tools/bugpoint/ExtractFunction.cpp

   1 //===- ExtractFunction.cpp - Extract a function from Program --------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements several methods that are used to extract functions,
  10 // loops, or portions of a module from the rest of the module.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "BugDriver.h"
  15 #include "llvm/IR/Constants.h"
  16 #include "llvm/IR/DataLayout.h"
  17 #include "llvm/IR/DerivedTypes.h"
  18 #include "llvm/IR/LLVMContext.h"
  19 #include "llvm/IR/LegacyPassManager.h"
  20 #include "llvm/IR/Module.h"
  21 #include "llvm/IR/Verifier.h"
  22 #include "llvm/Pass.h"
  23 #include "llvm/Support/CommandLine.h"
  24 #include "llvm/Support/Debug.h"
  25 #include "llvm/Support/FileUtilities.h"
  26 #include "llvm/Support/Path.h"
  27 #include "llvm/Support/Signals.h"
  28 #include "llvm/Support/ToolOutputFile.h"
  29 #include "llvm/Transforms/IPO.h"
  30 #include "llvm/Transforms/Scalar.h"
  31 #include "llvm/Transforms/Utils/Cloning.h"
  32 #include "llvm/Transforms/Utils/CodeExtractor.h"
  33 #include <set>
  34 using namespace llvm;
  35
  36 #define DEBUG_TYPE "bugpoint"
  37
  38 namespace llvm {
  39 bool DisableSimplifyCFG = false;
  40 extern cl::opt<std::string> OutputPrefix;
  41 } // End llvm namespace
  42
  43 namespace {
  44 cl::opt<bool> NoDCE("disable-dce",
  45                     cl::desc("Do not use the -dce pass to reduce testcases"));
  46 cl::opt<bool, true>
  47     NoSCFG("disable-simplifycfg", cl::location(DisableSimplifyCFG),
  48            cl::desc("Do not use the -simplifycfg pass to reduce testcases"));
  49
  50 Function *globalInitUsesExternalBA(GlobalVariable *GV) {
  51   if (!GV->hasInitializer())
  52     return nullptr;
  53
  54   Constant *I = GV->getInitializer();
  55
  56   // walk the values used by the initializer
  57   // (and recurse into things like ConstantExpr)
  58   std::vector<Constant *> Todo;
  59   std::set<Constant *> Done;
  60   Todo.push_back(I);
  61
  62   while (!Todo.empty()) {
  63     Constant *V = Todo.back();
  64     Todo.pop_back();
  65     Done.insert(V);
  66
  67     if (BlockAddress *BA = dyn_cast<BlockAddress>(V)) {
  68       Function *F = BA->getFunction();
  69       if (F->isDeclaration())
  70         return F;
  71     }
  72
  73     for (User::op_iterator i = V->op_begin(), e = V->op_end(); i != e; ++i) {
  74       Constant *C = dyn_cast<Constant>(*i);
  75       if (C && !isa<GlobalValue>(C) && !Done.count(C))
  76         Todo.push_back(C);
  77     }
  78   }
  79   return nullptr;
  80 }
  81 } // end anonymous namespace
  82
  83 std::unique_ptr<Module>
  84 BugDriver::deleteInstructionFromProgram(const Instruction *I,
  85                                         unsigned Simplification) {
  86   // FIXME, use vmap?
  87   std::unique_ptr<Module> Clone = CloneModule(*Program);
  88
  89   const BasicBlock *PBB = I->getParent();
  90   const Function *PF = PBB->getParent();
  91
  92   Module::iterator RFI = Clone->begin(); // Get iterator to corresponding fn
  93   std::advance(
  94       RFI, std::distance(PF->getParent()->begin(), Module::const_iterator(PF)));
  95
  96   Function::iterator RBI = RFI->begin(); // Get iterator to corresponding BB
  97   std::advance(RBI, std::distance(PF->begin(), Function::const_iterator(PBB)));
  98
  99   BasicBlock::iterator RI = RBI->begin(); // Get iterator to corresponding inst
 100   std::advance(RI, std::distance(PBB->begin(), BasicBlock::const_iterator(I)));
 101   Instruction *TheInst = &*RI; // Got the corresponding instruction!
 102
 103   // If this instruction produces a value, replace any users with null values
 104   if (!TheInst->getType()->isVoidTy())
 105     TheInst->replaceAllUsesWith(Constant::getNullValue(TheInst->getType()));
 106
 107   // Remove the instruction from the program.
 108   TheInst->getParent()->getInstList().erase(TheInst);
 109
 110   // Spiff up the output a little bit.
 111   std::vector<std::string> Passes;
 112
 113   /// Can we get rid of the -disable-* options?
 114   if (Simplification > 1 && !NoDCE)
 115     Passes.push_back("dce");
 116   if (Simplification && !DisableSimplifyCFG)
 117     Passes.push_back("simplifycfg"); // Delete dead control flow
 118
 119   Passes.push_back("verify");
 120   std::unique_ptr<Module> New = runPassesOn(Clone.get(), Passes);
 121   if (!New) {
 122     errs() << "Instruction removal failed.  Sorry. :(  Please report a bug!\n";
 123     exit(1);
 124   }
 125   return New;
 126 }
 127
 128 std::unique_ptr<Module>
 129 BugDriver::performFinalCleanups(std::unique_ptr<Module> M,
 130                                 bool MayModifySemantics) {
 131   // Make all functions external, so GlobalDCE doesn't delete them...
 132   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
 133     I->setLinkage(GlobalValue::ExternalLinkage);
 134
 135   std::vector<std::string> CleanupPasses;
 136   CleanupPasses.push_back("globaldce");
 137
 138   if (MayModifySemantics)
 139     CleanupPasses.push_back("deadarghaX0r");
 140   else
 141     CleanupPasses.push_back("deadargelim");
 142
 143   std::unique_ptr<Module> New = runPassesOn(M.get(), CleanupPasses);
 144   if (!New) {
 145     errs() << "Final cleanups failed.  Sorry. :(  Please report a bug!\n";
 146     return nullptr;
 147   }
 148   return New;
 149 }
 150
 151 std::unique_ptr<Module> BugDriver::extractLoop(Module *M) {
 152   std::vector<std::string> LoopExtractPasses;
 153   LoopExtractPasses.push_back("loop-extract-single");
 154
 155   std::unique_ptr<Module> NewM = runPassesOn(M, LoopExtractPasses);
 156   if (!NewM) {
 157     outs() << "*** Loop extraction failed: ";
 158     EmitProgressBitcode(*M, "loopextraction", true);
 159     outs() << "*** Sorry. :(  Please report a bug!\n";
 160     return nullptr;
 161   }
 162
 163   // Check to see if we created any new functions.  If not, no loops were
 164   // extracted and we should return null.  Limit the number of loops we extract
 165   // to avoid taking forever.
 166   static unsigned NumExtracted = 32;
 167   if (M->size() == NewM->size() || --NumExtracted == 0) {
 168     return nullptr;
 169   } else {
 170     assert(M->size() < NewM->size() && "Loop extract removed functions?");
 171     Module::iterator MI = NewM->begin();
 172     for (unsigned i = 0, e = M->size(); i != e; ++i)
 173       ++MI;
 174   }
 175
 176   return NewM;
 177 }
 178
 179 static void eliminateAliases(GlobalValue *GV) {
 180   // First, check whether a GlobalAlias references this definition.
 181   // GlobalAlias MAY NOT reference declarations.
 182   for (;;) {
 183     // 1. Find aliases
 184     SmallVector<GlobalAlias *, 1> aliases;
 185     Module *M = GV->getParent();
 186     for (Module::alias_iterator I = M->alias_begin(), E = M->alias_end();
 187          I != E; ++I)
 188       if (I->getAliasee()->stripPointerCasts() == GV)
 189         aliases.push_back(&*I);
 190     if (aliases.empty())
 191       break;
 192     // 2. Resolve aliases
 193     for (unsigned i = 0, e = aliases.size(); i < e; ++i) {
 194       aliases[i]->replaceAllUsesWith(aliases[i]->getAliasee());
 195       aliases[i]->eraseFromParent();
 196     }
 197     // 3. Repeat until no more aliases found; there might
 198     // be an alias to an alias...
 199   }
 200 }
 201
 202 //
 203 // DeleteGlobalInitializer - "Remove" the global variable by deleting its
 204 // initializer,
 205 // making it external.
 206 //
 207 void llvm::DeleteGlobalInitializer(GlobalVariable *GV) {
 208   eliminateAliases(GV);
 209   GV->setInitializer(nullptr);
 210   GV->setComdat(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 = StructType::get(Int32Ty, TorList[0].first->getType());
 234   for (unsigned i = 0, e = TorList.size(); i != e; ++i) {
 235     Constant *Elts[] = {ConstantInt::get(Int32Ty, TorList[i].second),
 236                         TorList[i].first};
 237     ArrayElts.push_back(ConstantStruct::get(STy, Elts));
 238   }
 239   return ConstantArray::get(
 240       ArrayType::get(ArrayElts[0]->getType(), ArrayElts.size()), ArrayElts);
 241 }
 242
 243 /// SplitStaticCtorDtor - A module was recently split into two parts, M1/M2, and
 244 /// M1 has all of the global variables.  If M2 contains any functions that are
 245 /// static ctors/dtors, we need to add an llvm.global_[cd]tors global to M2, and
 246 /// prune appropriate entries out of M1s list.
 247 static void SplitStaticCtorDtor(const char *GlobalName, Module *M1, Module *M2,
 248                                 ValueToValueMapTy &VMap) {
 249   GlobalVariable *GV = M1->getNamedGlobal(GlobalName);
 250   if (!GV || GV->isDeclaration() || GV->hasLocalLinkage() || !GV->use_empty())
 251     return;
 252
 253   std::vector<std::pair<Function *, int>> M1Tors, M2Tors;
 254   ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
 255   if (!InitList)
 256     return;
 257
 258   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
 259     if (ConstantStruct *CS =
 260             dyn_cast<ConstantStruct>(InitList->getOperand(i))) {
 261       if (CS->getNumOperands() != 2)
 262         return; // Not array of 2-element structs.
 263
 264       if (CS->getOperand(1)->isNullValue())
 265         break; // Found a null terminator, stop here.
 266
 267       ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
 268       int Priority = CI ? CI->getSExtValue() : 0;
 269
 270       Constant *FP = CS->getOperand(1);
 271       if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
 272         if (CE->isCast())
 273           FP = CE->getOperand(0);
 274       if (Function *F = dyn_cast<Function>(FP)) {
 275         if (!F->isDeclaration())
 276           M1Tors.push_back(std::make_pair(F, Priority));
 277         else {
 278           // Map to M2's version of the function.
 279           F = cast<Function>(VMap[F]);
 280           M2Tors.push_back(std::make_pair(F, Priority));
 281         }
 282       }
 283     }
 284   }
 285
 286   GV->eraseFromParent();
 287   if (!M1Tors.empty()) {
 288     Constant *M1Init = GetTorInit(M1Tors);
 289     new GlobalVariable(*M1, M1Init->getType(), false,
 290                        GlobalValue::AppendingLinkage, M1Init, GlobalName);
 291   }
 292
 293   GV = M2->getNamedGlobal(GlobalName);
 294   assert(GV && "Not a clone of M1?");
 295   assert(GV->use_empty() && "llvm.ctors shouldn't have uses!");
 296
 297   GV->eraseFromParent();
 298   if (!M2Tors.empty()) {
 299     Constant *M2Init = GetTorInit(M2Tors);
 300     new GlobalVariable(*M2, M2Init->getType(), false,
 301                        GlobalValue::AppendingLinkage, M2Init, GlobalName);
 302   }
 303 }
 304
 305 std::unique_ptr<Module>
 306 llvm::SplitFunctionsOutOfModule(Module *M, const std::vector<Function *> &F,
 307                                 ValueToValueMapTy &VMap) {
 308   // Make sure functions & globals are all external so that linkage
 309   // between the two modules will work.
 310   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
 311     I->setLinkage(GlobalValue::ExternalLinkage);
 312   for (Module::global_iterator I = M->global_begin(), E = M->global_end();
 313        I != E; ++I) {
 314     if (I->hasName() && I->getName()[0] == '\01')
 315       I->setName(I->getName().substr(1));
 316     I->setLinkage(GlobalValue::ExternalLinkage);
 317   }
 318
 319   ValueToValueMapTy NewVMap;
 320   std::unique_ptr<Module> New = CloneModule(*M, NewVMap);
 321
 322   // Remove the Test functions from the Safe module
 323   std::set<Function *> TestFunctions;
 324   for (unsigned i = 0, e = F.size(); i != e; ++i) {
 325     Function *TNOF = cast<Function>(VMap[F[i]]);
 326     LLVM_DEBUG(errs() << "Removing function ");
 327     LLVM_DEBUG(TNOF->printAsOperand(errs(), false));
 328     LLVM_DEBUG(errs() << "\n");
 329     TestFunctions.insert(cast<Function>(NewVMap[TNOF]));
 330     DeleteFunctionBody(TNOF); // Function is now external in this module!
 331   }
 332
 333   // Remove the Safe functions from the Test module
 334   for (Function &I : *New)
 335     if (!TestFunctions.count(&I))
 336       DeleteFunctionBody(&I);
 337
 338   // Try to split the global initializers evenly
 339   for (GlobalVariable &I : M->globals()) {
 340     GlobalVariable *GV = cast<GlobalVariable>(NewVMap[&I]);
 341     if (Function *TestFn = globalInitUsesExternalBA(&I)) {
 342       if (Function *SafeFn = globalInitUsesExternalBA(GV)) {
 343         errs() << "*** Error: when reducing functions, encountered "
 344                   "the global '";
 345         GV->printAsOperand(errs(), false);
 346         errs() << "' with an initializer that references blockaddresses "
 347                   "from safe function '"
 348                << SafeFn->getName() << "' and from test function '"
 349                << TestFn->getName() << "'.\n";
 350         exit(1);
 351       }
 352       DeleteGlobalInitializer(&I); // Delete the initializer to make it external
 353     } else {
 354       // If we keep it in the safe module, then delete it in the test module
 355       DeleteGlobalInitializer(GV);
 356     }
 357   }
 358
 359   // Make sure that there is a global ctor/dtor array in both halves of the
 360   // module if they both have static ctor/dtor functions.
 361   SplitStaticCtorDtor("llvm.global_ctors", M, New.get(), NewVMap);
 362   SplitStaticCtorDtor("llvm.global_dtors", M, New.get(), NewVMap);
 363
 364   return New;
 365 }
 366
 367 //===----------------------------------------------------------------------===//
 368 // Basic Block Extraction Code
 369 //===----------------------------------------------------------------------===//
 370
 371 std::unique_ptr<Module>
 372 BugDriver::extractMappedBlocksFromModule(const std::vector<BasicBlock *> &BBs,
 373                                          Module *M) {
 374   auto Temp = sys::fs::TempFile::create(OutputPrefix + "-extractblocks%%%%%%%");
 375   if (!Temp) {
 376     outs() << "*** Basic Block extraction failed!\n";
 377     errs() << "Error creating temporary file: " << toString(Temp.takeError())
 378            << "\n";
 379     EmitProgressBitcode(*M, "basicblockextractfail", true);
 380     return nullptr;
 381   }
 382   DiscardTemp Discard{*Temp};
 383
 384   // Extract all of the blocks except the ones in BBs.
 385   SmallVector<BasicBlock *, 32> BlocksToExtract;
 386   for (Function &F : *M)
 387     for (BasicBlock &BB : F)
 388       // Check if this block is going to be extracted.
 389       if (std::find(BBs.begin(), BBs.end(), &BB) == BBs.end())
 390         BlocksToExtract.push_back(&BB);
 391
 392   raw_fd_ostream OS(Temp->FD, /*shouldClose*/ false);
 393   for (BasicBlock *BB : BBs) {
 394     // If the BB doesn't have a name, give it one so we have something to key
 395     // off of.
 396     if (!BB->hasName())
 397       BB->setName("tmpbb");
 398     OS << BB->getParent()->getName() << " " << BB->getName() << "\n";
 399   }
 400   OS.flush();
 401   if (OS.has_error()) {
 402     errs() << "Error writing list of blocks to not extract\n";
 403     EmitProgressBitcode(*M, "basicblockextractfail", true);
 404     OS.clear_error();
 405     return nullptr;
 406   }
 407
 408   std::string uniqueFN = "--extract-blocks-file=";
 409   uniqueFN += Temp->TmpName;
 410
 411   std::vector<std::string> PI;
 412   PI.push_back("extract-blocks");
 413   std::unique_ptr<Module> Ret = runPassesOn(M, PI, {uniqueFN});
 414
 415   if (!Ret) {
 416     outs() << "*** Basic Block extraction failed, please report a bug!\n";
 417     EmitProgressBitcode(*M, "basicblockextractfail", true);
 418   }
 419   return Ret;
 420 }