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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 LLVM_DEFINE_ONCE_FLAG(mutex_init_flag);
25 
initializeMutex()26 static void initializeMutex() {
27   ManagedStaticMutex = new sys::Mutex();
28 }
29 
getManagedStaticMutex()30 static sys::Mutex* getManagedStaticMutex() {
31   // We need to use a function local static here, since this can get called
32   // during a static constructor and we need to guarantee that it's initialized
33   // correctly.
34   llvm::call_once(mutex_init_flag, initializeMutex);
35   return ManagedStaticMutex;
36 }
37 
RegisterManagedStatic(void * (* Creator)(),void (* Deleter)(void *)) const38 void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
39                                               void (*Deleter)(void*)) const {
40   assert(Creator);
41   if (llvm_is_multithreaded()) {
42     MutexGuard Lock(*getManagedStaticMutex());
43 
44     if (!Ptr.load(std::memory_order_relaxed)) {
45       void *Tmp = Creator();
46 
47       Ptr.store(Tmp, std::memory_order_release);
48       DeleterFn = Deleter;
49 
50       // Add to list of managed statics.
51       Next = StaticList;
52       StaticList = this;
53     }
54   } else {
55     assert(!Ptr && !DeleterFn && !Next &&
56            "Partially initialized ManagedStatic!?");
57     Ptr = Creator();
58     DeleterFn = Deleter;
59 
60     // Add to list of managed statics.
61     Next = StaticList;
62     StaticList = this;
63   }
64 }
65 
destroy() const66 void ManagedStaticBase::destroy() const {
67   assert(DeleterFn && "ManagedStatic not initialized correctly!");
68   assert(StaticList == this &&
69          "Not destroyed in reverse order of construction?");
70   // Unlink from list.
71   StaticList = Next;
72   Next = nullptr;
73 
74   // Destroy memory.
75   DeleterFn(Ptr);
76 
77   // Cleanup.
78   Ptr = nullptr;
79   DeleterFn = nullptr;
80 }
81 
82 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
llvm_shutdown()83 void llvm::llvm_shutdown() {
84   MutexGuard Lock(*getManagedStaticMutex());
85 
86   while (StaticList)
87     StaticList->destroy();
88 }
89