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>
36 using namespace llvm;
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>
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 ///
57 Module *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() != Type::getVoidTy(I->getContext()))
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 
102 static const PassInfo *getPI(Pass *P) {
103   const PassInfo *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 ///
112 Module *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 PassInfo*> CleanupPasses;
118   CleanupPasses.push_back(getPI(createGlobalDCEPass()));
119   CleanupPasses.push_back(getPI(createDeadTypeEliminationPass()));
120 
121   if (MayModifySemantics)
122     CleanupPasses.push_back(getPI(createDeadArgHackingPass()));
123   else
124     CleanupPasses.push_back(getPI(createDeadArgEliminationPass()));
125 
126   Module *New = runPassesOn(M, CleanupPasses);
127   if (New == 0) {
128     errs() << "Final cleanups failed.  Sorry. :(  Please report a bug!\n";
129     return M;
130   }
131   delete M;
132   return New;
133 }
134 
135 
136 /// ExtractLoop - Given a module, extract up to one loop from it into a new
137 /// function.  This returns null if there are no extractable loops in the
138 /// program or if the loop extractor crashes.
139 Module *BugDriver::ExtractLoop(Module *M) {
140   std::vector<const PassInfo*> LoopExtractPasses;
141   LoopExtractPasses.push_back(getPI(createSingleLoopExtractorPass()));
142 
143   Module *NewM = runPassesOn(M, LoopExtractPasses);
144   if (NewM == 0) {
145     Module *Old = swapProgramIn(M);
146     outs() << "*** Loop extraction failed: ";
147     EmitProgressBitcode("loopextraction", true);
148     outs() << "*** Sorry. :(  Please report a bug!\n";
149     swapProgramIn(Old);
150     return 0;
151   }
152 
153   // Check to see if we created any new functions.  If not, no loops were
154   // extracted and we should return null.  Limit the number of loops we extract
155   // to avoid taking forever.
156   static unsigned NumExtracted = 32;
157   if (M->size() == NewM->size() || --NumExtracted == 0) {
158     delete NewM;
159     return 0;
160   } else {
161     assert(M->size() < NewM->size() && "Loop extract removed functions?");
162     Module::iterator MI = NewM->begin();
163     for (unsigned i = 0, e = M->size(); i != e; ++i)
164       ++MI;
165   }
166 
167   return NewM;
168 }
169 
170 
171 // DeleteFunctionBody - "Remove" the function by deleting all of its basic
172 // blocks, making it external.
173 //
174 void llvm::DeleteFunctionBody(Function *F) {
175   // delete the body of the function...
176   F->deleteBody();
177   assert(F->isDeclaration() && "This didn't make the function external!");
178 }
179 
180 /// GetTorInit - Given a list of entries for static ctors/dtors, return them
181 /// as a constant array.
182 static Constant *GetTorInit(std::vector<std::pair<Function*, int> > &TorList) {
183   assert(!TorList.empty() && "Don't create empty tor list!");
184   std::vector<Constant*> ArrayElts;
185   for (unsigned i = 0, e = TorList.size(); i != e; ++i) {
186     std::vector<Constant*> Elts;
187     Elts.push_back(ConstantInt::get(
188           Type::getInt32Ty(TorList[i].first->getContext()), TorList[i].second));
189     Elts.push_back(TorList[i].first);
190     ArrayElts.push_back(ConstantStruct::get(TorList[i].first->getContext(),
191                                             Elts, false));
192   }
193   return ConstantArray::get(ArrayType::get(ArrayElts[0]->getType(),
194                                            ArrayElts.size()),
195                             ArrayElts);
196 }
197 
198 /// SplitStaticCtorDtor - A module was recently split into two parts, M1/M2, and
199 /// M1 has all of the global variables.  If M2 contains any functions that are
200 /// static ctors/dtors, we need to add an llvm.global_[cd]tors global to M2, and
201 /// prune appropriate entries out of M1s list.
202 static void SplitStaticCtorDtor(const char *GlobalName, Module *M1, Module *M2,
203                                 DenseMap<const Value*, Value*> ValueMap) {
204   GlobalVariable *GV = M1->getNamedGlobal(GlobalName);
205   if (!GV || GV->isDeclaration() || GV->hasLocalLinkage() ||
206       !GV->use_empty()) return;
207 
208   std::vector<std::pair<Function*, int> > M1Tors, M2Tors;
209   ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
210   if (!InitList) return;
211 
212   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
213     if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
214       if (CS->getNumOperands() != 2) return;  // Not array of 2-element structs.
215 
216       if (CS->getOperand(1)->isNullValue())
217         break;  // Found a null terminator, stop here.
218 
219       ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
220       int Priority = CI ? CI->getSExtValue() : 0;
221 
222       Constant *FP = CS->getOperand(1);
223       if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
224         if (CE->isCast())
225           FP = CE->getOperand(0);
226       if (Function *F = dyn_cast<Function>(FP)) {
227         if (!F->isDeclaration())
228           M1Tors.push_back(std::make_pair(F, Priority));
229         else {
230           // Map to M2's version of the function.
231           F = cast<Function>(ValueMap[F]);
232           M2Tors.push_back(std::make_pair(F, Priority));
233         }
234       }
235     }
236   }
237 
238   GV->eraseFromParent();
239   if (!M1Tors.empty()) {
240     Constant *M1Init = GetTorInit(M1Tors);
241     new GlobalVariable(*M1, M1Init->getType(), false,
242                        GlobalValue::AppendingLinkage,
243                        M1Init, GlobalName);
244   }
245 
246   GV = M2->getNamedGlobal(GlobalName);
247   assert(GV && "Not a clone of M1?");
248   assert(GV->use_empty() && "llvm.ctors shouldn't have uses!");
249 
250   GV->eraseFromParent();
251   if (!M2Tors.empty()) {
252     Constant *M2Init = GetTorInit(M2Tors);
253     new GlobalVariable(*M2, M2Init->getType(), false,
254                        GlobalValue::AppendingLinkage,
255                        M2Init, GlobalName);
256   }
257 }
258 
259 
260 /// SplitFunctionsOutOfModule - Given a module and a list of functions in the
261 /// module, split the functions OUT of the specified module, and place them in
262 /// the new module.
263 Module *
264 llvm::SplitFunctionsOutOfModule(Module *M,
265                                 const std::vector<Function*> &F,
266                                 DenseMap<const Value*, Value*> &ValueMap) {
267   // Make sure functions & globals are all external so that linkage
268   // between the two modules will work.
269   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
270     I->setLinkage(GlobalValue::ExternalLinkage);
271   for (Module::global_iterator I = M->global_begin(), E = M->global_end();
272        I != E; ++I) {
273     if (I->hasName() && I->getName()[0] == '\01')
274       I->setName(I->getName().substr(1));
275     I->setLinkage(GlobalValue::ExternalLinkage);
276   }
277 
278   DenseMap<const Value*, Value*> NewValueMap;
279   Module *New = CloneModule(M, NewValueMap);
280 
281   // Make sure global initializers exist only in the safe module (CBE->.so)
282   for (Module::global_iterator I = New->global_begin(), E = New->global_end();
283        I != E; ++I)
284     I->setInitializer(0);  // Delete the initializer to make it external
285 
286   // Remove the Test functions from the Safe module
287   std::set<Function *> TestFunctions;
288   for (unsigned i = 0, e = F.size(); i != e; ++i) {
289     Function *TNOF = cast<Function>(ValueMap[F[i]]);
290     DEBUG(errs() << "Removing function ");
291     DEBUG(WriteAsOperand(errs(), TNOF, false));
292     DEBUG(errs() << "\n");
293     TestFunctions.insert(cast<Function>(NewValueMap[TNOF]));
294     DeleteFunctionBody(TNOF);       // Function is now external in this module!
295   }
296 
297 
298   // Remove the Safe functions from the Test module
299   for (Module::iterator I = New->begin(), E = New->end(); I != E; ++I)
300     if (!TestFunctions.count(I))
301       DeleteFunctionBody(I);
302 
303 
304   // Make sure that there is a global ctor/dtor array in both halves of the
305   // module if they both have static ctor/dtor functions.
306   SplitStaticCtorDtor("llvm.global_ctors", M, New, NewValueMap);
307   SplitStaticCtorDtor("llvm.global_dtors", M, New, NewValueMap);
308 
309   return New;
310 }
311 
312 //===----------------------------------------------------------------------===//
313 // Basic Block Extraction Code
314 //===----------------------------------------------------------------------===//
315 
316 /// ExtractMappedBlocksFromModule - Extract all but the specified basic blocks
317 /// into their own functions.  The only detail is that M is actually a module
318 /// cloned from the one the BBs are in, so some mapping needs to be performed.
319 /// If this operation fails for some reason (ie the implementation is buggy),
320 /// this function should return null, otherwise it returns a new Module.
321 Module *BugDriver::ExtractMappedBlocksFromModule(const
322                                                  std::vector<BasicBlock*> &BBs,
323                                                  Module *M) {
324   sys::Path uniqueFilename(OutputPrefix + "-extractblocks");
325   std::string ErrMsg;
326   if (uniqueFilename.createTemporaryFileOnDisk(true, &ErrMsg)) {
327     outs() << "*** Basic Block extraction failed!\n";
328     errs() << "Error creating temporary file: " << ErrMsg << "\n";
329     M = swapProgramIn(M);
330     EmitProgressBitcode("basicblockextractfail", true);
331     swapProgramIn(M);
332     return 0;
333   }
334   sys::RemoveFileOnSignal(uniqueFilename);
335 
336   std::string ErrorInfo;
337   raw_fd_ostream BlocksToNotExtractFile(uniqueFilename.c_str(), ErrorInfo);
338   if (!ErrorInfo.empty()) {
339     outs() << "*** Basic Block extraction failed!\n";
340     errs() << "Error writing list of blocks to not extract: " << ErrorInfo
341            << "\n";
342     M = swapProgramIn(M);
343     EmitProgressBitcode("basicblockextractfail", true);
344     swapProgramIn(M);
345     return 0;
346   }
347   for (std::vector<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
348        I != E; ++I) {
349     BasicBlock *BB = *I;
350     // If the BB doesn't have a name, give it one so we have something to key
351     // off of.
352     if (!BB->hasName()) BB->setName("tmpbb");
353     BlocksToNotExtractFile << BB->getParent()->getNameStr() << " "
354                            << BB->getName() << "\n";
355   }
356   BlocksToNotExtractFile.close();
357 
358   std::string uniqueFN = "--extract-blocks-file=" + uniqueFilename.str();
359   const char *ExtraArg = uniqueFN.c_str();
360 
361   std::vector<const PassInfo*> PI;
362   std::vector<BasicBlock *> EmptyBBs; // This parameter is ignored.
363   PI.push_back(getPI(createBlockExtractorPass(EmptyBBs)));
364   Module *Ret = runPassesOn(M, PI, false, 1, &ExtraArg);
365 
366   uniqueFilename.eraseFromDisk(); // Free disk space
367 
368   if (Ret == 0) {
369     outs() << "*** Basic Block extraction failed, please report a bug!\n";
370     M = swapProgramIn(M);
371     EmitProgressBitcode("basicblockextractfail", true);
372     swapProgramIn(M);
373   }
374   return Ret;
375 }
376