C++ AllocaInst::getParent方法代码示例

void Lint::visitAllocaInst(AllocaInst &I) {
  if (isa<ConstantInt>(I.getArraySize()))
    // This isn't undefined behavior, it's just an obvious pessimization.
    Assert(&I.getParent()->getParent()->getEntryBlock() == I.getParent(),
           "Pessimization: Static alloca outside of entry block", &I);

  // TODO: Check for an unusual size (MSB set?)
}

void LowerIntrinsics::AutomaticallyRootValue(AllocaInst &AI, Type *Ty,
                                             ArrayRef<Value *> Indices) {
  Module *M = AI.getParent()->getParent()->getParent();
  LLVMContext &C = M->getContext();
  Type *Int32Ty = Type::getInt32Ty(C);

  switch (Ty->getTypeID()) {
  case Type::PointerTyID: {
    if (cast<PointerType>(Ty)->getAddressSpace() < 1)
      break;

    // Create the GEP, if necessary.
    Instruction *BaseInst = &AI;
    if (Indices.size() > 1) {
      BaseInst = GetElementPtrInst::Create(&AI, Indices);
      BaseInst->insertAfter(&AI);
    }

    // Cast the value to an i8** to make a type-compatible intrinsic call.
    Type *PtrTy = PointerType::get(Type::getInt8PtrTy(C), 0);
    Instruction *GCRootArg = new BitCastInst(BaseInst, PtrTy);
    GCRootArg->insertAfter(BaseInst);

    // Cast the addrspace of the root to i8* to make type-compatible with call.
    Constant *AddressSpace =
      ConstantInt::get(Type::getInt64Ty(C), cast<PointerType>(Ty)->getAddressSpace());
    Constant *GCMetadataArg =
      ConstantExpr::getIntToPtr(AddressSpace, Type::getInt8PtrTy(C));

    // Create an intrinsic call.
    Value *Args[2];
    Args[0] = GCRootArg;
    Args[1] = GCMetadataArg;
    Function *GCRootFn = Intrinsic::getDeclaration(M, Intrinsic::gcroot);
    CallInst *Call = CallInst::Create(GCRootFn, Args);
    Call->insertAfter(GCRootArg);
    break;
  }

  case Type::StructTyID:
  case Type::ArrayTyID:
  case Type::VectorTyID: {
    // Skip auto-rooting structs for because we explicitly root these
    // by allocaing pointers on the stack.
    /*
    SmallVector<Value *, 8> NewIndices(Indices.begin(), Indices.end());
    NewIndices.push_back(ConstantInt::get(Int32Ty, 0));
    for (unsigned i = 0; i < Ty->getNumContainedTypes(); ++i) {
      NewIndices[NewIndices.size() - 1] = ConstantInt::get(Int32Ty, i);
      AutomaticallyRootValue(AI, Ty->getContainedType(i), NewIndices);
    }
    */
    break;
  }

  default:
    break;
  }
}

//
// Method: visitAllocaInst()
//
// Description:
//  This method instruments an alloca instruction so that it is zero'ed out
//  before any data is loaded from it.
//
void
InitAllocas::visitAllocaInst (AllocaInst & AI) {
  //
  // Scan for a place to insert the instruction to initialize the
  // allocated memory.
  //
  Instruction * InsertPt = getInsertionPoint (AI);

  //
  // Zero the alloca with a memset.  If this is done more efficiently with stores
  // SelectionDAG will lower it appropriately based on target information.
  //
  TargetData & TD = getAnalysis<TargetData>();

  //
  // Get various types that we'll need.
  //
  Type * Int1Type    = IntegerType::getInt1Ty(AI.getContext());
  Type * Int8Type    = IntegerType::getInt8Ty(AI.getContext());
  Type * Int32Type   = IntegerType::getInt32Ty(AI.getContext());
  Type * VoidPtrType = getVoidPtrType (AI.getContext());
  Type * AllocType = AI.getAllocatedType();

  //
  // Create a call to memset.
  //
  Module * M = AI.getParent()->getParent()->getParent();
  Function * Memset = cast<Function>(M->getFunction ("llvm.memset.p0i8.i32"));
  std::vector<Value *> args;
  args.push_back (castTo (&AI, VoidPtrType, AI.getName().str(), InsertPt));
  args.push_back (ConstantInt::get(Int8Type, 0));
  args.push_back (ConstantInt::get(Int32Type,TD.getTypeAllocSize(AllocType)));
  args.push_back (ConstantInt::get(Int32Type,
                                   TD.getABITypeAlignment(AllocType)));
  args.push_back (ConstantInt::get(Int1Type, 0));
  CallInst::Create (Memset, args, "", InsertPt);

  //
  // Update statistics.
  //
  ++InitedAllocas;
  return;
}

void PromoteMem2Reg::run() {
  Function &F = *DF.getRoot()->getParent();

  if (AST) PointerAllocaValues.resize(Allocas.size());
  AllocaDbgDeclares.resize(Allocas.size());

  AllocaInfo Info;
  LargeBlockInfo LBI;

  for (unsigned AllocaNum = 0; AllocaNum != Allocas.size(); ++AllocaNum) {
    AllocaInst *AI = Allocas[AllocaNum];

    assert(isAllocaPromotable(AI) &&
           "Cannot promote non-promotable alloca!");
    assert(AI->getParent()->getParent() == &F &&
           "All allocas should be in the same function, which is same as DF!");

    if (AI->use_empty()) {
      // If there are no uses of the alloca, just delete it now.
      if (AST) AST->deleteValue(AI);
      AI->eraseFromParent();

      // Remove the alloca from the Allocas list, since it has been processed
      RemoveFromAllocasList(AllocaNum);
      ++NumDeadAlloca;
      continue;
    }
    
    // Calculate the set of read and write-locations for each alloca.  This is
    // analogous to finding the 'uses' and 'definitions' of each variable.
    Info.AnalyzeAlloca(AI);

    // 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.
    if (Info.DefiningBlocks.size() == 1) {
      RewriteSingleStoreAlloca(AI, Info, LBI);

      // Finally, after the scan, check to see if the store is all that is left.
      if (Info.UsingBlocks.empty()) {
        // Record debuginfo for the store and remove the declaration's debuginfo.
        if (DbgDeclareInst *DDI = Info.DbgDeclare) {
          ConvertDebugDeclareToDebugValue(DDI, Info.OnlyStore);
          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);
        
        // The alloca has been processed, move on.
        RemoveFromAllocasList(AllocaNum);
        
        ++NumSingleStore;
        continue;
      }
    }
    
    // If the alloca is only read and written in one basic block, just perform a
    // linear sweep over the block to eliminate it.
    if (Info.OnlyUsedInOneBlock) {
      PromoteSingleBlockAlloca(AI, Info, LBI);
      
      // Finally, after the scan, check to see if the stores are all that is
      // left.
      if (Info.UsingBlocks.empty()) {
        
        // Remove the (now dead) stores and alloca.
        while (!AI->use_empty()) {
          StoreInst *SI = cast<StoreInst>(AI->use_back());
          // Record debuginfo for the store before removing it.
          if (DbgDeclareInst *DDI = Info.DbgDeclare)
            ConvertDebugDeclareToDebugValue(DDI, SI);
          SI->eraseFromParent();
          LBI.deleteValue(SI);
        }
        
        if (AST) AST->deleteValue(AI);
        AI->eraseFromParent();
        LBI.deleteValue(AI);
        
        // The alloca has been processed, move on.
        RemoveFromAllocasList(AllocaNum);
        
        // The alloca's debuginfo can be removed as well.
        if (DbgDeclareInst *DDI = Info.DbgDeclare)
          DDI->eraseFromParent();

        ++NumLocalPromoted;
        continue;
      }
    }
    
    // If we haven't computed a numbering for the BB's in the function, do so
    // now.
    if (BBNumbers.empty()) {
      unsigned ID = 0;
      for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
//.........这里部分代码省略.........

void AMDGPUPromoteAlloca::handleAlloca(AllocaInst &I) {
  // Array allocations are probably not worth handling, since an allocation of
  // the array type is the canonical form.
  if (!I.isStaticAlloca() || I.isArrayAllocation())
    return;

  IRBuilder<> Builder(&I);

  // First try to replace the alloca with a vector
  Type *AllocaTy = I.getAllocatedType();

  DEBUG(dbgs() << "Trying to promote " << I << '\n');

  if (tryPromoteAllocaToVector(&I))
    return;

  DEBUG(dbgs() << " alloca is not a candidate for vectorization.\n");

  const Function &ContainingFunction = *I.getParent()->getParent();

  // FIXME: We should also try to get this value from the reqd_work_group_size
  // function attribute if it is available.
  unsigned WorkGroupSize = AMDGPU::getMaximumWorkGroupSize(ContainingFunction);

  int AllocaSize =
      WorkGroupSize * Mod->getDataLayout().getTypeAllocSize(AllocaTy);

  if (AllocaSize > LocalMemAvailable) {
    DEBUG(dbgs() << " Not enough local memory to promote alloca.\n");
    return;
  }

  std::vector<Value*> WorkList;

  if (!collectUsesWithPtrTypes(&I, WorkList)) {
    DEBUG(dbgs() << " Do not know how to convert all uses\n");
    return;
  }

  DEBUG(dbgs() << "Promoting alloca to local memory\n");
  LocalMemAvailable -= AllocaSize;

  Function *F = I.getParent()->getParent();

  Type *GVTy = ArrayType::get(I.getAllocatedType(), WorkGroupSize);
  GlobalVariable *GV = new GlobalVariable(
      *Mod, GVTy, false, GlobalValue::InternalLinkage,
      UndefValue::get(GVTy),
      Twine(F->getName()) + Twine('.') + I.getName(),
      nullptr,
      GlobalVariable::NotThreadLocal,
      AMDGPUAS::LOCAL_ADDRESS);
  GV->setUnnamedAddr(true);
  GV->setAlignment(I.getAlignment());

  Value *TCntY, *TCntZ;

  std::tie(TCntY, TCntZ) = getLocalSizeYZ(Builder);
  Value *TIdX = getWorkitemID(Builder, 0);
  Value *TIdY = getWorkitemID(Builder, 1);
  Value *TIdZ = getWorkitemID(Builder, 2);

  Value *Tmp0 = Builder.CreateMul(TCntY, TCntZ, "", true, true);
  Tmp0 = Builder.CreateMul(Tmp0, TIdX);
  Value *Tmp1 = Builder.CreateMul(TIdY, TCntZ, "", true, true);
  Value *TID = Builder.CreateAdd(Tmp0, Tmp1);
  TID = Builder.CreateAdd(TID, TIdZ);

  Value *Indices[] = {
    Constant::getNullValue(Type::getInt32Ty(Mod->getContext())),
    TID
  };

  Value *Offset = Builder.CreateInBoundsGEP(GVTy, GV, Indices);
  I.mutateType(Offset->getType());
  I.replaceAllUsesWith(Offset);
  I.eraseFromParent();

  for (Value *V : WorkList) {
    CallInst *Call = dyn_cast<CallInst>(V);
    if (!Call) {
      Type *EltTy = V->getType()->getPointerElementType();
      PointerType *NewTy = PointerType::get(EltTy, AMDGPUAS::LOCAL_ADDRESS);

      // The operand's value should be corrected on its own.
      if (isa<AddrSpaceCastInst>(V))
        continue;

      // FIXME: It doesn't really make sense to try to do this for all
      // instructions.
      V->mutateType(NewTy);
      continue;
    }

    IntrinsicInst *Intr = dyn_cast<IntrinsicInst>(Call);
    if (!Intr) {
      // FIXME: What is this for? It doesn't make sense to promote arbitrary
      // function calls. If the call is to a defined function that can also be
      // promoted, we should be able to do this once that function is also
      // rewritten.
//.........这里部分代码省略.........

/// If it is possible to inline the specified call site,
/// do so and update the CallGraph for this operation.
///
/// This function also does some basic book-keeping to update the IR.  The
/// InlinedArrayAllocas map keeps track of any allocas that are already
/// available from other functions inlined into the caller.  If we are able to
/// inline this call site we attempt to reuse already available allocas or add
/// any new allocas to the set if not possible.
static bool InlineCallIfPossible(CallSite CS, InlineFunctionInfo &IFI,
                                 InlinedArrayAllocasTy &InlinedArrayAllocas,
                                 int InlineHistory, bool InsertLifetime) {
  Function *Callee = CS.getCalledFunction();
  Function *Caller = CS.getCaller();

  // Try to inline the function.  Get the list of static allocas that were
  // inlined.
  if (!InlineFunction(CS, IFI, InsertLifetime))
    return false;

  AdjustCallerSSPLevel(Caller, Callee);

  // Look at all of the allocas that we inlined through this call site.  If we
  // have already inlined other allocas through other calls into this function,
  // then we know that they have disjoint lifetimes and that we can merge them.
  //
  // There are many heuristics possible for merging these allocas, and the
  // different options have different tradeoffs.  One thing that we *really*
  // don't want to hurt is SRoA: once inlining happens, often allocas are no
  // longer address taken and so they can be promoted.
  //
  // Our "solution" for that is to only merge allocas whose outermost type is an
  // array type.  These are usually not promoted because someone is using a
  // variable index into them.  These are also often the most important ones to
  // merge.
  //
  // A better solution would be to have real memory lifetime markers in the IR
  // and not have the inliner do any merging of allocas at all.  This would
  // allow the backend to do proper stack slot coloring of all allocas that
  // *actually make it to the backend*, which is really what we want.
  //
  // Because we don't have this information, we do this simple and useful hack.
  //
  SmallPtrSet<AllocaInst*, 16> UsedAllocas;
  
  // When processing our SCC, check to see if CS was inlined from some other
  // call site.  For example, if we're processing "A" in this code:
  //   A() { B() }
  //   B() { x = alloca ... C() }
  //   C() { y = alloca ... }
  // Assume that C was not inlined into B initially, and so we're processing A
  // and decide to inline B into A.  Doing this makes an alloca available for
  // reuse and makes a callsite (C) available for inlining.  When we process
  // the C call site we don't want to do any alloca merging between X and Y
  // because their scopes are not disjoint.  We could make this smarter by
  // keeping track of the inline history for each alloca in the
  // InlinedArrayAllocas but this isn't likely to be a significant win.
  if (InlineHistory != -1)  // Only do merging for top-level call sites in SCC.
    return true;
  
  // Loop over all the allocas we have so far and see if they can be merged with
  // a previously inlined alloca.  If not, remember that we had it.
  for (unsigned AllocaNo = 0, e = IFI.StaticAllocas.size();
       AllocaNo != e; ++AllocaNo) {
    AllocaInst *AI = IFI.StaticAllocas[AllocaNo];
    
    // Don't bother trying to merge array allocations (they will usually be
    // canonicalized to be an allocation *of* an array), or allocations whose
    // type is not itself an array (because we're afraid of pessimizing SRoA).
    ArrayType *ATy = dyn_cast<ArrayType>(AI->getAllocatedType());
    if (!ATy || AI->isArrayAllocation())
      continue;
    
    // Get the list of all available allocas for this array type.
    std::vector<AllocaInst*> &AllocasForType = InlinedArrayAllocas[ATy];
    
    // Loop over the allocas in AllocasForType to see if we can reuse one.  Note
    // that we have to be careful not to reuse the same "available" alloca for
    // multiple different allocas that we just inlined, we use the 'UsedAllocas'
    // set to keep track of which "available" allocas are being used by this
    // function.  Also, AllocasForType can be empty of course!
    bool MergedAwayAlloca = false;
    for (unsigned i = 0, e = AllocasForType.size(); i != e; ++i) {
      AllocaInst *AvailableAlloca = AllocasForType[i];

      unsigned Align1 = AI->getAlignment(),
               Align2 = AvailableAlloca->getAlignment();
      
      // The available alloca has to be in the right function, not in some other
      // function in this SCC.
      if (AvailableAlloca->getParent() != AI->getParent())
        continue;
      
      // If the inlined function already uses this alloca then we can't reuse
      // it.
      if (!UsedAllocas.insert(AvailableAlloca).second)
        continue;
      
      // Otherwise, we *can* reuse it, RAUW AI into AvailableAlloca and declare
      // success!
      DEBUG(dbgs() << "    ***MERGED ALLOCA: " << *AI << "\n\t\tINTO: "
//.........这里部分代码省略.........

// FIXME: Should try to pick the most likely to be profitable allocas first.
bool AMDGPUPromoteAlloca::handleAlloca(AllocaInst &I, bool SufficientLDS) {
  // Array allocations are probably not worth handling, since an allocation of
  // the array type is the canonical form.
  if (!I.isStaticAlloca() || I.isArrayAllocation())
    return false;

  IRBuilder<> Builder(&I);

  // First try to replace the alloca with a vector
  Type *AllocaTy = I.getAllocatedType();

  DEBUG(dbgs() << "Trying to promote " << I << '\n');

  if (tryPromoteAllocaToVector(&I, AS))
    return true; // Promoted to vector.

  const Function &ContainingFunction = *I.getParent()->getParent();
  CallingConv::ID CC = ContainingFunction.getCallingConv();

  // Don't promote the alloca to LDS for shader calling conventions as the work
  // item ID intrinsics are not supported for these calling conventions.
  // Furthermore not all LDS is available for some of the stages.
  switch (CC) {
  case CallingConv::AMDGPU_KERNEL:
  case CallingConv::SPIR_KERNEL:
    break;
  default:
    DEBUG(dbgs() << " promote alloca to LDS not supported with calling convention.\n");
    return false;
  }

  // Not likely to have sufficient local memory for promotion.
  if (!SufficientLDS)
    return false;

  const AMDGPUSubtarget &ST =
    TM->getSubtarget<AMDGPUSubtarget>(ContainingFunction);
  unsigned WorkGroupSize = ST.getFlatWorkGroupSizes(ContainingFunction).second;

  const DataLayout &DL = Mod->getDataLayout();

  unsigned Align = I.getAlignment();
  if (Align == 0)
    Align = DL.getABITypeAlignment(I.getAllocatedType());

  // FIXME: This computed padding is likely wrong since it depends on inverse
  // usage order.
  //
  // FIXME: It is also possible that if we're allowed to use all of the memory
  // could could end up using more than the maximum due to alignment padding.

  uint32_t NewSize = alignTo(CurrentLocalMemUsage, Align);
  uint32_t AllocSize = WorkGroupSize * DL.getTypeAllocSize(AllocaTy);
  NewSize += AllocSize;

  if (NewSize > LocalMemLimit) {
    DEBUG(dbgs() << "  " << AllocSize
          << " bytes of local memory not available to promote\n");
    return false;
  }

  CurrentLocalMemUsage = NewSize;

  std::vector<Value*> WorkList;

  if (!collectUsesWithPtrTypes(&I, &I, WorkList)) {
    DEBUG(dbgs() << " Do not know how to convert all uses\n");
    return false;
  }

  DEBUG(dbgs() << "Promoting alloca to local memory\n");

  Function *F = I.getParent()->getParent();

  Type *GVTy = ArrayType::get(I.getAllocatedType(), WorkGroupSize);
  GlobalVariable *GV = new GlobalVariable(
      *Mod, GVTy, false, GlobalValue::InternalLinkage,
      UndefValue::get(GVTy),
      Twine(F->getName()) + Twine('.') + I.getName(),
      nullptr,
      GlobalVariable::NotThreadLocal,
      AS.LOCAL_ADDRESS);
  GV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
  GV->setAlignment(I.getAlignment());

  Value *TCntY, *TCntZ;

  std::tie(TCntY, TCntZ) = getLocalSizeYZ(Builder);
  Value *TIdX = getWorkitemID(Builder, 0);
  Value *TIdY = getWorkitemID(Builder, 1);
  Value *TIdZ = getWorkitemID(Builder, 2);

  Value *Tmp0 = Builder.CreateMul(TCntY, TCntZ, "", true, true);
  Tmp0 = Builder.CreateMul(Tmp0, TIdX);
  Value *Tmp1 = Builder.CreateMul(TIdY, TCntZ, "", true, true);
  Value *TID = Builder.CreateAdd(Tmp0, Tmp1);
  TID = Builder.CreateAdd(TID, TIdZ);

  Value *Indices[] = {
//.........这里部分代码省略.........

/// InlineCallIfPossible - If it is possible to inline the specified call site,
/// do so and update the CallGraph for this operation.
///
/// This function also does some basic book-keeping to update the IR.  The
/// InlinedArrayAllocas map keeps track of any allocas that are already
/// available from other  functions inlined into the caller.  If we are able to
/// inline this call site we attempt to reuse already available allocas or add
/// any new allocas to the set if not possible.
static bool InlineCallIfPossible(CallSite CS, InlineFunctionInfo &IFI,
                                 InlinedArrayAllocasTy &InlinedArrayAllocas) {
  Function *Callee = CS.getCalledFunction();
  Function *Caller = CS.getCaller();

  // Try to inline the function.  Get the list of static allocas that were
  // inlined.
  if (!InlineFunction(CS, IFI))
    return false;

  // If the inlined function had a higher stack protection level than the
  // calling function, then bump up the caller's stack protection level.
  if (Callee->hasFnAttr(Attribute::StackProtectReq))
    Caller->addFnAttr(Attribute::StackProtectReq);
  else if (Callee->hasFnAttr(Attribute::StackProtect) &&
           !Caller->hasFnAttr(Attribute::StackProtectReq))
    Caller->addFnAttr(Attribute::StackProtect);

  
  // Look at all of the allocas that we inlined through this call site.  If we
  // have already inlined other allocas through other calls into this function,
  // then we know that they have disjoint lifetimes and that we can merge them.
  //
  // There are many heuristics possible for merging these allocas, and the
  // different options have different tradeoffs.  One thing that we *really*
  // don't want to hurt is SRoA: once inlining happens, often allocas are no
  // longer address taken and so they can be promoted.
  //
  // Our "solution" for that is to only merge allocas whose outermost type is an
  // array type.  These are usually not promoted because someone is using a
  // variable index into them.  These are also often the most important ones to
  // merge.
  //
  // A better solution would be to have real memory lifetime markers in the IR
  // and not have the inliner do any merging of allocas at all.  This would
  // allow the backend to do proper stack slot coloring of all allocas that
  // *actually make it to the backend*, which is really what we want.
  //
  // Because we don't have this information, we do this simple and useful hack.
  //
  SmallPtrSet<AllocaInst*, 16> UsedAllocas;
  
  // Loop over all the allocas we have so far and see if they can be merged with
  // a previously inlined alloca.  If not, remember that we had it.
  for (unsigned AllocaNo = 0, e = IFI.StaticAllocas.size();
       AllocaNo != e; ++AllocaNo) {
    AllocaInst *AI = IFI.StaticAllocas[AllocaNo];
    
    // Don't bother trying to merge array allocations (they will usually be
    // canonicalized to be an allocation *of* an array), or allocations whose
    // type is not itself an array (because we're afraid of pessimizing SRoA).
    const ArrayType *ATy = dyn_cast<ArrayType>(AI->getAllocatedType());
    if (ATy == 0 || AI->isArrayAllocation())
      continue;
    
    // Get the list of all available allocas for this array type.
    std::vector<AllocaInst*> &AllocasForType = InlinedArrayAllocas[ATy];
    
    // Loop over the allocas in AllocasForType to see if we can reuse one.  Note
    // that we have to be careful not to reuse the same "available" alloca for
    // multiple different allocas that we just inlined, we use the 'UsedAllocas'
    // set to keep track of which "available" allocas are being used by this
    // function.  Also, AllocasForType can be empty of course!
    bool MergedAwayAlloca = false;
    for (unsigned i = 0, e = AllocasForType.size(); i != e; ++i) {
      AllocaInst *AvailableAlloca = AllocasForType[i];
      
      // The available alloca has to be in the right function, not in some other
      // function in this SCC.
      if (AvailableAlloca->getParent() != AI->getParent())
        continue;
      
      // If the inlined function already uses this alloca then we can't reuse
      // it.
      if (!UsedAllocas.insert(AvailableAlloca))
        continue;
      
      // Otherwise, we *can* reuse it, RAUW AI into AvailableAlloca and declare
      // success!
      DEBUG(dbgs() << "    ***MERGED ALLOCA: " << *AI);
      
      AI->replaceAllUsesWith(AvailableAlloca);
      AI->eraseFromParent();
      MergedAwayAlloca = true;
      ++NumMergedAllocas;
      break;
    }

    // If we already nuked the alloca, we're done with it.
    if (MergedAwayAlloca)
      continue;

//.........这里部分代码省略.........

void PromoteMem2Reg::run() {
  Function &F = *DT.getRoot()->getParent();

  AllocaDbgDeclares.resize(Allocas.size());

  AllocaInfo Info;
  LargeBlockInfo LBI;
  ForwardIDFCalculator IDF(DT);

  for (unsigned AllocaNum = 0; AllocaNum != Allocas.size(); ++AllocaNum) {
    AllocaInst *AI = Allocas[AllocaNum];

    assert(isAllocaPromotable(AI) && "Cannot promote non-promotable alloca!");
    assert(AI->getParent()->getParent() == &F &&
           "All allocas should be in the same function, which is same as DF!");

    removeLifetimeIntrinsicUsers(AI);

    if (AI->use_empty()) {
      // If there are no uses of the alloca, just delete it now.
      AI->eraseFromParent();

      // Remove the alloca from the Allocas list, since it has been processed
      RemoveFromAllocasList(AllocaNum);
      ++NumDeadAlloca;
      continue;
    }

    // Calculate the set of read and write-locations for each alloca.  This is
    // analogous to finding the 'uses' and 'definitions' of each variable.
    Info.AnalyzeAlloca(AI);

    // 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.
    if (Info.DefiningBlocks.size() == 1) {
      if (rewriteSingleStoreAlloca(AI, Info, LBI, SQ.DL, DT, AC)) {
        // The alloca has been processed, move on.
        RemoveFromAllocasList(AllocaNum);
        ++NumSingleStore;
        continue;
      }
    }

    // If the alloca is only read and written in one basic block, just perform a
    // linear sweep over the block to eliminate it.
    if (Info.OnlyUsedInOneBlock &&
        promoteSingleBlockAlloca(AI, Info, LBI, SQ.DL, DT, AC)) {
      // The alloca has been processed, move on.
      RemoveFromAllocasList(AllocaNum);
      continue;
    }

    // If we haven't computed a numbering for the BB's in the function, do so
    // now.
    if (BBNumbers.empty()) {
      unsigned ID = 0;
      for (auto &BB : F)
        BBNumbers[&BB] = ID++;
    }

    // Remember the dbg.declare intrinsic describing this alloca, if any.
    if (!Info.DbgDeclares.empty())
      AllocaDbgDeclares[AllocaNum] = Info.DbgDeclares;

    // Keep the reverse mapping of the 'Allocas' array for the rename pass.
    AllocaLookup[Allocas[AllocaNum]] = AllocaNum;

    // At this point, we're committed to promoting the alloca using IDF's, and
    // the standard SSA construction algorithm.  Determine which blocks need PHI
    // nodes and see if we can optimize out some work by avoiding insertion of
    // dead phi nodes.

    // Unique the set of defining blocks for efficient lookup.
    SmallPtrSet<BasicBlock *, 32> DefBlocks;
    DefBlocks.insert(Info.DefiningBlocks.begin(), Info.DefiningBlocks.end());

    // Determine which blocks the value is live in.  These are blocks which lead
    // to uses.
    SmallPtrSet<BasicBlock *, 32> LiveInBlocks;
    ComputeLiveInBlocks(AI, Info, DefBlocks, LiveInBlocks);

    // At this point, we're committed to promoting the alloca using IDF's, and
    // the standard SSA construction algorithm.  Determine which blocks need phi
    // nodes and see if we can optimize out some work by avoiding insertion of
    // dead phi nodes.
    IDF.setLiveInBlocks(LiveInBlocks);
    IDF.setDefiningBlocks(DefBlocks);
    SmallVector<BasicBlock *, 32> PHIBlocks;
    IDF.calculate(PHIBlocks);
    if (PHIBlocks.size() > 1)
      llvm::sort(PHIBlocks, [this](BasicBlock *A, BasicBlock *B) {
        return BBNumbers.lookup(A) < BBNumbers.lookup(B);
      });

    unsigned CurrentVersion = 0;
    for (BasicBlock *BB : PHIBlocks)
      QueuePhiNode(BB, AllocaNum, CurrentVersion);
  }

  if (Allocas.empty())
//.........这里部分代码省略.........

/// Look at all of the allocas that we inlined through this call site.  If we
/// have already inlined other allocas through other calls into this function,
/// then we know that they have disjoint lifetimes and that we can merge them.
///
/// There are many heuristics possible for merging these allocas, and the
/// different options have different tradeoffs.  One thing that we *really*
/// don't want to hurt is SRoA: once inlining happens, often allocas are no
/// longer address taken and so they can be promoted.
///
/// Our "solution" for that is to only merge allocas whose outermost type is an
/// array type.  These are usually not promoted because someone is using a
/// variable index into them.  These are also often the most important ones to
/// merge.
///
/// A better solution would be to have real memory lifetime markers in the IR
/// and not have the inliner do any merging of allocas at all.  This would
/// allow the backend to do proper stack slot coloring of all allocas that
/// *actually make it to the backend*, which is really what we want.
///
/// Because we don't have this information, we do this simple and useful hack.
static void mergeInlinedArrayAllocas(
    Function *Caller, InlineFunctionInfo &IFI,
    InlinedArrayAllocasTy &InlinedArrayAllocas, int InlineHistory) {
  SmallPtrSet<AllocaInst *, 16> UsedAllocas;

  // When processing our SCC, check to see if CS was inlined from some other
  // call site.  For example, if we're processing "A" in this code:
  //   A() { B() }
  //   B() { x = alloca ... C() }
  //   C() { y = alloca ... }
  // Assume that C was not inlined into B initially, and so we're processing A
  // and decide to inline B into A.  Doing this makes an alloca available for
  // reuse and makes a callsite (C) available for inlining.  When we process
  // the C call site we don't want to do any alloca merging between X and Y
  // because their scopes are not disjoint.  We could make this smarter by
  // keeping track of the inline history for each alloca in the
  // InlinedArrayAllocas but this isn't likely to be a significant win.
  if (InlineHistory != -1) // Only do merging for top-level call sites in SCC.
    return;

  // Loop over all the allocas we have so far and see if they can be merged with
  // a previously inlined alloca.  If not, remember that we had it.
  for (unsigned AllocaNo = 0, e = IFI.StaticAllocas.size(); AllocaNo != e;
       ++AllocaNo) {
    AllocaInst *AI = IFI.StaticAllocas[AllocaNo];

    // Don't bother trying to merge array allocations (they will usually be
    // canonicalized to be an allocation *of* an array), or allocations whose
    // type is not itself an array (because we're afraid of pessimizing SRoA).
    ArrayType *ATy = dyn_cast<ArrayType>(AI->getAllocatedType());
    if (!ATy || AI->isArrayAllocation())
      continue;

    // Get the list of all available allocas for this array type.
    std::vector<AllocaInst *> &AllocasForType = InlinedArrayAllocas[ATy];

    // Loop over the allocas in AllocasForType to see if we can reuse one.  Note
    // that we have to be careful not to reuse the same "available" alloca for
    // multiple different allocas that we just inlined, we use the 'UsedAllocas'
    // set to keep track of which "available" allocas are being used by this
    // function.  Also, AllocasForType can be empty of course!
    bool MergedAwayAlloca = false;
    for (AllocaInst *AvailableAlloca : AllocasForType) {
      unsigned Align1 = AI->getAlignment(),
               Align2 = AvailableAlloca->getAlignment();

      // The available alloca has to be in the right function, not in some other
      // function in this SCC.
      if (AvailableAlloca->getParent() != AI->getParent())
        continue;

      // If the inlined function already uses this alloca then we can't reuse
      // it.
      if (!UsedAllocas.insert(AvailableAlloca).second)
        continue;

      // Otherwise, we *can* reuse it, RAUW AI into AvailableAlloca and declare
      // success!
      LLVM_DEBUG(dbgs() << "    ***MERGED ALLOCA: " << *AI
                        << "\n\t\tINTO: " << *AvailableAlloca << '\n');

      // Move affected dbg.declare calls immediately after the new alloca to
      // avoid the situation when a dbg.declare precedes its alloca.
      if (auto *L = LocalAsMetadata::getIfExists(AI))
        if (auto *MDV = MetadataAsValue::getIfExists(AI->getContext(), L))
          for (User *U : MDV->users())
            if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(U))
              DDI->moveBefore(AvailableAlloca->getNextNode());

      AI->replaceAllUsesWith(AvailableAlloca);

      if (Align1 != Align2) {
        if (!Align1 || !Align2) {
          const DataLayout &DL = Caller->getParent()->getDataLayout();
          unsigned TypeAlign = DL.getABITypeAlignment(AI->getAllocatedType());

          Align1 = Align1 ? Align1 : TypeAlign;
          Align2 = Align2 ? Align2 : TypeAlign;
        }

//.........这里部分代码省略.........

bool AllocaMerging::runOnFunction(Function& F)
{
	cheerp::PointerAnalyzer & PA = getAnalysis<cheerp::PointerAnalyzer>();
	cheerp::Registerize & registerize = getAnalysis<cheerp::Registerize>();
	cheerp::TypeSupport types(*F.getParent());
	AllocaInfos allocaInfos;
	// Gather all the allocas
	for(BasicBlock& BB: F)
		analyzeBlock(registerize, BB, allocaInfos);
	if (allocaInfos.size() < 2)
		return false;
	bool Changed = false;
	BasicBlock& entryBlock=F.getEntryBlock();
	// Look if we can merge allocas of the same type
	for(auto targetCandidate=allocaInfos.begin();targetCandidate!=allocaInfos.end();++targetCandidate)
	{
		AllocaInst* targetAlloca = targetCandidate->first;
		Type* targetType = targetAlloca->getAllocatedType();
		// The range storing the sum of all ranges merged into target
		cheerp::Registerize::LiveRange targetRange(targetCandidate->second);
		// If the range is empty, we have an alloca that we can't analyze
		if (targetRange.empty())
			continue;
		std::vector<AllocaInfos::iterator> mergeSet;
		auto sourceCandidate=targetCandidate;
		++sourceCandidate;
		for(;sourceCandidate!=allocaInfos.end();++sourceCandidate)
		{
			AllocaInst* sourceAlloca = sourceCandidate->first;
			Type* sourceType = sourceAlloca->getAllocatedType();
			// Bail out for non compatible types
			if(!areTypesEquivalent(types, PA, targetType, sourceType))
				continue;
			const cheerp::Registerize::LiveRange& sourceRange = sourceCandidate->second;
			// Bail out if this source candidate is not analyzable
			if(sourceRange.empty())
				continue;
			// Bail out if the allocas interfere
			if(targetRange.doesInterfere(sourceRange))
				continue;
			// Add the range to the target range and the source alloca to the mergeSet
			mergeSet.push_back(sourceCandidate);
			PA.invalidate(sourceAlloca);
			targetRange.merge(sourceRange);
		}

		// If the merge set is empty try another target
		if(mergeSet.empty())
			continue;

		PA.invalidate(targetAlloca);

		if(!Changed)
			registerize.invalidateLiveRangeForAllocas(F);

		// Make sure that this alloca is in the entry block
		if(targetAlloca->getParent()!=&entryBlock)
			targetAlloca->moveBefore(entryBlock.begin());
		// We can merge the allocas
		for(const AllocaInfos::iterator& it: mergeSet)
		{
			AllocaInst* allocaToMerge = it->first;
			Instruction* targetVal=targetAlloca;
			if(targetVal->getType()!=allocaToMerge->getType())
			{
				targetVal=new BitCastInst(targetVal, allocaToMerge->getType());
				targetVal->insertAfter(targetAlloca);
			}
			allocaToMerge->replaceAllUsesWith(targetVal);
			allocaToMerge->eraseFromParent();
			if(targetVal != targetAlloca)
				PA.getPointerKind(targetVal);
			allocaInfos.erase(it);
			NumAllocaMerged++;
		}
		PA.getPointerKind(targetAlloca);
		Changed = true;
	}
	if(Changed)
		registerize.computeLiveRangeForAllocas(F);
	return Changed;
}

//
// Method: TransformCSSAllocasToMallocs()
//
// Description:
//  This method is given the set of DSNodes from the stack safety pass that
//  have been marked for promotion.  It then finds all alloca instructions
//  that have not been marked type-unknown and promotes them to heap
//  allocations.
//
void
ConvertUnsafeAllocas::TransformCSSAllocasToMallocs (Module & M,
                                                    std::set<DSNode *> & cssAllocaNodes) {
  for (Module::iterator FI = M.begin(); FI != M.end(); ++FI) {
    //
    // Skip functions that have no DSGraph.  These are probably functions with
    // no function body and are, hence, cannot be analyzed.
    //
    if (!(budsPass->hasDSGraph (*FI))) continue;

    //
    // Get the DSGraph for the current function.
    //
    DSGraph *DSG = budsPass->getDSGraph(*FI);

    //
    // Search for alloca instructions that need promotion and add them to the
    // worklist.
    //
    std::vector<AllocaInst *> Worklist;
    for (Function::iterator BB = FI->begin(); BB != FI->end(); ++BB) {
      for (BasicBlock::iterator ii = BB->begin(); ii != BB->end(); ++ii) {
        Instruction * I = ii;

        if (AllocaInst * AI = dyn_cast<AllocaInst>(I)) {
          //
          // Get the DSNode for the allocation.
          //
          DSNode *DSN = DSG->getNodeForValue(AI).getNode();
          assert (DSN && "No DSNode for alloca!\n");

          //
          // If the alloca is type-known, we do not need to promote it, so
          // don't bother with it.
          //
          if (DSN->isNodeCompletelyFolded()) continue;

          //
          // Determine if the DSNode for the alloca is one of those marked as
          // unsafe by the stack safety analysis pass.  If not, then we do not
          // need to promote it.
          //
          if (cssAllocaNodes.find(DSN) == cssAllocaNodes.end()) continue;

          //
          // If the DSNode for this alloca is already listed in the
          // unsafeAllocaNode vector, remove it since we are processing it here
          //
          std::list<DSNode *>::iterator NodeI = find (unsafeAllocaNodes.begin(),
                                                      unsafeAllocaNodes.end(),
                                                      DSN);
          if (NodeI != unsafeAllocaNodes.end()) {
            unsafeAllocaNodes.erase(NodeI);
          }

          //
          // This alloca needs to be changed to a malloc.  Add it to the
          // worklist.
          //
          Worklist.push_back (AI);
        }
      }
    }

    //
    // Update the statistics.
    //
    if (Worklist.size())
      ConvAllocas += Worklist.size();

    //
    // Convert everything in the worklist into a malloc instruction.
    //
    while (Worklist.size()) {
      //
      // Grab an alloca from the worklist.
      //
      AllocaInst * AI = Worklist.back();
      Worklist.pop_back();

      //
      // Get the DSNode for this alloca.
      //
      DSNode *DSN = DSG->getNodeForValue(AI).getNode();
      assert (DSN && "No DSNode for alloca!\n");

      //
      // Promote the alloca and remove it from the program.
      //
      promoteAlloca (AI, DSN);
      AI->getParent()->getInstList().erase(AI);
//.........这里部分代码省略.........