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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 ///
     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 ///
    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.
    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 //
    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.
    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.
    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 *
    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.
    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