ExtractFunction.cpp revision 9e081004dad1c3cae7de82ad412c3f19a1a48d48 
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/Constants.h"
17#include "llvm/DerivedTypes.h"
18#include "llvm/LLVMContext.h"
19#include "llvm/Module.h"
20#include "llvm/PassManager.h"
21#include "llvm/Pass.h"
22#include "llvm/Analysis/Verifier.h"
23#include "llvm/Assembly/Writer.h"
24#include "llvm/Transforms/IPO.h"
25#include "llvm/Transforms/Scalar.h"
26#include "llvm/Transforms/Utils/Cloning.h"
27#include "llvm/Transforms/Utils/FunctionUtils.h"
28#include "llvm/Target/TargetData.h"
29#include "llvm/Support/CommandLine.h"
30#include "llvm/Support/Debug.h"
31#include "llvm/Support/FileUtilities.h"
32#include "llvm/Support/raw_ostream.h"
33#include "llvm/System/Path.h"
34#include "llvm/System/Signals.h"
35#include <set>
36using namespace llvm;
37
38namespace llvm {
39  bool DisableSimplifyCFG = false;
40  extern cl::opt<std::string> OutputPrefix;
41} // End llvm namespace
42
43namespace {
44  cl::opt<bool>
45  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
52/// deleteInstructionFromProgram - This method clones the current Program and
53/// deletes the specified instruction from the cloned module.  It then runs a
54/// series of cleanup passes (ADCE and SimplifyCFG) to eliminate any code which
55/// depends on the value.  The modified module is then returned.
56///
57Module *BugDriver::deleteInstructionFromProgram(const Instruction *I,
58                                                unsigned Simplification) const {
59  Module *Result = CloneModule(Program);
60
61  const BasicBlock *PBB = I->getParent();
62  const Function *PF = PBB->getParent();
63
64  Module::iterator RFI = Result->begin(); // Get iterator to corresponding fn
65  std::advance(RFI, std::distance(PF->getParent()->begin(),
66                                  Module::const_iterator(PF)));
67
68  Function::iterator RBI = RFI->begin();  // Get iterator to corresponding BB
69  std::advance(RBI, std::distance(PF->begin(), Function::const_iterator(PBB)));
70
71  BasicBlock::iterator RI = RBI->begin(); // Get iterator to corresponding inst
72  std::advance(RI, std::distance(PBB->begin(), BasicBlock::const_iterator(I)));
73  Instruction *TheInst = RI;              // Got the corresponding instruction!
74
75  // If this instruction produces a value, replace any users with null values
76  if (!TheInst->getType()->isVoidTy())
77    TheInst->replaceAllUsesWith(Constant::getNullValue(TheInst->getType()));
78
79  // Remove the instruction from the program.
80  TheInst->getParent()->getInstList().erase(TheInst);
81
82
83  //writeProgramToFile("current.bc", Result);
84
85  // Spiff up the output a little bit.
86  PassManager Passes;
87  // Make sure that the appropriate target data is always used...
88  Passes.add(new TargetData(Result));
89
90  /// FIXME: If this used runPasses() like the methods below, we could get rid
91  /// of the -disable-* options!
92  if (Simplification > 1 && !NoDCE)
93    Passes.add(createDeadCodeEliminationPass());
94  if (Simplification && !DisableSimplifyCFG)
95    Passes.add(createCFGSimplificationPass());      // Delete dead control flow
96
97  Passes.add(createVerifierPass());
98  Passes.run(*Result);
99  return Result;
100}
101
102static const StaticPassInfo *getPI(Pass *P) {
103  const StaticPassInfo *PI = P->getPassInfo();
104  delete P;
105  return PI;
106}
107
108/// performFinalCleanups - This method clones the current Program and performs
109/// a series of cleanups intended to get rid of extra cruft on the module
110/// before handing it to the user.
111///
112Module *BugDriver::performFinalCleanups(Module *M, bool MayModifySemantics) {
113  // Make all functions external, so GlobalDCE doesn't delete them...
114  for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
115    I->setLinkage(GlobalValue::ExternalLinkage);
116
117  std::vector<const StaticPassInfo*> CleanupPasses;
118  CleanupPasses.push_back(getPI(createGlobalDCEPass()));
119
120  if (MayModifySemantics)
121    CleanupPasses.push_back(getPI(createDeadArgHackingPass()));
122  else
123    CleanupPasses.push_back(getPI(createDeadArgEliminationPass()));
124
125  CleanupPasses.push_back(getPI(createDeadTypeEliminationPass()));
126
127  Module *New = runPassesOn(M, CleanupPasses);
128  if (New == 0) {
129    errs() << "Final cleanups failed.  Sorry. :(  Please report a bug!\n";
130    return M;
131  }
132  delete M;
133  return New;
134}
135
136
137/// ExtractLoop - Given a module, extract up to one loop from it into a new
138/// function.  This returns null if there are no extractable loops in the
139/// program or if the loop extractor crashes.
140Module *BugDriver::ExtractLoop(Module *M) {
141  std::vector<const StaticPassInfo*> LoopExtractPasses;
142  LoopExtractPasses.push_back(getPI(createSingleLoopExtractorPass()));
143
144  Module *NewM = runPassesOn(M, LoopExtractPasses);
145  if (NewM == 0) {
146    Module *Old = swapProgramIn(M);
147    outs() << "*** Loop extraction failed: ";
148    EmitProgressBitcode("loopextraction", true);
149    outs() << "*** Sorry. :(  Please report a bug!\n";
150    swapProgramIn(Old);
151    return 0;
152  }
153
154  // Check to see if we created any new functions.  If not, no loops were
155  // extracted and we should return null.  Limit the number of loops we extract
156  // to avoid taking forever.
157  static unsigned NumExtracted = 32;
158  if (M->size() == NewM->size() || --NumExtracted == 0) {
159    delete NewM;
160    return 0;
161  } else {
162    assert(M->size() < NewM->size() && "Loop extract removed functions?");
163    Module::iterator MI = NewM->begin();
164    for (unsigned i = 0, e = M->size(); i != e; ++i)
165      ++MI;
166  }
167
168  return NewM;
169}
170
171
172// DeleteFunctionBody - "Remove" the function by deleting all of its basic
173// blocks, making it external.
174//
175void llvm::DeleteFunctionBody(Function *F) {
176  // delete the body of the function...
177  F->deleteBody();
178  assert(F->isDeclaration() && "This didn't make the function external!");
179}
180
181/// GetTorInit - Given a list of entries for static ctors/dtors, return them
182/// as a constant array.
183static Constant *GetTorInit(std::vector<std::pair<Function*, int> > &TorList) {
184  assert(!TorList.empty() && "Don't create empty tor list!");
185  std::vector<Constant*> ArrayElts;
186  for (unsigned i = 0, e = TorList.size(); i != e; ++i) {
187    std::vector<Constant*> Elts;
188    Elts.push_back(ConstantInt::get(
189          Type::getInt32Ty(TorList[i].first->getContext()), TorList[i].second));
190    Elts.push_back(TorList[i].first);
191    ArrayElts.push_back(ConstantStruct::get(TorList[i].first->getContext(),
192                                            Elts, false));
193  }
194  return ConstantArray::get(ArrayType::get(ArrayElts[0]->getType(),
195                                           ArrayElts.size()),
196                            ArrayElts);
197}
198
199/// SplitStaticCtorDtor - A module was recently split into two parts, M1/M2, and
200/// M1 has all of the global variables.  If M2 contains any functions that are
201/// static ctors/dtors, we need to add an llvm.global_[cd]tors global to M2, and
202/// prune appropriate entries out of M1s list.
203static void SplitStaticCtorDtor(const char *GlobalName, Module *M1, Module *M2,
204                                ValueMap<const Value*, Value*> VMap) {
205  GlobalVariable *GV = M1->getNamedGlobal(GlobalName);
206  if (!GV || GV->isDeclaration() || GV->hasLocalLinkage() ||
207      !GV->use_empty()) return;
208
209  std::vector<std::pair<Function*, int> > M1Tors, M2Tors;
210  ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
211  if (!InitList) return;
212
213  for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
214    if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
215      if (CS->getNumOperands() != 2) return;  // Not array of 2-element structs.
216
217      if (CS->getOperand(1)->isNullValue())
218        break;  // Found a null terminator, stop here.
219
220      ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
221      int Priority = CI ? CI->getSExtValue() : 0;
222
223      Constant *FP = CS->getOperand(1);
224      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
225        if (CE->isCast())
226          FP = CE->getOperand(0);
227      if (Function *F = dyn_cast<Function>(FP)) {
228        if (!F->isDeclaration())
229          M1Tors.push_back(std::make_pair(F, Priority));
230        else {
231          // Map to M2's version of the function.
232          F = cast<Function>(VMap[F]);
233          M2Tors.push_back(std::make_pair(F, Priority));
234        }
235      }
236    }
237  }
238
239  GV->eraseFromParent();
240  if (!M1Tors.empty()) {
241    Constant *M1Init = GetTorInit(M1Tors);
242    new GlobalVariable(*M1, M1Init->getType(), false,
243                       GlobalValue::AppendingLinkage,
244                       M1Init, GlobalName);
245  }
246
247  GV = M2->getNamedGlobal(GlobalName);
248  assert(GV && "Not a clone of M1?");
249  assert(GV->use_empty() && "llvm.ctors shouldn't have uses!");
250
251  GV->eraseFromParent();
252  if (!M2Tors.empty()) {
253    Constant *M2Init = GetTorInit(M2Tors);
254    new GlobalVariable(*M2, M2Init->getType(), false,
255                       GlobalValue::AppendingLinkage,
256                       M2Init, GlobalName);
257  }
258}
259
260
261/// SplitFunctionsOutOfModule - Given a module and a list of functions in the
262/// module, split the functions OUT of the specified module, and place them in
263/// the new module.
264Module *
265llvm::SplitFunctionsOutOfModule(Module *M,
266                                const std::vector<Function*> &F,
267                                ValueMap<const Value*, Value*> &VMap) {
268  // Make sure functions & globals are all external so that linkage
269  // between the two modules will work.
270  for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
271    I->setLinkage(GlobalValue::ExternalLinkage);
272  for (Module::global_iterator I = M->global_begin(), E = M->global_end();
273       I != E; ++I) {
274    if (I->hasName() && I->getName()[0] == '\01')
275      I->setName(I->getName().substr(1));
276    I->setLinkage(GlobalValue::ExternalLinkage);
277  }
278
279  ValueMap<const Value*, Value*> NewVMap;
280  Module *New = CloneModule(M, NewVMap);
281
282  // Make sure global initializers exist only in the safe module (CBE->.so)
283  for (Module::global_iterator I = New->global_begin(), E = New->global_end();
284       I != E; ++I)
285    I->setInitializer(0);  // Delete the initializer to make it external
286
287  // Remove the Test functions from the Safe module
288  std::set<Function *> TestFunctions;
289  for (unsigned i = 0, e = F.size(); i != e; ++i) {
290    Function *TNOF = cast<Function>(VMap[F[i]]);
291    DEBUG(errs() << "Removing function ");
292    DEBUG(WriteAsOperand(errs(), TNOF, false));
293    DEBUG(errs() << "\n");
294    TestFunctions.insert(cast<Function>(NewVMap[TNOF]));
295    DeleteFunctionBody(TNOF);       // Function is now external in this module!
296  }
297
298
299  // Remove the Safe functions from the Test module
300  for (Module::iterator I = New->begin(), E = New->end(); I != E; ++I)
301    if (!TestFunctions.count(I))
302      DeleteFunctionBody(I);
303
304
305  // Make sure that there is a global ctor/dtor array in both halves of the
306  // module if they both have static ctor/dtor functions.
307  SplitStaticCtorDtor("llvm.global_ctors", M, New, NewVMap);
308  SplitStaticCtorDtor("llvm.global_dtors", M, New, NewVMap);
309
310  return New;
311}
312
313//===----------------------------------------------------------------------===//
314// Basic Block Extraction Code
315//===----------------------------------------------------------------------===//
316
317/// ExtractMappedBlocksFromModule - Extract all but the specified basic blocks
318/// into their own functions.  The only detail is that M is actually a module
319/// cloned from the one the BBs are in, so some mapping needs to be performed.
320/// If this operation fails for some reason (ie the implementation is buggy),
321/// this function should return null, otherwise it returns a new Module.
322Module *BugDriver::ExtractMappedBlocksFromModule(const
323                                                 std::vector<BasicBlock*> &BBs,
324                                                 Module *M) {
325  sys::Path uniqueFilename(OutputPrefix + "-extractblocks");
326  std::string ErrMsg;
327  if (uniqueFilename.createTemporaryFileOnDisk(true, &ErrMsg)) {
328    outs() << "*** Basic Block extraction failed!\n";
329    errs() << "Error creating temporary file: " << ErrMsg << "\n";
330    M = swapProgramIn(M);
331    EmitProgressBitcode("basicblockextractfail", true);
332    swapProgramIn(M);
333    return 0;
334  }
335  sys::RemoveFileOnSignal(uniqueFilename);
336
337  std::string ErrorInfo;
338  raw_fd_ostream BlocksToNotExtractFile(uniqueFilename.c_str(), ErrorInfo);
339  if (!ErrorInfo.empty()) {
340    outs() << "*** Basic Block extraction failed!\n";
341    errs() << "Error writing list of blocks to not extract: " << ErrorInfo
342           << "\n";
343    M = swapProgramIn(M);
344    EmitProgressBitcode("basicblockextractfail", true);
345    swapProgramIn(M);
346    return 0;
347  }
348  for (std::vector<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
349       I != E; ++I) {
350    BasicBlock *BB = *I;
351    // If the BB doesn't have a name, give it one so we have something to key
352    // off of.
353    if (!BB->hasName()) BB->setName("tmpbb");
354    BlocksToNotExtractFile << BB->getParent()->getNameStr() << " "
355                           << BB->getName() << "\n";
356  }
357  BlocksToNotExtractFile.close();
358
359  std::string uniqueFN = "--extract-blocks-file=" + uniqueFilename.str();
360  const char *ExtraArg = uniqueFN.c_str();
361
362  std::vector<const StaticPassInfo*> PI;
363  std::vector<BasicBlock *> EmptyBBs; // This parameter is ignored.
364  PI.push_back(getPI(createBlockExtractorPass(EmptyBBs)));
365  Module *Ret = runPassesOn(M, PI, false, 1, &ExtraArg);
366
367  uniqueFilename.eraseFromDisk(); // Free disk space
368
369  if (Ret == 0) {
370    outs() << "*** Basic Block extraction failed, please report a bug!\n";
371    M = swapProgramIn(M);
372    EmitProgressBitcode("basicblockextractfail", true);
373    swapProgramIn(M);
374  }
375  return Ret;
376}
377