lib/Support/ManagedStatic.cpp

   1 //===-- ManagedStatic.cpp - Static Global wrapper -------------------------===//
   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 the ManagedStatic class and llvm_shutdown().
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Support/ManagedStatic.h"
  15 #include "llvm/Config/config.h"
  16 #include "llvm/Support/Mutex.h"
  17 #include "llvm/Support/MutexGuard.h"
  18 #include "llvm/Support/Threading.h"
  19 #include <cassert>
  20 using namespace llvm;
  21
  22 static const ManagedStaticBase *StaticList = nullptr;
  23 static sys::Mutex *ManagedStaticMutex = nullptr;
  24 static llvm::once_flag mutex_init_flag;
  25
  26 static void initializeMutex() {
  27   ManagedStaticMutex = new sys::Mutex();
  28 }
  29
  30 static sys::Mutex* getManagedStaticMutex() {
  31   llvm::call_once(mutex_init_flag, initializeMutex);
  32   return ManagedStaticMutex;
  33 }
  34
  35 void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
  36                                               void (*Deleter)(void*)) const {
  37   assert(Creator);
  38   if (llvm_is_multithreaded()) {
  39     MutexGuard Lock(*getManagedStaticMutex());
  40
  41     if (!Ptr.load(std::memory_order_relaxed)) {
  42       void *Tmp = Creator();
  43
  44       Ptr.store(Tmp, std::memory_order_release);
  45       DeleterFn = Deleter;
  46
  47       // Add to list of managed statics.
  48       Next = StaticList;
  49       StaticList = this;
  50     }
  51   } else {
  52     assert(!Ptr && !DeleterFn && !Next &&
  53            "Partially initialized ManagedStatic!?");
  54     Ptr = Creator();
  55     DeleterFn = Deleter;
  56
  57     // Add to list of managed statics.
  58     Next = StaticList;
  59     StaticList = this;
  60   }
  61 }
  62
  63 void ManagedStaticBase::destroy() const {
  64   assert(DeleterFn && "ManagedStatic not initialized correctly!");
  65   assert(StaticList == this &&
  66          "Not destroyed in reverse order of construction?");
  67   // Unlink from list.
  68   StaticList = Next;
  69   Next = nullptr;
  70
  71   // Destroy memory.
  72   DeleterFn(Ptr);
  73
  74   // Cleanup.
  75   Ptr = nullptr;
  76   DeleterFn = nullptr;
  77 }
  78
  79 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
  80 void llvm::llvm_shutdown() {
  81   MutexGuard Lock(*getManagedStaticMutex());
  82
  83   while (StaticList)
  84     StaticList->destroy();
  85 }