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