C++ BasicBlock::getInstList方法代码示例

// GetSJSwitch - Return the switch statement that controls which handler
// (if any) gets called and the value returned to that handler.
LowerSetJmp::SwitchValuePair LowerSetJmp::GetSJSwitch(Function* Func,
                                                      BasicBlock* Rethrow)
{
  if (SwitchValMap[Func].first) return SwitchValMap[Func];

  BasicBlock* LongJmpPre = BasicBlock::Create("LongJmpBlkPre", Func);
  BasicBlock::InstListType& LongJmpPreIL = LongJmpPre->getInstList();

  // Keep track of the preliminary basic block for some of the other
  // transformations.
  PrelimBBMap[Func] = LongJmpPre;

  // Grab the exception.
  CallInst* Cond = CallInst::Create(IsLJException, "IsLJExcept");
  LongJmpPreIL.push_back(Cond);

  // The "decision basic block" gets the number associated with the
  // setjmp call returning to switch on and the value returned by
  // longjmp.
  BasicBlock* DecisionBB = BasicBlock::Create("LJDecisionBB", Func);
  BasicBlock::InstListType& DecisionBBIL = DecisionBB->getInstList();

  BranchInst::Create(DecisionBB, Rethrow, Cond, LongJmpPre);

  // Fill in the "decision" basic block.
  CallInst* LJVal = CallInst::Create(GetLJValue, "LJVal");
  DecisionBBIL.push_back(LJVal);
  CallInst* SJNum = CallInst::Create(TryCatchLJ, GetSetJmpMap(Func), "SJNum");
  DecisionBBIL.push_back(SJNum);

  SwitchInst* SI = SwitchInst::Create(SJNum, Rethrow, 0, DecisionBB);
  return SwitchValMap[Func] = SwitchValuePair(SI, LJVal);
}

void Graph::printGraphFromMod() {
 int InstCount = 0;
 for (iplist<Function>::iterator It = M->getFunctionList().begin(); It != M->getFunctionList().end(); ++It) {
  Function * Fn = It;
   
  for (iplist<BasicBlock>::iterator I = Fn->getBasicBlockList().begin(); I != Fn->getBasicBlockList().end(); ++I) {
    BasicBlock * Bb = I;
    DEBUG (errs() << Bb << '\n');
    BasicBlock * PSBB = Bb->getSinglePredecessor();
    if (PSBB != NULL) {
      DEBUG (errs() << "Single Predecessor: \n" << PSBB << "\n_______________________" << '\n');
    }
    else if ((PSBB = (Bb->getUniquePredecessor())) != NULL)
      DEBUG (errs() << "Unique Predecessor: " << PSBB << '\n');
    else {
      DEBUG (errs() << "No Predecessor\n_______________________\n");
    }
    // print the instructions
    for (iplist<Instruction>::iterator X = Bb->getInstList().begin(); X != Bb->getInstList().end(); ++X) {
       InstCount++;
       DEBUG (errs() << (*X).getOpcodeName() << '\n');
    }
    DEBUG (errs() << "\n\n\n");
  }
 }
 DEBUG (errs() << "Instruction Count = " << InstCount << "\n");
}

/// FoldBlockIntoPredecessor - Folds a basic block into its predecessor if it
/// only has one predecessor, and that predecessor only has one successor.
/// The LoopInfo Analysis that is passed will be kept consistent.  If folding is
/// successful references to the containing loop must be removed from
/// ScalarEvolution by calling ScalarEvolution::forgetLoop because SE may have
/// references to the eliminated BB.  The argument ForgottenLoops contains a set
/// of loops that have already been forgotten to prevent redundant, expensive
/// calls to ScalarEvolution::forgetLoop.  Returns the new combined block.
static BasicBlock *
FoldBlockIntoPredecessor(BasicBlock *BB, LoopInfo* LI, LPPassManager *LPM,
                         SmallPtrSetImpl<Loop *> &ForgottenLoops) {
  // Merge basic blocks into their predecessor if there is only one distinct
  // pred, and if there is only one distinct successor of the predecessor, and
  // if there are no PHI nodes.
  BasicBlock *OnlyPred = BB->getSinglePredecessor();
  if (!OnlyPred) return nullptr;

  if (OnlyPred->getTerminator()->getNumSuccessors() != 1)
    return nullptr;

  DEBUG(dbgs() << "Merging: " << *BB << "into: " << *OnlyPred);

  // Resolve any PHI nodes at the start of the block.  They are all
  // guaranteed to have exactly one entry if they exist, unless there are
  // multiple duplicate (but guaranteed to be equal) entries for the
  // incoming edges.  This occurs when there are multiple edges from
  // OnlyPred to OnlySucc.
  FoldSingleEntryPHINodes(BB);

  // Delete the unconditional branch from the predecessor...
  OnlyPred->getInstList().pop_back();

  // Make all PHI nodes that referred to BB now refer to Pred as their
  // source...
  BB->replaceAllUsesWith(OnlyPred);

  // Move all definitions in the successor to the predecessor...
  OnlyPred->getInstList().splice(OnlyPred->end(), BB->getInstList());

  // OldName will be valid until erased.
  StringRef OldName = BB->getName();

  // Erase basic block from the function...

  // ScalarEvolution holds references to loop exit blocks.
  if (LPM) {
    if (auto *SEWP =
            LPM->getAnalysisIfAvailable<ScalarEvolutionWrapperPass>()) {
      if (Loop *L = LI->getLoopFor(BB)) {
        if (ForgottenLoops.insert(L).second)
          SEWP->getSE().forgetLoop(L);
      }
    }
  }
  LI->removeBlock(BB);

  // Inherit predecessor's name if it exists...
  if (!OldName.empty() && !OnlyPred->hasName())
    OnlyPred->setName(OldName);

  BB->eraseFromParent();

  return OnlyPred;
}

/// Folds a basic block into its predecessor if it only has one predecessor, and
/// that predecessor only has one successor.
/// The LoopInfo Analysis that is passed will be kept consistent.
static BasicBlock *
foldBlockIntoPredecessor(BasicBlock *BB, LoopInfo *LI, ScalarEvolution *SE,
                         DominatorTree *DT) {
  // Merge basic blocks into their predecessor if there is only one distinct
  // pred, and if there is only one distinct successor of the predecessor, and
  // if there are no PHI nodes.
  BasicBlock *OnlyPred = BB->getSinglePredecessor();
  if (!OnlyPred) return nullptr;

  if (OnlyPred->getTerminator()->getNumSuccessors() != 1)
    return nullptr;

  LLVM_DEBUG(dbgs() << "Merging: " << *BB << "into: " << *OnlyPred);

  // Resolve any PHI nodes at the start of the block.  They are all
  // guaranteed to have exactly one entry if they exist, unless there are
  // multiple duplicate (but guaranteed to be equal) entries for the
  // incoming edges.  This occurs when there are multiple edges from
  // OnlyPred to OnlySucc.
  FoldSingleEntryPHINodes(BB);

  // Delete the unconditional branch from the predecessor...
  OnlyPred->getInstList().pop_back();

  // Make all PHI nodes that referred to BB now refer to Pred as their
  // source...
  BB->replaceAllUsesWith(OnlyPred);

  // Move all definitions in the successor to the predecessor...
  OnlyPred->getInstList().splice(OnlyPred->end(), BB->getInstList());

  // OldName will be valid until erased.
  StringRef OldName = BB->getName();

  // Erase the old block and update dominator info.
  if (DT)
    if (DomTreeNode *DTN = DT->getNode(BB)) {
      DomTreeNode *PredDTN = DT->getNode(OnlyPred);
      SmallVector<DomTreeNode *, 8> Children(DTN->begin(), DTN->end());
      for (auto *DI : Children)
        DT->changeImmediateDominator(DI, PredDTN);

      DT->eraseNode(BB);
    }

  LI->removeBlock(BB);

  // Inherit predecessor's name if it exists...
  if (!OldName.empty() && !OnlyPred->hasName())
    OnlyPred->setName(OldName);

  BB->eraseFromParent();

  return OnlyPred;
}

void Graph::printInstrTotal() {
 int InstCount = 0;
 for (iplist<Function>::iterator It = M->getFunctionList().begin(); It != M->getFunctionList().end(); ++It) {
  Function * Fn = It;
  for (iplist<BasicBlock>::iterator I = Fn->getBasicBlockList().begin(); I != Fn->getBasicBlockList().end(); ++I) {
    BasicBlock * Bb = I;
    for (iplist<Instruction>::iterator X = Bb->getInstList().begin(); X != Bb->getInstList().end(); ++X) {
       InstCount++;
    }
  }
 }
 DEBUG (errs() << "Instruction Count = " << InstCount << "\n");
}

// processSwitchInst - Replace the specified switch instruction with a sequence
// of chained if-then insts in a balanced binary search.
//
void LowerSwitch::processSwitchInst(SwitchInst *SI) {
  BasicBlock *CurBlock = SI->getParent();
  BasicBlock *OrigBlock = CurBlock;
  Function *F = CurBlock->getParent();
  Value *Val = SI->getOperand(0);  // The value we are switching on...
  BasicBlock* Default = SI->getDefaultDest();

  // If there is only the default destination, don't bother with the code below.
  if (SI->getNumOperands() == 2) {
    BranchInst::Create(SI->getDefaultDest(), CurBlock);
    CurBlock->getInstList().erase(SI);
    return;
  }

  // Create a new, empty default block so that the new hierarchy of
  // if-then statements go to this and the PHI nodes are happy.
  BasicBlock* NewDefault = BasicBlock::Create(SI->getContext(), "NewDefault");
  F->getBasicBlockList().insert(Default, NewDefault);

  BranchInst::Create(Default, NewDefault);

  // If there is an entry in any PHI nodes for the default edge, make sure
  // to update them as well.
  for (BasicBlock::iterator I = Default->begin(); isa<PHINode>(I); ++I) {
    PHINode *PN = cast<PHINode>(I);
    int BlockIdx = PN->getBasicBlockIndex(OrigBlock);
    assert(BlockIdx != -1 && "Switch didn't go to this successor??");
    PN->setIncomingBlock((unsigned)BlockIdx, NewDefault);
  }

  // Prepare cases vector.
  CaseVector Cases;
  unsigned numCmps = Clusterify(Cases, SI);

  DEBUG(dbgs() << "Clusterify finished. Total clusters: " << Cases.size()
               << ". Total compares: " << numCmps << "\n");
  DEBUG(dbgs() << "Cases: " << Cases << "\n");
  (void)numCmps;
  
  BasicBlock* SwitchBlock = switchConvert(Cases.begin(), Cases.end(), Val,
                                          OrigBlock, NewDefault);

  // Branch to our shiny new if-then stuff...
  BranchInst::Create(SwitchBlock, OrigBlock);

  // We are now done with the switch instruction, delete it.
  CurBlock->getInstList().erase(SI);
}

/// ChangeToUnreachable - Insert an unreachable instruction before the specified
/// instruction, making it and the rest of the code in the block dead.
static void ChangeToUnreachable(Instruction *I, bool UseLLVMTrap) {
  BasicBlock *BB = I->getParent();
  // Loop over all of the successors, removing BB's entry from any PHI
  // nodes.
  for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
    (*SI)->removePredecessor(BB);
  
  // Insert a call to llvm.trap right before this.  This turns the undefined
  // behavior into a hard fail instead of falling through into random code.
  if (UseLLVMTrap) {
    Function *TrapFn =
      Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap);
    CallInst *CallTrap = CallInst::Create(TrapFn, "", I);
    CallTrap->setDebugLoc(I->getDebugLoc());
  }
  new UnreachableInst(I->getContext(), I);
  
  // All instructions after this are dead.
  BasicBlock::iterator BBI = I, BBE = BB->end();
  while (BBI != BBE) {
    if (!BBI->use_empty())
      BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
    BB->getInstList().erase(BBI++);
  }
}

/// See comments in Cloning.h.
BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
                                  ValueToValueMapTy &VMap,
                                  const Twine &NameSuffix, Function *F,
                                  ClonedCodeInfo *CodeInfo) {
  BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F);
  if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);

  bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
  
  // Loop over all instructions, and copy them over.
  for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
       II != IE; ++II) {
    Instruction *NewInst = II->clone();
    if (II->hasName())
      NewInst->setName(II->getName()+NameSuffix);
    NewBB->getInstList().push_back(NewInst);
    VMap[&*II] = NewInst; // Add instruction map to value.

    hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
    if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
      if (isa<ConstantInt>(AI->getArraySize()))
        hasStaticAllocas = true;
      else
        hasDynamicAllocas = true;
    }
  }
  
  if (CodeInfo) {
    CodeInfo->ContainsCalls          |= hasCalls;
    CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
    CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && 
                                        BB != &BB->getParent()->getEntryBlock();
  }
  return NewBB;
}

bool UnreachableBlockElim::runOnFunction(Function &F) {
  SmallPtrSet<BasicBlock*, 8> Reachable;

  // Mark all reachable blocks.
  for (df_ext_iterator<Function*, SmallPtrSet<BasicBlock*, 8> > I =
       df_ext_begin(&F, Reachable), E = df_ext_end(&F, Reachable); I != E; ++I)
    /* Mark all reachable blocks */;

  // Loop over all dead blocks, remembering them and deleting all instructions
  // in them.
  std::vector<BasicBlock*> DeadBlocks;
  for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
    if (!Reachable.count(I)) {
      BasicBlock *BB = I;
      DeadBlocks.push_back(BB);
      while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
        PN->replaceAllUsesWith(Constant::getNullValue(PN->getType()));
        BB->getInstList().pop_front();
      }
      for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
        (*SI)->removePredecessor(BB);
      BB->dropAllReferences();
    }

  // Actually remove the blocks now.
  ProfileInfo *PI = getAnalysisIfAvailable<ProfileInfo>();
  for (unsigned i = 0, e = DeadBlocks.size(); i != e; ++i) {
    if (PI) PI->removeBlock(DeadBlocks[i]);
    DeadBlocks[i]->eraseFromParent();
  }

  return DeadBlocks.size();
}

static bool eliminateUnreachableBlock(Function &F) {
  df_iterator_default_set<BasicBlock*> Reachable;

  // Mark all reachable blocks.
  for (BasicBlock *BB : depth_first_ext(&F, Reachable))
    (void)BB/* Mark all reachable blocks */;

  // Loop over all dead blocks, remembering them and deleting all instructions
  // in them.
  std::vector<BasicBlock*> DeadBlocks;
  for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
    if (!Reachable.count(&*I)) {
      BasicBlock *BB = &*I;
      DeadBlocks.push_back(BB);
      while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
        PN->replaceAllUsesWith(Constant::getNullValue(PN->getType()));
        BB->getInstList().pop_front();
      }
      for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
        (*SI)->removePredecessor(BB);
      BB->dropAllReferences();
    }

  // Actually remove the blocks now.
  for (unsigned i = 0, e = DeadBlocks.size(); i != e; ++i) {
    DeadBlocks[i]->eraseFromParent();
  }

  return !DeadBlocks.empty();
}

// visitInvokeInst - Converting the "invoke" instruction is fairly
// straight-forward. The old exception part is replaced by a query asking
// if this is a longjmp exception. If it is, then it goes to the longjmp
// exception blocks. Otherwise, control is passed the old exception.
void LowerSetJmp::visitInvokeInst(InvokeInst& II)
{
  if (II.getCalledFunction())
    if (!IsTransformableFunction(II.getCalledFunction()->getName()) ||
        II.getCalledFunction()->isIntrinsic()) return;

  BasicBlock* BB = II.getParent();

  // If not reachable from a setjmp call, don't transform.
  if (!DFSBlocks.count(BB)) return;

  BasicBlock* ExceptBB = II.getUnwindDest();

  Function* Func = BB->getParent();
  BasicBlock* NewExceptBB = BasicBlock::Create("InvokeExcept", Func);
  BasicBlock::InstListType& InstList = NewExceptBB->getInstList();

  // If this is a longjmp exception, then branch to the preliminary BB of
  // the longjmp exception handling. Otherwise, go to the old exception.
  CallInst* IsLJExcept = CallInst::Create(IsLJException, "IsLJExcept");
  InstList.push_back(IsLJExcept);

  BranchInst::Create(PrelimBBMap[Func], ExceptBB, IsLJExcept, NewExceptBB);

  II.setUnwindDest(NewExceptBB);
  ++InvokesTransformed;
}

/// Fold the loop tail into the loop exit by speculating the loop tail
/// instructions. Typically, this is a single post-increment. In the case of a
/// simple 2-block loop, hoisting the increment can be much better than
/// duplicating the entire loop header. In the case of loops with early exits,
/// rotation will not work anyway, but simplifyLoopLatch will put the loop in
/// canonical form so downstream passes can handle it.
///
/// I don't believe this invalidates SCEV.
bool LoopRotate::simplifyLoopLatch(Loop *L) {
  BasicBlock *Latch = L->getLoopLatch();
  if (!Latch || Latch->hasAddressTaken())
    return false;

  BranchInst *Jmp = dyn_cast<BranchInst>(Latch->getTerminator());
  if (!Jmp || !Jmp->isUnconditional())
    return false;

  BasicBlock *LastExit = Latch->getSinglePredecessor();
  if (!LastExit || !L->isLoopExiting(LastExit))
    return false;

  BranchInst *BI = dyn_cast<BranchInst>(LastExit->getTerminator());
  if (!BI)
    return false;

  if (!shouldSpeculateInstrs(Latch->begin(), Jmp))
    return false;

  DEBUG(dbgs() << "Folding loop latch " << Latch->getName() << " into "
        << LastExit->getName() << "\n");

  // Hoist the instructions from Latch into LastExit.
  LastExit->getInstList().splice(BI, Latch->getInstList(), Latch->begin(), Jmp);

  unsigned FallThruPath = BI->getSuccessor(0) == Latch ? 0 : 1;
  BasicBlock *Header = Jmp->getSuccessor(0);
  assert(Header == L->getHeader() && "expected a backward branch");

  // Remove Latch from the CFG so that LastExit becomes the new Latch.
  BI->setSuccessor(FallThruPath, Header);
  Latch->replaceSuccessorsPhiUsesWith(LastExit);
  Jmp->eraseFromParent();

  // Nuke the Latch block.
  assert(Latch->empty() && "unable to evacuate Latch");
  LI->removeBlock(Latch);
  if (DominatorTreeWrapperPass *DTWP =
          getAnalysisIfAvailable<DominatorTreeWrapperPass>())
    DTWP->getDomTree().eraseNode(Latch);
  Latch->eraseFromParent();
  return true;
}

Instruction::Instruction(Type *ty, unsigned it, Use *Ops, unsigned NumOps,
                         Instruction *InsertBefore)
  : User(ty, Value::InstructionVal + it, Ops, NumOps), Parent(nullptr) {

  // If requested, insert this instruction into a basic block...
  if (InsertBefore) {
    BasicBlock *BB = InsertBefore->getParent();
    assert(BB && "Instruction to insert before is not in a basic block!");
    BB->getInstList().insert(InsertBefore->getIterator(), this);
  }
}

/// HandleCallsInBlockInlinedThroughInvoke - When we inline a basic block into
/// an invoke, we have to turn all of the calls that can throw into
/// invokes.  This function analyze BB to see if there are any calls, and if so,
/// it rewrites them to be invokes that jump to InvokeDest and fills in the PHI
/// nodes in that block with the values specified in InvokeDestPHIValues.
///
/// Returns true to indicate that the next block should be skipped.
static bool HandleCallsInBlockInlinedThroughInvoke(BasicBlock *BB,
                                                   InvokeInliningInfo &Invoke) {
  LandingPadInst *LPI = Invoke.getLandingPadInst();

  for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
    Instruction *I = BBI++;

    if (LandingPadInst *L = dyn_cast<LandingPadInst>(I)) {
      unsigned NumClauses = LPI->getNumClauses();
      L->reserveClauses(NumClauses);
      for (unsigned i = 0; i != NumClauses; ++i)
        L->addClause(LPI->getClause(i));
    }

    // We only need to check for function calls: inlined invoke
    // instructions require no special handling.
    CallInst *CI = dyn_cast<CallInst>(I);

    // If this call cannot unwind, don't convert it to an invoke.
    // Inline asm calls cannot throw.
    if (!CI || CI->doesNotThrow() || isa<InlineAsm>(CI->getCalledValue()))
      continue;

    // Convert this function call into an invoke instruction.  First, split the
    // basic block.
    BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc");

    // Delete the unconditional branch inserted by splitBasicBlock
    BB->getInstList().pop_back();

    // Create the new invoke instruction.
    ImmutableCallSite CS(CI);
    SmallVector<Value*, 8> InvokeArgs(CS.arg_begin(), CS.arg_end());
    InvokeInst *II = InvokeInst::Create(CI->getCalledValue(), Split,
                                        Invoke.getOuterResumeDest(),
                                        InvokeArgs, CI->getName(), BB);
    II->setCallingConv(CI->getCallingConv());
    II->setAttributes(CI->getAttributes());
    
    // Make sure that anything using the call now uses the invoke!  This also
    // updates the CallGraph if present, because it uses a WeakVH.
    CI->replaceAllUsesWith(II);

    // Delete the original call
    Split->getInstList().pop_front();

    // Update any PHI nodes in the exceptional block to indicate that there is
    // now a new entry in them.
    Invoke.addIncomingPHIValuesFor(BB);
    return false;
  }

  return false;
}

/// FoldBlockIntoPredecessor - Folds a basic block into its predecessor if it
/// only has one predecessor, and that predecessor only has one successor.
/// The LoopInfo Analysis that is passed will be kept consistent.
/// Returns the new combined block.
static BasicBlock *FoldBlockIntoPredecessor(BasicBlock *BB, LoopInfo* LI) {
  // Merge basic blocks into their predecessor if there is only one distinct
  // pred, and if there is only one distinct successor of the predecessor, and
  // if there are no PHI nodes.
  BasicBlock *OnlyPred = BB->getSinglePredecessor();
  if (!OnlyPred) return 0;

  if (OnlyPred->getTerminator()->getNumSuccessors() != 1)
    return 0;

  DOUT << "Merging: " << *BB << "into: " << *OnlyPred;

  // Resolve any PHI nodes at the start of the block.  They are all
  // guaranteed to have exactly one entry if they exist, unless there are
  // multiple duplicate (but guaranteed to be equal) entries for the
  // incoming edges.  This occurs when there are multiple edges from
  // OnlyPred to OnlySucc.
  FoldSingleEntryPHINodes(BB);

  // Delete the unconditional branch from the predecessor...
  OnlyPred->getInstList().pop_back();

  // Move all definitions in the successor to the predecessor...
  OnlyPred->getInstList().splice(OnlyPred->end(), BB->getInstList());

  // Make all PHI nodes that referred to BB now refer to Pred as their
  // source...
  BB->replaceAllUsesWith(OnlyPred);

  std::string OldName = BB->getName();

  // Erase basic block from the function...
  LI->removeBlock(BB);
  BB->eraseFromParent();

  // Inherit predecessor's name if it exists...
  if (!OldName.empty() && !OnlyPred->hasName())
    OnlyPred->setName(OldName);

  return OnlyPred;
}