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/Support/Debug.h"
  14 #include "llvm/Support/raw_ostream.h"
  15
  16 using namespace llvm;
  17
  18 #define DEBUG_TYPE "slotindexes"
  19
  20 char SlotIndexes::ID = 0;
  21 INITIALIZE_PASS(SlotIndexes, DEBUG_TYPE,
  22                 "Slot index numbering", false, false)
  23
  24 STATISTIC(NumLocalRenum,  "Number of local renumberings");
  25 STATISTIC(NumGlobalRenum, "Number of global renumberings");
  26
  27 void SlotIndexes::getAnalysisUsage(AnalysisUsage &au) const {
  28   au.setPreservesAll();
  29   MachineFunctionPass::getAnalysisUsage(au);
  30 }
  31
  32 void SlotIndexes::releaseMemory() {
  33   mi2iMap.clear();
  34   MBBRanges.clear();
  35   idx2MBBMap.clear();
  36   indexList.clear();
  37   ileAllocator.Reset();
  38 }
  39
  40 bool SlotIndexes::runOnMachineFunction(MachineFunction &fn) {
  41
  42   // Compute numbering as follows:
  43   // Grab an iterator to the start of the index list.
  44   // Iterate over all MBBs, and within each MBB all MIs, keeping the MI
  45   // iterator in lock-step (though skipping it over indexes which have
  46   // null pointers in the instruction field).
  47   // At each iteration assert that the instruction pointed to in the index
  48   // is the same one pointed to by the MI iterator. This
  49
  50   // FIXME: This can be simplified. The mi2iMap_, Idx2MBBMap, etc. should
  51   // only need to be set up once after the first numbering is computed.
  52
  53   mf = &fn;
  54
  55   // Check that the list contains only the sentinal.
  56   assert(indexList.empty() && "Index list non-empty at initial numbering?");
  57   assert(idx2MBBMap.empty() &&
  58          "Index -> MBB mapping non-empty at initial numbering?");
  59   assert(MBBRanges.empty() &&
  60          "MBB -> Index mapping non-empty at initial numbering?");
  61   assert(mi2iMap.empty() &&
  62          "MachineInstr -> Index mapping non-empty at initial numbering?");
  63
  64   unsigned index = 0;
  65   MBBRanges.resize(mf->getNumBlockIDs());
  66   idx2MBBMap.reserve(mf->size());
  67
  68   indexList.push_back(createEntry(nullptr, index));
  69
  70   // Iterate over the function.
  71   for (MachineBasicBlock &MBB : *mf) {
  72     // Insert an index for the MBB start.
  73     SlotIndex blockStartIndex(&indexList.back(), SlotIndex::Slot_Block);
  74
  75     for (MachineInstr &MI : MBB) {
  76       if (MI.isDebugInstr())
  77         continue;
  78
  79       // Insert a store index for the instr.
  80       indexList.push_back(createEntry(&MI, index += SlotIndex::InstrDist));
  81
  82       // Save this base index in the maps.
  83       mi2iMap.insert(std::make_pair(
  84           &MI, SlotIndex(&indexList.back(), SlotIndex::Slot_Block)));
  85     }
  86
  87     // We insert one blank instructions between basic blocks.
  88     indexList.push_back(createEntry(nullptr, index += SlotIndex::InstrDist));
  89
  90     MBBRanges[MBB.getNumber()].first = blockStartIndex;
  91     MBBRanges[MBB.getNumber()].second = SlotIndex(&indexList.back(),
  92                                                    SlotIndex::Slot_Block);
  93     idx2MBBMap.push_back(IdxMBBPair(blockStartIndex, &MBB));
  94   }
  95
  96   // Sort the Idx2MBBMap
  97   llvm::sort(idx2MBBMap, Idx2MBBCompare());
  98
  99   LLVM_DEBUG(mf->print(dbgs(), this));
 100
 101   // And we're done!
 102   return false;
 103 }
 104
 105 void SlotIndexes::removeMachineInstrFromMaps(MachineInstr &MI) {
 106   assert(!MI.isBundledWithPred() &&
 107          "Use removeSingleMachineInstrFromMaps() instread");
 108   Mi2IndexMap::iterator mi2iItr = mi2iMap.find(&MI);
 109   if (mi2iItr == mi2iMap.end())
 110     return;
 111
 112   SlotIndex MIIndex = mi2iItr->second;
 113   IndexListEntry &MIEntry = *MIIndex.listEntry();
 114   assert(MIEntry.getInstr() == &MI && "Instruction indexes broken.");
 115   mi2iMap.erase(mi2iItr);
 116   // FIXME: Eventually we want to actually delete these indexes.
 117   MIEntry.setInstr(nullptr);
 118 }
 119
 120 void SlotIndexes::removeSingleMachineInstrFromMaps(MachineInstr &MI) {
 121   Mi2IndexMap::iterator mi2iItr = mi2iMap.find(&MI);
 122   if (mi2iItr == mi2iMap.end())
 123     return;
 124
 125   SlotIndex MIIndex = mi2iItr->second;
 126   IndexListEntry &MIEntry = *MIIndex.listEntry();
 127   assert(MIEntry.getInstr() == &MI && "Instruction indexes broken.");
 128   mi2iMap.erase(mi2iItr);
 129
 130   // When removing the first instruction of a bundle update mapping to next
 131   // instruction.
 132   if (MI.isBundledWithSucc()) {
 133     // Only the first instruction of a bundle should have an index assigned.
 134     assert(!MI.isBundledWithPred() && "Should have first bundle isntruction");
 135
 136     MachineBasicBlock::instr_iterator Next = std::next(MI.getIterator());
 137     MachineInstr &NextMI = *Next;
 138     MIEntry.setInstr(&NextMI);
 139     mi2iMap.insert(std::make_pair(&NextMI, MIIndex));
 140     return;
 141   } else {
 142     // FIXME: Eventually we want to actually delete these indexes.
 143     MIEntry.setInstr(nullptr);
 144   }
 145 }
 146
 147 void SlotIndexes::renumberIndexes() {
 148   // Renumber updates the index of every element of the index list.
 149   LLVM_DEBUG(dbgs() << "\n*** Renumbering SlotIndexes ***\n");
 150   ++NumGlobalRenum;
 151
 152   unsigned index = 0;
 153
 154   for (IndexList::iterator I = indexList.begin(), E = indexList.end();
 155        I != E; ++I) {
 156     I->setIndex(index);
 157     index += SlotIndex::InstrDist;
 158   }
 159 }
 160
 161 // Renumber indexes locally after curItr was inserted, but failed to get a new
 162 // index.
 163 void SlotIndexes::renumberIndexes(IndexList::iterator curItr) {
 164   // Number indexes with half the default spacing so we can catch up quickly.
 165   const unsigned Space = SlotIndex::InstrDist/2;
 166   static_assert((Space & 3) == 0, "InstrDist must be a multiple of 2*NUM");
 167
 168   IndexList::iterator startItr = std::prev(curItr);
 169   unsigned index = startItr->getIndex();
 170   do {
 171     curItr->setIndex(index += Space);
 172     ++curItr;
 173     // If the next index is bigger, we have caught up.
 174   } while (curItr != indexList.end() && curItr->getIndex() <= index);
 175
 176   LLVM_DEBUG(dbgs() << "\n*** Renumbered SlotIndexes " << startItr->getIndex()
 177                     << '-' << index << " ***\n");
 178   ++NumLocalRenum;
 179 }
 180
 181 // Repair indexes after adding and removing instructions.
 182 void SlotIndexes::repairIndexesInRange(MachineBasicBlock *MBB,
 183                                        MachineBasicBlock::iterator Begin,
 184                                        MachineBasicBlock::iterator End) {
 185   // FIXME: Is this really necessary? The only caller repairIntervalsForRange()
 186   // does the same thing.
 187   // Find anchor points, which are at the beginning/end of blocks or at
 188   // instructions that already have indexes.
 189   while (Begin != MBB->begin() && !hasIndex(*Begin))
 190     --Begin;
 191   while (End != MBB->end() && !hasIndex(*End))
 192     ++End;
 193
 194   bool includeStart = (Begin == MBB->begin());
 195   SlotIndex startIdx;
 196   if (includeStart)
 197     startIdx = getMBBStartIdx(MBB);
 198   else
 199     startIdx = getInstructionIndex(*Begin);
 200
 201   SlotIndex endIdx;
 202   if (End == MBB->end())
 203     endIdx = getMBBEndIdx(MBB);
 204   else
 205     endIdx = getInstructionIndex(*End);
 206
 207   // FIXME: Conceptually, this code is implementing an iterator on MBB that
 208   // optionally includes an additional position prior to MBB->begin(), indicated
 209   // by the includeStart flag. This is done so that we can iterate MIs in a MBB
 210   // in parallel with SlotIndexes, but there should be a better way to do this.
 211   IndexList::iterator ListB = startIdx.listEntry()->getIterator();
 212   IndexList::iterator ListI = endIdx.listEntry()->getIterator();
 213   MachineBasicBlock::iterator MBBI = End;
 214   bool pastStart = false;
 215   while (ListI != ListB || MBBI != Begin || (includeStart && !pastStart)) {
 216     assert(ListI->getIndex() >= startIdx.getIndex() &&
 217            (includeStart || !pastStart) &&
 218            "Decremented past the beginning of region to repair.");
 219
 220     MachineInstr *SlotMI = ListI->getInstr();
 221     MachineInstr *MI = (MBBI != MBB->end() && !pastStart) ? &*MBBI : nullptr;
 222     bool MBBIAtBegin = MBBI == Begin && (!includeStart || pastStart);
 223
 224     if (SlotMI == MI && !MBBIAtBegin) {
 225       --ListI;
 226       if (MBBI != Begin)
 227         --MBBI;
 228       else
 229         pastStart = true;
 230     } else if (MI && mi2iMap.find(MI) == mi2iMap.end()) {
 231       if (MBBI != Begin)
 232         --MBBI;
 233       else
 234         pastStart = true;
 235     } else {
 236       --ListI;
 237       if (SlotMI)
 238         removeMachineInstrFromMaps(*SlotMI);
 239     }
 240   }
 241
 242   // In theory this could be combined with the previous loop, but it is tricky
 243   // to update the IndexList while we are iterating it.
 244   for (MachineBasicBlock::iterator I = End; I != Begin;) {
 245     --I;
 246     MachineInstr &MI = *I;
 247     if (!MI.isDebugInstr() && mi2iMap.find(&MI) == mi2iMap.end())
 248       insertMachineInstrInMaps(MI);
 249   }
 250 }
 251
 252 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 253 LLVM_DUMP_METHOD void SlotIndexes::dump() const {
 254   for (IndexList::const_iterator itr = indexList.begin();
 255        itr != indexList.end(); ++itr) {
 256     dbgs() << itr->getIndex() << " ";
 257
 258     if (itr->getInstr()) {
 259       dbgs() << *itr->getInstr();
 260     } else {
 261       dbgs() << "\n";
 262     }
 263   }
 264
 265   for (unsigned i = 0, e = MBBRanges.size(); i != e; ++i)
 266     dbgs() << "%bb." << i << "\t[" << MBBRanges[i].first << ';'
 267            << MBBRanges[i].second << ")\n";
 268 }
 269 #endif
 270
 271 // Print a SlotIndex to a raw_ostream.
 272 void SlotIndex::print(raw_ostream &os) const {
 273   if (isValid())
 274     os << listEntry()->getIndex() << "Berd"[getSlot()];
 275   else
 276     os << "invalid";
 277 }
 278
 279 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 280 // Dump a SlotIndex to stderr.
 281 LLVM_DUMP_METHOD void SlotIndex::dump() const {
 282   print(dbgs());
 283   dbgs() << "\n";
 284 }
 285 #endif
 286