src/llvm/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/Atomic.h"
  17 #include <cassert>
  18 using namespace llvm;
  19
  20 static const ManagedStaticBase *StaticList = 0;
  21
  22 void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
  23                                               void (*Deleter)(void*)) const {
  24   if (llvm_is_multithreaded()) {
  25     llvm_acquire_global_lock();
  26
  27     if (Ptr == 0) {
  28       void* tmp = Creator ? Creator() : 0;
  29
  30       TsanHappensBefore(this);
  31       sys::MemoryFence();
  32
  33       // This write is racy against the first read in the ManagedStatic
  34       // accessors. The race is benign because it does a second read after a
  35       // memory fence, at which point it isn't possible to get a partial value.
  36       TsanIgnoreWritesBegin();
  37       Ptr = tmp;
  38       TsanIgnoreWritesEnd();
  39       DeleterFn = Deleter;
  40
  41       // Add to list of managed statics.
  42       Next = StaticList;
  43       StaticList = this;
  44     }
  45
  46     llvm_release_global_lock();
  47   } else {
  48     assert(Ptr == 0 && DeleterFn == 0 && Next == 0 &&
  49            "Partially initialized ManagedStatic!?");
  50     Ptr = Creator ? Creator() : 0;
  51     DeleterFn = Deleter;
  52
  53     // Add to list of managed statics.
  54     Next = StaticList;
  55     StaticList = this;
  56   }
  57 }
  58
  59 void ManagedStaticBase::destroy() const {
  60   assert(DeleterFn && "ManagedStatic not initialized correctly!");
  61   assert(StaticList == this &&
  62          "Not destroyed in reverse order of construction?");
  63   // Unlink from list.
  64   StaticList = Next;
  65   Next = 0;
  66
  67   // Destroy memory.
  68   DeleterFn(Ptr);
  69
  70   // Cleanup.
  71   Ptr = 0;
  72   DeleterFn = 0;
  73 }
  74
  75 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
  76 void llvm::llvm_shutdown() {
  77   while (StaticList)
  78     StaticList->destroy();
  79
  80   if (llvm_is_multithreaded()) llvm_stop_multithreaded();
  81 }