Identify Analysis pass.
Do not run analysis pass again if analysis info is still available.
This fixes PR1441.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48476 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/AliasDebugger.cpp b/lib/Analysis/AliasDebugger.cpp
index dd766e9..6b534e9 100644
--- a/lib/Analysis/AliasDebugger.cpp
+++ b/lib/Analysis/AliasDebugger.cpp
@@ -43,6 +43,9 @@
     static char ID; // Class identification, replacement for typeinfo
     AliasDebugger() : ModulePass((intptr_t)&ID) {}
 
+    /// isAnalysis - Return true if this pass is  implementing an analysis pass.
+    virtual bool isAnalysis() const { return true; }
+
     bool runOnModule(Module &M) {
       InitializeAliasAnalysis(this);                 // set up super class