xref: /freebsd/contrib/llvm-project/llvm/lib/CodeGen/SlotIndexes.cpp (revision ec0ea6efa1ad229d75c394c1a9b9cac33af2b1d3)
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), mf(nullptr) {
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 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.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   // 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.isDebugOrPseudoInstr() && mi2iMap.find(&MI) == mi2iMap.end())
245       insertMachineInstrInMaps(MI);
246   }
247 }
248 
249 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
250 LLVM_DUMP_METHOD void SlotIndexes::dump() const {
251   for (const IndexListEntry &ILE : indexList) {
252     dbgs() << ILE.getIndex() << " ";
253 
254     if (ILE.getInstr()) {
255       dbgs() << *ILE.getInstr();
256     } else {
257       dbgs() << "\n";
258     }
259   }
260 
261   for (unsigned i = 0, e = MBBRanges.size(); i != e; ++i)
262     dbgs() << "%bb." << i << "\t[" << MBBRanges[i].first << ';'
263            << MBBRanges[i].second << ")\n";
264 }
265 #endif
266 
267 // Print a SlotIndex to a raw_ostream.
268 void SlotIndex::print(raw_ostream &os) const {
269   if (isValid())
270     os << listEntry()->getIndex() << "Berd"[getSlot()];
271   else
272     os << "invalid";
273 }
274 
275 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
276 // Dump a SlotIndex to stderr.
277 LLVM_DUMP_METHOD void SlotIndex::dump() const {
278   print(dbgs());
279   dbgs() << "\n";
280 }
281 #endif
282