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