lib/CodeGen/SlotIndexes.cpp

   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/Config/llvm-config.h"
  14 #include "llvm/Support/Debug.h"
  15 #include "llvm/Support/raw_ostream.h"
  16
  17 using namespace llvm;
  18
  19 #define DEBUG_TYPE "slotindexes"
  20
  21 char SlotIndexes::ID = 0;
  22 INITIALIZE_PASS(SlotIndexes, DEBUG_TYPE,
  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 (MachineBasicBlock &MBB : *mf) {
  73     // Insert an index for the MBB start.
  74     SlotIndex blockStartIndex(&indexList.back(), SlotIndex::Slot_Block);
  75
  76     for (MachineInstr &MI : MBB) {
  77       if (MI.isDebugInstr())
  78         continue;
  79
  80       // Insert a store index for the instr.
  81       indexList.push_back(createEntry(&MI, index += SlotIndex::InstrDist));
  82
  83       // Save this base index in the maps.
  84       mi2iMap.insert(std::make_pair(
  85           &MI, SlotIndex(&indexList.back(), SlotIndex::Slot_Block)));
  86     }
  87
  88     // We insert one blank instructions between basic blocks.
  89     indexList.push_back(createEntry(nullptr, index += SlotIndex::InstrDist));
  90
  91     MBBRanges[MBB.getNumber()].first = blockStartIndex;
  92     MBBRanges[MBB.getNumber()].second = SlotIndex(&indexList.back(),
  93                                                    SlotIndex::Slot_Block);
  94     idx2MBBMap.push_back(IdxMBBPair(blockStartIndex, &MBB));
  95   }
  96
  97   // Sort the Idx2MBBMap
  98   llvm::sort(idx2MBBMap, Idx2MBBCompare());
  99
 100   LLVM_DEBUG(mf->print(dbgs(), this));
 101
 102   // And we're done!
 103   return false;
 104 }
 105
 106 void SlotIndexes::removeMachineInstrFromMaps(MachineInstr &MI) {
 107   assert(!MI.isBundledWithPred() &&
 108          "Use removeSingleMachineInstrFromMaps() instread");
 109   Mi2IndexMap::iterator mi2iItr = mi2iMap.find(&MI);
 110   if (mi2iItr == mi2iMap.end())
 111     return;
 112
 113   SlotIndex MIIndex = mi2iItr->second;
 114   IndexListEntry &MIEntry = *MIIndex.listEntry();
 115   assert(MIEntry.getInstr() == &MI && "Instruction indexes broken.");
 116   mi2iMap.erase(mi2iItr);
 117   // FIXME: Eventually we want to actually delete these indexes.
 118   MIEntry.setInstr(nullptr);
 119 }
 120
 121 void SlotIndexes::removeSingleMachineInstrFromMaps(MachineInstr &MI) {
 122   Mi2IndexMap::iterator mi2iItr = mi2iMap.find(&MI);
 123   if (mi2iItr == mi2iMap.end())
 124     return;
 125
 126   SlotIndex MIIndex = mi2iItr->second;
 127   IndexListEntry &MIEntry = *MIIndex.listEntry();
 128   assert(MIEntry.getInstr() == &MI && "Instruction indexes broken.");
 129   mi2iMap.erase(mi2iItr);
 130
 131   // When removing the first instruction of a bundle update mapping to next
 132   // instruction.
 133   if (MI.isBundledWithSucc()) {
 134     // Only the first instruction of a bundle should have an index assigned.
 135     assert(!MI.isBundledWithPred() && "Should have first bundle isntruction");
 136
 137     MachineBasicBlock::instr_iterator Next = std::next(MI.getIterator());
 138     MachineInstr &NextMI = *Next;
 139     MIEntry.setInstr(&NextMI);
 140     mi2iMap.insert(std::make_pair(&NextMI, MIIndex));
 141     return;
 142   } else {
 143     // FIXME: Eventually we want to actually delete these indexes.
 144     MIEntry.setInstr(nullptr);
 145   }
 146 }
 147
 148 void SlotIndexes::renumberIndexes() {
 149   // Renumber updates the index of every element of the index list.
 150   LLVM_DEBUG(dbgs() << "\n*** Renumbering SlotIndexes ***\n");
 151   ++NumGlobalRenum;
 152
 153   unsigned index = 0;
 154
 155   for (IndexList::iterator I = indexList.begin(), E = indexList.end();
 156        I != E; ++I) {
 157     I->setIndex(index);
 158     index += SlotIndex::InstrDist;
 159   }
 160 }
 161
 162 // Renumber indexes locally after curItr was inserted, but failed to get a new
 163 // index.
 164 void SlotIndexes::renumberIndexes(IndexList::iterator curItr) {
 165   // Number indexes with half the default spacing so we can catch up quickly.
 166   const unsigned Space = SlotIndex::InstrDist/2;
 167   static_assert((Space & 3) == 0, "InstrDist must be a multiple of 2*NUM");
 168
 169   IndexList::iterator startItr = std::prev(curItr);
 170   unsigned index = startItr->getIndex();
 171   do {
 172     curItr->setIndex(index += Space);
 173     ++curItr;
 174     // If the next index is bigger, we have caught up.
 175   } while (curItr != indexList.end() && curItr->getIndex() <= index);
 176
 177   LLVM_DEBUG(dbgs() << "\n*** Renumbered SlotIndexes " << startItr->getIndex()
 178                     << '-' << index << " ***\n");
 179   ++NumLocalRenum;
 180 }
 181
 182 // Repair indexes after adding and removing instructions.
 183 void SlotIndexes::repairIndexesInRange(MachineBasicBlock *MBB,
 184                                        MachineBasicBlock::iterator Begin,
 185                                        MachineBasicBlock::iterator End) {
 186   // FIXME: Is this really necessary? The only caller repairIntervalsForRange()
 187   // does the same thing.
 188   // Find anchor points, which are at the beginning/end of blocks or at
 189   // instructions that already have indexes.
 190   while (Begin != MBB->begin() && !hasIndex(*Begin))
 191     --Begin;
 192   while (End != MBB->end() && !hasIndex(*End))
 193     ++End;
 194
 195   bool includeStart = (Begin == MBB->begin());
 196   SlotIndex startIdx;
 197   if (includeStart)
 198     startIdx = getMBBStartIdx(MBB);
 199   else
 200     startIdx = getInstructionIndex(*Begin);
 201
 202   SlotIndex endIdx;
 203   if (End == MBB->end())
 204     endIdx = getMBBEndIdx(MBB);
 205   else
 206     endIdx = getInstructionIndex(*End);
 207
 208   // FIXME: Conceptually, this code is implementing an iterator on MBB that
 209   // optionally includes an additional position prior to MBB->begin(), indicated
 210   // by the includeStart flag. This is done so that we can iterate MIs in a MBB
 211   // in parallel with SlotIndexes, but there should be a better way to do this.
 212   IndexList::iterator ListB = startIdx.listEntry()->getIterator();
 213   IndexList::iterator ListI = endIdx.listEntry()->getIterator();
 214   MachineBasicBlock::iterator MBBI = End;
 215   bool pastStart = false;
 216   while (ListI != ListB || MBBI != Begin || (includeStart && !pastStart)) {
 217     assert(ListI->getIndex() >= startIdx.getIndex() &&
 218            (includeStart || !pastStart) &&
 219            "Decremented past the beginning of region to repair.");
 220
 221     MachineInstr *SlotMI = ListI->getInstr();
 222     MachineInstr *MI = (MBBI != MBB->end() && !pastStart) ? &*MBBI : nullptr;
 223     bool MBBIAtBegin = MBBI == Begin && (!includeStart || pastStart);
 224
 225     if (SlotMI == MI && !MBBIAtBegin) {
 226       --ListI;
 227       if (MBBI != Begin)
 228         --MBBI;
 229       else
 230         pastStart = true;
 231     } else if (MI && mi2iMap.find(MI) == mi2iMap.end()) {
 232       if (MBBI != Begin)
 233         --MBBI;
 234       else
 235         pastStart = true;
 236     } else {
 237       --ListI;
 238       if (SlotMI)
 239         removeMachineInstrFromMaps(*SlotMI);
 240     }
 241   }
 242
 243   // In theory this could be combined with the previous loop, but it is tricky
 244   // to update the IndexList while we are iterating it.
 245   for (MachineBasicBlock::iterator I = End; I != Begin;) {
 246     --I;
 247     MachineInstr &MI = *I;
 248     if (!MI.isDebugInstr() && mi2iMap.find(&MI) == mi2iMap.end())
 249       insertMachineInstrInMaps(MI);
 250   }
 251 }
 252
 253 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 254 LLVM_DUMP_METHOD void SlotIndexes::dump() const {
 255   for (IndexList::const_iterator itr = indexList.begin();
 256        itr != indexList.end(); ++itr) {
 257     dbgs() << itr->getIndex() << " ";
 258
 259     if (itr->getInstr()) {
 260       dbgs() << *itr->getInstr();
 261     } else {
 262       dbgs() << "\n";
 263     }
 264   }
 265
 266   for (unsigned i = 0, e = MBBRanges.size(); i != e; ++i)
 267     dbgs() << "%bb." << i << "\t[" << MBBRanges[i].first << ';'
 268            << MBBRanges[i].second << ")\n";
 269 }
 270 #endif
 271
 272 // Print a SlotIndex to a raw_ostream.
 273 void SlotIndex::print(raw_ostream &os) const {
 274   if (isValid())
 275     os << listEntry()->getIndex() << "Berd"[getSlot()];
 276   else
 277     os << "invalid";
 278 }
 279
 280 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 281 // Dump a SlotIndex to stderr.
 282 LLVM_DUMP_METHOD void SlotIndex::dump() const {
 283   print(dbgs());
 284   dbgs() << "\n";
 285 }
 286 #endif
 287