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 
16 using namespace clang;
17 using namespace CodeGen;
18 
19 namespace clang {
20 namespace CodeGen {
21 
22 struct CGCoroData {
23   // Stores the llvm.coro.id emitted in the function so that we can supply it
24   // as the first argument to coro.begin, coro.alloc and coro.free intrinsics.
25   // Note: llvm.coro.id returns a token that cannot be directly expressed in a
26   // builtin.
27   llvm::CallInst *CoroId = nullptr;
28   // If coro.id came from the builtin, remember the expression to give better
29   // diagnostic. If CoroIdExpr is nullptr, the coro.id was created by
30   // EmitCoroutineBody.
31   CallExpr const *CoroIdExpr = nullptr;
32 };
33 }
34 }
35 
36 clang::CodeGen::CodeGenFunction::CGCoroInfo::CGCoroInfo() {}
37 CodeGenFunction::CGCoroInfo::~CGCoroInfo() {}
38 
39 static bool createCoroData(CodeGenFunction &CGF,
40                            CodeGenFunction::CGCoroInfo &CurCoro,
41                            llvm::CallInst *CoroId, CallExpr const *CoroIdExpr) {
42   if (CurCoro.Data) {
43     if (CurCoro.Data->CoroIdExpr)
44       CGF.CGM.Error(CoroIdExpr->getLocStart(),
45                     "only one __builtin_coro_id can be used in a function");
46     else if (CoroIdExpr)
47       CGF.CGM.Error(CoroIdExpr->getLocStart(),
48                     "__builtin_coro_id shall not be used in a C++ coroutine");
49     else
50       llvm_unreachable("EmitCoroutineBodyStatement called twice?");
51 
52     return false;
53   }
54 
55   CurCoro.Data = std::unique_ptr<CGCoroData>(new CGCoroData);
56   CurCoro.Data->CoroId = CoroId;
57   CurCoro.Data->CoroIdExpr = CoroIdExpr;
58   return true;
59 }
60 
61 // Emit coroutine intrinsic and patch up arguments of the token type.
62 RValue CodeGenFunction::EmitCoroutineIntrinsic(const CallExpr *E,
63                                                unsigned int IID) {
64   SmallVector<llvm::Value *, 8> Args;
65   switch (IID) {
66   default:
67     break;
68   // The following three intrinsics take a token parameter referring to a token
69   // returned by earlier call to @llvm.coro.id. Since we cannot represent it in
70   // builtins, we patch it up here.
71   case llvm::Intrinsic::coro_alloc:
72   case llvm::Intrinsic::coro_begin:
73   case llvm::Intrinsic::coro_free: {
74     if (CurCoro.Data && CurCoro.Data->CoroId) {
75       Args.push_back(CurCoro.Data->CoroId);
76       break;
77     }
78     CGM.Error(E->getLocStart(), "this builtin expect that __builtin_coro_id has"
79                                 " been used earlier in this function");
80     // Fallthrough to the next case to add TokenNone as the first argument.
81   }
82   // @llvm.coro.suspend takes a token parameter. Add token 'none' as the first
83   // argument.
84   case llvm::Intrinsic::coro_suspend:
85     Args.push_back(llvm::ConstantTokenNone::get(getLLVMContext()));
86     break;
87   }
88   for (auto &Arg : E->arguments())
89     Args.push_back(EmitScalarExpr(Arg));
90 
91   llvm::Value *F = CGM.getIntrinsic(IID);
92   llvm::CallInst *Call = Builder.CreateCall(F, Args);
93 
94   // If we see @llvm.coro.id remember it in the CoroData. We will update
95   // coro.alloc, coro.begin and coro.free intrinsics to refer to it.
96   if (IID == llvm::Intrinsic::coro_id) {
97     createCoroData(*this, CurCoro, Call, E);
98   }
99   return RValue::get(Call);
100 }
101