llvm/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
  22 static std::recursive_mutex *getManagedStaticMutex() {
  23   static std::recursive_mutex m;
  24   return &m;
  25 }
  26
  27 void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
  28                                               void (*Deleter)(void*)) const {
  29   assert(Creator);
  30   if (llvm_is_multithreaded()) {
  31     std::lock_guard<std::recursive_mutex> Lock(*getManagedStaticMutex());
  32
  33     if (!Ptr.load(std::memory_order_relaxed)) {
  34       void *Tmp = Creator();
  35
  36       Ptr.store(Tmp, std::memory_order_release);
  37       DeleterFn = Deleter;
  38
  39       // Add to list of managed statics.
  40       Next = StaticList;
  41       StaticList = this;
  42     }
  43   } else {
  44     assert(!Ptr && !DeleterFn && !Next &&
  45            "Partially initialized ManagedStatic!?");
  46     Ptr = Creator();
  47     DeleterFn = Deleter;
  48
  49     // Add to list of managed statics.
  50     Next = StaticList;
  51     StaticList = this;
  52   }
  53 }
  54
  55 void ManagedStaticBase::destroy() const {
  56   assert(DeleterFn && "ManagedStatic not initialized correctly!");
  57   assert(StaticList == this &&
  58          "Not destroyed in reverse order of construction?");
  59   // Unlink from list.
  60   StaticList = Next;
  61   Next = nullptr;
  62
  63   // Destroy memory.
  64   DeleterFn(Ptr);
  65
  66   // Cleanup.
  67   Ptr = nullptr;
  68   DeleterFn = nullptr;
  69 }
  70
  71 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
  72 /// IMPORTANT: it's only safe to call llvm_shutdown() in single thread,
  73 /// without any other threads executing LLVM APIs.
  74 /// llvm_shutdown() should be the last use of LLVM APIs.
  75 void llvm::llvm_shutdown() {
  76   while (StaticList)
  77     StaticList->destroy();
  78 }