C++ ValueToValueMapTy类代码示例

/// Connect the unrolling prolog code to the original loop.
/// The unrolling prolog code contains code to execute the
/// 'extra' iterations if the run-time trip count modulo the
/// unroll count is non-zero.
///
/// This function performs the following:
/// - Create PHI nodes at prolog end block to combine values
///   that exit the prolog code and jump around the prolog.
/// - Add a PHI operand to a PHI node at the loop exit block
///   for values that exit the prolog and go around the loop.
/// - Branch around the original loop if the trip count is less
///   than the unroll factor.
///
static void ConnectProlog(Loop *L, Value *BECount, unsigned Count,
                          BasicBlock *PrologExit,
                          BasicBlock *OriginalLoopLatchExit,
                          BasicBlock *PreHeader, BasicBlock *NewPreHeader,
                          ValueToValueMapTy &VMap, DominatorTree *DT,
                          LoopInfo *LI, bool PreserveLCSSA) {
  // Loop structure should be the following:
  // Preheader
  //  PrologHeader
  //  ...
  //  PrologLatch
  //  PrologExit
  //   NewPreheader
  //    Header
  //    ...
  //    Latch
  //      LatchExit
  BasicBlock *Latch = L->getLoopLatch();
  assert(Latch && "Loop must have a latch");
  BasicBlock *PrologLatch = cast<BasicBlock>(VMap[Latch]);

  // Create a PHI node for each outgoing value from the original loop
  // (which means it is an outgoing value from the prolog code too).
  // The new PHI node is inserted in the prolog end basic block.
  // The new PHI node value is added as an operand of a PHI node in either
  // the loop header or the loop exit block.
  for (BasicBlock *Succ : successors(Latch)) {
    for (PHINode &PN : Succ->phis()) {
      // Add a new PHI node to the prolog end block and add the
      // appropriate incoming values.
      // TODO: This code assumes that the PrologExit (or the LatchExit block for
      // prolog loop) contains only one predecessor from the loop, i.e. the
      // PrologLatch. When supporting multiple-exiting block loops, we can have
      // two or more blocks that have the LatchExit as the target in the
      // original loop.
      PHINode *NewPN = PHINode::Create(PN.getType(), 2, PN.getName() + ".unr",
                                       PrologExit->getFirstNonPHI());
      // Adding a value to the new PHI node from the original loop preheader.
      // This is the value that skips all the prolog code.
      if (L->contains(&PN)) {
        // Succ is loop header.
        NewPN->addIncoming(PN.getIncomingValueForBlock(NewPreHeader),
                           PreHeader);
      } else {
        // Succ is LatchExit.
        NewPN->addIncoming(UndefValue::get(PN.getType()), PreHeader);
      }

      Value *V = PN.getIncomingValueForBlock(Latch);
      if (Instruction *I = dyn_cast<Instruction>(V)) {
        if (L->contains(I)) {
          V = VMap.lookup(I);
        }
      }
      // Adding a value to the new PHI node from the last prolog block
      // that was created.
      NewPN->addIncoming(V, PrologLatch);

      // Update the existing PHI node operand with the value from the
      // new PHI node.  How this is done depends on if the existing
      // PHI node is in the original loop block, or the exit block.
      if (L->contains(&PN)) {
        PN.setIncomingValue(PN.getBasicBlockIndex(NewPreHeader), NewPN);
      } else {
        PN.addIncoming(NewPN, PrologExit);
      }
    }
  }

  // Make sure that created prolog loop is in simplified form
  SmallVector<BasicBlock *, 4> PrologExitPreds;
  Loop *PrologLoop = LI->getLoopFor(PrologLatch);
  if (PrologLoop) {
    for (BasicBlock *PredBB : predecessors(PrologExit))
      if (PrologLoop->contains(PredBB))
        PrologExitPreds.push_back(PredBB);

    SplitBlockPredecessors(PrologExit, PrologExitPreds, ".unr-lcssa", DT, LI,
                           nullptr, PreserveLCSSA);
  }

  // Create a branch around the original loop, which is taken if there are no
  // iterations remaining to be executed after running the prologue.
  Instruction *InsertPt = PrologExit->getTerminator();
  IRBuilder<> B(InsertPt);

  assert(Count != 0 && "nonsensical Count!");
//.........这里部分代码省略.........

/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
/// except that it does some simple constant prop and DCE on the fly.  The
/// effect of this is to copy significantly less code in cases where (for
/// example) a function call with constant arguments is inlined, and those
/// constant arguments cause a significant amount of code in the callee to be
/// dead.  Since this doesn't produce an exact copy of the input, it can't be
/// used for things like CloneFunction or CloneModule.
void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
                                     ValueToValueMapTy &VMap,
                                     bool ModuleLevelChanges,
                                     SmallVectorImpl<ReturnInst*> &Returns,
                                     const char *NameSuffix, 
                                     ClonedCodeInfo *CodeInfo,
                                     const DataLayout *DL,
                                     Instruction *TheCall) {
  assert(NameSuffix && "NameSuffix cannot be null!");
  
#ifndef NDEBUG
  for (Function::const_arg_iterator II = OldFunc->arg_begin(), 
       E = OldFunc->arg_end(); II != E; ++II)
    assert(VMap.count(II) && "No mapping from source argument specified!");
#endif

  PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
                            NameSuffix, CodeInfo, DL);

  // Clone the entry block, and anything recursively reachable from it.
  std::vector<const BasicBlock*> CloneWorklist;
  CloneWorklist.push_back(&OldFunc->getEntryBlock());
  while (!CloneWorklist.empty()) {
    const BasicBlock *BB = CloneWorklist.back();
    CloneWorklist.pop_back();
    PFC.CloneBlock(BB, CloneWorklist);
  }
  
  // Loop over all of the basic blocks in the old function.  If the block was
  // reachable, we have cloned it and the old block is now in the value map:
  // insert it into the new function in the right order.  If not, ignore it.
  //
  // Defer PHI resolution until rest of function is resolved.
  SmallVector<const PHINode*, 16> PHIToResolve;
  for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
       BI != BE; ++BI) {
    Value *V = VMap[BI];
    BasicBlock *NewBB = cast_or_null<BasicBlock>(V);
    if (NewBB == 0) continue;  // Dead block.

    // Add the new block to the new function.
    NewFunc->getBasicBlockList().push_back(NewBB);

    // Handle PHI nodes specially, as we have to remove references to dead
    // blocks.
    for (BasicBlock::const_iterator I = BI->begin(), E = BI->end(); I != E; ++I)
      if (const PHINode *PN = dyn_cast<PHINode>(I))
        PHIToResolve.push_back(PN);
      else
        break;

    // Finally, remap the terminator instructions, as those can't be remapped
    // until all BBs are mapped.
    RemapInstruction(NewBB->getTerminator(), VMap,
                     ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
  }
  
  // Defer PHI resolution until rest of function is resolved, PHI resolution
  // requires the CFG to be up-to-date.
  for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
    const PHINode *OPN = PHIToResolve[phino];
    unsigned NumPreds = OPN->getNumIncomingValues();
    const BasicBlock *OldBB = OPN->getParent();
    BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]);

    // Map operands for blocks that are live and remove operands for blocks
    // that are dead.
    for (; phino != PHIToResolve.size() &&
         PHIToResolve[phino]->getParent() == OldBB; ++phino) {
      OPN = PHIToResolve[phino];
      PHINode *PN = cast<PHINode>(VMap[OPN]);
      for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
        Value *V = VMap[PN->getIncomingBlock(pred)];
        if (BasicBlock *MappedBlock = cast_or_null<BasicBlock>(V)) {
          Value *InVal = MapValue(PN->getIncomingValue(pred),
                                  VMap, 
                        ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
          assert(InVal && "Unknown input value?");
          PN->setIncomingValue(pred, InVal);
          PN->setIncomingBlock(pred, MappedBlock);
        } else {
          PN->removeIncomingValue(pred, false);
          --pred, --e;  // Revisit the next entry.
        }
      } 
    }
    
    // The loop above has removed PHI entries for those blocks that are dead
    // and has updated others.  However, if a block is live (i.e. copied over)
    // but its terminator has been changed to not go to this block, then our
    // phi nodes will have invalid entries.  Update the PHI nodes in this
    // case.
    PHINode *PN = cast<PHINode>(NewBB->begin());
//.........这里部分代码省略.........

/// Connect the unrolling epilog code to the original loop.
/// The unrolling epilog code contains code to execute the
/// 'extra' iterations if the run-time trip count modulo the
/// unroll count is non-zero.
///
/// This function performs the following:
/// - Update PHI nodes at the unrolling loop exit and epilog loop exit
/// - Create PHI nodes at the unrolling loop exit to combine
///   values that exit the unrolling loop code and jump around it.
/// - Update PHI operands in the epilog loop by the new PHI nodes
/// - Branch around the epilog loop if extra iters (ModVal) is zero.
///
static void ConnectEpilog(Loop *L, Value *ModVal, BasicBlock *NewExit,
                          BasicBlock *Exit, BasicBlock *PreHeader,
                          BasicBlock *EpilogPreHeader, BasicBlock *NewPreHeader,
                          ValueToValueMapTy &VMap, DominatorTree *DT,
                          LoopInfo *LI, bool PreserveLCSSA)  {
  BasicBlock *Latch = L->getLoopLatch();
  assert(Latch && "Loop must have a latch");
  BasicBlock *EpilogLatch = cast<BasicBlock>(VMap[Latch]);

  // Loop structure should be the following:
  //
  // PreHeader
  // NewPreHeader
  //   Header
  //   ...
  //   Latch
  // NewExit (PN)
  // EpilogPreHeader
  //   EpilogHeader
  //   ...
  //   EpilogLatch
  // Exit (EpilogPN)

  // Update PHI nodes at NewExit and Exit.
  for (PHINode &PN : NewExit->phis()) {
    // PN should be used in another PHI located in Exit block as
    // Exit was split by SplitBlockPredecessors into Exit and NewExit
    // Basicaly it should look like:
    // NewExit:
    //   PN = PHI [I, Latch]
    // ...
    // Exit:
    //   EpilogPN = PHI [PN, EpilogPreHeader]
    //
    // There is EpilogPreHeader incoming block instead of NewExit as
    // NewExit was spilt 1 more time to get EpilogPreHeader.
    assert(PN.hasOneUse() && "The phi should have 1 use");
    PHINode *EpilogPN = cast<PHINode>(PN.use_begin()->getUser());
    assert(EpilogPN->getParent() == Exit && "EpilogPN should be in Exit block");

    // Add incoming PreHeader from branch around the Loop
    PN.addIncoming(UndefValue::get(PN.getType()), PreHeader);

    Value *V = PN.getIncomingValueForBlock(Latch);
    Instruction *I = dyn_cast<Instruction>(V);
    if (I && L->contains(I))
      // If value comes from an instruction in the loop add VMap value.
      V = VMap.lookup(I);
    // For the instruction out of the loop, constant or undefined value
    // insert value itself.
    EpilogPN->addIncoming(V, EpilogLatch);

    assert(EpilogPN->getBasicBlockIndex(EpilogPreHeader) >= 0 &&
          "EpilogPN should have EpilogPreHeader incoming block");
    // Change EpilogPreHeader incoming block to NewExit.
    EpilogPN->setIncomingBlock(EpilogPN->getBasicBlockIndex(EpilogPreHeader),
                               NewExit);
    // Now PHIs should look like:
    // NewExit:
    //   PN = PHI [I, Latch], [undef, PreHeader]
    // ...
    // Exit:
    //   EpilogPN = PHI [PN, NewExit], [VMap[I], EpilogLatch]
  }

  // Create PHI nodes at NewExit (from the unrolling loop Latch and PreHeader).
  // Update corresponding PHI nodes in epilog loop.
  for (BasicBlock *Succ : successors(Latch)) {
    // Skip this as we already updated phis in exit blocks.
    if (!L->contains(Succ))
      continue;
    for (PHINode &PN : Succ->phis()) {
      // Add new PHI nodes to the loop exit block and update epilog
      // PHIs with the new PHI values.
      PHINode *NewPN = PHINode::Create(PN.getType(), 2, PN.getName() + ".unr",
                                       NewExit->getFirstNonPHI());
      // Adding a value to the new PHI node from the unrolling loop preheader.
      NewPN->addIncoming(PN.getIncomingValueForBlock(NewPreHeader), PreHeader);
      // Adding a value to the new PHI node from the unrolling loop latch.
      NewPN->addIncoming(PN.getIncomingValueForBlock(Latch), Latch);

      // Update the existing PHI node operand with the value from the new PHI
      // node.  Corresponding instruction in epilog loop should be PHI.
      PHINode *VPN = cast<PHINode>(VMap[&PN]);
      VPN->setIncomingValue(VPN->getBasicBlockIndex(EpilogPreHeader), NewPN);
    }
  }

//.........这里部分代码省略.........

//.........这里部分代码省略.........
    // To handle this case we need to take mod by Count one more time.
    ModVal = B.CreateURem(ModValAdd,
                          ConstantInt::get(BECount->getType(), Count),
                          "xtraiter");
  }
  Value *BranchVal =
      UseEpilogRemainder ? B.CreateICmpULT(BECount,
                                           ConstantInt::get(BECount->getType(),
                                                            Count - 1)) :
                           B.CreateIsNotNull(ModVal, "lcmp.mod");
  BasicBlock *RemainderLoop = UseEpilogRemainder ? NewExit : PrologPreHeader;
  BasicBlock *UnrollingLoop = UseEpilogRemainder ? NewPreHeader : PrologExit;
  // Branch to either remainder (extra iterations) loop or unrolling loop.
  B.CreateCondBr(BranchVal, RemainderLoop, UnrollingLoop);
  PreHeaderBR->eraseFromParent();
  if (DT) {
    if (UseEpilogRemainder)
      DT->changeImmediateDominator(NewExit, PreHeader);
    else
      DT->changeImmediateDominator(PrologExit, PreHeader);
  }
  Function *F = Header->getParent();
  // Get an ordered list of blocks in the loop to help with the ordering of the
  // cloned blocks in the prolog/epilog code
  LoopBlocksDFS LoopBlocks(L);
  LoopBlocks.perform(LI);

  //
  // For each extra loop iteration, create a copy of the loop's basic blocks
  // and generate a condition that branches to the copy depending on the
  // number of 'left over' iterations.
  //
  std::vector<BasicBlock *> NewBlocks;
  ValueToValueMapTy VMap;

  // For unroll factor 2 remainder loop will have 1 iterations.
  // Do not create 1 iteration loop.
  bool CreateRemainderLoop = (Count != 2);

  // Clone all the basic blocks in the loop. If Count is 2, we don't clone
  // the loop, otherwise we create a cloned loop to execute the extra
  // iterations. This function adds the appropriate CFG connections.
  BasicBlock *InsertBot = UseEpilogRemainder ? LatchExit : PrologExit;
  BasicBlock *InsertTop = UseEpilogRemainder ? EpilogPreHeader : PrologPreHeader;
  Loop *remainderLoop = CloneLoopBlocks(
      L, ModVal, CreateRemainderLoop, UseEpilogRemainder, UnrollRemainder,
      InsertTop, InsertBot,
      NewPreHeader, NewBlocks, LoopBlocks, VMap, DT, LI);

  // Insert the cloned blocks into the function.
  F->getBasicBlockList().splice(InsertBot->getIterator(),
                                F->getBasicBlockList(),
                                NewBlocks[0]->getIterator(),
                                F->end());

  // Now the loop blocks are cloned and the other exiting blocks from the
  // remainder are connected to the original Loop's exit blocks. The remaining
  // work is to update the phi nodes in the original loop, and take in the
  // values from the cloned region.
  for (auto *BB : OtherExits) {
   for (auto &II : *BB) {

     // Given we preserve LCSSA form, we know that the values used outside the
     // loop will be used through these phi nodes at the exit blocks that are
     // transformed below.
     if (!isa<PHINode>(II))

// Clone OldFunc into NewFunc, transforming the old arguments into references to
// VMap values.
//
void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
                             ValueToValueMapTy &VMap,
                             bool ModuleLevelChanges,
                             SmallVectorImpl<ReturnInst*> &Returns,
                             const char *NameSuffix, ClonedCodeInfo *CodeInfo,
                             ValueMapTypeRemapper *TypeMapper,
                             ValueMaterializer *Materializer) {
  assert(NameSuffix && "NameSuffix cannot be null!");

#ifndef NDEBUG
  for (Function::const_arg_iterator I = OldFunc->arg_begin(), 
       E = OldFunc->arg_end(); I != E; ++I)
    assert(VMap.count(I) && "No mapping from source argument specified!");
#endif

  // Copy all attributes other than those stored in the AttributeSet.  We need
  // to remap the parameter indices of the AttributeSet.
  AttributeSet NewAttrs = NewFunc->getAttributes();
  NewFunc->copyAttributesFrom(OldFunc);
  NewFunc->setAttributes(NewAttrs);

  AttributeSet OldAttrs = OldFunc->getAttributes();
  // Clone any argument attributes that are present in the VMap.
  for (const Argument &OldArg : OldFunc->args())
    if (Argument *NewArg = dyn_cast<Argument>(VMap[&OldArg])) {
      AttributeSet attrs =
          OldAttrs.getParamAttributes(OldArg.getArgNo() + 1);
      if (attrs.getNumSlots() > 0)
        NewArg->addAttr(attrs);
    }

  NewFunc->setAttributes(
      NewFunc->getAttributes()
          .addAttributes(NewFunc->getContext(), AttributeSet::ReturnIndex,
                         OldAttrs.getRetAttributes())
          .addAttributes(NewFunc->getContext(), AttributeSet::FunctionIndex,
                         OldAttrs.getFnAttributes()));

  // Loop over all of the basic blocks in the function, cloning them as
  // appropriate.  Note that we save BE this way in order to handle cloning of
  // recursive functions into themselves.
  //
  for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
       BI != BE; ++BI) {
    const BasicBlock &BB = *BI;

    // Create a new basic block and copy instructions into it!
    BasicBlock *CBB = CloneBasicBlock(&BB, VMap, NameSuffix, NewFunc, CodeInfo);

    // Add basic block mapping.
    VMap[&BB] = CBB;

    // It is only legal to clone a function if a block address within that
    // function is never referenced outside of the function.  Given that, we
    // want to map block addresses from the old function to block addresses in
    // the clone. (This is different from the generic ValueMapper
    // implementation, which generates an invalid blockaddress when
    // cloning a function.)
    if (BB.hasAddressTaken()) {
      Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
                                              const_cast<BasicBlock*>(&BB));
      VMap[OldBBAddr] = BlockAddress::get(NewFunc, CBB);                                         
    }

    // Note return instructions for the caller.
    if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
      Returns.push_back(RI);
  }

  // Loop over all of the instructions in the function, fixing up operand
  // references as we go.  This uses VMap to do all the hard work.
  for (Function::iterator BB = cast<BasicBlock>(VMap[OldFunc->begin()]),
         BE = NewFunc->end(); BB != BE; ++BB)
    // Loop over all instructions, fixing each one as we find it...
    for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
      RemapInstruction(II, VMap,
                       ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
                       TypeMapper, Materializer);
}

  Function*
  specializeFunction(Function *f, Value*const* args)
  // make a copy of f
  // specialize on the arguments, a null means that that argument isn't known 
  {
    assert(!f->isDeclaration());
    ValueToValueMapTy vmap;

    unsigned int i = 0;
    unsigned int j = 0;
    std::vector<std::string> argNames;
    std::string baseName = specializeName(f, argNames);

    for (Function::arg_iterator itr = f->arg_begin(); itr != f->arg_end(); itr++, i++) {
      while (argNames[j] != "?") j++;
      if (args[i] != NULL) {
        Value* arg = (Value*) &(*itr);

        assert(arg->getType() == args[i]->getType()
	       && "Specializing argument with concrete value of wrong type!");

        vmap.insert(std::pair<Value*, WeakVH>(arg, args[i]));
        PrevirtType pt = PrevirtType::abstract(args[i]);
        argNames[j] = pt.to_string();
        /*
        if (const ConstantInt* ci = dyn_cast<const ConstantInt> (args[i])) {
          argNames[j] = ci->getValue().toString(10, true);
        } else if (const Constant* c = dyn_cast<const Constant>(args[i])) {
          if (c->isNullValue()) {
            argNames[j] = "null";
          } else {
            assert(false);
          }
        } else if (const )
        } else {
          assert(false);
        }
        */
      }
      j++;
    }
    assert (i == f->getArgumentList().size());

    baseName += "(";
    for (std::vector<std::string>::const_iterator it = argNames.begin(), be = argNames.begin(), en = argNames.end(); it != en; ++it) {
      if (it != be) baseName += ",";
      baseName += *it;
    }
    baseName += ")";

    Function *result = f->getParent()->getFunction(baseName);
    // If specialized function already exists, no reason
    // to create another one. In fact, can cause the process
    // to diverge. XXX This needs to be a more sophisticated
    // check
    if (!result) {
      ClonedCodeInfo info;
      result = llvm::CloneFunction(f, vmap, true, &info);
      result->setName(baseName);
    }

    return result;
  }

/// UnswitchNontrivialCondition - We determined that the loop is profitable
/// to unswitch when LIC equal Val.  Split it into loop versions and test the
/// condition outside of either loop.  Return the loops created as Out1/Out2.
void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
                                               Loop *L) {
  Function *F = loopHeader->getParent();
  DEBUG(dbgs() << "loop-unswitch: Unswitching loop %"
        << loopHeader->getName() << " [" << L->getBlocks().size()
        << " blocks] in Function " << F->getName()
        << " when '" << *Val << "' == " << *LIC << "\n");

  if (ScalarEvolution *SE = getAnalysisIfAvailable<ScalarEvolution>())
    SE->forgetLoop(L);

  LoopBlocks.clear();
  NewBlocks.clear();

  // First step, split the preheader and exit blocks, and add these blocks to
  // the LoopBlocks list.
  BasicBlock *NewPreheader = SplitEdge(loopPreheader, loopHeader, this);
  LoopBlocks.push_back(NewPreheader);

  // We want the loop to come after the preheader, but before the exit blocks.
  LoopBlocks.insert(LoopBlocks.end(), L->block_begin(), L->block_end());

  SmallVector<BasicBlock*, 8> ExitBlocks;
  L->getUniqueExitBlocks(ExitBlocks);

  // Split all of the edges from inside the loop to their exit blocks.  Update
  // the appropriate Phi nodes as we do so.
  SplitExitEdges(L, ExitBlocks);

  // The exit blocks may have been changed due to edge splitting, recompute.
  ExitBlocks.clear();
  L->getUniqueExitBlocks(ExitBlocks);

  // Add exit blocks to the loop blocks.
  LoopBlocks.insert(LoopBlocks.end(), ExitBlocks.begin(), ExitBlocks.end());

  // Next step, clone all of the basic blocks that make up the loop (including
  // the loop preheader and exit blocks), keeping track of the mapping between
  // the instructions and blocks.
  NewBlocks.reserve(LoopBlocks.size());
  ValueToValueMapTy VMap;
  for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) {
    BasicBlock *NewBB = CloneBasicBlock(LoopBlocks[i], VMap, ".us", F);

    NewBlocks.push_back(NewBB);
    VMap[LoopBlocks[i]] = NewBB;  // Keep the BB mapping.
    LPM->cloneBasicBlockSimpleAnalysis(LoopBlocks[i], NewBB, L);
  }

  // Splice the newly inserted blocks into the function right before the
  // original preheader.
  F->getBasicBlockList().splice(NewPreheader, F->getBasicBlockList(),
                                NewBlocks[0], F->end());

  // Now we create the new Loop object for the versioned loop.
  Loop *NewLoop = CloneLoop(L, L->getParentLoop(), VMap, LI, LPM);

  // Recalculate unswitching quota, inherit simplified switches info for NewBB,
  // Probably clone more loop-unswitch related loop properties.
  BranchesInfo.cloneData(NewLoop, L, VMap);

  Loop *ParentLoop = L->getParentLoop();
  if (ParentLoop) {
    // Make sure to add the cloned preheader and exit blocks to the parent loop
    // as well.
    ParentLoop->addBasicBlockToLoop(NewBlocks[0], LI->getBase());
  }

  for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
    BasicBlock *NewExit = cast<BasicBlock>(VMap[ExitBlocks[i]]);
    // The new exit block should be in the same loop as the old one.
    if (Loop *ExitBBLoop = LI->getLoopFor(ExitBlocks[i]))
      ExitBBLoop->addBasicBlockToLoop(NewExit, LI->getBase());

    assert(NewExit->getTerminator()->getNumSuccessors() == 1 &&
           "Exit block should have been split to have one successor!");
    BasicBlock *ExitSucc = NewExit->getTerminator()->getSuccessor(0);

    // If the successor of the exit block had PHI nodes, add an entry for
    // NewExit.
    for (BasicBlock::iterator I = ExitSucc->begin();
         PHINode *PN = dyn_cast<PHINode>(I); ++I) {
      Value *V = PN->getIncomingValueForBlock(ExitBlocks[i]);
      ValueToValueMapTy::iterator It = VMap.find(V);
      if (It != VMap.end()) V = It->second;
      PN->addIncoming(V, NewExit);
    }

    if (LandingPadInst *LPad = NewExit->getLandingPadInst()) {
      PHINode *PN = PHINode::Create(LPad->getType(), 0, "",
                                    ExitSucc->getFirstInsertionPt());

      for (pred_iterator I = pred_begin(ExitSucc), E = pred_end(ExitSucc);
           I != E; ++I) {
        BasicBlock *BB = *I;
        LandingPadInst *LPI = BB->getLandingPadInst();
        LPI->replaceAllUsesWith(PN);
//.........这里部分代码省略.........

void WorklessInstrument::CloneInnerLoop(Loop * pLoop, vector<BasicBlock *> & vecAdd, ValueToValueMapTy & VMap, set<BasicBlock *> & setCloned)
{
	Function * pFunction = pLoop->getHeader()->getParent();
	BasicBlock * pPreHeader = vecAdd[0];

	SmallVector<BasicBlock *, 4> ExitBlocks;
	pLoop->getExitBlocks(ExitBlocks);

	set<BasicBlock *> setExitBlocks;

	for(unsigned long i = 0; i < ExitBlocks.size(); i++)
	{
		setExitBlocks.insert(ExitBlocks[i]);
	}

	for(unsigned long i = 0; i < ExitBlocks.size(); i++ )
	{
		VMap[ExitBlocks[i]] = ExitBlocks[i];
	}

	vector<BasicBlock *> ToClone;
	vector<BasicBlock *> BeenCloned;

	
	//clone loop
	ToClone.push_back(pLoop->getHeader());

	while(ToClone.size()>0)
	{
		BasicBlock * pCurrent = ToClone.back();
		ToClone.pop_back();

		WeakVH & BBEntry = VMap[pCurrent];
		if (BBEntry)
		{
			continue;
		}

		BasicBlock * NewBB;
		BBEntry = NewBB = BasicBlock::Create(pCurrent->getContext(), "", pFunction);

		if(pCurrent->hasName())
		{
			NewBB->setName(pCurrent->getName() + ".CPI");
		}

		if(pCurrent->hasAddressTaken())
		{
			errs() << "hasAddressTaken branch\n" ;
			exit(0);
		}

		for(BasicBlock::const_iterator II = pCurrent->begin(); II != pCurrent->end(); ++II )
		{
			Instruction * NewInst = II->clone();
			if(II->hasName())
			{
				NewInst->setName(II->getName() + ".CPI");
			}
			VMap[II] = NewInst;
			NewBB->getInstList().push_back(NewInst);
		}

		const TerminatorInst *TI = pCurrent->getTerminator();
		for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
		{
			ToClone.push_back(TI->getSuccessor(i));
		}

		setCloned.insert(NewBB);
		BeenCloned.push_back(NewBB);
	}

	//remap value used inside loop
	vector<BasicBlock *>::iterator itVecBegin = BeenCloned.begin();
	vector<BasicBlock *>::iterator itVecEnd = BeenCloned.end();

	for(; itVecBegin != itVecEnd; itVecBegin ++)
	{
		for(BasicBlock::iterator II = (*itVecBegin)->begin(); II != (*itVecBegin)->end(); II ++ )
		{
			//II->dump();
			RemapInstruction(II, VMap);
		}
	}

	//add to the else if body
	BasicBlock * pElseBody = vecAdd[1];

	BasicBlock * pClonedHeader = cast<BasicBlock>(VMap[pLoop->getHeader()]);

	BranchInst::Create(pClonedHeader, pElseBody);

	//errs() << pPreHeader->getName() << "\n";
	for(BasicBlock::iterator II = pClonedHeader->begin(); II != pClonedHeader->end(); II ++ )
	{
		if(PHINode * pPHI = dyn_cast<PHINode>(II))
		{
			vector<int> vecToRemoved;
			for (unsigned i = 0, e = pPHI->getNumIncomingValues(); i != e; ++i) 
//.........这里部分代码省略.........

/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
/// except that it does some simple constant prop and DCE on the fly.  The
/// effect of this is to copy significantly less code in cases where (for
/// example) a function call with constant arguments is inlined, and those
/// constant arguments cause a significant amount of code in the callee to be
/// dead.  Since this doesn't produce an exact copy of the input, it can't be
/// used for things like CloneFunction or CloneModule.
void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
                                     ValueToValueMapTy &VMap,
                                     bool ModuleLevelChanges,
                                     SmallVectorImpl<ReturnInst*> &Returns,
                                     const char *NameSuffix,
                                     ClonedCodeInfo *CodeInfo,
                                     const TargetData *TD,
                                     Instruction *TheCall) {
    assert(NameSuffix && "NameSuffix cannot be null!");

#ifndef NDEBUG
    for (Function::const_arg_iterator II = OldFunc->arg_begin(),
            E = OldFunc->arg_end(); II != E; ++II)
        assert(VMap.count(II) && "No mapping from source argument specified!");
#endif

    PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
                              Returns, NameSuffix, CodeInfo, TD);

    // Clone the entry block, and anything recursively reachable from it.
    std::vector<const BasicBlock*> CloneWorklist;
    CloneWorklist.push_back(&OldFunc->getEntryBlock());
    while (!CloneWorklist.empty()) {
        const BasicBlock *BB = CloneWorklist.back();
        CloneWorklist.pop_back();
        PFC.CloneBlock(BB, CloneWorklist);
    }

    // Loop over all of the basic blocks in the old function.  If the block was
    // reachable, we have cloned it and the old block is now in the value map:
    // insert it into the new function in the right order.  If not, ignore it.
    //
    // Defer PHI resolution until rest of function is resolved.
    SmallVector<const PHINode*, 16> PHIToResolve;
    for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
            BI != BE; ++BI) {
        Value *V = VMap[BI];
        BasicBlock *NewBB = cast_or_null<BasicBlock>(V);
        if (NewBB == 0) continue;  // Dead block.

        // Add the new block to the new function.
        NewFunc->getBasicBlockList().push_back(NewBB);

        // Loop over all of the instructions in the block, fixing up operand
        // references as we go.  This uses VMap to do all the hard work.
        //
        BasicBlock::iterator I = NewBB->begin();

        DebugLoc TheCallDL;
        if (TheCall)
            TheCallDL = TheCall->getDebugLoc();

        // Handle PHI nodes specially, as we have to remove references to dead
        // blocks.
        if (PHINode *PN = dyn_cast<PHINode>(I)) {
            // Skip over all PHI nodes, remembering them for later.
            BasicBlock::const_iterator OldI = BI->begin();
            for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
                PHIToResolve.push_back(cast<PHINode>(OldI));
        }

        // Otherwise, remap the rest of the instructions normally.
        for (; I != NewBB->end(); ++I)
            RemapInstruction(I, VMap,
                             ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
    }

    // Defer PHI resolution until rest of function is resolved, PHI resolution
    // requires the CFG to be up-to-date.
    for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
        const PHINode *OPN = PHIToResolve[phino];
        unsigned NumPreds = OPN->getNumIncomingValues();
        const BasicBlock *OldBB = OPN->getParent();
        BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]);

        // Map operands for blocks that are live and remove operands for blocks
        // that are dead.
        for (; phino != PHIToResolve.size() &&
                PHIToResolve[phino]->getParent() == OldBB; ++phino) {
            OPN = PHIToResolve[phino];
            PHINode *PN = cast<PHINode>(VMap[OPN]);
            for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
                Value *V = VMap[PN->getIncomingBlock(pred)];
                if (BasicBlock *MappedBlock = cast_or_null<BasicBlock>(V)) {
                    Value *InVal = MapValue(PN->getIncomingValue(pred),
                                            VMap,
                                            ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
                    assert(InVal && "Unknown input value?");
                    PN->setIncomingValue(pred, InVal);
                    PN->setIncomingBlock(pred, MappedBlock);
                } else {
                    PN->removeIncomingValue(pred, false);
                    --pred, --e;  // Revisit the next entry.
//.........这里部分代码省略.........