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      1 //===- Miscompilation.cpp - Debug program miscompilations -----------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file implements optimizer and code generation miscompilation debugging
     11 // support.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #include "BugDriver.h"
     16 #include "ListReducer.h"
     17 #include "ToolRunner.h"
     18 #include "llvm/Analysis/Verifier.h"
     19 #include "llvm/Config/config.h"   // for HAVE_LINK_R
     20 #include "llvm/IR/Constants.h"
     21 #include "llvm/IR/DerivedTypes.h"
     22 #include "llvm/IR/Instructions.h"
     23 #include "llvm/IR/Module.h"
     24 #include "llvm/Linker.h"
     25 #include "llvm/Pass.h"
     26 #include "llvm/Support/CommandLine.h"
     27 #include "llvm/Support/FileUtilities.h"
     28 #include "llvm/Transforms/Utils/Cloning.h"
     29 using namespace llvm;
     30 
     31 namespace llvm {
     32   extern cl::opt<std::string> OutputPrefix;
     33   extern cl::list<std::string> InputArgv;
     34 }
     35 
     36 namespace {
     37   static llvm::cl::opt<bool>
     38     DisableLoopExtraction("disable-loop-extraction",
     39         cl::desc("Don't extract loops when searching for miscompilations"),
     40         cl::init(false));
     41   static llvm::cl::opt<bool>
     42     DisableBlockExtraction("disable-block-extraction",
     43         cl::desc("Don't extract blocks when searching for miscompilations"),
     44         cl::init(false));
     45 
     46   class ReduceMiscompilingPasses : public ListReducer<std::string> {
     47     BugDriver &BD;
     48   public:
     49     ReduceMiscompilingPasses(BugDriver &bd) : BD(bd) {}
     50 
     51     virtual TestResult doTest(std::vector<std::string> &Prefix,
     52                               std::vector<std::string> &Suffix,
     53                               std::string &Error);
     54   };
     55 }
     56 
     57 /// TestResult - After passes have been split into a test group and a control
     58 /// group, see if they still break the program.
     59 ///
     60 ReduceMiscompilingPasses::TestResult
     61 ReduceMiscompilingPasses::doTest(std::vector<std::string> &Prefix,
     62                                  std::vector<std::string> &Suffix,
     63                                  std::string &Error) {
     64   // First, run the program with just the Suffix passes.  If it is still broken
     65   // with JUST the kept passes, discard the prefix passes.
     66   outs() << "Checking to see if '" << getPassesString(Suffix)
     67          << "' compiles correctly: ";
     68 
     69   std::string BitcodeResult;
     70   if (BD.runPasses(BD.getProgram(), Suffix, BitcodeResult, false/*delete*/,
     71                    true/*quiet*/)) {
     72     errs() << " Error running this sequence of passes"
     73            << " on the input program!\n";
     74     BD.setPassesToRun(Suffix);
     75     BD.EmitProgressBitcode(BD.getProgram(), "pass-error",  false);
     76     exit(BD.debugOptimizerCrash());
     77   }
     78 
     79   // Check to see if the finished program matches the reference output...
     80   bool Diff = BD.diffProgram(BD.getProgram(), BitcodeResult, "",
     81                              true /*delete bitcode*/, &Error);
     82   if (!Error.empty())
     83     return InternalError;
     84   if (Diff) {
     85     outs() << " nope.\n";
     86     if (Suffix.empty()) {
     87       errs() << BD.getToolName() << ": I'm confused: the test fails when "
     88              << "no passes are run, nondeterministic program?\n";
     89       exit(1);
     90     }
     91     return KeepSuffix;         // Miscompilation detected!
     92   }
     93   outs() << " yup.\n";      // No miscompilation!
     94 
     95   if (Prefix.empty()) return NoFailure;
     96 
     97   // Next, see if the program is broken if we run the "prefix" passes first,
     98   // then separately run the "kept" passes.
     99   outs() << "Checking to see if '" << getPassesString(Prefix)
    100          << "' compiles correctly: ";
    101 
    102   // If it is not broken with the kept passes, it's possible that the prefix
    103   // passes must be run before the kept passes to break it.  If the program
    104   // WORKS after the prefix passes, but then fails if running the prefix AND
    105   // kept passes, we can update our bitcode file to include the result of the
    106   // prefix passes, then discard the prefix passes.
    107   //
    108   if (BD.runPasses(BD.getProgram(), Prefix, BitcodeResult, false/*delete*/,
    109                    true/*quiet*/)) {
    110     errs() << " Error running this sequence of passes"
    111            << " on the input program!\n";
    112     BD.setPassesToRun(Prefix);
    113     BD.EmitProgressBitcode(BD.getProgram(), "pass-error",  false);
    114     exit(BD.debugOptimizerCrash());
    115   }
    116 
    117   // If the prefix maintains the predicate by itself, only keep the prefix!
    118   Diff = BD.diffProgram(BD.getProgram(), BitcodeResult, "", false, &Error);
    119   if (!Error.empty())
    120     return InternalError;
    121   if (Diff) {
    122     outs() << " nope.\n";
    123     sys::fs::remove(BitcodeResult);
    124     return KeepPrefix;
    125   }
    126   outs() << " yup.\n";      // No miscompilation!
    127 
    128   // Ok, so now we know that the prefix passes work, try running the suffix
    129   // passes on the result of the prefix passes.
    130   //
    131   OwningPtr<Module> PrefixOutput(ParseInputFile(BitcodeResult,
    132                                                 BD.getContext()));
    133   if (!PrefixOutput) {
    134     errs() << BD.getToolName() << ": Error reading bitcode file '"
    135            << BitcodeResult << "'!\n";
    136     exit(1);
    137   }
    138   sys::fs::remove(BitcodeResult);
    139 
    140   // Don't check if there are no passes in the suffix.
    141   if (Suffix.empty())
    142     return NoFailure;
    143 
    144   outs() << "Checking to see if '" << getPassesString(Suffix)
    145             << "' passes compile correctly after the '"
    146             << getPassesString(Prefix) << "' passes: ";
    147 
    148   OwningPtr<Module> OriginalInput(BD.swapProgramIn(PrefixOutput.take()));
    149   if (BD.runPasses(BD.getProgram(), Suffix, BitcodeResult, false/*delete*/,
    150                    true/*quiet*/)) {
    151     errs() << " Error running this sequence of passes"
    152            << " on the input program!\n";
    153     BD.setPassesToRun(Suffix);
    154     BD.EmitProgressBitcode(BD.getProgram(), "pass-error",  false);
    155     exit(BD.debugOptimizerCrash());
    156   }
    157 
    158   // Run the result...
    159   Diff = BD.diffProgram(BD.getProgram(), BitcodeResult, "",
    160                         true /*delete bitcode*/, &Error);
    161   if (!Error.empty())
    162     return InternalError;
    163   if (Diff) {
    164     outs() << " nope.\n";
    165     return KeepSuffix;
    166   }
    167 
    168   // Otherwise, we must not be running the bad pass anymore.
    169   outs() << " yup.\n";      // No miscompilation!
    170   // Restore orig program & free test.
    171   delete BD.swapProgramIn(OriginalInput.take());
    172   return NoFailure;
    173 }
    174 
    175 namespace {
    176   class ReduceMiscompilingFunctions : public ListReducer<Function*> {
    177     BugDriver &BD;
    178     bool (*TestFn)(BugDriver &, Module *, Module *, std::string &);
    179   public:
    180     ReduceMiscompilingFunctions(BugDriver &bd,
    181                                 bool (*F)(BugDriver &, Module *, Module *,
    182                                           std::string &))
    183       : BD(bd), TestFn(F) {}
    184 
    185     virtual TestResult doTest(std::vector<Function*> &Prefix,
    186                               std::vector<Function*> &Suffix,
    187                               std::string &Error) {
    188       if (!Suffix.empty()) {
    189         bool Ret = TestFuncs(Suffix, Error);
    190         if (!Error.empty())
    191           return InternalError;
    192         if (Ret)
    193           return KeepSuffix;
    194       }
    195       if (!Prefix.empty()) {
    196         bool Ret = TestFuncs(Prefix, Error);
    197         if (!Error.empty())
    198           return InternalError;
    199         if (Ret)
    200           return KeepPrefix;
    201       }
    202       return NoFailure;
    203     }
    204 
    205     bool TestFuncs(const std::vector<Function*> &Prefix, std::string &Error);
    206   };
    207 }
    208 
    209 /// TestMergedProgram - Given two modules, link them together and run the
    210 /// program, checking to see if the program matches the diff. If there is
    211 /// an error, return NULL. If not, return the merged module. The Broken argument
    212 /// will be set to true if the output is different. If the DeleteInputs
    213 /// argument is set to true then this function deletes both input
    214 /// modules before it returns.
    215 ///
    216 static Module *TestMergedProgram(const BugDriver &BD, Module *M1, Module *M2,
    217                                  bool DeleteInputs, std::string &Error,
    218                                  bool &Broken) {
    219   // Link the two portions of the program back to together.
    220   std::string ErrorMsg;
    221   if (!DeleteInputs) {
    222     M1 = CloneModule(M1);
    223     M2 = CloneModule(M2);
    224   }
    225   if (Linker::LinkModules(M1, M2, Linker::DestroySource, &ErrorMsg)) {
    226     errs() << BD.getToolName() << ": Error linking modules together:"
    227            << ErrorMsg << '\n';
    228     exit(1);
    229   }
    230   delete M2;   // We are done with this module.
    231 
    232   // Execute the program.
    233   Broken = BD.diffProgram(M1, "", "", false, &Error);
    234   if (!Error.empty()) {
    235     // Delete the linked module
    236     delete M1;
    237     return NULL;
    238   }
    239   return M1;
    240 }
    241 
    242 /// TestFuncs - split functions in a Module into two groups: those that are
    243 /// under consideration for miscompilation vs. those that are not, and test
    244 /// accordingly. Each group of functions becomes a separate Module.
    245 ///
    246 bool ReduceMiscompilingFunctions::TestFuncs(const std::vector<Function*> &Funcs,
    247                                             std::string &Error) {
    248   // Test to see if the function is misoptimized if we ONLY run it on the
    249   // functions listed in Funcs.
    250   outs() << "Checking to see if the program is misoptimized when "
    251          << (Funcs.size()==1 ? "this function is" : "these functions are")
    252          << " run through the pass"
    253          << (BD.getPassesToRun().size() == 1 ? "" : "es") << ":";
    254   PrintFunctionList(Funcs);
    255   outs() << '\n';
    256 
    257   // Create a clone for two reasons:
    258   // * If the optimization passes delete any function, the deleted function
    259   //   will be in the clone and Funcs will still point to valid memory
    260   // * If the optimization passes use interprocedural information to break
    261   //   a function, we want to continue with the original function. Otherwise
    262   //   we can conclude that a function triggers the bug when in fact one
    263   //   needs a larger set of original functions to do so.
    264   ValueToValueMapTy VMap;
    265   Module *Clone = CloneModule(BD.getProgram(), VMap);
    266   Module *Orig = BD.swapProgramIn(Clone);
    267 
    268   std::vector<Function*> FuncsOnClone;
    269   for (unsigned i = 0, e = Funcs.size(); i != e; ++i) {
    270     Function *F = cast<Function>(VMap[Funcs[i]]);
    271     FuncsOnClone.push_back(F);
    272   }
    273 
    274   // Split the module into the two halves of the program we want.
    275   VMap.clear();
    276   Module *ToNotOptimize = CloneModule(BD.getProgram(), VMap);
    277   Module *ToOptimize = SplitFunctionsOutOfModule(ToNotOptimize, FuncsOnClone,
    278                                                  VMap);
    279 
    280   // Run the predicate, note that the predicate will delete both input modules.
    281   bool Broken = TestFn(BD, ToOptimize, ToNotOptimize, Error);
    282 
    283   delete BD.swapProgramIn(Orig);
    284 
    285   return Broken;
    286 }
    287 
    288 /// DisambiguateGlobalSymbols - Give anonymous global values names.
    289 ///
    290 static void DisambiguateGlobalSymbols(Module *M) {
    291   for (Module::global_iterator I = M->global_begin(), E = M->global_end();
    292        I != E; ++I)
    293     if (!I->hasName())
    294       I->setName("anon_global");
    295   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
    296     if (!I->hasName())
    297       I->setName("anon_fn");
    298 }
    299 
    300 /// ExtractLoops - Given a reduced list of functions that still exposed the bug,
    301 /// check to see if we can extract the loops in the region without obscuring the
    302 /// bug.  If so, it reduces the amount of code identified.
    303 ///
    304 static bool ExtractLoops(BugDriver &BD,
    305                          bool (*TestFn)(BugDriver &, Module *, Module *,
    306                                         std::string &),
    307                          std::vector<Function*> &MiscompiledFunctions,
    308                          std::string &Error) {
    309   bool MadeChange = false;
    310   while (1) {
    311     if (BugpointIsInterrupted) return MadeChange;
    312 
    313     ValueToValueMapTy VMap;
    314     Module *ToNotOptimize = CloneModule(BD.getProgram(), VMap);
    315     Module *ToOptimize = SplitFunctionsOutOfModule(ToNotOptimize,
    316                                                    MiscompiledFunctions,
    317                                                    VMap);
    318     Module *ToOptimizeLoopExtracted = BD.ExtractLoop(ToOptimize);
    319     if (!ToOptimizeLoopExtracted) {
    320       // If the loop extractor crashed or if there were no extractible loops,
    321       // then this chapter of our odyssey is over with.
    322       delete ToNotOptimize;
    323       delete ToOptimize;
    324       return MadeChange;
    325     }
    326 
    327     errs() << "Extracted a loop from the breaking portion of the program.\n";
    328 
    329     // Bugpoint is intentionally not very trusting of LLVM transformations.  In
    330     // particular, we're not going to assume that the loop extractor works, so
    331     // we're going to test the newly loop extracted program to make sure nothing
    332     // has broken.  If something broke, then we'll inform the user and stop
    333     // extraction.
    334     AbstractInterpreter *AI = BD.switchToSafeInterpreter();
    335     bool Failure;
    336     Module *New = TestMergedProgram(BD, ToOptimizeLoopExtracted, ToNotOptimize,
    337                                     false, Error, Failure);
    338     if (!New)
    339       return false;
    340 
    341     // Delete the original and set the new program.
    342     Module *Old = BD.swapProgramIn(New);
    343     for (unsigned i = 0, e = MiscompiledFunctions.size(); i != e; ++i)
    344       MiscompiledFunctions[i] = cast<Function>(VMap[MiscompiledFunctions[i]]);
    345     delete Old;
    346 
    347     if (Failure) {
    348       BD.switchToInterpreter(AI);
    349 
    350       // Merged program doesn't work anymore!
    351       errs() << "  *** ERROR: Loop extraction broke the program. :("
    352              << " Please report a bug!\n";
    353       errs() << "      Continuing on with un-loop-extracted version.\n";
    354 
    355       BD.writeProgramToFile(OutputPrefix + "-loop-extract-fail-tno.bc",
    356                             ToNotOptimize);
    357       BD.writeProgramToFile(OutputPrefix + "-loop-extract-fail-to.bc",
    358                             ToOptimize);
    359       BD.writeProgramToFile(OutputPrefix + "-loop-extract-fail-to-le.bc",
    360                             ToOptimizeLoopExtracted);
    361 
    362       errs() << "Please submit the "
    363              << OutputPrefix << "-loop-extract-fail-*.bc files.\n";
    364       delete ToOptimize;
    365       delete ToNotOptimize;
    366       delete ToOptimizeLoopExtracted;
    367       return MadeChange;
    368     }
    369     delete ToOptimize;
    370     BD.switchToInterpreter(AI);
    371 
    372     outs() << "  Testing after loop extraction:\n";
    373     // Clone modules, the tester function will free them.
    374     Module *TOLEBackup = CloneModule(ToOptimizeLoopExtracted, VMap);
    375     Module *TNOBackup  = CloneModule(ToNotOptimize, VMap);
    376 
    377     for (unsigned i = 0, e = MiscompiledFunctions.size(); i != e; ++i)
    378       MiscompiledFunctions[i] = cast<Function>(VMap[MiscompiledFunctions[i]]);
    379 
    380     Failure = TestFn(BD, ToOptimizeLoopExtracted, ToNotOptimize, Error);
    381     if (!Error.empty())
    382       return false;
    383 
    384     ToOptimizeLoopExtracted = TOLEBackup;
    385     ToNotOptimize = TNOBackup;
    386 
    387     if (!Failure) {
    388       outs() << "*** Loop extraction masked the problem.  Undoing.\n";
    389       // If the program is not still broken, then loop extraction did something
    390       // that masked the error.  Stop loop extraction now.
    391 
    392       std::vector<std::pair<std::string, FunctionType*> > MisCompFunctions;
    393       for (unsigned i = 0, e = MiscompiledFunctions.size(); i != e; ++i) {
    394         Function *F = MiscompiledFunctions[i];
    395         MisCompFunctions.push_back(std::make_pair(F->getName(),
    396                                                   F->getFunctionType()));
    397       }
    398 
    399       std::string ErrorMsg;
    400       if (Linker::LinkModules(ToNotOptimize, ToOptimizeLoopExtracted,
    401                               Linker::DestroySource, &ErrorMsg)){
    402         errs() << BD.getToolName() << ": Error linking modules together:"
    403                << ErrorMsg << '\n';
    404         exit(1);
    405       }
    406 
    407       MiscompiledFunctions.clear();
    408       for (unsigned i = 0, e = MisCompFunctions.size(); i != e; ++i) {
    409         Function *NewF = ToNotOptimize->getFunction(MisCompFunctions[i].first);
    410 
    411         assert(NewF && "Function not found??");
    412         MiscompiledFunctions.push_back(NewF);
    413       }
    414 
    415       delete ToOptimizeLoopExtracted;
    416       BD.setNewProgram(ToNotOptimize);
    417       return MadeChange;
    418     }
    419 
    420     outs() << "*** Loop extraction successful!\n";
    421 
    422     std::vector<std::pair<std::string, FunctionType*> > MisCompFunctions;
    423     for (Module::iterator I = ToOptimizeLoopExtracted->begin(),
    424            E = ToOptimizeLoopExtracted->end(); I != E; ++I)
    425       if (!I->isDeclaration())
    426         MisCompFunctions.push_back(std::make_pair(I->getName(),
    427                                                   I->getFunctionType()));
    428 
    429     // Okay, great!  Now we know that we extracted a loop and that loop
    430     // extraction both didn't break the program, and didn't mask the problem.
    431     // Replace the current program with the loop extracted version, and try to
    432     // extract another loop.
    433     std::string ErrorMsg;
    434     if (Linker::LinkModules(ToNotOptimize, ToOptimizeLoopExtracted,
    435                             Linker::DestroySource, &ErrorMsg)){
    436       errs() << BD.getToolName() << ": Error linking modules together:"
    437              << ErrorMsg << '\n';
    438       exit(1);
    439     }
    440     delete ToOptimizeLoopExtracted;
    441 
    442     // All of the Function*'s in the MiscompiledFunctions list are in the old
    443     // module.  Update this list to include all of the functions in the
    444     // optimized and loop extracted module.
    445     MiscompiledFunctions.clear();
    446     for (unsigned i = 0, e = MisCompFunctions.size(); i != e; ++i) {
    447       Function *NewF = ToNotOptimize->getFunction(MisCompFunctions[i].first);
    448 
    449       assert(NewF && "Function not found??");
    450       MiscompiledFunctions.push_back(NewF);
    451     }
    452 
    453     BD.setNewProgram(ToNotOptimize);
    454     MadeChange = true;
    455   }
    456 }
    457 
    458 namespace {
    459   class ReduceMiscompiledBlocks : public ListReducer<BasicBlock*> {
    460     BugDriver &BD;
    461     bool (*TestFn)(BugDriver &, Module *, Module *, std::string &);
    462     std::vector<Function*> FunctionsBeingTested;
    463   public:
    464     ReduceMiscompiledBlocks(BugDriver &bd,
    465                             bool (*F)(BugDriver &, Module *, Module *,
    466                                       std::string &),
    467                             const std::vector<Function*> &Fns)
    468       : BD(bd), TestFn(F), FunctionsBeingTested(Fns) {}
    469 
    470     virtual TestResult doTest(std::vector<BasicBlock*> &Prefix,
    471                               std::vector<BasicBlock*> &Suffix,
    472                               std::string &Error) {
    473       if (!Suffix.empty()) {
    474         bool Ret = TestFuncs(Suffix, Error);
    475         if (!Error.empty())
    476           return InternalError;
    477         if (Ret)
    478           return KeepSuffix;
    479       }
    480       if (!Prefix.empty()) {
    481         bool Ret = TestFuncs(Prefix, Error);
    482         if (!Error.empty())
    483           return InternalError;
    484         if (Ret)
    485           return KeepPrefix;
    486       }
    487       return NoFailure;
    488     }
    489 
    490     bool TestFuncs(const std::vector<BasicBlock*> &BBs, std::string &Error);
    491   };
    492 }
    493 
    494 /// TestFuncs - Extract all blocks for the miscompiled functions except for the
    495 /// specified blocks.  If the problem still exists, return true.
    496 ///
    497 bool ReduceMiscompiledBlocks::TestFuncs(const std::vector<BasicBlock*> &BBs,
    498                                         std::string &Error) {
    499   // Test to see if the function is misoptimized if we ONLY run it on the
    500   // functions listed in Funcs.
    501   outs() << "Checking to see if the program is misoptimized when all ";
    502   if (!BBs.empty()) {
    503     outs() << "but these " << BBs.size() << " blocks are extracted: ";
    504     for (unsigned i = 0, e = BBs.size() < 10 ? BBs.size() : 10; i != e; ++i)
    505       outs() << BBs[i]->getName() << " ";
    506     if (BBs.size() > 10) outs() << "...";
    507   } else {
    508     outs() << "blocks are extracted.";
    509   }
    510   outs() << '\n';
    511 
    512   // Split the module into the two halves of the program we want.
    513   ValueToValueMapTy VMap;
    514   Module *Clone = CloneModule(BD.getProgram(), VMap);
    515   Module *Orig = BD.swapProgramIn(Clone);
    516   std::vector<Function*> FuncsOnClone;
    517   std::vector<BasicBlock*> BBsOnClone;
    518   for (unsigned i = 0, e = FunctionsBeingTested.size(); i != e; ++i) {
    519     Function *F = cast<Function>(VMap[FunctionsBeingTested[i]]);
    520     FuncsOnClone.push_back(F);
    521   }
    522   for (unsigned i = 0, e = BBs.size(); i != e; ++i) {
    523     BasicBlock *BB = cast<BasicBlock>(VMap[BBs[i]]);
    524     BBsOnClone.push_back(BB);
    525   }
    526   VMap.clear();
    527 
    528   Module *ToNotOptimize = CloneModule(BD.getProgram(), VMap);
    529   Module *ToOptimize = SplitFunctionsOutOfModule(ToNotOptimize,
    530                                                  FuncsOnClone,
    531                                                  VMap);
    532 
    533   // Try the extraction.  If it doesn't work, then the block extractor crashed
    534   // or something, in which case bugpoint can't chase down this possibility.
    535   if (Module *New = BD.ExtractMappedBlocksFromModule(BBsOnClone, ToOptimize)) {
    536     delete ToOptimize;
    537     // Run the predicate,
    538     // note that the predicate will delete both input modules.
    539     bool Ret = TestFn(BD, New, ToNotOptimize, Error);
    540     delete BD.swapProgramIn(Orig);
    541     return Ret;
    542   }
    543   delete BD.swapProgramIn(Orig);
    544   delete ToOptimize;
    545   delete ToNotOptimize;
    546   return false;
    547 }
    548 
    549 
    550 /// ExtractBlocks - Given a reduced list of functions that still expose the bug,
    551 /// extract as many basic blocks from the region as possible without obscuring
    552 /// the bug.
    553 ///
    554 static bool ExtractBlocks(BugDriver &BD,
    555                           bool (*TestFn)(BugDriver &, Module *, Module *,
    556                                          std::string &),
    557                           std::vector<Function*> &MiscompiledFunctions,
    558                           std::string &Error) {
    559   if (BugpointIsInterrupted) return false;
    560 
    561   std::vector<BasicBlock*> Blocks;
    562   for (unsigned i = 0, e = MiscompiledFunctions.size(); i != e; ++i)
    563     for (Function::iterator I = MiscompiledFunctions[i]->begin(),
    564            E = MiscompiledFunctions[i]->end(); I != E; ++I)
    565       Blocks.push_back(I);
    566 
    567   // Use the list reducer to identify blocks that can be extracted without
    568   // obscuring the bug.  The Blocks list will end up containing blocks that must
    569   // be retained from the original program.
    570   unsigned OldSize = Blocks.size();
    571 
    572   // Check to see if all blocks are extractible first.
    573   bool Ret = ReduceMiscompiledBlocks(BD, TestFn, MiscompiledFunctions)
    574                                   .TestFuncs(std::vector<BasicBlock*>(), Error);
    575   if (!Error.empty())
    576     return false;
    577   if (Ret) {
    578     Blocks.clear();
    579   } else {
    580     ReduceMiscompiledBlocks(BD, TestFn,
    581                             MiscompiledFunctions).reduceList(Blocks, Error);
    582     if (!Error.empty())
    583       return false;
    584     if (Blocks.size() == OldSize)
    585       return false;
    586   }
    587 
    588   ValueToValueMapTy VMap;
    589   Module *ProgClone = CloneModule(BD.getProgram(), VMap);
    590   Module *ToExtract = SplitFunctionsOutOfModule(ProgClone,
    591                                                 MiscompiledFunctions,
    592                                                 VMap);
    593   Module *Extracted = BD.ExtractMappedBlocksFromModule(Blocks, ToExtract);
    594   if (Extracted == 0) {
    595     // Weird, extraction should have worked.
    596     errs() << "Nondeterministic problem extracting blocks??\n";
    597     delete ProgClone;
    598     delete ToExtract;
    599     return false;
    600   }
    601 
    602   // Otherwise, block extraction succeeded.  Link the two program fragments back
    603   // together.
    604   delete ToExtract;
    605 
    606   std::vector<std::pair<std::string, FunctionType*> > MisCompFunctions;
    607   for (Module::iterator I = Extracted->begin(), E = Extracted->end();
    608        I != E; ++I)
    609     if (!I->isDeclaration())
    610       MisCompFunctions.push_back(std::make_pair(I->getName(),
    611                                                 I->getFunctionType()));
    612 
    613   std::string ErrorMsg;
    614   if (Linker::LinkModules(ProgClone, Extracted, Linker::DestroySource,
    615                           &ErrorMsg)) {
    616     errs() << BD.getToolName() << ": Error linking modules together:"
    617            << ErrorMsg << '\n';
    618     exit(1);
    619   }
    620   delete Extracted;
    621 
    622   // Set the new program and delete the old one.
    623   BD.setNewProgram(ProgClone);
    624 
    625   // Update the list of miscompiled functions.
    626   MiscompiledFunctions.clear();
    627 
    628   for (unsigned i = 0, e = MisCompFunctions.size(); i != e; ++i) {
    629     Function *NewF = ProgClone->getFunction(MisCompFunctions[i].first);
    630     assert(NewF && "Function not found??");
    631     MiscompiledFunctions.push_back(NewF);
    632   }
    633 
    634   return true;
    635 }
    636 
    637 
    638 /// DebugAMiscompilation - This is a generic driver to narrow down
    639 /// miscompilations, either in an optimization or a code generator.
    640 ///
    641 static std::vector<Function*>
    642 DebugAMiscompilation(BugDriver &BD,
    643                      bool (*TestFn)(BugDriver &, Module *, Module *,
    644                                     std::string &),
    645                      std::string &Error) {
    646   // Okay, now that we have reduced the list of passes which are causing the
    647   // failure, see if we can pin down which functions are being
    648   // miscompiled... first build a list of all of the non-external functions in
    649   // the program.
    650   std::vector<Function*> MiscompiledFunctions;
    651   Module *Prog = BD.getProgram();
    652   for (Module::iterator I = Prog->begin(), E = Prog->end(); I != E; ++I)
    653     if (!I->isDeclaration())
    654       MiscompiledFunctions.push_back(I);
    655 
    656   // Do the reduction...
    657   if (!BugpointIsInterrupted)
    658     ReduceMiscompilingFunctions(BD, TestFn).reduceList(MiscompiledFunctions,
    659                                                        Error);
    660   if (!Error.empty()) {
    661     errs() << "\n***Cannot reduce functions: ";
    662     return MiscompiledFunctions;
    663   }
    664   outs() << "\n*** The following function"
    665          << (MiscompiledFunctions.size() == 1 ? " is" : "s are")
    666          << " being miscompiled: ";
    667   PrintFunctionList(MiscompiledFunctions);
    668   outs() << '\n';
    669 
    670   // See if we can rip any loops out of the miscompiled functions and still
    671   // trigger the problem.
    672 
    673   if (!BugpointIsInterrupted && !DisableLoopExtraction) {
    674     bool Ret = ExtractLoops(BD, TestFn, MiscompiledFunctions, Error);
    675     if (!Error.empty())
    676       return MiscompiledFunctions;
    677     if (Ret) {
    678       // Okay, we extracted some loops and the problem still appears.  See if
    679       // we can eliminate some of the created functions from being candidates.
    680       DisambiguateGlobalSymbols(BD.getProgram());
    681 
    682       // Do the reduction...
    683       if (!BugpointIsInterrupted)
    684         ReduceMiscompilingFunctions(BD, TestFn).reduceList(MiscompiledFunctions,
    685                                                            Error);
    686       if (!Error.empty())
    687         return MiscompiledFunctions;
    688 
    689       outs() << "\n*** The following function"
    690              << (MiscompiledFunctions.size() == 1 ? " is" : "s are")
    691              << " being miscompiled: ";
    692       PrintFunctionList(MiscompiledFunctions);
    693       outs() << '\n';
    694     }
    695   }
    696 
    697   if (!BugpointIsInterrupted && !DisableBlockExtraction) {
    698     bool Ret = ExtractBlocks(BD, TestFn, MiscompiledFunctions, Error);
    699     if (!Error.empty())
    700       return MiscompiledFunctions;
    701     if (Ret) {
    702       // Okay, we extracted some blocks and the problem still appears.  See if
    703       // we can eliminate some of the created functions from being candidates.
    704       DisambiguateGlobalSymbols(BD.getProgram());
    705 
    706       // Do the reduction...
    707       ReduceMiscompilingFunctions(BD, TestFn).reduceList(MiscompiledFunctions,
    708                                                          Error);
    709       if (!Error.empty())
    710         return MiscompiledFunctions;
    711 
    712       outs() << "\n*** The following function"
    713              << (MiscompiledFunctions.size() == 1 ? " is" : "s are")
    714              << " being miscompiled: ";
    715       PrintFunctionList(MiscompiledFunctions);
    716       outs() << '\n';
    717     }
    718   }
    719 
    720   return MiscompiledFunctions;
    721 }
    722 
    723 /// TestOptimizer - This is the predicate function used to check to see if the
    724 /// "Test" portion of the program is misoptimized.  If so, return true.  In any
    725 /// case, both module arguments are deleted.
    726 ///
    727 static bool TestOptimizer(BugDriver &BD, Module *Test, Module *Safe,
    728                           std::string &Error) {
    729   // Run the optimization passes on ToOptimize, producing a transformed version
    730   // of the functions being tested.
    731   outs() << "  Optimizing functions being tested: ";
    732   Module *Optimized = BD.runPassesOn(Test, BD.getPassesToRun(),
    733                                      /*AutoDebugCrashes*/true);
    734   outs() << "done.\n";
    735   delete Test;
    736 
    737   outs() << "  Checking to see if the merged program executes correctly: ";
    738   bool Broken;
    739   Module *New = TestMergedProgram(BD, Optimized, Safe, true, Error, Broken);
    740   if (New) {
    741     outs() << (Broken ? " nope.\n" : " yup.\n");
    742     // Delete the original and set the new program.
    743     delete BD.swapProgramIn(New);
    744   }
    745   return Broken;
    746 }
    747 
    748 
    749 /// debugMiscompilation - This method is used when the passes selected are not
    750 /// crashing, but the generated output is semantically different from the
    751 /// input.
    752 ///
    753 void BugDriver::debugMiscompilation(std::string *Error) {
    754   // Make sure something was miscompiled...
    755   if (!BugpointIsInterrupted)
    756     if (!ReduceMiscompilingPasses(*this).reduceList(PassesToRun, *Error)) {
    757       if (Error->empty())
    758         errs() << "*** Optimized program matches reference output!  No problem"
    759                << " detected...\nbugpoint can't help you with your problem!\n";
    760       return;
    761     }
    762 
    763   outs() << "\n*** Found miscompiling pass"
    764          << (getPassesToRun().size() == 1 ? "" : "es") << ": "
    765          << getPassesString(getPassesToRun()) << '\n';
    766   EmitProgressBitcode(Program, "passinput");
    767 
    768   std::vector<Function *> MiscompiledFunctions =
    769     DebugAMiscompilation(*this, TestOptimizer, *Error);
    770   if (!Error->empty())
    771     return;
    772 
    773   // Output a bunch of bitcode files for the user...
    774   outs() << "Outputting reduced bitcode files which expose the problem:\n";
    775   ValueToValueMapTy VMap;
    776   Module *ToNotOptimize = CloneModule(getProgram(), VMap);
    777   Module *ToOptimize = SplitFunctionsOutOfModule(ToNotOptimize,
    778                                                  MiscompiledFunctions,
    779                                                  VMap);
    780 
    781   outs() << "  Non-optimized portion: ";
    782   EmitProgressBitcode(ToNotOptimize, "tonotoptimize", true);
    783   delete ToNotOptimize;  // Delete hacked module.
    784 
    785   outs() << "  Portion that is input to optimizer: ";
    786   EmitProgressBitcode(ToOptimize, "tooptimize");
    787   delete ToOptimize;      // Delete hacked module.
    788 
    789   return;
    790 }
    791 
    792 /// CleanupAndPrepareModules - Get the specified modules ready for code
    793 /// generator testing.
    794 ///
    795 static void CleanupAndPrepareModules(BugDriver &BD, Module *&Test,
    796                                      Module *Safe) {
    797   // Clean up the modules, removing extra cruft that we don't need anymore...
    798   Test = BD.performFinalCleanups(Test);
    799 
    800   // If we are executing the JIT, we have several nasty issues to take care of.
    801   if (!BD.isExecutingJIT()) return;
    802 
    803   // First, if the main function is in the Safe module, we must add a stub to
    804   // the Test module to call into it.  Thus, we create a new function `main'
    805   // which just calls the old one.
    806   if (Function *oldMain = Safe->getFunction("main"))
    807     if (!oldMain->isDeclaration()) {
    808       // Rename it
    809       oldMain->setName("llvm_bugpoint_old_main");
    810       // Create a NEW `main' function with same type in the test module.
    811       Function *newMain = Function::Create(oldMain->getFunctionType(),
    812                                            GlobalValue::ExternalLinkage,
    813                                            "main", Test);
    814       // Create an `oldmain' prototype in the test module, which will
    815       // corresponds to the real main function in the same module.
    816       Function *oldMainProto = Function::Create(oldMain->getFunctionType(),
    817                                                 GlobalValue::ExternalLinkage,
    818                                                 oldMain->getName(), Test);
    819       // Set up and remember the argument list for the main function.
    820       std::vector<Value*> args;
    821       for (Function::arg_iterator
    822              I = newMain->arg_begin(), E = newMain->arg_end(),
    823              OI = oldMain->arg_begin(); I != E; ++I, ++OI) {
    824         I->setName(OI->getName());    // Copy argument names from oldMain
    825         args.push_back(I);
    826       }
    827 
    828       // Call the old main function and return its result
    829       BasicBlock *BB = BasicBlock::Create(Safe->getContext(), "entry", newMain);
    830       CallInst *call = CallInst::Create(oldMainProto, args, "", BB);
    831 
    832       // If the type of old function wasn't void, return value of call
    833       ReturnInst::Create(Safe->getContext(), call, BB);
    834     }
    835 
    836   // The second nasty issue we must deal with in the JIT is that the Safe
    837   // module cannot directly reference any functions defined in the test
    838   // module.  Instead, we use a JIT API call to dynamically resolve the
    839   // symbol.
    840 
    841   // Add the resolver to the Safe module.
    842   // Prototype: void *getPointerToNamedFunction(const char* Name)
    843   Constant *resolverFunc =
    844     Safe->getOrInsertFunction("getPointerToNamedFunction",
    845                     Type::getInt8PtrTy(Safe->getContext()),
    846                     Type::getInt8PtrTy(Safe->getContext()),
    847                        (Type *)0);
    848 
    849   // Use the function we just added to get addresses of functions we need.
    850   for (Module::iterator F = Safe->begin(), E = Safe->end(); F != E; ++F) {
    851     if (F->isDeclaration() && !F->use_empty() && &*F != resolverFunc &&
    852         !F->isIntrinsic() /* ignore intrinsics */) {
    853       Function *TestFn = Test->getFunction(F->getName());
    854 
    855       // Don't forward functions which are external in the test module too.
    856       if (TestFn && !TestFn->isDeclaration()) {
    857         // 1. Add a string constant with its name to the global file
    858         Constant *InitArray =
    859           ConstantDataArray::getString(F->getContext(), F->getName());
    860         GlobalVariable *funcName =
    861           new GlobalVariable(*Safe, InitArray->getType(), true /*isConstant*/,
    862                              GlobalValue::InternalLinkage, InitArray,
    863                              F->getName() + "_name");
    864 
    865         // 2. Use `GetElementPtr *funcName, 0, 0' to convert the string to an
    866         // sbyte* so it matches the signature of the resolver function.
    867 
    868         // GetElementPtr *funcName, ulong 0, ulong 0
    869         std::vector<Constant*> GEPargs(2,
    870                      Constant::getNullValue(Type::getInt32Ty(F->getContext())));
    871         Value *GEP = ConstantExpr::getGetElementPtr(funcName, GEPargs);
    872         std::vector<Value*> ResolverArgs;
    873         ResolverArgs.push_back(GEP);
    874 
    875         // Rewrite uses of F in global initializers, etc. to uses of a wrapper
    876         // function that dynamically resolves the calls to F via our JIT API
    877         if (!F->use_empty()) {
    878           // Create a new global to hold the cached function pointer.
    879           Constant *NullPtr = ConstantPointerNull::get(F->getType());
    880           GlobalVariable *Cache =
    881             new GlobalVariable(*F->getParent(), F->getType(),
    882                                false, GlobalValue::InternalLinkage,
    883                                NullPtr,F->getName()+".fpcache");
    884 
    885           // Construct a new stub function that will re-route calls to F
    886           FunctionType *FuncTy = F->getFunctionType();
    887           Function *FuncWrapper = Function::Create(FuncTy,
    888                                                    GlobalValue::InternalLinkage,
    889                                                    F->getName() + "_wrapper",
    890                                                    F->getParent());
    891           BasicBlock *EntryBB  = BasicBlock::Create(F->getContext(),
    892                                                     "entry", FuncWrapper);
    893           BasicBlock *DoCallBB = BasicBlock::Create(F->getContext(),
    894                                                     "usecache", FuncWrapper);
    895           BasicBlock *LookupBB = BasicBlock::Create(F->getContext(),
    896                                                     "lookupfp", FuncWrapper);
    897 
    898           // Check to see if we already looked up the value.
    899           Value *CachedVal = new LoadInst(Cache, "fpcache", EntryBB);
    900           Value *IsNull = new ICmpInst(*EntryBB, ICmpInst::ICMP_EQ, CachedVal,
    901                                        NullPtr, "isNull");
    902           BranchInst::Create(LookupBB, DoCallBB, IsNull, EntryBB);
    903 
    904           // Resolve the call to function F via the JIT API:
    905           //
    906           // call resolver(GetElementPtr...)
    907           CallInst *Resolver =
    908             CallInst::Create(resolverFunc, ResolverArgs, "resolver", LookupBB);
    909 
    910           // Cast the result from the resolver to correctly-typed function.
    911           CastInst *CastedResolver =
    912             new BitCastInst(Resolver,
    913                             PointerType::getUnqual(F->getFunctionType()),
    914                             "resolverCast", LookupBB);
    915 
    916           // Save the value in our cache.
    917           new StoreInst(CastedResolver, Cache, LookupBB);
    918           BranchInst::Create(DoCallBB, LookupBB);
    919 
    920           PHINode *FuncPtr = PHINode::Create(NullPtr->getType(), 2,
    921                                              "fp", DoCallBB);
    922           FuncPtr->addIncoming(CastedResolver, LookupBB);
    923           FuncPtr->addIncoming(CachedVal, EntryBB);
    924 
    925           // Save the argument list.
    926           std::vector<Value*> Args;
    927           for (Function::arg_iterator i = FuncWrapper->arg_begin(),
    928                  e = FuncWrapper->arg_end(); i != e; ++i)
    929             Args.push_back(i);
    930 
    931           // Pass on the arguments to the real function, return its result
    932           if (F->getReturnType()->isVoidTy()) {
    933             CallInst::Create(FuncPtr, Args, "", DoCallBB);
    934             ReturnInst::Create(F->getContext(), DoCallBB);
    935           } else {
    936             CallInst *Call = CallInst::Create(FuncPtr, Args,
    937                                               "retval", DoCallBB);
    938             ReturnInst::Create(F->getContext(),Call, DoCallBB);
    939           }
    940 
    941           // Use the wrapper function instead of the old function
    942           F->replaceAllUsesWith(FuncWrapper);
    943         }
    944       }
    945     }
    946   }
    947 
    948   if (verifyModule(*Test) || verifyModule(*Safe)) {
    949     errs() << "Bugpoint has a bug, which corrupted a module!!\n";
    950     abort();
    951   }
    952 }
    953 
    954 
    955 
    956 /// TestCodeGenerator - This is the predicate function used to check to see if
    957 /// the "Test" portion of the program is miscompiled by the code generator under
    958 /// test.  If so, return true.  In any case, both module arguments are deleted.
    959 ///
    960 static bool TestCodeGenerator(BugDriver &BD, Module *Test, Module *Safe,
    961                               std::string &Error) {
    962   CleanupAndPrepareModules(BD, Test, Safe);
    963 
    964   SmallString<128> TestModuleBC;
    965   int TestModuleFD;
    966   error_code EC = sys::fs::createTemporaryFile("bugpoint.test", "bc",
    967                                                TestModuleFD, TestModuleBC);
    968   if (EC) {
    969     errs() << BD.getToolName() << "Error making unique filename: "
    970            << EC.message() << "\n";
    971     exit(1);
    972   }
    973   if (BD.writeProgramToFile(TestModuleBC.str(), TestModuleFD, Test)) {
    974     errs() << "Error writing bitcode to `" << TestModuleBC.str()
    975            << "'\nExiting.";
    976     exit(1);
    977   }
    978   delete Test;
    979 
    980   FileRemover TestModuleBCRemover(TestModuleBC.str(), !SaveTemps);
    981 
    982   // Make the shared library
    983   SmallString<128> SafeModuleBC;
    984   int SafeModuleFD;
    985   EC = sys::fs::createTemporaryFile("bugpoint.safe", "bc", SafeModuleFD,
    986                                     SafeModuleBC);
    987   if (EC) {
    988     errs() << BD.getToolName() << "Error making unique filename: "
    989            << EC.message() << "\n";
    990     exit(1);
    991   }
    992 
    993   if (BD.writeProgramToFile(SafeModuleBC.str(), SafeModuleFD, Safe)) {
    994     errs() << "Error writing bitcode to `" << SafeModuleBC.str()
    995            << "'\nExiting.";
    996     exit(1);
    997   }
    998 
    999   FileRemover SafeModuleBCRemover(SafeModuleBC.str(), !SaveTemps);
   1000 
   1001   std::string SharedObject = BD.compileSharedObject(SafeModuleBC.str(), Error);
   1002   if (!Error.empty())
   1003     return false;
   1004   delete Safe;
   1005 
   1006   FileRemover SharedObjectRemover(SharedObject, !SaveTemps);
   1007 
   1008   // Run the code generator on the `Test' code, loading the shared library.
   1009   // The function returns whether or not the new output differs from reference.
   1010   bool Result = BD.diffProgram(BD.getProgram(), TestModuleBC.str(),
   1011                                SharedObject, false, &Error);
   1012   if (!Error.empty())
   1013     return false;
   1014 
   1015   if (Result)
   1016     errs() << ": still failing!\n";
   1017   else
   1018     errs() << ": didn't fail.\n";
   1019 
   1020   return Result;
   1021 }
   1022 
   1023 
   1024 /// debugCodeGenerator - debug errors in LLC, LLI, or CBE.
   1025 ///
   1026 bool BugDriver::debugCodeGenerator(std::string *Error) {
   1027   if ((void*)SafeInterpreter == (void*)Interpreter) {
   1028     std::string Result = executeProgramSafely(Program, "bugpoint.safe.out",
   1029                                               Error);
   1030     if (Error->empty()) {
   1031       outs() << "\n*** The \"safe\" i.e. 'known good' backend cannot match "
   1032              << "the reference diff.  This may be due to a\n    front-end "
   1033              << "bug or a bug in the original program, but this can also "
   1034              << "happen if bugpoint isn't running the program with the "
   1035              << "right flags or input.\n    I left the result of executing "
   1036              << "the program with the \"safe\" backend in this file for "
   1037              << "you: '"
   1038              << Result << "'.\n";
   1039     }
   1040     return true;
   1041   }
   1042 
   1043   DisambiguateGlobalSymbols(Program);
   1044 
   1045   std::vector<Function*> Funcs = DebugAMiscompilation(*this, TestCodeGenerator,
   1046                                                       *Error);
   1047   if (!Error->empty())
   1048     return true;
   1049 
   1050   // Split the module into the two halves of the program we want.
   1051   ValueToValueMapTy VMap;
   1052   Module *ToNotCodeGen = CloneModule(getProgram(), VMap);
   1053   Module *ToCodeGen = SplitFunctionsOutOfModule(ToNotCodeGen, Funcs, VMap);
   1054 
   1055   // Condition the modules
   1056   CleanupAndPrepareModules(*this, ToCodeGen, ToNotCodeGen);
   1057 
   1058   SmallString<128> TestModuleBC;
   1059   int TestModuleFD;
   1060   error_code EC = sys::fs::createTemporaryFile("bugpoint.test", "bc",
   1061                                                TestModuleFD, TestModuleBC);
   1062   if (EC) {
   1063     errs() << getToolName() << "Error making unique filename: "
   1064            << EC.message() << "\n";
   1065     exit(1);
   1066   }
   1067 
   1068   if (writeProgramToFile(TestModuleBC.str(), TestModuleFD, ToCodeGen)) {
   1069     errs() << "Error writing bitcode to `" << TestModuleBC.str()
   1070            << "'\nExiting.";
   1071     exit(1);
   1072   }
   1073   delete ToCodeGen;
   1074 
   1075   // Make the shared library
   1076   SmallString<128> SafeModuleBC;
   1077   int SafeModuleFD;
   1078   EC = sys::fs::createTemporaryFile("bugpoint.safe", "bc", SafeModuleFD,
   1079                                     SafeModuleBC);
   1080   if (EC) {
   1081     errs() << getToolName() << "Error making unique filename: "
   1082            << EC.message() << "\n";
   1083     exit(1);
   1084   }
   1085 
   1086   if (writeProgramToFile(SafeModuleBC.str(), SafeModuleFD, ToNotCodeGen)) {
   1087     errs() << "Error writing bitcode to `" << SafeModuleBC.str()
   1088            << "'\nExiting.";
   1089     exit(1);
   1090   }
   1091   std::string SharedObject = compileSharedObject(SafeModuleBC.str(), *Error);
   1092   if (!Error->empty())
   1093     return true;
   1094   delete ToNotCodeGen;
   1095 
   1096   outs() << "You can reproduce the problem with the command line: \n";
   1097   if (isExecutingJIT()) {
   1098     outs() << "  lli -load " << SharedObject << " " << TestModuleBC.str();
   1099   } else {
   1100     outs() << "  llc " << TestModuleBC.str() << " -o " << TestModuleBC.str()
   1101            << ".s\n";
   1102     outs() << "  gcc " << SharedObject << " " << TestModuleBC.str()
   1103               << ".s -o " << TestModuleBC.str() << ".exe";
   1104 #if defined (HAVE_LINK_R)
   1105     outs() << " -Wl,-R.";
   1106 #endif
   1107     outs() << "\n";
   1108     outs() << "  " << TestModuleBC.str() << ".exe";
   1109   }
   1110   for (unsigned i = 0, e = InputArgv.size(); i != e; ++i)
   1111     outs() << " " << InputArgv[i];
   1112   outs() << '\n';
   1113   outs() << "The shared object was created with:\n  llc -march=c "
   1114          << SafeModuleBC.str() << " -o temporary.c\n"
   1115          << "  gcc -xc temporary.c -O2 -o " << SharedObject;
   1116   if (TargetTriple.getArch() == Triple::sparc)
   1117     outs() << " -G";              // Compile a shared library, `-G' for Sparc
   1118   else
   1119     outs() << " -fPIC -shared";   // `-shared' for Linux/X86, maybe others
   1120 
   1121   outs() << " -fno-strict-aliasing\n";
   1122 
   1123   return false;
   1124 }
   1125