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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/ToolOutputFile.h"
33 #include "llvm/Support/Path.h"
34 #include "llvm/Support/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 ///
deleteInstructionFromProgram(const Instruction * I,unsigned Simplification)57 Module *BugDriver::deleteInstructionFromProgram(const Instruction *I,
58                                                 unsigned Simplification) {
59   // FIXME, use vmap?
60   Module *Clone = CloneModule(Program);
61 
62   const BasicBlock *PBB = I->getParent();
63   const Function *PF = PBB->getParent();
64 
65   Module::iterator RFI = Clone->begin(); // Get iterator to corresponding fn
66   std::advance(RFI, std::distance(PF->getParent()->begin(),
67                                   Module::const_iterator(PF)));
68 
69   Function::iterator RBI = RFI->begin();  // Get iterator to corresponding BB
70   std::advance(RBI, std::distance(PF->begin(), Function::const_iterator(PBB)));
71 
72   BasicBlock::iterator RI = RBI->begin(); // Get iterator to corresponding inst
73   std::advance(RI, std::distance(PBB->begin(), BasicBlock::const_iterator(I)));
74   Instruction *TheInst = RI;              // Got the corresponding instruction!
75 
76   // If this instruction produces a value, replace any users with null values
77   if (!TheInst->getType()->isVoidTy())
78     TheInst->replaceAllUsesWith(Constant::getNullValue(TheInst->getType()));
79 
80   // Remove the instruction from the program.
81   TheInst->getParent()->getInstList().erase(TheInst);
82 
83   // Spiff up the output a little bit.
84   std::vector<std::string> Passes;
85 
86   /// Can we get rid of the -disable-* options?
87   if (Simplification > 1 && !NoDCE)
88     Passes.push_back("dce");
89   if (Simplification && !DisableSimplifyCFG)
90     Passes.push_back("simplifycfg");      // Delete dead control flow
91 
92   Passes.push_back("verify");
93   Module *New = runPassesOn(Clone, Passes);
94   delete Clone;
95   if (!New) {
96     errs() << "Instruction removal failed.  Sorry. :(  Please report a bug!\n";
97     exit(1);
98   }
99   return New;
100 }
101 
102 /// performFinalCleanups - This method clones the current Program and performs
103 /// a series of cleanups intended to get rid of extra cruft on the module
104 /// before handing it to the user.
105 ///
performFinalCleanups(Module * M,bool MayModifySemantics)106 Module *BugDriver::performFinalCleanups(Module *M, bool MayModifySemantics) {
107   // Make all functions external, so GlobalDCE doesn't delete them...
108   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
109     I->setLinkage(GlobalValue::ExternalLinkage);
110 
111   std::vector<std::string> CleanupPasses;
112   CleanupPasses.push_back("globaldce");
113 
114   if (MayModifySemantics)
115     CleanupPasses.push_back("deadarghaX0r");
116   else
117     CleanupPasses.push_back("deadargelim");
118 
119   Module *New = runPassesOn(M, CleanupPasses);
120   if (New == 0) {
121     errs() << "Final cleanups failed.  Sorry. :(  Please report a bug!\n";
122     return M;
123   }
124   delete M;
125   return New;
126 }
127 
128 
129 /// ExtractLoop - Given a module, extract up to one loop from it into a new
130 /// function.  This returns null if there are no extractable loops in the
131 /// program or if the loop extractor crashes.
ExtractLoop(Module * M)132 Module *BugDriver::ExtractLoop(Module *M) {
133   std::vector<std::string> LoopExtractPasses;
134   LoopExtractPasses.push_back("loop-extract-single");
135 
136   Module *NewM = runPassesOn(M, LoopExtractPasses);
137   if (NewM == 0) {
138     outs() << "*** Loop extraction failed: ";
139     EmitProgressBitcode(M, "loopextraction", true);
140     outs() << "*** Sorry. :(  Please report a bug!\n";
141     return 0;
142   }
143 
144   // Check to see if we created any new functions.  If not, no loops were
145   // extracted and we should return null.  Limit the number of loops we extract
146   // to avoid taking forever.
147   static unsigned NumExtracted = 32;
148   if (M->size() == NewM->size() || --NumExtracted == 0) {
149     delete NewM;
150     return 0;
151   } else {
152     assert(M->size() < NewM->size() && "Loop extract removed functions?");
153     Module::iterator MI = NewM->begin();
154     for (unsigned i = 0, e = M->size(); i != e; ++i)
155       ++MI;
156   }
157 
158   return NewM;
159 }
160 
161 
162 // DeleteFunctionBody - "Remove" the function by deleting all of its basic
163 // blocks, making it external.
164 //
DeleteFunctionBody(Function * F)165 void llvm::DeleteFunctionBody(Function *F) {
166   // delete the body of the function...
167   F->deleteBody();
168   assert(F->isDeclaration() && "This didn't make the function external!");
169 }
170 
171 /// GetTorInit - Given a list of entries for static ctors/dtors, return them
172 /// as a constant array.
GetTorInit(std::vector<std::pair<Function *,int>> & TorList)173 static Constant *GetTorInit(std::vector<std::pair<Function*, int> > &TorList) {
174   assert(!TorList.empty() && "Don't create empty tor list!");
175   std::vector<Constant*> ArrayElts;
176   Type *Int32Ty = Type::getInt32Ty(TorList[0].first->getContext());
177 
178   StructType *STy =
179     StructType::get(Int32Ty, TorList[0].first->getType(), NULL);
180   for (unsigned i = 0, e = TorList.size(); i != e; ++i) {
181     Constant *Elts[] = {
182       ConstantInt::get(Int32Ty, TorList[i].second),
183       TorList[i].first
184     };
185     ArrayElts.push_back(ConstantStruct::get(STy, Elts));
186   }
187   return ConstantArray::get(ArrayType::get(ArrayElts[0]->getType(),
188                                            ArrayElts.size()),
189                             ArrayElts);
190 }
191 
192 /// SplitStaticCtorDtor - A module was recently split into two parts, M1/M2, and
193 /// M1 has all of the global variables.  If M2 contains any functions that are
194 /// static ctors/dtors, we need to add an llvm.global_[cd]tors global to M2, and
195 /// prune appropriate entries out of M1s list.
SplitStaticCtorDtor(const char * GlobalName,Module * M1,Module * M2,ValueToValueMapTy & VMap)196 static void SplitStaticCtorDtor(const char *GlobalName, Module *M1, Module *M2,
197                                 ValueToValueMapTy &VMap) {
198   GlobalVariable *GV = M1->getNamedGlobal(GlobalName);
199   if (!GV || GV->isDeclaration() || GV->hasLocalLinkage() ||
200       !GV->use_empty()) return;
201 
202   std::vector<std::pair<Function*, int> > M1Tors, M2Tors;
203   ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
204   if (!InitList) return;
205 
206   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
207     if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
208       if (CS->getNumOperands() != 2) return;  // Not array of 2-element structs.
209 
210       if (CS->getOperand(1)->isNullValue())
211         break;  // Found a null terminator, stop here.
212 
213       ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
214       int Priority = CI ? CI->getSExtValue() : 0;
215 
216       Constant *FP = CS->getOperand(1);
217       if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
218         if (CE->isCast())
219           FP = CE->getOperand(0);
220       if (Function *F = dyn_cast<Function>(FP)) {
221         if (!F->isDeclaration())
222           M1Tors.push_back(std::make_pair(F, Priority));
223         else {
224           // Map to M2's version of the function.
225           F = cast<Function>(VMap[F]);
226           M2Tors.push_back(std::make_pair(F, Priority));
227         }
228       }
229     }
230   }
231 
232   GV->eraseFromParent();
233   if (!M1Tors.empty()) {
234     Constant *M1Init = GetTorInit(M1Tors);
235     new GlobalVariable(*M1, M1Init->getType(), false,
236                        GlobalValue::AppendingLinkage,
237                        M1Init, GlobalName);
238   }
239 
240   GV = M2->getNamedGlobal(GlobalName);
241   assert(GV && "Not a clone of M1?");
242   assert(GV->use_empty() && "llvm.ctors shouldn't have uses!");
243 
244   GV->eraseFromParent();
245   if (!M2Tors.empty()) {
246     Constant *M2Init = GetTorInit(M2Tors);
247     new GlobalVariable(*M2, M2Init->getType(), false,
248                        GlobalValue::AppendingLinkage,
249                        M2Init, GlobalName);
250   }
251 }
252 
253 
254 /// SplitFunctionsOutOfModule - Given a module and a list of functions in the
255 /// module, split the functions OUT of the specified module, and place them in
256 /// the new module.
257 Module *
SplitFunctionsOutOfModule(Module * M,const std::vector<Function * > & F,ValueToValueMapTy & VMap)258 llvm::SplitFunctionsOutOfModule(Module *M,
259                                 const std::vector<Function*> &F,
260                                 ValueToValueMapTy &VMap) {
261   // Make sure functions & globals are all external so that linkage
262   // between the two modules will work.
263   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
264     I->setLinkage(GlobalValue::ExternalLinkage);
265   for (Module::global_iterator I = M->global_begin(), E = M->global_end();
266        I != E; ++I) {
267     if (I->hasName() && I->getName()[0] == '\01')
268       I->setName(I->getName().substr(1));
269     I->setLinkage(GlobalValue::ExternalLinkage);
270   }
271 
272   ValueToValueMapTy NewVMap;
273   Module *New = CloneModule(M, NewVMap);
274 
275   // Make sure global initializers exist only in the safe module (CBE->.so)
276   for (Module::global_iterator I = New->global_begin(), E = New->global_end();
277        I != E; ++I)
278     I->setInitializer(0);  // Delete the initializer to make it external
279 
280   // Remove the Test functions from the Safe module
281   std::set<Function *> TestFunctions;
282   for (unsigned i = 0, e = F.size(); i != e; ++i) {
283     Function *TNOF = cast<Function>(VMap[F[i]]);
284     DEBUG(errs() << "Removing function ");
285     DEBUG(WriteAsOperand(errs(), TNOF, false));
286     DEBUG(errs() << "\n");
287     TestFunctions.insert(cast<Function>(NewVMap[TNOF]));
288     DeleteFunctionBody(TNOF);       // Function is now external in this module!
289   }
290 
291 
292   // Remove the Safe functions from the Test module
293   for (Module::iterator I = New->begin(), E = New->end(); I != E; ++I)
294     if (!TestFunctions.count(I))
295       DeleteFunctionBody(I);
296 
297 
298   // Make sure that there is a global ctor/dtor array in both halves of the
299   // module if they both have static ctor/dtor functions.
300   SplitStaticCtorDtor("llvm.global_ctors", M, New, NewVMap);
301   SplitStaticCtorDtor("llvm.global_dtors", M, New, NewVMap);
302 
303   return New;
304 }
305 
306 //===----------------------------------------------------------------------===//
307 // Basic Block Extraction Code
308 //===----------------------------------------------------------------------===//
309 
310 /// ExtractMappedBlocksFromModule - Extract all but the specified basic blocks
311 /// into their own functions.  The only detail is that M is actually a module
312 /// cloned from the one the BBs are in, so some mapping needs to be performed.
313 /// If this operation fails for some reason (ie the implementation is buggy),
314 /// this function should return null, otherwise it returns a new Module.
ExtractMappedBlocksFromModule(const std::vector<BasicBlock * > & BBs,Module * M)315 Module *BugDriver::ExtractMappedBlocksFromModule(const
316                                                  std::vector<BasicBlock*> &BBs,
317                                                  Module *M) {
318   sys::Path uniqueFilename(OutputPrefix + "-extractblocks");
319   std::string ErrMsg;
320   if (uniqueFilename.createTemporaryFileOnDisk(true, &ErrMsg)) {
321     outs() << "*** Basic Block extraction failed!\n";
322     errs() << "Error creating temporary file: " << ErrMsg << "\n";
323     EmitProgressBitcode(M, "basicblockextractfail", true);
324     return 0;
325   }
326   sys::RemoveFileOnSignal(uniqueFilename);
327 
328   std::string ErrorInfo;
329   tool_output_file BlocksToNotExtractFile(uniqueFilename.c_str(), ErrorInfo);
330   if (!ErrorInfo.empty()) {
331     outs() << "*** Basic Block extraction failed!\n";
332     errs() << "Error writing list of blocks to not extract: " << ErrorInfo
333            << "\n";
334     EmitProgressBitcode(M, "basicblockextractfail", true);
335     return 0;
336   }
337   for (std::vector<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
338        I != E; ++I) {
339     BasicBlock *BB = *I;
340     // If the BB doesn't have a name, give it one so we have something to key
341     // off of.
342     if (!BB->hasName()) BB->setName("tmpbb");
343     BlocksToNotExtractFile.os() << BB->getParent()->getNameStr() << " "
344                                 << BB->getName() << "\n";
345   }
346   BlocksToNotExtractFile.os().close();
347   if (BlocksToNotExtractFile.os().has_error()) {
348     errs() << "Error writing list of blocks to not extract: " << ErrorInfo
349            << "\n";
350     EmitProgressBitcode(M, "basicblockextractfail", true);
351     BlocksToNotExtractFile.os().clear_error();
352     return 0;
353   }
354   BlocksToNotExtractFile.keep();
355 
356   std::string uniqueFN = "--extract-blocks-file=" + uniqueFilename.str();
357   const char *ExtraArg = uniqueFN.c_str();
358 
359   std::vector<std::string> PI;
360   PI.push_back("extract-blocks");
361   Module *Ret = runPassesOn(M, PI, false, 1, &ExtraArg);
362 
363   uniqueFilename.eraseFromDisk(); // Free disk space
364 
365   if (Ret == 0) {
366     outs() << "*** Basic Block extraction failed, please report a bug!\n";
367     EmitProgressBitcode(M, "basicblockextractfail", true);
368   }
369   return Ret;
370 }
371