1 //===-- SlotIndexes.cpp - Slot Indexes Pass  ------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "llvm/CodeGen/SlotIndexes.h"
11 #include "llvm/ADT/Statistic.h"
12 #include "llvm/CodeGen/MachineFunction.h"
13 #include "llvm/Support/Debug.h"
14 #include "llvm/Support/raw_ostream.h"
15 #include "llvm/Target/TargetInstrInfo.h"
16 
17 using namespace llvm;
18 
19 #define DEBUG_TYPE "slotindexes"
20 
21 char SlotIndexes::ID = 0;
22 INITIALIZE_PASS(SlotIndexes, "slotindexes",
23                 "Slot index numbering", false, false)
24 
25 STATISTIC(NumLocalRenum,  "Number of local renumberings");
26 STATISTIC(NumGlobalRenum, "Number of global renumberings");
27 
getAnalysisUsage(AnalysisUsage & au) const28 void SlotIndexes::getAnalysisUsage(AnalysisUsage &au) const {
29   au.setPreservesAll();
30   MachineFunctionPass::getAnalysisUsage(au);
31 }
32 
releaseMemory()33 void SlotIndexes::releaseMemory() {
34   mi2iMap.clear();
35   MBBRanges.clear();
36   idx2MBBMap.clear();
37   indexList.clear();
38   ileAllocator.Reset();
39 }
40 
runOnMachineFunction(MachineFunction & fn)41 bool SlotIndexes::runOnMachineFunction(MachineFunction &fn) {
42 
43   // Compute numbering as follows:
44   // Grab an iterator to the start of the index list.
45   // Iterate over all MBBs, and within each MBB all MIs, keeping the MI
46   // iterator in lock-step (though skipping it over indexes which have
47   // null pointers in the instruction field).
48   // At each iteration assert that the instruction pointed to in the index
49   // is the same one pointed to by the MI iterator. This
50 
51   // FIXME: This can be simplified. The mi2iMap_, Idx2MBBMap, etc. should
52   // only need to be set up once after the first numbering is computed.
53 
54   mf = &fn;
55 
56   // Check that the list contains only the sentinal.
57   assert(indexList.empty() && "Index list non-empty at initial numbering?");
58   assert(idx2MBBMap.empty() &&
59          "Index -> MBB mapping non-empty at initial numbering?");
60   assert(MBBRanges.empty() &&
61          "MBB -> Index mapping non-empty at initial numbering?");
62   assert(mi2iMap.empty() &&
63          "MachineInstr -> Index mapping non-empty at initial numbering?");
64 
65   unsigned index = 0;
66   MBBRanges.resize(mf->getNumBlockIDs());
67   idx2MBBMap.reserve(mf->size());
68 
69   indexList.push_back(createEntry(nullptr, index));
70 
71   // Iterate over the function.
72   for (MachineFunction::iterator mbbItr = mf->begin(), mbbEnd = mf->end();
73        mbbItr != mbbEnd; ++mbbItr) {
74     MachineBasicBlock *mbb = &*mbbItr;
75 
76     // Insert an index for the MBB start.
77     SlotIndex blockStartIndex(&indexList.back(), SlotIndex::Slot_Block);
78 
79     for (MachineBasicBlock::iterator miItr = mbb->begin(), miEnd = mbb->end();
80          miItr != miEnd; ++miItr) {
81       MachineInstr *mi = miItr;
82       if (mi->isDebugValue())
83         continue;
84 
85       // Insert a store index for the instr.
86       indexList.push_back(createEntry(mi, index += SlotIndex::InstrDist));
87 
88       // Save this base index in the maps.
89       mi2iMap.insert(std::make_pair(mi, SlotIndex(&indexList.back(),
90                                                   SlotIndex::Slot_Block)));
91     }
92 
93     // We insert one blank instructions between basic blocks.
94     indexList.push_back(createEntry(nullptr, index += SlotIndex::InstrDist));
95 
96     MBBRanges[mbb->getNumber()].first = blockStartIndex;
97     MBBRanges[mbb->getNumber()].second = SlotIndex(&indexList.back(),
98                                                    SlotIndex::Slot_Block);
99     idx2MBBMap.push_back(IdxMBBPair(blockStartIndex, mbb));
100   }
101 
102   // Sort the Idx2MBBMap
103   std::sort(idx2MBBMap.begin(), idx2MBBMap.end(), Idx2MBBCompare());
104 
105   DEBUG(mf->print(dbgs(), this));
106 
107   // And we're done!
108   return false;
109 }
110 
renumberIndexes()111 void SlotIndexes::renumberIndexes() {
112   // Renumber updates the index of every element of the index list.
113   DEBUG(dbgs() << "\n*** Renumbering SlotIndexes ***\n");
114   ++NumGlobalRenum;
115 
116   unsigned index = 0;
117 
118   for (IndexList::iterator I = indexList.begin(), E = indexList.end();
119        I != E; ++I) {
120     I->setIndex(index);
121     index += SlotIndex::InstrDist;
122   }
123 }
124 
125 // Renumber indexes locally after curItr was inserted, but failed to get a new
126 // index.
renumberIndexes(IndexList::iterator curItr)127 void SlotIndexes::renumberIndexes(IndexList::iterator curItr) {
128   // Number indexes with half the default spacing so we can catch up quickly.
129   const unsigned Space = SlotIndex::InstrDist/2;
130   static_assert((Space & 3) == 0, "InstrDist must be a multiple of 2*NUM");
131 
132   IndexList::iterator startItr = std::prev(curItr);
133   unsigned index = startItr->getIndex();
134   do {
135     curItr->setIndex(index += Space);
136     ++curItr;
137     // If the next index is bigger, we have caught up.
138   } while (curItr != indexList.end() && curItr->getIndex() <= index);
139 
140   DEBUG(dbgs() << "\n*** Renumbered SlotIndexes " << startItr->getIndex() << '-'
141                << index << " ***\n");
142   ++NumLocalRenum;
143 }
144 
145 // Repair indexes after adding and removing instructions.
repairIndexesInRange(MachineBasicBlock * MBB,MachineBasicBlock::iterator Begin,MachineBasicBlock::iterator End)146 void SlotIndexes::repairIndexesInRange(MachineBasicBlock *MBB,
147                                        MachineBasicBlock::iterator Begin,
148                                        MachineBasicBlock::iterator End) {
149   // FIXME: Is this really necessary? The only caller repairIntervalsForRange()
150   // does the same thing.
151   // Find anchor points, which are at the beginning/end of blocks or at
152   // instructions that already have indexes.
153   while (Begin != MBB->begin() && !hasIndex(Begin))
154     --Begin;
155   while (End != MBB->end() && !hasIndex(End))
156     ++End;
157 
158   bool includeStart = (Begin == MBB->begin());
159   SlotIndex startIdx;
160   if (includeStart)
161     startIdx = getMBBStartIdx(MBB);
162   else
163     startIdx = getInstructionIndex(Begin);
164 
165   SlotIndex endIdx;
166   if (End == MBB->end())
167     endIdx = getMBBEndIdx(MBB);
168   else
169     endIdx = getInstructionIndex(End);
170 
171   // FIXME: Conceptually, this code is implementing an iterator on MBB that
172   // optionally includes an additional position prior to MBB->begin(), indicated
173   // by the includeStart flag. This is done so that we can iterate MIs in a MBB
174   // in parallel with SlotIndexes, but there should be a better way to do this.
175   IndexList::iterator ListB = startIdx.listEntry()->getIterator();
176   IndexList::iterator ListI = endIdx.listEntry()->getIterator();
177   MachineBasicBlock::iterator MBBI = End;
178   bool pastStart = false;
179   while (ListI != ListB || MBBI != Begin || (includeStart && !pastStart)) {
180     assert(ListI->getIndex() >= startIdx.getIndex() &&
181            (includeStart || !pastStart) &&
182            "Decremented past the beginning of region to repair.");
183 
184     MachineInstr *SlotMI = ListI->getInstr();
185     MachineInstr *MI = (MBBI != MBB->end() && !pastStart) ? MBBI : nullptr;
186     bool MBBIAtBegin = MBBI == Begin && (!includeStart || pastStart);
187 
188     if (SlotMI == MI && !MBBIAtBegin) {
189       --ListI;
190       if (MBBI != Begin)
191         --MBBI;
192       else
193         pastStart = true;
194     } else if (MI && mi2iMap.find(MI) == mi2iMap.end()) {
195       if (MBBI != Begin)
196         --MBBI;
197       else
198         pastStart = true;
199     } else {
200       --ListI;
201       if (SlotMI)
202         removeMachineInstrFromMaps(SlotMI);
203     }
204   }
205 
206   // In theory this could be combined with the previous loop, but it is tricky
207   // to update the IndexList while we are iterating it.
208   for (MachineBasicBlock::iterator I = End; I != Begin;) {
209     --I;
210     MachineInstr *MI = I;
211     if (!MI->isDebugValue() && mi2iMap.find(MI) == mi2iMap.end())
212       insertMachineInstrInMaps(MI);
213   }
214 }
215 
216 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dump() const217 void SlotIndexes::dump() const {
218   for (IndexList::const_iterator itr = indexList.begin();
219        itr != indexList.end(); ++itr) {
220     dbgs() << itr->getIndex() << " ";
221 
222     if (itr->getInstr()) {
223       dbgs() << *itr->getInstr();
224     } else {
225       dbgs() << "\n";
226     }
227   }
228 
229   for (unsigned i = 0, e = MBBRanges.size(); i != e; ++i)
230     dbgs() << "BB#" << i << "\t[" << MBBRanges[i].first << ';'
231            << MBBRanges[i].second << ")\n";
232 }
233 #endif
234 
235 // Print a SlotIndex to a raw_ostream.
print(raw_ostream & os) const236 void SlotIndex::print(raw_ostream &os) const {
237   if (isValid())
238     os << listEntry()->getIndex() << "Berd"[getSlot()];
239   else
240     os << "invalid";
241 }
242 
243 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
244 // Dump a SlotIndex to stderr.
dump() const245 void SlotIndex::dump() const {
246   print(dbgs());
247   dbgs() << "\n";
248 }
249 #endif
250 
251