1 //===- Coroutines.cpp -----------------------------------------------------===//
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 file implements the common infrastructure for Coroutine Passes.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "CoroInstr.h"
14 #include "CoroInternal.h"
15 #include "llvm/ADT/SmallVector.h"
16 #include "llvm/ADT/StringRef.h"
17 #include "llvm/Analysis/CallGraph.h"
18 #include "llvm/IR/Attributes.h"
19 #include "llvm/IR/Constants.h"
20 #include "llvm/IR/DerivedTypes.h"
21 #include "llvm/IR/Function.h"
22 #include "llvm/IR/InstIterator.h"
23 #include "llvm/IR/Instructions.h"
24 #include "llvm/IR/IntrinsicInst.h"
25 #include "llvm/IR/Intrinsics.h"
26 #include "llvm/IR/Module.h"
27 #include "llvm/IR/Type.h"
28 #include "llvm/Support/Casting.h"
29 #include "llvm/Support/ErrorHandling.h"
30 #include "llvm/Transforms/Utils/Local.h"
31 #include <cassert>
32 #include <cstddef>
33 #include <utility>
34 
35 using namespace llvm;
36 
37 // Construct the lowerer base class and initialize its members.
38 coro::LowererBase::LowererBase(Module &M)
39     : TheModule(M), Context(M.getContext()),
40       Int8Ptr(Type::getInt8PtrTy(Context)),
41       ResumeFnType(FunctionType::get(Type::getVoidTy(Context), Int8Ptr,
42                                      /*isVarArg=*/false)),
43       NullPtr(ConstantPointerNull::get(Int8Ptr)) {}
44 
45 // Creates a sequence of instructions to obtain a resume function address using
46 // llvm.coro.subfn.addr. It generates the following sequence:
47 //
48 //    call i8* @llvm.coro.subfn.addr(i8* %Arg, i8 %index)
49 //    bitcast i8* %2 to void(i8*)*
50 
51 Value *coro::LowererBase::makeSubFnCall(Value *Arg, int Index,
52                                         Instruction *InsertPt) {
53   auto *IndexVal = ConstantInt::get(Type::getInt8Ty(Context), Index);
54   auto *Fn = Intrinsic::getDeclaration(&TheModule, Intrinsic::coro_subfn_addr);
55 
56   assert(Index >= CoroSubFnInst::IndexFirst &&
57          Index < CoroSubFnInst::IndexLast &&
58          "makeSubFnCall: Index value out of range");
59   auto *Call = CallInst::Create(Fn, {Arg, IndexVal}, "", InsertPt);
60 
61   auto *Bitcast =
62       new BitCastInst(Call, ResumeFnType->getPointerTo(), "", InsertPt);
63   return Bitcast;
64 }
65 
66 // NOTE: Must be sorted!
67 static const char *const CoroIntrinsics[] = {
68     "llvm.coro.align",
69     "llvm.coro.alloc",
70     "llvm.coro.async.context.alloc",
71     "llvm.coro.async.context.dealloc",
72     "llvm.coro.async.resume",
73     "llvm.coro.async.size.replace",
74     "llvm.coro.async.store_resume",
75     "llvm.coro.begin",
76     "llvm.coro.destroy",
77     "llvm.coro.done",
78     "llvm.coro.end",
79     "llvm.coro.end.async",
80     "llvm.coro.frame",
81     "llvm.coro.free",
82     "llvm.coro.id",
83     "llvm.coro.id.async",
84     "llvm.coro.id.retcon",
85     "llvm.coro.id.retcon.once",
86     "llvm.coro.noop",
87     "llvm.coro.prepare.async",
88     "llvm.coro.prepare.retcon",
89     "llvm.coro.promise",
90     "llvm.coro.resume",
91     "llvm.coro.save",
92     "llvm.coro.size",
93     "llvm.coro.subfn.addr",
94     "llvm.coro.suspend",
95     "llvm.coro.suspend.async",
96     "llvm.coro.suspend.retcon",
97 };
98 
99 #ifndef NDEBUG
100 static bool isCoroutineIntrinsicName(StringRef Name) {
101   return Intrinsic::lookupLLVMIntrinsicByName(CoroIntrinsics, Name) != -1;
102 }
103 #endif
104 
105 bool coro::declaresAnyIntrinsic(const Module &M) {
106   for (StringRef Name : CoroIntrinsics) {
107     assert(isCoroutineIntrinsicName(Name) && "not a coroutine intrinsic");
108     if (M.getNamedValue(Name))
109       return true;
110   }
111 
112   return false;
113 }
114 
115 // Verifies if a module has named values listed. Also, in debug mode verifies
116 // that names are intrinsic names.
117 bool coro::declaresIntrinsics(const Module &M,
118                               const std::initializer_list<StringRef> List) {
119   for (StringRef Name : List) {
120     assert(isCoroutineIntrinsicName(Name) && "not a coroutine intrinsic");
121     if (M.getNamedValue(Name))
122       return true;
123   }
124 
125   return false;
126 }
127 
128 // Replace all coro.frees associated with the provided CoroId either with 'null'
129 // if Elide is true and with its frame parameter otherwise.
130 void coro::replaceCoroFree(CoroIdInst *CoroId, bool Elide) {
131   SmallVector<CoroFreeInst *, 4> CoroFrees;
132   for (User *U : CoroId->users())
133     if (auto CF = dyn_cast<CoroFreeInst>(U))
134       CoroFrees.push_back(CF);
135 
136   if (CoroFrees.empty())
137     return;
138 
139   Value *Replacement =
140       Elide ? ConstantPointerNull::get(Type::getInt8PtrTy(CoroId->getContext()))
141             : CoroFrees.front()->getFrame();
142 
143   for (CoroFreeInst *CF : CoroFrees) {
144     CF->replaceAllUsesWith(Replacement);
145     CF->eraseFromParent();
146   }
147 }
148 
149 static void clear(coro::Shape &Shape) {
150   Shape.CoroBegin = nullptr;
151   Shape.CoroEnds.clear();
152   Shape.CoroSizes.clear();
153   Shape.CoroSuspends.clear();
154 
155   Shape.FrameTy = nullptr;
156   Shape.FramePtr = nullptr;
157   Shape.AllocaSpillBlock = nullptr;
158 }
159 
160 static CoroSaveInst *createCoroSave(CoroBeginInst *CoroBegin,
161                                     CoroSuspendInst *SuspendInst) {
162   Module *M = SuspendInst->getModule();
163   auto *Fn = Intrinsic::getDeclaration(M, Intrinsic::coro_save);
164   auto *SaveInst =
165       cast<CoroSaveInst>(CallInst::Create(Fn, CoroBegin, "", SuspendInst));
166   assert(!SuspendInst->getCoroSave());
167   SuspendInst->setArgOperand(0, SaveInst);
168   return SaveInst;
169 }
170 
171 // Collect "interesting" coroutine intrinsics.
172 void coro::Shape::buildFrom(Function &F) {
173   bool HasFinalSuspend = false;
174   bool HasUnwindCoroEnd = false;
175   size_t FinalSuspendIndex = 0;
176   clear(*this);
177   SmallVector<CoroFrameInst *, 8> CoroFrames;
178   SmallVector<CoroSaveInst *, 2> UnusedCoroSaves;
179 
180   for (Instruction &I : instructions(F)) {
181     if (auto II = dyn_cast<IntrinsicInst>(&I)) {
182       switch (II->getIntrinsicID()) {
183       default:
184         continue;
185       case Intrinsic::coro_size:
186         CoroSizes.push_back(cast<CoroSizeInst>(II));
187         break;
188       case Intrinsic::coro_align:
189         CoroAligns.push_back(cast<CoroAlignInst>(II));
190         break;
191       case Intrinsic::coro_frame:
192         CoroFrames.push_back(cast<CoroFrameInst>(II));
193         break;
194       case Intrinsic::coro_save:
195         // After optimizations, coro_suspends using this coro_save might have
196         // been removed, remember orphaned coro_saves to remove them later.
197         if (II->use_empty())
198           UnusedCoroSaves.push_back(cast<CoroSaveInst>(II));
199         break;
200       case Intrinsic::coro_suspend_async: {
201         auto *Suspend = cast<CoroSuspendAsyncInst>(II);
202         Suspend->checkWellFormed();
203         CoroSuspends.push_back(Suspend);
204         break;
205       }
206       case Intrinsic::coro_suspend_retcon: {
207         auto Suspend = cast<CoroSuspendRetconInst>(II);
208         CoroSuspends.push_back(Suspend);
209         break;
210       }
211       case Intrinsic::coro_suspend: {
212         auto Suspend = cast<CoroSuspendInst>(II);
213         CoroSuspends.push_back(Suspend);
214         if (Suspend->isFinal()) {
215           if (HasFinalSuspend)
216             report_fatal_error(
217               "Only one suspend point can be marked as final");
218           HasFinalSuspend = true;
219           FinalSuspendIndex = CoroSuspends.size() - 1;
220         }
221         break;
222       }
223       case Intrinsic::coro_begin: {
224         auto CB = cast<CoroBeginInst>(II);
225 
226         // Ignore coro id's that aren't pre-split.
227         auto Id = dyn_cast<CoroIdInst>(CB->getId());
228         if (Id && !Id->getInfo().isPreSplit())
229           break;
230 
231         if (CoroBegin)
232           report_fatal_error(
233                 "coroutine should have exactly one defining @llvm.coro.begin");
234         CB->addRetAttr(Attribute::NonNull);
235         CB->addRetAttr(Attribute::NoAlias);
236         CB->removeFnAttr(Attribute::NoDuplicate);
237         CoroBegin = CB;
238         break;
239       }
240       case Intrinsic::coro_end_async:
241       case Intrinsic::coro_end:
242         CoroEnds.push_back(cast<AnyCoroEndInst>(II));
243         if (auto *AsyncEnd = dyn_cast<CoroAsyncEndInst>(II)) {
244           AsyncEnd->checkWellFormed();
245         }
246 
247         if (CoroEnds.back()->isUnwind())
248           HasUnwindCoroEnd = true;
249 
250         if (CoroEnds.back()->isFallthrough() && isa<CoroEndInst>(II)) {
251           // Make sure that the fallthrough coro.end is the first element in the
252           // CoroEnds vector.
253           // Note: I don't think this is neccessary anymore.
254           if (CoroEnds.size() > 1) {
255             if (CoroEnds.front()->isFallthrough())
256               report_fatal_error(
257                   "Only one coro.end can be marked as fallthrough");
258             std::swap(CoroEnds.front(), CoroEnds.back());
259           }
260         }
261         break;
262       }
263     }
264   }
265 
266   // If for some reason, we were not able to find coro.begin, bailout.
267   if (!CoroBegin) {
268     // Replace coro.frame which are supposed to be lowered to the result of
269     // coro.begin with undef.
270     auto *Undef = UndefValue::get(Type::getInt8PtrTy(F.getContext()));
271     for (CoroFrameInst *CF : CoroFrames) {
272       CF->replaceAllUsesWith(Undef);
273       CF->eraseFromParent();
274     }
275 
276     // Replace all coro.suspend with undef and remove related coro.saves if
277     // present.
278     for (AnyCoroSuspendInst *CS : CoroSuspends) {
279       CS->replaceAllUsesWith(UndefValue::get(CS->getType()));
280       CS->eraseFromParent();
281       if (auto *CoroSave = CS->getCoroSave())
282         CoroSave->eraseFromParent();
283     }
284 
285     // Replace all coro.ends with unreachable instruction.
286     for (AnyCoroEndInst *CE : CoroEnds)
287       changeToUnreachable(CE);
288 
289     return;
290   }
291 
292   auto Id = CoroBegin->getId();
293   switch (auto IdIntrinsic = Id->getIntrinsicID()) {
294   case Intrinsic::coro_id: {
295     auto SwitchId = cast<CoroIdInst>(Id);
296     this->ABI = coro::ABI::Switch;
297     this->SwitchLowering.HasFinalSuspend = HasFinalSuspend;
298     this->SwitchLowering.HasUnwindCoroEnd = HasUnwindCoroEnd;
299     this->SwitchLowering.ResumeSwitch = nullptr;
300     this->SwitchLowering.PromiseAlloca = SwitchId->getPromise();
301     this->SwitchLowering.ResumeEntryBlock = nullptr;
302 
303     for (auto *AnySuspend : CoroSuspends) {
304       auto Suspend = dyn_cast<CoroSuspendInst>(AnySuspend);
305       if (!Suspend) {
306 #ifndef NDEBUG
307         AnySuspend->dump();
308 #endif
309         report_fatal_error("coro.id must be paired with coro.suspend");
310       }
311 
312       if (!Suspend->getCoroSave())
313         createCoroSave(CoroBegin, Suspend);
314     }
315     break;
316   }
317   case Intrinsic::coro_id_async: {
318     auto *AsyncId = cast<CoroIdAsyncInst>(Id);
319     AsyncId->checkWellFormed();
320     this->ABI = coro::ABI::Async;
321     this->AsyncLowering.Context = AsyncId->getStorage();
322     this->AsyncLowering.ContextArgNo = AsyncId->getStorageArgumentIndex();
323     this->AsyncLowering.ContextHeaderSize = AsyncId->getStorageSize();
324     this->AsyncLowering.ContextAlignment =
325         AsyncId->getStorageAlignment().value();
326     this->AsyncLowering.AsyncFuncPointer = AsyncId->getAsyncFunctionPointer();
327     this->AsyncLowering.AsyncCC = F.getCallingConv();
328     break;
329   };
330   case Intrinsic::coro_id_retcon:
331   case Intrinsic::coro_id_retcon_once: {
332     auto ContinuationId = cast<AnyCoroIdRetconInst>(Id);
333     ContinuationId->checkWellFormed();
334     this->ABI = (IdIntrinsic == Intrinsic::coro_id_retcon
335                   ? coro::ABI::Retcon
336                   : coro::ABI::RetconOnce);
337     auto Prototype = ContinuationId->getPrototype();
338     this->RetconLowering.ResumePrototype = Prototype;
339     this->RetconLowering.Alloc = ContinuationId->getAllocFunction();
340     this->RetconLowering.Dealloc = ContinuationId->getDeallocFunction();
341     this->RetconLowering.ReturnBlock = nullptr;
342     this->RetconLowering.IsFrameInlineInStorage = false;
343 
344     // Determine the result value types, and make sure they match up with
345     // the values passed to the suspends.
346     auto ResultTys = getRetconResultTypes();
347     auto ResumeTys = getRetconResumeTypes();
348 
349     for (auto *AnySuspend : CoroSuspends) {
350       auto Suspend = dyn_cast<CoroSuspendRetconInst>(AnySuspend);
351       if (!Suspend) {
352 #ifndef NDEBUG
353         AnySuspend->dump();
354 #endif
355         report_fatal_error("coro.id.retcon.* must be paired with "
356                            "coro.suspend.retcon");
357       }
358 
359       // Check that the argument types of the suspend match the results.
360       auto SI = Suspend->value_begin(), SE = Suspend->value_end();
361       auto RI = ResultTys.begin(), RE = ResultTys.end();
362       for (; SI != SE && RI != RE; ++SI, ++RI) {
363         auto SrcTy = (*SI)->getType();
364         if (SrcTy != *RI) {
365           // The optimizer likes to eliminate bitcasts leading into variadic
366           // calls, but that messes with our invariants.  Re-insert the
367           // bitcast and ignore this type mismatch.
368           if (CastInst::isBitCastable(SrcTy, *RI)) {
369             auto BCI = new BitCastInst(*SI, *RI, "", Suspend);
370             SI->set(BCI);
371             continue;
372           }
373 
374 #ifndef NDEBUG
375           Suspend->dump();
376           Prototype->getFunctionType()->dump();
377 #endif
378           report_fatal_error("argument to coro.suspend.retcon does not "
379                              "match corresponding prototype function result");
380         }
381       }
382       if (SI != SE || RI != RE) {
383 #ifndef NDEBUG
384         Suspend->dump();
385         Prototype->getFunctionType()->dump();
386 #endif
387         report_fatal_error("wrong number of arguments to coro.suspend.retcon");
388       }
389 
390       // Check that the result type of the suspend matches the resume types.
391       Type *SResultTy = Suspend->getType();
392       ArrayRef<Type*> SuspendResultTys;
393       if (SResultTy->isVoidTy()) {
394         // leave as empty array
395       } else if (auto SResultStructTy = dyn_cast<StructType>(SResultTy)) {
396         SuspendResultTys = SResultStructTy->elements();
397       } else {
398         // forms an ArrayRef using SResultTy, be careful
399         SuspendResultTys = SResultTy;
400       }
401       if (SuspendResultTys.size() != ResumeTys.size()) {
402 #ifndef NDEBUG
403         Suspend->dump();
404         Prototype->getFunctionType()->dump();
405 #endif
406         report_fatal_error("wrong number of results from coro.suspend.retcon");
407       }
408       for (size_t I = 0, E = ResumeTys.size(); I != E; ++I) {
409         if (SuspendResultTys[I] != ResumeTys[I]) {
410 #ifndef NDEBUG
411           Suspend->dump();
412           Prototype->getFunctionType()->dump();
413 #endif
414           report_fatal_error("result from coro.suspend.retcon does not "
415                              "match corresponding prototype function param");
416         }
417       }
418     }
419     break;
420   }
421 
422   default:
423     llvm_unreachable("coro.begin is not dependent on a coro.id call");
424   }
425 
426   // The coro.free intrinsic is always lowered to the result of coro.begin.
427   for (CoroFrameInst *CF : CoroFrames) {
428     CF->replaceAllUsesWith(CoroBegin);
429     CF->eraseFromParent();
430   }
431 
432   // Move final suspend to be the last element in the CoroSuspends vector.
433   if (ABI == coro::ABI::Switch &&
434       SwitchLowering.HasFinalSuspend &&
435       FinalSuspendIndex != CoroSuspends.size() - 1)
436     std::swap(CoroSuspends[FinalSuspendIndex], CoroSuspends.back());
437 
438   // Remove orphaned coro.saves.
439   for (CoroSaveInst *CoroSave : UnusedCoroSaves)
440     CoroSave->eraseFromParent();
441 }
442 
443 static void propagateCallAttrsFromCallee(CallInst *Call, Function *Callee) {
444   Call->setCallingConv(Callee->getCallingConv());
445   // TODO: attributes?
446 }
447 
448 static void addCallToCallGraph(CallGraph *CG, CallInst *Call, Function *Callee){
449   if (CG)
450     (*CG)[Call->getFunction()]->addCalledFunction(Call, (*CG)[Callee]);
451 }
452 
453 Value *coro::Shape::emitAlloc(IRBuilder<> &Builder, Value *Size,
454                               CallGraph *CG) const {
455   switch (ABI) {
456   case coro::ABI::Switch:
457     llvm_unreachable("can't allocate memory in coro switch-lowering");
458 
459   case coro::ABI::Retcon:
460   case coro::ABI::RetconOnce: {
461     auto Alloc = RetconLowering.Alloc;
462     Size = Builder.CreateIntCast(Size,
463                                  Alloc->getFunctionType()->getParamType(0),
464                                  /*is signed*/ false);
465     auto *Call = Builder.CreateCall(Alloc, Size);
466     propagateCallAttrsFromCallee(Call, Alloc);
467     addCallToCallGraph(CG, Call, Alloc);
468     return Call;
469   }
470   case coro::ABI::Async:
471     llvm_unreachable("can't allocate memory in coro async-lowering");
472   }
473   llvm_unreachable("Unknown coro::ABI enum");
474 }
475 
476 void coro::Shape::emitDealloc(IRBuilder<> &Builder, Value *Ptr,
477                               CallGraph *CG) const {
478   switch (ABI) {
479   case coro::ABI::Switch:
480     llvm_unreachable("can't allocate memory in coro switch-lowering");
481 
482   case coro::ABI::Retcon:
483   case coro::ABI::RetconOnce: {
484     auto Dealloc = RetconLowering.Dealloc;
485     Ptr = Builder.CreateBitCast(Ptr,
486                                 Dealloc->getFunctionType()->getParamType(0));
487     auto *Call = Builder.CreateCall(Dealloc, Ptr);
488     propagateCallAttrsFromCallee(Call, Dealloc);
489     addCallToCallGraph(CG, Call, Dealloc);
490     return;
491   }
492   case coro::ABI::Async:
493     llvm_unreachable("can't allocate memory in coro async-lowering");
494   }
495   llvm_unreachable("Unknown coro::ABI enum");
496 }
497 
498 [[noreturn]] static void fail(const Instruction *I, const char *Reason,
499                               Value *V) {
500 #ifndef NDEBUG
501   I->dump();
502   if (V) {
503     errs() << "  Value: ";
504     V->printAsOperand(llvm::errs());
505     errs() << '\n';
506   }
507 #endif
508   report_fatal_error(Reason);
509 }
510 
511 /// Check that the given value is a well-formed prototype for the
512 /// llvm.coro.id.retcon.* intrinsics.
513 static void checkWFRetconPrototype(const AnyCoroIdRetconInst *I, Value *V) {
514   auto F = dyn_cast<Function>(V->stripPointerCasts());
515   if (!F)
516     fail(I, "llvm.coro.id.retcon.* prototype not a Function", V);
517 
518   auto FT = F->getFunctionType();
519 
520   if (isa<CoroIdRetconInst>(I)) {
521     bool ResultOkay;
522     if (FT->getReturnType()->isPointerTy()) {
523       ResultOkay = true;
524     } else if (auto SRetTy = dyn_cast<StructType>(FT->getReturnType())) {
525       ResultOkay = (!SRetTy->isOpaque() &&
526                     SRetTy->getNumElements() > 0 &&
527                     SRetTy->getElementType(0)->isPointerTy());
528     } else {
529       ResultOkay = false;
530     }
531     if (!ResultOkay)
532       fail(I, "llvm.coro.id.retcon prototype must return pointer as first "
533               "result", F);
534 
535     if (FT->getReturnType() !=
536           I->getFunction()->getFunctionType()->getReturnType())
537       fail(I, "llvm.coro.id.retcon prototype return type must be same as"
538               "current function return type", F);
539   } else {
540     // No meaningful validation to do here for llvm.coro.id.unique.once.
541   }
542 
543   if (FT->getNumParams() == 0 || !FT->getParamType(0)->isPointerTy())
544     fail(I, "llvm.coro.id.retcon.* prototype must take pointer as "
545             "its first parameter", F);
546 }
547 
548 /// Check that the given value is a well-formed allocator.
549 static void checkWFAlloc(const Instruction *I, Value *V) {
550   auto F = dyn_cast<Function>(V->stripPointerCasts());
551   if (!F)
552     fail(I, "llvm.coro.* allocator not a Function", V);
553 
554   auto FT = F->getFunctionType();
555   if (!FT->getReturnType()->isPointerTy())
556     fail(I, "llvm.coro.* allocator must return a pointer", F);
557 
558   if (FT->getNumParams() != 1 ||
559       !FT->getParamType(0)->isIntegerTy())
560     fail(I, "llvm.coro.* allocator must take integer as only param", F);
561 }
562 
563 /// Check that the given value is a well-formed deallocator.
564 static void checkWFDealloc(const Instruction *I, Value *V) {
565   auto F = dyn_cast<Function>(V->stripPointerCasts());
566   if (!F)
567     fail(I, "llvm.coro.* deallocator not a Function", V);
568 
569   auto FT = F->getFunctionType();
570   if (!FT->getReturnType()->isVoidTy())
571     fail(I, "llvm.coro.* deallocator must return void", F);
572 
573   if (FT->getNumParams() != 1 ||
574       !FT->getParamType(0)->isPointerTy())
575     fail(I, "llvm.coro.* deallocator must take pointer as only param", F);
576 }
577 
578 static void checkConstantInt(const Instruction *I, Value *V,
579                              const char *Reason) {
580   if (!isa<ConstantInt>(V)) {
581     fail(I, Reason, V);
582   }
583 }
584 
585 void AnyCoroIdRetconInst::checkWellFormed() const {
586   checkConstantInt(this, getArgOperand(SizeArg),
587                    "size argument to coro.id.retcon.* must be constant");
588   checkConstantInt(this, getArgOperand(AlignArg),
589                    "alignment argument to coro.id.retcon.* must be constant");
590   checkWFRetconPrototype(this, getArgOperand(PrototypeArg));
591   checkWFAlloc(this, getArgOperand(AllocArg));
592   checkWFDealloc(this, getArgOperand(DeallocArg));
593 }
594 
595 static void checkAsyncFuncPointer(const Instruction *I, Value *V) {
596   auto *AsyncFuncPtrAddr = dyn_cast<GlobalVariable>(V->stripPointerCasts());
597   if (!AsyncFuncPtrAddr)
598     fail(I, "llvm.coro.id.async async function pointer not a global", V);
599 }
600 
601 void CoroIdAsyncInst::checkWellFormed() const {
602   checkConstantInt(this, getArgOperand(SizeArg),
603                    "size argument to coro.id.async must be constant");
604   checkConstantInt(this, getArgOperand(AlignArg),
605                    "alignment argument to coro.id.async must be constant");
606   checkConstantInt(this, getArgOperand(StorageArg),
607                    "storage argument offset to coro.id.async must be constant");
608   checkAsyncFuncPointer(this, getArgOperand(AsyncFuncPtrArg));
609 }
610 
611 static void checkAsyncContextProjectFunction(const Instruction *I,
612                                              Function *F) {
613   auto *FunTy = cast<FunctionType>(F->getValueType());
614   if (!FunTy->getReturnType()->isPointerTy())
615     fail(I,
616          "llvm.coro.suspend.async resume function projection function must "
617          "return a ptr type",
618          F);
619   if (FunTy->getNumParams() != 1 || !FunTy->getParamType(0)->isPointerTy())
620     fail(I,
621          "llvm.coro.suspend.async resume function projection function must "
622          "take one ptr type as parameter",
623          F);
624 }
625 
626 void CoroSuspendAsyncInst::checkWellFormed() const {
627   checkAsyncContextProjectFunction(this, getAsyncContextProjectionFunction());
628 }
629 
630 void CoroAsyncEndInst::checkWellFormed() const {
631   auto *MustTailCallFunc = getMustTailCallFunction();
632   if (!MustTailCallFunc)
633     return;
634   auto *FnTy = MustTailCallFunc->getFunctionType();
635   if (FnTy->getNumParams() != (arg_size() - 3))
636     fail(this,
637          "llvm.coro.end.async must tail call function argument type must "
638          "match the tail arguments",
639          MustTailCallFunc);
640 }
641