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>
35 using namespace llvm;
36 
37 #define DEBUG_TYPE "bugpoint"
38 
39 namespace llvm {
40 bool DisableSimplifyCFG = false;
41 extern cl::opt<std::string> OutputPrefix;
42 } // End llvm namespace
43 
44 namespace {
45 cl::opt<bool> 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 Function *globalInitUsesExternalBA(GlobalVariable *GV) {
52   if (!GV->hasInitializer())
53     return nullptr;
54 
55   Constant *I = GV->getInitializer();
56 
57   // walk the values used by the initializer
58   // (and recurse into things like ConstantExpr)
59   std::vector<Constant *> Todo;
60   std::set<Constant *> Done;
61   Todo.push_back(I);
62 
63   while (!Todo.empty()) {
64     Constant *V = Todo.back();
65     Todo.pop_back();
66     Done.insert(V);
67 
68     if (BlockAddress *BA = dyn_cast<BlockAddress>(V)) {
69       Function *F = BA->getFunction();
70       if (F->isDeclaration())
71         return F;
72     }
73 
74     for (User::op_iterator i = V->op_begin(), e = V->op_end(); i != e; ++i) {
75       Constant *C = dyn_cast<Constant>(*i);
76       if (C && !isa<GlobalValue>(C) && !Done.count(C))
77         Todo.push_back(C);
78     }
79   }
80   return nullptr;
81 }
82 } // end anonymous namespace
83 
84 std::unique_ptr<Module>
85 BugDriver::deleteInstructionFromProgram(const Instruction *I,
86                                         unsigned Simplification) {
87   // FIXME, use vmap?
88   std::unique_ptr<Module> Clone = CloneModule(*Program);
89 
90   const BasicBlock *PBB = I->getParent();
91   const Function *PF = PBB->getParent();
92 
93   Module::iterator RFI = Clone->begin(); // Get iterator to corresponding fn
94   std::advance(
95       RFI, std::distance(PF->getParent()->begin(), Module::const_iterator(PF)));
96 
97   Function::iterator RBI = RFI->begin(); // Get iterator to corresponding BB
98   std::advance(RBI, std::distance(PF->begin(), Function::const_iterator(PBB)));
99 
100   BasicBlock::iterator RI = RBI->begin(); // Get iterator to corresponding inst
101   std::advance(RI, std::distance(PBB->begin(), BasicBlock::const_iterator(I)));
102   Instruction *TheInst = &*RI; // Got the corresponding instruction!
103 
104   // If this instruction produces a value, replace any users with null values
105   if (!TheInst->getType()->isVoidTy())
106     TheInst->replaceAllUsesWith(Constant::getNullValue(TheInst->getType()));
107 
108   // Remove the instruction from the program.
109   TheInst->getParent()->getInstList().erase(TheInst);
110 
111   // Spiff up the output a little bit.
112   std::vector<std::string> Passes;
113 
114   /// Can we get rid of the -disable-* options?
115   if (Simplification > 1 && !NoDCE)
116     Passes.push_back("dce");
117   if (Simplification && !DisableSimplifyCFG)
118     Passes.push_back("simplifycfg"); // Delete dead control flow
119 
120   Passes.push_back("verify");
121   std::unique_ptr<Module> New = runPassesOn(Clone.get(), Passes);
122   if (!New) {
123     errs() << "Instruction removal failed.  Sorry. :(  Please report a bug!\n";
124     exit(1);
125   }
126   return New;
127 }
128 
129 std::unique_ptr<Module>
130 BugDriver::performFinalCleanups(std::unique_ptr<Module> M,
131                                 bool MayModifySemantics) {
132   // Make all functions external, so GlobalDCE doesn't delete them...
133   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
134     I->setLinkage(GlobalValue::ExternalLinkage);
135 
136   std::vector<std::string> CleanupPasses;
137   CleanupPasses.push_back("globaldce");
138 
139   if (MayModifySemantics)
140     CleanupPasses.push_back("deadarghaX0r");
141   else
142     CleanupPasses.push_back("deadargelim");
143 
144   std::unique_ptr<Module> New = runPassesOn(M.get(), CleanupPasses);
145   if (!New) {
146     errs() << "Final cleanups failed.  Sorry. :(  Please report a bug!\n";
147     return nullptr;
148   }
149   return New;
150 }
151 
152 std::unique_ptr<Module> BugDriver::extractLoop(Module *M) {
153   std::vector<std::string> LoopExtractPasses;
154   LoopExtractPasses.push_back("loop-extract-single");
155 
156   std::unique_ptr<Module> NewM = runPassesOn(M, LoopExtractPasses);
157   if (!NewM) {
158     outs() << "*** Loop extraction failed: ";
159     EmitProgressBitcode(*M, "loopextraction", true);
160     outs() << "*** Sorry. :(  Please report a bug!\n";
161     return nullptr;
162   }
163 
164   // Check to see if we created any new functions.  If not, no loops were
165   // extracted and we should return null.  Limit the number of loops we extract
166   // to avoid taking forever.
167   static unsigned NumExtracted = 32;
168   if (M->size() == NewM->size() || --NumExtracted == 0) {
169     return nullptr;
170   } else {
171     assert(M->size() < NewM->size() && "Loop extract removed functions?");
172     Module::iterator MI = NewM->begin();
173     for (unsigned i = 0, e = M->size(); i != e; ++i)
174       ++MI;
175   }
176 
177   return NewM;
178 }
179 
180 static void eliminateAliases(GlobalValue *GV) {
181   // First, check whether a GlobalAlias references this definition.
182   // GlobalAlias MAY NOT reference declarations.
183   for (;;) {
184     // 1. Find aliases
185     SmallVector<GlobalAlias *, 1> aliases;
186     Module *M = GV->getParent();
187     for (Module::alias_iterator I = M->alias_begin(), E = M->alias_end();
188          I != E; ++I)
189       if (I->getAliasee()->stripPointerCasts() == GV)
190         aliases.push_back(&*I);
191     if (aliases.empty())
192       break;
193     // 2. Resolve aliases
194     for (unsigned i = 0, e = aliases.size(); i < e; ++i) {
195       aliases[i]->replaceAllUsesWith(aliases[i]->getAliasee());
196       aliases[i]->eraseFromParent();
197     }
198     // 3. Repeat until no more aliases found; there might
199     // be an alias to an alias...
200   }
201 }
202 
203 //
204 // DeleteGlobalInitializer - "Remove" the global variable by deleting its
205 // initializer,
206 // making it external.
207 //
208 void llvm::DeleteGlobalInitializer(GlobalVariable *GV) {
209   eliminateAliases(GV);
210   GV->setInitializer(nullptr);
211   GV->setComdat(nullptr);
212 }
213 
214 // DeleteFunctionBody - "Remove" the function by deleting all of its basic
215 // blocks, making it external.
216 //
217 void llvm::DeleteFunctionBody(Function *F) {
218   eliminateAliases(F);
219   // Function declarations can't have comdats.
220   F->setComdat(nullptr);
221 
222   // delete the body of the function...
223   F->deleteBody();
224   assert(F->isDeclaration() && "This didn't make the function external!");
225 }
226 
227 /// GetTorInit - Given a list of entries for static ctors/dtors, return them
228 /// as a constant array.
229 static Constant *GetTorInit(std::vector<std::pair<Function *, int>> &TorList) {
230   assert(!TorList.empty() && "Don't create empty tor list!");
231   std::vector<Constant *> ArrayElts;
232   Type *Int32Ty = Type::getInt32Ty(TorList[0].first->getContext());
233 
234   StructType *STy = StructType::get(Int32Ty, TorList[0].first->getType());
235   for (unsigned i = 0, e = TorList.size(); i != e; ++i) {
236     Constant *Elts[] = {ConstantInt::get(Int32Ty, TorList[i].second),
237                         TorList[i].first};
238     ArrayElts.push_back(ConstantStruct::get(STy, Elts));
239   }
240   return ConstantArray::get(
241       ArrayType::get(ArrayElts[0]->getType(), ArrayElts.size()), ArrayElts);
242 }
243 
244 /// SplitStaticCtorDtor - A module was recently split into two parts, M1/M2, and
245 /// M1 has all of the global variables.  If M2 contains any functions that are
246 /// static ctors/dtors, we need to add an llvm.global_[cd]tors global to M2, and
247 /// prune appropriate entries out of M1s list.
248 static void SplitStaticCtorDtor(const char *GlobalName, Module *M1, Module *M2,
249                                 ValueToValueMapTy &VMap) {
250   GlobalVariable *GV = M1->getNamedGlobal(GlobalName);
251   if (!GV || GV->isDeclaration() || GV->hasLocalLinkage() || !GV->use_empty())
252     return;
253 
254   std::vector<std::pair<Function *, int>> M1Tors, M2Tors;
255   ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
256   if (!InitList)
257     return;
258 
259   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
260     if (ConstantStruct *CS =
261             dyn_cast<ConstantStruct>(InitList->getOperand(i))) {
262       if (CS->getNumOperands() != 2)
263         return; // Not array of 2-element structs.
264 
265       if (CS->getOperand(1)->isNullValue())
266         break; // Found a null terminator, stop here.
267 
268       ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
269       int Priority = CI ? CI->getSExtValue() : 0;
270 
271       Constant *FP = CS->getOperand(1);
272       if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
273         if (CE->isCast())
274           FP = CE->getOperand(0);
275       if (Function *F = dyn_cast<Function>(FP)) {
276         if (!F->isDeclaration())
277           M1Tors.push_back(std::make_pair(F, Priority));
278         else {
279           // Map to M2's version of the function.
280           F = cast<Function>(VMap[F]);
281           M2Tors.push_back(std::make_pair(F, Priority));
282         }
283       }
284     }
285   }
286 
287   GV->eraseFromParent();
288   if (!M1Tors.empty()) {
289     Constant *M1Init = GetTorInit(M1Tors);
290     new GlobalVariable(*M1, M1Init->getType(), false,
291                        GlobalValue::AppendingLinkage, M1Init, GlobalName);
292   }
293 
294   GV = M2->getNamedGlobal(GlobalName);
295   assert(GV && "Not a clone of M1?");
296   assert(GV->use_empty() && "llvm.ctors shouldn't have uses!");
297 
298   GV->eraseFromParent();
299   if (!M2Tors.empty()) {
300     Constant *M2Init = GetTorInit(M2Tors);
301     new GlobalVariable(*M2, M2Init->getType(), false,
302                        GlobalValue::AppendingLinkage, M2Init, GlobalName);
303   }
304 }
305 
306 std::unique_ptr<Module>
307 llvm::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   // Remove the Safe functions from the Test module
335   for (Function &I : *New)
336     if (!TestFunctions.count(&I))
337       DeleteFunctionBody(&I);
338 
339   // Try to split the global initializers evenly
340   for (GlobalVariable &I : M->globals()) {
341     GlobalVariable *GV = cast<GlobalVariable>(NewVMap[&I]);
342     if (Function *TestFn = globalInitUsesExternalBA(&I)) {
343       if (Function *SafeFn = globalInitUsesExternalBA(GV)) {
344         errs() << "*** Error: when reducing functions, encountered "
345                   "the global '";
346         GV->printAsOperand(errs(), false);
347         errs() << "' with an initializer that references blockaddresses "
348                   "from safe function '"
349                << SafeFn->getName() << "' and from test function '"
350                << 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 
372 std::unique_ptr<Module>
373 BugDriver::extractMappedBlocksFromModule(const std::vector<BasicBlock *> &BBs,
374                                          Module *M) {
375   auto Temp = sys::fs::TempFile::create(OutputPrefix + "-extractblocks%%%%%%%");
376   if (!Temp) {
377     outs() << "*** Basic Block extraction failed!\n";
378     errs() << "Error creating temporary file: " << toString(Temp.takeError())
379            << "\n";
380     EmitProgressBitcode(*M, "basicblockextractfail", true);
381     return nullptr;
382   }
383   DiscardTemp Discard{*Temp};
384 
385   // Extract all of the blocks except the ones in BBs.
386   SmallVector<BasicBlock *, 32> BlocksToExtract;
387   for (Function &F : *M)
388     for (BasicBlock &BB : F)
389       // Check if this block is going to be extracted.
390       if (std::find(BBs.begin(), BBs.end(), &BB) == BBs.end())
391         BlocksToExtract.push_back(&BB);
392 
393   raw_fd_ostream OS(Temp->FD, /*shouldClose*/ false);
394   for (BasicBlock *BB : BBs) {
395     // If the BB doesn't have a name, give it one so we have something to key
396     // off of.
397     if (!BB->hasName())
398       BB->setName("tmpbb");
399     OS << BB->getParent()->getName() << " " << BB->getName() << "\n";
400   }
401   OS.flush();
402   if (OS.has_error()) {
403     errs() << "Error writing list of blocks to not extract\n";
404     EmitProgressBitcode(*M, "basicblockextractfail", true);
405     OS.clear_error();
406     return nullptr;
407   }
408 
409   std::string uniqueFN = "--extract-blocks-file=";
410   uniqueFN += Temp->TmpName;
411   const char *ExtraArg = uniqueFN.c_str();
412 
413   std::vector<std::string> PI;
414   PI.push_back("extract-blocks");
415   std::unique_ptr<Module> Ret = runPassesOn(M, PI, 1, &ExtraArg);
416 
417   if (!Ret) {
418     outs() << "*** Basic Block extraction failed, please report a bug!\n";
419     EmitProgressBitcode(*M, "basicblockextractfail", true);
420   }
421   return Ret;
422 }
423