lib/Transforms/Instrumentation/TraceValues.cpp - llvm - Git at Google

 //===- TraceValues.cpp - Value Tracing for debugging ----------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file was developed by the LLVM research group and is distributed under
 // the University of Illinois Open Source License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // Support for inserting LLVM code to print values at basic block and function
 // exits.
 //
 //===----------------------------------------------------------------------===//

 #include "llvm/Transforms/Instrumentation.h"
 #include "llvm/Constants.h"
 #include "llvm/DerivedTypes.h"
 #include "llvm/Instructions.h"
 #include "llvm/Module.h"
 #include "llvm/Pass.h"
 #include "llvm/Assembly/Writer.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/ADT/StringExtras.h"
 #include <algorithm>
 #include <sstream>
 using namespace llvm;

 static cl::opt<bool>
 DisablePtrHashing("tracedisablehashdisable", cl::Hidden,
                   cl::desc("Disable pointer hashing in the -trace or -tracem "
                            "passes"));

 static cl::list<std::string>
 TraceFuncNames("tracefunc", cl::desc("Only trace specific functions in the "
                                      "-trace or -tracem passes"),
                cl::value_desc("function"), cl::Hidden);

 static void TraceValuesAtBBExit(BasicBlock *BB,
                                 Function *Printf, Function* HashPtrToSeqNum,
                              std::vector<Instruction*> *valuesStoredInFunction);

 // We trace a particular function if no functions to trace were specified
 // or if the function is in the specified list.
 //
 inline static bool
 TraceThisFunction(Function &F)
 {
   if (TraceFuncNames.empty()) return true;

   return std::find(TraceFuncNames.begin(), TraceFuncNames.end(), F.getName())
                   != TraceFuncNames.end();
 }


 namespace {
   struct ExternalFuncs {
     Function *PrintfFunc, *HashPtrFunc, *ReleasePtrFunc;
     Function *RecordPtrFunc, *PushOnEntryFunc, *ReleaseOnReturnFunc;
     void doInitialization(Module &M); // Add prototypes for external functions
   };

   class InsertTraceCode : public FunctionPass {
   protected:
     ExternalFuncs externalFuncs;
   public:

     // Add a prototype for runtime functions not already in the program.
     //
     bool doInitialization(Module &M);

     //--------------------------------------------------------------------------
     // Function InsertCodeToTraceValues
     //
     // Inserts tracing code for all live values at basic block and/or function
     // exits as specified by `traceBasicBlockExits' and `traceFunctionExits'.
     //
     bool doit(Function *M);

     virtual void handleBasicBlock(BasicBlock *BB,
                                   std::vector<Instruction*> &VI) = 0;

     // runOnFunction - This method does the work.
     //
     bool runOnFunction(Function &F);

     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
       AU.setPreservesCFG();
     }
   };

   struct FunctionTracer : public InsertTraceCode {
     // Ignore basic blocks here...
     virtual void handleBasicBlock(BasicBlock *BB,
                                   std::vector<Instruction*> &VI) {}
   };

   struct BasicBlockTracer : public InsertTraceCode {
     // Trace basic blocks here...
     virtual void handleBasicBlock(BasicBlock *BB,
                                   std::vector<Instruction*> &VI) {
       TraceValuesAtBBExit(BB, externalFuncs.PrintfFunc,
                           externalFuncs.HashPtrFunc, &VI);
     }
   };

   // Register the passes...
   RegisterOpt<FunctionTracer>  X("tracem","Insert Function trace code only");
   RegisterOpt<BasicBlockTracer> Y("trace","Insert BB and Function trace code");
 } // end anonymous namespace

 /// Just trace functions
 FunctionPass *llvm::createTraceValuesPassForFunction() {
   return new FunctionTracer();
 }

 /// Trace BB's and functions
 FunctionPass *llvm::createTraceValuesPassForBasicBlocks() {
   return new BasicBlockTracer();
 }

 // Add a prototype for external functions used by the tracing code and require
 // the trace library for this module.
 //
 void ExternalFuncs::doInitialization(Module &M) {
   M.addLibrary("trace");
   const Type *SBP = PointerType::get(Type::SByteTy);
   const FunctionType *MTy =
     FunctionType::get(Type::IntTy, std::vector<const Type*>(1, SBP), true);
   PrintfFunc = M.getOrInsertFunction("printf", MTy);

   // uint (sbyte*)
   HashPtrFunc = M.getOrInsertFunction("HashPointerToSeqNum", Type::UIntTy, SBP,
                                       (Type *)0);

   // void (sbyte*)
   ReleasePtrFunc = M.getOrInsertFunction("ReleasePointerSeqNum",
                                          Type::VoidTy, SBP, (Type *)0);
   RecordPtrFunc  = M.getOrInsertFunction("RecordPointer",
                                          Type::VoidTy, SBP, (Type *)0);

   PushOnEntryFunc = M.getOrInsertFunction("PushPointerSet", Type::VoidTy,
                                           (Type *)0);
   ReleaseOnReturnFunc = M.getOrInsertFunction("ReleasePointersPopSet",
                                               Type::VoidTy, (Type *)0);
 }


 // Add a prototype for external functions used by the tracing code.
 //
 bool InsertTraceCode::doInitialization(Module &M) {
   externalFuncs.doInitialization(M);
   return false;
 }


 static inline GlobalVariable *getStringRef(Module *M, const std::string &str) {
   // Create a constant internal string reference...
   Constant *Init = ConstantArray::get(str);

   // Create the global variable and record it in the module
   // The GV will be renamed to a unique name if needed.
   GlobalVariable *GV = new GlobalVariable(Init->getType(), true,
                                           GlobalValue::InternalLinkage, Init,
                                           "trstr");
   M->getGlobalList().push_back(GV);
   return GV;
 }


 //
 // Check if this instruction has any uses outside its basic block,
 // or if it used by either a Call or Return instruction (ditto).
 // (Values stored to memory within this BB are live at end of BB but are
 // traced at the store instruction, not where they are computed.)
 //
 static inline bool LiveAtBBExit(const Instruction* I) {
   const BasicBlock *BB = I->getParent();
   for (Value::use_const_iterator U = I->use_begin(); U != I->use_end(); ++U)
     if (const Instruction *UI = dyn_cast<Instruction>(*U))
       if (UI->getParent() != BB || isa<ReturnInst>(UI))
         return true;

   return false;
 }


 static inline bool TraceThisOpCode(unsigned opCode) {
   // Explicitly test for opCodes *not* to trace so that any new opcodes will
   // be traced by default (VoidTy's are already excluded)
   //
   return (opCode  < Instruction::OtherOpsBegin &&
           opCode != Instruction::Alloca &&
           opCode != Instruction::PHI &&
           opCode != Instruction::Cast);
 }


 // Trace a value computed by an instruction if it is non-void, it is computed
 // by a real computation, not just a copy (see TraceThisOpCode), and
 // -- it is a load instruction: we want to check values read from memory
 // -- or it is live at exit from the basic block (i.e., ignore local temps)
 //
 static bool ShouldTraceValue(const Instruction *I) {
   return
     I->getType() != Type::VoidTy &&
     TraceThisOpCode(I->getOpcode()) &&
     (isa<LoadInst>(I) || LiveAtBBExit(I));
 }

 static std::string getPrintfCodeFor(const Value *V) {
   if (V == 0) return "";
   if (V->getType()->isFloatingPoint())
     return "%g";
   else if (V->getType() == Type::LabelTy)
     return "0x%p";
   else if (isa<PointerType>(V->getType()))
     return DisablePtrHashing ? "0x%p" : "%d";
   else if (V->getType()->isIntegral())
     return "%d";

   assert(0 && "Illegal value to print out...");
   return "";
 }


 static void InsertPrintInst(Value *V, BasicBlock *BB, Instruction *InsertBefore,
                             std::string Message,
                             Function *Printf, Function* HashPtrToSeqNum) {
   // Escape Message by replacing all % characters with %% chars.
   std::string Tmp;
   std::swap(Tmp, Message);
   std::string::iterator I = std::find(Tmp.begin(), Tmp.end(), '%');
   while (I != Tmp.end()) {
     Message.append(Tmp.begin(), I);
     Message += "%%";
     ++I; // Make sure to erase the % as well...
     Tmp.erase(Tmp.begin(), I);
     I = std::find(Tmp.begin(), Tmp.end(), '%');
   }
   Message += Tmp;
   Module *Mod = BB->getParent()->getParent();

   // Turn the marker string into a global variable...
   GlobalVariable *fmtVal = getStringRef(Mod, Message+getPrintfCodeFor(V)+"\n");

   // Turn the format string into an sbyte *
   Constant *GEP=ConstantExpr::getGetElementPtr(fmtVal,
                 std::vector<Constant*>(2,Constant::getNullValue(Type::LongTy)));

   // Insert a call to the hash function if this is a pointer value
   if (V && isa<PointerType>(V->getType()) && !DisablePtrHashing) {
     const Type *SBP = PointerType::get(Type::SByteTy);
     if (V->getType() != SBP)     // Cast pointer to be sbyte*
       V = new CastInst(V, SBP, "Hash_cast", InsertBefore);

     std::vector<Value*> HashArgs(1, V);
     V = new CallInst(HashPtrToSeqNum, HashArgs, "ptrSeqNum", InsertBefore);
   }

   // Insert the first print instruction to print the string flag:
   std::vector<Value*> PrintArgs;
   PrintArgs.push_back(GEP);
   if (V) PrintArgs.push_back(V);
   new CallInst(Printf, PrintArgs, "trace", InsertBefore);
 }


 static void InsertVerbosePrintInst(Value *V, BasicBlock *BB,
                                    Instruction *InsertBefore,
                                    const std::string &Message, Function *Printf,
                                    Function* HashPtrToSeqNum) {
   std::ostringstream OutStr;
   if (V) WriteAsOperand(OutStr, V);
   InsertPrintInst(V, BB, InsertBefore, Message+OutStr.str()+" = ",
                   Printf, HashPtrToSeqNum);
 }

 static void
 InsertReleaseInst(Value *V, BasicBlock *BB,
                   Instruction *InsertBefore,
                   Function* ReleasePtrFunc) {

   const Type *SBP = PointerType::get(Type::SByteTy);
   if (V->getType() != SBP)    // Cast pointer to be sbyte*
     V = new CastInst(V, SBP, "RPSN_cast", InsertBefore);

   std::vector<Value*> releaseArgs(1, V);
   new CallInst(ReleasePtrFunc, releaseArgs, "", InsertBefore);
 }

 static void
 InsertRecordInst(Value *V, BasicBlock *BB,
                  Instruction *InsertBefore,
                  Function* RecordPtrFunc) {
     const Type *SBP = PointerType::get(Type::SByteTy);
   if (V->getType() != SBP)     // Cast pointer to be sbyte*
     V = new CastInst(V, SBP, "RP_cast", InsertBefore);

   std::vector<Value*> releaseArgs(1, V);
   new CallInst(RecordPtrFunc, releaseArgs, "", InsertBefore);
 }

 // Look for alloca and free instructions. These are the ptrs to release.
 // Release the free'd pointers immediately.  Record the alloca'd pointers
 // to be released on return from the current function.
 //
 static void
 ReleasePtrSeqNumbers(BasicBlock *BB,
                      ExternalFuncs& externalFuncs) {

   for (BasicBlock::iterator II=BB->begin(), IE = BB->end(); II != IE; ++II)
     if (FreeInst *FI = dyn_cast<FreeInst>(II))
       InsertReleaseInst(FI->getOperand(0), BB, FI,externalFuncs.ReleasePtrFunc);
     else if (AllocaInst *AI = dyn_cast<AllocaInst>(II))
       InsertRecordInst(AI, BB, AI->getNext(), externalFuncs.RecordPtrFunc);
 }


 // Insert print instructions at the end of basic block BB for each value
 // computed in BB that is live at the end of BB,
 // or that is stored to memory in BB.
 // If the value is stored to memory, we load it back before printing it
 // We also return all such loaded values in the vector valuesStoredInFunction
 // for printing at the exit from the function.  (Note that in each invocation
 // of the function, this will only get the last value stored for each static
 // store instruction).
 //
 static void TraceValuesAtBBExit(BasicBlock *BB,
                                 Function *Printf, Function* HashPtrToSeqNum,
                             std::vector<Instruction*> *valuesStoredInFunction) {
   // Get an iterator to point to the insertion location, which is
   // just before the terminator instruction.
   //
   TerminatorInst *InsertPos = BB->getTerminator();

   std::ostringstream OutStr;
   WriteAsOperand(OutStr, BB, false);
   InsertPrintInst(0, BB, InsertPos, "LEAVING BB:" + OutStr.str(),
                   Printf, HashPtrToSeqNum);

   // Insert a print instruction for each instruction preceding InsertPos.
   // The print instructions must go before InsertPos, so we use the
   // instruction *preceding* InsertPos to check when to terminate the loop.
   //
   for (BasicBlock::iterator II = BB->begin(); &*II != InsertPos; ++II) {
     if (StoreInst *SI = dyn_cast<StoreInst>(II)) {
       // Trace the stored value and address
       InsertVerbosePrintInst(SI->getOperand(0), BB, InsertPos,
                              "  (store value) ", Printf, HashPtrToSeqNum);
       InsertVerbosePrintInst(SI->getOperand(1), BB, InsertPos,
                              "  (store addr ) ", Printf, HashPtrToSeqNum);
     }
     else if (ShouldTraceValue(II))
       InsertVerbosePrintInst(II, BB, InsertPos, "  ", Printf, HashPtrToSeqNum);
   }
 }

 static inline void InsertCodeToShowFunctionEntry(Function &F, Function *Printf,
                                                  Function* HashPtrToSeqNum){
   // Get an iterator to point to the insertion location
   BasicBlock &BB = F.getEntryBlock();
   Instruction *InsertPos = BB.begin();

   std::ostringstream OutStr;
   WriteAsOperand(OutStr, &F);
   InsertPrintInst(0, &BB, InsertPos, "ENTERING FUNCTION: " + OutStr.str(),
                   Printf, HashPtrToSeqNum);

   // Now print all the incoming arguments
   unsigned ArgNo = 0;
   for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I, ++ArgNo){
     InsertVerbosePrintInst(I, &BB, InsertPos,
                            "  Arg #" + utostr(ArgNo) + ": ", Printf,
                            HashPtrToSeqNum);
   }
 }


 static inline void InsertCodeToShowFunctionExit(BasicBlock *BB,
                                                 Function *Printf,
                                                 Function* HashPtrToSeqNum) {
   // Get an iterator to point to the insertion location
   ReturnInst *Ret = cast<ReturnInst>(BB->getTerminator());

   std::ostringstream OutStr;
   WriteAsOperand(OutStr, BB->getParent(), true);
   InsertPrintInst(0, BB, Ret, "LEAVING  FUNCTION: " + OutStr.str(),
                   Printf, HashPtrToSeqNum);

   // print the return value, if any
   if (BB->getParent()->getReturnType() != Type::VoidTy)
     InsertPrintInst(Ret->getReturnValue(), BB, Ret, "  Returning: ",
                     Printf, HashPtrToSeqNum);
 }


 bool InsertTraceCode::runOnFunction(Function &F) {
   if (!TraceThisFunction(F))
     return false;

   std::vector<Instruction*> valuesStoredInFunction;
   std::vector<BasicBlock*>  exitBlocks;

   // Insert code to trace values at function entry
   InsertCodeToShowFunctionEntry(F, externalFuncs.PrintfFunc,
                                 externalFuncs.HashPtrFunc);

   // Push a pointer set for recording alloca'd pointers at entry.
   if (!DisablePtrHashing)
     new CallInst(externalFuncs.PushOnEntryFunc, std::vector<Value*>(), "",
                  F.getEntryBlock().begin());

   for (Function::iterator BB = F.begin(); BB != F.end(); ++BB) {
     if (isa<ReturnInst>(BB->getTerminator()))
       exitBlocks.push_back(BB); // record this as an exit block

     // Insert trace code if this basic block is interesting...
     handleBasicBlock(BB, valuesStoredInFunction);

     if (!DisablePtrHashing)          // release seq. numbers on free/ret
       ReleasePtrSeqNumbers(BB, externalFuncs);
   }

   for (unsigned i=0; i != exitBlocks.size(); ++i)
     {
       // Insert code to trace values at function exit
       InsertCodeToShowFunctionExit(exitBlocks[i], externalFuncs.PrintfFunc,
                                    externalFuncs.HashPtrFunc);

       // Release all recorded pointers before RETURN.  Do this LAST!
       if (!DisablePtrHashing)
         new CallInst(externalFuncs.ReleaseOnReturnFunc, std::vector<Value*>(),
                      "", exitBlocks[i]->getTerminator());
     }

   return true;
 }
	//===- TraceValues.cpp - Value Tracing for debugging ----------------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file was developed by the LLVM research group and is distributed under
	// the University of Illinois Open Source License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// Support for inserting LLVM code to print values at basic block and function
	// exits.
	//
	//===----------------------------------------------------------------------===//

	#include "llvm/Transforms/Instrumentation.h"
	#include "llvm/Constants.h"
	#include "llvm/DerivedTypes.h"
	#include "llvm/Instructions.h"
	#include "llvm/Module.h"
	#include "llvm/Pass.h"
	#include "llvm/Assembly/Writer.h"
	#include "llvm/Support/CommandLine.h"
	#include "llvm/ADT/StringExtras.h"
	#include <algorithm>
	#include <sstream>
	using namespace llvm;

	static cl::opt<bool>
	DisablePtrHashing("tracedisablehashdisable", cl::Hidden,
	cl::desc("Disable pointer hashing in the -trace or -tracem "
	"passes"));

	static cl::list<std::string>
	TraceFuncNames("tracefunc", cl::desc("Only trace specific functions in the "
	"-trace or -tracem passes"),
	cl::value_desc("function"), cl::Hidden);

	static void TraceValuesAtBBExit(BasicBlock *BB,
	Function Printf, Function HashPtrToSeqNum,
	std::vector<Instruction> valuesStoredInFunction);

	// We trace a particular function if no functions to trace were specified
	// or if the function is in the specified list.
	//
	inline static bool
	TraceThisFunction(Function &F)
	{
	if (TraceFuncNames.empty()) return true;

	return std::find(TraceFuncNames.begin(), TraceFuncNames.end(), F.getName())
	!= TraceFuncNames.end();
	}


	namespace {
	struct ExternalFuncs {
	Function PrintfFunc, HashPtrFunc, *ReleasePtrFunc;
	Function RecordPtrFunc, PushOnEntryFunc, *ReleaseOnReturnFunc;
	void doInitialization(Module &M); // Add prototypes for external functions
	};

	class InsertTraceCode : public FunctionPass {
	protected:
	ExternalFuncs externalFuncs;
	public:

	// Add a prototype for runtime functions not already in the program.
	//
	bool doInitialization(Module &M);

	//--------------------------------------------------------------------------
	// Function InsertCodeToTraceValues
	//
	// Inserts tracing code for all live values at basic block and/or function
	// exits as specified by `traceBasicBlockExits' and `traceFunctionExits'.
	//
	bool doit(Function *M);

	virtual void handleBasicBlock(BasicBlock *BB,
	std::vector<Instruction*> &VI) = 0;

	// runOnFunction - This method does the work.
	//
	bool runOnFunction(Function &F);

	virtual void getAnalysisUsage(AnalysisUsage &AU) const {
	AU.setPreservesCFG();
	}
	};

	struct FunctionTracer : public InsertTraceCode {
	// Ignore basic blocks here...
	virtual void handleBasicBlock(BasicBlock *BB,
	std::vector<Instruction*> &VI) {}
	};

	struct BasicBlockTracer : public InsertTraceCode {
	// Trace basic blocks here...
	virtual void handleBasicBlock(BasicBlock *BB,
	std::vector<Instruction*> &VI) {
	TraceValuesAtBBExit(BB, externalFuncs.PrintfFunc,
	externalFuncs.HashPtrFunc, &VI);
	}
	};

	// Register the passes...
	RegisterOpt<FunctionTracer> X("tracem","Insert Function trace code only");
	RegisterOpt<BasicBlockTracer> Y("trace","Insert BB and Function trace code");
	} // end anonymous namespace

	/// Just trace functions
	FunctionPass *llvm::createTraceValuesPassForFunction() {
	return new FunctionTracer();
	}

	/// Trace BB's and functions
	FunctionPass *llvm::createTraceValuesPassForBasicBlocks() {
	return new BasicBlockTracer();
	}

	// Add a prototype for external functions used by the tracing code and require
	// the trace library for this module.
	//
	void ExternalFuncs::doInitialization(Module &M) {
	M.addLibrary("trace");
	const Type *SBP = PointerType::get(Type::SByteTy);
	const FunctionType *MTy =
	FunctionType::get(Type::IntTy, std::vector<const Type*>(1, SBP), true);
	PrintfFunc = M.getOrInsertFunction("printf", MTy);

	// uint (sbyte*)
	HashPtrFunc = M.getOrInsertFunction("HashPointerToSeqNum", Type::UIntTy, SBP,
	(Type *)0);

	// void (sbyte*)
	ReleasePtrFunc = M.getOrInsertFunction("ReleasePointerSeqNum",
	Type::VoidTy, SBP, (Type *)0);
	RecordPtrFunc = M.getOrInsertFunction("RecordPointer",
	Type::VoidTy, SBP, (Type *)0);

	PushOnEntryFunc = M.getOrInsertFunction("PushPointerSet", Type::VoidTy,
	(Type *)0);
	ReleaseOnReturnFunc = M.getOrInsertFunction("ReleasePointersPopSet",
	Type::VoidTy, (Type *)0);
	}


	// Add a prototype for external functions used by the tracing code.
	//
	bool InsertTraceCode::doInitialization(Module &M) {
	externalFuncs.doInitialization(M);
	return false;
	}


	static inline GlobalVariable getStringRef(Module M, const std::string &str) {
	// Create a constant internal string reference...
	Constant *Init = ConstantArray::get(str);

	// Create the global variable and record it in the module
	// The GV will be renamed to a unique name if needed.
	GlobalVariable *GV = new GlobalVariable(Init->getType(), true,
	GlobalValue::InternalLinkage, Init,
	"trstr");
	M->getGlobalList().push_back(GV);
	return GV;
	}


	//
	// Check if this instruction has any uses outside its basic block,
	// or if it used by either a Call or Return instruction (ditto).
	// (Values stored to memory within this BB are live at end of BB but are
	// traced at the store instruction, not where they are computed.)
	//
	static inline bool LiveAtBBExit(const Instruction* I) {
	const BasicBlock *BB = I->getParent();
	for (Value::use_const_iterator U = I->use_begin(); U != I->use_end(); ++U)
	if (const Instruction UI = dyn_cast<Instruction>(U))
	if (UI->getParent() != BB \|\| isa<ReturnInst>(UI))
	return true;

	return false;
	}


	static inline bool TraceThisOpCode(unsigned opCode) {
	// Explicitly test for opCodes not to trace so that any new opcodes will
	// be traced by default (VoidTy's are already excluded)
	//
	return (opCode < Instruction::OtherOpsBegin &&
	opCode != Instruction::Alloca &&
	opCode != Instruction::PHI &&
	opCode != Instruction::Cast);
	}


	// Trace a value computed by an instruction if it is non-void, it is computed
	// by a real computation, not just a copy (see TraceThisOpCode), and
	// -- it is a load instruction: we want to check values read from memory
	// -- or it is live at exit from the basic block (i.e., ignore local temps)
	//
	static bool ShouldTraceValue(const Instruction *I) {
	return
	I->getType() != Type::VoidTy &&
	TraceThisOpCode(I->getOpcode()) &&
	(isa<LoadInst>(I) \|\| LiveAtBBExit(I));
	}

	static std::string getPrintfCodeFor(const Value *V) {
	if (V == 0) return "";
	if (V->getType()->isFloatingPoint())
	return "%g";
	else if (V->getType() == Type::LabelTy)
	return "0x%p";
	else if (isa<PointerType>(V->getType()))
	return DisablePtrHashing ? "0x%p" : "%d";
	else if (V->getType()->isIntegral())
	return "%d";

	assert(0 && "Illegal value to print out...");
	return "";
	}


	static void InsertPrintInst(Value V, BasicBlock BB, Instruction *InsertBefore,
	std::string Message,
	Function Printf, Function HashPtrToSeqNum) {
	// Escape Message by replacing all % characters with %% chars.
	std::string Tmp;
	std::swap(Tmp, Message);
	std::string::iterator I = std::find(Tmp.begin(), Tmp.end(), '%');
	while (I != Tmp.end()) {
	Message.append(Tmp.begin(), I);
	Message += "%%";
	++I; // Make sure to erase the % as well...
	Tmp.erase(Tmp.begin(), I);
	I = std::find(Tmp.begin(), Tmp.end(), '%');
	}
	Message += Tmp;
	Module *Mod = BB->getParent()->getParent();

	// Turn the marker string into a global variable...
	GlobalVariable *fmtVal = getStringRef(Mod, Message+getPrintfCodeFor(V)+"\n");

	// Turn the format string into an sbyte *
	Constant *GEP=ConstantExpr::getGetElementPtr(fmtVal,
	std::vector<Constant*>(2,Constant::getNullValue(Type::LongTy)));

	// Insert a call to the hash function if this is a pointer value
	if (V && isa<PointerType>(V->getType()) && !DisablePtrHashing) {
	const Type *SBP = PointerType::get(Type::SByteTy);
	if (V->getType() != SBP) // Cast pointer to be sbyte*
	V = new CastInst(V, SBP, "Hash_cast", InsertBefore);

	std::vector<Value*> HashArgs(1, V);
	V = new CallInst(HashPtrToSeqNum, HashArgs, "ptrSeqNum", InsertBefore);
	}

	// Insert the first print instruction to print the string flag:
	std::vector<Value*> PrintArgs;
	PrintArgs.push_back(GEP);
	if (V) PrintArgs.push_back(V);
	new CallInst(Printf, PrintArgs, "trace", InsertBefore);
	}


	static void InsertVerbosePrintInst(Value V, BasicBlock BB,
	Instruction *InsertBefore,
	const std::string &Message, Function *Printf,
	Function* HashPtrToSeqNum) {
	std::ostringstream OutStr;
	if (V) WriteAsOperand(OutStr, V);
	InsertPrintInst(V, BB, InsertBefore, Message+OutStr.str()+" = ",
	Printf, HashPtrToSeqNum);
	}

	static void
	InsertReleaseInst(Value V, BasicBlock BB,
	Instruction *InsertBefore,
	Function* ReleasePtrFunc) {

	const Type *SBP = PointerType::get(Type::SByteTy);
	if (V->getType() != SBP) // Cast pointer to be sbyte*
	V = new CastInst(V, SBP, "RPSN_cast", InsertBefore);

	std::vector<Value*> releaseArgs(1, V);
	new CallInst(ReleasePtrFunc, releaseArgs, "", InsertBefore);
	}

	static void
	InsertRecordInst(Value V, BasicBlock BB,
	Instruction *InsertBefore,
	Function* RecordPtrFunc) {
	const Type *SBP = PointerType::get(Type::SByteTy);
	if (V->getType() != SBP) // Cast pointer to be sbyte*
	V = new CastInst(V, SBP, "RP_cast", InsertBefore);

	std::vector<Value*> releaseArgs(1, V);
	new CallInst(RecordPtrFunc, releaseArgs, "", InsertBefore);
	}

	// Look for alloca and free instructions. These are the ptrs to release.
	// Release the free'd pointers immediately. Record the alloca'd pointers
	// to be released on return from the current function.
	//
	static void
	ReleasePtrSeqNumbers(BasicBlock *BB,
	ExternalFuncs& externalFuncs) {

	for (BasicBlock::iterator II=BB->begin(), IE = BB->end(); II != IE; ++II)
	if (FreeInst *FI = dyn_cast<FreeInst>(II))
	InsertReleaseInst(FI->getOperand(0), BB, FI,externalFuncs.ReleasePtrFunc);
	else if (AllocaInst *AI = dyn_cast<AllocaInst>(II))
	InsertRecordInst(AI, BB, AI->getNext(), externalFuncs.RecordPtrFunc);
	}


	// Insert print instructions at the end of basic block BB for each value
	// computed in BB that is live at the end of BB,
	// or that is stored to memory in BB.
	// If the value is stored to memory, we load it back before printing it
	// We also return all such loaded values in the vector valuesStoredInFunction
	// for printing at the exit from the function. (Note that in each invocation
	// of the function, this will only get the last value stored for each static
	// store instruction).
	//
	static void TraceValuesAtBBExit(BasicBlock *BB,
	Function Printf, Function HashPtrToSeqNum,
	std::vector<Instruction> valuesStoredInFunction) {
	// Get an iterator to point to the insertion location, which is
	// just before the terminator instruction.
	//
	TerminatorInst *InsertPos = BB->getTerminator();

	std::ostringstream OutStr;
	WriteAsOperand(OutStr, BB, false);
	InsertPrintInst(0, BB, InsertPos, "LEAVING BB:" + OutStr.str(),
	Printf, HashPtrToSeqNum);

	// Insert a print instruction for each instruction preceding InsertPos.
	// The print instructions must go before InsertPos, so we use the
	// instruction preceding InsertPos to check when to terminate the loop.
	//
	for (BasicBlock::iterator II = BB->begin(); &*II != InsertPos; ++II) {
	if (StoreInst *SI = dyn_cast<StoreInst>(II)) {
	// Trace the stored value and address
	InsertVerbosePrintInst(SI->getOperand(0), BB, InsertPos,
	" (store value) ", Printf, HashPtrToSeqNum);
	InsertVerbosePrintInst(SI->getOperand(1), BB, InsertPos,
	" (store addr ) ", Printf, HashPtrToSeqNum);
	}
	else if (ShouldTraceValue(II))
	InsertVerbosePrintInst(II, BB, InsertPos, " ", Printf, HashPtrToSeqNum);
	}
	}

	static inline void InsertCodeToShowFunctionEntry(Function &F, Function *Printf,
	Function* HashPtrToSeqNum){
	// Get an iterator to point to the insertion location
	BasicBlock &BB = F.getEntryBlock();
	Instruction *InsertPos = BB.begin();

	std::ostringstream OutStr;
	WriteAsOperand(OutStr, &F);
	InsertPrintInst(0, &BB, InsertPos, "ENTERING FUNCTION: " + OutStr.str(),
	Printf, HashPtrToSeqNum);

	// Now print all the incoming arguments
	unsigned ArgNo = 0;
	for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I, ++ArgNo){
	InsertVerbosePrintInst(I, &BB, InsertPos,
	" Arg #" + utostr(ArgNo) + ": ", Printf,
	HashPtrToSeqNum);
	}
	}


	static inline void InsertCodeToShowFunctionExit(BasicBlock *BB,
	Function *Printf,
	Function* HashPtrToSeqNum) {
	// Get an iterator to point to the insertion location
	ReturnInst *Ret = cast<ReturnInst>(BB->getTerminator());

	std::ostringstream OutStr;
	WriteAsOperand(OutStr, BB->getParent(), true);
	InsertPrintInst(0, BB, Ret, "LEAVING FUNCTION: " + OutStr.str(),
	Printf, HashPtrToSeqNum);

	// print the return value, if any
	if (BB->getParent()->getReturnType() != Type::VoidTy)
	InsertPrintInst(Ret->getReturnValue(), BB, Ret, " Returning: ",
	Printf, HashPtrToSeqNum);
	}


	bool InsertTraceCode::runOnFunction(Function &F) {
	if (!TraceThisFunction(F))
	return false;

	std::vector<Instruction*> valuesStoredInFunction;
	std::vector<BasicBlock*> exitBlocks;

	// Insert code to trace values at function entry
	InsertCodeToShowFunctionEntry(F, externalFuncs.PrintfFunc,
	externalFuncs.HashPtrFunc);

	// Push a pointer set for recording alloca'd pointers at entry.
	if (!DisablePtrHashing)
	new CallInst(externalFuncs.PushOnEntryFunc, std::vector<Value*>(), "",
	F.getEntryBlock().begin());

	for (Function::iterator BB = F.begin(); BB != F.end(); ++BB) {
	if (isa<ReturnInst>(BB->getTerminator()))
	exitBlocks.push_back(BB); // record this as an exit block

	// Insert trace code if this basic block is interesting...
	handleBasicBlock(BB, valuesStoredInFunction);

	if (!DisablePtrHashing) // release seq. numbers on free/ret
	ReleasePtrSeqNumbers(BB, externalFuncs);
	}

	for (unsigned i=0; i != exitBlocks.size(); ++i)
	{
	// Insert code to trace values at function exit
	InsertCodeToShowFunctionExit(exitBlocks[i], externalFuncs.PrintfFunc,
	externalFuncs.HashPtrFunc);

	// Release all recorded pointers before RETURN. Do this LAST!
	if (!DisablePtrHashing)
	new CallInst(externalFuncs.ReleaseOnReturnFunc, std::vector<Value*>(),
	"", exitBlocks[i]->getTerminator());
	}

	return true;
	}