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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).release();
     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 static void eliminateAliases(GlobalValue *GV) {
    183   // First, check whether a GlobalAlias references this definition.
    184   // GlobalAlias MAY NOT reference declarations.
    185   for (;;) {
    186     // 1. Find aliases
    187     SmallVector<GlobalAlias*,1> aliases;
    188     Module *M = GV->getParent();
    189     for (Module::alias_iterator I=M->alias_begin(), E=M->alias_end(); I!=E; ++I)
    190       if (I->getAliasee()->stripPointerCasts() == GV)
    191         aliases.push_back(&*I);
    192     if (aliases.empty())
    193       break;
    194     // 2. Resolve aliases
    195     for (unsigned i=0, e=aliases.size(); i<e; ++i) {
    196       aliases[i]->replaceAllUsesWith(aliases[i]->getAliasee());
    197       aliases[i]->eraseFromParent();
    198     }
    199     // 3. Repeat until no more aliases found; there might
    200     // be an alias to an alias...
    201   }
    202 }
    203 
    204 //
    205 // DeleteGlobalInitializer - "Remove" the global variable by deleting its initializer,
    206 // making it external.
    207 //
    208 void llvm::DeleteGlobalInitializer(GlobalVariable *GV) {
    209   eliminateAliases(GV);
    210   GV->setInitializer(nullptr);
    211 }
    212 
    213 // DeleteFunctionBody - "Remove" the function by deleting all of its basic
    214 // blocks, making it external.
    215 //
    216 void llvm::DeleteFunctionBody(Function *F) {
    217   eliminateAliases(F);
    218   // Function declarations can't have comdats.
    219   F->setComdat(nullptr);
    220 
    221   // delete the body of the function...
    222   F->deleteBody();
    223   assert(F->isDeclaration() && "This didn't make the function external!");
    224 }
    225 
    226 /// GetTorInit - Given a list of entries for static ctors/dtors, return them
    227 /// as a constant array.
    228 static Constant *GetTorInit(std::vector<std::pair<Function*, int> > &TorList) {
    229   assert(!TorList.empty() && "Don't create empty tor list!");
    230   std::vector<Constant*> ArrayElts;
    231   Type *Int32Ty = Type::getInt32Ty(TorList[0].first->getContext());
    232 
    233   StructType *STy =
    234       StructType::get(Int32Ty, TorList[0].first->getType(), nullptr);
    235   for (unsigned i = 0, e = TorList.size(); i != e; ++i) {
    236     Constant *Elts[] = {
    237       ConstantInt::get(Int32Ty, TorList[i].second),
    238       TorList[i].first
    239     };
    240     ArrayElts.push_back(ConstantStruct::get(STy, Elts));
    241   }
    242   return ConstantArray::get(ArrayType::get(ArrayElts[0]->getType(),
    243                                            ArrayElts.size()),
    244                             ArrayElts);
    245 }
    246 
    247 /// SplitStaticCtorDtor - A module was recently split into two parts, M1/M2, and
    248 /// M1 has all of the global variables.  If M2 contains any functions that are
    249 /// static ctors/dtors, we need to add an llvm.global_[cd]tors global to M2, and
    250 /// prune appropriate entries out of M1s list.
    251 static void SplitStaticCtorDtor(const char *GlobalName, Module *M1, Module *M2,
    252                                 ValueToValueMapTy &VMap) {
    253   GlobalVariable *GV = M1->getNamedGlobal(GlobalName);
    254   if (!GV || GV->isDeclaration() || GV->hasLocalLinkage() ||
    255       !GV->use_empty()) return;
    256 
    257   std::vector<std::pair<Function*, int> > M1Tors, M2Tors;
    258   ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
    259   if (!InitList) return;
    260 
    261   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
    262     if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
    263       if (CS->getNumOperands() != 2) return;  // Not array of 2-element structs.
    264 
    265       if (CS->getOperand(1)->isNullValue())
    266         break;  // Found a null terminator, stop here.
    267 
    268       ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
    269       int Priority = CI ? CI->getSExtValue() : 0;
    270 
    271       Constant *FP = CS->getOperand(1);
    272       if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
    273         if (CE->isCast())
    274           FP = CE->getOperand(0);
    275       if (Function *F = dyn_cast<Function>(FP)) {
    276         if (!F->isDeclaration())
    277           M1Tors.push_back(std::make_pair(F, Priority));
    278         else {
    279           // Map to M2's version of the function.
    280           F = cast<Function>(VMap[F]);
    281           M2Tors.push_back(std::make_pair(F, Priority));
    282         }
    283       }
    284     }
    285   }
    286 
    287   GV->eraseFromParent();
    288   if (!M1Tors.empty()) {
    289     Constant *M1Init = GetTorInit(M1Tors);
    290     new GlobalVariable(*M1, M1Init->getType(), false,
    291                        GlobalValue::AppendingLinkage,
    292                        M1Init, GlobalName);
    293   }
    294 
    295   GV = M2->getNamedGlobal(GlobalName);
    296   assert(GV && "Not a clone of M1?");
    297   assert(GV->use_empty() && "llvm.ctors shouldn't have uses!");
    298 
    299   GV->eraseFromParent();
    300   if (!M2Tors.empty()) {
    301     Constant *M2Init = GetTorInit(M2Tors);
    302     new GlobalVariable(*M2, M2Init->getType(), false,
    303                        GlobalValue::AppendingLinkage,
    304                        M2Init, GlobalName);
    305   }
    306 }
    307 
    308 std::unique_ptr<Module>
    309 llvm::SplitFunctionsOutOfModule(Module *M, const std::vector<Function *> &F,
    310                                 ValueToValueMapTy &VMap) {
    311   // Make sure functions & globals are all external so that linkage
    312   // between the two modules will work.
    313   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
    314     I->setLinkage(GlobalValue::ExternalLinkage);
    315   for (Module::global_iterator I = M->global_begin(), E = M->global_end();
    316        I != E; ++I) {
    317     if (I->hasName() && I->getName()[0] == '\01')
    318       I->setName(I->getName().substr(1));
    319     I->setLinkage(GlobalValue::ExternalLinkage);
    320   }
    321 
    322   ValueToValueMapTy NewVMap;
    323   std::unique_ptr<Module> New = CloneModule(M, NewVMap);
    324 
    325   // Remove the Test functions from the Safe module
    326   std::set<Function *> TestFunctions;
    327   for (unsigned i = 0, e = F.size(); i != e; ++i) {
    328     Function *TNOF = cast<Function>(VMap[F[i]]);
    329     DEBUG(errs() << "Removing function ");
    330     DEBUG(TNOF->printAsOperand(errs(), false));
    331     DEBUG(errs() << "\n");
    332     TestFunctions.insert(cast<Function>(NewVMap[TNOF]));
    333     DeleteFunctionBody(TNOF);       // Function is now external in this module!
    334   }
    335 
    336 
    337   // Remove the Safe functions from the Test module
    338   for (Function &I : *New)
    339     if (!TestFunctions.count(&I))
    340       DeleteFunctionBody(&I);
    341 
    342   // Try to split the global initializers evenly
    343   for (GlobalVariable &I : M->globals()) {
    344     GlobalVariable *GV = cast<GlobalVariable>(NewVMap[&I]);
    345     if (Function *TestFn = globalInitUsesExternalBA(&I)) {
    346       if (Function *SafeFn = globalInitUsesExternalBA(GV)) {
    347         errs() << "*** Error: when reducing functions, encountered "
    348                   "the global '";
    349         GV->printAsOperand(errs(), false);
    350         errs() << "' with an initializer that references blockaddresses "
    351                   "from safe function '" << SafeFn->getName()
    352                << "' and from test function '" << TestFn->getName() << "'.\n";
    353         exit(1);
    354       }
    355       DeleteGlobalInitializer(&I); // Delete the initializer to make it external
    356     } else {
    357       // If we keep it in the safe module, then delete it in the test module
    358       DeleteGlobalInitializer(GV);
    359     }
    360   }
    361 
    362   // Make sure that there is a global ctor/dtor array in both halves of the
    363   // module if they both have static ctor/dtor functions.
    364   SplitStaticCtorDtor("llvm.global_ctors", M, New.get(), NewVMap);
    365   SplitStaticCtorDtor("llvm.global_dtors", M, New.get(), NewVMap);
    366 
    367   return New;
    368 }
    369 
    370 //===----------------------------------------------------------------------===//
    371 // Basic Block Extraction Code
    372 //===----------------------------------------------------------------------===//
    373 
    374 std::unique_ptr<Module>
    375 BugDriver::extractMappedBlocksFromModule(const std::vector<BasicBlock *> &BBs,
    376                                          Module *M) {
    377   SmallString<128> Filename;
    378   int FD;
    379   std::error_code EC = sys::fs::createUniqueFile(
    380       OutputPrefix + "-extractblocks%%%%%%%", FD, Filename);
    381   if (EC) {
    382     outs() << "*** Basic Block extraction failed!\n";
    383     errs() << "Error creating temporary file: " << EC.message() << "\n";
    384     EmitProgressBitcode(M, "basicblockextractfail", true);
    385     return nullptr;
    386   }
    387   sys::RemoveFileOnSignal(Filename);
    388 
    389   tool_output_file BlocksToNotExtractFile(Filename.c_str(), FD);
    390   for (std::vector<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
    391        I != E; ++I) {
    392     BasicBlock *BB = *I;
    393     // If the BB doesn't have a name, give it one so we have something to key
    394     // off of.
    395     if (!BB->hasName()) BB->setName("tmpbb");
    396     BlocksToNotExtractFile.os() << BB->getParent()->getName() << " "
    397                                 << BB->getName() << "\n";
    398   }
    399   BlocksToNotExtractFile.os().close();
    400   if (BlocksToNotExtractFile.os().has_error()) {
    401     errs() << "Error writing list of blocks to not extract\n";
    402     EmitProgressBitcode(M, "basicblockextractfail", true);
    403     BlocksToNotExtractFile.os().clear_error();
    404     return nullptr;
    405   }
    406   BlocksToNotExtractFile.keep();
    407 
    408   std::string uniqueFN = "--extract-blocks-file=";
    409   uniqueFN += Filename.str();
    410   const char *ExtraArg = uniqueFN.c_str();
    411 
    412   std::vector<std::string> PI;
    413   PI.push_back("extract-blocks");
    414   std::unique_ptr<Module> Ret = runPassesOn(M, PI, 1, &ExtraArg);
    415 
    416   sys::fs::remove(Filename.c_str());
    417 
    418   if (!Ret) {
    419     outs() << "*** Basic Block extraction failed, please report a bug!\n";
    420     EmitProgressBitcode(M, "basicblockextractfail", true);
    421   }
    422   return Ret;
    423 }
    424