Package: llvm-toolchain-6.0 / 1:6.0.1-10

D40146-JumpThreading-backport-1.diff Patch series | download
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Index: llvm-toolchain-6.0-6.0.1/include/llvm/IR/Dominators.h
===================================================================
--- llvm-toolchain-6.0-6.0.1.orig/include/llvm/IR/Dominators.h
+++ llvm-toolchain-6.0-6.0.1/include/llvm/IR/Dominators.h
@@ -290,6 +290,90 @@ public:
   void print(raw_ostream &OS, const Module *M = nullptr) const override;
 };
 
+//===-------------------------------------
+/// \brief Class to defer updates to a DominatorTree.
+///
+/// Definition: Applying updates to every edge insertion and deletion is
+/// expensive and not necessary. When one needs the DominatorTree for analysis
+/// they can request a flush() to perform a larger batch update. This has the
+/// advantage of the DominatorTree inspecting the set of updates to find
+/// duplicates or unnecessary subtree updates.
+///
+/// The scope of DeferredDominance operates at a Function level.
+///
+/// It is not necessary for the user to scrub the updates for duplicates or
+/// updates that point to the same block (Delete, BB_A, BB_A). Performance
+/// can be gained if the caller attempts to batch updates before submitting
+/// to applyUpdates(ArrayRef) in cases where duplicate edge requests will
+/// occur.
+///
+/// It is required for the state of the LLVM IR to be applied *before*
+/// submitting updates. The update routines must analyze the current state
+/// between a pair of (From, To) basic blocks to determine if the update
+/// needs to be queued.
+/// Example (good):
+///     TerminatorInstructionBB->removeFromParent();
+///     DDT->deleteEdge(BB, Successor);
+/// Example (bad):
+///     DDT->deleteEdge(BB, Successor);
+///     TerminatorInstructionBB->removeFromParent();
+class DeferredDominance {
+public:
+  DeferredDominance(DominatorTree &DT_) : DT(DT_) {}
+
+  /// \brief Queues multiple updates and discards duplicates.
+  void applyUpdates(ArrayRef<DominatorTree::UpdateType> Updates);
+
+  /// \brief Helper method for a single edge insertion. It's almost always
+  /// better to batch updates and call applyUpdates to quickly remove duplicate
+  /// edges. This is best used when there is only a single insertion needed to
+  /// update Dominators.
+  void insertEdge(BasicBlock *From, BasicBlock *To);
+
+  /// \brief Helper method for a single edge deletion. It's almost always better
+  /// to batch updates and call applyUpdates to quickly remove duplicate edges.
+  /// This is best used when there is only a single deletion needed to update
+  /// Dominators.
+  void deleteEdge(BasicBlock *From, BasicBlock *To);
+
+  /// \brief Delays the deletion of a basic block until a flush() event.
+  void deleteBB(BasicBlock *DelBB);
+
+  /// \brief Returns true if DelBB is awaiting deletion at a flush() event.
+  bool pendingDeletedBB(BasicBlock *DelBB);
+
+  /// \brief Flushes all pending updates and block deletions. Returns a
+  /// correct DominatorTree reference to be used by the caller for analysis.
+  DominatorTree &flush();
+
+  /// \brief Drops all internal state and forces a (slow) recalculation of the
+  /// DominatorTree based on the current state of the LLVM IR in F. This should
+  /// only be used in corner cases such as the Entry block of F being deleted.
+  void recalculate(Function &F);
+
+  /// \brief Debug method to help view the state of pending updates.
+  LLVM_DUMP_METHOD void dump() const;
+
+private:
+  DominatorTree &DT;
+  SmallVector<DominatorTree::UpdateType, 16> PendUpdates;
+  SmallPtrSet<BasicBlock *, 8> DeletedBBs;
+
+  /// Apply an update (Kind, From, To) to the internal queued updates. The
+  /// update is only added when determined to be necessary. Checks for
+  /// self-domination, unnecessary updates, duplicate requests, and balanced
+  /// pairs of requests are all performed. Returns true if the update is
+  /// queued and false if it is discarded.
+  bool applyUpdate(DominatorTree::UpdateKind Kind, BasicBlock *From,
+                   BasicBlock *To);
+
+  /// Performs all pending basic block deletions. We have to defer the deletion
+  /// of these blocks until after the DominatorTree updates are applied. The
+  /// internal workings of the DominatorTree code expect every update's From
+  /// and To blocks to exist and to be a member of the same Function.
+  bool flushDelBB();
+};
+
 } // end namespace llvm
 
 #endif // LLVM_IR_DOMINATORS_H
Index: llvm-toolchain-6.0-6.0.1/include/llvm/Transforms/Scalar/JumpThreading.h
===================================================================
--- llvm-toolchain-6.0-6.0.1.orig/include/llvm/Transforms/Scalar/JumpThreading.h
+++ llvm-toolchain-6.0-6.0.1/include/llvm/Transforms/Scalar/JumpThreading.h
@@ -34,6 +34,7 @@ class BinaryOperator;
 class BranchInst;
 class CmpInst;
 class Constant;
+class DeferredDominance;
 class Function;
 class Instruction;
 class IntrinsicInst;
@@ -77,6 +78,7 @@ class JumpThreadingPass : public PassInf
   TargetLibraryInfo *TLI;
   LazyValueInfo *LVI;
   AliasAnalysis *AA;
+  DeferredDominance *DDT;
   std::unique_ptr<BlockFrequencyInfo> BFI;
   std::unique_ptr<BranchProbabilityInfo> BPI;
   bool HasProfileData = false;
@@ -107,8 +109,8 @@ public:
 
   // Glue for old PM.
   bool runImpl(Function &F, TargetLibraryInfo *TLI_, LazyValueInfo *LVI_,
-               AliasAnalysis *AA_, bool HasProfileData_,
-               std::unique_ptr<BlockFrequencyInfo> BFI_,
+               AliasAnalysis *AA_, DeferredDominance *DDT_,
+               bool HasProfileData_, std::unique_ptr<BlockFrequencyInfo> BFI_,
                std::unique_ptr<BranchProbabilityInfo> BPI_);
 
   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
Index: llvm-toolchain-6.0-6.0.1/include/llvm/Transforms/Utils/BasicBlockUtils.h
===================================================================
--- llvm-toolchain-6.0-6.0.1.orig/include/llvm/Transforms/Utils/BasicBlockUtils.h
+++ llvm-toolchain-6.0-6.0.1/include/llvm/Transforms/Utils/BasicBlockUtils.h
@@ -27,6 +27,7 @@ namespace llvm {
 
 class BlockFrequencyInfo;
 class BranchProbabilityInfo;
+class DeferredDominance;
 class DominatorTree;
 class Function;
 class Instruction;
@@ -38,7 +39,7 @@ class TargetLibraryInfo;
 class Value;
 
 /// Delete the specified block, which must have no predecessors.
-void DeleteDeadBlock(BasicBlock *BB);
+void DeleteDeadBlock(BasicBlock *BB, DeferredDominance *DDT = nullptr);
 
 /// We know that BB has one predecessor. If there are any single-entry PHI nodes
 /// in it, fold them away. This handles the case when all entries to the PHI
Index: llvm-toolchain-6.0-6.0.1/include/llvm/Transforms/Utils/Local.h
===================================================================
--- llvm-toolchain-6.0-6.0.1.orig/include/llvm/Transforms/Utils/Local.h
+++ llvm-toolchain-6.0-6.0.1/include/llvm/Transforms/Utils/Local.h
@@ -117,7 +117,8 @@ struct SimplifyCFGOptions {
 /// conditions and indirectbr addresses this might make dead if
 /// DeleteDeadConditions is true.
 bool ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions = false,
-                            const TargetLibraryInfo *TLI = nullptr);
+                            const TargetLibraryInfo *TLI = nullptr,
+                            DeferredDominance *DDT = nullptr);
 
 //===----------------------------------------------------------------------===//
 //  Local dead code elimination.
@@ -171,18 +172,21 @@ bool SimplifyInstructionsInBlock(BasicBl
 ///
 /// .. and delete the predecessor corresponding to the '1', this will attempt to
 /// recursively fold the 'and' to 0.
-void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred);
+void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
+                                  DeferredDominance *DDT = nullptr);
 
 /// BB is a block with one predecessor and its predecessor is known to have one
 /// successor (BB!). Eliminate the edge between them, moving the instructions in
 /// the predecessor into BB. This deletes the predecessor block.
-void MergeBasicBlockIntoOnlyPred(BasicBlock *BB, DominatorTree *DT = nullptr);
+void MergeBasicBlockIntoOnlyPred(BasicBlock *BB, DominatorTree *DT = nullptr,
+                                 DeferredDominance *DDT = nullptr);
 
 /// BB is known to contain an unconditional branch, and contains no instructions
 /// other than PHI nodes, potential debug intrinsics and the branch. If
 /// possible, eliminate BB by rewriting all the predecessors to branch to the
 /// successor block and return true. If we can't transform, return false.
-bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB);
+bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
+                                             DeferredDominance *DDT = nullptr);
 
 /// Check for and eliminate duplicate PHI nodes in this block. This doesn't try
 /// to be clever about PHI nodes which differ only in the order of the incoming
@@ -382,7 +386,8 @@ unsigned removeAllNonTerminatorAndEHPadI
 /// Insert an unreachable instruction before the specified
 /// instruction, making it and the rest of the code in the block dead.
 unsigned changeToUnreachable(Instruction *I, bool UseLLVMTrap,
-                             bool PreserveLCSSA = false);
+                             bool PreserveLCSSA = false,
+                             DeferredDominance *DDT = nullptr);
 
 /// Convert the CallInst to InvokeInst with the specified unwind edge basic
 /// block.  This also splits the basic block where CI is located, because
@@ -397,12 +402,13 @@ BasicBlock *changeToInvokeAndSplitBasicB
 ///
 /// \param BB  Block whose terminator will be replaced.  Its terminator must
 ///            have an unwind successor.
-void removeUnwindEdge(BasicBlock *BB);
+void removeUnwindEdge(BasicBlock *BB, DeferredDominance *DDT = nullptr);
 
 /// Remove all blocks that can not be reached from the function's entry.
 ///
 /// Returns true if any basic block was removed.
-bool removeUnreachableBlocks(Function &F, LazyValueInfo *LVI = nullptr);
+bool removeUnreachableBlocks(Function &F, LazyValueInfo *LVI = nullptr,
+                             DeferredDominance *DDT = nullptr);
 
 /// Combine the metadata of two instructions so that K can replace J
 ///
Index: llvm-toolchain-6.0-6.0.1/lib/IR/Dominators.cpp
===================================================================
--- llvm-toolchain-6.0-6.0.1.orig/lib/IR/Dominators.cpp
+++ llvm-toolchain-6.0-6.0.1/lib/IR/Dominators.cpp
@@ -18,6 +18,7 @@
 #include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/IR/CFG.h"
+#include "llvm/IR/Constants.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/Support/CommandLine.h"
@@ -389,3 +390,190 @@ void DominatorTreeWrapperPass::print(raw
   DT.print(OS);
 }
 
+//===----------------------------------------------------------------------===//
+//  DeferredDominance Implementation
+//===----------------------------------------------------------------------===//
+//
+// The implementation details of the DeferredDominance class which allows
+// one to queue updates to a DominatorTree.
+//
+//===----------------------------------------------------------------------===//
+
+/// \brief Queues multiple updates and discards duplicates.
+void DeferredDominance::applyUpdates(
+    ArrayRef<DominatorTree::UpdateType> Updates) {
+  SmallVector<DominatorTree::UpdateType, 8> Seen;
+  for (auto U : Updates)
+    // Avoid duplicates to applyUpdate() to save on analysis.
+    if (std::none_of(Seen.begin(), Seen.end(),
+                     [U](DominatorTree::UpdateType S) { return S == U; })) {
+      Seen.push_back(U);
+      applyUpdate(U.getKind(), U.getFrom(), U.getTo());
+    }
+}
+
+/// \brief Helper method for a single edge insertion. It's almost always better
+/// to batch updates and call applyUpdates to quickly remove duplicate edges.
+/// This is best used when there is only a single insertion needed to update
+/// Dominators.
+void DeferredDominance::insertEdge(BasicBlock *From, BasicBlock *To) {
+  applyUpdate(DominatorTree::Insert, From, To);
+}
+
+/// \brief Helper method for a single edge deletion. It's almost always better
+/// to batch updates and call applyUpdates to quickly remove duplicate edges.
+/// This is best used when there is only a single deletion needed to update
+/// Dominators.
+void DeferredDominance::deleteEdge(BasicBlock *From, BasicBlock *To) {
+  applyUpdate(DominatorTree::Delete, From, To);
+}
+
+/// \brief Delays the deletion of a basic block until a flush() event.
+void DeferredDominance::deleteBB(BasicBlock *DelBB) {
+  assert(DelBB && "Invalid push_back of nullptr DelBB.");
+  assert(pred_empty(DelBB) && "DelBB has one or more predecessors.");
+  // DelBB is unreachable and all its instructions are dead.
+  while (!DelBB->empty()) {
+    Instruction &I = DelBB->back();
+    // Replace used instructions with an arbitrary value (undef).
+    if (!I.use_empty())
+      I.replaceAllUsesWith(llvm::UndefValue::get(I.getType()));
+    DelBB->getInstList().pop_back();
+  }
+  // Make sure DelBB has a valid terminator instruction. As long as DelBB is a
+  // Child of Function F it must contain valid IR.
+  new UnreachableInst(DelBB->getContext(), DelBB);
+  DeletedBBs.insert(DelBB);
+}
+
+/// \brief Returns true if DelBB is awaiting deletion at a flush() event.
+bool DeferredDominance::pendingDeletedBB(BasicBlock *DelBB) {
+  if (DeletedBBs.empty())
+    return false;
+  return DeletedBBs.count(DelBB) != 0;
+}
+
+/// \brief Flushes all pending updates and block deletions. Returns a
+/// correct DominatorTree reference to be used by the caller for analysis.
+DominatorTree &DeferredDominance::flush() {
+  // Updates to DT must happen before blocks are deleted below. Otherwise the
+  // DT traversal will encounter badref blocks and assert.
+  if (!PendUpdates.empty()) {
+    DT.applyUpdates(PendUpdates);
+    PendUpdates.clear();
+  }
+  flushDelBB();
+  return DT;
+}
+
+/// \brief Drops all internal state and forces a (slow) recalculation of the
+/// DominatorTree based on the current state of the LLVM IR in F. This should
+/// only be used in corner cases such as the Entry block of F being deleted.
+void DeferredDominance::recalculate(Function &F) {
+  // flushDelBB must be flushed before the recalculation. The state of the IR
+  // must be consistent before the DT traversal algorithm determines the
+  // actual DT.
+  if (flushDelBB() || !PendUpdates.empty()) {
+    DT.recalculate(F);
+    PendUpdates.clear();
+  }
+}
+
+/// \brief Debug method to help view the state of pending updates.
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+LLVM_DUMP_METHOD void DeferredDominance::dump() const {
+  raw_ostream &OS = llvm::dbgs();
+  OS << "PendUpdates:\n";
+  int I = 0;
+  for (auto U : PendUpdates) {
+    OS << "  " << I << " : ";
+    ++I;
+    if (U.getKind() == DominatorTree::Insert)
+      OS << "Insert, ";
+    else
+      OS << "Delete, ";
+    BasicBlock *From = U.getFrom();
+    if (From) {
+      auto S = From->getName();
+      if (!From->hasName())
+        S = "(no name)";
+      OS << S << "(" << From << "), ";
+    } else {
+      OS << "(badref), ";
+    }
+    BasicBlock *To = U.getTo();
+    if (To) {
+      auto S = To->getName();
+      if (!To->hasName())
+        S = "(no_name)";
+      OS << S << "(" << To << ")\n";
+    } else {
+      OS << "(badref)\n";
+    }
+  }
+  OS << "DeletedBBs:\n";
+  I = 0;
+  for (auto BB : DeletedBBs) {
+    OS << "  " << I << " : ";
+    ++I;
+    if (BB->hasName())
+      OS << BB->getName() << "(";
+    else
+      OS << "(no_name)(";
+    OS << BB << ")\n";
+  }
+}
+#endif
+
+/// Apply an update (Kind, From, To) to the internal queued updates. The
+/// update is only added when determined to be necessary. Checks for
+/// self-domination, unnecessary updates, duplicate requests, and balanced
+/// pairs of requests are all performed. Returns true if the update is
+/// queued and false if it is discarded.
+bool DeferredDominance::applyUpdate(DominatorTree::UpdateKind Kind,
+                                    BasicBlock *From, BasicBlock *To) {
+  if (From == To)
+    return false; // Cannot dominate self; discard update.
+
+  // Discard updates by inspecting the current state of successors of From.
+  // Since applyUpdate() must be called *after* the Terminator of From is
+  // altered we can determine if the update is unnecessary.
+  bool HasEdge = std::any_of(succ_begin(From), succ_end(From),
+                             [To](BasicBlock *B) { return B == To; });
+  if (Kind == DominatorTree::Insert && !HasEdge)
+    return false; // Unnecessary Insert: edge does not exist in IR.
+  if (Kind == DominatorTree::Delete && HasEdge)
+    return false; // Unnecessary Delete: edge still exists in IR.
+
+  // Analyze pending updates to determine if the update is unnecessary.
+  DominatorTree::UpdateType Update = {Kind, From, To};
+  DominatorTree::UpdateType Invert = {Kind != DominatorTree::Insert
+                                          ? DominatorTree::Insert
+                                          : DominatorTree::Delete,
+                                      From, To};
+  for (auto I = PendUpdates.begin(), E = PendUpdates.end(); I != E; ++I) {
+    if (Update == *I)
+      return false; // Discard duplicate updates.
+    if (Invert == *I) {
+      // Update and Invert are both valid (equivalent to a no-op). Remove
+      // Invert from PendUpdates and discard the Update.
+      PendUpdates.erase(I);
+      return false;
+    }
+  }
+  PendUpdates.push_back(Update); // Save the valid update.
+  return true;
+}
+
+/// Performs all pending basic block deletions. We have to defer the deletion
+/// of these blocks until after the DominatorTree updates are applied. The
+/// internal workings of the DominatorTree code expect every update's From
+/// and To blocks to exist and to be a member of the same Function.
+bool DeferredDominance::flushDelBB() {
+  if (DeletedBBs.empty())
+    return false;
+  for (auto *BB : DeletedBBs)
+    BB->eraseFromParent();
+  DeletedBBs.clear();
+  return true;
+}
Index: llvm-toolchain-6.0-6.0.1/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
===================================================================
--- llvm-toolchain-6.0-6.0.1.orig/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ llvm-toolchain-6.0-6.0.1/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -77,6 +77,7 @@ namespace {
     bool runOnFunction(Function &F) override;
 
     void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.addRequired<DominatorTreeWrapperPass>();
       AU.addRequired<LazyValueInfoWrapperPass>();
       AU.addPreserved<GlobalsAAWrapperPass>();
     }
@@ -88,6 +89,7 @@ char CorrelatedValuePropagation::ID = 0;
 
 INITIALIZE_PASS_BEGIN(CorrelatedValuePropagation, "correlated-propagation",
                 "Value Propagation", false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(LazyValueInfoWrapperPass)
 INITIALIZE_PASS_END(CorrelatedValuePropagation, "correlated-propagation",
                 "Value Propagation", false, false)
Index: llvm-toolchain-6.0-6.0.1/lib/Transforms/Scalar/JumpThreading.cpp
===================================================================
--- llvm-toolchain-6.0-6.0.1.orig/lib/Transforms/Scalar/JumpThreading.cpp
+++ llvm-toolchain-6.0-6.0.1/lib/Transforms/Scalar/JumpThreading.cpp
@@ -131,10 +131,11 @@ namespace {
     bool runOnFunction(Function &F) override;
 
     void getAnalysisUsage(AnalysisUsage &AU) const override {
-      if (PrintLVIAfterJumpThreading)
-        AU.addRequired<DominatorTreeWrapperPass>();
+      AU.addRequired<DominatorTreeWrapperPass>();
+      AU.addPreserved<DominatorTreeWrapperPass>();
       AU.addRequired<AAResultsWrapperPass>();
       AU.addRequired<LazyValueInfoWrapperPass>();
+      AU.addPreserved<LazyValueInfoWrapperPass>();
       AU.addPreserved<GlobalsAAWrapperPass>();
       AU.addRequired<TargetLibraryInfoWrapperPass>();
     }
@@ -148,6 +149,7 @@ char JumpThreading::ID = 0;
 
 INITIALIZE_PASS_BEGIN(JumpThreading, "jump-threading",
                 "Jump Threading", false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(LazyValueInfoWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
@@ -278,8 +280,12 @@ bool JumpThreading::runOnFunction(Functi
   if (skipFunction(F))
     return false;
   auto TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
+  // Get DT analysis before LVI. When LVI is initialized it conditionally adds
+  // DT if it's available.
+  auto DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
   auto LVI = &getAnalysis<LazyValueInfoWrapperPass>().getLVI();
   auto AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
+  DeferredDominance DDT(*DT);
   std::unique_ptr<BlockFrequencyInfo> BFI;
   std::unique_ptr<BranchProbabilityInfo> BPI;
   bool HasProfileData = F.hasProfileData();
@@ -289,12 +295,11 @@ bool JumpThreading::runOnFunction(Functi
     BFI.reset(new BlockFrequencyInfo(F, *BPI, LI));
   }
 
-  bool Changed = Impl.runImpl(F, TLI, LVI, AA, HasProfileData, std::move(BFI),
-                              std::move(BPI));
+  bool Changed = Impl.runImpl(F, TLI, LVI, AA, &DDT, HasProfileData,
+                              std::move(BFI), std::move(BPI));
   if (PrintLVIAfterJumpThreading) {
     dbgs() << "LVI for function '" << F.getName() << "':\n";
-    LVI->printLVI(F, getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
-                  dbgs());
+    LVI->printLVI(F, *DT, dbgs());
   }
   return Changed;
 }
@@ -302,8 +307,12 @@ bool JumpThreading::runOnFunction(Functi
 PreservedAnalyses JumpThreadingPass::run(Function &F,
                                          FunctionAnalysisManager &AM) {
   auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
+  // Get DT analysis before LVI. When LVI is initialized it conditionally adds
+  // DT if it's available.
+  auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
   auto &LVI = AM.getResult<LazyValueAnalysis>(F);
   auto &AA = AM.getResult<AAManager>(F);
+  DeferredDominance DDT(DT);
 
   std::unique_ptr<BlockFrequencyInfo> BFI;
   std::unique_ptr<BranchProbabilityInfo> BPI;
@@ -313,25 +322,28 @@ PreservedAnalyses JumpThreadingPass::run
     BFI.reset(new BlockFrequencyInfo(F, *BPI, LI));
   }
 
-  bool Changed = runImpl(F, &TLI, &LVI, &AA, HasProfileData, std::move(BFI),
-                         std::move(BPI));
+  bool Changed = runImpl(F, &TLI, &LVI, &AA, &DDT, HasProfileData,
+                         std::move(BFI), std::move(BPI));
 
   if (!Changed)
     return PreservedAnalyses::all();
   PreservedAnalyses PA;
   PA.preserve<GlobalsAA>();
+  PA.preserve<DominatorTreeAnalysis>();
+  PA.preserve<LazyValueAnalysis>();
   return PA;
 }
 
 bool JumpThreadingPass::runImpl(Function &F, TargetLibraryInfo *TLI_,
                                 LazyValueInfo *LVI_, AliasAnalysis *AA_,
-                                bool HasProfileData_,
+                                DeferredDominance *DDT_, bool HasProfileData_,
                                 std::unique_ptr<BlockFrequencyInfo> BFI_,
                                 std::unique_ptr<BranchProbabilityInfo> BPI_) {
   DEBUG(dbgs() << "Jump threading on function '" << F.getName() << "'\n");
   TLI = TLI_;
   LVI = LVI_;
   AA = AA_;
+  DDT = DDT_;
   BFI.reset();
   BPI.reset();
   // When profile data is available, we need to update edge weights after
@@ -353,7 +365,7 @@ bool JumpThreadingPass::runImpl(Function
   // back edges. This works for normal cases but not for unreachable blocks as
   // they may have cycle with no back edge.
   bool EverChanged = false;
-  EverChanged |= removeUnreachableBlocks(F, LVI);
+  EverChanged |= removeUnreachableBlocks(F, LVI, DDT);
 
   FindLoopHeaders(F);
 
@@ -368,6 +380,10 @@ bool JumpThreadingPass::runImpl(Function
 
       ++I;
 
+      // Don't thread branches over a block that's slated for deletion.
+      if (DDT->pendingDeletedBB(BB))
+        continue;
+
       // If the block is trivially dead, zap it.  This eliminates the successor
       // edges which simplifies the CFG.
       if (pred_empty(BB) &&
@@ -376,7 +392,7 @@ bool JumpThreadingPass::runImpl(Function
               << "' with terminator: " << *BB->getTerminator() << '\n');
         LoopHeaders.erase(BB);
         LVI->eraseBlock(BB);
-        DeleteDeadBlock(BB);
+        DeleteDeadBlock(BB, DDT);
         Changed = true;
         continue;
       }
@@ -400,7 +416,7 @@ bool JumpThreadingPass::runImpl(Function
         // awesome, but it allows us to use AssertingVH to prevent nasty
         // dangling pointer issues within LazyValueInfo.
         LVI->eraseBlock(BB);
-        if (TryToSimplifyUncondBranchFromEmptyBlock(BB))
+        if (TryToSimplifyUncondBranchFromEmptyBlock(BB, DDT))
           Changed = true;
       }
     }
@@ -408,6 +424,7 @@ bool JumpThreadingPass::runImpl(Function
   } while (Changed);
 
   LoopHeaders.clear();
+  DDT->flush();
   return EverChanged;
 }
 
@@ -931,8 +948,8 @@ static bool hasAddressTakenAndUsed(Basic
 bool JumpThreadingPass::ProcessBlock(BasicBlock *BB) {
   // If the block is trivially dead, just return and let the caller nuke it.
   // This simplifies other transformations.
-  if (pred_empty(BB) &&
-      BB != &BB->getParent()->getEntryBlock())
+  if (DDT->pendingDeletedBB(BB) ||
+      (pred_empty(BB) && BB != &BB->getParent()->getEntryBlock()))
     return false;
 
   // If this block has a single predecessor, and if that pred has a single
@@ -948,7 +965,7 @@ bool JumpThreadingPass::ProcessBlock(Bas
         LoopHeaders.insert(BB);
 
       LVI->eraseBlock(SinglePred);
-      MergeBasicBlockIntoOnlyPred(BB);
+      MergeBasicBlockIntoOnlyPred(BB, nullptr, DDT);
 
       // Now that BB is merged into SinglePred (i.e. SinglePred Code followed by
       // BB code within one basic block `BB`), we need to invalidate the LVI
@@ -1031,18 +1048,23 @@ bool JumpThreadingPass::ProcessBlock(Bas
   // successors to branch to.  Let GetBestDestForJumpOnUndef decide.
   if (isa<UndefValue>(Condition)) {
     unsigned BestSucc = GetBestDestForJumpOnUndef(BB);
+    std::vector<DominatorTree::UpdateType> Updates;
 
     // Fold the branch/switch.
     TerminatorInst *BBTerm = BB->getTerminator();
+    Updates.reserve(BBTerm->getNumSuccessors());
     for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i) {
       if (i == BestSucc) continue;
-      BBTerm->getSuccessor(i)->removePredecessor(BB, true);
+      BasicBlock *Succ = BBTerm->getSuccessor(i);
+      Succ->removePredecessor(BB, true);
+      Updates.push_back({DominatorTree::Delete, BB, Succ});
     }
 
     DEBUG(dbgs() << "  In block '" << BB->getName()
           << "' folding undef terminator: " << *BBTerm << '\n');
     BranchInst::Create(BBTerm->getSuccessor(BestSucc), BBTerm);
     BBTerm->eraseFromParent();
+    DDT->applyUpdates(Updates);
     return true;
   }
 
@@ -1053,7 +1075,7 @@ bool JumpThreadingPass::ProcessBlock(Bas
     DEBUG(dbgs() << "  In block '" << BB->getName()
           << "' folding terminator: " << *BB->getTerminator() << '\n');
     ++NumFolds;
-    ConstantFoldTerminator(BB, true);
+    ConstantFoldTerminator(BB, true, nullptr, DDT);
     return true;
   }
 
@@ -1086,7 +1108,8 @@ bool JumpThreadingPass::ProcessBlock(Bas
       if (Ret != LazyValueInfo::Unknown) {
         unsigned ToRemove = Ret == LazyValueInfo::True ? 1 : 0;
         unsigned ToKeep = Ret == LazyValueInfo::True ? 0 : 1;
-        CondBr->getSuccessor(ToRemove)->removePredecessor(BB, true);
+        BasicBlock *ToRemoveSucc = CondBr->getSuccessor(ToRemove);
+        ToRemoveSucc->removePredecessor(BB, true);
         BranchInst::Create(CondBr->getSuccessor(ToKeep), CondBr);
         CondBr->eraseFromParent();
         if (CondCmp->use_empty())
@@ -1104,6 +1127,7 @@ bool JumpThreadingPass::ProcessBlock(Bas
             ConstantInt::getFalse(CondCmp->getType());
           ReplaceFoldableUses(CondCmp, CI);
         }
+        DDT->deleteEdge(BB, ToRemoveSucc);
         return true;
       }
 
@@ -1182,9 +1206,12 @@ bool JumpThreadingPass::ProcessImpliedCo
     Optional<bool> Implication =
         isImpliedCondition(PBI->getCondition(), Cond, DL, CondIsTrue);
     if (Implication) {
-      BI->getSuccessor(*Implication ? 1 : 0)->removePredecessor(BB);
-      BranchInst::Create(BI->getSuccessor(*Implication ? 0 : 1), BI);
+      BasicBlock *KeepSucc = BI->getSuccessor(*Implication ? 0 : 1);
+      BasicBlock *RemoveSucc = BI->getSuccessor(*Implication ? 1 : 0);
+      RemoveSucc->removePredecessor(BB);
+      BranchInst::Create(KeepSucc, BI);
       BI->eraseFromParent();
+      DDT->deleteEdge(BB, RemoveSucc);
       return true;
     }
     CurrentBB = CurrentPred;
@@ -1594,17 +1621,22 @@ bool JumpThreadingPass::ProcessThreadabl
     if (PredWithKnownDest ==
         (size_t)std::distance(pred_begin(BB), pred_end(BB))) {
       bool SeenFirstBranchToOnlyDest = false;
+      std::vector <DominatorTree::UpdateType> Updates;
+      Updates.reserve(BB->getTerminator()->getNumSuccessors() - 1);
       for (BasicBlock *SuccBB : successors(BB)) {
-        if (SuccBB == OnlyDest && !SeenFirstBranchToOnlyDest)
+        if (SuccBB == OnlyDest && !SeenFirstBranchToOnlyDest) {
           SeenFirstBranchToOnlyDest = true; // Don't modify the first branch.
-        else
+        } else {
           SuccBB->removePredecessor(BB, true); // This is unreachable successor.
+          Updates.push_back({DominatorTree::Delete, BB, SuccBB});
+        }
       }
 
       // Finally update the terminator.
       TerminatorInst *Term = BB->getTerminator();
       BranchInst::Create(OnlyDest, Term);
       Term->eraseFromParent();
+      DDT->applyUpdates(Updates);
 
       // If the condition is now dead due to the removal of the old terminator,
       // erase it.
@@ -1979,6 +2011,10 @@ bool JumpThreadingPass::ThreadEdge(Basic
       PredTerm->setSuccessor(i, NewBB);
     }
 
+  DDT->applyUpdates({{DominatorTree::Insert, NewBB, SuccBB},
+                     {DominatorTree::Insert, PredBB, NewBB},
+                     {DominatorTree::Delete, PredBB, BB}});
+
   // At this point, the IR is fully up to date and consistent.  Do a quick scan
   // over the new instructions and zap any that are constants or dead.  This
   // frequently happens because of phi translation.
@@ -1998,20 +2034,42 @@ bool JumpThreadingPass::ThreadEdge(Basic
 BasicBlock *JumpThreadingPass::SplitBlockPreds(BasicBlock *BB,
                                                ArrayRef<BasicBlock *> Preds,
                                                const char *Suffix) {
+  SmallVector<BasicBlock *, 2> NewBBs;
+
   // Collect the frequencies of all predecessors of BB, which will be used to
-  // update the edge weight on BB->SuccBB.
-  BlockFrequency PredBBFreq(0);
+  // update the edge weight of the result of splitting predecessors.
+  DenseMap<BasicBlock *, BlockFrequency> FreqMap;
   if (HasProfileData)
     for (auto Pred : Preds)
-      PredBBFreq += BFI->getBlockFreq(Pred) * BPI->getEdgeProbability(Pred, BB);
+      FreqMap.insert(std::make_pair(
+          Pred, BFI->getBlockFreq(Pred) * BPI->getEdgeProbability(Pred, BB)));
+
+  // In the case when BB is a LandingPad block we create 2 new predecessors
+  // instead of just one.
+  if (BB->isLandingPad()) {
+    std::string NewName = std::string(Suffix) + ".split-lp";
+    SplitLandingPadPredecessors(BB, Preds, Suffix, NewName.c_str(), NewBBs);
+  } else {
+    NewBBs.push_back(SplitBlockPredecessors(BB, Preds, Suffix));
+  }
 
-  BasicBlock *PredBB = SplitBlockPredecessors(BB, Preds, Suffix);
+  std::vector<DominatorTree::UpdateType> Updates;
+  Updates.reserve((2 * Preds.size()) + NewBBs.size());
+  for (auto NewBB : NewBBs) {
+    BlockFrequency NewBBFreq(0);
+    Updates.push_back({DominatorTree::Insert, NewBB, BB});
+    for (auto Pred : predecessors(NewBB)) {
+      Updates.push_back({DominatorTree::Delete, Pred, BB});
+      Updates.push_back({DominatorTree::Insert, Pred, NewBB});
+      if (HasProfileData) // Update frequencies between Pred -> NewBB.
+        NewBBFreq += FreqMap.lookup(Pred);
+    }
+    if (HasProfileData) // Apply the summed frequency to NewBB.
+      BFI->setBlockFreq(NewBB, NewBBFreq.getFrequency());
+  }
 
-  // Set the block frequency of the newly created PredBB, which is the sum of
-  // frequencies of Preds.
-  if (HasProfileData)
-    BFI->setBlockFreq(PredBB, PredBBFreq.getFrequency());
-  return PredBB;
+  DDT->applyUpdates(Updates);
+  return NewBBs[0];
 }
 
 bool JumpThreadingPass::doesBlockHaveProfileData(BasicBlock *BB) {
@@ -2155,6 +2213,7 @@ bool JumpThreadingPass::DuplicateCondBra
   }
 
   // And finally, do it!  Start by factoring the predecessors if needed.
+  std::vector<DominatorTree::UpdateType> Updates;
   BasicBlock *PredBB;
   if (PredBBs.size() == 1)
     PredBB = PredBBs[0];
@@ -2163,6 +2222,7 @@ bool JumpThreadingPass::DuplicateCondBra
           << " common predecessors.\n");
     PredBB = SplitBlockPreds(BB, PredBBs, ".thr_comm");
   }
+  Updates.push_back({DominatorTree::Delete, PredBB, BB});
 
   // Okay, we decided to do this!  Clone all the instructions in BB onto the end
   // of PredBB.
@@ -2175,7 +2235,11 @@ bool JumpThreadingPass::DuplicateCondBra
   BranchInst *OldPredBranch = dyn_cast<BranchInst>(PredBB->getTerminator());
 
   if (!OldPredBranch || !OldPredBranch->isUnconditional()) {
-    PredBB = SplitEdge(PredBB, BB);
+    BasicBlock *OldPredBB = PredBB;
+    PredBB = SplitEdge(OldPredBB, BB);
+    Updates.push_back({DominatorTree::Insert, OldPredBB, PredBB});
+    Updates.push_back({DominatorTree::Insert, PredBB, BB});
+    Updates.push_back({DominatorTree::Delete, OldPredBB, BB});
     OldPredBranch = cast<BranchInst>(PredBB->getTerminator());
   }
 
@@ -2217,6 +2281,10 @@ bool JumpThreadingPass::DuplicateCondBra
       // Otherwise, insert the new instruction into the block.
       New->setName(BI->getName());
       PredBB->getInstList().insert(OldPredBranch->getIterator(), New);
+      // Update Dominance from simplified New instruction operands.
+      for (unsigned i = 0, e = New->getNumOperands(); i != e; ++i)
+        if (BasicBlock *SuccBB = dyn_cast<BasicBlock>(New->getOperand(i)))
+          Updates.push_back({DominatorTree::Insert, PredBB, SuccBB});
     }
   }
 
@@ -2272,6 +2340,7 @@ bool JumpThreadingPass::DuplicateCondBra
 
   // Remove the unconditional branch at the end of the PredBB block.
   OldPredBranch->eraseFromParent();
+  DDT->applyUpdates(Updates);
 
   ++NumDupes;
   return true;
@@ -2344,6 +2413,8 @@ bool JumpThreadingPass::TryToUnfoldSelec
       // The select is now dead.
       SI->eraseFromParent();
 
+      DDT->applyUpdates({{DominatorTree::Insert, NewBB, BB},
+                         {DominatorTree::Insert, Pred, NewBB}});
       // Update any other PHI nodes in BB.
       for (BasicBlock::iterator BI = BB->begin();
            PHINode *Phi = dyn_cast<PHINode>(BI); ++BI)
@@ -2422,11 +2493,25 @@ bool JumpThreadingPass::TryToUnfoldSelec
     // Expand the select.
     TerminatorInst *Term =
         SplitBlockAndInsertIfThen(SI->getCondition(), SI, false);
+    BasicBlock *SplitBB = SI->getParent();
+    BasicBlock *NewBB = Term->getParent();
     PHINode *NewPN = PHINode::Create(SI->getType(), 2, "", SI);
     NewPN->addIncoming(SI->getTrueValue(), Term->getParent());
     NewPN->addIncoming(SI->getFalseValue(), BB);
     SI->replaceAllUsesWith(NewPN);
     SI->eraseFromParent();
+    // NewBB and SplitBB are newly created blocks which require insertion.
+    std::vector<DominatorTree::UpdateType> Updates;
+    Updates.reserve((2 * SplitBB->getTerminator()->getNumSuccessors()) + 3);
+    Updates.push_back({DominatorTree::Insert, BB, SplitBB});
+    Updates.push_back({DominatorTree::Insert, BB, NewBB});
+    Updates.push_back({DominatorTree::Insert, NewBB, SplitBB});
+    // BB's successors were moved to SplitBB, update DDT accordingly.
+    for (auto *Succ : successors(SplitBB)) {
+      Updates.push_back({DominatorTree::Delete, BB, Succ});
+      Updates.push_back({DominatorTree::Insert, SplitBB, Succ});
+    }
+    DDT->applyUpdates(Updates);
     return true;
   }
   return false;
@@ -2513,8 +2598,8 @@ bool JumpThreadingPass::ThreadGuard(Basi
   if (!TrueDestIsSafe && !FalseDestIsSafe)
     return false;
 
-  BasicBlock *UnguardedBlock = TrueDestIsSafe ? TrueDest : FalseDest;
-  BasicBlock *GuardedBlock = FalseDestIsSafe ? TrueDest : FalseDest;
+  BasicBlock *PredUnguardedBlock = TrueDestIsSafe ? TrueDest : FalseDest;
+  BasicBlock *PredGuardedBlock = FalseDestIsSafe ? TrueDest : FalseDest;
 
   ValueToValueMapTy UnguardedMapping, GuardedMapping;
   Instruction *AfterGuard = Guard->getNextNode();
@@ -2523,18 +2608,29 @@ bool JumpThreadingPass::ThreadGuard(Basi
     return false;
   // Duplicate all instructions before the guard and the guard itself to the
   // branch where implication is not proved.
-  GuardedBlock = DuplicateInstructionsInSplitBetween(
-      BB, GuardedBlock, AfterGuard, GuardedMapping);
+  BasicBlock *GuardedBlock = DuplicateInstructionsInSplitBetween(
+      BB, PredGuardedBlock, AfterGuard, GuardedMapping);
   assert(GuardedBlock && "Could not create the guarded block?");
   // Duplicate all instructions before the guard in the unguarded branch.
   // Since we have successfully duplicated the guarded block and this block
   // has fewer instructions, we expect it to succeed.
-  UnguardedBlock = DuplicateInstructionsInSplitBetween(BB, UnguardedBlock,
-                                                       Guard, UnguardedMapping);
+  BasicBlock *UnguardedBlock = DuplicateInstructionsInSplitBetween(
+      BB, PredUnguardedBlock, Guard, UnguardedMapping);
   assert(UnguardedBlock && "Could not create the unguarded block?");
   DEBUG(dbgs() << "Moved guard " << *Guard << " to block "
                << GuardedBlock->getName() << "\n");
-
+  // DuplicateInstructionsInSplitBetween inserts a new block "BB.split" between
+  // PredBB and BB. We need to perform two inserts and one delete for each of
+  // the above calls to update Dominators.
+  DDT->applyUpdates(
+      {// Guarded block split.
+       {DominatorTree::Delete, PredGuardedBlock, BB},
+       {DominatorTree::Insert, PredGuardedBlock, GuardedBlock},
+       {DominatorTree::Insert, GuardedBlock, BB},
+       // Unguarded block split.
+       {DominatorTree::Delete, PredUnguardedBlock, BB},
+       {DominatorTree::Insert, PredUnguardedBlock, UnguardedBlock},
+       {DominatorTree::Insert, UnguardedBlock, BB}});
   // Some instructions before the guard may still have uses. For them, we need
   // to create Phi nodes merging their copies in both guarded and unguarded
   // branches. Those instructions that have no uses can be just removed.
Index: llvm-toolchain-6.0-6.0.1/lib/Transforms/Utils/BasicBlockUtils.cpp
===================================================================
--- llvm-toolchain-6.0-6.0.1.orig/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ llvm-toolchain-6.0-6.0.1/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -45,16 +45,22 @@
 
 using namespace llvm;
 
-void llvm::DeleteDeadBlock(BasicBlock *BB) {
+void llvm::DeleteDeadBlock(BasicBlock *BB, DeferredDominance *DDT) {
   assert((pred_begin(BB) == pred_end(BB) ||
          // Can delete self loop.
          BB->getSinglePredecessor() == BB) && "Block is not dead!");
   TerminatorInst *BBTerm = BB->getTerminator();
+  std::vector<DominatorTree::UpdateType> Updates;
 
   // Loop through all of our successors and make sure they know that one
   // of their predecessors is going away.
-  for (BasicBlock *Succ : BBTerm->successors())
+  if (DDT)
+    Updates.reserve(BBTerm->getNumSuccessors());
+  for (BasicBlock *Succ : BBTerm->successors()) {
     Succ->removePredecessor(BB);
+    if (DDT)
+      Updates.push_back({DominatorTree::Delete, BB, Succ});
+  }
 
   // Zap all the instructions in the block.
   while (!BB->empty()) {
@@ -69,8 +75,12 @@ void llvm::DeleteDeadBlock(BasicBlock *B
     BB->getInstList().pop_back();
   }
 
-  // Zap the block!
-  BB->eraseFromParent();
+  if (DDT) {
+    DDT->applyUpdates(Updates);
+    DDT->deleteBB(BB); // Deferred deletion of BB.
+  } else {
+    BB->eraseFromParent(); // Zap the block!
+  }
 }
 
 void llvm::FoldSingleEntryPHINodes(BasicBlock *BB,
Index: llvm-toolchain-6.0-6.0.1/lib/Transforms/Utils/Local.cpp
===================================================================
--- llvm-toolchain-6.0-6.0.1.orig/lib/Transforms/Utils/Local.cpp
+++ llvm-toolchain-6.0-6.0.1/lib/Transforms/Utils/Local.cpp
@@ -100,7 +100,8 @@ STATISTIC(NumRemoved, "Number of unreach
 /// conditions and indirectbr addresses this might make dead if
 /// DeleteDeadConditions is true.
 bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
-                                  const TargetLibraryInfo *TLI) {
+                                  const TargetLibraryInfo *TLI,
+                                  DeferredDominance *DDT) {
   TerminatorInst *T = BB->getTerminator();
   IRBuilder<> Builder(T);
 
@@ -123,6 +124,8 @@ bool llvm::ConstantFoldTerminator(BasicB
       // Replace the conditional branch with an unconditional one.
       Builder.CreateBr(Destination);
       BI->eraseFromParent();
+      if (DDT)
+        DDT->deleteEdge(BB, OldDest);
       return true;
     }
 
@@ -193,9 +196,12 @@ bool llvm::ConstantFoldTerminator(BasicB
                           createBranchWeights(Weights));
         }
         // Remove this entry.
-        DefaultDest->removePredecessor(SI->getParent());
+        BasicBlock *ParentBB = SI->getParent();
+        DefaultDest->removePredecessor(ParentBB);
         i = SI->removeCase(i);
         e = SI->case_end();
+        if (DDT)
+          DDT->deleteEdge(ParentBB, DefaultDest);
         continue;
       }
 
@@ -221,14 +227,20 @@ bool llvm::ConstantFoldTerminator(BasicB
       // Insert the new branch.
       Builder.CreateBr(TheOnlyDest);
       BasicBlock *BB = SI->getParent();
+      std::vector <DominatorTree::UpdateType> Updates;
+      if (DDT)
+        Updates.reserve(SI->getNumSuccessors() - 1);
 
       // Remove entries from PHI nodes which we no longer branch to...
       for (BasicBlock *Succ : SI->successors()) {
         // Found case matching a constant operand?
-        if (Succ == TheOnlyDest)
+        if (Succ == TheOnlyDest) {
           TheOnlyDest = nullptr; // Don't modify the first branch to TheOnlyDest
-        else
+        } else {
           Succ->removePredecessor(BB);
+          if (DDT)
+            Updates.push_back({DominatorTree::Delete, BB, Succ});
+        }
       }
 
       // Delete the old switch.
@@ -236,6 +248,8 @@ bool llvm::ConstantFoldTerminator(BasicB
       SI->eraseFromParent();
       if (DeleteDeadConditions)
         RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
+      if (DDT)
+        DDT->applyUpdates(Updates);
       return true;
     }
 
@@ -281,14 +295,23 @@ bool llvm::ConstantFoldTerminator(BasicB
     if (auto *BA =
           dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) {
       BasicBlock *TheOnlyDest = BA->getBasicBlock();
+      std::vector <DominatorTree::UpdateType> Updates;
+      if (DDT)
+        Updates.reserve(IBI->getNumDestinations() - 1);
+
       // Insert the new branch.
       Builder.CreateBr(TheOnlyDest);
 
       for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
-        if (IBI->getDestination(i) == TheOnlyDest)
+        if (IBI->getDestination(i) == TheOnlyDest) {
           TheOnlyDest = nullptr;
-        else
-          IBI->getDestination(i)->removePredecessor(IBI->getParent());
+        } else {
+          BasicBlock *ParentBB = IBI->getParent();
+          BasicBlock *DestBB = IBI->getDestination(i);
+          DestBB->removePredecessor(ParentBB);
+          if (DDT)
+            Updates.push_back({DominatorTree::Delete, ParentBB, DestBB});
+        }
       }
       Value *Address = IBI->getAddress();
       IBI->eraseFromParent();
@@ -303,6 +326,8 @@ bool llvm::ConstantFoldTerminator(BasicB
         new UnreachableInst(BB->getContext(), BB);
       }
 
+      if (DDT)
+        DDT->applyUpdates(Updates);
       return true;
     }
   }
@@ -579,7 +604,8 @@ bool llvm::SimplifyInstructionsInBlock(B
 ///
 /// .. and delete the predecessor corresponding to the '1', this will attempt to
 /// recursively fold the and to 0.
-void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred) {
+void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
+                                        DeferredDominance *DDT) {
   // This only adjusts blocks with PHI nodes.
   if (!isa<PHINode>(BB->begin()))
     return;
@@ -602,13 +628,18 @@ void llvm::RemovePredecessorAndSimplify(
     // of the block.
     if (PhiIt != OldPhiIt) PhiIt = &BB->front();
   }
+  if (DDT)
+    DDT->deleteEdge(Pred, BB);
 }
 
 /// MergeBasicBlockIntoOnlyPred - DestBB is a block with one predecessor and its
 /// predecessor is known to have one successor (DestBB!).  Eliminate the edge
 /// between them, moving the instructions in the predecessor into DestBB and
 /// deleting the predecessor block.
-void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, DominatorTree *DT) {
+void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, DominatorTree *DT,
+                                       DeferredDominance *DDT) {
+  assert(!(DT && DDT) && "Cannot call with both DT and DDT.");
+
   // If BB has single-entry PHI nodes, fold them.
   while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
     Value *NewVal = PN->getIncomingValue(0);
@@ -621,6 +652,25 @@ void llvm::MergeBasicBlockIntoOnlyPred(B
   BasicBlock *PredBB = DestBB->getSinglePredecessor();
   assert(PredBB && "Block doesn't have a single predecessor!");
 
+  bool ReplaceEntryBB = false;
+  if (PredBB == &DestBB->getParent()->getEntryBlock())
+    ReplaceEntryBB = true;
+
+  // Deferred DT update: Collect all the edges that enter PredBB. These
+  // dominator edges will be redirected to DestBB.
+  std::vector <DominatorTree::UpdateType> Updates;
+  if (DDT && !ReplaceEntryBB) {
+    Updates.reserve(1 +
+                    (2 * std::distance(pred_begin(PredBB), pred_end(PredBB))));
+    Updates.push_back({DominatorTree::Delete, PredBB, DestBB});
+    for (auto I = pred_begin(PredBB), E = pred_end(PredBB); I != E; ++I) {
+      Updates.push_back({DominatorTree::Delete, *I, PredBB});
+      // This predecessor of PredBB may already have DestBB as a successor.
+      if (llvm::find(successors(*I), DestBB) == succ_end(*I))
+        Updates.push_back({DominatorTree::Insert, *I, DestBB});
+    }
+  }
+
   // Zap anything that took the address of DestBB.  Not doing this will give the
   // address an invalid value.
   if (DestBB->hasAddressTaken()) {
@@ -641,7 +691,7 @@ void llvm::MergeBasicBlockIntoOnlyPred(B
 
   // If the PredBB is the entry block of the function, move DestBB up to
   // become the entry block after we erase PredBB.
-  if (PredBB == &DestBB->getParent()->getEntryBlock())
+  if (ReplaceEntryBB)
     DestBB->moveAfter(PredBB);
 
   if (DT) {
@@ -653,8 +703,19 @@ void llvm::MergeBasicBlockIntoOnlyPred(B
       DT->eraseNode(PredBB);
     }
   }
-  // Nuke BB.
-  PredBB->eraseFromParent();
+
+  if (DDT) {
+    DDT->deleteBB(PredBB); // Deferred deletion of BB.
+    if (ReplaceEntryBB)
+      // The entry block was removed and there is no external interface for the
+      // dominator tree to be notified of this change. In this corner-case we
+      // recalculate the entire tree.
+      DDT->recalculate(*(DestBB->getParent()));
+    else
+      DDT->applyUpdates(Updates);
+  } else {
+    PredBB->eraseFromParent(); // Nuke BB.
+  }
 }
 
 /// CanMergeValues - Return true if we can choose one of these values to use
@@ -861,7 +922,8 @@ static void redirectValuesFromPredecesso
 /// potential side-effect free intrinsics and the branch.  If possible,
 /// eliminate BB by rewriting all the predecessors to branch to the successor
 /// block and return true.  If we can't transform, return false.
-bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB) {
+bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
+                                                   DeferredDominance *DDT) {
   assert(BB != &BB->getParent()->getEntryBlock() &&
          "TryToSimplifyUncondBranchFromEmptyBlock called on entry block!");
 
@@ -902,6 +964,19 @@ bool llvm::TryToSimplifyUncondBranchFrom
 
   DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
 
+  std::vector<DominatorTree::UpdateType> Updates;
+  if (DDT) {
+    Updates.reserve(1 + (2 * std::distance(pred_begin(BB), pred_end(BB))));
+    Updates.push_back({DominatorTree::Delete, BB, Succ});
+    // All predecessors of BB will be moved to Succ.
+    for (auto I = pred_begin(BB), E = pred_end(BB); I != E; ++I) {
+      Updates.push_back({DominatorTree::Delete, *I, BB});
+      // This predecessor of BB may already have Succ as a successor.
+      if (llvm::find(successors(*I), Succ) == succ_end(*I))
+        Updates.push_back({DominatorTree::Insert, *I, Succ});
+    }
+  }
+
   if (isa<PHINode>(Succ->begin())) {
     // If there is more than one pred of succ, and there are PHI nodes in
     // the successor, then we need to add incoming edges for the PHI nodes
@@ -946,7 +1021,13 @@ bool llvm::TryToSimplifyUncondBranchFrom
   // Everything that jumped to BB now goes to Succ.
   BB->replaceAllUsesWith(Succ);
   if (!Succ->hasName()) Succ->takeName(BB);
-  BB->eraseFromParent();              // Delete the old basic block.
+
+  if (DDT) {
+    DDT->deleteBB(BB); // Deferred deletion of the old basic block.
+    DDT->applyUpdates(Updates);
+  } else {
+    BB->eraseFromParent(); // Delete the old basic block.
+  }
   return true;
 }
 
@@ -1448,13 +1529,19 @@ unsigned llvm::removeAllNonTerminatorAnd
 }
 
 unsigned llvm::changeToUnreachable(Instruction *I, bool UseLLVMTrap,
-                                   bool PreserveLCSSA) {
+                                   bool PreserveLCSSA, DeferredDominance *DDT) {
   BasicBlock *BB = I->getParent();
+  std::vector <DominatorTree::UpdateType> Updates;
+
   // Loop over all of the successors, removing BB's entry from any PHI
   // nodes.
-  for (BasicBlock *Successor : successors(BB))
+  if (DDT)
+    Updates.reserve(BB->getTerminator()->getNumSuccessors());
+  for (BasicBlock *Successor : successors(BB)) {
     Successor->removePredecessor(BB, PreserveLCSSA);
-
+    if (DDT)
+      Updates.push_back({DominatorTree::Delete, BB, Successor});
+  }
   // Insert a call to llvm.trap right before this.  This turns the undefined
   // behavior into a hard fail instead of falling through into random code.
   if (UseLLVMTrap) {
@@ -1474,11 +1561,13 @@ unsigned llvm::changeToUnreachable(Instr
     BB->getInstList().erase(BBI++);
     ++NumInstrsRemoved;
   }
+  if (DDT)
+    DDT->applyUpdates(Updates);
   return NumInstrsRemoved;
 }
 
 /// changeToCall - Convert the specified invoke into a normal call.
-static void changeToCall(InvokeInst *II) {
+static void changeToCall(InvokeInst *II, DeferredDominance *DDT = nullptr) {
   SmallVector<Value*, 8> Args(II->arg_begin(), II->arg_end());
   SmallVector<OperandBundleDef, 1> OpBundles;
   II->getOperandBundlesAsDefs(OpBundles);
@@ -1491,11 +1580,16 @@ static void changeToCall(InvokeInst *II)
   II->replaceAllUsesWith(NewCall);
 
   // Follow the call by a branch to the normal destination.
-  BranchInst::Create(II->getNormalDest(), II);
+  BasicBlock *NormalDestBB = II->getNormalDest();
+  BranchInst::Create(NormalDestBB, II);
 
   // Update PHI nodes in the unwind destination
-  II->getUnwindDest()->removePredecessor(II->getParent());
+  BasicBlock *BB = II->getParent();
+  BasicBlock *UnwindDestBB = II->getUnwindDest();
+  UnwindDestBB->removePredecessor(BB);
   II->eraseFromParent();
+  if (DDT)
+    DDT->deleteEdge(BB, UnwindDestBB);
 }
 
 BasicBlock *llvm::changeToInvokeAndSplitBasicBlock(CallInst *CI,
@@ -1536,7 +1630,8 @@ BasicBlock *llvm::changeToInvokeAndSplit
 }
 
 static bool markAliveBlocks(Function &F,
-                            SmallPtrSetImpl<BasicBlock*> &Reachable) {
+                            SmallPtrSetImpl<BasicBlock*> &Reachable,
+                            DeferredDominance *DDT = nullptr) {
   SmallVector<BasicBlock*, 128> Worklist;
   BasicBlock *BB = &F.front();
   Worklist.push_back(BB);
@@ -1556,7 +1651,7 @@ static bool markAliveBlocks(Function &F,
         if (II->getIntrinsicID() == Intrinsic::assume) {
           if (match(II->getArgOperand(0), m_CombineOr(m_Zero(), m_Undef()))) {
             // Don't insert a call to llvm.trap right before the unreachable.
-            changeToUnreachable(II, false);
+            changeToUnreachable(II, false, false, DDT);
             Changed = true;
             break;
           }
@@ -1573,7 +1668,8 @@ static bool markAliveBlocks(Function &F,
           // still be useful for widening.
           if (match(II->getArgOperand(0), m_Zero()))
             if (!isa<UnreachableInst>(II->getNextNode())) {
-              changeToUnreachable(II->getNextNode(), /*UseLLVMTrap=*/ false);
+              changeToUnreachable(II->getNextNode(), /*UseLLVMTrap=*/false,
+                                  false, DDT);
               Changed = true;
               break;
             }
@@ -1583,7 +1679,7 @@ static bool markAliveBlocks(Function &F,
       if (auto *CI = dyn_cast<CallInst>(&I)) {
         Value *Callee = CI->getCalledValue();
         if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
-          changeToUnreachable(CI, /*UseLLVMTrap=*/false);
+          changeToUnreachable(CI, /*UseLLVMTrap=*/false, false, DDT);
           Changed = true;
           break;
         }
@@ -1593,7 +1689,7 @@ static bool markAliveBlocks(Function &F,
           // though.
           if (!isa<UnreachableInst>(CI->getNextNode())) {
             // Don't insert a call to llvm.trap right before the unreachable.
-            changeToUnreachable(CI->getNextNode(), false);
+            changeToUnreachable(CI->getNextNode(), false, false, DDT);
             Changed = true;
           }
           break;
@@ -1612,7 +1708,7 @@ static bool markAliveBlocks(Function &F,
         if (isa<UndefValue>(Ptr) ||
             (isa<ConstantPointerNull>(Ptr) &&
              SI->getPointerAddressSpace() == 0)) {
-          changeToUnreachable(SI, true);
+          changeToUnreachable(SI, true, false, DDT);
           Changed = true;
           break;
         }
@@ -1624,16 +1720,20 @@ static bool markAliveBlocks(Function &F,
       // Turn invokes that call 'nounwind' functions into ordinary calls.
       Value *Callee = II->getCalledValue();
       if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
-        changeToUnreachable(II, true);
+        changeToUnreachable(II, true, false, DDT);
         Changed = true;
       } else if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(&F)) {
         if (II->use_empty() && II->onlyReadsMemory()) {
           // jump to the normal destination branch.
-          BranchInst::Create(II->getNormalDest(), II);
-          II->getUnwindDest()->removePredecessor(II->getParent());
+          BasicBlock *NormalDestBB = II->getNormalDest();
+          BasicBlock *UnwindDestBB = II->getUnwindDest();
+          BranchInst::Create(NormalDestBB, II);
+          UnwindDestBB->removePredecessor(II->getParent());
           II->eraseFromParent();
+          if (DDT)
+            DDT->deleteEdge(BB, UnwindDestBB);
         } else
-          changeToCall(II);
+          changeToCall(II, DDT);
         Changed = true;
       }
     } else if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(Terminator)) {
@@ -1679,7 +1779,7 @@ static bool markAliveBlocks(Function &F,
       }
     }
 
-    Changed |= ConstantFoldTerminator(BB, true);
+    Changed |= ConstantFoldTerminator(BB, true, nullptr, DDT);
     for (BasicBlock *Successor : successors(BB))
       if (Reachable.insert(Successor).second)
         Worklist.push_back(Successor);
@@ -1687,11 +1787,11 @@ static bool markAliveBlocks(Function &F,
   return Changed;
 }
 
-void llvm::removeUnwindEdge(BasicBlock *BB) {
+void llvm::removeUnwindEdge(BasicBlock *BB, DeferredDominance *DDT) {
   TerminatorInst *TI = BB->getTerminator();
 
   if (auto *II = dyn_cast<InvokeInst>(TI)) {
-    changeToCall(II);
+    changeToCall(II, DDT);
     return;
   }
 
@@ -1719,15 +1819,18 @@ void llvm::removeUnwindEdge(BasicBlock *
   UnwindDest->removePredecessor(BB);
   TI->replaceAllUsesWith(NewTI);
   TI->eraseFromParent();
+  if (DDT)
+    DDT->deleteEdge(BB, UnwindDest);
 }
 
 /// removeUnreachableBlocks - Remove blocks that are not reachable, even
 /// if they are in a dead cycle.  Return true if a change was made, false
 /// otherwise. If `LVI` is passed, this function preserves LazyValueInfo
 /// after modifying the CFG.
-bool llvm::removeUnreachableBlocks(Function &F, LazyValueInfo *LVI) {
+bool llvm::removeUnreachableBlocks(Function &F, LazyValueInfo *LVI,
+                                   DeferredDominance *DDT) {
   SmallPtrSet<BasicBlock*, 16> Reachable;
-  bool Changed = markAliveBlocks(F, Reachable);
+  bool Changed = markAliveBlocks(F, Reachable, DDT);
 
   // If there are unreachable blocks in the CFG...
   if (Reachable.size() == F.size())
@@ -1737,25 +1840,39 @@ bool llvm::removeUnreachableBlocks(Funct
   NumRemoved += F.size()-Reachable.size();
 
   // Loop over all of the basic blocks that are not reachable, dropping all of
-  // their internal references...
-  for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB) {
-    if (Reachable.count(&*BB))
+  // their internal references. Update DDT and LVI if available.
+  std::vector <DominatorTree::UpdateType> Updates;
+  for (Function::iterator I = ++F.begin(), E = F.end(); I != E; ++I) {
+    auto *BB = &*I;
+    if (Reachable.count(BB))
       continue;
-
-    for (BasicBlock *Successor : successors(&*BB))
+    for (BasicBlock *Successor : successors(BB)) {
       if (Reachable.count(Successor))
-        Successor->removePredecessor(&*BB);
+        Successor->removePredecessor(BB);
+      if (DDT)
+        Updates.push_back({DominatorTree::Delete, BB, Successor});
+    }
     if (LVI)
-      LVI->eraseBlock(&*BB);
+      LVI->eraseBlock(BB);
     BB->dropAllReferences();
   }
 
-  for (Function::iterator I = ++F.begin(); I != F.end();)
-    if (!Reachable.count(&*I))
-      I = F.getBasicBlockList().erase(I);
-    else
+  for (Function::iterator I = ++F.begin(); I != F.end();) {
+    auto *BB = &*I;
+    if (Reachable.count(BB)) {
+      ++I;
+      continue;
+    }
+    if (DDT) {
+      DDT->deleteBB(BB); // deferred deletion of BB.
       ++I;
+    } else {
+      I = F.getBasicBlockList().erase(I);
+    }
+  }
 
+  if (DDT)
+    DDT->applyUpdates(Updates);
   return true;
 }
 
Index: llvm-toolchain-6.0-6.0.1/test/Analysis/LazyValueAnalysis/lvi-after-jumpthreading.ll
===================================================================
--- llvm-toolchain-6.0-6.0.1.orig/test/Analysis/LazyValueAnalysis/lvi-after-jumpthreading.ll
+++ llvm-toolchain-6.0-6.0.1/test/Analysis/LazyValueAnalysis/lvi-after-jumpthreading.ll
@@ -19,10 +19,13 @@ entry:
 ; CHECK-NEXT:     ; LatticeVal for: 'i32 %a' is: overdefined
 ; CHECK-NEXT:     ; LatticeVal for: 'i32 %length' is: overdefined
 ; CHECK-NEXT:     ; LatticeVal for: '  %iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ]' in BB: '%backedge' is: constantrange<0, 400>
+; CHECK-NEXT:     ; LatticeVal for: '  %iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ]' in BB: '%exit' is: constantrange<399, 400>
 ; CHECK-NEXT:  %iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ]
 ; CHECK-NEXT:     ; LatticeVal for: '  %iv.next = add nsw i32 %iv, 1' in BB: '%backedge' is: constantrange<1, 401>
+; CHECK-NEXT:     ; LatticeVal for: '  %iv.next = add nsw i32 %iv, 1' in BB: '%exit' is: constantrange<400, 401>
 ; CHECK-NEXT:  %iv.next = add nsw i32 %iv, 1
 ; CHECK-NEXT:     ; LatticeVal for: '  %cont = icmp slt i32 %iv.next, 400' in BB: '%backedge' is: overdefined
+; CHECK-NEXT:     ; LatticeVal for: '  %cont = icmp slt i32 %iv.next, 400' in BB: '%exit' is: constantrange<0, -1>
 ; CHECK-NEXT:  %cont = icmp slt i32 %iv.next, 400
 ; CHECK-NOT: loop
 loop:
Index: llvm-toolchain-6.0-6.0.1/test/Transforms/JumpThreading/ddt-crash.ll
===================================================================
--- /dev/null
+++ llvm-toolchain-6.0-6.0.1/test/Transforms/JumpThreading/ddt-crash.ll
@@ -0,0 +1,265 @@
+; RUN: opt < %s -jump-threading -disable-output
+
+%struct.ham = type { i8, i8, i16, i32 }
+%struct.zot = type { i32 (...)** }
+%struct.quux.0 = type { %struct.wombat }
+%struct.wombat = type { %struct.zot }
+
+@global = external global %struct.ham*, align 8
+@global.1 = external constant i8*
+
+declare i32 @wombat.2()
+
+define void @blam() {
+bb:
+  %tmp = load i32, i32* undef
+  %tmp1 = icmp eq i32 %tmp, 0
+  br i1 %tmp1, label %bb11, label %bb2
+
+bb2:
+  %tmp3 = tail call i32 @wombat.2()
+  switch i32 %tmp3, label %bb4 [
+    i32 0, label %bb5
+    i32 1, label %bb7
+    i32 2, label %bb7
+    i32 3, label %bb11
+  ]
+
+bb4:
+  br label %bb7
+
+bb5:
+  %tmp6 = tail call i32 @wombat.2()
+  br label %bb7
+
+bb7:
+  %tmp8 = phi i32 [ 0, %bb5 ], [ 1, %bb4 ], [ 2, %bb2 ], [ 2, %bb2 ]
+  %tmp9 = icmp eq i32 %tmp8, 0
+  br i1 %tmp9, label %bb11, label %bb10
+
+bb10:
+  ret void
+
+bb11:
+  ret void
+}
+
+define void @spam(%struct.ham* %arg) {
+bb:
+  %tmp = load i8, i8* undef, align 8
+  switch i8 %tmp, label %bb11 [
+    i8 1, label %bb11
+    i8 2, label %bb11
+    i8 3, label %bb1
+    i8 4, label %bb1
+  ]
+
+bb1:
+  br label %bb2
+
+bb2:
+  %tmp3 = phi i32 [ 0, %bb1 ], [ %tmp3, %bb8 ]
+  br label %bb4
+
+bb4:
+  %tmp5 = load i8, i8* undef, align 8
+  switch i8 %tmp5, label %bb11 [
+    i8 0, label %bb11
+    i8 1, label %bb10
+    i8 2, label %bb10
+    i8 3, label %bb6
+    i8 4, label %bb6
+  ]
+
+bb6:
+  br label %bb7
+
+bb7:
+  br i1 undef, label %bb8, label %bb10
+
+bb8:
+  %tmp9 = icmp eq %struct.ham* undef, %arg
+  br i1 %tmp9, label %bb10, label %bb2
+
+bb10:
+  switch i32 %tmp3, label %bb4 [
+    i32 0, label %bb14
+    i32 1, label %bb11
+    i32 2, label %bb12
+  ]
+
+bb11:
+  unreachable
+
+bb12:
+  %tmp13 = load %struct.ham*, %struct.ham** undef
+  br label %bb14
+
+bb14:
+  %tmp15 = phi %struct.ham* [ %tmp13, %bb12 ], [ null, %bb10 ]
+  br label %bb16
+
+bb16:
+  %tmp17 = load i8, i8* undef, align 8
+  switch i8 %tmp17, label %bb11 [
+    i8 0, label %bb11
+    i8 11, label %bb18
+    i8 12, label %bb18
+  ]
+
+bb18:
+  br label %bb19
+
+bb19:
+  br label %bb20
+
+bb20:
+  %tmp21 = load %struct.ham*, %struct.ham** undef
+  switch i8 undef, label %bb22 [
+    i8 0, label %bb4
+    i8 11, label %bb10
+    i8 12, label %bb10
+  ]
+
+bb22:
+  br label %bb23
+
+bb23:
+  %tmp24 = icmp eq %struct.ham* %tmp21, null
+  br i1 %tmp24, label %bb35, label %bb25
+
+bb25:
+  %tmp26 = icmp eq %struct.ham* %tmp15, null
+  br i1 %tmp26, label %bb34, label %bb27
+
+bb27:
+  %tmp28 = load %struct.ham*, %struct.ham** undef
+  %tmp29 = icmp eq %struct.ham* %tmp28, %tmp21
+  br i1 %tmp29, label %bb35, label %bb30
+
+bb30:
+  br label %bb31
+
+bb31:
+  %tmp32 = load i8, i8* undef, align 8
+  %tmp33 = icmp eq i8 %tmp32, 0
+  br i1 %tmp33, label %bb31, label %bb34
+
+bb34:
+  br label %bb35
+
+bb35:
+  %tmp36 = phi i1 [ true, %bb34 ], [ false, %bb23 ], [ true, %bb27 ]
+  br label %bb37
+
+bb37:
+  %tmp38 = icmp eq %struct.ham* %tmp15, null
+  br i1 %tmp38, label %bb39, label %bb41
+
+bb39:
+  %tmp40 = load %struct.ham*, %struct.ham** @global
+  br label %bb41
+
+bb41:
+  %tmp42 = select i1 %tmp36, %struct.ham* undef, %struct.ham* undef
+  ret void
+}
+
+declare i32 @foo(...)
+
+define void @zot() align 2 personality i8* bitcast (i32 (...)* @foo to i8*) {
+bb:
+  invoke void @bar()
+          to label %bb1 unwind label %bb3
+
+bb1:
+  invoke void @bar()
+          to label %bb2 unwind label %bb4
+
+bb2:
+  invoke void @bar()
+          to label %bb6 unwind label %bb17
+
+bb3:
+  %tmp = landingpad { i8*, i32 }
+          catch i8* bitcast (i8** @global.1 to i8*)
+          catch i8* null
+  unreachable
+
+bb4:
+  %tmp5 = landingpad { i8*, i32 }
+          catch i8* bitcast (i8** @global.1 to i8*)
+          catch i8* null
+  unreachable
+
+bb6:
+  invoke void @bar()
+          to label %bb7 unwind label %bb19
+
+bb7:
+  invoke void @bar()
+          to label %bb10 unwind label %bb8
+
+bb8:
+  %tmp9 = landingpad { i8*, i32 }
+          cleanup
+          catch i8* bitcast (i8** @global.1 to i8*)
+          catch i8* null
+  unreachable
+
+bb10:
+  %tmp11 = load i32 (%struct.zot*)*, i32 (%struct.zot*)** undef, align 8
+  %tmp12 = invoke i32 %tmp11(%struct.zot* nonnull undef)
+          to label %bb13 unwind label %bb21
+
+bb13:
+  invoke void @bar()
+          to label %bb14 unwind label %bb23
+
+bb14:
+  %tmp15 = load i32 (%struct.zot*)*, i32 (%struct.zot*)** undef, align 8
+  %tmp16 = invoke i32 %tmp15(%struct.zot* nonnull undef)
+          to label %bb26 unwind label %bb23
+
+bb17:
+  %tmp18 = landingpad { i8*, i32 }
+          catch i8* bitcast (i8** @global.1 to i8*)
+          catch i8* null
+  unreachable
+
+bb19:
+  %tmp20 = landingpad { i8*, i32 }
+          catch i8* bitcast (i8** @global.1 to i8*)
+          catch i8* null
+  unreachable
+
+bb21:
+  %tmp22 = landingpad { i8*, i32 }
+          catch i8* bitcast (i8** @global.1 to i8*)
+          catch i8* null
+  unreachable
+
+bb23:
+  %tmp24 = phi %struct.quux.0* [ null, %bb26 ], [ null, %bb14 ], [ undef, %bb13 ]
+  %tmp25 = landingpad { i8*, i32 }
+          catch i8* bitcast (i8** @global.1 to i8*)
+          catch i8* null
+  br label %bb30
+
+bb26:
+  %tmp27 = load i32 (%struct.zot*)*, i32 (%struct.zot*)** undef, align 8
+  %tmp28 = invoke i32 %tmp27(%struct.zot* nonnull undef)
+          to label %bb29 unwind label %bb23
+
+bb29:
+  unreachable
+
+bb30:
+  %tmp31 = icmp eq %struct.quux.0* %tmp24, null
+  br i1 %tmp31, label %bb32, label %bb29
+
+bb32:
+  unreachable
+}
+
+declare void @bar()
Index: llvm-toolchain-6.0-6.0.1/test/Transforms/JumpThreading/ddt-crash2.ll
===================================================================
--- /dev/null
+++ llvm-toolchain-6.0-6.0.1/test/Transforms/JumpThreading/ddt-crash2.ll
@@ -0,0 +1,40 @@
+; RUN: opt < %s -jump-threading -disable-output
+
+%struct.aaa = type { i8 }
+
+define void @chrome(%struct.aaa* noalias sret %arg) local_unnamed_addr #0 align 2 personality i8* bitcast (i32 (...)* @chrome2 to i8*) {
+bb:
+  %tmp = load i32, i32* undef, align 4
+  %tmp1 = icmp eq i32 %tmp, 0
+  br i1 %tmp1, label %bb2, label %bb13
+
+bb2:
+  %tmp3 = getelementptr inbounds %struct.aaa, %struct.aaa* %arg, i64 0, i32 0
+  %tmp4 = load i8, i8* %tmp3, align 1
+  %tmp5 = icmp eq i8 %tmp4, 0
+  br i1 %tmp5, label %bb6, label %bb7
+
+bb6:
+  store i8 0, i8* %tmp3, align 1
+  br label %bb7
+
+bb7:
+  %tmp8 = load i8, i8* %tmp3, align 1
+  %tmp9 = icmp ne i8 %tmp8, 0
+  %tmp10 = select i1 %tmp9, i1 true, i1 false
+  br i1 %tmp10, label %bb12, label %bb11
+
+bb11:
+  br label %bb12
+
+bb12:
+  br i1 %tmp9, label %bb14, label %bb13
+
+bb13:
+  unreachable
+
+bb14:
+  ret void
+}
+
+declare i32 @chrome2(...)
Index: llvm-toolchain-6.0-6.0.1/test/Transforms/JumpThreading/lvi-tristate.ll
===================================================================
--- /dev/null
+++ llvm-toolchain-6.0-6.0.1/test/Transforms/JumpThreading/lvi-tristate.ll
@@ -0,0 +1,50 @@
+; RUN: opt -jump-threading -simplifycfg -S < %s | FileCheck %s
+; CHECK-NOT: bb6:
+; CHECK-NOT: bb7:
+; CHECK-NOT: bb8:
+; CHECK-NOT: bb11:
+; CHECK-NOT: bb12:
+; CHECK: bb:
+; CHECK: bb2:
+; CHECK: bb4:
+; CHECK: bb10:
+; CHECK: bb13:
+declare void @ham()
+
+define void @hoge() {
+bb:
+  %tmp = and i32 undef, 1073741823
+  %tmp1 = icmp eq i32 %tmp, 2
+  br i1 %tmp1, label %bb12, label %bb2
+
+bb2:
+  %tmp3 = icmp eq i32 %tmp, 3
+  br i1 %tmp3, label %bb13, label %bb4
+
+bb4:
+  %tmp5 = icmp eq i32 %tmp, 5
+  br i1 %tmp5, label %bb6, label %bb7
+
+bb6:
+  tail call void @ham()
+  br label %bb7
+
+bb7:
+  br i1 %tmp3, label %bb13, label %bb8
+
+bb8:
+  %tmp9 = icmp eq i32 %tmp, 4
+  br i1 %tmp9, label %bb13, label %bb10
+
+bb10:
+  br i1 %tmp9, label %bb11, label %bb13
+
+bb11:
+  br label %bb13
+
+bb12:
+  br label %bb2
+
+bb13:
+  ret void
+}
Index: llvm-toolchain-6.0-6.0.1/unittests/IR/CMakeLists.txt
===================================================================
--- llvm-toolchain-6.0-6.0.1.orig/unittests/IR/CMakeLists.txt
+++ llvm-toolchain-6.0-6.0.1/unittests/IR/CMakeLists.txt
@@ -15,6 +15,7 @@ set(IRSources
   ConstantsTest.cpp
   DebugInfoTest.cpp
   DebugTypeODRUniquingTest.cpp
+  DeferredDominanceTest.cpp
   DominatorTreeTest.cpp
   DominatorTreeBatchUpdatesTest.cpp
   FunctionTest.cpp
Index: llvm-toolchain-6.0-6.0.1/unittests/IR/DeferredDominanceTest.cpp
===================================================================
--- /dev/null
+++ llvm-toolchain-6.0-6.0.1/unittests/IR/DeferredDominanceTest.cpp
@@ -0,0 +1,344 @@
+//===- llvm/unittests/IR/DeferredDominanceTest.cpp - DDT unit tests -------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/AsmParser/Parser.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/SourceMgr.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+static std::unique_ptr<Module> makeLLVMModule(LLVMContext &Context,
+                                              StringRef ModuleStr) {
+  SMDiagnostic Err;
+  std::unique_ptr<Module> M = parseAssemblyString(ModuleStr, Err, Context);
+  assert(M && "Bad LLVM IR?");
+  return M;
+}
+
+TEST(DeferredDominance, BasicOperations) {
+  StringRef FuncName = "f";
+  StringRef ModuleString =
+      "define i32 @f(i32 %i, i32 *%p) {\n"
+      " bb0:\n"
+      "   store i32 %i, i32 *%p\n"
+      "   switch i32 %i, label %bb1 [\n"
+      "     i32 0, label %bb2\n"
+      "     i32 1, label %bb2\n"
+      "     i32 2, label %bb3\n"
+      "   ]\n"
+      " bb1:\n"
+      "   ret i32 1\n"
+      " bb2:\n"
+      "   ret i32 2\n"
+      " bb3:\n"
+      "   ret i32 3\n"
+      "}\n";
+  // Make the module.
+  LLVMContext Context;
+  std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleString);
+  Function *F = M->getFunction(FuncName);
+  ASSERT_NE(F, nullptr) << "Couldn't get function " << FuncName << ".";
+
+  // Make the DDT.
+  DominatorTree DT(*F);
+  DeferredDominance DDT(DT);
+  ASSERT_TRUE(DDT.flush().verify());
+
+  Function::iterator FI = F->begin();
+  BasicBlock *BB0 = &*FI++;
+  BasicBlock *BB1 = &*FI++;
+  BasicBlock *BB2 = &*FI++;
+  BasicBlock *BB3 = &*FI++;
+
+  // Test discards of invalid self-domination updates. These use the single
+  // short-hand interface but are still queued inside DDT.
+  DDT.deleteEdge(BB0, BB0);
+  DDT.insertEdge(BB1, BB1);
+
+  // Delete edge bb0 -> bb3 and push the update twice to verify duplicate
+  // entries are discarded.
+  std::vector<DominatorTree::UpdateType> Updates;
+  Updates.reserve(4);
+  Updates.push_back({DominatorTree::Delete, BB0, BB3});
+  Updates.push_back({DominatorTree::Delete, BB0, BB3});
+
+  // Unnecessary Insert: no edge bb1 -> bb2 after change to bb0.
+  Updates.push_back({DominatorTree::Insert, BB1, BB2});
+  // Unnecessary Delete: edge exists bb0 -> bb1 after change to bb0.
+  Updates.push_back({DominatorTree::Delete, BB0, BB1});
+
+  // CFG Change: remove edge bb0 -> bb3 and one duplicate edge bb0 -> bb2.
+  EXPECT_EQ(BB0->getTerminator()->getNumSuccessors(), 4u);
+  BB0->getTerminator()->eraseFromParent();
+  BranchInst::Create(BB1, BB2, ConstantInt::getTrue(F->getContext()), BB0);
+  EXPECT_EQ(BB0->getTerminator()->getNumSuccessors(), 2u);
+
+  // Deletion of a BasicBlock is an immediate event. We remove all uses to the
+  // contained Instructions and change the Terminator to "unreachable" when
+  // queued for deletion. Its parent is still F until DDT.flush() is called. We
+  // don't defer this action because it can cause problems for other transforms
+  // or analysis as it's part of the actual CFG. We only defer updates to the
+  // DominatorTree. This code will crash if it is placed before the
+  // BranchInst::Create() call above.
+  ASSERT_FALSE(isa<UnreachableInst>(BB3->getTerminator()));
+  EXPECT_FALSE(DDT.pendingDeletedBB(BB3));
+  DDT.deleteBB(BB3);
+  EXPECT_TRUE(DDT.pendingDeletedBB(BB3));
+  ASSERT_TRUE(isa<UnreachableInst>(BB3->getTerminator()));
+  EXPECT_EQ(BB3->getParent(), F);
+
+  // Verify. Updates to DDT must be applied *after* all changes to the CFG
+  // (including block deletion).
+  DDT.applyUpdates(Updates);
+  ASSERT_TRUE(DDT.flush().verify());
+}
+
+TEST(DeferredDominance, PairedUpdate) {
+  StringRef FuncName = "f";
+  StringRef ModuleString =
+      "define i32 @f(i32 %i, i32 *%p) {\n"
+      " bb0:\n"
+      "   store i32 %i, i32 *%p\n"
+      "   switch i32 %i, label %bb1 [\n"
+      "     i32 0, label %bb2\n"
+      "     i32 1, label %bb2\n"
+      "   ]\n"
+      " bb1:\n"
+      "   ret i32 1\n"
+      " bb2:\n"
+      "   ret i32 2\n"
+      "}\n";
+  // Make the module.
+  LLVMContext Context;
+  std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleString);
+  Function *F = M->getFunction(FuncName);
+  ASSERT_NE(F, nullptr) << "Couldn't get function " << FuncName << ".";
+
+  // Make the DDT.
+  DominatorTree DT(*F);
+  DeferredDominance DDT(DT);
+  ASSERT_TRUE(DDT.flush().verify());
+
+  Function::iterator FI = F->begin();
+  BasicBlock *BB0 = &*FI++;
+  BasicBlock *BB1 = &*FI++;
+  BasicBlock *BB2 = &*FI++;
+
+  // CFG Change: only edge from bb0 is bb0 -> bb1.
+  EXPECT_EQ(BB0->getTerminator()->getNumSuccessors(), 3u);
+  BB0->getTerminator()->eraseFromParent();
+  BranchInst::Create(BB1, BB0);
+  EXPECT_EQ(BB0->getTerminator()->getNumSuccessors(), 1u);
+
+  // Must be done after the CFG change. The applyUpdate() routine analyzes the
+  // current state of the CFG.
+  DDT.deleteEdge(BB0, BB2);
+
+  // CFG Change: bb0 now has bb0 -> bb1 and bb0 -> bb2.
+  // With this change no dominance has been altered from the original IR. DT
+  // doesn't care if the type of TerminatorInstruction changed, only if the
+  // unique edges have.
+  EXPECT_EQ(BB0->getTerminator()->getNumSuccessors(), 1u);
+  BB0->getTerminator()->eraseFromParent();
+  BranchInst::Create(BB1, BB2, ConstantInt::getTrue(F->getContext()), BB0);
+  EXPECT_EQ(BB0->getTerminator()->getNumSuccessors(), 2u);
+
+  // Must be done after the CFG change. The applyUpdate() routine analyzes the
+  // current state of the CFG. This DDT update pairs with the previous one and
+  // is cancelled out before ever applying updates to DT.
+  DDT.insertEdge(BB0, BB2);
+
+  // Test the empty DeletedBB list.
+  EXPECT_FALSE(DDT.pendingDeletedBB(BB0));
+  EXPECT_FALSE(DDT.pendingDeletedBB(BB1));
+  EXPECT_FALSE(DDT.pendingDeletedBB(BB2));
+
+  // The DT has no changes, this flush() simply returns a reference to the
+  // internal DT calculated at the beginning of this test.
+  ASSERT_TRUE(DDT.flush().verify());
+}
+
+TEST(DeferredDominance, ReplaceEntryBB) {
+  StringRef FuncName = "f";
+  StringRef ModuleString =
+      "define i32 @f() {\n"
+      "bb0:\n"
+      "   br label %bb1\n"
+      " bb1:\n"
+      "   ret i32 1\n"
+      "}\n";
+  // Make the module.
+  LLVMContext Context;
+  std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleString);
+  Function *F = M->getFunction(FuncName);
+  ASSERT_NE(F, nullptr) << "Couldn't get function " << FuncName << ".";
+
+  // Make the DDT.
+  DominatorTree DT(*F);
+  DeferredDominance DDT(DT);
+  ASSERT_TRUE(DDT.flush().verify());
+
+  Function::iterator FI = F->begin();
+  BasicBlock *BB0 = &*FI++;
+  BasicBlock *BB1 = &*FI++;
+
+  // Add a block as the new function entry BB. We also link it to BB0.
+  BasicBlock *NewEntry =
+      BasicBlock::Create(F->getContext(), "new_entry", F, BB0);
+  BranchInst::Create(BB0, NewEntry);
+  EXPECT_EQ(F->begin()->getName(), NewEntry->getName());
+  EXPECT_TRUE(&F->getEntryBlock() == NewEntry);
+
+  // Insert the new edge between new_eentry -> bb0. Without this the
+  // recalculate() call below will not actually recalculate the DT as there
+  // are no changes pending and no blocks deleted.
+  DDT.insertEdge(NewEntry, BB0);
+
+  // Changing the Entry BB requires a full recalulation.
+  DDT.recalculate(*F);
+  ASSERT_TRUE(DDT.flush().verify());
+
+  // CFG Change: remove new_edge -> bb0 and redirect to new_edge -> bb1.
+  EXPECT_EQ(NewEntry->getTerminator()->getNumSuccessors(), 1u);
+  NewEntry->getTerminator()->eraseFromParent();
+  BranchInst::Create(BB1, NewEntry);
+  EXPECT_EQ(BB0->getTerminator()->getNumSuccessors(), 1u);
+
+  // Update the DDT. At this point bb0 now has no predecessors but is still a
+  // Child of F.
+  DDT.applyUpdates({{DominatorTree::Delete, NewEntry, BB0},
+                    {DominatorTree::Insert, NewEntry, BB1}});
+  ASSERT_TRUE(DDT.flush().verify());
+
+  // Now remove bb0 from F.
+  ASSERT_FALSE(isa<UnreachableInst>(BB0->getTerminator()));
+  EXPECT_FALSE(DDT.pendingDeletedBB(BB0));
+  DDT.deleteBB(BB0);
+  EXPECT_TRUE(DDT.pendingDeletedBB(BB0));
+  ASSERT_TRUE(isa<UnreachableInst>(BB0->getTerminator()));
+  EXPECT_EQ(BB0->getParent(), F);
+
+  // Perform a full recalculation of the DDT. It is not necessary here but we
+  // do this to test the case when there are no pending DT updates but there are
+  // pending deleted BBs.
+  DDT.recalculate(*F);
+  ASSERT_TRUE(DDT.flush().verify());
+}
+
+TEST(DeferredDominance, InheritedPreds) {
+  StringRef FuncName = "f";
+  StringRef ModuleString =
+      "define i32 @f(i32 %i, i32 *%p) {\n"
+      " bb0:\n"
+      "   store i32 %i, i32 *%p\n"
+      "   switch i32 %i, label %bb1 [\n"
+      "     i32 2, label %bb2\n"
+      "     i32 3, label %bb3\n"
+      "   ]\n"
+      " bb1:\n"
+      "   br label %bb3\n"
+      " bb2:\n"
+      "   br label %bb3\n"
+      " bb3:\n"
+      "   ret i32 3\n"
+      "}\n";
+  // Make the module.
+  LLVMContext Context;
+  std::unique_ptr<Module> M = makeLLVMModule(Context, ModuleString);
+  Function *F = M->getFunction(FuncName);
+  ASSERT_NE(F, nullptr) << "Couldn't get function " << FuncName << ".";
+
+  // Make the DDT.
+  DominatorTree DT(*F);
+  DeferredDominance DDT(DT);
+  ASSERT_TRUE(DDT.flush().verify());
+
+  Function::iterator FI = F->begin();
+  BasicBlock *BB0 = &*FI++;
+  BasicBlock *BB1 = &*FI++;
+  BasicBlock *BB2 = &*FI++;
+  BasicBlock *BB3 = &*FI++;
+
+  // There are several CFG locations where we have:
+  //
+  //   pred1..predN
+  //    |        |
+  //    +> curr <+    converted into:   pred1..predN curr
+  //        |                            |        |
+  //        v                            +> succ <+
+  //       succ
+  //
+  // There is a specific shape of this we have to be careful of:
+  //
+  //   pred1..predN
+  //   ||        |
+  //   |+> curr <+    converted into:   pred1..predN curr
+  //   |    |                            |        |
+  //   |    v                            +> succ <+
+  //   +-> succ
+  //
+  // While the final CFG form is functionally identical the updates to
+  // DDT are not. In the first case we must have DDT.insertEdge(Pred1, Succ)
+  // while in the latter case we must *NOT* have DDT.insertEdge(Pred1, Succ).
+
+  // CFG Change: bb0 now only has bb0 -> bb1 and bb0 -> bb3. We are preparing to
+  // remove bb2.
+  EXPECT_EQ(BB0->getTerminator()->getNumSuccessors(), 3u);
+  BB0->getTerminator()->eraseFromParent();
+  BranchInst::Create(BB1, BB3, ConstantInt::getTrue(F->getContext()), BB0);
+  EXPECT_EQ(BB0->getTerminator()->getNumSuccessors(), 2u);
+
+  // Remove bb2 from F. This has to happen before the call to applyUpdates() for
+  // DDT to detect there is no longer an edge between bb2 -> bb3. The deleteBB()
+  // method converts bb2's TI into "unreachable".
+  ASSERT_FALSE(isa<UnreachableInst>(BB2->getTerminator()));
+  EXPECT_FALSE(DDT.pendingDeletedBB(BB2));
+  DDT.deleteBB(BB2);
+  EXPECT_TRUE(DDT.pendingDeletedBB(BB2));
+  ASSERT_TRUE(isa<UnreachableInst>(BB2->getTerminator()));
+  EXPECT_EQ(BB2->getParent(), F);
+
+  // Queue up the DDT updates.
+  std::vector<DominatorTree::UpdateType> Updates;
+  Updates.reserve(4);
+  Updates.push_back({DominatorTree::Delete, BB0, BB2});
+  Updates.push_back({DominatorTree::Delete, BB2, BB3});
+
+  // Handle the specific shape case next.
+  // CFG Change: bb0 now only branches to bb3. We are preparing to remove bb1.
+  EXPECT_EQ(BB0->getTerminator()->getNumSuccessors(), 2u);
+  BB0->getTerminator()->eraseFromParent();
+  BranchInst::Create(BB3, BB0);
+  EXPECT_EQ(BB0->getTerminator()->getNumSuccessors(), 1u);
+
+  // Remove bb1 from F. This has to happen before the call to applyUpdates() for
+  // DDT to detect there is no longer an edge between bb1 -> bb3. The deleteBB()
+  // method converts bb1's TI into "unreachable".
+  ASSERT_FALSE(isa<UnreachableInst>(BB1->getTerminator()));
+  EXPECT_FALSE(DDT.pendingDeletedBB(BB1));
+  DDT.deleteBB(BB1);
+  EXPECT_TRUE(DDT.pendingDeletedBB(BB1));
+  ASSERT_TRUE(isa<UnreachableInst>(BB1->getTerminator()));
+  EXPECT_EQ(BB1->getParent(), F);
+
+  // Update the DDT. In this case we don't call DDT.insertEdge(BB0, BB3) because
+  // the edge previously existed at the start of this test when DT was first
+  // created.
+  Updates.push_back({DominatorTree::Delete, BB0, BB1});
+  Updates.push_back({DominatorTree::Delete, BB1, BB3});
+
+  // Verify everything.
+  DDT.applyUpdates(Updates);
+  ASSERT_TRUE(DDT.flush().verify());
+}