[llvm-commits] [llvm] r71796 - /llvm/trunk/include/llvm/Support/ManagedStatic.h

[Owen Anderson]

Author: resistor
Date: Thu May 14 16:26:50 2009
New Revision: 71796

URL: http://llvm.org/viewvc/llvm-project?rev=71796&view=rev
Log:
Make ManagedStatic threadsafe by using atomic operations.

Modified:
    llvm/trunk/include/llvm/Support/ManagedStatic.h

Modified: llvm/trunk/include/llvm/Support/ManagedStatic.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/ManagedStatic.h?rev=71796&r1=71795&r2=71796&view=diff

==============================================================================
--- llvm/trunk/include/llvm/Support/ManagedStatic.h (original)
+++ llvm/trunk/include/llvm/Support/ManagedStatic.h Thu May 14 16:26:50 2009
@@ -14,6 +14,8 @@
 #ifndef LLVM_SUPPORT_MANAGED_STATIC_H
 #define LLVM_SUPPORT_MANAGED_STATIC_H
 
+#include "llvm/System/Atomic.h"
+
 namespace llvm {
 
 /// object_deleter - Helper method for ManagedStatic.
@@ -26,6 +28,8 @@
 /// ManagedStaticBase - Common base class for ManagedStatic instances.
 class ManagedStaticBase {
 protected:
+  sys::cas_flag InitFlag;
+  
   // This should only be used as a static variable, which guarantees that this
   // will be zero initialized.
   mutable void *Ptr;
@@ -51,19 +55,47 @@
 
   // Accessors.
   C &operator*() {
-    if (!Ptr) LazyInit();
+    sys::cas_flag OldFlag = sys::CompareAndSwap(&InitFlag, 1, 0);
+    if (OldFlag == 0) {
+      LazyInit();
+      sys::MemoryFence();
+      InitFlag = 2;
+    } else if (OldFlag == 1)
+      while (OldFlag == 1) ;
+      
     return *static_cast<C*>(Ptr);
   }
   C *operator->() {
-    if (!Ptr) LazyInit();
+    sys::cas_flag OldFlag = sys::CompareAndSwap(&InitFlag, 1, 0);
+    if (OldFlag == 0) {
+      LazyInit();
+      sys::MemoryFence();
+      InitFlag = 2;
+    } else if (OldFlag == 1)
+      while (OldFlag == 1) ;
+    
     return static_cast<C*>(Ptr);
   }
   const C &operator*() const {
-    if (!Ptr) LazyInit();
+    sys::cas_flag OldFlag = sys::CompareAndSwap(&InitFlag, 1, 0);
+    if (OldFlag == 0) {
+      LazyInit();
+      sys::MemoryFence();
+      InitFlag = 2;
+    } else if (OldFlag == 1)
+      while (OldFlag == 1) ;
+    
     return *static_cast<C*>(Ptr);
   }
   const C *operator->() const {
-    if (!Ptr) LazyInit();
+    sys::cas_flag OldFlag = sys::CompareAndSwap(&InitFlag, 1, 0);
+    if (OldFlag == 0) {
+      LazyInit();
+      sys::MemoryFence();
+      InitFlag = 2;
+    } else if (OldFlag == 1)
+      while (OldFlag == 1) ;
+    
     return static_cast<C*>(Ptr);
   }