1 files changed, 0 insertions, 6081 deletions

diff --git a/contrib/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/contrib/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
deleted file mode 100644
index 6e2ef67408d9..000000000000
--- a/contrib/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ /dev/null
@@ -1,6081 +0,0 @@
-//===- SimplifyCFG.cpp - Code to perform CFG simplification ---------------===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-//
-// Peephole optimize the CFG.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/ADT/APInt.h"
-#include "llvm/ADT/ArrayRef.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/Optional.h"
-#include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/SetOperations.h"
-#include "llvm/ADT/SetVector.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/StringRef.h"
-#include "llvm/Analysis/AssumptionCache.h"
-#include "llvm/Analysis/ConstantFolding.h"
-#include "llvm/Analysis/EHPersonalities.h"
-#include "llvm/Analysis/InstructionSimplify.h"
-#include "llvm/Analysis/MemorySSA.h"
-#include "llvm/Analysis/MemorySSAUpdater.h"
-#include "llvm/Analysis/TargetTransformInfo.h"
-#include "llvm/Analysis/ValueTracking.h"
-#include "llvm/IR/Attributes.h"
-#include "llvm/IR/BasicBlock.h"
-#include "llvm/IR/CFG.h"
-#include "llvm/IR/CallSite.h"
-#include "llvm/IR/Constant.h"
-#include "llvm/IR/ConstantRange.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/DataLayout.h"
-#include "llvm/IR/DerivedTypes.h"
-#include "llvm/IR/Function.h"
-#include "llvm/IR/GlobalValue.h"
-#include "llvm/IR/GlobalVariable.h"
-#include "llvm/IR/IRBuilder.h"
-#include "llvm/IR/InstrTypes.h"
-#include "llvm/IR/Instruction.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/IntrinsicInst.h"
-#include "llvm/IR/Intrinsics.h"
-#include "llvm/IR/LLVMContext.h"
-#include "llvm/IR/MDBuilder.h"
-#include "llvm/IR/Metadata.h"
-#include "llvm/IR/Module.h"
-#include "llvm/IR/NoFolder.h"
-#include "llvm/IR/Operator.h"
-#include "llvm/IR/PatternMatch.h"
-#include "llvm/IR/Type.h"
-#include "llvm/IR/Use.h"
-#include "llvm/IR/User.h"
-#include "llvm/IR/Value.h"
-#include "llvm/Support/Casting.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/KnownBits.h"
-#include "llvm/Support/MathExtras.h"
-#include "llvm/Support/raw_ostream.h"
-#include "llvm/Transforms/Utils/BasicBlockUtils.h"
-#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/Transforms/Utils/ValueMapper.h"
-#include <algorithm>
-#include <cassert>
-#include <climits>
-#include <cstddef>
-#include <cstdint>
-#include <iterator>
-#include <map>
-#include <set>
-#include <tuple>
-#include <utility>
-#include <vector>
-
-using namespace llvm;
-using namespace PatternMatch;
-
-#define DEBUG_TYPE "simplifycfg"
-
-// Chosen as 2 so as to be cheap, but still to have enough power to fold
-// a select, so the "clamp" idiom (of a min followed by a max) will be caught.
-// To catch this, we need to fold a compare and a select, hence '2' being the
-// minimum reasonable default.
-static cl::opt<unsigned> PHINodeFoldingThreshold(
-    "phi-node-folding-threshold", cl::Hidden, cl::init(2),
-    cl::desc(
-        "Control the amount of phi node folding to perform (default = 2)"));
-
-static cl::opt<bool> DupRet(
-    "simplifycfg-dup-ret", cl::Hidden, cl::init(false),
-    cl::desc("Duplicate return instructions into unconditional branches"));
-
-static cl::opt<bool>
-    SinkCommon("simplifycfg-sink-common", cl::Hidden, cl::init(true),
-               cl::desc("Sink common instructions down to the end block"));
-
-static cl::opt<bool> HoistCondStores(
-    "simplifycfg-hoist-cond-stores", cl::Hidden, cl::init(true),
-    cl::desc("Hoist conditional stores if an unconditional store precedes"));
-
-static cl::opt<bool> MergeCondStores(
-    "simplifycfg-merge-cond-stores", cl::Hidden, cl::init(true),
-    cl::desc("Hoist conditional stores even if an unconditional store does not "
-             "precede - hoist multiple conditional stores into a single "
-             "predicated store"));
-
-static cl::opt<bool> MergeCondStoresAggressively(
-    "simplifycfg-merge-cond-stores-aggressively", cl::Hidden, cl::init(false),
-    cl::desc("When merging conditional stores, do so even if the resultant "
-             "basic blocks are unlikely to be if-converted as a result"));
-
-static cl::opt<bool> SpeculateOneExpensiveInst(
-    "speculate-one-expensive-inst", cl::Hidden, cl::init(true),
-    cl::desc("Allow exactly one expensive instruction to be speculatively "
-             "executed"));
-
-static cl::opt<unsigned> MaxSpeculationDepth(
-    "max-speculation-depth", cl::Hidden, cl::init(10),
-    cl::desc("Limit maximum recursion depth when calculating costs of "
-             "speculatively executed instructions"));
-
-STATISTIC(NumBitMaps, "Number of switch instructions turned into bitmaps");
-STATISTIC(NumLinearMaps,
-          "Number of switch instructions turned into linear mapping");
-STATISTIC(NumLookupTables,
-          "Number of switch instructions turned into lookup tables");
-STATISTIC(
-    NumLookupTablesHoles,
-    "Number of switch instructions turned into lookup tables (holes checked)");
-STATISTIC(NumTableCmpReuses, "Number of reused switch table lookup compares");
-STATISTIC(NumSinkCommons,
-          "Number of common instructions sunk down to the end block");
-STATISTIC(NumSpeculations, "Number of speculative executed instructions");
-
-namespace {
-
-// The first field contains the value that the switch produces when a certain
-// case group is selected, and the second field is a vector containing the
-// cases composing the case group.
-using SwitchCaseResultVectorTy =
-    SmallVector<std::pair<Constant *, SmallVector<ConstantInt *, 4>>, 2>;
-
-// The first field contains the phi node that generates a result of the switch
-// and the second field contains the value generated for a certain case in the
-// switch for that PHI.
-using SwitchCaseResultsTy = SmallVector<std::pair<PHINode *, Constant *>, 4>;
-
-/// ValueEqualityComparisonCase - Represents a case of a switch.
-struct ValueEqualityComparisonCase {
-  ConstantInt *Value;
-  BasicBlock *Dest;
-
-  ValueEqualityComparisonCase(ConstantInt *Value, BasicBlock *Dest)
-      : Value(Value), Dest(Dest) {}
-
-  bool operator<(ValueEqualityComparisonCase RHS) const {
-    // Comparing pointers is ok as we only rely on the order for uniquing.
-    return Value < RHS.Value;
-  }
-
-  bool operator==(BasicBlock *RHSDest) const { return Dest == RHSDest; }
-};
-
-class SimplifyCFGOpt {
-  const TargetTransformInfo &TTI;
-  const DataLayout &DL;
-  SmallPtrSetImpl<BasicBlock *> *LoopHeaders;
-  const SimplifyCFGOptions &Options;
-  bool Resimplify;
-
-  Value *isValueEqualityComparison(Instruction *TI);
-  BasicBlock *GetValueEqualityComparisonCases(
-      Instruction *TI, std::vector<ValueEqualityComparisonCase> &Cases);
-  bool SimplifyEqualityComparisonWithOnlyPredecessor(Instruction *TI,
-                                                     BasicBlock *Pred,
-                                                     IRBuilder<> &Builder);
-  bool FoldValueComparisonIntoPredecessors(Instruction *TI,
-                                           IRBuilder<> &Builder);
-
-  bool SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder);
-  bool SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder);
-  bool SimplifySingleResume(ResumeInst *RI);
-  bool SimplifyCommonResume(ResumeInst *RI);
-  bool SimplifyCleanupReturn(CleanupReturnInst *RI);
-  bool SimplifyUnreachable(UnreachableInst *UI);
-  bool SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder);
-  bool SimplifyIndirectBr(IndirectBrInst *IBI);
-  bool SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder);
-  bool SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder);
-
-  bool tryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI,
-                                             IRBuilder<> &Builder);
-
-public:
-  SimplifyCFGOpt(const TargetTransformInfo &TTI, const DataLayout &DL,
-                 SmallPtrSetImpl<BasicBlock *> *LoopHeaders,
-                 const SimplifyCFGOptions &Opts)
-      : TTI(TTI), DL(DL), LoopHeaders(LoopHeaders), Options(Opts) {}
-
-  bool run(BasicBlock *BB);
-  bool simplifyOnce(BasicBlock *BB);
-
-  // Helper to set Resimplify and return change indication.
-  bool requestResimplify() {
-    Resimplify = true;
-    return true;
-  }
-};
-
-} // end anonymous namespace
-
-/// Return true if it is safe to merge these two
-/// terminator instructions together.
-static bool
-SafeToMergeTerminators(Instruction *SI1, Instruction *SI2,
-                       SmallSetVector<BasicBlock *, 4> *FailBlocks = nullptr) {
-  if (SI1 == SI2)
-    return false; // Can't merge with self!
-
-  // It is not safe to merge these two switch instructions if they have a common
-  // successor, and if that successor has a PHI node, and if *that* PHI node has
-  // conflicting incoming values from the two switch blocks.
-  BasicBlock *SI1BB = SI1->getParent();
-  BasicBlock *SI2BB = SI2->getParent();
-
-  SmallPtrSet<BasicBlock *, 16> SI1Succs(succ_begin(SI1BB), succ_end(SI1BB));
-  bool Fail = false;
-  for (BasicBlock *Succ : successors(SI2BB))
-    if (SI1Succs.count(Succ))
-      for (BasicBlock::iterator BBI = Succ->begin(); isa<PHINode>(BBI); ++BBI) {
-        PHINode *PN = cast<PHINode>(BBI);
-        if (PN->getIncomingValueForBlock(SI1BB) !=
-            PN->getIncomingValueForBlock(SI2BB)) {
-          if (FailBlocks)
-            FailBlocks->insert(Succ);
-          Fail = true;
-        }
-      }
-
-  return !Fail;
-}
-
-/// Return true if it is safe and profitable to merge these two terminator
-/// instructions together, where SI1 is an unconditional branch. PhiNodes will
-/// store all PHI nodes in common successors.
-static bool
-isProfitableToFoldUnconditional(BranchInst *SI1, BranchInst *SI2,
-                                Instruction *Cond,
-                                SmallVectorImpl<PHINode *> &PhiNodes) {
-  if (SI1 == SI2)
-    return false; // Can't merge with self!
-  assert(SI1->isUnconditional() && SI2->isConditional());
-
-  // We fold the unconditional branch if we can easily update all PHI nodes in
-  // common successors:
-  // 1> We have a constant incoming value for the conditional branch;
-  // 2> We have "Cond" as the incoming value for the unconditional branch;
-  // 3> SI2->getCondition() and Cond have same operands.
-  CmpInst *Ci2 = dyn_cast<CmpInst>(SI2->getCondition());
-  if (!Ci2)
-    return false;
-  if (!(Cond->getOperand(0) == Ci2->getOperand(0) &&
-        Cond->getOperand(1) == Ci2->getOperand(1)) &&
-      !(Cond->getOperand(0) == Ci2->getOperand(1) &&
-        Cond->getOperand(1) == Ci2->getOperand(0)))
-    return false;
-
-  BasicBlock *SI1BB = SI1->getParent();
-  BasicBlock *SI2BB = SI2->getParent();
-  SmallPtrSet<BasicBlock *, 16> SI1Succs(succ_begin(SI1BB), succ_end(SI1BB));
-  for (BasicBlock *Succ : successors(SI2BB))
-    if (SI1Succs.count(Succ))
-      for (BasicBlock::iterator BBI = Succ->begin(); isa<PHINode>(BBI); ++BBI) {
-        PHINode *PN = cast<PHINode>(BBI);
-        if (PN->getIncomingValueForBlock(SI1BB) != Cond ||
-            !isa<ConstantInt>(PN->getIncomingValueForBlock(SI2BB)))
-          return false;
-        PhiNodes.push_back(PN);
-      }
-  return true;
-}
-
-/// Update PHI nodes in Succ to indicate that there will now be entries in it
-/// from the 'NewPred' block. The values that will be flowing into the PHI nodes
-/// will be the same as those coming in from ExistPred, an existing predecessor
-/// of Succ.
-static void AddPredecessorToBlock(BasicBlock *Succ, BasicBlock *NewPred,
-                                  BasicBlock *ExistPred,
-                                  MemorySSAUpdater *MSSAU = nullptr) {
-  for (PHINode &PN : Succ->phis())
-    PN.addIncoming(PN.getIncomingValueForBlock(ExistPred), NewPred);
-  if (MSSAU)
-    if (auto *MPhi = MSSAU->getMemorySSA()->getMemoryAccess(Succ))
-      MPhi->addIncoming(MPhi->getIncomingValueForBlock(ExistPred), NewPred);
-}
-
-/// Compute an abstract "cost" of speculating the given instruction,
-/// which is assumed to be safe to speculate. TCC_Free means cheap,
-/// TCC_Basic means less cheap, and TCC_Expensive means prohibitively
-/// expensive.
-static unsigned ComputeSpeculationCost(const User *I,
-                                       const TargetTransformInfo &TTI) {
-  assert(isSafeToSpeculativelyExecute(I) &&
-         "Instruction is not safe to speculatively execute!");
-  return TTI.getUserCost(I);
-}
-
-/// If we have a merge point of an "if condition" as accepted above,
-/// return true if the specified value dominates the block.  We
-/// don't handle the true generality of domination here, just a special case
-/// which works well enough for us.
-///
-/// If AggressiveInsts is non-null, and if V does not dominate BB, we check to
-/// see if V (which must be an instruction) and its recursive operands
-/// that do not dominate BB have a combined cost lower than CostRemaining and
-/// are non-trapping.  If both are true, the instruction is inserted into the
-/// set and true is returned.
-///
-/// The cost for most non-trapping instructions is defined as 1 except for
-/// Select whose cost is 2.
-///
-/// After this function returns, CostRemaining is decreased by the cost of
-/// V plus its non-dominating operands.  If that cost is greater than
-/// CostRemaining, false is returned and CostRemaining is undefined.
-static bool DominatesMergePoint(Value *V, BasicBlock *BB,
-                                SmallPtrSetImpl<Instruction *> &AggressiveInsts,
-                                unsigned &CostRemaining,
-                                const TargetTransformInfo &TTI,
-                                unsigned Depth = 0) {
-  // It is possible to hit a zero-cost cycle (phi/gep instructions for example),
-  // so limit the recursion depth.
-  // TODO: While this recursion limit does prevent pathological behavior, it
-  // would be better to track visited instructions to avoid cycles.
-  if (Depth == MaxSpeculationDepth)
-    return false;
-
-  Instruction *I = dyn_cast<Instruction>(V);
-  if (!I) {
-    // Non-instructions all dominate instructions, but not all constantexprs
-    // can be executed unconditionally.
-    if (ConstantExpr *C = dyn_cast<ConstantExpr>(V))
-      if (C->canTrap())
-        return false;
-    return true;
-  }
-  BasicBlock *PBB = I->getParent();
-
-  // We don't want to allow weird loops that might have the "if condition" in
-  // the bottom of this block.
-  if (PBB == BB)
-    return false;
-
-  // If this instruction is defined in a block that contains an unconditional
-  // branch to BB, then it must be in the 'conditional' part of the "if
-  // statement".  If not, it definitely dominates the region.
-  BranchInst *BI = dyn_cast<BranchInst>(PBB->getTerminator());
-  if (!BI || BI->isConditional() || BI->getSuccessor(0) != BB)
-    return true;
-
-  // If we have seen this instruction before, don't count it again.
-  if (AggressiveInsts.count(I))
-    return true;
-
-  // Okay, it looks like the instruction IS in the "condition".  Check to
-  // see if it's a cheap instruction to unconditionally compute, and if it
-  // only uses stuff defined outside of the condition.  If so, hoist it out.
-  if (!isSafeToSpeculativelyExecute(I))
-    return false;
-
-  unsigned Cost = ComputeSpeculationCost(I, TTI);
-
-  // Allow exactly one instruction to be speculated regardless of its cost
-  // (as long as it is safe to do so).
-  // This is intended to flatten the CFG even if the instruction is a division
-  // or other expensive operation. The speculation of an expensive instruction
-  // is expected to be undone in CodeGenPrepare if the speculation has not
-  // enabled further IR optimizations.
-  if (Cost > CostRemaining &&
-      (!SpeculateOneExpensiveInst || !AggressiveInsts.empty() || Depth > 0))
-    return false;
-
-  // Avoid unsigned wrap.
-  CostRemaining = (Cost > CostRemaining) ? 0 : CostRemaining - Cost;
-
-  // Okay, we can only really hoist these out if their operands do
-  // not take us over the cost threshold.
-  for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
-    if (!DominatesMergePoint(*i, BB, AggressiveInsts, CostRemaining, TTI,
-                             Depth + 1))
-      return false;
-  // Okay, it's safe to do this!  Remember this instruction.
-  AggressiveInsts.insert(I);
-  return true;
-}
-
-/// Extract ConstantInt from value, looking through IntToPtr
-/// and PointerNullValue. Return NULL if value is not a constant int.
-static ConstantInt *GetConstantInt(Value *V, const DataLayout &DL) {
-  // Normal constant int.
-  ConstantInt *CI = dyn_cast<ConstantInt>(V);
-  if (CI || !isa<Constant>(V) || !V->getType()->isPointerTy())
-    return CI;
-
-  // This is some kind of pointer constant. Turn it into a pointer-sized
-  // ConstantInt if possible.
-  IntegerType *PtrTy = cast<IntegerType>(DL.getIntPtrType(V->getType()));
-
-  // Null pointer means 0, see SelectionDAGBuilder::getValue(const Value*).
-  if (isa<ConstantPointerNull>(V))
-    return ConstantInt::get(PtrTy, 0);
-
-  // IntToPtr const int.
-  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
-    if (CE->getOpcode() == Instruction::IntToPtr)
-      if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(0))) {
-        // The constant is very likely to have the right type already.
-        if (CI->getType() == PtrTy)
-          return CI;
-        else
-          return cast<ConstantInt>(
-              ConstantExpr::getIntegerCast(CI, PtrTy, /*isSigned=*/false));
-      }
-  return nullptr;
-}
-
-namespace {
-
-/// Given a chain of or (||) or and (&&) comparison of a value against a
-/// constant, this will try to recover the information required for a switch
-/// structure.
-/// It will depth-first traverse the chain of comparison, seeking for patterns
-/// like %a == 12 or %a < 4 and combine them to produce a set of integer
-/// representing the different cases for the switch.
-/// Note that if the chain is composed of '||' it will build the set of elements
-/// that matches the comparisons (i.e. any of this value validate the chain)
-/// while for a chain of '&&' it will build the set elements that make the test
-/// fail.
-struct ConstantComparesGatherer {
-  const DataLayout &DL;
-
-  /// Value found for the switch comparison
-  Value *CompValue = nullptr;
-
-  /// Extra clause to be checked before the switch
-  Value *Extra = nullptr;
-
-  /// Set of integers to match in switch
-  SmallVector<ConstantInt *, 8> Vals;
-
-  /// Number of comparisons matched in the and/or chain
-  unsigned UsedICmps = 0;
-
-  /// Construct and compute the result for the comparison instruction Cond
-  ConstantComparesGatherer(Instruction *Cond, const DataLayout &DL) : DL(DL) {
-    gather(Cond);
-  }
-
-  ConstantComparesGatherer(const ConstantComparesGatherer &) = delete;
-  ConstantComparesGatherer &
-  operator=(const ConstantComparesGatherer &) = delete;
-
-private:
-  /// Try to set the current value used for the comparison, it succeeds only if
-  /// it wasn't set before or if the new value is the same as the old one
-  bool setValueOnce(Value *NewVal) {
-    if (CompValue && CompValue != NewVal)
-      return false;
-    CompValue = NewVal;
-    return (CompValue != nullptr);
-  }
-
-  /// Try to match Instruction "I" as a comparison against a constant and
-  /// populates the array Vals with the set of values that match (or do not
-  /// match depending on isEQ).
-  /// Return false on failure. On success, the Value the comparison matched
-  /// against is placed in CompValue.
-  /// If CompValue is already set, the function is expected to fail if a match
-  /// is found but the value compared to is different.
-  bool matchInstruction(Instruction *I, bool isEQ) {
-    // If this is an icmp against a constant, handle this as one of the cases.
-    ICmpInst *ICI;
-    ConstantInt *C;
-    if (!((ICI = dyn_cast<ICmpInst>(I)) &&
-          (C = GetConstantInt(I->getOperand(1), DL)))) {
-      return false;
-    }
-
-    Value *RHSVal;
-    const APInt *RHSC;
-
-    // Pattern match a special case
-    // (x & ~2^z) == y --> x == y || x == y|2^z
-    // This undoes a transformation done by instcombine to fuse 2 compares.
-    if (ICI->getPredicate() == (isEQ ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE)) {
-      // It's a little bit hard to see why the following transformations are
-      // correct. Here is a CVC3 program to verify them for 64-bit values:
-
-      /*
-         ONE  : BITVECTOR(64) = BVZEROEXTEND(0bin1, 63);
-         x    : BITVECTOR(64);
-         y    : BITVECTOR(64);
-         z    : BITVECTOR(64);
-         mask : BITVECTOR(64) = BVSHL(ONE, z);
-         QUERY( (y & ~mask = y) =>
-                ((x & ~mask = y) <=> (x = y OR x = (y |  mask)))
-         );
-         QUERY( (y |  mask = y) =>
-                ((x |  mask = y) <=> (x = y OR x = (y & ~mask)))
-         );
-      */
-
-      // Please note that each pattern must be a dual implication (<--> or
-      // iff). One directional implication can create spurious matches. If the
-      // implication is only one-way, an unsatisfiable condition on the left
-      // side can imply a satisfiable condition on the right side. Dual
-      // implication ensures that satisfiable conditions are transformed to
-      // other satisfiable conditions and unsatisfiable conditions are
-      // transformed to other unsatisfiable conditions.
-
-      // Here is a concrete example of a unsatisfiable condition on the left
-      // implying a satisfiable condition on the right:
-      //
-      // mask = (1 << z)
-      // (x & ~mask) == y  --> (x == y || x == (y | mask))
-      //
-      // Substituting y = 3, z = 0 yields:
-      // (x & -2) == 3 --> (x == 3 || x == 2)
-
-      // Pattern match a special case:
-      /*
-        QUERY( (y & ~mask = y) =>
-               ((x & ~mask = y) <=> (x = y OR x = (y |  mask)))
-        );
-      */
-      if (match(ICI->getOperand(0),
-                m_And(m_Value(RHSVal), m_APInt(RHSC)))) {
-        APInt Mask = ~*RHSC;
-        if (Mask.isPowerOf2() && (C->getValue() & ~Mask) == C->getValue()) {
-          // If we already have a value for the switch, it has to match!
-          if (!setValueOnce(RHSVal))
-            return false;
-
-          Vals.push_back(C);
-          Vals.push_back(
-              ConstantInt::get(C->getContext(),
-                               C->getValue() | Mask));
-          UsedICmps++;
-          return true;
-        }
-      }
-
-      // Pattern match a special case:
-      /*
-        QUERY( (y |  mask = y) =>
-               ((x |  mask = y) <=> (x = y OR x = (y & ~mask)))
-        );
-      */
-      if (match(ICI->getOperand(0),
-                m_Or(m_Value(RHSVal), m_APInt(RHSC)))) {
-        APInt Mask = *RHSC;
-        if (Mask.isPowerOf2() && (C->getValue() | Mask) == C->getValue()) {
-          // If we already have a value for the switch, it has to match!
-          if (!setValueOnce(RHSVal))
-            return false;
-
-          Vals.push_back(C);
-          Vals.push_back(ConstantInt::get(C->getContext(),
-                                          C->getValue() & ~Mask));
-          UsedICmps++;
-          return true;
-        }
-      }
-
-      // If we already have a value for the switch, it has to match!
-      if (!setValueOnce(ICI->getOperand(0)))
-        return false;
-
-      UsedICmps++;
-      Vals.push_back(C);
-      return ICI->getOperand(0);
-    }
-
-    // If we have "x ult 3", for example, then we can add 0,1,2 to the set.
-    ConstantRange Span = ConstantRange::makeAllowedICmpRegion(
-        ICI->getPredicate(), C->getValue());
-
-    // Shift the range if the compare is fed by an add. This is the range
-    // compare idiom as emitted by instcombine.
-    Value *CandidateVal = I->getOperand(0);
-    if (match(I->getOperand(0), m_Add(m_Value(RHSVal), m_APInt(RHSC)))) {
-      Span = Span.subtract(*RHSC);
-      CandidateVal = RHSVal;
-    }
-
-    // If this is an and/!= check, then we are looking to build the set of
-    // value that *don't* pass the and chain. I.e. to turn "x ugt 2" into
-    // x != 0 && x != 1.
-    if (!isEQ)
-      Span = Span.inverse();
-
-    // If there are a ton of values, we don't want to make a ginormous switch.
-    if (Span.isSizeLargerThan(8) || Span.isEmptySet()) {
-      return false;
-    }
-
-    // If we already have a value for the switch, it has to match!
-    if (!setValueOnce(CandidateVal))
-      return false;
-
-    // Add all values from the range to the set
-    for (APInt Tmp = Span.getLower(); Tmp != Span.getUpper(); ++Tmp)
-      Vals.push_back(ConstantInt::get(I->getContext(), Tmp));
-
-    UsedICmps++;
-    return true;
-  }
-
-  /// Given a potentially 'or'd or 'and'd together collection of icmp
-  /// eq/ne/lt/gt instructions that compare a value against a constant, extract
-  /// the value being compared, and stick the list constants into the Vals
-  /// vector.
-  /// One "Extra" case is allowed to differ from the other.
-  void gather(Value *V) {
-    Instruction *I = dyn_cast<Instruction>(V);
-    bool isEQ = (I->getOpcode() == Instruction::Or);
-
-    // Keep a stack (SmallVector for efficiency) for depth-first traversal
-    SmallVector<Value *, 8> DFT;
-    SmallPtrSet<Value *, 8> Visited;
-
-    // Initialize
-    Visited.insert(V);
-    DFT.push_back(V);
-
-    while (!DFT.empty()) {
-      V = DFT.pop_back_val();
-
-      if (Instruction *I = dyn_cast<Instruction>(V)) {
-        // If it is a || (or && depending on isEQ), process the operands.
-        if (I->getOpcode() == (isEQ ? Instruction::Or : Instruction::And)) {
-          if (Visited.insert(I->getOperand(1)).second)
-            DFT.push_back(I->getOperand(1));
-          if (Visited.insert(I->getOperand(0)).second)
-            DFT.push_back(I->getOperand(0));
-          continue;
-        }
-
-        // Try to match the current instruction
-        if (matchInstruction(I, isEQ))
-          // Match succeed, continue the loop
-          continue;
-      }
-
-      // One element of the sequence of || (or &&) could not be match as a
-      // comparison against the same value as the others.
-      // We allow only one "Extra" case to be checked before the switch
-      if (!Extra) {
-        Extra = V;
-        continue;
-      }
-      // Failed to parse a proper sequence, abort now
-      CompValue = nullptr;
-      break;
-    }
-  }
-};
-
-} // end anonymous namespace
-
-static void EraseTerminatorAndDCECond(Instruction *TI,
-                                      MemorySSAUpdater *MSSAU = nullptr) {
-  Instruction *Cond = nullptr;
-  if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
-    Cond = dyn_cast<Instruction>(SI->getCondition());
-  } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
-    if (BI->isConditional())
-      Cond = dyn_cast<Instruction>(BI->getCondition());
-  } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(TI)) {
-    Cond = dyn_cast<Instruction>(IBI->getAddress());
-  }
-
-  TI->eraseFromParent();
-  if (Cond)
-    RecursivelyDeleteTriviallyDeadInstructions(Cond, nullptr, MSSAU);
-}
-
-/// Return true if the specified terminator checks
-/// to see if a value is equal to constant integer value.
-Value *SimplifyCFGOpt::isValueEqualityComparison(Instruction *TI) {
-  Value *CV = nullptr;
-  if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
-    // Do not permit merging of large switch instructions into their
-    // predecessors unless there is only one predecessor.
-    if (!SI->getParent()->hasNPredecessorsOrMore(128 / SI->getNumSuccessors()))
-      CV = SI->getCondition();
-  } else if (BranchInst *BI = dyn_cast<BranchInst>(TI))
-    if (BI->isConditional() && BI->getCondition()->hasOneUse())
-      if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) {
-        if (ICI->isEquality() && GetConstantInt(ICI->getOperand(1), DL))
-          CV = ICI->getOperand(0);
-      }
-
-  // Unwrap any lossless ptrtoint cast.
-  if (CV) {
-    if (PtrToIntInst *PTII = dyn_cast<PtrToIntInst>(CV)) {
-      Value *Ptr = PTII->getPointerOperand();
-      if (PTII->getType() == DL.getIntPtrType(Ptr->getType()))
-        CV = Ptr;
-    }
-  }
-  return CV;
-}
-
-/// Given a value comparison instruction,
-/// decode all of the 'cases' that it represents and return the 'default' block.
-BasicBlock *SimplifyCFGOpt::GetValueEqualityComparisonCases(
-    Instruction *TI, std::vector<ValueEqualityComparisonCase> &Cases) {
-  if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
-    Cases.reserve(SI->getNumCases());
-    for (auto Case : SI->cases())
-      Cases.push_back(ValueEqualityComparisonCase(Case.getCaseValue(),
-                                                  Case.getCaseSuccessor()));
-    return SI->getDefaultDest();
-  }
-
-  BranchInst *BI = cast<BranchInst>(TI);
-  ICmpInst *ICI = cast<ICmpInst>(BI->getCondition());
-  BasicBlock *Succ = BI->getSuccessor(ICI->getPredicate() == ICmpInst::ICMP_NE);
-  Cases.push_back(ValueEqualityComparisonCase(
-      GetConstantInt(ICI->getOperand(1), DL), Succ));
-  return BI->getSuccessor(ICI->getPredicate() == ICmpInst::ICMP_EQ);
-}
-
-/// Given a vector of bb/value pairs, remove any entries
-/// in the list that match the specified block.
-static void
-EliminateBlockCases(BasicBlock *BB,
-                    std::vector<ValueEqualityComparisonCase> &Cases) {
-  Cases.erase(std::remove(Cases.begin(), Cases.end(), BB), Cases.end());
-}
-
-/// Return true if there are any keys in C1 that exist in C2 as well.
-static bool ValuesOverlap(std::vector<ValueEqualityComparisonCase> &C1,
-                          std::vector<ValueEqualityComparisonCase> &C2) {
-  std::vector<ValueEqualityComparisonCase> *V1 = &C1, *V2 = &C2;
-
-  // Make V1 be smaller than V2.
-  if (V1->size() > V2->size())
-    std::swap(V1, V2);
-
-  if (V1->empty())
-    return false;
-  if (V1->size() == 1) {
-    // Just scan V2.
-    ConstantInt *TheVal = (*V1)[0].Value;
-    for (unsigned i = 0, e = V2->size(); i != e; ++i)
-      if (TheVal == (*V2)[i].Value)
-        return true;
-  }
-
-  // Otherwise, just sort both lists and compare element by element.
-  array_pod_sort(V1->begin(), V1->end());
-  array_pod_sort(V2->begin(), V2->end());
-  unsigned i1 = 0, i2 = 0, e1 = V1->size(), e2 = V2->size();
-  while (i1 != e1 && i2 != e2) {
-    if ((*V1)[i1].Value == (*V2)[i2].Value)
-      return true;
-    if ((*V1)[i1].Value < (*V2)[i2].Value)
-      ++i1;
-    else
-      ++i2;
-  }
-  return false;
-}
-
-// Set branch weights on SwitchInst. This sets the metadata if there is at
-// least one non-zero weight.
-static void setBranchWeights(SwitchInst *SI, ArrayRef<uint32_t> Weights) {
-  // Check that there is at least one non-zero weight. Otherwise, pass
-  // nullptr to setMetadata which will erase the existing metadata.
-  MDNode *N = nullptr;
-  if (llvm::any_of(Weights, [](uint32_t W) { return W != 0; }))
-    N = MDBuilder(SI->getParent()->getContext()).createBranchWeights(Weights);
-  SI->setMetadata(LLVMContext::MD_prof, N);
-}
-
-// Similar to the above, but for branch and select instructions that take
-// exactly 2 weights.
-static void setBranchWeights(Instruction *I, uint32_t TrueWeight,
-                             uint32_t FalseWeight) {
-  assert(isa<BranchInst>(I) || isa<SelectInst>(I));
-  // Check that there is at least one non-zero weight. Otherwise, pass
-  // nullptr to setMetadata which will erase the existing metadata.
-  MDNode *N = nullptr;
-  if (TrueWeight || FalseWeight)
-    N = MDBuilder(I->getParent()->getContext())
-            .createBranchWeights(TrueWeight, FalseWeight);
-  I->setMetadata(LLVMContext::MD_prof, N);
-}
-
-/// If TI is known to be a terminator instruction and its block is known to
-/// only have a single predecessor block, check to see if that predecessor is
-/// also a value comparison with the same value, and if that comparison
-/// determines the outcome of this comparison. If so, simplify TI. This does a
-/// very limited form of jump threading.
-bool SimplifyCFGOpt::SimplifyEqualityComparisonWithOnlyPredecessor(
-    Instruction *TI, BasicBlock *Pred, IRBuilder<> &Builder) {
-  Value *PredVal = isValueEqualityComparison(Pred->getTerminator());
-  if (!PredVal)
-    return false; // Not a value comparison in predecessor.
-
-  Value *ThisVal = isValueEqualityComparison(TI);
-  assert(ThisVal && "This isn't a value comparison!!");
-  if (ThisVal != PredVal)
-    return false; // Different predicates.
-
-  // TODO: Preserve branch weight metadata, similarly to how
-  // FoldValueComparisonIntoPredecessors preserves it.
-
-  // Find out information about when control will move from Pred to TI's block.
-  std::vector<ValueEqualityComparisonCase> PredCases;
-  BasicBlock *PredDef =
-      GetValueEqualityComparisonCases(Pred->getTerminator(), PredCases);
-  EliminateBlockCases(PredDef, PredCases); // Remove default from cases.
-
-  // Find information about how control leaves this block.
-  std::vector<ValueEqualityComparisonCase> ThisCases;
-  BasicBlock *ThisDef = GetValueEqualityComparisonCases(TI, ThisCases);
-  EliminateBlockCases(ThisDef, ThisCases); // Remove default from cases.
-
-  // If TI's block is the default block from Pred's comparison, potentially
-  // simplify TI based on this knowledge.
-  if (PredDef == TI->getParent()) {
-    // If we are here, we know that the value is none of those cases listed in
-    // PredCases.  If there are any cases in ThisCases that are in PredCases, we
-    // can simplify TI.
-    if (!ValuesOverlap(PredCases, ThisCases))
-      return false;
-
-    if (isa<BranchInst>(TI)) {
-      // Okay, one of the successors of this condbr is dead.  Convert it to a
-      // uncond br.
-      assert(ThisCases.size() == 1 && "Branch can only have one case!");
-      // Insert the new branch.
-      Instruction *NI = Builder.CreateBr(ThisDef);
-      (void)NI;
-
-      // Remove PHI node entries for the dead edge.
-      ThisCases[0].Dest->removePredecessor(TI->getParent());
-
-      LLVM_DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
-                        << "Through successor TI: " << *TI << "Leaving: " << *NI
-                        << "\n");
-
-      EraseTerminatorAndDCECond(TI);
-      return true;
-    }
-
-    SwitchInstProfUpdateWrapper SI = *cast<SwitchInst>(TI);
-    // Okay, TI has cases that are statically dead, prune them away.
-    SmallPtrSet<Constant *, 16> DeadCases;
-    for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
-      DeadCases.insert(PredCases[i].Value);
-
-    LLVM_DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
-                      << "Through successor TI: " << *TI);
-
-    for (SwitchInst::CaseIt i = SI->case_end(), e = SI->case_begin(); i != e;) {
-      --i;
-      if (DeadCases.count(i->getCaseValue())) {
-        i->getCaseSuccessor()->removePredecessor(TI->getParent());
-        SI.removeCase(i);
-      }
-    }
-    LLVM_DEBUG(dbgs() << "Leaving: " << *TI << "\n");
-    return true;
-  }
-
-  // Otherwise, TI's block must correspond to some matched value.  Find out
-  // which value (or set of values) this is.
-  ConstantInt *TIV = nullptr;
-  BasicBlock *TIBB = TI->getParent();
-  for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
-    if (PredCases[i].Dest == TIBB) {
-      if (TIV)
-        return false; // Cannot handle multiple values coming to this block.
-      TIV = PredCases[i].Value;
-    }
-  assert(TIV && "No edge from pred to succ?");
-
-  // Okay, we found the one constant that our value can be if we get into TI's
-  // BB.  Find out which successor will unconditionally be branched to.
-  BasicBlock *TheRealDest = nullptr;
-  for (unsigned i = 0, e = ThisCases.size(); i != e; ++i)
-    if (ThisCases[i].Value == TIV) {
-      TheRealDest = ThisCases[i].Dest;
-      break;
-    }
-
-  // If not handled by any explicit cases, it is handled by the default case.
-  if (!TheRealDest)
-    TheRealDest = ThisDef;
-
-  // Remove PHI node entries for dead edges.
-  BasicBlock *CheckEdge = TheRealDest;
-  for (BasicBlock *Succ : successors(TIBB))
-    if (Succ != CheckEdge)
-      Succ->removePredecessor(TIBB);
-    else
-      CheckEdge = nullptr;
-
-  // Insert the new branch.
-  Instruction *NI = Builder.CreateBr(TheRealDest);
-  (void)NI;
-
-  LLVM_DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
-                    << "Through successor TI: " << *TI << "Leaving: " << *NI
-                    << "\n");
-
-  EraseTerminatorAndDCECond(TI);
-  return true;
-}
-
-namespace {
-
-/// This class implements a stable ordering of constant
-/// integers that does not depend on their address.  This is important for
-/// applications that sort ConstantInt's to ensure uniqueness.
-struct ConstantIntOrdering {
-  bool operator()(const ConstantInt *LHS, const ConstantInt *RHS) const {
-    return LHS->getValue().ult(RHS->getValue());
-  }
-};
-
-} // end anonymous namespace
-
-static int ConstantIntSortPredicate(ConstantInt *const *P1,
-                                    ConstantInt *const *P2) {
-  const ConstantInt *LHS = *P1;
-  const ConstantInt *RHS = *P2;
-  if (LHS == RHS)
-    return 0;
-  return LHS->getValue().ult(RHS->getValue()) ? 1 : -1;
-}
-
-static inline bool HasBranchWeights(const Instruction *I) {
-  MDNode *ProfMD = I->getMetadata(LLVMContext::MD_prof);
-  if (ProfMD && ProfMD->getOperand(0))
-    if (MDString *MDS = dyn_cast<MDString>(ProfMD->getOperand(0)))
-      return MDS->getString().equals("branch_weights");
-
-  return false;
-}
-
-/// Get Weights of a given terminator, the default weight is at the front
-/// of the vector. If TI is a conditional eq, we need to swap the branch-weight
-/// metadata.
-static void GetBranchWeights(Instruction *TI,
-                             SmallVectorImpl<uint64_t> &Weights) {
-  MDNode *MD = TI->getMetadata(LLVMContext::MD_prof);
-  assert(MD);
-  for (unsigned i = 1, e = MD->getNumOperands(); i < e; ++i) {
-    ConstantInt *CI = mdconst::extract<ConstantInt>(MD->getOperand(i));
-    Weights.push_back(CI->getValue().getZExtValue());
-  }
-
-  // If TI is a conditional eq, the default case is the false case,
-  // and the corresponding branch-weight data is at index 2. We swap the
-  // default weight to be the first entry.
-  if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
-    assert(Weights.size() == 2);
-    ICmpInst *ICI = cast<ICmpInst>(BI->getCondition());
-    if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
-      std::swap(Weights.front(), Weights.back());
-  }
-}
-
-/// Keep halving the weights until all can fit in uint32_t.
-static void FitWeights(MutableArrayRef<uint64_t> Weights) {
-  uint64_t Max = *std::max_element(Weights.begin(), Weights.end());
-  if (Max > UINT_MAX) {
-    unsigned Offset = 32 - countLeadingZeros(Max);
-    for (uint64_t &I : Weights)
-      I >>= Offset;
-  }
-}
-
-/// The specified terminator is a value equality comparison instruction
-/// (either a switch or a branch on "X == c").
-/// See if any of the predecessors of the terminator block are value comparisons
-/// on the same value.  If so, and if safe to do so, fold them together.
-bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(Instruction *TI,
-                                                         IRBuilder<> &Builder) {
-  BasicBlock *BB = TI->getParent();
-  Value *CV = isValueEqualityComparison(TI); // CondVal
-  assert(CV && "Not a comparison?");
-  bool Changed = false;
-
-  SmallVector<BasicBlock *, 16> Preds(pred_begin(BB), pred_end(BB));
-  while (!Preds.empty()) {
-    BasicBlock *Pred = Preds.pop_back_val();
-
-    // See if the predecessor is a comparison with the same value.
-    Instruction *PTI = Pred->getTerminator();
-    Value *PCV = isValueEqualityComparison(PTI); // PredCondVal
-
-    if (PCV == CV && TI != PTI) {
-      SmallSetVector<BasicBlock*, 4> FailBlocks;
-      if (!SafeToMergeTerminators(TI, PTI, &FailBlocks)) {
-        for (auto *Succ : FailBlocks) {
-          if (!SplitBlockPredecessors(Succ, TI->getParent(), ".fold.split"))
-            return false;
-        }
-      }
-
-      // Figure out which 'cases' to copy from SI to PSI.
-      std::vector<ValueEqualityComparisonCase> BBCases;
-      BasicBlock *BBDefault = GetValueEqualityComparisonCases(TI, BBCases);
-
-      std::vector<ValueEqualityComparisonCase> PredCases;
-      BasicBlock *PredDefault = GetValueEqualityComparisonCases(PTI, PredCases);
-
-      // Based on whether the default edge from PTI goes to BB or not, fill in
-      // PredCases and PredDefault with the new switch cases we would like to
-      // build.
-      SmallVector<BasicBlock *, 8> NewSuccessors;
-
-      // Update the branch weight metadata along the way
-      SmallVector<uint64_t, 8> Weights;
-      bool PredHasWeights = HasBranchWeights(PTI);
-      bool SuccHasWeights = HasBranchWeights(TI);
-
-      if (PredHasWeights) {
-        GetBranchWeights(PTI, Weights);
-        // branch-weight metadata is inconsistent here.
-        if (Weights.size() != 1 + PredCases.size())
-          PredHasWeights = SuccHasWeights = false;
-      } else if (SuccHasWeights)
-        // If there are no predecessor weights but there are successor weights,
-        // populate Weights with 1, which will later be scaled to the sum of
-        // successor's weights
-        Weights.assign(1 + PredCases.size(), 1);
-
-      SmallVector<uint64_t, 8> SuccWeights;
-      if (SuccHasWeights) {
-        GetBranchWeights(TI, SuccWeights);
-        // branch-weight metadata is inconsistent here.
-        if (SuccWeights.size() != 1 + BBCases.size())
-          PredHasWeights = SuccHasWeights = false;
-      } else if (PredHasWeights)
-        SuccWeights.assign(1 + BBCases.size(), 1);
-
-      if (PredDefault == BB) {
-        // If this is the default destination from PTI, only the edges in TI
-        // that don't occur in PTI, or that branch to BB will be activated.
-        std::set<ConstantInt *, ConstantIntOrdering> PTIHandled;
-        for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
-          if (PredCases[i].Dest != BB)
-            PTIHandled.insert(PredCases[i].Value);
-          else {
-            // The default destination is BB, we don't need explicit targets.
-            std::swap(PredCases[i], PredCases.back());
-
-            if (PredHasWeights || SuccHasWeights) {
-              // Increase weight for the default case.
-              Weights[0] += Weights[i + 1];
-              std::swap(Weights[i + 1], Weights.back());
-              Weights.pop_back();
-            }
-
-            PredCases.pop_back();
-            --i;
-            --e;
-          }
-
-        // Reconstruct the new switch statement we will be building.
-        if (PredDefault != BBDefault) {
-          PredDefault->removePredecessor(Pred);
-          PredDefault = BBDefault;
-          NewSuccessors.push_back(BBDefault);
-        }
-
-        unsigned CasesFromPred = Weights.size();
-        uint64_t ValidTotalSuccWeight = 0;
-        for (unsigned i = 0, e = BBCases.size(); i != e; ++i)
-          if (!PTIHandled.count(BBCases[i].Value) &&
-              BBCases[i].Dest != BBDefault) {
-            PredCases.push_back(BBCases[i]);
-            NewSuccessors.push_back(BBCases[i].Dest);
-            if (SuccHasWeights || PredHasWeights) {
-              // The default weight is at index 0, so weight for the ith case
-              // should be at index i+1. Scale the cases from successor by
-              // PredDefaultWeight (Weights[0]).
-              Weights.push_back(Weights[0] * SuccWeights[i + 1]);
-              ValidTotalSuccWeight += SuccWeights[i + 1];
-            }
-          }
-
-        if (SuccHasWeights || PredHasWeights) {
-          ValidTotalSuccWeight += SuccWeights[0];
-          // Scale the cases from predecessor by ValidTotalSuccWeight.
-          for (unsigned i = 1; i < CasesFromPred; ++i)
-            Weights[i] *= ValidTotalSuccWeight;
-          // Scale the default weight by SuccDefaultWeight (SuccWeights[0]).
-          Weights[0] *= SuccWeights[0];
-        }
-      } else {
-        // If this is not the default destination from PSI, only the edges
-        // in SI that occur in PSI with a destination of BB will be
-        // activated.
-        std::set<ConstantInt *, ConstantIntOrdering> PTIHandled;
-        std::map<ConstantInt *, uint64_t> WeightsForHandled;
-        for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
-          if (PredCases[i].Dest == BB) {
-            PTIHandled.insert(PredCases[i].Value);
-
-            if (PredHasWeights || SuccHasWeights) {
-              WeightsForHandled[PredCases[i].Value] = Weights[i + 1];
-              std::swap(Weights[i + 1], Weights.back());
-              Weights.pop_back();
-            }
-
-            std::swap(PredCases[i], PredCases.back());
-            PredCases.pop_back();
-            --i;
-            --e;
-          }
-
-        // Okay, now we know which constants were sent to BB from the
-        // predecessor.  Figure out where they will all go now.
-        for (unsigned i = 0, e = BBCases.size(); i != e; ++i)
-          if (PTIHandled.count(BBCases[i].Value)) {
-            // If this is one we are capable of getting...
-            if (PredHasWeights || SuccHasWeights)
-              Weights.push_back(WeightsForHandled[BBCases[i].Value]);
-            PredCases.push_back(BBCases[i]);
-            NewSuccessors.push_back(BBCases[i].Dest);
-            PTIHandled.erase(
-                BBCases[i].Value); // This constant is taken care of
-          }
-
-        // If there are any constants vectored to BB that TI doesn't handle,
-        // they must go to the default destination of TI.
-        for (ConstantInt *I : PTIHandled) {
-          if (PredHasWeights || SuccHasWeights)
-            Weights.push_back(WeightsForHandled[I]);
-          PredCases.push_back(ValueEqualityComparisonCase(I, BBDefault));
-          NewSuccessors.push_back(BBDefault);
-        }
-      }
-
-      // Okay, at this point, we know which new successor Pred will get.  Make
-      // sure we update the number of entries in the PHI nodes for these
-      // successors.
-      for (BasicBlock *NewSuccessor : NewSuccessors)
-        AddPredecessorToBlock(NewSuccessor, Pred, BB);
-
-      Builder.SetInsertPoint(PTI);
-      // Convert pointer to int before we switch.
-      if (CV->getType()->isPointerTy()) {
-        CV = Builder.CreatePtrToInt(CV, DL.getIntPtrType(CV->getType()),
-                                    "magicptr");
-      }
-
-      // Now that the successors are updated, create the new Switch instruction.
-      SwitchInst *NewSI =
-          Builder.CreateSwitch(CV, PredDefault, PredCases.size());
-      NewSI->setDebugLoc(PTI->getDebugLoc());
-      for (ValueEqualityComparisonCase &V : PredCases)
-        NewSI->addCase(V.Value, V.Dest);
-
-      if (PredHasWeights || SuccHasWeights) {
-        // Halve the weights if any of them cannot fit in an uint32_t
-        FitWeights(Weights);
-
-        SmallVector<uint32_t, 8> MDWeights(Weights.begin(), Weights.end());
-
-        setBranchWeights(NewSI, MDWeights);
-      }
-
-      EraseTerminatorAndDCECond(PTI);
-
-      // Okay, last check.  If BB is still a successor of PSI, then we must
-      // have an infinite loop case.  If so, add an infinitely looping block
-      // to handle the case to preserve the behavior of the code.
-      BasicBlock *InfLoopBlock = nullptr;
-      for (unsigned i = 0, e = NewSI->getNumSuccessors(); i != e; ++i)
-        if (NewSI->getSuccessor(i) == BB) {
-          if (!InfLoopBlock) {
-            // Insert it at the end of the function, because it's either code,
-            // or it won't matter if it's hot. :)
-            InfLoopBlock = BasicBlock::Create(BB->getContext(), "infloop",
-                                              BB->getParent());
-            BranchInst::Create(InfLoopBlock, InfLoopBlock);
-          }
-          NewSI->setSuccessor(i, InfLoopBlock);
-        }
-
-      Changed = true;
-    }
-  }
-  return Changed;
-}
-
-// If we would need to insert a select that uses the value of this invoke
-// (comments in HoistThenElseCodeToIf explain why we would need to do this), we
-// can't hoist the invoke, as there is nowhere to put the select in this case.
-static bool isSafeToHoistInvoke(BasicBlock *BB1, BasicBlock *BB2,
-                                Instruction *I1, Instruction *I2) {
-  for (BasicBlock *Succ : successors(BB1)) {
-    for (const PHINode &PN : Succ->phis()) {
-      Value *BB1V = PN.getIncomingValueForBlock(BB1);
-      Value *BB2V = PN.getIncomingValueForBlock(BB2);
-      if (BB1V != BB2V && (BB1V == I1 || BB2V == I2)) {
-        return false;
-      }
-    }
-  }
-  return true;
-}
-
-static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I);
-
-/// Given a conditional branch that goes to BB1 and BB2, hoist any common code
-/// in the two blocks up into the branch block. The caller of this function
-/// guarantees that BI's block dominates BB1 and BB2.
-static bool HoistThenElseCodeToIf(BranchInst *BI,
-                                  const TargetTransformInfo &TTI) {
-  // This does very trivial matching, with limited scanning, to find identical
-  // instructions in the two blocks.  In particular, we don't want to get into
-  // O(M*N) situations here where M and N are the sizes of BB1 and BB2.  As
-  // such, we currently just scan for obviously identical instructions in an
-  // identical order.
-  BasicBlock *BB1 = BI->getSuccessor(0); // The true destination.
-  BasicBlock *BB2 = BI->getSuccessor(1); // The false destination
-
-  BasicBlock::iterator BB1_Itr = BB1->begin();
-  BasicBlock::iterator BB2_Itr = BB2->begin();
-
-  Instruction *I1 = &*BB1_Itr++, *I2 = &*BB2_Itr++;
-  // Skip debug info if it is not identical.
-  DbgInfoIntrinsic *DBI1 = dyn_cast<DbgInfoIntrinsic>(I1);
-  DbgInfoIntrinsic *DBI2 = dyn_cast<DbgInfoIntrinsic>(I2);
-  if (!DBI1 || !DBI2 || !DBI1->isIdenticalToWhenDefined(DBI2)) {
-    while (isa<DbgInfoIntrinsic>(I1))
-      I1 = &*BB1_Itr++;
-    while (isa<DbgInfoIntrinsic>(I2))
-      I2 = &*BB2_Itr++;
-  }
-  // FIXME: Can we define a safety predicate for CallBr?
-  if (isa<PHINode>(I1) || !I1->isIdenticalToWhenDefined(I2) ||
-      (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2)) ||
-      isa<CallBrInst>(I1))
-    return false;
-
-  BasicBlock *BIParent = BI->getParent();
-
-  bool Changed = false;
-  do {
-    // If we are hoisting the terminator instruction, don't move one (making a
-    // broken BB), instead clone it, and remove BI.
-    if (I1->isTerminator())
-      goto HoistTerminator;
-
-    // If we're going to hoist a call, make sure that the two instructions we're
-    // commoning/hoisting are both marked with musttail, or neither of them is
-    // marked as such. Otherwise, we might end up in a situation where we hoist
-    // from a block where the terminator is a `ret` to a block where the terminator
-    // is a `br`, and `musttail` calls expect to be followed by a return.
-    auto *C1 = dyn_cast<CallInst>(I1);
-    auto *C2 = dyn_cast<CallInst>(I2);
-    if (C1 && C2)
-      if (C1->isMustTailCall() != C2->isMustTailCall())
-        return Changed;
-
-    if (!TTI.isProfitableToHoist(I1) || !TTI.isProfitableToHoist(I2))
-      return Changed;
-
-    if (isa<DbgInfoIntrinsic>(I1) || isa<DbgInfoIntrinsic>(I2)) {
-      assert (isa<DbgInfoIntrinsic>(I1) && isa<DbgInfoIntrinsic>(I2));
-      // The debug location is an integral part of a debug info intrinsic
-      // and can't be separated from it or replaced.  Instead of attempting
-      // to merge locations, simply hoist both copies of the intrinsic.
-      BIParent->getInstList().splice(BI->getIterator(),
-                                     BB1->getInstList(), I1);
-      BIParent->getInstList().splice(BI->getIterator(),
-                                     BB2->getInstList(), I2);
-      Changed = true;
-    } else {
-      // For a normal instruction, we just move one to right before the branch,
-      // then replace all uses of the other with the first.  Finally, we remove
-      // the now redundant second instruction.
-      BIParent->getInstList().splice(BI->getIterator(),
-                                     BB1->getInstList(), I1);
-      if (!I2->use_empty())
-        I2->replaceAllUsesWith(I1);
-      I1->andIRFlags(I2);
-      unsigned KnownIDs[] = {LLVMContext::MD_tbaa,
-                             LLVMContext::MD_range,
-                             LLVMContext::MD_fpmath,
-                             LLVMContext::MD_invariant_load,
-                             LLVMContext::MD_nonnull,
-                             LLVMContext::MD_invariant_group,
-                             LLVMContext::MD_align,
-                             LLVMContext::MD_dereferenceable,
-                             LLVMContext::MD_dereferenceable_or_null,
-                             LLVMContext::MD_mem_parallel_loop_access,
-                             LLVMContext::MD_access_group};
-      combineMetadata(I1, I2, KnownIDs, true);
-
-      // I1 and I2 are being combined into a single instruction.  Its debug
-      // location is the merged locations of the original instructions.
-      I1->applyMergedLocation(I1->getDebugLoc(), I2->getDebugLoc());
-
-      I2->eraseFromParent();
-      Changed = true;
-    }
-
-    I1 = &*BB1_Itr++;
-    I2 = &*BB2_Itr++;
-    // Skip debug info if it is not identical.
-    DbgInfoIntrinsic *DBI1 = dyn_cast<DbgInfoIntrinsic>(I1);
-    DbgInfoIntrinsic *DBI2 = dyn_cast<DbgInfoIntrinsic>(I2);
-    if (!DBI1 || !DBI2 || !DBI1->isIdenticalToWhenDefined(DBI2)) {
-      while (isa<DbgInfoIntrinsic>(I1))
-        I1 = &*BB1_Itr++;
-      while (isa<DbgInfoIntrinsic>(I2))
-        I2 = &*BB2_Itr++;
-    }
-  } while (I1->isIdenticalToWhenDefined(I2));
-
-  return true;
-
-HoistTerminator:
-  // It may not be possible to hoist an invoke.
-  // FIXME: Can we define a safety predicate for CallBr?
-  if (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2))
-    return Changed;
-
-  // TODO: callbr hoisting currently disabled pending further study.
-  if (isa<CallBrInst>(I1))
-    return Changed;
-
-  for (BasicBlock *Succ : successors(BB1)) {
-    for (PHINode &PN : Succ->phis()) {
-      Value *BB1V = PN.getIncomingValueForBlock(BB1);
-      Value *BB2V = PN.getIncomingValueForBlock(BB2);
-      if (BB1V == BB2V)
-        continue;
-
-      // Check for passingValueIsAlwaysUndefined here because we would rather
-      // eliminate undefined control flow then converting it to a select.
-      if (passingValueIsAlwaysUndefined(BB1V, &PN) ||
-          passingValueIsAlwaysUndefined(BB2V, &PN))
-        return Changed;
-
-      if (isa<ConstantExpr>(BB1V) && !isSafeToSpeculativelyExecute(BB1V))
-        return Changed;
-      if (isa<ConstantExpr>(BB2V) && !isSafeToSpeculativelyExecute(BB2V))
-        return Changed;
-    }
-  }
-
-  // Okay, it is safe to hoist the terminator.
-  Instruction *NT = I1->clone();
-  BIParent->getInstList().insert(BI->getIterator(), NT);
-  if (!NT->getType()->isVoidTy()) {
-    I1->replaceAllUsesWith(NT);
-    I2->replaceAllUsesWith(NT);
-    NT->takeName(I1);
-  }
-
-  // Ensure terminator gets a debug location, even an unknown one, in case
-  // it involves inlinable calls.
-  NT->applyMergedLocation(I1->getDebugLoc(), I2->getDebugLoc());
-
-  // PHIs created below will adopt NT's merged DebugLoc.
-  IRBuilder<NoFolder> Builder(NT);
-
-  // Hoisting one of the terminators from our successor is a great thing.
-  // Unfortunately, the successors of the if/else blocks may have PHI nodes in
-  // them.  If they do, all PHI entries for BB1/BB2 must agree for all PHI
-  // nodes, so we insert select instruction to compute the final result.
-  std::map<std::pair<Value *, Value *>, SelectInst *> InsertedSelects;
-  for (BasicBlock *Succ : successors(BB1)) {
-    for (PHINode &PN : Succ->phis()) {
-      Value *BB1V = PN.getIncomingValueForBlock(BB1);
-      Value *BB2V = PN.getIncomingValueForBlock(BB2);
-      if (BB1V == BB2V)
-        continue;
-
-      // These values do not agree.  Insert a select instruction before NT
-      // that determines the right value.
-      SelectInst *&SI = InsertedSelects[std::make_pair(BB1V, BB2V)];
-      if (!SI)
-        SI = cast<SelectInst>(
-            Builder.CreateSelect(BI->getCondition(), BB1V, BB2V,
-                                 BB1V->getName() + "." + BB2V->getName(), BI));
-
-      // Make the PHI node use the select for all incoming values for BB1/BB2
-      for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
-        if (PN.getIncomingBlock(i) == BB1 || PN.getIncomingBlock(i) == BB2)
-          PN.setIncomingValue(i, SI);
-    }
-  }
-
-  // Update any PHI nodes in our new successors.
-  for (BasicBlock *Succ : successors(BB1))
-    AddPredecessorToBlock(Succ, BIParent, BB1);
-
-  EraseTerminatorAndDCECond(BI);
-  return true;
-}
-
-// All instructions in Insts belong to different blocks that all unconditionally
-// branch to a common successor. Analyze each instruction and return true if it
-// would be possible to sink them into their successor, creating one common
-// instruction instead. For every value that would be required to be provided by
-// PHI node (because an operand varies in each input block), add to PHIOperands.
-static bool canSinkInstructions(
-    ArrayRef<Instruction *> Insts,
-    DenseMap<Instruction *, SmallVector<Value *, 4>> &PHIOperands) {
-  // Prune out obviously bad instructions to move. Any non-store instruction
-  // must have exactly one use, and we check later that use is by a single,
-  // common PHI instruction in the successor.
-  for (auto *I : Insts) {
-    // These instructions may change or break semantics if moved.
-    if (isa<PHINode>(I) || I->isEHPad() || isa<AllocaInst>(I) ||
-        I->getType()->isTokenTy())
-      return false;
-
-    // Conservatively return false if I is an inline-asm instruction. Sinking
-    // and merging inline-asm instructions can potentially create arguments
-    // that cannot satisfy the inline-asm constraints.
-    if (const auto *C = dyn_cast<CallBase>(I))
-      if (C->isInlineAsm())
-        return false;
-
-    // Everything must have only one use too, apart from stores which
-    // have no uses.
-    if (!isa<StoreInst>(I) && !I->hasOneUse())
-      return false;
-  }
-
-  const Instruction *I0 = Insts.front();
-  for (auto *I : Insts)
-    if (!I->isSameOperationAs(I0))
-      return false;
-
-  // All instructions in Insts are known to be the same opcode. If they aren't
-  // stores, check the only user of each is a PHI or in the same block as the
-  // instruction, because if a user is in the same block as an instruction
-  // we're contemplating sinking, it must already be determined to be sinkable.
-  if (!isa<StoreInst>(I0)) {
-    auto *PNUse = dyn_cast<PHINode>(*I0->user_begin());
-    auto *Succ = I0->getParent()->getTerminator()->getSuccessor(0);
-    if (!all_of(Insts, [&PNUse,&Succ](const Instruction *I) -> bool {
-          auto *U = cast<Instruction>(*I->user_begin());
-          return (PNUse &&
-                  PNUse->getParent() == Succ &&
-                  PNUse->getIncomingValueForBlock(I->getParent()) == I) ||
-                 U->getParent() == I->getParent();
-        }))
-      return false;
-  }
-
-  // Because SROA can't handle speculating stores of selects, try not
-  // to sink loads or stores of allocas when we'd have to create a PHI for
-  // the address operand. Also, because it is likely that loads or stores
-  // of allocas will disappear when Mem2Reg/SROA is run, don't sink them.
-  // This can cause code churn which can have unintended consequences down
-  // the line - see https://llvm.org/bugs/show_bug.cgi?id=30244.
-  // FIXME: This is a workaround for a deficiency in SROA - see
-  // https://llvm.org/bugs/show_bug.cgi?id=30188
-  if (isa<StoreInst>(I0) && any_of(Insts, [](const Instruction *I) {
-        return isa<AllocaInst>(I->getOperand(1));
-      }))
-    return false;
-  if (isa<LoadInst>(I0) && any_of(Insts, [](const Instruction *I) {
-        return isa<AllocaInst>(I->getOperand(0));
-      }))
-    return false;
-
-  for (unsigned OI = 0, OE = I0->getNumOperands(); OI != OE; ++OI) {
-    if (I0->getOperand(OI)->getType()->isTokenTy())
-      // Don't touch any operand of token type.
-      return false;
-
-    auto SameAsI0 = [&I0, OI](const Instruction *I) {
-      assert(I->getNumOperands() == I0->getNumOperands());
-      return I->getOperand(OI) == I0->getOperand(OI);
-    };
-    if (!all_of(Insts, SameAsI0)) {
-      if (!canReplaceOperandWithVariable(I0, OI))
-        // We can't create a PHI from this GEP.
-        return false;
-      // Don't create indirect calls! The called value is the final operand.
-      if (isa<CallBase>(I0) && OI == OE - 1) {
-        // FIXME: if the call was *already* indirect, we should do this.
-        return false;
-      }
-      for (auto *I : Insts)
-        PHIOperands[I].push_back(I->getOperand(OI));
-    }
-  }
-  return true;
-}
-
-// Assuming canSinkLastInstruction(Blocks) has returned true, sink the last
-// instruction of every block in Blocks to their common successor, commoning
-// into one instruction.
-static bool sinkLastInstruction(ArrayRef<BasicBlock*> Blocks) {
-  auto *BBEnd = Blocks[0]->getTerminator()->getSuccessor(0);
-
-  // canSinkLastInstruction returning true guarantees that every block has at
-  // least one non-terminator instruction.
-  SmallVector<Instruction*,4> Insts;
-  for (auto *BB : Blocks) {
-    Instruction *I = BB->getTerminator();
-    do {
-      I = I->getPrevNode();
-    } while (isa<DbgInfoIntrinsic>(I) && I != &BB->front());
-    if (!isa<DbgInfoIntrinsic>(I))
-      Insts.push_back(I);
-  }
-
-  // The only checking we need to do now is that all users of all instructions
-  // are the same PHI node. canSinkLastInstruction should have checked this but
-  // it is slightly over-aggressive - it gets confused by commutative instructions
-  // so double-check it here.
-  Instruction *I0 = Insts.front();
-  if (!isa<StoreInst>(I0)) {
-    auto *PNUse = dyn_cast<PHINode>(*I0->user_begin());
-    if (!all_of(Insts, [&PNUse](const Instruction *I) -> bool {
-          auto *U = cast<Instruction>(*I->user_begin());
-          return U == PNUse;
-        }))
-      return false;
-  }
-
-  // We don't need to do any more checking here; canSinkLastInstruction should
-  // have done it all for us.
-  SmallVector<Value*, 4> NewOperands;
-  for (unsigned O = 0, E = I0->getNumOperands(); O != E; ++O) {
-    // This check is different to that in canSinkLastInstruction. There, we
-    // cared about the global view once simplifycfg (and instcombine) have
-    // completed - it takes into account PHIs that become trivially
-    // simplifiable.  However here we need a more local view; if an operand
-    // differs we create a PHI and rely on instcombine to clean up the very
-    // small mess we may make.
-    bool NeedPHI = any_of(Insts, [&I0, O](const Instruction *I) {
-      return I->getOperand(O) != I0->getOperand(O);
-    });
-    if (!NeedPHI) {
-      NewOperands.push_back(I0->getOperand(O));
-      continue;
-    }
-
-    // Create a new PHI in the successor block and populate it.
-    auto *Op = I0->getOperand(O);
-    assert(!Op->getType()->isTokenTy() && "Can't PHI tokens!");
-    auto *PN = PHINode::Create(Op->getType(), Insts.size(),
-                               Op->getName() + ".sink", &BBEnd->front());
-    for (auto *I : Insts)
-      PN->addIncoming(I->getOperand(O), I->getParent());
-    NewOperands.push_back(PN);
-  }
-
-  // Arbitrarily use I0 as the new "common" instruction; remap its operands
-  // and move it to the start of the successor block.
-  for (unsigned O = 0, E = I0->getNumOperands(); O != E; ++O)
-    I0->getOperandUse(O).set(NewOperands[O]);
-  I0->moveBefore(&*BBEnd->getFirstInsertionPt());
-
-  // Update metadata and IR flags, and merge debug locations.
-  for (auto *I : Insts)
-    if (I != I0) {
-      // The debug location for the "common" instruction is the merged locations
-      // of all the commoned instructions.  We start with the original location
-      // of the "common" instruction and iteratively merge each location in the
-      // loop below.
-      // This is an N-way merge, which will be inefficient if I0 is a CallInst.
-      // However, as N-way merge for CallInst is rare, so we use simplified API
-      // instead of using complex API for N-way merge.
-      I0->applyMergedLocation(I0->getDebugLoc(), I->getDebugLoc());
-      combineMetadataForCSE(I0, I, true);
-      I0->andIRFlags(I);
-    }
-
-  if (!isa<StoreInst>(I0)) {
-    // canSinkLastInstruction checked that all instructions were used by
-    // one and only one PHI node. Find that now, RAUW it to our common
-    // instruction and nuke it.
-    assert(I0->hasOneUse());
-    auto *PN = cast<PHINode>(*I0->user_begin());
-    PN->replaceAllUsesWith(I0);
-    PN->eraseFromParent();
-  }
-
-  // Finally nuke all instructions apart from the common instruction.
-  for (auto *I : Insts)
-    if (I != I0)
-      I->eraseFromParent();
-
-  return true;
-}
-
-namespace {
-
-  // LockstepReverseIterator - Iterates through instructions
-  // in a set of blocks in reverse order from the first non-terminator.
-  // For example (assume all blocks have size n):
-  //   LockstepReverseIterator I([B1, B2, B3]);
-  //   *I-- = [B1[n], B2[n], B3[n]];
-  //   *I-- = [B1[n-1], B2[n-1], B3[n-1]];
-  //   *I-- = [B1[n-2], B2[n-2], B3[n-2]];
-  //   ...
-  class LockstepReverseIterator {
-    ArrayRef<BasicBlock*> Blocks;
-    SmallVector<Instruction*,4> Insts;
-    bool Fail;
-
-  public:
-    LockstepReverseIterator(ArrayRef<BasicBlock*> Blocks) : Blocks(Blocks) {
-      reset();
-    }
-
-    void reset() {
-      Fail = false;
-      Insts.clear();
-      for (auto *BB : Blocks) {
-        Instruction *Inst = BB->getTerminator();
-        for (Inst = Inst->getPrevNode(); Inst && isa<DbgInfoIntrinsic>(Inst);)
-          Inst = Inst->getPrevNode();
-        if (!Inst) {
-          // Block wasn't big enough.
-          Fail = true;
-          return;
-        }
-        Insts.push_back(Inst);
-      }
-    }
-
-    bool isValid() const {
-      return !Fail;
-    }
-
-    void operator--() {
-      if (Fail)
-        return;
-      for (auto *&Inst : Insts) {
-        for (Inst = Inst->getPrevNode(); Inst && isa<DbgInfoIntrinsic>(Inst);)
-          Inst = Inst->getPrevNode();
-        // Already at beginning of block.
-        if (!Inst) {
-          Fail = true;
-          return;
-        }
-      }
-    }
-
-    ArrayRef<Instruction*> operator * () const {
-      return Insts;
-    }
-  };
-
-} // end anonymous namespace
-
-/// Check whether BB's predecessors end with unconditional branches. If it is
-/// true, sink any common code from the predecessors to BB.
-/// We also allow one predecessor to end with conditional branch (but no more
-/// than one).
-static bool SinkCommonCodeFromPredecessors(BasicBlock *BB) {
-  // We support two situations:
-  //   (1) all incoming arcs are unconditional
-  //   (2) one incoming arc is conditional
-  //
-  // (2) is very common in switch defaults and
-  // else-if patterns;
-  //
-  //   if (a) f(1);
-  //   else if (b) f(2);
-  //
-  // produces:
-  //
-  //       [if]
-  //      /    \
-  //    [f(1)] [if]
-  //      |     | \
-  //      |     |  |
-  //      |  [f(2)]|
-  //       \    | /
-  //        [ end ]
-  //
-  // [end] has two unconditional predecessor arcs and one conditional. The
-  // conditional refers to the implicit empty 'else' arc. This conditional
-  // arc can also be caused by an empty default block in a switch.
-  //
-  // In this case, we attempt to sink code from all *unconditional* arcs.
-  // If we can sink instructions from these arcs (determined during the scan
-  // phase below) we insert a common successor for all unconditional arcs and
-  // connect that to [end], to enable sinking:
-  //
-  //       [if]
-  //      /    \
-  //    [x(1)] [if]
-  //      |     | \
-  //      |     |  \
-  //      |  [x(2)] |
-  //       \   /    |
-  //   [sink.split] |
-  //         \     /
-  //         [ end ]
-  //
-  SmallVector<BasicBlock*,4> UnconditionalPreds;
-  Instruction *Cond = nullptr;
-  for (auto *B : predecessors(BB)) {
-    auto *T = B->getTerminator();
-    if (isa<BranchInst>(T) && cast<BranchInst>(T)->isUnconditional())
-      UnconditionalPreds.push_back(B);
-    else if ((isa<BranchInst>(T) || isa<SwitchInst>(T)) && !Cond)
-      Cond = T;
-    else
-      return false;
-  }
-  if (UnconditionalPreds.size() < 2)
-    return false;
-
-  bool Changed = false;
-  // We take a two-step approach to tail sinking. First we scan from the end of
-  // each block upwards in lockstep. If the n'th instruction from the end of each
-  // block can be sunk, those instructions are added to ValuesToSink and we
-  // carry on. If we can sink an instruction but need to PHI-merge some operands
-  // (because they're not identical in each instruction) we add these to
-  // PHIOperands.
-  unsigned ScanIdx = 0;
-  SmallPtrSet<Value*,4> InstructionsToSink;
-  DenseMap<Instruction*, SmallVector<Value*,4>> PHIOperands;
-  LockstepReverseIterator LRI(UnconditionalPreds);
-  while (LRI.isValid() &&
-         canSinkInstructions(*LRI, PHIOperands)) {
-    LLVM_DEBUG(dbgs() << "SINK: instruction can be sunk: " << *(*LRI)[0]
-                      << "\n");
-    InstructionsToSink.insert((*LRI).begin(), (*LRI).end());
-    ++ScanIdx;
-    --LRI;
-  }
-
-  auto ProfitableToSinkInstruction = [&](LockstepReverseIterator &LRI) {
-    unsigned NumPHIdValues = 0;
-    for (auto *I : *LRI)
-      for (auto *V : PHIOperands[I])
-        if (InstructionsToSink.count(V) == 0)
-          ++NumPHIdValues;
-    LLVM_DEBUG(dbgs() << "SINK: #phid values: " << NumPHIdValues << "\n");
-    unsigned NumPHIInsts = NumPHIdValues / UnconditionalPreds.size();
-    if ((NumPHIdValues % UnconditionalPreds.size()) != 0)
-        NumPHIInsts++;
-
-    return NumPHIInsts <= 1;
-  };
-
-  if (ScanIdx > 0 && Cond) {
-    // Check if we would actually sink anything first! This mutates the CFG and
-    // adds an extra block. The goal in doing this is to allow instructions that
-    // couldn't be sunk before to be sunk - obviously, speculatable instructions
-    // (such as trunc, add) can be sunk and predicated already. So we check that
-    // we're going to sink at least one non-speculatable instruction.
-    LRI.reset();
-    unsigned Idx = 0;
-    bool Profitable = false;
-    while (ProfitableToSinkInstruction(LRI) && Idx < ScanIdx) {
-      if (!isSafeToSpeculativelyExecute((*LRI)[0])) {
-        Profitable = true;
-        break;
-      }
-      --LRI;
-      ++Idx;
-    }
-    if (!Profitable)
-      return false;
-
-    LLVM_DEBUG(dbgs() << "SINK: Splitting edge\n");
-    // We have a conditional edge and we're going to sink some instructions.
-    // Insert a new block postdominating all blocks we're going to sink from.
-    if (!SplitBlockPredecessors(BB, UnconditionalPreds, ".sink.split"))
-      // Edges couldn't be split.
-      return false;
-    Changed = true;
-  }
-
-  // Now that we've analyzed all potential sinking candidates, perform the
-  // actual sink. We iteratively sink the last non-terminator of the source
-  // blocks into their common successor unless doing so would require too
-  // many PHI instructions to be generated (currently only one PHI is allowed
-  // per sunk instruction).
-  //
-  // We can use InstructionsToSink to discount values needing PHI-merging that will
-  // actually be sunk in a later iteration. This allows us to be more
-  // aggressive in what we sink. This does allow a false positive where we
-  // sink presuming a later value will also be sunk, but stop half way through
-  // and never actually sink it which means we produce more PHIs than intended.
-  // This is unlikely in practice though.
-  for (unsigned SinkIdx = 0; SinkIdx != ScanIdx; ++SinkIdx) {
-    LLVM_DEBUG(dbgs() << "SINK: Sink: "
-                      << *UnconditionalPreds[0]->getTerminator()->getPrevNode()
-                      << "\n");
-
-    // Because we've sunk every instruction in turn, the current instruction to
-    // sink is always at index 0.
-    LRI.reset();
-    if (!ProfitableToSinkInstruction(LRI)) {
-      // Too many PHIs would be created.
-      LLVM_DEBUG(
-          dbgs() << "SINK: stopping here, too many PHIs would be created!\n");
-      break;
-    }
-
-    if (!sinkLastInstruction(UnconditionalPreds))
-      return Changed;
-    NumSinkCommons++;
-    Changed = true;
-  }
-  return Changed;
-}
-
-/// Determine if we can hoist sink a sole store instruction out of a
-/// conditional block.
-///
-/// We are looking for code like the following:
-///   BrBB:
-///     store i32 %add, i32* %arrayidx2
-///     ... // No other stores or function calls (we could be calling a memory
-///     ... // function).
-///     %cmp = icmp ult %x, %y
-///     br i1 %cmp, label %EndBB, label %ThenBB
-///   ThenBB:
-///     store i32 %add5, i32* %arrayidx2
-///     br label EndBB
-///   EndBB:
-///     ...
-///   We are going to transform this into:
-///   BrBB:
-///     store i32 %add, i32* %arrayidx2
-///     ... //
-///     %cmp = icmp ult %x, %y
-///     %add.add5 = select i1 %cmp, i32 %add, %add5
-///     store i32 %add.add5, i32* %arrayidx2
-///     ...
-///
-/// \return The pointer to the value of the previous store if the store can be
-///         hoisted into the predecessor block. 0 otherwise.
-static Value *isSafeToSpeculateStore(Instruction *I, BasicBlock *BrBB,
-                                     BasicBlock *StoreBB, BasicBlock *EndBB) {
-  StoreInst *StoreToHoist = dyn_cast<StoreInst>(I);
-  if (!StoreToHoist)
-    return nullptr;
-
-  // Volatile or atomic.
-  if (!StoreToHoist->isSimple())
-    return nullptr;
-
-  Value *StorePtr = StoreToHoist->getPointerOperand();
-
-  // Look for a store to the same pointer in BrBB.
-  unsigned MaxNumInstToLookAt = 9;
-  for (Instruction &CurI : reverse(BrBB->instructionsWithoutDebug())) {
-    if (!MaxNumInstToLookAt)
-      break;
-    --MaxNumInstToLookAt;
-
-    // Could be calling an instruction that affects memory like free().
-    if (CurI.mayHaveSideEffects() && !isa<StoreInst>(CurI))
-      return nullptr;
-
-    if (auto *SI = dyn_cast<StoreInst>(&CurI)) {
-      // Found the previous store make sure it stores to the same location.
-      if (SI->getPointerOperand() == StorePtr)
-        // Found the previous store, return its value operand.
-        return SI->getValueOperand();
-      return nullptr; // Unknown store.
-    }
-  }
-
-  return nullptr;
-}
-
-/// Speculate a conditional basic block flattening the CFG.
-///
-/// Note that this is a very risky transform currently. Speculating
-/// instructions like this is most often not desirable. Instead, there is an MI
-/// pass which can do it with full awareness of the resource constraints.
-/// However, some cases are "obvious" and we should do directly. An example of
-/// this is speculating a single, reasonably cheap instruction.
-///
-/// There is only one distinct advantage to flattening the CFG at the IR level:
-/// it makes very common but simplistic optimizations such as are common in
-/// instcombine and the DAG combiner more powerful by removing CFG edges and
-/// modeling their effects with easier to reason about SSA value graphs.
-///
-///
-/// An illustration of this transform is turning this IR:
-/// \code
-///   BB:
-///     %cmp = icmp ult %x, %y
-///     br i1 %cmp, label %EndBB, label %ThenBB
-///   ThenBB:
-///     %sub = sub %x, %y
-///     br label BB2
-///   EndBB:
-///     %phi = phi [ %sub, %ThenBB ], [ 0, %EndBB ]
-///     ...
-/// \endcode
-///
-/// Into this IR:
-/// \code
-///   BB:
-///     %cmp = icmp ult %x, %y
-///     %sub = sub %x, %y
-///     %cond = select i1 %cmp, 0, %sub
-///     ...
-/// \endcode
-///
-/// \returns true if the conditional block is removed.
-static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB,
-                                   const TargetTransformInfo &TTI) {
-  // Be conservative for now. FP select instruction can often be expensive.
-  Value *BrCond = BI->getCondition();
-  if (isa<FCmpInst>(BrCond))
-    return false;
-
-  BasicBlock *BB = BI->getParent();
-  BasicBlock *EndBB = ThenBB->getTerminator()->getSuccessor(0);
-
-  // If ThenBB is actually on the false edge of the conditional branch, remember
-  // to swap the select operands later.
-  bool Invert = false;
-  if (ThenBB != BI->getSuccessor(0)) {
-    assert(ThenBB == BI->getSuccessor(1) && "No edge from 'if' block?");
-    Invert = true;
-  }
-  assert(EndBB == BI->getSuccessor(!Invert) && "No edge from to end block");
-
-  // Keep a count of how many times instructions are used within ThenBB when
-  // they are candidates for sinking into ThenBB. Specifically:
-  // - They are defined in BB, and
-  // - They have no side effects, and
-  // - All of their uses are in ThenBB.
-  SmallDenseMap<Instruction *, unsigned, 4> SinkCandidateUseCounts;
-
-  SmallVector<Instruction *, 4> SpeculatedDbgIntrinsics;
-
-  unsigned SpeculationCost = 0;
-  Value *SpeculatedStoreValue = nullptr;
-  StoreInst *SpeculatedStore = nullptr;
-  for (BasicBlock::iterator BBI = ThenBB->begin(),
-                            BBE = std::prev(ThenBB->end());
-       BBI != BBE; ++BBI) {
-    Instruction *I = &*BBI;
-    // Skip debug info.
-    if (isa<DbgInfoIntrinsic>(I)) {
-      SpeculatedDbgIntrinsics.push_back(I);
-      continue;
-    }
-
-    // Only speculatively execute a single instruction (not counting the
-    // terminator) for now.
-    ++SpeculationCost;
-    if (SpeculationCost > 1)
-      return false;
-
-    // Don't hoist the instruction if it's unsafe or expensive.
-    if (!isSafeToSpeculativelyExecute(I) &&
-        !(HoistCondStores && (SpeculatedStoreValue = isSafeToSpeculateStore(
-                                  I, BB, ThenBB, EndBB))))
-      return false;
-    if (!SpeculatedStoreValue &&
-        ComputeSpeculationCost(I, TTI) >
-            PHINodeFoldingThreshold * TargetTransformInfo::TCC_Basic)
-      return false;
-
-    // Store the store speculation candidate.
-    if (SpeculatedStoreValue)
-      SpeculatedStore = cast<StoreInst>(I);
-
-    // Do not hoist the instruction if any of its operands are defined but not
-    // used in BB. The transformation will prevent the operand from
-    // being sunk into the use block.
-    for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) {
-      Instruction *OpI = dyn_cast<Instruction>(*i);
-      if (!OpI || OpI->getParent() != BB || OpI->mayHaveSideEffects())
-        continue; // Not a candidate for sinking.
-
-      ++SinkCandidateUseCounts[OpI];
-    }
-  }
-
-  // Consider any sink candidates which are only used in ThenBB as costs for
-  // speculation. Note, while we iterate over a DenseMap here, we are summing
-  // and so iteration order isn't significant.
-  for (SmallDenseMap<Instruction *, unsigned, 4>::iterator
-           I = SinkCandidateUseCounts.begin(),
-           E = SinkCandidateUseCounts.end();
-       I != E; ++I)
-    if (I->first->hasNUses(I->second)) {
-      ++SpeculationCost;
-      if (SpeculationCost > 1)
-        return false;
-    }
-
-  // Check that the PHI nodes can be converted to selects.
-  bool HaveRewritablePHIs = false;
-  for (PHINode &PN : EndBB->phis()) {
-    Value *OrigV = PN.getIncomingValueForBlock(BB);
-    Value *ThenV = PN.getIncomingValueForBlock(ThenBB);
-
-    // FIXME: Try to remove some of the duplication with HoistThenElseCodeToIf.
-    // Skip PHIs which are trivial.
-    if (ThenV == OrigV)
-      continue;
-
-    // Don't convert to selects if we could remove undefined behavior instead.
-    if (passingValueIsAlwaysUndefined(OrigV, &PN) ||
-        passingValueIsAlwaysUndefined(ThenV, &PN))
-      return false;
-
-    HaveRewritablePHIs = true;
-    ConstantExpr *OrigCE = dyn_cast<ConstantExpr>(OrigV);
-    ConstantExpr *ThenCE = dyn_cast<ConstantExpr>(ThenV);
-    if (!OrigCE && !ThenCE)
-      continue; // Known safe and cheap.
-
-    if ((ThenCE && !isSafeToSpeculativelyExecute(ThenCE)) ||
-        (OrigCE && !isSafeToSpeculativelyExecute(OrigCE)))
-      return false;
-    unsigned OrigCost = OrigCE ? ComputeSpeculationCost(OrigCE, TTI) : 0;
-    unsigned ThenCost = ThenCE ? ComputeSpeculationCost(ThenCE, TTI) : 0;
-    unsigned MaxCost =
-        2 * PHINodeFoldingThreshold * TargetTransformInfo::TCC_Basic;
-    if (OrigCost + ThenCost > MaxCost)
-      return false;
-
-    // Account for the cost of an unfolded ConstantExpr which could end up
-    // getting expanded into Instructions.
-    // FIXME: This doesn't account for how many operations are combined in the
-    // constant expression.
-    ++SpeculationCost;
-    if (SpeculationCost > 1)
-      return false;
-  }
-
-  // If there are no PHIs to process, bail early. This helps ensure idempotence
-  // as well.
-  if (!HaveRewritablePHIs && !(HoistCondStores && SpeculatedStoreValue))
-    return false;
-
-  // If we get here, we can hoist the instruction and if-convert.
-  LLVM_DEBUG(dbgs() << "SPECULATIVELY EXECUTING BB" << *ThenBB << "\n";);
-
-  // Insert a select of the value of the speculated store.
-  if (SpeculatedStoreValue) {
-    IRBuilder<NoFolder> Builder(BI);
-    Value *TrueV = SpeculatedStore->getValueOperand();
-    Value *FalseV = SpeculatedStoreValue;
-    if (Invert)
-      std::swap(TrueV, FalseV);
-    Value *S = Builder.CreateSelect(
-        BrCond, TrueV, FalseV, "spec.store.select", BI);
-    SpeculatedStore->setOperand(0, S);
-    SpeculatedStore->applyMergedLocation(BI->getDebugLoc(),
-                                         SpeculatedStore->getDebugLoc());
-  }
-
-  // Metadata can be dependent on the condition we are hoisting above.
-  // Conservatively strip all metadata on the instruction.
-  for (auto &I : *ThenBB)
-    I.dropUnknownNonDebugMetadata();
-
-  // Hoist the instructions.
-  BB->getInstList().splice(BI->getIterator(), ThenBB->getInstList(),
-                           ThenBB->begin(), std::prev(ThenBB->end()));
-
-  // Insert selects and rewrite the PHI operands.
-  IRBuilder<NoFolder> Builder(BI);
-  for (PHINode &PN : EndBB->phis()) {
-    unsigned OrigI = PN.getBasicBlockIndex(BB);
-    unsigned ThenI = PN.getBasicBlockIndex(ThenBB);
-    Value *OrigV = PN.getIncomingValue(OrigI);
-    Value *ThenV = PN.getIncomingValue(ThenI);
-
-    // Skip PHIs which are trivial.
-    if (OrigV == ThenV)
-      continue;
-
-    // Create a select whose true value is the speculatively executed value and
-    // false value is the preexisting value. Swap them if the branch
-    // destinations were inverted.
-    Value *TrueV = ThenV, *FalseV = OrigV;
-    if (Invert)
-      std::swap(TrueV, FalseV);
-    Value *V = Builder.CreateSelect(
-        BrCond, TrueV, FalseV, "spec.select", BI);
-    PN.setIncomingValue(OrigI, V);
-    PN.setIncomingValue(ThenI, V);
-  }
-
-  // Remove speculated dbg intrinsics.
-  // FIXME: Is it possible to do this in a more elegant way? Moving/merging the
-  // dbg value for the different flows and inserting it after the select.
-  for (Instruction *I : SpeculatedDbgIntrinsics)
-    I->eraseFromParent();
-
-  ++NumSpeculations;
-  return true;
-}
-
-/// Return true if we can thread a branch across this block.
-static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) {
-  unsigned Size = 0;
-
-  for (Instruction &I : BB->instructionsWithoutDebug()) {
-    if (Size > 10)
-      return false; // Don't clone large BB's.
-    ++Size;
-
-    // We can only support instructions that do not define values that are
-    // live outside of the current basic block.
-    for (User *U : I.users()) {
-      Instruction *UI = cast<Instruction>(U);
-      if (UI->getParent() != BB || isa<PHINode>(UI))
-        return false;
-    }
-
-    // Looks ok, continue checking.
-  }
-
-  return true;
-}
-
-/// If we have a conditional branch on a PHI node value that is defined in the
-/// same block as the branch and if any PHI entries are constants, thread edges
-/// corresponding to that entry to be branches to their ultimate destination.
-static bool FoldCondBranchOnPHI(BranchInst *BI, const DataLayout &DL,
-                                AssumptionCache *AC) {
-  BasicBlock *BB = BI->getParent();
-  PHINode *PN = dyn_cast<PHINode>(BI->getCondition());
-  // NOTE: we currently cannot transform this case if the PHI node is used
-  // outside of the block.
-  if (!PN || PN->getParent() != BB || !PN->hasOneUse())
-    return false;
-
-  // Degenerate case of a single entry PHI.
-  if (PN->getNumIncomingValues() == 1) {
-    FoldSingleEntryPHINodes(PN->getParent());
-    return true;
-  }
-
-  // Now we know that this block has multiple preds and two succs.
-  if (!BlockIsSimpleEnoughToThreadThrough(BB))
-    return false;
-
-  // Can't fold blocks that contain noduplicate or convergent calls.
-  if (any_of(*BB, [](const Instruction &I) {
-        const CallInst *CI = dyn_cast<CallInst>(&I);
-        return CI && (CI->cannotDuplicate() || CI->isConvergent());
-      }))
-    return false;
-
-  // Okay, this is a simple enough basic block.  See if any phi values are
-  // constants.
-  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
-    ConstantInt *CB = dyn_cast<ConstantInt>(PN->getIncomingValue(i));
-    if (!CB || !CB->getType()->isIntegerTy(1))
-      continue;
-
-    // Okay, we now know that all edges from PredBB should be revectored to
-    // branch to RealDest.
-    BasicBlock *PredBB = PN->getIncomingBlock(i);
-    BasicBlock *RealDest = BI->getSuccessor(!CB->getZExtValue());
-
-    if (RealDest == BB)
-      continue; // Skip self loops.
-    // Skip if the predecessor's terminator is an indirect branch.
-    if (isa<IndirectBrInst>(PredBB->getTerminator()))
-      continue;
-
-    // The dest block might have PHI nodes, other predecessors and other
-    // difficult cases.  Instead of being smart about this, just insert a new
-    // block that jumps to the destination block, effectively splitting
-    // the edge we are about to create.
-    BasicBlock *EdgeBB =
-        BasicBlock::Create(BB->getContext(), RealDest->getName() + ".critedge",
-                           RealDest->getParent(), RealDest);
-    BranchInst *CritEdgeBranch = BranchInst::Create(RealDest, EdgeBB);
-    CritEdgeBranch->setDebugLoc(BI->getDebugLoc());
-
-    // Update PHI nodes.
-    AddPredecessorToBlock(RealDest, EdgeBB, BB);
-
-    // BB may have instructions that are being threaded over.  Clone these
-    // instructions into EdgeBB.  We know that there will be no uses of the
-    // cloned instructions outside of EdgeBB.
-    BasicBlock::iterator InsertPt = EdgeBB->begin();
-    DenseMap<Value *, Value *> TranslateMap; // Track translated values.
-    for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) {
-      if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
-        TranslateMap[PN] = PN->getIncomingValueForBlock(PredBB);
-        continue;
-      }
-      // Clone the instruction.
-      Instruction *N = BBI->clone();
-      if (BBI->hasName())
-        N->setName(BBI->getName() + ".c");
-
-      // Update operands due to translation.
-      for (User::op_iterator i = N->op_begin(), e = N->op_end(); i != e; ++i) {
-        DenseMap<Value *, Value *>::iterator PI = TranslateMap.find(*i);
-        if (PI != TranslateMap.end())
-          *i = PI->second;
-      }
-
-      // Check for trivial simplification.
-      if (Value *V = SimplifyInstruction(N, {DL, nullptr, nullptr, AC})) {
-        if (!BBI->use_empty())
-          TranslateMap[&*BBI] = V;
-        if (!N->mayHaveSideEffects()) {
-          N->deleteValue(); // Instruction folded away, don't need actual inst
-          N = nullptr;
-        }
-      } else {
-        if (!BBI->use_empty())
-          TranslateMap[&*BBI] = N;
-      }
-      // Insert the new instruction into its new home.
-      if (N)
-        EdgeBB->getInstList().insert(InsertPt, N);
-
-      // Register the new instruction with the assumption cache if necessary.
-      if (auto *II = dyn_cast_or_null<IntrinsicInst>(N))
-        if (II->getIntrinsicID() == Intrinsic::assume)
-          AC->registerAssumption(II);
-    }
-
-    // Loop over all of the edges from PredBB to BB, changing them to branch
-    // to EdgeBB instead.
-    Instruction *PredBBTI = PredBB->getTerminator();
-    for (unsigned i = 0, e = PredBBTI->getNumSuccessors(); i != e; ++i)
-      if (PredBBTI->getSuccessor(i) == BB) {
-        BB->removePredecessor(PredBB);
-        PredBBTI->setSuccessor(i, EdgeBB);
-      }
-
-    // Recurse, simplifying any other constants.
-    return FoldCondBranchOnPHI(BI, DL, AC) || true;
-  }
-
-  return false;
-}
-
-/// Given a BB that starts with the specified two-entry PHI node,
-/// see if we can eliminate it.
-static bool FoldTwoEntryPHINode(PHINode *PN, const TargetTransformInfo &TTI,
-                                const DataLayout &DL) {
-  // Ok, this is a two entry PHI node.  Check to see if this is a simple "if
-  // statement", which has a very simple dominance structure.  Basically, we
-  // are trying to find the condition that is being branched on, which
-  // subsequently causes this merge to happen.  We really want control
-  // dependence information for this check, but simplifycfg can't keep it up
-  // to date, and this catches most of the cases we care about anyway.
-  BasicBlock *BB = PN->getParent();
-  const Function *Fn = BB->getParent();
-  if (Fn && Fn->hasFnAttribute(Attribute::OptForFuzzing))
-    return false;
-
-  BasicBlock *IfTrue, *IfFalse;
-  Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse);
-  if (!IfCond ||
-      // Don't bother if the branch will be constant folded trivially.
-      isa<ConstantInt>(IfCond))
-    return false;
-
-  // Okay, we found that we can merge this two-entry phi node into a select.
-  // Doing so would require us to fold *all* two entry phi nodes in this block.
-  // At some point this becomes non-profitable (particularly if the target
-  // doesn't support cmov's).  Only do this transformation if there are two or
-  // fewer PHI nodes in this block.
-  unsigned NumPhis = 0;
-  for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++NumPhis, ++I)
-    if (NumPhis > 2)
-      return false;
-
-  // Loop over the PHI's seeing if we can promote them all to select
-  // instructions.  While we are at it, keep track of the instructions
-  // that need to be moved to the dominating block.
-  SmallPtrSet<Instruction *, 4> AggressiveInsts;
-  unsigned MaxCostVal0 = PHINodeFoldingThreshold,
-           MaxCostVal1 = PHINodeFoldingThreshold;
-  MaxCostVal0 *= TargetTransformInfo::TCC_Basic;
-  MaxCostVal1 *= TargetTransformInfo::TCC_Basic;
-
-  for (BasicBlock::iterator II = BB->begin(); isa<PHINode>(II);) {
-    PHINode *PN = cast<PHINode>(II++);
-    if (Value *V = SimplifyInstruction(PN, {DL, PN})) {
-      PN->replaceAllUsesWith(V);
-      PN->eraseFromParent();
-      continue;
-    }
-
-    if (!DominatesMergePoint(PN->getIncomingValue(0), BB, AggressiveInsts,
-                             MaxCostVal0, TTI) ||
-        !DominatesMergePoint(PN->getIncomingValue(1), BB, AggressiveInsts,
-                             MaxCostVal1, TTI))
-      return false;
-  }
-
-  // If we folded the first phi, PN dangles at this point.  Refresh it.  If
-  // we ran out of PHIs then we simplified them all.
-  PN = dyn_cast<PHINode>(BB->begin());
-  if (!PN)
-    return true;
-
-  // Don't fold i1 branches on PHIs which contain binary operators.  These can
-  // often be turned into switches and other things.
-  if (PN->getType()->isIntegerTy(1) &&
-      (isa<BinaryOperator>(PN->getIncomingValue(0)) ||
-       isa<BinaryOperator>(PN->getIncomingValue(1)) ||
-       isa<BinaryOperator>(IfCond)))
-    return false;
-
-  // If all PHI nodes are promotable, check to make sure that all instructions
-  // in the predecessor blocks can be promoted as well. If not, we won't be able
-  // to get rid of the control flow, so it's not worth promoting to select
-  // instructions.
-  BasicBlock *DomBlock = nullptr;
-  BasicBlock *IfBlock1 = PN->getIncomingBlock(0);
-  BasicBlock *IfBlock2 = PN->getIncomingBlock(1);
-  if (cast<BranchInst>(IfBlock1->getTerminator())->isConditional()) {
-    IfBlock1 = nullptr;
-  } else {
-    DomBlock = *pred_begin(IfBlock1);
-    for (BasicBlock::iterator I = IfBlock1->begin(); !I->isTerminator(); ++I)
-      if (!AggressiveInsts.count(&*I) && !isa<DbgInfoIntrinsic>(I)) {
-        // This is not an aggressive instruction that we can promote.
-        // Because of this, we won't be able to get rid of the control flow, so
-        // the xform is not worth it.
-        return false;
-      }
-  }
-
-  if (cast<BranchInst>(IfBlock2->getTerminator())->isConditional()) {
-    IfBlock2 = nullptr;
-  } else {
-    DomBlock = *pred_begin(IfBlock2);
-    for (BasicBlock::iterator I = IfBlock2->begin(); !I->isTerminator(); ++I)
-      if (!AggressiveInsts.count(&*I) && !isa<DbgInfoIntrinsic>(I)) {
-        // This is not an aggressive instruction that we can promote.
-        // Because of this, we won't be able to get rid of the control flow, so
-        // the xform is not worth it.
-        return false;
-      }
-  }
-
-  LLVM_DEBUG(dbgs() << "FOUND IF CONDITION!  " << *IfCond
-                    << "  T: " << IfTrue->getName()
-                    << "  F: " << IfFalse->getName() << "\n");
-
-  // If we can still promote the PHI nodes after this gauntlet of tests,
-  // do all of the PHI's now.
-  Instruction *InsertPt = DomBlock->getTerminator();
-  IRBuilder<NoFolder> Builder(InsertPt);
-
-  // Move all 'aggressive' instructions, which are defined in the
-  // conditional parts of the if's up to the dominating block.
-  if (IfBlock1)
-    hoistAllInstructionsInto(DomBlock, InsertPt, IfBlock1);
-  if (IfBlock2)
-    hoistAllInstructionsInto(DomBlock, InsertPt, IfBlock2);
-
-  while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
-    // Change the PHI node into a select instruction.
-    Value *TrueVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse);
-    Value *FalseVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue);
-
-    Value *Sel = Builder.CreateSelect(IfCond, TrueVal, FalseVal, "", InsertPt);
-    PN->replaceAllUsesWith(Sel);
-    Sel->takeName(PN);
-    PN->eraseFromParent();
-  }
-
-  // At this point, IfBlock1 and IfBlock2 are both empty, so our if statement
-  // has been flattened.  Change DomBlock to jump directly to our new block to
-  // avoid other simplifycfg's kicking in on the diamond.
-  Instruction *OldTI = DomBlock->getTerminator();
-  Builder.SetInsertPoint(OldTI);
-  Builder.CreateBr(BB);
-  OldTI->eraseFromParent();
-  return true;
-}
-
-/// If we found a conditional branch that goes to two returning blocks,
-/// try to merge them together into one return,
-/// introducing a select if the return values disagree.
-static bool SimplifyCondBranchToTwoReturns(BranchInst *BI,
-                                           IRBuilder<> &Builder) {
-  assert(BI->isConditional() && "Must be a conditional branch");
-  BasicBlock *TrueSucc = BI->getSuccessor(0);
-  BasicBlock *FalseSucc = BI->getSuccessor(1);
-  ReturnInst *TrueRet = cast<ReturnInst>(TrueSucc->getTerminator());
-  ReturnInst *FalseRet = cast<ReturnInst>(FalseSucc->getTerminator());
-
-  // Check to ensure both blocks are empty (just a return) or optionally empty
-  // with PHI nodes.  If there are other instructions, merging would cause extra
-  // computation on one path or the other.
-  if (!TrueSucc->getFirstNonPHIOrDbg()->isTerminator())
-    return false;
-  if (!FalseSucc->getFirstNonPHIOrDbg()->isTerminator())
-    return false;
-
-  Builder.SetInsertPoint(BI);
-  // Okay, we found a branch that is going to two return nodes.  If
-  // there is no return value for this function, just change the
-  // branch into a return.
-  if (FalseRet->getNumOperands() == 0) {
-    TrueSucc->removePredecessor(BI->getParent());
-    FalseSucc->removePredecessor(BI->getParent());
-    Builder.CreateRetVoid();
-    EraseTerminatorAndDCECond(BI);
-    return true;
-  }
-
-  // Otherwise, figure out what the true and false return values are
-  // so we can insert a new select instruction.
-  Value *TrueValue = TrueRet->getReturnValue();
-  Value *FalseValue = FalseRet->getReturnValue();
-
-  // Unwrap any PHI nodes in the return blocks.
-  if (PHINode *TVPN = dyn_cast_or_null<PHINode>(TrueValue))
-    if (TVPN->getParent() == TrueSucc)
-      TrueValue = TVPN->getIncomingValueForBlock(BI->getParent());
-  if (PHINode *FVPN = dyn_cast_or_null<PHINode>(FalseValue))
-    if (FVPN->getParent() == FalseSucc)
-      FalseValue = FVPN->getIncomingValueForBlock(BI->getParent());
-
-  // In order for this transformation to be safe, we must be able to
-  // unconditionally execute both operands to the return.  This is
-  // normally the case, but we could have a potentially-trapping
-  // constant expression that prevents this transformation from being
-  // safe.
-  if (ConstantExpr *TCV = dyn_cast_or_null<ConstantExpr>(TrueValue))
-    if (TCV->canTrap())
-      return false;
-  if (ConstantExpr *FCV = dyn_cast_or_null<ConstantExpr>(FalseValue))
-    if (FCV->canTrap())
-      return false;
-
-  // Okay, we collected all the mapped values and checked them for sanity, and
-  // defined to really do this transformation.  First, update the CFG.
-  TrueSucc->removePredecessor(BI->getParent());
-  FalseSucc->removePredecessor(BI->getParent());
-
-  // Insert select instructions where needed.
-  Value *BrCond = BI->getCondition();
-  if (TrueValue) {
-    // Insert a select if the results differ.
-    if (TrueValue == FalseValue || isa<UndefValue>(FalseValue)) {
-    } else if (isa<UndefValue>(TrueValue)) {
-      TrueValue = FalseValue;
-    } else {
-      TrueValue =
-          Builder.CreateSelect(BrCond, TrueValue, FalseValue, "retval", BI);
-    }
-  }
-
-  Value *RI =
-      !TrueValue ? Builder.CreateRetVoid() : Builder.CreateRet(TrueValue);
-
-  (void)RI;
-
-  LLVM_DEBUG(dbgs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"
-                    << "\n  " << *BI << "NewRet = " << *RI << "TRUEBLOCK: "
-                    << *TrueSucc << "FALSEBLOCK: " << *FalseSucc);
-
-  EraseTerminatorAndDCECond(BI);
-
-  return true;
-}
-
-/// Return true if the given instruction is available
-/// in its predecessor block. If yes, the instruction will be removed.
-static bool tryCSEWithPredecessor(Instruction *Inst, BasicBlock *PB) {
-  if (!isa<BinaryOperator>(Inst) && !isa<CmpInst>(Inst))
-    return false;
-  for (Instruction &I : *PB) {
-    Instruction *PBI = &I;
-    // Check whether Inst and PBI generate the same value.
-    if (Inst->isIdenticalTo(PBI)) {
-      Inst->replaceAllUsesWith(PBI);
-      Inst->eraseFromParent();
-      return true;
-    }
-  }
-  return false;
-}
-
-/// Return true if either PBI or BI has branch weight available, and store
-/// the weights in {Pred|Succ}{True|False}Weight. If one of PBI and BI does
-/// not have branch weight, use 1:1 as its weight.
-static bool extractPredSuccWeights(BranchInst *PBI, BranchInst *BI,
-                                   uint64_t &PredTrueWeight,
-                                   uint64_t &PredFalseWeight,
-                                   uint64_t &SuccTrueWeight,
-                                   uint64_t &SuccFalseWeight) {
-  bool PredHasWeights =
-      PBI->extractProfMetadata(PredTrueWeight, PredFalseWeight);
-  bool SuccHasWeights =
-      BI->extractProfMetadata(SuccTrueWeight, SuccFalseWeight);
-  if (PredHasWeights || SuccHasWeights) {
-    if (!PredHasWeights)
-      PredTrueWeight = PredFalseWeight = 1;
-    if (!SuccHasWeights)
-      SuccTrueWeight = SuccFalseWeight = 1;
-    return true;
-  } else {
-    return false;
-  }
-}
-
-/// If this basic block is simple enough, and if a predecessor branches to us
-/// and one of our successors, fold the block into the predecessor and use
-/// logical operations to pick the right destination.
-bool llvm::FoldBranchToCommonDest(BranchInst *BI, MemorySSAUpdater *MSSAU,
-                                  unsigned BonusInstThreshold) {
-  BasicBlock *BB = BI->getParent();
-
-  const unsigned PredCount = pred_size(BB);
-
-  Instruction *Cond = nullptr;
-  if (BI->isConditional())
-    Cond = dyn_cast<Instruction>(BI->getCondition());
-  else {
-    // For unconditional branch, check for a simple CFG pattern, where
-    // BB has a single predecessor and BB's successor is also its predecessor's
-    // successor. If such pattern exists, check for CSE between BB and its
-    // predecessor.
-    if (BasicBlock *PB = BB->getSinglePredecessor())
-      if (BranchInst *PBI = dyn_cast<BranchInst>(PB->getTerminator()))
-        if (PBI->isConditional() &&
-            (BI->getSuccessor(0) == PBI->getSuccessor(0) ||
-             BI->getSuccessor(0) == PBI->getSuccessor(1))) {
-          for (auto I = BB->instructionsWithoutDebug().begin(),
-                    E = BB->instructionsWithoutDebug().end();
-               I != E;) {
-            Instruction *Curr = &*I++;
-            if (isa<CmpInst>(Curr)) {
-              Cond = Curr;
-              break;
-            }
-            // Quit if we can't remove this instruction.
-            if (!tryCSEWithPredecessor(Curr, PB))
-              return false;
-          }
-        }
-
-    if (!Cond)
-      return false;
-  }
-
-  if (!Cond || (!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) ||
-      Cond->getParent() != BB || !Cond->hasOneUse())
-    return false;
-
-  // Make sure the instruction after the condition is the cond branch.
-  BasicBlock::iterator CondIt = ++Cond->getIterator();
-
-  // Ignore dbg intrinsics.
-  while (isa<DbgInfoIntrinsic>(CondIt))
-    ++CondIt;
-
-  if (&*CondIt != BI)
-    return false;
-
-  // Only allow this transformation if computing the condition doesn't involve
-  // too many instructions and these involved instructions can be executed
-  // unconditionally. We denote all involved instructions except the condition
-  // as "bonus instructions", and only allow this transformation when the
-  // number of the bonus instructions we'll need to create when cloning into
-  // each predecessor does not exceed a certain threshold.
-  unsigned NumBonusInsts = 0;
-  for (auto I = BB->begin(); Cond != &*I; ++I) {
-    // Ignore dbg intrinsics.
-    if (isa<DbgInfoIntrinsic>(I))
-      continue;
-    if (!I->hasOneUse() || !isSafeToSpeculativelyExecute(&*I))
-      return false;
-    // I has only one use and can be executed unconditionally.
-    Instruction *User = dyn_cast<Instruction>(I->user_back());
-    if (User == nullptr || User->getParent() != BB)
-      return false;
-    // I is used in the same BB. Since BI uses Cond and doesn't have more slots
-    // to use any other instruction, User must be an instruction between next(I)
-    // and Cond.
-
-    // Account for the cost of duplicating this instruction into each
-    // predecessor.
-    NumBonusInsts += PredCount;
-    // Early exits once we reach the limit.
-    if (NumBonusInsts > BonusInstThreshold)
-      return false;
-  }
-
-  // Cond is known to be a compare or binary operator.  Check to make sure that
-  // neither operand is a potentially-trapping constant expression.
-  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Cond->getOperand(0)))
-    if (CE->canTrap())
-      return false;
-  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Cond->getOperand(1)))
-    if (CE->canTrap())
-      return false;
-
-  // Finally, don't infinitely unroll conditional loops.
-  BasicBlock *TrueDest = BI->getSuccessor(0);
-  BasicBlock *FalseDest = (BI->isConditional()) ? BI->getSuccessor(1) : nullptr;
-  if (TrueDest == BB || FalseDest == BB)
-    return false;
-
-  for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
-    BasicBlock *PredBlock = *PI;
-    BranchInst *PBI = dyn_cast<BranchInst>(PredBlock->getTerminator());
-
-    // Check that we have two conditional branches.  If there is a PHI node in
-    // the common successor, verify that the same value flows in from both
-    // blocks.
-    SmallVector<PHINode *, 4> PHIs;
-    if (!PBI || PBI->isUnconditional() ||
-        (BI->isConditional() && !SafeToMergeTerminators(BI, PBI)) ||
-        (!BI->isConditional() &&
-         !isProfitableToFoldUnconditional(BI, PBI, Cond, PHIs)))
-      continue;
-
-    // Determine if the two branches share a common destination.
-    Instruction::BinaryOps Opc = Instruction::BinaryOpsEnd;
-    bool InvertPredCond = false;
-
-    if (BI->isConditional()) {
-      if (PBI->getSuccessor(0) == TrueDest) {
-        Opc = Instruction::Or;
-      } else if (PBI->getSuccessor(1) == FalseDest) {
-        Opc = Instruction::And;
-      } else if (PBI->getSuccessor(0) == FalseDest) {
-        Opc = Instruction::And;
-        InvertPredCond = true;
-      } else if (PBI->getSuccessor(1) == TrueDest) {
-        Opc = Instruction::Or;
-        InvertPredCond = true;
-      } else {
-        continue;
-      }
-    } else {
-      if (PBI->getSuccessor(0) != TrueDest && PBI->getSuccessor(1) != TrueDest)
-        continue;
-    }
-
-    LLVM_DEBUG(dbgs() << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB);
-    IRBuilder<> Builder(PBI);
-
-    // If we need to invert the condition in the pred block to match, do so now.
-    if (InvertPredCond) {
-      Value *NewCond = PBI->getCondition();
-
-      if (NewCond->hasOneUse() && isa<CmpInst>(NewCond)) {
-        CmpInst *CI = cast<CmpInst>(NewCond);
-        CI->setPredicate(CI->getInversePredicate());
-      } else {
-        NewCond =
-            Builder.CreateNot(NewCond, PBI->getCondition()->getName() + ".not");
-      }
-
-      PBI->setCondition(NewCond);
-      PBI->swapSuccessors();
-    }
-
-    // If we have bonus instructions, clone them into the predecessor block.
-    // Note that there may be multiple predecessor blocks, so we cannot move
-    // bonus instructions to a predecessor block.
-    ValueToValueMapTy VMap; // maps original values to cloned values
-    // We already make sure Cond is the last instruction before BI. Therefore,
-    // all instructions before Cond other than DbgInfoIntrinsic are bonus
-    // instructions.
-    for (auto BonusInst = BB->begin(); Cond != &*BonusInst; ++BonusInst) {
-      if (isa<DbgInfoIntrinsic>(BonusInst))
-        continue;
-      Instruction *NewBonusInst = BonusInst->clone();
-      RemapInstruction(NewBonusInst, VMap,
-                       RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
-      VMap[&*BonusInst] = NewBonusInst;
-
-      // If we moved a load, we cannot any longer claim any knowledge about
-      // its potential value. The previous information might have been valid
-      // only given the branch precondition.
-      // For an analogous reason, we must also drop all the metadata whose
-      // semantics we don't understand.
-      NewBonusInst->dropUnknownNonDebugMetadata();
-
-      PredBlock->getInstList().insert(PBI->getIterator(), NewBonusInst);
-      NewBonusInst->takeName(&*BonusInst);
-      BonusInst->setName(BonusInst->getName() + ".old");
-    }
-
-    // Clone Cond into the predecessor basic block, and or/and the
-    // two conditions together.
-    Instruction *CondInPred = Cond->clone();
-    RemapInstruction(CondInPred, VMap,
-                     RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
-    PredBlock->getInstList().insert(PBI->getIterator(), CondInPred);
-    CondInPred->takeName(Cond);
-    Cond->setName(CondInPred->getName() + ".old");
-
-    if (BI->isConditional()) {
-      Instruction *NewCond = cast<Instruction>(
-          Builder.CreateBinOp(Opc, PBI->getCondition(), CondInPred, "or.cond"));
-      PBI->setCondition(NewCond);
-
-      uint64_t PredTrueWeight, PredFalseWeight, SuccTrueWeight, SuccFalseWeight;
-      bool HasWeights =
-          extractPredSuccWeights(PBI, BI, PredTrueWeight, PredFalseWeight,
-                                 SuccTrueWeight, SuccFalseWeight);
-      SmallVector<uint64_t, 8> NewWeights;
-
-      if (PBI->getSuccessor(0) == BB) {
-        if (HasWeights) {
-          // PBI: br i1 %x, BB, FalseDest
-          // BI:  br i1 %y, TrueDest, FalseDest
-          // TrueWeight is TrueWeight for PBI * TrueWeight for BI.
-          NewWeights.push_back(PredTrueWeight * SuccTrueWeight);
-          // FalseWeight is FalseWeight for PBI * TotalWeight for BI +
-          //               TrueWeight for PBI * FalseWeight for BI.
-          // We assume that total weights of a BranchInst can fit into 32 bits.
-          // Therefore, we will not have overflow using 64-bit arithmetic.
-          NewWeights.push_back(PredFalseWeight *
-                                   (SuccFalseWeight + SuccTrueWeight) +
-                               PredTrueWeight * SuccFalseWeight);
-        }
-        AddPredecessorToBlock(TrueDest, PredBlock, BB, MSSAU);
-        PBI->setSuccessor(0, TrueDest);
-      }
-      if (PBI->getSuccessor(1) == BB) {
-        if (HasWeights) {
-          // PBI: br i1 %x, TrueDest, BB
-          // BI:  br i1 %y, TrueDest, FalseDest
-          // TrueWeight is TrueWeight for PBI * TotalWeight for BI +
-          //              FalseWeight for PBI * TrueWeight for BI.
-          NewWeights.push_back(PredTrueWeight *
-                                   (SuccFalseWeight + SuccTrueWeight) +
-                               PredFalseWeight * SuccTrueWeight);
-          // FalseWeight is FalseWeight for PBI * FalseWeight for BI.
-          NewWeights.push_back(PredFalseWeight * SuccFalseWeight);
-        }
-        AddPredecessorToBlock(FalseDest, PredBlock, BB, MSSAU);
-        PBI->setSuccessor(1, FalseDest);
-      }
-      if (NewWeights.size() == 2) {
-        // Halve the weights if any of them cannot fit in an uint32_t
-        FitWeights(NewWeights);
-
-        SmallVector<uint32_t, 8> MDWeights(NewWeights.begin(),
-                                           NewWeights.end());
-        setBranchWeights(PBI, MDWeights[0], MDWeights[1]);
-      } else
-        PBI->setMetadata(LLVMContext::MD_prof, nullptr);
-    } else {
-      // Update PHI nodes in the common successors.
-      for (unsigned i = 0, e = PHIs.size(); i != e; ++i) {
-        ConstantInt *PBI_C = cast<ConstantInt>(
-            PHIs[i]->getIncomingValueForBlock(PBI->getParent()));
-        assert(PBI_C->getType()->isIntegerTy(1));
-        Instruction *MergedCond = nullptr;
-        if (PBI->getSuccessor(0) == TrueDest) {
-          // Create (PBI_Cond and PBI_C) or (!PBI_Cond and BI_Value)
-          // PBI_C is true: PBI_Cond or (!PBI_Cond and BI_Value)
-          //       is false: !PBI_Cond and BI_Value
-          Instruction *NotCond = cast<Instruction>(
-              Builder.CreateNot(PBI->getCondition(), "not.cond"));
-          MergedCond = cast<Instruction>(
-               Builder.CreateBinOp(Instruction::And, NotCond, CondInPred,
-                                   "and.cond"));
-          if (PBI_C->isOne())
-            MergedCond = cast<Instruction>(Builder.CreateBinOp(
-                Instruction::Or, PBI->getCondition(), MergedCond, "or.cond"));
-        } else {
-          // Create (PBI_Cond and BI_Value) or (!PBI_Cond and PBI_C)
-          // PBI_C is true: (PBI_Cond and BI_Value) or (!PBI_Cond)
-          //       is false: PBI_Cond and BI_Value
-          MergedCond = cast<Instruction>(Builder.CreateBinOp(
-              Instruction::And, PBI->getCondition(), CondInPred, "and.cond"));
-          if (PBI_C->isOne()) {
-            Instruction *NotCond = cast<Instruction>(
-                Builder.CreateNot(PBI->getCondition(), "not.cond"));
-            MergedCond = cast<Instruction>(Builder.CreateBinOp(
-                Instruction::Or, NotCond, MergedCond, "or.cond"));
-          }
-        }
-        // Update PHI Node.
-	PHIs[i]->setIncomingValueForBlock(PBI->getParent(), MergedCond);
-      }
-
-      // PBI is changed to branch to TrueDest below. Remove itself from
-      // potential phis from all other successors.
-      if (MSSAU)
-        MSSAU->changeCondBranchToUnconditionalTo(PBI, TrueDest);
-
-      // Change PBI from Conditional to Unconditional.
-      BranchInst *New_PBI = BranchInst::Create(TrueDest, PBI);
-      EraseTerminatorAndDCECond(PBI, MSSAU);
-      PBI = New_PBI;
-    }
-
-    // If BI was a loop latch, it may have had associated loop metadata.
-    // We need to copy it to the new latch, that is, PBI.
-    if (MDNode *LoopMD = BI->getMetadata(LLVMContext::MD_loop))
-      PBI->setMetadata(LLVMContext::MD_loop, LoopMD);
-
-    // TODO: If BB is reachable from all paths through PredBlock, then we
-    // could replace PBI's branch probabilities with BI's.
-
-    // Copy any debug value intrinsics into the end of PredBlock.
-    for (Instruction &I : *BB)
-      if (isa<DbgInfoIntrinsic>(I))
-        I.clone()->insertBefore(PBI);
-
-    return true;
-  }
-  return false;
-}
-
-// If there is only one store in BB1 and BB2, return it, otherwise return
-// nullptr.
-static StoreInst *findUniqueStoreInBlocks(BasicBlock *BB1, BasicBlock *BB2) {
-  StoreInst *S = nullptr;
-  for (auto *BB : {BB1, BB2}) {
-    if (!BB)
-      continue;
-    for (auto &I : *BB)
-      if (auto *SI = dyn_cast<StoreInst>(&I)) {
-        if (S)
-          // Multiple stores seen.
-          return nullptr;
-        else
-          S = SI;
-      }
-  }
-  return S;
-}
-
-static Value *ensureValueAvailableInSuccessor(Value *V, BasicBlock *BB,
-                                              Value *AlternativeV = nullptr) {
-  // PHI is going to be a PHI node that allows the value V that is defined in
-  // BB to be referenced in BB's only successor.
-  //
-  // If AlternativeV is nullptr, the only value we care about in PHI is V. It
-  // doesn't matter to us what the other operand is (it'll never get used). We
-  // could just create a new PHI with an undef incoming value, but that could
-  // increase register pressure if EarlyCSE/InstCombine can't fold it with some
-  // other PHI. So here we directly look for some PHI in BB's successor with V
-  // as an incoming operand. If we find one, we use it, else we create a new
-  // one.
-  //
-  // If AlternativeV is not nullptr, we care about both incoming values in PHI.
-  // PHI must be exactly: phi <ty> [ %BB, %V ], [ %OtherBB, %AlternativeV]
-  // where OtherBB is the single other predecessor of BB's only successor.
-  PHINode *PHI = nullptr;
-  BasicBlock *Succ = BB->getSingleSuccessor();
-
-  for (auto I = Succ->begin(); isa<PHINode>(I); ++I)
-    if (cast<PHINode>(I)->getIncomingValueForBlock(BB) == V) {
-      PHI = cast<PHINode>(I);
-      if (!AlternativeV)
-        break;
-
-      assert(Succ->hasNPredecessors(2));
-      auto PredI = pred_begin(Succ);
-      BasicBlock *OtherPredBB = *PredI == BB ? *++PredI : *PredI;
-      if (PHI->getIncomingValueForBlock(OtherPredBB) == AlternativeV)
-        break;
-      PHI = nullptr;
-    }
-  if (PHI)
-    return PHI;
-
-  // If V is not an instruction defined in BB, just return it.
-  if (!AlternativeV &&
-      (!isa<Instruction>(V) || cast<Instruction>(V)->getParent() != BB))
-    return V;
-
-  PHI = PHINode::Create(V->getType(), 2, "simplifycfg.merge", &Succ->front());
-  PHI->addIncoming(V, BB);
-  for (BasicBlock *PredBB : predecessors(Succ))
-    if (PredBB != BB)
-      PHI->addIncoming(
-          AlternativeV ? AlternativeV : UndefValue::get(V->getType()), PredBB);
-  return PHI;
-}
-
-static bool mergeConditionalStoreToAddress(BasicBlock *PTB, BasicBlock *PFB,
-                                           BasicBlock *QTB, BasicBlock *QFB,
-                                           BasicBlock *PostBB, Value *Address,
-                                           bool InvertPCond, bool InvertQCond,
-                                           const DataLayout &DL) {
-  auto IsaBitcastOfPointerType = [](const Instruction &I) {
-    return Operator::getOpcode(&I) == Instruction::BitCast &&
-           I.getType()->isPointerTy();
-  };
-
-  // If we're not in aggressive mode, we only optimize if we have some
-  // confidence that by optimizing we'll allow P and/or Q to be if-converted.
-  auto IsWorthwhile = [&](BasicBlock *BB) {
-    if (!BB)
-      return true;
-    // Heuristic: if the block can be if-converted/phi-folded and the
-    // instructions inside are all cheap (arithmetic/GEPs), it's worthwhile to
-    // thread this store.
-    unsigned N = 0;
-    for (auto &I : BB->instructionsWithoutDebug()) {
-      // Cheap instructions viable for folding.
-      if (isa<BinaryOperator>(I) || isa<GetElementPtrInst>(I) ||
-          isa<StoreInst>(I))
-        ++N;
-      // Free instructions.
-      else if (I.isTerminator() || IsaBitcastOfPointerType(I))
-        continue;
-      else
-        return false;
-    }
-    // The store we want to merge is counted in N, so add 1 to make sure
-    // we're counting the instructions that would be left.
-    return N <= (PHINodeFoldingThreshold + 1);
-  };
-
-  if (!MergeCondStoresAggressively &&
-      (!IsWorthwhile(PTB) || !IsWorthwhile(PFB) || !IsWorthwhile(QTB) ||
-       !IsWorthwhile(QFB)))
-    return false;
-
-  // For every pointer, there must be exactly two stores, one coming from
-  // PTB or PFB, and the other from QTB or QFB. We don't support more than one
-  // store (to any address) in PTB,PFB or QTB,QFB.
-  // FIXME: We could relax this restriction with a bit more work and performance
-  // testing.
-  StoreInst *PStore = findUniqueStoreInBlocks(PTB, PFB);
-  StoreInst *QStore = findUniqueStoreInBlocks(QTB, QFB);
-  if (!PStore || !QStore)
-    return false;
-
-  // Now check the stores are compatible.
-  if (!QStore->isUnordered() || !PStore->isUnordered())
-    return false;
-
-  // Check that sinking the store won't cause program behavior changes. Sinking
-  // the store out of the Q blocks won't change any behavior as we're sinking
-  // from a block to its unconditional successor. But we're moving a store from
-  // the P blocks down through the middle block (QBI) and past both QFB and QTB.
-  // So we need to check that there are no aliasing loads or stores in
-  // QBI, QTB and QFB. We also need to check there are no conflicting memory
-  // operations between PStore and the end of its parent block.
-  //
-  // The ideal way to do this is to query AliasAnalysis, but we don't
-  // preserve AA currently so that is dangerous. Be super safe and just
-  // check there are no other memory operations at all.
-  for (auto &I : *QFB->getSinglePredecessor())
-    if (I.mayReadOrWriteMemory())
-      return false;
-  for (auto &I : *QFB)
-    if (&I != QStore && I.mayReadOrWriteMemory())
-      return false;
-  if (QTB)
-    for (auto &I : *QTB)
-      if (&I != QStore && I.mayReadOrWriteMemory())
-        return false;
-  for (auto I = BasicBlock::iterator(PStore), E = PStore->getParent()->end();
-       I != E; ++I)
-    if (&*I != PStore && I->mayReadOrWriteMemory())
-      return false;
-
-  // If PostBB has more than two predecessors, we need to split it so we can
-  // sink the store.
-  if (std::next(pred_begin(PostBB), 2) != pred_end(PostBB)) {
-    // We know that QFB's only successor is PostBB. And QFB has a single
-    // predecessor. If QTB exists, then its only successor is also PostBB.
-    // If QTB does not exist, then QFB's only predecessor has a conditional
-    // branch to QFB and PostBB.
-    BasicBlock *TruePred = QTB ? QTB : QFB->getSinglePredecessor();
-    BasicBlock *NewBB = SplitBlockPredecessors(PostBB, { QFB, TruePred},
-                                               "condstore.split");
-    if (!NewBB)
-      return false;
-    PostBB = NewBB;
-  }
-
-  // OK, we're going to sink the stores to PostBB. The store has to be
-  // conditional though, so first create the predicate.
-  Value *PCond = cast<BranchInst>(PFB->getSinglePredecessor()->getTerminator())
-                     ->getCondition();
-  Value *QCond = cast<BranchInst>(QFB->getSinglePredecessor()->getTerminator())
-                     ->getCondition();
-
-  Value *PPHI = ensureValueAvailableInSuccessor(PStore->getValueOperand(),
-                                                PStore->getParent());
-  Value *QPHI = ensureValueAvailableInSuccessor(QStore->getValueOperand(),
-                                                QStore->getParent(), PPHI);
-
-  IRBuilder<> QB(&*PostBB->getFirstInsertionPt());
-
-  Value *PPred = PStore->getParent() == PTB ? PCond : QB.CreateNot(PCond);
-  Value *QPred = QStore->getParent() == QTB ? QCond : QB.CreateNot(QCond);
-
-  if (InvertPCond)
-    PPred = QB.CreateNot(PPred);
-  if (InvertQCond)
-    QPred = QB.CreateNot(QPred);
-  Value *CombinedPred = QB.CreateOr(PPred, QPred);
-
-  auto *T =
-      SplitBlockAndInsertIfThen(CombinedPred, &*QB.GetInsertPoint(), false);
-  QB.SetInsertPoint(T);
-  StoreInst *SI = cast<StoreInst>(QB.CreateStore(QPHI, Address));
-  AAMDNodes AAMD;
-  PStore->getAAMetadata(AAMD, /*Merge=*/false);
-  PStore->getAAMetadata(AAMD, /*Merge=*/true);
-  SI->setAAMetadata(AAMD);
-  unsigned PAlignment = PStore->getAlignment();
-  unsigned QAlignment = QStore->getAlignment();
-  unsigned TypeAlignment =
-      DL.getABITypeAlignment(SI->getValueOperand()->getType());
-  unsigned MinAlignment;
-  unsigned MaxAlignment;
-  std::tie(MinAlignment, MaxAlignment) = std::minmax(PAlignment, QAlignment);
-  // Choose the minimum alignment. If we could prove both stores execute, we
-  // could use biggest one.  In this case, though, we only know that one of the
-  // stores executes.  And we don't know it's safe to take the alignment from a
-  // store that doesn't execute.
-  if (MinAlignment != 0) {
-    // Choose the minimum of all non-zero alignments.
-    SI->setAlignment(MinAlignment);
-  } else if (MaxAlignment != 0) {
-    // Choose the minimal alignment between the non-zero alignment and the ABI
-    // default alignment for the type of the stored value.
-    SI->setAlignment(std::min(MaxAlignment, TypeAlignment));
-  } else {
-    // If both alignments are zero, use ABI default alignment for the type of
-    // the stored value.
-    SI->setAlignment(TypeAlignment);
-  }
-
-  QStore->eraseFromParent();
-  PStore->eraseFromParent();
-
-  return true;
-}
-
-static bool mergeConditionalStores(BranchInst *PBI, BranchInst *QBI,
-                                   const DataLayout &DL) {
-  // The intention here is to find diamonds or triangles (see below) where each
-  // conditional block contains a store to the same address. Both of these
-  // stores are conditional, so they can't be unconditionally sunk. But it may
-  // be profitable to speculatively sink the stores into one merged store at the
-  // end, and predicate the merged store on the union of the two conditions of
-  // PBI and QBI.
-  //
-  // This can reduce the number of stores executed if both of the conditions are
-  // true, and can allow the blocks to become small enough to be if-converted.
-  // This optimization will also chain, so that ladders of test-and-set
-  // sequences can be if-converted away.
-  //
-  // We only deal with simple diamonds or triangles:
-  //
-  //     PBI       or      PBI        or a combination of the two
-  //    /   \               | \
-  //   PTB  PFB             |  PFB
-  //    \   /               | /
-  //     QBI                QBI
-  //    /  \                | \
-  //   QTB  QFB             |  QFB
-  //    \  /                | /
-  //    PostBB            PostBB
-  //
-  // We model triangles as a type of diamond with a nullptr "true" block.
-  // Triangles are canonicalized so that the fallthrough edge is represented by
-  // a true condition, as in the diagram above.
-  BasicBlock *PTB = PBI->getSuccessor(0);
-  BasicBlock *PFB = PBI->getSuccessor(1);
-  BasicBlock *QTB = QBI->getSuccessor(0);
-  BasicBlock *QFB = QBI->getSuccessor(1);
-  BasicBlock *PostBB = QFB->getSingleSuccessor();
-
-  // Make sure we have a good guess for PostBB. If QTB's only successor is
-  // QFB, then QFB is a better PostBB.
-  if (QTB->getSingleSuccessor() == QFB)
-    PostBB = QFB;
-
-  // If we couldn't find a good PostBB, stop.
-  if (!PostBB)
-    return false;
-
-  bool InvertPCond = false, InvertQCond = false;
-  // Canonicalize fallthroughs to the true branches.
-  if (PFB == QBI->getParent()) {
-    std::swap(PFB, PTB);
-    InvertPCond = true;
-  }
-  if (QFB == PostBB) {
-    std::swap(QFB, QTB);
-    InvertQCond = true;
-  }
-
-  // From this point on we can assume PTB or QTB may be fallthroughs but PFB
-  // and QFB may not. Model fallthroughs as a nullptr block.
-  if (PTB == QBI->getParent())
-    PTB = nullptr;
-  if (QTB == PostBB)
-    QTB = nullptr;
-
-  // Legality bailouts. We must have at least the non-fallthrough blocks and
-  // the post-dominating block, and the non-fallthroughs must only have one
-  // predecessor.
-  auto HasOnePredAndOneSucc = [](BasicBlock *BB, BasicBlock *P, BasicBlock *S) {
-    return BB->getSinglePredecessor() == P && BB->getSingleSuccessor() == S;
-  };
-  if (!HasOnePredAndOneSucc(PFB, PBI->getParent(), QBI->getParent()) ||
-      !HasOnePredAndOneSucc(QFB, QBI->getParent(), PostBB))
-    return false;
-  if ((PTB && !HasOnePredAndOneSucc(PTB, PBI->getParent(), QBI->getParent())) ||
-      (QTB && !HasOnePredAndOneSucc(QTB, QBI->getParent(), PostBB)))
-    return false;
-  if (!QBI->getParent()->hasNUses(2))
-    return false;
-
-  // OK, this is a sequence of two diamonds or triangles.
-  // Check if there are stores in PTB or PFB that are repeated in QTB or QFB.
-  SmallPtrSet<Value *, 4> PStoreAddresses, QStoreAddresses;
-  for (auto *BB : {PTB, PFB}) {
-    if (!BB)
-      continue;
-    for (auto &I : *BB)
-      if (StoreInst *SI = dyn_cast<StoreInst>(&I))
-        PStoreAddresses.insert(SI->getPointerOperand());
-  }
-  for (auto *BB : {QTB, QFB}) {
-    if (!BB)
-      continue;
-    for (auto &I : *BB)
-      if (StoreInst *SI = dyn_cast<StoreInst>(&I))
-        QStoreAddresses.insert(SI->getPointerOperand());
-  }
-
-  set_intersect(PStoreAddresses, QStoreAddresses);
-  // set_intersect mutates PStoreAddresses in place. Rename it here to make it
-  // clear what it contains.
-  auto &CommonAddresses = PStoreAddresses;
-
-  bool Changed = false;
-  for (auto *Address : CommonAddresses)
-    Changed |= mergeConditionalStoreToAddress(
-        PTB, PFB, QTB, QFB, PostBB, Address, InvertPCond, InvertQCond, DL);
-  return Changed;
-}
-
-/// If we have a conditional branch as a predecessor of another block,
-/// this function tries to simplify it.  We know
-/// that PBI and BI are both conditional branches, and BI is in one of the
-/// successor blocks of PBI - PBI branches to BI.
-static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI,
-                                           const DataLayout &DL) {
-  assert(PBI->isConditional() && BI->isConditional());
-  BasicBlock *BB = BI->getParent();
-
-  // If this block ends with a branch instruction, and if there is a
-  // predecessor that ends on a branch of the same condition, make
-  // this conditional branch redundant.
-  if (PBI->getCondition() == BI->getCondition() &&
-      PBI->getSuccessor(0) != PBI->getSuccessor(1)) {
-    // Okay, the outcome of this conditional branch is statically
-    // knowable.  If this block had a single pred, handle specially.
-    if (BB->getSinglePredecessor()) {
-      // Turn this into a branch on constant.
-      bool CondIsTrue = PBI->getSuccessor(0) == BB;
-      BI->setCondition(
-          ConstantInt::get(Type::getInt1Ty(BB->getContext()), CondIsTrue));
-      return true; // Nuke the branch on constant.
-    }
-
-    // Otherwise, if there are multiple predecessors, insert a PHI that merges
-    // in the constant and simplify the block result.  Subsequent passes of
-    // simplifycfg will thread the block.
-    if (BlockIsSimpleEnoughToThreadThrough(BB)) {
-      pred_iterator PB = pred_begin(BB), PE = pred_end(BB);
-      PHINode *NewPN = PHINode::Create(
-          Type::getInt1Ty(BB->getContext()), std::distance(PB, PE),
-          BI->getCondition()->getName() + ".pr", &BB->front());
-      // Okay, we're going to insert the PHI node.  Since PBI is not the only
-      // predecessor, compute the PHI'd conditional value for all of the preds.
-      // Any predecessor where the condition is not computable we keep symbolic.
-      for (pred_iterator PI = PB; PI != PE; ++PI) {
-        BasicBlock *P = *PI;
-        if ((PBI = dyn_cast<BranchInst>(P->getTerminator())) && PBI != BI &&
-            PBI->isConditional() && PBI->getCondition() == BI->getCondition() &&
-            PBI->getSuccessor(0) != PBI->getSuccessor(1)) {
-          bool CondIsTrue = PBI->getSuccessor(0) == BB;
-          NewPN->addIncoming(
-              ConstantInt::get(Type::getInt1Ty(BB->getContext()), CondIsTrue),
-              P);
-        } else {
-          NewPN->addIncoming(BI->getCondition(), P);
-        }
-      }
-
-      BI->setCondition(NewPN);
-      return true;
-    }
-  }
-
-  if (auto *CE = dyn_cast<ConstantExpr>(BI->getCondition()))
-    if (CE->canTrap())
-      return false;
-
-  // If both branches are conditional and both contain stores to the same
-  // address, remove the stores from the conditionals and create a conditional
-  // merged store at the end.
-  if (MergeCondStores && mergeConditionalStores(PBI, BI, DL))
-    return true;
-
-  // If this is a conditional branch in an empty block, and if any
-  // predecessors are a conditional branch to one of our destinations,
-  // fold the conditions into logical ops and one cond br.
-
-  // Ignore dbg intrinsics.
-  if (&*BB->instructionsWithoutDebug().begin() != BI)
-    return false;
-
-  int PBIOp, BIOp;
-  if (PBI->getSuccessor(0) == BI->getSuccessor(0)) {
-    PBIOp = 0;
-    BIOp = 0;
-  } else if (PBI->getSuccessor(0) == BI->getSuccessor(1)) {
-    PBIOp = 0;
-    BIOp = 1;
-  } else if (PBI->getSuccessor(1) == BI->getSuccessor(0)) {
-    PBIOp = 1;
-    BIOp = 0;
-  } else if (PBI->getSuccessor(1) == BI->getSuccessor(1)) {
-    PBIOp = 1;
-    BIOp = 1;
-  } else {
-    return false;
-  }
-
-  // Check to make sure that the other destination of this branch
-  // isn't BB itself.  If so, this is an infinite loop that will
-  // keep getting unwound.
-  if (PBI->getSuccessor(PBIOp) == BB)
-    return false;
-
-  // Do not perform this transformation if it would require
-  // insertion of a large number of select instructions. For targets
-  // without predication/cmovs, this is a big pessimization.
-
-  // Also do not perform this transformation if any phi node in the common
-  // destination block can trap when reached by BB or PBB (PR17073). In that
-  // case, it would be unsafe to hoist the operation into a select instruction.
-
-  BasicBlock *CommonDest = PBI->getSuccessor(PBIOp);
-  unsigned NumPhis = 0;
-  for (BasicBlock::iterator II = CommonDest->begin(); isa<PHINode>(II);
-       ++II, ++NumPhis) {
-    if (NumPhis > 2) // Disable this xform.
-      return false;
-
-    PHINode *PN = cast<PHINode>(II);
-    Value *BIV = PN->getIncomingValueForBlock(BB);
-    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BIV))
-      if (CE->canTrap())
-        return false;
-
-    unsigned PBBIdx = PN->getBasicBlockIndex(PBI->getParent());
-    Value *PBIV = PN->getIncomingValue(PBBIdx);
-    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(PBIV))
-      if (CE->canTrap())
-        return false;
-  }
-
-  // Finally, if everything is ok, fold the branches to logical ops.
-  BasicBlock *OtherDest = BI->getSuccessor(BIOp ^ 1);
-
-  LLVM_DEBUG(dbgs() << "FOLDING BRs:" << *PBI->getParent()
-                    << "AND: " << *BI->getParent());
-
-  // If OtherDest *is* BB, then BB is a basic block with a single conditional
-  // branch in it, where one edge (OtherDest) goes back to itself but the other
-  // exits.  We don't *know* that the program avoids the infinite loop
-  // (even though that seems likely).  If we do this xform naively, we'll end up
-  // recursively unpeeling the loop.  Since we know that (after the xform is
-  // done) that the block *is* infinite if reached, we just make it an obviously
-  // infinite loop with no cond branch.
-  if (OtherDest == BB) {
-    // Insert it at the end of the function, because it's either code,
-    // or it won't matter if it's hot. :)
-    BasicBlock *InfLoopBlock =
-        BasicBlock::Create(BB->getContext(), "infloop", BB->getParent());
-    BranchInst::Create(InfLoopBlock, InfLoopBlock);
-    OtherDest = InfLoopBlock;
-  }
-
-  LLVM_DEBUG(dbgs() << *PBI->getParent()->getParent());
-
-  // BI may have other predecessors.  Because of this, we leave
-  // it alone, but modify PBI.
-
-  // Make sure we get to CommonDest on True&True directions.
-  Value *PBICond = PBI->getCondition();
-  IRBuilder<NoFolder> Builder(PBI);
-  if (PBIOp)
-    PBICond = Builder.CreateNot(PBICond, PBICond->getName() + ".not");
-
-  Value *BICond = BI->getCondition();
-  if (BIOp)
-    BICond = Builder.CreateNot(BICond, BICond->getName() + ".not");
-
-  // Merge the conditions.
-  Value *Cond = Builder.CreateOr(PBICond, BICond, "brmerge");
-
-  // Modify PBI to branch on the new condition to the new dests.
-  PBI->setCondition(Cond);
-  PBI->setSuccessor(0, CommonDest);
-  PBI->setSuccessor(1, OtherDest);
-
-  // Update branch weight for PBI.
-  uint64_t PredTrueWeight, PredFalseWeight, SuccTrueWeight, SuccFalseWeight;
-  uint64_t PredCommon, PredOther, SuccCommon, SuccOther;
-  bool HasWeights =
-      extractPredSuccWeights(PBI, BI, PredTrueWeight, PredFalseWeight,
-                             SuccTrueWeight, SuccFalseWeight);
-  if (HasWeights) {
-    PredCommon = PBIOp ? PredFalseWeight : PredTrueWeight;
-    PredOther = PBIOp ? PredTrueWeight : PredFalseWeight;
-    SuccCommon = BIOp ? SuccFalseWeight : SuccTrueWeight;
-    SuccOther = BIOp ? SuccTrueWeight : SuccFalseWeight;
-    // The weight to CommonDest should be PredCommon * SuccTotal +
-    //                                    PredOther * SuccCommon.
-    // The weight to OtherDest should be PredOther * SuccOther.
-    uint64_t NewWeights[2] = {PredCommon * (SuccCommon + SuccOther) +
-                                  PredOther * SuccCommon,
-                              PredOther * SuccOther};
-    // Halve the weights if any of them cannot fit in an uint32_t
-    FitWeights(NewWeights);
-
-    setBranchWeights(PBI, NewWeights[0], NewWeights[1]);
-  }
-
-  // OtherDest may have phi nodes.  If so, add an entry from PBI's
-  // block that are identical to the entries for BI's block.
-  AddPredecessorToBlock(OtherDest, PBI->getParent(), BB);
-
-  // We know that the CommonDest already had an edge from PBI to
-  // it.  If it has PHIs though, the PHIs may have different
-  // entries for BB and PBI's BB.  If so, insert a select to make
-  // them agree.
-  for (PHINode &PN : CommonDest->phis()) {
-    Value *BIV = PN.getIncomingValueForBlock(BB);
-    unsigned PBBIdx = PN.getBasicBlockIndex(PBI->getParent());
-    Value *PBIV = PN.getIncomingValue(PBBIdx);
-    if (BIV != PBIV) {
-      // Insert a select in PBI to pick the right value.
-      SelectInst *NV = cast<SelectInst>(
-          Builder.CreateSelect(PBICond, PBIV, BIV, PBIV->getName() + ".mux"));
-      PN.setIncomingValue(PBBIdx, NV);
-      // Although the select has the same condition as PBI, the original branch
-      // weights for PBI do not apply to the new select because the select's
-      // 'logical' edges are incoming edges of the phi that is eliminated, not
-      // the outgoing edges of PBI.
-      if (HasWeights) {
-        uint64_t PredCommon = PBIOp ? PredFalseWeight : PredTrueWeight;
-        uint64_t PredOther = PBIOp ? PredTrueWeight : PredFalseWeight;
-        uint64_t SuccCommon = BIOp ? SuccFalseWeight : SuccTrueWeight;
-        uint64_t SuccOther = BIOp ? SuccTrueWeight : SuccFalseWeight;
-        // The weight to PredCommonDest should be PredCommon * SuccTotal.
-        // The weight to PredOtherDest should be PredOther * SuccCommon.
-        uint64_t NewWeights[2] = {PredCommon * (SuccCommon + SuccOther),
-                                  PredOther * SuccCommon};
-
-        FitWeights(NewWeights);
-
-        setBranchWeights(NV, NewWeights[0], NewWeights[1]);
-      }
-    }
-  }
-
-  LLVM_DEBUG(dbgs() << "INTO: " << *PBI->getParent());
-  LLVM_DEBUG(dbgs() << *PBI->getParent()->getParent());
-
-  // This basic block is probably dead.  We know it has at least
-  // one fewer predecessor.
-  return true;
-}
-
-// Simplifies a terminator by replacing it with a branch to TrueBB if Cond is
-// true or to FalseBB if Cond is false.
-// Takes care of updating the successors and removing the old terminator.
-// Also makes sure not to introduce new successors by assuming that edges to
-// non-successor TrueBBs and FalseBBs aren't reachable.
-static bool SimplifyTerminatorOnSelect(Instruction *OldTerm, Value *Cond,
-                                       BasicBlock *TrueBB, BasicBlock *FalseBB,
-                                       uint32_t TrueWeight,
-                                       uint32_t FalseWeight) {
-  // Remove any superfluous successor edges from the CFG.
-  // First, figure out which successors to preserve.
-  // If TrueBB and FalseBB are equal, only try to preserve one copy of that
-  // successor.
-  BasicBlock *KeepEdge1 = TrueBB;
-  BasicBlock *KeepEdge2 = TrueBB != FalseBB ? FalseBB : nullptr;
-
-  // Then remove the rest.
-  for (BasicBlock *Succ : successors(OldTerm)) {
-    // Make sure only to keep exactly one copy of each edge.
-    if (Succ == KeepEdge1)
-      KeepEdge1 = nullptr;
-    else if (Succ == KeepEdge2)
-      KeepEdge2 = nullptr;
-    else
-      Succ->removePredecessor(OldTerm->getParent(),
-                              /*KeepOneInputPHIs=*/true);
-  }
-
-  IRBuilder<> Builder(OldTerm);
-  Builder.SetCurrentDebugLocation(OldTerm->getDebugLoc());
-
-  // Insert an appropriate new terminator.
-  if (!KeepEdge1 && !KeepEdge2) {
-    if (TrueBB == FalseBB)
-      // We were only looking for one successor, and it was present.
-      // Create an unconditional branch to it.
-      Builder.CreateBr(TrueBB);
-    else {
-      // We found both of the successors we were looking for.
-      // Create a conditional branch sharing the condition of the select.
-      BranchInst *NewBI = Builder.CreateCondBr(Cond, TrueBB, FalseBB);
-      if (TrueWeight != FalseWeight)
-        setBranchWeights(NewBI, TrueWeight, FalseWeight);
-    }
-  } else if (KeepEdge1 && (KeepEdge2 || TrueBB == FalseBB)) {
-    // Neither of the selected blocks were successors, so this
-    // terminator must be unreachable.
-    new UnreachableInst(OldTerm->getContext(), OldTerm);
-  } else {
-    // One of the selected values was a successor, but the other wasn't.
-    // Insert an unconditional branch to the one that was found;
-    // the edge to the one that wasn't must be unreachable.
-    if (!KeepEdge1)
-      // Only TrueBB was found.
-      Builder.CreateBr(TrueBB);
-    else
-      // Only FalseBB was found.
-      Builder.CreateBr(FalseBB);
-  }
-
-  EraseTerminatorAndDCECond(OldTerm);
-  return true;
-}
-
-// Replaces
-//   (switch (select cond, X, Y)) on constant X, Y
-// with a branch - conditional if X and Y lead to distinct BBs,
-// unconditional otherwise.
-static bool SimplifySwitchOnSelect(SwitchInst *SI, SelectInst *Select) {
-  // Check for constant integer values in the select.
-  ConstantInt *TrueVal = dyn_cast<ConstantInt>(Select->getTrueValue());
-  ConstantInt *FalseVal = dyn_cast<ConstantInt>(Select->getFalseValue());
-  if (!TrueVal || !FalseVal)
-    return false;
-
-  // Find the relevant condition and destinations.
-  Value *Condition = Select->getCondition();
-  BasicBlock *TrueBB = SI->findCaseValue(TrueVal)->getCaseSuccessor();
-  BasicBlock *FalseBB = SI->findCaseValue(FalseVal)->getCaseSuccessor();
-
-  // Get weight for TrueBB and FalseBB.
-  uint32_t TrueWeight = 0, FalseWeight = 0;
-  SmallVector<uint64_t, 8> Weights;
-  bool HasWeights = HasBranchWeights(SI);
-  if (HasWeights) {
-    GetBranchWeights(SI, Weights);
-    if (Weights.size() == 1 + SI->getNumCases()) {
-      TrueWeight =
-          (uint32_t)Weights[SI->findCaseValue(TrueVal)->getSuccessorIndex()];
-      FalseWeight =
-          (uint32_t)Weights[SI->findCaseValue(FalseVal)->getSuccessorIndex()];
-    }
-  }
-
-  // Perform the actual simplification.
-  return SimplifyTerminatorOnSelect(SI, Condition, TrueBB, FalseBB, TrueWeight,
-                                    FalseWeight);
-}
-
-// Replaces
-//   (indirectbr (select cond, blockaddress(@fn, BlockA),
-//                             blockaddress(@fn, BlockB)))
-// with
-//   (br cond, BlockA, BlockB).
-static bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI) {
-  // Check that both operands of the select are block addresses.
-  BlockAddress *TBA = dyn_cast<BlockAddress>(SI->getTrueValue());
-  BlockAddress *FBA = dyn_cast<BlockAddress>(SI->getFalseValue());
-  if (!TBA || !FBA)
-    return false;
-
-  // Extract the actual blocks.
-  BasicBlock *TrueBB = TBA->getBasicBlock();
-  BasicBlock *FalseBB = FBA->getBasicBlock();
-
-  // Perform the actual simplification.
-  return SimplifyTerminatorOnSelect(IBI, SI->getCondition(), TrueBB, FalseBB, 0,
-                                    0);
-}
-
-/// This is called when we find an icmp instruction
-/// (a seteq/setne with a constant) as the only instruction in a
-/// block that ends with an uncond branch.  We are looking for a very specific
-/// pattern that occurs when "A == 1 || A == 2 || A == 3" gets simplified.  In
-/// this case, we merge the first two "or's of icmp" into a switch, but then the
-/// default value goes to an uncond block with a seteq in it, we get something
-/// like:
-///
-///   switch i8 %A, label %DEFAULT [ i8 1, label %end    i8 2, label %end ]
-/// DEFAULT:
-///   %tmp = icmp eq i8 %A, 92
-///   br label %end
-/// end:
-///   ... = phi i1 [ true, %entry ], [ %tmp, %DEFAULT ], [ true, %entry ]
-///
-/// We prefer to split the edge to 'end' so that there is a true/false entry to
-/// the PHI, merging the third icmp into the switch.
-bool SimplifyCFGOpt::tryToSimplifyUncondBranchWithICmpInIt(
-    ICmpInst *ICI, IRBuilder<> &Builder) {
-  BasicBlock *BB = ICI->getParent();
-
-  // If the block has any PHIs in it or the icmp has multiple uses, it is too
-  // complex.
-  if (isa<PHINode>(BB->begin()) || !ICI->hasOneUse())
-    return false;
-
-  Value *V = ICI->getOperand(0);
-  ConstantInt *Cst = cast<ConstantInt>(ICI->getOperand(1));
-
-  // The pattern we're looking for is where our only predecessor is a switch on
-  // 'V' and this block is the default case for the switch.  In this case we can
-  // fold the compared value into the switch to simplify things.
-  BasicBlock *Pred = BB->getSinglePredecessor();
-  if (!Pred || !isa<SwitchInst>(Pred->getTerminator()))
-    return false;
-
-  SwitchInst *SI = cast<SwitchInst>(Pred->getTerminator());
-  if (SI->getCondition() != V)
-    return false;
-
-  // If BB is reachable on a non-default case, then we simply know the value of
-  // V in this block.  Substitute it and constant fold the icmp instruction
-  // away.
-  if (SI->getDefaultDest() != BB) {
-    ConstantInt *VVal = SI->findCaseDest(BB);
-    assert(VVal && "Should have a unique destination value");
-    ICI->setOperand(0, VVal);
-
-    if (Value *V = SimplifyInstruction(ICI, {DL, ICI})) {
-      ICI->replaceAllUsesWith(V);
-      ICI->eraseFromParent();
-    }
-    // BB is now empty, so it is likely to simplify away.
-    return requestResimplify();
-  }
-
-  // Ok, the block is reachable from the default dest.  If the constant we're
-  // comparing exists in one of the other edges, then we can constant fold ICI
-  // and zap it.
-  if (SI->findCaseValue(Cst) != SI->case_default()) {
-    Value *V;
-    if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
-      V = ConstantInt::getFalse(BB->getContext());
-    else
-      V = ConstantInt::getTrue(BB->getContext());
-
-    ICI->replaceAllUsesWith(V);
-    ICI->eraseFromParent();
-    // BB is now empty, so it is likely to simplify away.
-    return requestResimplify();
-  }
-
-  // The use of the icmp has to be in the 'end' block, by the only PHI node in
-  // the block.
-  BasicBlock *SuccBlock = BB->getTerminator()->getSuccessor(0);
-  PHINode *PHIUse = dyn_cast<PHINode>(ICI->user_back());
-  if (PHIUse == nullptr || PHIUse != &SuccBlock->front() ||
-      isa<PHINode>(++BasicBlock::iterator(PHIUse)))
-    return false;
-
-  // If the icmp is a SETEQ, then the default dest gets false, the new edge gets
-  // true in the PHI.
-  Constant *DefaultCst = ConstantInt::getTrue(BB->getContext());
-  Constant *NewCst = ConstantInt::getFalse(BB->getContext());
-
-  if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
-    std::swap(DefaultCst, NewCst);
-
-  // Replace ICI (which is used by the PHI for the default value) with true or
-  // false depending on if it is EQ or NE.
-  ICI->replaceAllUsesWith(DefaultCst);
-  ICI->eraseFromParent();
-
-  // Okay, the switch goes to this block on a default value.  Add an edge from
-  // the switch to the merge point on the compared value.
-  BasicBlock *NewBB =
-      BasicBlock::Create(BB->getContext(), "switch.edge", BB->getParent(), BB);
-  {
-    SwitchInstProfUpdateWrapper SIW(*SI);
-    auto W0 = SIW.getSuccessorWeight(0);
-    SwitchInstProfUpdateWrapper::CaseWeightOpt NewW;
-    if (W0) {
-      NewW = ((uint64_t(*W0) + 1) >> 1);
-      SIW.setSuccessorWeight(0, *NewW);
-    }
-    SIW.addCase(Cst, NewBB, NewW);
-  }
-
-  // NewBB branches to the phi block, add the uncond branch and the phi entry.
-  Builder.SetInsertPoint(NewBB);
-  Builder.SetCurrentDebugLocation(SI->getDebugLoc());
-  Builder.CreateBr(SuccBlock);
-  PHIUse->addIncoming(NewCst, NewBB);
-  return true;
-}
-
-/// The specified branch is a conditional branch.
-/// Check to see if it is branching on an or/and chain of icmp instructions, and
-/// fold it into a switch instruction if so.
-static bool SimplifyBranchOnICmpChain(BranchInst *BI, IRBuilder<> &Builder,
-                                      const DataLayout &DL) {
-  Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
-  if (!Cond)
-    return false;
-
-  // Change br (X == 0 | X == 1), T, F into a switch instruction.
-  // If this is a bunch of seteq's or'd together, or if it's a bunch of
-  // 'setne's and'ed together, collect them.
-
-  // Try to gather values from a chain of and/or to be turned into a switch
-  ConstantComparesGatherer ConstantCompare(Cond, DL);
-  // Unpack the result
-  SmallVectorImpl<ConstantInt *> &Values = ConstantCompare.Vals;
-  Value *CompVal = ConstantCompare.CompValue;
-  unsigned UsedICmps = ConstantCompare.UsedICmps;
-  Value *ExtraCase = ConstantCompare.Extra;
-
-  // If we didn't have a multiply compared value, fail.
-  if (!CompVal)
-    return false;
-
-  // Avoid turning single icmps into a switch.
-  if (UsedICmps <= 1)
-    return false;
-
-  bool TrueWhenEqual = (Cond->getOpcode() == Instruction::Or);
-
-  // There might be duplicate constants in the list, which the switch
-  // instruction can't handle, remove them now.
-  array_pod_sort(Values.begin(), Values.end(), ConstantIntSortPredicate);
-  Values.erase(std::unique(Values.begin(), Values.end()), Values.end());
-
-  // If Extra was used, we require at least two switch values to do the
-  // transformation.  A switch with one value is just a conditional branch.
-  if (ExtraCase && Values.size() < 2)
-    return false;
-
-  // TODO: Preserve branch weight metadata, similarly to how
-  // FoldValueComparisonIntoPredecessors preserves it.
-
-  // Figure out which block is which destination.
-  BasicBlock *DefaultBB = BI->getSuccessor(1);
-  BasicBlock *EdgeBB = BI->getSuccessor(0);
-  if (!TrueWhenEqual)
-    std::swap(DefaultBB, EdgeBB);
-
-  BasicBlock *BB = BI->getParent();
-
-  LLVM_DEBUG(dbgs() << "Converting 'icmp' chain with " << Values.size()
-                    << " cases into SWITCH.  BB is:\n"
-                    << *BB);
-
-  // If there are any extra values that couldn't be folded into the switch
-  // then we evaluate them with an explicit branch first.  Split the block
-  // right before the condbr to handle it.
-  if (ExtraCase) {
-    BasicBlock *NewBB =
-        BB->splitBasicBlock(BI->getIterator(), "switch.early.test");
-    // Remove the uncond branch added to the old block.
-    Instruction *OldTI = BB->getTerminator();
-    Builder.SetInsertPoint(OldTI);
-
-    if (TrueWhenEqual)
-      Builder.CreateCondBr(ExtraCase, EdgeBB, NewBB);
-    else
-      Builder.CreateCondBr(ExtraCase, NewBB, EdgeBB);
-
-    OldTI->eraseFromParent();
-
-    // If there are PHI nodes in EdgeBB, then we need to add a new entry to them
-    // for the edge we just added.
-    AddPredecessorToBlock(EdgeBB, BB, NewBB);
-
-    LLVM_DEBUG(dbgs() << "  ** 'icmp' chain unhandled condition: " << *ExtraCase
-                      << "\nEXTRABB = " << *BB);
-    BB = NewBB;
-  }
-
-  Builder.SetInsertPoint(BI);
-  // Convert pointer to int before we switch.
-  if (CompVal->getType()->isPointerTy()) {
-    CompVal = Builder.CreatePtrToInt(
-        CompVal, DL.getIntPtrType(CompVal->getType()), "magicptr");
-  }
-
-  // Create the new switch instruction now.
-  SwitchInst *New = Builder.CreateSwitch(CompVal, DefaultBB, Values.size());
-
-  // Add all of the 'cases' to the switch instruction.
-  for (unsigned i = 0, e = Values.size(); i != e; ++i)
-    New->addCase(Values[i], EdgeBB);
-
-  // We added edges from PI to the EdgeBB.  As such, if there were any
-  // PHI nodes in EdgeBB, they need entries to be added corresponding to
-  // the number of edges added.
-  for (BasicBlock::iterator BBI = EdgeBB->begin(); isa<PHINode>(BBI); ++BBI) {
-    PHINode *PN = cast<PHINode>(BBI);
-    Value *InVal = PN->getIncomingValueForBlock(BB);
-    for (unsigned i = 0, e = Values.size() - 1; i != e; ++i)
-      PN->addIncoming(InVal, BB);
-  }
-
-  // Erase the old branch instruction.
-  EraseTerminatorAndDCECond(BI);
-
-  LLVM_DEBUG(dbgs() << "  ** 'icmp' chain result is:\n" << *BB << '\n');
-  return true;
-}
-
-bool SimplifyCFGOpt::SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder) {
-  if (isa<PHINode>(RI->getValue()))
-    return SimplifyCommonResume(RI);
-  else if (isa<LandingPadInst>(RI->getParent()->getFirstNonPHI()) &&
-           RI->getValue() == RI->getParent()->getFirstNonPHI())
-    // The resume must unwind the exception that caused control to branch here.
-    return SimplifySingleResume(RI);
-
-  return false;
-}
-
-// Simplify resume that is shared by several landing pads (phi of landing pad).
-bool SimplifyCFGOpt::SimplifyCommonResume(ResumeInst *RI) {
-  BasicBlock *BB = RI->getParent();
-
-  // Check that there are no other instructions except for debug intrinsics
-  // between the phi of landing pads (RI->getValue()) and resume instruction.
-  BasicBlock::iterator I = cast<Instruction>(RI->getValue())->getIterator(),
-                       E = RI->getIterator();
-  while (++I != E)
-    if (!isa<DbgInfoIntrinsic>(I))
-      return false;
-
-  SmallSetVector<BasicBlock *, 4> TrivialUnwindBlocks;
-  auto *PhiLPInst = cast<PHINode>(RI->getValue());
-
-  // Check incoming blocks to see if any of them are trivial.
-  for (unsigned Idx = 0, End = PhiLPInst->getNumIncomingValues(); Idx != End;
-       Idx++) {
-    auto *IncomingBB = PhiLPInst->getIncomingBlock(Idx);
-    auto *IncomingValue = PhiLPInst->getIncomingValue(Idx);
-
-    // If the block has other successors, we can not delete it because
-    // it has other dependents.
-    if (IncomingBB->getUniqueSuccessor() != BB)
-      continue;
-
-    auto *LandingPad = dyn_cast<LandingPadInst>(IncomingBB->getFirstNonPHI());
-    // Not the landing pad that caused the control to branch here.
-    if (IncomingValue != LandingPad)
-      continue;
-
-    bool isTrivial = true;
-
-    I = IncomingBB->getFirstNonPHI()->getIterator();
-    E = IncomingBB->getTerminator()->getIterator();
-    while (++I != E)
-      if (!isa<DbgInfoIntrinsic>(I)) {
-        isTrivial = false;
-        break;
-      }
-
-    if (isTrivial)
-      TrivialUnwindBlocks.insert(IncomingBB);
-  }
-
-  // If no trivial unwind blocks, don't do any simplifications.
-  if (TrivialUnwindBlocks.empty())
-    return false;
-
-  // Turn all invokes that unwind here into calls.
-  for (auto *TrivialBB : TrivialUnwindBlocks) {
-    // Blocks that will be simplified should be removed from the phi node.
-    // Note there could be multiple edges to the resume block, and we need
-    // to remove them all.
-    while (PhiLPInst->getBasicBlockIndex(TrivialBB) != -1)
-      BB->removePredecessor(TrivialBB, true);
-
-    for (pred_iterator PI = pred_begin(TrivialBB), PE = pred_end(TrivialBB);
-         PI != PE;) {
-      BasicBlock *Pred = *PI++;
-      removeUnwindEdge(Pred);
-    }
-
-    // In each SimplifyCFG run, only the current processed block can be erased.
-    // Otherwise, it will break the iteration of SimplifyCFG pass. So instead
-    // of erasing TrivialBB, we only remove the branch to the common resume
-    // block so that we can later erase the resume block since it has no
-    // predecessors.
-    TrivialBB->getTerminator()->eraseFromParent();
-    new UnreachableInst(RI->getContext(), TrivialBB);
-  }
-
-  // Delete the resume block if all its predecessors have been removed.
-  if (pred_empty(BB))
-    BB->eraseFromParent();
-
-  return !TrivialUnwindBlocks.empty();
-}
-
-// Simplify resume that is only used by a single (non-phi) landing pad.
-bool SimplifyCFGOpt::SimplifySingleResume(ResumeInst *RI) {
-  BasicBlock *BB = RI->getParent();
-  LandingPadInst *LPInst = dyn_cast<LandingPadInst>(BB->getFirstNonPHI());
-  assert(RI->getValue() == LPInst &&
-         "Resume must unwind the exception that caused control to here");
-
-  // Check that there are no other instructions except for debug intrinsics.
-  BasicBlock::iterator I = LPInst->getIterator(), E = RI->getIterator();
-  while (++I != E)
-    if (!isa<DbgInfoIntrinsic>(I))
-      return false;
-
-  // Turn all invokes that unwind here into calls and delete the basic block.
-  for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;) {
-    BasicBlock *Pred = *PI++;
-    removeUnwindEdge(Pred);
-  }
-
-  // The landingpad is now unreachable.  Zap it.
-  if (LoopHeaders)
-    LoopHeaders->erase(BB);
-  BB->eraseFromParent();
-  return true;
-}
-
-static bool removeEmptyCleanup(CleanupReturnInst *RI) {
-  // If this is a trivial cleanup pad that executes no instructions, it can be
-  // eliminated.  If the cleanup pad continues to the caller, any predecessor
-  // that is an EH pad will be updated to continue to the caller and any
-  // predecessor that terminates with an invoke instruction will have its invoke
-  // instruction converted to a call instruction.  If the cleanup pad being
-  // simplified does not continue to the caller, each predecessor will be
-  // updated to continue to the unwind destination of the cleanup pad being
-  // simplified.
-  BasicBlock *BB = RI->getParent();
-  CleanupPadInst *CPInst = RI->getCleanupPad();
-  if (CPInst->getParent() != BB)
-    // This isn't an empty cleanup.
-    return false;
-
-  // We cannot kill the pad if it has multiple uses.  This typically arises
-  // from unreachable basic blocks.
-  if (!CPInst->hasOneUse())
-    return false;
-
-  // Check that there are no other instructions except for benign intrinsics.
-  BasicBlock::iterator I = CPInst->getIterator(), E = RI->getIterator();
-  while (++I != E) {
-    auto *II = dyn_cast<IntrinsicInst>(I);
-    if (!II)
-      return false;
-
-    Intrinsic::ID IntrinsicID = II->getIntrinsicID();
-    switch (IntrinsicID) {
-    case Intrinsic::dbg_declare:
-    case Intrinsic::dbg_value:
-    case Intrinsic::dbg_label:
-    case Intrinsic::lifetime_end:
-      break;
-    default:
-      return false;
-    }
-  }
-
-  // If the cleanup return we are simplifying unwinds to the caller, this will
-  // set UnwindDest to nullptr.
-  BasicBlock *UnwindDest = RI->getUnwindDest();
-  Instruction *DestEHPad = UnwindDest ? UnwindDest->getFirstNonPHI() : nullptr;
-
-  // We're about to remove BB from the control flow.  Before we do, sink any
-  // PHINodes into the unwind destination.  Doing this before changing the
-  // control flow avoids some potentially slow checks, since we can currently
-  // be certain that UnwindDest and BB have no common predecessors (since they
-  // are both EH pads).
-  if (UnwindDest) {
-    // First, go through the PHI nodes in UnwindDest and update any nodes that
-    // reference the block we are removing
-    for (BasicBlock::iterator I = UnwindDest->begin(),
-                              IE = DestEHPad->getIterator();
-         I != IE; ++I) {
-      PHINode *DestPN = cast<PHINode>(I);
-
-      int Idx = DestPN->getBasicBlockIndex(BB);
-      // Since BB unwinds to UnwindDest, it has to be in the PHI node.
-      assert(Idx != -1);
-      // This PHI node has an incoming value that corresponds to a control
-      // path through the cleanup pad we are removing.  If the incoming
-      // value is in the cleanup pad, it must be a PHINode (because we
-      // verified above that the block is otherwise empty).  Otherwise, the
-      // value is either a constant or a value that dominates the cleanup
-      // pad being removed.
-      //
-      // Because BB and UnwindDest are both EH pads, all of their
-      // predecessors must unwind to these blocks, and since no instruction
-      // can have multiple unwind destinations, there will be no overlap in
-      // incoming blocks between SrcPN and DestPN.
-      Value *SrcVal = DestPN->getIncomingValue(Idx);
-      PHINode *SrcPN = dyn_cast<PHINode>(SrcVal);
-
-      // Remove the entry for the block we are deleting.
-      DestPN->removeIncomingValue(Idx, false);
-
-      if (SrcPN && SrcPN->getParent() == BB) {
-        // If the incoming value was a PHI node in the cleanup pad we are
-        // removing, we need to merge that PHI node's incoming values into
-        // DestPN.
-        for (unsigned SrcIdx = 0, SrcE = SrcPN->getNumIncomingValues();
-             SrcIdx != SrcE; ++SrcIdx) {
-          DestPN->addIncoming(SrcPN->getIncomingValue(SrcIdx),
-                              SrcPN->getIncomingBlock(SrcIdx));
-        }
-      } else {
-        // Otherwise, the incoming value came from above BB and
-        // so we can just reuse it.  We must associate all of BB's
-        // predecessors with this value.
-        for (auto *pred : predecessors(BB)) {
-          DestPN->addIncoming(SrcVal, pred);
-        }
-      }
-    }
-
-    // Sink any remaining PHI nodes directly into UnwindDest.
-    Instruction *InsertPt = DestEHPad;
-    for (BasicBlock::iterator I = BB->begin(),
-                              IE = BB->getFirstNonPHI()->getIterator();
-         I != IE;) {
-      // The iterator must be incremented here because the instructions are
-      // being moved to another block.
-      PHINode *PN = cast<PHINode>(I++);
-      if (PN->use_empty())
-        // If the PHI node has no uses, just leave it.  It will be erased
-        // when we erase BB below.
-        continue;
-
-      // Otherwise, sink this PHI node into UnwindDest.
-      // Any predecessors to UnwindDest which are not already represented
-      // must be back edges which inherit the value from the path through
-      // BB.  In this case, the PHI value must reference itself.
-      for (auto *pred : predecessors(UnwindDest))
-        if (pred != BB)
-          PN->addIncoming(PN, pred);
-      PN->moveBefore(InsertPt);
-    }
-  }
-
-  for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;) {
-    // The iterator must be updated here because we are removing this pred.
-    BasicBlock *PredBB = *PI++;
-    if (UnwindDest == nullptr) {
-      removeUnwindEdge(PredBB);
-    } else {
-      Instruction *TI = PredBB->getTerminator();
-      TI->replaceUsesOfWith(BB, UnwindDest);
-    }
-  }
-
-  // The cleanup pad is now unreachable.  Zap it.
-  BB->eraseFromParent();
-  return true;
-}
-
-// Try to merge two cleanuppads together.
-static bool mergeCleanupPad(CleanupReturnInst *RI) {
-  // Skip any cleanuprets which unwind to caller, there is nothing to merge
-  // with.
-  BasicBlock *UnwindDest = RI->getUnwindDest();
-  if (!UnwindDest)
-    return false;
-
-  // This cleanupret isn't the only predecessor of this cleanuppad, it wouldn't
-  // be safe to merge without code duplication.
-  if (UnwindDest->getSinglePredecessor() != RI->getParent())
-    return false;
-
-  // Verify that our cleanuppad's unwind destination is another cleanuppad.
-  auto *SuccessorCleanupPad = dyn_cast<CleanupPadInst>(&UnwindDest->front());
-  if (!SuccessorCleanupPad)
-    return false;
-
-  CleanupPadInst *PredecessorCleanupPad = RI->getCleanupPad();
-  // Replace any uses of the successor cleanupad with the predecessor pad
-  // The only cleanuppad uses should be this cleanupret, it's cleanupret and
-  // funclet bundle operands.
-  SuccessorCleanupPad->replaceAllUsesWith(PredecessorCleanupPad);
-  // Remove the old cleanuppad.
-  SuccessorCleanupPad->eraseFromParent();
-  // Now, we simply replace the cleanupret with a branch to the unwind
-  // destination.
-  BranchInst::Create(UnwindDest, RI->getParent());
-  RI->eraseFromParent();
-
-  return true;
-}
-
-bool SimplifyCFGOpt::SimplifyCleanupReturn(CleanupReturnInst *RI) {
-  // It is possible to transiantly have an undef cleanuppad operand because we
-  // have deleted some, but not all, dead blocks.
-  // Eventually, this block will be deleted.
-  if (isa<UndefValue>(RI->getOperand(0)))
-    return false;
-
-  if (mergeCleanupPad(RI))
-    return true;
-
-  if (removeEmptyCleanup(RI))
-    return true;
-
-  return false;
-}
-
-bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) {
-  BasicBlock *BB = RI->getParent();
-  if (!BB->getFirstNonPHIOrDbg()->isTerminator())
-    return false;
-
-  // Find predecessors that end with branches.
-  SmallVector<BasicBlock *, 8> UncondBranchPreds;
-  SmallVector<BranchInst *, 8> CondBranchPreds;
-  for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
-    BasicBlock *P = *PI;
-    Instruction *PTI = P->getTerminator();
-    if (BranchInst *BI = dyn_cast<BranchInst>(PTI)) {
-      if (BI->isUnconditional())
-        UncondBranchPreds.push_back(P);
-      else
-        CondBranchPreds.push_back(BI);
-    }
-  }
-
-  // If we found some, do the transformation!
-  if (!UncondBranchPreds.empty() && DupRet) {
-    while (!UncondBranchPreds.empty()) {
-      BasicBlock *Pred = UncondBranchPreds.pop_back_val();
-      LLVM_DEBUG(dbgs() << "FOLDING: " << *BB
-                        << "INTO UNCOND BRANCH PRED: " << *Pred);
-      (void)FoldReturnIntoUncondBranch(RI, BB, Pred);
-    }
-
-    // If we eliminated all predecessors of the block, delete the block now.
-    if (pred_empty(BB)) {
-      // We know there are no successors, so just nuke the block.
-      if (LoopHeaders)
-        LoopHeaders->erase(BB);
-      BB->eraseFromParent();
-    }
-
-    return true;
-  }
-
-  // Check out all of the conditional branches going to this return
-  // instruction.  If any of them just select between returns, change the
-  // branch itself into a select/return pair.
-  while (!CondBranchPreds.empty()) {
-    BranchInst *BI = CondBranchPreds.pop_back_val();
-
-    // Check to see if the non-BB successor is also a return block.
-    if (isa<ReturnInst>(BI->getSuccessor(0)->getTerminator()) &&
-        isa<ReturnInst>(BI->getSuccessor(1)->getTerminator()) &&
-        SimplifyCondBranchToTwoReturns(BI, Builder))
-      return true;
-  }
-  return false;
-}
-
-bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) {
-  BasicBlock *BB = UI->getParent();
-
-  bool Changed = false;
-
-  // If there are any instructions immediately before the unreachable that can
-  // be removed, do so.
-  while (UI->getIterator() != BB->begin()) {
-    BasicBlock::iterator BBI = UI->getIterator();
-    --BBI;
-    // Do not delete instructions that can have side effects which might cause
-    // the unreachable to not be reachable; specifically, calls and volatile
-    // operations may have this effect.
-    if (isa<CallInst>(BBI) && !isa<DbgInfoIntrinsic>(BBI))
-      break;
-
-    if (BBI->mayHaveSideEffects()) {
-      if (auto *SI = dyn_cast<StoreInst>(BBI)) {
-        if (SI->isVolatile())
-          break;
-      } else if (auto *LI = dyn_cast<LoadInst>(BBI)) {
-        if (LI->isVolatile())
-          break;
-      } else if (auto *RMWI = dyn_cast<AtomicRMWInst>(BBI)) {
-        if (RMWI->isVolatile())
-          break;
-      } else if (auto *CXI = dyn_cast<AtomicCmpXchgInst>(BBI)) {
-        if (CXI->isVolatile())
-          break;
-      } else if (isa<CatchPadInst>(BBI)) {
-        // A catchpad may invoke exception object constructors and such, which
-        // in some languages can be arbitrary code, so be conservative by
-        // default.
-        // For CoreCLR, it just involves a type test, so can be removed.
-        if (classifyEHPersonality(BB->getParent()->getPersonalityFn()) !=
-            EHPersonality::CoreCLR)
-          break;
-      } else if (!isa<FenceInst>(BBI) && !isa<VAArgInst>(BBI) &&
-                 !isa<LandingPadInst>(BBI)) {
-        break;
-      }
-      // Note that deleting LandingPad's here is in fact okay, although it
-      // involves a bit of subtle reasoning. If this inst is a LandingPad,
-      // all the predecessors of this block will be the unwind edges of Invokes,
-      // and we can therefore guarantee this block will be erased.
-    }
-
-    // Delete this instruction (any uses are guaranteed to be dead)
-    if (!BBI->use_empty())
-      BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
-    BBI->eraseFromParent();
-    Changed = true;
-  }
-
-  // If the unreachable instruction is the first in the block, take a gander
-  // at all of the predecessors of this instruction, and simplify them.
-  if (&BB->front() != UI)
-    return Changed;
-
-  SmallVector<BasicBlock *, 8> Preds(pred_begin(BB), pred_end(BB));
-  for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
-    Instruction *TI = Preds[i]->getTerminator();
-    IRBuilder<> Builder(TI);
-    if (auto *BI = dyn_cast<BranchInst>(TI)) {
-      if (BI->isUnconditional()) {
-        if (BI->getSuccessor(0) == BB) {
-          new UnreachableInst(TI->getContext(), TI);
-          TI->eraseFromParent();
-          Changed = true;
-        }
-      } else {
-        Value* Cond = BI->getCondition();
-        if (BI->getSuccessor(0) == BB) {
-          Builder.CreateAssumption(Builder.CreateNot(Cond));
-          Builder.CreateBr(BI->getSuccessor(1));
-          EraseTerminatorAndDCECond(BI);
-        } else if (BI->getSuccessor(1) == BB) {
-          Builder.CreateAssumption(Cond);
-          Builder.CreateBr(BI->getSuccessor(0));
-          EraseTerminatorAndDCECond(BI);
-          Changed = true;
-        }
-      }
-    } else if (auto *SI = dyn_cast<SwitchInst>(TI)) {
-      SwitchInstProfUpdateWrapper SU(*SI);
-      for (auto i = SU->case_begin(), e = SU->case_end(); i != e;) {
-        if (i->getCaseSuccessor() != BB) {
-          ++i;
-          continue;
-        }
-        BB->removePredecessor(SU->getParent());
-        i = SU.removeCase(i);
-        e = SU->case_end();
-        Changed = true;
-      }
-    } else if (auto *II = dyn_cast<InvokeInst>(TI)) {
-      if (II->getUnwindDest() == BB) {
-        removeUnwindEdge(TI->getParent());
-        Changed = true;
-      }
-    } else if (auto *CSI = dyn_cast<CatchSwitchInst>(TI)) {
-      if (CSI->getUnwindDest() == BB) {
-        removeUnwindEdge(TI->getParent());
-        Changed = true;
-        continue;
-      }
-
-      for (CatchSwitchInst::handler_iterator I = CSI->handler_begin(),
-                                             E = CSI->handler_end();
-           I != E; ++I) {
-        if (*I == BB) {
-          CSI->removeHandler(I);
-          --I;
-          --E;
-          Changed = true;
-        }
-      }
-      if (CSI->getNumHandlers() == 0) {
-        BasicBlock *CatchSwitchBB = CSI->getParent();
-        if (CSI->hasUnwindDest()) {
-          // Redirect preds to the unwind dest
-          CatchSwitchBB->replaceAllUsesWith(CSI->getUnwindDest());
-        } else {
-          // Rewrite all preds to unwind to caller (or from invoke to call).
-          SmallVector<BasicBlock *, 8> EHPreds(predecessors(CatchSwitchBB));
-          for (BasicBlock *EHPred : EHPreds)
-            removeUnwindEdge(EHPred);
-        }
-        // The catchswitch is no longer reachable.
-        new UnreachableInst(CSI->getContext(), CSI);
-        CSI->eraseFromParent();
-        Changed = true;
-      }
-    } else if (isa<CleanupReturnInst>(TI)) {
-      new UnreachableInst(TI->getContext(), TI);
-      TI->eraseFromParent();
-      Changed = true;
-    }
-  }
-
-  // If this block is now dead, remove it.
-  if (pred_empty(BB) && BB != &BB->getParent()->getEntryBlock()) {
-    // We know there are no successors, so just nuke the block.
-    if (LoopHeaders)
-      LoopHeaders->erase(BB);
-    BB->eraseFromParent();
-    return true;
-  }
-
-  return Changed;
-}
-
-static bool CasesAreContiguous(SmallVectorImpl<ConstantInt *> &Cases) {
-  assert(Cases.size() >= 1);
-
-  array_pod_sort(Cases.begin(), Cases.end(), ConstantIntSortPredicate);
-  for (size_t I = 1, E = Cases.size(); I != E; ++I) {
-    if (Cases[I - 1]->getValue() != Cases[I]->getValue() + 1)
-      return false;
-  }
-  return true;
-}
-
-/// Turn a switch with two reachable destinations into an integer range
-/// comparison and branch.
-static bool TurnSwitchRangeIntoICmp(SwitchInst *SI, IRBuilder<> &Builder) {
-  assert(SI->getNumCases() > 1 && "Degenerate switch?");
-
-  bool HasDefault =
-      !isa<UnreachableInst>(SI->getDefaultDest()->getFirstNonPHIOrDbg());
-
-  // Partition the cases into two sets with different destinations.
-  BasicBlock *DestA = HasDefault ? SI->getDefaultDest() : nullptr;
-  BasicBlock *DestB = nullptr;
-  SmallVector<ConstantInt *, 16> CasesA;
-  SmallVector<ConstantInt *, 16> CasesB;
-
-  for (auto Case : SI->cases()) {
-    BasicBlock *Dest = Case.getCaseSuccessor();
-    if (!DestA)
-      DestA = Dest;
-    if (Dest == DestA) {
-      CasesA.push_back(Case.getCaseValue());
-      continue;
-    }
-    if (!DestB)
-      DestB = Dest;
-    if (Dest == DestB) {
-      CasesB.push_back(Case.getCaseValue());
-      continue;
-    }
-    return false; // More than two destinations.
-  }
-
-  assert(DestA && DestB &&
-         "Single-destination switch should have been folded.");
-  assert(DestA != DestB);
-  assert(DestB != SI->getDefaultDest());
-  assert(!CasesB.empty() && "There must be non-default cases.");
-  assert(!CasesA.empty() || HasDefault);
-
-  // Figure out if one of the sets of cases form a contiguous range.
-  SmallVectorImpl<ConstantInt *> *ContiguousCases = nullptr;
-  BasicBlock *ContiguousDest = nullptr;
-  BasicBlock *OtherDest = nullptr;
-  if (!CasesA.empty() && CasesAreContiguous(CasesA)) {
-    ContiguousCases = &CasesA;
-    ContiguousDest = DestA;
-    OtherDest = DestB;
-  } else if (CasesAreContiguous(CasesB)) {
-    ContiguousCases = &CasesB;
-    ContiguousDest = DestB;
-    OtherDest = DestA;
-  } else
-    return false;
-
-  // Start building the compare and branch.
-
-  Constant *Offset = ConstantExpr::getNeg(ContiguousCases->back());
-  Constant *NumCases =
-      ConstantInt::get(Offset->getType(), ContiguousCases->size());
-
-  Value *Sub = SI->getCondition();
-  if (!Offset->isNullValue())
-    Sub = Builder.CreateAdd(Sub, Offset, Sub->getName() + ".off");
-
-  Value *Cmp;
-  // If NumCases overflowed, then all possible values jump to the successor.
-  if (NumCases->isNullValue() && !ContiguousCases->empty())
-    Cmp = ConstantInt::getTrue(SI->getContext());
-  else
-    Cmp = Builder.CreateICmpULT(Sub, NumCases, "switch");
-  BranchInst *NewBI = Builder.CreateCondBr(Cmp, ContiguousDest, OtherDest);
-
-  // Update weight for the newly-created conditional branch.
-  if (HasBranchWeights(SI)) {
-    SmallVector<uint64_t, 8> Weights;
-    GetBranchWeights(SI, Weights);
-    if (Weights.size() == 1 + SI->getNumCases()) {
-      uint64_t TrueWeight = 0;
-      uint64_t FalseWeight = 0;
-      for (size_t I = 0, E = Weights.size(); I != E; ++I) {
-        if (SI->getSuccessor(I) == ContiguousDest)
-          TrueWeight += Weights[I];
-        else
-          FalseWeight += Weights[I];
-      }
-      while (TrueWeight > UINT32_MAX || FalseWeight > UINT32_MAX) {
-        TrueWeight /= 2;
-        FalseWeight /= 2;
-      }
-      setBranchWeights(NewBI, TrueWeight, FalseWeight);
-    }
-  }
-
-  // Prune obsolete incoming values off the successors' PHI nodes.
-  for (auto BBI = ContiguousDest->begin(); isa<PHINode>(BBI); ++BBI) {
-    unsigned PreviousEdges = ContiguousCases->size();
-    if (ContiguousDest == SI->getDefaultDest())
-      ++PreviousEdges;
-    for (unsigned I = 0, E = PreviousEdges - 1; I != E; ++I)
-      cast<PHINode>(BBI)->removeIncomingValue(SI->getParent());
-  }
-  for (auto BBI = OtherDest->begin(); isa<PHINode>(BBI); ++BBI) {
-    unsigned PreviousEdges = SI->getNumCases() - ContiguousCases->size();
-    if (OtherDest == SI->getDefaultDest())
-      ++PreviousEdges;
-    for (unsigned I = 0, E = PreviousEdges - 1; I != E; ++I)
-      cast<PHINode>(BBI)->removeIncomingValue(SI->getParent());
-  }
-
-  // Drop the switch.
-  SI->eraseFromParent();
-
-  return true;
-}
-
-/// Compute masked bits for the condition of a switch
-/// and use it to remove dead cases.
-static bool eliminateDeadSwitchCases(SwitchInst *SI, AssumptionCache *AC,
-                                     const DataLayout &DL) {
-  Value *Cond = SI->getCondition();
-  unsigned Bits = Cond->getType()->getIntegerBitWidth();
-  KnownBits Known = computeKnownBits(Cond, DL, 0, AC, SI);
-
-  // We can also eliminate cases by determining that their values are outside of
-  // the limited range of the condition based on how many significant (non-sign)
-  // bits are in the condition value.
-  unsigned ExtraSignBits = ComputeNumSignBits(Cond, DL, 0, AC, SI) - 1;
-  unsigned MaxSignificantBitsInCond = Bits - ExtraSignBits;
-
-  // Gather dead cases.
-  SmallVector<ConstantInt *, 8> DeadCases;
-  for (auto &Case : SI->cases()) {
-    const APInt &CaseVal = Case.getCaseValue()->getValue();
-    if (Known.Zero.intersects(CaseVal) || !Known.One.isSubsetOf(CaseVal) ||
-        (CaseVal.getMinSignedBits() > MaxSignificantBitsInCond)) {
-      DeadCases.push_back(Case.getCaseValue());
-      LLVM_DEBUG(dbgs() << "SimplifyCFG: switch case " << CaseVal
-                        << " is dead.\n");
-    }
-  }
-
-  // If we can prove that the cases must cover all possible values, the
-  // default destination becomes dead and we can remove it.  If we know some
-  // of the bits in the value, we can use that to more precisely compute the
-  // number of possible unique case values.
-  bool HasDefault =
-      !isa<UnreachableInst>(SI->getDefaultDest()->getFirstNonPHIOrDbg());
-  const unsigned NumUnknownBits =
-      Bits - (Known.Zero | Known.One).countPopulation();
-  assert(NumUnknownBits <= Bits);
-  if (HasDefault && DeadCases.empty() &&
-      NumUnknownBits < 64 /* avoid overflow */ &&
-      SI->getNumCases() == (1ULL << NumUnknownBits)) {
-    LLVM_DEBUG(dbgs() << "SimplifyCFG: switch default is dead.\n");
-    BasicBlock *NewDefault =
-        SplitBlockPredecessors(SI->getDefaultDest(), SI->getParent(), "");
-    SI->setDefaultDest(&*NewDefault);
-    SplitBlock(&*NewDefault, &NewDefault->front());
-    auto *OldTI = NewDefault->getTerminator();
-    new UnreachableInst(SI->getContext(), OldTI);
-    EraseTerminatorAndDCECond(OldTI);
-    return true;
-  }
-
-  if (DeadCases.empty())
-    return false;
-
-  SwitchInstProfUpdateWrapper SIW(*SI);
-  for (ConstantInt *DeadCase : DeadCases) {
-    SwitchInst::CaseIt CaseI = SI->findCaseValue(DeadCase);
-    assert(CaseI != SI->case_default() &&
-           "Case was not found. Probably mistake in DeadCases forming.");
-    // Prune unused values from PHI nodes.
-    CaseI->getCaseSuccessor()->removePredecessor(SI->getParent());
-    SIW.removeCase(CaseI);
-  }
-
-  return true;
-}
-
-/// If BB would be eligible for simplification by
-/// TryToSimplifyUncondBranchFromEmptyBlock (i.e. it is empty and terminated
-/// by an unconditional branch), look at the phi node for BB in the successor
-/// block and see if the incoming value is equal to CaseValue. If so, return
-/// the phi node, and set PhiIndex to BB's index in the phi node.
-static PHINode *FindPHIForConditionForwarding(ConstantInt *CaseValue,
-                                              BasicBlock *BB, int *PhiIndex) {
-  if (BB->getFirstNonPHIOrDbg() != BB->getTerminator())
-    return nullptr; // BB must be empty to be a candidate for simplification.
-  if (!BB->getSinglePredecessor())
-    return nullptr; // BB must be dominated by the switch.
-
-  BranchInst *Branch = dyn_cast<BranchInst>(BB->getTerminator());
-  if (!Branch || !Branch->isUnconditional())
-    return nullptr; // Terminator must be unconditional branch.
-
-  BasicBlock *Succ = Branch->getSuccessor(0);
-
-  for (PHINode &PHI : Succ->phis()) {
-    int Idx = PHI.getBasicBlockIndex(BB);
-    assert(Idx >= 0 && "PHI has no entry for predecessor?");
-
-    Value *InValue = PHI.getIncomingValue(Idx);
-    if (InValue != CaseValue)
-      continue;
-
-    *PhiIndex = Idx;
-    return &PHI;
-  }
-
-  return nullptr;
-}
-
-/// Try to forward the condition of a switch instruction to a phi node
-/// dominated by the switch, if that would mean that some of the destination
-/// blocks of the switch can be folded away. Return true if a change is made.
-static bool ForwardSwitchConditionToPHI(SwitchInst *SI) {
-  using ForwardingNodesMap = DenseMap<PHINode *, SmallVector<int, 4>>;
-
-  ForwardingNodesMap ForwardingNodes;
-  BasicBlock *SwitchBlock = SI->getParent();
-  bool Changed = false;
-  for (auto &Case : SI->cases()) {
-    ConstantInt *CaseValue = Case.getCaseValue();
-    BasicBlock *CaseDest = Case.getCaseSuccessor();
-
-    // Replace phi operands in successor blocks that are using the constant case
-    // value rather than the switch condition variable:
-    //   switchbb:
-    //   switch i32 %x, label %default [
-    //     i32 17, label %succ
-    //   ...
-    //   succ:
-    //     %r = phi i32 ... [ 17, %switchbb ] ...
-    // -->
-    //     %r = phi i32 ... [ %x, %switchbb ] ...
-
-    for (PHINode &Phi : CaseDest->phis()) {
-      // This only works if there is exactly 1 incoming edge from the switch to
-      // a phi. If there is >1, that means multiple cases of the switch map to 1
-      // value in the phi, and that phi value is not the switch condition. Thus,
-      // this transform would not make sense (the phi would be invalid because
-      // a phi can't have different incoming values from the same block).
-      int SwitchBBIdx = Phi.getBasicBlockIndex(SwitchBlock);
-      if (Phi.getIncomingValue(SwitchBBIdx) == CaseValue &&
-          count(Phi.blocks(), SwitchBlock) == 1) {
-        Phi.setIncomingValue(SwitchBBIdx, SI->getCondition());
-        Changed = true;
-      }
-    }
-
-    // Collect phi nodes that are indirectly using this switch's case constants.
-    int PhiIdx;
-    if (auto *Phi = FindPHIForConditionForwarding(CaseValue, CaseDest, &PhiIdx))
-      ForwardingNodes[Phi].push_back(PhiIdx);
-  }
-
-  for (auto &ForwardingNode : ForwardingNodes) {
-    PHINode *Phi = ForwardingNode.first;
-    SmallVectorImpl<int> &Indexes = ForwardingNode.second;
-    if (Indexes.size() < 2)
-      continue;
-
-    for (int Index : Indexes)
-      Phi->setIncomingValue(Index, SI->getCondition());
-    Changed = true;
-  }
-
-  return Changed;
-}
-
-/// Return true if the backend will be able to handle
-/// initializing an array of constants like C.
-static bool ValidLookupTableConstant(Constant *C, const TargetTransformInfo &TTI) {
-  if (C->isThreadDependent())
-    return false;
-  if (C->isDLLImportDependent())
-    return false;
-
-  if (!isa<ConstantFP>(C) && !isa<ConstantInt>(C) &&
-      !isa<ConstantPointerNull>(C) && !isa<GlobalValue>(C) &&
-      !isa<UndefValue>(C) && !isa<ConstantExpr>(C))
-    return false;
-
-  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
-    if (!CE->isGEPWithNoNotionalOverIndexing())
-      return false;
-    if (!ValidLookupTableConstant(CE->getOperand(0), TTI))
-      return false;
-  }
-
-  if (!TTI.shouldBuildLookupTablesForConstant(C))
-    return false;
-
-  return true;
-}
-
-/// If V is a Constant, return it. Otherwise, try to look up
-/// its constant value in ConstantPool, returning 0 if it's not there.
-static Constant *
-LookupConstant(Value *V,
-               const SmallDenseMap<Value *, Constant *> &ConstantPool) {
-  if (Constant *C = dyn_cast<Constant>(V))
-    return C;
-  return ConstantPool.lookup(V);
-}
-
-/// Try to fold instruction I into a constant. This works for
-/// simple instructions such as binary operations where both operands are
-/// constant or can be replaced by constants from the ConstantPool. Returns the
-/// resulting constant on success, 0 otherwise.
-static Constant *
-ConstantFold(Instruction *I, const DataLayout &DL,
-             const SmallDenseMap<Value *, Constant *> &ConstantPool) {
-  if (SelectInst *Select = dyn_cast<SelectInst>(I)) {
-    Constant *A = LookupConstant(Select->getCondition(), ConstantPool);
-    if (!A)
-      return nullptr;
-    if (A->isAllOnesValue())
-      return LookupConstant(Select->getTrueValue(), ConstantPool);
-    if (A->isNullValue())
-      return LookupConstant(Select->getFalseValue(), ConstantPool);
-    return nullptr;
-  }
-
-  SmallVector<Constant *, 4> COps;
-  for (unsigned N = 0, E = I->getNumOperands(); N != E; ++N) {
-    if (Constant *A = LookupConstant(I->getOperand(N), ConstantPool))
-      COps.push_back(A);
-    else
-      return nullptr;
-  }
-
-  if (CmpInst *Cmp = dyn_cast<CmpInst>(I)) {
-    return ConstantFoldCompareInstOperands(Cmp->getPredicate(), COps[0],
-                                           COps[1], DL);
-  }
-
-  return ConstantFoldInstOperands(I, COps, DL);
-}
-
-/// Try to determine the resulting constant values in phi nodes
-/// at the common destination basic block, *CommonDest, for one of the case
-/// destionations CaseDest corresponding to value CaseVal (0 for the default
-/// case), of a switch instruction SI.
-static bool
-GetCaseResults(SwitchInst *SI, ConstantInt *CaseVal, BasicBlock *CaseDest,
-               BasicBlock **CommonDest,
-               SmallVectorImpl<std::pair<PHINode *, Constant *>> &Res,
-               const DataLayout &DL, const TargetTransformInfo &TTI) {
-  // The block from which we enter the common destination.
-  BasicBlock *Pred = SI->getParent();
-
-  // If CaseDest is empty except for some side-effect free instructions through
-  // which we can constant-propagate the CaseVal, continue to its successor.
-  SmallDenseMap<Value *, Constant *> ConstantPool;
-  ConstantPool.insert(std::make_pair(SI->getCondition(), CaseVal));
-  for (Instruction &I :CaseDest->instructionsWithoutDebug()) {
-    if (I.isTerminator()) {
-      // If the terminator is a simple branch, continue to the next block.
-      if (I.getNumSuccessors() != 1 || I.isExceptionalTerminator())
-        return false;
-      Pred = CaseDest;
-      CaseDest = I.getSuccessor(0);
-    } else if (Constant *C = ConstantFold(&I, DL, ConstantPool)) {
-      // Instruction is side-effect free and constant.
-
-      // If the instruction has uses outside this block or a phi node slot for
-      // the block, it is not safe to bypass the instruction since it would then
-      // no longer dominate all its uses.
-      for (auto &Use : I.uses()) {
-        User *User = Use.getUser();
-        if (Instruction *I = dyn_cast<Instruction>(User))
-          if (I->getParent() == CaseDest)
-            continue;
-        if (PHINode *Phi = dyn_cast<PHINode>(User))
-          if (Phi->getIncomingBlock(Use) == CaseDest)
-            continue;
-        return false;
-      }
-
-      ConstantPool.insert(std::make_pair(&I, C));
-    } else {
-      break;
-    }
-  }
-
-  // If we did not have a CommonDest before, use the current one.
-  if (!*CommonDest)
-    *CommonDest = CaseDest;
-  // If the destination isn't the common one, abort.
-  if (CaseDest != *CommonDest)
-    return false;
-
-  // Get the values for this case from phi nodes in the destination block.
-  for (PHINode &PHI : (*CommonDest)->phis()) {
-    int Idx = PHI.getBasicBlockIndex(Pred);
-    if (Idx == -1)
-      continue;
-
-    Constant *ConstVal =
-        LookupConstant(PHI.getIncomingValue(Idx), ConstantPool);
-    if (!ConstVal)
-      return false;
-
-    // Be conservative about which kinds of constants we support.
-    if (!ValidLookupTableConstant(ConstVal, TTI))
-      return false;
-
-    Res.push_back(std::make_pair(&PHI, ConstVal));
-  }
-
-  return Res.size() > 0;
-}
-
-// Helper function used to add CaseVal to the list of cases that generate
-// Result. Returns the updated number of cases that generate this result.
-static uintptr_t MapCaseToResult(ConstantInt *CaseVal,
-                                 SwitchCaseResultVectorTy &UniqueResults,
-                                 Constant *Result) {
-  for (auto &I : UniqueResults) {
-    if (I.first == Result) {
-      I.second.push_back(CaseVal);
-      return I.second.size();
-    }
-  }
-  UniqueResults.push_back(
-      std::make_pair(Result, SmallVector<ConstantInt *, 4>(1, CaseVal)));
-  return 1;
-}
-
-// Helper function that initializes a map containing
-// results for the PHI node of the common destination block for a switch
-// instruction. Returns false if multiple PHI nodes have been found or if
-// there is not a common destination block for the switch.
-static bool
-InitializeUniqueCases(SwitchInst *SI, PHINode *&PHI, BasicBlock *&CommonDest,
-                      SwitchCaseResultVectorTy &UniqueResults,
-                      Constant *&DefaultResult, const DataLayout &DL,
-                      const TargetTransformInfo &TTI,
-                      uintptr_t MaxUniqueResults, uintptr_t MaxCasesPerResult) {
-  for (auto &I : SI->cases()) {
-    ConstantInt *CaseVal = I.getCaseValue();
-
-    // Resulting value at phi nodes for this case value.
-    SwitchCaseResultsTy Results;
-    if (!GetCaseResults(SI, CaseVal, I.getCaseSuccessor(), &CommonDest, Results,
-                        DL, TTI))
-      return false;
-
-    // Only one value per case is permitted.
-    if (Results.size() > 1)
-      return false;
-
-    // Add the case->result mapping to UniqueResults.
-    const uintptr_t NumCasesForResult =
-        MapCaseToResult(CaseVal, UniqueResults, Results.begin()->second);
-
-    // Early out if there are too many cases for this result.
-    if (NumCasesForResult > MaxCasesPerResult)
-      return false;
-
-    // Early out if there are too many unique results.
-    if (UniqueResults.size() > MaxUniqueResults)
-      return false;
-
-    // Check the PHI consistency.
-    if (!PHI)
-      PHI = Results[0].first;
-    else if (PHI != Results[0].first)
-      return false;
-  }
-  // Find the default result value.
-  SmallVector<std::pair<PHINode *, Constant *>, 1> DefaultResults;
-  BasicBlock *DefaultDest = SI->getDefaultDest();
-  GetCaseResults(SI, nullptr, SI->getDefaultDest(), &CommonDest, DefaultResults,
-                 DL, TTI);
-  // If the default value is not found abort unless the default destination
-  // is unreachable.
-  DefaultResult =
-      DefaultResults.size() == 1 ? DefaultResults.begin()->second : nullptr;
-  if ((!DefaultResult &&
-       !isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg())))
-    return false;
-
-  return true;
-}
-
-// Helper function that checks if it is possible to transform a switch with only
-// two cases (or two cases + default) that produces a result into a select.
-// Example:
-// switch (a) {
-//   case 10:                %0 = icmp eq i32 %a, 10
-//     return 10;            %1 = select i1 %0, i32 10, i32 4
-//   case 20:        ---->   %2 = icmp eq i32 %a, 20
-//     return 2;             %3 = select i1 %2, i32 2, i32 %1
-//   default:
-//     return 4;
-// }
-static Value *ConvertTwoCaseSwitch(const SwitchCaseResultVectorTy &ResultVector,
-                                   Constant *DefaultResult, Value *Condition,
-                                   IRBuilder<> &Builder) {
-  assert(ResultVector.size() == 2 &&
-         "We should have exactly two unique results at this point");
-  // If we are selecting between only two cases transform into a simple
-  // select or a two-way select if default is possible.
-  if (ResultVector[0].second.size() == 1 &&
-      ResultVector[1].second.size() == 1) {
-    ConstantInt *const FirstCase = ResultVector[0].second[0];
-    ConstantInt *const SecondCase = ResultVector[1].second[0];
-
-    bool DefaultCanTrigger = DefaultResult;
-    Value *SelectValue = ResultVector[1].first;
-    if (DefaultCanTrigger) {
-      Value *const ValueCompare =
-          Builder.CreateICmpEQ(Condition, SecondCase, "switch.selectcmp");
-      SelectValue = Builder.CreateSelect(ValueCompare, ResultVector[1].first,
-                                         DefaultResult, "switch.select");
-    }
-    Value *const ValueCompare =
-        Builder.CreateICmpEQ(Condition, FirstCase, "switch.selectcmp");
-    return Builder.CreateSelect(ValueCompare, ResultVector[0].first,
-                                SelectValue, "switch.select");
-  }
-
-  return nullptr;
-}
-
-// Helper function to cleanup a switch instruction that has been converted into
-// a select, fixing up PHI nodes and basic blocks.
-static void RemoveSwitchAfterSelectConversion(SwitchInst *SI, PHINode *PHI,
-                                              Value *SelectValue,
-                                              IRBuilder<> &Builder) {
-  BasicBlock *SelectBB = SI->getParent();
-  while (PHI->getBasicBlockIndex(SelectBB) >= 0)
-    PHI->removeIncomingValue(SelectBB);
-  PHI->addIncoming(SelectValue, SelectBB);
-
-  Builder.CreateBr(PHI->getParent());
-
-  // Remove the switch.
-  for (unsigned i = 0, e = SI->getNumSuccessors(); i < e; ++i) {
-    BasicBlock *Succ = SI->getSuccessor(i);
-
-    if (Succ == PHI->getParent())
-      continue;
-    Succ->removePredecessor(SelectBB);
-  }
-  SI->eraseFromParent();
-}
-
-/// If the switch is only used to initialize one or more
-/// phi nodes in a common successor block with only two different
-/// constant values, replace the switch with select.
-static bool switchToSelect(SwitchInst *SI, IRBuilder<> &Builder,
-                           const DataLayout &DL,
-                           const TargetTransformInfo &TTI) {
-  Value *const Cond = SI->getCondition();
-  PHINode *PHI = nullptr;
-  BasicBlock *CommonDest = nullptr;
-  Constant *DefaultResult;
-  SwitchCaseResultVectorTy UniqueResults;
-  // Collect all the cases that will deliver the same value from the switch.
-  if (!InitializeUniqueCases(SI, PHI, CommonDest, UniqueResults, DefaultResult,
-                             DL, TTI, 2, 1))
-    return false;
-  // Selects choose between maximum two values.
-  if (UniqueResults.size() != 2)
-    return false;
-  assert(PHI != nullptr && "PHI for value select not found");
-
-  Builder.SetInsertPoint(SI);
-  Value *SelectValue =
-      ConvertTwoCaseSwitch(UniqueResults, DefaultResult, Cond, Builder);
-  if (SelectValue) {
-    RemoveSwitchAfterSelectConversion(SI, PHI, SelectValue, Builder);
-    return true;
-  }
-  // The switch couldn't be converted into a select.
-  return false;
-}
-
-namespace {
-
-/// This class represents a lookup table that can be used to replace a switch.
-class SwitchLookupTable {
-public:
-  /// Create a lookup table to use as a switch replacement with the contents
-  /// of Values, using DefaultValue to fill any holes in the table.
-  SwitchLookupTable(
-      Module &M, uint64_t TableSize, ConstantInt *Offset,
-      const SmallVectorImpl<std::pair<ConstantInt *, Constant *>> &Values,
-      Constant *DefaultValue, const DataLayout &DL, const StringRef &FuncName);
-
-  /// Build instructions with Builder to retrieve the value at
-  /// the position given by Index in the lookup table.
-  Value *BuildLookup(Value *Index, IRBuilder<> &Builder);
-
-  /// Return true if a table with TableSize elements of
-  /// type ElementType would fit in a target-legal register.
-  static bool WouldFitInRegister(const DataLayout &DL, uint64_t TableSize,
-                                 Type *ElementType);
-
-private:
-  // Depending on the contents of the table, it can be represented in
-  // different ways.
-  enum {
-    // For tables where each element contains the same value, we just have to
-    // store that single value and return it for each lookup.
-    SingleValueKind,
-
-    // For tables where there is a linear relationship between table index
-    // and values. We calculate the result with a simple multiplication
-    // and addition instead of a table lookup.
-    LinearMapKind,
-
-    // For small tables with integer elements, we can pack them into a bitmap
-    // that fits into a target-legal register. Values are retrieved by
-    // shift and mask operations.
-    BitMapKind,
-
-    // The table is stored as an array of values. Values are retrieved by load
-    // instructions from the table.
-    ArrayKind
-  } Kind;
-
-  // For SingleValueKind, this is the single value.
-  Constant *SingleValue = nullptr;
-
-  // For BitMapKind, this is the bitmap.
-  ConstantInt *BitMap = nullptr;
-  IntegerType *BitMapElementTy = nullptr;
-
-  // For LinearMapKind, these are the constants used to derive the value.
-  ConstantInt *LinearOffset = nullptr;
-  ConstantInt *LinearMultiplier = nullptr;
-
-  // For ArrayKind, this is the array.
-  GlobalVariable *Array = nullptr;
-};
-
-} // end anonymous namespace
-
-SwitchLookupTable::SwitchLookupTable(
-    Module &M, uint64_t TableSize, ConstantInt *Offset,
-    const SmallVectorImpl<std::pair<ConstantInt *, Constant *>> &Values,
-    Constant *DefaultValue, const DataLayout &DL, const StringRef &FuncName) {
-  assert(Values.size() && "Can't build lookup table without values!");
-  assert(TableSize >= Values.size() && "Can't fit values in table!");
-
-  // If all values in the table are equal, this is that value.
-  SingleValue = Values.begin()->second;
-
-  Type *ValueType = Values.begin()->second->getType();
-
-  // Build up the table contents.
-  SmallVector<Constant *, 64> TableContents(TableSize);
-  for (size_t I = 0, E = Values.size(); I != E; ++I) {
-    ConstantInt *CaseVal = Values[I].first;
-    Constant *CaseRes = Values[I].second;
-    assert(CaseRes->getType() == ValueType);
-
-    uint64_t Idx = (CaseVal->getValue() - Offset->getValue()).getLimitedValue();
-    TableContents[Idx] = CaseRes;
-
-    if (CaseRes != SingleValue)
-      SingleValue = nullptr;
-  }
-
-  // Fill in any holes in the table with the default result.
-  if (Values.size() < TableSize) {
-    assert(DefaultValue &&
-           "Need a default value to fill the lookup table holes.");
-    assert(DefaultValue->getType() == ValueType);
-    for (uint64_t I = 0; I < TableSize; ++I) {
-      if (!TableContents[I])
-        TableContents[I] = DefaultValue;
-    }
-
-    if (DefaultValue != SingleValue)
-      SingleValue = nullptr;
-  }
-
-  // If each element in the table contains the same value, we only need to store
-  // that single value.
-  if (SingleValue) {
-    Kind = SingleValueKind;
-    return;
-  }
-
-  // Check if we can derive the value with a linear transformation from the
-  // table index.
-  if (isa<IntegerType>(ValueType)) {
-    bool LinearMappingPossible = true;
-    APInt PrevVal;
-    APInt DistToPrev;
-    assert(TableSize >= 2 && "Should be a SingleValue table.");
-    // Check if there is the same distance between two consecutive values.
-    for (uint64_t I = 0; I < TableSize; ++I) {
-      ConstantInt *ConstVal = dyn_cast<ConstantInt>(TableContents[I]);
-      if (!ConstVal) {
-        // This is an undef. We could deal with it, but undefs in lookup tables
-        // are very seldom. It's probably not worth the additional complexity.
-        LinearMappingPossible = false;
-        break;
-      }
-      const APInt &Val = ConstVal->getValue();
-      if (I != 0) {
-        APInt Dist = Val - PrevVal;
-        if (I == 1) {
-          DistToPrev = Dist;
-        } else if (Dist != DistToPrev) {
-          LinearMappingPossible = false;
-          break;
-        }
-      }
-      PrevVal = Val;
-    }
-    if (LinearMappingPossible) {
-      LinearOffset = cast<ConstantInt>(TableContents[0]);
-      LinearMultiplier = ConstantInt::get(M.getContext(), DistToPrev);
-      Kind = LinearMapKind;
-      ++NumLinearMaps;
-      return;
-    }
-  }
-
-  // If the type is integer and the table fits in a register, build a bitmap.
-  if (WouldFitInRegister(DL, TableSize, ValueType)) {
-    IntegerType *IT = cast<IntegerType>(ValueType);
-    APInt TableInt(TableSize * IT->getBitWidth(), 0);
-    for (uint64_t I = TableSize; I > 0; --I) {
-      TableInt <<= IT->getBitWidth();
-      // Insert values into the bitmap. Undef values are set to zero.
-      if (!isa<UndefValue>(TableContents[I - 1])) {
-        ConstantInt *Val = cast<ConstantInt>(TableContents[I - 1]);
-        TableInt |= Val->getValue().zext(TableInt.getBitWidth());
-      }
-    }
-    BitMap = ConstantInt::get(M.getContext(), TableInt);
-    BitMapElementTy = IT;
-    Kind = BitMapKind;
-    ++NumBitMaps;
-    return;
-  }
-
-  // Store the table in an array.
-  ArrayType *ArrayTy = ArrayType::get(ValueType, TableSize);
-  Constant *Initializer = ConstantArray::get(ArrayTy, TableContents);
-
-  Array = new GlobalVariable(M, ArrayTy, /*isConstant=*/true,
-                             GlobalVariable::PrivateLinkage, Initializer,
-                             "switch.table." + FuncName);
-  Array->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
-  // Set the alignment to that of an array items. We will be only loading one
-  // value out of it.
-  Array->setAlignment(DL.getPrefTypeAlignment(ValueType));
-  Kind = ArrayKind;
-}
-
-Value *SwitchLookupTable::BuildLookup(Value *Index, IRBuilder<> &Builder) {
-  switch (Kind) {
-  case SingleValueKind:
-    return SingleValue;
-  case LinearMapKind: {
-    // Derive the result value from the input value.
-    Value *Result = Builder.CreateIntCast(Index, LinearMultiplier->getType(),
-                                          false, "switch.idx.cast");
-    if (!LinearMultiplier->isOne())
-      Result = Builder.CreateMul(Result, LinearMultiplier, "switch.idx.mult");
-    if (!LinearOffset->isZero())
-      Result = Builder.CreateAdd(Result, LinearOffset, "switch.offset");
-    return Result;
-  }
-  case BitMapKind: {
-    // Type of the bitmap (e.g. i59).
-    IntegerType *MapTy = BitMap->getType();
-
-    // Cast Index to the same type as the bitmap.
-    // Note: The Index is <= the number of elements in the table, so
-    // truncating it to the width of the bitmask is safe.
-    Value *ShiftAmt = Builder.CreateZExtOrTrunc(Index, MapTy, "switch.cast");
-
-    // Multiply the shift amount by the element width.
-    ShiftAmt = Builder.CreateMul(
-        ShiftAmt, ConstantInt::get(MapTy, BitMapElementTy->getBitWidth()),
-        "switch.shiftamt");
-
-    // Shift down.
-    Value *DownShifted =
-        Builder.CreateLShr(BitMap, ShiftAmt, "switch.downshift");
-    // Mask off.
-    return Builder.CreateTrunc(DownShifted, BitMapElementTy, "switch.masked");
-  }
-  case ArrayKind: {
-    // Make sure the table index will not overflow when treated as signed.
-    IntegerType *IT = cast<IntegerType>(Index->getType());
-    uint64_t TableSize =
-        Array->getInitializer()->getType()->getArrayNumElements();
-    if (TableSize > (1ULL << (IT->getBitWidth() - 1)))
-      Index = Builder.CreateZExt(
-          Index, IntegerType::get(IT->getContext(), IT->getBitWidth() + 1),
-          "switch.tableidx.zext");
-
-    Value *GEPIndices[] = {Builder.getInt32(0), Index};
-    Value *GEP = Builder.CreateInBoundsGEP(Array->getValueType(), Array,
-                                           GEPIndices, "switch.gep");
-    return Builder.CreateLoad(
-        cast<ArrayType>(Array->getValueType())->getElementType(), GEP,
-        "switch.load");
-  }
-  }
-  llvm_unreachable("Unknown lookup table kind!");
-}
-
-bool SwitchLookupTable::WouldFitInRegister(const DataLayout &DL,
-                                           uint64_t TableSize,
-                                           Type *ElementType) {
-  auto *IT = dyn_cast<IntegerType>(ElementType);
-  if (!IT)
-    return false;
-  // FIXME: If the type is wider than it needs to be, e.g. i8 but all values
-  // are <= 15, we could try to narrow the type.
-
-  // Avoid overflow, fitsInLegalInteger uses unsigned int for the width.
-  if (TableSize >= UINT_MAX / IT->getBitWidth())
-    return false;
-  return DL.fitsInLegalInteger(TableSize * IT->getBitWidth());
-}
-
-/// Determine whether a lookup table should be built for this switch, based on
-/// the number of cases, size of the table, and the types of the results.
-static bool
-ShouldBuildLookupTable(SwitchInst *SI, uint64_t TableSize,
-                       const TargetTransformInfo &TTI, const DataLayout &DL,
-                       const SmallDenseMap<PHINode *, Type *> &ResultTypes) {
-  if (SI->getNumCases() > TableSize || TableSize >= UINT64_MAX / 10)
-    return false; // TableSize overflowed, or mul below might overflow.
-
-  bool AllTablesFitInRegister = true;
-  bool HasIllegalType = false;
-  for (const auto &I : ResultTypes) {
-    Type *Ty = I.second;
-
-    // Saturate this flag to true.
-    HasIllegalType = HasIllegalType || !TTI.isTypeLegal(Ty);
-
-    // Saturate this flag to false.
-    AllTablesFitInRegister =
-        AllTablesFitInRegister &&
-        SwitchLookupTable::WouldFitInRegister(DL, TableSize, Ty);
-
-    // If both flags saturate, we're done. NOTE: This *only* works with
-    // saturating flags, and all flags have to saturate first due to the
-    // non-deterministic behavior of iterating over a dense map.
-    if (HasIllegalType && !AllTablesFitInRegister)
-      break;
-  }
-
-  // If each table would fit in a register, we should build it anyway.
-  if (AllTablesFitInRegister)
-    return true;
-
-  // Don't build a table that doesn't fit in-register if it has illegal types.
-  if (HasIllegalType)
-    return false;
-
-  // The table density should be at least 40%. This is the same criterion as for
-  // jump tables, see SelectionDAGBuilder::handleJTSwitchCase.
-  // FIXME: Find the best cut-off.
-  return SI->getNumCases() * 10 >= TableSize * 4;
-}
-
-/// Try to reuse the switch table index compare. Following pattern:
-/// \code
-///     if (idx < tablesize)
-///        r = table[idx]; // table does not contain default_value
-///     else
-///        r = default_value;
-///     if (r != default_value)
-///        ...
-/// \endcode
-/// Is optimized to:
-/// \code
-///     cond = idx < tablesize;
-///     if (cond)
-///        r = table[idx];
-///     else
-///        r = default_value;
-///     if (cond)
-///        ...
-/// \endcode
-/// Jump threading will then eliminate the second if(cond).
-static void reuseTableCompare(
-    User *PhiUser, BasicBlock *PhiBlock, BranchInst *RangeCheckBranch,
-    Constant *DefaultValue,
-    const SmallVectorImpl<std::pair<ConstantInt *, Constant *>> &Values) {
-  ICmpInst *CmpInst = dyn_cast<ICmpInst>(PhiUser);
-  if (!CmpInst)
-    return;
-
-  // We require that the compare is in the same block as the phi so that jump
-  // threading can do its work afterwards.
-  if (CmpInst->getParent() != PhiBlock)
-    return;
-
-  Constant *CmpOp1 = dyn_cast<Constant>(CmpInst->getOperand(1));
-  if (!CmpOp1)
-    return;
-
-  Value *RangeCmp = RangeCheckBranch->getCondition();
-  Constant *TrueConst = ConstantInt::getTrue(RangeCmp->getType());
-  Constant *FalseConst = ConstantInt::getFalse(RangeCmp->getType());
-
-  // Check if the compare with the default value is constant true or false.
-  Constant *DefaultConst = ConstantExpr::getICmp(CmpInst->getPredicate(),
-                                                 DefaultValue, CmpOp1, true);
-  if (DefaultConst != TrueConst && DefaultConst != FalseConst)
-    return;
-
-  // Check if the compare with the case values is distinct from the default
-  // compare result.
-  for (auto ValuePair : Values) {
-    Constant *CaseConst = ConstantExpr::getICmp(CmpInst->getPredicate(),
-                                                ValuePair.second, CmpOp1, true);
-    if (!CaseConst || CaseConst == DefaultConst || isa<UndefValue>(CaseConst))
-      return;
-    assert((CaseConst == TrueConst || CaseConst == FalseConst) &&
-           "Expect true or false as compare result.");
-  }
-
-  // Check if the branch instruction dominates the phi node. It's a simple
-  // dominance check, but sufficient for our needs.
-  // Although this check is invariant in the calling loops, it's better to do it
-  // at this late stage. Practically we do it at most once for a switch.
-  BasicBlock *BranchBlock = RangeCheckBranch->getParent();
-  for (auto PI = pred_begin(PhiBlock), E = pred_end(PhiBlock); PI != E; ++PI) {
-    BasicBlock *Pred = *PI;
-    if (Pred != BranchBlock && Pred->getUniquePredecessor() != BranchBlock)
-      return;
-  }
-
-  if (DefaultConst == FalseConst) {
-    // The compare yields the same result. We can replace it.
-    CmpInst->replaceAllUsesWith(RangeCmp);
-    ++NumTableCmpReuses;
-  } else {
-    // The compare yields the same result, just inverted. We can replace it.
-    Value *InvertedTableCmp = BinaryOperator::CreateXor(
-        RangeCmp, ConstantInt::get(RangeCmp->getType(), 1), "inverted.cmp",
-        RangeCheckBranch);
-    CmpInst->replaceAllUsesWith(InvertedTableCmp);
-    ++NumTableCmpReuses;
-  }
-}
-
-/// If the switch is only used to initialize one or more phi nodes in a common
-/// successor block with different constant values, replace the switch with
-/// lookup tables.
-static bool SwitchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
-                                const DataLayout &DL,
-                                const TargetTransformInfo &TTI) {
-  assert(SI->getNumCases() > 1 && "Degenerate switch?");
-
-  Function *Fn = SI->getParent()->getParent();
-  // Only build lookup table when we have a target that supports it or the
-  // attribute is not set.
-  if (!TTI.shouldBuildLookupTables() ||
-      (Fn->getFnAttribute("no-jump-tables").getValueAsString() == "true"))
-    return false;
-
-  // FIXME: If the switch is too sparse for a lookup table, perhaps we could
-  // split off a dense part and build a lookup table for that.
-
-  // FIXME: This creates arrays of GEPs to constant strings, which means each
-  // GEP needs a runtime relocation in PIC code. We should just build one big
-  // string and lookup indices into that.
-
-  // Ignore switches with less than three cases. Lookup tables will not make
-  // them faster, so we don't analyze them.
-  if (SI->getNumCases() < 3)
-    return false;
-
-  // Figure out the corresponding result for each case value and phi node in the
-  // common destination, as well as the min and max case values.
-  assert(!empty(SI->cases()));
-  SwitchInst::CaseIt CI = SI->case_begin();
-  ConstantInt *MinCaseVal = CI->getCaseValue();
-  ConstantInt *MaxCaseVal = CI->getCaseValue();
-
-  BasicBlock *CommonDest = nullptr;
-
-  using ResultListTy = SmallVector<std::pair<ConstantInt *, Constant *>, 4>;
-  SmallDenseMap<PHINode *, ResultListTy> ResultLists;
-
-  SmallDenseMap<PHINode *, Constant *> DefaultResults;
-  SmallDenseMap<PHINode *, Type *> ResultTypes;
-  SmallVector<PHINode *, 4> PHIs;
-
-  for (SwitchInst::CaseIt E = SI->case_end(); CI != E; ++CI) {
-    ConstantInt *CaseVal = CI->getCaseValue();
-    if (CaseVal->getValue().slt(MinCaseVal->getValue()))
-      MinCaseVal = CaseVal;
-    if (CaseVal->getValue().sgt(MaxCaseVal->getValue()))
-      MaxCaseVal = CaseVal;
-
-    // Resulting value at phi nodes for this case value.
-    using ResultsTy = SmallVector<std::pair<PHINode *, Constant *>, 4>;
-    ResultsTy Results;
-    if (!GetCaseResults(SI, CaseVal, CI->getCaseSuccessor(), &CommonDest,
-                        Results, DL, TTI))
-      return false;
-
-    // Append the result from this case to the list for each phi.
-    for (const auto &I : Results) {
-      PHINode *PHI = I.first;
-      Constant *Value = I.second;
-      if (!ResultLists.count(PHI))
-        PHIs.push_back(PHI);
-      ResultLists[PHI].push_back(std::make_pair(CaseVal, Value));
-    }
-  }
-
-  // Keep track of the result types.
-  for (PHINode *PHI : PHIs) {
-    ResultTypes[PHI] = ResultLists[PHI][0].second->getType();
-  }
-
-  uint64_t NumResults = ResultLists[PHIs[0]].size();
-  APInt RangeSpread = MaxCaseVal->getValue() - MinCaseVal->getValue();
-  uint64_t TableSize = RangeSpread.getLimitedValue() + 1;
-  bool TableHasHoles = (NumResults < TableSize);
-
-  // If the table has holes, we need a constant result for the default case
-  // or a bitmask that fits in a register.
-  SmallVector<std::pair<PHINode *, Constant *>, 4> DefaultResultsList;
-  bool HasDefaultResults =
-      GetCaseResults(SI, nullptr, SI->getDefaultDest(), &CommonDest,
-                     DefaultResultsList, DL, TTI);
-
-  bool NeedMask = (TableHasHoles && !HasDefaultResults);
-  if (NeedMask) {
-    // As an extra penalty for the validity test we require more cases.
-    if (SI->getNumCases() < 4) // FIXME: Find best threshold value (benchmark).
-      return false;
-    if (!DL.fitsInLegalInteger(TableSize))
-      return false;
-  }
-
-  for (const auto &I : DefaultResultsList) {
-    PHINode *PHI = I.first;
-    Constant *Result = I.second;
-    DefaultResults[PHI] = Result;
-  }
-
-  if (!ShouldBuildLookupTable(SI, TableSize, TTI, DL, ResultTypes))
-    return false;
-
-  // Create the BB that does the lookups.
-  Module &Mod = *CommonDest->getParent()->getParent();
-  BasicBlock *LookupBB = BasicBlock::Create(
-      Mod.getContext(), "switch.lookup", CommonDest->getParent(), CommonDest);
-
-  // Compute the table index value.
-  Builder.SetInsertPoint(SI);
-  Value *TableIndex;
-  if (MinCaseVal->isNullValue())
-    TableIndex = SI->getCondition();
-  else
-    TableIndex = Builder.CreateSub(SI->getCondition(), MinCaseVal,
-                                   "switch.tableidx");
-
-  // Compute the maximum table size representable by the integer type we are
-  // switching upon.
-  unsigned CaseSize = MinCaseVal->getType()->getPrimitiveSizeInBits();
-  uint64_t MaxTableSize = CaseSize > 63 ? UINT64_MAX : 1ULL << CaseSize;
-  assert(MaxTableSize >= TableSize &&
-         "It is impossible for a switch to have more entries than the max "
-         "representable value of its input integer type's size.");
-
-  // If the default destination is unreachable, or if the lookup table covers
-  // all values of the conditional variable, branch directly to the lookup table
-  // BB. Otherwise, check that the condition is within the case range.
-  const bool DefaultIsReachable =
-      !isa<UnreachableInst>(SI->getDefaultDest()->getFirstNonPHIOrDbg());
-  const bool GeneratingCoveredLookupTable = (MaxTableSize == TableSize);
-  BranchInst *RangeCheckBranch = nullptr;
-
-  if (!DefaultIsReachable || GeneratingCoveredLookupTable) {
-    Builder.CreateBr(LookupBB);
-    // Note: We call removeProdecessor later since we need to be able to get the
-    // PHI value for the default case in case we're using a bit mask.
-  } else {
-    Value *Cmp = Builder.CreateICmpULT(
-        TableIndex, ConstantInt::get(MinCaseVal->getType(), TableSize));
-    RangeCheckBranch =
-        Builder.CreateCondBr(Cmp, LookupBB, SI->getDefaultDest());
-  }
-
-  // Populate the BB that does the lookups.
-  Builder.SetInsertPoint(LookupBB);
-
-  if (NeedMask) {
-    // Before doing the lookup, we do the hole check. The LookupBB is therefore
-    // re-purposed to do the hole check, and we create a new LookupBB.
-    BasicBlock *MaskBB = LookupBB;
-    MaskBB->setName("switch.hole_check");
-    LookupBB = BasicBlock::Create(Mod.getContext(), "switch.lookup",
-                                  CommonDest->getParent(), CommonDest);
-
-    // Make the mask's bitwidth at least 8-bit and a power-of-2 to avoid
-    // unnecessary illegal types.
-    uint64_t TableSizePowOf2 = NextPowerOf2(std::max(7ULL, TableSize - 1ULL));
-    APInt MaskInt(TableSizePowOf2, 0);
-    APInt One(TableSizePowOf2, 1);
-    // Build bitmask; fill in a 1 bit for every case.
-    const ResultListTy &ResultList = ResultLists[PHIs[0]];
-    for (size_t I = 0, E = ResultList.size(); I != E; ++I) {
-      uint64_t Idx = (ResultList[I].first->getValue() - MinCaseVal->getValue())
-                         .getLimitedValue();
-      MaskInt |= One << Idx;
-    }
-    ConstantInt *TableMask = ConstantInt::get(Mod.getContext(), MaskInt);
-
-    // Get the TableIndex'th bit of the bitmask.
-    // If this bit is 0 (meaning hole) jump to the default destination,
-    // else continue with table lookup.
-    IntegerType *MapTy = TableMask->getType();
-    Value *MaskIndex =
-        Builder.CreateZExtOrTrunc(TableIndex, MapTy, "switch.maskindex");
-    Value *Shifted = Builder.CreateLShr(TableMask, MaskIndex, "switch.shifted");
-    Value *LoBit = Builder.CreateTrunc(
-        Shifted, Type::getInt1Ty(Mod.getContext()), "switch.lobit");
-    Builder.CreateCondBr(LoBit, LookupBB, SI->getDefaultDest());
-
-    Builder.SetInsertPoint(LookupBB);
-    AddPredecessorToBlock(SI->getDefaultDest(), MaskBB, SI->getParent());
-  }
-
-  if (!DefaultIsReachable || GeneratingCoveredLookupTable) {
-    // We cached PHINodes in PHIs. To avoid accessing deleted PHINodes later,
-    // do not delete PHINodes here.
-    SI->getDefaultDest()->removePredecessor(SI->getParent(),
-                                            /*KeepOneInputPHIs=*/true);
-  }
-
-  bool ReturnedEarly = false;
-  for (PHINode *PHI : PHIs) {
-    const ResultListTy &ResultList = ResultLists[PHI];
-
-    // If using a bitmask, use any value to fill the lookup table holes.
-    Constant *DV = NeedMask ? ResultLists[PHI][0].second : DefaultResults[PHI];
-    StringRef FuncName = Fn->getName();
-    SwitchLookupTable Table(Mod, TableSize, MinCaseVal, ResultList, DV, DL,
-                            FuncName);
-
-    Value *Result = Table.BuildLookup(TableIndex, Builder);
-
-    // If the result is used to return immediately from the function, we want to
-    // do that right here.
-    if (PHI->hasOneUse() && isa<ReturnInst>(*PHI->user_begin()) &&
-        PHI->user_back() == CommonDest->getFirstNonPHIOrDbg()) {
-      Builder.CreateRet(Result);
-      ReturnedEarly = true;
-      break;
-    }
-
-    // Do a small peephole optimization: re-use the switch table compare if
-    // possible.
-    if (!TableHasHoles && HasDefaultResults && RangeCheckBranch) {
-      BasicBlock *PhiBlock = PHI->getParent();
-      // Search for compare instructions which use the phi.
-      for (auto *User : PHI->users()) {
-        reuseTableCompare(User, PhiBlock, RangeCheckBranch, DV, ResultList);
-      }
-    }
-
-    PHI->addIncoming(Result, LookupBB);
-  }
-
-  if (!ReturnedEarly)
-    Builder.CreateBr(CommonDest);
-
-  // Remove the switch.
-  for (unsigned i = 0, e = SI->getNumSuccessors(); i < e; ++i) {
-    BasicBlock *Succ = SI->getSuccessor(i);
-
-    if (Succ == SI->getDefaultDest())
-      continue;
-    Succ->removePredecessor(SI->getParent());
-  }
-  SI->eraseFromParent();
-
-  ++NumLookupTables;
-  if (NeedMask)
-    ++NumLookupTablesHoles;
-  return true;
-}
-
-static bool isSwitchDense(ArrayRef<int64_t> Values) {
-  // See also SelectionDAGBuilder::isDense(), which this function was based on.
-  uint64_t Diff = (uint64_t)Values.back() - (uint64_t)Values.front();
-  uint64_t Range = Diff + 1;
-  uint64_t NumCases = Values.size();
-  // 40% is the default density for building a jump table in optsize/minsize mode.
-  uint64_t MinDensity = 40;
-
-  return NumCases * 100 >= Range * MinDensity;
-}
-
-/// Try to transform a switch that has "holes" in it to a contiguous sequence
-/// of cases.
-///
-/// A switch such as: switch(i) {case 5: case 9: case 13: case 17:} can be
-/// range-reduced to: switch ((i-5) / 4) {case 0: case 1: case 2: case 3:}.
-///
-/// This converts a sparse switch into a dense switch which allows better
-/// lowering and could also allow transforming into a lookup table.
-static bool ReduceSwitchRange(SwitchInst *SI, IRBuilder<> &Builder,
-                              const DataLayout &DL,
-                              const TargetTransformInfo &TTI) {
-  auto *CondTy = cast<IntegerType>(SI->getCondition()->getType());
-  if (CondTy->getIntegerBitWidth() > 64 ||
-      !DL.fitsInLegalInteger(CondTy->getIntegerBitWidth()))
-    return false;
-  // Only bother with this optimization if there are more than 3 switch cases;
-  // SDAG will only bother creating jump tables for 4 or more cases.
-  if (SI->getNumCases() < 4)
-    return false;
-
-  // This transform is agnostic to the signedness of the input or case values. We
-  // can treat the case values as signed or unsigned. We can optimize more common
-  // cases such as a sequence crossing zero {-4,0,4,8} if we interpret case values
-  // as signed.
-  SmallVector<int64_t,4> Values;
-  for (auto &C : SI->cases())
-    Values.push_back(C.getCaseValue()->getValue().getSExtValue());
-  llvm::sort(Values);
-
-  // If the switch is already dense, there's nothing useful to do here.
-  if (isSwitchDense(Values))
-    return false;
-
-  // First, transform the values such that they start at zero and ascend.
-  int64_t Base = Values[0];
-  for (auto &V : Values)
-    V -= (uint64_t)(Base);
-
-  // Now we have signed numbers that have been shifted so that, given enough
-  // precision, there are no negative values. Since the rest of the transform
-  // is bitwise only, we switch now to an unsigned representation.
-
-  // This transform can be done speculatively because it is so cheap - it
-  // results in a single rotate operation being inserted.
-  // FIXME: It's possible that optimizing a switch on powers of two might also
-  // be beneficial - flag values are often powers of two and we could use a CLZ
-  // as the key function.
-
-  // countTrailingZeros(0) returns 64. As Values is guaranteed to have more than
-  // one element and LLVM disallows duplicate cases, Shift is guaranteed to be
-  // less than 64.
-  unsigned Shift = 64;
-  for (auto &V : Values)
-    Shift = std::min(Shift, countTrailingZeros((uint64_t)V));
-  assert(Shift < 64);
-  if (Shift > 0)
-    for (auto &V : Values)
-      V = (int64_t)((uint64_t)V >> Shift);
-
-  if (!isSwitchDense(Values))
-    // Transform didn't create a dense switch.
-    return false;
-
-  // The obvious transform is to shift the switch condition right and emit a
-  // check that the condition actually cleanly divided by GCD, i.e.
-  //   C & (1 << Shift - 1) == 0
-  // inserting a new CFG edge to handle the case where it didn't divide cleanly.
-  //
-  // A cheaper way of doing this is a simple ROTR(C, Shift). This performs the
-  // shift and puts the shifted-off bits in the uppermost bits. If any of these
-  // are nonzero then the switch condition will be very large and will hit the
-  // default case.
-
-  auto *Ty = cast<IntegerType>(SI->getCondition()->getType());
-  Builder.SetInsertPoint(SI);
-  auto *ShiftC = ConstantInt::get(Ty, Shift);
-  auto *Sub = Builder.CreateSub(SI->getCondition(), ConstantInt::get(Ty, Base));
-  auto *LShr = Builder.CreateLShr(Sub, ShiftC);
-  auto *Shl = Builder.CreateShl(Sub, Ty->getBitWidth() - Shift);
-  auto *Rot = Builder.CreateOr(LShr, Shl);
-  SI->replaceUsesOfWith(SI->getCondition(), Rot);
-
-  for (auto Case : SI->cases()) {
-    auto *Orig = Case.getCaseValue();
-    auto Sub = Orig->getValue() - APInt(Ty->getBitWidth(), Base);
-    Case.setValue(
-        cast<ConstantInt>(ConstantInt::get(Ty, Sub.lshr(ShiftC->getValue()))));
-  }
-  return true;
-}
-
-bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) {
-  BasicBlock *BB = SI->getParent();
-
-  if (isValueEqualityComparison(SI)) {
-    // If we only have one predecessor, and if it is a branch on this value,
-    // see if that predecessor totally determines the outcome of this switch.
-    if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
-      if (SimplifyEqualityComparisonWithOnlyPredecessor(SI, OnlyPred, Builder))
-        return requestResimplify();
-
-    Value *Cond = SI->getCondition();
-    if (SelectInst *Select = dyn_cast<SelectInst>(Cond))
-      if (SimplifySwitchOnSelect(SI, Select))
-        return requestResimplify();
-
-    // If the block only contains the switch, see if we can fold the block
-    // away into any preds.
-    if (SI == &*BB->instructionsWithoutDebug().begin())
-      if (FoldValueComparisonIntoPredecessors(SI, Builder))
-        return requestResimplify();
-  }
-
-  // Try to transform the switch into an icmp and a branch.
-  if (TurnSwitchRangeIntoICmp(SI, Builder))
-    return requestResimplify();
-
-  // Remove unreachable cases.
-  if (eliminateDeadSwitchCases(SI, Options.AC, DL))
-    return requestResimplify();
-
-  if (switchToSelect(SI, Builder, DL, TTI))
-    return requestResimplify();
-
-  if (Options.ForwardSwitchCondToPhi && ForwardSwitchConditionToPHI(SI))
-    return requestResimplify();
-
-  // The conversion from switch to lookup tables results in difficult-to-analyze
-  // code and makes pruning branches much harder. This is a problem if the
-  // switch expression itself can still be restricted as a result of inlining or
-  // CVP. Therefore, only apply this transformation during late stages of the
-  // optimisation pipeline.
-  if (Options.ConvertSwitchToLookupTable &&
-      SwitchToLookupTable(SI, Builder, DL, TTI))
-    return requestResimplify();
-
-  if (ReduceSwitchRange(SI, Builder, DL, TTI))
-    return requestResimplify();
-
-  return false;
-}
-
-bool SimplifyCFGOpt::SimplifyIndirectBr(IndirectBrInst *IBI) {
-  BasicBlock *BB = IBI->getParent();
-  bool Changed = false;
-
-  // Eliminate redundant destinations.
-  SmallPtrSet<Value *, 8> Succs;
-  for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
-    BasicBlock *Dest = IBI->getDestination(i);
-    if (!Dest->hasAddressTaken() || !Succs.insert(Dest).second) {
-      Dest->removePredecessor(BB);
-      IBI->removeDestination(i);
-      --i;
-      --e;
-      Changed = true;
-    }
-  }
-
-  if (IBI->getNumDestinations() == 0) {
-    // If the indirectbr has no successors, change it to unreachable.
-    new UnreachableInst(IBI->getContext(), IBI);
-    EraseTerminatorAndDCECond(IBI);
-    return true;
-  }
-
-  if (IBI->getNumDestinations() == 1) {
-    // If the indirectbr has one successor, change it to a direct branch.
-    BranchInst::Create(IBI->getDestination(0), IBI);
-    EraseTerminatorAndDCECond(IBI);
-    return true;
-  }
-
-  if (SelectInst *SI = dyn_cast<SelectInst>(IBI->getAddress())) {
-    if (SimplifyIndirectBrOnSelect(IBI, SI))
-      return requestResimplify();
-  }
-  return Changed;
-}
-
-/// Given an block with only a single landing pad and a unconditional branch
-/// try to find another basic block which this one can be merged with.  This
-/// handles cases where we have multiple invokes with unique landing pads, but
-/// a shared handler.
-///
-/// We specifically choose to not worry about merging non-empty blocks
-/// here.  That is a PRE/scheduling problem and is best solved elsewhere.  In
-/// practice, the optimizer produces empty landing pad blocks quite frequently
-/// when dealing with exception dense code.  (see: instcombine, gvn, if-else
-/// sinking in this file)
-///
-/// This is primarily a code size optimization.  We need to avoid performing
-/// any transform which might inhibit optimization (such as our ability to
-/// specialize a particular handler via tail commoning).  We do this by not
-/// merging any blocks which require us to introduce a phi.  Since the same
-/// values are flowing through both blocks, we don't lose any ability to
-/// specialize.  If anything, we make such specialization more likely.
-///
-/// TODO - This transformation could remove entries from a phi in the target
-/// block when the inputs in the phi are the same for the two blocks being
-/// merged.  In some cases, this could result in removal of the PHI entirely.
-static bool TryToMergeLandingPad(LandingPadInst *LPad, BranchInst *BI,
-                                 BasicBlock *BB) {
-  auto Succ = BB->getUniqueSuccessor();
-  assert(Succ);
-  // If there's a phi in the successor block, we'd likely have to introduce
-  // a phi into the merged landing pad block.
-  if (isa<PHINode>(*Succ->begin()))
-    return false;
-
-  for (BasicBlock *OtherPred : predecessors(Succ)) {
-    if (BB == OtherPred)
-      continue;
-    BasicBlock::iterator I = OtherPred->begin();
-    LandingPadInst *LPad2 = dyn_cast<LandingPadInst>(I);
-    if (!LPad2 || !LPad2->isIdenticalTo(LPad))
-      continue;
-    for (++I; isa<DbgInfoIntrinsic>(I); ++I)
-      ;
-    BranchInst *BI2 = dyn_cast<BranchInst>(I);
-    if (!BI2 || !BI2->isIdenticalTo(BI))
-      continue;
-
-    // We've found an identical block.  Update our predecessors to take that
-    // path instead and make ourselves dead.
-    SmallPtrSet<BasicBlock *, 16> Preds;
-    Preds.insert(pred_begin(BB), pred_end(BB));
-    for (BasicBlock *Pred : Preds) {
-      InvokeInst *II = cast<InvokeInst>(Pred->getTerminator());
-      assert(II->getNormalDest() != BB && II->getUnwindDest() == BB &&
-             "unexpected successor");
-      II->setUnwindDest(OtherPred);
-    }
-
-    // The debug info in OtherPred doesn't cover the merged control flow that
-    // used to go through BB.  We need to delete it or update it.
-    for (auto I = OtherPred->begin(), E = OtherPred->end(); I != E;) {
-      Instruction &Inst = *I;
-      I++;
-      if (isa<DbgInfoIntrinsic>(Inst))
-        Inst.eraseFromParent();
-    }
-
-    SmallPtrSet<BasicBlock *, 16> Succs;
-    Succs.insert(succ_begin(BB), succ_end(BB));
-    for (BasicBlock *Succ : Succs) {
-      Succ->removePredecessor(BB);
-    }
-
-    IRBuilder<> Builder(BI);
-    Builder.CreateUnreachable();
-    BI->eraseFromParent();
-    return true;
-  }
-  return false;
-}
-
-bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI,
-                                          IRBuilder<> &Builder) {
-  BasicBlock *BB = BI->getParent();
-  BasicBlock *Succ = BI->getSuccessor(0);
-
-  // If the Terminator is the only non-phi instruction, simplify the block.
-  // If LoopHeader is provided, check if the block or its successor is a loop
-  // header. (This is for early invocations before loop simplify and
-  // vectorization to keep canonical loop forms for nested loops. These blocks
-  // can be eliminated when the pass is invoked later in the back-end.)
-  // Note that if BB has only one predecessor then we do not introduce new
-  // backedge, so we can eliminate BB.
-  bool NeedCanonicalLoop =
-      Options.NeedCanonicalLoop &&
-      (LoopHeaders && BB->hasNPredecessorsOrMore(2) &&
-       (LoopHeaders->count(BB) || LoopHeaders->count(Succ)));
-  BasicBlock::iterator I = BB->getFirstNonPHIOrDbg()->getIterator();
-  if (I->isTerminator() && BB != &BB->getParent()->getEntryBlock() &&
-      !NeedCanonicalLoop && TryToSimplifyUncondBranchFromEmptyBlock(BB))
-    return true;
-
-  // If the only instruction in the block is a seteq/setne comparison against a
-  // constant, try to simplify the block.
-  if (ICmpInst *ICI = dyn_cast<ICmpInst>(I))
-    if (ICI->isEquality() && isa<ConstantInt>(ICI->getOperand(1))) {
-      for (++I; isa<DbgInfoIntrinsic>(I); ++I)
-        ;
-      if (I->isTerminator() &&
-          tryToSimplifyUncondBranchWithICmpInIt(ICI, Builder))
-        return true;
-    }
-
-  // See if we can merge an empty landing pad block with another which is
-  // equivalent.
-  if (LandingPadInst *LPad = dyn_cast<LandingPadInst>(I)) {
-    for (++I; isa<DbgInfoIntrinsic>(I); ++I)
-      ;
-    if (I->isTerminator() && TryToMergeLandingPad(LPad, BI, BB))
-      return true;
-  }
-
-  // If this basic block is ONLY a compare and a branch, and if a predecessor
-  // branches to us and our successor, fold the comparison into the
-  // predecessor and use logical operations to update the incoming value
-  // for PHI nodes in common successor.
-  if (FoldBranchToCommonDest(BI, nullptr, Options.BonusInstThreshold))
-    return requestResimplify();
-  return false;
-}
-
-static BasicBlock *allPredecessorsComeFromSameSource(BasicBlock *BB) {
-  BasicBlock *PredPred = nullptr;
-  for (auto *P : predecessors(BB)) {
-    BasicBlock *PPred = P->getSinglePredecessor();
-    if (!PPred || (PredPred && PredPred != PPred))
-      return nullptr;
-    PredPred = PPred;
-  }
-  return PredPred;
-}
-
-bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
-  BasicBlock *BB = BI->getParent();
-  const Function *Fn = BB->getParent();
-  if (Fn && Fn->hasFnAttribute(Attribute::OptForFuzzing))
-    return false;
-
-  // Conditional branch
-  if (isValueEqualityComparison(BI)) {
-    // If we only have one predecessor, and if it is a branch on this value,
-    // see if that predecessor totally determines the outcome of this
-    // switch.
-    if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
-      if (SimplifyEqualityComparisonWithOnlyPredecessor(BI, OnlyPred, Builder))
-        return requestResimplify();
-
-    // This block must be empty, except for the setcond inst, if it exists.
-    // Ignore dbg intrinsics.
-    auto I = BB->instructionsWithoutDebug().begin();
-    if (&*I == BI) {
-      if (FoldValueComparisonIntoPredecessors(BI, Builder))
-        return requestResimplify();
-    } else if (&*I == cast<Instruction>(BI->getCondition())) {
-      ++I;
-      if (&*I == BI && FoldValueComparisonIntoPredecessors(BI, Builder))
-        return requestResimplify();
-    }
-  }
-
-  // Try to turn "br (X == 0 | X == 1), T, F" into a switch instruction.
-  if (SimplifyBranchOnICmpChain(BI, Builder, DL))
-    return true;
-
-  // If this basic block has dominating predecessor blocks and the dominating
-  // blocks' conditions imply BI's condition, we know the direction of BI.
-  Optional<bool> Imp = isImpliedByDomCondition(BI->getCondition(), BI, DL);
-  if (Imp) {
-    // Turn this into a branch on constant.
-    auto *OldCond = BI->getCondition();
-    ConstantInt *TorF = *Imp ? ConstantInt::getTrue(BB->getContext())
-                             : ConstantInt::getFalse(BB->getContext());
-    BI->setCondition(TorF);
-    RecursivelyDeleteTriviallyDeadInstructions(OldCond);
-    return requestResimplify();
-  }
-
-  // If this basic block is ONLY a compare and a branch, and if a predecessor
-  // branches to us and one of our successors, fold the comparison into the
-  // predecessor and use logical operations to pick the right destination.
-  if (FoldBranchToCommonDest(BI, nullptr, Options.BonusInstThreshold))
-    return requestResimplify();
-
-  // We have a conditional branch to two blocks that are only reachable
-  // from BI.  We know that the condbr dominates the two blocks, so see if
-  // there is any identical code in the "then" and "else" blocks.  If so, we
-  // can hoist it up to the branching block.
-  if (BI->getSuccessor(0)->getSinglePredecessor()) {
-    if (BI->getSuccessor(1)->getSinglePredecessor()) {
-      if (HoistThenElseCodeToIf(BI, TTI))
-        return requestResimplify();
-    } else {
-      // If Successor #1 has multiple preds, we may be able to conditionally
-      // execute Successor #0 if it branches to Successor #1.
-      Instruction *Succ0TI = BI->getSuccessor(0)->getTerminator();
-      if (Succ0TI->getNumSuccessors() == 1 &&
-          Succ0TI->getSuccessor(0) == BI->getSuccessor(1))
-        if (SpeculativelyExecuteBB(BI, BI->getSuccessor(0), TTI))
-          return requestResimplify();
-    }
-  } else if (BI->getSuccessor(1)->getSinglePredecessor()) {
-    // If Successor #0 has multiple preds, we may be able to conditionally
-    // execute Successor #1 if it branches to Successor #0.
-    Instruction *Succ1TI = BI->getSuccessor(1)->getTerminator();
-    if (Succ1TI->getNumSuccessors() == 1 &&
-        Succ1TI->getSuccessor(0) == BI->getSuccessor(0))
-      if (SpeculativelyExecuteBB(BI, BI->getSuccessor(1), TTI))
-        return requestResimplify();
-  }
-
-  // If this is a branch on a phi node in the current block, thread control
-  // through this block if any PHI node entries are constants.
-  if (PHINode *PN = dyn_cast<PHINode>(BI->getCondition()))
-    if (PN->getParent() == BI->getParent())
-      if (FoldCondBranchOnPHI(BI, DL, Options.AC))
-        return requestResimplify();
-
-  // Scan predecessor blocks for conditional branches.
-  for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
-    if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator()))
-      if (PBI != BI && PBI->isConditional())
-        if (SimplifyCondBranchToCondBranch(PBI, BI, DL))
-          return requestResimplify();
-
-  // Look for diamond patterns.
-  if (MergeCondStores)
-    if (BasicBlock *PrevBB = allPredecessorsComeFromSameSource(BB))
-      if (BranchInst *PBI = dyn_cast<BranchInst>(PrevBB->getTerminator()))
-        if (PBI != BI && PBI->isConditional())
-          if (mergeConditionalStores(PBI, BI, DL))
-            return requestResimplify();
-
-  return false;
-}
-
-/// Check if passing a value to an instruction will cause undefined behavior.
-static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I) {
-  Constant *C = dyn_cast<Constant>(V);
-  if (!C)
-    return false;
-
-  if (I->use_empty())
-    return false;
-
-  if (C->isNullValue() || isa<UndefValue>(C)) {
-    // Only look at the first use, avoid hurting compile time with long uselists
-    User *Use = *I->user_begin();
-
-    // Now make sure that there are no instructions in between that can alter
-    // control flow (eg. calls)
-    for (BasicBlock::iterator
-             i = ++BasicBlock::iterator(I),
-             UI = BasicBlock::iterator(dyn_cast<Instruction>(Use));
-         i != UI; ++i)
-      if (i == I->getParent()->end() || i->mayHaveSideEffects())
-        return false;
-
-    // Look through GEPs. A load from a GEP derived from NULL is still undefined
-    if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Use))
-      if (GEP->getPointerOperand() == I)
-        return passingValueIsAlwaysUndefined(V, GEP);
-
-    // Look through bitcasts.
-    if (BitCastInst *BC = dyn_cast<BitCastInst>(Use))
-      return passingValueIsAlwaysUndefined(V, BC);
-
-    // Load from null is undefined.
-    if (LoadInst *LI = dyn_cast<LoadInst>(Use))
-      if (!LI->isVolatile())
-        return !NullPointerIsDefined(LI->getFunction(),
-                                     LI->getPointerAddressSpace());
-
-    // Store to null is undefined.
-    if (StoreInst *SI = dyn_cast<StoreInst>(Use))
-      if (!SI->isVolatile())
-        return (!NullPointerIsDefined(SI->getFunction(),
-                                      SI->getPointerAddressSpace())) &&
-               SI->getPointerOperand() == I;
-
-    // A call to null is undefined.
-    if (auto CS = CallSite(Use))
-      return !NullPointerIsDefined(CS->getFunction()) &&
-             CS.getCalledValue() == I;
-  }
-  return false;
-}
-
-/// If BB has an incoming value that will always trigger undefined behavior
-/// (eg. null pointer dereference), remove the branch leading here.
-static bool removeUndefIntroducingPredecessor(BasicBlock *BB) {
-  for (PHINode &PHI : BB->phis())
-    for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i)
-      if (passingValueIsAlwaysUndefined(PHI.getIncomingValue(i), &PHI)) {
-        Instruction *T = PHI.getIncomingBlock(i)->getTerminator();
-        IRBuilder<> Builder(T);
-        if (BranchInst *BI = dyn_cast<BranchInst>(T)) {
-          BB->removePredecessor(PHI.getIncomingBlock(i));
-          // Turn uncoditional branches into unreachables and remove the dead
-          // destination from conditional branches.
-          if (BI->isUnconditional())
-            Builder.CreateUnreachable();
-          else
-            Builder.CreateBr(BI->getSuccessor(0) == BB ? BI->getSuccessor(1)
-                                                       : BI->getSuccessor(0));
-          BI->eraseFromParent();
-          return true;
-        }
-        // TODO: SwitchInst.
-      }
-
-  return false;
-}
-
-bool SimplifyCFGOpt::simplifyOnce(BasicBlock *BB) {
-  bool Changed = false;
-
-  assert(BB && BB->getParent() && "Block not embedded in function!");
-  assert(BB->getTerminator() && "Degenerate basic block encountered!");
-
-  // Remove basic blocks that have no predecessors (except the entry block)...
-  // or that just have themself as a predecessor.  These are unreachable.
-  if ((pred_empty(BB) && BB != &BB->getParent()->getEntryBlock()) ||
-      BB->getSinglePredecessor() == BB) {
-    LLVM_DEBUG(dbgs() << "Removing BB: \n" << *BB);
-    DeleteDeadBlock(BB);
-    return true;
-  }
-
-  // Check to see if we can constant propagate this terminator instruction
-  // away...
-  Changed |= ConstantFoldTerminator(BB, true);
-
-  // Check for and eliminate duplicate PHI nodes in this block.
-  Changed |= EliminateDuplicatePHINodes(BB);
-
-  // Check for and remove branches that will always cause undefined behavior.
-  Changed |= removeUndefIntroducingPredecessor(BB);
-
-  // Merge basic blocks into their predecessor if there is only one distinct
-  // pred, and if there is only one distinct successor of the predecessor, and
-  // if there are no PHI nodes.
-  if (MergeBlockIntoPredecessor(BB))
-    return true;
-
-  if (SinkCommon && Options.SinkCommonInsts)
-    Changed |= SinkCommonCodeFromPredecessors(BB);
-
-  IRBuilder<> Builder(BB);
-
-  // If there is a trivial two-entry PHI node in this basic block, and we can
-  // eliminate it, do so now.
-  if (auto *PN = dyn_cast<PHINode>(BB->begin()))
-    if (PN->getNumIncomingValues() == 2)
-      Changed |= FoldTwoEntryPHINode(PN, TTI, DL);
-
-  Builder.SetInsertPoint(BB->getTerminator());
-  if (auto *BI = dyn_cast<BranchInst>(BB->getTerminator())) {
-    if (BI->isUnconditional()) {
-      if (SimplifyUncondBranch(BI, Builder))
-        return true;
-    } else {
-      if (SimplifyCondBranch(BI, Builder))
-        return true;
-    }
-  } else if (auto *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
-    if (SimplifyReturn(RI, Builder))
-      return true;
-  } else if (auto *RI = dyn_cast<ResumeInst>(BB->getTerminator())) {
-    if (SimplifyResume(RI, Builder))
-      return true;
-  } else if (auto *RI = dyn_cast<CleanupReturnInst>(BB->getTerminator())) {
-    if (SimplifyCleanupReturn(RI))
-      return true;
-  } else if (auto *SI = dyn_cast<SwitchInst>(BB->getTerminator())) {
-    if (SimplifySwitch(SI, Builder))
-      return true;
-  } else if (auto *UI = dyn_cast<UnreachableInst>(BB->getTerminator())) {
-    if (SimplifyUnreachable(UI))
-      return true;
-  } else if (auto *IBI = dyn_cast<IndirectBrInst>(BB->getTerminator())) {
-    if (SimplifyIndirectBr(IBI))
-      return true;
-  }
-
-  return Changed;
-}
-
-bool SimplifyCFGOpt::run(BasicBlock *BB) {
-  bool Changed = false;
-
-  // Repeated simplify BB as long as resimplification is requested.
-  do {
-    Resimplify = false;
-
-    // Perform one round of simplifcation. Resimplify flag will be set if
-    // another iteration is requested.
-    Changed |= simplifyOnce(BB);
-  } while (Resimplify);
-
-  return Changed;
-}
-
-bool llvm::simplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI,
-                       const SimplifyCFGOptions &Options,
-                       SmallPtrSetImpl<BasicBlock *> *LoopHeaders) {
-  return SimplifyCFGOpt(TTI, BB->getModule()->getDataLayout(), LoopHeaders,
-                        Options)
-      .run(BB);
-}