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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> NoDCE("disable-dce",
     46                     cl::desc("Do not use the -dce pass to reduce testcases"));
     47 cl::opt<bool, true>
     48     NoSCFG("disable-simplifycfg", cl::location(DisableSimplifyCFG),
     49            cl::desc("Do not use the -simplifycfg pass to reduce testcases"));
     50 
     51 Function *globalInitUsesExternalBA(GlobalVariable *GV) {
     52   if (!GV->hasInitializer())
     53     return nullptr;
     54 
     55   Constant *I = GV->getInitializer();
     56 
     57   // walk the values used by the initializer
     58   // (and recurse into things like ConstantExpr)
     59   std::vector<Constant *> Todo;
     60   std::set<Constant *> Done;
     61   Todo.push_back(I);
     62 
     63   while (!Todo.empty()) {
     64     Constant *V = Todo.back();
     65     Todo.pop_back();
     66     Done.insert(V);
     67 
     68     if (BlockAddress *BA = dyn_cast<BlockAddress>(V)) {
     69       Function *F = BA->getFunction();
     70       if (F->isDeclaration())
     71         return F;
     72     }
     73 
     74     for (User::op_iterator i = V->op_begin(), e = V->op_end(); i != e; ++i) {
     75       Constant *C = dyn_cast<Constant>(*i);
     76       if (C && !isa<GlobalValue>(C) && !Done.count(C))
     77         Todo.push_back(C);
     78     }
     79   }
     80   return nullptr;
     81 }
     82 } // end anonymous namespace
     83 
     84 std::unique_ptr<Module>
     85 BugDriver::deleteInstructionFromProgram(const Instruction *I,
     86                                         unsigned Simplification) {
     87   // FIXME, use vmap?
     88   std::unique_ptr<Module> Clone = CloneModule(*Program);
     89 
     90   const BasicBlock *PBB = I->getParent();
     91   const Function *PF = PBB->getParent();
     92 
     93   Module::iterator RFI = Clone->begin(); // Get iterator to corresponding fn
     94   std::advance(
     95       RFI, std::distance(PF->getParent()->begin(), Module::const_iterator(PF)));
     96 
     97   Function::iterator RBI = RFI->begin(); // Get iterator to corresponding BB
     98   std::advance(RBI, std::distance(PF->begin(), Function::const_iterator(PBB)));
     99 
    100   BasicBlock::iterator RI = RBI->begin(); // Get iterator to corresponding inst
    101   std::advance(RI, std::distance(PBB->begin(), BasicBlock::const_iterator(I)));
    102   Instruction *TheInst = &*RI; // Got the corresponding instruction!
    103 
    104   // If this instruction produces a value, replace any users with null values
    105   if (!TheInst->getType()->isVoidTy())
    106     TheInst->replaceAllUsesWith(Constant::getNullValue(TheInst->getType()));
    107 
    108   // Remove the instruction from the program.
    109   TheInst->getParent()->getInstList().erase(TheInst);
    110 
    111   // Spiff up the output a little bit.
    112   std::vector<std::string> Passes;
    113 
    114   /// Can we get rid of the -disable-* options?
    115   if (Simplification > 1 && !NoDCE)
    116     Passes.push_back("dce");
    117   if (Simplification && !DisableSimplifyCFG)
    118     Passes.push_back("simplifycfg"); // Delete dead control flow
    119 
    120   Passes.push_back("verify");
    121   std::unique_ptr<Module> New = runPassesOn(Clone.get(), Passes);
    122   if (!New) {
    123     errs() << "Instruction removal failed.  Sorry. :(  Please report a bug!\n";
    124     exit(1);
    125   }
    126   return New;
    127 }
    128 
    129 std::unique_ptr<Module>
    130 BugDriver::performFinalCleanups(std::unique_ptr<Module> M,
    131                                 bool MayModifySemantics) {
    132   // Make all functions external, so GlobalDCE doesn't delete them...
    133   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
    134     I->setLinkage(GlobalValue::ExternalLinkage);
    135 
    136   std::vector<std::string> CleanupPasses;
    137   CleanupPasses.push_back("globaldce");
    138 
    139   if (MayModifySemantics)
    140     CleanupPasses.push_back("deadarghaX0r");
    141   else
    142     CleanupPasses.push_back("deadargelim");
    143 
    144   std::unique_ptr<Module> New = runPassesOn(M.get(), CleanupPasses);
    145   if (!New) {
    146     errs() << "Final cleanups failed.  Sorry. :(  Please report a bug!\n";
    147     return nullptr;
    148   }
    149   return New;
    150 }
    151 
    152 std::unique_ptr<Module> BugDriver::extractLoop(Module *M) {
    153   std::vector<std::string> LoopExtractPasses;
    154   LoopExtractPasses.push_back("loop-extract-single");
    155 
    156   std::unique_ptr<Module> NewM = runPassesOn(M, LoopExtractPasses);
    157   if (!NewM) {
    158     outs() << "*** Loop extraction failed: ";
    159     EmitProgressBitcode(*M, "loopextraction", true);
    160     outs() << "*** Sorry. :(  Please report a bug!\n";
    161     return nullptr;
    162   }
    163 
    164   // Check to see if we created any new functions.  If not, no loops were
    165   // extracted and we should return null.  Limit the number of loops we extract
    166   // to avoid taking forever.
    167   static unsigned NumExtracted = 32;
    168   if (M->size() == NewM->size() || --NumExtracted == 0) {
    169     return nullptr;
    170   } else {
    171     assert(M->size() < NewM->size() && "Loop extract removed functions?");
    172     Module::iterator MI = NewM->begin();
    173     for (unsigned i = 0, e = M->size(); i != e; ++i)
    174       ++MI;
    175   }
    176 
    177   return NewM;
    178 }
    179 
    180 static void eliminateAliases(GlobalValue *GV) {
    181   // First, check whether a GlobalAlias references this definition.
    182   // GlobalAlias MAY NOT reference declarations.
    183   for (;;) {
    184     // 1. Find aliases
    185     SmallVector<GlobalAlias *, 1> aliases;
    186     Module *M = GV->getParent();
    187     for (Module::alias_iterator I = M->alias_begin(), E = M->alias_end();
    188          I != E; ++I)
    189       if (I->getAliasee()->stripPointerCasts() == GV)
    190         aliases.push_back(&*I);
    191     if (aliases.empty())
    192       break;
    193     // 2. Resolve aliases
    194     for (unsigned i = 0, e = aliases.size(); i < e; ++i) {
    195       aliases[i]->replaceAllUsesWith(aliases[i]->getAliasee());
    196       aliases[i]->eraseFromParent();
    197     }
    198     // 3. Repeat until no more aliases found; there might
    199     // be an alias to an alias...
    200   }
    201 }
    202 
    203 //
    204 // DeleteGlobalInitializer - "Remove" the global variable by deleting its
    205 // initializer,
    206 // making it external.
    207 //
    208 void llvm::DeleteGlobalInitializer(GlobalVariable *GV) {
    209   eliminateAliases(GV);
    210   GV->setInitializer(nullptr);
    211   GV->setComdat(nullptr);
    212 }
    213 
    214 // DeleteFunctionBody - "Remove" the function by deleting all of its basic
    215 // blocks, making it external.
    216 //
    217 void llvm::DeleteFunctionBody(Function *F) {
    218   eliminateAliases(F);
    219   // Function declarations can't have comdats.
    220   F->setComdat(nullptr);
    221 
    222   // delete the body of the function...
    223   F->deleteBody();
    224   assert(F->isDeclaration() && "This didn't make the function external!");
    225 }
    226 
    227 /// GetTorInit - Given a list of entries for static ctors/dtors, return them
    228 /// as a constant array.
    229 static Constant *GetTorInit(std::vector<std::pair<Function *, int>> &TorList) {
    230   assert(!TorList.empty() && "Don't create empty tor list!");
    231   std::vector<Constant *> ArrayElts;
    232   Type *Int32Ty = Type::getInt32Ty(TorList[0].first->getContext());
    233 
    234   StructType *STy = StructType::get(Int32Ty, TorList[0].first->getType());
    235   for (unsigned i = 0, e = TorList.size(); i != e; ++i) {
    236     Constant *Elts[] = {ConstantInt::get(Int32Ty, TorList[i].second),
    237                         TorList[i].first};
    238     ArrayElts.push_back(ConstantStruct::get(STy, Elts));
    239   }
    240   return ConstantArray::get(
    241       ArrayType::get(ArrayElts[0]->getType(), ArrayElts.size()), ArrayElts);
    242 }
    243 
    244 /// SplitStaticCtorDtor - A module was recently split into two parts, M1/M2, and
    245 /// M1 has all of the global variables.  If M2 contains any functions that are
    246 /// static ctors/dtors, we need to add an llvm.global_[cd]tors global to M2, and
    247 /// prune appropriate entries out of M1s list.
    248 static void SplitStaticCtorDtor(const char *GlobalName, Module *M1, Module *M2,
    249                                 ValueToValueMapTy &VMap) {
    250   GlobalVariable *GV = M1->getNamedGlobal(GlobalName);
    251   if (!GV || GV->isDeclaration() || GV->hasLocalLinkage() || !GV->use_empty())
    252     return;
    253 
    254   std::vector<std::pair<Function *, int>> M1Tors, M2Tors;
    255   ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
    256   if (!InitList)
    257     return;
    258 
    259   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
    260     if (ConstantStruct *CS =
    261             dyn_cast<ConstantStruct>(InitList->getOperand(i))) {
    262       if (CS->getNumOperands() != 2)
    263         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, M1Init, GlobalName);
    292   }
    293 
    294   GV = M2->getNamedGlobal(GlobalName);
    295   assert(GV && "Not a clone of M1?");
    296   assert(GV->use_empty() && "llvm.ctors shouldn't have uses!");
    297 
    298   GV->eraseFromParent();
    299   if (!M2Tors.empty()) {
    300     Constant *M2Init = GetTorInit(M2Tors);
    301     new GlobalVariable(*M2, M2Init->getType(), false,
    302                        GlobalValue::AppendingLinkage, M2Init, GlobalName);
    303   }
    304 }
    305 
    306 std::unique_ptr<Module>
    307 llvm::SplitFunctionsOutOfModule(Module *M, const std::vector<Function *> &F,
    308                                 ValueToValueMapTy &VMap) {
    309   // Make sure functions & globals are all external so that linkage
    310   // between the two modules will work.
    311   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
    312     I->setLinkage(GlobalValue::ExternalLinkage);
    313   for (Module::global_iterator I = M->global_begin(), E = M->global_end();
    314        I != E; ++I) {
    315     if (I->hasName() && I->getName()[0] == '\01')
    316       I->setName(I->getName().substr(1));
    317     I->setLinkage(GlobalValue::ExternalLinkage);
    318   }
    319 
    320   ValueToValueMapTy NewVMap;
    321   std::unique_ptr<Module> New = CloneModule(*M, NewVMap);
    322 
    323   // Remove the Test functions from the Safe module
    324   std::set<Function *> TestFunctions;
    325   for (unsigned i = 0, e = F.size(); i != e; ++i) {
    326     Function *TNOF = cast<Function>(VMap[F[i]]);
    327     LLVM_DEBUG(errs() << "Removing function ");
    328     LLVM_DEBUG(TNOF->printAsOperand(errs(), false));
    329     LLVM_DEBUG(errs() << "\n");
    330     TestFunctions.insert(cast<Function>(NewVMap[TNOF]));
    331     DeleteFunctionBody(TNOF); // Function is now external in this module!
    332   }
    333 
    334   // Remove the Safe functions from the Test module
    335   for (Function &I : *New)
    336     if (!TestFunctions.count(&I))
    337       DeleteFunctionBody(&I);
    338 
    339   // Try to split the global initializers evenly
    340   for (GlobalVariable &I : M->globals()) {
    341     GlobalVariable *GV = cast<GlobalVariable>(NewVMap[&I]);
    342     if (Function *TestFn = globalInitUsesExternalBA(&I)) {
    343       if (Function *SafeFn = globalInitUsesExternalBA(GV)) {
    344         errs() << "*** Error: when reducing functions, encountered "
    345                   "the global '";
    346         GV->printAsOperand(errs(), false);
    347         errs() << "' with an initializer that references blockaddresses "
    348                   "from safe function '"
    349                << SafeFn->getName() << "' and from test function '"
    350                << TestFn->getName() << "'.\n";
    351         exit(1);
    352       }
    353       DeleteGlobalInitializer(&I); // Delete the initializer to make it external
    354     } else {
    355       // If we keep it in the safe module, then delete it in the test module
    356       DeleteGlobalInitializer(GV);
    357     }
    358   }
    359 
    360   // Make sure that there is a global ctor/dtor array in both halves of the
    361   // module if they both have static ctor/dtor functions.
    362   SplitStaticCtorDtor("llvm.global_ctors", M, New.get(), NewVMap);
    363   SplitStaticCtorDtor("llvm.global_dtors", M, New.get(), NewVMap);
    364 
    365   return New;
    366 }
    367 
    368 //===----------------------------------------------------------------------===//
    369 // Basic Block Extraction Code
    370 //===----------------------------------------------------------------------===//
    371 
    372 std::unique_ptr<Module>
    373 BugDriver::extractMappedBlocksFromModule(const std::vector<BasicBlock *> &BBs,
    374                                          Module *M) {
    375   auto Temp = sys::fs::TempFile::create(OutputPrefix + "-extractblocks%%%%%%%");
    376   if (!Temp) {
    377     outs() << "*** Basic Block extraction failed!\n";
    378     errs() << "Error creating temporary file: " << toString(Temp.takeError())
    379            << "\n";
    380     EmitProgressBitcode(*M, "basicblockextractfail", true);
    381     return nullptr;
    382   }
    383   DiscardTemp Discard{*Temp};
    384 
    385   // Extract all of the blocks except the ones in BBs.
    386   SmallVector<BasicBlock *, 32> BlocksToExtract;
    387   for (Function &F : *M)
    388     for (BasicBlock &BB : F)
    389       // Check if this block is going to be extracted.
    390       if (std::find(BBs.begin(), BBs.end(), &BB) == BBs.end())
    391         BlocksToExtract.push_back(&BB);
    392 
    393   raw_fd_ostream OS(Temp->FD, /*shouldClose*/ false);
    394   for (BasicBlock *BB : BBs) {
    395     // If the BB doesn't have a name, give it one so we have something to key
    396     // off of.
    397     if (!BB->hasName())
    398       BB->setName("tmpbb");
    399     OS << BB->getParent()->getName() << " " << BB->getName() << "\n";
    400   }
    401   OS.flush();
    402   if (OS.has_error()) {
    403     errs() << "Error writing list of blocks to not extract\n";
    404     EmitProgressBitcode(*M, "basicblockextractfail", true);
    405     OS.clear_error();
    406     return nullptr;
    407   }
    408 
    409   std::string uniqueFN = "--extract-blocks-file=";
    410   uniqueFN += Temp->TmpName;
    411   const char *ExtraArg = uniqueFN.c_str();
    412 
    413   std::vector<std::string> PI;
    414   PI.push_back("extract-blocks");
    415   std::unique_ptr<Module> Ret = runPassesOn(M, PI, 1, &ExtraArg);
    416 
    417   if (!Ret) {
    418     outs() << "*** Basic Block extraction failed, please report a bug!\n";
    419     EmitProgressBitcode(*M, "basicblockextractfail", true);
    420   }
    421   return Ret;
    422 }
    423