Revert r279242 - it's failing the tests

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279247 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 117 insertions, 191 deletions

diff --git a/lib/Target/MSP430/MSP430BranchSelector.cpp b/lib/Target/MSP430/MSP430BranchSelector.cpp
index 7df151f58ba..8bb695bc364 100644
--- a/lib/Target/MSP430/MSP430BranchSelector.cpp
+++ b/lib/Target/MSP430/MSP430BranchSelector.cpp
@@ -26,86 +26,64 @@
 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 {
-class MSP430BSel : public MachineFunctionPass {
-
-  typedef SmallVector<int, 16> OffsetVector;
-
-  MachineFunction *MF;
-  const MSP430InstrInfo *TII;
-
-  unsigned measureFunction(OffsetVector &BlockOffsets,
-                           MachineBasicBlock *FromBB = nullptr);
-  bool expandBranches(OffsetVector &BlockOffsets);
+  struct MSP430BSel : public MachineFunctionPass {
+    static char ID;
+    MSP430BSel() : MachineFunctionPass(ID) {}
 
-public:
-  static char ID;
-  MSP430BSel() : MachineFunctionPass(ID) {}
+    /// BlockSizes - The sizes of the basic blocks in the function.
+    std::vector<unsigned> BlockSizes;
 
-  bool runOnMachineFunction(MachineFunction &MF) override;
+    bool runOnMachineFunction(MachineFunction &Fn) override;
 
-  MachineFunctionProperties getRequiredProperties() const override {
-    return MachineFunctionProperties().set(
-        MachineFunctionProperties::Property::AllVRegsAllocated);
-  }
+    MachineFunctionProperties getRequiredProperties() const override {
+      return MachineFunctionProperties().set(
+          MachineFunctionProperties::Property::AllVRegsAllocated);
+    }
 
-  const char *getPassName() const override { return MSP430_BR_SELECT_NAME; }
-};
-char MSP430BSel::ID = 0;
+    const char *getPassName() const override {
+      return "MSP430 Branch Selector";
+    }
+  };
+  char MSP430BSel::ID = 0;
 }
 
-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);
+/// createMSP430BranchSelectionPass - returns an instance of the Branch
+/// Selection Pass
+///
+FunctionPass *llvm::createMSP430BranchSelectionPass() {
+  return new MSP430BSel();
 }
 
-/// Measure each basic block, fill the BlockOffsets, and return the size of
-/// the function, starting with BB
-unsigned MSP430BSel::measureFunction(OffsetVector &BlockOffsets,
-                                     MachineBasicBlock *FromBB) {
+bool MSP430BSel::runOnMachineFunction(MachineFunction &Fn) {
+  const MSP430InstrInfo *TII =
+      static_cast<const MSP430InstrInfo *>(Fn.getSubtarget().getInstrInfo());
   // Give the blocks of the function a dense, in-order, numbering.
-  MF->RenumberBlocks(FromBB);
-
-  MachineFunction::iterator Begin;
-  if (FromBB == nullptr) {
-    Begin = MF->begin();
-  } else {
-    Begin = FromBB->getIterator();
+  Fn.RenumberBlocks();
+  BlockSizes.resize(Fn.getNumBlockIDs());
+
+  // 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;
   }
 
-  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);
-    }
+  // 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;
   }
-  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:
@@ -115,143 +93,91 @@ bool MSP430BSel::expandBranches(OffsetVector &BlockOffsets) {
   //     b!CC $PC+6
   //     b MBB
   //
-  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;
-      }
-
-      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;
-      }
-
-      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);
+  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;
         }
 
-        // 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;
-      }
-
-      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!");
+        // 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;
+
+          for (unsigned i = MBB.getNumber(), e = Dest->getNumber(); i != e; ++i)
+            BranchSize += BlockSizes[i];
+        }
 
-        // The BCC operands are:
-        // 0. Target MBB
-        // 1. MSP430 branch predicate
-        SmallVector<MachineOperand, 1> Cond;
-        Cond.push_back(MI->getOperand(1));
+        // If this branch is in range, ignore it.
+        if (isInt<10>(BranchSize)) {
+          MBBStartOffset += 2;
+          continue;
+        }
 
-        // 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);
-      }
+        // 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]);
+
+          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();
 
-      // Remove the old branch from the function.
-      OldBranch.eraseFromParent();
+        // 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;
 
-      // 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;
+        ++NumExpanded;
+        MadeChange = true;
       }
-      MBBStartOffset += InstrSizeDiff;
-
-      ++NumExpanded;
-      MadeChange = true;
     }
+    EverMadeChange |= MadeChange;
   }
-  return MadeChange;
-}
-
-bool MSP430BSel::runOnMachineFunction(MachineFunction &mf) {
-  MF = &mf;
-  TII = static_cast<const MSP430InstrInfo *>(MF->getSubtarget().getInstrInfo());
-
-  // 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;
-  }
-
-  // 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();
+  BlockSizes.clear();
+  return true;
 }