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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/Mutex.h"
     19 #include <cassert>
     20 
     21 using namespace llvm;
     22 
     23 bool llvm::llvm_is_multithreaded() {
     24 #if LLVM_ENABLE_THREADS != 0
     25   return true;
     26 #else
     27   return false;
     28 #endif
     29 }
     30 
     31 #if LLVM_ENABLE_THREADS != 0 && defined(HAVE_PTHREAD_H)
     32 #include <pthread.h>
     33 
     34 struct ThreadInfo {
     35   void (*UserFn)(void *);
     36   void *UserData;
     37 };
     38 static void *ExecuteOnThread_Dispatch(void *Arg) {
     39   ThreadInfo *TI = reinterpret_cast<ThreadInfo*>(Arg);
     40   TI->UserFn(TI->UserData);
     41   return nullptr;
     42 }
     43 
     44 void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
     45                                   unsigned RequestedStackSize) {
     46   ThreadInfo Info = { Fn, UserData };
     47   pthread_attr_t Attr;
     48   pthread_t Thread;
     49 
     50   // Construct the attributes object.
     51   if (::pthread_attr_init(&Attr) != 0)
     52     return;
     53 
     54   // Set the requested stack size, if given.
     55   if (RequestedStackSize != 0) {
     56     if (::pthread_attr_setstacksize(&Attr, RequestedStackSize) != 0)
     57       goto error;
     58   }
     59 
     60   // Construct and execute the thread.
     61   if (::pthread_create(&Thread, &Attr, ExecuteOnThread_Dispatch, &Info) != 0)
     62     goto error;
     63 
     64   // Wait for the thread and clean up.
     65   ::pthread_join(Thread, nullptr);
     66 
     67  error:
     68   ::pthread_attr_destroy(&Attr);
     69 }
     70 #elif LLVM_ENABLE_THREADS!=0 && defined(LLVM_ON_WIN32)
     71 #include "Windows/WindowsSupport.h"
     72 #include <process.h>
     73 
     74 struct ThreadInfo {
     75   void (*func)(void*);
     76   void *param;
     77 };
     78 
     79 static unsigned __stdcall ThreadCallback(void *param) {
     80   struct ThreadInfo *info = reinterpret_cast<struct ThreadInfo *>(param);
     81   info->func(info->param);
     82 
     83   return 0;
     84 }
     85 
     86 void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
     87                                   unsigned RequestedStackSize) {
     88   struct ThreadInfo param = { Fn, UserData };
     89 
     90   HANDLE hThread = (HANDLE)::_beginthreadex(NULL,
     91                                             RequestedStackSize, ThreadCallback,
     92                                             &param, 0, NULL);
     93 
     94   if (hThread) {
     95     // We actually don't care whether the wait succeeds or fails, in
     96     // the same way we don't care whether the pthread_join call succeeds
     97     // or fails.  There's not much we could do if this were to fail. But
     98     // on success, this call will wait until the thread finishes executing
     99     // before returning.
    100     (void)::WaitForSingleObject(hThread, INFINITE);
    101     ::CloseHandle(hThread);
    102   }
    103 }
    104 #else
    105 // Support for non-Win32, non-pthread implementation.
    106 void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
    107                                   unsigned RequestedStackSize) {
    108   (void) RequestedStackSize;
    109   Fn(UserData);
    110 }
    111 
    112 #endif
    113