Fix the build on Cygwin.  Patch by Aaron Gray.

llvm-svn: 74510
diff --git a/llvm/lib/Analysis/IPA/Andersens.cpp b/llvm/lib/Analysis/IPA/Andersens.cpp
index 4ace049..3fb6526 100644
--- a/llvm/lib/Analysis/IPA/Andersens.cpp
+++ b/llvm/lib/Analysis/IPA/Andersens.cpp
@@ -211,7 +211,7 @@
     // for each location equivalent Node.
     struct Node {
     private:
-      static unsigned Counter;
+      static volatile sys::cas_flag Counter;
 
     public:
       Value *Val;
@@ -618,7 +618,7 @@
 static RegisterAnalysisGroup<AliasAnalysis> Y(X);
 
 // Initialize Timestamp Counter (static).
-unsigned Andersens::Node::Counter = 0;
+volatile llvm::sys::cas_flag Andersens::Node::Counter = 0;
 
 ModulePass *llvm::createAndersensPass() { return new Andersens(); }