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 (isa<StructType>(TheInst->getType()))
77     TheInst->replaceAllUsesWith(UndefValue::get(TheInst->getType()));
78   else if (TheInst->getType() != Type::getVoidTy(I->getContext()))
79     TheInst->replaceAllUsesWith(Constant::getNullValue(TheInst->getType()));
80 
81   // Remove the instruction from the program.
82   TheInst->getParent()->getInstList().erase(TheInst);
83 
84 
85   //writeProgramToFile("current.bc", Result);
86 
87   // Spiff up the output a little bit.
88   PassManager Passes;
89   // Make sure that the appropriate target data is always used...
90   Passes.add(new TargetData(Result));
91 
92   /// FIXME: If this used runPasses() like the methods below, we could get rid
93   /// of the -disable-* options!
94   if (Simplification > 1 && !NoDCE)
95     Passes.add(createDeadCodeEliminationPass());
96   if (Simplification && !DisableSimplifyCFG)
97     Passes.add(createCFGSimplificationPass());      // Delete dead control flow
98 
99   Passes.add(createVerifierPass());
100   Passes.run(*Result);
101   return Result;
102 }
103 
104 static const PassInfo *getPI(Pass *P) {
105   const PassInfo *PI = P->getPassInfo();
106   delete P;
107   return PI;
108 }
109 
110 /// performFinalCleanups - This method clones the current Program and performs
111 /// a series of cleanups intended to get rid of extra cruft on the module
112 /// before handing it to the user.
113 ///
114 Module *BugDriver::performFinalCleanups(Module *M, bool MayModifySemantics) {
115   // Make all functions external, so GlobalDCE doesn't delete them...
116   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
117     I->setLinkage(GlobalValue::ExternalLinkage);
118 
119   std::vector<const PassInfo*> CleanupPasses;
120   CleanupPasses.push_back(getPI(createGlobalDCEPass()));
121   CleanupPasses.push_back(getPI(createDeadTypeEliminationPass()));
122 
123   if (MayModifySemantics)
124     CleanupPasses.push_back(getPI(createDeadArgHackingPass()));
125   else
126     CleanupPasses.push_back(getPI(createDeadArgEliminationPass()));
127 
128   Module *New = runPassesOn(M, CleanupPasses);
129   if (New == 0) {
130     errs() << "Final cleanups failed.  Sorry. :(  Please report a bug!\n";
131     return M;
132   }
133   delete M;
134   return New;
135 }
136 
137 
138 /// ExtractLoop - Given a module, extract up to one loop from it into a new
139 /// function.  This returns null if there are no extractable loops in the
140 /// program or if the loop extractor crashes.
141 Module *BugDriver::ExtractLoop(Module *M) {
142   std::vector<const PassInfo*> LoopExtractPasses;
143   LoopExtractPasses.push_back(getPI(createSingleLoopExtractorPass()));
144 
145   Module *NewM = runPassesOn(M, LoopExtractPasses);
146   if (NewM == 0) {
147     Module *Old = swapProgramIn(M);
148     outs() << "*** Loop extraction failed: ";
149     EmitProgressBitcode("loopextraction", true);
150     outs() << "*** Sorry. :(  Please report a bug!\n";
151     swapProgramIn(Old);
152     return 0;
153   }
154 
155   // Check to see if we created any new functions.  If not, no loops were
156   // extracted and we should return null.  Limit the number of loops we extract
157   // to avoid taking forever.
158   static unsigned NumExtracted = 32;
159   if (M->size() == NewM->size() || --NumExtracted == 0) {
160     delete NewM;
161     return 0;
162   } else {
163     assert(M->size() < NewM->size() && "Loop extract removed functions?");
164     Module::iterator MI = NewM->begin();
165     for (unsigned i = 0, e = M->size(); i != e; ++i)
166       ++MI;
167   }
168 
169   return NewM;
170 }
171 
172 
173 // DeleteFunctionBody - "Remove" the function by deleting all of its basic
174 // blocks, making it external.
175 //
176 void llvm::DeleteFunctionBody(Function *F) {
177   // delete the body of the function...
178   F->deleteBody();
179   assert(F->isDeclaration() && "This didn't make the function external!");
180 }
181 
182 /// GetTorInit - Given a list of entries for static ctors/dtors, return them
183 /// as a constant array.
184 static Constant *GetTorInit(std::vector<std::pair<Function*, int> > &TorList) {
185   assert(!TorList.empty() && "Don't create empty tor list!");
186   std::vector<Constant*> ArrayElts;
187   for (unsigned i = 0, e = TorList.size(); i != e; ++i) {
188     std::vector<Constant*> Elts;
189     Elts.push_back(ConstantInt::get(
190           Type::getInt32Ty(TorList[i].first->getContext()), TorList[i].second));
191     Elts.push_back(TorList[i].first);
192     ArrayElts.push_back(ConstantStruct::get(TorList[i].first->getContext(),
193                                             Elts, false));
194   }
195   return ConstantArray::get(ArrayType::get(ArrayElts[0]->getType(),
196                                            ArrayElts.size()),
197                             ArrayElts);
198 }
199 
200 /// SplitStaticCtorDtor - A module was recently split into two parts, M1/M2, and
201 /// M1 has all of the global variables.  If M2 contains any functions that are
202 /// static ctors/dtors, we need to add an llvm.global_[cd]tors global to M2, and
203 /// prune appropriate entries out of M1s list.
204 static void SplitStaticCtorDtor(const char *GlobalName, Module *M1, Module *M2,
205                                 DenseMap<const Value*, Value*> ValueMap) {
206   GlobalVariable *GV = M1->getNamedGlobal(GlobalName);
207   if (!GV || GV->isDeclaration() || GV->hasLocalLinkage() ||
208       !GV->use_empty()) return;
209 
210   std::vector<std::pair<Function*, int> > M1Tors, M2Tors;
211   ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
212   if (!InitList) return;
213 
214   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
215     if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
216       if (CS->getNumOperands() != 2) return;  // Not array of 2-element structs.
217 
218       if (CS->getOperand(1)->isNullValue())
219         break;  // Found a null terminator, stop here.
220 
221       ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
222       int Priority = CI ? CI->getSExtValue() : 0;
223 
224       Constant *FP = CS->getOperand(1);
225       if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
226         if (CE->isCast())
227           FP = CE->getOperand(0);
228       if (Function *F = dyn_cast<Function>(FP)) {
229         if (!F->isDeclaration())
230           M1Tors.push_back(std::make_pair(F, Priority));
231         else {
232           // Map to M2's version of the function.
233           F = cast<Function>(ValueMap[F]);
234           M2Tors.push_back(std::make_pair(F, Priority));
235         }
236       }
237     }
238   }
239 
240   GV->eraseFromParent();
241   if (!M1Tors.empty()) {
242     Constant *M1Init = GetTorInit(M1Tors);
243     new GlobalVariable(*M1, M1Init->getType(), false,
244                        GlobalValue::AppendingLinkage,
245                        M1Init, GlobalName);
246   }
247 
248   GV = M2->getNamedGlobal(GlobalName);
249   assert(GV && "Not a clone of M1?");
250   assert(GV->use_empty() && "llvm.ctors shouldn't have uses!");
251 
252   GV->eraseFromParent();
253   if (!M2Tors.empty()) {
254     Constant *M2Init = GetTorInit(M2Tors);
255     new GlobalVariable(*M2, M2Init->getType(), false,
256                        GlobalValue::AppendingLinkage,
257                        M2Init, GlobalName);
258   }
259 }
260 
261 
262 /// SplitFunctionsOutOfModule - Given a module and a list of functions in the
263 /// module, split the functions OUT of the specified module, and place them in
264 /// the new module.
265 Module *
266 llvm::SplitFunctionsOutOfModule(Module *M,
267                                 const std::vector<Function*> &F,
268                                 DenseMap<const Value*, Value*> &ValueMap) {
269   // Make sure functions & globals are all external so that linkage
270   // between the two modules will work.
271   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
272     I->setLinkage(GlobalValue::ExternalLinkage);
273   for (Module::global_iterator I = M->global_begin(), E = M->global_end();
274        I != E; ++I) {
275     if (I->hasName() && I->getName()[0] == '\01')
276       I->setName(I->getName().substr(1));
277     I->setLinkage(GlobalValue::ExternalLinkage);
278   }
279 
280   DenseMap<const Value*, Value*> NewValueMap;
281   Module *New = CloneModule(M, NewValueMap);
282 
283   // Make sure global initializers exist only in the safe module (CBE->.so)
284   for (Module::global_iterator I = New->global_begin(), E = New->global_end();
285        I != E; ++I)
286     I->setInitializer(0);  // Delete the initializer to make it external
287 
288   // Remove the Test functions from the Safe module
289   std::set<Function *> TestFunctions;
290   for (unsigned i = 0, e = F.size(); i != e; ++i) {
291     Function *TNOF = cast<Function>(ValueMap[F[i]]);
292     DEBUG(errs() << "Removing function ");
293     DEBUG(WriteAsOperand(errs(), TNOF, false));
294     DEBUG(errs() << "\n");
295     TestFunctions.insert(cast<Function>(NewValueMap[TNOF]));
296     DeleteFunctionBody(TNOF);       // Function is now external in this module!
297   }
298 
299 
300   // Remove the Safe functions from the Test module
301   for (Module::iterator I = New->begin(), E = New->end(); I != E; ++I)
302     if (!TestFunctions.count(I))
303       DeleteFunctionBody(I);
304 
305 
306   // Make sure that there is a global ctor/dtor array in both halves of the
307   // module if they both have static ctor/dtor functions.
308   SplitStaticCtorDtor("llvm.global_ctors", M, New, NewValueMap);
309   SplitStaticCtorDtor("llvm.global_dtors", M, New, NewValueMap);
310 
311   return New;
312 }
313 
314 //===----------------------------------------------------------------------===//
315 // Basic Block Extraction Code
316 //===----------------------------------------------------------------------===//
317 
318 /// ExtractMappedBlocksFromModule - Extract all but the specified basic blocks
319 /// into their own functions.  The only detail is that M is actually a module
320 /// cloned from the one the BBs are in, so some mapping needs to be performed.
321 /// If this operation fails for some reason (ie the implementation is buggy),
322 /// this function should return null, otherwise it returns a new Module.
323 Module *BugDriver::ExtractMappedBlocksFromModule(const
324                                                  std::vector<BasicBlock*> &BBs,
325                                                  Module *M) {
326   char *ExtraArg = NULL;
327 
328   sys::Path uniqueFilename(OutputPrefix + "-extractblocks");
329   std::string ErrMsg;
330   if (uniqueFilename.createTemporaryFileOnDisk(true, &ErrMsg)) {
331     outs() << "*** Basic Block extraction failed!\n";
332     errs() << "Error creating temporary file: " << ErrMsg << "\n";
333     M = swapProgramIn(M);
334     EmitProgressBitcode("basicblockextractfail", true);
335     swapProgramIn(M);
336     return 0;
337   }
338   sys::RemoveFileOnSignal(uniqueFilename);
339 
340   std::string ErrorInfo;
341   raw_fd_ostream BlocksToNotExtractFile(uniqueFilename.c_str(), ErrorInfo);
342   if (!ErrorInfo.empty()) {
343     outs() << "*** Basic Block extraction failed!\n";
344     errs() << "Error writing list of blocks to not extract: " << ErrorInfo
345            << "\n";
346     M = swapProgramIn(M);
347     EmitProgressBitcode("basicblockextractfail", true);
348     swapProgramIn(M);
349     return 0;
350   }
351   for (std::vector<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
352        I != E; ++I) {
353     BasicBlock *BB = *I;
354     // If the BB doesn't have a name, give it one so we have something to key
355     // off of.
356     if (!BB->hasName()) BB->setName("tmpbb");
357     BlocksToNotExtractFile << BB->getParent()->getNameStr() << " "
358                            << BB->getName() << "\n";
359   }
360   BlocksToNotExtractFile.close();
361 
362   const char *uniqueFN = uniqueFilename.c_str();
363   ExtraArg = (char*)malloc(23 + strlen(uniqueFN));
364   strcat(strcpy(ExtraArg, "--extract-blocks-file="), uniqueFN);
365 
366   std::vector<const PassInfo*> PI;
367   std::vector<BasicBlock *> EmptyBBs; // This parameter is ignored.
368   PI.push_back(getPI(createBlockExtractorPass(EmptyBBs)));
369   Module *Ret = runPassesOn(M, PI, false, 1, &ExtraArg);
370 
371   if (uniqueFilename.exists())
372     uniqueFilename.eraseFromDisk(); // Free disk space
373   free(ExtraArg);
374 
375   if (Ret == 0) {
376     outs() << "*** Basic Block extraction failed, please report a bug!\n";
377     M = swapProgramIn(M);
378     EmitProgressBitcode("basicblockextractfail", true);
379     swapProgramIn(M);
380   }
381   return Ret;
382 }
383