1 //===----- CGCoroutine.cpp - Emit LLVM Code for C++ coroutines ------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This contains code dealing with C++ code generation of coroutines.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "CodeGenFunction.h"
15 #include "clang/AST/StmtCXX.h"
16 
17 using namespace clang;
18 using namespace CodeGen;
19 
20 namespace clang {
21 namespace CodeGen {
22 
23 struct CGCoroData {
24   // Stores the llvm.coro.id emitted in the function so that we can supply it
25   // as the first argument to coro.begin, coro.alloc and coro.free intrinsics.
26   // Note: llvm.coro.id returns a token that cannot be directly expressed in a
27   // builtin.
28   llvm::CallInst *CoroId = nullptr;
29   // If coro.id came from the builtin, remember the expression to give better
30   // diagnostic. If CoroIdExpr is nullptr, the coro.id was created by
31   // EmitCoroutineBody.
32   CallExpr const *CoroIdExpr = nullptr;
33 };
34 }
35 }
36 
37 clang::CodeGen::CodeGenFunction::CGCoroInfo::CGCoroInfo() {}
38 CodeGenFunction::CGCoroInfo::~CGCoroInfo() {}
39 
40 static void createCoroData(CodeGenFunction &CGF,
41                            CodeGenFunction::CGCoroInfo &CurCoro,
42                            llvm::CallInst *CoroId,
43                            CallExpr const *CoroIdExpr = nullptr) {
44   if (CurCoro.Data) {
45     if (CurCoro.Data->CoroIdExpr)
46       CGF.CGM.Error(CoroIdExpr->getLocStart(),
47                     "only one __builtin_coro_id can be used in a function");
48     else if (CoroIdExpr)
49       CGF.CGM.Error(CoroIdExpr->getLocStart(),
50                     "__builtin_coro_id shall not be used in a C++ coroutine");
51     else
52       llvm_unreachable("EmitCoroutineBodyStatement called twice?");
53 
54     return;
55   }
56 
57   CurCoro.Data = std::unique_ptr<CGCoroData>(new CGCoroData);
58   CurCoro.Data->CoroId = CoroId;
59   CurCoro.Data->CoroIdExpr = CoroIdExpr;
60 }
61 
62 void CodeGenFunction::EmitCoroutineBody(const CoroutineBodyStmt &S) {
63   auto *NullPtr = llvm::ConstantPointerNull::get(Builder.getInt8PtrTy());
64   auto &TI = CGM.getContext().getTargetInfo();
65   unsigned NewAlign = TI.getNewAlign() / TI.getCharWidth();
66 
67   auto *CoroId = Builder.CreateCall(
68       CGM.getIntrinsic(llvm::Intrinsic::coro_id),
69       {Builder.getInt32(NewAlign), NullPtr, NullPtr, NullPtr});
70   createCoroData(*this, CurCoro, CoroId);
71 
72   EmitScalarExpr(S.getAllocate());
73   // FIXME: Emit the rest of the coroutine.
74   EmitStmt(S.getDeallocate());
75 }
76 
77 // Emit coroutine intrinsic and patch up arguments of the token type.
78 RValue CodeGenFunction::EmitCoroutineIntrinsic(const CallExpr *E,
79                                                unsigned int IID) {
80   SmallVector<llvm::Value *, 8> Args;
81   switch (IID) {
82   default:
83     break;
84   // The following three intrinsics take a token parameter referring to a token
85   // returned by earlier call to @llvm.coro.id. Since we cannot represent it in
86   // builtins, we patch it up here.
87   case llvm::Intrinsic::coro_alloc:
88   case llvm::Intrinsic::coro_begin:
89   case llvm::Intrinsic::coro_free: {
90     if (CurCoro.Data && CurCoro.Data->CoroId) {
91       Args.push_back(CurCoro.Data->CoroId);
92       break;
93     }
94     CGM.Error(E->getLocStart(), "this builtin expect that __builtin_coro_id has"
95                                 " been used earlier in this function");
96     // Fallthrough to the next case to add TokenNone as the first argument.
97   }
98   // @llvm.coro.suspend takes a token parameter. Add token 'none' as the first
99   // argument.
100   case llvm::Intrinsic::coro_suspend:
101     Args.push_back(llvm::ConstantTokenNone::get(getLLVMContext()));
102     break;
103   }
104   for (auto &Arg : E->arguments())
105     Args.push_back(EmitScalarExpr(Arg));
106 
107   llvm::Value *F = CGM.getIntrinsic(IID);
108   llvm::CallInst *Call = Builder.CreateCall(F, Args);
109 
110   // If we see @llvm.coro.id remember it in the CoroData. We will update
111   // coro.alloc, coro.begin and coro.free intrinsics to refer to it.
112   if (IID == llvm::Intrinsic::coro_id) {
113     createCoroData(*this, CurCoro, Call, E);
114   }
115   return RValue::get(Call);
116 }
117