text: //===-- SlotIndexes.cpp - Slot Indexes Pass  ------------------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/CodeGen/SlotIndexes.h"
  #include "llvm/ADT/Statistic.h"
  #include "llvm/CodeGen/MachineFunction.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/raw_ostream.h"
  #include "llvm/Target/TargetInstrInfo.h"
  
  using namespace llvm;
  
  #define DEBUG_TYPE "slotindexes"
  
  char SlotIndexes::ID = 0;
  INITIALIZE_PASS(SlotIndexes, "slotindexes",
                  "Slot index numbering", false, false)
  
  STATISTIC(NumLocalRenum,  "Number of local renumberings");
  STATISTIC(NumGlobalRenum, "Number of global renumberings");
  
  void SlotIndexes::getAnalysisUsage(AnalysisUsage &au) const {
    au.setPreservesAll();
    MachineFunctionPass::getAnalysisUsage(au);
  }
  
  void SlotIndexes::releaseMemory() {
    mi2iMap.clear();
    MBBRanges.clear();
    idx2MBBMap.clear();
    indexList.clear();
    ileAllocator.Reset();
  }
  
  bool SlotIndexes::runOnMachineFunction(MachineFunction &fn) {
  
    // Compute numbering as follows:
    // Grab an iterator to the start of the index list.
    // Iterate over all MBBs, and within each MBB all MIs, keeping the MI
    // iterator in lock-step (though skipping it over indexes which have
    // null pointers in the instruction field).
    // At each iteration assert that the instruction pointed to in the index
    // is the same one pointed to by the MI iterator. This
  
    // FIXME: This can be simplified. The mi2iMap_, Idx2MBBMap, etc. should
    // only need to be set up once after the first numbering is computed.
  
    mf = &fn;
  
    // Check that the list contains only the sentinal.
    assert(indexList.empty() && "Index list non-empty at initial numbering?");
    assert(idx2MBBMap.empty() &&
           "Index -> MBB mapping non-empty at initial numbering?");
    assert(MBBRanges.empty() &&
           "MBB -> Index mapping non-empty at initial numbering?");
    assert(mi2iMap.empty() &&
           "MachineInstr -> Index mapping non-empty at initial numbering?");
  
    unsigned index = 0;
    MBBRanges.resize(mf->getNumBlockIDs());
    idx2MBBMap.reserve(mf->size());
  
    indexList.push_back(createEntry(nullptr, index));
  
    // Iterate over the function.
    for (MachineFunction::iterator mbbItr = mf->begin(), mbbEnd = mf->end();
         mbbItr != mbbEnd; ++mbbItr) {
      MachineBasicBlock *mbb = &*mbbItr;
  
      // Insert an index for the MBB start.
      SlotIndex blockStartIndex(&indexList.back(), SlotIndex::Slot_Block);
  
      for (MachineBasicBlock::iterator miItr = mbb->begin(), miEnd = mbb->end();
           miItr != miEnd; ++miItr) {
        MachineInstr *mi = miItr;
        if (mi->isDebugValue())
          continue;
  
        // Insert a store index for the instr.
        indexList.push_back(createEntry(mi, index += SlotIndex::InstrDist));
  
        // Save this base index in the maps.
        mi2iMap.insert(std::make_pair(mi, SlotIndex(&indexList.back(),
                                                    SlotIndex::Slot_Block)));
      }
  
      // We insert one blank instructions between basic blocks.
      indexList.push_back(createEntry(nullptr, index += SlotIndex::InstrDist));
  
      MBBRanges[mbb->getNumber()].first = blockStartIndex;
      MBBRanges[mbb->getNumber()].second = SlotIndex(&indexList.back(),
                                                     SlotIndex::Slot_Block);
      idx2MBBMap.push_back(IdxMBBPair(blockStartIndex, mbb));
    }
  
    // Sort the Idx2MBBMap
    std::sort(idx2MBBMap.begin(), idx2MBBMap.end(), Idx2MBBCompare());
  
    DEBUG(mf->print(dbgs(), this));
  
    // And we're done!
    return false;
  }
  
  void SlotIndexes::renumberIndexes() {
    // Renumber updates the index of every element of the index list.
    DEBUG(dbgs() << "\n*** Renumbering SlotIndexes ***\n");
    ++NumGlobalRenum;
  
    unsigned index = 0;
  
    for (IndexList::iterator I = indexList.begin(), E = indexList.end();
         I != E; ++I) {
      I->setIndex(index);
      index += SlotIndex::InstrDist;
    }
  }
  
  // Renumber indexes locally after curItr was inserted, but failed to get a new
  // index.
  void SlotIndexes::renumberIndexes(IndexList::iterator curItr) {
    // Number indexes with half the default spacing so we can catch up quickly.
    const unsigned Space = SlotIndex::InstrDist/2;
    assert((Space & 3) == 0 && "InstrDist must be a multiple of 2*NUM");
  
    IndexList::iterator startItr = std::prev(curItr);
    unsigned index = startItr->getIndex();
    do {
      curItr->setIndex(index += Space);
      ++curItr;
      // If the next index is bigger, we have caught up.
    } while (curItr != indexList.end() && curItr->getIndex() <= index);
  
    DEBUG(dbgs() << "\n*** Renumbered SlotIndexes " << startItr->getIndex() << '-'
                 << index << " ***\n");
    ++NumLocalRenum;
  }
  
  // Repair indexes after adding and removing instructions.
  void SlotIndexes::repairIndexesInRange(MachineBasicBlock *MBB,
                                         MachineBasicBlock::iterator Begin,
                                         MachineBasicBlock::iterator End) {
    // FIXME: Is this really necessary? The only caller repairIntervalsForRange()
    // does the same thing.
    // Find anchor points, which are at the beginning/end of blocks or at
    // instructions that already have indexes.
    while (Begin != MBB->begin() && !hasIndex(Begin))
      --Begin;
    while (End != MBB->end() && !hasIndex(End))
      ++End;
  
    bool includeStart = (Begin == MBB->begin());
    SlotIndex startIdx;
    if (includeStart)
      startIdx = getMBBStartIdx(MBB);
    else
      startIdx = getInstructionIndex(Begin);
  
    SlotIndex endIdx;
    if (End == MBB->end())
      endIdx = getMBBEndIdx(MBB);
    else
      endIdx = getInstructionIndex(End);
  
    // FIXME: Conceptually, this code is implementing an iterator on MBB that
    // optionally includes an additional position prior to MBB->begin(), indicated
    // by the includeStart flag. This is done so that we can iterate MIs in a MBB
    // in parallel with SlotIndexes, but there should be a better way to do this.
    IndexList::iterator ListB = startIdx.listEntry();
    IndexList::iterator ListI = endIdx.listEntry();
    MachineBasicBlock::iterator MBBI = End;
    bool pastStart = false;
    while (ListI != ListB || MBBI != Begin || (includeStart && !pastStart)) {
      assert(ListI->getIndex() >= startIdx.getIndex() &&
             (includeStart || !pastStart) &&
             "Decremented past the beginning of region to repair.");
  
      MachineInstr *SlotMI = ListI->getInstr();
      MachineInstr *MI = (MBBI != MBB->end() && !pastStart) ? MBBI : nullptr;
      bool MBBIAtBegin = MBBI == Begin && (!includeStart || pastStart);
  
      if (SlotMI == MI && !MBBIAtBegin) {
        --ListI;
        if (MBBI != Begin)
          --MBBI;
        else
          pastStart = true;
      } else if (MI && mi2iMap.find(MI) == mi2iMap.end()) {
        if (MBBI != Begin)
          --MBBI;
        else
          pastStart = true;
      } else {
        --ListI;
        if (SlotMI)
          removeMachineInstrFromMaps(SlotMI);
      }
    }
  
    // In theory this could be combined with the previous loop, but it is tricky
    // to update the IndexList while we are iterating it.
    for (MachineBasicBlock::iterator I = End; I != Begin;) {
      --I;
      MachineInstr *MI = I;
      if (!MI->isDebugValue() && mi2iMap.find(MI) == mi2iMap.end())
        insertMachineInstrInMaps(MI);
    }
  }
  
  #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
  void SlotIndexes::dump() const {
    for (IndexList::const_iterator itr = indexList.begin();
         itr != indexList.end(); ++itr) {
      dbgs() << itr->getIndex() << " ";
  
      if (itr->getInstr()) {
        dbgs() << *itr->getInstr();
      } else {
        dbgs() << "\n";
      }
    }
  
    for (unsigned i = 0, e = MBBRanges.size(); i != e; ++i)
      dbgs() << "BB#" << i << "\t[" << MBBRanges[i].first << ';'
             << MBBRanges[i].second << ")\n";
  }
  #endif
  
  // Print a SlotIndex to a raw_ostream.
  void SlotIndex::print(raw_ostream &os) const {
    if (isValid())
      os << listEntry()->getIndex() << "Berd"[getSlot()];
    else
      os << "invalid";
  }
  
  #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
  // Dump a SlotIndex to stderr.
  void SlotIndex::dump() const {
    print(dbgs());
    dbgs() << "\n";
  }
  #endif
  
  