lib/System/Threading.cpp

   1 //===-- llvm/System/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 implements llvm_start_multithreaded() and friends.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/System/Threading.h"
  15 #include "llvm/System/Atomic.h"
  16 #include "llvm/System/Mutex.h"
  17 #include "llvm/Config/config.h"
  18 #include <cassert>
  19
  20 using namespace llvm;
  21
  22 static bool multithreaded_mode = false;
  23
  24 static sys::Mutex* global_lock = 0;
  25
  26 bool llvm::llvm_start_multithreaded() {
  27 #ifdef LLVM_MULTITHREADED
  28   assert(!multithreaded_mode && "Already multithreaded!");
  29   multithreaded_mode = true;
  30   global_lock = new sys::Mutex(true);
  31
  32   // We fence here to ensure that all initialization is complete BEFORE we
  33   // return from llvm_start_multithreaded().
  34   sys::MemoryFence();
  35   return true;
  36 #else
  37   return false;
  38 #endif
  39 }
  40
  41 void llvm::llvm_stop_multithreaded() {
  42 #ifdef LLVM_MULTITHREADED
  43   assert(multithreaded_mode && "Not currently multithreaded!");
  44
  45   // We fence here to insure that all threaded operations are complete BEFORE we
  46   // return from llvm_stop_multithreaded().
  47   sys::MemoryFence();
  48
  49   multithreaded_mode = false;
  50   delete global_lock;
  51 #endif
  52 }
  53
  54 bool llvm::llvm_is_multithreaded() {
  55   return multithreaded_mode;
  56 }
  57
  58 void llvm::llvm_acquire_global_lock() {
  59   if (multithreaded_mode) global_lock->acquire();
  60 }
  61
  62 void llvm::llvm_release_global_lock() {
  63   if (multithreaded_mode) global_lock->release();
  64 }