1//===----- CGCoroutine.cpp - Emit LLVM Code for C++ coroutines ------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This contains code dealing with C++ code generation of coroutines.
10//
11//===----------------------------------------------------------------------===//
12
13#include "CGCleanup.h"
14#include "CodeGenFunction.h"
15#include "llvm/ADT/ScopeExit.h"
16#include "clang/AST/StmtCXX.h"
17#include "clang/AST/StmtVisitor.h"
18
19using namespace clang;
20using namespace CodeGen;
21
22using llvm::Value;
23using llvm::BasicBlock;
24
25namespace {
26enum class AwaitKind { Init, Normal, Yield, Final };
27static constexpr llvm::StringLiteral AwaitKindStr[] = {"init", "await", "yield",
28                                                       "final"};
29}
30
31struct clang::CodeGen::CGCoroData {
32  // What is the current await expression kind and how many
33  // await/yield expressions were encountered so far.
34  // These are used to generate pretty labels for await expressions in LLVM IR.
35  AwaitKind CurrentAwaitKind = AwaitKind::Init;
36  unsigned AwaitNum = 0;
37  unsigned YieldNum = 0;
38
39  // How many co_return statements are in the coroutine. Used to decide whether
40  // we need to add co_return; equivalent at the end of the user authored body.
41  unsigned CoreturnCount = 0;
42
43  // A branch to this block is emitted when coroutine needs to suspend.
44  llvm::BasicBlock *SuspendBB = nullptr;
45
46  // The promise type's 'unhandled_exception' handler, if it defines one.
47  Stmt *ExceptionHandler = nullptr;
48
49  // A temporary i1 alloca that stores whether 'await_resume' threw an
50  // exception. If it did, 'true' is stored in this variable, and the coroutine
51  // body must be skipped. If the promise type does not define an exception
52  // handler, this is null.
53  llvm::Value *ResumeEHVar = nullptr;
54
55  // Stores the jump destination just before the coroutine memory is freed.
56  // This is the destination that every suspend point jumps to for the cleanup
57  // branch.
58  CodeGenFunction::JumpDest CleanupJD;
59
60  // Stores the jump destination just before the final suspend. The co_return
61  // statements jumps to this point after calling return_xxx promise member.
62  CodeGenFunction::JumpDest FinalJD;
63
64  // Stores the llvm.coro.id emitted in the function so that we can supply it
65  // as the first argument to coro.begin, coro.alloc and coro.free intrinsics.
66  // Note: llvm.coro.id returns a token that cannot be directly expressed in a
67  // builtin.
68  llvm::CallInst *CoroId = nullptr;
69
70  // Stores the llvm.coro.begin emitted in the function so that we can replace
71  // all coro.frame intrinsics with direct SSA value of coro.begin that returns
72  // the address of the coroutine frame of the current coroutine.
73  llvm::CallInst *CoroBegin = nullptr;
74
75  // Stores the last emitted coro.free for the deallocate expressions, we use it
76  // to wrap dealloc code with if(auto mem = coro.free) dealloc(mem).
77  llvm::CallInst *LastCoroFree = nullptr;
78
79  // If coro.id came from the builtin, remember the expression to give better
80  // diagnostic. If CoroIdExpr is nullptr, the coro.id was created by
81  // EmitCoroutineBody.
82  CallExpr const *CoroIdExpr = nullptr;
83};
84
85// Defining these here allows to keep CGCoroData private to this file.
86clang::CodeGen::CodeGenFunction::CGCoroInfo::CGCoroInfo() {}
87CodeGenFunction::CGCoroInfo::~CGCoroInfo() {}
88
89static void createCoroData(CodeGenFunction &CGF,
90                           CodeGenFunction::CGCoroInfo &CurCoro,
91                           llvm::CallInst *CoroId,
92                           CallExpr const *CoroIdExpr = nullptr) {
93  if (CurCoro.Data) {
94    if (CurCoro.Data->CoroIdExpr)
95      CGF.CGM.Error(CoroIdExpr->getBeginLoc(),
96                    "only one __builtin_coro_id can be used in a function");
97    else if (CoroIdExpr)
98      CGF.CGM.Error(CoroIdExpr->getBeginLoc(),
99                    "__builtin_coro_id shall not be used in a C++ coroutine");
100    else
101      llvm_unreachable("EmitCoroutineBodyStatement called twice?");
102
103    return;
104  }
105
106  CurCoro.Data = std::unique_ptr<CGCoroData>(new CGCoroData);
107  CurCoro.Data->CoroId = CoroId;
108  CurCoro.Data->CoroIdExpr = CoroIdExpr;
109}
110
111// Synthesize a pretty name for a suspend point.
112static SmallString<32> buildSuspendPrefixStr(CGCoroData &Coro, AwaitKind Kind) {
113  unsigned No = 0;
114  switch (Kind) {
115  case AwaitKind::Init:
116  case AwaitKind::Final:
117    break;
118  case AwaitKind::Normal:
119    No = ++Coro.AwaitNum;
120    break;
121  case AwaitKind::Yield:
122    No = ++Coro.YieldNum;
123    break;
124  }
125  SmallString<32> Prefix(AwaitKindStr[static_cast<unsigned>(Kind)]);
126  if (No > 1) {
127    Twine(No).toVector(Prefix);
128  }
129  return Prefix;
130}
131
132static bool memberCallExpressionCanThrow(const Expr *E) {
133  if (const auto *CE = dyn_cast<CXXMemberCallExpr>(E))
134    if (const auto *Proto =
135            CE->getMethodDecl()->getType()->getAs<FunctionProtoType>())
136      if (isNoexceptExceptionSpec(Proto->getExceptionSpecType()) &&
137          Proto->canThrow() == CT_Cannot)
138        return false;
139  return true;
140}
141
142// Emit suspend expression which roughly looks like:
143//
144//   auto && x = CommonExpr();
145//   if (!x.await_ready()) {
146//      llvm_coro_save();
147//      x.await_suspend(...);     (*)
148//      llvm_coro_suspend(); (**)
149//   }
150//   x.await_resume();
151//
152// where the result of the entire expression is the result of x.await_resume()
153//
154//   (*) If x.await_suspend return type is bool, it allows to veto a suspend:
155//      if (x.await_suspend(...))
156//        llvm_coro_suspend();
157//
158//  (**) llvm_coro_suspend() encodes three possible continuations as
159//       a switch instruction:
160//
161//  %where-to = call i8 @llvm.coro.suspend(...)
162//  switch i8 %where-to, label %coro.ret [ ; jump to epilogue to suspend
163//    i8 0, label %yield.ready   ; go here when resumed
164//    i8 1, label %yield.cleanup ; go here when destroyed
165//  ]
166//
167//  See llvm's docs/Coroutines.rst for more details.
168//
169namespace {
170  struct LValueOrRValue {
171    LValue LV;
172    RValue RV;
173  };
174}
175static LValueOrRValue emitSuspendExpression(CodeGenFunction &CGF, CGCoroData &Coro,
176                                    CoroutineSuspendExpr const &S,
177                                    AwaitKind Kind, AggValueSlot aggSlot,
178                                    bool ignoreResult, bool forLValue) {
179  auto *E = S.getCommonExpr();
180
181  auto Binder =
182      CodeGenFunction::OpaqueValueMappingData::bind(CGF, S.getOpaqueValue(), E);
183  auto UnbindOnExit = llvm::make_scope_exit([&] { Binder.unbind(CGF); });
184
185  auto Prefix = buildSuspendPrefixStr(Coro, Kind);
186  BasicBlock *ReadyBlock = CGF.createBasicBlock(Prefix + Twine(".ready"));
187  BasicBlock *SuspendBlock = CGF.createBasicBlock(Prefix + Twine(".suspend"));
188  BasicBlock *CleanupBlock = CGF.createBasicBlock(Prefix + Twine(".cleanup"));
189
190  // If expression is ready, no need to suspend.
191  CGF.EmitBranchOnBoolExpr(S.getReadyExpr(), ReadyBlock, SuspendBlock, 0);
192
193  // Otherwise, emit suspend logic.
194  CGF.EmitBlock(SuspendBlock);
195
196  auto &Builder = CGF.Builder;
197  llvm::Function *CoroSave = CGF.CGM.getIntrinsic(llvm::Intrinsic::coro_save);
198  auto *NullPtr = llvm::ConstantPointerNull::get(CGF.CGM.Int8PtrTy);
199  auto *SaveCall = Builder.CreateCall(CoroSave, {NullPtr});
200
201  auto *SuspendRet = CGF.EmitScalarExpr(S.getSuspendExpr());
202  if (SuspendRet != nullptr && SuspendRet->getType()->isIntegerTy(1)) {
203    // Veto suspension if requested by bool returning await_suspend.
204    BasicBlock *RealSuspendBlock =
205        CGF.createBasicBlock(Prefix + Twine(".suspend.bool"));
206    CGF.Builder.CreateCondBr(SuspendRet, RealSuspendBlock, ReadyBlock);
207    CGF.EmitBlock(RealSuspendBlock);
208  }
209
210  // Emit the suspend point.
211  const bool IsFinalSuspend = (Kind == AwaitKind::Final);
212  llvm::Function *CoroSuspend =
213      CGF.CGM.getIntrinsic(llvm::Intrinsic::coro_suspend);
214  auto *SuspendResult = Builder.CreateCall(
215      CoroSuspend, {SaveCall, Builder.getInt1(IsFinalSuspend)});
216
217  // Create a switch capturing three possible continuations.
218  auto *Switch = Builder.CreateSwitch(SuspendResult, Coro.SuspendBB, 2);
219  Switch->addCase(Builder.getInt8(0), ReadyBlock);
220  Switch->addCase(Builder.getInt8(1), CleanupBlock);
221
222  // Emit cleanup for this suspend point.
223  CGF.EmitBlock(CleanupBlock);
224  CGF.EmitBranchThroughCleanup(Coro.CleanupJD);
225
226  // Emit await_resume expression.
227  CGF.EmitBlock(ReadyBlock);
228
229  // Exception handling requires additional IR. If the 'await_resume' function
230  // is marked as 'noexcept', we avoid generating this additional IR.
231  CXXTryStmt *TryStmt = nullptr;
232  if (Coro.ExceptionHandler && Kind == AwaitKind::Init &&
233      memberCallExpressionCanThrow(S.getResumeExpr())) {
234    Coro.ResumeEHVar =
235        CGF.CreateTempAlloca(Builder.getInt1Ty(), Prefix + Twine("resume.eh"));
236    Builder.CreateFlagStore(true, Coro.ResumeEHVar);
237
238    auto Loc = S.getResumeExpr()->getExprLoc();
239    auto *Catch = new (CGF.getContext())
240        CXXCatchStmt(Loc, /*exDecl=*/nullptr, Coro.ExceptionHandler);
241    auto *TryBody =
242        CompoundStmt::Create(CGF.getContext(), S.getResumeExpr(), Loc, Loc);
243    TryStmt = CXXTryStmt::Create(CGF.getContext(), Loc, TryBody, Catch);
244    CGF.EnterCXXTryStmt(*TryStmt);
245  }
246
247  LValueOrRValue Res;
248  if (forLValue)
249    Res.LV = CGF.EmitLValue(S.getResumeExpr());
250  else
251    Res.RV = CGF.EmitAnyExpr(S.getResumeExpr(), aggSlot, ignoreResult);
252
253  if (TryStmt) {
254    Builder.CreateFlagStore(false, Coro.ResumeEHVar);
255    CGF.ExitCXXTryStmt(*TryStmt);
256  }
257
258  return Res;
259}
260
261RValue CodeGenFunction::EmitCoawaitExpr(const CoawaitExpr &E,
262                                        AggValueSlot aggSlot,
263                                        bool ignoreResult) {
264  return emitSuspendExpression(*this, *CurCoro.Data, E,
265                               CurCoro.Data->CurrentAwaitKind, aggSlot,
266                               ignoreResult, /*forLValue*/false).RV;
267}
268RValue CodeGenFunction::EmitCoyieldExpr(const CoyieldExpr &E,
269                                        AggValueSlot aggSlot,
270                                        bool ignoreResult) {
271  return emitSuspendExpression(*this, *CurCoro.Data, E, AwaitKind::Yield,
272                               aggSlot, ignoreResult, /*forLValue*/false).RV;
273}
274
275void CodeGenFunction::EmitCoreturnStmt(CoreturnStmt const &S) {
276  ++CurCoro.Data->CoreturnCount;
277  const Expr *RV = S.getOperand();
278  if (RV && RV->getType()->isVoidType()) {
279    // Make sure to evaluate the expression of a co_return with a void
280    // expression for side effects.
281    RunCleanupsScope cleanupScope(*this);
282    EmitIgnoredExpr(RV);
283  }
284  EmitStmt(S.getPromiseCall());
285  EmitBranchThroughCleanup(CurCoro.Data->FinalJD);
286}
287
288
289#ifndef NDEBUG
290static QualType getCoroutineSuspendExprReturnType(const ASTContext &Ctx,
291  const CoroutineSuspendExpr *E) {
292  const auto *RE = E->getResumeExpr();
293  // Is it possible for RE to be a CXXBindTemporaryExpr wrapping
294  // a MemberCallExpr?
295  assert(isa<CallExpr>(RE) && "unexpected suspend expression type");
296  return cast<CallExpr>(RE)->getCallReturnType(Ctx);
297}
298#endif
299
300LValue
301CodeGenFunction::EmitCoawaitLValue(const CoawaitExpr *E) {
302  assert(getCoroutineSuspendExprReturnType(getContext(), E)->isReferenceType() &&
303         "Can't have a scalar return unless the return type is a "
304         "reference type!");
305  return emitSuspendExpression(*this, *CurCoro.Data, *E,
306                               CurCoro.Data->CurrentAwaitKind, AggValueSlot::ignored(),
307                               /*ignoreResult*/false, /*forLValue*/true).LV;
308}
309
310LValue
311CodeGenFunction::EmitCoyieldLValue(const CoyieldExpr *E) {
312  assert(getCoroutineSuspendExprReturnType(getContext(), E)->isReferenceType() &&
313         "Can't have a scalar return unless the return type is a "
314         "reference type!");
315  return emitSuspendExpression(*this, *CurCoro.Data, *E,
316                               AwaitKind::Yield, AggValueSlot::ignored(),
317                               /*ignoreResult*/false, /*forLValue*/true).LV;
318}
319
320// Hunts for the parameter reference in the parameter copy/move declaration.
321namespace {
322struct GetParamRef : public StmtVisitor<GetParamRef> {
323public:
324  DeclRefExpr *Expr = nullptr;
325  GetParamRef() {}
326  void VisitDeclRefExpr(DeclRefExpr *E) {
327    assert(Expr == nullptr && "multilple declref in param move");
328    Expr = E;
329  }
330  void VisitStmt(Stmt *S) {
331    for (auto *C : S->children()) {
332      if (C)
333        Visit(C);
334    }
335  }
336};
337}
338
339// This class replaces references to parameters to their copies by changing
340// the addresses in CGF.LocalDeclMap and restoring back the original values in
341// its destructor.
342
343namespace {
344  struct ParamReferenceReplacerRAII {
345    CodeGenFunction::DeclMapTy SavedLocals;
346    CodeGenFunction::DeclMapTy& LocalDeclMap;
347
348    ParamReferenceReplacerRAII(CodeGenFunction::DeclMapTy &LocalDeclMap)
349        : LocalDeclMap(LocalDeclMap) {}
350
351    void addCopy(DeclStmt const *PM) {
352      // Figure out what param it refers to.
353
354      assert(PM->isSingleDecl());
355      VarDecl const*VD = static_cast<VarDecl const*>(PM->getSingleDecl());
356      Expr const *InitExpr = VD->getInit();
357      GetParamRef Visitor;
358      Visitor.Visit(const_cast<Expr*>(InitExpr));
359      assert(Visitor.Expr);
360      DeclRefExpr *DREOrig = Visitor.Expr;
361      auto *PD = DREOrig->getDecl();
362
363      auto it = LocalDeclMap.find(PD);
364      assert(it != LocalDeclMap.end() && "parameter is not found");
365      SavedLocals.insert({ PD, it->second });
366
367      auto copyIt = LocalDeclMap.find(VD);
368      assert(copyIt != LocalDeclMap.end() && "parameter copy is not found");
369      it->second = copyIt->getSecond();
370    }
371
372    ~ParamReferenceReplacerRAII() {
373      for (auto&& SavedLocal : SavedLocals) {
374        LocalDeclMap.insert({SavedLocal.first, SavedLocal.second});
375      }
376    }
377  };
378}
379
380// For WinEH exception representation backend needs to know what funclet coro.end
381// belongs to. That information is passed in a funclet bundle.
382static SmallVector<llvm::OperandBundleDef, 1>
383getBundlesForCoroEnd(CodeGenFunction &CGF) {
384  SmallVector<llvm::OperandBundleDef, 1> BundleList;
385
386  if (llvm::Instruction *EHPad = CGF.CurrentFuncletPad)
387    BundleList.emplace_back("funclet", EHPad);
388
389  return BundleList;
390}
391
392namespace {
393// We will insert coro.end to cut any of the destructors for objects that
394// do not need to be destroyed once the coroutine is resumed.
395// See llvm/docs/Coroutines.rst for more details about coro.end.
396struct CallCoroEnd final : public EHScopeStack::Cleanup {
397  void Emit(CodeGenFunction &CGF, Flags flags) override {
398    auto &CGM = CGF.CGM;
399    auto *NullPtr = llvm::ConstantPointerNull::get(CGF.Int8PtrTy);
400    llvm::Function *CoroEndFn = CGM.getIntrinsic(llvm::Intrinsic::coro_end);
401    // See if we have a funclet bundle to associate coro.end with. (WinEH)
402    auto Bundles = getBundlesForCoroEnd(CGF);
403    auto *CoroEnd = CGF.Builder.CreateCall(
404        CoroEndFn, {NullPtr, CGF.Builder.getTrue()}, Bundles);
405    if (Bundles.empty()) {
406      // Otherwise, (landingpad model), create a conditional branch that leads
407      // either to a cleanup block or a block with EH resume instruction.
408      auto *ResumeBB = CGF.getEHResumeBlock(/*isCleanup=*/true);
409      auto *CleanupContBB = CGF.createBasicBlock("cleanup.cont");
410      CGF.Builder.CreateCondBr(CoroEnd, ResumeBB, CleanupContBB);
411      CGF.EmitBlock(CleanupContBB);
412    }
413  }
414};
415}
416
417namespace {
418// Make sure to call coro.delete on scope exit.
419struct CallCoroDelete final : public EHScopeStack::Cleanup {
420  Stmt *Deallocate;
421
422  // Emit "if (coro.free(CoroId, CoroBegin)) Deallocate;"
423
424  // Note: That deallocation will be emitted twice: once for a normal exit and
425  // once for exceptional exit. This usage is safe because Deallocate does not
426  // contain any declarations. The SubStmtBuilder::makeNewAndDeleteExpr()
427  // builds a single call to a deallocation function which is safe to emit
428  // multiple times.
429  void Emit(CodeGenFunction &CGF, Flags) override {
430    // Remember the current point, as we are going to emit deallocation code
431    // first to get to coro.free instruction that is an argument to a delete
432    // call.
433    BasicBlock *SaveInsertBlock = CGF.Builder.GetInsertBlock();
434
435    auto *FreeBB = CGF.createBasicBlock("coro.free");
436    CGF.EmitBlock(FreeBB);
437    CGF.EmitStmt(Deallocate);
438
439    auto *AfterFreeBB = CGF.createBasicBlock("after.coro.free");
440    CGF.EmitBlock(AfterFreeBB);
441
442    // We should have captured coro.free from the emission of deallocate.
443    auto *CoroFree = CGF.CurCoro.Data->LastCoroFree;
444    if (!CoroFree) {
445      CGF.CGM.Error(Deallocate->getBeginLoc(),
446                    "Deallocation expressoin does not refer to coro.free");
447      return;
448    }
449
450    // Get back to the block we were originally and move coro.free there.
451    auto *InsertPt = SaveInsertBlock->getTerminator();
452    CoroFree->moveBefore(InsertPt);
453    CGF.Builder.SetInsertPoint(InsertPt);
454
455    // Add if (auto *mem = coro.free) Deallocate;
456    auto *NullPtr = llvm::ConstantPointerNull::get(CGF.Int8PtrTy);
457    auto *Cond = CGF.Builder.CreateICmpNE(CoroFree, NullPtr);
458    CGF.Builder.CreateCondBr(Cond, FreeBB, AfterFreeBB);
459
460    // No longer need old terminator.
461    InsertPt->eraseFromParent();
462    CGF.Builder.SetInsertPoint(AfterFreeBB);
463  }
464  explicit CallCoroDelete(Stmt *DeallocStmt) : Deallocate(DeallocStmt) {}
465};
466}
467
468namespace {
469struct GetReturnObjectManager {
470  CodeGenFunction &CGF;
471  CGBuilderTy &Builder;
472  const CoroutineBodyStmt &S;
473
474  Address GroActiveFlag;
475  CodeGenFunction::AutoVarEmission GroEmission;
476
477  GetReturnObjectManager(CodeGenFunction &CGF, const CoroutineBodyStmt &S)
478      : CGF(CGF), Builder(CGF.Builder), S(S), GroActiveFlag(Address::invalid()),
479        GroEmission(CodeGenFunction::AutoVarEmission::invalid()) {}
480
481  // The gro variable has to outlive coroutine frame and coroutine promise, but,
482  // it can only be initialized after coroutine promise was created, thus, we
483  // split its emission in two parts. EmitGroAlloca emits an alloca and sets up
484  // cleanups. Later when coroutine promise is available we initialize the gro
485  // and sets the flag that the cleanup is now active.
486
487  void EmitGroAlloca() {
488    auto *GroDeclStmt = dyn_cast<DeclStmt>(S.getResultDecl());
489    if (!GroDeclStmt) {
490      // If get_return_object returns void, no need to do an alloca.
491      return;
492    }
493
494    auto *GroVarDecl = cast<VarDecl>(GroDeclStmt->getSingleDecl());
495
496    // Set GRO flag that it is not initialized yet
497    GroActiveFlag =
498      CGF.CreateTempAlloca(Builder.getInt1Ty(), CharUnits::One(), "gro.active");
499    Builder.CreateStore(Builder.getFalse(), GroActiveFlag);
500
501    GroEmission = CGF.EmitAutoVarAlloca(*GroVarDecl);
502
503    // Remember the top of EHStack before emitting the cleanup.
504    auto old_top = CGF.EHStack.stable_begin();
505    CGF.EmitAutoVarCleanups(GroEmission);
506    auto top = CGF.EHStack.stable_begin();
507
508    // Make the cleanup conditional on gro.active
509    for (auto b = CGF.EHStack.find(top), e = CGF.EHStack.find(old_top);
510      b != e; b++) {
511      if (auto *Cleanup = dyn_cast<EHCleanupScope>(&*b)) {
512        assert(!Cleanup->hasActiveFlag() && "cleanup already has active flag?");
513        Cleanup->setActiveFlag(GroActiveFlag);
514        Cleanup->setTestFlagInEHCleanup();
515        Cleanup->setTestFlagInNormalCleanup();
516      }
517    }
518  }
519
520  void EmitGroInit() {
521    if (!GroActiveFlag.isValid()) {
522      // No Gro variable was allocated. Simply emit the call to
523      // get_return_object.
524      CGF.EmitStmt(S.getResultDecl());
525      return;
526    }
527
528    CGF.EmitAutoVarInit(GroEmission);
529    Builder.CreateStore(Builder.getTrue(), GroActiveFlag);
530  }
531};
532}
533
534static void emitBodyAndFallthrough(CodeGenFunction &CGF,
535                                   const CoroutineBodyStmt &S, Stmt *Body) {
536  CGF.EmitStmt(Body);
537  const bool CanFallthrough = CGF.Builder.GetInsertBlock();
538  if (CanFallthrough)
539    if (Stmt *OnFallthrough = S.getFallthroughHandler())
540      CGF.EmitStmt(OnFallthrough);
541}
542
543void CodeGenFunction::EmitCoroutineBody(const CoroutineBodyStmt &S) {
544  auto *NullPtr = llvm::ConstantPointerNull::get(Builder.getInt8PtrTy());
545  auto &TI = CGM.getContext().getTargetInfo();
546  unsigned NewAlign = TI.getNewAlign() / TI.getCharWidth();
547
548  auto *EntryBB = Builder.GetInsertBlock();
549  auto *AllocBB = createBasicBlock("coro.alloc");
550  auto *InitBB = createBasicBlock("coro.init");
551  auto *FinalBB = createBasicBlock("coro.final");
552  auto *RetBB = createBasicBlock("coro.ret");
553
554  auto *CoroId = Builder.CreateCall(
555      CGM.getIntrinsic(llvm::Intrinsic::coro_id),
556      {Builder.getInt32(NewAlign), NullPtr, NullPtr, NullPtr});
557  createCoroData(*this, CurCoro, CoroId);
558  CurCoro.Data->SuspendBB = RetBB;
559
560  // Backend is allowed to elide memory allocations, to help it, emit
561  // auto mem = coro.alloc() ? 0 : ... allocation code ...;
562  auto *CoroAlloc = Builder.CreateCall(
563      CGM.getIntrinsic(llvm::Intrinsic::coro_alloc), {CoroId});
564
565  Builder.CreateCondBr(CoroAlloc, AllocBB, InitBB);
566
567  EmitBlock(AllocBB);
568  auto *AllocateCall = EmitScalarExpr(S.getAllocate());
569  auto *AllocOrInvokeContBB = Builder.GetInsertBlock();
570
571  // Handle allocation failure if 'ReturnStmtOnAllocFailure' was provided.
572  if (auto *RetOnAllocFailure = S.getReturnStmtOnAllocFailure()) {
573    auto *RetOnFailureBB = createBasicBlock("coro.ret.on.failure");
574
575    // See if allocation was successful.
576    auto *NullPtr = llvm::ConstantPointerNull::get(Int8PtrTy);
577    auto *Cond = Builder.CreateICmpNE(AllocateCall, NullPtr);
578    Builder.CreateCondBr(Cond, InitBB, RetOnFailureBB);
579
580    // If not, return OnAllocFailure object.
581    EmitBlock(RetOnFailureBB);
582    EmitStmt(RetOnAllocFailure);
583  }
584  else {
585    Builder.CreateBr(InitBB);
586  }
587
588  EmitBlock(InitBB);
589
590  // Pass the result of the allocation to coro.begin.
591  auto *Phi = Builder.CreatePHI(VoidPtrTy, 2);
592  Phi->addIncoming(NullPtr, EntryBB);
593  Phi->addIncoming(AllocateCall, AllocOrInvokeContBB);
594  auto *CoroBegin = Builder.CreateCall(
595      CGM.getIntrinsic(llvm::Intrinsic::coro_begin), {CoroId, Phi});
596  CurCoro.Data->CoroBegin = CoroBegin;
597
598  GetReturnObjectManager GroManager(*this, S);
599  GroManager.EmitGroAlloca();
600
601  CurCoro.Data->CleanupJD = getJumpDestInCurrentScope(RetBB);
602  {
603    ParamReferenceReplacerRAII ParamReplacer(LocalDeclMap);
604    CodeGenFunction::RunCleanupsScope ResumeScope(*this);
605    EHStack.pushCleanup<CallCoroDelete>(NormalAndEHCleanup, S.getDeallocate());
606
607    // Create parameter copies. We do it before creating a promise, since an
608    // evolution of coroutine TS may allow promise constructor to observe
609    // parameter copies.
610    for (auto *PM : S.getParamMoves()) {
611      EmitStmt(PM);
612      ParamReplacer.addCopy(cast<DeclStmt>(PM));
613      // TODO: if(CoroParam(...)) need to surround ctor and dtor
614      // for the copy, so that llvm can elide it if the copy is
615      // not needed.
616    }
617
618    EmitStmt(S.getPromiseDeclStmt());
619
620    Address PromiseAddr = GetAddrOfLocalVar(S.getPromiseDecl());
621    auto *PromiseAddrVoidPtr =
622        new llvm::BitCastInst(PromiseAddr.getPointer(), VoidPtrTy, "", CoroId);
623    // Update CoroId to refer to the promise. We could not do it earlier because
624    // promise local variable was not emitted yet.
625    CoroId->setArgOperand(1, PromiseAddrVoidPtr);
626
627    // Now we have the promise, initialize the GRO
628    GroManager.EmitGroInit();
629
630    EHStack.pushCleanup<CallCoroEnd>(EHCleanup);
631
632    CurCoro.Data->CurrentAwaitKind = AwaitKind::Init;
633    CurCoro.Data->ExceptionHandler = S.getExceptionHandler();
634    EmitStmt(S.getInitSuspendStmt());
635    CurCoro.Data->FinalJD = getJumpDestInCurrentScope(FinalBB);
636
637    CurCoro.Data->CurrentAwaitKind = AwaitKind::Normal;
638
639    if (CurCoro.Data->ExceptionHandler) {
640      // If we generated IR to record whether an exception was thrown from
641      // 'await_resume', then use that IR to determine whether the coroutine
642      // body should be skipped.
643      // If we didn't generate the IR (perhaps because 'await_resume' was marked
644      // as 'noexcept'), then we skip this check.
645      BasicBlock *ContBB = nullptr;
646      if (CurCoro.Data->ResumeEHVar) {
647        BasicBlock *BodyBB = createBasicBlock("coro.resumed.body");
648        ContBB = createBasicBlock("coro.resumed.cont");
649        Value *SkipBody = Builder.CreateFlagLoad(CurCoro.Data->ResumeEHVar,
650                                                 "coro.resumed.eh");
651        Builder.CreateCondBr(SkipBody, ContBB, BodyBB);
652        EmitBlock(BodyBB);
653      }
654
655      auto Loc = S.getBeginLoc();
656      CXXCatchStmt Catch(Loc, /*exDecl=*/nullptr,
657                         CurCoro.Data->ExceptionHandler);
658      auto *TryStmt =
659          CXXTryStmt::Create(getContext(), Loc, S.getBody(), &Catch);
660
661      EnterCXXTryStmt(*TryStmt);
662      emitBodyAndFallthrough(*this, S, TryStmt->getTryBlock());
663      ExitCXXTryStmt(*TryStmt);
664
665      if (ContBB)
666        EmitBlock(ContBB);
667    }
668    else {
669      emitBodyAndFallthrough(*this, S, S.getBody());
670    }
671
672    // See if we need to generate final suspend.
673    const bool CanFallthrough = Builder.GetInsertBlock();
674    const bool HasCoreturns = CurCoro.Data->CoreturnCount > 0;
675    if (CanFallthrough || HasCoreturns) {
676      EmitBlock(FinalBB);
677      CurCoro.Data->CurrentAwaitKind = AwaitKind::Final;
678      EmitStmt(S.getFinalSuspendStmt());
679    } else {
680      // We don't need FinalBB. Emit it to make sure the block is deleted.
681      EmitBlock(FinalBB, /*IsFinished=*/true);
682    }
683  }
684
685  EmitBlock(RetBB);
686  // Emit coro.end before getReturnStmt (and parameter destructors), since
687  // resume and destroy parts of the coroutine should not include them.
688  llvm::Function *CoroEnd = CGM.getIntrinsic(llvm::Intrinsic::coro_end);
689  Builder.CreateCall(CoroEnd, {NullPtr, Builder.getFalse()});
690
691  if (Stmt *Ret = S.getReturnStmt())
692    EmitStmt(Ret);
693}
694
695// Emit coroutine intrinsic and patch up arguments of the token type.
696RValue CodeGenFunction::EmitCoroutineIntrinsic(const CallExpr *E,
697                                               unsigned int IID) {
698  SmallVector<llvm::Value *, 8> Args;
699  switch (IID) {
700  default:
701    break;
702  // The coro.frame builtin is replaced with an SSA value of the coro.begin
703  // intrinsic.
704  case llvm::Intrinsic::coro_frame: {
705    if (CurCoro.Data && CurCoro.Data->CoroBegin) {
706      return RValue::get(CurCoro.Data->CoroBegin);
707    }
708    CGM.Error(E->getBeginLoc(), "this builtin expect that __builtin_coro_begin "
709                                "has been used earlier in this function");
710    auto NullPtr = llvm::ConstantPointerNull::get(Builder.getInt8PtrTy());
711    return RValue::get(NullPtr);
712  }
713  // The following three intrinsics take a token parameter referring to a token
714  // returned by earlier call to @llvm.coro.id. Since we cannot represent it in
715  // builtins, we patch it up here.
716  case llvm::Intrinsic::coro_alloc:
717  case llvm::Intrinsic::coro_begin:
718  case llvm::Intrinsic::coro_free: {
719    if (CurCoro.Data && CurCoro.Data->CoroId) {
720      Args.push_back(CurCoro.Data->CoroId);
721      break;
722    }
723    CGM.Error(E->getBeginLoc(), "this builtin expect that __builtin_coro_id has"
724                                " been used earlier in this function");
725    // Fallthrough to the next case to add TokenNone as the first argument.
726    LLVM_FALLTHROUGH;
727  }
728  // @llvm.coro.suspend takes a token parameter. Add token 'none' as the first
729  // argument.
730  case llvm::Intrinsic::coro_suspend:
731    Args.push_back(llvm::ConstantTokenNone::get(getLLVMContext()));
732    break;
733  }
734  for (const Expr *Arg : E->arguments())
735    Args.push_back(EmitScalarExpr(Arg));
736
737  llvm::Function *F = CGM.getIntrinsic(IID);
738  llvm::CallInst *Call = Builder.CreateCall(F, Args);
739
740  // Note: The following code is to enable to emit coro.id and coro.begin by
741  // hand to experiment with coroutines in C.
742  // If we see @llvm.coro.id remember it in the CoroData. We will update
743  // coro.alloc, coro.begin and coro.free intrinsics to refer to it.
744  if (IID == llvm::Intrinsic::coro_id) {
745    createCoroData(*this, CurCoro, Call, E);
746  }
747  else if (IID == llvm::Intrinsic::coro_begin) {
748    if (CurCoro.Data)
749      CurCoro.Data->CoroBegin = Call;
750  }
751  else if (IID == llvm::Intrinsic::coro_free) {
752    // Remember the last coro_free as we need it to build the conditional
753    // deletion of the coroutine frame.
754    if (CurCoro.Data)
755      CurCoro.Data->LastCoroFree = Call;
756  }
757  return RValue::get(Call);
758}
759