vendor/llvm-project/llvmorg-11-init-20887-g2e10b7a39b9vendor/llvm-project/master

1 files changed, 1837 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/RDFGraph.cpp b/llvm/lib/CodeGen/RDFGraph.cpp
new file mode 100644
index 000000000000..437a6b030096
--- /dev/null
+++ b/llvm/lib/CodeGen/RDFGraph.cpp
@@ -0,0 +1,1837 @@
+//===- RDFGraph.cpp -------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Target-independent, SSA-based data flow graph for register data flow (RDF).
+//
+#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineDominanceFrontier.h"
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineOperand.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/RDFGraph.h"
+#include "llvm/CodeGen/RDFRegisters.h"
+#include "llvm/CodeGen/TargetInstrInfo.h"
+#include "llvm/CodeGen/TargetLowering.h"
+#include "llvm/CodeGen/TargetRegisterInfo.h"
+#include "llvm/CodeGen/TargetSubtargetInfo.h"
+#include "llvm/IR/Function.h"
+#include "llvm/MC/LaneBitmask.h"
+#include "llvm/MC/MCInstrDesc.h"
+#include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
+#include <cstring>
+#include <iterator>
+#include <set>
+#include <utility>
+#include <vector>
+
+using namespace llvm;
+using namespace rdf;
+
+// Printing functions. Have them here first, so that the rest of the code
+// can use them.
+namespace llvm {
+namespace rdf {
+
+raw_ostream &operator<< (raw_ostream &OS, const PrintLaneMaskOpt &P) {
+  if (!P.Mask.all())
+    OS << ':' << PrintLaneMask(P.Mask);
+  return OS;
+}
+
+raw_ostream &operator<< (raw_ostream &OS, const Print<RegisterRef> &P) {
+  auto &TRI = P.G.getTRI();
+  if (P.Obj.Reg > 0 && P.Obj.Reg < TRI.getNumRegs())
+    OS << TRI.getName(P.Obj.Reg);
+  else
+    OS << '#' << P.Obj.Reg;
+  OS << PrintLaneMaskOpt(P.Obj.Mask);
+  return OS;
+}
+
+raw_ostream &operator<< (raw_ostream &OS, const Print<NodeId> &P) {
+  auto NA = P.G.addr<NodeBase*>(P.Obj);
+  uint16_t Attrs = NA.Addr->getAttrs();
+  uint16_t Kind = NodeAttrs::kind(Attrs);
+  uint16_t Flags = NodeAttrs::flags(Attrs);
+  switch (NodeAttrs::type(Attrs)) {
+    case NodeAttrs::Code:
+      switch (Kind) {
+        case NodeAttrs::Func:   OS << 'f'; break;
+        case NodeAttrs::Block:  OS << 'b'; break;
+        case NodeAttrs::Stmt:   OS << 's'; break;
+        case NodeAttrs::Phi:    OS << 'p'; break;
+        default:                OS << "c?"; break;
+      }
+      break;
+    case NodeAttrs::Ref:
+      if (Flags & NodeAttrs::Undef)
+        OS << '/';
+      if (Flags & NodeAttrs::Dead)
+        OS << '\\';
+      if (Flags & NodeAttrs::Preserving)
+        OS << '+';
+      if (Flags & NodeAttrs::Clobbering)
+        OS << '~';
+      switch (Kind) {
+        case NodeAttrs::Use:    OS << 'u'; break;
+        case NodeAttrs::Def:    OS << 'd'; break;
+        case NodeAttrs::Block:  OS << 'b'; break;
+        default:                OS << "r?"; break;
+      }
+      break;
+    default:
+      OS << '?';
+      break;
+  }
+  OS << P.Obj;
+  if (Flags & NodeAttrs::Shadow)
+    OS << '"';
+  return OS;
+}
+
+static void printRefHeader(raw_ostream &OS, const NodeAddr<RefNode*> RA,
+                const DataFlowGraph &G) {
+  OS << Print<NodeId>(RA.Id, G) << '<'
+     << Print<RegisterRef>(RA.Addr->getRegRef(G), G) << '>';
+  if (RA.Addr->getFlags() & NodeAttrs::Fixed)
+    OS << '!';
+}
+
+raw_ostream &operator<< (raw_ostream &OS, const Print<NodeAddr<DefNode*>> &P) {
+  printRefHeader(OS, P.Obj, P.G);
+  OS << '(';
+  if (NodeId N = P.Obj.Addr->getReachingDef())
+    OS << Print<NodeId>(N, P.G);
+  OS << ',';
+  if (NodeId N = P.Obj.Addr->getReachedDef())
+    OS << Print<NodeId>(N, P.G);
+  OS << ',';
+  if (NodeId N = P.Obj.Addr->getReachedUse())
+    OS << Print<NodeId>(N, P.G);
+  OS << "):";
+  if (NodeId N = P.Obj.Addr->getSibling())
+    OS << Print<NodeId>(N, P.G);
+  return OS;
+}
+
+raw_ostream &operator<< (raw_ostream &OS, const Print<NodeAddr<UseNode*>> &P) {
+  printRefHeader(OS, P.Obj, P.G);
+  OS << '(';
+  if (NodeId N = P.Obj.Addr->getReachingDef())
+    OS << Print<NodeId>(N, P.G);
+  OS << "):";
+  if (NodeId N = P.Obj.Addr->getSibling())
+    OS << Print<NodeId>(N, P.G);
+  return OS;
+}
+
+raw_ostream &operator<< (raw_ostream &OS,
+      const Print<NodeAddr<PhiUseNode*>> &P) {
+  printRefHeader(OS, P.Obj, P.G);
+  OS << '(';
+  if (NodeId N = P.Obj.Addr->getReachingDef())
+    OS << Print<NodeId>(N, P.G);
+  OS << ',';
+  if (NodeId N = P.Obj.Addr->getPredecessor())
+    OS << Print<NodeId>(N, P.G);
+  OS << "):";
+  if (NodeId N = P.Obj.Addr->getSibling())
+    OS << Print<NodeId>(N, P.G);
+  return OS;
+}
+
+raw_ostream &operator<< (raw_ostream &OS, const Print<NodeAddr<RefNode*>> &P) {
+  switch (P.Obj.Addr->getKind()) {
+    case NodeAttrs::Def:
+      OS << PrintNode<DefNode*>(P.Obj, P.G);
+      break;
+    case NodeAttrs::Use:
+      if (P.Obj.Addr->getFlags() & NodeAttrs::PhiRef)
+        OS << PrintNode<PhiUseNode*>(P.Obj, P.G);
+      else
+        OS << PrintNode<UseNode*>(P.Obj, P.G);
+      break;
+  }
+  return OS;
+}
+
+raw_ostream &operator<< (raw_ostream &OS, const Print<NodeList> &P) {
+  unsigned N = P.Obj.size();
+  for (auto I : P.Obj) {
+    OS << Print<NodeId>(I.Id, P.G);
+    if (--N)
+      OS << ' ';
+  }
+  return OS;
+}
+
+raw_ostream &operator<< (raw_ostream &OS, const Print<NodeSet> &P) {
+  unsigned N = P.Obj.size();
+  for (auto I : P.Obj) {
+    OS << Print<NodeId>(I, P.G);
+    if (--N)
+      OS << ' ';
+  }
+  return OS;
+}
+
+namespace {
+
+  template <typename T>
+  struct PrintListV {
+    PrintListV(const NodeList &L, const DataFlowGraph &G) : List(L), G(G) {}
+
+    using Type = T;
+    const NodeList &List;
+    const DataFlowGraph &G;
+  };
+
+  template <typename T>
+  raw_ostream &operator<< (raw_ostream &OS, const PrintListV<T> &P) {
+    unsigned N = P.List.size();
+    for (NodeAddr<T> A : P.List) {
+      OS << PrintNode<T>(A, P.G);
+      if (--N)
+        OS << ", ";
+    }
+    return OS;
+  }
+
+} // end anonymous namespace
+
+raw_ostream &operator<< (raw_ostream &OS, const Print<NodeAddr<PhiNode*>> &P) {
+  OS << Print<NodeId>(P.Obj.Id, P.G) << ": phi ["
+     << PrintListV<RefNode*>(P.Obj.Addr->members(P.G), P.G) << ']';
+  return OS;
+}
+
+raw_ostream &operator<<(raw_ostream &OS, const Print<NodeAddr<StmtNode *>> &P) {
+  const MachineInstr &MI = *P.Obj.Addr->getCode();
+  unsigned Opc = MI.getOpcode();
+  OS << Print<NodeId>(P.Obj.Id, P.G) << ": " << P.G.getTII().getName(Opc);
+  // Print the target for calls and branches (for readability).
+  if (MI.isCall() || MI.isBranch()) {
+    MachineInstr::const_mop_iterator T =
+          llvm::find_if(MI.operands(),
+                        [] (const MachineOperand &Op) -> bool {
+                          return Op.isMBB() || Op.isGlobal() || Op.isSymbol();
+                        });
+    if (T != MI.operands_end()) {
+      OS << ' ';
+      if (T->isMBB())
+        OS << printMBBReference(*T->getMBB());
+      else if (T->isGlobal())
+        OS << T->getGlobal()->getName();
+      else if (T->isSymbol())
+        OS << T->getSymbolName();
+    }
+  }
+  OS << " [" << PrintListV<RefNode*>(P.Obj.Addr->members(P.G), P.G) << ']';
+  return OS;
+}
+
+raw_ostream &operator<< (raw_ostream &OS,
+      const Print<NodeAddr<InstrNode*>> &P) {
+  switch (P.Obj.Addr->getKind()) {
+    case NodeAttrs::Phi:
+      OS << PrintNode<PhiNode*>(P.Obj, P.G);
+      break;
+    case NodeAttrs::Stmt:
+      OS << PrintNode<StmtNode*>(P.Obj, P.G);
+      break;
+    default:
+      OS << "instr? " << Print<NodeId>(P.Obj.Id, P.G);
+      break;
+  }
+  return OS;
+}
+
+raw_ostream &operator<< (raw_ostream &OS,
+      const Print<NodeAddr<BlockNode*>> &P) {
+  MachineBasicBlock *BB = P.Obj.Addr->getCode();
+  unsigned NP = BB->pred_size();
+  std::vector<int> Ns;
+  auto PrintBBs = [&OS] (std::vector<int> Ns) -> void {
+    unsigned N = Ns.size();
+    for (int I : Ns) {
+      OS << "%bb." << I;
+      if (--N)
+        OS << ", ";
+    }
+  };
+
+  OS << Print<NodeId>(P.Obj.Id, P.G) << ": --- " << printMBBReference(*BB)
+     << " --- preds(" << NP << "): ";
+  for (MachineBasicBlock *B : BB->predecessors())
+    Ns.push_back(B->getNumber());
+  PrintBBs(Ns);
+
+  unsigned NS = BB->succ_size();
+  OS << "  succs(" << NS << "): ";
+  Ns.clear();
+  for (MachineBasicBlock *B : BB->successors())
+    Ns.push_back(B->getNumber());
+  PrintBBs(Ns);
+  OS << '\n';
+
+  for (auto I : P.Obj.Addr->members(P.G))
+    OS << PrintNode<InstrNode*>(I, P.G) << '\n';
+  return OS;
+}
+
+raw_ostream &operator<<(raw_ostream &OS, const Print<NodeAddr<FuncNode *>> &P) {
+  OS << "DFG dump:[\n" << Print<NodeId>(P.Obj.Id, P.G) << ": Function: "
+     << P.Obj.Addr->getCode()->getName() << '\n';
+  for (auto I : P.Obj.Addr->members(P.G))
+    OS << PrintNode<BlockNode*>(I, P.G) << '\n';
+  OS << "]\n";
+  return OS;
+}
+
+raw_ostream &operator<< (raw_ostream &OS, const Print<RegisterSet> &P) {
+  OS << '{';
+  for (auto I : P.Obj)
+    OS << ' ' << Print<RegisterRef>(I, P.G);
+  OS << " }";
+  return OS;
+}
+
+raw_ostream &operator<< (raw_ostream &OS, const Print<RegisterAggr> &P) {
+  P.Obj.print(OS);
+  return OS;
+}
+
+raw_ostream &operator<< (raw_ostream &OS,
+      const Print<DataFlowGraph::DefStack> &P) {
+  for (auto I = P.Obj.top(), E = P.Obj.bottom(); I != E; ) {
+    OS << Print<NodeId>(I->Id, P.G)
+       << '<' << Print<RegisterRef>(I->Addr->getRegRef(P.G), P.G) << '>';
+    I.down();
+    if (I != E)
+      OS << ' ';
+  }
+  return OS;
+}
+
+} // end namespace rdf
+} // end namespace llvm
+
+// Node allocation functions.
+//
+// Node allocator is like a slab memory allocator: it allocates blocks of
+// memory in sizes that are multiples of the size of a node. Each block has
+// the same size. Nodes are allocated from the currently active block, and
+// when it becomes full, a new one is created.
+// There is a mapping scheme between node id and its location in a block,
+// and within that block is described in the header file.
+//
+void NodeAllocator::startNewBlock() {
+  void *T = MemPool.Allocate(NodesPerBlock*NodeMemSize, NodeMemSize);
+  char *P = static_cast<char*>(T);
+  Blocks.push_back(P);
+  // Check if the block index is still within the allowed range, i.e. less
+  // than 2^N, where N is the number of bits in NodeId for the block index.
+  // BitsPerIndex is the number of bits per node index.
+  assert((Blocks.size() < ((size_t)1 << (8*sizeof(NodeId)-BitsPerIndex))) &&
+         "Out of bits for block index");
+  ActiveEnd = P;
+}
+
+bool NodeAllocator::needNewBlock() {
+  if (Blocks.empty())
+    return true;
+
+  char *ActiveBegin = Blocks.back();
+  uint32_t Index = (ActiveEnd-ActiveBegin)/NodeMemSize;
+  return Index >= NodesPerBlock;
+}
+
+NodeAddr<NodeBase*> NodeAllocator::New() {
+  if (needNewBlock())
+    startNewBlock();
+
+  uint32_t ActiveB = Blocks.size()-1;
+  uint32_t Index = (ActiveEnd - Blocks[ActiveB])/NodeMemSize;
+  NodeAddr<NodeBase*> NA = { reinterpret_cast<NodeBase*>(ActiveEnd),
+                             makeId(ActiveB, Index) };
+  ActiveEnd += NodeMemSize;
+  return NA;
+}
+
+NodeId NodeAllocator::id(const NodeBase *P) const {
+  uintptr_t A = reinterpret_cast<uintptr_t>(P);
+  for (unsigned i = 0, n = Blocks.size(); i != n; ++i) {
+    uintptr_t B = reinterpret_cast<uintptr_t>(Blocks[i]);
+    if (A < B || A >= B + NodesPerBlock*NodeMemSize)
+      continue;
+    uint32_t Idx = (A-B)/NodeMemSize;
+    return makeId(i, Idx);
+  }
+  llvm_unreachable("Invalid node address");
+}
+
+void NodeAllocator::clear() {
+  MemPool.Reset();
+  Blocks.clear();
+  ActiveEnd = nullptr;
+}
+
+// Insert node NA after "this" in the circular chain.
+void NodeBase::append(NodeAddr<NodeBase*> NA) {
+  NodeId Nx = Next;
+  // If NA is already "next", do nothing.
+  if (Next != NA.Id) {
+    Next = NA.Id;
+    NA.Addr->Next = Nx;
+  }
+}
+
+// Fundamental node manipulator functions.
+
+// Obtain the register reference from a reference node.
+RegisterRef RefNode::getRegRef(const DataFlowGraph &G) const {
+  assert(NodeAttrs::type(Attrs) == NodeAttrs::Ref);
+  if (NodeAttrs::flags(Attrs) & NodeAttrs::PhiRef)
+    return G.unpack(Ref.PR);
+  assert(Ref.Op != nullptr);
+  return G.makeRegRef(*Ref.Op);
+}
+
+// Set the register reference in the reference node directly (for references
+// in phi nodes).
+void RefNode::setRegRef(RegisterRef RR, DataFlowGraph &G) {
+  assert(NodeAttrs::type(Attrs) == NodeAttrs::Ref);
+  assert(NodeAttrs::flags(Attrs) & NodeAttrs::PhiRef);
+  Ref.PR = G.pack(RR);
+}
+
+// Set the register reference in the reference node based on a machine
+// operand (for references in statement nodes).
+void RefNode::setRegRef(MachineOperand *Op, DataFlowGraph &G) {
+  assert(NodeAttrs::type(Attrs) == NodeAttrs::Ref);
+  assert(!(NodeAttrs::flags(Attrs) & NodeAttrs::PhiRef));
+  (void)G;
+  Ref.Op = Op;
+}
+
+// Get the owner of a given reference node.
+NodeAddr<NodeBase*> RefNode::getOwner(const DataFlowGraph &G) {
+  NodeAddr<NodeBase*> NA = G.addr<NodeBase*>(getNext());
+
+  while (NA.Addr != this) {
+    if (NA.Addr->getType() == NodeAttrs::Code)
+      return NA;
+    NA = G.addr<NodeBase*>(NA.Addr->getNext());
+  }
+  llvm_unreachable("No owner in circular list");
+}
+
+// Connect the def node to the reaching def node.
+void DefNode::linkToDef(NodeId Self, NodeAddr<DefNode*> DA) {
+  Ref.RD = DA.Id;
+  Ref.Sib = DA.Addr->getReachedDef();
+  DA.Addr->setReachedDef(Self);
+}
+
+// Connect the use node to the reaching def node.
+void UseNode::linkToDef(NodeId Self, NodeAddr<DefNode*> DA) {
+  Ref.RD = DA.Id;
+  Ref.Sib = DA.Addr->getReachedUse();
+  DA.Addr->setReachedUse(Self);
+}
+
+// Get the first member of the code node.
+NodeAddr<NodeBase*> CodeNode::getFirstMember(const DataFlowGraph &G) const {
+  if (Code.FirstM == 0)
+    return NodeAddr<NodeBase*>();
+  return G.addr<NodeBase*>(Code.FirstM);
+}
+
+// Get the last member of the code node.
+NodeAddr<NodeBase*> CodeNode::getLastMember(const DataFlowGraph &G) const {
+  if (Code.LastM == 0)
+    return NodeAddr<NodeBase*>();
+  return G.addr<NodeBase*>(Code.LastM);
+}
+
+// Add node NA at the end of the member list of the given code node.
+void CodeNode::addMember(NodeAddr<NodeBase*> NA, const DataFlowGraph &G) {
+  NodeAddr<NodeBase*> ML = getLastMember(G);
+  if (ML.Id != 0) {
+    ML.Addr->append(NA);
+  } else {
+    Code.FirstM = NA.Id;
+    NodeId Self = G.id(this);
+    NA.Addr->setNext(Self);
+  }
+  Code.LastM = NA.Id;
+}
+
+// Add node NA after member node MA in the given code node.
+void CodeNode::addMemberAfter(NodeAddr<NodeBase*> MA, NodeAddr<NodeBase*> NA,
+      const DataFlowGraph &G) {
+  MA.Addr->append(NA);
+  if (Code.LastM == MA.Id)
+    Code.LastM = NA.Id;
+}
+
+// Remove member node NA from the given code node.
+void CodeNode::removeMember(NodeAddr<NodeBase*> NA, const DataFlowGraph &G) {
+  NodeAddr<NodeBase*> MA = getFirstMember(G);
+  assert(MA.Id != 0);
+
+  // Special handling if the member to remove is the first member.
+  if (MA.Id == NA.Id) {
+    if (Code.LastM == MA.Id) {
+      // If it is the only member, set both first and last to 0.
+      Code.FirstM = Code.LastM = 0;
+    } else {
+      // Otherwise, advance the first member.
+      Code.FirstM = MA.Addr->getNext();
+    }
+    return;
+  }
+
+  while (MA.Addr != this) {
+    NodeId MX = MA.Addr->getNext();
+    if (MX == NA.Id) {
+      MA.Addr->setNext(NA.Addr->getNext());
+      // If the member to remove happens to be the last one, update the
+      // LastM indicator.
+      if (Code.LastM == NA.Id)
+        Code.LastM = MA.Id;
+      return;
+    }
+    MA = G.addr<NodeBase*>(MX);
+  }
+  llvm_unreachable("No such member");
+}
+
+// Return the list of all members of the code node.
+NodeList CodeNode::members(const DataFlowGraph &G) const {
+  static auto True = [] (NodeAddr<NodeBase*>) -> bool { return true; };
+  return members_if(True, G);
+}
+
+// Return the owner of the given instr node.
+NodeAddr<NodeBase*> InstrNode::getOwner(const DataFlowGraph &G) {
+  NodeAddr<NodeBase*> NA = G.addr<NodeBase*>(getNext());
+
+  while (NA.Addr != this) {
+    assert(NA.Addr->getType() == NodeAttrs::Code);
+    if (NA.Addr->getKind() == NodeAttrs::Block)
+      return NA;
+    NA = G.addr<NodeBase*>(NA.Addr->getNext());
+  }
+  llvm_unreachable("No owner in circular list");
+}
+
+// Add the phi node PA to the given block node.
+void BlockNode::addPhi(NodeAddr<PhiNode*> PA, const DataFlowGraph &G) {
+  NodeAddr<NodeBase*> M = getFirstMember(G);
+  if (M.Id == 0) {
+    addMember(PA, G);
+    return;
+  }
+
+  assert(M.Addr->getType() == NodeAttrs::Code);
+  if (M.Addr->getKind() == NodeAttrs::Stmt) {
+    // If the first member of the block is a statement, insert the phi as
+    // the first member.
+    Code.FirstM = PA.Id;
+    PA.Addr->setNext(M.Id);
+  } else {
+    // If the first member is a phi, find the last phi, and append PA to it.
+    assert(M.Addr->getKind() == NodeAttrs::Phi);
+    NodeAddr<NodeBase*> MN = M;
+    do {
+      M = MN;
+      MN = G.addr<NodeBase*>(M.Addr->getNext());
+      assert(MN.Addr->getType() == NodeAttrs::Code);
+    } while (MN.Addr->getKind() == NodeAttrs::Phi);
+
+    // M is the last phi.
+    addMemberAfter(M, PA, G);
+  }
+}
+
+// Find the block node corresponding to the machine basic block BB in the
+// given func node.
+NodeAddr<BlockNode*> FuncNode::findBlock(const MachineBasicBlock *BB,
+      const DataFlowGraph &G) const {
+  auto EqBB = [BB] (NodeAddr<NodeBase*> NA) -> bool {
+    return NodeAddr<BlockNode*>(NA).Addr->getCode() == BB;
+  };
+  NodeList Ms = members_if(EqBB, G);
+  if (!Ms.empty())
+    return Ms[0];
+  return NodeAddr<BlockNode*>();
+}
+
+// Get the block node for the entry block in the given function.
+NodeAddr<BlockNode*> FuncNode::getEntryBlock(const DataFlowGraph &G) {
+  MachineBasicBlock *EntryB = &getCode()->front();
+  return findBlock(EntryB, G);
+}
+
+// Target operand information.
+//
+
+// For a given instruction, check if there are any bits of RR that can remain
+// unchanged across this def.
+bool TargetOperandInfo::isPreserving(const MachineInstr &In, unsigned OpNum)
+      const {
+  return TII.isPredicated(In);
+}
+
+// Check if the definition of RR produces an unspecified value.
+bool TargetOperandInfo::isClobbering(const MachineInstr &In, unsigned OpNum)
+      const {
+  const MachineOperand &Op = In.getOperand(OpNum);
+  if (Op.isRegMask())
+    return true;
+  assert(Op.isReg());
+  if (In.isCall())
+    if (Op.isDef() && Op.isDead())
+      return true;
+  return false;
+}
+
+// Check if the given instruction specifically requires
+bool TargetOperandInfo::isFixedReg(const MachineInstr &In, unsigned OpNum)
+      const {
+  if (In.isCall() || In.isReturn() || In.isInlineAsm())
+    return true;
+  // Check for a tail call.
+  if (In.isBranch())
+    for (const MachineOperand &O : In.operands())
+      if (O.isGlobal() || O.isSymbol())
+        return true;
+
+  const MCInstrDesc &D = In.getDesc();
+  if (!D.getImplicitDefs() && !D.getImplicitUses())
+    return false;
+  const MachineOperand &Op = In.getOperand(OpNum);
+  // If there is a sub-register, treat the operand as non-fixed. Currently,
+  // fixed registers are those that are listed in the descriptor as implicit
+  // uses or defs, and those lists do not allow sub-registers.
+  if (Op.getSubReg() != 0)
+    return false;
+  Register Reg = Op.getReg();
+  const MCPhysReg *ImpR = Op.isDef() ? D.getImplicitDefs()
+                                     : D.getImplicitUses();
+  if (!ImpR)
+    return false;
+  while (*ImpR)
+    if (*ImpR++ == Reg)
+      return true;
+  return false;
+}
+
+//
+// The data flow graph construction.
+//
+
+DataFlowGraph::DataFlowGraph(MachineFunction &mf, const TargetInstrInfo &tii,
+      const TargetRegisterInfo &tri, const MachineDominatorTree &mdt,
+      const MachineDominanceFrontier &mdf, const TargetOperandInfo &toi)
+    : MF(mf), TII(tii), TRI(tri), PRI(tri, mf), MDT(mdt), MDF(mdf), TOI(toi),
+      LiveIns(PRI) {
+}
+
+// The implementation of the definition stack.
+// Each register reference has its own definition stack. In particular,
+// for a register references "Reg" and "Reg:subreg" will each have their
+// own definition stacks.
+
+// Construct a stack iterator.
+DataFlowGraph::DefStack::Iterator::Iterator(const DataFlowGraph::DefStack &S,
+      bool Top) : DS(S) {
+  if (!Top) {
+    // Initialize to bottom.
+    Pos = 0;
+    return;
+  }
+  // Initialize to the top, i.e. top-most non-delimiter (or 0, if empty).
+  Pos = DS.Stack.size();
+  while (Pos > 0 && DS.isDelimiter(DS.Stack[Pos-1]))
+    Pos--;
+}
+
+// Return the size of the stack, including block delimiters.
+unsigned DataFlowGraph::DefStack::size() const {
+  unsigned S = 0;
+  for (auto I = top(), E = bottom(); I != E; I.down())
+    S++;
+  return S;
+}
+
+// Remove the top entry from the stack. Remove all intervening delimiters
+// so that after this, the stack is either empty, or the top of the stack
+// is a non-delimiter.
+void DataFlowGraph::DefStack::pop() {
+  assert(!empty());
+  unsigned P = nextDown(Stack.size());
+  Stack.resize(P);
+}
+
+// Push a delimiter for block node N on the stack.
+void DataFlowGraph::DefStack::start_block(NodeId N) {
+  assert(N != 0);
+  Stack.push_back(NodeAddr<DefNode*>(nullptr, N));
+}
+
+// Remove all nodes from the top of the stack, until the delimited for
+// block node N is encountered. Remove the delimiter as well. In effect,
+// this will remove from the stack all definitions from block N.
+void DataFlowGraph::DefStack::clear_block(NodeId N) {
+  assert(N != 0);
+  unsigned P = Stack.size();
+  while (P > 0) {
+    bool Found = isDelimiter(Stack[P-1], N);
+    P--;
+    if (Found)
+      break;
+  }
+  // This will also remove the delimiter, if found.
+  Stack.resize(P);
+}
+
+// Move the stack iterator up by one.
+unsigned DataFlowGraph::DefStack::nextUp(unsigned P) const {
+  // Get the next valid position after P (skipping all delimiters).
+  // The input position P does not have to point to a non-delimiter.
+  unsigned SS = Stack.size();
+  bool IsDelim;
+  assert(P < SS);
+  do {
+    P++;
+    IsDelim = isDelimiter(Stack[P-1]);
+  } while (P < SS && IsDelim);
+  assert(!IsDelim);
+  return P;
+}
+
+// Move the stack iterator down by one.
+unsigned DataFlowGraph::DefStack::nextDown(unsigned P) const {
+  // Get the preceding valid position before P (skipping all delimiters).
+  // The input position P does not have to point to a non-delimiter.
+  assert(P > 0 && P <= Stack.size());
+  bool IsDelim = isDelimiter(Stack[P-1]);
+  do {
+    if (--P == 0)
+      break;
+    IsDelim = isDelimiter(Stack[P-1]);
+  } while (P > 0 && IsDelim);
+  assert(!IsDelim);
+  return P;
+}
+
+// Register information.
+
+RegisterSet DataFlowGraph::getLandingPadLiveIns() const {
+  RegisterSet LR;
+  const Function &F = MF.getFunction();
+  const Constant *PF = F.hasPersonalityFn() ? F.getPersonalityFn()
+                                            : nullptr;
+  const TargetLowering &TLI = *MF.getSubtarget().getTargetLowering();
+  if (RegisterId R = TLI.getExceptionPointerRegister(PF))
+    LR.insert(RegisterRef(R));
+  if (!isFuncletEHPersonality(classifyEHPersonality(PF))) {
+    if (RegisterId R = TLI.getExceptionSelectorRegister(PF))
+      LR.insert(RegisterRef(R));
+  }
+  return LR;
+}
+
+// Node management functions.
+
+// Get the pointer to the node with the id N.
+NodeBase *DataFlowGraph::ptr(NodeId N) const {
+  if (N == 0)
+    return nullptr;
+  return Memory.ptr(N);
+}
+
+// Get the id of the node at the address P.
+NodeId DataFlowGraph::id(const NodeBase *P) const {
+  if (P == nullptr)
+    return 0;
+  return Memory.id(P);
+}
+
+// Allocate a new node and set the attributes to Attrs.
+NodeAddr<NodeBase*> DataFlowGraph::newNode(uint16_t Attrs) {
+  NodeAddr<NodeBase*> P = Memory.New();
+  P.Addr->init();
+  P.Addr->setAttrs(Attrs);
+  return P;
+}
+
+// Make a copy of the given node B, except for the data-flow links, which
+// are set to 0.
+NodeAddr<NodeBase*> DataFlowGraph::cloneNode(const NodeAddr<NodeBase*> B) {
+  NodeAddr<NodeBase*> NA = newNode(0);
+  memcpy(NA.Addr, B.Addr, sizeof(NodeBase));
+  // Ref nodes need to have the data-flow links reset.
+  if (NA.Addr->getType() == NodeAttrs::Ref) {
+    NodeAddr<RefNode*> RA = NA;
+    RA.Addr->setReachingDef(0);
+    RA.Addr->setSibling(0);
+    if (NA.Addr->getKind() == NodeAttrs::Def) {
+      NodeAddr<DefNode*> DA = NA;
+      DA.Addr->setReachedDef(0);
+      DA.Addr->setReachedUse(0);
+    }
+  }
+  return NA;
+}
+
+// Allocation routines for specific node types/kinds.
+
+NodeAddr<UseNode*> DataFlowGraph::newUse(NodeAddr<InstrNode*> Owner,
+      MachineOperand &Op, uint16_t Flags) {
+  NodeAddr<UseNode*> UA = newNode(NodeAttrs::Ref | NodeAttrs::Use | Flags);
+  UA.Addr->setRegRef(&Op, *this);
+  return UA;
+}
+
+NodeAddr<PhiUseNode*> DataFlowGraph::newPhiUse(NodeAddr<PhiNode*> Owner,
+      RegisterRef RR, NodeAddr<BlockNode*> PredB, uint16_t Flags) {
+  NodeAddr<PhiUseNode*> PUA = newNode(NodeAttrs::Ref | NodeAttrs::Use | Flags);
+  assert(Flags & NodeAttrs::PhiRef);
+  PUA.Addr->setRegRef(RR, *this);
+  PUA.Addr->setPredecessor(PredB.Id);
+  return PUA;
+}
+
+NodeAddr<DefNode*> DataFlowGraph::newDef(NodeAddr<InstrNode*> Owner,
+      MachineOperand &Op, uint16_t Flags) {
+  NodeAddr<DefNode*> DA = newNode(NodeAttrs::Ref | NodeAttrs::Def | Flags);
+  DA.Addr->setRegRef(&Op, *this);
+  return DA;
+}
+
+NodeAddr<DefNode*> DataFlowGraph::newDef(NodeAddr<InstrNode*> Owner,
+      RegisterRef RR, uint16_t Flags) {
+  NodeAddr<DefNode*> DA = newNode(NodeAttrs::Ref | NodeAttrs::Def | Flags);
+  assert(Flags & NodeAttrs::PhiRef);
+  DA.Addr->setRegRef(RR, *this);
+  return DA;
+}
+
+NodeAddr<PhiNode*> DataFlowGraph::newPhi(NodeAddr<BlockNode*> Owner) {
+  NodeAddr<PhiNode*> PA = newNode(NodeAttrs::Code | NodeAttrs::Phi);
+  Owner.Addr->addPhi(PA, *this);
+  return PA;
+}
+
+NodeAddr<StmtNode*> DataFlowGraph::newStmt(NodeAddr<BlockNode*> Owner,
+      MachineInstr *MI) {
+  NodeAddr<StmtNode*> SA = newNode(NodeAttrs::Code | NodeAttrs::Stmt);
+  SA.Addr->setCode(MI);
+  Owner.Addr->addMember(SA, *this);
+  return SA;
+}
+
+NodeAddr<BlockNode*> DataFlowGraph::newBlock(NodeAddr<FuncNode*> Owner,
+      MachineBasicBlock *BB) {
+  NodeAddr<BlockNode*> BA = newNode(NodeAttrs::Code | NodeAttrs::Block);
+  BA.Addr->setCode(BB);
+  Owner.Addr->addMember(BA, *this);
+  return BA;
+}
+
+NodeAddr<FuncNode*> DataFlowGraph::newFunc(MachineFunction *MF) {
+  NodeAddr<FuncNode*> FA = newNode(NodeAttrs::Code | NodeAttrs::Func);
+  FA.Addr->setCode(MF);
+  return FA;
+}
+
+// Build the data flow graph.
+void DataFlowGraph::build(unsigned Options) {
+  reset();
+  Func = newFunc(&MF);
+
+  if (MF.empty())
+    return;
+
+  for (MachineBasicBlock &B : MF) {
+    NodeAddr<BlockNode*> BA = newBlock(Func, &B);
+    BlockNodes.insert(std::make_pair(&B, BA));
+    for (MachineInstr &I : B) {
+      if (I.isDebugInstr())
+        continue;
+      buildStmt(BA, I);
+    }
+  }
+
+  NodeAddr<BlockNode*> EA = Func.Addr->getEntryBlock(*this);
+  NodeList Blocks = Func.Addr->members(*this);
+
+  // Collect information about block references.
+  RegisterSet AllRefs;
+  for (NodeAddr<BlockNode*> BA : Blocks)
+    for (NodeAddr<InstrNode*> IA : BA.Addr->members(*this))
+      for (NodeAddr<RefNode*> RA : IA.Addr->members(*this))
+        AllRefs.insert(RA.Addr->getRegRef(*this));
+
+  // Collect function live-ins and entry block live-ins.
+  MachineRegisterInfo &MRI = MF.getRegInfo();
+  MachineBasicBlock &EntryB = *EA.Addr->getCode();
+  assert(EntryB.pred_empty() && "Function entry block has predecessors");
+  for (std::pair<unsigned,unsigned> P : MRI.liveins())
+    LiveIns.insert(RegisterRef(P.first));
+  if (MRI.tracksLiveness()) {
+    for (auto I : EntryB.liveins())
+      LiveIns.insert(RegisterRef(I.PhysReg, I.LaneMask));
+  }
+
+  // Add function-entry phi nodes for the live-in registers.
+  //for (std::pair<RegisterId,LaneBitmask> P : LiveIns) {
+  for (auto I = LiveIns.rr_begin(), E = LiveIns.rr_end(); I != E; ++I) {
+    RegisterRef RR = *I;
+    NodeAddr<PhiNode*> PA = newPhi(EA);
+    uint16_t PhiFlags = NodeAttrs::PhiRef | NodeAttrs::Preserving;
+    NodeAddr<DefNode*> DA = newDef(PA, RR, PhiFlags);
+    PA.Addr->addMember(DA, *this);
+  }
+
+  // Add phis for landing pads.
+  // Landing pads, unlike usual backs blocks, are not entered through
+  // branches in the program, or fall-throughs from other blocks. They
+  // are entered from the exception handling runtime and target's ABI
+  // may define certain registers as defined on entry to such a block.
+  RegisterSet EHRegs = getLandingPadLiveIns();
+  if (!EHRegs.empty()) {
+    for (NodeAddr<BlockNode*> BA : Blocks) {
+      const MachineBasicBlock &B = *BA.Addr->getCode();
+      if (!B.isEHPad())
+        continue;
+
+      // Prepare a list of NodeIds of the block's predecessors.
+      NodeList Preds;
+      for (MachineBasicBlock *PB : B.predecessors())
+        Preds.push_back(findBlock(PB));
+
+      // Build phi nodes for each live-in.
+      for (RegisterRef RR : EHRegs) {
+        NodeAddr<PhiNode*> PA = newPhi(BA);
+        uint16_t PhiFlags = NodeAttrs::PhiRef | NodeAttrs::Preserving;
+        // Add def:
+        NodeAddr<DefNode*> DA = newDef(PA, RR, PhiFlags);
+        PA.Addr->addMember(DA, *this);
+        // Add uses (no reaching defs for phi uses):
+        for (NodeAddr<BlockNode*> PBA : Preds) {
+          NodeAddr<PhiUseNode*> PUA = newPhiUse(PA, RR, PBA);
+          PA.Addr->addMember(PUA, *this);
+        }
+      }
+    }
+  }
+
+  // Build a map "PhiM" which will contain, for each block, the set
+  // of references that will require phi definitions in that block.
+  BlockRefsMap PhiM;
+  for (NodeAddr<BlockNode*> BA : Blocks)
+    recordDefsForDF(PhiM, BA);
+  for (NodeAddr<BlockNode*> BA : Blocks)
+    buildPhis(PhiM, AllRefs, BA);
+
+  // Link all the refs. This will recursively traverse the dominator tree.
+  DefStackMap DM;
+  linkBlockRefs(DM, EA);
+
+  // Finally, remove all unused phi nodes.
+  if (!(Options & BuildOptions::KeepDeadPhis))
+    removeUnusedPhis();
+}
+
+RegisterRef DataFlowGraph::makeRegRef(unsigned Reg, unsigned Sub) const {
+  assert(PhysicalRegisterInfo::isRegMaskId(Reg) ||
+         Register::isPhysicalRegister(Reg));
+  assert(Reg != 0);
+  if (Sub != 0)
+    Reg = TRI.getSubReg(Reg, Sub);
+  return RegisterRef(Reg);
+}
+
+RegisterRef DataFlowGraph::makeRegRef(const MachineOperand &Op) const {
+  assert(Op.isReg() || Op.isRegMask());
+  if (Op.isReg())
+    return makeRegRef(Op.getReg(), Op.getSubReg());
+  return RegisterRef(PRI.getRegMaskId(Op.getRegMask()), LaneBitmask::getAll());
+}
+
+RegisterRef DataFlowGraph::restrictRef(RegisterRef AR, RegisterRef BR) const {
+  if (AR.Reg == BR.Reg) {
+    LaneBitmask M = AR.Mask & BR.Mask;
+    return M.any() ? RegisterRef(AR.Reg, M) : RegisterRef();
+  }
+#ifndef NDEBUG
+//  RegisterRef NAR = PRI.normalize(AR);
+//  RegisterRef NBR = PRI.normalize(BR);
+//  assert(NAR.Reg != NBR.Reg);
+#endif
+  // This isn't strictly correct, because the overlap may happen in the
+  // part masked out.
+  if (PRI.alias(AR, BR))
+    return AR;
+  return RegisterRef();
+}
+
+// For each stack in the map DefM, push the delimiter for block B on it.
+void DataFlowGraph::markBlock(NodeId B, DefStackMap &DefM) {
+  // Push block delimiters.
+  for (auto I = DefM.begin(), E = DefM.end(); I != E; ++I)
+    I->second.start_block(B);
+}
+
+// Remove all definitions coming from block B from each stack in DefM.
+void DataFlowGraph::releaseBlock(NodeId B, DefStackMap &DefM) {
+  // Pop all defs from this block from the definition stack. Defs that were
+  // added to the map during the traversal of instructions will not have a
+  // delimiter, but for those, the whole stack will be emptied.
+  for (auto I = DefM.begin(), E = DefM.end(); I != E; ++I)
+    I->second.clear_block(B);
+
+  // Finally, remove empty stacks from the map.
+  for (auto I = DefM.begin(), E = DefM.end(), NextI = I; I != E; I = NextI) {
+    NextI = std::next(I);
+    // This preserves the validity of iterators other than I.
+    if (I->second.empty())
+      DefM.erase(I);
+  }
+}
+
+// Push all definitions from the instruction node IA to an appropriate
+// stack in DefM.
+void DataFlowGraph::pushAllDefs(NodeAddr<InstrNode*> IA, DefStackMap &DefM) {
+  pushClobbers(IA, DefM);
+  pushDefs(IA, DefM);
+}
+
+// Push all definitions from the instruction node IA to an appropriate
+// stack in DefM.
+void DataFlowGraph::pushClobbers(NodeAddr<InstrNode*> IA, DefStackMap &DefM) {
+  NodeSet Visited;
+  std::set<RegisterId> Defined;
+
+  // The important objectives of this function are:
+  // - to be able to handle instructions both while the graph is being
+  //   constructed, and after the graph has been constructed, and
+  // - maintain proper ordering of definitions on the stack for each
+  //   register reference:
+  //   - if there are two or more related defs in IA (i.e. coming from
+  //     the same machine operand), then only push one def on the stack,
+  //   - if there are multiple unrelated defs of non-overlapping
+  //     subregisters of S, then the stack for S will have both (in an
+  //     unspecified order), but the order does not matter from the data-
+  //     -flow perspective.
+
+  for (NodeAddr<DefNode*> DA : IA.Addr->members_if(IsDef, *this)) {
+    if (Visited.count(DA.Id))
+      continue;
+    if (!(DA.Addr->getFlags() & NodeAttrs::Clobbering))
+      continue;
+
+    NodeList Rel = getRelatedRefs(IA, DA);
+    NodeAddr<DefNode*> PDA = Rel.front();
+    RegisterRef RR = PDA.Addr->getRegRef(*this);
+
+    // Push the definition on the stack for the register and all aliases.
+    // The def stack traversal in linkNodeUp will check the exact aliasing.
+    DefM[RR.Reg].push(DA);
+    Defined.insert(RR.Reg);
+    for (RegisterId A : PRI.getAliasSet(RR.Reg)) {
+      // Check that we don't push the same def twice.
+      assert(A != RR.Reg);
+      if (!Defined.count(A))
+        DefM[A].push(DA);
+    }
+    // Mark all the related defs as visited.
+    for (NodeAddr<NodeBase*> T : Rel)
+      Visited.insert(T.Id);
+  }
+}
+
+// Push all definitions from the instruction node IA to an appropriate
+// stack in DefM.
+void DataFlowGraph::pushDefs(NodeAddr<InstrNode*> IA, DefStackMap &DefM) {
+  NodeSet Visited;
+#ifndef NDEBUG
+  std::set<RegisterId> Defined;
+#endif
+
+  // The important objectives of this function are:
+  // - to be able to handle instructions both while the graph is being
+  //   constructed, and after the graph has been constructed, and
+  // - maintain proper ordering of definitions on the stack for each
+  //   register reference:
+  //   - if there are two or more related defs in IA (i.e. coming from
+  //     the same machine operand), then only push one def on the stack,
+  //   - if there are multiple unrelated defs of non-overlapping
+  //     subregisters of S, then the stack for S will have both (in an
+  //     unspecified order), but the order does not matter from the data-
+  //     -flow perspective.
+
+  for (NodeAddr<DefNode*> DA : IA.Addr->members_if(IsDef, *this)) {
+    if (Visited.count(DA.Id))
+      continue;
+    if (DA.Addr->getFlags() & NodeAttrs::Clobbering)
+      continue;
+
+    NodeList Rel = getRelatedRefs(IA, DA);
+    NodeAddr<DefNode*> PDA = Rel.front();
+    RegisterRef RR = PDA.Addr->getRegRef(*this);
+#ifndef NDEBUG
+    // Assert if the register is defined in two or more unrelated defs.
+    // This could happen if there are two or more def operands defining it.
+    if (!Defined.insert(RR.Reg).second) {
+      MachineInstr *MI = NodeAddr<StmtNode*>(IA).Addr->getCode();
+      dbgs() << "Multiple definitions of register: "
+             << Print<RegisterRef>(RR, *this) << " in\n  " << *MI << "in "
+             << printMBBReference(*MI->getParent()) << '\n';
+      llvm_unreachable(nullptr);
+    }
+#endif
+    // Push the definition on the stack for the register and all aliases.
+    // The def stack traversal in linkNodeUp will check the exact aliasing.
+    DefM[RR.Reg].push(DA);
+    for (RegisterId A : PRI.getAliasSet(RR.Reg)) {
+      // Check that we don't push the same def twice.
+      assert(A != RR.Reg);
+      DefM[A].push(DA);
+    }
+    // Mark all the related defs as visited.
+    for (NodeAddr<NodeBase*> T : Rel)
+      Visited.insert(T.Id);
+  }
+}
+
+// Return the list of all reference nodes related to RA, including RA itself.
+// See "getNextRelated" for the meaning of a "related reference".
+NodeList DataFlowGraph::getRelatedRefs(NodeAddr<InstrNode*> IA,
+      NodeAddr<RefNode*> RA) const {
+  assert(IA.Id != 0 && RA.Id != 0);
+
+  NodeList Refs;
+  NodeId Start = RA.Id;
+  do {
+    Refs.push_back(RA);
+    RA = getNextRelated(IA, RA);
+  } while (RA.Id != 0 && RA.Id != Start);
+  return Refs;
+}
+
+// Clear all information in the graph.
+void DataFlowGraph::reset() {
+  Memory.clear();
+  BlockNodes.clear();
+  Func = NodeAddr<FuncNode*>();
+}
+
+// Return the next reference node in the instruction node IA that is related
+// to RA. Conceptually, two reference nodes are related if they refer to the
+// same instance of a register access, but differ in flags or other minor
+// characteristics. Specific examples of related nodes are shadow reference
+// nodes.
+// Return the equivalent of nullptr if there are no more related references.
+NodeAddr<RefNode*> DataFlowGraph::getNextRelated(NodeAddr<InstrNode*> IA,
+      NodeAddr<RefNode*> RA) const {
+  assert(IA.Id != 0 && RA.Id != 0);
+
+  auto Related = [this,RA](NodeAddr<RefNode*> TA) -> bool {
+    if (TA.Addr->getKind() != RA.Addr->getKind())
+      return false;
+    if (TA.Addr->getRegRef(*this) != RA.Addr->getRegRef(*this))
+      return false;
+    return true;
+  };
+  auto RelatedStmt = [&Related,RA](NodeAddr<RefNode*> TA) -> bool {
+    return Related(TA) &&
+           &RA.Addr->getOp() == &TA.Addr->getOp();
+  };
+  auto RelatedPhi = [&Related,RA](NodeAddr<RefNode*> TA) -> bool {
+    if (!Related(TA))
+      return false;
+    if (TA.Addr->getKind() != NodeAttrs::Use)
+      return true;
+    // For phi uses, compare predecessor blocks.
+    const NodeAddr<const PhiUseNode*> TUA = TA;
+    const NodeAddr<const PhiUseNode*> RUA = RA;
+    return TUA.Addr->getPredecessor() == RUA.Addr->getPredecessor();
+  };
+
+  RegisterRef RR = RA.Addr->getRegRef(*this);
+  if (IA.Addr->getKind() == NodeAttrs::Stmt)
+    return RA.Addr->getNextRef(RR, RelatedStmt, true, *this);
+  return RA.Addr->getNextRef(RR, RelatedPhi, true, *this);
+}
+
+// Find the next node related to RA in IA that satisfies condition P.
+// If such a node was found, return a pair where the second element is the
+// located node. If such a node does not exist, return a pair where the
+// first element is the element after which such a node should be inserted,
+// and the second element is a null-address.
+template <typename Predicate>
+std::pair<NodeAddr<RefNode*>,NodeAddr<RefNode*>>
+DataFlowGraph::locateNextRef(NodeAddr<InstrNode*> IA, NodeAddr<RefNode*> RA,
+      Predicate P) const {
+  assert(IA.Id != 0 && RA.Id != 0);
+
+  NodeAddr<RefNode*> NA;
+  NodeId Start = RA.Id;
+  while (true) {
+    NA = getNextRelated(IA, RA);
+    if (NA.Id == 0 || NA.Id == Start)
+      break;
+    if (P(NA))
+      break;
+    RA = NA;
+  }
+
+  if (NA.Id != 0 && NA.Id != Start)
+    return std::make_pair(RA, NA);
+  return std::make_pair(RA, NodeAddr<RefNode*>());
+}
+
+// Get the next shadow node in IA corresponding to RA, and optionally create
+// such a node if it does not exist.
+NodeAddr<RefNode*> DataFlowGraph::getNextShadow(NodeAddr<InstrNode*> IA,
+      NodeAddr<RefNode*> RA, bool Create) {
+  assert(IA.Id != 0 && RA.Id != 0);
+
+  uint16_t Flags = RA.Addr->getFlags() | NodeAttrs::Shadow;
+  auto IsShadow = [Flags] (NodeAddr<RefNode*> TA) -> bool {
+    return TA.Addr->getFlags() == Flags;
+  };
+  auto Loc = locateNextRef(IA, RA, IsShadow);
+  if (Loc.second.Id != 0 || !Create)
+    return Loc.second;
+
+  // Create a copy of RA and mark is as shadow.
+  NodeAddr<RefNode*> NA = cloneNode(RA);
+  NA.Addr->setFlags(Flags | NodeAttrs::Shadow);
+  IA.Addr->addMemberAfter(Loc.first, NA, *this);
+  return NA;
+}
+
+// Get the next shadow node in IA corresponding to RA. Return null-address
+// if such a node does not exist.
+NodeAddr<RefNode*> DataFlowGraph::getNextShadow(NodeAddr<InstrNode*> IA,
+      NodeAddr<RefNode*> RA) const {
+  assert(IA.Id != 0 && RA.Id != 0);
+  uint16_t Flags = RA.Addr->getFlags() | NodeAttrs::Shadow;
+  auto IsShadow = [Flags] (NodeAddr<RefNode*> TA) -> bool {
+    return TA.Addr->getFlags() == Flags;
+  };
+  return locateNextRef(IA, RA, IsShadow).second;
+}
+
+// Create a new statement node in the block node BA that corresponds to
+// the machine instruction MI.
+void DataFlowGraph::buildStmt(NodeAddr<BlockNode*> BA, MachineInstr &In) {
+  NodeAddr<StmtNode*> SA = newStmt(BA, &In);
+
+  auto isCall = [] (const MachineInstr &In) -> bool {
+    if (In.isCall())
+      return true;
+    // Is tail call?
+    if (In.isBranch()) {
+      for (const MachineOperand &Op : In.operands())
+        if (Op.isGlobal() || Op.isSymbol())
+          return true;
+      // Assume indirect branches are calls. This is for the purpose of
+      // keeping implicit operands, and so it won't hurt on intra-function
+      // indirect branches.
+      if (In.isIndirectBranch())
+        return true;
+    }
+    return false;
+  };
+
+  auto isDefUndef = [this] (const MachineInstr &In, RegisterRef DR) -> bool {
+    // This instruction defines DR. Check if there is a use operand that
+    // would make DR live on entry to the instruction.
+    for (const MachineOperand &Op : In.operands()) {
+      if (!Op.isReg() || Op.getReg() == 0 || !Op.isUse() || Op.isUndef())
+        continue;
+      RegisterRef UR = makeRegRef(Op);
+      if (PRI.alias(DR, UR))
+        return false;
+    }
+    return true;
+  };
+
+  bool IsCall = isCall(In);
+  unsigned NumOps = In.getNumOperands();
+
+  // Avoid duplicate implicit defs. This will not detect cases of implicit
+  // defs that define registers that overlap, but it is not clear how to
+  // interpret that in the absence of explicit defs. Overlapping explicit
+  // defs are likely illegal already.
+  BitVector DoneDefs(TRI.getNumRegs());
+  // Process explicit defs first.
+  for (unsigned OpN = 0; OpN < NumOps; ++OpN) {
+    MachineOperand &Op = In.getOperand(OpN);
+    if (!Op.isReg() || !Op.isDef() || Op.isImplicit())
+      continue;
+    Register R = Op.getReg();
+    if (!R || !Register::isPhysicalRegister(R))
+      continue;
+    uint16_t Flags = NodeAttrs::None;
+    if (TOI.isPreserving(In, OpN)) {
+      Flags |= NodeAttrs::Preserving;
+      // If the def is preserving, check if it is also undefined.
+      if (isDefUndef(In, makeRegRef(Op)))
+        Flags |= NodeAttrs::Undef;
+    }
+    if (TOI.isClobbering(In, OpN))
+      Flags |= NodeAttrs::Clobbering;
+    if (TOI.isFixedReg(In, OpN))
+      Flags |= NodeAttrs::Fixed;
+    if (IsCall && Op.isDead())
+      Flags |= NodeAttrs::Dead;
+    NodeAddr<DefNode*> DA = newDef(SA, Op, Flags);
+    SA.Addr->addMember(DA, *this);
+    assert(!DoneDefs.test(R));
+    DoneDefs.set(R);
+  }
+
+  // Process reg-masks (as clobbers).
+  BitVector DoneClobbers(TRI.getNumRegs());
+  for (unsigned OpN = 0; OpN < NumOps; ++OpN) {
+    MachineOperand &Op = In.getOperand(OpN);
+    if (!Op.isRegMask())
+      continue;
+    uint16_t Flags = NodeAttrs::Clobbering | NodeAttrs::Fixed |
+                     NodeAttrs::Dead;
+    NodeAddr<DefNode*> DA = newDef(SA, Op, Flags);
+    SA.Addr->addMember(DA, *this);
+    // Record all clobbered registers in DoneDefs.
+    const uint32_t *RM = Op.getRegMask();
+    for (unsigned i = 1, e = TRI.getNumRegs(); i != e; ++i)
+      if (!(RM[i/32] & (1u << (i%32))))
+        DoneClobbers.set(i);
+  }
+
+  // Process implicit defs, skipping those that have already been added
+  // as explicit.
+  for (unsigned OpN = 0; OpN < NumOps; ++OpN) {
+    MachineOperand &Op = In.getOperand(OpN);
+    if (!Op.isReg() || !Op.isDef() || !Op.isImplicit())
+      continue;
+    Register R = Op.getReg();
+    if (!R || !Register::isPhysicalRegister(R) || DoneDefs.test(R))
+      continue;
+    RegisterRef RR = makeRegRef(Op);
+    uint16_t Flags = NodeAttrs::None;
+    if (TOI.isPreserving(In, OpN)) {
+      Flags |= NodeAttrs::Preserving;
+      // If the def is preserving, check if it is also undefined.
+      if (isDefUndef(In, RR))
+        Flags |= NodeAttrs::Undef;
+    }
+    if (TOI.isClobbering(In, OpN))
+      Flags |= NodeAttrs::Clobbering;
+    if (TOI.isFixedReg(In, OpN))
+      Flags |= NodeAttrs::Fixed;
+    if (IsCall && Op.isDead()) {
+      if (DoneClobbers.test(R))
+        continue;
+      Flags |= NodeAttrs::Dead;
+    }
+    NodeAddr<DefNode*> DA = newDef(SA, Op, Flags);
+    SA.Addr->addMember(DA, *this);
+    DoneDefs.set(R);
+  }
+
+  for (unsigned OpN = 0; OpN < NumOps; ++OpN) {
+    MachineOperand &Op = In.getOperand(OpN);
+    if (!Op.isReg() || !Op.isUse())
+      continue;
+    Register R = Op.getReg();
+    if (!R || !Register::isPhysicalRegister(R))
+      continue;
+    uint16_t Flags = NodeAttrs::None;
+    if (Op.isUndef())
+      Flags |= NodeAttrs::Undef;
+    if (TOI.isFixedReg(In, OpN))
+      Flags |= NodeAttrs::Fixed;
+    NodeAddr<UseNode*> UA = newUse(SA, Op, Flags);
+    SA.Addr->addMember(UA, *this);
+  }
+}
+
+// Scan all defs in the block node BA and record in PhiM the locations of
+// phi nodes corresponding to these defs.
+void DataFlowGraph::recordDefsForDF(BlockRefsMap &PhiM,
+      NodeAddr<BlockNode*> BA) {
+  // Check all defs from block BA and record them in each block in BA's
+  // iterated dominance frontier. This information will later be used to
+  // create phi nodes.
+  MachineBasicBlock *BB = BA.Addr->getCode();
+  assert(BB);
+  auto DFLoc = MDF.find(BB);
+  if (DFLoc == MDF.end() || DFLoc->second.empty())
+    return;
+
+  // Traverse all instructions in the block and collect the set of all
+  // defined references. For each reference there will be a phi created
+  // in the block's iterated dominance frontier.
+  // This is done to make sure that each defined reference gets only one
+  // phi node, even if it is defined multiple times.
+  RegisterSet Defs;
+  for (NodeAddr<InstrNode*> IA : BA.Addr->members(*this))
+    for (NodeAddr<RefNode*> RA : IA.Addr->members_if(IsDef, *this))
+      Defs.insert(RA.Addr->getRegRef(*this));
+
+  // Calculate the iterated dominance frontier of BB.
+  const MachineDominanceFrontier::DomSetType &DF = DFLoc->second;
+  SetVector<MachineBasicBlock*> IDF(DF.begin(), DF.end());
+  for (unsigned i = 0; i < IDF.size(); ++i) {
+    auto F = MDF.find(IDF[i]);
+    if (F != MDF.end())
+      IDF.insert(F->second.begin(), F->second.end());
+  }
+
+  // Finally, add the set of defs to each block in the iterated dominance
+  // frontier.
+  for (auto DB : IDF) {
+    NodeAddr<BlockNode*> DBA = findBlock(DB);
+    PhiM[DBA.Id].insert(Defs.begin(), Defs.end());
+  }
+}
+
+// Given the locations of phi nodes in the map PhiM, create the phi nodes
+// that are located in the block node BA.
+void DataFlowGraph::buildPhis(BlockRefsMap &PhiM, RegisterSet &AllRefs,
+      NodeAddr<BlockNode*> BA) {
+  // Check if this blocks has any DF defs, i.e. if there are any defs
+  // that this block is in the iterated dominance frontier of.
+  auto HasDF = PhiM.find(BA.Id);
+  if (HasDF == PhiM.end() || HasDF->second.empty())
+    return;
+
+  // First, remove all R in Refs in such that there exists T in Refs
+  // such that T covers R. In other words, only leave those refs that
+  // are not covered by another ref (i.e. maximal with respect to covering).
+
+  auto MaxCoverIn = [this] (RegisterRef RR, RegisterSet &RRs) -> RegisterRef {
+    for (RegisterRef I : RRs)
+      if (I != RR && RegisterAggr::isCoverOf(I, RR, PRI))
+        RR = I;
+    return RR;
+  };
+
+  RegisterSet MaxDF;
+  for (RegisterRef I : HasDF->second)
+    MaxDF.insert(MaxCoverIn(I, HasDF->second));
+
+  std::vector<RegisterRef> MaxRefs;
+  for (RegisterRef I : MaxDF)
+    MaxRefs.push_back(MaxCoverIn(I, AllRefs));
+
+  // Now, for each R in MaxRefs, get the alias closure of R. If the closure
+  // only has R in it, create a phi a def for R. Otherwise, create a phi,
+  // and add a def for each S in the closure.
+
+  // Sort the refs so that the phis will be created in a deterministic order.
+  llvm::sort(MaxRefs);
+  // Remove duplicates.
+  auto NewEnd = std::unique(MaxRefs.begin(), MaxRefs.end());
+  MaxRefs.erase(NewEnd, MaxRefs.end());
+
+  auto Aliased = [this,&MaxRefs](RegisterRef RR,
+                                 std::vector<unsigned> &Closure) -> bool {
+    for (unsigned I : Closure)
+      if (PRI.alias(RR, MaxRefs[I]))
+        return true;
+    return false;
+  };
+
+  // Prepare a list of NodeIds of the block's predecessors.
+  NodeList Preds;
+  const MachineBasicBlock *MBB = BA.Addr->getCode();
+  for (MachineBasicBlock *PB : MBB->predecessors())
+    Preds.push_back(findBlock(PB));
+
+  while (!MaxRefs.empty()) {
+    // Put the first element in the closure, and then add all subsequent
+    // elements from MaxRefs to it, if they alias at least one element
+    // already in the closure.
+    // ClosureIdx: vector of indices in MaxRefs of members of the closure.
+    std::vector<unsigned> ClosureIdx = { 0 };
+    for (unsigned i = 1; i != MaxRefs.size(); ++i)
+      if (Aliased(MaxRefs[i], ClosureIdx))
+        ClosureIdx.push_back(i);
+
+    // Build a phi for the closure.
+    unsigned CS = ClosureIdx.size();
+    NodeAddr<PhiNode*> PA = newPhi(BA);
+
+    // Add defs.
+    for (unsigned X = 0; X != CS; ++X) {
+      RegisterRef RR = MaxRefs[ClosureIdx[X]];
+      uint16_t PhiFlags = NodeAttrs::PhiRef | NodeAttrs::Preserving;
+      NodeAddr<DefNode*> DA = newDef(PA, RR, PhiFlags);
+      PA.Addr->addMember(DA, *this);
+    }
+    // Add phi uses.
+    for (NodeAddr<BlockNode*> PBA : Preds) {
+      for (unsigned X = 0; X != CS; ++X) {
+        RegisterRef RR = MaxRefs[ClosureIdx[X]];
+        NodeAddr<PhiUseNode*> PUA = newPhiUse(PA, RR, PBA);
+        PA.Addr->addMember(PUA, *this);
+      }
+    }
+
+    // Erase from MaxRefs all elements in the closure.
+    auto Begin = MaxRefs.begin();
+    for (unsigned i = ClosureIdx.size(); i != 0; --i)
+      MaxRefs.erase(Begin + ClosureIdx[i-1]);
+  }
+}
+
+// Remove any unneeded phi nodes that were created during the build process.
+void DataFlowGraph::removeUnusedPhis() {
+  // This will remove unused phis, i.e. phis where each def does not reach
+  // any uses or other defs. This will not detect or remove circular phi
+  // chains that are otherwise dead. Unused/dead phis are created during
+  // the build process and this function is intended to remove these cases
+  // that are easily determinable to be unnecessary.
+
+  SetVector<NodeId> PhiQ;
+  for (NodeAddr<BlockNode*> BA : Func.Addr->members(*this)) {
+    for (auto P : BA.Addr->members_if(IsPhi, *this))
+      PhiQ.insert(P.Id);
+  }
+
+  static auto HasUsedDef = [](NodeList &Ms) -> bool {
+    for (NodeAddr<NodeBase*> M : Ms) {
+      if (M.Addr->getKind() != NodeAttrs::Def)
+        continue;
+      NodeAddr<DefNode*> DA = M;
+      if (DA.Addr->getReachedDef() != 0 || DA.Addr->getReachedUse() != 0)
+        return true;
+    }
+    return false;
+  };
+
+  // Any phi, if it is removed, may affect other phis (make them dead).
+  // For each removed phi, collect the potentially affected phis and add
+  // them back to the queue.
+  while (!PhiQ.empty()) {
+    auto PA = addr<PhiNode*>(PhiQ[0]);
+    PhiQ.remove(PA.Id);
+    NodeList Refs = PA.Addr->members(*this);
+    if (HasUsedDef(Refs))
+      continue;
+    for (NodeAddr<RefNode*> RA : Refs) {
+      if (NodeId RD = RA.Addr->getReachingDef()) {
+        auto RDA = addr<DefNode*>(RD);
+        NodeAddr<InstrNode*> OA = RDA.Addr->getOwner(*this);
+        if (IsPhi(OA))
+          PhiQ.insert(OA.Id);
+      }
+      if (RA.Addr->isDef())
+        unlinkDef(RA, true);
+      else
+        unlinkUse(RA, true);
+    }
+    NodeAddr<BlockNode*> BA = PA.Addr->getOwner(*this);
+    BA.Addr->removeMember(PA, *this);
+  }
+}
+
+// For a given reference node TA in an instruction node IA, connect the
+// reaching def of TA to the appropriate def node. Create any shadow nodes
+// as appropriate.
+template <typename T>
+void DataFlowGraph::linkRefUp(NodeAddr<InstrNode*> IA, NodeAddr<T> TA,
+      DefStack &DS) {
+  if (DS.empty())
+    return;
+  RegisterRef RR = TA.Addr->getRegRef(*this);
+  NodeAddr<T> TAP;
+
+  // References from the def stack that have been examined so far.
+  RegisterAggr Defs(PRI);
+
+  for (auto I = DS.top(), E = DS.bottom(); I != E; I.down()) {
+    RegisterRef QR = I->Addr->getRegRef(*this);
+
+    // Skip all defs that are aliased to any of the defs that we have already
+    // seen. If this completes a cover of RR, stop the stack traversal.
+    bool Alias = Defs.hasAliasOf(QR);
+    bool Cover = Defs.insert(QR).hasCoverOf(RR);
+    if (Alias) {
+      if (Cover)
+        break;
+      continue;
+    }
+
+    // The reaching def.
+    NodeAddr<DefNode*> RDA = *I;
+
+    // Pick the reached node.
+    if (TAP.Id == 0) {
+      TAP = TA;
+    } else {
+      // Mark the existing ref as "shadow" and create a new shadow.
+      TAP.Addr->setFlags(TAP.Addr->getFlags() | NodeAttrs::Shadow);
+      TAP = getNextShadow(IA, TAP, true);
+    }
+
+    // Create the link.
+    TAP.Addr->linkToDef(TAP.Id, RDA);
+
+    if (Cover)
+      break;
+  }
+}
+
+// Create data-flow links for all reference nodes in the statement node SA.
+template <typename Predicate>
+void DataFlowGraph::linkStmtRefs(DefStackMap &DefM, NodeAddr<StmtNode*> SA,
+      Predicate P) {
+#ifndef NDEBUG
+  RegisterSet Defs;
+#endif
+
+  // Link all nodes (upwards in the data-flow) with their reaching defs.
+  for (NodeAddr<RefNode*> RA : SA.Addr->members_if(P, *this)) {
+    uint16_t Kind = RA.Addr->getKind();
+    assert(Kind == NodeAttrs::Def || Kind == NodeAttrs::Use);
+    RegisterRef RR = RA.Addr->getRegRef(*this);
+#ifndef NDEBUG
+    // Do not expect multiple defs of the same reference.
+    assert(Kind != NodeAttrs::Def || !Defs.count(RR));
+    Defs.insert(RR);
+#endif
+
+    auto F = DefM.find(RR.Reg);
+    if (F == DefM.end())
+      continue;
+    DefStack &DS = F->second;
+    if (Kind == NodeAttrs::Use)
+      linkRefUp<UseNode*>(SA, RA, DS);
+    else if (Kind == NodeAttrs::Def)
+      linkRefUp<DefNode*>(SA, RA, DS);
+    else
+      llvm_unreachable("Unexpected node in instruction");
+  }
+}
+
+// Create data-flow links for all instructions in the block node BA. This
+// will include updating any phi nodes in BA.
+void DataFlowGraph::linkBlockRefs(DefStackMap &DefM, NodeAddr<BlockNode*> BA) {
+  // Push block delimiters.
+  markBlock(BA.Id, DefM);
+
+  auto IsClobber = [] (NodeAddr<RefNode*> RA) -> bool {
+    return IsDef(RA) && (RA.Addr->getFlags() & NodeAttrs::Clobbering);
+  };
+  auto IsNoClobber = [] (NodeAddr<RefNode*> RA) -> bool {
+    return IsDef(RA) && !(RA.Addr->getFlags() & NodeAttrs::Clobbering);
+  };
+
+  assert(BA.Addr && "block node address is needed to create a data-flow link");
+  // For each non-phi instruction in the block, link all the defs and uses
+  // to their reaching defs. For any member of the block (including phis),
+  // push the defs on the corresponding stacks.
+  for (NodeAddr<InstrNode*> IA : BA.Addr->members(*this)) {
+    // Ignore phi nodes here. They will be linked part by part from the
+    // predecessors.
+    if (IA.Addr->getKind() == NodeAttrs::Stmt) {
+      linkStmtRefs(DefM, IA, IsUse);
+      linkStmtRefs(DefM, IA, IsClobber);
+    }
+
+    // Push the definitions on the stack.
+    pushClobbers(IA, DefM);
+
+    if (IA.Addr->getKind() == NodeAttrs::Stmt)
+      linkStmtRefs(DefM, IA, IsNoClobber);
+
+    pushDefs(IA, DefM);
+  }
+
+  // Recursively process all children in the dominator tree.
+  MachineDomTreeNode *N = MDT.getNode(BA.Addr->getCode());
+  for (auto I : *N) {
+    MachineBasicBlock *SB = I->getBlock();
+    NodeAddr<BlockNode*> SBA = findBlock(SB);
+    linkBlockRefs(DefM, SBA);
+  }
+
+  // Link the phi uses from the successor blocks.
+  auto IsUseForBA = [BA](NodeAddr<NodeBase*> NA) -> bool {
+    if (NA.Addr->getKind() != NodeAttrs::Use)
+      return false;
+    assert(NA.Addr->getFlags() & NodeAttrs::PhiRef);
+    NodeAddr<PhiUseNode*> PUA = NA;
+    return PUA.Addr->getPredecessor() == BA.Id;
+  };
+
+  RegisterSet EHLiveIns = getLandingPadLiveIns();
+  MachineBasicBlock *MBB = BA.Addr->getCode();
+
+  for (MachineBasicBlock *SB : MBB->successors()) {
+    bool IsEHPad = SB->isEHPad();
+    NodeAddr<BlockNode*> SBA = findBlock(SB);
+    for (NodeAddr<InstrNode*> IA : SBA.Addr->members_if(IsPhi, *this)) {
+      // Do not link phi uses for landing pad live-ins.
+      if (IsEHPad) {
+        // Find what register this phi is for.
+        NodeAddr<RefNode*> RA = IA.Addr->getFirstMember(*this);
+        assert(RA.Id != 0);
+        if (EHLiveIns.count(RA.Addr->getRegRef(*this)))
+          continue;
+      }
+      // Go over each phi use associated with MBB, and link it.
+      for (auto U : IA.Addr->members_if(IsUseForBA, *this)) {
+        NodeAddr<PhiUseNode*> PUA = U;
+        RegisterRef RR = PUA.Addr->getRegRef(*this);
+        linkRefUp<UseNode*>(IA, PUA, DefM[RR.Reg]);
+      }
+    }
+  }
+
+  // Pop all defs from this block from the definition stacks.
+  releaseBlock(BA.Id, DefM);
+}
+
+// Remove the use node UA from any data-flow and structural links.
+void DataFlowGraph::unlinkUseDF(NodeAddr<UseNode*> UA) {
+  NodeId RD = UA.Addr->getReachingDef();
+  NodeId Sib = UA.Addr->getSibling();
+
+  if (RD == 0) {
+    assert(Sib == 0);
+    return;
+  }
+
+  auto RDA = addr<DefNode*>(RD);
+  auto TA = addr<UseNode*>(RDA.Addr->getReachedUse());
+  if (TA.Id == UA.Id) {
+    RDA.Addr->setReachedUse(Sib);
+    return;
+  }
+
+  while (TA.Id != 0) {
+    NodeId S = TA.Addr->getSibling();
+    if (S == UA.Id) {
+      TA.Addr->setSibling(UA.Addr->getSibling());
+      return;
+    }
+    TA = addr<UseNode*>(S);
+  }
+}
+
+// Remove the def node DA from any data-flow and structural links.
+void DataFlowGraph::unlinkDefDF(NodeAddr<DefNode*> DA) {
+  //
+  //         RD
+  //         | reached
+  //         | def
+  //         :
+  //         .
+  //        +----+
+  // ... -- | DA | -- ... -- 0  : sibling chain of DA
+  //        +----+
+  //         |  | reached
+  //         |  : def
+  //         |  .
+  //         | ...  : Siblings (defs)
+  //         |
+  //         : reached
+  //         . use
+  //        ... : sibling chain of reached uses
+
+  NodeId RD = DA.Addr->getReachingDef();
+
+  // Visit all siblings of the reached def and reset their reaching defs.
+  // Also, defs reached by DA are now "promoted" to being reached by RD,
+  // so all of them will need to be spliced into the sibling chain where
+  // DA belongs.
+  auto getAllNodes = [this] (NodeId N) -> NodeList {
+    NodeList Res;
+    while (N) {
+      auto RA = addr<RefNode*>(N);
+      // Keep the nodes in the exact sibling order.
+      Res.push_back(RA);
+      N = RA.Addr->getSibling();
+    }
+    return Res;
+  };
+  NodeList ReachedDefs = getAllNodes(DA.Addr->getReachedDef());
+  NodeList ReachedUses = getAllNodes(DA.Addr->getReachedUse());
+
+  if (RD == 0) {
+    for (NodeAddr<RefNode*> I : ReachedDefs)
+      I.Addr->setSibling(0);
+    for (NodeAddr<RefNode*> I : ReachedUses)
+      I.Addr->setSibling(0);
+  }
+  for (NodeAddr<DefNode*> I : ReachedDefs)
+    I.Addr->setReachingDef(RD);
+  for (NodeAddr<UseNode*> I : ReachedUses)
+    I.Addr->setReachingDef(RD);
+
+  NodeId Sib = DA.Addr->getSibling();
+  if (RD == 0) {
+    assert(Sib == 0);
+    return;
+  }
+
+  // Update the reaching def node and remove DA from the sibling list.
+  auto RDA = addr<DefNode*>(RD);
+  auto TA = addr<DefNode*>(RDA.Addr->getReachedDef());
+  if (TA.Id == DA.Id) {
+    // If DA is the first reached def, just update the RD's reached def
+    // to the DA's sibling.
+    RDA.Addr->setReachedDef(Sib);
+  } else {
+    // Otherwise, traverse the sibling list of the reached defs and remove
+    // DA from it.
+    while (TA.Id != 0) {
+      NodeId S = TA.Addr->getSibling();
+      if (S == DA.Id) {
+        TA.Addr->setSibling(Sib);
+        break;
+      }
+      TA = addr<DefNode*>(S);
+    }
+  }
+
+  // Splice the DA's reached defs into the RDA's reached def chain.
+  if (!ReachedDefs.empty()) {
+    auto Last = NodeAddr<DefNode*>(ReachedDefs.back());
+    Last.Addr->setSibling(RDA.Addr->getReachedDef());
+    RDA.Addr->setReachedDef(ReachedDefs.front().Id);
+  }
+  // Splice the DA's reached uses into the RDA's reached use chain.
+  if (!ReachedUses.empty()) {
+    auto Last = NodeAddr<UseNode*>(ReachedUses.back());
+    Last.Addr->setSibling(RDA.Addr->getReachedUse());
+    RDA.Addr->setReachedUse(ReachedUses.front().Id);
+  }
+}