LLVM  4.0.0
Threading.cpp
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1 //===-- llvm/Support/Threading.cpp- Control multithreading mode --*- C++ -*-==//
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 file defines helper functions for running LLVM in a multi-threaded
11 // environment.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/Support/Threading.h"
16 #include "llvm/Config/config.h"
17 #include "llvm/Support/Atomic.h"
18 #include "llvm/Support/Host.h"
19 #include "llvm/Support/Mutex.h"
20 #include "llvm/Support/thread.h"
21 #include <cassert>
22 
23 using namespace llvm;
24 
26 #if LLVM_ENABLE_THREADS != 0
27  return true;
28 #else
29  return false;
30 #endif
31 }
32 
33 #if LLVM_ENABLE_THREADS != 0 && defined(HAVE_PTHREAD_H)
34 #include <pthread.h>
35 
36 struct ThreadInfo {
37  void (*UserFn)(void *);
38  void *UserData;
39 };
40 static void *ExecuteOnThread_Dispatch(void *Arg) {
41  ThreadInfo *TI = reinterpret_cast<ThreadInfo*>(Arg);
42  TI->UserFn(TI->UserData);
43  return nullptr;
44 }
45 
46 void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
47  unsigned RequestedStackSize) {
48  ThreadInfo Info = { Fn, UserData };
49  pthread_attr_t Attr;
50  pthread_t Thread;
51 
52  // Construct the attributes object.
53  if (::pthread_attr_init(&Attr) != 0)
54  return;
55 
56  // Set the requested stack size, if given.
57  if (RequestedStackSize != 0) {
58  if (::pthread_attr_setstacksize(&Attr, RequestedStackSize) != 0)
59  goto error;
60  }
61 
62  // Construct and execute the thread.
63  if (::pthread_create(&Thread, &Attr, ExecuteOnThread_Dispatch, &Info) != 0)
64  goto error;
65 
66  // Wait for the thread and clean up.
67  ::pthread_join(Thread, nullptr);
68 
69  error:
70  ::pthread_attr_destroy(&Attr);
71 }
72 #elif LLVM_ENABLE_THREADS!=0 && defined(LLVM_ON_WIN32)
73 #include "Windows/WindowsSupport.h"
74 #include <process.h>
75 
76 // Windows will at times define MemoryFence.
77 #ifdef MemoryFence
78 #undef MemoryFence
79 #endif
80 
81 struct ThreadInfo {
82  void (*func)(void*);
83  void *param;
84 };
85 
86 static unsigned __stdcall ThreadCallback(void *param) {
87  struct ThreadInfo *info = reinterpret_cast<struct ThreadInfo *>(param);
88  info->func(info->param);
89 
90  return 0;
91 }
92 
93 void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
94  unsigned RequestedStackSize) {
95  struct ThreadInfo param = { Fn, UserData };
96 
97  HANDLE hThread = (HANDLE)::_beginthreadex(NULL,
98  RequestedStackSize, ThreadCallback,
99  &param, 0, NULL);
100 
101  if (hThread) {
102  // We actually don't care whether the wait succeeds or fails, in
103  // the same way we don't care whether the pthread_join call succeeds
104  // or fails. There's not much we could do if this were to fail. But
105  // on success, this call will wait until the thread finishes executing
106  // before returning.
107  (void)::WaitForSingleObject(hThread, INFINITE);
108  ::CloseHandle(hThread);
109  }
110 }
111 #else
112 // Support for non-Win32, non-pthread implementation.
113 void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
114  unsigned RequestedStackSize) {
115  (void) RequestedStackSize;
116  Fn(UserData);
117 }
118 
119 #endif
120 
122 #if !LLVM_ENABLE_THREADS
123  return 1;
124 #endif
125  int NumPhysical = sys::getHostNumPhysicalCores();
126  if (NumPhysical == -1)
127  return thread::hardware_concurrency();
128  return NumPhysical;
129 }
unsigned heavyweight_hardware_concurrency()
Get the amount of currency to use for tasks requiring significant memory or other resources...
Definition: Threading.cpp:121
void * UserData
Definition: Threading.cpp:38
static void * ExecuteOnThread_Dispatch(void *Arg)
Definition: Threading.cpp:40
int getHostNumPhysicalCores()
Get the number of physical cores (as opposed to logical cores returned from thread::hardware_concurre...
Definition: Host.cpp:1291
lazy value info
bool llvm_is_multithreaded()
Returns true if LLVM is compiled with support for multi-threading, and false otherwise.
Definition: Threading.cpp:25
void llvm_execute_on_thread(void(*UserFn)(void *), void *UserData, unsigned RequestedStackSize=0)
llvm_execute_on_thread - Execute the given UserFn on a separate thread, passing it the provided UserD...
Definition: Threading.cpp:46
Error error(const Twine &Message)
void(* UserFn)(void *)
Definition: Threading.cpp:37