diff --git a/lib/Target/PIC16/AsmPrinter/PIC16AsmPrinter.cpp b/lib/Target/PIC16/AsmPrinter/PIC16AsmPrinter.cpp
index 3f719b9..08b49c8 100644
--- a/lib/Target/PIC16/AsmPrinter/PIC16AsmPrinter.cpp
+++ b/lib/Target/PIC16/AsmPrinter/PIC16AsmPrinter.cpp
@@ -53,6 +53,45 @@
   return true;
 }
 
+static int getFunctionColor(const Function *F) {
+  if (F->hasSection()) {
+    std::string Sectn = F->getSection();
+    std::string StrToFind = "Overlay=";
+    unsigned Pos = Sectn.find(StrToFind);
+
+    // Retreive the color number if the key is found.
+    if (Pos != std::string::npos) {
+      Pos += StrToFind.length();
+      std::string Color = "";
+      char c = Sectn.at(Pos);
+      // A Color can only consist of digits.
+      while (c >= '0' && c<= '9') {
+        Color.append(1,c);
+        Pos++;
+        if (Pos >= Sectn.length())
+          break;
+        c = Sectn.at(Pos);
+      }
+      return atoi(Color.c_str());
+    }
+  }
+
+  // Color was not set for function, so return -1.
+  return -1;
+}
+
+// Color the Auto section of the given function. 
+void PIC16AsmPrinter::ColorAutoSection(const Function *F) {
+  std::string SectionName = PAN::getAutosSectionName(CurrentFnName);
+  PIC16Section* Section = PTOF->findPIC16Section(SectionName);
+  if (Section != NULL) {
+    int Color = getFunctionColor(F);
+    if (Color >= 0)
+      Section->setColor(Color);
+  }
+}
+
+
 /// runOnMachineFunction - This emits the frame section, autos section and 
 /// assembly for each instruction. Also takes care of function begin debug
 /// directive and file begin debug directive (if required) for the function.
@@ -68,6 +107,9 @@
   const Function *F = MF.getFunction();
   CurrentFnName = Mang->getMangledName(F);
 
+  // Put the color information from function to its auto section.
+  ColorAutoSection(F);
+
   // Emit the function frame (args and temps).
   EmitFunctionFrame(MF);
 
@@ -255,7 +297,6 @@
   EmitDefinedVars(M);
   EmitIData(M);
   EmitUData(M);
-  EmitAllAutos(M);
   EmitRomData(M);
   EmitUserSections(M);
   return Result;
@@ -330,6 +371,7 @@
 }
 
 bool PIC16AsmPrinter::doFinalization(Module &M) {
+  EmitAllAutos(M);
   printLibcallDecls();
   DbgInfo.EndModule(M);
   O << "\n\t" << "END\n";
@@ -343,8 +385,10 @@
   // Emit the data section name.
   O << "\n"; 
   
-  const MCSection *fPDataSection =
-    getObjFileLowering().SectionForFrame(CurrentFnName);
+  PIC16Section *fPDataSection = const_cast<PIC16Section *>(getObjFileLowering().
+                                SectionForFrame(CurrentFnName));
+ 
+  fPDataSection->setColor(getFunctionColor(F)); 
   OutStreamer.SwitchSection(fPDataSection);
   
   // Emit function frame label
diff --git a/lib/Target/PIC16/AsmPrinter/PIC16AsmPrinter.h b/lib/Target/PIC16/AsmPrinter/PIC16AsmPrinter.h
index 580e2fd..b13d9ce 100644
--- a/lib/Target/PIC16/AsmPrinter/PIC16AsmPrinter.h
+++ b/lib/Target/PIC16/AsmPrinter/PIC16AsmPrinter.h
@@ -63,6 +63,7 @@
     void EmitSingleSection(const PIC16Section *S);
     void EmitSectionList(Module &M, 
                          const std::vector< PIC16Section *> &SList);
+    void ColorAutoSection(const Function *F);
   protected:
     bool doInitialization(Module &M);
     bool doFinalization(Module &M);
diff --git a/lib/Target/PIC16/Makefile b/lib/Target/PIC16/Makefile
index f913675..4382eba 100644
--- a/lib/Target/PIC16/Makefile
+++ b/lib/Target/PIC16/Makefile
@@ -17,7 +17,7 @@
 		PIC16GenDAGISel.inc PIC16GenCallingConv.inc \
 		PIC16GenSubtarget.inc
 
-DIRS = AsmPrinter TargetInfo
+DIRS = AsmPrinter TargetInfo PIC16Passes
 
 include $(LEVEL)/Makefile.common
 
diff --git a/lib/Target/PIC16/PIC16ABINames.h b/lib/Target/PIC16/PIC16ABINames.h
index 7fa1721..7f4c2f1 100644
--- a/lib/Target/PIC16/PIC16ABINames.h
+++ b/lib/Target/PIC16/PIC16ABINames.h
@@ -304,6 +304,21 @@
         }
       }
     }
+
+    /// Return Overlay Name for the section.
+    /// The ABI Convention is: @<Color>.##.<section_tag>
+    /// The section_tag is retrieved from the SectName parameter and
+    /// and Color is passed in parameter.
+    static inline std::string  getOverlayName(std::string SectName, int Color) {
+      // FIXME: Only autos_section and frame_section are colored.
+      // So check and assert if the passed SectName does not have AUTOS_SECTION
+      // or FRAME_SECTION tag in it.
+      std::ostringstream o;
+      o << getTagName(PREFIX_SYMBOL) << Color << ".##" 
+        << SectName.substr(SectName.find("."));
+
+      return o.str();
+    } 
   }; // class PAN.
 } // end namespace llvm;
 
diff --git a/lib/Target/PIC16/PIC16Passes/Makefile b/lib/Target/PIC16/PIC16Passes/Makefile
new file mode 100644
index 0000000..cbb34b3
--- /dev/null
+++ b/lib/Target/PIC16/PIC16Passes/Makefile
@@ -0,0 +1,17 @@
+##===- lib/Target/PIC16/PIC16Passes/Makefile -----------*- Makefile -*-===##
+# 
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source 
+# License. See LICENSE.TXT for details.
+# 
+##===----------------------------------------------------------------------===##
+LEVEL = ../../../..
+TARGET = PIC16
+LIBRARYNAME = LLVMpic16passes
+BUILD_ARCHIVE = 1
+
+
+
+include $(LEVEL)/Makefile.common
+
diff --git a/lib/Target/PIC16/PIC16Passes/PIC16Overlay.cpp b/lib/Target/PIC16/PIC16Passes/PIC16Overlay.cpp
new file mode 100644
index 0000000..197c398
--- /dev/null
+++ b/lib/Target/PIC16/PIC16Passes/PIC16Overlay.cpp
@@ -0,0 +1,181 @@
+//===-- PIC16Overlay.cpp - Implementation for PIC16 Frame Overlay===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source 
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains the PIC16 Frame Overlay implementation.
+//
+//===----------------------------------------------------------------------===//
+
+
+#include "llvm/Analysis/CallGraph.h"
+#include "llvm/Pass.h"
+#include "llvm/Module.h"
+#include "llvm/Instructions.h"
+#include "llvm/Value.h"
+#include "PIC16Overlay.h"
+#include "llvm/Function.h"
+#include <cstdlib>
+#include <sstream>
+using namespace llvm;
+
+namespace llvm {
+  char PIC16FrameOverlay::ID = 0;
+  ModulePass *createPIC16OverlayPass() { return new PIC16FrameOverlay(); }
+}
+
+void PIC16FrameOverlay::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.setPreservesAll();
+  AU.addRequired<CallGraph>();
+}
+
+void PIC16FrameOverlay::DFSTraverse(CallGraphNode *CGN, unsigned Depth) {
+  // Do not set any color for external calling node.
+  if (Depth != 0 && CGN->getFunction()) {
+    unsigned Color = getColor(CGN->getFunction());
+
+    // Handle indirectly called functions
+    if (Color >= PIC16Overlay::StartIndirectCallColor || 
+        Depth >= PIC16Overlay::StartIndirectCallColor) {
+      // All functions called from an indirectly called function are given
+      // an unique color.
+      if (Color < PIC16Overlay::StartIndirectCallColor &&
+          Depth >= PIC16Overlay::StartIndirectCallColor)
+        setColor(CGN->getFunction(), Depth);
+
+      for (unsigned int i = 0; i < CGN->size(); i++)
+        DFSTraverse((*CGN)[i], ++IndirectCallColor);
+      return;
+    }
+    // Just return if the node already has a color greater than the current 
+    // depth. A node must be colored with the maximum depth that it has.
+    if (Color >= Depth)
+      return;
+    
+    Depth = ModifyDepthForInterrupt(CGN, Depth);  
+    setColor(CGN->getFunction(), Depth);
+  }
+  
+  // Color all children of this node with color depth+1.
+  for (unsigned int i = 0; i < CGN->size(); i++)
+    DFSTraverse((*CGN)[i], Depth+1);
+}
+
+unsigned PIC16FrameOverlay::ModifyDepthForInterrupt(CallGraphNode *CGN,
+                                                    unsigned Depth) {
+  Function *Fn = CGN->getFunction();
+
+  // Return original Depth if function or section for function do not exist.
+  if (!Fn || !Fn->hasSection())
+    return Depth;
+
+  // Return original Depth if this function is not marked as interrupt.
+  if (Fn->getSection().find("interrupt") == string::npos)
+    return Depth;
+
+  Depth = Depth + InterruptDepth;
+  return Depth;
+}
+
+void PIC16FrameOverlay::setColor(Function *Fn, unsigned Color) {
+  std::string Section = "";
+  if (Fn->hasSection())
+    Section = Fn->getSection();
+
+  size_t Pos = Section.find(OverlayStr);
+
+  // Convert Color to string.
+  std::stringstream ss;
+  ss << Color;
+  std::string ColorString = ss.str();
+
+  // If color is already set then reset it with the new value. Else append 
+  // the Color string to section.
+  if (Pos != std::string::npos) {
+    Pos += OverlayStr.length();
+    char c = Section.at(Pos);
+    unsigned OldColorLength = 0;  
+    while (c >= '0' && c<= '9') {
+      OldColorLength++;    
+      if (Pos < Section.length() - 1)
+        Pos++;
+      else
+        break;
+      c = Section.at(Pos);
+    }
+    // Replace old color with new one.
+    Section.replace(Pos-OldColorLength +1, OldColorLength, ColorString); 
+  }
+  else {
+    // Append Color information to section string.
+    if (Fn->hasSection())
+      Section.append(" ");
+    Section.append(OverlayStr + ColorString);
+  }
+  Fn->setSection(Section);
+}
+
+unsigned PIC16FrameOverlay::getColor(Function *Fn) {
+  int Color = 0;
+  if (!Fn->hasSection())
+    return 0;
+
+  std::string Section = Fn->getSection();
+  size_t Pos = Section.find(OverlayStr);
+  
+  // Return 0 if Color is not set.
+  if (Pos == std::string::npos)
+    return 0;
+
+  // Set Pos to after "Overlay=".
+  Pos += OverlayStr.length();
+  char c = Section.at(Pos);
+  std::string ColorString = "";
+
+  // Find the string representing Color. A Color can only consist of digits.
+  while (c >= '0' && c<= '9') { 
+    ColorString.append(1,c);
+    if (Pos < Section.length() - 1)
+      Pos++;
+    else
+      break;
+    c = Section.at(Pos);
+  }
+  Color = atoi(ColorString.c_str());
+  
+  return Color;    
+}
+
+bool PIC16FrameOverlay::runOnModule(Module &M) {
+  CallGraph &CG = getAnalysis<CallGraph>();
+  CallGraphNode *ECN = CG.getExternalCallingNode();
+
+  MarkIndirectlyCalledFunctions(M); 
+  // Since External Calling Node is the base function, do a depth first 
+  // traversal of CallGraph with ECN as root. Each node with be marked with 
+  // a color that is max(color(callers)) + 1.
+  if(ECN) {
+    DFSTraverse(ECN, 0);
+  }
+  return false;
+}
+
+void PIC16FrameOverlay::MarkIndirectlyCalledFunctions(Module &M) {
+  // If the use of a function is not a call instruction then this
+  // function might be called indirectly. In that case give it
+  // an unique color.
+  for (Module::iterator MI = M.begin(), E = M.end(); MI != E; ++MI) {
+    for (Value::use_iterator I = MI->use_begin(), E = MI->use_end(); I != E;
+         ++I) {
+      if ((!isa<CallInst>(I) && !isa<InvokeInst>(I))
+          || !CallSite(cast<Instruction>(I)).isCallee(I)) {
+        setColor(MI, ++IndirectCallColor);
+        break;
+      }
+    }
+  }
+}
diff --git a/lib/Target/PIC16/PIC16Passes/PIC16Overlay.h b/lib/Target/PIC16/PIC16Passes/PIC16Overlay.h
new file mode 100644
index 0000000..d70c4e7
--- /dev/null
+++ b/lib/Target/PIC16/PIC16Passes/PIC16Overlay.h
@@ -0,0 +1,55 @@
+//===-- PIC16FrameOverlay.h - Interface for PIC16 Frame Overlay -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source 
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains the PIC16 Overlay infrastructure.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef PIC16FRAMEOVERLAY_H
+#define PIC16FRAMEOVERLAY_H
+ 
+#include "llvm/Analysis/CallGraph.h"
+#include "llvm/Pass.h"
+#include "llvm/CallGraphSCCPass.h"
+
+using std::string;
+using namespace llvm;
+
+namespace  llvm {
+  namespace PIC16Overlay {
+    enum OverlayConsts {
+      StartInterruptColor = 200,
+      StartIndirectCallColor = 300
+    }; 
+  }
+  class PIC16FrameOverlay : public ModulePass {
+    std::string OverlayStr;
+    unsigned InterruptDepth;
+    unsigned IndirectCallColor;
+  public:
+    static char ID; // Class identification 
+    PIC16FrameOverlay() : ModulePass(&ID) {
+      OverlayStr = "Overlay=";
+      InterruptDepth = PIC16Overlay::StartInterruptColor;
+      IndirectCallColor = PIC16Overlay::StartIndirectCallColor;
+    }
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const; 
+    virtual bool runOnModule(Module &M);
+
+  private: 
+    unsigned getColor(Function *Fn);
+    void setColor(Function *Fn, unsigned Color);
+    unsigned ModifyDepthForInterrupt(CallGraphNode *CGN, unsigned Depth);
+    void MarkIndirectlyCalledFunctions(Module &M);
+    void DFSTraverse(CallGraphNode *CGN, unsigned Depth);
+  };
+}  // End of  namespace
+
+#endif
diff --git a/lib/Target/PIC16/PIC16Section.cpp b/lib/Target/PIC16/PIC16Section.cpp
index 7029501..a96ebb8 100644
--- a/lib/Target/PIC16/PIC16Section.cpp
+++ b/lib/Target/PIC16/PIC16Section.cpp
@@ -68,8 +68,13 @@
 // A generic way to print all types of sections.
 void PIC16Section::PrintSwitchToSection(const MCAsmInfo &MAI,
                                           raw_ostream &OS) const {
-  // Print name.
-  OS << getName() << '\t';
+ 
+  // If the section is overlaid(i.e. it has a color), print overlay name for 
+  // it. Otherwise print its normal name.
+  if (Color != -1)
+    OS << PAN::getOverlayName(getName(), Color) << '\t';
+  else
+    OS << getName() << '\t';
 
   // Print type.
   switch (getType()) {
diff --git a/lib/Target/PIC16/PIC16Section.h b/lib/Target/PIC16/PIC16Section.h
index 693ac3a..3a8bbfb 100644
--- a/lib/Target/PIC16/PIC16Section.h
+++ b/lib/Target/PIC16/PIC16Section.h
@@ -57,6 +57,7 @@
 
     /// Return the Color of the section.
     int getColor() const { return Color; }
+    void setColor(int color) { Color = color; }
 
     /// Return the size of the section.
     unsigned getSize() const { return Size; }
diff --git a/lib/Target/PIC16/PIC16TargetObjectFile.cpp b/lib/Target/PIC16/PIC16TargetObjectFile.cpp
index 11c579c..7eedf7f 100644
--- a/lib/Target/PIC16/PIC16TargetObjectFile.cpp
+++ b/lib/Target/PIC16/PIC16TargetObjectFile.cpp
@@ -25,6 +25,18 @@
 PIC16TargetObjectFile::~PIC16TargetObjectFile() {
 }
 
+/// Find a pic16 section. Return null if not found. Do not create one.
+PIC16Section *PIC16TargetObjectFile::
+findPIC16Section(const std::string &Name) {
+  /// Return if we have an already existing one.
+  PIC16Section *Entry = SectionsByName[Name];
+  if (Entry)
+    return Entry;
+
+  return NULL;
+}
+
+
 /// Find a pic16 section. If not found, create one.
 PIC16Section *PIC16TargetObjectFile::
 getPIC16Section(const std::string &Name, PIC16SectionType Ty, 
diff --git a/lib/Target/PIC16/PIC16TargetObjectFile.h b/lib/Target/PIC16/PIC16TargetObjectFile.h
index 6ec5512..ca07bed 100644
--- a/lib/Target/PIC16/PIC16TargetObjectFile.h
+++ b/lib/Target/PIC16/PIC16TargetObjectFile.h
@@ -116,6 +116,9 @@
     ~PIC16TargetObjectFile();
     void Initialize(MCContext &Ctx, const TargetMachine &TM);
 
+    /// Return the section with the given Name. Null if not found.
+    PIC16Section *findPIC16Section(const std::string &Name);
+
     /// Override section allocations for user specified sections.
     virtual const MCSection *
     getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind, 
@@ -127,6 +130,7 @@
                                                     Mangler *Mang,
                                                     const TargetMachine&) const;
 
+
     /// Return a code section for a function.
     const PIC16Section *SectionForCode (const std::string &FnName) const;