llvm/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->eraseFromParent();
 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
 137   if (MayModifySemantics)
 138     CleanupPasses.push_back("deadarghaX0r");
 139   else
 140     CleanupPasses.push_back("deadargelim");
 141
 142   std::unique_ptr<Module> New = runPassesOn(M.get(), CleanupPasses);
 143   if (!New) {
 144     errs() << "Final cleanups failed.  Sorry. :(  Please report a bug!\n";
 145     return nullptr;
 146   }
 147   return New;
 148 }
 149
 150 std::unique_ptr<Module> BugDriver::extractLoop(Module *M) {
 151   std::vector<std::string> LoopExtractPasses;
 152   LoopExtractPasses.push_back("loop-extract-single");
 153
 154   std::unique_ptr<Module> NewM = runPassesOn(M, LoopExtractPasses);
 155   if (!NewM) {
 156     outs() << "*** Loop extraction failed: ";
 157     EmitProgressBitcode(*M, "loopextraction", true);
 158     outs() << "*** Sorry. :(  Please report a bug!\n";
 159     return nullptr;
 160   }
 161
 162   // Check to see if we created any new functions.  If not, no loops were
 163   // extracted and we should return null.  Limit the number of loops we extract
 164   // to avoid taking forever.
 165   static unsigned NumExtracted = 32;
 166   if (M->size() == NewM->size() || --NumExtracted == 0) {
 167     return nullptr;
 168   } else {
 169     assert(M->size() < NewM->size() && "Loop extract removed functions?");
 170     Module::iterator MI = NewM->begin();
 171     for (unsigned i = 0, e = M->size(); i != e; ++i)
 172       ++MI;
 173   }
 174
 175   return NewM;
 176 }
 177
 178 static void eliminateAliases(GlobalValue *GV) {
 179   // First, check whether a GlobalAlias references this definition.
 180   // GlobalAlias MAY NOT reference declarations.
 181   for (;;) {
 182     // 1. Find aliases
 183     SmallVector<GlobalAlias *, 1> aliases;
 184     Module *M = GV->getParent();
 185     for (Module::alias_iterator I = M->alias_begin(), E = M->alias_end();
 186          I != E; ++I)
 187       if (I->getAliasee()->stripPointerCasts() == GV)
 188         aliases.push_back(&*I);
 189     if (aliases.empty())
 190       break;
 191     // 2. Resolve aliases
 192     for (unsigned i = 0, e = aliases.size(); i < e; ++i) {
 193       aliases[i]->replaceAllUsesWith(aliases[i]->getAliasee());
 194       aliases[i]->eraseFromParent();
 195     }
 196     // 3. Repeat until no more aliases found; there might
 197     // be an alias to an alias...
 198   }
 199 }
 200
 201 //
 202 // DeleteGlobalInitializer - "Remove" the global variable by deleting its
 203 // initializer,
 204 // making it external.
 205 //
 206 void llvm::DeleteGlobalInitializer(GlobalVariable *GV) {
 207   eliminateAliases(GV);
 208   GV->setInitializer(nullptr);
 209   GV->setComdat(nullptr);
 210 }
 211
 212 // DeleteFunctionBody - "Remove" the function by deleting all of its basic
 213 // blocks, making it external.
 214 //
 215 void llvm::DeleteFunctionBody(Function *F) {
 216   eliminateAliases(F);
 217   // Function declarations can't have comdats.
 218   F->setComdat(nullptr);
 219
 220   // delete the body of the function...
 221   F->deleteBody();
 222   assert(F->isDeclaration() && "This didn't make the function external!");
 223 }
 224
 225 /// GetTorInit - Given a list of entries for static ctors/dtors, return them
 226 /// as a constant array.
 227 static Constant *GetTorInit(std::vector<std::pair<Function *, int>> &TorList) {
 228   assert(!TorList.empty() && "Don't create empty tor list!");
 229   std::vector<Constant *> ArrayElts;
 230   Type *Int32Ty = Type::getInt32Ty(TorList[0].first->getContext());
 231
 232   StructType *STy = StructType::get(Int32Ty, TorList[0].first->getType());
 233   for (unsigned i = 0, e = TorList.size(); i != e; ++i) {
 234     Constant *Elts[] = {ConstantInt::get(Int32Ty, TorList[i].second),
 235                         TorList[i].first};
 236     ArrayElts.push_back(ConstantStruct::get(STy, Elts));
 237   }
 238   return ConstantArray::get(
 239       ArrayType::get(ArrayElts[0]->getType(), ArrayElts.size()), ArrayElts);
 240 }
 241
 242 /// SplitStaticCtorDtor - A module was recently split into two parts, M1/M2, and
 243 /// M1 has all of the global variables.  If M2 contains any functions that are
 244 /// static ctors/dtors, we need to add an llvm.global_[cd]tors global to M2, and
 245 /// prune appropriate entries out of M1s list.
 246 static void SplitStaticCtorDtor(const char *GlobalName, Module *M1, Module *M2,
 247                                 ValueToValueMapTy &VMap) {
 248   GlobalVariable *GV = M1->getNamedGlobal(GlobalName);
 249   if (!GV || GV->isDeclaration() || GV->hasLocalLinkage() || !GV->use_empty())
 250     return;
 251
 252   std::vector<std::pair<Function *, int>> M1Tors, M2Tors;
 253   ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
 254   if (!InitList)
 255     return;
 256
 257   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
 258     if (ConstantStruct *CS =
 259             dyn_cast<ConstantStruct>(InitList->getOperand(i))) {
 260       if (CS->getNumOperands() != 2)
 261         return; // Not array of 2-element structs.
 262
 263       if (CS->getOperand(1)->isNullValue())
 264         break; // Found a null terminator, stop here.
 265
 266       ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
 267       int Priority = CI ? CI->getSExtValue() : 0;
 268
 269       Constant *FP = CS->getOperand(1);
 270       if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
 271         if (CE->isCast())
 272           FP = CE->getOperand(0);
 273       if (Function *F = dyn_cast<Function>(FP)) {
 274         if (!F->isDeclaration())
 275           M1Tors.push_back(std::make_pair(F, Priority));
 276         else {
 277           // Map to M2's version of the function.
 278           F = cast<Function>(VMap[F]);
 279           M2Tors.push_back(std::make_pair(F, Priority));
 280         }
 281       }
 282     }
 283   }
 284
 285   GV->eraseFromParent();
 286   if (!M1Tors.empty()) {
 287     Constant *M1Init = GetTorInit(M1Tors);
 288     new GlobalVariable(*M1, M1Init->getType(), false,
 289                        GlobalValue::AppendingLinkage, M1Init, GlobalName);
 290   }
 291
 292   GV = M2->getNamedGlobal(GlobalName);
 293   assert(GV && "Not a clone of M1?");
 294   assert(GV->use_empty() && "llvm.ctors shouldn't have uses!");
 295
 296   GV->eraseFromParent();
 297   if (!M2Tors.empty()) {
 298     Constant *M2Init = GetTorInit(M2Tors);
 299     new GlobalVariable(*M2, M2Init->getType(), false,
 300                        GlobalValue::AppendingLinkage, M2Init, GlobalName);
 301   }
 302 }
 303
 304 std::unique_ptr<Module>
 305 llvm::SplitFunctionsOutOfModule(Module *M, const std::vector<Function *> &F,
 306                                 ValueToValueMapTy &VMap) {
 307   // Make sure functions & globals are all external so that linkage
 308   // between the two modules will work.
 309   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
 310     I->setLinkage(GlobalValue::ExternalLinkage);
 311   for (Module::global_iterator I = M->global_begin(), E = M->global_end();
 312        I != E; ++I) {
 313     if (I->hasName() && I->getName()[0] == '\01')
 314       I->setName(I->getName().substr(1));
 315     I->setLinkage(GlobalValue::ExternalLinkage);
 316   }
 317
 318   ValueToValueMapTy NewVMap;
 319   std::unique_ptr<Module> New = CloneModule(*M, NewVMap);
 320
 321   // Remove the Test functions from the Safe module
 322   std::set<Function *> TestFunctions;
 323   for (unsigned i = 0, e = F.size(); i != e; ++i) {
 324     Function *TNOF = cast<Function>(VMap[F[i]]);
 325     LLVM_DEBUG(errs() << "Removing function ");
 326     LLVM_DEBUG(TNOF->printAsOperand(errs(), false));
 327     LLVM_DEBUG(errs() << "\n");
 328     TestFunctions.insert(cast<Function>(NewVMap[TNOF]));
 329     DeleteFunctionBody(TNOF); // Function is now external in this module!
 330   }
 331
 332   // Remove the Safe functions from the Test module
 333   for (Function &I : *New)
 334     if (!TestFunctions.count(&I))
 335       DeleteFunctionBody(&I);
 336
 337   // Try to split the global initializers evenly
 338   for (GlobalVariable &I : M->globals()) {
 339     GlobalVariable *GV = cast<GlobalVariable>(NewVMap[&I]);
 340     if (Function *TestFn = globalInitUsesExternalBA(&I)) {
 341       if (Function *SafeFn = globalInitUsesExternalBA(GV)) {
 342         errs() << "*** Error: when reducing functions, encountered "
 343                   "the global '";
 344         GV->printAsOperand(errs(), false);
 345         errs() << "' with an initializer that references blockaddresses "
 346                   "from safe function '"
 347                << SafeFn->getName() << "' and from test function '"
 348                << TestFn->getName() << "'.\n";
 349         exit(1);
 350       }
 351       DeleteGlobalInitializer(&I); // Delete the initializer to make it external
 352     } else {
 353       // If we keep it in the safe module, then delete it in the test module
 354       DeleteGlobalInitializer(GV);
 355     }
 356   }
 357
 358   // Make sure that there is a global ctor/dtor array in both halves of the
 359   // module if they both have static ctor/dtor functions.
 360   SplitStaticCtorDtor("llvm.global_ctors", M, New.get(), NewVMap);
 361   SplitStaticCtorDtor("llvm.global_dtors", M, New.get(), NewVMap);
 362
 363   return New;
 364 }
 365
 366 //===----------------------------------------------------------------------===//
 367 // Basic Block Extraction Code
 368 //===----------------------------------------------------------------------===//
 369
 370 std::unique_ptr<Module>
 371 BugDriver::extractMappedBlocksFromModule(const std::vector<BasicBlock *> &BBs,
 372                                          Module *M) {
 373   auto Temp = sys::fs::TempFile::create(OutputPrefix + "-extractblocks%%%%%%%");
 374   if (!Temp) {
 375     outs() << "*** Basic Block extraction failed!\n";
 376     errs() << "Error creating temporary file: " << toString(Temp.takeError())
 377            << "\n";
 378     EmitProgressBitcode(*M, "basicblockextractfail", true);
 379     return nullptr;
 380   }
 381   DiscardTemp Discard{*Temp};
 382
 383   // Extract all of the blocks except the ones in BBs.
 384   SmallVector<BasicBlock *, 32> BlocksToExtract;
 385   for (Function &F : *M)
 386     for (BasicBlock &BB : F)
 387       // Check if this block is going to be extracted.
 388       if (!llvm::is_contained(BBs, &BB))
 389         BlocksToExtract.push_back(&BB);
 390
 391   raw_fd_ostream OS(Temp->FD, /*shouldClose*/ false);
 392   for (BasicBlock *BB : BBs) {
 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())
 396       BB->setName("tmpbb");
 397     OS << BB->getParent()->getName() << " " << BB->getName() << "\n";
 398   }
 399   OS.flush();
 400   if (OS.has_error()) {
 401     errs() << "Error writing list of blocks to not extract\n";
 402     EmitProgressBitcode(*M, "basicblockextractfail", true);
 403     OS.clear_error();
 404     return nullptr;
 405   }
 406
 407   std::string uniqueFN = "--extract-blocks-file=";
 408   uniqueFN += Temp->TmpName;
 409
 410   std::vector<std::string> PI;
 411   PI.push_back("extract-blocks");
 412   std::unique_ptr<Module> Ret = runPassesOn(M, PI, {uniqueFN});
 413
 414   if (!Ret) {
 415     outs() << "*** Basic Block extraction failed, please report a bug!\n";
 416     EmitProgressBitcode(*M, "basicblockextractfail", true);
 417   }
 418   return Ret;
 419 }