1 files changed, 0 insertions, 2106 deletions

diff --git a/contrib/llvm/lib/CodeGen/BranchFolding.cpp b/contrib/llvm/lib/CodeGen/BranchFolding.cpp
deleted file mode 100644
index fb54b5d6c8d8..000000000000
--- a/contrib/llvm/lib/CodeGen/BranchFolding.cpp
+++ /dev/null
@@ -1,2106 +0,0 @@
-//===- BranchFolding.cpp - Fold machine code branch instructions ----------===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-//
-// This pass forwards branches to unconditional branches to make them branch
-// directly to the target block.  This pass often results in dead MBB's, which
-// it then removes.
-//
-// Note that this pass must be run after register allocation, it cannot handle
-// SSA form. It also must handle virtual registers for targets that emit virtual
-// ISA (e.g. NVPTX).
-//
-//===----------------------------------------------------------------------===//
-
-#include "BranchFolding.h"
-#include "llvm/ADT/BitVector.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallSet.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/CodeGen/Analysis.h"
-#include "llvm/CodeGen/LivePhysRegs.h"
-#include "llvm/CodeGen/MachineBasicBlock.h"
-#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
-#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
-#include "llvm/CodeGen/MachineFunction.h"
-#include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/CodeGen/MachineInstr.h"
-#include "llvm/CodeGen/MachineInstrBuilder.h"
-#include "llvm/CodeGen/MachineJumpTableInfo.h"
-#include "llvm/CodeGen/MachineLoopInfo.h"
-#include "llvm/CodeGen/MachineModuleInfo.h"
-#include "llvm/CodeGen/MachineOperand.h"
-#include "llvm/CodeGen/MachineRegisterInfo.h"
-#include "llvm/CodeGen/TargetInstrInfo.h"
-#include "llvm/CodeGen/TargetOpcodes.h"
-#include "llvm/CodeGen/TargetPassConfig.h"
-#include "llvm/CodeGen/TargetRegisterInfo.h"
-#include "llvm/CodeGen/TargetSubtargetInfo.h"
-#include "llvm/IR/DebugInfoMetadata.h"
-#include "llvm/IR/DebugLoc.h"
-#include "llvm/IR/Function.h"
-#include "llvm/MC/LaneBitmask.h"
-#include "llvm/MC/MCRegisterInfo.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/BlockFrequency.h"
-#include "llvm/Support/BranchProbability.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/raw_ostream.h"
-#include "llvm/Target/TargetMachine.h"
-#include <cassert>
-#include <cstddef>
-#include <iterator>
-#include <numeric>
-#include <vector>
-
-using namespace llvm;
-
-#define DEBUG_TYPE "branch-folder"
-
-STATISTIC(NumDeadBlocks, "Number of dead blocks removed");
-STATISTIC(NumBranchOpts, "Number of branches optimized");
-STATISTIC(NumTailMerge , "Number of block tails merged");
-STATISTIC(NumHoist     , "Number of times common instructions are hoisted");
-STATISTIC(NumTailCalls,  "Number of tail calls optimized");
-
-static cl::opt<cl::boolOrDefault> FlagEnableTailMerge("enable-tail-merge",
-                              cl::init(cl::BOU_UNSET), cl::Hidden);
-
-// Throttle for huge numbers of predecessors (compile speed problems)
-static cl::opt<unsigned>
-TailMergeThreshold("tail-merge-threshold",
-          cl::desc("Max number of predecessors to consider tail merging"),
-          cl::init(150), cl::Hidden);
-
-// Heuristic for tail merging (and, inversely, tail duplication).
-// TODO: This should be replaced with a target query.
-static cl::opt<unsigned>
-TailMergeSize("tail-merge-size",
-              cl::desc("Min number of instructions to consider tail merging"),
-              cl::init(3), cl::Hidden);
-
-namespace {
-
-  /// BranchFolderPass - Wrap branch folder in a machine function pass.
-  class BranchFolderPass : public MachineFunctionPass {
-  public:
-    static char ID;
-
-    explicit BranchFolderPass(): MachineFunctionPass(ID) {}
-
-    bool runOnMachineFunction(MachineFunction &MF) override;
-
-    void getAnalysisUsage(AnalysisUsage &AU) const override {
-      AU.addRequired<MachineBlockFrequencyInfo>();
-      AU.addRequired<MachineBranchProbabilityInfo>();
-      AU.addRequired<TargetPassConfig>();
-      MachineFunctionPass::getAnalysisUsage(AU);
-    }
-  };
-
-} // end anonymous namespace
-
-char BranchFolderPass::ID = 0;
-
-char &llvm::BranchFolderPassID = BranchFolderPass::ID;
-
-INITIALIZE_PASS(BranchFolderPass, DEBUG_TYPE,
-                "Control Flow Optimizer", false, false)
-
-bool BranchFolderPass::runOnMachineFunction(MachineFunction &MF) {
-  if (skipFunction(MF.getFunction()))
-    return false;
-
-  TargetPassConfig *PassConfig = &getAnalysis<TargetPassConfig>();
-  // TailMerge can create jump into if branches that make CFG irreducible for
-  // HW that requires structurized CFG.
-  bool EnableTailMerge = !MF.getTarget().requiresStructuredCFG() &&
-                         PassConfig->getEnableTailMerge();
-  BranchFolder::MBFIWrapper MBBFreqInfo(
-      getAnalysis<MachineBlockFrequencyInfo>());
-  BranchFolder Folder(EnableTailMerge, /*CommonHoist=*/true, MBBFreqInfo,
-                      getAnalysis<MachineBranchProbabilityInfo>());
-  return Folder.OptimizeFunction(MF, MF.getSubtarget().getInstrInfo(),
-                                 MF.getSubtarget().getRegisterInfo(),
-                                 getAnalysisIfAvailable<MachineModuleInfo>());
-}
-
-BranchFolder::BranchFolder(bool defaultEnableTailMerge, bool CommonHoist,
-                           MBFIWrapper &FreqInfo,
-                           const MachineBranchProbabilityInfo &ProbInfo,
-                           unsigned MinTailLength)
-    : EnableHoistCommonCode(CommonHoist), MinCommonTailLength(MinTailLength),
-      MBBFreqInfo(FreqInfo), MBPI(ProbInfo) {
-  if (MinCommonTailLength == 0)
-    MinCommonTailLength = TailMergeSize;
-  switch (FlagEnableTailMerge) {
-  case cl::BOU_UNSET: EnableTailMerge = defaultEnableTailMerge; break;
-  case cl::BOU_TRUE: EnableTailMerge = true; break;
-  case cl::BOU_FALSE: EnableTailMerge = false; break;
-  }
-}
-
-void BranchFolder::RemoveDeadBlock(MachineBasicBlock *MBB) {
-  assert(MBB->pred_empty() && "MBB must be dead!");
-  LLVM_DEBUG(dbgs() << "\nRemoving MBB: " << *MBB);
-
-  MachineFunction *MF = MBB->getParent();
-  // drop all successors.
-  while (!MBB->succ_empty())
-    MBB->removeSuccessor(MBB->succ_end()-1);
-
-  // Avoid matching if this pointer gets reused.
-  TriedMerging.erase(MBB);
-
-  // Remove the block.
-  MF->erase(MBB);
-  EHScopeMembership.erase(MBB);
-  if (MLI)
-    MLI->removeBlock(MBB);
-}
-
-bool BranchFolder::OptimizeFunction(MachineFunction &MF,
-                                    const TargetInstrInfo *tii,
-                                    const TargetRegisterInfo *tri,
-                                    MachineModuleInfo *mmi,
-                                    MachineLoopInfo *mli, bool AfterPlacement) {
-  if (!tii) return false;
-
-  TriedMerging.clear();
-
-  MachineRegisterInfo &MRI = MF.getRegInfo();
-  AfterBlockPlacement = AfterPlacement;
-  TII = tii;
-  TRI = tri;
-  MMI = mmi;
-  MLI = mli;
-  this->MRI = &MRI;
-
-  UpdateLiveIns = MRI.tracksLiveness() && TRI->trackLivenessAfterRegAlloc(MF);
-  if (!UpdateLiveIns)
-    MRI.invalidateLiveness();
-
-  // Fix CFG.  The later algorithms expect it to be right.
-  bool MadeChange = false;
-  for (MachineBasicBlock &MBB : MF) {
-    MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
-    SmallVector<MachineOperand, 4> Cond;
-    if (!TII->analyzeBranch(MBB, TBB, FBB, Cond, true))
-      MadeChange |= MBB.CorrectExtraCFGEdges(TBB, FBB, !Cond.empty());
-  }
-
-  // Recalculate EH scope membership.
-  EHScopeMembership = getEHScopeMembership(MF);
-
-  bool MadeChangeThisIteration = true;
-  while (MadeChangeThisIteration) {
-    MadeChangeThisIteration    = TailMergeBlocks(MF);
-    // No need to clean up if tail merging does not change anything after the
-    // block placement.
-    if (!AfterBlockPlacement || MadeChangeThisIteration)
-      MadeChangeThisIteration |= OptimizeBranches(MF);
-    if (EnableHoistCommonCode)
-      MadeChangeThisIteration |= HoistCommonCode(MF);
-    MadeChange |= MadeChangeThisIteration;
-  }
-
-  // See if any jump tables have become dead as the code generator
-  // did its thing.
-  MachineJumpTableInfo *JTI = MF.getJumpTableInfo();
-  if (!JTI)
-    return MadeChange;
-
-  // Walk the function to find jump tables that are live.
-  BitVector JTIsLive(JTI->getJumpTables().size());
-  for (const MachineBasicBlock &BB : MF) {
-    for (const MachineInstr &I : BB)
-      for (const MachineOperand &Op : I.operands()) {
-        if (!Op.isJTI()) continue;
-
-        // Remember that this JT is live.
-        JTIsLive.set(Op.getIndex());
-      }
-  }
-
-  // Finally, remove dead jump tables.  This happens when the
-  // indirect jump was unreachable (and thus deleted).
-  for (unsigned i = 0, e = JTIsLive.size(); i != e; ++i)
-    if (!JTIsLive.test(i)) {
-      JTI->RemoveJumpTable(i);
-      MadeChange = true;
-    }
-
-  return MadeChange;
-}
-
-//===----------------------------------------------------------------------===//
-//  Tail Merging of Blocks
-//===----------------------------------------------------------------------===//
-
-/// HashMachineInstr - Compute a hash value for MI and its operands.
-static unsigned HashMachineInstr(const MachineInstr &MI) {
-  unsigned Hash = MI.getOpcode();
-  for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
-    const MachineOperand &Op = MI.getOperand(i);
-
-    // Merge in bits from the operand if easy. We can't use MachineOperand's
-    // hash_code here because it's not deterministic and we sort by hash value
-    // later.
-    unsigned OperandHash = 0;
-    switch (Op.getType()) {
-    case MachineOperand::MO_Register:
-      OperandHash = Op.getReg();
-      break;
-    case MachineOperand::MO_Immediate:
-      OperandHash = Op.getImm();
-      break;
-    case MachineOperand::MO_MachineBasicBlock:
-      OperandHash = Op.getMBB()->getNumber();
-      break;
-    case MachineOperand::MO_FrameIndex:
-    case MachineOperand::MO_ConstantPoolIndex:
-    case MachineOperand::MO_JumpTableIndex:
-      OperandHash = Op.getIndex();
-      break;
-    case MachineOperand::MO_GlobalAddress:
-    case MachineOperand::MO_ExternalSymbol:
-      // Global address / external symbol are too hard, don't bother, but do
-      // pull in the offset.
-      OperandHash = Op.getOffset();
-      break;
-    default:
-      break;
-    }
-
-    Hash += ((OperandHash << 3) | Op.getType()) << (i & 31);
-  }
-  return Hash;
-}
-
-/// HashEndOfMBB - Hash the last instruction in the MBB.
-static unsigned HashEndOfMBB(const MachineBasicBlock &MBB) {
-  MachineBasicBlock::const_iterator I = MBB.getLastNonDebugInstr();
-  if (I == MBB.end())
-    return 0;
-
-  return HashMachineInstr(*I);
-}
-
-///  Whether MI should be counted as an instruction when calculating common tail.
-static bool countsAsInstruction(const MachineInstr &MI) {
-  return !(MI.isDebugInstr() || MI.isCFIInstruction());
-}
-
-/// ComputeCommonTailLength - Given two machine basic blocks, compute the number
-/// of instructions they actually have in common together at their end.  Return
-/// iterators for the first shared instruction in each block.
-static unsigned ComputeCommonTailLength(MachineBasicBlock *MBB1,
-                                        MachineBasicBlock *MBB2,
-                                        MachineBasicBlock::iterator &I1,
-                                        MachineBasicBlock::iterator &I2) {
-  I1 = MBB1->end();
-  I2 = MBB2->end();
-
-  unsigned TailLen = 0;
-  while (I1 != MBB1->begin() && I2 != MBB2->begin()) {
-    --I1; --I2;
-    // Skip debugging pseudos; necessary to avoid changing the code.
-    while (!countsAsInstruction(*I1)) {
-      if (I1==MBB1->begin()) {
-        while (!countsAsInstruction(*I2)) {
-          if (I2==MBB2->begin()) {
-            // I1==DBG at begin; I2==DBG at begin
-            goto SkipTopCFIAndReturn;
-          }
-          --I2;
-        }
-        ++I2;
-        // I1==DBG at begin; I2==non-DBG, or first of DBGs not at begin
-        goto SkipTopCFIAndReturn;
-      }
-      --I1;
-    }
-    // I1==first (untested) non-DBG preceding known match
-    while (!countsAsInstruction(*I2)) {
-      if (I2==MBB2->begin()) {
-        ++I1;
-        // I1==non-DBG, or first of DBGs not at begin; I2==DBG at begin
-        goto SkipTopCFIAndReturn;
-      }
-      --I2;
-    }
-    // I1, I2==first (untested) non-DBGs preceding known match
-    if (!I1->isIdenticalTo(*I2) ||
-        // FIXME: This check is dubious. It's used to get around a problem where
-        // people incorrectly expect inline asm directives to remain in the same
-        // relative order. This is untenable because normal compiler
-        // optimizations (like this one) may reorder and/or merge these
-        // directives.
-        I1->isInlineAsm()) {
-      ++I1; ++I2;
-      break;
-    }
-    ++TailLen;
-  }
-  // Back past possible debugging pseudos at beginning of block.  This matters
-  // when one block differs from the other only by whether debugging pseudos
-  // are present at the beginning. (This way, the various checks later for
-  // I1==MBB1->begin() work as expected.)
-  if (I1 == MBB1->begin() && I2 != MBB2->begin()) {
-    --I2;
-    while (I2->isDebugInstr()) {
-      if (I2 == MBB2->begin())
-        return TailLen;
-      --I2;
-    }
-    ++I2;
-  }
-  if (I2 == MBB2->begin() && I1 != MBB1->begin()) {
-    --I1;
-    while (I1->isDebugInstr()) {
-      if (I1 == MBB1->begin())
-        return TailLen;
-      --I1;
-    }
-    ++I1;
-  }
-
-SkipTopCFIAndReturn:
-  // Ensure that I1 and I2 do not point to a CFI_INSTRUCTION. This can happen if
-  // I1 and I2 are non-identical when compared and then one or both of them ends
-  // up pointing to a CFI instruction after being incremented. For example:
-  /*
-    BB1:
-    ...
-    INSTRUCTION_A
-    ADD32ri8  <- last common instruction
-    ...
-    BB2:
-    ...
-    INSTRUCTION_B
-    CFI_INSTRUCTION
-    ADD32ri8  <- last common instruction
-    ...
-  */
-  // When INSTRUCTION_A and INSTRUCTION_B are compared as not equal, after
-  // incrementing the iterators, I1 will point to ADD, however I2 will point to
-  // the CFI instruction. Later on, this leads to BB2 being 'hacked off' at the
-  // wrong place (in ReplaceTailWithBranchTo()) which results in losing this CFI
-  // instruction.
-  while (I1 != MBB1->end() && I1->isCFIInstruction()) {
-    ++I1;
-  }
-
-  while (I2 != MBB2->end() && I2->isCFIInstruction()) {
-    ++I2;
-  }
-
-  return TailLen;
-}
-
-void BranchFolder::replaceTailWithBranchTo(MachineBasicBlock::iterator OldInst,
-                                           MachineBasicBlock &NewDest) {
-  if (UpdateLiveIns) {
-    // OldInst should always point to an instruction.
-    MachineBasicBlock &OldMBB = *OldInst->getParent();
-    LiveRegs.clear();
-    LiveRegs.addLiveOuts(OldMBB);
-    // Move backward to the place where will insert the jump.
-    MachineBasicBlock::iterator I = OldMBB.end();
-    do {
-      --I;
-      LiveRegs.stepBackward(*I);
-    } while (I != OldInst);
-
-    // Merging the tails may have switched some undef operand to non-undef ones.
-    // Add IMPLICIT_DEFS into OldMBB as necessary to have a definition of the
-    // register.
-    for (MachineBasicBlock::RegisterMaskPair P : NewDest.liveins()) {
-      // We computed the liveins with computeLiveIn earlier and should only see
-      // full registers:
-      assert(P.LaneMask == LaneBitmask::getAll() &&
-             "Can only handle full register.");
-      MCPhysReg Reg = P.PhysReg;
-      if (!LiveRegs.available(*MRI, Reg))
-        continue;
-      DebugLoc DL;
-      BuildMI(OldMBB, OldInst, DL, TII->get(TargetOpcode::IMPLICIT_DEF), Reg);
-    }
-  }
-
-  TII->ReplaceTailWithBranchTo(OldInst, &NewDest);
-  ++NumTailMerge;
-}
-
-MachineBasicBlock *BranchFolder::SplitMBBAt(MachineBasicBlock &CurMBB,
-                                            MachineBasicBlock::iterator BBI1,
-                                            const BasicBlock *BB) {
-  if (!TII->isLegalToSplitMBBAt(CurMBB, BBI1))
-    return nullptr;
-
-  MachineFunction &MF = *CurMBB.getParent();
-
-  // Create the fall-through block.
-  MachineFunction::iterator MBBI = CurMBB.getIterator();
-  MachineBasicBlock *NewMBB = MF.CreateMachineBasicBlock(BB);
-  CurMBB.getParent()->insert(++MBBI, NewMBB);
-
-  // Move all the successors of this block to the specified block.
-  NewMBB->transferSuccessors(&CurMBB);
-
-  // Add an edge from CurMBB to NewMBB for the fall-through.
-  CurMBB.addSuccessor(NewMBB);
-
-  // Splice the code over.
-  NewMBB->splice(NewMBB->end(), &CurMBB, BBI1, CurMBB.end());
-
-  // NewMBB belongs to the same loop as CurMBB.
-  if (MLI)
-    if (MachineLoop *ML = MLI->getLoopFor(&CurMBB))
-      ML->addBasicBlockToLoop(NewMBB, MLI->getBase());
-
-  // NewMBB inherits CurMBB's block frequency.
-  MBBFreqInfo.setBlockFreq(NewMBB, MBBFreqInfo.getBlockFreq(&CurMBB));
-
-  if (UpdateLiveIns)
-    computeAndAddLiveIns(LiveRegs, *NewMBB);
-
-  // Add the new block to the EH scope.
-  const auto &EHScopeI = EHScopeMembership.find(&CurMBB);
-  if (EHScopeI != EHScopeMembership.end()) {
-    auto n = EHScopeI->second;
-    EHScopeMembership[NewMBB] = n;
-  }
-
-  return NewMBB;
-}
-
-/// EstimateRuntime - Make a rough estimate for how long it will take to run
-/// the specified code.
-static unsigned EstimateRuntime(MachineBasicBlock::iterator I,
-                                MachineBasicBlock::iterator E) {
-  unsigned Time = 0;
-  for (; I != E; ++I) {
-    if (!countsAsInstruction(*I))
-      continue;
-    if (I->isCall())
-      Time += 10;
-    else if (I->mayLoad() || I->mayStore())
-      Time += 2;
-    else
-      ++Time;
-  }
-  return Time;
-}
-
-// CurMBB needs to add an unconditional branch to SuccMBB (we removed these
-// branches temporarily for tail merging).  In the case where CurMBB ends
-// with a conditional branch to the next block, optimize by reversing the
-// test and conditionally branching to SuccMBB instead.
-static void FixTail(MachineBasicBlock *CurMBB, MachineBasicBlock *SuccBB,
-                    const TargetInstrInfo *TII) {
-  MachineFunction *MF = CurMBB->getParent();
-  MachineFunction::iterator I = std::next(MachineFunction::iterator(CurMBB));
-  MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
-  SmallVector<MachineOperand, 4> Cond;
-  DebugLoc dl = CurMBB->findBranchDebugLoc();
-  if (I != MF->end() && !TII->analyzeBranch(*CurMBB, TBB, FBB, Cond, true)) {
-    MachineBasicBlock *NextBB = &*I;
-    if (TBB == NextBB && !Cond.empty() && !FBB) {
-      if (!TII->reverseBranchCondition(Cond)) {
-        TII->removeBranch(*CurMBB);
-        TII->insertBranch(*CurMBB, SuccBB, nullptr, Cond, dl);
-        return;
-      }
-    }
-  }
-  TII->insertBranch(*CurMBB, SuccBB, nullptr,
-                    SmallVector<MachineOperand, 0>(), dl);
-}
-
-bool
-BranchFolder::MergePotentialsElt::operator<(const MergePotentialsElt &o) const {
-  if (getHash() < o.getHash())
-    return true;
-  if (getHash() > o.getHash())
-    return false;
-  if (getBlock()->getNumber() < o.getBlock()->getNumber())
-    return true;
-  if (getBlock()->getNumber() > o.getBlock()->getNumber())
-    return false;
-  // _GLIBCXX_DEBUG checks strict weak ordering, which involves comparing
-  // an object with itself.
-#ifndef _GLIBCXX_DEBUG
-  llvm_unreachable("Predecessor appears twice");
-#else
-  return false;
-#endif
-}
-
-BlockFrequency
-BranchFolder::MBFIWrapper::getBlockFreq(const MachineBasicBlock *MBB) const {
-  auto I = MergedBBFreq.find(MBB);
-
-  if (I != MergedBBFreq.end())
-    return I->second;
-
-  return MBFI.getBlockFreq(MBB);
-}
-
-void BranchFolder::MBFIWrapper::setBlockFreq(const MachineBasicBlock *MBB,
-                                             BlockFrequency F) {
-  MergedBBFreq[MBB] = F;
-}
-
-raw_ostream &
-BranchFolder::MBFIWrapper::printBlockFreq(raw_ostream &OS,
-                                          const MachineBasicBlock *MBB) const {
-  return MBFI.printBlockFreq(OS, getBlockFreq(MBB));
-}
-
-raw_ostream &
-BranchFolder::MBFIWrapper::printBlockFreq(raw_ostream &OS,
-                                          const BlockFrequency Freq) const {
-  return MBFI.printBlockFreq(OS, Freq);
-}
-
-void BranchFolder::MBFIWrapper::view(const Twine &Name, bool isSimple) {
-  MBFI.view(Name, isSimple);
-}
-
-uint64_t
-BranchFolder::MBFIWrapper::getEntryFreq() const {
-  return MBFI.getEntryFreq();
-}
-
-/// CountTerminators - Count the number of terminators in the given
-/// block and set I to the position of the first non-terminator, if there
-/// is one, or MBB->end() otherwise.
-static unsigned CountTerminators(MachineBasicBlock *MBB,
-                                 MachineBasicBlock::iterator &I) {
-  I = MBB->end();
-  unsigned NumTerms = 0;
-  while (true) {
-    if (I == MBB->begin()) {
-      I = MBB->end();
-      break;
-    }
-    --I;
-    if (!I->isTerminator()) break;
-    ++NumTerms;
-  }
-  return NumTerms;
-}
-
-/// A no successor, non-return block probably ends in unreachable and is cold.
-/// Also consider a block that ends in an indirect branch to be a return block,
-/// since many targets use plain indirect branches to return.
-static bool blockEndsInUnreachable(const MachineBasicBlock *MBB) {
-  if (!MBB->succ_empty())
-    return false;
-  if (MBB->empty())
-    return true;
-  return !(MBB->back().isReturn() || MBB->back().isIndirectBranch());
-}
-
-/// ProfitableToMerge - Check if two machine basic blocks have a common tail
-/// and decide if it would be profitable to merge those tails.  Return the
-/// length of the common tail and iterators to the first common instruction
-/// in each block.
-/// MBB1, MBB2      The blocks to check
-/// MinCommonTailLength  Minimum size of tail block to be merged.
-/// CommonTailLen   Out parameter to record the size of the shared tail between
-///                 MBB1 and MBB2
-/// I1, I2          Iterator references that will be changed to point to the first
-///                 instruction in the common tail shared by MBB1,MBB2
-/// SuccBB          A common successor of MBB1, MBB2 which are in a canonical form
-///                 relative to SuccBB
-/// PredBB          The layout predecessor of SuccBB, if any.
-/// EHScopeMembership  map from block to EH scope #.
-/// AfterPlacement  True if we are merging blocks after layout. Stricter
-///                 thresholds apply to prevent undoing tail-duplication.
-static bool
-ProfitableToMerge(MachineBasicBlock *MBB1, MachineBasicBlock *MBB2,
-                  unsigned MinCommonTailLength, unsigned &CommonTailLen,
-                  MachineBasicBlock::iterator &I1,
-                  MachineBasicBlock::iterator &I2, MachineBasicBlock *SuccBB,
-                  MachineBasicBlock *PredBB,
-                  DenseMap<const MachineBasicBlock *, int> &EHScopeMembership,
-                  bool AfterPlacement) {
-  // It is never profitable to tail-merge blocks from two different EH scopes.
-  if (!EHScopeMembership.empty()) {
-    auto EHScope1 = EHScopeMembership.find(MBB1);
-    assert(EHScope1 != EHScopeMembership.end());
-    auto EHScope2 = EHScopeMembership.find(MBB2);
-    assert(EHScope2 != EHScopeMembership.end());
-    if (EHScope1->second != EHScope2->second)
-      return false;
-  }
-
-  CommonTailLen = ComputeCommonTailLength(MBB1, MBB2, I1, I2);
-  if (CommonTailLen == 0)
-    return false;
-  LLVM_DEBUG(dbgs() << "Common tail length of " << printMBBReference(*MBB1)
-                    << " and " << printMBBReference(*MBB2) << " is "
-                    << CommonTailLen << '\n');
-
-  // It's almost always profitable to merge any number of non-terminator
-  // instructions with the block that falls through into the common successor.
-  // This is true only for a single successor. For multiple successors, we are
-  // trading a conditional branch for an unconditional one.
-  // TODO: Re-visit successor size for non-layout tail merging.
-  if ((MBB1 == PredBB || MBB2 == PredBB) &&
-      (!AfterPlacement || MBB1->succ_size() == 1)) {
-    MachineBasicBlock::iterator I;
-    unsigned NumTerms = CountTerminators(MBB1 == PredBB ? MBB2 : MBB1, I);
-    if (CommonTailLen > NumTerms)
-      return true;
-  }
-
-  // If these are identical non-return blocks with no successors, merge them.
-  // Such blocks are typically cold calls to noreturn functions like abort, and
-  // are unlikely to become a fallthrough target after machine block placement.
-  // Tail merging these blocks is unlikely to create additional unconditional
-  // branches, and will reduce the size of this cold code.
-  if (I1 == MBB1->begin() && I2 == MBB2->begin() &&
-      blockEndsInUnreachable(MBB1) && blockEndsInUnreachable(MBB2))
-    return true;
-
-  // If one of the blocks can be completely merged and happens to be in
-  // a position where the other could fall through into it, merge any number
-  // of instructions, because it can be done without a branch.
-  // TODO: If the blocks are not adjacent, move one of them so that they are?
-  if (MBB1->isLayoutSuccessor(MBB2) && I2 == MBB2->begin())
-    return true;
-  if (MBB2->isLayoutSuccessor(MBB1) && I1 == MBB1->begin())
-    return true;
-
-  // If both blocks are identical and end in a branch, merge them unless they
-  // both have a fallthrough predecessor and successor.
-  // We can only do this after block placement because it depends on whether
-  // there are fallthroughs, and we don't know until after layout.
-  if (AfterPlacement && I1 == MBB1->begin() && I2 == MBB2->begin()) {
-    auto BothFallThrough = [](MachineBasicBlock *MBB) {
-      if (MBB->succ_size() != 0 && !MBB->canFallThrough())
-        return false;
-      MachineFunction::iterator I(MBB);
-      MachineFunction *MF = MBB->getParent();
-      return (MBB != &*MF->begin()) && std::prev(I)->canFallThrough();
-    };
-    if (!BothFallThrough(MBB1) || !BothFallThrough(MBB2))
-      return true;
-  }
-
-  // If both blocks have an unconditional branch temporarily stripped out,
-  // count that as an additional common instruction for the following
-  // heuristics. This heuristic is only accurate for single-succ blocks, so to
-  // make sure that during layout merging and duplicating don't crash, we check
-  // for that when merging during layout.
-  unsigned EffectiveTailLen = CommonTailLen;
-  if (SuccBB && MBB1 != PredBB && MBB2 != PredBB &&
-      (MBB1->succ_size() == 1 || !AfterPlacement) &&
-      !MBB1->back().isBarrier() &&
-      !MBB2->back().isBarrier())
-    ++EffectiveTailLen;
-
-  // Check if the common tail is long enough to be worthwhile.
-  if (EffectiveTailLen >= MinCommonTailLength)
-    return true;
-
-  // If we are optimizing for code size, 2 instructions in common is enough if
-  // we don't have to split a block.  At worst we will be introducing 1 new
-  // branch instruction, which is likely to be smaller than the 2
-  // instructions that would be deleted in the merge.
-  MachineFunction *MF = MBB1->getParent();
-  return EffectiveTailLen >= 2 && MF->getFunction().hasOptSize() &&
-         (I1 == MBB1->begin() || I2 == MBB2->begin());
-}
-
-unsigned BranchFolder::ComputeSameTails(unsigned CurHash,
-                                        unsigned MinCommonTailLength,
-                                        MachineBasicBlock *SuccBB,
-                                        MachineBasicBlock *PredBB) {
-  unsigned maxCommonTailLength = 0U;
-  SameTails.clear();
-  MachineBasicBlock::iterator TrialBBI1, TrialBBI2;
-  MPIterator HighestMPIter = std::prev(MergePotentials.end());
-  for (MPIterator CurMPIter = std::prev(MergePotentials.end()),
-                  B = MergePotentials.begin();
-       CurMPIter != B && CurMPIter->getHash() == CurHash; --CurMPIter) {
-    for (MPIterator I = std::prev(CurMPIter); I->getHash() == CurHash; --I) {
-      unsigned CommonTailLen;
-      if (ProfitableToMerge(CurMPIter->getBlock(), I->getBlock(),
-                            MinCommonTailLength,
-                            CommonTailLen, TrialBBI1, TrialBBI2,
-                            SuccBB, PredBB,
-                            EHScopeMembership,
-                            AfterBlockPlacement)) {
-        if (CommonTailLen > maxCommonTailLength) {
-          SameTails.clear();
-          maxCommonTailLength = CommonTailLen;
-          HighestMPIter = CurMPIter;
-          SameTails.push_back(SameTailElt(CurMPIter, TrialBBI1));
-        }
-        if (HighestMPIter == CurMPIter &&
-            CommonTailLen == maxCommonTailLength)
-          SameTails.push_back(SameTailElt(I, TrialBBI2));
-      }
-      if (I == B)
-        break;
-    }
-  }
-  return maxCommonTailLength;
-}
-
-void BranchFolder::RemoveBlocksWithHash(unsigned CurHash,
-                                        MachineBasicBlock *SuccBB,
-                                        MachineBasicBlock *PredBB) {
-  MPIterator CurMPIter, B;
-  for (CurMPIter = std::prev(MergePotentials.end()),
-      B = MergePotentials.begin();
-       CurMPIter->getHash() == CurHash; --CurMPIter) {
-    // Put the unconditional branch back, if we need one.
-    MachineBasicBlock *CurMBB = CurMPIter->getBlock();
-    if (SuccBB && CurMBB != PredBB)
-      FixTail(CurMBB, SuccBB, TII);
-    if (CurMPIter == B)
-      break;
-  }
-  if (CurMPIter->getHash() != CurHash)
-    CurMPIter++;
-  MergePotentials.erase(CurMPIter, MergePotentials.end());
-}
-
-bool BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB,
-                                             MachineBasicBlock *SuccBB,
-                                             unsigned maxCommonTailLength,
-                                             unsigned &commonTailIndex) {
-  commonTailIndex = 0;
-  unsigned TimeEstimate = ~0U;
-  for (unsigned i = 0, e = SameTails.size(); i != e; ++i) {
-    // Use PredBB if possible; that doesn't require a new branch.
-    if (SameTails[i].getBlock() == PredBB) {
-      commonTailIndex = i;
-      break;
-    }
-    // Otherwise, make a (fairly bogus) choice based on estimate of
-    // how long it will take the various blocks to execute.
-    unsigned t = EstimateRuntime(SameTails[i].getBlock()->begin(),
-                                 SameTails[i].getTailStartPos());
-    if (t <= TimeEstimate) {
-      TimeEstimate = t;
-      commonTailIndex = i;
-    }
-  }
-
-  MachineBasicBlock::iterator BBI =
-    SameTails[commonTailIndex].getTailStartPos();
-  MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock();
-
-  LLVM_DEBUG(dbgs() << "\nSplitting " << printMBBReference(*MBB) << ", size "
-                    << maxCommonTailLength);
-
-  // If the split block unconditionally falls-thru to SuccBB, it will be
-  // merged. In control flow terms it should then take SuccBB's name. e.g. If
-  // SuccBB is an inner loop, the common tail is still part of the inner loop.
-  const BasicBlock *BB = (SuccBB && MBB->succ_size() == 1) ?
-    SuccBB->getBasicBlock() : MBB->getBasicBlock();
-  MachineBasicBlock *newMBB = SplitMBBAt(*MBB, BBI, BB);
-  if (!newMBB) {
-    LLVM_DEBUG(dbgs() << "... failed!");
-    return false;
-  }
-
-  SameTails[commonTailIndex].setBlock(newMBB);
-  SameTails[commonTailIndex].setTailStartPos(newMBB->begin());
-
-  // If we split PredBB, newMBB is the new predecessor.
-  if (PredBB == MBB)
-    PredBB = newMBB;
-
-  return true;
-}
-
-static void
-mergeOperations(MachineBasicBlock::iterator MBBIStartPos,
-                MachineBasicBlock &MBBCommon) {
-  MachineBasicBlock *MBB = MBBIStartPos->getParent();
-  // Note CommonTailLen does not necessarily matches the size of
-  // the common BB nor all its instructions because of debug
-  // instructions differences.
-  unsigned CommonTailLen = 0;
-  for (auto E = MBB->end(); MBBIStartPos != E; ++MBBIStartPos)
-    ++CommonTailLen;
-
-  MachineBasicBlock::reverse_iterator MBBI = MBB->rbegin();
-  MachineBasicBlock::reverse_iterator MBBIE = MBB->rend();
-  MachineBasicBlock::reverse_iterator MBBICommon = MBBCommon.rbegin();
-  MachineBasicBlock::reverse_iterator MBBIECommon = MBBCommon.rend();
-
-  while (CommonTailLen--) {
-    assert(MBBI != MBBIE && "Reached BB end within common tail length!");
-    (void)MBBIE;
-
-    if (!countsAsInstruction(*MBBI)) {
-      ++MBBI;
-      continue;
-    }
-
-    while ((MBBICommon != MBBIECommon) && !countsAsInstruction(*MBBICommon))
-      ++MBBICommon;
-
-    assert(MBBICommon != MBBIECommon &&
-           "Reached BB end within common tail length!");
-    assert(MBBICommon->isIdenticalTo(*MBBI) && "Expected matching MIIs!");
-
-    // Merge MMOs from memory operations in the common block.
-    if (MBBICommon->mayLoad() || MBBICommon->mayStore())
-      MBBICommon->cloneMergedMemRefs(*MBB->getParent(), {&*MBBICommon, &*MBBI});
-    // Drop undef flags if they aren't present in all merged instructions.
-    for (unsigned I = 0, E = MBBICommon->getNumOperands(); I != E; ++I) {
-      MachineOperand &MO = MBBICommon->getOperand(I);
-      if (MO.isReg() && MO.isUndef()) {
-        const MachineOperand &OtherMO = MBBI->getOperand(I);
-        if (!OtherMO.isUndef())
-          MO.setIsUndef(false);
-      }
-    }
-
-    ++MBBI;
-    ++MBBICommon;
-  }
-}
-
-void BranchFolder::mergeCommonTails(unsigned commonTailIndex) {
-  MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock();
-
-  std::vector<MachineBasicBlock::iterator> NextCommonInsts(SameTails.size());
-  for (unsigned int i = 0 ; i != SameTails.size() ; ++i) {
-    if (i != commonTailIndex) {
-      NextCommonInsts[i] = SameTails[i].getTailStartPos();
-      mergeOperations(SameTails[i].getTailStartPos(), *MBB);
-    } else {
-      assert(SameTails[i].getTailStartPos() == MBB->begin() &&
-          "MBB is not a common tail only block");
-    }
-  }
-
-  for (auto &MI : *MBB) {
-    if (!countsAsInstruction(MI))
-      continue;
-    DebugLoc DL = MI.getDebugLoc();
-    for (unsigned int i = 0 ; i < NextCommonInsts.size() ; i++) {
-      if (i == commonTailIndex)
-        continue;
-
-      auto &Pos = NextCommonInsts[i];
-      assert(Pos != SameTails[i].getBlock()->end() &&
-          "Reached BB end within common tail");
-      while (!countsAsInstruction(*Pos)) {
-        ++Pos;
-        assert(Pos != SameTails[i].getBlock()->end() &&
-            "Reached BB end within common tail");
-      }
-      assert(MI.isIdenticalTo(*Pos) && "Expected matching MIIs!");
-      DL = DILocation::getMergedLocation(DL, Pos->getDebugLoc());
-      NextCommonInsts[i] = ++Pos;
-    }
-    MI.setDebugLoc(DL);
-  }
-
-  if (UpdateLiveIns) {
-    LivePhysRegs NewLiveIns(*TRI);
-    computeLiveIns(NewLiveIns, *MBB);
-    LiveRegs.init(*TRI);
-
-    // The flag merging may lead to some register uses no longer using the
-    // <undef> flag, add IMPLICIT_DEFs in the predecessors as necessary.
-    for (MachineBasicBlock *Pred : MBB->predecessors()) {
-      LiveRegs.clear();
-      LiveRegs.addLiveOuts(*Pred);
-      MachineBasicBlock::iterator InsertBefore = Pred->getFirstTerminator();
-      for (unsigned Reg : NewLiveIns) {
-        if (!LiveRegs.available(*MRI, Reg))
-          continue;
-        DebugLoc DL;
-        BuildMI(*Pred, InsertBefore, DL, TII->get(TargetOpcode::IMPLICIT_DEF),
-                Reg);
-      }
-    }
-
-    MBB->clearLiveIns();
-    addLiveIns(*MBB, NewLiveIns);
-  }
-}
-
-// See if any of the blocks in MergePotentials (which all have SuccBB as a
-// successor, or all have no successor if it is null) can be tail-merged.
-// If there is a successor, any blocks in MergePotentials that are not
-// tail-merged and are not immediately before Succ must have an unconditional
-// branch to Succ added (but the predecessor/successor lists need no
-// adjustment). The lone predecessor of Succ that falls through into Succ,
-// if any, is given in PredBB.
-// MinCommonTailLength - Except for the special cases below, tail-merge if
-// there are at least this many instructions in common.
-bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB,
-                                      MachineBasicBlock *PredBB,
-                                      unsigned MinCommonTailLength) {
-  bool MadeChange = false;
-
-  LLVM_DEBUG(
-      dbgs() << "\nTryTailMergeBlocks: ";
-      for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i) dbgs()
-      << printMBBReference(*MergePotentials[i].getBlock())
-      << (i == e - 1 ? "" : ", ");
-      dbgs() << "\n"; if (SuccBB) {
-        dbgs() << "  with successor " << printMBBReference(*SuccBB) << '\n';
-        if (PredBB)
-          dbgs() << "  which has fall-through from "
-                 << printMBBReference(*PredBB) << "\n";
-      } dbgs() << "Looking for common tails of at least "
-               << MinCommonTailLength << " instruction"
-               << (MinCommonTailLength == 1 ? "" : "s") << '\n';);
-
-  // Sort by hash value so that blocks with identical end sequences sort
-  // together.
-  array_pod_sort(MergePotentials.begin(), MergePotentials.end());
-
-  // Walk through equivalence sets looking for actual exact matches.
-  while (MergePotentials.size() > 1) {
-    unsigned CurHash = MergePotentials.back().getHash();
-
-    // Build SameTails, identifying the set of blocks with this hash code
-    // and with the maximum number of instructions in common.
-    unsigned maxCommonTailLength = ComputeSameTails(CurHash,
-                                                    MinCommonTailLength,
-                                                    SuccBB, PredBB);
-
-    // If we didn't find any pair that has at least MinCommonTailLength
-    // instructions in common, remove all blocks with this hash code and retry.
-    if (SameTails.empty()) {
-      RemoveBlocksWithHash(CurHash, SuccBB, PredBB);
-      continue;
-    }
-
-    // If one of the blocks is the entire common tail (and not the entry
-    // block, which we can't jump to), we can treat all blocks with this same
-    // tail at once.  Use PredBB if that is one of the possibilities, as that
-    // will not introduce any extra branches.
-    MachineBasicBlock *EntryBB =
-        &MergePotentials.front().getBlock()->getParent()->front();
-    unsigned commonTailIndex = SameTails.size();
-    // If there are two blocks, check to see if one can be made to fall through
-    // into the other.
-    if (SameTails.size() == 2 &&
-        SameTails[0].getBlock()->isLayoutSuccessor(SameTails[1].getBlock()) &&
-        SameTails[1].tailIsWholeBlock())
-      commonTailIndex = 1;
-    else if (SameTails.size() == 2 &&
-             SameTails[1].getBlock()->isLayoutSuccessor(
-                                                     SameTails[0].getBlock()) &&
-             SameTails[0].tailIsWholeBlock())
-      commonTailIndex = 0;
-    else {
-      // Otherwise just pick one, favoring the fall-through predecessor if
-      // there is one.
-      for (unsigned i = 0, e = SameTails.size(); i != e; ++i) {
-        MachineBasicBlock *MBB = SameTails[i].getBlock();
-        if (MBB == EntryBB && SameTails[i].tailIsWholeBlock())
-          continue;
-        if (MBB == PredBB) {
-          commonTailIndex = i;
-          break;
-        }
-        if (SameTails[i].tailIsWholeBlock())
-          commonTailIndex = i;
-      }
-    }
-
-    if (commonTailIndex == SameTails.size() ||
-        (SameTails[commonTailIndex].getBlock() == PredBB &&
-         !SameTails[commonTailIndex].tailIsWholeBlock())) {
-      // None of the blocks consist entirely of the common tail.
-      // Split a block so that one does.
-      if (!CreateCommonTailOnlyBlock(PredBB, SuccBB,
-                                     maxCommonTailLength, commonTailIndex)) {
-        RemoveBlocksWithHash(CurHash, SuccBB, PredBB);
-        continue;
-      }
-    }
-
-    MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock();
-
-    // Recompute common tail MBB's edge weights and block frequency.
-    setCommonTailEdgeWeights(*MBB);
-
-    // Merge debug locations, MMOs and undef flags across identical instructions
-    // for common tail.
-    mergeCommonTails(commonTailIndex);
-
-    // MBB is common tail.  Adjust all other BB's to jump to this one.
-    // Traversal must be forwards so erases work.
-    LLVM_DEBUG(dbgs() << "\nUsing common tail in " << printMBBReference(*MBB)
-                      << " for ");
-    for (unsigned int i=0, e = SameTails.size(); i != e; ++i) {
-      if (commonTailIndex == i)
-        continue;
-      LLVM_DEBUG(dbgs() << printMBBReference(*SameTails[i].getBlock())
-                        << (i == e - 1 ? "" : ", "));
-      // Hack the end off BB i, making it jump to BB commonTailIndex instead.
-      replaceTailWithBranchTo(SameTails[i].getTailStartPos(), *MBB);
-      // BB i is no longer a predecessor of SuccBB; remove it from the worklist.
-      MergePotentials.erase(SameTails[i].getMPIter());
-    }
-    LLVM_DEBUG(dbgs() << "\n");
-    // We leave commonTailIndex in the worklist in case there are other blocks
-    // that match it with a smaller number of instructions.
-    MadeChange = true;
-  }
-  return MadeChange;
-}
-
-bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
-  bool MadeChange = false;
-  if (!EnableTailMerge)
-    return MadeChange;
-
-  // First find blocks with no successors.
-  // Block placement may create new tail merging opportunities for these blocks.
-  MergePotentials.clear();
-  for (MachineBasicBlock &MBB : MF) {
-    if (MergePotentials.size() == TailMergeThreshold)
-      break;
-    if (!TriedMerging.count(&MBB) && MBB.succ_empty())
-      MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(MBB), &MBB));
-  }
-
-  // If this is a large problem, avoid visiting the same basic blocks
-  // multiple times.
-  if (MergePotentials.size() == TailMergeThreshold)
-    for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
-      TriedMerging.insert(MergePotentials[i].getBlock());
-
-  // See if we can do any tail merging on those.
-  if (MergePotentials.size() >= 2)
-    MadeChange |= TryTailMergeBlocks(nullptr, nullptr, MinCommonTailLength);
-
-  // Look at blocks (IBB) with multiple predecessors (PBB).
-  // We change each predecessor to a canonical form, by
-  // (1) temporarily removing any unconditional branch from the predecessor
-  // to IBB, and
-  // (2) alter conditional branches so they branch to the other block
-  // not IBB; this may require adding back an unconditional branch to IBB
-  // later, where there wasn't one coming in.  E.g.
-  //   Bcc IBB
-  //   fallthrough to QBB
-  // here becomes
-  //   Bncc QBB
-  // with a conceptual B to IBB after that, which never actually exists.
-  // With those changes, we see whether the predecessors' tails match,
-  // and merge them if so.  We change things out of canonical form and
-  // back to the way they were later in the process.  (OptimizeBranches
-  // would undo some of this, but we can't use it, because we'd get into
-  // a compile-time infinite loop repeatedly doing and undoing the same
-  // transformations.)
-
-  for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end();
-       I != E; ++I) {
-    if (I->pred_size() < 2) continue;
-    SmallPtrSet<MachineBasicBlock *, 8> UniquePreds;
-    MachineBasicBlock *IBB = &*I;
-    MachineBasicBlock *PredBB = &*std::prev(I);
-    MergePotentials.clear();
-    MachineLoop *ML;
-
-    // Bail if merging after placement and IBB is the loop header because
-    // -- If merging predecessors that belong to the same loop as IBB, the
-    // common tail of merged predecessors may become the loop top if block
-    // placement is called again and the predecessors may branch to this common
-    // tail and require more branches. This can be relaxed if
-    // MachineBlockPlacement::findBestLoopTop is more flexible.
-    // --If merging predecessors that do not belong to the same loop as IBB, the
-    // loop info of IBB's loop and the other loops may be affected. Calling the
-    // block placement again may make big change to the layout and eliminate the
-    // reason to do tail merging here.
-    if (AfterBlockPlacement && MLI) {
-      ML = MLI->getLoopFor(IBB);
-      if (ML && IBB == ML->getHeader())
-        continue;
-    }
-
-    for (MachineBasicBlock *PBB : I->predecessors()) {
-      if (MergePotentials.size() == TailMergeThreshold)
-        break;
-
-      if (TriedMerging.count(PBB))
-        continue;
-
-      // Skip blocks that loop to themselves, can't tail merge these.
-      if (PBB == IBB)
-        continue;
-
-      // Visit each predecessor only once.
-      if (!UniquePreds.insert(PBB).second)
-        continue;
-
-      // Skip blocks which may jump to a landing pad. Can't tail merge these.
-      if (PBB->hasEHPadSuccessor())
-        continue;
-
-      // After block placement, only consider predecessors that belong to the
-      // same loop as IBB.  The reason is the same as above when skipping loop
-      // header.
-      if (AfterBlockPlacement && MLI)
-        if (ML != MLI->getLoopFor(PBB))
-          continue;
-
-      MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
-      SmallVector<MachineOperand, 4> Cond;
-      if (!TII->analyzeBranch(*PBB, TBB, FBB, Cond, true)) {
-        // Failing case: IBB is the target of a cbr, and we cannot reverse the
-        // branch.
-        SmallVector<MachineOperand, 4> NewCond(Cond);
-        if (!Cond.empty() && TBB == IBB) {
-          if (TII->reverseBranchCondition(NewCond))
-            continue;
-          // This is the QBB case described above
-          if (!FBB) {
-            auto Next = ++PBB->getIterator();
-            if (Next != MF.end())
-              FBB = &*Next;
-          }
-        }
-
-        // Remove the unconditional branch at the end, if any.
-        if (TBB && (Cond.empty() || FBB)) {
-          DebugLoc dl = PBB->findBranchDebugLoc();
-          TII->removeBranch(*PBB);
-          if (!Cond.empty())
-            // reinsert conditional branch only, for now
-            TII->insertBranch(*PBB, (TBB == IBB) ? FBB : TBB, nullptr,
-                              NewCond, dl);
-        }
-
-        MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(*PBB), PBB));
-      }
-    }
-
-    // If this is a large problem, avoid visiting the same basic blocks multiple
-    // times.
-    if (MergePotentials.size() == TailMergeThreshold)
-      for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
-        TriedMerging.insert(MergePotentials[i].getBlock());
-
-    if (MergePotentials.size() >= 2)
-      MadeChange |= TryTailMergeBlocks(IBB, PredBB, MinCommonTailLength);
-
-    // Reinsert an unconditional branch if needed. The 1 below can occur as a
-    // result of removing blocks in TryTailMergeBlocks.
-    PredBB = &*std::prev(I); // this may have been changed in TryTailMergeBlocks
-    if (MergePotentials.size() == 1 &&
-        MergePotentials.begin()->getBlock() != PredBB)
-      FixTail(MergePotentials.begin()->getBlock(), IBB, TII);
-  }
-
-  return MadeChange;
-}
-
-void BranchFolder::setCommonTailEdgeWeights(MachineBasicBlock &TailMBB) {
-  SmallVector<BlockFrequency, 2> EdgeFreqLs(TailMBB.succ_size());
-  BlockFrequency AccumulatedMBBFreq;
-
-  // Aggregate edge frequency of successor edge j:
-  //  edgeFreq(j) = sum (freq(bb) * edgeProb(bb, j)),
-  //  where bb is a basic block that is in SameTails.
-  for (const auto &Src : SameTails) {
-    const MachineBasicBlock *SrcMBB = Src.getBlock();
-    BlockFrequency BlockFreq = MBBFreqInfo.getBlockFreq(SrcMBB);
-    AccumulatedMBBFreq += BlockFreq;
-
-    // It is not necessary to recompute edge weights if TailBB has less than two
-    // successors.
-    if (TailMBB.succ_size() <= 1)
-      continue;
-
-    auto EdgeFreq = EdgeFreqLs.begin();
-
-    for (auto SuccI = TailMBB.succ_begin(), SuccE = TailMBB.succ_end();
-         SuccI != SuccE; ++SuccI, ++EdgeFreq)
-      *EdgeFreq += BlockFreq * MBPI.getEdgeProbability(SrcMBB, *SuccI);
-  }
-
-  MBBFreqInfo.setBlockFreq(&TailMBB, AccumulatedMBBFreq);
-
-  if (TailMBB.succ_size() <= 1)
-    return;
-
-  auto SumEdgeFreq =
-      std::accumulate(EdgeFreqLs.begin(), EdgeFreqLs.end(), BlockFrequency(0))
-          .getFrequency();
-  auto EdgeFreq = EdgeFreqLs.begin();
-
-  if (SumEdgeFreq > 0) {
-    for (auto SuccI = TailMBB.succ_begin(), SuccE = TailMBB.succ_end();
-         SuccI != SuccE; ++SuccI, ++EdgeFreq) {
-      auto Prob = BranchProbability::getBranchProbability(
-          EdgeFreq->getFrequency(), SumEdgeFreq);
-      TailMBB.setSuccProbability(SuccI, Prob);
-    }
-  }
-}
-
-//===----------------------------------------------------------------------===//
-//  Branch Optimization
-//===----------------------------------------------------------------------===//
-
-bool BranchFolder::OptimizeBranches(MachineFunction &MF) {
-  bool MadeChange = false;
-
-  // Make sure blocks are numbered in order
-  MF.RenumberBlocks();
-  // Renumbering blocks alters EH scope membership, recalculate it.
-  EHScopeMembership = getEHScopeMembership(MF);
-
-  for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end();
-       I != E; ) {
-    MachineBasicBlock *MBB = &*I++;
-    MadeChange |= OptimizeBlock(MBB);
-
-    // If it is dead, remove it.
-    if (MBB->pred_empty()) {
-      RemoveDeadBlock(MBB);
-      MadeChange = true;
-      ++NumDeadBlocks;
-    }
-  }
-
-  return MadeChange;
-}
-
-// Blocks should be considered empty if they contain only debug info;
-// else the debug info would affect codegen.
-static bool IsEmptyBlock(MachineBasicBlock *MBB) {
-  return MBB->getFirstNonDebugInstr() == MBB->end();
-}
-
-// Blocks with only debug info and branches should be considered the same
-// as blocks with only branches.
-static bool IsBranchOnlyBlock(MachineBasicBlock *MBB) {
-  MachineBasicBlock::iterator I = MBB->getFirstNonDebugInstr();
-  assert(I != MBB->end() && "empty block!");
-  return I->isBranch();
-}
-
-/// IsBetterFallthrough - Return true if it would be clearly better to
-/// fall-through to MBB1 than to fall through into MBB2.  This has to return
-/// a strict ordering, returning true for both (MBB1,MBB2) and (MBB2,MBB1) will
-/// result in infinite loops.
-static bool IsBetterFallthrough(MachineBasicBlock *MBB1,
-                                MachineBasicBlock *MBB2) {
-  // Right now, we use a simple heuristic.  If MBB2 ends with a call, and
-  // MBB1 doesn't, we prefer to fall through into MBB1.  This allows us to
-  // optimize branches that branch to either a return block or an assert block
-  // into a fallthrough to the return.
-  MachineBasicBlock::iterator MBB1I = MBB1->getLastNonDebugInstr();
-  MachineBasicBlock::iterator MBB2I = MBB2->getLastNonDebugInstr();
-  if (MBB1I == MBB1->end() || MBB2I == MBB2->end())
-    return false;
-
-  // If there is a clear successor ordering we make sure that one block
-  // will fall through to the next
-  if (MBB1->isSuccessor(MBB2)) return true;
-  if (MBB2->isSuccessor(MBB1)) return false;
-
-  return MBB2I->isCall() && !MBB1I->isCall();
-}
-
-/// getBranchDebugLoc - Find and return, if any, the DebugLoc of the branch
-/// instructions on the block.
-static DebugLoc getBranchDebugLoc(MachineBasicBlock &MBB) {
-  MachineBasicBlock::iterator I = MBB.getLastNonDebugInstr();
-  if (I != MBB.end() && I->isBranch())
-    return I->getDebugLoc();
-  return DebugLoc();
-}
-
-static void copyDebugInfoToPredecessor(const TargetInstrInfo *TII,
-                                       MachineBasicBlock &MBB,
-                                       MachineBasicBlock &PredMBB) {
-  auto InsertBefore = PredMBB.getFirstTerminator();
-  for (MachineInstr &MI : MBB.instrs())
-    if (MI.isDebugInstr()) {
-      TII->duplicate(PredMBB, InsertBefore, MI);
-      LLVM_DEBUG(dbgs() << "Copied debug entity from empty block to pred: "
-                        << MI);
-    }
-}
-
-static void copyDebugInfoToSuccessor(const TargetInstrInfo *TII,
-                                     MachineBasicBlock &MBB,
-                                     MachineBasicBlock &SuccMBB) {
-  auto InsertBefore = SuccMBB.SkipPHIsAndLabels(SuccMBB.begin());
-  for (MachineInstr &MI : MBB.instrs())
-    if (MI.isDebugInstr()) {
-      TII->duplicate(SuccMBB, InsertBefore, MI);
-      LLVM_DEBUG(dbgs() << "Copied debug entity from empty block to succ: "
-                        << MI);
-    }
-}
-
-// Try to salvage DBG_VALUE instructions from an otherwise empty block. If such
-// a basic block is removed we would lose the debug information unless we have
-// copied the information to a predecessor/successor.
-//
-// TODO: This function only handles some simple cases. An alternative would be
-// to run a heavier analysis, such as the LiveDebugValues pass, before we do
-// branch folding.
-static void salvageDebugInfoFromEmptyBlock(const TargetInstrInfo *TII,
-                                           MachineBasicBlock &MBB) {
-  assert(IsEmptyBlock(&MBB) && "Expected an empty block (except debug info).");
-  // If this MBB is the only predecessor of a successor it is legal to copy
-  // DBG_VALUE instructions to the beginning of the successor.
-  for (MachineBasicBlock *SuccBB : MBB.successors())
-    if (SuccBB->pred_size() == 1)
-      copyDebugInfoToSuccessor(TII, MBB, *SuccBB);
-  // If this MBB is the only successor of a predecessor it is legal to copy the
-  // DBG_VALUE instructions to the end of the predecessor (just before the
-  // terminators, assuming that the terminator isn't affecting the DBG_VALUE).
-  for (MachineBasicBlock *PredBB : MBB.predecessors())
-    if (PredBB->succ_size() == 1)
-      copyDebugInfoToPredecessor(TII, MBB, *PredBB);
-}
-
-bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
-  bool MadeChange = false;
-  MachineFunction &MF = *MBB->getParent();
-ReoptimizeBlock:
-
-  MachineFunction::iterator FallThrough = MBB->getIterator();
-  ++FallThrough;
-
-  // Make sure MBB and FallThrough belong to the same EH scope.
-  bool SameEHScope = true;
-  if (!EHScopeMembership.empty() && FallThrough != MF.end()) {
-    auto MBBEHScope = EHScopeMembership.find(MBB);
-    assert(MBBEHScope != EHScopeMembership.end());
-    auto FallThroughEHScope = EHScopeMembership.find(&*FallThrough);
-    assert(FallThroughEHScope != EHScopeMembership.end());
-    SameEHScope = MBBEHScope->second == FallThroughEHScope->second;
-  }
-
-  // If this block is empty, make everyone use its fall-through, not the block
-  // explicitly.  Landing pads should not do this since the landing-pad table
-  // points to this block.  Blocks with their addresses taken shouldn't be
-  // optimized away.
-  if (IsEmptyBlock(MBB) && !MBB->isEHPad() && !MBB->hasAddressTaken() &&
-      SameEHScope) {
-    salvageDebugInfoFromEmptyBlock(TII, *MBB);
-    // Dead block?  Leave for cleanup later.
-    if (MBB->pred_empty()) return MadeChange;
-
-    if (FallThrough == MF.end()) {
-      // TODO: Simplify preds to not branch here if possible!
-    } else if (FallThrough->isEHPad()) {
-      // Don't rewrite to a landing pad fallthough.  That could lead to the case
-      // where a BB jumps to more than one landing pad.
-      // TODO: Is it ever worth rewriting predecessors which don't already
-      // jump to a landing pad, and so can safely jump to the fallthrough?
-    } else if (MBB->isSuccessor(&*FallThrough)) {
-      // Rewrite all predecessors of the old block to go to the fallthrough
-      // instead.
-      while (!MBB->pred_empty()) {
-        MachineBasicBlock *Pred = *(MBB->pred_end()-1);
-        Pred->ReplaceUsesOfBlockWith(MBB, &*FallThrough);
-      }
-      // If MBB was the target of a jump table, update jump tables to go to the
-      // fallthrough instead.
-      if (MachineJumpTableInfo *MJTI = MF.getJumpTableInfo())
-        MJTI->ReplaceMBBInJumpTables(MBB, &*FallThrough);
-      MadeChange = true;
-    }
-    return MadeChange;
-  }
-
-  // Check to see if we can simplify the terminator of the block before this
-  // one.
-  MachineBasicBlock &PrevBB = *std::prev(MachineFunction::iterator(MBB));
-
-  MachineBasicBlock *PriorTBB = nullptr, *PriorFBB = nullptr;
-  SmallVector<MachineOperand, 4> PriorCond;
-  bool PriorUnAnalyzable =
-      TII->analyzeBranch(PrevBB, PriorTBB, PriorFBB, PriorCond, true);
-  if (!PriorUnAnalyzable) {
-    // If the CFG for the prior block has extra edges, remove them.
-    MadeChange |= PrevBB.CorrectExtraCFGEdges(PriorTBB, PriorFBB,
-                                              !PriorCond.empty());
-
-    // If the previous branch is conditional and both conditions go to the same
-    // destination, remove the branch, replacing it with an unconditional one or
-    // a fall-through.
-    if (PriorTBB && PriorTBB == PriorFBB) {
-      DebugLoc dl = getBranchDebugLoc(PrevBB);
-      TII->removeBranch(PrevBB);
-      PriorCond.clear();
-      if (PriorTBB != MBB)
-        TII->insertBranch(PrevBB, PriorTBB, nullptr, PriorCond, dl);
-      MadeChange = true;
-      ++NumBranchOpts;
-      goto ReoptimizeBlock;
-    }
-
-    // If the previous block unconditionally falls through to this block and
-    // this block has no other predecessors, move the contents of this block
-    // into the prior block. This doesn't usually happen when SimplifyCFG
-    // has been used, but it can happen if tail merging splits a fall-through
-    // predecessor of a block.
-    // This has to check PrevBB->succ_size() because EH edges are ignored by
-    // AnalyzeBranch.
-    if (PriorCond.empty() && !PriorTBB && MBB->pred_size() == 1 &&
-        PrevBB.succ_size() == 1 &&
-        !MBB->hasAddressTaken() && !MBB->isEHPad()) {
-      LLVM_DEBUG(dbgs() << "\nMerging into block: " << PrevBB
-                        << "From MBB: " << *MBB);
-      // Remove redundant DBG_VALUEs first.
-      if (PrevBB.begin() != PrevBB.end()) {
-        MachineBasicBlock::iterator PrevBBIter = PrevBB.end();
-        --PrevBBIter;
-        MachineBasicBlock::iterator MBBIter = MBB->begin();
-        // Check if DBG_VALUE at the end of PrevBB is identical to the
-        // DBG_VALUE at the beginning of MBB.
-        while (PrevBBIter != PrevBB.begin() && MBBIter != MBB->end()
-               && PrevBBIter->isDebugInstr() && MBBIter->isDebugInstr()) {
-          if (!MBBIter->isIdenticalTo(*PrevBBIter))
-            break;
-          MachineInstr &DuplicateDbg = *MBBIter;
-          ++MBBIter; -- PrevBBIter;
-          DuplicateDbg.eraseFromParent();
-        }
-      }
-      PrevBB.splice(PrevBB.end(), MBB, MBB->begin(), MBB->end());
-      PrevBB.removeSuccessor(PrevBB.succ_begin());
-      assert(PrevBB.succ_empty());
-      PrevBB.transferSuccessors(MBB);
-      MadeChange = true;
-      return MadeChange;
-    }
-
-    // If the previous branch *only* branches to *this* block (conditional or
-    // not) remove the branch.
-    if (PriorTBB == MBB && !PriorFBB) {
-      TII->removeBranch(PrevBB);
-      MadeChange = true;
-      ++NumBranchOpts;
-      goto ReoptimizeBlock;
-    }
-
-    // If the prior block branches somewhere else on the condition and here if
-    // the condition is false, remove the uncond second branch.
-    if (PriorFBB == MBB) {
-      DebugLoc dl = getBranchDebugLoc(PrevBB);
-      TII->removeBranch(PrevBB);
-      TII->insertBranch(PrevBB, PriorTBB, nullptr, PriorCond, dl);
-      MadeChange = true;
-      ++NumBranchOpts;
-      goto ReoptimizeBlock;
-    }
-
-    // If the prior block branches here on true and somewhere else on false, and
-    // if the branch condition is reversible, reverse the branch to create a
-    // fall-through.
-    if (PriorTBB == MBB) {
-      SmallVector<MachineOperand, 4> NewPriorCond(PriorCond);
-      if (!TII->reverseBranchCondition(NewPriorCond)) {
-        DebugLoc dl = getBranchDebugLoc(PrevBB);
-        TII->removeBranch(PrevBB);
-        TII->insertBranch(PrevBB, PriorFBB, nullptr, NewPriorCond, dl);
-        MadeChange = true;
-        ++NumBranchOpts;
-        goto ReoptimizeBlock;
-      }
-    }
-
-    // If this block has no successors (e.g. it is a return block or ends with
-    // a call to a no-return function like abort or __cxa_throw) and if the pred
-    // falls through into this block, and if it would otherwise fall through
-    // into the block after this, move this block to the end of the function.
-    //
-    // We consider it more likely that execution will stay in the function (e.g.
-    // due to loops) than it is to exit it.  This asserts in loops etc, moving
-    // the assert condition out of the loop body.
-    if (MBB->succ_empty() && !PriorCond.empty() && !PriorFBB &&
-        MachineFunction::iterator(PriorTBB) == FallThrough &&
-        !MBB->canFallThrough()) {
-      bool DoTransform = true;
-
-      // We have to be careful that the succs of PredBB aren't both no-successor
-      // blocks.  If neither have successors and if PredBB is the second from
-      // last block in the function, we'd just keep swapping the two blocks for
-      // last.  Only do the swap if one is clearly better to fall through than
-      // the other.
-      if (FallThrough == --MF.end() &&
-          !IsBetterFallthrough(PriorTBB, MBB))
-        DoTransform = false;
-
-      if (DoTransform) {
-        // Reverse the branch so we will fall through on the previous true cond.
-        SmallVector<MachineOperand, 4> NewPriorCond(PriorCond);
-        if (!TII->reverseBranchCondition(NewPriorCond)) {
-          LLVM_DEBUG(dbgs() << "\nMoving MBB: " << *MBB
-                            << "To make fallthrough to: " << *PriorTBB << "\n");
-
-          DebugLoc dl = getBranchDebugLoc(PrevBB);
-          TII->removeBranch(PrevBB);
-          TII->insertBranch(PrevBB, MBB, nullptr, NewPriorCond, dl);
-
-          // Move this block to the end of the function.
-          MBB->moveAfter(&MF.back());
-          MadeChange = true;
-          ++NumBranchOpts;
-          return MadeChange;
-        }
-      }
-    }
-  }
-
-  if (!IsEmptyBlock(MBB) && MBB->pred_size() == 1 &&
-      MF.getFunction().hasOptSize()) {
-    // Changing "Jcc foo; foo: jmp bar;" into "Jcc bar;" might change the branch
-    // direction, thereby defeating careful block placement and regressing
-    // performance. Therefore, only consider this for optsize functions.
-    MachineInstr &TailCall = *MBB->getFirstNonDebugInstr();
-    if (TII->isUnconditionalTailCall(TailCall)) {
-      MachineBasicBlock *Pred = *MBB->pred_begin();
-      MachineBasicBlock *PredTBB = nullptr, *PredFBB = nullptr;
-      SmallVector<MachineOperand, 4> PredCond;
-      bool PredAnalyzable =
-          !TII->analyzeBranch(*Pred, PredTBB, PredFBB, PredCond, true);
-
-      if (PredAnalyzable && !PredCond.empty() && PredTBB == MBB &&
-          PredTBB != PredFBB) {
-        // The predecessor has a conditional branch to this block which consists
-        // of only a tail call. Try to fold the tail call into the conditional
-        // branch.
-        if (TII->canMakeTailCallConditional(PredCond, TailCall)) {
-          // TODO: It would be nice if analyzeBranch() could provide a pointer
-          // to the branch instruction so replaceBranchWithTailCall() doesn't
-          // have to search for it.
-          TII->replaceBranchWithTailCall(*Pred, PredCond, TailCall);
-          ++NumTailCalls;
-          Pred->removeSuccessor(MBB);
-          MadeChange = true;
-          return MadeChange;
-        }
-      }
-      // If the predecessor is falling through to this block, we could reverse
-      // the branch condition and fold the tail call into that. However, after
-      // that we might have to re-arrange the CFG to fall through to the other
-      // block and there is a high risk of regressing code size rather than
-      // improving it.
-    }
-  }
-
-  // Analyze the branch in the current block.
-  MachineBasicBlock *CurTBB = nullptr, *CurFBB = nullptr;
-  SmallVector<MachineOperand, 4> CurCond;
-  bool CurUnAnalyzable =
-      TII->analyzeBranch(*MBB, CurTBB, CurFBB, CurCond, true);
-  if (!CurUnAnalyzable) {
-    // If the CFG for the prior block has extra edges, remove them.
-    MadeChange |= MBB->CorrectExtraCFGEdges(CurTBB, CurFBB, !CurCond.empty());
-
-    // If this is a two-way branch, and the FBB branches to this block, reverse
-    // the condition so the single-basic-block loop is faster.  Instead of:
-    //    Loop: xxx; jcc Out; jmp Loop
-    // we want:
-    //    Loop: xxx; jncc Loop; jmp Out
-    if (CurTBB && CurFBB && CurFBB == MBB && CurTBB != MBB) {
-      SmallVector<MachineOperand, 4> NewCond(CurCond);
-      if (!TII->reverseBranchCondition(NewCond)) {
-        DebugLoc dl = getBranchDebugLoc(*MBB);
-        TII->removeBranch(*MBB);
-        TII->insertBranch(*MBB, CurFBB, CurTBB, NewCond, dl);
-        MadeChange = true;
-        ++NumBranchOpts;
-        goto ReoptimizeBlock;
-      }
-    }
-
-    // If this branch is the only thing in its block, see if we can forward
-    // other blocks across it.
-    if (CurTBB && CurCond.empty() && !CurFBB &&
-        IsBranchOnlyBlock(MBB) && CurTBB != MBB &&
-        !MBB->hasAddressTaken() && !MBB->isEHPad()) {
-      DebugLoc dl = getBranchDebugLoc(*MBB);
-      // This block may contain just an unconditional branch.  Because there can
-      // be 'non-branch terminators' in the block, try removing the branch and
-      // then seeing if the block is empty.
-      TII->removeBranch(*MBB);
-      // If the only things remaining in the block are debug info, remove these
-      // as well, so this will behave the same as an empty block in non-debug
-      // mode.
-      if (IsEmptyBlock(MBB)) {
-        // Make the block empty, losing the debug info (we could probably
-        // improve this in some cases.)
-        MBB->erase(MBB->begin(), MBB->end());
-      }
-      // If this block is just an unconditional branch to CurTBB, we can
-      // usually completely eliminate the block.  The only case we cannot
-      // completely eliminate the block is when the block before this one
-      // falls through into MBB and we can't understand the prior block's branch
-      // condition.
-      if (MBB->empty()) {
-        bool PredHasNoFallThrough = !PrevBB.canFallThrough();
-        if (PredHasNoFallThrough || !PriorUnAnalyzable ||
-            !PrevBB.isSuccessor(MBB)) {
-          // If the prior block falls through into us, turn it into an
-          // explicit branch to us to make updates simpler.
-          if (!PredHasNoFallThrough && PrevBB.isSuccessor(MBB) &&
-              PriorTBB != MBB && PriorFBB != MBB) {
-            if (!PriorTBB) {
-              assert(PriorCond.empty() && !PriorFBB &&
-                     "Bad branch analysis");
-              PriorTBB = MBB;
-            } else {
-              assert(!PriorFBB && "Machine CFG out of date!");
-              PriorFBB = MBB;
-            }
-            DebugLoc pdl = getBranchDebugLoc(PrevBB);
-            TII->removeBranch(PrevBB);
-            TII->insertBranch(PrevBB, PriorTBB, PriorFBB, PriorCond, pdl);
-          }
-
-          // Iterate through all the predecessors, revectoring each in-turn.
-          size_t PI = 0;
-          bool DidChange = false;
-          bool HasBranchToSelf = false;
-          while(PI != MBB->pred_size()) {
-            MachineBasicBlock *PMBB = *(MBB->pred_begin() + PI);
-            if (PMBB == MBB) {
-              // If this block has an uncond branch to itself, leave it.
-              ++PI;
-              HasBranchToSelf = true;
-            } else {
-              DidChange = true;
-              PMBB->ReplaceUsesOfBlockWith(MBB, CurTBB);
-              // If this change resulted in PMBB ending in a conditional
-              // branch where both conditions go to the same destination,
-              // change this to an unconditional branch (and fix the CFG).
-              MachineBasicBlock *NewCurTBB = nullptr, *NewCurFBB = nullptr;
-              SmallVector<MachineOperand, 4> NewCurCond;
-              bool NewCurUnAnalyzable = TII->analyzeBranch(
-                  *PMBB, NewCurTBB, NewCurFBB, NewCurCond, true);
-              if (!NewCurUnAnalyzable && NewCurTBB && NewCurTBB == NewCurFBB) {
-                DebugLoc pdl = getBranchDebugLoc(*PMBB);
-                TII->removeBranch(*PMBB);
-                NewCurCond.clear();
-                TII->insertBranch(*PMBB, NewCurTBB, nullptr, NewCurCond, pdl);
-                MadeChange = true;
-                ++NumBranchOpts;
-                PMBB->CorrectExtraCFGEdges(NewCurTBB, nullptr, false);
-              }
-            }
-          }
-
-          // Change any jumptables to go to the new MBB.
-          if (MachineJumpTableInfo *MJTI = MF.getJumpTableInfo())
-            MJTI->ReplaceMBBInJumpTables(MBB, CurTBB);
-          if (DidChange) {
-            ++NumBranchOpts;
-            MadeChange = true;
-            if (!HasBranchToSelf) return MadeChange;
-          }
-        }
-      }
-
-      // Add the branch back if the block is more than just an uncond branch.
-      TII->insertBranch(*MBB, CurTBB, nullptr, CurCond, dl);
-    }
-  }
-
-  // If the prior block doesn't fall through into this block, and if this
-  // block doesn't fall through into some other block, see if we can find a
-  // place to move this block where a fall-through will happen.
-  if (!PrevBB.canFallThrough()) {
-    // Now we know that there was no fall-through into this block, check to
-    // see if it has a fall-through into its successor.
-    bool CurFallsThru = MBB->canFallThrough();
-
-    if (!MBB->isEHPad()) {
-      // Check all the predecessors of this block.  If one of them has no fall
-      // throughs, move this block right after it.
-      for (MachineBasicBlock *PredBB : MBB->predecessors()) {
-        // Analyze the branch at the end of the pred.
-        MachineBasicBlock *PredTBB = nullptr, *PredFBB = nullptr;
-        SmallVector<MachineOperand, 4> PredCond;
-        if (PredBB != MBB && !PredBB->canFallThrough() &&
-            !TII->analyzeBranch(*PredBB, PredTBB, PredFBB, PredCond, true) &&
-            (!CurFallsThru || !CurTBB || !CurFBB) &&
-            (!CurFallsThru || MBB->getNumber() >= PredBB->getNumber())) {
-          // If the current block doesn't fall through, just move it.
-          // If the current block can fall through and does not end with a
-          // conditional branch, we need to append an unconditional jump to
-          // the (current) next block.  To avoid a possible compile-time
-          // infinite loop, move blocks only backward in this case.
-          // Also, if there are already 2 branches here, we cannot add a third;
-          // this means we have the case
-          // Bcc next
-          // B elsewhere
-          // next:
-          if (CurFallsThru) {
-            MachineBasicBlock *NextBB = &*std::next(MBB->getIterator());
-            CurCond.clear();
-            TII->insertBranch(*MBB, NextBB, nullptr, CurCond, DebugLoc());
-          }
-          MBB->moveAfter(PredBB);
-          MadeChange = true;
-          goto ReoptimizeBlock;
-        }
-      }
-    }
-
-    if (!CurFallsThru) {
-      // Check all successors to see if we can move this block before it.
-      for (MachineBasicBlock *SuccBB : MBB->successors()) {
-        // Analyze the branch at the end of the block before the succ.
-        MachineFunction::iterator SuccPrev = --SuccBB->getIterator();
-
-        // If this block doesn't already fall-through to that successor, and if
-        // the succ doesn't already have a block that can fall through into it,
-        // and if the successor isn't an EH destination, we can arrange for the
-        // fallthrough to happen.
-        if (SuccBB != MBB && &*SuccPrev != MBB &&
-            !SuccPrev->canFallThrough() && !CurUnAnalyzable &&
-            !SuccBB->isEHPad()) {
-          MBB->moveBefore(SuccBB);
-          MadeChange = true;
-          goto ReoptimizeBlock;
-        }
-      }
-
-      // Okay, there is no really great place to put this block.  If, however,
-      // the block before this one would be a fall-through if this block were
-      // removed, move this block to the end of the function. There is no real
-      // advantage in "falling through" to an EH block, so we don't want to
-      // perform this transformation for that case.
-      //
-      // Also, Windows EH introduced the possibility of an arbitrary number of
-      // successors to a given block.  The analyzeBranch call does not consider
-      // exception handling and so we can get in a state where a block
-      // containing a call is followed by multiple EH blocks that would be
-      // rotated infinitely at the end of the function if the transformation
-      // below were performed for EH "FallThrough" blocks.  Therefore, even if
-      // that appears not to be happening anymore, we should assume that it is
-      // possible and not remove the "!FallThrough()->isEHPad" condition below.
-      MachineBasicBlock *PrevTBB = nullptr, *PrevFBB = nullptr;
-      SmallVector<MachineOperand, 4> PrevCond;
-      if (FallThrough != MF.end() &&
-          !FallThrough->isEHPad() &&
-          !TII->analyzeBranch(PrevBB, PrevTBB, PrevFBB, PrevCond, true) &&
-          PrevBB.isSuccessor(&*FallThrough)) {
-        MBB->moveAfter(&MF.back());
-        MadeChange = true;
-        return MadeChange;
-      }
-    }
-  }
-
-  return MadeChange;
-}
-
-//===----------------------------------------------------------------------===//
-//  Hoist Common Code
-//===----------------------------------------------------------------------===//
-
-bool BranchFolder::HoistCommonCode(MachineFunction &MF) {
-  bool MadeChange = false;
-  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ) {
-    MachineBasicBlock *MBB = &*I++;
-    MadeChange |= HoistCommonCodeInSuccs(MBB);
-  }
-
-  return MadeChange;
-}
-
-/// findFalseBlock - BB has a fallthrough. Find its 'false' successor given
-/// its 'true' successor.
-static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB,
-                                         MachineBasicBlock *TrueBB) {
-  for (MachineBasicBlock *SuccBB : BB->successors())
-    if (SuccBB != TrueBB)
-      return SuccBB;
-  return nullptr;
-}
-
-template <class Container>
-static void addRegAndItsAliases(unsigned Reg, const TargetRegisterInfo *TRI,
-                                Container &Set) {
-  if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
-    for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
-      Set.insert(*AI);
-  } else {
-    Set.insert(Reg);
-  }
-}
-
-/// findHoistingInsertPosAndDeps - Find the location to move common instructions
-/// in successors to. The location is usually just before the terminator,
-/// however if the terminator is a conditional branch and its previous
-/// instruction is the flag setting instruction, the previous instruction is
-/// the preferred location. This function also gathers uses and defs of the
-/// instructions from the insertion point to the end of the block. The data is
-/// used by HoistCommonCodeInSuccs to ensure safety.
-static
-MachineBasicBlock::iterator findHoistingInsertPosAndDeps(MachineBasicBlock *MBB,
-                                                  const TargetInstrInfo *TII,
-                                                  const TargetRegisterInfo *TRI,
-                                                  SmallSet<unsigned,4> &Uses,
-                                                  SmallSet<unsigned,4> &Defs) {
-  MachineBasicBlock::iterator Loc = MBB->getFirstTerminator();
-  if (!TII->isUnpredicatedTerminator(*Loc))
-    return MBB->end();
-
-  for (const MachineOperand &MO : Loc->operands()) {
-    if (!MO.isReg())
-      continue;
-    unsigned Reg = MO.getReg();
-    if (!Reg)
-      continue;
-    if (MO.isUse()) {
-      addRegAndItsAliases(Reg, TRI, Uses);
-    } else {
-      if (!MO.isDead())
-        // Don't try to hoist code in the rare case the terminator defines a
-        // register that is later used.
-        return MBB->end();
-
-      // If the terminator defines a register, make sure we don't hoist
-      // the instruction whose def might be clobbered by the terminator.
-      addRegAndItsAliases(Reg, TRI, Defs);
-    }
-  }
-
-  if (Uses.empty())
-    return Loc;
-  // If the terminator is the only instruction in the block and Uses is not
-  // empty (or we would have returned above), we can still safely hoist
-  // instructions just before the terminator as long as the Defs/Uses are not
-  // violated (which is checked in HoistCommonCodeInSuccs).
-  if (Loc == MBB->begin())
-    return Loc;
-
-  // The terminator is probably a conditional branch, try not to separate the
-  // branch from condition setting instruction.
-  MachineBasicBlock::iterator PI =
-    skipDebugInstructionsBackward(std::prev(Loc), MBB->begin());
-
-  bool IsDef = false;
-  for (const MachineOperand &MO : PI->operands()) {
-    // If PI has a regmask operand, it is probably a call. Separate away.
-    if (MO.isRegMask())
-      return Loc;
-    if (!MO.isReg() || MO.isUse())
-      continue;
-    unsigned Reg = MO.getReg();
-    if (!Reg)
-      continue;
-    if (Uses.count(Reg)) {
-      IsDef = true;
-      break;
-    }
-  }
-  if (!IsDef)
-    // The condition setting instruction is not just before the conditional
-    // branch.
-    return Loc;
-
-  // Be conservative, don't insert instruction above something that may have
-  // side-effects. And since it's potentially bad to separate flag setting
-  // instruction from the conditional branch, just abort the optimization
-  // completely.
-  // Also avoid moving code above predicated instruction since it's hard to
-  // reason about register liveness with predicated instruction.
-  bool DontMoveAcrossStore = true;
-  if (!PI->isSafeToMove(nullptr, DontMoveAcrossStore) || TII->isPredicated(*PI))
-    return MBB->end();
-
-  // Find out what registers are live. Note this routine is ignoring other live
-  // registers which are only used by instructions in successor blocks.
-  for (const MachineOperand &MO : PI->operands()) {
-    if (!MO.isReg())
-      continue;
-    unsigned Reg = MO.getReg();
-    if (!Reg)
-      continue;
-    if (MO.isUse()) {
-      addRegAndItsAliases(Reg, TRI, Uses);
-    } else {
-      if (Uses.erase(Reg)) {
-        if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
-          for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs)
-            Uses.erase(*SubRegs); // Use sub-registers to be conservative
-        }
-      }
-      addRegAndItsAliases(Reg, TRI, Defs);
-    }
-  }
-
-  return PI;
-}
-
-bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
-  MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
-  SmallVector<MachineOperand, 4> Cond;
-  if (TII->analyzeBranch(*MBB, TBB, FBB, Cond, true) || !TBB || Cond.empty())
-    return false;
-
-  if (!FBB) FBB = findFalseBlock(MBB, TBB);
-  if (!FBB)
-    // Malformed bcc? True and false blocks are the same?
-    return false;
-
-  // Restrict the optimization to cases where MBB is the only predecessor,
-  // it is an obvious win.
-  if (TBB->pred_size() > 1 || FBB->pred_size() > 1)
-    return false;
-
-  // Find a suitable position to hoist the common instructions to. Also figure
-  // out which registers are used or defined by instructions from the insertion
-  // point to the end of the block.
-  SmallSet<unsigned, 4> Uses, Defs;
-  MachineBasicBlock::iterator Loc =
-    findHoistingInsertPosAndDeps(MBB, TII, TRI, Uses, Defs);
-  if (Loc == MBB->end())
-    return false;
-
-  bool HasDups = false;
-  SmallSet<unsigned, 4> ActiveDefsSet, AllDefsSet;
-  MachineBasicBlock::iterator TIB = TBB->begin();
-  MachineBasicBlock::iterator FIB = FBB->begin();
-  MachineBasicBlock::iterator TIE = TBB->end();
-  MachineBasicBlock::iterator FIE = FBB->end();
-  while (TIB != TIE && FIB != FIE) {
-    // Skip dbg_value instructions. These do not count.
-    TIB = skipDebugInstructionsForward(TIB, TIE);
-    FIB = skipDebugInstructionsForward(FIB, FIE);
-    if (TIB == TIE || FIB == FIE)
-      break;
-
-    if (!TIB->isIdenticalTo(*FIB, MachineInstr::CheckKillDead))
-      break;
-
-    if (TII->isPredicated(*TIB))
-      // Hard to reason about register liveness with predicated instruction.
-      break;
-
-    bool IsSafe = true;
-    for (MachineOperand &MO : TIB->operands()) {
-      // Don't attempt to hoist instructions with register masks.
-      if (MO.isRegMask()) {
-        IsSafe = false;
-        break;
-      }
-      if (!MO.isReg())
-        continue;
-      unsigned Reg = MO.getReg();
-      if (!Reg)
-        continue;
-      if (MO.isDef()) {
-        if (Uses.count(Reg)) {
-          // Avoid clobbering a register that's used by the instruction at
-          // the point of insertion.
-          IsSafe = false;
-          break;
-        }
-
-        if (Defs.count(Reg) && !MO.isDead()) {
-          // Don't hoist the instruction if the def would be clobber by the
-          // instruction at the point insertion. FIXME: This is overly
-          // conservative. It should be possible to hoist the instructions
-          // in BB2 in the following example:
-          // BB1:
-          // r1, eflag = op1 r2, r3
-          // brcc eflag
-          //
-          // BB2:
-          // r1 = op2, ...
-          //    = op3, killed r1
-          IsSafe = false;
-          break;
-        }
-      } else if (!ActiveDefsSet.count(Reg)) {
-        if (Defs.count(Reg)) {
-          // Use is defined by the instruction at the point of insertion.
-          IsSafe = false;
-          break;
-        }
-
-        if (MO.isKill() && Uses.count(Reg))
-          // Kills a register that's read by the instruction at the point of
-          // insertion. Remove the kill marker.
-          MO.setIsKill(false);
-      }
-    }
-    if (!IsSafe)
-      break;
-
-    bool DontMoveAcrossStore = true;
-    if (!TIB->isSafeToMove(nullptr, DontMoveAcrossStore))
-      break;
-
-    // Remove kills from ActiveDefsSet, these registers had short live ranges.
-    for (const MachineOperand &MO : TIB->operands()) {
-      if (!MO.isReg() || !MO.isUse() || !MO.isKill())
-        continue;
-      unsigned Reg = MO.getReg();
-      if (!Reg)
-        continue;
-      if (!AllDefsSet.count(Reg)) {
-        continue;
-      }
-      if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
-        for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
-          ActiveDefsSet.erase(*AI);
-      } else {
-        ActiveDefsSet.erase(Reg);
-      }
-    }
-
-    // Track local defs so we can update liveins.
-    for (const MachineOperand &MO : TIB->operands()) {
-      if (!MO.isReg() || !MO.isDef() || MO.isDead())
-        continue;
-      unsigned Reg = MO.getReg();
-      if (!Reg || TargetRegisterInfo::isVirtualRegister(Reg))
-        continue;
-      addRegAndItsAliases(Reg, TRI, ActiveDefsSet);
-      addRegAndItsAliases(Reg, TRI, AllDefsSet);
-    }
-
-    HasDups = true;
-    ++TIB;
-    ++FIB;
-  }
-
-  if (!HasDups)
-    return false;
-
-  MBB->splice(Loc, TBB, TBB->begin(), TIB);
-  FBB->erase(FBB->begin(), FIB);
-
-  if (UpdateLiveIns) {
-    recomputeLiveIns(*TBB);
-    recomputeLiveIns(*FBB);
-  }
-
-  ++NumHoist;
-  return true;
-}