
+ for (auto *CMD : Shape.CoroMarkDones) {
+ Builder.SetInsertPoint(CMD);
+ // Done state is represented by storing zero in ResumeFnAddr.
+ auto *GepIndex = Builder.CreateStructGEP(
+ Shape.FrameTy, Shape.FramePtr, coro::Shape::SwitchFieldIndex::Resume,
+ "ResumeFn.addr");
+ auto *NullPtr = ConstantPointerNull::get(cast<PointerType>(
+ Shape.FrameTy->getTypeAtIndex(coro::Shape::SwitchFieldIndex::Resume)));
+ Builder.CreateStore(NullPtr, GepIndex);
+ CMD->eraseFromParent();
+ }
+
+ Shape.CoroMarkDones.clear();
+}
+
static void splitSwitchCoroutine(Function &F, coro::Shape &Shape,
SmallVectorImpl<Function *> &Clones) {
assert(Shape.ABI == coro::ABI::Switch);
+ handleCoroMarkDone(F, Shape);
createResumeEntryBlock(F, Shape);
auto ResumeClone = createClone(F, ".resume", Shape,
CoroCloner::Kind::SwitchResume);
Index: llvm/lib/Transforms/Coroutines/CoroInternal.h
===================================================================
--- llvm/lib/Transforms/Coroutines/CoroInternal.h
+++ llvm/lib/Transforms/Coroutines/CoroInternal.h
@@ -101,6 +101,7 @@
SmallVector<CoroSizeInst *, 2> CoroSizes;
SmallVector<AnyCoroSuspendInst *, 4> CoroSuspends;
SmallVector<CallInst*, 2> SwiftErrorOps;
+ SmallVector<CoroMarkDoneInst *, 1> CoroMarkDones;
// Field indexes for special fields in the switch lowering.
struct SwitchFieldIndex {
Index: llvm/lib/Transforms/Coroutines/CoroInstr.h
===================================================================
--- llvm/lib/Transforms/Coroutines/CoroInstr.h
+++ llvm/lib/Transforms/Coroutines/CoroInstr.h
@@ -599,6 +599,18 @@
}
};
+/// This represents the llvm.coro.mark.done instruction.
+class LLVM_LIBRARY_VISIBILITY CoroMarkDoneInst : public IntrinsicInst {
+public:
+ // Methods to support type inquiry through isa, cast, and dyn_cast:
+ static bool classof(const IntrinsicInst *I) {
+ return I->getIntrinsicID() == Intrinsic::coro_mark_done;
+ }
+ static bool classof(const Value *V) {
+ return isa<IntrinsicInst>(V) && classof(cast<IntrinsicInst>(V));
+ }
+};
+
class LLVM_LIBRARY_VISIBILITY AnyCoroEndInst : public IntrinsicInst {
enum { FrameArg, UnwindArg };
Index: llvm/include/llvm/IR/Intrinsics.td
===================================================================
--- llvm/include/llvm/IR/Intrinsics.td
+++ llvm/include/llvm/IR/Intrinsics.td
@@ -1286,6 +1286,8 @@
[IntrNoMem, ReadNone<ArgIndex<0>>,
ReadNone<ArgIndex<1>>]>;
+def int_coro_mark_done : Intrinsic<[], [], []>;
+
// Coroutine Manipulation Intrinsics.
def int_coro_resume : Intrinsic<[], [llvm_ptr_ty], [Throws]>;
Index: llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
===================================================================
--- llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
+++ llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
@@ -626,6 +626,7 @@
case Intrinsic::coro_size:
case Intrinsic::coro_suspend:
case Intrinsic::coro_param:
+ case Intrinsic::coro_mark_done:
case Intrinsic::coro_subfn_addr:
// These intrinsics don't actually represent code after lowering.
return 0;
Index: llvm/docs/Coroutines.rst
===================================================================
--- llvm/docs/Coroutines.rst
+++ llvm/docs/Coroutines.rst
@@ -1644,6 +1644,54 @@
In a yield-once coroutine, it is undefined behavior if the coroutine
executes a call to ``llvm.coro.suspend.retcon`` after resuming in any way.
+.. _coro.mark.done:
+
+'llvm.coro.mark.done' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+::
+
+ declare void @llvm.coro.mark.done()
+
+Overview:
+"""""""""
+
+The '``llvm.coro.mark.done``' is used by a frontend to mark a coroutine suspended
+at the final suspend point. After '``llvm.coro.mark.done``' is called, `llvm.coro.done()`
+should return true. All of the '``llvm.coro.mark.done``' would be lowered in CoroSplit pass.
+This intrinsic is only supported for switched-resume coroutines.
+
+Arguments:
+""""""""""
+
+The '``llvm.coro.mark.done``' doesn't require any argument. The basic assumption here is that
+the coroutines in LLVM wouldn't be inlined before splitted. So there is no ambiguousity about the
+coroutine that the '``llvm.coro.mark.done``' refers to.
+
+Semantics:
+""""""""""
+
+After '``llvm.coro.mark.done``' is called in a coroutine function, the corresponding coroutine is
+considered suspend at final suspend point. In other words, it isn't allowed to resume the coroutine
+any more.
+
+Example:
+""""""""
+
+In C++'s specification, [dcl.fct.def.coroutine]/p14 says:
+> If the evaluation of the expression promise.unhandled_Âexception() exits via an exception,
+> the coroutine is considered suspended at the final suspend point.
+
+In this case, the frontend could generate following code:
+
+.. code-block:: c++
+
+ try {
+ promise.unhandled_Âexception();
+ } catch (...) {
+ call void @llvm.coro.mark.done();
+ throw;
+ }
+
.. _coro.param:
'llvm.coro.param' Intrinsic
Index: clang/test/CodeGenCoroutines/coro-throw-from-unhandled_exception.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCoroutines/coro-throw-from-unhandled_exception.cpp
@@ -0,0 +1,43 @@
+// RUN: %clang_cc1 -std=c++20 \
+// RUN: -triple=x86_64-unknown-linux-gnu -emit-llvm -o - %s \
+// RUN: -fexceptions -fcxx-exceptions -disable-llvm-passes \
+// RUN: | FileCheck %s
+
+#include "Inputs/coroutine.h"
+
+struct throwing_task {
+ struct promise_type {
+ auto get_return_object() { return throwing_task{}; }
+ auto initial_suspend() { return std::suspend_always{}; }
+ auto final_suspend() noexcept { return std::suspend_never{}; }
+ void return_void() {}
+ void unhandled_exception() { throw 43; }
+ };
+};
+
+throwing_task f() {
+ // CHECK: invoke void @_ZN13throwing_task12promise_type19unhandled_exceptionEv
+ // CHECK-NEXT: to label %{{.+}} unwind label %[[LPAD:.+]]
+ // CHECK: [[LPAD]]
+ // CHECK: br label %[[CATCH:.+]]
+ // CHECK: [[CATCH]]
+ // CHECK-NOT: br label
+ // CHECK: call void @llvm.coro.mark.done
+ // CHECK-NEXT: invoke void @__cxa_rethrow()
+ co_return;
+}
+
+struct nothrowing_task {
+ struct promise_type {
+ auto get_return_object() { return nothrowing_task{}; }
+ auto initial_suspend() { return std::suspend_always{}; }
+ auto final_suspend() noexcept { return std::suspend_never{}; }
+ void return_void() {}
+ void unhandled_exception() noexcept {}
+ };
+};
+
+nothrowing_task f2() {
+ // CHECK: call void @_ZN15nothrowing_task12promise_type19unhandled_exceptionEv
+ co_return;
+}
Index: clang/test/CodeGenCoroutines/coro-await-resume-eh.cpp
===================================================================
--- clang/test/CodeGenCoroutines/coro-await-resume-eh.cpp
+++ clang/test/CodeGenCoroutines/coro-await-resume-eh.cpp
@@ -51,6 +51,8 @@
// CHECK: invoke void @_ZN13throwing_task12promise_type19unhandled_exceptionEv
// CHECK-NEXT: to label %[[RESUMEENDCATCH:.+]] unwind label
// CHECK: [[RESUMEENDCATCH]]:
+ // CHECK-NEXT: br label %[[TRY_CONT:.+]]
+ // CHECK: [[TRY_CONT]]
// CHECK-NEXT: invoke void @__cxa_end_catch()
// CHECK-NEXT: to label %[[RESUMEENDCATCHCONT:.+]] unwind label
// CHECK: [[RESUMEENDCATCHCONT]]:
Index: clang/test/CodeGenCoroutines/coro-await-resume-eh-exp-namespace.cpp
===================================================================
--- clang/test/CodeGenCoroutines/coro-await-resume-eh-exp-namespace.cpp
+++ clang/test/CodeGenCoroutines/coro-await-resume-eh-exp-namespace.cpp
@@ -53,6 +53,8 @@
// CHECK: invoke void @_ZN13throwing_task12promise_type19unhandled_exceptionEv
// CHECK-NEXT: to label %[[RESUMEENDCATCH:.+]] unwind label
// CHECK: [[RESUMEENDCATCH]]:
+ // CHECK-NEXT: br label %[[TRY_CONT:.+]]
+ // CHECK: [[TRY_CONT]]
// CHECK-NEXT: invoke void @__cxa_end_catch()
// CHECK-NEXT: to label %[[RESUMEENDCATCHCONT:.+]] unwind label
// CHECK: [[RESUMEENDCATCHCONT]]:
Index: clang/lib/Sema/SemaCoroutine.cpp
===================================================================
--- clang/lib/Sema/SemaCoroutine.cpp
+++ clang/lib/Sema/SemaCoroutine.cpp
@@ -1476,7 +1476,43 @@
return false;
}
- this->OnException = UnhandledException.get();
+ // [dcl.fct.def.coroutine]/p14
+ // If the evaluation of the expression promise.unhandled_Âexception() exits
+ // via an exception, the coroutine is considered suspended at the final
+ // suspend point.
+ //
+ // To implement this, it convert the call to promise.unhandled_exception() to:
+ // ```
+ // try {
+ // promise.unhandled_exception();
+ // } catch (...) {
+ // __builtin_coro_mark_done();
+ // throw; // Re-throw the exception
+ // thrown from promise.unhandled_Âexception()
+ // }
+ // ```
+ //
+ // The call to __builtin_coro_mark_done would mark current coroutine as
+ // done. In other words, the coroutine is considered suspended at the final
+ // suspend point.
+ auto *TryBody = CompoundStmt::Create(S.getASTContext(),
+ UnhandledException.get(), Loc, Loc);
+
+ Expr *MarkDone =
+ S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_mark_done, {});
+ ExprResult Rethrow =
+ S.BuildCXXThrow(Loc, nullptr, /*IsThrownVarInScope=*/false);
+ if (Rethrow.isInvalid())
+ return false;
+ auto *CatchBody = CompoundStmt::Create(S.getASTContext(),
+ {MarkDone, Rethrow.get()}, Loc, Loc);
+ if (!CatchBody)
+ return false;
+
+ auto *Catch = new (S.getASTContext()) CXXCatchStmt(Loc, nullptr, CatchBody);
+
+ this->OnException =
+ CXXTryStmt::Create(S.getASTContext(), Loc, TryBody, Catch);
return true;
}
Index: clang/lib/CodeGen/CGBuiltin.cpp
===================================================================
--- clang/lib/CodeGen/CGBuiltin.cpp
+++ clang/lib/CodeGen/CGBuiltin.cpp
@@ -4696,6 +4696,8 @@
return EmitCoroutineIntrinsic(E, Intrinsic::coro_suspend);
case Builtin::BI__builtin_coro_param:
return EmitCoroutineIntrinsic(E, Intrinsic::coro_param);
+ case Builtin::BI__builtin_coro_mark_done:
+ return EmitCoroutineIntrinsic(E, Intrinsic::coro_mark_done);
// OpenCL v2.0 s6.13.16.2, Built-in pipe read and write functions
case Builtin::BIread_pipe:
Index: clang/include/clang/Basic/Builtins.def
===================================================================
--- clang/include/clang/Basic/Builtins.def
+++ clang/include/clang/Basic/Builtins.def
@@ -1611,6 +1611,7 @@
LANGBUILTIN(__builtin_coro_begin, "v*v*", "n", COR_LANG)
LANGBUILTIN(__builtin_coro_end, "bv*Ib", "n", COR_LANG)
LANGBUILTIN(__builtin_coro_suspend, "cIb", "n", COR_LANG)
+LANGBUILTIN(__builtin_coro_mark_done, "v", "n", COR_LANG)
LANGBUILTIN(__builtin_coro_param, "bv*v*", "n", COR_LANG)
// OpenCL v2.0 s6.13.16, s9.17.3.5 - Pipe functions.
Index: clang/docs/LanguageExtensions.rst
===================================================================
--- clang/docs/LanguageExtensions.rst
+++ clang/docs/LanguageExtensions.rst
@@ -3007,6 +3007,7 @@
void *__builtin_coro_begin(void *memory)
void __builtin_coro_end(void *coro_frame, bool unwind)
char __builtin_coro_suspend(bool final)
+ void __builtin_coro_mark_done()
bool __builtin_coro_param(void *original, void *copy)
Note that there is no builtin matching the `llvm.coro.save` intrinsic. LLVM
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