lib/Support/Threading.cpp


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147

//===-- llvm/Support/Threading.cpp- Control multithreading mode --*- C++ -*-==//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements llvm_start_multithreaded() and friends.
//
//===----------------------------------------------------------------------===//

#include "llvm/Support/Threading.h"
#include "llvm/Config/config.h"
#include "llvm/Support/Atomic.h"
#include "llvm/Support/Mutex.h"
#include <cassert>

using namespace llvm;

static bool multithreaded_mode = false;

static sys::Mutex* global_lock = 0;

bool llvm::llvm_start_multithreaded() {
#if LLVM_ENABLE_THREADS != 0
  assert(!multithreaded_mode && "Already multithreaded!");
  multithreaded_mode = true;
  global_lock = new sys::Mutex(true);

  // We fence here to ensure that all initialization is complete BEFORE we
  // return from llvm_start_multithreaded().
  sys::MemoryFence();
  return true;
#else
  return false;
#endif
}

void llvm::llvm_stop_multithreaded() {
#if LLVM_ENABLE_THREADS != 0
  assert(multithreaded_mode && "Not currently multithreaded!");

  // We fence here to insure that all threaded operations are complete BEFORE we
  // return from llvm_stop_multithreaded().
  sys::MemoryFence();

  multithreaded_mode = false;
  delete global_lock;
#endif
}

bool llvm::llvm_is_multithreaded() {
  return multithreaded_mode;
}

void llvm::llvm_acquire_global_lock() {
  if (multithreaded_mode) global_lock->acquire();
}

void llvm::llvm_release_global_lock() {
  if (multithreaded_mode) global_lock->release();
}

#if LLVM_ENABLE_THREADS != 0 && defined(HAVE_PTHREAD_H)
#include <pthread.h>

struct ThreadInfo {
  void (*UserFn)(void *);
  void *UserData;
};
static void *ExecuteOnThread_Dispatch(void *Arg) {
  ThreadInfo *TI = reinterpret_cast<ThreadInfo*>(Arg);
  TI->UserFn(TI->UserData);
  return 0;
}

void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
                                  unsigned RequestedStackSize) {
  ThreadInfo Info = { Fn, UserData };
  pthread_attr_t Attr;
  pthread_t Thread;

  // Construct the attributes object.
  if (::pthread_attr_init(&Attr) != 0)
    return;

  // Set the requested stack size, if given.
  if (RequestedStackSize != 0) {
    if (::pthread_attr_setstacksize(&Attr, RequestedStackSize) != 0)
      goto error;
  }

  // Construct and execute the thread.
  if (::pthread_create(&Thread, &Attr, ExecuteOnThread_Dispatch, &Info) != 0)
    goto error;

  // Wait for the thread and clean up.
  ::pthread_join(Thread, 0);

 error:
  ::pthread_attr_destroy(&Attr);
}
#elif LLVM_ENABLE_THREADS!=0 && defined(LLVM_ON_WIN32)
#include "Windows/Windows.h"
#include <process.h>

struct ThreadInfo {
  void (*func)(void*);
  void *param;
};

static unsigned __stdcall ThreadCallback(void *param) {
  struct ThreadInfo *info = reinterpret_cast<struct ThreadInfo *>(param);
  info->func(info->param);

  return 0;
}

void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
                                  unsigned RequestedStackSize) {
  struct ThreadInfo param = { Fn, UserData };

  HANDLE hThread = (HANDLE)::_beginthreadex(NULL,
                                            RequestedStackSize, ThreadCallback,
                                            &param, 0, NULL);

  if (hThread) {
    // We actually don't care whether the wait succeeds or fails, in
    // the same way we don't care whether the pthread_join call succeeds
    // or fails.  There's not much we could do if this were to fail. But
    // on success, this call will wait until the thread finishes executing
    // before returning.
    (void)::WaitForSingleObject(hThread, INFINITE);
    ::CloseHandle(hThread);
  }
}
#else
// Support for non-Win32, non-pthread implementation.
void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
                                  unsigned RequestedStackSize) {
  (void) RequestedStackSize;
  Fn(UserData);
}

#endif