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

lib/Analysis/AliasDebugger.cpp

@@ -43,6 +43,9 @@ namespace {
     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