lib/Support/ManagedStatic.cpp

   1 //===-- ManagedStatic.cpp - Static Global wrapper -------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements the ManagedStatic class and llvm_shutdown().
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/Support/ManagedStatic.h"
  14 #include "llvm/Config/config.h"
  15 #include "llvm/Support/Mutex.h"
  16 #include "llvm/Support/MutexGuard.h"
  17 #include "llvm/Support/Threading.h"
  18 #include <cassert>
  19 using namespace llvm;
  20
  21 static const ManagedStaticBase *StaticList = nullptr;
  22 static sys::Mutex *ManagedStaticMutex = nullptr;
  23 static llvm::once_flag mutex_init_flag;
  24
  25 static void initializeMutex() {
  26   ManagedStaticMutex = new sys::Mutex();
  27 }
  28
  29 static sys::Mutex* getManagedStaticMutex() {
  30   llvm::call_once(mutex_init_flag, initializeMutex);
  31   return ManagedStaticMutex;
  32 }
  33
  34 void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
  35                                               void (*Deleter)(void*)) const {
  36   assert(Creator);
  37   if (llvm_is_multithreaded()) {
  38     MutexGuard Lock(*getManagedStaticMutex());
  39
  40     if (!Ptr.load(std::memory_order_relaxed)) {
  41       void *Tmp = Creator();
  42
  43       Ptr.store(Tmp, std::memory_order_release);
  44       DeleterFn = Deleter;
  45
  46       // Add to list of managed statics.
  47       Next = StaticList;
  48       StaticList = this;
  49     }
  50   } else {
  51     assert(!Ptr && !DeleterFn && !Next &&
  52            "Partially initialized ManagedStatic!?");
  53     Ptr = Creator();
  54     DeleterFn = Deleter;
  55
  56     // Add to list of managed statics.
  57     Next = StaticList;
  58     StaticList = this;
  59   }
  60 }
  61
  62 void ManagedStaticBase::destroy() const {
  63   assert(DeleterFn && "ManagedStatic not initialized correctly!");
  64   assert(StaticList == this &&
  65          "Not destroyed in reverse order of construction?");
  66   // Unlink from list.
  67   StaticList = Next;
  68   Next = nullptr;
  69
  70   // Destroy memory.
  71   DeleterFn(Ptr);
  72
  73   // Cleanup.
  74   Ptr = nullptr;
  75   DeleterFn = nullptr;
  76 }
  77
  78 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
  79 void llvm::llvm_shutdown() {
  80   MutexGuard Lock(*getManagedStaticMutex());
  81
  82   while (StaticList)
  83     StaticList->destroy();
  84 }