MFC r309124:

Upgrade our copies of clang, llvm, lldb, compiler-rt and libc++ to 3.9.0
release, and add lld 3.9.0.  Also completely revamp the build system for
clang, llvm, lldb and their related tools.

Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
support to build; see UPDATING for more information.

Release notes for llvm, clang and lld are available here:
<http://llvm.org/releases/3.9.0/docs/ReleaseNotes.html>
<http://llvm.org/releases/3.9.0/tools/clang/docs/ReleaseNotes.html>
<http://llvm.org/releases/3.9.0/tools/lld/docs/ReleaseNotes.html>

Thanks to Ed Maste, Bryan Drewery, Andrew Turner, Antoine Brodin and Jan
Beich for their help.

Relnotes:	yes

MFC r309147:

Pull in r282174 from upstream llvm trunk (by Krzysztof Parzyszek):

  [PPC] Set SP after loading data from stack frame, if no red zone is
  present

  Follow-up to r280705: Make sure that the SP is only restored after
  all data is loaded from the stack frame, if there is no red zone.

  This completes the fix for
  https://llvm.org/bugs/show_bug.cgi?id=26519.

  Differential Revision: https://reviews.llvm.org/D24466

Reported by:    Mark Millard
PR:             214433

MFC r309149:

Pull in r283060 from upstream llvm trunk (by Hal Finkel):

  [PowerPC] Refactor soft-float support, and enable PPC64 soft float

  This change enables soft-float for PowerPC64, and also makes
  soft-float disable all vector instruction sets for both 32-bit and
  64-bit modes. This latter part is necessary because the PPC backend
  canonicalizes many Altivec vector types to floating-point types, and
  so soft-float breaks scalarization support for many operations. Both
  for embedded targets and for operating-system kernels desiring
  soft-float support, it seems reasonable that disabling hardware
  floating-point also disables vector instructions (embedded targets
  without hardware floating point support are unlikely to have Altivec,
  etc. and operating system kernels desiring not to use floating-point
  registers to lower syscall cost are unlikely to want to use vector
  registers either). If someone needs this to work, we'll need to
  change the fact that we promote many Altivec operations to act on
  v4f32. To make it possible to disable Altivec when soft-float is
  enabled, hardware floating-point support needs to be expressed as a
  positive feature, like the others, and not a negative feature,
  because target features cannot have dependencies on the disabling of
  some other feature. So +soft-float has now become -hard-float.

  Fixes PR26970.

Pull in r283061 from upstream clang trunk (by Hal Finkel):

  [PowerPC] Enable soft-float for PPC64, and +soft-float -> -hard-float

  Enable soft-float support on PPC64, as the backend now supports it.
  Also, the backend now uses -hard-float instead of +soft-float, so set
  the target features accordingly.

  Fixes PR26970.

Reported by:	Mark Millard
PR:		214433

MFC r309212:

Add a few missed clang 3.9.0 files to OptionalObsoleteFiles.

MFC r309262:

Fix packaging for clang, lldb and lld 3.9.0

During the upgrade of clang/llvm etc to 3.9.0 in r309124, the PACKAGE
directive in the usr.bin/clang/*.mk files got dropped accidentally.

Restore it, with a few minor changes and additions:
* Correct license in clang.ucl to NCSA
* Add PACKAGE=clang for clang and most of the "ll" tools
* Put lldb in its own package
* Put lld in its own package

Reviewed by:	gjb, jmallett
Differential Revision: https://reviews.freebsd.org/D8666

MFC r309656:

During the bootstrap phase, when building the minimal llvm library on
PowerPC, add lib/Support/Atomic.cpp.  This is needed because upstream
llvm revision r271821 disabled the use of std::call_once, which causes
some fallback functions from Atomic.cpp to be used instead.

Reported by:	Mark Millard
PR:		214902

MFC r309835:

Tentatively apply https://reviews.llvm.org/D18730 to work around gcc PR
70528 (bogus error: constructor required before non-static data member).
This should fix buildworld with the external gcc package.

Reported by:	https://jenkins.freebsd.org/job/FreeBSD_HEAD_amd64_gcc/

MFC r310194:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
3.9.1 release.

Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
support to build; see UPDATING for more information.

Release notes for llvm, clang and lld will be available here:
<http://releases.llvm.org/3.9.1/docs/ReleaseNotes.html>
<http://releases.llvm.org/3.9.1/tools/clang/docs/ReleaseNotes.html>
<http://releases.llvm.org/3.9.1/tools/lld/docs/ReleaseNotes.html>

Relnotes:	yes

1 files changed, 380 insertions, 117 deletions

diff --git a/contrib/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/contrib/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index 0d68f18..861a50c 100644
--- a/contrib/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/contrib/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -16,8 +16,8 @@
 // case, we need to generate code to execute these 'left over' iterations.
 //
 // The current strategy generates an if-then-else sequence prior to the
-// unrolled loop to execute the 'left over' iterations.  Other strategies
-// include generate a loop before or after the unrolled loop.
+// unrolled loop to execute the 'left over' iterations before or after the
+// unrolled loop.
 //
 //===----------------------------------------------------------------------===//
 
@@ -60,91 +60,220 @@ STATISTIC(NumRuntimeUnrolled,
 ///   than the unroll factor.
 ///
 static void ConnectProlog(Loop *L, Value *BECount, unsigned Count,
-                          BasicBlock *LastPrologBB, BasicBlock *PrologEnd,
-                          BasicBlock *OrigPH, BasicBlock *NewPH,
-                          ValueToValueMapTy &VMap, DominatorTree *DT,
-                          LoopInfo *LI, bool PreserveLCSSA) {
+                          BasicBlock *PrologExit, BasicBlock *PreHeader,
+                          BasicBlock *NewPreHeader, ValueToValueMapTy &VMap,
+                          DominatorTree *DT, LoopInfo *LI, bool PreserveLCSSA) {
   BasicBlock *Latch = L->getLoopLatch();
   assert(Latch && "Loop must have a latch");
+  BasicBlock *PrologLatch = cast<BasicBlock>(VMap[Latch]);
 
   // Create a PHI node for each outgoing value from the original loop
   // (which means it is an outgoing value from the prolog code too).
   // The new PHI node is inserted in the prolog end basic block.
-  // The new PHI name is added as an operand of a PHI node in either
+  // The new PHI node value is added as an operand of a PHI node in either
   // the loop header or the loop exit block.
-  for (succ_iterator SBI = succ_begin(Latch), SBE = succ_end(Latch);
-       SBI != SBE; ++SBI) {
-    for (BasicBlock::iterator BBI = (*SBI)->begin();
-         PHINode *PN = dyn_cast<PHINode>(BBI); ++BBI) {
-
+  for (BasicBlock *Succ : successors(Latch)) {
+    for (Instruction &BBI : *Succ) {
+      PHINode *PN = dyn_cast<PHINode>(&BBI);
+      // Exit when we passed all PHI nodes.
+      if (!PN)
+        break;
       // Add a new PHI node to the prolog end block and add the
       // appropriate incoming values.
-      PHINode *NewPN = PHINode::Create(PN->getType(), 2, PN->getName()+".unr",
-                                       PrologEnd->getTerminator());
+      PHINode *NewPN = PHINode::Create(PN->getType(), 2, PN->getName() + ".unr",
+                                       PrologExit->getFirstNonPHI());
       // Adding a value to the new PHI node from the original loop preheader.
       // This is the value that skips all the prolog code.
       if (L->contains(PN)) {
-        NewPN->addIncoming(PN->getIncomingValueForBlock(NewPH), OrigPH);
+        NewPN->addIncoming(PN->getIncomingValueForBlock(NewPreHeader),
+                           PreHeader);
       } else {
-        NewPN->addIncoming(UndefValue::get(PN->getType()), OrigPH);
+        NewPN->addIncoming(UndefValue::get(PN->getType()), PreHeader);
       }
 
       Value *V = PN->getIncomingValueForBlock(Latch);
       if (Instruction *I = dyn_cast<Instruction>(V)) {
         if (L->contains(I)) {
-          V = VMap[I];
+          V = VMap.lookup(I);
         }
       }
       // Adding a value to the new PHI node from the last prolog block
       // that was created.
-      NewPN->addIncoming(V, LastPrologBB);
+      NewPN->addIncoming(V, PrologLatch);
 
       // Update the existing PHI node operand with the value from the
       // new PHI node.  How this is done depends on if the existing
       // PHI node is in the original loop block, or the exit block.
       if (L->contains(PN)) {
-        PN->setIncomingValue(PN->getBasicBlockIndex(NewPH), NewPN);
+        PN->setIncomingValue(PN->getBasicBlockIndex(NewPreHeader), NewPN);
       } else {
-        PN->addIncoming(NewPN, PrologEnd);
+        PN->addIncoming(NewPN, PrologExit);
       }
     }
   }
 
-  // Create a branch around the orignal loop, which is taken if there are no
+  // Create a branch around the original loop, which is taken if there are no
   // iterations remaining to be executed after running the prologue.
-  Instruction *InsertPt = PrologEnd->getTerminator();
+  Instruction *InsertPt = PrologExit->getTerminator();
   IRBuilder<> B(InsertPt);
 
   assert(Count != 0 && "nonsensical Count!");
 
-  // If BECount <u (Count - 1) then (BECount + 1) & (Count - 1) == (BECount + 1)
-  // (since Count is a power of 2).  This means %xtraiter is (BECount + 1) and
-  // and all of the iterations of this loop were executed by the prologue.  Note
-  // that if BECount <u (Count - 1) then (BECount + 1) cannot unsigned-overflow.
+  // If BECount <u (Count - 1) then (BECount + 1) % Count == (BECount + 1)
+  // This means %xtraiter is (BECount + 1) and all of the iterations of this
+  // loop were executed by the prologue.  Note that if BECount <u (Count - 1)
+  // then (BECount + 1) cannot unsigned-overflow.
   Value *BrLoopExit =
       B.CreateICmpULT(BECount, ConstantInt::get(BECount->getType(), Count - 1));
   BasicBlock *Exit = L->getUniqueExitBlock();
   assert(Exit && "Loop must have a single exit block only");
   // Split the exit to maintain loop canonicalization guarantees
-  SmallVector<BasicBlock*, 4> Preds(pred_begin(Exit), pred_end(Exit));
+  SmallVector<BasicBlock*, 4> Preds(predecessors(Exit));
   SplitBlockPredecessors(Exit, Preds, ".unr-lcssa", DT, LI,
                          PreserveLCSSA);
   // Add the branch to the exit block (around the unrolled loop)
-  B.CreateCondBr(BrLoopExit, Exit, NewPH);
+  B.CreateCondBr(BrLoopExit, Exit, NewPreHeader);
+  InsertPt->eraseFromParent();
+}
+
+/// Connect the unrolling epilog code to the original loop.
+/// The unrolling epilog code contains code to execute the
+/// 'extra' iterations if the run-time trip count modulo the
+/// unroll count is non-zero.
+///
+/// This function performs the following:
+/// - Update PHI nodes at the unrolling loop exit and epilog loop exit
+/// - Create PHI nodes at the unrolling loop exit to combine
+///   values that exit the unrolling loop code and jump around it.
+/// - Update PHI operands in the epilog loop by the new PHI nodes
+/// - Branch around the epilog loop if extra iters (ModVal) is zero.
+///
+static void ConnectEpilog(Loop *L, Value *ModVal, BasicBlock *NewExit,
+                          BasicBlock *Exit, BasicBlock *PreHeader,
+                          BasicBlock *EpilogPreHeader, BasicBlock *NewPreHeader,
+                          ValueToValueMapTy &VMap, DominatorTree *DT,
+                          LoopInfo *LI, bool PreserveLCSSA)  {
+  BasicBlock *Latch = L->getLoopLatch();
+  assert(Latch && "Loop must have a latch");
+  BasicBlock *EpilogLatch = cast<BasicBlock>(VMap[Latch]);
+
+  // Loop structure should be the following:
+  //
+  // PreHeader
+  // NewPreHeader
+  //   Header
+  //   ...
+  //   Latch
+  // NewExit (PN)
+  // EpilogPreHeader
+  //   EpilogHeader
+  //   ...
+  //   EpilogLatch
+  // Exit (EpilogPN)
+
+  // Update PHI nodes at NewExit and Exit.
+  for (Instruction &BBI : *NewExit) {
+    PHINode *PN = dyn_cast<PHINode>(&BBI);
+    // Exit when we passed all PHI nodes.
+    if (!PN)
+      break;
+    // PN should be used in another PHI located in Exit block as
+    // Exit was split by SplitBlockPredecessors into Exit and NewExit
+    // Basicaly it should look like:
+    // NewExit:
+    //   PN = PHI [I, Latch]
+    // ...
+    // Exit:
+    //   EpilogPN = PHI [PN, EpilogPreHeader]
+    //
+    // There is EpilogPreHeader incoming block instead of NewExit as
+    // NewExit was spilt 1 more time to get EpilogPreHeader.
+    assert(PN->hasOneUse() && "The phi should have 1 use");
+    PHINode *EpilogPN = cast<PHINode> (PN->use_begin()->getUser());
+    assert(EpilogPN->getParent() == Exit && "EpilogPN should be in Exit block");
+
+    // Add incoming PreHeader from branch around the Loop
+    PN->addIncoming(UndefValue::get(PN->getType()), PreHeader);
+
+    Value *V = PN->getIncomingValueForBlock(Latch);
+    Instruction *I = dyn_cast<Instruction>(V);
+    if (I && L->contains(I))
+      // If value comes from an instruction in the loop add VMap value.
+      V = VMap.lookup(I);
+    // For the instruction out of the loop, constant or undefined value
+    // insert value itself.
+    EpilogPN->addIncoming(V, EpilogLatch);
+
+    assert(EpilogPN->getBasicBlockIndex(EpilogPreHeader) >= 0 &&
+          "EpilogPN should have EpilogPreHeader incoming block");
+    // Change EpilogPreHeader incoming block to NewExit.
+    EpilogPN->setIncomingBlock(EpilogPN->getBasicBlockIndex(EpilogPreHeader),
+                               NewExit);
+    // Now PHIs should look like:
+    // NewExit:
+    //   PN = PHI [I, Latch], [undef, PreHeader]
+    // ...
+    // Exit:
+    //   EpilogPN = PHI [PN, NewExit], [VMap[I], EpilogLatch]
+  }
+
+  // Create PHI nodes at NewExit (from the unrolling loop Latch and PreHeader).
+  // Update corresponding PHI nodes in epilog loop.
+  for (BasicBlock *Succ : successors(Latch)) {
+    // Skip this as we already updated phis in exit blocks.
+    if (!L->contains(Succ))
+      continue;
+    for (Instruction &BBI : *Succ) {
+      PHINode *PN = dyn_cast<PHINode>(&BBI);
+      // Exit when we passed all PHI nodes.
+      if (!PN)
+        break;
+      // Add new PHI nodes to the loop exit block and update epilog
+      // PHIs with the new PHI values.
+      PHINode *NewPN = PHINode::Create(PN->getType(), 2, PN->getName() + ".unr",
+                                       NewExit->getFirstNonPHI());
+      // Adding a value to the new PHI node from the unrolling loop preheader.
+      NewPN->addIncoming(PN->getIncomingValueForBlock(NewPreHeader), PreHeader);
+      // Adding a value to the new PHI node from the unrolling loop latch.
+      NewPN->addIncoming(PN->getIncomingValueForBlock(Latch), Latch);
+
+      // Update the existing PHI node operand with the value from the new PHI
+      // node.  Corresponding instruction in epilog loop should be PHI.
+      PHINode *VPN = cast<PHINode>(VMap[&BBI]);
+      VPN->setIncomingValue(VPN->getBasicBlockIndex(EpilogPreHeader), NewPN);
+    }
+  }
+
+  Instruction *InsertPt = NewExit->getTerminator();
+  IRBuilder<> B(InsertPt);
+  Value *BrLoopExit = B.CreateIsNotNull(ModVal, "lcmp.mod");
+  assert(Exit && "Loop must have a single exit block only");
+  // Split the exit to maintain loop canonicalization guarantees
+  SmallVector<BasicBlock*, 4> Preds(predecessors(Exit));
+  SplitBlockPredecessors(Exit, Preds, ".epilog-lcssa", DT, LI,
+                         PreserveLCSSA);
+  // Add the branch to the exit block (around the unrolling loop)
+  B.CreateCondBr(BrLoopExit, EpilogPreHeader, Exit);
   InsertPt->eraseFromParent();
 }
 
 /// Create a clone of the blocks in a loop and connect them together.
-/// If UnrollProlog is true, loop structure will not be cloned, otherwise a new
-/// loop will be created including all cloned blocks, and the iterator of it
-/// switches to count NewIter down to 0.
+/// If CreateRemainderLoop is false, loop structure will not be cloned,
+/// otherwise a new loop will be created including all cloned blocks, and the
+/// iterator of it switches to count NewIter down to 0.
+/// The cloned blocks should be inserted between InsertTop and InsertBot.
+/// If loop structure is cloned InsertTop should be new preheader, InsertBot
+/// new loop exit.
 ///
-static void CloneLoopBlocks(Loop *L, Value *NewIter, const bool UnrollProlog,
+static void CloneLoopBlocks(Loop *L, Value *NewIter,
+                            const bool CreateRemainderLoop,
+                            const bool UseEpilogRemainder,
                             BasicBlock *InsertTop, BasicBlock *InsertBot,
+                            BasicBlock *Preheader,
                             std::vector<BasicBlock *> &NewBlocks,
                             LoopBlocksDFS &LoopBlocks, ValueToValueMapTy &VMap,
                             LoopInfo *LI) {
-  BasicBlock *Preheader = L->getLoopPreheader();
+  StringRef suffix = UseEpilogRemainder ? "epil" : "prol";
   BasicBlock *Header = L->getHeader();
   BasicBlock *Latch = L->getLoopLatch();
   Function *F = Header->getParent();
@@ -152,7 +281,7 @@ static void CloneLoopBlocks(Loop *L, Value *NewIter, const bool UnrollProlog,
   LoopBlocksDFS::RPOIterator BlockEnd = LoopBlocks.endRPO();
   Loop *NewLoop = nullptr;
   Loop *ParentLoop = L->getParentLoop();
-  if (!UnrollProlog) {
+  if (CreateRemainderLoop) {
     NewLoop = new Loop();
     if (ParentLoop)
       ParentLoop->addChildLoop(NewLoop);
@@ -163,7 +292,7 @@ static void CloneLoopBlocks(Loop *L, Value *NewIter, const bool UnrollProlog,
   // For each block in the original loop, create a new copy,
   // and update the value map with the newly created values.
   for (LoopBlocksDFS::RPOIterator BB = BlockBegin; BB != BlockEnd; ++BB) {
-    BasicBlock *NewBB = CloneBasicBlock(*BB, VMap, ".prol", F);
+    BasicBlock *NewBB = CloneBasicBlock(*BB, VMap, "." + suffix, F);
     NewBlocks.push_back(NewBB);
 
     if (NewLoop)
@@ -176,19 +305,20 @@ static void CloneLoopBlocks(Loop *L, Value *NewIter, const bool UnrollProlog,
       // For the first block, add a CFG connection to this newly
       // created block.
       InsertTop->getTerminator()->setSuccessor(0, NewBB);
-
     }
+
     if (Latch == *BB) {
-      // For the last block, if UnrollProlog is true, create a direct jump to
-      // InsertBot. If not, create a loop back to cloned head.
+      // For the last block, if CreateRemainderLoop is false, create a direct
+      // jump to InsertBot. If not, create a loop back to cloned head.
       VMap.erase((*BB)->getTerminator());
       BasicBlock *FirstLoopBB = cast<BasicBlock>(VMap[Header]);
       BranchInst *LatchBR = cast<BranchInst>(NewBB->getTerminator());
       IRBuilder<> Builder(LatchBR);
-      if (UnrollProlog) {
+      if (!CreateRemainderLoop) {
         Builder.CreateBr(InsertBot);
       } else {
-        PHINode *NewIdx = PHINode::Create(NewIter->getType(), 2, "prol.iter",
+        PHINode *NewIdx = PHINode::Create(NewIter->getType(), 2,
+                                          suffix + ".iter",
                                           FirstLoopBB->getFirstNonPHI());
         Value *IdxSub =
             Builder.CreateSub(NewIdx, ConstantInt::get(NewIdx->getType(), 1),
@@ -207,9 +337,15 @@ static void CloneLoopBlocks(Loop *L, Value *NewIter, const bool UnrollProlog,
   // cloned loop.
   for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
     PHINode *NewPHI = cast<PHINode>(VMap[&*I]);
-    if (UnrollProlog) {
-      VMap[&*I] = NewPHI->getIncomingValueForBlock(Preheader);
-      cast<BasicBlock>(VMap[Header])->getInstList().erase(NewPHI);
+    if (!CreateRemainderLoop) {
+      if (UseEpilogRemainder) {
+        unsigned idx = NewPHI->getBasicBlockIndex(Preheader);
+        NewPHI->setIncomingBlock(idx, InsertTop);
+        NewPHI->removeIncomingValue(Latch, false);
+      } else {
+        VMap[&*I] = NewPHI->getIncomingValueForBlock(Preheader);
+        cast<BasicBlock>(VMap[Header])->getInstList().erase(NewPHI);
+      }
     } else {
       unsigned idx = NewPHI->getBasicBlockIndex(Preheader);
       NewPHI->setIncomingBlock(idx, InsertTop);
@@ -217,8 +353,8 @@ static void CloneLoopBlocks(Loop *L, Value *NewIter, const bool UnrollProlog,
       idx = NewPHI->getBasicBlockIndex(Latch);
       Value *InVal = NewPHI->getIncomingValue(idx);
       NewPHI->setIncomingBlock(idx, NewLatch);
-      if (VMap[InVal])
-        NewPHI->setIncomingValue(idx, VMap[InVal]);
+      if (Value *V = VMap.lookup(InVal))
+        NewPHI->setIncomingValue(idx, V);
     }
   }
   if (NewLoop) {
@@ -254,11 +390,11 @@ static void CloneLoopBlocks(Loop *L, Value *NewIter, const bool UnrollProlog,
   }
 }
 
-/// Insert code in the prolog code when unrolling a loop with a
+/// Insert code in the prolog/epilog code when unrolling a loop with a
 /// run-time trip-count.
 ///
 /// This method assumes that the loop unroll factor is total number
-/// of loop bodes in the loop after unrolling. (Some folks refer
+/// of loop bodies in the loop after unrolling. (Some folks refer
 /// to the unroll factor as the number of *extra* copies added).
 /// We assume also that the loop unroll factor is a power-of-two. So, after
 /// unrolling the loop, the number of loop bodies executed is 2,
@@ -266,37 +402,56 @@ static void CloneLoopBlocks(Loop *L, Value *NewIter, const bool UnrollProlog,
 /// instruction in SimplifyCFG.cpp.  Then, the backend decides how code for
 /// the switch instruction is generated.
 ///
+/// ***Prolog case***
 ///        extraiters = tripcount % loopfactor
 ///        if (extraiters == 0) jump Loop:
-///        else jump Prol
+///        else jump Prol:
 /// Prol:  LoopBody;
 ///        extraiters -= 1                 // Omitted if unroll factor is 2.
 ///        if (extraiters != 0) jump Prol: // Omitted if unroll factor is 2.
-///        if (tripcount < loopfactor) jump End
+///        if (tripcount < loopfactor) jump End:
 /// Loop:
 /// ...
 /// End:
 ///
-bool llvm::UnrollRuntimeLoopProlog(Loop *L, unsigned Count,
-                                   bool AllowExpensiveTripCount, LoopInfo *LI,
-                                   ScalarEvolution *SE, DominatorTree *DT,
-                                   bool PreserveLCSSA) {
+/// ***Epilog case***
+///        extraiters = tripcount % loopfactor
+///        if (tripcount < loopfactor) jump LoopExit:
+///        unroll_iters = tripcount - extraiters
+/// Loop:  LoopBody; (executes unroll_iter times);
+///        unroll_iter -= 1
+///        if (unroll_iter != 0) jump Loop:
+/// LoopExit:
+///        if (extraiters == 0) jump EpilExit:
+/// Epil:  LoopBody; (executes extraiters times)
+///        extraiters -= 1                 // Omitted if unroll factor is 2.
+///        if (extraiters != 0) jump Epil: // Omitted if unroll factor is 2.
+/// EpilExit:
+
+bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
+                                      bool AllowExpensiveTripCount,
+                                      bool UseEpilogRemainder,
+                                      LoopInfo *LI, ScalarEvolution *SE,
+                                      DominatorTree *DT, bool PreserveLCSSA) {
   // for now, only unroll loops that contain a single exit
   if (!L->getExitingBlock())
     return false;
 
   // Make sure the loop is in canonical form, and there is a single
   // exit block only.
-  if (!L->isLoopSimplifyForm() || !L->getUniqueExitBlock())
+  if (!L->isLoopSimplifyForm())
+    return false;
+  BasicBlock *Exit = L->getUniqueExitBlock(); // successor out of loop
+  if (!Exit)
     return false;
 
-  // Use Scalar Evolution to compute the trip count.  This allows more
-  // loops to be unrolled than relying on induction var simplification
+  // Use Scalar Evolution to compute the trip count. This allows more loops to
+  // be unrolled than relying on induction var simplification.
   if (!SE)
     return false;
 
-  // Only unroll loops with a computable trip count and the trip count needs
-  // to be an int value (allowing a pointer type is a TODO item)
+  // Only unroll loops with a computable trip count, and the trip count needs
+  // to be an int value (allowing a pointer type is a TODO item).
   const SCEV *BECountSC = SE->getBackedgeTakenCount(L);
   if (isa<SCEVCouldNotCompute>(BECountSC) ||
       !BECountSC->getType()->isIntegerTy())
@@ -304,21 +459,19 @@ bool llvm::UnrollRuntimeLoopProlog(Loop *L, unsigned Count,
 
   unsigned BEWidth = cast<IntegerType>(BECountSC->getType())->getBitWidth();
 
-  // Add 1 since the backedge count doesn't include the first loop iteration
+  // Add 1 since the backedge count doesn't include the first loop iteration.
   const SCEV *TripCountSC =
       SE->getAddExpr(BECountSC, SE->getConstant(BECountSC->getType(), 1));
   if (isa<SCEVCouldNotCompute>(TripCountSC))
     return false;
 
   BasicBlock *Header = L->getHeader();
+  BasicBlock *PreHeader = L->getLoopPreheader();
+  BranchInst *PreHeaderBR = cast<BranchInst>(PreHeader->getTerminator());
   const DataLayout &DL = Header->getModule()->getDataLayout();
   SCEVExpander Expander(*SE, DL, "loop-unroll");
-  if (!AllowExpensiveTripCount && Expander.isHighCostExpansion(TripCountSC, L))
-    return false;
-
-  // We only handle cases when the unroll factor is a power of 2.
-  // Count is the loop unroll factor, the number of extra copies added + 1.
-  if (!isPowerOf2_32(Count))
+  if (!AllowExpensiveTripCount &&
+      Expander.isHighCostExpansion(TripCountSC, L, PreHeaderBR))
     return false;
 
   // This constraint lets us deal with an overflowing trip count easily; see the
@@ -326,51 +479,115 @@ bool llvm::UnrollRuntimeLoopProlog(Loop *L, unsigned Count,
   if (Log2_32(Count) > BEWidth)
     return false;
 
-  // If this loop is nested, then the loop unroller changes the code in
-  // parent loop, so the Scalar Evolution pass needs to be run again
+  // If this loop is nested, then the loop unroller changes the code in the
+  // parent loop, so the Scalar Evolution pass needs to be run again.
   if (Loop *ParentLoop = L->getParentLoop())
     SE->forgetLoop(ParentLoop);
 
-  BasicBlock *PH = L->getLoopPreheader();
   BasicBlock *Latch = L->getLoopLatch();
-  // It helps to splits the original preheader twice, one for the end of the
-  // prolog code and one for a new loop preheader
-  BasicBlock *PEnd = SplitEdge(PH, Header, DT, LI);
-  BasicBlock *NewPH = SplitBlock(PEnd, PEnd->getTerminator(), DT, LI);
-  BranchInst *PreHeaderBR = cast<BranchInst>(PH->getTerminator());
 
+  // Loop structure is the following:
+  //
+  // PreHeader
+  //   Header
+  //   ...
+  //   Latch
+  // Exit
+
+  BasicBlock *NewPreHeader;
+  BasicBlock *NewExit = nullptr;
+  BasicBlock *PrologExit = nullptr;
+  BasicBlock *EpilogPreHeader = nullptr;
+  BasicBlock *PrologPreHeader = nullptr;
+
+  if (UseEpilogRemainder) {
+    // If epilog remainder
+    // Split PreHeader to insert a branch around loop for unrolling.
+    NewPreHeader = SplitBlock(PreHeader, PreHeader->getTerminator(), DT, LI);
+    NewPreHeader->setName(PreHeader->getName() + ".new");
+    // Split Exit to create phi nodes from branch above.
+    SmallVector<BasicBlock*, 4> Preds(predecessors(Exit));
+    NewExit = SplitBlockPredecessors(Exit, Preds, ".unr-lcssa",
+                                     DT, LI, PreserveLCSSA);
+    // Split NewExit to insert epilog remainder loop.
+    EpilogPreHeader = SplitBlock(NewExit, NewExit->getTerminator(), DT, LI);
+    EpilogPreHeader->setName(Header->getName() + ".epil.preheader");
+  } else {
+    // If prolog remainder
+    // Split the original preheader twice to insert prolog remainder loop
+    PrologPreHeader = SplitEdge(PreHeader, Header, DT, LI);
+    PrologPreHeader->setName(Header->getName() + ".prol.preheader");
+    PrologExit = SplitBlock(PrologPreHeader, PrologPreHeader->getTerminator(),
+                            DT, LI);
+    PrologExit->setName(Header->getName() + ".prol.loopexit");
+    // Split PrologExit to get NewPreHeader.
+    NewPreHeader = SplitBlock(PrologExit, PrologExit->getTerminator(), DT, LI);
+    NewPreHeader->setName(PreHeader->getName() + ".new");
+  }
+  // Loop structure should be the following:
+  //  Epilog             Prolog
+  //
+  // PreHeader         PreHeader
+  // *NewPreHeader     *PrologPreHeader
+  //   Header          *PrologExit
+  //   ...             *NewPreHeader
+  //   Latch             Header
+  // *NewExit            ...
+  // *EpilogPreHeader    Latch
+  // Exit              Exit
+
+  // Calculate conditions for branch around loop for unrolling
+  // in epilog case and around prolog remainder loop in prolog case.
   // Compute the number of extra iterations required, which is:
-  //  extra iterations = run-time trip count % (loop unroll factor + 1)
+  //  extra iterations = run-time trip count % loop unroll factor
+  PreHeaderBR = cast<BranchInst>(PreHeader->getTerminator());
   Value *TripCount = Expander.expandCodeFor(TripCountSC, TripCountSC->getType(),
                                             PreHeaderBR);
   Value *BECount = Expander.expandCodeFor(BECountSC, BECountSC->getType(),
                                           PreHeaderBR);
-
   IRBuilder<> B(PreHeaderBR);
-  Value *ModVal = B.CreateAnd(TripCount, Count - 1, "xtraiter");
-
-  // If ModVal is zero, we know that either
-  //  1. there are no iteration to be run in the prologue loop
-  // OR
-  //  2. the addition computing TripCount overflowed
-  //
-  // If (2) is true, we know that TripCount really is (1 << BEWidth) and so the
-  // number of iterations that remain to be run in the original loop is a
-  // multiple Count == (1 << Log2(Count)) because Log2(Count) <= BEWidth (we
-  // explicitly check this above).
-
-  Value *BranchVal = B.CreateIsNotNull(ModVal, "lcmp.mod");
-
-  // Branch to either the extra iterations or the cloned/unrolled loop
-  // We will fix up the true branch label when adding loop body copies
-  B.CreateCondBr(BranchVal, PEnd, PEnd);
-  assert(PreHeaderBR->isUnconditional() &&
-         PreHeaderBR->getSuccessor(0) == PEnd &&
-         "CFG edges in Preheader are not correct");
+  Value *ModVal;
+  // Calculate ModVal = (BECount + 1) % Count.
+  // Note that TripCount is BECount + 1.
+  if (isPowerOf2_32(Count)) {
+    // When Count is power of 2 we don't BECount for epilog case, however we'll
+    // need it for a branch around unrolling loop for prolog case.
+    ModVal = B.CreateAnd(TripCount, Count - 1, "xtraiter");
+    //  1. There are no iterations to be run in the prolog/epilog loop.
+    // OR
+    //  2. The addition computing TripCount overflowed.
+    //
+    // If (2) is true, we know that TripCount really is (1 << BEWidth) and so
+    // the number of iterations that remain to be run in the original loop is a
+    // multiple Count == (1 << Log2(Count)) because Log2(Count) <= BEWidth (we
+    // explicitly check this above).
+  } else {
+    // As (BECount + 1) can potentially unsigned overflow we count
+    // (BECount % Count) + 1 which is overflow safe as BECount % Count < Count.
+    Value *ModValTmp = B.CreateURem(BECount,
+                                    ConstantInt::get(BECount->getType(),
+                                                     Count));
+    Value *ModValAdd = B.CreateAdd(ModValTmp,
+                                   ConstantInt::get(ModValTmp->getType(), 1));
+    // At that point (BECount % Count) + 1 could be equal to Count.
+    // To handle this case we need to take mod by Count one more time.
+    ModVal = B.CreateURem(ModValAdd,
+                          ConstantInt::get(BECount->getType(), Count),
+                          "xtraiter");
+  }
+  Value *BranchVal =
+      UseEpilogRemainder ? B.CreateICmpULT(BECount,
+                                           ConstantInt::get(BECount->getType(),
+                                                            Count - 1)) :
+                           B.CreateIsNotNull(ModVal, "lcmp.mod");
+  BasicBlock *RemainderLoop = UseEpilogRemainder ? NewExit : PrologPreHeader;
+  BasicBlock *UnrollingLoop = UseEpilogRemainder ? NewPreHeader : PrologExit;
+  // Branch to either remainder (extra iterations) loop or unrolling loop.
+  B.CreateCondBr(BranchVal, RemainderLoop, UnrollingLoop);
   PreHeaderBR->eraseFromParent();
   Function *F = Header->getParent();
   // Get an ordered list of blocks in the loop to help with the ordering of the
-  // cloned blocks in the prolog code
+  // cloned blocks in the prolog/epilog code
   LoopBlocksDFS LoopBlocks(L);
   LoopBlocks.perform(LI);
 
@@ -382,34 +599,80 @@ bool llvm::UnrollRuntimeLoopProlog(Loop *L, unsigned Count,
   std::vector<BasicBlock *> NewBlocks;
   ValueToValueMapTy VMap;
 
-  bool UnrollPrologue = Count == 2;
+  // For unroll factor 2 remainder loop will have 1 iterations.
+  // Do not create 1 iteration loop.
+  bool CreateRemainderLoop = (Count != 2);
 
   // Clone all the basic blocks in the loop. If Count is 2, we don't clone
   // the loop, otherwise we create a cloned loop to execute the extra
   // iterations. This function adds the appropriate CFG connections.
-  CloneLoopBlocks(L, ModVal, UnrollPrologue, PH, PEnd, NewBlocks, LoopBlocks,
-                  VMap, LI);
-
-  // Insert the cloned blocks into function just before the original loop
-  F->getBasicBlockList().splice(PEnd->getIterator(), F->getBasicBlockList(),
-                                NewBlocks[0]->getIterator(), F->end());
-
-  // Rewrite the cloned instruction operands to use the values
-  // created when the clone is created.
-  for (unsigned i = 0, e = NewBlocks.size(); i != e; ++i) {
-    for (BasicBlock::iterator I = NewBlocks[i]->begin(),
-                              E = NewBlocks[i]->end();
-         I != E; ++I) {
-      RemapInstruction(&*I, VMap,
-                       RF_NoModuleLevelChanges | RF_IgnoreMissingEntries);
+  BasicBlock *InsertBot = UseEpilogRemainder ? Exit : PrologExit;
+  BasicBlock *InsertTop = UseEpilogRemainder ? EpilogPreHeader : PrologPreHeader;
+  CloneLoopBlocks(L, ModVal, CreateRemainderLoop, UseEpilogRemainder, InsertTop,
+                  InsertBot, NewPreHeader, NewBlocks, LoopBlocks, VMap, LI);
+
+  // Insert the cloned blocks into the function.
+  F->getBasicBlockList().splice(InsertBot->getIterator(),
+                                F->getBasicBlockList(),
+                                NewBlocks[0]->getIterator(),
+                                F->end());
+
+  // Loop structure should be the following:
+  //  Epilog             Prolog
+  //
+  // PreHeader         PreHeader
+  // NewPreHeader      PrologPreHeader
+  //   Header            PrologHeader
+  //   ...               ...
+  //   Latch             PrologLatch
+  // NewExit           PrologExit
+  // EpilogPreHeader   NewPreHeader
+  //   EpilogHeader      Header
+  //   ...               ...
+  //   EpilogLatch       Latch
+  // Exit              Exit
+
+  // Rewrite the cloned instruction operands to use the values created when the
+  // clone is created.
+  for (BasicBlock *BB : NewBlocks) {
+    for (Instruction &I : *BB) {
+      RemapInstruction(&I, VMap,
+                       RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
     }
   }
 
-  // Connect the prolog code to the original loop and update the
-  // PHI functions.
-  BasicBlock *LastLoopBB = cast<BasicBlock>(VMap[Latch]);
-  ConnectProlog(L, BECount, Count, LastLoopBB, PEnd, PH, NewPH, VMap, DT, LI,
-                PreserveLCSSA);
+  if (UseEpilogRemainder) {
+    // Connect the epilog code to the original loop and update the
+    // PHI functions.
+    ConnectEpilog(L, ModVal, NewExit, Exit, PreHeader,
+                  EpilogPreHeader, NewPreHeader, VMap, DT, LI,
+                  PreserveLCSSA);
+
+    // Update counter in loop for unrolling.
+    // I should be multiply of Count.
+    IRBuilder<> B2(NewPreHeader->getTerminator());
+    Value *TestVal = B2.CreateSub(TripCount, ModVal, "unroll_iter");
+    BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
+    B2.SetInsertPoint(LatchBR);
+    PHINode *NewIdx = PHINode::Create(TestVal->getType(), 2, "niter",
+                                      Header->getFirstNonPHI());
+    Value *IdxSub =
+        B2.CreateSub(NewIdx, ConstantInt::get(NewIdx->getType(), 1),
+                     NewIdx->getName() + ".nsub");
+    Value *IdxCmp;
+    if (LatchBR->getSuccessor(0) == Header)
+      IdxCmp = B2.CreateIsNotNull(IdxSub, NewIdx->getName() + ".ncmp");
+    else
+      IdxCmp = B2.CreateIsNull(IdxSub, NewIdx->getName() + ".ncmp");
+    NewIdx->addIncoming(TestVal, NewPreHeader);
+    NewIdx->addIncoming(IdxSub, Latch);
+    LatchBR->setCondition(IdxCmp);
+  } else {
+    // Connect the prolog code to the original loop and update the
+    // PHI functions.
+    ConnectProlog(L, BECount, Count, PrologExit, PreHeader, NewPreHeader,
+                  VMap, DT, LI, PreserveLCSSA);
+  }
   NumRuntimeUnrolled++;
   return true;
 }