vendor/llvm/llvm-r72732

1 files changed, 932 insertions, 0 deletions

diff --git a/tools/bugpoint/Miscompilation.cpp b/tools/bugpoint/Miscompilation.cpp
new file mode 100644
index 000000000000..7e8ff78a9cf2
--- /dev/null
+++ b/tools/bugpoint/Miscompilation.cpp
@@ -0,0 +1,932 @@
+//===- Miscompilation.cpp - Debug program miscompilations -----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements optimizer and code generation miscompilation debugging
+// support.
+//
+//===----------------------------------------------------------------------===//
+
+#include "BugDriver.h"
+#include "ListReducer.h"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Instructions.h"
+#include "llvm/Linker.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/Support/Mangler.h"
+#include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/FileUtilities.h"
+#include "llvm/Config/config.h"   // for HAVE_LINK_R
+using namespace llvm;
+
+namespace llvm {
+  extern cl::list<std::string> InputArgv;
+}
+
+namespace {
+  static llvm::cl::opt<bool> 
+    DisableLoopExtraction("disable-loop-extraction", 
+        cl::desc("Don't extract loops when searching for miscompilations"),
+        cl::init(false));
+
+  class ReduceMiscompilingPasses : public ListReducer<const PassInfo*> {
+    BugDriver &BD;
+  public:
+    ReduceMiscompilingPasses(BugDriver &bd) : BD(bd) {}
+
+    virtual TestResult doTest(std::vector<const PassInfo*> &Prefix,
+                              std::vector<const PassInfo*> &Suffix);
+  };
+}
+
+/// TestResult - After passes have been split into a test group and a control
+/// group, see if they still break the program.
+///
+ReduceMiscompilingPasses::TestResult
+ReduceMiscompilingPasses::doTest(std::vector<const PassInfo*> &Prefix,
+                                 std::vector<const PassInfo*> &Suffix) {
+  // First, run the program with just the Suffix passes.  If it is still broken
+  // with JUST the kept passes, discard the prefix passes.
+  std::cout << "Checking to see if '" << getPassesString(Suffix)
+            << "' compile correctly: ";
+
+  std::string BitcodeResult;
+  if (BD.runPasses(Suffix, BitcodeResult, false/*delete*/, true/*quiet*/)) {
+    std::cerr << " Error running this sequence of passes"
+              << " on the input program!\n";
+    BD.setPassesToRun(Suffix);
+    BD.EmitProgressBitcode("pass-error",  false);
+    exit(BD.debugOptimizerCrash());
+  }
+
+  // Check to see if the finished program matches the reference output...
+  if (BD.diffProgram(BitcodeResult, "", true /*delete bitcode*/)) {
+    std::cout << " nope.\n";
+    if (Suffix.empty()) {
+      std::cerr << BD.getToolName() << ": I'm confused: the test fails when "
+                << "no passes are run, nondeterministic program?\n";
+      exit(1);
+    }
+    return KeepSuffix;         // Miscompilation detected!
+  }
+  std::cout << " yup.\n";      // No miscompilation!
+
+  if (Prefix.empty()) return NoFailure;
+
+  // Next, see if the program is broken if we run the "prefix" passes first,
+  // then separately run the "kept" passes.
+  std::cout << "Checking to see if '" << getPassesString(Prefix)
+            << "' compile correctly: ";
+
+  // If it is not broken with the kept passes, it's possible that the prefix
+  // passes must be run before the kept passes to break it.  If the program
+  // WORKS after the prefix passes, but then fails if running the prefix AND
+  // kept passes, we can update our bitcode file to include the result of the
+  // prefix passes, then discard the prefix passes.
+  //
+  if (BD.runPasses(Prefix, BitcodeResult, false/*delete*/, true/*quiet*/)) {
+    std::cerr << " Error running this sequence of passes"
+              << " on the input program!\n";
+    BD.setPassesToRun(Prefix);
+    BD.EmitProgressBitcode("pass-error",  false);
+    exit(BD.debugOptimizerCrash());
+  }
+
+  // If the prefix maintains the predicate by itself, only keep the prefix!
+  if (BD.diffProgram(BitcodeResult)) {
+    std::cout << " nope.\n";
+    sys::Path(BitcodeResult).eraseFromDisk();
+    return KeepPrefix;
+  }
+  std::cout << " yup.\n";      // No miscompilation!
+
+  // Ok, so now we know that the prefix passes work, try running the suffix
+  // passes on the result of the prefix passes.
+  //
+  Module *PrefixOutput = ParseInputFile(BitcodeResult);
+  if (PrefixOutput == 0) {
+    std::cerr << BD.getToolName() << ": Error reading bitcode file '"
+              << BitcodeResult << "'!\n";
+    exit(1);
+  }
+  sys::Path(BitcodeResult).eraseFromDisk();  // No longer need the file on disk
+
+  // Don't check if there are no passes in the suffix.
+  if (Suffix.empty())
+    return NoFailure;
+
+  std::cout << "Checking to see if '" << getPassesString(Suffix)
+            << "' passes compile correctly after the '"
+            << getPassesString(Prefix) << "' passes: ";
+
+  Module *OriginalInput = BD.swapProgramIn(PrefixOutput);
+  if (BD.runPasses(Suffix, BitcodeResult, false/*delete*/, true/*quiet*/)) {
+    std::cerr << " Error running this sequence of passes"
+              << " on the input program!\n";
+    BD.setPassesToRun(Suffix);
+    BD.EmitProgressBitcode("pass-error",  false);
+    exit(BD.debugOptimizerCrash());
+  }
+
+  // Run the result...
+  if (BD.diffProgram(BitcodeResult, "", true/*delete bitcode*/)) {
+    std::cout << " nope.\n";
+    delete OriginalInput;     // We pruned down the original input...
+    return KeepSuffix;
+  }
+
+  // Otherwise, we must not be running the bad pass anymore.
+  std::cout << " yup.\n";      // No miscompilation!
+  delete BD.swapProgramIn(OriginalInput); // Restore orig program & free test
+  return NoFailure;
+}
+
+namespace {
+  class ReduceMiscompilingFunctions : public ListReducer<Function*> {
+    BugDriver &BD;
+    bool (*TestFn)(BugDriver &, Module *, Module *);
+  public:
+    ReduceMiscompilingFunctions(BugDriver &bd,
+                                bool (*F)(BugDriver &, Module *, Module *))
+      : 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;
+      return NoFailure;
+    }
+
+    bool TestFuncs(const std::vector<Function*> &Prefix);
+  };
+}
+
+/// TestMergedProgram - Given two modules, link them together and run the
+/// program, checking to see if the program matches the diff.  If the diff
+/// matches, return false, otherwise return true.  If the DeleteInputs argument
+/// is set to true then this function deletes both input modules before it
+/// returns.
+///
+static bool TestMergedProgram(BugDriver &BD, Module *M1, Module *M2,
+                              bool DeleteInputs) {
+  // Link the two portions of the program back to together.
+  std::string ErrorMsg;
+  if (!DeleteInputs) {
+    M1 = CloneModule(M1);
+    M2 = CloneModule(M2);
+  }
+  if (Linker::LinkModules(M1, M2, &ErrorMsg)) {
+    std::cerr << BD.getToolName() << ": Error linking modules together:"
+              << ErrorMsg << '\n';
+    exit(1);
+  }
+  delete M2;   // We are done with this module.
+
+  Module *OldProgram = BD.swapProgramIn(M1);
+
+  // 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;
+  return Broken;
+}
+
+/// TestFuncs - split functions in a Module into two groups: those that are
+/// 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){
+  // Test to see if the function is misoptimized if we ONLY run it on the
+  // functions listed in Funcs.
+  std::cout << "Checking to see if the program is misoptimized when "
+            << (Funcs.size()==1 ? "this function is" : "these functions are")
+            << " run through the pass"
+            << (BD.getPassesToRun().size() == 1 ? "" : "es") << ":";
+  PrintFunctionList(Funcs);
+  std::cout << '\n';
+
+  // Split the module into the two halves of the program we want.
+  DenseMap<const Value*, Value*> ValueMap;
+  Module *ToNotOptimize = CloneModule(BD.getProgram(), ValueMap);
+  Module *ToOptimize = SplitFunctionsOutOfModule(ToNotOptimize, Funcs,
+                                                 ValueMap);
+
+  // Run the predicate, note that the predicate will delete both input modules.
+  return TestFn(BD, ToOptimize, ToNotOptimize);
+}
+
+/// DisambiguateGlobalSymbols - Mangle symbols to guarantee uniqueness by
+/// modifying predominantly internal symbols rather than external ones.
+///
+static void DisambiguateGlobalSymbols(Module *M) {
+  // Try not to cause collisions by minimizing chances of renaming an
+  // already-external symbol, so take in external globals and functions as-is.
+  // The code should work correctly without disambiguation (assuming the same
+  // mangler is used by the two code generators), but having symbols with the
+  // same name causes warnings to be emitted by the code generator.
+  Mangler Mang(*M);
+  // Agree with the CBE on symbol naming
+  Mang.markCharUnacceptable('.');
+  Mang.setPreserveAsmNames(true);
+  for (Module::global_iterator I = M->global_begin(), E = M->global_end();
+       I != E; ++I)
+    I->setName(Mang.getValueName(I));
+  for (Module::iterator  I = M->begin(),  E = M->end();  I != E; ++I)
+    I->setName(Mang.getValueName(I));
+}
+
+/// ExtractLoops - Given a reduced list of functions that still exposed the bug,
+/// check to see if we can extract the loops in the region without obscuring the
+/// 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 MadeChange = false;
+  while (1) {
+    if (BugpointIsInterrupted) return MadeChange;
+    
+    DenseMap<const Value*, Value*> ValueMap;
+    Module *ToNotOptimize = CloneModule(BD.getProgram(), ValueMap);
+    Module *ToOptimize = SplitFunctionsOutOfModule(ToNotOptimize,
+                                                   MiscompiledFunctions,
+                                                   ValueMap);
+    Module *ToOptimizeLoopExtracted = BD.ExtractLoop(ToOptimize);
+    if (!ToOptimizeLoopExtracted) {
+      // If the loop extractor crashed or if there were no extractible loops,
+      // then this chapter of our odyssey is over with.
+      delete ToNotOptimize;
+      delete ToOptimize;
+      return MadeChange;
+    }
+
+    std::cerr << "Extracted a loop from the breaking portion of the program.\n";
+
+    // Bugpoint is intentionally not very trusting of LLVM transformations.  In
+    // particular, we're not going to assume that the loop extractor works, so
+    // we're going to test the newly loop extracted program to make sure nothing
+    // has broken.  If something broke, then we'll inform the user and stop
+    // extraction.
+    AbstractInterpreter *AI = BD.switchToSafeInterpreter();
+    if (TestMergedProgram(BD, ToOptimizeLoopExtracted, ToNotOptimize, false)) {
+      BD.switchToInterpreter(AI);
+
+      // Merged program doesn't work anymore!
+      std::cerr << "  *** ERROR: Loop extraction broke the program. :("
+                << " Please report a bug!\n";
+      std::cerr << "      Continuing on with un-loop-extracted version.\n";
+
+      BD.writeProgramToFile("bugpoint-loop-extract-fail-tno.bc", ToNotOptimize);
+      BD.writeProgramToFile("bugpoint-loop-extract-fail-to.bc", ToOptimize);
+      BD.writeProgramToFile("bugpoint-loop-extract-fail-to-le.bc",
+                            ToOptimizeLoopExtracted);
+
+      std::cerr << "Please submit the bugpoint-loop-extract-fail-*.bc files.\n";
+      delete ToOptimize;
+      delete ToNotOptimize;
+      delete ToOptimizeLoopExtracted;
+      return MadeChange;
+    }
+    delete ToOptimize;
+    BD.switchToInterpreter(AI);
+
+    std::cout << "  Testing after loop extraction:\n";
+    // Clone modules, the tester function will free them.
+    Module *TOLEBackup = CloneModule(ToOptimizeLoopExtracted);
+    Module *TNOBackup  = CloneModule(ToNotOptimize);
+    if (!TestFn(BD, ToOptimizeLoopExtracted, ToNotOptimize)) {
+      std::cout << "*** 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.
+      delete TOLEBackup;
+      delete TNOBackup;
+      return MadeChange;
+    }
+    ToOptimizeLoopExtracted = TOLEBackup;
+    ToNotOptimize = TNOBackup;
+
+    std::cout << "*** Loop extraction successful!\n";
+
+    std::vector<std::pair<std::string, const FunctionType*> > MisCompFunctions;
+    for (Module::iterator I = ToOptimizeLoopExtracted->begin(),
+           E = ToOptimizeLoopExtracted->end(); I != E; ++I)
+      if (!I->isDeclaration())
+        MisCompFunctions.push_back(std::make_pair(I->getName(),
+                                                  I->getFunctionType()));
+
+    // Okay, great!  Now we know that we extracted a loop and that loop
+    // extraction both didn't break the program, and didn't mask the problem.
+    // Replace the current program with the loop extracted version, and try to
+    // extract another loop.
+    std::string ErrorMsg;
+    if (Linker::LinkModules(ToNotOptimize, ToOptimizeLoopExtracted, &ErrorMsg)){
+      std::cerr << BD.getToolName() << ": Error linking modules together:"
+                << ErrorMsg << '\n';
+      exit(1);
+    }
+    delete ToOptimizeLoopExtracted;
+
+    // All of the Function*'s in the MiscompiledFunctions list are in the old
+    // module.  Update this list to include all of the functions in the
+    // optimized and loop extracted module.
+    MiscompiledFunctions.clear();
+    for (unsigned i = 0, e = MisCompFunctions.size(); i != e; ++i) {
+      Function *NewF = ToNotOptimize->getFunction(MisCompFunctions[i].first);
+                                                  
+      assert(NewF && "Function not found??");
+      assert(NewF->getFunctionType() == MisCompFunctions[i].second && 
+             "found wrong function type?");
+      MiscompiledFunctions.push_back(NewF);
+    }
+
+    BD.setNewProgram(ToNotOptimize);
+    MadeChange = true;
+  }
+}
+
+namespace {
+  class ReduceMiscompiledBlocks : public ListReducer<BasicBlock*> {
+    BugDriver &BD;
+    bool (*TestFn)(BugDriver &, Module *, Module *);
+    std::vector<Function*> FunctionsBeingTested;
+  public:
+    ReduceMiscompiledBlocks(BugDriver &bd,
+                            bool (*F)(BugDriver &, Module *, Module *),
+                            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;
+      return NoFailure;
+    }
+
+    bool TestFuncs(const std::vector<BasicBlock*> &Prefix);
+  };
+}
+
+/// 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) {
+  // Test to see if the function is misoptimized if we ONLY run it on the
+  // functions listed in Funcs.
+  std::cout << "Checking to see if the program is misoptimized when all ";
+  if (!BBs.empty()) {
+    std::cout << "but these " << BBs.size() << " blocks are extracted: ";
+    for (unsigned i = 0, e = BBs.size() < 10 ? BBs.size() : 10; i != e; ++i)
+      std::cout << BBs[i]->getName() << " ";
+    if (BBs.size() > 10) std::cout << "...";
+  } else {
+    std::cout << "blocks are extracted.";
+  }
+  std::cout << '\n';
+
+  // Split the module into the two halves of the program we want.
+  DenseMap<const Value*, Value*> ValueMap;
+  Module *ToNotOptimize = CloneModule(BD.getProgram(), ValueMap);
+  Module *ToOptimize = SplitFunctionsOutOfModule(ToNotOptimize,
+                                                 FunctionsBeingTested,
+                                                 ValueMap);
+
+  // Try the extraction.  If it doesn't work, then the block extractor crashed
+  // or something, in which case bugpoint can't chase down this possibility.
+  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);
+  }
+  delete ToOptimize;
+  delete ToNotOptimize;
+  return false;
+}
+
+
+/// ExtractBlocks - Given a reduced list of functions that still expose the bug,
+/// extract as many basic blocks from the region as possible without obscuring
+/// the bug.
+///
+static bool ExtractBlocks(BugDriver &BD,
+                          bool (*TestFn)(BugDriver &, Module *, Module *),
+                          std::vector<Function*> &MiscompiledFunctions) {
+  if (BugpointIsInterrupted) return false;
+  
+  std::vector<BasicBlock*> Blocks;
+  for (unsigned i = 0, e = MiscompiledFunctions.size(); i != e; ++i)
+    for (Function::iterator I = MiscompiledFunctions[i]->begin(),
+           E = MiscompiledFunctions[i]->end(); I != E; ++I)
+      Blocks.push_back(I);
+
+  // Use the list reducer to identify blocks that can be extracted without
+  // obscuring the bug.  The Blocks list will end up containing blocks that must
+  // be retained from the original program.
+  unsigned OldSize = Blocks.size();
+
+  // Check to see if all blocks are extractible first.
+  if (ReduceMiscompiledBlocks(BD, TestFn,
+                  MiscompiledFunctions).TestFuncs(std::vector<BasicBlock*>())) {
+    Blocks.clear();
+  } else {
+    ReduceMiscompiledBlocks(BD, TestFn,MiscompiledFunctions).reduceList(Blocks);
+    if (Blocks.size() == OldSize)
+      return false;
+  }
+
+  DenseMap<const Value*, Value*> ValueMap;
+  Module *ProgClone = CloneModule(BD.getProgram(), ValueMap);
+  Module *ToExtract = SplitFunctionsOutOfModule(ProgClone,
+                                                MiscompiledFunctions,
+                                                ValueMap);
+  Module *Extracted = BD.ExtractMappedBlocksFromModule(Blocks, ToExtract);
+  if (Extracted == 0) {
+    // Weird, extraction should have worked.
+    std::cerr << "Nondeterministic problem extracting blocks??\n";
+    delete ProgClone;
+    delete ToExtract;
+    return false;
+  }
+
+  // Otherwise, block extraction succeeded.  Link the two program fragments back
+  // together.
+  delete ToExtract;
+
+  std::vector<std::pair<std::string, const FunctionType*> > MisCompFunctions;
+  for (Module::iterator I = Extracted->begin(), E = Extracted->end();
+       I != E; ++I)
+    if (!I->isDeclaration())
+      MisCompFunctions.push_back(std::make_pair(I->getName(),
+                                                I->getFunctionType()));
+
+  std::string ErrorMsg;
+  if (Linker::LinkModules(ProgClone, Extracted, &ErrorMsg)) {
+    std::cerr << BD.getToolName() << ": Error linking modules together:"
+              << ErrorMsg << '\n';
+    exit(1);
+  }
+  delete Extracted;
+
+  // Set the new program and delete the old one.
+  BD.setNewProgram(ProgClone);
+
+  // Update the list of miscompiled functions.
+  MiscompiledFunctions.clear();
+
+  for (unsigned i = 0, e = MisCompFunctions.size(); i != e; ++i) {
+    Function *NewF = ProgClone->getFunction(MisCompFunctions[i].first);
+    assert(NewF && "Function not found??");
+    assert(NewF->getFunctionType() == MisCompFunctions[i].second && 
+           "Function has wrong type??");
+    MiscompiledFunctions.push_back(NewF);
+  }
+
+  return true;
+}
+
+
+/// DebugAMiscompilation - This is a generic driver to narrow down
+/// miscompilations, either in an optimization or a code generator.
+///
+static std::vector<Function*>
+DebugAMiscompilation(BugDriver &BD,
+                     bool (*TestFn)(BugDriver &, Module *, Module *)) {
+  // 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
+  // the program.
+  std::vector<Function*> MiscompiledFunctions;
+  Module *Prog = BD.getProgram();
+  for (Module::iterator I = Prog->begin(), E = Prog->end(); I != E; ++I)
+    if (!I->isDeclaration())
+      MiscompiledFunctions.push_back(I);
+
+  // Do the reduction...
+  if (!BugpointIsInterrupted)
+    ReduceMiscompilingFunctions(BD, TestFn).reduceList(MiscompiledFunctions);
+
+  std::cout << "\n*** The following function"
+            << (MiscompiledFunctions.size() == 1 ? " is" : "s are")
+            << " being miscompiled: ";
+  PrintFunctionList(MiscompiledFunctions);
+  std::cout << '\n';
+
+  // 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.
+
+    // Loop extraction can introduce functions with the same name (foo_code).
+    // Make sure to disambiguate the symbols so that when the program is split
+    // apart that we can link it back together again.
+    DisambiguateGlobalSymbols(BD.getProgram());
+
+    // Do the reduction...
+    if (!BugpointIsInterrupted)
+      ReduceMiscompilingFunctions(BD, TestFn).reduceList(MiscompiledFunctions);
+
+    std::cout << "\n*** The following function"
+              << (MiscompiledFunctions.size() == 1 ? " is" : "s are")
+              << " being miscompiled: ";
+    PrintFunctionList(MiscompiledFunctions);
+    std::cout << '\n';
+  }
+
+  if (!BugpointIsInterrupted &&
+      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.
+
+    // Block extraction can introduce functions with the same name (foo_code).
+    // Make sure to disambiguate the symbols so that when the program is split
+    // apart that we can link it back together again.
+    DisambiguateGlobalSymbols(BD.getProgram());
+
+    // Do the reduction...
+    ReduceMiscompilingFunctions(BD, TestFn).reduceList(MiscompiledFunctions);
+
+    std::cout << "\n*** The following function"
+              << (MiscompiledFunctions.size() == 1 ? " is" : "s are")
+              << " being miscompiled: ";
+    PrintFunctionList(MiscompiledFunctions);
+    std::cout << '\n';
+  }
+
+  return MiscompiledFunctions;
+}
+
+/// TestOptimizer - This is the predicate function used to check to see if the
+/// "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) {
+  // Run the optimization passes on ToOptimize, producing a transformed version
+  // of the functions being tested.
+  std::cout << "  Optimizing functions being tested: ";
+  Module *Optimized = BD.runPassesOn(Test, BD.getPassesToRun(),
+                                     /*AutoDebugCrashes*/true);
+  std::cout << "done.\n";
+  delete Test;
+
+  std::cout << "  Checking to see if the merged program executes correctly: ";
+  bool Broken = TestMergedProgram(BD, Optimized, Safe, true);
+  std::cout << (Broken ? " nope.\n" : " yup.\n");
+  return Broken;
+}
+
+
+/// debugMiscompilation - This method is used when the passes selected are not
+/// crashing, but the generated output is semantically different from the
+/// input.
+///
+bool BugDriver::debugMiscompilation() {
+  // Make sure something was miscompiled...
+  if (!BugpointIsInterrupted)
+    if (!ReduceMiscompilingPasses(*this).reduceList(PassesToRun)) {
+      std::cerr << "*** Optimized program matches reference output!  No problem"
+                << " detected...\nbugpoint can't help you with your problem!\n";
+      return false;
+    }
+
+  std::cout << "\n*** Found miscompiling pass"
+            << (getPassesToRun().size() == 1 ? "" : "es") << ": "
+            << getPassesString(getPassesToRun()) << '\n';
+  EmitProgressBitcode("passinput");
+
+  std::vector<Function*> MiscompiledFunctions =
+    DebugAMiscompilation(*this, TestOptimizer);
+
+  // Output a bunch of bitcode files for the user...
+  std::cout << "Outputting reduced bitcode files which expose the problem:\n";
+  DenseMap<const Value*, Value*> ValueMap;
+  Module *ToNotOptimize = CloneModule(getProgram(), ValueMap);
+  Module *ToOptimize = SplitFunctionsOutOfModule(ToNotOptimize,
+                                                 MiscompiledFunctions,
+                                                 ValueMap);
+
+  std::cout << "  Non-optimized portion: ";
+  ToNotOptimize = swapProgramIn(ToNotOptimize);
+  EmitProgressBitcode("tonotoptimize", true);
+  setNewProgram(ToNotOptimize);   // Delete hacked module.
+
+  std::cout << "  Portion that is input to optimizer: ";
+  ToOptimize = swapProgramIn(ToOptimize);
+  EmitProgressBitcode("tooptimize");
+  setNewProgram(ToOptimize);      // Delete hacked module.
+
+  return false;
+}
+
+/// CleanupAndPrepareModules - Get the specified modules ready for code
+/// generator testing.
+///
+static void CleanupAndPrepareModules(BugDriver &BD, Module *&Test,
+                                     Module *Safe) {
+  // Clean up the modules, removing extra cruft that we don't need anymore...
+  Test = BD.performFinalCleanups(Test);
+
+  // If we are executing the JIT, we have several nasty issues to take care of.
+  if (!BD.isExecutingJIT()) return;
+
+  // First, if the main function is in the Safe module, we must add a stub to
+  // the Test module to call into it.  Thus, we create a new function `main'
+  // which just calls the old one.
+  if (Function *oldMain = Safe->getFunction("main"))
+    if (!oldMain->isDeclaration()) {
+      // Rename it
+      oldMain->setName("llvm_bugpoint_old_main");
+      // Create a NEW `main' function with same type in the test module.
+      Function *newMain = Function::Create(oldMain->getFunctionType(),
+                                           GlobalValue::ExternalLinkage,
+                                           "main", Test);
+      // Create an `oldmain' prototype in the test module, which will
+      // corresponds to the real main function in the same module.
+      Function *oldMainProto = Function::Create(oldMain->getFunctionType(),
+                                                GlobalValue::ExternalLinkage,
+                                                oldMain->getName(), Test);
+      // Set up and remember the argument list for the main function.
+      std::vector<Value*> args;
+      for (Function::arg_iterator
+             I = newMain->arg_begin(), E = newMain->arg_end(),
+             OI = oldMain->arg_begin(); I != E; ++I, ++OI) {
+        I->setName(OI->getName());    // Copy argument names from oldMain
+        args.push_back(I);
+      }
+
+      // Call the old main function and return its result
+      BasicBlock *BB = BasicBlock::Create("entry", newMain);
+      CallInst *call = CallInst::Create(oldMainProto, args.begin(), args.end(),
+                                        "", BB);
+
+      // If the type of old function wasn't void, return value of call
+      ReturnInst::Create(call, BB);
+    }
+
+  // The second nasty issue we must deal with in the JIT is that the Safe
+  // module cannot directly reference any functions defined in the test
+  // module.  Instead, we use a JIT API call to dynamically resolve the
+  // symbol.
+
+  // Add the resolver to the Safe module.
+  // Prototype: void *getPointerToNamedFunction(const char* Name)
+  Constant *resolverFunc =
+    Safe->getOrInsertFunction("getPointerToNamedFunction",
+                              PointerType::getUnqual(Type::Int8Ty),
+                              PointerType::getUnqual(Type::Int8Ty), (Type *)0);
+
+  // Use the function we just added to get addresses of functions we need.
+  for (Module::iterator F = Safe->begin(), E = Safe->end(); F != E; ++F) {
+    if (F->isDeclaration() && !F->use_empty() && &*F != resolverFunc &&
+        !F->isIntrinsic() /* ignore intrinsics */) {
+      Function *TestFn = Test->getFunction(F->getName());
+
+      // Don't forward functions which are external in the test module too.
+      if (TestFn && !TestFn->isDeclaration()) {
+        // 1. Add a string constant with its name to the global file
+        Constant *InitArray = ConstantArray::get(F->getName());
+        GlobalVariable *funcName =
+          new GlobalVariable(InitArray->getType(), true /*isConstant*/,
+                             GlobalValue::InternalLinkage, InitArray,
+                             F->getName() + "_name", Safe);
+
+        // 2. Use `GetElementPtr *funcName, 0, 0' to convert the string to an
+        // sbyte* so it matches the signature of the resolver function.
+
+        // GetElementPtr *funcName, ulong 0, ulong 0
+        std::vector<Constant*> GEPargs(2,Constant::getNullValue(Type::Int32Ty));
+        Value *GEP = ConstantExpr::getGetElementPtr(funcName, &GEPargs[0], 2);
+        std::vector<Value*> ResolverArgs;
+        ResolverArgs.push_back(GEP);
+
+        // Rewrite uses of F in global initializers, etc. to uses of a wrapper
+        // function that dynamically resolves the calls to F via our JIT API
+        if (!F->use_empty()) {
+          // Create a new global to hold the cached function pointer.
+          Constant *NullPtr = ConstantPointerNull::get(F->getType());
+          GlobalVariable *Cache =
+            new GlobalVariable(F->getType(), false,GlobalValue::InternalLinkage,
+                               NullPtr,F->getName()+".fpcache", F->getParent());
+
+          // Construct a new stub function that will re-route calls to F
+          const FunctionType *FuncTy = F->getFunctionType();
+          Function *FuncWrapper = Function::Create(FuncTy,
+                                                   GlobalValue::InternalLinkage,
+                                                   F->getName() + "_wrapper",
+                                                   F->getParent());
+          BasicBlock *EntryBB  = BasicBlock::Create("entry", FuncWrapper);
+          BasicBlock *DoCallBB = BasicBlock::Create("usecache", FuncWrapper);
+          BasicBlock *LookupBB = BasicBlock::Create("lookupfp", FuncWrapper);
+
+          // Check to see if we already looked up the value.
+          Value *CachedVal = new LoadInst(Cache, "fpcache", EntryBB);
+          Value *IsNull = new ICmpInst(ICmpInst::ICMP_EQ, CachedVal,
+                                       NullPtr, "isNull", EntryBB);
+          BranchInst::Create(LookupBB, DoCallBB, IsNull, EntryBB);
+
+          // Resolve the call to function F via the JIT API:
+          //
+          // call resolver(GetElementPtr...)
+          CallInst *Resolver =
+            CallInst::Create(resolverFunc, ResolverArgs.begin(),
+                             ResolverArgs.end(), "resolver", LookupBB);
+
+          // Cast the result from the resolver to correctly-typed function.
+          CastInst *CastedResolver =
+            new BitCastInst(Resolver,
+                            PointerType::getUnqual(F->getFunctionType()),
+                            "resolverCast", LookupBB);
+
+          // Save the value in our cache.
+          new StoreInst(CastedResolver, Cache, LookupBB);
+          BranchInst::Create(DoCallBB, LookupBB);
+
+          PHINode *FuncPtr = PHINode::Create(NullPtr->getType(),
+                                             "fp", DoCallBB);
+          FuncPtr->addIncoming(CastedResolver, LookupBB);
+          FuncPtr->addIncoming(CachedVal, EntryBB);
+
+          // Save the argument list.
+          std::vector<Value*> Args;
+          for (Function::arg_iterator i = FuncWrapper->arg_begin(),
+                 e = FuncWrapper->arg_end(); i != e; ++i)
+            Args.push_back(i);
+
+          // Pass on the arguments to the real function, return its result
+          if (F->getReturnType() == Type::VoidTy) {
+            CallInst::Create(FuncPtr, Args.begin(), Args.end(), "", DoCallBB);
+            ReturnInst::Create(DoCallBB);
+          } else {
+            CallInst *Call = CallInst::Create(FuncPtr, Args.begin(), Args.end(),
+                                              "retval", DoCallBB);
+            ReturnInst::Create(Call, DoCallBB);
+          }
+
+          // Use the wrapper function instead of the old function
+          F->replaceAllUsesWith(FuncWrapper);
+        }
+      }
+    }
+  }
+
+  if (verifyModule(*Test) || verifyModule(*Safe)) {
+    std::cerr << "Bugpoint has a bug, which corrupted a module!!\n";
+    abort();
+  }
+}
+
+
+
+/// TestCodeGenerator - This is the predicate function used to check to see if
+/// 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) {
+  CleanupAndPrepareModules(BD, Test, Safe);
+
+  sys::Path TestModuleBC("bugpoint.test.bc");
+  std::string ErrMsg;
+  if (TestModuleBC.makeUnique(true, &ErrMsg)) {
+    std::cerr << BD.getToolName() << "Error making unique filename: "
+              << ErrMsg << "\n";
+    exit(1);
+  }
+  if (BD.writeProgramToFile(TestModuleBC.toString(), Test)) {
+    std::cerr << "Error writing bitcode to `" << TestModuleBC << "'\nExiting.";
+    exit(1);
+  }
+  delete Test;
+
+  // Make the shared library
+  sys::Path SafeModuleBC("bugpoint.safe.bc");
+  if (SafeModuleBC.makeUnique(true, &ErrMsg)) {
+    std::cerr << BD.getToolName() << "Error making unique filename: "
+              << ErrMsg << "\n";
+    exit(1);
+  }
+
+  if (BD.writeProgramToFile(SafeModuleBC.toString(), Safe)) {
+    std::cerr << "Error writing bitcode to `" << SafeModuleBC << "'\nExiting.";
+    exit(1);
+  }
+  std::string SharedObject = BD.compileSharedObject(SafeModuleBC.toString());
+  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.toString(), SharedObject, false);
+
+  if (Result)
+    std::cerr << ": still failing!\n";
+  else
+    std::cerr << ": didn't fail.\n";
+  TestModuleBC.eraseFromDisk();
+  SafeModuleBC.eraseFromDisk();
+  sys::Path(SharedObject).eraseFromDisk();
+
+  return Result;
+}
+
+
+/// debugCodeGenerator - debug errors in LLC, LLI, or CBE.
+///
+bool BugDriver::debugCodeGenerator() {
+  if ((void*)SafeInterpreter == (void*)Interpreter) {
+    std::string Result = executeProgramSafely("bugpoint.safe.out");
+    std::cout << "\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);
+
+  // Split the module into the two halves of the program we want.
+  DenseMap<const Value*, Value*> ValueMap;
+  Module *ToNotCodeGen = CloneModule(getProgram(), ValueMap);
+  Module *ToCodeGen = SplitFunctionsOutOfModule(ToNotCodeGen, Funcs, ValueMap);
+
+  // Condition the modules
+  CleanupAndPrepareModules(*this, ToCodeGen, ToNotCodeGen);
+
+  sys::Path TestModuleBC("bugpoint.test.bc");
+  std::string ErrMsg;
+  if (TestModuleBC.makeUnique(true, &ErrMsg)) {
+    std::cerr << getToolName() << "Error making unique filename: "
+              << ErrMsg << "\n";
+    exit(1);
+  }
+
+  if (writeProgramToFile(TestModuleBC.toString(), ToCodeGen)) {
+    std::cerr << "Error writing bitcode to `" << TestModuleBC << "'\nExiting.";
+    exit(1);
+  }
+  delete ToCodeGen;
+
+  // Make the shared library
+  sys::Path SafeModuleBC("bugpoint.safe.bc");
+  if (SafeModuleBC.makeUnique(true, &ErrMsg)) {
+    std::cerr << getToolName() << "Error making unique filename: "
+              << ErrMsg << "\n";
+    exit(1);
+  }
+
+  if (writeProgramToFile(SafeModuleBC.toString(), ToNotCodeGen)) {
+    std::cerr << "Error writing bitcode to `" << SafeModuleBC << "'\nExiting.";
+    exit(1);
+  }
+  std::string SharedObject = compileSharedObject(SafeModuleBC.toString());
+  delete ToNotCodeGen;
+
+  std::cout << "You can reproduce the problem with the command line: \n";
+  if (isExecutingJIT()) {
+    std::cout << "  lli -load " << SharedObject << " " << TestModuleBC;
+  } else {
+    std::cout << "  llc -f " << TestModuleBC << " -o " << TestModuleBC<< ".s\n";
+    std::cout << "  gcc " << SharedObject << " " << TestModuleBC
+              << ".s -o " << TestModuleBC << ".exe";
+#if defined (HAVE_LINK_R)
+    std::cout << " -Wl,-R.";
+#endif
+    std::cout << "\n";
+    std::cout << "  " << TestModuleBC << ".exe";
+  }
+  for (unsigned i=0, e = InputArgv.size(); i != e; ++i)
+    std::cout << " " << InputArgv[i];
+  std::cout << '\n';
+  std::cout << "The shared object was created with:\n  llc -march=c "
+            << SafeModuleBC << " -o temporary.c\n"
+            << "  gcc -xc temporary.c -O2 -o " << SharedObject
+#if defined(sparc) || defined(__sparc__) || defined(__sparcv9)
+            << " -G"            // Compile a shared library, `-G' for Sparc
+#else
+            << " -fPIC -shared"       // `-shared' for Linux/X86, maybe others
+#endif
+            << " -fno-strict-aliasing\n";
+
+  return false;
+}