[Hexagon] Generate more hardware loops

[bcahoon]

Summary

Hexagon is now able to more hardware loop opportunities. This patch also adds more tests for hardware loops.

[bcahoon]

Changed the ComparisonKinds struct back to using an enum, as it was in the original version.

lib/Target/Hexagon/HexagonHardwareLoops.cpp

 // normalizes induction variables, and the Loop Strength Reduction pass
 // run by 'llc' may also make changes to the induction variable.
 // The pattern detected by this phase is due to running Strength Reduction.
 //
 // Criteria for hardware loops:
 //  - Countable loops (w/ ind. var for a trip count)
 //  - Assumes loops are normalized by IndVarSimplify
 //  - Try inner-most loops first
-//  - No nested hardware loops.
 //  - No function calls in loops.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/SmallSet.h"
 #include "Hexagon.h"
 #include "HexagonSubtarget.h"
 #include "llvm/ADT/Statistic.h"

 #include <algorithm>
 #include <vector>
 
 using namespace llvm;
 
 #define DEBUG_TYPE "hwloops"
 
 #ifndef NDEBUG
-static cl::opt<int> HWLoopLimit("max-hwloop", cl::Hidden, cl::init(-1));
+static cl::opt<int> HWLoopLimit("hexagon-max-hwloop", cl::Hidden, cl::init(-1));
+
+// Option to create preheader only for a specific function.
+static cl::opt<std::string> PHFn("hexagon-hwloop-phfn", cl::Hidden,
+                                 cl::init(""));
 #endif
 
+// Option to create a preheader if one doesn't exist.
+static cl::opt<bool> HWCreatePreheader("hexagon-hwloop-preheader",
+    cl::Hidden, cl::init(true),
+    cl::desc("Add a preheader to a hardware loop if one doesn't exist"));
+
 STATISTIC(NumHWLoops, "Number of loops converted to hardware loops");
 
 namespace llvm {
   void initializeHexagonHardwareLoopsPass(PassRegistry&);
 }
 
 namespace {
   class CountValue;
public:
 
     void getAnalysisUsage(AnalysisUsage &AU) const override {
       AU.addRequired<MachineDominatorTree>();
       AU.addRequired<MachineLoopInfo>();
       MachineFunctionPass::getAnalysisUsage(AU);
     }
 
   private:
+    typedef char Comparison;
+
     /// Kinds of comparisons in the compare instructions.
-    struct Comparison {
-      enum Kind {
-        EQ  = 0x01,
-        NE  = 0x02,
-        L   = 0x04, // Less-than property.
-        G   = 0x08, // Greater-than property.
-        U   = 0x40, // Unsigned property.
-        LTs = L,
-        LEs = L | EQ,
-        GTs = G,
-        GEs = G | EQ,
-        LTu = L      | U,
-        LEu = L | EQ | U,
-        GTu = G      | U,
-        GEu = G | EQ | U
-      };
+    struct ComparisonKinds {
+      static const Comparison EQ  = 0x01;
+      static const Comparison NE  = 0x02;
+      static const Comparison L   = 0x04;
+      static const Comparison G   = 0x08;
+      static const Comparison U   = 0x40;
+      static const Comparison LEs = L | EQ;
+      static const Comparison GTs = G;
+      static const Comparison LEu = L | EQ | U;
+      static const Comparison GTu = G      | U;
 
-      static Kind getSwappedComparison(Kind Cmp) {
-        assert ((!((Cmp & L) && (Cmp & G))) && "Malformed comparison operator");
+      static Comparison getSwappedComparison(Comparison Cmp) {
+        assert ((!((Cmp & L) && (Cmp & G))) && "Undefined comparison operator");
         if ((Cmp & L) || (Cmp & G))
-          return (Kind)(Cmp ^ (L|G));
+          return Cmp ^ (L|G);
         return Cmp;
       }
+
+      static Comparison getNegatedComparison(Comparison Cmp) {
+        if ((Cmp & L) || (Cmp & G))
+          return ((Cmp ^ (L | G)) ^ EQ);
+        if ((Cmp & NE) || (Cmp & EQ))
+          return (Cmp ^ (EQ | NE));
+        return 0;
+      }
+
+      static bool isSigned(Comparison Cmp) {
+        return (Cmp & (L | G) && !(Cmp & U));
+      }
+
+      static bool isUnsigned(Comparison Cmp) {
+        return (Cmp & U);
+      }
+
     };
 
     /// \brief Find the register that contains the loop controlling
     /// induction variable.
     /// If successful, it will return true and set the \p Reg, \p IVBump
     /// and \p IVOp arguments.  Otherwise it will return false.
     /// The returned induction register is the register R that follows the
     /// following induction pattern:
     /// loop:
     ///   R = phi ..., [ R.next, LatchBlock ]
     ///   R.next = R + #bump
     ///   if (R.next < #N) goto loop
     /// IVBump is the immediate value added to R, and IVOp is the instruction
     /// "R.next = R + #bump".
     bool findInductionRegister(MachineLoop *L, unsigned &Reg,
                                int64_t &IVBump, MachineInstr *&IVOp) const;
 
+    /// \brief Return the comparison kind for the specified opcode.
+    Comparison getComparisonKind(unsigned CondOpc, MachineOperand *InitialValue,
+                                 const MachineOperand *Endvalue,
+                                 int64_t IVBump) const;
+
     /// \brief Analyze the statements in a loop to determine if the loop
     /// has a computable trip count and, if so, return a value that represents
     /// the trip count expression.
     CountValue *getLoopTripCount(MachineLoop *L,
                                  SmallVectorImpl<MachineInstr *> &OldInsts);
 
     /// \brief Return the expression that represents the number of times
     /// a loop iterates.  The function takes the operands that represent the
     /// loop start value, loop end value, and induction value.  Based upon
     /// these operands, the function attempts to compute the trip count.
     /// If the trip count is not directly available (as an immediate value,
     /// or a register), the function will attempt to insert computation of it
     /// to the loop's preheader.
     CountValue *computeCount(MachineLoop *Loop,
                              const MachineOperand *Start,
                              const MachineOperand *End,
                              unsigned IVReg,
                              int64_t IVBump,
-                             Comparison::Kind Cmp) const;
+                             Comparison Cmp) const;
 
     /// \brief Return true if the instruction is not valid within a hardware
     /// loop.
     bool isInvalidLoopOperation(const MachineInstr *MI) const;
 
     /// \brief Return true if the loop contains an instruction that inhibits
     /// using the hardware loop.
     bool containsInvalidInstruction(MachineLoop *L) const;
private:
     MachineBasicBlock *createPreheaderForLoop(MachineLoop *L);
   };
 
   char HexagonHardwareLoops::ID = 0;
 #ifndef NDEBUG
   int HexagonHardwareLoops::Counter = 0;
 #endif
 
+  // Avoid linking errors in the non-optimized builds.
+  typedef HexagonHardwareLoops HWL;
+  const HWL::Comparison HWL::ComparisonKinds::EQ;
+  const HWL::Comparison HWL::ComparisonKinds::NE;
+  const HWL::Comparison HWL::ComparisonKinds::L;
+  const HWL::Comparison HWL::ComparisonKinds::G;
+  const HWL::Comparison HWL::ComparisonKinds::U;
+  const HWL::Comparison HWL::ComparisonKinds::LEs;
+  const HWL::Comparison HWL::ComparisonKinds::GTs;
+  const HWL::Comparison HWL::ComparisonKinds::LEu;
+  const HWL::Comparison HWL::ComparisonKinds::GTu;
+
   /// \brief Abstraction for a trip count of a loop. A smaller version
   /// of the MachineOperand class without the concerns of changing the
   /// operand representation.
   class CountValue {
   public:
     enum CountValueType {
       CV_Register,
       CV_Immediate
for (MachineLoopInfo::iterator I = MLI->begin(), E = MLI->end();
     MachineLoop *L = *I;
     if (!L->getParentLoop())
       Changed |= convertToHardwareLoop(L);
   }
 
   return Changed;
 }
 
+/// \brief Return the latch block if it's one of the exiting blocks. Otherwise,
+/// return the exiting block. Return 'null' when multiple exiting blocks are
+/// present.
+static MachineBasicBlock* getExitingBlock(MachineLoop *L) {
+  if (MachineBasicBlock *Latch = L->getLoopLatch()) {
+    if (L->isLoopExiting(Latch))
+      return Latch;
+    else
+      return L->getExitingBlock();
+  }
+  return nullptr;
+}
 
 bool HexagonHardwareLoops::findInductionRegister(MachineLoop *L,
                                                  unsigned &Reg,
                                                  int64_t &IVBump,
                                                  MachineInstr *&IVOp
                                                  ) const {
   MachineBasicBlock *Header = L->getHeader();
   MachineBasicBlock *Preheader = L->getLoopPreheader();
   MachineBasicBlock *Latch = L->getLoopLatch();
-  if (!Header || !Preheader || !Latch)
+  MachineBasicBlock *ExitingBlock = getExitingBlock(L);
+  if (!Header || !Preheader || !Latch || !ExitingBlock)
     return false;
 
   // This pair represents an induction register together with an immediate
   // value that will be added to it in each loop iteration.
   typedef std::pair<unsigned,int64_t> RegisterBump;
 
   // Mapping:  R.next -> (R, bump), where R, R.next and bump are derived
   // from an induction operation
for (unsigned i = 1, n = Phi->getNumOperands(); i < n; i += 2) {
           IndMap.insert(std::make_pair(UpdReg, std::make_pair(IndReg, V)));
         }
       }
     }  // for (i)
   }  // for (instr)
 
   SmallVector<MachineOperand,2> Cond;
   MachineBasicBlock *TB = nullptr, *FB = nullptr;
-  bool NotAnalyzed = TII->AnalyzeBranch(*Latch, TB, FB, Cond, false);
+  bool NotAnalyzed = TII->AnalyzeBranch(*ExitingBlock, TB, FB, Cond, false);
   if (NotAnalyzed)
     return false;
-  
   unsigned PredR, PredPos, PredRegFlags;
   if (!TII->getPredReg(Cond, PredR, PredPos, PredRegFlags))
     return false;
 
   MachineInstr *PredI = MRI->getVRegDef(PredR);
   if (!PredI->isCompare())
     return false;
 
   unsigned CmpReg1 = 0, CmpReg2 = 0;
   int CmpImm = 0, CmpMask = 0;
   bool CmpAnalyzed = TII->analyzeCompare(PredI, CmpReg1, CmpReg2,
                                          CmpMask, CmpImm);
   // Fail if the compare was not analyzed, or it's not comparing a register
   // with an immediate value.  Not checking the mask here, since we handle
-  // the individual compare opcodes (including CMPb) later on.
+  // the individual compare opcodes (including A4_cmpb*) later on.
   if (!CmpAnalyzed)
     return false;
 
   // Exactly one of the input registers to the comparison should be among
   // the induction registers.
   InductionMap::iterator IndMapEnd = IndMap.end();
   InductionMap::iterator F = IndMapEnd;
   if (CmpReg1 != 0) {
if (F == IndMapEnd)
     return false;
 
   Reg = F->second.first;
   IVBump = F->second.second;
   IVOp = MRI->getVRegDef(F->first);
   return true;
 }
 
+// Return the comparison kind for the specified opcode.
+HexagonHardwareLoops::Comparison
+HexagonHardwareLoops::getComparisonKind(unsigned CondOpc,
+                                        MachineOperand *InitialValue,
+                                        const MachineOperand *EndValue,
+                                        int64_t IVBump) const {
+  Comparison Cmp = 0;
+  switch (CondOpc) {
+  case Hexagon::C2_cmpeqi:
+  case Hexagon::C2_cmpeq:
+  case Hexagon::C2_cmpeqp:
+    Cmp = ComparisonKinds::EQ;
+    break;
+  case Hexagon::C4_cmpneq:
+  case Hexagon::C4_cmpneqi:
+    Cmp = ComparisonKinds::NE;
+    break;
+  case Hexagon::C4_cmplte:
+    Cmp = ComparisonKinds::LEs;
+    break;
+  case Hexagon::C4_cmplteu:
+    Cmp = ComparisonKinds::LEu;
+    break;
+  case Hexagon::C2_cmpgtui:
+  case Hexagon::C2_cmpgtu:
+  case Hexagon::C2_cmpgtup:
+    Cmp = ComparisonKinds::GTu;
+    break;
+  case Hexagon::C2_cmpgti:
+  case Hexagon::C2_cmpgt:
+  case Hexagon::C2_cmpgtp:
+    Cmp = ComparisonKinds::GTs;
+    break;
+  default:
+    return 0;
+  }
+  return Cmp;
+}
 
 /// \brief Analyze the statements in a loop to determine if the loop has
 /// a computable trip count and, if so, return a value that represents
 /// the trip count expression.
 ///
 /// This function iterates over the phi nodes in the loop to check for
 /// induction variable patterns that are used in the calculation for
 /// the number of time the loop is executed.
 CountValue *HexagonHardwareLoops::getLoopTripCount(MachineLoop *L,
-                                    SmallVectorImpl<MachineInstr *> &OldInsts) {
   MachineBasicBlock *TopMBB = L->getTopBlock();
   MachineBasicBlock::pred_iterator PI = TopMBB->pred_begin();
   assert(PI != TopMBB->pred_end() &&
          "Loop must have more than one incoming edge!");
   MachineBasicBlock *Backedge = *PI++;
   if (PI == TopMBB->pred_end())  // dead loop?
     return nullptr;
   MachineBasicBlock *Incoming = *PI++;
   if (PI != TopMBB->pred_end())  // multiple backedges?
     return nullptr;
 
   // Make sure there is one incoming and one backedge and determine which
   // is which.
   if (L->contains(Incoming)) {
     if (L->contains(Backedge))
       return nullptr;
     std::swap(Incoming, Backedge);
   } else if (!L->contains(Backedge))
     return nullptr;
 
   // Look for the cmp instruction to determine if we can get a useful trip
   // count.  The trip count can be either a register or an immediate.  The
   // location of the value depends upon the type (reg or imm).
-  MachineBasicBlock *Latch = L->getLoopLatch();
-  if (!Latch)
+  MachineBasicBlock *ExitingBlock = getExitingBlock(L);
+  if (!ExitingBlock)
     return nullptr;
 
   unsigned IVReg = 0;
   int64_t IVBump = 0;
   MachineInstr *IVOp;
   bool FoundIV = findInductionRegister(L, IVReg, IVBump, IVOp);
   if (!FoundIV)
     return nullptr;
 
   MachineBasicBlock *Preheader = L->getLoopPreheader();
 
   MachineOperand *InitialValue = nullptr;
   MachineInstr *IV_Phi = MRI->getVRegDef(IVReg);
+  MachineBasicBlock *Latch = L->getLoopLatch();
   for (unsigned i = 1, n = IV_Phi->getNumOperands(); i < n; i += 2) {
     MachineBasicBlock *MBB = IV_Phi->getOperand(i+1).getMBB();
     if (MBB == Preheader)
       InitialValue = &IV_Phi->getOperand(i);
     else if (MBB == Latch)
       IVReg = IV_Phi->getOperand(i).getReg();  // Want IV reg after bump.
   }
   if (!InitialValue)
     return nullptr;
 
   SmallVector<MachineOperand,2> Cond;
   MachineBasicBlock *TB = nullptr, *FB = nullptr;
   bool NotAnalyzed = TII->AnalyzeBranch(*Latch, TB, FB, Cond, false);
   if (NotAnalyzed)
     return nullptr;
 
   MachineBasicBlock *Header = L->getHeader();
   // TB must be non-null.  If FB is also non-null, one of them must be
   // the header.  Otherwise, branch to TB could be exiting the loop, and
   // the fall through can go to the header.
   assert (TB && "Latch block without a branch?");
+  if (ExitingBlock != Latch && (TB == Latch || FB == Latch)) {
+    MachineBasicBlock *LTB = 0, *LFB = 0;
+    SmallVector<MachineOperand,2> LCond;
+    bool NotAnalyzed = TII->AnalyzeBranch(*Latch, LTB, LFB, LCond, false);
+    if (NotAnalyzed)
+      return nullptr;
+    if (TB == Latch)
+      (LTB == Header) ? TB = LTB: TB = LFB;
+    else // FB == Latch
+      (LTB == Header) ? FB = LTB: FB = LFB;
+  }
   assert ((!FB || TB == Header || FB == Header) && "Branches not to header?");
   if (!TB || (FB && TB != Header && FB != Header))
     return nullptr;
 
   // Branches of form "if (!P) ..." cause HexagonInstrInfo::AnalyzeBranch
   // to put imm(0), followed by P in the vector Cond.
   // If TB is not the header, it means that the "not-taken" path must lead
   // to the header.
CountValue *HexagonHardwareLoops::getLoopTripCount(MachineLoop *L,
   OldInsts.push_back(CondI);
   OldInsts.push_back(IVOp);
 
   // Sadly, the following code gets information based on the position
   // of the operands in the compare instruction.  This has to be done
   // this way, because the comparisons check for a specific relationship
   // between the operands (e.g. is-less-than), rather than to find out
   // what relationship the operands are in (as on PPC).
-  Comparison::Kind Cmp;
+  Comparison Cmp;
   bool isSwapped = false;
   const MachineOperand &Op1 = CondI->getOperand(1);
   const MachineOperand &Op2 = CondI->getOperand(2);
   const MachineOperand *EndValue = nullptr;
 
   if (Op1.isReg()) {
     if (Op2.isImm() || Op1.getReg() == IVReg)
       EndValue = &Op2;
     else {
       EndValue = &Op1;
       isSwapped = true;
     }
   }
 
   if (!EndValue)
     return nullptr;
 
-  switch (CondOpc) {
-    case Hexagon::C2_cmpeqi:
-    case Hexagon::C2_cmpeq:
-      Cmp = !Negated ? Comparison::EQ : Comparison::NE;
-      break;
-    case Hexagon::C2_cmpgtui:
-    case Hexagon::C2_cmpgtu:
-      Cmp = !Negated ? Comparison::GTu : Comparison::LEu;
-      break;
-    case Hexagon::C2_cmpgti:
-    case Hexagon::C2_cmpgt:
-      Cmp = !Negated ? Comparison::GTs : Comparison::LEs;
-      break;
-    // Very limited support for byte/halfword compares.
-    case Hexagon::A4_cmpbeqi:
-    case Hexagon::A4_cmpheqi: {
-      if (IVBump != 1)
-        return nullptr;
-
-      int64_t InitV, EndV;
-      // Since the comparisons are "ri", the EndValue should be an
-      // immediate.  Check it just in case.
-      assert(EndValue->isImm() && "Unrecognized latch comparison");
-      EndV = EndValue->getImm();
-      // Allow InitialValue to be a register defined with an immediate.
-      if (InitialValue->isReg()) {
-        if (!defWithImmediate(InitialValue->getReg()))
-          return nullptr;
-        InitV = getImmediate(*InitialValue);
-      } else {
-        assert(InitialValue->isImm());
-        InitV = InitialValue->getImm();
-      }
-      if (InitV >= EndV)
-        return nullptr;
-      if (CondOpc == Hexagon::A4_cmpbeqi) {
-        if (!isInt<8>(InitV) || !isInt<8>(EndV))
-          return nullptr;
-      } else {  // Hexagon::CMPhEQri_V4
-        if (!isInt<16>(InitV) || !isInt<16>(EndV))
-          return nullptr;
-      }
-      Cmp = !Negated ? Comparison::EQ : Comparison::NE;
-      break;
-    }
-    default:
-      return nullptr;
-  }
-
+  Cmp = getComparisonKind(CondOpc, InitialValue, EndValue, IVBump);
+  if (!Cmp)
+  if (Negated)
+    Cmp = ComparisonKinds::getNegatedComparison(Cmp);
   if (isSwapped)
-   Cmp = Comparison::getSwappedComparison(Cmp);
+    Cmp = ComparisonKinds::getSwappedComparison(Cmp);
 
   if (InitialValue->isReg()) {
     unsigned R = InitialValue->getReg();
     MachineBasicBlock *DefBB = MRI->getVRegDef(R)->getParent();
     if (!MDT->properlyDominates(DefBB, Header))
       return nullptr;
     OldInsts.push_back(MRI->getVRegDef(R));
   }

 /// number of times a loop iterates.  The function takes the operands that
 /// represent the loop start value, loop end value, and induction value.
 /// Based upon these operands, the function attempts to compute the trip count.
 CountValue *HexagonHardwareLoops::computeCount(MachineLoop *Loop,
                                                const MachineOperand *Start,
                                                const MachineOperand *End,
                                                unsigned IVReg,
                                                int64_t IVBump,
-                                               Comparison::Kind Cmp) const {
+                                               Comparison Cmp) const {
   // Cannot handle comparison EQ, i.e. while (A == B).
-  if (Cmp == Comparison::EQ)
+  if (Cmp == ComparisonKinds::EQ)
     return nullptr;
 
   // Check if either the start or end values are an assignment of an immediate.
   // If so, use the immediate value rather than the register.
   if (Start->isReg()) {
     const MachineInstr *StartValInstr = MRI->getVRegDef(Start->getReg());
     if (StartValInstr && StartValInstr->getOpcode() == Hexagon::A2_tfrsi)
       Start = &StartValInstr->getOperand(1);
   }
   if (End->isReg()) {
     const MachineInstr *EndValInstr = MRI->getVRegDef(End->getReg());
     if (EndValInstr && EndValInstr->getOpcode() == Hexagon::A2_tfrsi)
       End = &EndValInstr->getOperand(1);
   }
 
   assert (Start->isReg() || Start->isImm());
   assert (End->isReg() || End->isImm());
 
-  bool CmpLess =     Cmp & Comparison::L;
-  bool CmpGreater =  Cmp & Comparison::G;
-  bool CmpHasEqual = Cmp & Comparison::EQ;
+  bool CmpLess =     Cmp & ComparisonKinds::L;
+  bool CmpGreater =  Cmp & ComparisonKinds::G;
+  bool CmpHasEqual = Cmp & ComparisonKinds::EQ;
 
   // Avoid certain wrap-arounds.  This doesn't detect all wrap-arounds.
-  // If loop executes while iv is "less" with the iv value going down, then
-  // the iv must wrap.
   if (CmpLess && IVBump < 0)
+    // Loop going while iv is "less" with the iv value going down.  Must wrap.
     return nullptr;
+
   // If loop executes while iv is "greater" with the iv value going up, then
   // the iv must wrap.
   if (CmpGreater && IVBump > 0)
+    // Loop going while iv is "greater" with the iv value going up.  Must wrap.
     return nullptr;
 
   if (Start->isImm() && End->isImm()) {
     // Both, start and end are immediates.
     int64_t StartV = Start->getImm();
     int64_t EndV = End->getImm();
     int64_t Dist = EndV - StartV;
     if (Dist == 0)
       return nullptr;
 
     bool Exact = (Dist % IVBump) == 0;
 
-    if (Cmp == Comparison::NE) {
+    if (Cmp == ComparisonKinds::NE) {
       if (!Exact)
         return nullptr;
       if ((Dist < 0) ^ (IVBump < 0))
         return nullptr;
     }
 
     // For comparisons that include the final value (i.e. include equality
     // with the final value), we need to increase the distance by 1.
CountValue *HexagonHardwareLoops::computeCount(MachineLoop *Loop,
   // If the induction variable bump is not a power of 2, quit.
   // Othwerise we'd need a general integer division.
   if (!isPowerOf2_64(std::abs(IVBump)))
     return nullptr;
 
   MachineBasicBlock *PH = Loop->getLoopPreheader();
   assert (PH && "Should have a preheader by now");
   MachineBasicBlock::iterator InsertPos = PH->getFirstTerminator();
-  DebugLoc DL = (InsertPos != PH->end()) ? InsertPos->getDebugLoc()
-                                         : DebugLoc();
+  DebugLoc DL;
+  if (InsertPos != PH->end())
+    InsertPos->getDebugLoc();
 
   // If Start is an immediate and End is a register, the trip count
   // will be "reg - imm".  Hexagon's "subtract immediate" instruction
   // is actually "reg + -imm".
 
   // If the loop IV is going downwards, i.e. if the bump is negative,
   // then the iteration count (computed as End-Start) will need to be
   // negated.  To avoid the negation, just swap Start and End.
if (CmpHasEqual) {
     if (Start->isImm())
       StartV--;
     else if (End->isImm())
       EndV++;
     else
       AdjV += 1;
   }
 
-  if (Cmp != Comparison::NE) {
+  if (Cmp != ComparisonKinds::NE) {
     if (Start->isImm())
       StartV -= (IVBump-1);
     else if (End->isImm())
       EndV += (IVBump-1);
     else
       AdjV += (IVBump-1);
   }
 
CountValue *HexagonHardwareLoops::computeCount(MachineLoop *Loop,
   // Avoid special case, where the start value is an imm(0).
   if (Start->isImm() && StartV == 0) {
     DistR = End->getReg();
     DistSR = End->getSubReg();
   } else {
     const MCInstrDesc &SubD = RegToReg ? TII->get(Hexagon::A2_sub) :
                               (RegToImm ? TII->get(Hexagon::A2_subri) :
                                           TII->get(Hexagon::A2_addi));
+    if (RegToReg || RegToImm) {    
       unsigned SubR = MRI->createVirtualRegister(IntRC);
       MachineInstrBuilder SubIB =
         BuildMI(*PH, InsertPos, DL, SubD, SubR);
 
-    if (RegToReg) {
+      if (RegToReg)
         SubIB.addReg(End->getReg(), 0, End->getSubReg())
-           .addReg(Start->getReg(), 0, Start->getSubReg());
-    } else if (RegToImm) {
+      else
         SubIB.addImm(EndV)
-           .addReg(Start->getReg(), 0, Start->getSubReg());
-    } else { // ImmToReg
+      DistR = SubR;
+    } else {
+      // If the loop has been unrolled, we should use the original loop count
+      // instead of recalculating the value. This will avoid additional
+      // 'Add' instruction.
+      const MachineInstr *EndValInstr = MRI->getVRegDef(End->getReg());
+      if (EndValInstr->getOpcode() == Hexagon::A2_addi &&
+          EndValInstr->getOperand(2).getImm() == StartV) {
+        DistR = EndValInstr->getOperand(1).getReg();
+      } else {
+        unsigned SubR = MRI->createVirtualRegister(IntRC);
+        MachineInstrBuilder SubIB =
+          BuildMI(*PH, InsertPos, DL, SubD, SubR);
         SubIB.addReg(End->getReg(), 0, End->getSubReg())
              .addImm(-StartV);
-    }
         DistR = SubR;
+      }
+    }
     DistSR = 0;
   }
 
   // From DistR, compute AdjR (register with the adjusted distance).
   unsigned AdjR, AdjSR;
 
   if (AdjV == 0) {
     AdjR = DistR;
CountValue *HexagonHardwareLoops::computeCount(MachineLoop *Loop,
   return new CountValue(CountValue::CV_Register, CountR, CountSR);
 }
 
 
 /// \brief Return true if the operation is invalid within hardware loop.
 bool HexagonHardwareLoops::isInvalidLoopOperation(
       const MachineInstr *MI) const {
 
-  // call is not allowed because the callee may use a hardware loop
-  if (MI->getDesc().isCall())
+  // Call is not allowed because the callee may use a hardware loop except for
+  // the case when the call never returns.
+  if (MI->getDesc().isCall() && MI->getOpcode() != Hexagon::CALLv3nr)
     return true;
 
   // do not allow nested hardware loops
   if (isHardwareLoop(MI))
     return true;
 
   // check if the instruction defines a hardware loop register
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
            E = MRI->use_end(); I != E; I = nextI) {
         nextI = std::next(I);  // I is invalidated by the setReg
         MachineOperand &Use = *I;
         MachineInstr *UseMI = I->getParent();
         if (UseMI == MI)
           continue;
         if (Use.isDebug())
           UseMI->getOperand(0).setReg(0U);
-        // This may also be a "instr -> phi -> instr" case which can
-        // be removed too.
       }
     }
 
     MI->eraseFromParent();
     for (unsigned i = 0; i < DeadPhis.size(); ++i)
       DeadPhis[i]->eraseFromParent();
   }
 }
if (Limit >= 0) {
     Counter++;
   }
 #endif
 
   // Does the loop contain any invalid instructions?
   if (containsInvalidInstruction(L))
     return false;
 
-  // Is the induction variable bump feeding the latch condition?
-  if (!fixupInductionVariable(L))
-    return false;
-
   MachineBasicBlock *LastMBB = L->getExitingBlock();
   // Don't generate hw loop if the loop has more than one exit.
   if (!LastMBB)
     return false;
 
   MachineBasicBlock::iterator LastI = LastMBB->getFirstTerminator();
   if (LastI == LastMBB->end())
     return false;
 
+  // Is the induction variable bump feeding the latch condition?
+  if (!fixupInductionVariable(L))
+    return false;
+
   // Ensure the loop has a preheader: the loop instruction will be
   // placed there.
-  bool NewPreheader = false;
   MachineBasicBlock *Preheader = L->getLoopPreheader();
   if (!Preheader) {
     Preheader = createPreheaderForLoop(L);
     if (!Preheader)
       return false;
-    NewPreheader = true;
   }
+
   MachineBasicBlock::iterator InsertPos = Preheader->getFirstTerminator();
 
   SmallVector<MachineInstr*, 2> OldInsts;
   // Are we able to determine the trip count for the loop?
   CountValue *TripCount = getLoopTripCount(L, OldInsts);
   if (!TripCount)
     return false;
 
   // Is the trip count available in the preheader?
   if (TripCount->isReg()) {
     // There will be a use of the register inserted into the preheader,
     // so make sure that the register is actually defined at that point.
     MachineInstr *TCDef = MRI->getVRegDef(TripCount->getReg());
     MachineBasicBlock *BBDef = TCDef->getParent();
-    if (!NewPreheader) {
-      if (!MDT->dominates(BBDef, Preheader))
-        return false;
-    } else {
-      // If we have just created a preheader, the dominator tree won't be
-      // aware of it.  Check if the definition of the register dominates
-      // the header, but is not the header itself.
-      if (!MDT->properlyDominates(BBDef, L->getHeader()))
-        return false;
-    }
   }
 
   // Determine the loop start.
-  MachineBasicBlock *LoopStart = L->getTopBlock();
-  if (L->getLoopLatch() != LastMBB) {
-    // When the exit and latch are not the same, use the latch block as the
-    // start.
-    // The loop start address is used only after the 1st iteration, and the
-    // loop latch may contains instrs. that need to be executed after the
-    // first iteration.
-    LoopStart = L->getLoopLatch();
-    // Make sure the latch is a successor of the exit, otherwise it won't work.
-    if (!LastMBB->isSuccessor(LoopStart))
+  MachineBasicBlock *TopBlock = L->getTopBlock();
+  MachineBasicBlock *ExitingBlock = getExitingBlock(L);
+  MachineBasicBlock *LoopStart = 0;
+  if (ExitingBlock !=  L->getLoopLatch()) {
+    MachineBasicBlock *TB = 0, *FB = 0;
+    SmallVector<MachineOperand, 2> Cond;
+
+    if (TII->AnalyzeBranch(*ExitingBlock, TB, FB, Cond, false))
+      return false;
+
+    if (L->contains(TB))
+      LoopStart = TB;
+    else if (L->contains(FB))
+      LoopStart = FB;
+    else
       return false;
   }
+  else
+    LoopStart = TopBlock;
 
   // Convert the loop to a hardware loop.
   DEBUG(dbgs() << "Change to hardware loop at "; L->dump());
   DebugLoc DL;
   if (InsertPos != Preheader->end())
     DL = InsertPos->getDebugLoc();
 
   if (TripCount->isReg()) {

 void HexagonHardwareLoops::setImmediate(MachineOperand &MO, int64_t Val) {
   if (MO.isImm()) {
     MO.setImm(Val);
     return;
   }
 
   assert(MO.isReg());
   unsigned R = MO.getReg();
-  MachineInstr *DI = defWithImmediate(R);
-  if (MRI->hasOneNonDBGUse(R)) {
-    // If R has only one use, then just change its defining instruction to
-    // the new immediate value.
-    DI->getOperand(1).setImm(Val);
-    return;
-  }
+  MachineInstr *DI = MRI->getVRegDef(R);
 
   const TargetRegisterClass *RC = MRI->getRegClass(R);
   unsigned NewR = MRI->createVirtualRegister(RC);
   MachineBasicBlock &B = *DI->getParent();
   DebugLoc DL = DI->getDebugLoc();
   BuildMI(B, DI, DL, TII->get(DI->getOpcode()), NewR)
     .addImm(Val);
   MO.setReg(NewR);
 }
 
 
 bool HexagonHardwareLoops::fixupInductionVariable(MachineLoop *L) {
   MachineBasicBlock *Header = L->getHeader();
-  MachineBasicBlock *Preheader = L->getLoopPreheader();
   MachineBasicBlock *Latch = L->getLoopLatch();
+  MachineBasicBlock *ExitingBlock = getExitingBlock(L);
 
-  if (!Header || !Preheader || !Latch)
+  if (!(Header && Latch && ExitingBlock))
     return false;
 
   // These data structures follow the same concept as the corresponding
   // ones in findInductionRegister (where some comments are).
   typedef std::pair<unsigned,int64_t> RegisterBump;
   typedef std::pair<unsigned,RegisterBump> RegisterInduction;
   typedef std::set<RegisterInduction> RegisterInductionSet;
 
for (instr_iterator I = Header->instr_begin(), E = Header->instr_end();
     // Have a PHI instruction.
     for (unsigned i = 1, n = Phi->getNumOperands(); i < n; i += 2) {
       if (Phi->getOperand(i+1).getMBB() != Latch)
         continue;
 
       unsigned PhiReg = Phi->getOperand(i).getReg();
       MachineInstr *DI = MRI->getVRegDef(PhiReg);
       unsigned UpdOpc = DI->getOpcode();
-      bool isAdd = (UpdOpc == Hexagon::A2_addi);
+      bool isAdd = (UpdOpc == Hexagon::A2_addi || UpdOpc == Hexagon::A2_addp);
 
       if (isAdd) {
         // If the register operand to the add/sub is the PHI we are looking
         // at, this meets the induction pattern.
         unsigned IndReg = DI->getOperand(1).getReg();
         if (MRI->getVRegDef(IndReg) == Phi) {
           unsigned UpdReg = DI->getOperand(0).getReg();
           int64_t V = DI->getOperand(2).getImm();

 
 
 /// \brief Create a preheader for a given loop.
 MachineBasicBlock *HexagonHardwareLoops::createPreheaderForLoop(
       MachineLoop *L) {
   if (MachineBasicBlock *TmpPH = L->getLoopPreheader())
     return TmpPH;
 
+  if (!HWCreatePreheader)
+    return nullptr;
+
   MachineBasicBlock *Header = L->getHeader();
   MachineBasicBlock *Latch = L->getLoopLatch();
+  MachineBasicBlock *ExitingBlock = getExitingBlock(L);
   MachineFunction *MF = Header->getParent();
   DebugLoc DL;
 
-  if (!Latch || Header->hasAddressTaken())
+#ifndef NDEBUG
+  if ((PHFn != "") && (PHFn != MF->getName()))
+    return nullptr;
+#endif
+
+  if (!Latch || !ExitingBlock || Header->hasAddressTaken())
     return nullptr;
 
   typedef MachineBasicBlock::instr_iterator instr_iterator;
 
   // Verify that all existing predecessors have analyzable branches
   // (or no branches at all).
   typedef std::vector<MachineBasicBlock*> MBBVector;
   MBBVector Preds(Header->pred_begin(), Header->pred_end());
   SmallVector<MachineOperand,2> Tmp1;
   MachineBasicBlock *TB = nullptr, *FB = nullptr;
 
-  if (TII->AnalyzeBranch(*Latch, TB, FB, Tmp1, false))
+  if (TII->AnalyzeBranch(*ExitingBlock, TB, FB, Tmp1, false))
     return nullptr;
 
   for (MBBVector::iterator I = Preds.begin(), E = Preds.end(); I != E; ++I) {
     MachineBasicBlock *PB = *I;
-    if (PB != Latch) {
-      bool NotAnalyzed = TII->AnalyzeBranch(*PB, TB, FB, Tmp1, false);
-      if (NotAnalyzed)
-        return nullptr;
-    }
-  }
 
   MachineBasicBlock *NewPH = MF->CreateMachineBasicBlock();
   MF->insert(Header, NewPH);
 
   if (Header->pred_size() > 2) {
     // Ensure that the header has only two predecessors: the preheader and
     // the loop latch.  Any additional predecessors of the header should
     // join at the newly created preheader.  Inspect all PHI nodes from the
#endif
   assert (!LatchNotAnalyzed && "Should be analyzable!");
   if (!TB && !FB)
     TII->InsertBranch(*Latch, Header, nullptr, EmptyCond, DL);
 
   // Finally, the branch from the preheader to the header.
   TII->InsertBranch(*NewPH, Header, nullptr, EmptyCond, DL);
   NewPH->addSuccessor(Header);
 
+  MachineLoop *ParentLoop = L->getParentLoop();
+  if (ParentLoop)
+    ParentLoop->addBasicBlockToLoop(NewPH, MLI->getBase());
+
+  // Update the dominator information with the new preheader.
+  if (MDT) {
+    MachineDomTreeNode *HDom = MDT->getNode(Header);
+    MDT->addNewBlock(NewPH, HDom->getIDom()->getBlock());
+    MDT->changeImmediateDominator(Header, NewPH);
+  }
+
   return NewPH;
 }

test/CodeGen/Hexagon/hwloop-lt.ll

 ; RUN: llc -march=hexagon -mcpu=hexagonv4 -O3 < %s | FileCheck %s
 
-
-; CHECK: test_pos1_ir_slt
+; CHECK-LABEL: @test_pos1_ir_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos1_ir_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 8531, %b
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ 8531, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 1
   %cmp = icmp slt i32 %inc, %b
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos2_ir_slt
+; CHECK-LABEL: @test_pos2_ir_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos2_ir_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 9152, %b
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ 9152, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 2
   %cmp = icmp slt i32 %inc, %b
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos4_ir_slt
+; CHECK-LABEL: @test_pos4_ir_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos4_ir_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 18851, %b
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ 18851, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 4
   %cmp = icmp slt i32 %inc, %b
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos8_ir_slt
+; CHECK-LABEL: @test_pos8_ir_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos8_ir_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 25466, %b
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ 25466, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 8
   %cmp = icmp slt i32 %inc, %b
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos16_ir_slt
+; CHECK-LABEL: @test_pos16_ir_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos16_ir_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 9295, %b
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ 9295, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 16
   %cmp = icmp slt i32 %inc, %b
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos1_ri_slt
+; CHECK-LABEL: @test_pos1_ri_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos1_ri_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 %a, 31236
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ %a, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 1
   %cmp = icmp slt i32 %inc, 31236
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos2_ri_slt
+; CHECK-LABEL: @test_pos2_ri_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos2_ri_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 %a, 22653
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ %a, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 2
   %cmp = icmp slt i32 %inc, 22653
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos4_ri_slt
+; CHECK-LABEL: @test_pos4_ri_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos4_ri_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 %a, 1431
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ %a, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 4
   %cmp = icmp slt i32 %inc, 1431
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos8_ri_slt
+; CHECK-LABEL: @test_pos8_ri_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos8_ri_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 %a, 22403
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ %a, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 8
   %cmp = icmp slt i32 %inc, 22403
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos16_ri_slt
+; CHECK-LABEL: @test_pos16_ri_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos16_ri_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 %a, 21715
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ %a, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 16
   %cmp = icmp slt i32 %inc, 21715
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos1_rr_slt
+; CHECK-LABEL: @test_pos1_rr_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos1_rr_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 %a, %b
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ %a, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 1
   %cmp = icmp slt i32 %inc, %b
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos2_rr_slt
+; CHECK-LABEL: @test_pos2_rr_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos2_rr_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 %a, %b
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ %a, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 2
   %cmp = icmp slt i32 %inc, %b
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos4_rr_slt
+; CHECK-LABEL: @test_pos4_rr_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos4_rr_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 %a, %b
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ %a, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 4
   %cmp = icmp slt i32 %inc, %b
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos8_rr_slt
+; CHECK-LABEL: @test_pos8_rr_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos8_rr_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 %a, %b
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ %a, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 8
   %cmp = icmp slt i32 %inc, %b
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
-
-
-; CHECK: test_pos16_rr_slt
+; CHECK-LABEL: @test_pos16_rr_slt
 ; CHECK: loop0
 ; a < b
 define void @test_pos16_rr_slt(i8* nocapture %p, i32 %a, i32 %b) nounwind {
 entry:
   %cmp3 = icmp slt i32 %a, %b
   br i1 %cmp3, label %for.body.lr.ph, label %for.end
 
-for.body.lr.ph:                                   ; preds = %entry
+for.body.lr.ph:
   br label %for.body
 
-for.body:                                         ; preds = %for.body.lr.ph, %for.body
+for.body:
   %i.04 = phi i32 [ %a, %for.body.lr.ph ], [ %inc, %for.body ]
   %arrayidx = getelementptr inbounds i8, i8* %p, i32 %i.04
   %0 = load i8, i8* %arrayidx, align 1
   %conv = zext i8 %0 to i32
   %add = add nsw i32 %conv, 1
   %conv1 = trunc i32 %add to i8
   store i8 %conv1, i8* %arrayidx, align 1
   %inc = add nsw i32 %i.04, 16
   %cmp = icmp slt i32 %inc, %b
   br i1 %cmp, label %for.body, label %for.end
 
-for.end:                                          ; preds = %for.body, %entry
+for.end:
   ret void
 }
 
 
 

test/CodeGen/Hexagon/hwloop-missed.ll

+; RUN: llc -march=hexagon -hexagon-hwloop-preheader < %s | FileCheck %s
+
+; Generate hardware loops when we also need to add a new preheader.
+; we should generate two hardware loops for this test case.
+
+; CHECK: loop0
+; CHECK: endloop0
+; CHECK: loop0
+; CHECK: endloop0
+
+@g = external global i32
+
+define void @test(i32* nocapture %a, i32* nocapture %b, i32 %n) nounwind {
+entry:
+  %tobool = icmp eq i32 %n, 0
+  br i1 %tobool, label %for.body4.preheader, label %for.body.preheader
+
+for.body.preheader:
+  br label %for.body
+
+for.body:
+  %arrayidx.phi = phi i32* [ %arrayidx.inc, %for.body ], [ %a, %for.body.preheader ]
+  %i.014 = phi i32 [ %inc, %for.body ], [ 0, %for.body.preheader ]
+  %0 = load i32, i32* @g, align 4
+  store i32 %0, i32* %arrayidx.phi, align 4
+  %inc = add nsw i32 %i.014, 1
+  %exitcond15 = icmp eq i32 %inc, 3
+  %arrayidx.inc = getelementptr i32, i32* %arrayidx.phi, i32 1
+  br i1 %exitcond15, label %for.body4.preheader.loopexit, label %for.body
+
+for.body4.preheader.loopexit:
+  br label %for.body4.preheader
+
+for.body4.preheader:
+  br label %for.body4
+
+for.body4:
+  %arrayidx5.phi = phi i32* [ %arrayidx5.inc, %for.body4 ], [ %b, %for.body4.preheader ]
+  %i1.013 = phi i32 [ %inc7, %for.body4 ], [ 0, %for.body4.preheader ]
+  %1 = load i32, i32* @g, align 4
+  store i32 %1, i32* %arrayidx5.phi, align 4
+  %inc7 = add nsw i32 %i1.013, 1
+  %exitcond = icmp eq i32 %inc7, 3
+  %arrayidx5.inc = getelementptr i32, i32* %arrayidx5.phi, i32 1
+  br i1 %exitcond, label %for.end8, label %for.body4
+
+for.end8:
+  ret void
+}

test/CodeGen/Hexagon/hwloop-preheader.ll

+; RUN: llc -march=hexagon -mcpu=hexagonv5 -hexagon-hwloop-preheader < %s
+; REQUIRES: asserts
+
+; Test that the preheader is added to the parent loop, otherwise
+; we generate an invalid hardware loop.
+
+; Function Attrs: nounwind readonly
+define void @test(i16 signext %n) #0 {
+entry:
+  br i1 undef, label %for.cond4.preheader.preheader.split.us, label %for.end22
+
+for.cond4.preheader.preheader.split.us:
+  %0 = sext i16 %n to i32
+  br label %for.body9.preheader.us
+
+for.body9.us:
+  %indvars.iv = phi i32 [ %indvars.iv.next.7, %for.body9.us ], [ 0, %for.body9.preheader.us ]
+  %indvars.iv.next.7 = add i32 %indvars.iv, 8
+  %lftr.wideiv.7 = trunc i32 %indvars.iv.next.7 to i16
+  %exitcond.7 = icmp slt i16 %lftr.wideiv.7, 0
+  br i1 %exitcond.7, label %for.body9.us, label %for.body9.us.ur
+
+for.body9.preheader.us:
+  %i.030.us.pmt = phi i32 [ %inc21.us.pmt, %for.end.loopexit.us ], [ 0, %for.cond4.preheader.preheader.split.us ]
+  br i1 undef, label %for.body9.us, label %for.body9.us.ur
+
+for.body9.us.ur:
+  %exitcond.ur.old = icmp eq i16 undef, %n
+  br i1 %exitcond.ur.old, label %for.end.loopexit.us, label %for.body9.us.ur
+
+for.end.loopexit.us:
+  %inc21.us.pmt = add i32 %i.030.us.pmt, 1
+  %exitcond33 = icmp eq i32 %inc21.us.pmt, %0
+  br i1 %exitcond33, label %for.end22, label %for.body9.preheader.us
+
+for.end22:
+  ret void
+}
+
+attributes #0 = { nounwind readonly "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf"="true" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }

test/CodeGen/Hexagon/hwloop1.ll

+; RUN: llc -march=hexagon < %s | FileCheck %s
+; Check that we generate hardware loop instructions.
+
+; Case 1 : Loop with a constant number of iterations.
+; CHECK-LABEL: @hwloop1
+; CHECK: loop0(.LBB{{.}}_{{.}}, #10)
+; CHECK: endloop0
+
+@a = common global [10 x i32] zeroinitializer, align 4
+define i32 @hwloop1() nounwind {
+entry:
+  br label %for.body
+for.body:
+  %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %arrayidx = getelementptr inbounds [10 x i32], [10 x i32]* @a, i32 0, i32 %i.01
+  store i32 %i.01, i32* %arrayidx, align 4
+  %inc = add nsw i32 %i.01, 1
+  %exitcond = icmp eq i32 %inc, 10
+  br i1 %exitcond, label %for.end, label %for.body
+for.end:
+  ret i32 0
+}
+
+; Case 2 : Loop with a run-time number of iterations.
+; CHECK-LABEL: @hwloop2
+; CHECK: loop0(.LBB{{.}}_{{.}}, r{{[0-9]+}})
+; CHECK: endloop0
+
+define i32 @hwloop2(i32 %n, i32* nocapture %b) nounwind {
+entry:
+  %cmp1 = icmp sgt i32 %n, 0
+  br i1 %cmp1, label %for.body.preheader, label %for.end
+
+for.body.preheader:
+  br label %for.body
+
+for.body:
+  %a.03 = phi i32 [ %add, %for.body ], [ 0, %for.body.preheader ]
+  %i.02 = phi i32 [ %inc, %for.body ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i32, i32* %b, i32 %i.02
+  %0 = load i32, i32* %arrayidx, align 4
+  %add = add nsw i32 %0, %a.03
+  %inc = add nsw i32 %i.02, 1
+  %exitcond = icmp eq i32 %inc, %n
+  br i1 %exitcond, label %for.end.loopexit, label %for.body
+
+for.end.loopexit:
+  br label %for.end
+
+for.end:
+  %a.0.lcssa = phi i32 [ 0, %entry ], [ %add, %for.end.loopexit ]
+  ret i32 %a.0.lcssa
+}
+
+; Case 3 : Induction variable increment more than 1.
+; CHECK-LABEL: @hwloop3
+; CHECK: lsr(r{{[0-9]+}}, #2)
+; CHECK: loop0(.LBB{{.}}_{{.}}, r{{[0-9]+}})
+; CHECK: endloop0
+
+define i32 @hwloop3(i32 %n, i32* nocapture %b) nounwind {
+entry:
+  %cmp1 = icmp sgt i32 %n, 0
+  br i1 %cmp1, label %for.body.preheader, label %for.end
+
+for.body.preheader:
+  br label %for.body
+
+for.body:
+  %a.03 = phi i32 [ %add, %for.body ], [ 0, %for.body.preheader ]
+  %i.02 = phi i32 [ %inc, %for.body ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i32, i32* %b, i32 %i.02
+  %0 = load i32, i32* %arrayidx, align 4
+  %add = add nsw i32 %0, %a.03
+  %inc = add nsw i32 %i.02, 4
+  %exitcond = icmp eq i32 %inc, %n
+  br i1 %exitcond, label %for.end.loopexit, label %for.body
+
+for.end.loopexit:
+  br label %for.end
+
+for.end:
+  %a.0.lcssa = phi i32 [ 0, %entry ], [ %add, %for.end.loopexit ]
+  ret i32 %a.0.lcssa
+}
+
+; Case 4 : Loop exit compare uses register instead of immediate value.
+; CHECK-LABEL: @hwloop4
+; CHECK: loop0(.LBB{{.}}_{{.}}, r{{[0-9]+}})
+; CHECK: endloop0
+
+define i32 @hwloop4(i32 %n, i32* nocapture %b) nounwind {
+entry:
+  %cmp1 = icmp sgt i32 %n, 0
+  br i1 %cmp1, label %for.body.preheader, label %for.end
+
+for.body.preheader:
+  br label %for.body
+
+for.body:
+  %i.02 = phi i32 [ %inc, %for.body ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i32, i32* %b, i32 %i.02
+  store i32 %i.02, i32* %arrayidx, align 4
+  %inc = add nsw i32 %i.02, 1
+  %exitcond = icmp eq i32 %inc, %n
+  br i1 %exitcond, label %for.end.loopexit, label %for.body
+
+for.end.loopexit:
+  br label %for.end
+
+for.end:
+  ret i32 0
+}
+
+; Case 5: After LSR, the initial value is 100 and the iv decrements to 0.
+; CHECK-LABEL: @hwloop5
+; CHECK: loop0(.LBB{{.}}_{{.}}, #100)
+; CHECK: endloop0
+
+define void @hwloop5(i32* nocapture %a, i32* nocapture %res) nounwind {
+entry:
+  br label %for.body
+
+for.body:
+  %i.03 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i32 %i.03
+  %0 = load i32, i32* %arrayidx, align 4
+  %mul = mul nsw i32 %0, %0
+  %arrayidx2 = getelementptr inbounds i32, i32* %res, i32 %i.03
+  store i32 %mul, i32* %arrayidx2, align 4
+  %inc = add nsw i32 %i.03, 1
+  %exitcond = icmp eq i32 %inc, 100
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+  ret void
+}
+
+; Case 6: Large immediate offset
+; CHECK-LABEL: @hwloop6
+; CHECK-NOT: loop0(.LBB{{.}}_{{.}}, #1024)
+; CHECK: loop0(.LBB{{.}}_{{.}}, r{{[0-9]+}})
+; CHECK: endloop0
+
+define void @hwloop6(i32* nocapture %a, i32* nocapture %res) nounwind {
+entry:
+  br label %for.body
+
+for.body:
+  %i.02 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %arrayidx = getelementptr inbounds i32, i32* %a, i32 %i.02
+  %0 = load i32, i32* %arrayidx, align 4
+  %arrayidx1 = getelementptr inbounds i32, i32* %res, i32 %i.02
+  store i32 %0, i32* %arrayidx1, align 4
+  %inc = add nsw i32 %i.02, 1
+  %exitcond = icmp eq i32 %inc, 1024
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+  ret void
+}

test/CodeGen/Hexagon/hwloop2.ll

+; RUN: llc -disable-lsr -march=hexagon < %s | FileCheck %s
+
+; Test for multiple phis with induction variables.
+
+; CHECK: loop0(.LBB{{.}}_{{.}}, r{{[0-9]+}})
+; CHECK: endloop0
+
+define i32 @hwloop4(i32* nocapture %s, i32* nocapture %a, i32 %n) {
+entry:
+  %cmp3 = icmp eq i32 %n, 0
+  br i1 %cmp3, label %for.end, label %for.body.lr.ph
+
+for.body.lr.ph:
+  %.pre = load i32, i32* %s, align 4
+  br label %for.body
+
+for.body:
+  %0 = phi i32 [ %.pre, %for.body.lr.ph ], [ %add1, %for.body ]
+  %j.05 = phi i32 [ 0, %for.body.lr.ph ], [ %add2, %for.body ]
+  %lsr.iv = phi i32 [ %lsr.iv.next, %for.body ], [ %n, %for.body.lr.ph ]
+  %lsr.iv1 = phi i32* [ %scevgep, %for.body ], [ %a, %for.body.lr.ph ]
+  %1 = load i32, i32* %lsr.iv1, align 4
+  %add1 = add nsw i32 %0, %1
+  store i32 %add1, i32* %s, align 4
+  %add2 = add nsw i32 %j.05, 1
+  %lsr.iv.next = add i32 %lsr.iv, -1
+  %scevgep = getelementptr i32, i32* %lsr.iv1, i32 1
+  %cmp = icmp eq i32 %lsr.iv.next, 0
+  br i1 %cmp, label %for.end.loopexit, label %for.body
+
+for.end.loopexit:
+  br label %for.end
+
+for.end:
+  %j.0.lcssa = phi i32 [ 0, %entry ], [ %add2, %for.end.loopexit ]
+  ret i32 %j.0.lcssa
+}

test/CodeGen/Hexagon/hwloop3.ll

+; RUN: llc -march=hexagon < %s | FileCheck %s
+;
+; Remove the unconditional jump to following instruction.
+
+; CHECK: endloop0
+; CHECK-NOT: jump [[L1:.]]
+; CHECK-NOT: [[L1]]
+
+define void @test(i32* nocapture %a, i32 %n) nounwind {
+entry:
+  br label %for.body
+
+for.body:
+  %arrayidx.phi = phi i32* [ %a, %entry ], [ %arrayidx.inc, %for.body ]
+  %i.02 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %0 = load i32, i32* %arrayidx.phi, align 4
+  %add = add nsw i32 %0, 1
+  store i32 %add, i32* %arrayidx.phi, align 4
+  %inc = add nsw i32 %i.02, 1
+  %exitcond = icmp eq i32 %inc, 100
+  %arrayidx.inc = getelementptr i32, i32* %arrayidx.phi, i32 1
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+  ret void
+}
+

test/CodeGen/Hexagon/hwloop4.ll

+; RUN: llc -march=hexagon -mcpu=hexagonv5 < %s | FileCheck %s
+;
+; Remove the unnecessary 'add' instruction used for the hardware loop setup.
+
+; CHECK: [[OP0:r[0-9]+]] = add([[OP1:r[0-9]+]], #-[[OP2:[0-9]+]]
+; CHECK-NOT: add([[OP0]], #[[OP2]])
+; CHECK: lsr([[OP1]], #{{[0-9]+}})
+; CHECK: loop0
+
+define void @matrix_mul_matrix(i32 %N, i32* nocapture %C, i16* nocapture readnone %A, i16* nocapture readnone %B) #0 {
+entry:
+  %cmp4 = icmp eq i32 %N, 0
+  br i1 %cmp4, label %for.end, label %for.body.preheader
+
+for.body.preheader:
+  %maxval = add i32 %N, -7
+  %0 = icmp sgt i32 %maxval, 0
+  br i1 %0, label %for.body.preheader9, label %for.body.ur.preheader
+
+for.body.preheader9:
+  br label %for.body
+
+for.body:
+  %arrayidx.phi = phi i32* [ %arrayidx.inc.7, %for.body ], [ %C, %for.body.preheader9 ]
+  %i.05 = phi i32 [ %inc.7, %for.body ], [ 0, %for.body.preheader9 ]
+  store i32 %i.05, i32* %arrayidx.phi, align 4
+  %inc = add i32 %i.05, 1
+  %arrayidx.inc = getelementptr i32, i32* %arrayidx.phi, i32 1
+  store i32 %inc, i32* %arrayidx.inc, align 4
+  %inc.1 = add i32 %i.05, 2
+  %arrayidx.inc.1 = getelementptr i32, i32* %arrayidx.phi, i32 2
+  store i32 %inc.1, i32* %arrayidx.inc.1, align 4
+  %inc.2 = add i32 %i.05, 3
+  %arrayidx.inc.2 = getelementptr i32, i32* %arrayidx.phi, i32 3
+  store i32 %inc.2, i32* %arrayidx.inc.2, align 4
+  %inc.3 = add i32 %i.05, 4
+  %arrayidx.inc.3 = getelementptr i32, i32* %arrayidx.phi, i32 4
+  store i32 %inc.3, i32* %arrayidx.inc.3, align 4
+  %inc.4 = add i32 %i.05, 5
+  %arrayidx.inc.4 = getelementptr i32, i32* %arrayidx.phi, i32 5
+  store i32 %inc.4, i32* %arrayidx.inc.4, align 4
+  %inc.5 = add i32 %i.05, 6
+  %arrayidx.inc.5 = getelementptr i32, i32* %arrayidx.phi, i32 6
+  store i32 %inc.5, i32* %arrayidx.inc.5, align 4
+  %inc.6 = add i32 %i.05, 7
+  %arrayidx.inc.6 = getelementptr i32, i32* %arrayidx.phi, i32 7
+  store i32 %inc.6, i32* %arrayidx.inc.6, align 4
+  %inc.7 = add i32 %i.05, 8
+  %exitcond.7 = icmp slt i32 %inc.7, %maxval
+  %arrayidx.inc.7 = getelementptr i32, i32* %arrayidx.phi, i32 8
+  br i1 %exitcond.7, label %for.body, label %for.end.loopexit.ur-lcssa
+
+for.end.loopexit.ur-lcssa:
+  %1 = icmp eq i32 %inc.7, %N
+  br i1 %1, label %for.end, label %for.body.ur.preheader
+
+for.body.ur.preheader:
+  %arrayidx.phi.ur.ph = phi i32* [ %C, %for.body.preheader ], [ %arrayidx.inc.7, %for.end.loopexit.ur-lcssa ]
+  %i.05.ur.ph = phi i32 [ 0, %for.body.preheader ], [ %inc.7, %for.end.loopexit.ur-lcssa ]
+  br label %for.body.ur
+
+for.body.ur:
+  %arrayidx.phi.ur = phi i32* [ %arrayidx.inc.ur, %for.body.ur ], [ %arrayidx.phi.ur.ph, %for.body.ur.preheader ]
+  %i.05.ur = phi i32 [ %inc.ur, %for.body.ur ], [ %i.05.ur.ph, %for.body.ur.preheader ]
+  store i32 %i.05.ur, i32* %arrayidx.phi.ur, align 4
+  %inc.ur = add i32 %i.05.ur, 1
+  %exitcond.ur = icmp eq i32 %inc.ur, %N
+  %arrayidx.inc.ur = getelementptr i32, i32* %arrayidx.phi.ur, i32 1
+  br i1 %exitcond.ur, label %for.end.loopexit, label %for.body.ur
+
+for.end.loopexit:
+  br label %for.end
+
+for.end:
+  ret void
+}