diff --git a/llvm/lib/Target/PIC16/PIC16Passes/Makefile b/llvm/lib/Target/PIC16/PIC16Passes/Makefile
new file mode 100644
index 000000000000..919562106a16
--- /dev/null
+++ b/llvm/lib/Target/PIC16/PIC16Passes/Makefile
@@ -0,0 +1,16 @@
+##===- lib/Target/PIC16/Makefile ---------------------------*- Makefile -*-===##
+# 
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source 
+# License. See LICENSE.TXT for details.
+# 
+##===----------------------------------------------------------------------===##
+LEVEL = ../../../..
+LIBRARYNAME = PIC16Passes
+TARGET = PIC16
+
+LOADABLE_MODULE = 1
+
+include $(LEVEL)/Makefile.common
+
diff --git a/llvm/lib/Target/PIC16/PIC16Passes/PIC16CallGraph.cpp b/llvm/lib/Target/PIC16/PIC16Passes/PIC16CallGraph.cpp
new file mode 100644
index 000000000000..7c792956ecf4
--- /dev/null
+++ b/llvm/lib/Target/PIC16/PIC16Passes/PIC16CallGraph.cpp
@@ -0,0 +1,162 @@
+#include "llvm/Analysis/CallGraph.h"
+#include "llvm/Pass.h"
+#include "llvm/Module.h"
+#include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+#include <vector>
+#include <iostream>
+using namespace llvm;
+using std::vector;
+using std::string;
+
+namespace {
+  class PIC16CallGraph : public ModulePass { 
+  public:
+    static char ID; // Class identification 
+    PIC16CallGraph() : ModulePass(&ID)  {}
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.setPreservesAll();
+      AU.addRequired<CallGraph>();
+    }
+    virtual bool runOnModule(Module &M) {
+      // Initially record that no interrupt has been found
+      InterruptFound = false;
+
+      CallGraph &CG = getAnalysis<CallGraph>();
+      for (CallGraph::iterator it = CG.begin() ; it != CG.end(); it++)
+      {
+        // External calling node doesn't have any function associated 
+        // with it
+        if (!it->first)
+          continue;
+
+        if (it->first->getName().str() == "main") {
+          // See if the main itself is interrupt function then report an error.
+          if (it->first->getSection().find("interrupt") != string::npos)
+             reportError("Function 'main' can't be interrupt function");
+          else  { 
+            // Set the MainLine tag for function main also. 
+            it->second->getFunction()->setSection("ML");
+            // mark the hierarchy 
+            markFunctionHierarchy(it->second, "ML");
+          }
+        } else if (it->first->getSection().find("interrupt") != string::npos) {
+          if (InterruptFound)
+            reportError("More than one interrupt functions defined in the module"); 
+
+          InterruptFound = true;
+          markFunctionHierarchy(it->second, "IL");
+        }
+      }
+     return false;
+    }
+  private: // Functions
+    // Makr function hierarchy for the MainLine or InterruptLine.
+    void markFunctionHierarchy(CallGraphNode *CGN, string StringMark);
+
+    // Error reporting for PIC16Pass
+    void reportError(string ErrorString, vector<string> &Values);
+    void reportError(string ErrorString);
+  private: // Data
+    // Records if the interrupt function has already been found.
+    // If more than one interrupt function is found then an error
+    // should be thrown.
+    bool InterruptFound; 
+  };
+  char PIC16CallGraph::ID =0;
+  static RegisterPass<PIC16CallGraph>
+  Y("pic16cg", "PIC16 CallGraph Construction");
+
+}  // End of anonymous namespace
+
+void PIC16CallGraph::reportError(string ErrorString) {
+  errs() << "ERROR : " << ErrorString << "\n";
+  exit(1);
+}
+
+void PIC16CallGraph::
+reportError (string ErrorString, vector<string> &Values) {
+  unsigned ValCount = Values.size();
+  string TargetString;
+  for (unsigned i=0; i<ValCount; ++i) {
+    TargetString = "%";
+    TargetString += ((char)i + '0');
+    ErrorString.replace(ErrorString.find(TargetString), TargetString.length(), Values[i]);
+  }
+  errs() << "ERROR : " << ErrorString << "\n";
+  exit(1);
+  //llvm_report_error(ErrorString);
+}
+
+void PIC16CallGraph::
+markFunctionHierarchy(CallGraphNode *CGN, string StringMark) {
+  string AlternateMark;
+  string SharedMark = "SL";
+  if (StringMark == "ML")
+    AlternateMark = "IL";
+  else
+    AlternateMark = "ML";
+
+  // Mark all the called functions
+  for(CallGraphNode::iterator cgn_it = CGN->begin(); 
+              cgn_it != CGN->end(); ++cgn_it) {
+     Function *CalledF = cgn_it->second->getFunction();
+
+     // If calling an external function then CallGraphNode
+     // will not be associated with any function.
+     if (!CalledF)
+       continue;
+
+     // Issue diagnostic if interrupt function is being called.
+     if (CalledF->getSection().find("interrupt") != string::npos) {
+       vector<string> Values;
+       Values.push_back(CalledF->getName().str());
+       reportError("Interrupt function (%0) can't be called", Values); 
+     }
+
+     // If already shared mark then no need to check any further.
+     // Also a great potential for recursion.
+     if (CalledF->getSection().find(SharedMark) != string::npos) {
+       continue;
+     }
+
+     // Has already been mark 
+     if (CalledF->getSection().find(StringMark) != string::npos) {
+       // Issue diagnostic
+       // Potential for recursion.
+     } else {
+       // Mark now
+       if (CalledF->getSection().find(AlternateMark) != string::npos) {
+         // Function is alternatively marked. It should be a shared one.
+        
+         // Shared functions should be clone. Clone here. 
+         Function *ClonedFunc = CloneFunction(CalledF); 
+
+         // Add the newly created function to the module.
+         CalledF->getParent()->getFunctionList().push_back(ClonedFunc);
+
+         // The new function should be for interrupt line. Therefore should have the
+         // name suffixed with IL and section attribute marked with IL. 
+         ClonedFunc->setName(CalledF->getName().str() + ".IL");
+         ClonedFunc->setSection("IL");
+
+         // Original function now should be for MainLine only. 
+         CalledF->setSection("ML");
+
+         // Update the CallSite 
+         CallSite CS = cgn_it->first;
+         CS.getInstruction()->getOperand(0)->setName(CalledF->getName().str() + ".shared");
+       } else {
+         // Function is not marked. It should be marked now.
+         CalledF->setSection(StringMark);
+       }
+     }
+     
+     // Before going any further mark all the called function by current
+     // function.
+     markFunctionHierarchy(cgn_it->second ,StringMark);
+  } // end of loop of all called functions.
+
+}