[coroutine] Implement llvm.coro.await.suspend intrinsic #79712
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@llvm/pr-subscribers-clang-modules @llvm/pr-subscribers-clang Author: None (fpasserby) ChangesImplement There are three different versions instead of one, because in Await-suspend block is simplified down to intrinsic calls only, for example for the symmetric transfer case: All the await-suspend logic is moved out into a helper function, generated for each suspension point. 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 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 Patch is 58.82 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/79712.diff 20 Files Affected:
diff --git a/clang/include/clang/AST/ExprCXX.h b/clang/include/clang/AST/ExprCXX.h
index a0e467b35778c5c..57a505036def409 100644
--- a/clang/include/clang/AST/ExprCXX.h
+++ b/clang/include/clang/AST/ExprCXX.h
@@ -5035,15 +5035,19 @@ class CoroutineSuspendExpr : public Expr {
enum SubExpr { Operand, Common, Ready, Suspend, Resume, Count };
Stmt *SubExprs[SubExpr::Count];
+ bool IsSuspendNoThrow = false;
OpaqueValueExpr *OpaqueValue = nullptr;
+ OpaqueValueExpr *OpaqueFramePtr = nullptr;
public:
CoroutineSuspendExpr(StmtClass SC, SourceLocation KeywordLoc, Expr *Operand,
Expr *Common, Expr *Ready, Expr *Suspend, Expr *Resume,
- OpaqueValueExpr *OpaqueValue)
+ bool IsSuspendNoThrow, OpaqueValueExpr *OpaqueValue,
+ OpaqueValueExpr *OpaqueFramePtr)
: Expr(SC, Resume->getType(), Resume->getValueKind(),
Resume->getObjectKind()),
- KeywordLoc(KeywordLoc), OpaqueValue(OpaqueValue) {
+ KeywordLoc(KeywordLoc), IsSuspendNoThrow(IsSuspendNoThrow),
+ OpaqueValue(OpaqueValue), OpaqueFramePtr(OpaqueFramePtr) {
SubExprs[SubExpr::Operand] = Operand;
SubExprs[SubExpr::Common] = Common;
SubExprs[SubExpr::Ready] = Ready;
@@ -5080,6 +5084,9 @@ class CoroutineSuspendExpr : public Expr {
/// getOpaqueValue - Return the opaque value placeholder.
OpaqueValueExpr *getOpaqueValue() const { return OpaqueValue; }
+ /// getOpaqueFramePtr - Return coroutine frame pointer placeholder.
+ OpaqueValueExpr *getOpaqueFramePtr() const { return OpaqueFramePtr; }
+
Expr *getReadyExpr() const {
return static_cast<Expr*>(SubExprs[SubExpr::Ready]);
}
@@ -5097,6 +5104,8 @@ class CoroutineSuspendExpr : public Expr {
return static_cast<Expr *>(SubExprs[SubExpr::Operand]);
}
+ bool isSuspendNoThrow() const { return IsSuspendNoThrow; }
+
SourceLocation getKeywordLoc() const { return KeywordLoc; }
SourceLocation getBeginLoc() const LLVM_READONLY { return KeywordLoc; }
@@ -5125,10 +5134,12 @@ class CoawaitExpr : public CoroutineSuspendExpr {
public:
CoawaitExpr(SourceLocation CoawaitLoc, Expr *Operand, Expr *Common,
- Expr *Ready, Expr *Suspend, Expr *Resume,
- OpaqueValueExpr *OpaqueValue, bool IsImplicit = false)
+ Expr *Ready, Expr *Suspend, Expr *Resume, bool IsSuspendNoThrow,
+ OpaqueValueExpr *OpaqueValue, OpaqueValueExpr *OpaqueFramePtr,
+ bool IsImplicit = false)
: CoroutineSuspendExpr(CoawaitExprClass, CoawaitLoc, Operand, Common,
- Ready, Suspend, Resume, OpaqueValue) {
+ Ready, Suspend, Resume, IsSuspendNoThrow,
+ OpaqueValue, OpaqueFramePtr) {
CoawaitBits.IsImplicit = IsImplicit;
}
@@ -5206,10 +5217,11 @@ class CoyieldExpr : public CoroutineSuspendExpr {
public:
CoyieldExpr(SourceLocation CoyieldLoc, Expr *Operand, Expr *Common,
- Expr *Ready, Expr *Suspend, Expr *Resume,
- OpaqueValueExpr *OpaqueValue)
+ Expr *Ready, Expr *Suspend, Expr *Resume, bool IsSuspendNoThrow,
+ OpaqueValueExpr *OpaqueValue, OpaqueValueExpr *OpaqueFramePtr)
: CoroutineSuspendExpr(CoyieldExprClass, CoyieldLoc, Operand, Common,
- Ready, Suspend, Resume, OpaqueValue) {}
+ Ready, Suspend, Resume, IsSuspendNoThrow,
+ OpaqueValue, OpaqueFramePtr) {}
CoyieldExpr(SourceLocation CoyieldLoc, QualType Ty, Expr *Operand,
Expr *Common)
: CoroutineSuspendExpr(CoyieldExprClass, CoyieldLoc, Ty, Operand,
diff --git a/clang/lib/CodeGen/CGCoroutine.cpp b/clang/lib/CodeGen/CGCoroutine.cpp
index 888d30bfb3e1d6a..1c768df41d43c09 100644
--- a/clang/lib/CodeGen/CGCoroutine.cpp
+++ b/clang/lib/CodeGen/CGCoroutine.cpp
@@ -212,9 +212,10 @@ static LValueOrRValue emitSuspendExpression(CodeGenFunction &CGF, CGCoroData &Co
bool ignoreResult, bool forLValue) {
auto *E = S.getCommonExpr();
- auto Binder =
+ auto CommonBinder =
CodeGenFunction::OpaqueValueMappingData::bind(CGF, S.getOpaqueValue(), E);
- auto UnbindOnExit = llvm::make_scope_exit([&] { Binder.unbind(CGF); });
+ auto UnbindCommonOnExit =
+ llvm::make_scope_exit([&] { CommonBinder.unbind(CGF); });
auto Prefix = buildSuspendPrefixStr(Coro, Kind);
BasicBlock *ReadyBlock = CGF.createBasicBlock(Prefix + Twine(".ready"));
@@ -232,16 +233,57 @@ static LValueOrRValue emitSuspendExpression(CodeGenFunction &CGF, CGCoroData &Co
auto *NullPtr = llvm::ConstantPointerNull::get(CGF.CGM.Int8PtrTy);
auto *SaveCall = Builder.CreateCall(CoroSave, {NullPtr});
- CGF.CurCoro.InSuspendBlock = true;
- auto *SuspendRet = CGF.EmitScalarExpr(S.getSuspendExpr());
- CGF.CurCoro.InSuspendBlock = false;
+ auto SuspendHelper = CodeGenFunction(CGF.CGM).generateAwaitSuspendHelper(
+ CGF.CurFn->getName(), Prefix, S);
- if (SuspendRet != nullptr && SuspendRet->getType()->isIntegerTy(1)) {
- // Veto suspension if requested by bool returning await_suspend.
- BasicBlock *RealSuspendBlock =
- CGF.createBasicBlock(Prefix + Twine(".suspend.bool"));
- CGF.Builder.CreateCondBr(SuspendRet, RealSuspendBlock, ReadyBlock);
- CGF.EmitBlock(RealSuspendBlock);
+ llvm::CallBase *SuspendRet = nullptr;
+
+ {
+ CGF.CurCoro.InSuspendBlock = true;
+
+ auto FramePtrBinder = CodeGenFunction::OpaqueValueMappingData::bind(
+ CGF, S.getOpaqueFramePtr(), S.getOpaqueFramePtr()->getSourceExpr());
+ auto UnbindFramePtrOnExit =
+ llvm::make_scope_exit([&] { FramePtrBinder.unbind(CGF); });
+
+ SmallVector<llvm::Value *, 3> SuspendHelperCallArgs;
+ SuspendHelperCallArgs.push_back(
+ CGF.getOrCreateOpaqueLValueMapping(S.getOpaqueValue()).getPointer(CGF));
+ SuspendHelperCallArgs.push_back(
+ CGF.getOrCreateOpaqueRValueMapping(S.getOpaqueFramePtr())
+ .getScalarVal());
+ SuspendHelperCallArgs.push_back(SuspendHelper);
+
+ auto IID = llvm::Intrinsic::coro_await_suspend;
+ if (S.getSuspendExpr()->getType()->isBooleanType())
+ IID = llvm::Intrinsic::coro_await_suspend_bool;
+ else if (S.getSuspendExpr()->getType()->isVoidPointerType())
+ IID = llvm::Intrinsic::coro_await_suspend_handle;
+
+ llvm::Function *AwaitSuspendIntrinsic = CGF.CGM.getIntrinsic(IID);
+ // FIXME: add call attributes?
+ if (S.isSuspendNoThrow()) {
+ SuspendRet = CGF.EmitNounwindRuntimeCall(AwaitSuspendIntrinsic,
+ SuspendHelperCallArgs);
+ } else {
+ SuspendRet =
+ CGF.EmitCallOrInvoke(AwaitSuspendIntrinsic, SuspendHelperCallArgs);
+ }
+
+ CGF.CurCoro.InSuspendBlock = false;
+ }
+
+ if (SuspendRet != nullptr) {
+ if (SuspendRet->getType()->isIntegerTy(1)) {
+ // Veto suspension if requested by bool returning await_suspend.
+ BasicBlock *RealSuspendBlock =
+ CGF.createBasicBlock(Prefix + Twine(".suspend.bool"));
+ CGF.Builder.CreateCondBr(SuspendRet, RealSuspendBlock, ReadyBlock);
+ CGF.EmitBlock(RealSuspendBlock);
+ } else if (SuspendRet->getType()->isPointerTy()) {
+ auto ResumeIntrinsic = CGF.CGM.getIntrinsic(llvm::Intrinsic::coro_resume);
+ Builder.CreateCall(ResumeIntrinsic, SuspendRet);
+ }
}
// Emit the suspend point.
@@ -338,6 +380,85 @@ static QualType getCoroutineSuspendExprReturnType(const ASTContext &Ctx,
}
#endif
+llvm::Function *
+CodeGenFunction::generateAwaitSuspendHelper(Twine const &CoroName,
+ Twine const &SuspendPointName,
+ CoroutineSuspendExpr const &S) {
+ std::string FuncName = "__await_suspend_helper_";
+ FuncName += CoroName.str();
+ FuncName += SuspendPointName.str();
+
+ ASTContext &C = getContext();
+
+ FunctionArgList args;
+
+ ImplicitParamDecl AwaiterDecl(C, C.VoidPtrTy, ImplicitParamKind::Other);
+ ImplicitParamDecl FrameDecl(C, C.VoidPtrTy, ImplicitParamKind::Other);
+ QualType ReturnTy = S.getSuspendExpr()->getType();
+
+ if (ReturnTy->isBooleanType()) {
+ ReturnTy = C.BoolTy;
+ } else if (ReturnTy->isVoidPointerType()) {
+ ReturnTy = C.VoidPtrTy;
+ } else {
+ ReturnTy = C.VoidTy;
+ }
+
+ args.push_back(&AwaiterDecl);
+ args.push_back(&FrameDecl);
+
+ const CGFunctionInfo &FI =
+ CGM.getTypes().arrangeBuiltinFunctionDeclaration(ReturnTy, args);
+
+ llvm::FunctionType *LTy = CGM.getTypes().GetFunctionType(FI);
+
+ llvm::Function *Fn = llvm::Function::Create(
+ LTy, llvm::GlobalValue::PrivateLinkage, FuncName, &CGM.getModule());
+
+ Fn->addParamAttr(0, llvm::Attribute::AttrKind::NonNull);
+ Fn->addParamAttr(0, llvm::Attribute::AttrKind::NoUndef);
+
+ Fn->addParamAttr(1, llvm::Attribute::AttrKind::NoUndef);
+
+ Fn->setMustProgress();
+ Fn->addFnAttr(llvm::Attribute::AttrKind::AlwaysInline);
+
+ if (S.isSuspendNoThrow()) {
+ Fn->addFnAttr(llvm::Attribute::AttrKind::NoUnwind);
+ }
+
+ StartFunction(GlobalDecl(), ReturnTy, Fn, FI, args);
+
+ llvm::Value *AwaiterPtr = Builder.CreateLoad(GetAddrOfLocalVar(&AwaiterDecl));
+ auto AwaiterLValue =
+ MakeNaturalAlignAddrLValue(AwaiterPtr, AwaiterDecl.getType());
+
+ // FIXME: mark as aliasing with awaiter?
+ // FIXME: TBAA?
+ // FIXME: emit in a better way (maybe egenerate AST in SemaCoroutine)?
+ auto FramePtrRValue =
+ RValue::get(Builder.CreateLoad(GetAddrOfLocalVar(&FrameDecl)));
+
+ auto AwaiterBinder = CodeGenFunction::OpaqueValueMappingData::bind(
+ *this, S.getOpaqueValue(), AwaiterLValue);
+ auto FramePtrBinder = CodeGenFunction::OpaqueValueMappingData::bind(
+ *this, S.getOpaqueFramePtr(), FramePtrRValue);
+
+ auto *SuspendRet = EmitScalarExpr(S.getSuspendExpr());
+
+ auto UnbindCommonOnExit =
+ llvm::make_scope_exit([&] { AwaiterBinder.unbind(*this); });
+ auto UnbindFramePtrOnExit =
+ llvm::make_scope_exit([&] { FramePtrBinder.unbind(*this); });
+ if (SuspendRet != nullptr) {
+ Fn->addRetAttr(llvm::Attribute::AttrKind::NoUndef);
+ Builder.CreateStore(SuspendRet, ReturnValue);
+ }
+
+ FinishFunction();
+ return Fn;
+}
+
LValue
CodeGenFunction::EmitCoawaitLValue(const CoawaitExpr *E) {
assert(getCoroutineSuspendExprReturnType(getContext(), E)->isReferenceType() &&
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 143ad64e8816b12..811dbd9aed44e46 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -350,6 +350,10 @@ class CodeGenFunction : public CodeGenTypeCache {
return isCoroutine() && CurCoro.InSuspendBlock;
}
+ llvm::Function *generateAwaitSuspendHelper(Twine const &CoroName,
+ Twine const &SuspendPointName,
+ CoroutineSuspendExpr const &S);
+
/// CurGD - The GlobalDecl for the current function being compiled.
GlobalDecl CurGD;
diff --git a/clang/lib/Sema/SemaCoroutine.cpp b/clang/lib/Sema/SemaCoroutine.cpp
index a969b9383563b22..a46744205d0f298 100644
--- a/clang/lib/Sema/SemaCoroutine.cpp
+++ b/clang/lib/Sema/SemaCoroutine.cpp
@@ -31,6 +31,8 @@
using namespace clang;
using namespace sema;
+static bool isNoThrow(Sema &S, const Stmt *E);
+
static LookupResult lookupMember(Sema &S, const char *Name, CXXRecordDecl *RD,
SourceLocation Loc, bool &Res) {
DeclarationName DN = S.PP.getIdentifierInfo(Name);
@@ -266,7 +268,7 @@ static ExprResult buildOperatorCoawaitCall(Sema &SemaRef, Scope *S,
}
static ExprResult buildCoroutineHandle(Sema &S, QualType PromiseType,
- SourceLocation Loc) {
+ Expr *FramePtr, SourceLocation Loc) {
QualType CoroHandleType = lookupCoroutineHandleType(S, PromiseType, Loc);
if (CoroHandleType.isNull())
return ExprError();
@@ -280,9 +282,6 @@ static ExprResult buildCoroutineHandle(Sema &S, QualType PromiseType,
return ExprError();
}
- Expr *FramePtr =
- S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_frame, {});
-
CXXScopeSpec SS;
ExprResult FromAddr =
S.BuildDeclarationNameExpr(SS, Found, /*NeedsADL=*/false);
@@ -296,6 +295,8 @@ struct ReadySuspendResumeResult {
enum AwaitCallType { ACT_Ready, ACT_Suspend, ACT_Resume };
Expr *Results[3];
OpaqueValueExpr *OpaqueValue;
+ OpaqueValueExpr *OpaqueFramePtr;
+ bool IsSuspendNoThrow;
bool IsInvalid;
};
@@ -380,66 +381,7 @@ static Expr *maybeTailCall(Sema &S, QualType RetType, Expr *E,
// __builtin_coro_resume so that the cleanup code are not inserted in-between
// the resume call and return instruction, which would interfere with the
// musttail call contract.
- JustAddress = S.MaybeCreateExprWithCleanups(JustAddress);
- return S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_resume,
- JustAddress);
-}
-
-/// The await_suspend call performed by co_await is essentially asynchronous
-/// to the execution of the coroutine. Inlining it normally into an unsplit
-/// coroutine can cause miscompilation because the coroutine CFG misrepresents
-/// the true control flow of the program: things that happen in the
-/// await_suspend are not guaranteed to happen prior to the resumption of the
-/// coroutine, and things that happen after the resumption of the coroutine
-/// (including its exit and the potential deallocation of the coroutine frame)
-/// are not guaranteed to happen only after the end of await_suspend.
-///
-/// See https://github.com/llvm/llvm-project/issues/56301 and
-/// https://reviews.llvm.org/D157070 for the example and the full discussion.
-///
-/// The short-term solution to this problem is to mark the call as uninlinable.
-/// But we don't want to do this if the call is known to be trivial, which is
-/// very common.
-///
-/// The long-term solution may introduce patterns like:
-///
-/// call @llvm.coro.await_suspend(ptr %awaiter, ptr %handle,
-/// ptr @awaitSuspendFn)
-///
-/// Then it is much easier to perform the safety analysis in the middle end.
-/// If it is safe to inline the call to awaitSuspend, we can replace it in the
-/// CoroEarly pass. Otherwise we could replace it in the CoroSplit pass.
-static void tryMarkAwaitSuspendNoInline(Sema &S, OpaqueValueExpr *Awaiter,
- CallExpr *AwaitSuspend) {
- // The method here to extract the awaiter decl is not precise.
- // This is intentional. Since it is hard to perform the analysis in the
- // frontend due to the complexity of C++'s type systems.
- // And we prefer to perform such analysis in the middle end since it is
- // easier to implement and more powerful.
- CXXRecordDecl *AwaiterDecl =
- Awaiter->getType().getNonReferenceType()->getAsCXXRecordDecl();
-
- if (AwaiterDecl && AwaiterDecl->field_empty())
- return;
-
- FunctionDecl *FD = AwaitSuspend->getDirectCallee();
-
- assert(FD);
-
- // If the `await_suspend()` function is marked as `always_inline` explicitly,
- // we should give the user the right to control the codegen.
- if (FD->hasAttr<NoInlineAttr>() || FD->hasAttr<AlwaysInlineAttr>())
- return;
-
- // This is problematic if the user calls the await_suspend standalone. But on
- // the on hand, it is not incorrect semantically since inlining is not part
- // of the standard. On the other hand, it is relatively rare to call
- // the await_suspend function standalone.
- //
- // And given we've already had the long-term plan, the current workaround
- // looks relatively tolerant.
- FD->addAttr(
- NoInlineAttr::CreateImplicit(S.getASTContext(), FD->getLocation()));
+ return S.MaybeCreateExprWithCleanups(JustAddress);
}
/// Build calls to await_ready, await_suspend, and await_resume for a co_await
@@ -461,7 +403,11 @@ static ReadySuspendResumeResult buildCoawaitCalls(Sema &S, VarDecl *CoroPromise,
// Assume valid until we see otherwise.
// Further operations are responsible for setting IsInalid to true.
- ReadySuspendResumeResult Calls = {{}, Operand, /*IsInvalid=*/false};
+ ReadySuspendResumeResult Calls = {{},
+ Operand,
+ /*OpaqueFramePtr=*/nullptr,
+ /*IsSuspendNoThrow=*/false,
+ /*IsInvalid=*/false};
using ACT = ReadySuspendResumeResult::AwaitCallType;
@@ -495,8 +441,17 @@ static ReadySuspendResumeResult buildCoawaitCalls(Sema &S, VarDecl *CoroPromise,
Calls.Results[ACT::ACT_Ready] = S.MaybeCreateExprWithCleanups(Conv.get());
}
+ Expr *GetFramePtr =
+ S.BuildBuiltinCallExpr(Loc, Builtin::BI__builtin_coro_frame, {});
+
+ OpaqueValueExpr *FramePtr = new (S.Context)
+ OpaqueValueExpr(Loc, GetFramePtr->getType(), VK_PRValue,
+ GetFramePtr->getObjectKind(), GetFramePtr);
+
+ Calls.OpaqueFramePtr = FramePtr;
+
ExprResult CoroHandleRes =
- buildCoroutineHandle(S, CoroPromise->getType(), Loc);
+ buildCoroutineHandle(S, CoroPromise->getType(), FramePtr, Loc);
if (CoroHandleRes.isInvalid()) {
Calls.IsInvalid = true;
return Calls;
@@ -513,10 +468,6 @@ static ReadySuspendResumeResult buildCoawaitCalls(Sema &S, VarDecl *CoroPromise,
// type Z.
QualType RetType = AwaitSuspend->getCallReturnType(S.Context);
- // We need to mark await_suspend as noinline temporarily. See the comment
- // of tryMarkAwaitSuspendNoInline for details.
- tryMarkAwaitSuspendNoInline(S, Operand, AwaitSuspend);
-
// Support for coroutine_handle returning await_suspend.
if (Expr *TailCallSuspend =
maybeTailCall(S, RetType, AwaitSuspend, Loc))
@@ -542,6 +493,10 @@ static ReadySuspendResumeResult buildCoawaitCalls(Sema &S, VarDecl *CoroPromise,
}
}
+ if (Calls.Results[ACT::ACT_Suspend]) {
+ Calls.IsSuspendNoThrow = isNoThrow(S, Calls.Results[ACT::ACT_Suspend]);
+ }
+
BuildSubExpr(ACT::ACT_Resume, "await_resume", std::nullopt);
// Make sure the awaiter object gets a chance to be cleaned up.
@@ -694,6 +649,59 @@ static FunctionScopeInfo *checkCoroutineContext(Sema &S, SourceLocation Loc,
return ScopeInfo;
}
+/// Recursively check \p E and all its children to see if any call target
+/// (including constructor call) is declared noexcept. Also any value returned
+/// from the call has a noexcept destructor.
+static bool isNoThrow(Sema &S, const Stmt *E) {
+ auto isDeclNoexcept = [&](const Decl *D, bool IsDtor = false) -> bool {
+ // In the case of dtor, the call to dtor is implicit and hence we should
+ // pass nullptr to canCalleeThrow.
+ if (Sema::canCalleeThrow(S, IsDtor ? nullptr : cast<Expr>(E), D)) {
+ return false;
+ }
+ return true;
+ };
+
+ if (auto *CE = dyn_cast<CXXConstructExpr>(E)) {
+ CXXConstructorDecl *Ctor = CE->getConstructor();
+ if (!isDeclNoexcept(Ctor)) {
+ return false;
+ }
+ // Check the corresponding destructor of the constructor.
+ if (!isDeclNoexcept(Ctor->getParent()->getDestructor(), /*IsDtor=*/true)) {
+ return false;
+ }
+ } else if (auto *CE = dyn_cast<CallExpr>(E)) {
+ if (CE->isTypeDependent())
+ return false;
+
+ if (!isDeclNoexcept(CE->getCalleeDecl())) {
+ return false;
+ }
+
+ QualType ReturnType = CE->getCallReturnType(S.getASTContext());
+ // Check the destructor of the call return type, if any.
+ if (ReturnType.isDestructedType() ==
+ QualType::DestructionKind::DK_cxx_destructor) {
+ const auto *T =
+ cast<RecordType>(ReturnType.getCanonicalType().getTypePtr());
+ if (!isDeclNoexcept(cast<CXXRecordDecl>(T->getDecl())->getDestructor(),
+ /*IsDtor=*/true)) {
+ return false;
+ }
+ }
+ }
+ for (const auto *Child : E->children()) {
+ if (!Child)
+ continue;
+ if (!isNoThrow(S, Child)) {
+ return false;
+ }
+ }
+
+ return true;
+}
+
/// Recursively check \p E and all its children to see if any call target
/// (including constructor call) is declared noexcept. Also any value returned
/// from the call has a noexcept destructor.
@@ -992,9 +1000,9 @@ ExprResult Sema::BuildR...
[truncated]
|
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✅ With the latest revision this PR passed the C/C++ code formatter. |
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Thanks for looking into this. I haven't looked it in details. Given this is complex, it should take a relative longer time.
Here is some quick feedbacks:
- Every time we change the non-static data members of AST nodes, we need to update the serializations. Otherwise, modules won't work.
- Every time we change the LLVM intrinsics, we need to change the documentation.
- Every time we change the LLVM with a functional change, we need a test in the LLVM part.
And there is something I haven't fully understand:
- I feel odd about
helperFunction. I don't understand the necessity and I feel we should make it in the middle end. - I feel odd about
IsSuspendNoThrow. Can't we make it simply during the CodeGen time by the attribute ofawait_suspend?. - I am wondering if we can get rid of the introduction of
OpaqueFramePtrfromCoroutineSuspendExpreither in CodeGen part or in Sema part.
But I am not sure if my feelings are correct. I need more time looking into it.
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Thank you for replying so quickly. |
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I got the reason why I felt __await_suspend_helper_ was odd. In my imagination, we only need to emit the function await_suspend(handle) to an LLVM function and pass that to llvm.coro.await.suspend directly.
But the conversion to the actual code may need some additional code. So the idea to wrap them into a helper function makes sense. I feel the name wrapper sounds better to me. Helper is too broad.
clang/lib/CodeGen/CGCoroutine.cpp
Outdated
| // FIXME: add call attributes? | ||
| if (AwaitSuspendCanThrow) | ||
| SuspendRet = | ||
| CGF.EmitCallOrInvoke(AwaitSuspendIntrinsic, SuspendHelperCallArgs); | ||
| else | ||
| SuspendRet = CGF.EmitNounwindRuntimeCall(AwaitSuspendIntrinsic, | ||
| SuspendHelperCallArgs); |
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CGF.EmitCallOrInvoke should be sufficient. We don't need to perform such optimizations here.
|
BTW, in my original comment, I said:
But this patch only implements the otherwise part. This is not a blocking issue. But we need a TODO or a FIXME here. |
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| FuncName += CoroName.str(); | ||
| FuncName += '_'; | ||
| FuncName += SuspendPointName.str(); |
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I feel it is better to concat the name of the awaiter instead of the coroutines and suspend number.
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I've tested it on seastar and libcppcoro tests and on the example from #72006. |
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I'll merge this since I find you may not have commit access. |
| // FIXME: add TBAA metadata to the loads | ||
| llvm::Value *AwaiterPtr = Builder.CreateLoad(GetAddrOfLocalVar(&AwaiterDecl)); | ||
| auto AwaiterLValue = | ||
| MakeNaturalAlignAddrLValue(AwaiterPtr, AwaiterDecl.getType()); |
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I wonder whether the type passed to MakeNaturalAlignAddrLValue is correct. AwaiterDecl.getType() is void *, but shouldn't S.getOpaqueValue() be passed?
I think this was causing a libc++ test to crash when ubsan was enabled (see #86898).
S.getOpaqueValue() and AwaiterLValue are passed to OpaqueValueMappingData::bind. clang mis-compiles when the lvalue has a larger alignment than the type of S.getOpaqueValue().
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Yeah.. it looks like it would be better to pass the type of S.getOpaqueValue(). The void* is simply a placeholder.
Would you like to handle this? I feel you are the better option since you can test it with your own patch. Otherwise I'll try to make it myself.
…pendWrapper Use the correct type for AwaiterDecl instead of using `void *`. See the discussion here: llvm#79712 (comment)
Implement
llvm.coro.await.suspendintrinsics, to deal with performance regression after prohibiting.await_suspendinlining, as suggested in #64945.Actually, there are three new intrinsics, which directly correspond to each of three forms of
await_suspend:There are three different versions instead of one, because in
boolcase it's result is used for resuming via a branch, and incoroutine_handlecase exceptions fromawait_suspendare 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:
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 ofvoidi1orptr, depending on the return type ofawait_suspend.Intrinsic calls are lowered during
CoroSplitpass, 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
FIXMEcomments.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.resumeis 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.