Add llvm_start_multithreaded(), which starts up the LLVM internals in thread-safe mode. Provide double-check locking

initialization of ManagedStatic's when running in thread-safe mode.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72151 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/ManagedStatic.cpp

@@ -12,21 +12,44 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/ManagedStatic.h"
+#include "llvm/Config/config.h"
+#include "llvm/System/Atomic.h"
+#include "llvm/System/Mutex.h"
 #include <cassert>
 using namespace llvm;
 
 static const ManagedStaticBase *StaticList = 0;
 
-void ManagedStaticBase::RegisterManagedStatic(void *ObjPtr,
+static sys::Mutex* ManagedStaticMutex = 0;
+
+void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
                                               void (*Deleter)(void*)) const {
-  assert(Ptr == 0 && DeleterFn == 0 && Next == 0 &&
-         "Partially init static?");
-  Ptr = ObjPtr;
-  DeleterFn = Deleter;
+  if (ManagedStaticMutex) {
+    ManagedStaticMutex->acquire();
+
+    if (Ptr == 0) {
+      void* tmp = Creator ? Creator() : 0;
+
+      sys::MemoryFence();
+      Ptr = tmp;
+      DeleterFn = Deleter;
+      
+      // Add to list of managed statics.
+      Next = StaticList;
+      StaticList = this;
+    }
+
+    ManagedStaticMutex->release();
+  } else {
+    assert(Ptr == 0 && DeleterFn == 0 && Next == 0 &&
+	   "Partially initialized ManagedStatic!?");
+    Ptr = Creator ? Creator() : 0;
+    DeleterFn = Deleter;
   
-  // Add to list of managed statics.
-  Next = StaticList;
-  StaticList = this;
+    // Add to list of managed statics.
+    Next = StaticList;
+    StaticList = this;
+  }
 }
 
 void ManagedStaticBase::destroy() const {
@@ -45,9 +68,23 @@ void ManagedStaticBase::destroy() const {
   DeleterFn = 0;
 }
 
+void llvm::llvm_start_multithreaded() {
+#if LLVM_MULTITHREADED
+  assert(ManagedStaticMutex == 0 && "Multithreaded LLVM already initialized!");
+  ManagedStaticMutex = new sys::Mutex(true);
+#else
+  assert(0 && "LLVM built without multithreading support!");
+#endif
+}
+
 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
 void llvm::llvm_shutdown() {
   while (StaticList)
     StaticList->destroy();
+
+  if (ManagedStaticMutex) {
+    delete ManagedStaticMutex;
+    ManagedStaticMutex = 0;
+  }
 }