llvm/lib/CodeGen/SlotIndexes.cpp

   1 //===-- SlotIndexes.cpp - Slot Indexes Pass  ------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/CodeGen/SlotIndexes.h"
  10 #include "llvm/ADT/Statistic.h"
  11 #include "llvm/CodeGen/MachineFunction.h"
  12 #include "llvm/Config/llvm-config.h"
  13 #include "llvm/InitializePasses.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
  23 SlotIndexes::SlotIndexes() : MachineFunctionPass(ID) {
  24   initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
  25 }
  26
  27 SlotIndexes::~SlotIndexes() {
  28   // The indexList's nodes are all allocated in the BumpPtrAllocator.
  29   indexList.clearAndLeakNodesUnsafely();
  30 }
  31
  32 INITIALIZE_PASS(SlotIndexes, DEBUG_TYPE,
  33                 "Slot index numbering", false, false)
  34
  35 STATISTIC(NumLocalRenum,  "Number of local renumberings");
  36
  37 void SlotIndexes::getAnalysisUsage(AnalysisUsage &au) const {
  38   au.setPreservesAll();
  39   MachineFunctionPass::getAnalysisUsage(au);
  40 }
  41
  42 void SlotIndexes::releaseMemory() {
  43   mi2iMap.clear();
  44   MBBRanges.clear();
  45   idx2MBBMap.clear();
  46   indexList.clear();
  47   ileAllocator.Reset();
  48 }
  49
  50 bool SlotIndexes::runOnMachineFunction(MachineFunction &fn) {
  51
  52   // Compute numbering as follows:
  53   // Grab an iterator to the start of the index list.
  54   // Iterate over all MBBs, and within each MBB all MIs, keeping the MI
  55   // iterator in lock-step (though skipping it over indexes which have
  56   // null pointers in the instruction field).
  57   // At each iteration assert that the instruction pointed to in the index
  58   // is the same one pointed to by the MI iterator. This
  59
  60   // FIXME: This can be simplified. The mi2iMap_, Idx2MBBMap, etc. should
  61   // only need to be set up once after the first numbering is computed.
  62
  63   mf = &fn;
  64
  65   // Check that the list contains only the sentinel.
  66   assert(indexList.empty() && "Index list non-empty at initial numbering?");
  67   assert(idx2MBBMap.empty() &&
  68          "Index -> MBB mapping non-empty at initial numbering?");
  69   assert(MBBRanges.empty() &&
  70          "MBB -> Index mapping non-empty at initial numbering?");
  71   assert(mi2iMap.empty() &&
  72          "MachineInstr -> Index mapping non-empty at initial numbering?");
  73
  74   unsigned index = 0;
  75   MBBRanges.resize(mf->getNumBlockIDs());
  76   idx2MBBMap.reserve(mf->size());
  77
  78   indexList.push_back(createEntry(nullptr, index));
  79
  80   // Iterate over the function.
  81   for (MachineBasicBlock &MBB : *mf) {
  82     // Insert an index for the MBB start.
  83     SlotIndex blockStartIndex(&indexList.back(), SlotIndex::Slot_Block);
  84
  85     for (MachineInstr &MI : MBB) {
  86       if (MI.isDebugOrPseudoInstr())
  87         continue;
  88
  89       // Insert a store index for the instr.
  90       indexList.push_back(createEntry(&MI, index += SlotIndex::InstrDist));
  91
  92       // Save this base index in the maps.
  93       mi2iMap.insert(std::make_pair(
  94           &MI, SlotIndex(&indexList.back(), SlotIndex::Slot_Block)));
  95     }
  96
  97     // We insert one blank instructions between basic blocks.
  98     indexList.push_back(createEntry(nullptr, index += SlotIndex::InstrDist));
  99
 100     MBBRanges[MBB.getNumber()].first = blockStartIndex;
 101     MBBRanges[MBB.getNumber()].second = SlotIndex(&indexList.back(),
 102                                                    SlotIndex::Slot_Block);
 103     idx2MBBMap.push_back(IdxMBBPair(blockStartIndex, &MBB));
 104   }
 105
 106   // Sort the Idx2MBBMap
 107   llvm::sort(idx2MBBMap, less_first());
 108
 109   LLVM_DEBUG(mf->print(dbgs(), this));
 110
 111   // And we're done!
 112   return false;
 113 }
 114
 115 void SlotIndexes::removeMachineInstrFromMaps(MachineInstr &MI,
 116                                              bool AllowBundled) {
 117   assert((AllowBundled || !MI.isBundledWithPred()) &&
 118          "Use removeSingleMachineInstrFromMaps() instead");
 119   Mi2IndexMap::iterator mi2iItr = mi2iMap.find(&MI);
 120   if (mi2iItr == mi2iMap.end())
 121     return;
 122
 123   SlotIndex MIIndex = mi2iItr->second;
 124   IndexListEntry &MIEntry = *MIIndex.listEntry();
 125   assert(MIEntry.getInstr() == &MI && "Instruction indexes broken.");
 126   mi2iMap.erase(mi2iItr);
 127   // FIXME: Eventually we want to actually delete these indexes.
 128   MIEntry.setInstr(nullptr);
 129 }
 130
 131 void SlotIndexes::removeSingleMachineInstrFromMaps(MachineInstr &MI) {
 132   Mi2IndexMap::iterator mi2iItr = mi2iMap.find(&MI);
 133   if (mi2iItr == mi2iMap.end())
 134     return;
 135
 136   SlotIndex MIIndex = mi2iItr->second;
 137   IndexListEntry &MIEntry = *MIIndex.listEntry();
 138   assert(MIEntry.getInstr() == &MI && "Instruction indexes broken.");
 139   mi2iMap.erase(mi2iItr);
 140
 141   // When removing the first instruction of a bundle update mapping to next
 142   // instruction.
 143   if (MI.isBundledWithSucc()) {
 144     // Only the first instruction of a bundle should have an index assigned.
 145     assert(!MI.isBundledWithPred() && "Should be first bundle instruction");
 146
 147     MachineBasicBlock::instr_iterator Next = std::next(MI.getIterator());
 148     MachineInstr &NextMI = *Next;
 149     MIEntry.setInstr(&NextMI);
 150     mi2iMap.insert(std::make_pair(&NextMI, MIIndex));
 151     return;
 152   } else {
 153     // FIXME: Eventually we want to actually delete these indexes.
 154     MIEntry.setInstr(nullptr);
 155   }
 156 }
 157
 158 // Renumber indexes locally after curItr was inserted, but failed to get a new
 159 // index.
 160 void SlotIndexes::renumberIndexes(IndexList::iterator curItr) {
 161   // Number indexes with half the default spacing so we can catch up quickly.
 162   const unsigned Space = SlotIndex::InstrDist/2;
 163   static_assert((Space & 3) == 0, "InstrDist must be a multiple of 2*NUM");
 164
 165   IndexList::iterator startItr = std::prev(curItr);
 166   unsigned index = startItr->getIndex();
 167   do {
 168     curItr->setIndex(index += Space);
 169     ++curItr;
 170     // If the next index is bigger, we have caught up.
 171   } while (curItr != indexList.end() && curItr->getIndex() <= index);
 172
 173   LLVM_DEBUG(dbgs() << "\n*** Renumbered SlotIndexes " << startItr->getIndex()
 174                     << '-' << index << " ***\n");
 175   ++NumLocalRenum;
 176 }
 177
 178 // Repair indexes after adding and removing instructions.
 179 void SlotIndexes::repairIndexesInRange(MachineBasicBlock *MBB,
 180                                        MachineBasicBlock::iterator Begin,
 181                                        MachineBasicBlock::iterator End) {
 182   bool includeStart = (Begin == MBB->begin());
 183   SlotIndex startIdx;
 184   if (includeStart)
 185     startIdx = getMBBStartIdx(MBB);
 186   else
 187     startIdx = getInstructionIndex(*--Begin);
 188
 189   SlotIndex endIdx;
 190   if (End == MBB->end())
 191     endIdx = getMBBEndIdx(MBB);
 192   else
 193     endIdx = getInstructionIndex(*End);
 194
 195   // FIXME: Conceptually, this code is implementing an iterator on MBB that
 196   // optionally includes an additional position prior to MBB->begin(), indicated
 197   // by the includeStart flag. This is done so that we can iterate MIs in a MBB
 198   // in parallel with SlotIndexes, but there should be a better way to do this.
 199   IndexList::iterator ListB = startIdx.listEntry()->getIterator();
 200   IndexList::iterator ListI = endIdx.listEntry()->getIterator();
 201   MachineBasicBlock::iterator MBBI = End;
 202   bool pastStart = false;
 203   while (ListI != ListB || MBBI != Begin || (includeStart && !pastStart)) {
 204     assert(ListI->getIndex() >= startIdx.getIndex() &&
 205            (includeStart || !pastStart) &&
 206            "Decremented past the beginning of region to repair.");
 207
 208     MachineInstr *SlotMI = ListI->getInstr();
 209     MachineInstr *MI = (MBBI != MBB->end() && !pastStart) ? &*MBBI : nullptr;
 210     bool MBBIAtBegin = MBBI == Begin && (!includeStart || pastStart);
 211
 212     if (SlotMI == MI && !MBBIAtBegin) {
 213       --ListI;
 214       if (MBBI != Begin)
 215         --MBBI;
 216       else
 217         pastStart = true;
 218     } else if (MI && !mi2iMap.contains(MI)) {
 219       if (MBBI != Begin)
 220         --MBBI;
 221       else
 222         pastStart = true;
 223     } else {
 224       --ListI;
 225       if (SlotMI)
 226         removeMachineInstrFromMaps(*SlotMI);
 227     }
 228   }
 229
 230   // In theory this could be combined with the previous loop, but it is tricky
 231   // to update the IndexList while we are iterating it.
 232   for (MachineBasicBlock::iterator I = End; I != Begin;) {
 233     --I;
 234     MachineInstr &MI = *I;
 235     if (!MI.isDebugOrPseudoInstr() && !mi2iMap.contains(&MI))
 236       insertMachineInstrInMaps(MI);
 237   }
 238 }
 239
 240 void SlotIndexes::packIndexes() {
 241   for (auto [Index, Entry] : enumerate(indexList))
 242     Entry.setIndex(Index * SlotIndex::InstrDist);
 243 }
 244
 245 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 246 LLVM_DUMP_METHOD void SlotIndexes::dump() const {
 247   for (const IndexListEntry &ILE : indexList) {
 248     dbgs() << ILE.getIndex() << " ";
 249
 250     if (ILE.getInstr()) {
 251       dbgs() << *ILE.getInstr();
 252     } else {
 253       dbgs() << "\n";
 254     }
 255   }
 256
 257   for (unsigned i = 0, e = MBBRanges.size(); i != e; ++i)
 258     dbgs() << "%bb." << i << "\t[" << MBBRanges[i].first << ';'
 259            << MBBRanges[i].second << ")\n";
 260 }
 261 #endif
 262
 263 // Print a SlotIndex to a raw_ostream.
 264 void SlotIndex::print(raw_ostream &os) const {
 265   if (isValid())
 266     os << listEntry()->getIndex() << "Berd"[getSlot()];
 267   else
 268     os << "invalid";
 269 }
 270
 271 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 272 // Dump a SlotIndex to stderr.
 273 LLVM_DUMP_METHOD void SlotIndex::dump() const {
 274   print(dbgs());
 275   dbgs() << "\n";
 276 }
 277 #endif