C++ LoadInst::getParent方法代码示例

/// RewriteSingleStoreAlloca - If there is only a single store to this value,
/// replace any loads of it that are directly dominated by the definition with
/// the value stored.
void PromoteMem2Reg::RewriteSingleStoreAlloca(AllocaInst *AI,
                                              AllocaInfo &Info,
                                              LargeBlockInfo &LBI) {
  StoreInst *OnlyStore = Info.OnlyStore;
  bool StoringGlobalVal = !isa<Instruction>(OnlyStore->getOperand(0));
  BasicBlock *StoreBB = OnlyStore->getParent();
  int StoreIndex = -1;

  // Clear out UsingBlocks.  We will reconstruct it here if needed.
  Info.UsingBlocks.clear();
  
  for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E; ) {
    Instruction *UserInst = cast<Instruction>(*UI++);
    if (!isa<LoadInst>(UserInst)) {
      assert(UserInst == OnlyStore && "Should only have load/stores");
      continue;
    }
    LoadInst *LI = cast<LoadInst>(UserInst);
    
    // Okay, if we have a load from the alloca, we want to replace it with the
    // only value stored to the alloca.  We can do this if the value is
    // dominated by the store.  If not, we use the rest of the mem2reg machinery
    // to insert the phi nodes as needed.
    if (!StoringGlobalVal) {  // Non-instructions are always dominated.
      if (LI->getParent() == StoreBB) {
        // If we have a use that is in the same block as the store, compare the
        // indices of the two instructions to see which one came first.  If the
        // load came before the store, we can't handle it.
        if (StoreIndex == -1)
          StoreIndex = LBI.getInstructionIndex(OnlyStore);

        if (unsigned(StoreIndex) > LBI.getInstructionIndex(LI)) {
          // Can't handle this load, bail out.
          Info.UsingBlocks.push_back(StoreBB);
          continue;
        }
        
      } else if (LI->getParent() != StoreBB &&
                 !dominates(StoreBB, LI->getParent())) {
        // If the load and store are in different blocks, use BB dominance to
        // check their relationships.  If the store doesn't dom the use, bail
        // out.
        Info.UsingBlocks.push_back(LI->getParent());
        continue;
      }
    }
    
    // Otherwise, we *can* safely rewrite this load.
    Value *ReplVal = OnlyStore->getOperand(0);
    // If the replacement value is the load, this must occur in unreachable
    // code.
    if (ReplVal == LI)
      ReplVal = UndefValue::get(LI->getType());
    LI->replaceAllUsesWith(ReplVal);
    if (AST && LI->getType()->isPointerTy())
      AST->deleteValue(LI);
    LI->eraseFromParent();
    LBI.deleteValue(LI);
  }
}

/// MoveExtToFormExtLoad - Move a zext or sext fed by a load into the same
/// basic block as the load, unless conditions are unfavorable. This allows
/// SelectionDAG to fold the extend into the load.
///
bool CodeGenPrepare::MoveExtToFormExtLoad(Instruction *I) {
    // Look for a load being extended.
    LoadInst *LI = dyn_cast<LoadInst>(I->getOperand(0));
    if (!LI) return false;

    // If they're already in the same block, there's nothing to do.
    if (LI->getParent() == I->getParent())
        return false;

    // If the load has other users and the truncate is not free, this probably
    // isn't worthwhile.
    if (!LI->hasOneUse() &&
            TLI && (TLI->isTypeLegal(TLI->getValueType(LI->getType())) ||
                    !TLI->isTypeLegal(TLI->getValueType(I->getType()))) &&
            !TLI->isTruncateFree(I->getType(), LI->getType()))
        return false;

    // Check whether the target supports casts folded into loads.
    unsigned LType;
    if (isa<ZExtInst>(I))
        LType = ISD::ZEXTLOAD;
    else {
        assert(isa<SExtInst>(I) && "Unexpected ext type!");
        LType = ISD::SEXTLOAD;
    }
    if (TLI && !TLI->isLoadExtLegal(LType, TLI->getValueType(LI->getType())))
        return false;

    // Move the extend into the same block as the load, so that SelectionDAG
    // can fold it.
    I->removeFromParent();
    I->insertAfter(LI);
    ++NumExtsMoved;
    return true;
}

void DSGraphStats::visitLoad(LoadInst &LI) {
  if (isNodeForValueUntyped(LI.getOperand(0), 0,LI.getParent()->getParent())) {
    NumUntypedMemAccesses++;
  } else {
    NumTypedMemAccesses++;
  }
}

void LLSTDebuggingPass::insertLoadInstCheck(Function& F)
{
    Value* BrokenPointerMessage = m_builder->CreateGlobalStringPtr("\npointer is broken\n");

    InstructionVector Loads;
    for (Function::iterator BB = F.begin(); BB != F.end(); ++BB)
    {
        for(BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
        {
            if (LoadInst* Load = dyn_cast<LoadInst>(II)) {
                Loads.push_back(Load);
            }
        }
    }

    for(std::size_t i = 0; i < Loads.size(); i++)
    {
        LoadInst* Load = dyn_cast<LoadInst>(Loads[i]);
        if (belongsToSmalltalkType( Load->getType() )) {

            //split BB right after load inst. The new BB contains code that will be executed if pointer is OK
            BasicBlock* PointerIsOkBB = Load->getParent()->splitBasicBlock(++( static_cast<BasicBlock::iterator>(Load) ));
            BasicBlock* PointerIsBrokenBB = BasicBlock::Create(m_module->getContext(), "", &F, PointerIsOkBB);
            BasicBlock* PointerIsNotSmallIntBB = BasicBlock::Create(m_module->getContext(), "", &F, PointerIsBrokenBB);

            Instruction* branchToPointerIsOkBB = ++( static_cast<BasicBlock::iterator>(Load) );
            //branchToPointerIsOkBB is created by splitBasicBlock() just after load inst
            //We force builder to insert instructions before branchToPointerIsOkBB
            m_builder->SetInsertPoint(branchToPointerIsOkBB);

            //If pointer to class is null, jump to PointerIsBroken, otherwise to PointerIsOkBB
            Value* objectPtr = m_builder->CreateBitCast( Load, m_baseTypes.object->getPointerTo());

            Value* isSmallInt = m_builder->CreateCall(isSmallInteger, objectPtr);
            m_builder->CreateCondBr(isSmallInt, PointerIsOkBB, PointerIsNotSmallIntBB);

            m_builder->SetInsertPoint(PointerIsNotSmallIntBB);
            Value* klassPtr = m_builder->CreateCall(getObjectClass, objectPtr);
            Value* pointerIsNull = m_builder->CreateICmpEQ(klassPtr, ConstantPointerNull::get(m_baseTypes.klass->getPointerTo()) );
            m_builder->CreateCondBr(pointerIsNull, PointerIsBrokenBB, PointerIsOkBB);

            branchToPointerIsOkBB->eraseFromParent(); //We don't need it anymore

            m_builder->SetInsertPoint(PointerIsBrokenBB);
            m_builder->CreateCall(_printf, BrokenPointerMessage);
            m_builder->CreateBr(PointerIsOkBB);
        }
    }
}

bool Scalarizer::visitLoadInst(LoadInst &LI) {
  if (!ScalarizeLoadStore)
    return false;
  if (!LI.isSimple())
    return false;

  VectorLayout Layout;
  if (!getVectorLayout(LI.getType(), LI.getAlignment(), Layout))
    return false;

  unsigned NumElems = Layout.VecTy->getNumElements();
  IRBuilder<> Builder(LI.getParent(), &LI);
  Scatterer Ptr = scatter(&LI, LI.getPointerOperand());
  ValueVector Res;
  Res.resize(NumElems);

  for (unsigned I = 0; I < NumElems; ++I)
    Res[I] = Builder.CreateAlignedLoad(Ptr[I], Layout.getElemAlign(I),
                                       LI.getName() + ".i" + Twine(I));
  gather(&LI, Res);
  return true;
}

/// PromoteSingleBlockAlloca - Many allocas are only used within a single basic
/// block.  If this is the case, avoid traversing the CFG and inserting a lot of
/// potentially useless PHI nodes by just performing a single linear pass over
/// the basic block using the Alloca.
///
/// If we cannot promote this alloca (because it is read before it is written),
/// return true.  This is necessary in cases where, due to control flow, the
/// alloca is potentially undefined on some control flow paths.  e.g. code like
/// this is potentially correct:
///
///   for (...) { if (c) { A = undef; undef = B; } }
///
/// ... so long as A is not used before undef is set.
///
void PromoteMem2Reg::PromoteSingleBlockAlloca(AllocaInst *AI, AllocaInfo &Info,
                                              LargeBlockInfo &LBI) {
  // The trickiest case to handle is when we have large blocks. Because of this,
  // this code is optimized assuming that large blocks happen.  This does not
  // significantly pessimize the small block case.  This uses LargeBlockInfo to
  // make it efficient to get the index of various operations in the block.
  
  // Clear out UsingBlocks.  We will reconstruct it here if needed.
  Info.UsingBlocks.clear();
  
  // Walk the use-def list of the alloca, getting the locations of all stores.
  typedef SmallVector<std::pair<unsigned, StoreInst*>, 64> StoresByIndexTy;
  StoresByIndexTy StoresByIndex;
  
  for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
       UI != E; ++UI) 
    if (StoreInst *SI = dyn_cast<StoreInst>(*UI))
      StoresByIndex.push_back(std::make_pair(LBI.getInstructionIndex(SI), SI));

  // If there are no stores to the alloca, just replace any loads with undef.
  if (StoresByIndex.empty()) {
    for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E;) 
      if (LoadInst *LI = dyn_cast<LoadInst>(*UI++)) {
        LI->replaceAllUsesWith(UndefValue::get(LI->getType()));
        if (AST && LI->getType()->isPointerTy())
          AST->deleteValue(LI);
        LBI.deleteValue(LI);
        LI->eraseFromParent();
      }
    return;
  }
  
  // Sort the stores by their index, making it efficient to do a lookup with a
  // binary search.
  std::sort(StoresByIndex.begin(), StoresByIndex.end());
  
  // Walk all of the loads from this alloca, replacing them with the nearest
  // store above them, if any.
  for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E;) {
    LoadInst *LI = dyn_cast<LoadInst>(*UI++);
    if (!LI) continue;
    
    unsigned LoadIdx = LBI.getInstructionIndex(LI);
    
    // Find the nearest store that has a lower than this load. 
    StoresByIndexTy::iterator I = 
      std::lower_bound(StoresByIndex.begin(), StoresByIndex.end(),
                       std::pair<unsigned, StoreInst*>(LoadIdx, static_cast<StoreInst*>(0)),
                       StoreIndexSearchPredicate());
    
    // If there is no store before this load, then we can't promote this load.
    if (I == StoresByIndex.begin()) {
      // Can't handle this load, bail out.
      Info.UsingBlocks.push_back(LI->getParent());
      continue;
    }
      
    // Otherwise, there was a store before this load, the load takes its value.
    --I;
    LI->replaceAllUsesWith(I->second->getOperand(0));
    if (AST && LI->getType()->isPointerTy())
      AST->deleteValue(LI);
    LI->eraseFromParent();
    LBI.deleteValue(LI);
  }
}

/// \brief Rewrite as many loads as possible given a single store.
///
/// When there is only a single store, we can use the domtree to trivially
/// replace all of the dominated loads with the stored value. Do so, and return
/// true if this has successfully promoted the alloca entirely. If this returns
/// false there were some loads which were not dominated by the single store
/// and thus must be phi-ed with undef. We fall back to the standard alloca
/// promotion algorithm in that case.
static bool rewriteSingleStoreAlloca(AllocaInst *AI, AllocaInfo &Info,
                                     LargeBlockInfo &LBI,
                                     DominatorTree &DT,
                                     AliasSetTracker *AST) {
  StoreInst *OnlyStore = Info.OnlyStore;
  bool StoringGlobalVal = !isa<Instruction>(OnlyStore->getOperand(0));
  BasicBlock *StoreBB = OnlyStore->getParent();
  int StoreIndex = -1;

  // Clear out UsingBlocks.  We will reconstruct it here if needed.
  Info.UsingBlocks.clear();

  for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E;) {
    Instruction *UserInst = cast<Instruction>(*UI++);
    if (!isa<LoadInst>(UserInst)) {
      assert(UserInst == OnlyStore && "Should only have load/stores");
      continue;
    }
    LoadInst *LI = cast<LoadInst>(UserInst);

    // Okay, if we have a load from the alloca, we want to replace it with the
    // only value stored to the alloca.  We can do this if the value is
    // dominated by the store.  If not, we use the rest of the mem2reg machinery
    // to insert the phi nodes as needed.
    if (!StoringGlobalVal) { // Non-instructions are always dominated.
      if (LI->getParent() == StoreBB) {
        // If we have a use that is in the same block as the store, compare the
        // indices of the two instructions to see which one came first.  If the
        // load came before the store, we can't handle it.
        if (StoreIndex == -1)
          StoreIndex = LBI.getInstructionIndex(OnlyStore);

        if (unsigned(StoreIndex) > LBI.getInstructionIndex(LI)) {
          // Can't handle this load, bail out.
          Info.UsingBlocks.push_back(StoreBB);
          continue;
        }

      } else if (LI->getParent() != StoreBB &&
                 !DT.dominates(StoreBB, LI->getParent())) {
        // If the load and store are in different blocks, use BB dominance to
        // check their relationships.  If the store doesn't dom the use, bail
        // out.
        Info.UsingBlocks.push_back(LI->getParent());
        continue;
      }
    }

    // Otherwise, we *can* safely rewrite this load.
    Value *ReplVal = OnlyStore->getOperand(0);
    // If the replacement value is the load, this must occur in unreachable
    // code.
    if (ReplVal == LI)
      ReplVal = UndefValue::get(LI->getType());
    LI->replaceAllUsesWith(ReplVal);
    if (AST && LI->getType()->isPointerTy())
      AST->deleteValue(LI);
    LI->eraseFromParent();
    LBI.deleteValue(LI);
  }

  // Finally, after the scan, check to see if the store is all that is left.
  if (!Info.UsingBlocks.empty())
    return false; // If not, we'll have to fall back for the remainder.

  // Record debuginfo for the store and remove the declaration's
  // debuginfo.
  if (DbgDeclareInst *DDI = Info.DbgDeclare) {
    DIBuilder DIB(*AI->getParent()->getParent()->getParent());
    ConvertDebugDeclareToDebugValue(DDI, Info.OnlyStore, DIB);
    DDI->eraseFromParent();
  }
  // Remove the (now dead) store and alloca.
  Info.OnlyStore->eraseFromParent();
  LBI.deleteValue(Info.OnlyStore);

  if (AST)
    AST->deleteValue(AI);
  AI->eraseFromParent();
  LBI.deleteValue(AI);
  return true;
}

/// Rewrite as many loads as possible given a single store.
///
/// When there is only a single store, we can use the domtree to trivially
/// replace all of the dominated loads with the stored value. Do so, and return
/// true if this has successfully promoted the alloca entirely. If this returns
/// false there were some loads which were not dominated by the single store
/// and thus must be phi-ed with undef. We fall back to the standard alloca
/// promotion algorithm in that case.
static bool rewriteSingleStoreAlloca(AllocaInst *AI, AllocaInfo &Info,
                                     LargeBlockInfo &LBI, const DataLayout &DL,
                                     DominatorTree &DT, AssumptionCache *AC) {
  StoreInst *OnlyStore = Info.OnlyStore;
  bool StoringGlobalVal = !isa<Instruction>(OnlyStore->getOperand(0));
  BasicBlock *StoreBB = OnlyStore->getParent();
  int StoreIndex = -1;

  // Clear out UsingBlocks.  We will reconstruct it here if needed.
  Info.UsingBlocks.clear();

  for (auto UI = AI->user_begin(), E = AI->user_end(); UI != E;) {
    Instruction *UserInst = cast<Instruction>(*UI++);
    if (!isa<LoadInst>(UserInst)) {
      assert(UserInst == OnlyStore && "Should only have load/stores");
      continue;
    }
    LoadInst *LI = cast<LoadInst>(UserInst);

    // Okay, if we have a load from the alloca, we want to replace it with the
    // only value stored to the alloca.  We can do this if the value is
    // dominated by the store.  If not, we use the rest of the mem2reg machinery
    // to insert the phi nodes as needed.
    if (!StoringGlobalVal) { // Non-instructions are always dominated.
      if (LI->getParent() == StoreBB) {
        // If we have a use that is in the same block as the store, compare the
        // indices of the two instructions to see which one came first.  If the
        // load came before the store, we can't handle it.
        if (StoreIndex == -1)
          StoreIndex = LBI.getInstructionIndex(OnlyStore);

        if (unsigned(StoreIndex) > LBI.getInstructionIndex(LI)) {
          // Can't handle this load, bail out.
          Info.UsingBlocks.push_back(StoreBB);
          continue;
        }
      } else if (LI->getParent() != StoreBB &&
                 !DT.dominates(StoreBB, LI->getParent())) {
        // If the load and store are in different blocks, use BB dominance to
        // check their relationships.  If the store doesn't dom the use, bail
        // out.
        Info.UsingBlocks.push_back(LI->getParent());
        continue;
      }
    }

    // Otherwise, we *can* safely rewrite this load.
    Value *ReplVal = OnlyStore->getOperand(0);
    // If the replacement value is the load, this must occur in unreachable
    // code.
    if (ReplVal == LI)
      ReplVal = UndefValue::get(LI->getType());

    // If the load was marked as nonnull we don't want to lose
    // that information when we erase this Load. So we preserve
    // it with an assume.
    if (AC && LI->getMetadata(LLVMContext::MD_nonnull) &&
        !isKnownNonZero(ReplVal, DL, 0, AC, LI, &DT))
      addAssumeNonNull(AC, LI);

    LI->replaceAllUsesWith(ReplVal);
    LI->eraseFromParent();
    LBI.deleteValue(LI);
  }

  // Finally, after the scan, check to see if the store is all that is left.
  if (!Info.UsingBlocks.empty())
    return false; // If not, we'll have to fall back for the remainder.

  // Record debuginfo for the store and remove the declaration's
  // debuginfo.
  for (DbgVariableIntrinsic *DII : Info.DbgDeclares) {
    DIBuilder DIB(*AI->getModule(), /*AllowUnresolved*/ false);
    ConvertDebugDeclareToDebugValue(DII, Info.OnlyStore, DIB);
    DII->eraseFromParent();
    LBI.deleteValue(DII);
  }
  // Remove the (now dead) store and alloca.
  Info.OnlyStore->eraseFromParent();
  LBI.deleteValue(Info.OnlyStore);

  AI->eraseFromParent();
  LBI.deleteValue(AI);
  return true;
}

//.........这里部分代码省略.........
      
      LoopUses.push_back(Use);
    }
  }
  
  // If there isn't a guaranteed-to-execute instruction, we can't promote.
  if (!GuaranteedToExecute)
    return;
  
  // Otherwise, this is safe to promote, lets do it!
  DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " <<*SomePtr<<'\n');  
  Changed = true;
  ++NumPromoted;

  // We use the SSAUpdater interface to insert phi nodes as required.
  SmallVector<PHINode*, 16> NewPHIs;
  SSAUpdater SSA(&NewPHIs);
  
  // It wants to know some value of the same type as what we'll be inserting.
  Value *SomeValue;
  if (isa<LoadInst>(LoopUses[0]))
    SomeValue = LoopUses[0];
  else
    SomeValue = cast<StoreInst>(LoopUses[0])->getOperand(0);
  SSA.Initialize(SomeValue->getType(), SomeValue->getName());

  // First step: bucket up uses of the pointers by the block they occur in.
  // This is important because we have to handle multiple defs/uses in a block
  // ourselves: SSAUpdater is purely for cross-block references.
  // FIXME: Want a TinyVector<Instruction*> since there is usually 0/1 element.
  DenseMap<BasicBlock*, std::vector<Instruction*> > UsesByBlock;
  for (unsigned i = 0, e = LoopUses.size(); i != e; ++i) {
    Instruction *User = LoopUses[i];
    UsesByBlock[User->getParent()].push_back(User);
  }
  
  // Okay, now we can iterate over all the blocks in the loop with uses,
  // processing them.  Keep track of which loads are loading a live-in value.
  SmallVector<LoadInst*, 32> LiveInLoads;
  DenseMap<Value*, Value*> ReplacedLoads;
  
  for (unsigned LoopUse = 0, e = LoopUses.size(); LoopUse != e; ++LoopUse) {
    Instruction *User = LoopUses[LoopUse];
    std::vector<Instruction*> &BlockUses = UsesByBlock[User->getParent()];
    
    // If this block has already been processed, ignore this repeat use.
    if (BlockUses.empty()) continue;
    
    // Okay, this is the first use in the block.  If this block just has a
    // single user in it, we can rewrite it trivially.
    if (BlockUses.size() == 1) {
      // If it is a store, it is a trivial def of the value in the block.
      if (isa<StoreInst>(User)) {
        SSA.AddAvailableValue(User->getParent(),
                              cast<StoreInst>(User)->getOperand(0));
      } else {
        // Otherwise it is a load, queue it to rewrite as a live-in load.
        LiveInLoads.push_back(cast<LoadInst>(User));
      }
      BlockUses.clear();
      continue;
    }
    
    // Otherwise, check to see if this block is all loads.  If so, we can queue
    // them all as live in loads.
    bool HasStore = false;