[C++11] Use std::atomic instead of LLVM's.

No intended functionality change.

llvm-svn: 202652
diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index 913bbc7..cbdfa33 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -36,7 +36,6 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringSet.h"
-#include "llvm/Support/Atomic.h"
 #include "llvm/Support/CrashRecoveryContext.h"
 #include "llvm/Support/Host.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -45,6 +44,7 @@
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Timer.h"
 #include "llvm/Support/raw_ostream.h"
+#include <atomic>
 #include <cstdio>
 #include <cstdlib>
 #include <sys/stat.h>
@@ -211,7 +211,7 @@
 /// \brief Tracks the number of ASTUnit objects that are currently active.
 ///
 /// Used for debugging purposes only.
-static llvm::sys::cas_flag ActiveASTUnitObjects;
+static std::atomic<unsigned> ActiveASTUnitObjects;
 
 ASTUnit::ASTUnit(bool _MainFileIsAST)
   : Reader(0), HadModuleLoaderFatalFailure(false),
@@ -228,10 +228,8 @@
     PreambleTopLevelHashValue(0),
     CurrentTopLevelHashValue(0),
     UnsafeToFree(false) { 
-  if (getenv("LIBCLANG_OBJTRACKING")) {
-    llvm::sys::AtomicIncrement(&ActiveASTUnitObjects);
-    fprintf(stderr, "+++ %d translation units\n", (int)ActiveASTUnitObjects);
-  }    
+  if (getenv("LIBCLANG_OBJTRACKING"))
+    fprintf(stderr, "+++ %u translation units\n", ++ActiveASTUnitObjects);
 }
 
 ASTUnit::~ASTUnit() {
@@ -264,10 +262,8 @@
 
   ClearCachedCompletionResults();  
   
-  if (getenv("LIBCLANG_OBJTRACKING")) {
-    llvm::sys::AtomicDecrement(&ActiveASTUnitObjects);
-    fprintf(stderr, "--- %d translation units\n", (int)ActiveASTUnitObjects);
-  }    
+  if (getenv("LIBCLANG_OBJTRACKING"))
+    fprintf(stderr, "--- %u translation units\n", --ActiveASTUnitObjects);
 }
 
 void ASTUnit::setPreprocessor(Preprocessor *pp) { PP = pp; }