1 //===--------- TaskDispatch.h - ORC task dispatch utils ---------*- C++ -*-===//
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 // Task and TaskDispatch classes.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_EXECUTIONENGINE_ORC_TASKDISPATCH_H
14 #define LLVM_EXECUTIONENGINE_ORC_TASKDISPATCH_H
15 
16 #include "llvm/Config/llvm-config.h"
17 #include "llvm/Support/Debug.h"
18 #include "llvm/Support/ExtensibleRTTI.h"
19 #include "llvm/Support/raw_ostream.h"
20 
21 #include <cassert>
22 #include <string>
23 
24 #if LLVM_ENABLE_THREADS
25 #include <condition_variable>
26 #include <mutex>
27 #include <thread>
28 #endif
29 
30 namespace llvm {
31 namespace orc {
32 
33 /// Represents an abstract task for ORC to run.
34 class Task : public RTTIExtends<Task, RTTIRoot> {
35 public:
36   static char ID;
37 
38   virtual ~Task() = default;
39 
40   /// Description of the task to be performed. Used for logging.
41   virtual void printDescription(raw_ostream &OS) = 0;
42 
43   /// Run the task.
44   virtual void run() = 0;
45 
46 private:
47   void anchor() override;
48 };
49 
50 /// Base class for generic tasks.
51 class GenericNamedTask : public RTTIExtends<GenericNamedTask, Task> {
52 public:
53   static char ID;
54   static const char *DefaultDescription;
55 };
56 
57 /// Generic task implementation.
58 template <typename FnT> class GenericNamedTaskImpl : public GenericNamedTask {
59 public:
60   GenericNamedTaskImpl(FnT &&Fn, std::string DescBuffer)
61       : Fn(std::forward<FnT>(Fn)), Desc(DescBuffer.c_str()),
62         DescBuffer(std::move(DescBuffer)) {}
63   GenericNamedTaskImpl(FnT &&Fn, const char *Desc)
64       : Fn(std::forward<FnT>(Fn)), Desc(Desc) {
65     assert(Desc && "Description cannot be null");
66   }
67   void printDescription(raw_ostream &OS) override { OS << Desc; }
68   void run() override { Fn(); }
69 
70 private:
71   FnT Fn;
72   const char *Desc;
73   std::string DescBuffer;
74 };
75 
76 /// Create a generic named task from a std::string description.
77 template <typename FnT>
78 std::unique_ptr<GenericNamedTask> makeGenericNamedTask(FnT &&Fn,
79                                                        std::string Desc) {
80   return std::make_unique<GenericNamedTaskImpl<FnT>>(std::forward<FnT>(Fn),
81                                                      std::move(Desc));
82 }
83 
84 /// Create a generic named task from a const char * description.
85 template <typename FnT>
86 std::unique_ptr<GenericNamedTask>
87 makeGenericNamedTask(FnT &&Fn, const char *Desc = nullptr) {
88   if (!Desc)
89     Desc = GenericNamedTask::DefaultDescription;
90   return std::make_unique<GenericNamedTaskImpl<FnT>>(std::forward<FnT>(Fn),
91                                                      Desc);
92 }
93 
94 /// Abstract base for classes that dispatch ORC Tasks.
95 class TaskDispatcher {
96 public:
97   virtual ~TaskDispatcher();
98 
99   /// Run the given task.
100   virtual void dispatch(std::unique_ptr<Task> T) = 0;
101 
102   /// Called by ExecutionSession. Waits until all tasks have completed.
103   virtual void shutdown() = 0;
104 };
105 
106 /// Runs all tasks on the current thread.
107 class InPlaceTaskDispatcher : public TaskDispatcher {
108 public:
109   void dispatch(std::unique_ptr<Task> T) override;
110   void shutdown() override;
111 };
112 
113 #if LLVM_ENABLE_THREADS
114 
115 class DynamicThreadPoolTaskDispatcher : public TaskDispatcher {
116 public:
117   void dispatch(std::unique_ptr<Task> T) override;
118   void shutdown() override;
119 private:
120   std::mutex DispatchMutex;
121   bool Running = true;
122   size_t Outstanding = 0;
123   std::condition_variable OutstandingCV;
124 };
125 
126 #endif // LLVM_ENABLE_THREADS
127 
128 } // End namespace orc
129 } // End namespace llvm
130 
131 #endif // LLVM_EXECUTIONENGINE_ORC_TASKDISPATCH_H
132