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      1 //===-- SlotIndexes.cpp - Slot Indexes Pass  ------------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 
     10 #include "llvm/CodeGen/SlotIndexes.h"
     11 #include "llvm/ADT/Statistic.h"
     12 #include "llvm/CodeGen/MachineFunction.h"
     13 #include "llvm/Support/Debug.h"
     14 #include "llvm/Support/raw_ostream.h"
     15 #include "llvm/Target/TargetInstrInfo.h"
     16 
     17 using namespace llvm;
     18 
     19 #define DEBUG_TYPE "slotindexes"
     20 
     21 char SlotIndexes::ID = 0;
     22 INITIALIZE_PASS(SlotIndexes, "slotindexes",
     23                 "Slot index numbering", false, false)
     24 
     25 STATISTIC(NumLocalRenum,  "Number of local renumberings");
     26 STATISTIC(NumGlobalRenum, "Number of global renumberings");
     27 
     28 void SlotIndexes::getAnalysisUsage(AnalysisUsage &au) const {
     29   au.setPreservesAll();
     30   MachineFunctionPass::getAnalysisUsage(au);
     31 }
     32 
     33 void SlotIndexes::releaseMemory() {
     34   mi2iMap.clear();
     35   MBBRanges.clear();
     36   idx2MBBMap.clear();
     37   indexList.clear();
     38   ileAllocator.Reset();
     39 }
     40 
     41 bool SlotIndexes::runOnMachineFunction(MachineFunction &fn) {
     42 
     43   // Compute numbering as follows:
     44   // Grab an iterator to the start of the index list.
     45   // Iterate over all MBBs, and within each MBB all MIs, keeping the MI
     46   // iterator in lock-step (though skipping it over indexes which have
     47   // null pointers in the instruction field).
     48   // At each iteration assert that the instruction pointed to in the index
     49   // is the same one pointed to by the MI iterator. This
     50 
     51   // FIXME: This can be simplified. The mi2iMap_, Idx2MBBMap, etc. should
     52   // only need to be set up once after the first numbering is computed.
     53 
     54   mf = &fn;
     55 
     56   // Check that the list contains only the sentinal.
     57   assert(indexList.empty() && "Index list non-empty at initial numbering?");
     58   assert(idx2MBBMap.empty() &&
     59          "Index -> MBB mapping non-empty at initial numbering?");
     60   assert(MBBRanges.empty() &&
     61          "MBB -> Index mapping non-empty at initial numbering?");
     62   assert(mi2iMap.empty() &&
     63          "MachineInstr -> Index mapping non-empty at initial numbering?");
     64 
     65   unsigned index = 0;
     66   MBBRanges.resize(mf->getNumBlockIDs());
     67   idx2MBBMap.reserve(mf->size());
     68 
     69   indexList.push_back(createEntry(nullptr, index));
     70 
     71   // Iterate over the function.
     72   for (MachineFunction::iterator mbbItr = mf->begin(), mbbEnd = mf->end();
     73        mbbItr != mbbEnd; ++mbbItr) {
     74     MachineBasicBlock *mbb = &*mbbItr;
     75 
     76     // Insert an index for the MBB start.
     77     SlotIndex blockStartIndex(&indexList.back(), SlotIndex::Slot_Block);
     78 
     79     for (MachineBasicBlock::iterator miItr = mbb->begin(), miEnd = mbb->end();
     80          miItr != miEnd; ++miItr) {
     81       MachineInstr *mi = miItr;
     82       if (mi->isDebugValue())
     83         continue;
     84 
     85       // Insert a store index for the instr.
     86       indexList.push_back(createEntry(mi, index += SlotIndex::InstrDist));
     87 
     88       // Save this base index in the maps.
     89       mi2iMap.insert(std::make_pair(mi, SlotIndex(&indexList.back(),
     90                                                   SlotIndex::Slot_Block)));
     91     }
     92 
     93     // We insert one blank instructions between basic blocks.
     94     indexList.push_back(createEntry(nullptr, index += SlotIndex::InstrDist));
     95 
     96     MBBRanges[mbb->getNumber()].first = blockStartIndex;
     97     MBBRanges[mbb->getNumber()].second = SlotIndex(&indexList.back(),
     98                                                    SlotIndex::Slot_Block);
     99     idx2MBBMap.push_back(IdxMBBPair(blockStartIndex, mbb));
    100   }
    101 
    102   // Sort the Idx2MBBMap
    103   std::sort(idx2MBBMap.begin(), idx2MBBMap.end(), Idx2MBBCompare());
    104 
    105   DEBUG(mf->print(dbgs(), this));
    106 
    107   // And we're done!
    108   return false;
    109 }
    110 
    111 void SlotIndexes::renumberIndexes() {
    112   // Renumber updates the index of every element of the index list.
    113   DEBUG(dbgs() << "\n*** Renumbering SlotIndexes ***\n");
    114   ++NumGlobalRenum;
    115 
    116   unsigned index = 0;
    117 
    118   for (IndexList::iterator I = indexList.begin(), E = indexList.end();
    119        I != E; ++I) {
    120     I->setIndex(index);
    121     index += SlotIndex::InstrDist;
    122   }
    123 }
    124 
    125 // Renumber indexes locally after curItr was inserted, but failed to get a new
    126 // index.
    127 void SlotIndexes::renumberIndexes(IndexList::iterator curItr) {
    128   // Number indexes with half the default spacing so we can catch up quickly.
    129   const unsigned Space = SlotIndex::InstrDist/2;
    130   assert((Space & 3) == 0 && "InstrDist must be a multiple of 2*NUM");
    131 
    132   IndexList::iterator startItr = std::prev(curItr);
    133   unsigned index = startItr->getIndex();
    134   do {
    135     curItr->setIndex(index += Space);
    136     ++curItr;
    137     // If the next index is bigger, we have caught up.
    138   } while (curItr != indexList.end() && curItr->getIndex() <= index);
    139 
    140   DEBUG(dbgs() << "\n*** Renumbered SlotIndexes " << startItr->getIndex() << '-'
    141                << index << " ***\n");
    142   ++NumLocalRenum;
    143 }
    144 
    145 // Repair indexes after adding and removing instructions.
    146 void SlotIndexes::repairIndexesInRange(MachineBasicBlock *MBB,
    147                                        MachineBasicBlock::iterator Begin,
    148                                        MachineBasicBlock::iterator End) {
    149   // FIXME: Is this really necessary? The only caller repairIntervalsForRange()
    150   // does the same thing.
    151   // Find anchor points, which are at the beginning/end of blocks or at
    152   // instructions that already have indexes.
    153   while (Begin != MBB->begin() && !hasIndex(Begin))
    154     --Begin;
    155   while (End != MBB->end() && !hasIndex(End))
    156     ++End;
    157 
    158   bool includeStart = (Begin == MBB->begin());
    159   SlotIndex startIdx;
    160   if (includeStart)
    161     startIdx = getMBBStartIdx(MBB);
    162   else
    163     startIdx = getInstructionIndex(Begin);
    164 
    165   SlotIndex endIdx;
    166   if (End == MBB->end())
    167     endIdx = getMBBEndIdx(MBB);
    168   else
    169     endIdx = getInstructionIndex(End);
    170 
    171   // FIXME: Conceptually, this code is implementing an iterator on MBB that
    172   // optionally includes an additional position prior to MBB->begin(), indicated
    173   // by the includeStart flag. This is done so that we can iterate MIs in a MBB
    174   // in parallel with SlotIndexes, but there should be a better way to do this.
    175   IndexList::iterator ListB = startIdx.listEntry();
    176   IndexList::iterator ListI = endIdx.listEntry();
    177   MachineBasicBlock::iterator MBBI = End;
    178   bool pastStart = false;
    179   while (ListI != ListB || MBBI != Begin || (includeStart && !pastStart)) {
    180     assert(ListI->getIndex() >= startIdx.getIndex() &&
    181            (includeStart || !pastStart) &&
    182            "Decremented past the beginning of region to repair.");
    183 
    184     MachineInstr *SlotMI = ListI->getInstr();
    185     MachineInstr *MI = (MBBI != MBB->end() && !pastStart) ? MBBI : nullptr;
    186     bool MBBIAtBegin = MBBI == Begin && (!includeStart || pastStart);
    187 
    188     if (SlotMI == MI && !MBBIAtBegin) {
    189       --ListI;
    190       if (MBBI != Begin)
    191         --MBBI;
    192       else
    193         pastStart = true;
    194     } else if (MI && mi2iMap.find(MI) == mi2iMap.end()) {
    195       if (MBBI != Begin)
    196         --MBBI;
    197       else
    198         pastStart = true;
    199     } else {
    200       --ListI;
    201       if (SlotMI)
    202         removeMachineInstrFromMaps(SlotMI);
    203     }
    204   }
    205 
    206   // In theory this could be combined with the previous loop, but it is tricky
    207   // to update the IndexList while we are iterating it.
    208   for (MachineBasicBlock::iterator I = End; I != Begin;) {
    209     --I;
    210     MachineInstr *MI = I;
    211     if (!MI->isDebugValue() && mi2iMap.find(MI) == mi2iMap.end())
    212       insertMachineInstrInMaps(MI);
    213   }
    214 }
    215 
    216 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
    217 void SlotIndexes::dump() const {
    218   for (IndexList::const_iterator itr = indexList.begin();
    219        itr != indexList.end(); ++itr) {
    220     dbgs() << itr->getIndex() << " ";
    221 
    222     if (itr->getInstr()) {
    223       dbgs() << *itr->getInstr();
    224     } else {
    225       dbgs() << "\n";
    226     }
    227   }
    228 
    229   for (unsigned i = 0, e = MBBRanges.size(); i != e; ++i)
    230     dbgs() << "BB#" << i << "\t[" << MBBRanges[i].first << ';'
    231            << MBBRanges[i].second << ")\n";
    232 }
    233 #endif
    234 
    235 // Print a SlotIndex to a raw_ostream.
    236 void SlotIndex::print(raw_ostream &os) const {
    237   if (isValid())
    238     os << listEntry()->getIndex() << "Berd"[getSlot()];
    239   else
    240     os << "invalid";
    241 }
    242 
    243 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
    244 // Dump a SlotIndex to stderr.
    245 void SlotIndex::dump() const {
    246   print(dbgs());
    247   dbgs() << "\n";
    248 }
    249 #endif
    250 
    251