ExtractFunction.cpp revision 302408 
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>
35using namespace llvm;
36
37#define DEBUG_TYPE "bugpoint"
38
39namespace llvm {
40  bool DisableSimplifyCFG = false;
41  extern cl::opt<std::string> OutputPrefix;
42} // End llvm namespace
43
44namespace {
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
85std::unique_ptr<Module>
86BugDriver::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
131std::unique_ptr<Module>
132BugDriver::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
154std::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
182static 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//
208void 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//
216void llvm::DeleteFunctionBody(Function *F) {
217  eliminateAliases(F);
218
219  // delete the body of the function...
220  F->deleteBody();
221  assert(F->isDeclaration() && "This didn't make the function external!");
222}
223
224/// GetTorInit - Given a list of entries for static ctors/dtors, return them
225/// as a constant array.
226static Constant *GetTorInit(std::vector<std::pair<Function*, int> > &TorList) {
227  assert(!TorList.empty() && "Don't create empty tor list!");
228  std::vector<Constant*> ArrayElts;
229  Type *Int32Ty = Type::getInt32Ty(TorList[0].first->getContext());
230
231  StructType *STy =
232      StructType::get(Int32Ty, TorList[0].first->getType(), nullptr);
233  for (unsigned i = 0, e = TorList.size(); i != e; ++i) {
234    Constant *Elts[] = {
235      ConstantInt::get(Int32Ty, TorList[i].second),
236      TorList[i].first
237    };
238    ArrayElts.push_back(ConstantStruct::get(STy, Elts));
239  }
240  return ConstantArray::get(ArrayType::get(ArrayElts[0]->getType(),
241                                           ArrayElts.size()),
242                            ArrayElts);
243}
244
245/// SplitStaticCtorDtor - A module was recently split into two parts, M1/M2, and
246/// M1 has all of the global variables.  If M2 contains any functions that are
247/// static ctors/dtors, we need to add an llvm.global_[cd]tors global to M2, and
248/// prune appropriate entries out of M1s list.
249static void SplitStaticCtorDtor(const char *GlobalName, Module *M1, Module *M2,
250                                ValueToValueMapTy &VMap) {
251  GlobalVariable *GV = M1->getNamedGlobal(GlobalName);
252  if (!GV || GV->isDeclaration() || GV->hasLocalLinkage() ||
253      !GV->use_empty()) return;
254
255  std::vector<std::pair<Function*, int> > M1Tors, M2Tors;
256  ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
257  if (!InitList) return;
258
259  for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
260    if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
261      if (CS->getNumOperands() != 2) 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,
290                       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,
302                       M2Init, GlobalName);
303  }
304}
305
306std::unique_ptr<Module>
307llvm::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    DEBUG(errs() << "Removing function ");
328    DEBUG(TNOF->printAsOperand(errs(), false));
329    DEBUG(errs() << "\n");
330    TestFunctions.insert(cast<Function>(NewVMap[TNOF]));
331    DeleteFunctionBody(TNOF);       // Function is now external in this module!
332  }
333
334
335  // Remove the Safe functions from the Test module
336  for (Function &I : *New)
337    if (!TestFunctions.count(&I))
338      DeleteFunctionBody(&I);
339
340  // Try to split the global initializers evenly
341  for (GlobalVariable &I : M->globals()) {
342    GlobalVariable *GV = cast<GlobalVariable>(NewVMap[&I]);
343    if (Function *TestFn = globalInitUsesExternalBA(&I)) {
344      if (Function *SafeFn = globalInitUsesExternalBA(GV)) {
345        errs() << "*** Error: when reducing functions, encountered "
346                  "the global '";
347        GV->printAsOperand(errs(), false);
348        errs() << "' with an initializer that references blockaddresses "
349                  "from safe function '" << SafeFn->getName()
350               << "' and from test function '" << 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
372std::unique_ptr<Module>
373BugDriver::extractMappedBlocksFromModule(const std::vector<BasicBlock *> &BBs,
374                                         Module *M) {
375  SmallString<128> Filename;
376  int FD;
377  std::error_code EC = sys::fs::createUniqueFile(
378      OutputPrefix + "-extractblocks%%%%%%%", FD, Filename);
379  if (EC) {
380    outs() << "*** Basic Block extraction failed!\n";
381    errs() << "Error creating temporary file: " << EC.message() << "\n";
382    EmitProgressBitcode(M, "basicblockextractfail", true);
383    return nullptr;
384  }
385  sys::RemoveFileOnSignal(Filename);
386
387  tool_output_file BlocksToNotExtractFile(Filename.c_str(), FD);
388  for (std::vector<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
389       I != E; ++I) {
390    BasicBlock *BB = *I;
391    // If the BB doesn't have a name, give it one so we have something to key
392    // off of.
393    if (!BB->hasName()) BB->setName("tmpbb");
394    BlocksToNotExtractFile.os() << BB->getParent()->getName() << " "
395                                << BB->getName() << "\n";
396  }
397  BlocksToNotExtractFile.os().close();
398  if (BlocksToNotExtractFile.os().has_error()) {
399    errs() << "Error writing list of blocks to not extract\n";
400    EmitProgressBitcode(M, "basicblockextractfail", true);
401    BlocksToNotExtractFile.os().clear_error();
402    return nullptr;
403  }
404  BlocksToNotExtractFile.keep();
405
406  std::string uniqueFN = "--extract-blocks-file=";
407  uniqueFN += Filename.str();
408  const char *ExtraArg = uniqueFN.c_str();
409
410  std::vector<std::string> PI;
411  PI.push_back("extract-blocks");
412  std::unique_ptr<Module> Ret = runPassesOn(M, PI, false, 1, &ExtraArg);
413
414  sys::fs::remove(Filename.c_str());
415
416  if (!Ret) {
417    outs() << "*** Basic Block extraction failed, please report a bug!\n";
418    EmitProgressBitcode(M, "basicblockextractfail", true);
419  }
420  return Ret;
421}
422