[llvm] 3ee580d - [ARM][LowOverheadLoops] Handle reductions

Sam Parker via llvm-commits llvm-commits at lists.llvm.org
Wed Jul 1 00:32:07 PDT 2020


Author: Sam Parker
Date: 2020-07-01T08:31:49+01:00
New Revision: 3ee580d0176f69a9f724469660f1d1805e0b6a06

URL: https://github.com/llvm/llvm-project/commit/3ee580d0176f69a9f724469660f1d1805e0b6a06
DIFF: https://github.com/llvm/llvm-project/commit/3ee580d0176f69a9f724469660f1d1805e0b6a06.diff

LOG: [ARM][LowOverheadLoops] Handle reductions

While validating live-out values, record instructions that look like
a reduction. This will comprise of a vector op (for now only vadd),
a vorr (vmov) which store the previous value of vadd and then a vpsel
in the exit block which is predicated upon a vctp. This vctp will
combine the last two iterations using the vmov and vadd into a vector
which can then be consumed by a vaddv.

Once we have determined that it's safe to perform tail-predication,
we need to change this sequence of instructions so that the
predication doesn't produce incorrect code. This involves changing
the register allocation of the vadd so it updates itself and the
predication on the final iteration will not update the falsely
predicated lanes. This mimics what the vmov, vctp and vpsel do and
so we then don't need any of those instructions.

Differential Revision: https://reviews.llvm.org/D75533

Added: 
    

Modified: 
    llvm/include/llvm/CodeGen/ReachingDefAnalysis.h
    llvm/lib/CodeGen/ReachingDefAnalysis.cpp
    llvm/lib/Target/ARM/ARMBaseInstrInfo.h
    llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
    llvm/test/CodeGen/Thumb2/LowOverheadLoops/reductions.ll
    llvm/test/CodeGen/Thumb2/LowOverheadLoops/vector-arith-codegen.ll

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/CodeGen/ReachingDefAnalysis.h b/llvm/include/llvm/CodeGen/ReachingDefAnalysis.h
index 1444d4c295af..a8a436337e07 100644
--- a/llvm/include/llvm/CodeGen/ReachingDefAnalysis.h
+++ b/llvm/include/llvm/CodeGen/ReachingDefAnalysis.h
@@ -189,6 +189,7 @@ class ReachingDefAnalysis : public MachineFunctionPass {
   /// definition is found, recursively search the predecessor blocks for them.
   void getLiveOuts(MachineBasicBlock *MBB, int PhysReg, InstSet &Defs,
                    BlockSet &VisitedBBs) const;
+  void getLiveOuts(MachineBasicBlock *MBB, int PhysReg, InstSet &Defs) const;
 
   /// For the given block, collect the instructions that use the live-in
   /// value of the provided register. Return whether the value is still

diff  --git a/llvm/lib/CodeGen/ReachingDefAnalysis.cpp b/llvm/lib/CodeGen/ReachingDefAnalysis.cpp
index ea667f1704f6..5bd8b4b8e27f 100644
--- a/llvm/lib/CodeGen/ReachingDefAnalysis.cpp
+++ b/llvm/lib/CodeGen/ReachingDefAnalysis.cpp
@@ -389,6 +389,12 @@ ReachingDefAnalysis::getGlobalUses(MachineInstr *MI, int PhysReg,
   }
 }
 
+void ReachingDefAnalysis::getLiveOuts(MachineBasicBlock *MBB, int PhysReg,
+                                      InstSet &Defs) const {
+  SmallPtrSet<MachineBasicBlock*, 2> VisitedBBs;
+  getLiveOuts(MBB, PhysReg, Defs, VisitedBBs);
+}
+
 void
 ReachingDefAnalysis::getLiveOuts(MachineBasicBlock *MBB, int PhysReg,
                                  InstSet &Defs, BlockSet &VisitedBBs) const {

diff  --git a/llvm/lib/Target/ARM/ARMBaseInstrInfo.h b/llvm/lib/Target/ARM/ARMBaseInstrInfo.h
index 5e3525ed8951..1a75b011ca59 100644
--- a/llvm/lib/Target/ARM/ARMBaseInstrInfo.h
+++ b/llvm/lib/Target/ARM/ARMBaseInstrInfo.h
@@ -679,7 +679,6 @@ static inline bool isSubImmOpcode(int Opc) {
 static inline bool isMovRegOpcode(int Opc) {
   return Opc == ARM::MOVr || Opc == ARM::tMOVr || Opc == ARM::t2MOVr;
 }
-
 /// isValidCoprocessorNumber - decide whether an explicit coprocessor
 /// number is legal in generic instructions like CDP. The answer can
 /// vary with the subtarget.

diff  --git a/llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp b/llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
index bb57fa5d0ea8..be75d6bef08c 100644
--- a/llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
+++ b/llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
@@ -201,12 +201,25 @@ namespace {
     PredicatedMI *getDivergent() const { return Divergent; }
   };
 
+  struct Reduction {
+    MachineInstr *Init;
+    MachineInstr &Copy;
+    MachineInstr &Reduce;
+    MachineInstr &VPSEL;
+
+    Reduction(MachineInstr *Init, MachineInstr *Mov, MachineInstr *Add,
+              MachineInstr *Sel)
+      : Init(Init), Copy(*Mov), Reduce(*Add), VPSEL(*Sel) { }
+  };
+
   struct LowOverheadLoop {
 
     MachineLoop &ML;
+    MachineBasicBlock *Preheader = nullptr;
     MachineLoopInfo &MLI;
     ReachingDefAnalysis &RDA;
     const TargetRegisterInfo &TRI;
+    const ARMBaseInstrInfo &TII;
     MachineFunction *MF = nullptr;
     MachineInstr *InsertPt = nullptr;
     MachineInstr *Start = nullptr;
@@ -218,14 +231,20 @@ namespace {
     SetVector<MachineInstr*> CurrentPredicate;
     SmallVector<VPTBlock, 4> VPTBlocks;
     SmallPtrSet<MachineInstr*, 4> ToRemove;
+    SmallVector<std::unique_ptr<Reduction>, 1> Reductions;
     SmallPtrSet<MachineInstr*, 4> BlockMasksToRecompute;
     bool Revert = false;
     bool CannotTailPredicate = false;
 
     LowOverheadLoop(MachineLoop &ML, MachineLoopInfo &MLI,
-                    ReachingDefAnalysis &RDA, const TargetRegisterInfo &TRI)
-      : ML(ML), MLI(MLI), RDA(RDA), TRI(TRI) {
+                    ReachingDefAnalysis &RDA, const TargetRegisterInfo &TRI,
+                    const ARMBaseInstrInfo &TII)
+      : ML(ML), MLI(MLI), RDA(RDA), TRI(TRI), TII(TII) {
       MF = ML.getHeader()->getParent();
+      if (auto *MBB = ML.getLoopPreheader())
+        Preheader = MBB;
+      else if (auto *MBB = MLI.findLoopPreheader(&ML, true))
+        Preheader = MBB;
     }
 
     // If this is an MVE instruction, check that we know how to use tail
@@ -249,9 +268,13 @@ namespace {
     // of elements to the loop start instruction.
     bool ValidateTailPredicate(MachineInstr *StartInsertPt);
 
+    // See whether the live-out instructions are a reduction that we can fixup
+    // later.
+    bool FindValidReduction(InstSet &LiveMIs, InstSet &LiveOutUsers);
+
     // Check that any values available outside of the loop will be the same
     // after tail predication conversion.
-    bool ValidateLiveOuts() const;
+    bool ValidateLiveOuts();
 
     // Is it safe to define LR with DLS/WLS?
     // LR can be defined if it is the operand to start, because it's the same
@@ -341,6 +364,8 @@ namespace {
 
     void ConvertVPTBlocks(LowOverheadLoop &LoLoop);
 
+    void FixupReductions(LowOverheadLoop &LoLoop) const;
+
     MachineInstr *ExpandLoopStart(LowOverheadLoop &LoLoop);
 
     void Expand(LowOverheadLoop &LoLoop);
@@ -481,7 +506,7 @@ bool LowOverheadLoop::ValidateTailPredicate(MachineInstr *StartInsertPt) {
   };
 
   // First, find the block that looks like the preheader.
-  MachineBasicBlock *MBB = MLI.findLoopPreheader(&ML, true);
+  MachineBasicBlock *MBB = Preheader;
   if (!MBB) {
     LLVM_DEBUG(dbgs() << "ARM Loops: Didn't find preheader.\n");
     return false;
@@ -626,7 +651,109 @@ static bool producesFalseLanesZero(MachineInstr &MI,
   return true;
 }
 
-bool LowOverheadLoop::ValidateLiveOuts() const {
+bool
+LowOverheadLoop::FindValidReduction(InstSet &LiveMIs, InstSet &LiveOutUsers) {
+  // Also check for reductions where the operation needs to be merging values
+  // from the last and previous loop iterations. This means an instruction
+  // producing a value and a vmov storing the value calculated in the previous
+  // iteration. So we can have two live-out regs, one produced by a vmov and
+  // both being consumed by a vpsel.
+  LLVM_DEBUG(dbgs() << "ARM Loops: Looking for reduction live-outs:\n";
+             for (auto *MI : LiveMIs)
+               dbgs() << " - " << *MI);
+
+  if (!Preheader)
+    return false;
+
+  // Expect a vmov, a vadd and a single vpsel user.
+  // TODO: This means we can't currently support multiple reductions in the
+  // loop.
+  if (LiveMIs.size() != 2 || LiveOutUsers.size() != 1)
+    return false;
+
+  MachineInstr *VPSEL = *LiveOutUsers.begin();
+  if (VPSEL->getOpcode() != ARM::MVE_VPSEL)
+    return false;
+
+  unsigned VPRIdx = llvm::findFirstVPTPredOperandIdx(*VPSEL) + 1;
+  MachineInstr *Pred = RDA.getMIOperand(VPSEL, VPRIdx);
+  if (!Pred || Pred != VCTP) {
+    LLVM_DEBUG(dbgs() << "ARM Loops: Not using equivalent predicate.\n");
+    return false;
+  }
+
+  MachineInstr *Reduce = RDA.getMIOperand(VPSEL, 1);
+  if (!Reduce)
+    return false;
+
+  assert(LiveMIs.count(Reduce) && "Expected MI to be live-out");
+
+  // TODO: Support more operations than VADD.
+  switch (VCTP->getOpcode()) {
+  default:
+    return false;
+  case ARM::MVE_VCTP8:
+    if (Reduce->getOpcode() != ARM::MVE_VADDi8)
+      return false;
+    break;
+  case ARM::MVE_VCTP16:
+    if (Reduce->getOpcode() != ARM::MVE_VADDi16)
+      return false;
+    break;
+  case ARM::MVE_VCTP32:
+    if (Reduce->getOpcode() != ARM::MVE_VADDi32)
+      return false;
+    break;
+  }
+
+  // Test that the reduce op is overwriting ones of its operands.
+  if (Reduce->getOperand(0).getReg() != Reduce->getOperand(1).getReg() &&
+      Reduce->getOperand(0).getReg() != Reduce->getOperand(2).getReg()) {
+    LLVM_DEBUG(dbgs() << "ARM Loops: Reducing op isn't overwriting itself.\n");
+    return false;
+  }
+
+  // Check that the VORR is actually a VMOV.
+  MachineInstr *Copy = RDA.getMIOperand(VPSEL, 2);
+  if (!Copy || Copy->getOpcode() != ARM::MVE_VORR ||
+      !Copy->getOperand(1).isReg() || !Copy->getOperand(2).isReg() ||
+      Copy->getOperand(1).getReg() != Copy->getOperand(2).getReg())
+    return false;
+
+  assert(LiveMIs.count(Copy) && "Expected MI to be live-out");
+
+  // Check that the vadd and vmov are only used by each other and the vpsel.
+  SmallPtrSet<MachineInstr*, 2> CopyUsers;
+  RDA.getGlobalUses(Copy, Copy->getOperand(0).getReg(), CopyUsers);
+  if (CopyUsers.size() > 2 || !CopyUsers.count(Reduce)) {
+    LLVM_DEBUG(dbgs() << "ARM Loops: Copy users unsupported.\n");
+    return false;
+  }
+
+  SmallPtrSet<MachineInstr*, 2> ReduceUsers;
+  RDA.getGlobalUses(Reduce, Reduce->getOperand(0).getReg(), ReduceUsers);
+  if (ReduceUsers.size() > 2 || !ReduceUsers.count(Copy)) {
+    LLVM_DEBUG(dbgs() << "ARM Loops: Reduce users unsupported.\n");
+    return false;
+  }
+
+  // Then find whether there's an instruction initialising the register that
+  // is storing the reduction.
+  SmallPtrSet<MachineInstr*, 2> Incoming;
+  RDA.getLiveOuts(Preheader, Copy->getOperand(1).getReg(), Incoming);
+  if (Incoming.size() > 1)
+    return false;
+
+  MachineInstr *Init = Incoming.empty() ? nullptr : *Incoming.begin();
+  LLVM_DEBUG(dbgs() << "ARM Loops: Found a reduction:\n"
+             << " - " << *Copy
+             << " - " << *Reduce
+             << " - " << *VPSEL);
+  Reductions.push_back(std::make_unique<Reduction>(Init, Copy, Reduce, VPSEL));
+  return true;
+}
+
+bool LowOverheadLoop::ValidateLiveOuts() {
   // We want to find out if the tail-predicated version of this loop will
   // produce the same values as the loop in its original form. For this to
   // be true, the newly inserted implicit predication must not change the
@@ -652,9 +779,9 @@ bool LowOverheadLoop::ValidateLiveOuts() const {
   SetVector<MachineInstr *> FalseLanesUnknown;
   SmallPtrSet<MachineInstr *, 4> FalseLanesZero;
   SmallPtrSet<MachineInstr *, 4> Predicated;
-  MachineBasicBlock *MBB = ML.getHeader();
+  MachineBasicBlock *Header = ML.getHeader();
 
-  for (auto &MI : *MBB) {
+  for (auto &MI : *Header) {
     const MCInstrDesc &MCID = MI.getDesc();
     uint64_t Flags = MCID.TSFlags;
     if ((Flags & ARMII::DomainMask) != ARMII::DomainMVE)
@@ -702,6 +829,9 @@ bool LowOverheadLoop::ValidateLiveOuts() const {
   // stored and then we can work towards the leaves, hopefully adding more
   // instructions to Predicated. Successfully terminating the loop means that
   // all the unknown values have to found to be masked by predicated user(s).
+  // For any unpredicated values, we store them in NonPredicated so that we
+  // can later check whether these form a reduction.
+  SmallPtrSet<MachineInstr*, 2> NonPredicated;
   for (auto *MI : reverse(FalseLanesUnknown)) {
     for (auto &MO : MI->operands()) {
       if (!isRegInClass(MO, QPRs) || !MO.isDef())
@@ -709,39 +839,48 @@ bool LowOverheadLoop::ValidateLiveOuts() const {
       if (!HasPredicatedUsers(MI, MO, Predicated)) {
         LLVM_DEBUG(dbgs() << "ARM Loops: Found an unknown def of : "
                           << TRI.getRegAsmName(MO.getReg()) << " at " << *MI);
-        return false;
+        NonPredicated.insert(MI);
+        continue;
       }
     }
     // Any unknown false lanes have been masked away by the user(s).
     Predicated.insert(MI);
   }
 
-  // Collect Q-regs that are live in the exit blocks. We don't collect scalars
-  // because they won't be affected by lane predication.
-  SmallSet<Register, 2> LiveOuts;
+  SmallPtrSet<MachineInstr *, 2> LiveOutMIs;
+  SmallPtrSet<MachineInstr*, 2> LiveOutUsers;
   SmallVector<MachineBasicBlock *, 2> ExitBlocks;
   ML.getExitBlocks(ExitBlocks);
-  for (auto *MBB : ExitBlocks)
-    for (const MachineBasicBlock::RegisterMaskPair &RegMask : MBB->liveins())
-      if (QPRs->contains(RegMask.PhysReg))
-        LiveOuts.insert(RegMask.PhysReg);
-
-  // Collect the instructions in the loop body that define the live-out values.
-  SmallPtrSet<MachineInstr *, 2> LiveMIs;
   assert(ML.getNumBlocks() == 1 && "Expected single block loop!");
-  for (auto Reg : LiveOuts)
-    if (auto *MI = RDA.getLocalLiveOutMIDef(MBB, Reg))
-      LiveMIs.insert(MI);
+  assert(ExitBlocks.size() == 1 && "Expected a single exit block");
+  MachineBasicBlock *ExitBB = ExitBlocks.front();
+  for (const MachineBasicBlock::RegisterMaskPair &RegMask : ExitBB->liveins()) {
+    // Check Q-regs that are live in the exit blocks. We don't collect scalars
+    // because they won't be affected by lane predication.
+    if (QPRs->contains(RegMask.PhysReg)) {
+      if (auto *MI = RDA.getLocalLiveOutMIDef(Header, RegMask.PhysReg))
+        LiveOutMIs.insert(MI);
+      RDA.getLiveInUses(ExitBB, RegMask.PhysReg, LiveOutUsers);
+    }
+  }
+
+  // If we have any non-predicated live-outs, they need to be part of a
+  // reduction that we can fixup later. The reduction that the form of an
+  // operation that uses its previous values through a vmov and then a vpsel
+  // resides in the exit blocks to select the final bytes from n and n-1
+  // iterations.
+  if (!NonPredicated.empty() &&
+      !FindValidReduction(NonPredicated, LiveOutUsers))
+    return false;
 
-  LLVM_DEBUG(dbgs() << "ARM Loops: Found loop live-outs:\n";
-             for (auto *MI : LiveMIs)
-               dbgs() << " - " << *MI);
   // We've already validated that any VPT predication within the loop will be
   // equivalent when we perform the predication transformation; so we know that
   // any VPT predicated instruction is predicated upon VCTP. Any live-out
-  // instruction needs to be predicated, so check this here.
-  for (auto *MI : LiveMIs)
-    if (!isVectorPredicated(MI))
+  // instruction needs to be predicated, so check this here. The instructions
+  // in NonPredicated have been found to be a reduction that we can ensure its
+  // legality.
+  for (auto *MI : LiveOutMIs)
+    if (!isVectorPredicated(MI) && !NonPredicated.count(MI))
       return false;
 
   return true;
@@ -949,14 +1088,12 @@ bool ARMLowOverheadLoops::ProcessLoop(MachineLoop *ML) {
     return nullptr;
   };
 
-  LowOverheadLoop LoLoop(*ML, *MLI, *RDA, *TRI);
+  LowOverheadLoop LoLoop(*ML, *MLI, *RDA, *TRI, *TII);
   // Search the preheader for the start intrinsic.
   // FIXME: I don't see why we shouldn't be supporting multiple predecessors
   // with potentially multiple set.loop.iterations, so we need to enable this.
-  if (auto *Preheader = ML->getLoopPreheader())
-    LoLoop.Start = SearchForStart(Preheader);
-  else if (auto *Preheader = MLI->findLoopPreheader(ML, true))
-    LoLoop.Start = SearchForStart(Preheader);
+  if (LoLoop.Preheader)
+    LoLoop.Start = SearchForStart(LoLoop.Preheader);
   else
     return false;
 
@@ -1210,6 +1347,61 @@ MachineInstr* ARMLowOverheadLoops::ExpandLoopStart(LowOverheadLoop &LoLoop) {
   return &*MIB;
 }
 
+void ARMLowOverheadLoops::FixupReductions(LowOverheadLoop &LoLoop) const {
+  LLVM_DEBUG(dbgs() << "ARM Loops: Fixing up reduction(s).\n");
+  auto BuildMov = [this](MachineInstr &InsertPt, Register To, Register From) {
+    MachineBasicBlock *MBB = InsertPt.getParent();
+    MachineInstrBuilder MIB =
+      BuildMI(*MBB, &InsertPt, InsertPt.getDebugLoc(), TII->get(ARM::MVE_VORR));
+    MIB.addDef(To);
+    MIB.addReg(From);
+    MIB.addReg(From);
+    MIB.addImm(0);
+    MIB.addReg(0);
+    MIB.addReg(To);
+    LLVM_DEBUG(dbgs() << "ARM Loops: Inserted VMOV: " << *MIB);
+  };
+
+  for (auto &Reduction : LoLoop.Reductions) {
+    MachineInstr &Copy = Reduction->Copy;
+    MachineInstr &Reduce = Reduction->Reduce;
+    Register DestReg = Copy.getOperand(0).getReg();
+
+    // Change the initialiser if present
+    if (Reduction->Init) {
+      MachineInstr *Init = Reduction->Init;
+
+      for (unsigned i = 0; i < Init->getNumOperands(); ++i) {
+        MachineOperand &MO = Init->getOperand(i);
+        if (MO.isReg() && MO.isUse() && MO.isTied() &&
+            Init->findTiedOperandIdx(i) == 0)
+          Init->getOperand(i).setReg(DestReg);
+      }
+      Init->getOperand(0).setReg(DestReg);
+      LLVM_DEBUG(dbgs() << "ARM Loops: Changed init regs: " << *Init);
+    } else
+      BuildMov(LoLoop.Preheader->instr_back(), DestReg, Copy.getOperand(1).getReg());
+
+    // Change the reducing op to write to the register that is used to copy
+    // its value on the next iteration. Also update the tied-def operand.
+    Reduce.getOperand(0).setReg(DestReg);
+    Reduce.getOperand(5).setReg(DestReg);
+    LLVM_DEBUG(dbgs() << "ARM Loops: Changed reduction regs: " << Reduce);
+
+    // Instead of a vpsel, just copy the register into the necessary one.
+    MachineInstr &VPSEL = Reduction->VPSEL;
+    if (VPSEL.getOperand(0).getReg() != DestReg)
+      BuildMov(VPSEL, VPSEL.getOperand(0).getReg(), DestReg);
+
+    // Remove the unnecessary instructions.
+    LLVM_DEBUG(dbgs() << "ARM Loops: Removing:\n"
+               << " - " << Copy
+               << " - " << VPSEL << "\n");
+    Copy.eraseFromParent();
+    VPSEL.eraseFromParent();
+  }
+}
+
 void ARMLowOverheadLoops::ConvertVPTBlocks(LowOverheadLoop &LoLoop) {
   auto RemovePredicate = [](MachineInstr *MI) {
     LLVM_DEBUG(dbgs() << "ARM Loops: Removing predicate from: " << *MI);
@@ -1363,8 +1555,10 @@ void ARMLowOverheadLoops::Expand(LowOverheadLoop &LoLoop) {
     RemoveDeadBranch(LoLoop.Start);
     LoLoop.End = ExpandLoopEnd(LoLoop);
     RemoveDeadBranch(LoLoop.End);
-    if (LoLoop.IsTailPredicationLegal())
+    if (LoLoop.IsTailPredicationLegal()) {
       ConvertVPTBlocks(LoLoop);
+      FixupReductions(LoLoop);
+    }
     for (auto *I : LoLoop.ToRemove) {
       LLVM_DEBUG(dbgs() << "ARM Loops: Erasing " << *I);
       I->eraseFromParent();

diff  --git a/llvm/test/CodeGen/Thumb2/LowOverheadLoops/reductions.ll b/llvm/test/CodeGen/Thumb2/LowOverheadLoops/reductions.ll
index 941cf2f20221..12c3ca0525f2 100644
--- a/llvm/test/CodeGen/Thumb2/LowOverheadLoops/reductions.ll
+++ b/llvm/test/CodeGen/Thumb2/LowOverheadLoops/reductions.ll
@@ -152,26 +152,16 @@ define dso_local arm_aapcs_vfpcc zeroext i8 @one_loop_sub_add_v16i8(i8* nocaptur
 ; CHECK-NEXT:    uxtbeq r0, r0
 ; CHECK-NEXT:    bxeq lr
 ; CHECK-NEXT:    push {r7, lr}
-; CHECK-NEXT:    add.w r3, r2, #15
-; CHECK-NEXT:    vmov.i32 q1, #0x0
-; CHECK-NEXT:    bic r3, r3, #15
-; CHECK-NEXT:    sub.w r12, r3, #16
-; CHECK-NEXT:    movs r3, #1
-; CHECK-NEXT:    add.w lr, r3, r12, lsr #4
-; CHECK-NEXT:    dls lr, lr
+; CHECK-NEXT:    vmov.i32 q0, #0x0
+; CHECK-NEXT:    dlstp.8 lr, r2
 ; CHECK-NEXT:  .LBB2_1: @ %vector.body
 ; CHECK-NEXT:    @ =>This Inner Loop Header: Depth=1
-; CHECK-NEXT:    vctp.8 r2
-; CHECK-NEXT:    vmov q0, q1
-; CHECK-NEXT:    vpstt
-; CHECK-NEXT:    vldrbt.u8 q1, [r1], #16
-; CHECK-NEXT:    vldrbt.u8 q2, [r0], #16
-; CHECK-NEXT:    subs r2, #16
+; CHECK-NEXT:    vldrb.u8 q1, [r1], #16
+; CHECK-NEXT:    vldrb.u8 q2, [r0], #16
 ; CHECK-NEXT:    vsub.i8 q1, q2, q1
-; CHECK-NEXT:    vadd.i8 q1, q1, q0
-; CHECK-NEXT:    le lr, .LBB2_1
+; CHECK-NEXT:    vadd.i8 q0, q1, q0
+; CHECK-NEXT:    letp lr, .LBB2_1
 ; CHECK-NEXT:  @ %bb.2: @ %middle.block
-; CHECK-NEXT:    vpsel q0, q1, q0
 ; CHECK-NEXT:    vaddv.u8 r0, q0
 ; CHECK-NEXT:    pop.w {r7, lr}
 ; CHECK-NEXT:    uxtb r0, r0
@@ -221,26 +211,16 @@ define dso_local arm_aapcs_vfpcc signext i16 @one_loop_sub_add_v8i16(i8* nocaptu
 ; CHECK-NEXT:    sxtheq r0, r0
 ; CHECK-NEXT:    bxeq lr
 ; CHECK-NEXT:    push {r7, lr}
-; CHECK-NEXT:    adds r3, r2, #7
-; CHECK-NEXT:    vmov.i32 q1, #0x0
-; CHECK-NEXT:    bic r3, r3, #7
-; CHECK-NEXT:    sub.w r12, r3, #8
-; CHECK-NEXT:    movs r3, #1
-; CHECK-NEXT:    add.w lr, r3, r12, lsr #3
-; CHECK-NEXT:    dls lr, lr
+; CHECK-NEXT:    vmov.i32 q0, #0x0
+; CHECK-NEXT:    dlstp.16 lr, r2
 ; CHECK-NEXT:  .LBB3_1: @ %vector.body
 ; CHECK-NEXT:    @ =>This Inner Loop Header: Depth=1
-; CHECK-NEXT:    vctp.16 r2
-; CHECK-NEXT:    vmov q0, q1
-; CHECK-NEXT:    vpstt
-; CHECK-NEXT:    vldrbt.u16 q1, [r0], #8
-; CHECK-NEXT:    vldrbt.u16 q2, [r1], #8
-; CHECK-NEXT:    subs r2, #8
+; CHECK-NEXT:    vldrb.u16 q1, [r0], #8
+; CHECK-NEXT:    vldrb.u16 q2, [r1], #8
 ; CHECK-NEXT:    vsub.i16 q1, q2, q1
-; CHECK-NEXT:    vadd.i16 q1, q1, q0
-; CHECK-NEXT:    le lr, .LBB3_1
+; CHECK-NEXT:    vadd.i16 q0, q1, q0
+; CHECK-NEXT:    letp lr, .LBB3_1
 ; CHECK-NEXT:  @ %bb.2: @ %middle.block
-; CHECK-NEXT:    vpsel q0, q1, q0
 ; CHECK-NEXT:    vaddv.u16 r0, q0
 ; CHECK-NEXT:    pop.w {r7, lr}
 ; CHECK-NEXT:    sxth r0, r0
@@ -292,26 +272,16 @@ define dso_local arm_aapcs_vfpcc zeroext i8 @one_loop_mul_add_v16i8(i8* nocaptur
 ; CHECK-NEXT:    uxtbeq r0, r0
 ; CHECK-NEXT:    bxeq lr
 ; CHECK-NEXT:    push {r7, lr}
-; CHECK-NEXT:    add.w r3, r2, #15
-; CHECK-NEXT:    vmov.i32 q1, #0x0
-; CHECK-NEXT:    bic r3, r3, #15
-; CHECK-NEXT:    sub.w r12, r3, #16
-; CHECK-NEXT:    movs r3, #1
-; CHECK-NEXT:    add.w lr, r3, r12, lsr #4
-; CHECK-NEXT:    dls lr, lr
+; CHECK-NEXT:    vmov.i32 q0, #0x0
+; CHECK-NEXT:    dlstp.8 lr, r2
 ; CHECK-NEXT:  .LBB4_1: @ %vector.body
 ; CHECK-NEXT:    @ =>This Inner Loop Header: Depth=1
-; CHECK-NEXT:    vctp.8 r2
-; CHECK-NEXT:    vmov q0, q1
-; CHECK-NEXT:    vpstt
-; CHECK-NEXT:    vldrbt.u8 q1, [r0], #16
-; CHECK-NEXT:    vldrbt.u8 q2, [r1], #16
-; CHECK-NEXT:    subs r2, #16
+; CHECK-NEXT:    vldrb.u8 q1, [r0], #16
+; CHECK-NEXT:    vldrb.u8 q2, [r1], #16
 ; CHECK-NEXT:    vmul.i8 q1, q2, q1
-; CHECK-NEXT:    vadd.i8 q1, q1, q0
-; CHECK-NEXT:    le lr, .LBB4_1
+; CHECK-NEXT:    vadd.i8 q0, q1, q0
+; CHECK-NEXT:    letp lr, .LBB4_1
 ; CHECK-NEXT:  @ %bb.2: @ %middle.block
-; CHECK-NEXT:    vpsel q0, q1, q0
 ; CHECK-NEXT:    vaddv.u8 r0, q0
 ; CHECK-NEXT:    pop.w {r7, lr}
 ; CHECK-NEXT:    uxtb r0, r0
@@ -361,26 +331,16 @@ define dso_local arm_aapcs_vfpcc signext i16 @one_loop_mul_add_v8i16(i8* nocaptu
 ; CHECK-NEXT:    sxtheq r0, r0
 ; CHECK-NEXT:    bxeq lr
 ; CHECK-NEXT:    push {r7, lr}
-; CHECK-NEXT:    adds r3, r2, #7
-; CHECK-NEXT:    vmov.i32 q1, #0x0
-; CHECK-NEXT:    bic r3, r3, #7
-; CHECK-NEXT:    sub.w r12, r3, #8
-; CHECK-NEXT:    movs r3, #1
-; CHECK-NEXT:    add.w lr, r3, r12, lsr #3
-; CHECK-NEXT:    dls lr, lr
+; CHECK-NEXT:    vmov.i32 q0, #0x0
+; CHECK-NEXT:    dlstp.16 lr, r2
 ; CHECK-NEXT:  .LBB5_1: @ %vector.body
 ; CHECK-NEXT:    @ =>This Inner Loop Header: Depth=1
-; CHECK-NEXT:    vctp.16 r2
-; CHECK-NEXT:    vmov q0, q1
-; CHECK-NEXT:    vpstt
-; CHECK-NEXT:    vldrbt.u16 q1, [r0], #8
-; CHECK-NEXT:    vldrbt.u16 q2, [r1], #8
-; CHECK-NEXT:    subs r2, #8
+; CHECK-NEXT:    vldrb.u16 q1, [r0], #8
+; CHECK-NEXT:    vldrb.u16 q2, [r1], #8
 ; CHECK-NEXT:    vmul.i16 q1, q2, q1
-; CHECK-NEXT:    vadd.i16 q1, q1, q0
-; CHECK-NEXT:    le lr, .LBB5_1
+; CHECK-NEXT:    vadd.i16 q0, q1, q0
+; CHECK-NEXT:    letp lr, .LBB5_1
 ; CHECK-NEXT:  @ %bb.2: @ %middle.block
-; CHECK-NEXT:    vpsel q0, q1, q0
 ; CHECK-NEXT:    vaddv.u16 r0, q0
 ; CHECK-NEXT:    pop.w {r7, lr}
 ; CHECK-NEXT:    sxth r0, r0
@@ -456,25 +416,19 @@ define dso_local arm_aapcs_vfpcc i32 @two_loops_mul_add_v4i32(i8* nocapture read
 ; CHECK-NEXT:    vaddv.u32 r12, q0
 ; CHECK-NEXT:    cbz r2, .LBB6_7
 ; CHECK-NEXT:  @ %bb.4: @ %vector.ph47
-; CHECK-NEXT:    movs r3, #1
-; CHECK-NEXT:    add.w lr, r3, r6, lsr #2
 ; CHECK-NEXT:    movs r3, #0
-; CHECK-NEXT:    dls lr, lr
+; CHECK-NEXT:    dlstp.32 lr, r2
 ; CHECK-NEXT:    vdup.32 q0, r3
-; CHECK-NEXT:    vmov.32 q0[0], r12
+; CHECK-NEXT:    vmov.32 q1[0], r12
 ; CHECK-NEXT:  .LBB6_5: @ %vector.body46
 ; CHECK-NEXT:    @ =>This Inner Loop Header: Depth=1
-; CHECK-NEXT:    vctp.32 r2
-; CHECK-NEXT:    vmov q1, q0
-; CHECK-NEXT:    vpstt
-; CHECK-NEXT:    vldrbt.u32 q0, [r0], #4
-; CHECK-NEXT:    vldrbt.u32 q2, [r1], #4
-; CHECK-NEXT:    subs r2, #4
+; CHECK-NEXT:    vldrb.u32 q0, [r0], #4
+; CHECK-NEXT:    vldrb.u32 q2, [r1], #4
 ; CHECK-NEXT:    vmul.i32 q0, q2, q0
-; CHECK-NEXT:    vadd.i32 q0, q0, q1
-; CHECK-NEXT:    le lr, .LBB6_5
+; CHECK-NEXT:    vadd.i32 q1, q0, q1
+; CHECK-NEXT:    letp lr, .LBB6_5
 ; CHECK-NEXT:  @ %bb.6: @ %middle.block44
-; CHECK-NEXT:    vpsel q0, q0, q1
+; CHECK-NEXT:    vmov q0, q1
 ; CHECK-NEXT:    vaddv.u32 r12, q0
 ; CHECK-NEXT:  .LBB6_7: @ %for.cond.cleanup7
 ; CHECK-NEXT:    mov r0, r12

diff  --git a/llvm/test/CodeGen/Thumb2/LowOverheadLoops/vector-arith-codegen.ll b/llvm/test/CodeGen/Thumb2/LowOverheadLoops/vector-arith-codegen.ll
index d2e9c584c257..26a570ac4c29 100644
--- a/llvm/test/CodeGen/Thumb2/LowOverheadLoops/vector-arith-codegen.ll
+++ b/llvm/test/CodeGen/Thumb2/LowOverheadLoops/vector-arith-codegen.ll
@@ -9,28 +9,19 @@ define dso_local i32 @mul_reduce_add(i32* noalias nocapture readonly %a, i32* no
 ; CHECK-NEXT:    moveq r0, #0
 ; CHECK-NEXT:    bxeq lr
 ; CHECK-NEXT:    push {r7, lr}
-; CHECK-NEXT:    adds r3, r2, #3
-; CHECK-NEXT:    vmov.i32 q0, #0x0
-; CHECK-NEXT:    bic r3, r3, #3
-; CHECK-NEXT:    sub.w r12, r3, #4
-; CHECK-NEXT:    movs r3, #1
-; CHECK-NEXT:    add.w lr, r3, r12, lsr #2
+; CHECK-NEXT:    vmov.i32 q1, #0x0
 ; CHECK-NEXT:    movs r3, #0
-; CHECK-NEXT:    dls lr, lr
+; CHECK-NEXT:    dlstp.32 lr, r2
 ; CHECK-NEXT:  .LBB0_1: @ %vector.body
 ; CHECK-NEXT:    @ =>This Inner Loop Header: Depth=1
-; CHECK-NEXT:    vctp.32 r2
-; CHECK-NEXT:    vmov q1, q0
-; CHECK-NEXT:    vpstt
-; CHECK-NEXT:    vldrwt.u32 q0, [r0], #16
-; CHECK-NEXT:    vldrwt.u32 q2, [r1], #16
+; CHECK-NEXT:    vldrw.u32 q0, [r0], #16
+; CHECK-NEXT:    vldrw.u32 q2, [r1], #16
 ; CHECK-NEXT:    adds r3, #4
 ; CHECK-NEXT:    vmul.i32 q0, q2, q0
-; CHECK-NEXT:    subs r2, #4
-; CHECK-NEXT:    vadd.i32 q0, q0, q1
-; CHECK-NEXT:    le lr, .LBB0_1
+; CHECK-NEXT:    vadd.i32 q1, q0, q1
+; CHECK-NEXT:    letp lr, .LBB0_1
 ; CHECK-NEXT:  @ %bb.2: @ %middle.block
-; CHECK-NEXT:    vpsel q0, q0, q1
+; CHECK-NEXT:    vmov q0, q1
 ; CHECK-NEXT:    vaddv.u32 r0, q0
 ; CHECK-NEXT:    pop {r7, pc}
 entry:
@@ -85,26 +76,17 @@ define dso_local i32 @mul_reduce_add_const(i32* noalias nocapture readonly %a, i
 ; CHECK-NEXT:    moveq r0, #0
 ; CHECK-NEXT:    bxeq lr
 ; CHECK-NEXT:    push {r7, lr}
-; CHECK-NEXT:    adds r1, r2, #3
-; CHECK-NEXT:    movs r3, #1
-; CHECK-NEXT:    bic r1, r1, #3
-; CHECK-NEXT:    vmov.i32 q0, #0x0
-; CHECK-NEXT:    subs r1, #4
-; CHECK-NEXT:    add.w lr, r3, r1, lsr #2
+; CHECK-NEXT:    vmov.i32 q1, #0x0
 ; CHECK-NEXT:    movs r1, #0
-; CHECK-NEXT:    dls lr, lr
+; CHECK-NEXT:    dlstp.32 lr, r2
 ; CHECK-NEXT:  .LBB1_1: @ %vector.body
 ; CHECK-NEXT:    @ =>This Inner Loop Header: Depth=1
-; CHECK-NEXT:    vctp.32 r2
-; CHECK-NEXT:    vmov q1, q0
-; CHECK-NEXT:    vpst
-; CHECK-NEXT:    vldrwt.u32 q0, [r0], #16
+; CHECK-NEXT:    vldrw.u32 q0, [r0], #16
 ; CHECK-NEXT:    adds r1, #4
-; CHECK-NEXT:    subs r2, #4
-; CHECK-NEXT:    vadd.i32 q0, q0, q1
-; CHECK-NEXT:    le lr, .LBB1_1
+; CHECK-NEXT:    vadd.i32 q1, q0, q1
+; CHECK-NEXT:    letp lr, .LBB1_1
 ; CHECK-NEXT:  @ %bb.2: @ %middle.block
-; CHECK-NEXT:    vpsel q0, q0, q1
+; CHECK-NEXT:    vmov q0, q1
 ; CHECK-NEXT:    vaddv.u32 r0, q0
 ; CHECK-NEXT:    pop {r7, pc}
 entry:
@@ -155,26 +137,17 @@ define dso_local i32 @add_reduce_add_const(i32* noalias nocapture readonly %a, i
 ; CHECK-NEXT:    moveq r0, #0
 ; CHECK-NEXT:    bxeq lr
 ; CHECK-NEXT:    push {r7, lr}
-; CHECK-NEXT:    adds r1, r2, #3
-; CHECK-NEXT:    movs r3, #1
-; CHECK-NEXT:    bic r1, r1, #3
-; CHECK-NEXT:    vmov.i32 q0, #0x0
-; CHECK-NEXT:    subs r1, #4
-; CHECK-NEXT:    add.w lr, r3, r1, lsr #2
+; CHECK-NEXT:    vmov.i32 q1, #0x0
 ; CHECK-NEXT:    movs r1, #0
-; CHECK-NEXT:    dls lr, lr
+; CHECK-NEXT:    dlstp.32 lr, r2
 ; CHECK-NEXT:  .LBB2_1: @ %vector.body
 ; CHECK-NEXT:    @ =>This Inner Loop Header: Depth=1
-; CHECK-NEXT:    vctp.32 r2
-; CHECK-NEXT:    vmov q1, q0
-; CHECK-NEXT:    vpst
-; CHECK-NEXT:    vldrwt.u32 q0, [r0], #16
+; CHECK-NEXT:    vldrw.u32 q0, [r0], #16
 ; CHECK-NEXT:    adds r1, #4
-; CHECK-NEXT:    subs r2, #4
-; CHECK-NEXT:    vadd.i32 q0, q0, q1
-; CHECK-NEXT:    le lr, .LBB2_1
+; CHECK-NEXT:    vadd.i32 q1, q0, q1
+; CHECK-NEXT:    letp lr, .LBB2_1
 ; CHECK-NEXT:  @ %bb.2: @ %middle.block
-; CHECK-NEXT:    vpsel q0, q0, q1
+; CHECK-NEXT:    vmov q0, q1
 ; CHECK-NEXT:    vaddv.u32 r0, q0
 ; CHECK-NEXT:    pop {r7, pc}
 entry:


        


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