tools/bugpoint/CrashDebugger.cpp - platform/external/llvm - Gitiles

 //===- CrashDebugger.cpp - Debug compilation crashes ----------------------===//
 //
 //                     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.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines the bugpoint internals that narrow down compilation crashes
 //
 //===----------------------------------------------------------------------===//

 #include "BugDriver.h"
 #include "ToolRunner.h"
 #include "ListReducer.h"
 #include "llvm/Constant.h"
 #include "llvm/DerivedTypes.h"
 #include "llvm/Instructions.h"
 #include "llvm/Module.h"
 #include "llvm/Pass.h"
 #include "llvm/PassManager.h"
 #include "llvm/SymbolTable.h"
 #include "llvm/Analysis/Verifier.h"
 #include "llvm/Bytecode/Writer.h"
 #include "llvm/Support/CFG.h"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils/Cloning.h"
 #include "llvm/Support/FileUtilities.h"
 #include "llvm/Support/CommandLine.h"
 #include <fstream>
 #include <set>
 using namespace llvm;

 namespace {
   cl::opt<bool>
   KeepMain("keep-main",
            cl::desc("Force function reduction to keep main"),
            cl::init(false));
 }

 namespace llvm {
   class ReducePassList : public ListReducer<const PassInfo*> {
     BugDriver &BD;
   public:
     ReducePassList(BugDriver &bd) : BD(bd) {}

     // doTest - Return true iff running the "removed" passes succeeds, and
     // running the "Kept" passes fail when run on the output of the "removed"
     // passes.  If we return true, we update the current module of bugpoint.
     //
     virtual TestResult doTest(std::vector<const PassInfo*> &Removed,
                               std::vector<const PassInfo*> &Kept);
   };
 }

 ReducePassList::TestResult
 ReducePassList::doTest(std::vector<const PassInfo*> &Prefix,
                        std::vector<const PassInfo*> &Suffix) {
   sys::Path PrefixOutput;
   Module *OrigProgram = 0;
   if (!Prefix.empty()) {
     std::cout << "Checking to see if these passes crash: "
               << getPassesString(Prefix) << ": ";
     std::string PfxOutput;
     if (BD.runPasses(Prefix, PfxOutput))
       return KeepPrefix;

     PrefixOutput.set(PfxOutput);
     OrigProgram = BD.Program;

     BD.Program = ParseInputFile(PrefixOutput.toString());
     if (BD.Program == 0) {
       std::cerr << BD.getToolName() << ": Error reading bytecode file '"
                 << PrefixOutput << "'!\n";
       exit(1);
     }
     PrefixOutput.eraseFromDisk();
   }

   std::cout << "Checking to see if these passes crash: "
             << getPassesString(Suffix) << ": ";

   if (BD.runPasses(Suffix)) {
     delete OrigProgram;            // The suffix crashes alone...
     return KeepSuffix;
   }

   // Nothing failed, restore state...
   if (OrigProgram) {
     delete BD.Program;
     BD.Program = OrigProgram;
   }
   return NoFailure;
 }

 namespace {
   /// ReduceCrashingGlobalVariables - This works by removing the global
   /// variable's initializer and seeing if the program still crashes. If it
   /// does, then we keep that program and try again.
   ///
   class ReduceCrashingGlobalVariables : public ListReducer<GlobalVariable*> {
     BugDriver &BD;
     bool (*TestFn)(BugDriver &, Module *);
   public:
     ReduceCrashingGlobalVariables(BugDriver &bd,
                                   bool (*testFn)(BugDriver&, Module*))
       : BD(bd), TestFn(testFn) {}

     virtual TestResult doTest(std::vector<GlobalVariable*>& Prefix,
                               std::vector<GlobalVariable*>& Kept) {
       if (!Kept.empty() && TestGlobalVariables(Kept))
         return KeepSuffix;

       if (!Prefix.empty() && TestGlobalVariables(Prefix))
         return KeepPrefix;

       return NoFailure;
     }

     bool TestGlobalVariables(std::vector<GlobalVariable*>& GVs);
   };
 }

 bool
 ReduceCrashingGlobalVariables::TestGlobalVariables(
                               std::vector<GlobalVariable*>& GVs) {
   // Clone the program to try hacking it apart...
   Module *M = CloneModule(BD.getProgram());

   // Convert list to set for fast lookup...
   std::set<GlobalVariable*> GVSet;

   for (unsigned i = 0, e = GVs.size(); i != e; ++i) {
     GlobalVariable* CMGV = M->getNamedGlobal(GVs[i]->getName());
     assert(CMGV && "Global Variable not in module?!");
     GVSet.insert(CMGV);
   }

   std::cout << "Checking for crash with only these global variables: ";
   PrintGlobalVariableList(GVs);
   std::cout << ": ";

   // Loop over and delete any global variables which we aren't supposed to be
   // playing with...
   for (Module::global_iterator I = M->global_begin(), E = M->global_end();
        I != E; ++I)
     if (I->hasInitializer()) {
       I->setInitializer(0);
       I->setLinkage(GlobalValue::ExternalLinkage);
     }

   // Try running the hacked up program...
   if (TestFn(BD, M)) {
     BD.setNewProgram(M);        // It crashed, keep the trimmed version...

     // Make sure to use global variable pointers that point into the now-current
     // module.
     GVs.assign(GVSet.begin(), GVSet.end());
     return true;
   }

   delete M;
   return false;
 }

 namespace llvm {
   /// ReduceCrashingFunctions reducer - This works by removing functions and
   /// seeing if the program still crashes. If it does, then keep the newer,
   /// smaller program.
   ///
   class ReduceCrashingFunctions : public ListReducer<Function*> {
     BugDriver &BD;
     bool (*TestFn)(BugDriver &, Module *);
   public:
     ReduceCrashingFunctions(BugDriver &bd,
                             bool (*testFn)(BugDriver &, Module *))
       : BD(bd), TestFn(testFn) {}

     virtual TestResult doTest(std::vector<Function*> &Prefix,
                               std::vector<Function*> &Kept) {
       if (!Kept.empty() && TestFuncs(Kept))
         return KeepSuffix;
       if (!Prefix.empty() && TestFuncs(Prefix))
         return KeepPrefix;
       return NoFailure;
     }

     bool TestFuncs(std::vector<Function*> &Prefix);
   };
 }

 bool ReduceCrashingFunctions::TestFuncs(std::vector<Function*> &Funcs) {

   //if main isn't present, claim there is no problem
   if (KeepMain && find(Funcs.begin(), Funcs.end(),
                        BD.getProgram()->getMainFunction()) == Funcs.end())
     return false;

   // Clone the program to try hacking it apart...
   Module *M = CloneModule(BD.getProgram());

   // Convert list to set for fast lookup...
   std::set<Function*> Functions;
   for (unsigned i = 0, e = Funcs.size(); i != e; ++i) {
     // FIXME: bugpoint should add names to all stripped symbols.
     assert(!Funcs[i]->getName().empty() &&
            "Bugpoint doesn't work on stripped modules yet PR718!");
     Function *CMF = M->getFunction(Funcs[i]->getName(),
                                    Funcs[i]->getFunctionType());
     assert(CMF && "Function not in module?!");
     Functions.insert(CMF);
   }

   std::cout << "Checking for crash with only these functions: ";
   PrintFunctionList(Funcs);
   std::cout << ": ";

   // Loop over and delete any functions which we aren't supposed to be playing
   // with...
   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
     if (!I->isExternal() && !Functions.count(I))
       DeleteFunctionBody(I);

   // Try running the hacked up program...
   if (TestFn(BD, M)) {
     BD.setNewProgram(M);        // It crashed, keep the trimmed version...

     // Make sure to use function pointers that point into the now-current
     // module.
     Funcs.assign(Functions.begin(), Functions.end());
     return true;
   }
   delete M;
   return false;
 }


 namespace {
   /// ReduceCrashingBlocks reducer - This works by setting the terminators of
   /// all terminators except the specified basic blocks to a 'ret' instruction,
   /// then running the simplify-cfg pass.  This has the effect of chopping up
   /// the CFG really fast which can reduce large functions quickly.
   ///
   class ReduceCrashingBlocks : public ListReducer<const BasicBlock*> {
     BugDriver &BD;
     bool (*TestFn)(BugDriver &, Module *);
   public:
     ReduceCrashingBlocks(BugDriver &bd, bool (*testFn)(BugDriver &, Module *))
       : BD(bd), TestFn(testFn) {}

     virtual TestResult doTest(std::vector<const BasicBlock*> &Prefix,
                               std::vector<const BasicBlock*> &Kept) {
       if (!Kept.empty() && TestBlocks(Kept))
         return KeepSuffix;
       if (!Prefix.empty() && TestBlocks(Prefix))
         return KeepPrefix;
       return NoFailure;
     }

     bool TestBlocks(std::vector<const BasicBlock*> &Prefix);
   };
 }

 bool ReduceCrashingBlocks::TestBlocks(std::vector<const BasicBlock*> &BBs) {
   // Clone the program to try hacking it apart...
   Module *M = CloneModule(BD.getProgram());

   // Convert list to set for fast lookup...
   std::set<BasicBlock*> Blocks;
   for (unsigned i = 0, e = BBs.size(); i != e; ++i) {
     // Convert the basic block from the original module to the new module...
     const Function *F = BBs[i]->getParent();
     Function *CMF = M->getFunction(F->getName(), F->getFunctionType());
     assert(CMF && "Function not in module?!");

     // Get the mapped basic block...
     Function::iterator CBI = CMF->begin();
     std::advance(CBI, std::distance(F->begin(),
                                     Function::const_iterator(BBs[i])));
     Blocks.insert(CBI);
   }

   std::cout << "Checking for crash with only these blocks:";
   unsigned NumPrint = Blocks.size();
   if (NumPrint > 10) NumPrint = 10;
   for (unsigned i = 0, e = NumPrint; i != e; ++i)
     std::cout << " " << BBs[i]->getName();
   if (NumPrint < Blocks.size())
     std::cout << "... <" << Blocks.size() << " total>";
   std::cout << ": ";

   // Loop over and delete any hack up any blocks that are not listed...
   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
     for (Function::iterator BB = I->begin(), E = I->end(); BB != E; ++BB)
       if (!Blocks.count(BB) && BB->getTerminator()->getNumSuccessors()) {
         // Loop over all of the successors of this block, deleting any PHI nodes
         // that might include it.
         for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
           (*SI)->removePredecessor(BB);

         if (BB->getTerminator()->getType() != Type::VoidTy)
           BB->getTerminator()->replaceAllUsesWith(
                       Constant::getNullValue(BB->getTerminator()->getType()));

         // Delete the old terminator instruction...
         BB->getInstList().pop_back();

         // Add a new return instruction of the appropriate type...
         const Type *RetTy = BB->getParent()->getReturnType();
         new ReturnInst(RetTy == Type::VoidTy ? 0 :
                        Constant::getNullValue(RetTy), BB);
       }

   // The CFG Simplifier pass may delete one of the basic blocks we are
   // interested in.  If it does we need to take the block out of the list.  Make
   // a "persistent mapping" by turning basic blocks into <function, name> pairs.
   // This won't work well if blocks are unnamed, but that is just the risk we
   // have to take.
   std::vector<std::pair<Function*, std::string> > BlockInfo;

   for (std::set<BasicBlock*>::iterator I = Blocks.begin(), E = Blocks.end();
        I != E; ++I)
     BlockInfo.push_back(std::make_pair((*I)->getParent(), (*I)->getName()));

   // Now run the CFG simplify pass on the function...
   PassManager Passes;
   Passes.add(createCFGSimplificationPass());
   Passes.add(createVerifierPass());
   Passes.run(*M);

   // Try running on the hacked up program...
   if (TestFn(BD, M)) {
     BD.setNewProgram(M);      // It crashed, keep the trimmed version...

     // Make sure to use basic block pointers that point into the now-current
     // module, and that they don't include any deleted blocks.
     BBs.clear();
     for (unsigned i = 0, e = BlockInfo.size(); i != e; ++i) {
       SymbolTable &ST = BlockInfo[i].first->getValueSymbolTable();
       SymbolTable::plane_iterator PI = ST.find(Type::LabelTy);
       if (PI != ST.plane_end() && PI->second.count(BlockInfo[i].second))
         BBs.push_back(cast<BasicBlock>(PI->second[BlockInfo[i].second]));
     }
     return true;
   }
   delete M;  // It didn't crash, try something else.
   return false;
 }

 /// DebugACrash - Given a predicate that determines whether a component crashes
 /// on a program, try to destructively reduce the program while still keeping
 /// the predicate true.
 static bool DebugACrash(BugDriver &BD,  bool (*TestFn)(BugDriver &, Module *)) {
   // See if we can get away with nuking some of the global variable initializers
   // in the program...
   if (BD.getProgram()->global_begin() != BD.getProgram()->global_end()) {
     // Now try to reduce the number of global variable initializers in the
     // module to something small.
     Module *M = CloneModule(BD.getProgram());
     bool DeletedInit = false;

     for (Module::global_iterator I = M->global_begin(), E = M->global_end();
          I != E; ++I)
       if (I->hasInitializer()) {
         I->setInitializer(0);
         I->setLinkage(GlobalValue::ExternalLinkage);
         DeletedInit = true;
       }

     if (!DeletedInit) {
       delete M;  // No change made...
     } else {
       // See if the program still causes a crash...
       std::cout << "\nChecking to see if we can delete global inits: ";

       if (TestFn(BD, M)) {      // Still crashes?
         BD.setNewProgram(M);
         std::cout << "\n*** Able to remove all global initializers!\n";
       } else {                  // No longer crashes?
         std::cout << "  - Removing all global inits hides problem!\n";
         delete M;

         std::vector<GlobalVariable*> GVs;

         for (Module::global_iterator I = BD.getProgram()->global_begin(),
                E = BD.getProgram()->global_end(); I != E; ++I)
           if (I->hasInitializer())
             GVs.push_back(I);

         if (GVs.size() > 1 && !BugpointIsInterrupted) {
           std::cout << "\n*** Attempting to reduce the number of global "
                     << "variables in the testcase\n";

           unsigned OldSize = GVs.size();
           ReduceCrashingGlobalVariables(BD, TestFn).reduceList(GVs);

           if (GVs.size() < OldSize)
             BD.EmitProgressBytecode("reduced-global-variables");
         }
       }
     }
   }

   // Now try to reduce the number of functions in the module to something small.
   std::vector<Function*> Functions;
   for (Module::iterator I = BD.getProgram()->begin(),
          E = BD.getProgram()->end(); I != E; ++I)
     if (!I->isExternal())
       Functions.push_back(I);

   if (Functions.size() > 1 && !BugpointIsInterrupted) {
     std::cout << "\n*** Attempting to reduce the number of functions "
       "in the testcase\n";

     unsigned OldSize = Functions.size();
     ReduceCrashingFunctions(BD, TestFn).reduceList(Functions);

     if (Functions.size() < OldSize)
       BD.EmitProgressBytecode("reduced-function");
   }

   // Attempt to delete entire basic blocks at a time to speed up
   // convergence... this actually works by setting the terminator of the blocks
   // to a return instruction then running simplifycfg, which can potentially
   // shrinks the code dramatically quickly
   //
   if (!DisableSimplifyCFG && !BugpointIsInterrupted) {
     std::vector<const BasicBlock*> Blocks;
     for (Module::const_iterator I = BD.getProgram()->begin(),
            E = BD.getProgram()->end(); I != E; ++I)
       for (Function::const_iterator FI = I->begin(), E = I->end(); FI !=E; ++FI)
         Blocks.push_back(FI);
     ReduceCrashingBlocks(BD, TestFn).reduceList(Blocks);
   }

   // FIXME: This should use the list reducer to converge faster by deleting
   // larger chunks of instructions at a time!
   unsigned Simplification = 2;
   do {
     if (BugpointIsInterrupted) break;
     --Simplification;
     std::cout << "\n*** Attempting to reduce testcase by deleting instruc"
               << "tions: Simplification Level #" << Simplification << '\n';

     // Now that we have deleted the functions that are unnecessary for the
     // program, try to remove instructions that are not necessary to cause the
     // crash.  To do this, we loop through all of the instructions in the
     // remaining functions, deleting them (replacing any values produced with
     // nulls), and then running ADCE and SimplifyCFG.  If the transformed input
     // still triggers failure, keep deleting until we cannot trigger failure
     // anymore.
     //
     unsigned InstructionsToSkipBeforeDeleting = 0;
   TryAgain:

     // Loop over all of the (non-terminator) instructions remaining in the
     // function, attempting to delete them.
     unsigned CurInstructionNum = 0;
     for (Module::const_iterator FI = BD.getProgram()->begin(),
            E = BD.getProgram()->end(); FI != E; ++FI)
       if (!FI->isExternal())
         for (Function::const_iterator BI = FI->begin(), E = FI->end(); BI != E;
              ++BI)
           for (BasicBlock::const_iterator I = BI->begin(), E = --BI->end();
                I != E; ++I, ++CurInstructionNum)
             if (InstructionsToSkipBeforeDeleting) {
               --InstructionsToSkipBeforeDeleting;
             } else {
               if (BugpointIsInterrupted) goto ExitLoops;

               std::cout << "Checking instruction '" << I->getName() << "': ";
               Module *M = BD.deleteInstructionFromProgram(I, Simplification);

               // Find out if the pass still crashes on this pass...
               if (TestFn(BD, M)) {
                 // Yup, it does, we delete the old module, and continue trying
                 // to reduce the testcase...
                 BD.setNewProgram(M);
                 InstructionsToSkipBeforeDeleting = CurInstructionNum;
                 goto TryAgain;  // I wish I had a multi-level break here!
               }

               // This pass didn't crash without this instruction, try the next
               // one.
               delete M;
             }

     if (InstructionsToSkipBeforeDeleting) {
       InstructionsToSkipBeforeDeleting = 0;
       goto TryAgain;
     }

   } while (Simplification);
 ExitLoops:

   // Try to clean up the testcase by running funcresolve and globaldce...
   if (!BugpointIsInterrupted) {
     std::cout << "\n*** Attempting to perform final cleanups: ";
     Module *M = CloneModule(BD.getProgram());
     M = BD.performFinalCleanups(M, true);

     // Find out if the pass still crashes on the cleaned up program...
     if (TestFn(BD, M)) {
       BD.setNewProgram(M);     // Yup, it does, keep the reduced version...
     } else {
       delete M;
     }
   }

   BD.EmitProgressBytecode("reduced-simplified");

   return false;
 }

 static bool TestForOptimizerCrash(BugDriver &BD, Module *M) {
   return BD.runPasses(M);
 }

 /// debugOptimizerCrash - This method is called when some pass crashes on input.
 /// It attempts to prune down the testcase to something reasonable, and figure
 /// out exactly which pass is crashing.
 ///
 bool BugDriver::debugOptimizerCrash(const std::string &ID) {
   std::cout << "\n*** Debugging optimizer crash!\n";

   // Reduce the list of passes which causes the optimizer to crash...
   if (!BugpointIsInterrupted)
     ReducePassList(*this).reduceList(PassesToRun);

   std::cout << "\n*** Found crashing pass"
             << (PassesToRun.size() == 1 ? ": " : "es: ")
             << getPassesString(PassesToRun) << '\n';

   EmitProgressBytecode(ID);

   return DebugACrash(*this, TestForOptimizerCrash);
 }

 static bool TestForCodeGenCrash(BugDriver &BD, Module *M) {
   try {
     std::cerr << '\n';
     BD.compileProgram(M);
     std::cerr << '\n';
     return false;
   } catch (ToolExecutionError &) {
     std::cerr << "<crash>\n";
     return true;  // Tool is still crashing.
   }
 }

 /// debugCodeGeneratorCrash - This method is called when the code generator
 /// crashes on an input.  It attempts to reduce the input as much as possible
 /// while still causing the code generator to crash.
 bool BugDriver::debugCodeGeneratorCrash() {
   std::cerr << "*** Debugging code generator crash!\n";

   return DebugACrash(*this, TestForCodeGenCrash);
 }
	//===- CrashDebugger.cpp - Debug compilation crashes ----------------------===//
	//
	// 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.
	//
	//===----------------------------------------------------------------------===//
	//
	// This file defines the bugpoint internals that narrow down compilation crashes
	//
	//===----------------------------------------------------------------------===//

	#include "BugDriver.h"
	#include "ToolRunner.h"
	#include "ListReducer.h"
	#include "llvm/Constant.h"
	#include "llvm/DerivedTypes.h"
	#include "llvm/Instructions.h"
	#include "llvm/Module.h"
	#include "llvm/Pass.h"
	#include "llvm/PassManager.h"
	#include "llvm/SymbolTable.h"
	#include "llvm/Analysis/Verifier.h"
	#include "llvm/Bytecode/Writer.h"
	#include "llvm/Support/CFG.h"
	#include "llvm/Transforms/Scalar.h"
	#include "llvm/Transforms/Utils/Cloning.h"
	#include "llvm/Support/FileUtilities.h"
	#include "llvm/Support/CommandLine.h"
	#include <fstream>
	#include <set>
	using namespace llvm;

	namespace {
	cl::opt<bool>
	KeepMain("keep-main",
	cl::desc("Force function reduction to keep main"),
	cl::init(false));
	}

	namespace llvm {
	class ReducePassList : public ListReducer<const PassInfo*> {
	BugDriver &BD;
	public:
	ReducePassList(BugDriver &bd) : BD(bd) {}

	// doTest - Return true iff running the "removed" passes succeeds, and
	// running the "Kept" passes fail when run on the output of the "removed"
	// passes. If we return true, we update the current module of bugpoint.
	//
	virtual TestResult doTest(std::vector<const PassInfo*> &Removed,
	std::vector<const PassInfo*> &Kept);
	};
	}

	ReducePassList::TestResult
	ReducePassList::doTest(std::vector<const PassInfo*> &Prefix,
	std::vector<const PassInfo*> &Suffix) {
	sys::Path PrefixOutput;
	Module *OrigProgram = 0;
	if (!Prefix.empty()) {
	std::cout << "Checking to see if these passes crash: "
	<< getPassesString(Prefix) << ": ";
	std::string PfxOutput;
	if (BD.runPasses(Prefix, PfxOutput))
	return KeepPrefix;

	PrefixOutput.set(PfxOutput);
	OrigProgram = BD.Program;

	BD.Program = ParseInputFile(PrefixOutput.toString());
	if (BD.Program == 0) {
	std::cerr << BD.getToolName() << ": Error reading bytecode file '"
	<< PrefixOutput << "'!\n";
	exit(1);
	}
	PrefixOutput.eraseFromDisk();
	}

	std::cout << "Checking to see if these passes crash: "
	<< getPassesString(Suffix) << ": ";

	if (BD.runPasses(Suffix)) {
	delete OrigProgram; // The suffix crashes alone...
	return KeepSuffix;
	}

	// Nothing failed, restore state...
	if (OrigProgram) {
	delete BD.Program;
	BD.Program = OrigProgram;
	}
	return NoFailure;
	}

	namespace {
	/// ReduceCrashingGlobalVariables - This works by removing the global
	/// variable's initializer and seeing if the program still crashes. If it
	/// does, then we keep that program and try again.
	///
	class ReduceCrashingGlobalVariables : public ListReducer<GlobalVariable*> {
	BugDriver &BD;
	bool (TestFn)(BugDriver &, Module );
	public:
	ReduceCrashingGlobalVariables(BugDriver &bd,
	bool (testFn)(BugDriver&, Module))
	: BD(bd), TestFn(testFn) {}

	virtual TestResult doTest(std::vector<GlobalVariable*>& Prefix,
	std::vector<GlobalVariable*>& Kept) {
	if (!Kept.empty() && TestGlobalVariables(Kept))
	return KeepSuffix;

	if (!Prefix.empty() && TestGlobalVariables(Prefix))
	return KeepPrefix;

	return NoFailure;
	}

	bool TestGlobalVariables(std::vector<GlobalVariable*>& GVs);
	};
	}

	bool
	ReduceCrashingGlobalVariables::TestGlobalVariables(
	std::vector<GlobalVariable*>& GVs) {
	// Clone the program to try hacking it apart...
	Module *M = CloneModule(BD.getProgram());

	// Convert list to set for fast lookup...
	std::set<GlobalVariable*> GVSet;

	for (unsigned i = 0, e = GVs.size(); i != e; ++i) {
	GlobalVariable* CMGV = M->getNamedGlobal(GVs[i]->getName());
	assert(CMGV && "Global Variable not in module?!");
	GVSet.insert(CMGV);
	}

	std::cout << "Checking for crash with only these global variables: ";
	PrintGlobalVariableList(GVs);
	std::cout << ": ";

	// Loop over and delete any global variables which we aren't supposed to be
	// playing with...
	for (Module::global_iterator I = M->global_begin(), E = M->global_end();
	I != E; ++I)
	if (I->hasInitializer()) {
	I->setInitializer(0);
	I->setLinkage(GlobalValue::ExternalLinkage);
	}

	// Try running the hacked up program...
	if (TestFn(BD, M)) {
	BD.setNewProgram(M); // It crashed, keep the trimmed version...

	// Make sure to use global variable pointers that point into the now-current
	// module.
	GVs.assign(GVSet.begin(), GVSet.end());
	return true;
	}

	delete M;
	return false;
	}

	namespace llvm {
	/// ReduceCrashingFunctions reducer - This works by removing functions and
	/// seeing if the program still crashes. If it does, then keep the newer,
	/// smaller program.
	///
	class ReduceCrashingFunctions : public ListReducer<Function*> {
	BugDriver &BD;
	bool (TestFn)(BugDriver &, Module );
	public:
	ReduceCrashingFunctions(BugDriver &bd,
	bool (testFn)(BugDriver &, Module ))
	: BD(bd), TestFn(testFn) {}

	virtual TestResult doTest(std::vector<Function*> &Prefix,
	std::vector<Function*> &Kept) {
	if (!Kept.empty() && TestFuncs(Kept))
	return KeepSuffix;
	if (!Prefix.empty() && TestFuncs(Prefix))
	return KeepPrefix;
	return NoFailure;
	}

	bool TestFuncs(std::vector<Function*> &Prefix);
	};
	}

	bool ReduceCrashingFunctions::TestFuncs(std::vector<Function*> &Funcs) {

	//if main isn't present, claim there is no problem
	if (KeepMain && find(Funcs.begin(), Funcs.end(),
	BD.getProgram()->getMainFunction()) == Funcs.end())
	return false;

	// Clone the program to try hacking it apart...
	Module *M = CloneModule(BD.getProgram());

	// Convert list to set for fast lookup...
	std::set<Function*> Functions;
	for (unsigned i = 0, e = Funcs.size(); i != e; ++i) {
	// FIXME: bugpoint should add names to all stripped symbols.
	assert(!Funcs[i]->getName().empty() &&
	"Bugpoint doesn't work on stripped modules yet PR718!");
	Function *CMF = M->getFunction(Funcs[i]->getName(),
	Funcs[i]->getFunctionType());
	assert(CMF && "Function not in module?!");
	Functions.insert(CMF);
	}

	std::cout << "Checking for crash with only these functions: ";
	PrintFunctionList(Funcs);
	std::cout << ": ";

	// Loop over and delete any functions which we aren't supposed to be playing
	// with...
	for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
	if (!I->isExternal() && !Functions.count(I))
	DeleteFunctionBody(I);

	// Try running the hacked up program...
	if (TestFn(BD, M)) {
	BD.setNewProgram(M); // It crashed, keep the trimmed version...

	// Make sure to use function pointers that point into the now-current
	// module.
	Funcs.assign(Functions.begin(), Functions.end());
	return true;
	}
	delete M;
	return false;
	}


	namespace {
	/// ReduceCrashingBlocks reducer - This works by setting the terminators of
	/// all terminators except the specified basic blocks to a 'ret' instruction,
	/// then running the simplify-cfg pass. This has the effect of chopping up
	/// the CFG really fast which can reduce large functions quickly.
	///
	class ReduceCrashingBlocks : public ListReducer<const BasicBlock*> {
	BugDriver &BD;
	bool (TestFn)(BugDriver &, Module );
	public:
	ReduceCrashingBlocks(BugDriver &bd, bool (testFn)(BugDriver &, Module ))
	: BD(bd), TestFn(testFn) {}

	virtual TestResult doTest(std::vector<const BasicBlock*> &Prefix,
	std::vector<const BasicBlock*> &Kept) {
	if (!Kept.empty() && TestBlocks(Kept))
	return KeepSuffix;
	if (!Prefix.empty() && TestBlocks(Prefix))
	return KeepPrefix;
	return NoFailure;
	}

	bool TestBlocks(std::vector<const BasicBlock*> &Prefix);
	};
	}

	bool ReduceCrashingBlocks::TestBlocks(std::vector<const BasicBlock*> &BBs) {
	// Clone the program to try hacking it apart...
	Module *M = CloneModule(BD.getProgram());

	// Convert list to set for fast lookup...
	std::set<BasicBlock*> Blocks;
	for (unsigned i = 0, e = BBs.size(); i != e; ++i) {
	// Convert the basic block from the original module to the new module...
	const Function *F = BBs[i]->getParent();
	Function *CMF = M->getFunction(F->getName(), F->getFunctionType());
	assert(CMF && "Function not in module?!");

	// Get the mapped basic block...
	Function::iterator CBI = CMF->begin();
	std::advance(CBI, std::distance(F->begin(),
	Function::const_iterator(BBs[i])));
	Blocks.insert(CBI);
	}

	std::cout << "Checking for crash with only these blocks:";
	unsigned NumPrint = Blocks.size();
	if (NumPrint > 10) NumPrint = 10;
	for (unsigned i = 0, e = NumPrint; i != e; ++i)
	std::cout << " " << BBs[i]->getName();
	if (NumPrint < Blocks.size())
	std::cout << "... <" << Blocks.size() << " total>";
	std::cout << ": ";

	// Loop over and delete any hack up any blocks that are not listed...
	for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
	for (Function::iterator BB = I->begin(), E = I->end(); BB != E; ++BB)
	if (!Blocks.count(BB) && BB->getTerminator()->getNumSuccessors()) {
	// Loop over all of the successors of this block, deleting any PHI nodes
	// that might include it.
	for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
	(*SI)->removePredecessor(BB);

	if (BB->getTerminator()->getType() != Type::VoidTy)
	BB->getTerminator()->replaceAllUsesWith(
	Constant::getNullValue(BB->getTerminator()->getType()));

	// Delete the old terminator instruction...
	BB->getInstList().pop_back();

	// Add a new return instruction of the appropriate type...
	const Type *RetTy = BB->getParent()->getReturnType();
	new ReturnInst(RetTy == Type::VoidTy ? 0 :
	Constant::getNullValue(RetTy), BB);
	}

	// The CFG Simplifier pass may delete one of the basic blocks we are
	// interested in. If it does we need to take the block out of the list. Make
	// a "persistent mapping" by turning basic blocks into <function, name> pairs.
	// This won't work well if blocks are unnamed, but that is just the risk we
	// have to take.
	std::vector<std::pair<Function*, std::string> > BlockInfo;

	for (std::set<BasicBlock*>::iterator I = Blocks.begin(), E = Blocks.end();
	I != E; ++I)
	BlockInfo.push_back(std::make_pair((I)->getParent(), (I)->getName()));

	// Now run the CFG simplify pass on the function...
	PassManager Passes;
	Passes.add(createCFGSimplificationPass());
	Passes.add(createVerifierPass());
	Passes.run(*M);

	// Try running on the hacked up program...
	if (TestFn(BD, M)) {
	BD.setNewProgram(M); // It crashed, keep the trimmed version...

	// Make sure to use basic block pointers that point into the now-current
	// module, and that they don't include any deleted blocks.
	BBs.clear();
	for (unsigned i = 0, e = BlockInfo.size(); i != e; ++i) {
	SymbolTable &ST = BlockInfo[i].first->getValueSymbolTable();
	SymbolTable::plane_iterator PI = ST.find(Type::LabelTy);
	if (PI != ST.plane_end() && PI->second.count(BlockInfo[i].second))
	BBs.push_back(cast<BasicBlock>(PI->second[BlockInfo[i].second]));
	}
	return true;
	}
	delete M; // It didn't crash, try something else.
	return false;
	}

	/// DebugACrash - Given a predicate that determines whether a component crashes
	/// on a program, try to destructively reduce the program while still keeping
	/// the predicate true.
	static bool DebugACrash(BugDriver &BD, bool (TestFn)(BugDriver &, Module )) {
	// See if we can get away with nuking some of the global variable initializers
	// in the program...
	if (BD.getProgram()->global_begin() != BD.getProgram()->global_end()) {
	// Now try to reduce the number of global variable initializers in the
	// module to something small.
	Module *M = CloneModule(BD.getProgram());
	bool DeletedInit = false;

	for (Module::global_iterator I = M->global_begin(), E = M->global_end();
	I != E; ++I)
	if (I->hasInitializer()) {
	I->setInitializer(0);
	I->setLinkage(GlobalValue::ExternalLinkage);
	DeletedInit = true;
	}

	if (!DeletedInit) {
	delete M; // No change made...
	} else {
	// See if the program still causes a crash...
	std::cout << "\nChecking to see if we can delete global inits: ";

	if (TestFn(BD, M)) { // Still crashes?
	BD.setNewProgram(M);
	std::cout << "\n*** Able to remove all global initializers!\n";
	} else { // No longer crashes?
	std::cout << " - Removing all global inits hides problem!\n";
	delete M;

	std::vector<GlobalVariable*> GVs;

	for (Module::global_iterator I = BD.getProgram()->global_begin(),
	E = BD.getProgram()->global_end(); I != E; ++I)
	if (I->hasInitializer())
	GVs.push_back(I);

	if (GVs.size() > 1 && !BugpointIsInterrupted) {
	std::cout << "\n*** Attempting to reduce the number of global "
	<< "variables in the testcase\n";

	unsigned OldSize = GVs.size();
	ReduceCrashingGlobalVariables(BD, TestFn).reduceList(GVs);

	if (GVs.size() < OldSize)
	BD.EmitProgressBytecode("reduced-global-variables");
	}
	}
	}
	}

	// Now try to reduce the number of functions in the module to something small.
	std::vector<Function*> Functions;
	for (Module::iterator I = BD.getProgram()->begin(),
	E = BD.getProgram()->end(); I != E; ++I)
	if (!I->isExternal())
	Functions.push_back(I);

	if (Functions.size() > 1 && !BugpointIsInterrupted) {
	std::cout << "\n*** Attempting to reduce the number of functions "
	"in the testcase\n";

	unsigned OldSize = Functions.size();
	ReduceCrashingFunctions(BD, TestFn).reduceList(Functions);

	if (Functions.size() < OldSize)
	BD.EmitProgressBytecode("reduced-function");
	}

	// Attempt to delete entire basic blocks at a time to speed up
	// convergence... this actually works by setting the terminator of the blocks
	// to a return instruction then running simplifycfg, which can potentially
	// shrinks the code dramatically quickly
	//
	if (!DisableSimplifyCFG && !BugpointIsInterrupted) {
	std::vector<const BasicBlock*> Blocks;
	for (Module::const_iterator I = BD.getProgram()->begin(),
	E = BD.getProgram()->end(); I != E; ++I)
	for (Function::const_iterator FI = I->begin(), E = I->end(); FI !=E; ++FI)
	Blocks.push_back(FI);
	ReduceCrashingBlocks(BD, TestFn).reduceList(Blocks);
	}

	// FIXME: This should use the list reducer to converge faster by deleting
	// larger chunks of instructions at a time!
	unsigned Simplification = 2;
	do {
	if (BugpointIsInterrupted) break;
	--Simplification;
	std::cout << "\n*** Attempting to reduce testcase by deleting instruc"
	<< "tions: Simplification Level #" << Simplification << '\n';

	// Now that we have deleted the functions that are unnecessary for the
	// program, try to remove instructions that are not necessary to cause the
	// crash. To do this, we loop through all of the instructions in the
	// remaining functions, deleting them (replacing any values produced with
	// nulls), and then running ADCE and SimplifyCFG. If the transformed input
	// still triggers failure, keep deleting until we cannot trigger failure
	// anymore.
	//
	unsigned InstructionsToSkipBeforeDeleting = 0;
	TryAgain:

	// Loop over all of the (non-terminator) instructions remaining in the
	// function, attempting to delete them.
	unsigned CurInstructionNum = 0;
	for (Module::const_iterator FI = BD.getProgram()->begin(),
	E = BD.getProgram()->end(); FI != E; ++FI)
	if (!FI->isExternal())
	for (Function::const_iterator BI = FI->begin(), E = FI->end(); BI != E;
	++BI)
	for (BasicBlock::const_iterator I = BI->begin(), E = --BI->end();
	I != E; ++I, ++CurInstructionNum)
	if (InstructionsToSkipBeforeDeleting) {
	--InstructionsToSkipBeforeDeleting;
	} else {
	if (BugpointIsInterrupted) goto ExitLoops;

	std::cout << "Checking instruction '" << I->getName() << "': ";
	Module *M = BD.deleteInstructionFromProgram(I, Simplification);

	// Find out if the pass still crashes on this pass...
	if (TestFn(BD, M)) {
	// Yup, it does, we delete the old module, and continue trying
	// to reduce the testcase...
	BD.setNewProgram(M);
	InstructionsToSkipBeforeDeleting = CurInstructionNum;
	goto TryAgain; // I wish I had a multi-level break here!
	}

	// This pass didn't crash without this instruction, try the next
	// one.
	delete M;
	}

	if (InstructionsToSkipBeforeDeleting) {
	InstructionsToSkipBeforeDeleting = 0;
	goto TryAgain;
	}

	} while (Simplification);
	ExitLoops:

	// Try to clean up the testcase by running funcresolve and globaldce...
	if (!BugpointIsInterrupted) {
	std::cout << "\n*** Attempting to perform final cleanups: ";
	Module *M = CloneModule(BD.getProgram());
	M = BD.performFinalCleanups(M, true);

	// Find out if the pass still crashes on the cleaned up program...
	if (TestFn(BD, M)) {
	BD.setNewProgram(M); // Yup, it does, keep the reduced version...
	} else {
	delete M;
	}
	}

	BD.EmitProgressBytecode("reduced-simplified");

	return false;
	}

	static bool TestForOptimizerCrash(BugDriver &BD, Module *M) {
	return BD.runPasses(M);
	}

	/// debugOptimizerCrash - This method is called when some pass crashes on input.
	/// It attempts to prune down the testcase to something reasonable, and figure
	/// out exactly which pass is crashing.
	///
	bool BugDriver::debugOptimizerCrash(const std::string &ID) {
	std::cout << "\n*** Debugging optimizer crash!\n";

	// Reduce the list of passes which causes the optimizer to crash...
	if (!BugpointIsInterrupted)
	ReducePassList(*this).reduceList(PassesToRun);

	std::cout << "\n*** Found crashing pass"
	<< (PassesToRun.size() == 1 ? ": " : "es: ")
	<< getPassesString(PassesToRun) << '\n';

	EmitProgressBytecode(ID);

	return DebugACrash(*this, TestForOptimizerCrash);
	}

	static bool TestForCodeGenCrash(BugDriver &BD, Module *M) {
	try {
	std::cerr << '\n';
	BD.compileProgram(M);
	std::cerr << '\n';
	return false;
	} catch (ToolExecutionError &) {
	std::cerr << "<crash>\n";
	return true; // Tool is still crashing.
	}
	}

	/// debugCodeGeneratorCrash - This method is called when the code generator
	/// crashes on an input. It attempts to reduce the input as much as possible
	/// while still causing the code generator to crash.
	bool BugDriver::debugCodeGeneratorCrash() {
	std::cerr << "*** Debugging code generator crash!\n";

	return DebugACrash(*this, TestForCodeGenCrash);
	}