[llvm] r279242 - Fix PR27500: on MSP430 the branch destination offset is measured in words, not bytes.

Anton Korobeynikov via llvm-commits llvm-commits at lists.llvm.org
Fri Aug 19 07:07:10 PDT 2016


Author: asl
Date: Fri Aug 19 09:07:10 2016
New Revision: 279242

URL: http://llvm.org/viewvc/llvm-project?rev=279242&view=rev
Log:
Fix PR27500: on MSP430 the branch destination offset is measured in words, not bytes.
In addition, the branch instructions will have proper BB destinations, not offsets, like before.

Patch by Vadzim Dambrouski!

Differential Revision: https://reviews.llvm.org/D20162


Added:
    llvm/trunk/test/CodeGen/MSP430/BranchSelector.ll
Modified:
    llvm/trunk/lib/Target/MSP430/MSP430BranchSelector.cpp

Modified: llvm/trunk/lib/Target/MSP430/MSP430BranchSelector.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/MSP430/MSP430BranchSelector.cpp?rev=279242&r1=279241&r2=279242&view=diff
==============================================================================
--- llvm/trunk/lib/Target/MSP430/MSP430BranchSelector.cpp (original)
+++ llvm/trunk/lib/Target/MSP430/MSP430BranchSelector.cpp Fri Aug 19 09:07:10 2016
@@ -26,64 +26,86 @@
 using namespace llvm;
 
 #define DEBUG_TYPE "msp430-branch-select"
+#define MSP430_BR_SELECT_NAME "MSP430 Branch Selector"
 
+static cl::opt<bool>
+    BranchSelectEnabled("msp430-branch-select", cl::Hidden, cl::init(true),
+                        cl::desc("Expand out of range branches"));
+
+STATISTIC(NumSplit, "Number of machine basic blocks split");
 STATISTIC(NumExpanded, "Number of branches expanded to long format");
 
 namespace {
-  struct MSP430BSel : public MachineFunctionPass {
-    static char ID;
-    MSP430BSel() : MachineFunctionPass(ID) {}
-
-    /// BlockSizes - The sizes of the basic blocks in the function.
-    std::vector<unsigned> BlockSizes;
-
-    bool runOnMachineFunction(MachineFunction &Fn) override;
-
-    MachineFunctionProperties getRequiredProperties() const override {
-      return MachineFunctionProperties().set(
-          MachineFunctionProperties::Property::AllVRegsAllocated);
-    }
+class MSP430BSel : public MachineFunctionPass {
 
-    const char *getPassName() const override {
-      return "MSP430 Branch Selector";
-    }
-  };
-  char MSP430BSel::ID = 0;
+  typedef SmallVector<int, 16> OffsetVector;
+
+  MachineFunction *MF;
+  const MSP430InstrInfo *TII;
+
+  unsigned measureFunction(OffsetVector &BlockOffsets,
+                           MachineBasicBlock *FromBB = nullptr);
+  bool expandBranches(OffsetVector &BlockOffsets);
+
+public:
+  static char ID;
+  MSP430BSel() : MachineFunctionPass(ID) {}
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  MachineFunctionProperties getRequiredProperties() const override {
+    return MachineFunctionProperties().set(
+        MachineFunctionProperties::Property::AllVRegsAllocated);
+  }
+
+  const char *getPassName() const override { return MSP430_BR_SELECT_NAME; }
+};
+char MSP430BSel::ID = 0;
 }
 
-/// createMSP430BranchSelectionPass - returns an instance of the Branch
-/// Selection Pass
-///
-FunctionPass *llvm::createMSP430BranchSelectionPass() {
-  return new MSP430BSel();
+static bool isInRage(int DistanceInBytes) {
+  // According to CC430 Family User's Guide, Section 4.5.1.3, branch
+  // instructions have the signed 10-bit word offset field, so first we need to
+  // convert the distance from bytes to words, then check if it fits in 10-bit
+  // signed integer.
+  const int WordSize = 2;
+
+  assert((DistanceInBytes % WordSize == 0) &&
+         "Branch offset should be word aligned!");
+
+  int Words = DistanceInBytes / WordSize;
+  return isInt<10>(Words);
 }
 
-bool MSP430BSel::runOnMachineFunction(MachineFunction &Fn) {
-  const MSP430InstrInfo *TII =
-      static_cast<const MSP430InstrInfo *>(Fn.getSubtarget().getInstrInfo());
+/// Measure each basic block, fill the BlockOffsets, and return the size of
+/// the function, starting with BB
+unsigned MSP430BSel::measureFunction(OffsetVector &BlockOffsets,
+                                     MachineBasicBlock *FromBB) {
   // Give the blocks of the function a dense, in-order, numbering.
-  Fn.RenumberBlocks();
-  BlockSizes.resize(Fn.getNumBlockIDs());
+  MF->RenumberBlocks(FromBB);
 
-  // Measure each MBB and compute a size for the entire function.
-  unsigned FuncSize = 0;
-  for (MachineBasicBlock &MBB : Fn) {
-    unsigned BlockSize = 0;
-    for (MachineInstr &MI : MBB)
-      BlockSize += TII->getInstSizeInBytes(MI);
-
-    BlockSizes[MBB.getNumber()] = BlockSize;
-    FuncSize += BlockSize;
+  MachineFunction::iterator Begin;
+  if (FromBB == nullptr) {
+    Begin = MF->begin();
+  } else {
+    Begin = FromBB->getIterator();
   }
 
-  // If the entire function is smaller than the displacement of a branch field,
-  // we know we don't need to shrink any branches in this function.  This is a
-  // common case.
-  if (FuncSize < (1 << 9)) {
-    BlockSizes.clear();
-    return false;
+  BlockOffsets.resize(MF->getNumBlockIDs());
+
+  unsigned TotalSize = BlockOffsets[Begin->getNumber()];
+  for (auto &MBB : make_range(Begin, MF->end())) {
+    BlockOffsets[MBB.getNumber()] = TotalSize;
+    for (MachineInstr &MI : MBB) {
+      TotalSize += TII->getInstSizeInBytes(MI);
+    }
   }
+  return TotalSize;
+}
 
+/// Do expand branches and split the basic blocks if necessary.
+/// Returns true if made any change.
+bool MSP430BSel::expandBranches(OffsetVector &BlockOffsets) {
   // For each conditional branch, if the offset to its destination is larger
   // than the offset field allows, transform it into a long branch sequence
   // like this:
@@ -93,91 +115,143 @@ bool MSP430BSel::runOnMachineFunction(Ma
   //     b!CC $PC+6
   //     b MBB
   //
-  bool MadeChange = true;
-  bool EverMadeChange = false;
-  while (MadeChange) {
-    // Iteratively expand branches until we reach a fixed point.
-    MadeChange = false;
-
-    for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
-         ++MFI) {
-      MachineBasicBlock &MBB = *MFI;
-      unsigned MBBStartOffset = 0;
-      for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
-           I != E; ++I) {
-        if ((I->getOpcode() != MSP430::JCC || I->getOperand(0).isImm()) &&
-            I->getOpcode() != MSP430::JMP) {
-          MBBStartOffset += TII->getInstSizeInBytes(*I);
-          continue;
-        }
+  bool MadeChange = false;
+  for (auto MBB = MF->begin(), E = MF->end(); MBB != E; ++MBB) {
+    unsigned MBBStartOffset = 0;
+    for (auto MI = MBB->begin(), EE = MBB->end(); MI != EE; ++MI) {
+      MBBStartOffset += TII->getInstSizeInBytes(*MI);
+
+      // If this instruction is not a short branch then skip it.
+      if (MI->getOpcode() != MSP430::JCC && MI->getOpcode() != MSP430::JMP) {
+        continue;
+      }
 
-        // Determine the offset from the current branch to the destination
-        // block.
-        MachineBasicBlock *Dest = I->getOperand(0).getMBB();
-
-        int BranchSize;
-        if (Dest->getNumber() <= MBB.getNumber()) {
-          // If this is a backwards branch, the delta is the offset from the
-          // start of this block to this branch, plus the sizes of all blocks
-          // from this block to the dest.
-          BranchSize = MBBStartOffset;
-
-          for (unsigned i = Dest->getNumber(), e = MBB.getNumber(); i != e; ++i)
-            BranchSize += BlockSizes[i];
-        } else {
-          // Otherwise, add the size of the blocks between this block and the
-          // dest to the number of bytes left in this block.
-          BranchSize = -MBBStartOffset;
+      MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
+      // Determine the distance from the current branch to the destination
+      // block. MBBStartOffset already includes the size of the current branch
+      // instruction.
+      int BlockDistance =
+          BlockOffsets[DestBB->getNumber()] - BlockOffsets[MBB->getNumber()];
+      int BranchDistance = BlockDistance - MBBStartOffset;
+
+      // If this branch is in range, ignore it.
+      if (isInRage(BranchDistance)) {
+        continue;
+      }
 
-          for (unsigned i = MBB.getNumber(), e = Dest->getNumber(); i != e; ++i)
-            BranchSize += BlockSizes[i];
+      DEBUG(dbgs() << "  Found a branch that needs expanding, BB#"
+                   << DestBB->getNumber() << ", Distance " << BranchDistance
+                   << "\n");
+
+      // If JCC is not the last instruction we need to split the MBB.
+      if (MI->getOpcode() == MSP430::JCC && std::next(MI) != EE) {
+
+        DEBUG(dbgs() << "  Found a basic block that needs to be split, BB#"
+                     << MBB->getNumber() << "\n");
+
+        // Create a new basic block.
+        MachineBasicBlock *NewBB =
+            MF->CreateMachineBasicBlock(MBB->getBasicBlock());
+        MF->insert(std::next(MBB), NewBB);
+
+        // Splice the instructions following MI over to the NewBB.
+        NewBB->splice(NewBB->end(), &*MBB, std::next(MI), MBB->end());
+
+        // Update the successor lists.
+        for (MachineBasicBlock *Succ : MBB->successors()) {
+          if (Succ == DestBB) {
+            continue;
+          }
+          MBB->replaceSuccessor(Succ, NewBB);
+          NewBB->addSuccessor(Succ);
         }
 
-        // If this branch is in range, ignore it.
-        if (isInt<10>(BranchSize)) {
-          MBBStartOffset += 2;
-          continue;
-        }
+        // We introduced a new MBB so all following blocks should be numbered
+        // and measured again.
+        measureFunction(BlockOffsets, &*MBB);
+
+        ++NumSplit;
+
+        // It may be not necessary to start all over at this point, but it's
+        // safer do this anyway.
+        return true;
+      }
 
-        // Otherwise, we have to expand it to a long branch.
-        unsigned NewSize;
-        MachineInstr &OldBranch = *I;
-        DebugLoc dl = OldBranch.getDebugLoc();
-
-        if (I->getOpcode() == MSP430::JMP) {
-          NewSize = 4;
-        } else {
-          // The BCC operands are:
-          // 0. MSP430 branch predicate
-          // 1. Target MBB
-          SmallVector<MachineOperand, 1> Cond;
-          Cond.push_back(I->getOperand(1));
-
-          // Jump over the uncond branch inst (i.e. $+6) on opposite condition.
-          TII->ReverseBranchCondition(Cond);
-          BuildMI(MBB, I, dl, TII->get(MSP430::JCC))
-            .addImm(4).addOperand(Cond[0]);
+      MachineInstr &OldBranch = *MI;
+      DebugLoc dl = OldBranch.getDebugLoc();
+      int InstrSizeDiff = -TII->getInstSizeInBytes(OldBranch);
+
+      if (MI->getOpcode() == MSP430::JCC) {
+        MachineBasicBlock *NextMBB = &*std::next(MBB);
+        assert(MBB->isSuccessor(NextMBB) &&
+               "This block must have a layout successor!");
+
+        // The BCC operands are:
+        // 0. Target MBB
+        // 1. MSP430 branch predicate
+        SmallVector<MachineOperand, 1> Cond;
+        Cond.push_back(MI->getOperand(1));
+
+        // Jump over the long branch on the opposite condition
+        TII->ReverseBranchCondition(Cond);
+        auto &NewInstr = BuildMI(*MBB, MI, dl, TII->get(MSP430::JCC))
+                             .addMBB(NextMBB)
+                             .addOperand(Cond[0]);
+        InstrSizeDiff += TII->getInstSizeInBytes(*NewInstr);
+      }
 
-          NewSize = 6;
-        }
-        // Uncond branch to the real destination.
-        I = BuildMI(MBB, I, dl, TII->get(MSP430::Bi)).addMBB(Dest);
+      // Unconditional branch to the real destination.
+      MI = BuildMI(*MBB, MI, dl, TII->get(MSP430::Bi)).addMBB(DestBB);
+      InstrSizeDiff += TII->getInstSizeInBytes(*MI);
+
+      // Remove the old branch from the function.
+      OldBranch.eraseFromParent();
+
+      // The size of a new instruction is different from the old one, so we need
+      // to correct all block offsets.
+      for (int i = MBB->getNumber() + 1, e = BlockOffsets.size(); i < e; ++i) {
+        BlockOffsets[i] += InstrSizeDiff;
+      }
+      MBBStartOffset += InstrSizeDiff;
 
-        // Remove the old branch from the function.
-        OldBranch.eraseFromParent();
+      ++NumExpanded;
+      MadeChange = true;
+    }
+  }
+  return MadeChange;
+}
 
-        // Remember that this instruction is NewSize bytes, increase the size of the
-        // block by NewSize-2, remember to iterate.
-        BlockSizes[MBB.getNumber()] += NewSize-2;
-        MBBStartOffset += NewSize;
+bool MSP430BSel::runOnMachineFunction(MachineFunction &mf) {
+  MF = &mf;
+  TII = static_cast<const MSP430InstrInfo *>(MF->getSubtarget().getInstrInfo());
 
-        ++NumExpanded;
-        MadeChange = true;
-      }
-    }
-    EverMadeChange |= MadeChange;
+  // If the pass is disabled, just bail early.
+  if (!BranchSelectEnabled)
+    return false;
+
+  DEBUG(dbgs() << "\n********** " MSP430_BR_SELECT_NAME " **********\n");
+
+  // BlockOffsets - Contains the distance from the beginning of the function to
+  // the beginning of each basic block.
+  OffsetVector BlockOffsets;
+
+  unsigned FunctionSize = measureFunction(BlockOffsets);
+  // If the entire function is smaller than the displacement of a branch field,
+  // we know we don't need to expand any branches in this
+  // function. This is a common case.
+  if (isInRage(FunctionSize)) {
+    return false;
   }
 
-  BlockSizes.clear();
-  return true;
+  // Iteratively expand branches until we reach a fixed point.
+  bool MadeChange = false;
+  while (expandBranches(BlockOffsets))
+    MadeChange = true;
+
+  return MadeChange;
+}
+
+/// Returns an instance of the Branch Selection Pass
+FunctionPass *llvm::createMSP430BranchSelectionPass() {
+  return new MSP430BSel();
 }

Added: llvm/trunk/test/CodeGen/MSP430/BranchSelector.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/MSP430/BranchSelector.ll?rev=279242&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/MSP430/BranchSelector.ll (added)
+++ llvm/trunk/test/CodeGen/MSP430/BranchSelector.ll Fri Aug 19 09:07:10 2016
@@ -0,0 +1,588 @@
+; RUN: llc < %s -march=msp430 | FileCheck %s
+target datalayout = "e-m:e-p:16:16-i32:16:32-a:16-n8:16"
+target triple = "msp430"
+
+ at reg = common global i16 0, align 2
+
+define void @WriteBurstPATable(i16 %count) #0 {
+entry:
+  br label %while.cond
+
+while.cond:
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  %v0 = load volatile i16, i16* @reg, align 2
+  %lnot = icmp eq i16 %v0, 0
+
+; This BB should be split and all branches should be expanded.
+; CHECK-LABEL: .LBB0_1:
+; CHECK: jne	.LBB0_2
+; CHECK: br	#.LBB0_1
+; CHECK: .LBB0_2:
+; CHECK: br	#.LBB0_4
+; CHECK: .LBB0_3:
+
+  br i1 %lnot, label %while.cond, label %while.end
+
+while.end:
+  %i.0.i.0.1822 = load volatile i16, i16* @reg, align 1
+  %cmp23 = icmp ult i16 %i.0.i.0.1822, %count
+  br i1 %cmp23, label %for.body, label %for.end
+
+for.body:
+  br label %while.cond6
+
+while.cond6:
+  %0 = load volatile i16, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 19, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  br label %for.inc
+
+for.inc:
+  %1 = load volatile i16, i16* @reg, align 2
+  %cmp = icmp ult i16 %1, %count
+
+; This branch should be expanded.
+; CHECK-LABEL: .LBB0_4:
+; CHECK: jhs	.LBB0_5
+; CHECK: br	#.LBB0_3
+; CHECK: .LBB0_5:
+
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:
+  ret void
+}
+
+define void @WriteSinglePATable() #0 {
+entry:
+  br label %begin
+begin:
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  store volatile i16 13, i16* @reg, align 2
+  store volatile i16 17, i16* @reg, align 2
+  store volatile i16 11, i16* @reg, align 2
+  %v2 = load volatile i16, i16* @reg, align 2
+  %lnot = icmp eq i16 %v2, 0
+
+; This branch should not be expanded
+; CHECK-LABEL: .LBB1_1:
+; CHECK: jeq	.LBB1_1
+; CHECK: BB#2:
+; CHECK: ret
+  br i1 %lnot, label %begin, label %end
+
+end:
+  ret void
+}




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