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
17using namespace llvm;
18
19#define DEBUG_TYPE "slotindexes"
20
21char SlotIndexes::ID = 0;
22
23SlotIndexes::SlotIndexes() : MachineFunctionPass(ID), mf(nullptr) {
24  initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
25}
26
27SlotIndexes::~SlotIndexes() {
28  // The indexList's nodes are all allocated in the BumpPtrAllocator.
29  indexList.clearAndLeakNodesUnsafely();
30}
31
32INITIALIZE_PASS(SlotIndexes, DEBUG_TYPE,
33                "Slot index numbering", false, false)
34
35STATISTIC(NumLocalRenum,  "Number of local renumberings");
36
37void SlotIndexes::getAnalysisUsage(AnalysisUsage &au) const {
38  au.setPreservesAll();
39  MachineFunctionPass::getAnalysisUsage(au);
40}
41
42void SlotIndexes::releaseMemory() {
43  mi2iMap.clear();
44  MBBRanges.clear();
45  idx2MBBMap.clear();
46  indexList.clear();
47  ileAllocator.Reset();
48}
49
50bool 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 sentinal.
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.isDebugInstr())
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
115void 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
131void 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.
160void 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.
179void SlotIndexes::repairIndexesInRange(MachineBasicBlock *MBB,
180                                       MachineBasicBlock::iterator Begin,
181                                       MachineBasicBlock::iterator End) {
182  // FIXME: Is this really necessary? The only caller repairIntervalsForRange()
183  // does the same thing.
184  // Find anchor points, which are at the beginning/end of blocks or at
185  // instructions that already have indexes.
186  while (Begin != MBB->begin() && !hasIndex(*Begin))
187    --Begin;
188  while (End != MBB->end() && !hasIndex(*End))
189    ++End;
190
191  bool includeStart = (Begin == MBB->begin());
192  SlotIndex startIdx;
193  if (includeStart)
194    startIdx = getMBBStartIdx(MBB);
195  else
196    startIdx = getInstructionIndex(*Begin);
197
198  SlotIndex endIdx;
199  if (End == MBB->end())
200    endIdx = getMBBEndIdx(MBB);
201  else
202    endIdx = getInstructionIndex(*End);
203
204  // FIXME: Conceptually, this code is implementing an iterator on MBB that
205  // optionally includes an additional position prior to MBB->begin(), indicated
206  // by the includeStart flag. This is done so that we can iterate MIs in a MBB
207  // in parallel with SlotIndexes, but there should be a better way to do this.
208  IndexList::iterator ListB = startIdx.listEntry()->getIterator();
209  IndexList::iterator ListI = endIdx.listEntry()->getIterator();
210  MachineBasicBlock::iterator MBBI = End;
211  bool pastStart = false;
212  while (ListI != ListB || MBBI != Begin || (includeStart && !pastStart)) {
213    assert(ListI->getIndex() >= startIdx.getIndex() &&
214           (includeStart || !pastStart) &&
215           "Decremented past the beginning of region to repair.");
216
217    MachineInstr *SlotMI = ListI->getInstr();
218    MachineInstr *MI = (MBBI != MBB->end() && !pastStart) ? &*MBBI : nullptr;
219    bool MBBIAtBegin = MBBI == Begin && (!includeStart || pastStart);
220
221    if (SlotMI == MI && !MBBIAtBegin) {
222      --ListI;
223      if (MBBI != Begin)
224        --MBBI;
225      else
226        pastStart = true;
227    } else if (MI && mi2iMap.find(MI) == mi2iMap.end()) {
228      if (MBBI != Begin)
229        --MBBI;
230      else
231        pastStart = true;
232    } else {
233      --ListI;
234      if (SlotMI)
235        removeMachineInstrFromMaps(*SlotMI);
236    }
237  }
238
239  // In theory this could be combined with the previous loop, but it is tricky
240  // to update the IndexList while we are iterating it.
241  for (MachineBasicBlock::iterator I = End; I != Begin;) {
242    --I;
243    MachineInstr &MI = *I;
244    if (!MI.isDebugInstr() && mi2iMap.find(&MI) == mi2iMap.end())
245      insertMachineInstrInMaps(MI);
246  }
247}
248
249#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
250LLVM_DUMP_METHOD void SlotIndexes::dump() const {
251  for (IndexList::const_iterator itr = indexList.begin();
252       itr != indexList.end(); ++itr) {
253    dbgs() << itr->getIndex() << " ";
254
255    if (itr->getInstr()) {
256      dbgs() << *itr->getInstr();
257    } else {
258      dbgs() << "\n";
259    }
260  }
261
262  for (unsigned i = 0, e = MBBRanges.size(); i != e; ++i)
263    dbgs() << "%bb." << i << "\t[" << MBBRanges[i].first << ';'
264           << MBBRanges[i].second << ")\n";
265}
266#endif
267
268// Print a SlotIndex to a raw_ostream.
269void SlotIndex::print(raw_ostream &os) const {
270  if (isValid())
271    os << listEntry()->getIndex() << "Berd"[getSlot()];
272  else
273    os << "invalid";
274}
275
276#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
277// Dump a SlotIndex to stderr.
278LLVM_DUMP_METHOD void SlotIndex::dump() const {
279  print(dbgs());
280  dbgs() << "\n";
281}
282#endif
283
284