//===----- CGCoroutine.cpp - Emit LLVM Code for C++ coroutines ------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This contains code dealing with C++ code generation of coroutines.
//
//===----------------------------------------------------------------------===//
#include "CGCleanup.h"
#include "CodeGenFunction.h"
#include "llvm/ADT/ScopeExit.h"
#include "clang/AST/StmtCXX.h"
#include "clang/AST/StmtVisitor.h"
using namespace clang;
using namespace CodeGen;
using llvm::Value;
using llvm::BasicBlock;
namespace {
enum class AwaitKind { Init, Normal, Yield, Final };
static constexpr llvm::StringLiteral AwaitKindStr[] = {"init", "await", "yield",
"final"};
}
struct clang::CodeGen::CGCoroData {
// What is the current await expression kind and how many
// await/yield expressions were encountered so far.
// These are used to generate pretty labels for await expressions in LLVM IR.
AwaitKind CurrentAwaitKind = AwaitKind::Init;
unsigned AwaitNum = 0;
unsigned YieldNum = 0;
// How many co_return statements are in the coroutine. Used to decide whether
// we need to add co_return; equivalent at the end of the user authored body.
unsigned CoreturnCount = 0;
// A branch to this block is emitted when coroutine needs to suspend.
llvm::BasicBlock *SuspendBB = nullptr;
// The promise type's 'unhandled_exception' handler, if it defines one.
Stmt *ExceptionHandler = nullptr;
// A temporary i1 alloca that stores whether 'await_resume' threw an
// exception. If it did, 'true' is stored in this variable, and the coroutine
// body must be skipped. If the promise type does not define an exception
// handler, this is null.
llvm::Value *ResumeEHVar = nullptr;
// Stores the jump destination just before the coroutine memory is freed.
// This is the destination that every suspend point jumps to for the cleanup
// branch.
CodeGenFunction::JumpDest CleanupJD;
// Stores the jump destination just before the final suspend. The co_return
// statements jumps to this point after calling return_xxx promise member.
CodeGenFunction::JumpDest FinalJD;
// Stores the llvm.coro.id emitted in the function so that we can supply it
// as the first argument to coro.begin, coro.alloc and coro.free intrinsics.
// Note: llvm.coro.id returns a token that cannot be directly expressed in a
// builtin.
llvm::CallInst *CoroId = nullptr;
// Stores the llvm.coro.begin emitted in the function so that we can replace
// all coro.frame intrinsics with direct SSA value of coro.begin that returns
// the address of the coroutine frame of the current coroutine.
llvm::CallInst *CoroBegin = nullptr;
// Stores the last emitted coro.free for the deallocate expressions, we use it
// to wrap dealloc code with if(auto mem = coro.free) dealloc(mem).
llvm::CallInst *LastCoroFree = nullptr;
// If coro.id came from the builtin, remember the expression to give better
// diagnostic. If CoroIdExpr is nullptr, the coro.id was created by
// EmitCoroutineBody.
CallExpr const *CoroIdExpr = nullptr;
};
// Defining these here allows to keep CGCoroData private to this file.
clang::CodeGen::CodeGenFunction::CGCoroInfo::CGCoroInfo() {}
CodeGenFunction::CGCoroInfo::~CGCoroInfo() {}
static void createCoroData(CodeGenFunction &CGF,
CodeGenFunction::CGCoroInfo &CurCoro,
llvm::CallInst *CoroId,
CallExpr const *CoroIdExpr = nullptr) {
if (CurCoro.Data) {
if (CurCoro.Data->CoroIdExpr)
CGF.CGM.Error(CoroIdExpr->getBeginLoc(),
"only one __builtin_coro_id can be used in a function");
else if (CoroIdExpr)
CGF.CGM.Error(CoroIdExpr->getBeginLoc(),
"__builtin_coro_id shall not be used in a C++ coroutine");
else
llvm_unreachable("EmitCoroutineBodyStatement called twice?");
return;
}
CurCoro.Data = std::unique_ptr<CGCoroData>(new CGCoroData);
CurCoro.Data->CoroId = CoroId;
CurCoro.Data->CoroIdExpr = CoroIdExpr;
}
// Synthesize a pretty name for a suspend point.
static SmallString<32> buildSuspendPrefixStr(CGCoroData &Coro, AwaitKind Kind) {
unsigned No = 0;
switch (Kind) {
case AwaitKind::Init:
case AwaitKind::Final:
break;
case AwaitKind::Normal:
No = ++Coro.AwaitNum;
break;
case AwaitKind::Yield:
No = ++Coro.YieldNum;
break;
}
SmallString<32> Prefix(AwaitKindStr[static_cast<unsigned>(Kind)]);
if (No > 1) {
Twine(No).toVector(Prefix);
}
return Prefix;
}
// Check if function can throw based on prototype noexcept, also works for
// destructors which are implicitly noexcept but can be marked noexcept(false).
static bool FunctionCanThrow(const FunctionDecl *D) {
const auto *Proto = D->getType()->getAs<FunctionProtoType>();
if (!Proto) {
// Function proto is not found, we conservatively assume throwing.
return true;
}
return !isNoexceptExceptionSpec(Proto->getExceptionSpecType()) ||
Proto->canThrow() != CT_Cannot;
}
static bool ResumeStmtCanThrow(const Stmt *S) {
if (const auto *CE = dyn_cast<CallExpr>(S)) {
const auto *Callee = CE->getDirectCallee();
if (!Callee)
// We don't have direct callee. Conservatively assume throwing.
return true;
if (FunctionCanThrow(Callee))
return true;
// Fall through to visit the children.
}
if (const auto *TE = dyn_cast<CXXBindTemporaryExpr>(S)) {
// Special handling of CXXBindTemporaryExpr here as calling of Dtor of the
// temporary is not part of `children()` as covered in the fall through.
// We need to mark entire statement as throwing if the destructor of the
// temporary throws.
const auto *Dtor = TE->getTemporary()->getDestructor();
if (FunctionCanThrow(Dtor))
return true;
// Fall through to visit the children.
}
for (const auto *child : S->children())
if (ResumeStmtCanThrow(child))
return true;
return false;
}
// Emit suspend expression which roughly looks like:
//
// auto && x = CommonExpr();
// if (!x.await_ready()) {
// llvm_coro_save();
// x.await_suspend(...); (*)
// llvm_coro_suspend(); (**)
// }
// x.await_resume();
//
// where the result of the entire expression is the result of x.await_resume()
//
// (*) If x.await_suspend return type is bool, it allows to veto a suspend:
// if (x.await_suspend(...))
// llvm_coro_suspend();
//
// (**) llvm_coro_suspend() encodes three possible continuations as
// a switch instruction:
//
// %where-to = call i8 @llvm.coro.suspend(...)
// switch i8 %where-to, label %coro.ret [ ; jump to epilogue to suspend
// i8 0, label %yield.ready ; go here when resumed
// i8 1, label %yield.cleanup ; go here when destroyed
// ]
//
// See llvm's docs/Coroutines.rst for more details.
//
namespace {
struct LValueOrRValue {
LValue LV;
RValue RV;
};
}
static LValueOrRValue emitSuspendExpression(CodeGenFunction &CGF, CGCoroData &Coro,
CoroutineSuspendExpr const &S,
AwaitKind Kind, AggValueSlot aggSlot,
bool ignoreResult, bool forLValue) {
auto *E = S.getCommonExpr();
auto Binder =
CodeGenFunction::OpaqueValueMappingData::bind(CGF, S.getOpaqueValue(), E);
auto UnbindOnExit = llvm::make_scope_exit([&] { Binder.unbind(CGF); });
auto Prefix = buildSuspendPrefixStr(Coro, Kind);
BasicBlock *ReadyBlock = CGF.createBasicBlock(Prefix + Twine(".ready"));
BasicBlock *SuspendBlock = CGF.createBasicBlock(Prefix + Twine(".suspend"));
BasicBlock *CleanupBlock = CGF.createBasicBlock(Prefix + Twine(".cleanup"));
// If expression is ready, no need to suspend.
CGF.EmitBranchOnBoolExpr(S.getReadyExpr(), ReadyBlock, SuspendBlock, 0);
// Otherwise, emit suspend logic.
CGF.EmitBlock(SuspendBlock);
auto &Builder = CGF.Builder;
llvm::Function *CoroSave = CGF.CGM.getIntrinsic(llvm::Intrinsic::coro_save);
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;
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);
}
// Emit the suspend point.
const bool IsFinalSuspend = (Kind == AwaitKind::Final);
llvm::Function *CoroSuspend =
CGF.CGM.getIntrinsic(llvm::Intrinsic::coro_suspend);
auto *SuspendResult = Builder.CreateCall(
CoroSuspend, {SaveCall, Builder.getInt1(IsFinalSuspend)});
// Create a switch capturing three possible continuations.
auto *Switch = Builder.CreateSwitch(SuspendResult, Coro.SuspendBB, 2);
Switch->addCase(Builder.getInt8(0), ReadyBlock);
Switch->addCase(Builder.getInt8(1), CleanupBlock);
// Emit cleanup for this suspend point.
CGF.EmitBlock(CleanupBlock);
CGF.EmitBranchThroughCleanup(Coro.CleanupJD);
// Emit await_resume expression.
CGF.EmitBlock(ReadyBlock);
// Exception handling requires additional IR. If the 'await_resume' function
// is marked as 'noexcept', we avoid generating this additional IR.
CXXTryStmt *TryStmt = nullptr;
if (Coro.ExceptionHandler && Kind == AwaitKind::Init &&
ResumeStmtCanThrow(S.getResumeExpr())) {
Coro.ResumeEHVar =
CGF.CreateTempAlloca(Builder.getInt1Ty(), Prefix + Twine("resume.eh"));
Builder.CreateFlagStore(true, Coro.ResumeEHVar);
auto Loc = S.getResumeExpr()->getExprLoc();
auto *Catch = new (CGF.getContext())
CXXCatchStmt(Loc, /*exDecl=*/nullptr, Coro.ExceptionHandler);
auto *TryBody = CompoundStmt::Create(CGF.getContext(), S.getResumeExpr(),
FPOptionsOverride(), Loc, Loc);
TryStmt = CXXTryStmt::Create(CGF.getContext(), Loc, TryBody, Catch);
CGF.EnterCXXTryStmt(*TryStmt);
CGF.EmitStmt(TryBody);
// We don't use EmitCXXTryStmt here. We need to store to ResumeEHVar that
// doesn't exist in the body.
Builder.CreateFlagStore(false, Coro.ResumeEHVar);
CGF.ExitCXXTryStmt(*TryStmt);
LValueOrRValue Res;
// We are not supposed to obtain the value from init suspend await_resume().
Res.RV = RValue::getIgnored();
return Res;
}
LValueOrRValue Res;
if (forLValue)
Res.LV = CGF.EmitLValue(S.getResumeExpr());
else
Res.RV = CGF.EmitAnyExpr(S.getResumeExpr(), aggSlot, ignoreResult);
return Res;
}
RValue CodeGenFunction::EmitCoawaitExpr(const CoawaitExpr &E,
AggValueSlot aggSlot,
bool ignoreResult) {
return emitSuspendExpression(*this, *CurCoro.Data, E,
CurCoro.Data->CurrentAwaitKind, aggSlot,
ignoreResult, /*forLValue*/false).RV;
}
RValue CodeGenFunction::EmitCoyieldExpr(const CoyieldExpr &E,
AggValueSlot aggSlot,
bool ignoreResult) {
return emitSuspendExpression(*this, *CurCoro.Data, E, AwaitKind::Yield,
aggSlot, ignoreResult, /*forLValue*/false).RV;
}
void CodeGenFunction::EmitCoreturnStmt(CoreturnStmt const &S) {
++CurCoro.Data->CoreturnCount;
const Expr *RV = S.getOperand();
if (RV && RV->getType()->isVoidType() && !isa<InitListExpr>(RV)) {
// Make sure to evaluate the non initlist expression of a co_return
// with a void expression for side effects.
RunCleanupsScope cleanupScope(*this);
EmitIgnoredExpr(RV);
}
EmitStmt(S.getPromiseCall());
EmitBranchThroughCleanup(CurCoro.Data->FinalJD);
}
#ifndef NDEBUG
static QualType getCoroutineSuspendExprReturnType(const ASTContext &Ctx,
const CoroutineSuspendExpr *E) {
const auto *RE = E->getResumeExpr();
// Is it possible for RE to be a CXXBindTemporaryExpr wrapping
// a MemberCallExpr?
assert(isa<CallExpr>(RE) && "unexpected suspend expression type");
return cast<CallExpr>(RE)->getCallReturnType(Ctx);
}
#endif
LValue
CodeGenFunction::EmitCoawaitLValue(const CoawaitExpr *E) {
assert(getCoroutineSuspendExprReturnType(getContext(), E)->isReferenceType() &&
"Can't have a scalar return unless the return type is a "
"reference type!");
return emitSuspendExpression(*this, *CurCoro.Data, *E,
CurCoro.Data->CurrentAwaitKind, AggValueSlot::ignored(),
/*ignoreResult*/false, /*forLValue*/true).LV;
}
LValue
CodeGenFunction::EmitCoyieldLValue(const CoyieldExpr *E) {
assert(getCoroutineSuspendExprReturnType(getContext(), E)->isReferenceType() &&
"Can't have a scalar return unless the return type is a "
"reference type!");
return emitSuspendExpression(*this, *CurCoro.Data, *E,
AwaitKind::Yield, AggValueSlot::ignored(),
/*ignoreResult*/false, /*forLValue*/true).LV;
}
// Hunts for the parameter reference in the parameter copy/move declaration.
namespace {
struct GetParamRef : public StmtVisitor<GetParamRef> {
public:
DeclRefExpr *Expr = nullptr;
GetParamRef() {}
void VisitDeclRefExpr(DeclRefExpr *E) {
assert(Expr == nullptr && "multilple declref in param move");
Expr = E;
}
void VisitStmt(Stmt *S) {
for (auto *C : S->children()) {
if (C)
Visit(C);
}
}
};
}
// This class replaces references to parameters to their copies by changing
// the addresses in CGF.LocalDeclMap and restoring back the original values in
// its destructor.
namespace {
struct ParamReferenceReplacerRAII {
CodeGenFunction::DeclMapTy SavedLocals;
CodeGenFunction::DeclMapTy& LocalDeclMap;
ParamReferenceReplacerRAII(CodeGenFunction::DeclMapTy &LocalDeclMap)
: LocalDeclMap(LocalDeclMap) {}
void addCopy(DeclStmt const *PM) {
// Figure out what param it refers to.
assert(PM->isSingleDecl());
VarDecl const*VD = static_cast<VarDecl const*>(PM->getSingleDecl());
Expr const *InitExpr = VD->getInit();
GetParamRef Visitor;
Visitor.Visit(const_cast<Expr*>(InitExpr));
assert(Visitor.Expr);
DeclRefExpr *DREOrig = Visitor.Expr;
auto *PD = DREOrig->getDecl();
auto it = LocalDeclMap.find(PD);
assert(it != LocalDeclMap.end() && "parameter is not found");
SavedLocals.insert({ PD, it->second });
auto copyIt = LocalDeclMap.find(VD);
assert(copyIt != LocalDeclMap.end() && "parameter copy is not found");
it->second = copyIt->getSecond();
}
~ParamReferenceReplacerRAII() {
for (auto&& SavedLocal : SavedLocals) {
LocalDeclMap.insert({SavedLocal.first, SavedLocal.second});
}
}
};
}
// For WinEH exception representation backend needs to know what funclet coro.end
// belongs to. That information is passed in a funclet bundle.
static SmallVector<llvm::OperandBundleDef, 1>
getBundlesForCoroEnd(CodeGenFunction &CGF) {
SmallVector<llvm::OperandBundleDef, 1> BundleList;
if (llvm::Instruction *EHPad = CGF.CurrentFuncletPad)
BundleList.emplace_back("funclet", EHPad);
return BundleList;
}
namespace {
// We will insert coro.end to cut any of the destructors for objects that
// do not need to be destroyed once the coroutine is resumed.
// See llvm/docs/Coroutines.rst for more details about coro.end.
struct CallCoroEnd final : public EHScopeStack::Cleanup {
void Emit(CodeGenFunction &CGF, Flags flags) override {
auto &CGM = CGF.CGM;
auto *NullPtr = llvm::ConstantPointerNull::get(CGF.Int8PtrTy);
llvm::Function *CoroEndFn = CGM.getIntrinsic(llvm::Intrinsic::coro_end);
// See if we have a funclet bundle to associate coro.end with. (WinEH)
auto Bundles = getBundlesForCoroEnd(CGF);
auto *CoroEnd =
CGF.Builder.CreateCall(CoroEndFn,
{NullPtr, CGF.Builder.getTrue(),
llvm::ConstantTokenNone::get(CoroEndFn->getContext())},
Bundles);
if (Bundles.empty()) {
// Otherwise, (landingpad model), create a conditional branch that leads
// either to a cleanup block or a block with EH resume instruction.
auto *ResumeBB = CGF.getEHResumeBlock(/*isCleanup=*/true);
auto *CleanupContBB = CGF.createBasicBlock("cleanup.cont");
CGF.Builder.CreateCondBr(CoroEnd, ResumeBB, CleanupContBB);
CGF.EmitBlock(CleanupContBB);
}
}
};
}
namespace {
// Make sure to call coro.delete on scope exit.
struct CallCoroDelete final : public EHScopeStack::Cleanup {
Stmt *Deallocate;
// Emit "if (coro.free(CoroId, CoroBegin)) Deallocate;"
// Note: That deallocation will be emitted twice: once for a normal exit and
// once for exceptional exit. This usage is safe because Deallocate does not
// contain any declarations. The SubStmtBuilder::makeNewAndDeleteExpr()
// builds a single call to a deallocation function which is safe to emit
// multiple times.
void Emit(CodeGenFunction &CGF, Flags) override {
// Remember the current point, as we are going to emit deallocation code
// first to get to coro.free instruction that is an argument to a delete
// call.
BasicBlock *SaveInsertBlock = CGF.Builder.GetInsertBlock();
auto *FreeBB = CGF.createBasicBlock("coro.free");
CGF.EmitBlock(FreeBB);
CGF.EmitStmt(Deallocate);
auto *AfterFreeBB = CGF.createBasicBlock("after.coro.free");
CGF.EmitBlock(AfterFreeBB);
// We should have captured coro.free from the emission of deallocate.
auto *CoroFree = CGF.CurCoro.Data->LastCoroFree;
if (!CoroFree) {
CGF.CGM.Error(Deallocate->getBeginLoc(),
"Deallocation expressoin does not refer to coro.free");
return;
}
// Get back to the block we were originally and move coro.free there.
auto *InsertPt = SaveInsertBlock->getTerminator();
CoroFree->moveBefore(InsertPt);
CGF.Builder.SetInsertPoint(InsertPt);
// Add if (auto *mem = coro.free) Deallocate;
auto *NullPtr = llvm::ConstantPointerNull::get(CGF.Int8PtrTy);
auto *Cond = CGF.Builder.CreateICmpNE(CoroFree, NullPtr);
CGF.Builder.CreateCondBr(Cond, FreeBB, AfterFreeBB);
// No longer need old terminator.
InsertPt->eraseFromParent();
CGF.Builder.SetInsertPoint(AfterFreeBB);
}
explicit CallCoroDelete(Stmt *DeallocStmt) : Deallocate(DeallocStmt) {}
};
}
namespace {
struct GetReturnObjectManager {
CodeGenFunction &CGF;
CGBuilderTy &Builder;
const CoroutineBodyStmt &S;
// When true, performs RVO for the return object.
bool DirectEmit = false;
Address GroActiveFlag;
CodeGenFunction::AutoVarEmission GroEmission;
GetReturnObjectManager(CodeGenFunction &CGF, const CoroutineBodyStmt &S)
: CGF(CGF), Builder(CGF.Builder), S(S), GroActiveFlag(Address::invalid()),
GroEmission(CodeGenFunction::AutoVarEmission::invalid()) {
// The call to get_return_object is sequenced before the call to
// initial_suspend and is invoked at most once, but there are caveats
// regarding on whether the prvalue result object may be initialized
// directly/eager or delayed, depending on the types involved.
//
// More info at https://github.com/cplusplus/papers/issues/1414
//
// The general cases:
// 1. Same type of get_return_object and coroutine return type (direct
// emission):
// - Constructed in the return slot.
// 2. Different types (delayed emission):
// - Constructed temporary object prior to initial suspend initialized with
// a call to get_return_object()
// - When coroutine needs to to return to the caller and needs to construct
// return value for the coroutine it is initialized with expiring value of
// the temporary obtained above.
//
// Direct emission for void returning coroutines or GROs.
DirectEmit = [&]() {
auto *RVI = S.getReturnValueInit();
assert(RVI && "expected RVI");
auto GroType = RVI->getType();
return CGF.getContext().hasSameType(GroType, CGF.FnRetTy);
}();
}
// The gro variable has to outlive coroutine frame and coroutine promise, but,
// it can only be initialized after coroutine promise was created, thus, we
// split its emission in two parts. EmitGroAlloca emits an alloca and sets up
// cleanups. Later when coroutine promise is available we initialize the gro
// and sets the flag that the cleanup is now active.
void EmitGroAlloca() {
if (DirectEmit)
return;
auto *GroDeclStmt = dyn_cast_or_null<DeclStmt>(S.getResultDecl());
if (!GroDeclStmt) {
// If get_return_object returns void, no need to do an alloca.
return;
}
auto *GroVarDecl = cast<VarDecl>(GroDeclStmt->getSingleDecl());
// Set GRO flag that it is not initialized yet
GroActiveFlag = CGF.CreateTempAlloca(Builder.getInt1Ty(), CharUnits::One(),
"gro.active");
Builder.CreateStore(Builder.getFalse(), GroActiveFlag);
GroEmission = CGF.EmitAutoVarAlloca(*GroVarDecl);
auto *GroAlloca = dyn_cast_or_null<llvm::AllocaInst>(
GroEmission.getOriginalAllocatedAddress().getPointer());
assert(GroAlloca && "expected alloca to be emitted");
GroAlloca->setMetadata(llvm::LLVMContext::MD_coro_outside_frame,
llvm::MDNode::get(CGF.CGM.getLLVMContext(), {}));
// Remember the top of EHStack before emitting the cleanup.
auto old_top = CGF.EHStack.stable_begin();
CGF.EmitAutoVarCleanups(GroEmission);
auto top = CGF.EHStack.stable_begin();
// Make the cleanup conditional on gro.active
for (auto b = CGF.EHStack.find(top), e = CGF.EHStack.find(old_top); b != e;
b++) {
if (auto *Cleanup = dyn_cast<EHCleanupScope>(&*b)) {
assert(!Cleanup->hasActiveFlag() && "cleanup already has active flag?");
Cleanup->setActiveFlag(GroActiveFlag);
Cleanup->setTestFlagInEHCleanup();
Cleanup->setTestFlagInNormalCleanup();
}
}
}
void EmitGroInit() {
if (DirectEmit) {
// ReturnValue should be valid as long as the coroutine's return type
// is not void. The assertion could help us to reduce the check later.
assert(CGF.ReturnValue.isValid() == (bool)S.getReturnStmt());
// Now we have the promise, initialize the GRO.
// We need to emit `get_return_object` first. According to:
// [dcl.fct.def.coroutine]p7
// The call to get_return_object is sequenced before the call to
// initial_suspend and is invoked at most once.
//
// So we couldn't emit return value when we emit return statment,
// otherwise the call to get_return_object wouldn't be in front
// of initial_suspend.
if (CGF.ReturnValue.isValid()) {
CGF.EmitAnyExprToMem(S.getReturnValue(), CGF.ReturnValue,
S.getReturnValue()->getType().getQualifiers(),
/*IsInit*/ true);
}
return;
}
if (!GroActiveFlag.isValid()) {
// No Gro variable was allocated. Simply emit the call to
// get_return_object.
CGF.EmitStmt(S.getResultDecl());
return;
}
CGF.EmitAutoVarInit(GroEmission);
Builder.CreateStore(Builder.getTrue(), GroActiveFlag);
}
};
} // namespace
static void emitBodyAndFallthrough(CodeGenFunction &CGF,
const CoroutineBodyStmt &S, Stmt *Body) {
CGF.EmitStmt(Body);
const bool CanFallthrough = CGF.Builder.GetInsertBlock();
if (CanFallthrough)
if (Stmt *OnFallthrough = S.getFallthroughHandler())
CGF.EmitStmt(OnFallthrough);
}
void CodeGenFunction::EmitCoroutineBody(const CoroutineBodyStmt &S) {
auto *NullPtr = llvm::ConstantPointerNull::get(Builder.getPtrTy());
auto &TI = CGM.getContext().getTargetInfo();
unsigned NewAlign = TI.getNewAlign() / TI.getCharWidth();
auto *EntryBB = Builder.GetInsertBlock();
auto *AllocBB = createBasicBlock("coro.alloc");
auto *InitBB = createBasicBlock("coro.init");
auto *FinalBB = createBasicBlock("coro.final");
auto *RetBB = createBasicBlock("coro.ret");
auto *CoroId = Builder.CreateCall(
CGM.getIntrinsic(llvm::Intrinsic::coro_id),
{Builder.getInt32(NewAlign), NullPtr, NullPtr, NullPtr});
createCoroData(*this, CurCoro, CoroId);
CurCoro.Data->SuspendBB = RetBB;
assert(ShouldEmitLifetimeMarkers &&
"Must emit lifetime intrinsics for coroutines");
// Backend is allowed to elide memory allocations, to help it, emit
// auto mem = coro.alloc() ? 0 : ... allocation code ...;
auto *CoroAlloc = Builder.CreateCall(
CGM.getIntrinsic(llvm::Intrinsic::coro_alloc), {CoroId});
Builder.CreateCondBr(CoroAlloc, AllocBB, InitBB);
EmitBlock(AllocBB);
auto *AllocateCall = EmitScalarExpr(S.getAllocate());
auto *AllocOrInvokeContBB = Builder.GetInsertBlock();
// Handle allocation failure if 'ReturnStmtOnAllocFailure' was provided.
if (auto *RetOnAllocFailure = S.getReturnStmtOnAllocFailure()) {
auto *RetOnFailureBB = createBasicBlock("coro.ret.on.failure");
// See if allocation was successful.
auto *NullPtr = llvm::ConstantPointerNull::get(Int8PtrTy);
auto *Cond = Builder.CreateICmpNE(AllocateCall, NullPtr);
// Expect the allocation to be successful.
emitCondLikelihoodViaExpectIntrinsic(Cond, Stmt::LH_Likely);
Builder.CreateCondBr(Cond, InitBB, RetOnFailureBB);
// If not, return OnAllocFailure object.
EmitBlock(RetOnFailureBB);
EmitStmt(RetOnAllocFailure);
}
else {
Builder.CreateBr(InitBB);
}
EmitBlock(InitBB);
// Pass the result of the allocation to coro.begin.
auto *Phi = Builder.CreatePHI(VoidPtrTy, 2);
Phi->addIncoming(NullPtr, EntryBB);
Phi->addIncoming(AllocateCall, AllocOrInvokeContBB);
auto *CoroBegin = Builder.CreateCall(
CGM.getIntrinsic(llvm::Intrinsic::coro_begin), {CoroId, Phi});
CurCoro.Data->CoroBegin = CoroBegin;
GetReturnObjectManager GroManager(*this, S);
GroManager.EmitGroAlloca();
CurCoro.Data->CleanupJD = getJumpDestInCurrentScope(RetBB);
{
CGDebugInfo *DI = getDebugInfo();
ParamReferenceReplacerRAII ParamReplacer(LocalDeclMap);
CodeGenFunction::RunCleanupsScope ResumeScope(*this);
EHStack.pushCleanup<CallCoroDelete>(NormalAndEHCleanup, S.getDeallocate());
// Create mapping between parameters and copy-params for coroutine function.
llvm::ArrayRef<const Stmt *> ParamMoves = S.getParamMoves();
assert(
(ParamMoves.size() == 0 || (ParamMoves.size() == FnArgs.size())) &&
"ParamMoves and FnArgs should be the same size for coroutine function");
if (ParamMoves.size() == FnArgs.size() && DI)
for (const auto Pair : llvm::zip(FnArgs, ParamMoves))
DI->getCoroutineParameterMappings().insert(
{std::get<0>(Pair), std::get<1>(Pair)});
// Create parameter copies. We do it before creating a promise, since an
// evolution of coroutine TS may allow promise constructor to observe
// parameter copies.
for (auto *PM : S.getParamMoves()) {
EmitStmt(PM);
ParamReplacer.addCopy(cast<DeclStmt>(PM));
// TODO: if(CoroParam(...)) need to surround ctor and dtor
// for the copy, so that llvm can elide it if the copy is
// not needed.
}
EmitStmt(S.getPromiseDeclStmt());
Address PromiseAddr = GetAddrOfLocalVar(S.getPromiseDecl());
auto *PromiseAddrVoidPtr =
new llvm::BitCastInst(PromiseAddr.getPointer(), VoidPtrTy, "", CoroId);
// Update CoroId to refer to the promise. We could not do it earlier because
// promise local variable was not emitted yet.
CoroId->setArgOperand(1, PromiseAddrVoidPtr);
// Now we have the promise, initialize the GRO
GroManager.EmitGroInit();
EHStack.pushCleanup<CallCoroEnd>(EHCleanup);
CurCoro.Data->CurrentAwaitKind = AwaitKind::Init;
CurCoro.Data->ExceptionHandler = S.getExceptionHandler();
EmitStmt(S.getInitSuspendStmt());
CurCoro.Data->FinalJD = getJumpDestInCurrentScope(FinalBB);
CurCoro.Data->CurrentAwaitKind = AwaitKind::Normal;
if (CurCoro.Data->ExceptionHandler) {
// If we generated IR to record whether an exception was thrown from
// 'await_resume', then use that IR to determine whether the coroutine
// body should be skipped.
// If we didn't generate the IR (perhaps because 'await_resume' was marked
// as 'noexcept'), then we skip this check.
BasicBlock *ContBB = nullptr;
if (CurCoro.Data->ResumeEHVar) {
BasicBlock *BodyBB = createBasicBlock("coro.resumed.body");
ContBB = createBasicBlock("coro.resumed.cont");
Value *SkipBody = Builder.CreateFlagLoad(CurCoro.Data->ResumeEHVar,
"coro.resumed.eh");
Builder.CreateCondBr(SkipBody, ContBB, BodyBB);
EmitBlock(BodyBB);
}
auto Loc = S.getBeginLoc();
CXXCatchStmt Catch(Loc, /*exDecl=*/nullptr,
CurCoro.Data->ExceptionHandler);
auto *TryStmt =
CXXTryStmt::Create(getContext(), Loc, S.getBody(), &Catch);
EnterCXXTryStmt(*TryStmt);
emitBodyAndFallthrough(*this, S, TryStmt->getTryBlock());
ExitCXXTryStmt(*TryStmt);
if (ContBB)
EmitBlock(ContBB);
}
else {
emitBodyAndFallthrough(*this, S, S.getBody());
}
// See if we need to generate final suspend.
const bool CanFallthrough = Builder.GetInsertBlock();
const bool HasCoreturns = CurCoro.Data->CoreturnCount > 0;
if (CanFallthrough || HasCoreturns) {
EmitBlock(FinalBB);
CurCoro.Data->CurrentAwaitKind = AwaitKind::Final;
EmitStmt(S.getFinalSuspendStmt());
} else {
// We don't need FinalBB. Emit it to make sure the block is deleted.
EmitBlock(FinalBB, /*IsFinished=*/true);
}
}
EmitBlock(RetBB);
// Emit coro.end before getReturnStmt (and parameter destructors), since
// resume and destroy parts of the coroutine should not include them.
llvm::Function *CoroEnd = CGM.getIntrinsic(llvm::Intrinsic::coro_end);
Builder.CreateCall(CoroEnd,
{NullPtr, Builder.getFalse(),
llvm::ConstantTokenNone::get(CoroEnd->getContext())});
if (Stmt *Ret = S.getReturnStmt()) {
// Since we already emitted the return value above, so we shouldn't
// emit it again here.
if (GroManager.DirectEmit)
cast<ReturnStmt>(Ret)->setRetValue(nullptr);
EmitStmt(Ret);
}
// LLVM require the frontend to mark the coroutine.
CurFn->setPresplitCoroutine();
if (CXXRecordDecl *RD = FnRetTy->getAsCXXRecordDecl();
RD && RD->hasAttr<CoroOnlyDestroyWhenCompleteAttr>())
CurFn->setCoroDestroyOnlyWhenComplete();
}
// Emit coroutine intrinsic and patch up arguments of the token type.
RValue CodeGenFunction::EmitCoroutineIntrinsic(const CallExpr *E,
unsigned int IID) {
SmallVector<llvm::Value *, 8> Args;
switch (IID) {
default:
break;
// The coro.frame builtin is replaced with an SSA value of the coro.begin
// intrinsic.
case llvm::Intrinsic::coro_frame: {
if (CurCoro.Data && CurCoro.Data->CoroBegin) {
return RValue::get(CurCoro.Data->CoroBegin);
}
CGM.Error(E->getBeginLoc(), "this builtin expect that __builtin_coro_begin "
"has been used earlier in this function");
auto *NullPtr = llvm::ConstantPointerNull::get(Builder.getPtrTy());
return RValue::get(NullPtr);
}
case llvm::Intrinsic::coro_size: {
auto &Context = getContext();
CanQualType SizeTy = Context.getSizeType();
llvm::IntegerType *T = Builder.getIntNTy(Context.getTypeSize(SizeTy));
llvm::Function *F = CGM.getIntrinsic(llvm::Intrinsic::coro_size, T);
return RValue::get(Builder.CreateCall(F));
}
case llvm::Intrinsic::coro_align: {
auto &Context = getContext();
CanQualType SizeTy = Context.getSizeType();
llvm::IntegerType *T = Builder.getIntNTy(Context.getTypeSize(SizeTy));
llvm::Function *F = CGM.getIntrinsic(llvm::Intrinsic::coro_align, T);
return RValue::get(Builder.CreateCall(F));
}
// The following three intrinsics take a token parameter referring to a token
// returned by earlier call to @llvm.coro.id. Since we cannot represent it in
// builtins, we patch it up here.
case llvm::Intrinsic::coro_alloc:
case llvm::Intrinsic::coro_begin:
case llvm::Intrinsic::coro_free: {
if (CurCoro.Data && CurCoro.Data->CoroId) {
Args.push_back(CurCoro.Data->CoroId);
break;
}
CGM.Error(E->getBeginLoc(), "this builtin expect that __builtin_coro_id has"
" been used earlier in this function");
// Fallthrough to the next case to add TokenNone as the first argument.
[[fallthrough]];
}
// @llvm.coro.suspend takes a token parameter. Add token 'none' as the first
// argument.
case llvm::Intrinsic::coro_suspend:
Args.push_back(llvm::ConstantTokenNone::get(getLLVMContext()));
break;
}
for (const Expr *Arg : E->arguments())
Args.push_back(EmitScalarExpr(Arg));
// @llvm.coro.end takes a token parameter. Add token 'none' as the last
// argument.
if (IID == llvm::Intrinsic::coro_end)
Args.push_back(llvm::ConstantTokenNone::get(getLLVMContext()));
llvm::Function *F = CGM.getIntrinsic(IID);
llvm::CallInst *Call = Builder.CreateCall(F, Args);
// Note: The following code is to enable to emit coro.id and coro.begin by
// hand to experiment with coroutines in C.
// If we see @llvm.coro.id remember it in the CoroData. We will update
// coro.alloc, coro.begin and coro.free intrinsics to refer to it.
if (IID == llvm::Intrinsic::coro_id) {
createCoroData(*this, CurCoro, Call, E);
}
else if (IID == llvm::Intrinsic::coro_begin) {
if (CurCoro.Data)
CurCoro.Data->CoroBegin = Call;
}
else if (IID == llvm::Intrinsic::coro_free) {
// Remember the last coro_free as we need it to build the conditional
// deletion of the coroutine frame.
if (CurCoro.Data)
CurCoro.Data->LastCoroFree = Call;
}
return RValue::get(Call);
}
