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>
34using namespace llvm;
35
36#define DEBUG_TYPE "bugpoint"
37
38namespace llvm {
39bool DisableSimplifyCFG = false;
40extern cl::opt<std::string> OutputPrefix;
41} // End llvm namespace
42
43namespace {
44cl::opt<bool> NoDCE("disable-dce",
45                    cl::desc("Do not use the -dce pass to reduce testcases"));
46cl::opt<bool, true>
47    NoSCFG("disable-simplifycfg", cl::location(DisableSimplifyCFG),
48           cl::desc("Do not use the -simplifycfg pass to reduce testcases"));
49
50Function *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
83std::unique_ptr<Module>
84BugDriver::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
128std::unique_ptr<Module>
129BugDriver::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
151std::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
179static 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//
207void 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//
216void 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.
228static 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.
247static 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
305std::unique_ptr<Module>
306llvm::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
371std::unique_ptr<Module>
372BugDriver::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 (!llvm::is_contained(BBs, &BB))
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}
421