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      1 //===- ExtractFunction.cpp - Extract a function from Program --------------===//
      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 several methods that are used to extract functions,
     11 // loops, or portions of a module from the rest of the module.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #include "BugDriver.h"
     16 #include "llvm/IR/Constants.h"
     17 #include "llvm/IR/DataLayout.h"
     18 #include "llvm/IR/DerivedTypes.h"
     19 #include "llvm/IR/LLVMContext.h"
     20 #include "llvm/IR/LegacyPassManager.h"
     21 #include "llvm/IR/Module.h"
     22 #include "llvm/IR/Verifier.h"
     23 #include "llvm/Pass.h"
     24 #include "llvm/Support/CommandLine.h"
     25 #include "llvm/Support/Debug.h"
     26 #include "llvm/Support/FileUtilities.h"
     27 #include "llvm/Support/Path.h"
     28 #include "llvm/Support/Signals.h"
     29 #include "llvm/Support/ToolOutputFile.h"
     30 #include "llvm/Transforms/IPO.h"
     31 #include "llvm/Transforms/Scalar.h"
     32 #include "llvm/Transforms/Utils/Cloning.h"
     33 #include "llvm/Transforms/Utils/CodeExtractor.h"
     34 #include <set>
     35 using namespace llvm;
     36 
     37 #define DEBUG_TYPE "bugpoint"
     38 
     39 namespace llvm {
     40   bool DisableSimplifyCFG = false;
     41   extern cl::opt<std::string> OutputPrefix;
     42 } // End llvm namespace
     43 
     44 namespace {
     45   cl::opt<bool>
     46   NoDCE ("disable-dce",
     47          cl::desc("Do not use the -dce pass to reduce testcases"));
     48   cl::opt<bool, true>
     49   NoSCFG("disable-simplifycfg", cl::location(DisableSimplifyCFG),
     50          cl::desc("Do not use the -simplifycfg pass to reduce testcases"));
     51 
     52   Function* globalInitUsesExternalBA(GlobalVariable* GV) {
     53     if (!GV->hasInitializer())
     54       return nullptr;
     55 
     56     Constant *I = GV->getInitializer();
     57 
     58     // walk the values used by the initializer
     59     // (and recurse into things like ConstantExpr)
     60     std::vector<Constant*> Todo;
     61     std::set<Constant*> Done;
     62     Todo.push_back(I);
     63 
     64     while (!Todo.empty()) {
     65       Constant* V = Todo.back();
     66       Todo.pop_back();
     67       Done.insert(V);
     68 
     69       if (BlockAddress *BA = dyn_cast<BlockAddress>(V)) {
     70         Function *F = BA->getFunction();
     71         if (F->isDeclaration())
     72           return F;
     73       }
     74 
     75       for (User::op_iterator i = V->op_begin(), e = V->op_end(); i != e; ++i) {
     76         Constant *C = dyn_cast<Constant>(*i);
     77         if (C && !isa<GlobalValue>(C) && !Done.count(C))
     78           Todo.push_back(C);
     79       }
     80     }
     81     return nullptr;
     82   }
     83 }  // end anonymous namespace
     84 
     85 std::unique_ptr<Module>
     86 BugDriver::deleteInstructionFromProgram(const Instruction *I,
     87                                         unsigned Simplification) {
     88   // FIXME, use vmap?
     89   Module *Clone = CloneModule(Program);
     90 
     91   const BasicBlock *PBB = I->getParent();
     92   const Function *PF = PBB->getParent();
     93 
     94   Module::iterator RFI = Clone->begin(); // Get iterator to corresponding fn
     95   std::advance(RFI, std::distance(PF->getParent()->begin(),
     96                                   Module::const_iterator(PF)));
     97 
     98   Function::iterator RBI = RFI->begin();  // Get iterator to corresponding BB
     99   std::advance(RBI, std::distance(PF->begin(), Function::const_iterator(PBB)));
    100 
    101   BasicBlock::iterator RI = RBI->begin(); // Get iterator to corresponding inst
    102   std::advance(RI, std::distance(PBB->begin(), BasicBlock::const_iterator(I)));
    103   Instruction *TheInst = RI;              // Got the corresponding instruction!
    104 
    105   // If this instruction produces a value, replace any users with null values
    106   if (!TheInst->getType()->isVoidTy())
    107     TheInst->replaceAllUsesWith(Constant::getNullValue(TheInst->getType()));
    108 
    109   // Remove the instruction from the program.
    110   TheInst->getParent()->getInstList().erase(TheInst);
    111 
    112   // Spiff up the output a little bit.
    113   std::vector<std::string> Passes;
    114 
    115   /// Can we get rid of the -disable-* options?
    116   if (Simplification > 1 && !NoDCE)
    117     Passes.push_back("dce");
    118   if (Simplification && !DisableSimplifyCFG)
    119     Passes.push_back("simplifycfg");      // Delete dead control flow
    120 
    121   Passes.push_back("verify");
    122   std::unique_ptr<Module> New = runPassesOn(Clone, Passes);
    123   delete Clone;
    124   if (!New) {
    125     errs() << "Instruction removal failed.  Sorry. :(  Please report a bug!\n";
    126     exit(1);
    127   }
    128   return New;
    129 }
    130 
    131 std::unique_ptr<Module>
    132 BugDriver::performFinalCleanups(Module *M, bool MayModifySemantics) {
    133   // Make all functions external, so GlobalDCE doesn't delete them...
    134   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
    135     I->setLinkage(GlobalValue::ExternalLinkage);
    136 
    137   std::vector<std::string> CleanupPasses;
    138   CleanupPasses.push_back("globaldce");
    139 
    140   if (MayModifySemantics)
    141     CleanupPasses.push_back("deadarghaX0r");
    142   else
    143     CleanupPasses.push_back("deadargelim");
    144 
    145   std::unique_ptr<Module> New = runPassesOn(M, CleanupPasses);
    146   if (!New) {
    147     errs() << "Final cleanups failed.  Sorry. :(  Please report a bug!\n";
    148     return nullptr;
    149   }
    150   delete M;
    151   return New;
    152 }
    153 
    154 std::unique_ptr<Module> BugDriver::extractLoop(Module *M) {
    155   std::vector<std::string> LoopExtractPasses;
    156   LoopExtractPasses.push_back("loop-extract-single");
    157 
    158   std::unique_ptr<Module> NewM = runPassesOn(M, LoopExtractPasses);
    159   if (!NewM) {
    160     outs() << "*** Loop extraction failed: ";
    161     EmitProgressBitcode(M, "loopextraction", true);
    162     outs() << "*** Sorry. :(  Please report a bug!\n";
    163     return nullptr;
    164   }
    165 
    166   // Check to see if we created any new functions.  If not, no loops were
    167   // extracted and we should return null.  Limit the number of loops we extract
    168   // to avoid taking forever.
    169   static unsigned NumExtracted = 32;
    170   if (M->size() == NewM->size() || --NumExtracted == 0) {
    171     return nullptr;
    172   } else {
    173     assert(M->size() < NewM->size() && "Loop extract removed functions?");
    174     Module::iterator MI = NewM->begin();
    175     for (unsigned i = 0, e = M->size(); i != e; ++i)
    176       ++MI;
    177   }
    178 
    179   return NewM;
    180 }
    181 
    182 
    183 // DeleteFunctionBody - "Remove" the function by deleting all of its basic
    184 // blocks, making it external.
    185 //
    186 void llvm::DeleteFunctionBody(Function *F) {
    187   // delete the body of the function...
    188   F->deleteBody();
    189   assert(F->isDeclaration() && "This didn't make the function external!");
    190 }
    191 
    192 /// GetTorInit - Given a list of entries for static ctors/dtors, return them
    193 /// as a constant array.
    194 static Constant *GetTorInit(std::vector<std::pair<Function*, int> > &TorList) {
    195   assert(!TorList.empty() && "Don't create empty tor list!");
    196   std::vector<Constant*> ArrayElts;
    197   Type *Int32Ty = Type::getInt32Ty(TorList[0].first->getContext());
    198 
    199   StructType *STy =
    200       StructType::get(Int32Ty, TorList[0].first->getType(), nullptr);
    201   for (unsigned i = 0, e = TorList.size(); i != e; ++i) {
    202     Constant *Elts[] = {
    203       ConstantInt::get(Int32Ty, TorList[i].second),
    204       TorList[i].first
    205     };
    206     ArrayElts.push_back(ConstantStruct::get(STy, Elts));
    207   }
    208   return ConstantArray::get(ArrayType::get(ArrayElts[0]->getType(),
    209                                            ArrayElts.size()),
    210                             ArrayElts);
    211 }
    212 
    213 /// SplitStaticCtorDtor - A module was recently split into two parts, M1/M2, and
    214 /// M1 has all of the global variables.  If M2 contains any functions that are
    215 /// static ctors/dtors, we need to add an llvm.global_[cd]tors global to M2, and
    216 /// prune appropriate entries out of M1s list.
    217 static void SplitStaticCtorDtor(const char *GlobalName, Module *M1, Module *M2,
    218                                 ValueToValueMapTy &VMap) {
    219   GlobalVariable *GV = M1->getNamedGlobal(GlobalName);
    220   if (!GV || GV->isDeclaration() || GV->hasLocalLinkage() ||
    221       !GV->use_empty()) return;
    222 
    223   std::vector<std::pair<Function*, int> > M1Tors, M2Tors;
    224   ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
    225   if (!InitList) return;
    226 
    227   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
    228     if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
    229       if (CS->getNumOperands() != 2) return;  // Not array of 2-element structs.
    230 
    231       if (CS->getOperand(1)->isNullValue())
    232         break;  // Found a null terminator, stop here.
    233 
    234       ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
    235       int Priority = CI ? CI->getSExtValue() : 0;
    236 
    237       Constant *FP = CS->getOperand(1);
    238       if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
    239         if (CE->isCast())
    240           FP = CE->getOperand(0);
    241       if (Function *F = dyn_cast<Function>(FP)) {
    242         if (!F->isDeclaration())
    243           M1Tors.push_back(std::make_pair(F, Priority));
    244         else {
    245           // Map to M2's version of the function.
    246           F = cast<Function>(VMap[F]);
    247           M2Tors.push_back(std::make_pair(F, Priority));
    248         }
    249       }
    250     }
    251   }
    252 
    253   GV->eraseFromParent();
    254   if (!M1Tors.empty()) {
    255     Constant *M1Init = GetTorInit(M1Tors);
    256     new GlobalVariable(*M1, M1Init->getType(), false,
    257                        GlobalValue::AppendingLinkage,
    258                        M1Init, GlobalName);
    259   }
    260 
    261   GV = M2->getNamedGlobal(GlobalName);
    262   assert(GV && "Not a clone of M1?");
    263   assert(GV->use_empty() && "llvm.ctors shouldn't have uses!");
    264 
    265   GV->eraseFromParent();
    266   if (!M2Tors.empty()) {
    267     Constant *M2Init = GetTorInit(M2Tors);
    268     new GlobalVariable(*M2, M2Init->getType(), false,
    269                        GlobalValue::AppendingLinkage,
    270                        M2Init, GlobalName);
    271   }
    272 }
    273 
    274 
    275 /// SplitFunctionsOutOfModule - Given a module and a list of functions in the
    276 /// module, split the functions OUT of the specified module, and place them in
    277 /// the new module.
    278 Module *
    279 llvm::SplitFunctionsOutOfModule(Module *M,
    280                                 const std::vector<Function*> &F,
    281                                 ValueToValueMapTy &VMap) {
    282   // Make sure functions & globals are all external so that linkage
    283   // between the two modules will work.
    284   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
    285     I->setLinkage(GlobalValue::ExternalLinkage);
    286   for (Module::global_iterator I = M->global_begin(), E = M->global_end();
    287        I != E; ++I) {
    288     if (I->hasName() && I->getName()[0] == '\01')
    289       I->setName(I->getName().substr(1));
    290     I->setLinkage(GlobalValue::ExternalLinkage);
    291   }
    292 
    293   ValueToValueMapTy NewVMap;
    294   Module *New = CloneModule(M, NewVMap);
    295 
    296   // Remove the Test functions from the Safe module
    297   std::set<Function *> TestFunctions;
    298   for (unsigned i = 0, e = F.size(); i != e; ++i) {
    299     Function *TNOF = cast<Function>(VMap[F[i]]);
    300     DEBUG(errs() << "Removing function ");
    301     DEBUG(TNOF->printAsOperand(errs(), false));
    302     DEBUG(errs() << "\n");
    303     TestFunctions.insert(cast<Function>(NewVMap[TNOF]));
    304     DeleteFunctionBody(TNOF);       // Function is now external in this module!
    305   }
    306 
    307 
    308   // Remove the Safe functions from the Test module
    309   for (Module::iterator I = New->begin(), E = New->end(); I != E; ++I)
    310     if (!TestFunctions.count(I))
    311       DeleteFunctionBody(I);
    312 
    313 
    314   // Try to split the global initializers evenly
    315   for (Module::global_iterator I = M->global_begin(), E = M->global_end();
    316        I != E; ++I) {
    317     GlobalVariable *GV = cast<GlobalVariable>(NewVMap[I]);
    318     if (Function *TestFn = globalInitUsesExternalBA(I)) {
    319       if (Function *SafeFn = globalInitUsesExternalBA(GV)) {
    320         errs() << "*** Error: when reducing functions, encountered "
    321                   "the global '";
    322         GV->printAsOperand(errs(), false);
    323         errs() << "' with an initializer that references blockaddresses "
    324                   "from safe function '" << SafeFn->getName()
    325                << "' and from test function '" << TestFn->getName() << "'.\n";
    326         exit(1);
    327       }
    328       I->setInitializer(nullptr);  // Delete the initializer to make it external
    329     } else {
    330       // If we keep it in the safe module, then delete it in the test module
    331       GV->setInitializer(nullptr);
    332     }
    333   }
    334 
    335   // Make sure that there is a global ctor/dtor array in both halves of the
    336   // module if they both have static ctor/dtor functions.
    337   SplitStaticCtorDtor("llvm.global_ctors", M, New, NewVMap);
    338   SplitStaticCtorDtor("llvm.global_dtors", M, New, NewVMap);
    339 
    340   return New;
    341 }
    342 
    343 //===----------------------------------------------------------------------===//
    344 // Basic Block Extraction Code
    345 //===----------------------------------------------------------------------===//
    346 
    347 std::unique_ptr<Module>
    348 BugDriver::extractMappedBlocksFromModule(const std::vector<BasicBlock *> &BBs,
    349                                          Module *M) {
    350   SmallString<128> Filename;
    351   int FD;
    352   std::error_code EC = sys::fs::createUniqueFile(
    353       OutputPrefix + "-extractblocks%%%%%%%", FD, Filename);
    354   if (EC) {
    355     outs() << "*** Basic Block extraction failed!\n";
    356     errs() << "Error creating temporary file: " << EC.message() << "\n";
    357     EmitProgressBitcode(M, "basicblockextractfail", true);
    358     return nullptr;
    359   }
    360   sys::RemoveFileOnSignal(Filename);
    361 
    362   tool_output_file BlocksToNotExtractFile(Filename.c_str(), FD);
    363   for (std::vector<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
    364        I != E; ++I) {
    365     BasicBlock *BB = *I;
    366     // If the BB doesn't have a name, give it one so we have something to key
    367     // off of.
    368     if (!BB->hasName()) BB->setName("tmpbb");
    369     BlocksToNotExtractFile.os() << BB->getParent()->getName() << " "
    370                                 << BB->getName() << "\n";
    371   }
    372   BlocksToNotExtractFile.os().close();
    373   if (BlocksToNotExtractFile.os().has_error()) {
    374     errs() << "Error writing list of blocks to not extract\n";
    375     EmitProgressBitcode(M, "basicblockextractfail", true);
    376     BlocksToNotExtractFile.os().clear_error();
    377     return nullptr;
    378   }
    379   BlocksToNotExtractFile.keep();
    380 
    381   std::string uniqueFN = "--extract-blocks-file=";
    382   uniqueFN += Filename.str();
    383   const char *ExtraArg = uniqueFN.c_str();
    384 
    385   std::vector<std::string> PI;
    386   PI.push_back("extract-blocks");
    387   std::unique_ptr<Module> Ret = runPassesOn(M, PI, false, 1, &ExtraArg);
    388 
    389   sys::fs::remove(Filename.c_str());
    390 
    391   if (!Ret) {
    392     outs() << "*** Basic Block extraction failed, please report a bug!\n";
    393     EmitProgressBitcode(M, "basicblockextractfail", true);
    394   }
    395   return Ret;
    396 }
    397