Remove use of exceptions from bugpoint. No deliberate functionality change!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101013 91177308-0d34-0410-b5e6-96231b3b80d8

10 files changed, 463 insertions, 341 deletions

diff --git a/tools/bugpoint/BugDriver.cpp b/tools/bugpoint/BugDriver.cpp
index d676a43..45a0d4d 100644
--- a/tools/bugpoint/BugDriver.cpp
+++ b/tools/bugpoint/BugDriver.cpp
@@ -115,30 +115,25 @@ bool BugDriver::addSources(const std::vector<std::string> &Filenames) {
   assert(Program == 0 && "Cannot call addSources multiple times!");
   assert(!Filenames.empty() && "Must specify at least on input filename!");
 
-  try {
-    // Load the first input file.
-    Program = ParseInputFile(Filenames[0], Context);
-    if (Program == 0) return true;
+  // Load the first input file.
+  Program = ParseInputFile(Filenames[0], Context);
+  if (Program == 0) return true;
     
-    if (!run_as_child)
-      outs() << "Read input file      : '" << Filenames[0] << "'\n";
+  if (!run_as_child)
+    outs() << "Read input file      : '" << Filenames[0] << "'\n";
 
-    for (unsigned i = 1, e = Filenames.size(); i != e; ++i) {
-      std::auto_ptr<Module> M(ParseInputFile(Filenames[i], Context));
-      if (M.get() == 0) return true;
+  for (unsigned i = 1, e = Filenames.size(); i != e; ++i) {
+    std::auto_ptr<Module> M(ParseInputFile(Filenames[i], Context));
+    if (M.get() == 0) return true;
 
-      if (!run_as_child)
-        outs() << "Linking in input file: '" << Filenames[i] << "'\n";
-      std::string ErrorMessage;
-      if (Linker::LinkModules(Program, M.get(), &ErrorMessage)) {
-        errs() << ToolName << ": error linking in '" << Filenames[i] << "': "
-               << ErrorMessage << '\n';
-        return true;
-      }
+    if (!run_as_child)
+      outs() << "Linking in input file: '" << Filenames[i] << "'\n";
+    std::string ErrorMessage;
+    if (Linker::LinkModules(Program, M.get(), &ErrorMessage)) {
+      errs() << ToolName << ": error linking in '" << Filenames[i] << "': "
+             << ErrorMessage << '\n';
+      return true;
     }
-  } catch (const std::string &Error) {
-    errs() << ToolName << ": error reading input '" << Error << "'\n";
-    return true;
   }
 
   if (!run_as_child)
@@ -153,7 +148,7 @@ bool BugDriver::addSources(const std::vector<std::string> &Filenames) {
 /// run - The top level method that is invoked after all of the instance
 /// variables are set up from command line arguments.
 ///
-bool BugDriver::run() {
+bool BugDriver::run(std::string &ErrMsg) {
   // The first thing to do is determine if we're running as a child. If we are,
   // then what to do is very narrow. This form of invocation is only called
   // from the runPasses method to actually run those passes in a child process.
@@ -165,7 +160,7 @@ bool BugDriver::run() {
   if (run_find_bugs) {
     // Rearrange the passes and apply them to the program. Repeat this process
     // until the user kills the program or we find a bug.
-    return runManyPasses(PassesToRun);
+    return runManyPasses(PassesToRun, ErrMsg);
   }
 
   // If we're not running as a child, the first thing that we must do is 
@@ -186,14 +181,13 @@ bool BugDriver::run() {
 
   // Test to see if we have a code generator crash.
   outs() << "Running the code generator to test for a crash: ";
-  try {
-    compileProgram(Program);
-    outs() << '\n';
-  } catch (ToolExecutionError &TEE) {
-    outs() << TEE.what();
-    return debugCodeGeneratorCrash();
+  std::string Error;
+  compileProgram(Program, &Error);
+  if (!Error.empty()) {
+    outs() << Error;
+    return debugCodeGeneratorCrash(ErrMsg);
   }
-
+  outs() << '\n';
 
   // Run the raw input to see where we are coming from.  If a reference output
   // was specified, make sure that the raw output matches it.  If not, it's a
@@ -202,8 +196,8 @@ bool BugDriver::run() {
   bool CreatedOutput = false;
   if (ReferenceOutputFile.empty()) {
     outs() << "Generating reference output from raw program: ";
-    if(!createReferenceFile(Program)){
-      return debugCodeGeneratorCrash();
+    if (!createReferenceFile(Program)) {
+      return debugCodeGeneratorCrash(ErrMsg);
     }
     CreatedOutput = true;
   }
@@ -217,24 +211,29 @@ bool BugDriver::run() {
   // matches, then we assume there is a miscompilation bug and try to 
   // diagnose it.
   outs() << "*** Checking the code generator...\n";
-  try {
-    if (!diffProgram()) {
-      outs() << "\n*** Output matches: Debugging miscompilation!\n";
-      return debugMiscompilation();
+  bool Diff = diffProgram("", "", false, &Error);
+  if (!Error.empty()) {
+    errs() << Error;
+    return debugCodeGeneratorCrash(ErrMsg);
+  }
+  if (!Diff) {
+    outs() << "\n*** Output matches: Debugging miscompilation!\n";
+    debugMiscompilation(&Error);
+    if (!Error.empty()) {
+      errs() << Error;
+      return debugCodeGeneratorCrash(ErrMsg);
     }
-  } catch (ToolExecutionError &TEE) {
-    errs() << TEE.what();
-    return debugCodeGeneratorCrash();
+    return false;
   }
 
   outs() << "\n*** Input program does not match reference diff!\n";
   outs() << "Debugging code generator problem!\n";
-  try {
-    return debugCodeGenerator();
-  } catch (ToolExecutionError &TEE) {
-    errs() << TEE.what();
-    return debugCodeGeneratorCrash();
+  bool Failure = debugCodeGenerator(&Error);
+  if (!Error.empty()) {
+    errs() << Error;
+    return debugCodeGeneratorCrash(ErrMsg);
   }
+  return Failure;
 }
 
 void llvm::PrintFunctionList(const std::vector<Function*> &Funcs) {
diff --git a/tools/bugpoint/BugDriver.h b/tools/bugpoint/BugDriver.h
index 819cc98..c3c847f 100644
--- a/tools/bugpoint/BugDriver.h
+++ b/tools/bugpoint/BugDriver.h
@@ -88,7 +88,7 @@ public:
   /// variables are set up from command line arguments. The \p as_child argument
   /// indicates whether the driver is to run in parent mode or child mode.
   ///
-  bool run();
+  bool run(std::string &ErrMsg);
 
   /// debugOptimizerCrash - This method is called when some optimizer pass
   /// crashes on input.  It attempts to prune down the testcase to something
@@ -99,12 +99,12 @@ public:
   /// 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 debugCodeGeneratorCrash();
+  bool debugCodeGeneratorCrash(std::string &Error);
 
   /// debugMiscompilation - This method is used when the passes selected are not
   /// crashing, but the generated output is semantically different from the
   /// input.
-  bool debugMiscompilation();
+  void debugMiscompilation(std::string *Error);
 
   /// debugPassMiscompilation - This method is called when the specified pass
   /// miscompiles Program as input.  It tries to reduce the testcase to
@@ -118,12 +118,13 @@ public:
   /// compileSharedObject - This method creates a SharedObject from a given
   /// BitcodeFile for debugging a code generator.
   ///
-  std::string compileSharedObject(const std::string &BitcodeFile);
+  std::string compileSharedObject(const std::string &BitcodeFile,
+                                  std::string &Error);
 
   /// debugCodeGenerator - This method narrows down a module to a function or
   /// set of functions, using the CBE as a ``safe'' code generator for other
   /// functions that are not under consideration.
-  bool debugCodeGenerator();
+  bool debugCodeGenerator(std::string *Error);
 
   /// isExecutingJIT - Returns true if bugpoint is currently testing the JIT
   ///
@@ -164,27 +165,29 @@ public:
   /// the specified one as the current program.
   void setNewProgram(Module *M);
 
-  /// compileProgram - Try to compile the specified module, throwing an
-  /// exception if an error occurs, or returning normally if not.  This is used
-  /// for code generation crash testing.
+  /// compileProgram - Try to compile the specified module, returning false and
+  /// setting Error if an error occurs.  This is used for code generation
+  /// crash testing.
   ///
-  void compileProgram(Module *M);
+  void compileProgram(Module *M, std::string *Error);
 
   /// executeProgram - This method runs "Program", capturing the output of the
-  /// program to a file, returning the filename of the file.  A recommended
-  /// filename may be optionally specified.  If there is a problem with the code
-  /// generator (e.g., llc crashes), this will throw an exception.
+  /// program to a file.  The recommended filename will be filled in with the
+  /// name of the file with the captured output.  If there is a problem with
+  /// the code generator (e.g., llc crashes), this will throw an exception.
   ///
-  std::string executeProgram(std::string RequestedOutputFilename = "",
-                             std::string Bitcode = "",
-                             const std::string &SharedObjects = "",
-                             AbstractInterpreter *AI = 0);
+  std::string executeProgram(std::string OutputFilename,
+                             std::string Bitcode,
+                             const std::string &SharedObjects,
+                             AbstractInterpreter *AI,
+                             std::string *Error);
 
   /// executeProgramSafely - Used to create reference output with the "safe"
   /// backend, if reference output is not provided.  If there is a problem with
-  /// the code generator (e.g., llc crashes), this will throw an exception.
+  /// the code generator (e.g., llc crashes), this will return false and set
+  /// Error.
   ///
-  std::string executeProgramSafely(std::string OutputFile = "");
+  std::string executeProgramSafely(std::string OutputFile, std::string *Error);
 
   /// createReferenceFile - calls compileProgram and then records the output
   /// into ReferenceOutputFile. Returns true if reference file created, false 
@@ -196,13 +199,14 @@ public:
 
   /// diffProgram - This method executes the specified module and diffs the
   /// output against the file specified by ReferenceOutputFile.  If the output
-  /// is different, true is returned.  If there is a problem with the code
-  /// generator (e.g., llc crashes), this will throw an exception.
+  /// is different, 1 is returned.  If there is a problem with the code
+  /// generator (e.g., llc crashes), this will return -1 and set Error.
   ///
   bool diffProgram(const std::string &BitcodeFile = "",
                    const std::string &SharedObj = "",
-                   bool RemoveBitcode = false);
-                   
+                   bool RemoveBitcode = false,
+                   std::string *Error = 0);
+
   /// EmitProgressBitcode - This function is used to output the current Program
   /// to a file named "bugpoint-ID.bc".
   ///
@@ -266,7 +270,8 @@ public:
   /// If the passes did not compile correctly, output the command required to 
   /// recreate the failure. This returns true if a compiler error is found.
   ///
-  bool runManyPasses(const std::vector<const PassInfo*> &AllPasses);
+  bool runManyPasses(const std::vector<const PassInfo*> &AllPasses,
+		     std::string &ErrMsg);
 
   /// writeProgramToFile - This writes the current "Program" to the named
   /// bitcode file.  If an error occurs, true is returned.
diff --git a/tools/bugpoint/CrashDebugger.cpp b/tools/bugpoint/CrashDebugger.cpp
index b51bdb4..46b33d2 100644
--- a/tools/bugpoint/CrashDebugger.cpp
+++ b/tools/bugpoint/CrashDebugger.cpp
@@ -53,13 +53,15 @@ namespace llvm {
     // 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);
+                              std::vector<const PassInfo*> &Kept,
+                              std::string &Error);
   };
 }
 
 ReducePassList::TestResult
 ReducePassList::doTest(std::vector<const PassInfo*> &Prefix,
-                       std::vector<const PassInfo*> &Suffix) {
+                       std::vector<const PassInfo*> &Suffix,
+                       std::string &Error) {
   sys::Path PrefixOutput;
   Module *OrigProgram = 0;
   if (!Prefix.empty()) {
@@ -107,27 +109,26 @@ namespace {
     bool (*TestFn)(BugDriver &, Module *);
   public:
     ReduceCrashingGlobalVariables(BugDriver &bd,
-                                  bool (*testFn)(BugDriver&, Module*))
+                                  bool (*testFn)(BugDriver &, Module *))
       : BD(bd), TestFn(testFn) {}
 
-    virtual TestResult doTest(std::vector<GlobalVariable*>& Prefix,
-                              std::vector<GlobalVariable*>& Kept) {
+    virtual TestResult doTest(std::vector<GlobalVariable*> &Prefix,
+                              std::vector<GlobalVariable*> &Kept,
+                              std::string &Error) {
       if (!Kept.empty() && TestGlobalVariables(Kept))
         return KeepSuffix;
-
       if (!Prefix.empty() && TestGlobalVariables(Prefix))
         return KeepPrefix;
-
       return NoFailure;
     }
 
-    bool TestGlobalVariables(std::vector<GlobalVariable*>& GVs);
+    bool TestGlobalVariables(std::vector<GlobalVariable*> &GVs);
   };
 }
 
 bool
 ReduceCrashingGlobalVariables::TestGlobalVariables(
-                              std::vector<GlobalVariable*>& GVs) {
+                              std::vector<GlobalVariable*> &GVs) {
   // Clone the program to try hacking it apart...
   DenseMap<const Value*, Value*> ValueMap;
   Module *M = CloneModule(BD.getProgram(), ValueMap);
@@ -182,7 +183,8 @@ namespace llvm {
       : BD(bd), TestFn(testFn) {}
 
     virtual TestResult doTest(std::vector<Function*> &Prefix,
-                              std::vector<Function*> &Kept) {
+                              std::vector<Function*> &Kept,
+                              std::string &Error) {
       if (!Kept.empty() && TestFuncs(Kept))
         return KeepSuffix;
       if (!Prefix.empty() && TestFuncs(Prefix))
@@ -253,7 +255,8 @@ namespace {
       : BD(bd), TestFn(testFn) {}
 
     virtual TestResult doTest(std::vector<const BasicBlock*> &Prefix,
-                              std::vector<const BasicBlock*> &Kept) {
+                              std::vector<const BasicBlock*> &Kept,
+                              std::string &Error) {
       if (!Kept.empty() && TestBlocks(Kept))
         return KeepSuffix;
       if (!Prefix.empty() && TestBlocks(Prefix))
@@ -355,7 +358,8 @@ namespace {
       : BD(bd), TestFn(testFn) {}
 
     virtual TestResult doTest(std::vector<const Instruction*> &Prefix,
-                              std::vector<const Instruction*> &Kept) {
+                              std::vector<const Instruction*> &Kept,
+                              std::string &Error) {
       if (!Kept.empty() && TestInsts(Kept))
         return KeepSuffix;
       if (!Prefix.empty() && TestInsts(Prefix))
@@ -421,7 +425,8 @@ bool ReduceCrashingInstructions::TestInsts(std::vector<const Instruction*>
 /// 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 *)) {
+static bool DebugACrash(BugDriver &BD, bool (*TestFn)(BugDriver &, Module *),
+                        std::string &Error) {
   // See if we can get away with nuking some of the global variable initializers
   // in the program...
   if (!NoGlobalRM &&
@@ -464,7 +469,9 @@ static bool DebugACrash(BugDriver &BD,  bool (*TestFn)(BugDriver &, Module *)) {
                     << "variables in the testcase\n";
 
           unsigned OldSize = GVs.size();
-          ReduceCrashingGlobalVariables(BD, TestFn).reduceList(GVs);
+          ReduceCrashingGlobalVariables(BD, TestFn).reduceList(GVs, Error);
+          if (!Error.empty())
+            return true;
 
           if (GVs.size() < OldSize)
             BD.EmitProgressBitcode("reduced-global-variables");
@@ -485,7 +492,7 @@ static bool DebugACrash(BugDriver &BD,  bool (*TestFn)(BugDriver &, Module *)) {
       "in the testcase\n";
 
     unsigned OldSize = Functions.size();
-    ReduceCrashingFunctions(BD, TestFn).reduceList(Functions);
+    ReduceCrashingFunctions(BD, TestFn).reduceList(Functions, Error);
 
     if (Functions.size() < OldSize)
       BD.EmitProgressBitcode("reduced-function");
@@ -503,7 +510,7 @@ static bool DebugACrash(BugDriver &BD,  bool (*TestFn)(BugDriver &, Module *)) {
       for (Function::const_iterator FI = I->begin(), E = I->end(); FI !=E; ++FI)
         Blocks.push_back(FI);
     unsigned OldSize = Blocks.size();
-    ReduceCrashingBlocks(BD, TestFn).reduceList(Blocks);
+    ReduceCrashingBlocks(BD, TestFn).reduceList(Blocks, Error);
     if (Blocks.size() < OldSize)
       BD.EmitProgressBitcode("reduced-blocks");
   }
@@ -521,7 +528,7 @@ static bool DebugACrash(BugDriver &BD,  bool (*TestFn)(BugDriver &, Module *)) {
           if (!isa<TerminatorInst>(I))
             Insts.push_back(I);
 
-    ReduceCrashingInstructions(BD, TestFn).reduceList(Insts);
+    ReduceCrashingInstructions(BD, TestFn).reduceList(Insts, Error);
   }
 
   // FIXME: This should use the list reducer to converge faster by deleting
@@ -614,9 +621,11 @@ static bool TestForOptimizerCrash(BugDriver &BD, Module *M) {
 bool BugDriver::debugOptimizerCrash(const std::string &ID) {
   outs() << "\n*** Debugging optimizer crash!\n";
 
+  std::string Error;
   // Reduce the list of passes which causes the optimizer to crash...
   if (!BugpointIsInterrupted)
-    ReducePassList(*this).reduceList(PassesToRun);
+    ReducePassList(*this).reduceList(PassesToRun, Error);
+  assert(Error.empty());
 
   outs() << "\n*** Found crashing pass"
          << (PassesToRun.size() == 1 ? ": " : "es: ")
@@ -624,25 +633,27 @@ bool BugDriver::debugOptimizerCrash(const std::string &ID) {
 
   EmitProgressBitcode(ID);
 
-  return DebugACrash(*this, TestForOptimizerCrash);
+  bool Success = DebugACrash(*this, TestForOptimizerCrash, Error);
+  assert(Error.empty());
+  return Success;
 }
 
 static bool TestForCodeGenCrash(BugDriver &BD, Module *M) {
-  try {
-    BD.compileProgram(M);
-    errs() << '\n';
-    return false;
-  } catch (ToolExecutionError &) {
+  std::string Error;
+  BD.compileProgram(M, &Error);
+  if (!Error.empty()) {
     errs() << "<crash>\n";
     return true;  // Tool is still crashing.
   }
+  errs() << '\n';
+  return false;
 }
 
 /// 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() {
+bool BugDriver::debugCodeGeneratorCrash(std::string &Error) {
   errs() << "*** Debugging code generator crash!\n";
 
-  return DebugACrash(*this, TestForCodeGenCrash);
+  return DebugACrash(*this, TestForCodeGenCrash, Error);
 }
diff --git a/tools/bugpoint/ExecutionDriver.cpp b/tools/bugpoint/ExecutionDriver.cpp
index 3b93a1a..9eb3314 100644
--- a/tools/bugpoint/ExecutionDriver.cpp
+++ b/tools/bugpoint/ExecutionDriver.cpp
@@ -278,15 +278,15 @@ bool BugDriver::initializeExecutionEnvironment() {
   return Interpreter == 0;
 }
 
-/// compileProgram - Try to compile the specified module, throwing an exception
-/// if an error occurs, or returning normally if not.  This is used for code
-/// generation crash testing.
+/// compileProgram - Try to compile the specified module, returning false and
+/// setting Error if an error occurs.  This is used for code generation
+/// crash testing.
 ///
-void BugDriver::compileProgram(Module *M) {
+void BugDriver::compileProgram(Module *M, std::string *Error) {
   // Emit the program to a bitcode file...
   sys::Path BitcodeFile (OutputPrefix + "-test-program.bc");
   std::string ErrMsg;
-  if (BitcodeFile.makeUnique(true,&ErrMsg)) {
+  if (BitcodeFile.makeUnique(true, &ErrMsg)) {
     errs() << ToolName << ": Error making unique filename: " << ErrMsg 
            << "\n";
     exit(1);
@@ -297,11 +297,11 @@ void BugDriver::compileProgram(Module *M) {
     exit(1);
   }
 
-    // Remove the temporary bitcode file when we are done.
+  // Remove the temporary bitcode file when we are done.
   FileRemover BitcodeFileRemover(BitcodeFile, !SaveTemps);
 
   // Actually compile the program!
-  Interpreter->compileProgram(BitcodeFile.str());
+  Interpreter->compileProgram(BitcodeFile.str(), Error);
 }
 
 
@@ -312,7 +312,8 @@ void BugDriver::compileProgram(Module *M) {
 std::string BugDriver::executeProgram(std::string OutputFile,
                                       std::string BitcodeFile,
                                       const std::string &SharedObj,
-                                      AbstractInterpreter *AI) {
+                                      AbstractInterpreter *AI,
+                                      std::string *Error) {
   if (AI == 0) AI = Interpreter;
   assert(AI && "Interpreter should have been created already!");
   bool CreatedBitcode = false;
@@ -355,9 +356,11 @@ std::string BugDriver::executeProgram(std::string OutputFile,
   if (!SharedObj.empty())
     SharedObjs.push_back(SharedObj);
 
-  int RetVal = AI->ExecuteProgram(BitcodeFile, InputArgv, InputFile,
-                                  OutputFile, AdditionalLinkerArgs, SharedObjs, 
+  int RetVal = AI->ExecuteProgram(BitcodeFile, InputArgv, InputFile, OutputFile,
+                                  Error, AdditionalLinkerArgs, SharedObjs,
                                   Timeout, MemoryLimit);
+  if (!Error->empty())
+    return OutputFile;
 
   if (RetVal == -1) {
     errs() << "<timeout>";
@@ -385,21 +388,28 @@ std::string BugDriver::executeProgram(std::string OutputFile,
 /// executeProgramSafely - Used to create reference output with the "safe"
 /// backend, if reference output is not provided.
 ///
-std::string BugDriver::executeProgramSafely(std::string OutputFile) {
-  std::string outFN = executeProgram(OutputFile, "", "", SafeInterpreter);
-  return outFN;
+std::string BugDriver::executeProgramSafely(std::string OutputFile,
+                                            std::string *Error) {
+  return executeProgram(OutputFile, "", "", SafeInterpreter, Error);
 }
 
-std::string BugDriver::compileSharedObject(const std::string &BitcodeFile) {
+std::string BugDriver::compileSharedObject(const std::string &BitcodeFile,
+                                           std::string &Error) {
   assert(Interpreter && "Interpreter should have been created already!");
   sys::Path OutputFile;
 
   // Using the known-good backend.
-  GCC::FileType FT = SafeInterpreter->OutputCode(BitcodeFile, OutputFile);
+  GCC::FileType FT = SafeInterpreter->OutputCode(BitcodeFile, OutputFile,
+                                                 Error);
+  if (!Error.empty())
+    return "";
 
   std::string SharedObjectFile;
-  if (gcc->MakeSharedObject(OutputFile.str(), FT,
-                            SharedObjectFile, AdditionalLinkerArgs))
+  bool Failure = gcc->MakeSharedObject(OutputFile.str(), FT, SharedObjectFile,
+                                       AdditionalLinkerArgs, Error);
+  if (!Error.empty())
+    return "";
+  if (Failure)
     exit(1);
 
   // Remove the intermediate C file
@@ -414,16 +424,14 @@ std::string BugDriver::compileSharedObject(const std::string &BitcodeFile) {
 /// this function.
 ///
 bool BugDriver::createReferenceFile(Module *M, const std::string &Filename) {
-  try {
-    compileProgram(Program);
-  } catch (ToolExecutionError &) {
+  std::string Error;
+  compileProgram(Program, &Error);
+  if (!Error.empty())
     return false;
-  }
-  try {
-    ReferenceOutputFile = executeProgramSafely(Filename);
-    outs() << "\nReference output is: " << ReferenceOutputFile << "\n\n";
-  } catch (ToolExecutionError &TEE) {
-    errs() << TEE.what();
+
+  ReferenceOutputFile = executeProgramSafely(Filename, &Error);
+  if (!Error.empty()) {
+    errs() << Error;
     if (Interpreter != SafeInterpreter) {
       errs() << "*** There is a bug running the \"safe\" backend.  Either"
              << " debug it (for example with the -run-cbe bugpoint option,"
@@ -432,19 +440,23 @@ bool BugDriver::createReferenceFile(Module *M, const std::string &Filename) {
     }
     return false;
   }
+  outs() << "\nReference output is: " << ReferenceOutputFile << "\n\n";
   return true;
 }
 
 /// diffProgram - This method executes the specified module and diffs the
 /// output against the file specified by ReferenceOutputFile.  If the output
-/// is different, true is returned.  If there is a problem with the code
-/// generator (e.g., llc crashes), this will throw an exception.
+/// is different, 1 is returned.  If there is a problem with the code
+/// generator (e.g., llc crashes), this will return -1 and set Error.
 ///
 bool BugDriver::diffProgram(const std::string &BitcodeFile,
                             const std::string &SharedObject,
-                            bool RemoveBitcode) {
+                            bool RemoveBitcode,
+                            std::string *ErrMsg) {
   // Execute the program, generating an output file...
-  sys::Path Output(executeProgram("", BitcodeFile, SharedObject, 0));
+  sys::Path Output(executeProgram("", BitcodeFile, SharedObject, 0, ErrMsg));
+  if (!ErrMsg->empty())
+    return false;
 
   std::string Error;
   bool FilesDifferent = false;
diff --git a/tools/bugpoint/FindBugs.cpp b/tools/bugpoint/FindBugs.cpp
index b27a25c..224c717 100644
--- a/tools/bugpoint/FindBugs.cpp
+++ b/tools/bugpoint/FindBugs.cpp
@@ -29,7 +29,8 @@ using namespace llvm;
 /// If the passes did not compile correctly, output the command required to 
 /// recreate the failure. This returns true if a compiler error is found.
 ///
-bool BugDriver::runManyPasses(const std::vector<const PassInfo*> &AllPasses) {
+bool BugDriver::runManyPasses(const std::vector<const PassInfo*> &AllPasses,
+                              std::string &ErrMsg) {
   setPassesToRun(AllPasses);
   outs() << "Starting bug finding procedure...\n\n";
   
@@ -74,33 +75,33 @@ bool BugDriver::runManyPasses(const std::vector<const PassInfo*> &AllPasses) {
     // Step 3: Compile the optimized code.
     //
     outs() << "Running the code generator to test for a crash: ";
-    try {
-      compileProgram(Program);
-      outs() << '\n';
-    } catch (ToolExecutionError &TEE) {
+    std::string Error;
+    compileProgram(Program, &Error);
+    if (!Error.empty()) {
       outs() << "\n*** compileProgram threw an exception: ";
-      outs() << TEE.what();
-      return debugCodeGeneratorCrash();
+      outs() << Error;
+      return debugCodeGeneratorCrash(ErrMsg);
     }
+    outs() << '\n';
     
     //
     // Step 4: Run the program and compare its output to the reference 
     // output (created above).
     //
     outs() << "*** Checking if passes caused miscompliation:\n";
-    try {
-      if (diffProgram(Filename, "", false)) {
-        outs() << "\n*** diffProgram returned true!\n";
-        debugMiscompilation();
+    bool Diff = diffProgram(Filename, "", false, &Error);
+    if (Error.empty() && Diff) {
+      outs() << "\n*** diffProgram returned true!\n";
+      debugMiscompilation(&Error);
+      if (Error.empty())
         return true;
-      } else {
-        outs() << "\n*** diff'd output matches!\n";
-      }
-    } catch (ToolExecutionError &TEE) {
-      errs() << TEE.what();
-      debugCodeGeneratorCrash();
+    }
+    if (!Error.empty()) {
+      errs() << Error;
+      debugCodeGeneratorCrash(ErrMsg);
       return true;
     }
+    outs() << "\n*** diff'd output matches!\n";
     
     sys::Path(Filename).eraseFromDisk();
     
diff --git a/tools/bugpoint/ListReducer.h b/tools/bugpoint/ListReducer.h
index 8036d1f..5e9cff0 100644
--- a/tools/bugpoint/ListReducer.h
+++ b/tools/bugpoint/ListReducer.h
@@ -16,6 +16,7 @@
 #define BUGPOINT_LIST_REDUCER_H
 
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/ErrorHandling.h"
 #include <vector>
 #include <cstdlib>
 #include <algorithm>
@@ -29,7 +30,8 @@ struct ListReducer {
   enum TestResult {
     NoFailure,         // No failure of the predicate was detected
     KeepSuffix,        // The suffix alone satisfies the predicate
-    KeepPrefix         // The prefix alone satisfies the predicate
+    KeepPrefix,        // The prefix alone satisfies the predicate
+    InternalError      // Encountered an error trying to run the predicate
   };
 
   virtual ~ListReducer() {}
@@ -40,16 +42,17 @@ struct ListReducer {
   // the prefix anyway, it can.
   //
   virtual TestResult doTest(std::vector<ElTy> &Prefix,
-                            std::vector<ElTy> &Kept) = 0;
+                            std::vector<ElTy> &Kept,
+                            std::string &Error) = 0;
 
   // reduceList - This function attempts to reduce the length of the specified
   // list while still maintaining the "test" property.  This is the core of the
   // "work" that bugpoint does.
   //
-  bool reduceList(std::vector<ElTy> &TheList) {
+  bool reduceList(std::vector<ElTy> &TheList, std::string &Error) {
     std::vector<ElTy> empty;
     std::srand(0x6e5ea738); // Seed the random number generator
-    switch (doTest(TheList, empty)) {
+    switch (doTest(TheList, empty, Error)) {
     case KeepPrefix:
       if (TheList.size() == 1) // we are done, it's the base case and it fails
         return true;
@@ -58,11 +61,15 @@ struct ListReducer {
 
     case KeepSuffix:
       // cannot be reached!
-      errs() << "bugpoint ListReducer internal error: selected empty set.\n";
-      abort();
+      llvm_unreachable("bugpoint ListReducer internal error: "
+                       "selected empty set.");
 
     case NoFailure:
       return false; // there is no failure with the full set of passes/funcs!
+
+    case InternalError:
+      assert(!Error.empty());
+      return true;
     }
 
     // Maximal number of allowed splitting iterations,
@@ -90,7 +97,7 @@ Backjump:
         std::random_shuffle(ShuffledList.begin(), ShuffledList.end());
         errs() << "\n\n*** Testing shuffled set...\n\n";
         // Check that random shuffle doesn't loose the bug
-        if (doTest(ShuffledList, empty) == KeepPrefix) {
+        if (doTest(ShuffledList, empty, Error) == KeepPrefix) {
           // If the bug is still here, use the shuffled list.
           TheList.swap(ShuffledList);
           MidTop = TheList.size();
@@ -109,7 +116,7 @@ Backjump:
       std::vector<ElTy> Prefix(TheList.begin(), TheList.begin()+Mid);
       std::vector<ElTy> Suffix(TheList.begin()+Mid, TheList.end());
 
-      switch (doTest(Prefix, Suffix)) {
+      switch (doTest(Prefix, Suffix, Error)) {
       case KeepSuffix:
         // The property still holds.  We can just drop the prefix elements, and
         // shorten the list to the "kept" elements.
@@ -133,7 +140,10 @@ Backjump:
         MidTop = Mid;
         NumOfIterationsWithoutProgress++;
         break;
+      case InternalError:
+        return true;  // Error was set by doTest.
       }
+      assert(Error.empty() && "doTest did not return InternalError for error");
     }
 
     // Probability of backjumping from the trimming loop back to the binary
@@ -167,12 +177,14 @@ Backjump:
           std::vector<ElTy> TestList(TheList);
           TestList.erase(TestList.begin()+i);
 
-          if (doTest(EmptyList, TestList) == KeepSuffix) {
+          if (doTest(EmptyList, TestList, Error) == KeepSuffix) {
             // We can trim down the list!
             TheList.swap(TestList);
             --i;  // Don't skip an element of the list
             Changed = true;
           }
+	  if (!Error.empty())
+	    return true;
         }
         // This can take a long time if left uncontrolled.  For now, don't
         // iterate.
diff --git a/tools/bugpoint/Miscompilation.cpp b/tools/bugpoint/Miscompilation.cpp
index c2b002f..96aab95 100644
--- a/tools/bugpoint/Miscompilation.cpp
+++ b/tools/bugpoint/Miscompilation.cpp
@@ -49,7 +49,8 @@ namespace {
     ReduceMiscompilingPasses(BugDriver &bd) : BD(bd) {}
 
     virtual TestResult doTest(std::vector<const PassInfo*> &Prefix,
-                              std::vector<const PassInfo*> &Suffix);
+                              std::vector<const PassInfo*> &Suffix,
+                              std::string &Error);
   };
 }
 
@@ -58,7 +59,8 @@ namespace {
 ///
 ReduceMiscompilingPasses::TestResult
 ReduceMiscompilingPasses::doTest(std::vector<const PassInfo*> &Prefix,
-                                 std::vector<const PassInfo*> &Suffix) {
+                                 std::vector<const PassInfo*> &Suffix,
+                                 std::string &Error) {
   // First, run the program with just the Suffix passes.  If it is still broken
   // with JUST the kept passes, discard the prefix passes.
   outs() << "Checking to see if '" << getPassesString(Suffix)
@@ -74,7 +76,11 @@ ReduceMiscompilingPasses::doTest(std::vector<const PassInfo*> &Prefix,
   }
   
   // Check to see if the finished program matches the reference output...
-  if (BD.diffProgram(BitcodeResult, "", true /*delete bitcode*/)) {
+  bool Diff = BD.diffProgram(BitcodeResult, "", true /*delete bitcode*/,
+                             &Error);
+  if (!Error.empty())
+    return InternalError;
+  if (Diff) {
     outs() << " nope.\n";
     if (Suffix.empty()) {
       errs() << BD.getToolName() << ": I'm confused: the test fails when "
@@ -107,7 +113,10 @@ ReduceMiscompilingPasses::doTest(std::vector<const PassInfo*> &Prefix,
   }
 
   // If the prefix maintains the predicate by itself, only keep the prefix!
-  if (BD.diffProgram(BitcodeResult)) {
+  Diff = BD.diffProgram(BitcodeResult, "", false, &Error);
+  if (!Error.empty())
+    return InternalError;
+  if (Diff) {
     outs() << " nope.\n";
     sys::Path(BitcodeResult).eraseFromDisk();
     return KeepPrefix;
@@ -143,7 +152,10 @@ ReduceMiscompilingPasses::doTest(std::vector<const PassInfo*> &Prefix,
   }
 
   // Run the result...
-  if (BD.diffProgram(BitcodeResult, "", true/*delete bitcode*/)) {
+  Diff = BD.diffProgram(BitcodeResult, "", true /*delete bitcode*/, &Error);
+  if (!Error.empty())
+    return InternalError;
+  if (Diff) {
     outs() << " nope.\n";
     delete OriginalInput;     // We pruned down the original input...
     return KeepSuffix;
@@ -158,22 +170,34 @@ ReduceMiscompilingPasses::doTest(std::vector<const PassInfo*> &Prefix,
 namespace {
   class ReduceMiscompilingFunctions : public ListReducer<Function*> {
     BugDriver &BD;
-    bool (*TestFn)(BugDriver &, Module *, Module *);
+    bool (*TestFn)(BugDriver &, Module *, Module *, std::string &);
   public:
     ReduceMiscompilingFunctions(BugDriver &bd,
-                                bool (*F)(BugDriver &, Module *, Module *))
+                                bool (*F)(BugDriver &, Module *, Module *,
+                                          std::string &))
       : BD(bd), TestFn(F) {}
 
     virtual TestResult doTest(std::vector<Function*> &Prefix,
-                              std::vector<Function*> &Suffix) {
-      if (!Suffix.empty() && TestFuncs(Suffix))
-        return KeepSuffix;
-      if (!Prefix.empty() && TestFuncs(Prefix))
-        return KeepPrefix;
+                              std::vector<Function*> &Suffix,
+                              std::string &Error) {
+      if (!Suffix.empty()) {
+        bool Ret = TestFuncs(Suffix, Error);
+        if (!Error.empty())
+          return InternalError;
+        if (Ret)
+          return KeepSuffix;
+      }
+      if (!Prefix.empty()) {
+        bool Ret = TestFuncs(Prefix, Error);
+        if (!Error.empty())
+          return InternalError;
+        if (Ret)
+          return KeepPrefix;
+      }
       return NoFailure;
     }
 
-    bool TestFuncs(const std::vector<Function*> &Prefix);
+    int TestFuncs(const std::vector<Function*> &Prefix, std::string &Error);
   };
 }
 
@@ -184,7 +208,7 @@ namespace {
 /// returns.
 ///
 static bool TestMergedProgram(BugDriver &BD, Module *M1, Module *M2,
-                              bool DeleteInputs) {
+                              bool DeleteInputs, std::string &Error) {
   // Link the two portions of the program back to together.
   std::string ErrorMsg;
   if (!DeleteInputs) {
@@ -202,11 +226,12 @@ static bool TestMergedProgram(BugDriver &BD, Module *M1, Module *M2,
 
   // Execute the program.  If it does not match the expected output, we must
   // return true.
-  bool Broken = BD.diffProgram();
-
-  // Delete the linked module & restore the original
-  BD.swapProgramIn(OldProgram);
-  delete M1;
+  bool Broken = BD.diffProgram("", "", false, &Error);
+  if (!Error.empty()) {
+    // Delete the linked module & restore the original
+    BD.swapProgramIn(OldProgram);
+    delete M1;
+  }
   return Broken;
 }
 
@@ -214,7 +239,8 @@ static bool TestMergedProgram(BugDriver &BD, Module *M1, Module *M2,
 /// under consideration for miscompilation vs. those that are not, and test
 /// accordingly. Each group of functions becomes a separate Module.
 ///
-bool ReduceMiscompilingFunctions::TestFuncs(const std::vector<Function*>&Funcs){
+int ReduceMiscompilingFunctions::TestFuncs(const std::vector<Function*> &Funcs,
+                                           std::string &Error) {
   // Test to see if the function is misoptimized if we ONLY run it on the
   // functions listed in Funcs.
   outs() << "Checking to see if the program is misoptimized when "
@@ -231,7 +257,7 @@ bool ReduceMiscompilingFunctions::TestFuncs(const std::vector<Function*>&Funcs){
                                                  ValueMap);
 
   // Run the predicate, note that the predicate will delete both input modules.
-  return TestFn(BD, ToOptimize, ToNotOptimize);
+  return TestFn(BD, ToOptimize, ToNotOptimize, Error);
 }
 
 /// DisambiguateGlobalSymbols - Give anonymous global values names.
@@ -251,8 +277,10 @@ static void DisambiguateGlobalSymbols(Module *M) {
 /// bug.  If so, it reduces the amount of code identified.
 ///
 static bool ExtractLoops(BugDriver &BD,
-                         bool (*TestFn)(BugDriver &, Module *, Module *),
-                         std::vector<Function*> &MiscompiledFunctions) {
+                         bool (*TestFn)(BugDriver &, Module *, Module *,
+                                        std::string &),
+                         std::vector<Function*> &MiscompiledFunctions,
+                         std::string &Error) {
   bool MadeChange = false;
   while (1) {
     if (BugpointIsInterrupted) return MadeChange;
@@ -279,7 +307,11 @@ static bool ExtractLoops(BugDriver &BD,
     // has broken.  If something broke, then we'll inform the user and stop
     // extraction.
     AbstractInterpreter *AI = BD.switchToSafeInterpreter();
-    if (TestMergedProgram(BD, ToOptimizeLoopExtracted, ToNotOptimize, false)) {
+    bool Failure = TestMergedProgram(BD, ToOptimizeLoopExtracted, ToNotOptimize,
+                                     false, Error);
+    if (!Error.empty())
+      return false;
+    if (Failure) {
       BD.switchToInterpreter(AI);
 
       // Merged program doesn't work anymore!
@@ -308,7 +340,10 @@ static bool ExtractLoops(BugDriver &BD,
     // Clone modules, the tester function will free them.
     Module *TOLEBackup = CloneModule(ToOptimizeLoopExtracted);
     Module *TNOBackup  = CloneModule(ToNotOptimize);
-    if (!TestFn(BD, ToOptimizeLoopExtracted, ToNotOptimize)) {
+    Failure = TestFn(BD, ToOptimizeLoopExtracted, ToNotOptimize, Error);
+    if (!Error.empty())
+      return false;
+    if (!Failure) {
       outs() << "*** Loop extraction masked the problem.  Undoing.\n";
       // If the program is not still broken, then loop extraction did something
       // that masked the error.  Stop loop extraction now.
@@ -361,31 +396,44 @@ static bool ExtractLoops(BugDriver &BD,
 namespace {
   class ReduceMiscompiledBlocks : public ListReducer<BasicBlock*> {
     BugDriver &BD;
-    bool (*TestFn)(BugDriver &, Module *, Module *);
+    bool (*TestFn)(BugDriver &, Module *, Module *, std::string &);
     std::vector<Function*> FunctionsBeingTested;
   public:
     ReduceMiscompiledBlocks(BugDriver &bd,
-                            bool (*F)(BugDriver &, Module *, Module *),
+                            bool (*F)(BugDriver &, Module *, Module *,
+                                      std::string &),
                             const std::vector<Function*> &Fns)
       : BD(bd), TestFn(F), FunctionsBeingTested(Fns) {}
 
     virtual TestResult doTest(std::vector<BasicBlock*> &Prefix,
-                              std::vector<BasicBlock*> &Suffix) {
-      if (!Suffix.empty() && TestFuncs(Suffix))
-        return KeepSuffix;
-      if (TestFuncs(Prefix))
-        return KeepPrefix;
+                              std::vector<BasicBlock*> &Suffix,
+                              std::string &Error) {
+      if (!Suffix.empty()) {
+        bool Ret = TestFuncs(Suffix, Error);
+        if (!Error.empty())
+          return InternalError;
+        if (Ret)
+          return KeepSuffix;
+      }
+      if (!Prefix.empty()) {
+        bool Ret = TestFuncs(Prefix, Error);
+        if (!Error.empty())
+          return InternalError;
+        if (Ret)
+          return KeepPrefix;
+      }
       return NoFailure;
     }
 
-    bool TestFuncs(const std::vector<BasicBlock*> &Prefix);
+    bool TestFuncs(const std::vector<BasicBlock*> &BBs, std::string &Error);
   };
 }
 
 /// TestFuncs - Extract all blocks for the miscompiled functions except for the
 /// specified blocks.  If the problem still exists, return true.
 ///
-bool ReduceMiscompiledBlocks::TestFuncs(const std::vector<BasicBlock*> &BBs) {
+bool ReduceMiscompiledBlocks::TestFuncs(const std::vector<BasicBlock*> &BBs,
+                                        std::string &Error) {
   // Test to see if the function is misoptimized if we ONLY run it on the
   // functions listed in Funcs.
   outs() << "Checking to see if the program is misoptimized when all ";
@@ -411,7 +459,7 @@ bool ReduceMiscompiledBlocks::TestFuncs(const std::vector<BasicBlock*> &BBs) {
   if (Module *New = BD.ExtractMappedBlocksFromModule(BBs, ToOptimize)) {
     delete ToOptimize;
     // Run the predicate, not that the predicate will delete both input modules.
-    return TestFn(BD, New, ToNotOptimize);
+    return TestFn(BD, New, ToNotOptimize, Error);
   }
   delete ToOptimize;
   delete ToNotOptimize;
@@ -424,8 +472,10 @@ bool ReduceMiscompiledBlocks::TestFuncs(const std::vector<BasicBlock*> &BBs) {
 /// the bug.
 ///
 static bool ExtractBlocks(BugDriver &BD,
-                          bool (*TestFn)(BugDriver &, Module *, Module *),
-                          std::vector<Function*> &MiscompiledFunctions) {
+                          bool (*TestFn)(BugDriver &, Module *, Module *,
+                                         std::string &),
+                          std::vector<Function*> &MiscompiledFunctions,
+                          std::string &Error) {
   if (BugpointIsInterrupted) return false;
   
   std::vector<BasicBlock*> Blocks;
@@ -440,11 +490,17 @@ static bool ExtractBlocks(BugDriver &BD,
   unsigned OldSize = Blocks.size();
 
   // Check to see if all blocks are extractible first.
-  if (ReduceMiscompiledBlocks(BD, TestFn,
-                  MiscompiledFunctions).TestFuncs(std::vector<BasicBlock*>())) {
+  bool Ret = ReduceMiscompiledBlocks(BD, TestFn, MiscompiledFunctions)
+                                  .TestFuncs(std::vector<BasicBlock*>(), Error);
+  if (!Error.empty())
+    return false;
+  if (Ret) {
     Blocks.clear();
   } else {
-    ReduceMiscompiledBlocks(BD, TestFn,MiscompiledFunctions).reduceList(Blocks);
+    ReduceMiscompiledBlocks(BD, TestFn,
+                            MiscompiledFunctions).reduceList(Blocks, Error);
+    if (!Error.empty())
+      return false;
     if (Blocks.size() == OldSize)
       return false;
   }
@@ -505,7 +561,9 @@ static bool ExtractBlocks(BugDriver &BD,
 ///
 static std::vector<Function*>
 DebugAMiscompilation(BugDriver &BD,
-                     bool (*TestFn)(BugDriver &, Module *, Module *)) {
+                     bool (*TestFn)(BugDriver &, Module *, Module *,
+                                    std::string &),
+                     std::string &Error) {
   // Okay, now that we have reduced the list of passes which are causing the
   // failure, see if we can pin down which functions are being
   // miscompiled... first build a list of all of the non-external functions in
@@ -518,7 +576,10 @@ DebugAMiscompilation(BugDriver &BD,
 
   // Do the reduction...
   if (!BugpointIsInterrupted)
-    ReduceMiscompilingFunctions(BD, TestFn).reduceList(MiscompiledFunctions);
+    ReduceMiscompilingFunctions(BD, TestFn).reduceList(MiscompiledFunctions,
+                                                       Error);
+  if (!Error.empty())
+    return MiscompiledFunctions;
 
   outs() << "\n*** The following function"
          << (MiscompiledFunctions.size() == 1 ? " is" : "s are")
@@ -529,37 +590,51 @@ DebugAMiscompilation(BugDriver &BD,
   // See if we can rip any loops out of the miscompiled functions and still
   // trigger the problem.
 
-  if (!BugpointIsInterrupted && !DisableLoopExtraction &&
-      ExtractLoops(BD, TestFn, MiscompiledFunctions)) {
-    // Okay, we extracted some loops and the problem still appears.  See if we
-    // can eliminate some of the created functions from being candidates.
-    DisambiguateGlobalSymbols(BD.getProgram());
-
-    // Do the reduction...
-    if (!BugpointIsInterrupted)
-      ReduceMiscompilingFunctions(BD, TestFn).reduceList(MiscompiledFunctions);
-
-    outs() << "\n*** The following function"
-           << (MiscompiledFunctions.size() == 1 ? " is" : "s are")
-           << " being miscompiled: ";
-    PrintFunctionList(MiscompiledFunctions);
-    outs() << '\n';
+  if (!BugpointIsInterrupted && !DisableLoopExtraction) {
+    bool Ret = ExtractLoops(BD, TestFn, MiscompiledFunctions, Error);
+    if (!Error.empty())
+      return MiscompiledFunctions;
+    if (Ret) {
+      // Okay, we extracted some loops and the problem still appears.  See if
+      // we can eliminate some of the created functions from being candidates.
+      DisambiguateGlobalSymbols(BD.getProgram());
+
+      // Do the reduction...
+      if (!BugpointIsInterrupted)
+        ReduceMiscompilingFunctions(BD, TestFn).reduceList(MiscompiledFunctions,
+                                                           Error);
+      if (!Error.empty())
+        return MiscompiledFunctions;
+
+      outs() << "\n*** The following function"
+             << (MiscompiledFunctions.size() == 1 ? " is" : "s are")
+             << " being miscompiled: ";
+      PrintFunctionList(MiscompiledFunctions);
+      outs() << '\n';
+    }
   }
 
-  if (!BugpointIsInterrupted && !DisableBlockExtraction && 
-      ExtractBlocks(BD, TestFn, MiscompiledFunctions)) {
-    // Okay, we extracted some blocks and the problem still appears.  See if we
-    // can eliminate some of the created functions from being candidates.
-    DisambiguateGlobalSymbols(BD.getProgram());
-
-    // Do the reduction...
-    ReduceMiscompilingFunctions(BD, TestFn).reduceList(MiscompiledFunctions);
-
-    outs() << "\n*** The following function"
-           << (MiscompiledFunctions.size() == 1 ? " is" : "s are")
-           << " being miscompiled: ";
-    PrintFunctionList(MiscompiledFunctions);
-    outs() << '\n';
+  if (!BugpointIsInterrupted && !DisableBlockExtraction) {
+    bool Ret = ExtractBlocks(BD, TestFn, MiscompiledFunctions, Error);
+    if (!Error.empty())
+      return MiscompiledFunctions;
+    if (Ret) {
+      // Okay, we extracted some blocks and the problem still appears.  See if
+      // we can eliminate some of the created functions from being candidates.
+      DisambiguateGlobalSymbols(BD.getProgram());
+
+      // Do the reduction...
+      ReduceMiscompilingFunctions(BD, TestFn).reduceList(MiscompiledFunctions,
+                                                         Error);
+      if (!Error.empty())
+        return MiscompiledFunctions;
+
+      outs() << "\n*** The following function"
+             << (MiscompiledFunctions.size() == 1 ? " is" : "s are")
+             << " being miscompiled: ";
+      PrintFunctionList(MiscompiledFunctions);
+      outs() << '\n';
+    }
   }
 
   return MiscompiledFunctions;
@@ -569,7 +644,8 @@ DebugAMiscompilation(BugDriver &BD,
 /// "Test" portion of the program is misoptimized.  If so, return true.  In any
 /// case, both module arguments are deleted.
 ///
-static bool TestOptimizer(BugDriver &BD, Module *Test, Module *Safe) {
+static bool TestOptimizer(BugDriver &BD, Module *Test, Module *Safe,
+                          std::string &Error) {
   // Run the optimization passes on ToOptimize, producing a transformed version
   // of the functions being tested.
   outs() << "  Optimizing functions being tested: ";
@@ -579,8 +655,8 @@ static bool TestOptimizer(BugDriver &BD, Module *Test, Module *Safe) {
   delete Test;
 
   outs() << "  Checking to see if the merged program executes correctly: ";
-  bool Broken = TestMergedProgram(BD, Optimized, Safe, true);
-  outs() << (Broken ? " nope.\n" : " yup.\n");
+  bool Broken = TestMergedProgram(BD, Optimized, Safe, true, Error);
+  if (Error.empty()) outs() << (Broken ? " nope.\n" : " yup.\n");
   return Broken;
 }
 
@@ -589,13 +665,14 @@ static bool TestOptimizer(BugDriver &BD, Module *Test, Module *Safe) {
 /// crashing, but the generated output is semantically different from the
 /// input.
 ///
-bool BugDriver::debugMiscompilation() {
+void BugDriver::debugMiscompilation(std::string *Error) {
   // Make sure something was miscompiled...
   if (!BugpointIsInterrupted)
-    if (!ReduceMiscompilingPasses(*this).reduceList(PassesToRun)) {
-      errs() << "*** Optimized program matches reference output!  No problem"
-             << " detected...\nbugpoint can't help you with your problem!\n";
-      return false;
+    if (!ReduceMiscompilingPasses(*this).reduceList(PassesToRun, *Error)) {
+      if (Error->empty())
+        errs() << "*** Optimized program matches reference output!  No problem"
+               << " detected...\nbugpoint can't help you with your problem!\n";
+      return;
     }
 
   outs() << "\n*** Found miscompiling pass"
@@ -603,8 +680,10 @@ bool BugDriver::debugMiscompilation() {
          << getPassesString(getPassesToRun()) << '\n';
   EmitProgressBitcode("passinput");
 
-  std::vector<Function*> MiscompiledFunctions =
-    DebugAMiscompilation(*this, TestOptimizer);
+  std::vector<Function *> MiscompiledFunctions = 
+    DebugAMiscompilation(*this, TestOptimizer, *Error);
+  if (!Error->empty())
+    return;
 
   // Output a bunch of bitcode files for the user...
   outs() << "Outputting reduced bitcode files which expose the problem:\n";
@@ -624,7 +703,7 @@ bool BugDriver::debugMiscompilation() {
   EmitProgressBitcode("tooptimize");
   setNewProgram(ToOptimize);      // Delete hacked module.
 
-  return false;
+  return;
 }
 
 /// CleanupAndPrepareModules - Get the specified modules ready for code
@@ -797,7 +876,8 @@ static void CleanupAndPrepareModules(BugDriver &BD, Module *&Test,
 /// the "Test" portion of the program is miscompiled by the code generator under
 /// test.  If so, return true.  In any case, both module arguments are deleted.
 ///
-static bool TestCodeGenerator(BugDriver &BD, Module *Test, Module *Safe) {
+static bool TestCodeGenerator(BugDriver &BD, Module *Test, Module *Safe,
+                              std::string &Error) {
   CleanupAndPrepareModules(BD, Test, Safe);
 
   sys::Path TestModuleBC("bugpoint.test.bc");
@@ -827,12 +907,16 @@ static bool TestCodeGenerator(BugDriver &BD, Module *Test, Module *Safe) {
            << "'\nExiting.";
     exit(1);
   }
-  std::string SharedObject = BD.compileSharedObject(SafeModuleBC.str());
+  std::string SharedObject = BD.compileSharedObject(SafeModuleBC.str(), Error);
+  if (!Error.empty())
+    return -1;
   delete Safe;
 
   // Run the code generator on the `Test' code, loading the shared library.
   // The function returns whether or not the new output differs from reference.
-  int Result = BD.diffProgram(TestModuleBC.str(), SharedObject, false);
+  bool Result = BD.diffProgram(TestModuleBC.str(), SharedObject, false, &Error);
+  if (!Error.empty())
+    return false;
 
   if (Result)
     errs() << ": still failing!\n";
@@ -848,23 +932,28 @@ static bool TestCodeGenerator(BugDriver &BD, Module *Test, Module *Safe) {
 
 /// debugCodeGenerator - debug errors in LLC, LLI, or CBE.
 ///
-bool BugDriver::debugCodeGenerator() {
+bool BugDriver::debugCodeGenerator(std::string *Error) {
   if ((void*)SafeInterpreter == (void*)Interpreter) {
-    std::string Result = executeProgramSafely("bugpoint.safe.out");
-    outs() << "\n*** The \"safe\" i.e. 'known good' backend cannot match "
-           << "the reference diff.  This may be due to a\n    front-end "
-           << "bug or a bug in the original program, but this can also "
-           << "happen if bugpoint isn't running the program with the "
-           << "right flags or input.\n    I left the result of executing "
-           << "the program with the \"safe\" backend in this file for "
-           << "you: '"
-           << Result << "'.\n";
+    std::string Result = executeProgramSafely("bugpoint.safe.out", Error);
+    if (Error->empty()) {
+      outs() << "\n*** The \"safe\" i.e. 'known good' backend cannot match "
+             << "the reference diff.  This may be due to a\n    front-end "
+             << "bug or a bug in the original program, but this can also "
+             << "happen if bugpoint isn't running the program with the "
+             << "right flags or input.\n    I left the result of executing "
+             << "the program with the \"safe\" backend in this file for "
+             << "you: '"
+             << Result << "'.\n";
+    }
     return true;
   }
 
   DisambiguateGlobalSymbols(Program);
 
-  std::vector<Function*> Funcs = DebugAMiscompilation(*this, TestCodeGenerator);
+  std::vector<Function*> Funcs = DebugAMiscompilation(*this, TestCodeGenerator,
+                                                      *Error);
+  if (!Error->empty())
+    return true;
 
   // Split the module into the two halves of the program we want.
   DenseMap<const Value*, Value*> ValueMap;
@@ -902,7 +991,9 @@ bool BugDriver::debugCodeGenerator() {
            << "'\nExiting.";
     exit(1);
   }
-  std::string SharedObject = compileSharedObject(SafeModuleBC.str());
+  std::string SharedObject = compileSharedObject(SafeModuleBC.str(), *Error);
+  if (!Error->empty())
+    return true;
   delete ToNotCodeGen;
 
   outs() << "You can reproduce the problem with the command line: \n";
@@ -919,7 +1010,7 @@ bool BugDriver::debugCodeGenerator() {
     outs() << "\n";
     outs() << "  " << TestModuleBC.str() << ".exe";
   }
-  for (unsigned i=0, e = InputArgv.size(); i != e; ++i)
+  for (unsigned i = 0, e = InputArgv.size(); i != e; ++i)
     outs() << " " << InputArgv[i];
   outs() << '\n';
   outs() << "The shared object was created with:\n  llc -march=c "
diff --git a/tools/bugpoint/ToolRunner.cpp b/tools/bugpoint/ToolRunner.cpp
index 62df0f1..9c8c2f9 100644
--- a/tools/bugpoint/ToolRunner.cpp
+++ b/tools/bugpoint/ToolRunner.cpp
@@ -50,11 +50,9 @@ namespace {
           cl::desc("Remote execution (rsh/ssh) extra options"));
 }
 
-ToolExecutionError::~ToolExecutionError() throw() { }
-
 /// RunProgramWithTimeout - This function provides an alternate interface
 /// to the sys::Program::ExecuteAndWait interface.
-/// @see sys:Program::ExecuteAndWait
+/// @see sys::Program::ExecuteAndWait
 static int RunProgramWithTimeout(const sys::Path &ProgramPath,
                                  const char **Args,
                                  const sys::Path &StdInFile,
@@ -86,7 +84,7 @@ static int RunProgramWithTimeout(const sys::Path &ProgramPath,
 /// Returns the remote program exit code or reports a remote client error if it
 /// fails. Remote client is required to return 255 if it failed or program exit
 /// code otherwise.
-/// @see sys:Program::ExecuteAndWait
+/// @see sys::Program::ExecuteAndWait
 static int RunProgramRemotelyWithTimeout(const sys::Path &RemoteClientPath,
                                          const char **Args,
                                          const sys::Path &StdInFile,
@@ -129,13 +127,13 @@ static int RunProgramRemotelyWithTimeout(const sys::Path &RemoteClientPath,
       ErrorFile.close();
     }
 
-    throw ToolExecutionError(OS.str());
+    errs() << OS;
   }
 
   return ReturnCode;
 }
 
-static void ProcessFailure(sys::Path ProgPath, const char** Args) {
+static std::string ProcessFailure(sys::Path ProgPath, const char** Args) {
   std::ostringstream OS;
   OS << "\nError running tool:\n ";
   for (const char **Arg = Args; *Arg; ++Arg)
@@ -162,7 +160,7 @@ static void ProcessFailure(sys::Path ProgPath, const char** Args) {
   }
 
   ErrorFilename.eraseFromDisk();
-  throw ToolExecutionError(OS.str());
+  return OS.str();
 }
 
 //===---------------------------------------------------------------------===//
@@ -183,6 +181,7 @@ namespace {
                                const std::vector<std::string> &Args,
                                const std::string &InputFile,
                                const std::string &OutputFile,
+                               std::string *Error,
                                const std::vector<std::string> &GCCArgs,
                                const std::vector<std::string> &SharedLibs =
                                std::vector<std::string>(),
@@ -195,6 +194,7 @@ int LLI::ExecuteProgram(const std::string &Bitcode,
                         const std::vector<std::string> &Args,
                         const std::string &InputFile,
                         const std::string &OutputFile,
+                        std::string *Error,
                         const std::vector<std::string> &GCCArgs,
                         const std::vector<std::string> &SharedLibs,
                         unsigned Timeout,
@@ -263,9 +263,10 @@ namespace {
                                const std::vector<std::string> &Args,
                                const std::string &InputFile,
                                const std::string &OutputFile,
+                               std::string *Error,
                                const std::vector<std::string> &GCCArgs,
                                const std::vector<std::string> &SharedLibs =
-                               std::vector<std::string>(),
+                                 std::vector<std::string>(),
                                unsigned Timeout = 0,
                                unsigned MemoryLimit = 0);
   };
@@ -275,6 +276,7 @@ int CustomExecutor::ExecuteProgram(const std::string &Bitcode,
                         const std::vector<std::string> &Args,
                         const std::string &InputFile,
                         const std::string &OutputFile,
+                        std::string *Error,
                         const std::vector<std::string> &GCCArgs,
                         const std::vector<std::string> &SharedLibs,
                         unsigned Timeout,
@@ -289,7 +291,7 @@ int CustomExecutor::ExecuteProgram(const std::string &Bitcode,
   ProgramArgs.push_back(0);
 
   // Add optional parameters to the running program from Argv
-  for (unsigned i=0, e = Args.size(); i != e; ++i)
+  for (unsigned i = 0, e = Args.size(); i != e; ++i)
     ProgramArgs.push_back(Args[i].c_str());
 
   return RunProgramWithTimeout(
@@ -351,7 +353,7 @@ AbstractInterpreter *AbstractInterpreter::createCustom(
 // LLC Implementation of AbstractIntepreter interface
 //
 GCC::FileType LLC::OutputCode(const std::string &Bitcode, 
-                              sys::Path &OutputAsmFile) {
+                              sys::Path &OutputAsmFile, std::string &Error) {
   const char *Suffix = (UseIntegratedAssembler ? ".llc.o" : ".llc.s");
   sys::Path uniqueFile(Bitcode + Suffix);
   std::string ErrMsg;
@@ -379,20 +381,19 @@ GCC::FileType LLC::OutputCode(const std::string &Bitcode,
   outs() << (UseIntegratedAssembler ? "<llc-ia>" : "<llc>");
   outs().flush();
   DEBUG(errs() << "\nAbout to run:\t";
-        for (unsigned i=0, e = LLCArgs.size()-1; i != e; ++i)
+        for (unsigned i = 0, e = LLCArgs.size()-1; i != e; ++i)
           errs() << " " << LLCArgs[i];
         errs() << "\n";
         );
   if (RunProgramWithTimeout(sys::Path(LLCPath), &LLCArgs[0],
                             sys::Path(), sys::Path(), sys::Path()))
-    ProcessFailure(sys::Path(LLCPath), &LLCArgs[0]);
-
-  return UseIntegratedAssembler ? GCC::ObjectFile : GCC::AsmFile;
+    Error = ProcessFailure(sys::Path(LLCPath), &LLCArgs[0]);
+  return UseIntegratedAssembler ? GCC::ObjectFile : GCC::AsmFile;  
 }
 
-void LLC::compileProgram(const std::string &Bitcode) {
+void LLC::compileProgram(const std::string &Bitcode, std::string *Error) {
   sys::Path OutputAsmFile;
-  OutputCode(Bitcode, OutputAsmFile);
+  OutputCode(Bitcode, OutputAsmFile, *Error);
   OutputAsmFile.eraseFromDisk();
 }
 
@@ -400,13 +401,14 @@ int LLC::ExecuteProgram(const std::string &Bitcode,
                         const std::vector<std::string> &Args,
                         const std::string &InputFile,
                         const std::string &OutputFile,
+                        std::string *Error,
                         const std::vector<std::string> &ArgsForGCC,
                         const std::vector<std::string> &SharedLibs,
                         unsigned Timeout,
                         unsigned MemoryLimit) {
 
   sys::Path OutputAsmFile;
-  GCC::FileType FileKind = OutputCode(Bitcode, OutputAsmFile);
+  GCC::FileType FileKind = OutputCode(Bitcode, OutputAsmFile, *Error);
   FileRemover OutFileRemover(OutputAsmFile, !SaveTemps);
 
   std::vector<std::string> GCCArgs(ArgsForGCC);
@@ -415,7 +417,7 @@ int LLC::ExecuteProgram(const std::string &Bitcode,
 
   // Assuming LLC worked, compile the result with GCC and run it.
   return gcc->ExecuteProgram(OutputAsmFile.str(), Args, FileKind,
-                             InputFile, OutputFile, GCCArgs,
+                             InputFile, OutputFile, Error, GCCArgs,
                              Timeout, MemoryLimit);
 }
 
@@ -460,12 +462,13 @@ namespace {
                                const std::vector<std::string> &Args,
                                const std::string &InputFile,
                                const std::string &OutputFile,
+                               std::string *Error,
                                const std::vector<std::string> &GCCArgs =
                                  std::vector<std::string>(),
                                const std::vector<std::string> &SharedLibs =
                                  std::vector<std::string>(), 
-                               unsigned Timeout =0,
-                               unsigned MemoryLimit =0);
+                               unsigned Timeout = 0,
+                               unsigned MemoryLimit = 0);
   };
 }
 
@@ -473,6 +476,7 @@ int JIT::ExecuteProgram(const std::string &Bitcode,
                         const std::vector<std::string> &Args,
                         const std::string &InputFile,
                         const std::string &OutputFile,
+                        std::string *Error,
                         const std::vector<std::string> &GCCArgs,
                         const std::vector<std::string> &SharedLibs,
                         unsigned Timeout,
@@ -524,7 +528,7 @@ AbstractInterpreter *AbstractInterpreter::createJIT(const char *Argv0,
 }
 
 GCC::FileType CBE::OutputCode(const std::string &Bitcode,
-                              sys::Path &OutputCFile) {
+                              sys::Path &OutputCFile, std::string &Error) {
   sys::Path uniqueFile(Bitcode+".cbe.c");
   std::string ErrMsg;
   if (uniqueFile.makeUnique(true, &ErrMsg)) {
@@ -533,34 +537,34 @@ GCC::FileType CBE::OutputCode(const std::string &Bitcode,
   }
   OutputCFile = uniqueFile;
   std::vector<const char *> LLCArgs;
-  LLCArgs.push_back (LLCPath.c_str());
+  LLCArgs.push_back(LLCPath.c_str());
 
   // Add any extra LLC args.
   for (unsigned i = 0, e = ToolArgs.size(); i != e; ++i)
     LLCArgs.push_back(ToolArgs[i].c_str());
 
-  LLCArgs.push_back ("-o");
-  LLCArgs.push_back (OutputCFile.c_str());   // Output to the C file
-  LLCArgs.push_back ("-march=c");            // Output C language
-  LLCArgs.push_back ("-f");                  // Overwrite as necessary...
-  LLCArgs.push_back (Bitcode.c_str());      // This is the input bitcode
-  LLCArgs.push_back (0);
+  LLCArgs.push_back("-o");
+  LLCArgs.push_back(OutputCFile.c_str());   // Output to the C file
+  LLCArgs.push_back("-march=c");            // Output C language
+  LLCArgs.push_back("-f");                  // Overwrite as necessary...
+  LLCArgs.push_back(Bitcode.c_str());      // This is the input bitcode
+  LLCArgs.push_back(0);
 
   outs() << "<cbe>"; outs().flush();
   DEBUG(errs() << "\nAbout to run:\t";
-        for (unsigned i=0, e = LLCArgs.size()-1; i != e; ++i)
+        for (unsigned i = 0, e = LLCArgs.size()-1; i != e; ++i)
           errs() << " " << LLCArgs[i];
         errs() << "\n";
         );
   if (RunProgramWithTimeout(LLCPath, &LLCArgs[0], sys::Path(), sys::Path(),
                             sys::Path()))
-    ProcessFailure(LLCPath, &LLCArgs[0]);
+    Error = ProcessFailure(LLCPath, &LLCArgs[0]);
   return GCC::CFile;
 }
 
-void CBE::compileProgram(const std::string &Bitcode) {
+void CBE::compileProgram(const std::string &Bitcode, std::string *Error) {
   sys::Path OutputCFile;
-  OutputCode(Bitcode, OutputCFile);
+  OutputCode(Bitcode, OutputCFile, *Error);
   OutputCFile.eraseFromDisk();
 }
 
@@ -568,12 +572,13 @@ int CBE::ExecuteProgram(const std::string &Bitcode,
                         const std::vector<std::string> &Args,
                         const std::string &InputFile,
                         const std::string &OutputFile,
+                        std::string *Error,
                         const std::vector<std::string> &ArgsForGCC,
                         const std::vector<std::string> &SharedLibs,
                         unsigned Timeout,
                         unsigned MemoryLimit) {
   sys::Path OutputCFile;
-  OutputCode(Bitcode, OutputCFile);
+  OutputCode(Bitcode, OutputCFile, *Error);
 
   FileRemover CFileRemove(OutputCFile, !SaveTemps);
 
@@ -581,7 +586,7 @@ int CBE::ExecuteProgram(const std::string &Bitcode,
   GCCArgs.insert(GCCArgs.end(), SharedLibs.begin(), SharedLibs.end());
 
   return gcc->ExecuteProgram(OutputCFile.str(), Args, GCC::CFile,
-                             InputFile, OutputFile, GCCArgs,
+                             InputFile, OutputFile, Error, GCCArgs,
                              Timeout, MemoryLimit);
 }
 
@@ -631,6 +636,7 @@ int GCC::ExecuteProgram(const std::string &ProgramFile,
                         FileType fileType,
                         const std::string &InputFile,
                         const std::string &OutputFile,
+                        std::string *Error,
                         const std::vector<std::string> &ArgsForGCC,
                         unsigned Timeout,
                         unsigned MemoryLimit) {
@@ -694,14 +700,14 @@ int GCC::ExecuteProgram(const std::string &ProgramFile,
 
   outs() << "<gcc>"; outs().flush();
   DEBUG(errs() << "\nAbout to run:\t";
-        for (unsigned i=0, e = GCCArgs.size()-1; i != e; ++i)
+        for (unsigned i = 0, e = GCCArgs.size()-1; i != e; ++i)
           errs() << " " << GCCArgs[i];
         errs() << "\n";
         );
   if (RunProgramWithTimeout(GCCPath, &GCCArgs[0], sys::Path(), sys::Path(),
         sys::Path())) {
-    ProcessFailure(GCCPath, &GCCArgs[0]);
-    exit(1);
+    *Error = ProcessFailure(GCCPath, &GCCArgs[0]);
+    return -1;
   }
 
   std::vector<const char*> ProgramArgs;
@@ -734,14 +740,14 @@ int GCC::ExecuteProgram(const std::string &ProgramFile,
   }
 
   // Add optional parameters to the running program from Argv
-  for (unsigned i=0, e = Args.size(); i != e; ++i)
+  for (unsigned i = 0, e = Args.size(); i != e; ++i)
     ProgramArgs.push_back(Args[i].c_str());
   ProgramArgs.push_back(0);                // NULL terminator
 
   // Now that we have a binary, run it!
   outs() << "<program>"; outs().flush();
   DEBUG(errs() << "\nAbout to run:\t";
-        for (unsigned i=0, e = ProgramArgs.size()-1; i != e; ++i)
+        for (unsigned i = 0, e = ProgramArgs.size()-1; i != e; ++i)
           errs() << " " << ProgramArgs[i];
         errs() << "\n";
         );
@@ -749,7 +755,7 @@ int GCC::ExecuteProgram(const std::string &ProgramFile,
   FileRemover OutputBinaryRemover(OutputBinary, !SaveTemps);
 
   if (RemoteClientPath.isEmpty()) {
-    DEBUG(errs() << "<run locally>";);
+    DEBUG(errs() << "<run locally>");
     return RunProgramWithTimeout(OutputBinary, &ProgramArgs[0],
         sys::Path(InputFile), sys::Path(OutputFile), sys::Path(OutputFile),
         Timeout, MemoryLimit);
@@ -763,7 +769,8 @@ int GCC::ExecuteProgram(const std::string &ProgramFile,
 
 int GCC::MakeSharedObject(const std::string &InputFile, FileType fileType,
                           std::string &OutputFile,
-                          const std::vector<std::string> &ArgsForGCC) {
+                          const std::vector<std::string> &ArgsForGCC,
+                          std::string &Error) {
   sys::Path uniqueFilename(InputFile+LTDL_SHLIB_EXT);
   std::string ErrMsg;
   if (uniqueFilename.makeUnique(true, &ErrMsg)) {
@@ -831,13 +838,13 @@ int GCC::MakeSharedObject(const std::string &InputFile, FileType fileType,
 
   outs() << "<gcc>"; outs().flush();
   DEBUG(errs() << "\nAbout to run:\t";
-        for (unsigned i=0, e = GCCArgs.size()-1; i != e; ++i)
+        for (unsigned i = 0, e = GCCArgs.size()-1; i != e; ++i)
           errs() << " " << GCCArgs[i];
         errs() << "\n";
         );
   if (RunProgramWithTimeout(GCCPath, &GCCArgs[0], sys::Path(), sys::Path(),
                             sys::Path())) {
-    ProcessFailure(GCCPath, &GCCArgs[0]);
+    Error = ProcessFailure(GCCPath, &GCCArgs[0]);
     return 1;
   }
   return 0;
diff --git a/tools/bugpoint/ToolRunner.h b/tools/bugpoint/ToolRunner.h
index 0f75e99..cba10f2 100644
--- a/tools/bugpoint/ToolRunner.h
+++ b/tools/bugpoint/ToolRunner.h
@@ -19,6 +19,7 @@
 
 #include "llvm/ADT/Triple.h"
 #include "llvm/Support/CommandLine.h"
+#include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/SystemUtils.h"
 #include "llvm/System/Path.h"
 #include <exception>
@@ -32,19 +33,6 @@ extern Triple TargetTriple;
 class CBE;
 class LLC;
 
-/// ToolExecutionError - An instance of this class is thrown by the
-/// AbstractInterpreter instances if there is an error running a tool (e.g., LLC
-/// crashes) which prevents execution of the program.
-///
-class ToolExecutionError : std::exception {
-  std::string Message;
-public:
-  explicit ToolExecutionError(const std::string &M) : Message(M) {}
-  virtual ~ToolExecutionError() throw();
-  virtual const char* what() const throw() { return Message.c_str(); }
-};
-
-
 //===---------------------------------------------------------------------===//
 // GCC abstraction
 //
@@ -75,6 +63,7 @@ public:
                      FileType fileType,
                      const std::string &InputFile,
                      const std::string &OutputFile,
+		     std::string *Error = 0,
                      const std::vector<std::string> &GCCArgs =
                          std::vector<std::string>(), 
                      unsigned Timeout = 0,
@@ -85,7 +74,8 @@ public:
   ///
   int MakeSharedObject(const std::string &InputFile, FileType fileType,
                        std::string &OutputFile,
-                       const std::vector<std::string> &ArgsForGCC);
+                       const std::vector<std::string> &ArgsForGCC,
+                       std::string &Error);
 };
 
 
@@ -118,26 +108,29 @@ public:
 
   /// compileProgram - Compile the specified program from bitcode to executable
   /// code.  This does not produce any output, it is only used when debugging
-  /// the code generator.  If the code generator fails, an exception should be
-  /// thrown, otherwise, this function will just return.
-  virtual void compileProgram(const std::string &Bitcode) {}
+  /// the code generator.  It returns false if the code generator fails.
+  virtual void compileProgram(const std::string &Bitcode, std::string *Error) {}
 
   /// OutputCode - Compile the specified program from bitcode to code
   /// understood by the GCC driver (either C or asm).  If the code generator
-  /// fails, an exception should be thrown, otherwise, this function returns the
-  /// type of code emitted.
+  /// fails, it sets Error, otherwise, this function returns the type of code
+  /// emitted.
   virtual GCC::FileType OutputCode(const std::string &Bitcode,
-                                   sys::Path &OutFile) {
-    throw std::string("OutputCode not supported by this AbstractInterpreter!");
+                                   sys::Path &OutFile, std::string &Error) {
+    Error = "OutputCode not supported by this AbstractInterpreter!";
+    return GCC::AsmFile;
   }
-  
+
   /// ExecuteProgram - Run the specified bitcode file, emitting output to the
-  /// specified filename.  This returns the exit code of the program.
+  /// specified filename.  This sets RetVal to the exit code of the program or
+  /// returns false if a problem was encountered that prevented execution of
+  /// the program.
   ///
   virtual int ExecuteProgram(const std::string &Bitcode,
                              const std::vector<std::string> &Args,
                              const std::string &InputFile,
                              const std::string &OutputFile,
+                             std::string *Error,
                              const std::vector<std::string> &GCCArgs =
                                std::vector<std::string>(),
                              const std::vector<std::string> &SharedLibs =
@@ -164,14 +157,14 @@ public:
 
   /// compileProgram - Compile the specified program from bitcode to executable
   /// code.  This does not produce any output, it is only used when debugging
-  /// the code generator.  If the code generator fails, an exception should be
-  /// thrown, otherwise, this function will just return.
-  virtual void compileProgram(const std::string &Bitcode);
+  /// the code generator.  Returns false if the code generator fails.
+  virtual void compileProgram(const std::string &Bitcode, std::string *Error);
 
   virtual int ExecuteProgram(const std::string &Bitcode,
                              const std::vector<std::string> &Args,
                              const std::string &InputFile,
                              const std::string &OutputFile,
+                             std::string *Error,
                              const std::vector<std::string> &GCCArgs =
                                std::vector<std::string>(),
                              const std::vector<std::string> &SharedLibs =
@@ -181,10 +174,10 @@ public:
 
   /// OutputCode - Compile the specified program from bitcode to code
   /// understood by the GCC driver (either C or asm).  If the code generator
-  /// fails, an exception should be thrown, otherwise, this function returns the
-  /// type of code emitted.
+  /// fails, it sets Error, otherwise, this function returns the type of code
+  /// emitted.
   virtual GCC::FileType OutputCode(const std::string &Bitcode,
-                                   sys::Path &OutFile);
+                                   sys::Path &OutFile, std::string &Error);
 };
 
 
@@ -212,14 +205,14 @@ public:
 
   /// compileProgram - Compile the specified program from bitcode to executable
   /// code.  This does not produce any output, it is only used when debugging
-  /// the code generator.  If the code generator fails, an exception should be
-  /// thrown, otherwise, this function will just return.
-  virtual void compileProgram(const std::string &Bitcode);
+  /// the code generator.  Returns false if the code generator fails.
+  virtual void compileProgram(const std::string &Bitcode, std::string *Error);
 
   virtual int ExecuteProgram(const std::string &Bitcode,
                              const std::vector<std::string> &Args,
                              const std::string &InputFile,
                              const std::string &OutputFile,
+                             std::string *Error,
                              const std::vector<std::string> &GCCArgs =
                                std::vector<std::string>(),
                              const std::vector<std::string> &SharedLibs =
@@ -227,9 +220,12 @@ public:
                              unsigned Timeout = 0,
                              unsigned MemoryLimit = 0);
 
+  /// OutputCode - Compile the specified program from bitcode to code
+  /// understood by the GCC driver (either C or asm).  If the code generator
+  /// fails, it sets Error, otherwise, this function returns the type of code
+  /// emitted.
   virtual GCC::FileType OutputCode(const std::string &Bitcode,
-                                   sys::Path &OutFile);
-  
+                                   sys::Path &OutFile, std::string &Error);
 };
 
 } // End llvm namespace
diff --git a/tools/bugpoint/bugpoint.cpp b/tools/bugpoint/bugpoint.cpp
index e14f31e..ba5234b 100644
--- a/tools/bugpoint/bugpoint.cpp
+++ b/tools/bugpoint/bugpoint.cpp
@@ -149,23 +149,11 @@ int main(int argc, char **argv) {
   // avoid filling up the disk, we prevent it
   sys::Process::PreventCoreFiles();
 
-  try {
-    return D.run();
-  } catch (ToolExecutionError &TEE) {
-    errs() << "Tool execution error: " << TEE.what() << '\n';
-  } catch (const std::string& msg) {
-    errs() << argv[0] << ": " << msg << "\n";
-  } catch (const std::bad_alloc&) {
-    errs() << "Oh no, a bugpoint process ran out of memory!\n"
-              "To increase the allocation limits for bugpoint child\n"
-              "processes, use the -mlimit option.\n";
-  } catch (const std::exception &e) {
-    errs() << "Whoops, a std::exception leaked out of bugpoint: "
-           << e.what() << "\n"
-           << "This is a bug in bugpoint!\n";
-  } catch (...) {
-    errs() << "Whoops, an exception leaked out of bugpoint.  "
-           << "This is a bug in bugpoint!\n";
+  std::string Error;
+  bool Failure = D.run(Error);
+  if (!Error.empty()) {
+    errs() << Error;
+    return 1;
   }
-  return 1;
+  return Failure;
 }