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 (MachineBasicBlock &MBB : *mf) {
73 // Insert an index for the MBB start.
74 SlotIndex blockStartIndex(&indexList.back(), SlotIndex::Slot_Block);
75
76 for (MachineInstr &MI : MBB) {
77 if (MI.isDebugValue())
78 continue;
79
80 // Insert a store index for the instr.
81 indexList.push_back(createEntry(&MI, index += SlotIndex::InstrDist));
82
83 // Save this base index in the maps.
84 mi2iMap.insert(std::make_pair(
85 &MI, SlotIndex(&indexList.back(), SlotIndex::Slot_Block)));
86 }
87
88 // We insert one blank instructions between basic blocks.
89 indexList.push_back(createEntry(nullptr, index += SlotIndex::InstrDist));
90
91 MBBRanges[MBB.getNumber()].first = blockStartIndex;
92 MBBRanges[MBB.getNumber()].second = SlotIndex(&indexList.back(),
93 SlotIndex::Slot_Block);
94 idx2MBBMap.push_back(IdxMBBPair(blockStartIndex, &MBB));
95 }
96
97 // Sort the Idx2MBBMap
98 std::sort(idx2MBBMap.begin(), idx2MBBMap.end(), Idx2MBBCompare());
99
100 DEBUG(mf->print(dbgs(), this));
101
102 // And we're done!
103 return false;
104 }
105
renumberIndexes()106 void SlotIndexes::renumberIndexes() {
107 // Renumber updates the index of every element of the index list.
108 DEBUG(dbgs() << "\n*** Renumbering SlotIndexes ***\n");
109 ++NumGlobalRenum;
110
111 unsigned index = 0;
112
113 for (IndexList::iterator I = indexList.begin(), E = indexList.end();
114 I != E; ++I) {
115 I->setIndex(index);
116 index += SlotIndex::InstrDist;
117 }
118 }
119
120 // Renumber indexes locally after curItr was inserted, but failed to get a new
121 // index.
renumberIndexes(IndexList::iterator curItr)122 void SlotIndexes::renumberIndexes(IndexList::iterator curItr) {
123 // Number indexes with half the default spacing so we can catch up quickly.
124 const unsigned Space = SlotIndex::InstrDist/2;
125 static_assert((Space & 3) == 0, "InstrDist must be a multiple of 2*NUM");
126
127 IndexList::iterator startItr = std::prev(curItr);
128 unsigned index = startItr->getIndex();
129 do {
130 curItr->setIndex(index += Space);
131 ++curItr;
132 // If the next index is bigger, we have caught up.
133 } while (curItr != indexList.end() && curItr->getIndex() <= index);
134
135 DEBUG(dbgs() << "\n*** Renumbered SlotIndexes " << startItr->getIndex() << '-'
136 << index << " ***\n");
137 ++NumLocalRenum;
138 }
139
140 // Repair indexes after adding and removing instructions.
repairIndexesInRange(MachineBasicBlock * MBB,MachineBasicBlock::iterator Begin,MachineBasicBlock::iterator End)141 void SlotIndexes::repairIndexesInRange(MachineBasicBlock *MBB,
142 MachineBasicBlock::iterator Begin,
143 MachineBasicBlock::iterator End) {
144 // FIXME: Is this really necessary? The only caller repairIntervalsForRange()
145 // does the same thing.
146 // Find anchor points, which are at the beginning/end of blocks or at
147 // instructions that already have indexes.
148 while (Begin != MBB->begin() && !hasIndex(*Begin))
149 --Begin;
150 while (End != MBB->end() && !hasIndex(*End))
151 ++End;
152
153 bool includeStart = (Begin == MBB->begin());
154 SlotIndex startIdx;
155 if (includeStart)
156 startIdx = getMBBStartIdx(MBB);
157 else
158 startIdx = getInstructionIndex(*Begin);
159
160 SlotIndex endIdx;
161 if (End == MBB->end())
162 endIdx = getMBBEndIdx(MBB);
163 else
164 endIdx = getInstructionIndex(*End);
165
166 // FIXME: Conceptually, this code is implementing an iterator on MBB that
167 // optionally includes an additional position prior to MBB->begin(), indicated
168 // by the includeStart flag. This is done so that we can iterate MIs in a MBB
169 // in parallel with SlotIndexes, but there should be a better way to do this.
170 IndexList::iterator ListB = startIdx.listEntry()->getIterator();
171 IndexList::iterator ListI = endIdx.listEntry()->getIterator();
172 MachineBasicBlock::iterator MBBI = End;
173 bool pastStart = false;
174 while (ListI != ListB || MBBI != Begin || (includeStart && !pastStart)) {
175 assert(ListI->getIndex() >= startIdx.getIndex() &&
176 (includeStart || !pastStart) &&
177 "Decremented past the beginning of region to repair.");
178
179 MachineInstr *SlotMI = ListI->getInstr();
180 MachineInstr *MI = (MBBI != MBB->end() && !pastStart) ? &*MBBI : nullptr;
181 bool MBBIAtBegin = MBBI == Begin && (!includeStart || pastStart);
182
183 if (SlotMI == MI && !MBBIAtBegin) {
184 --ListI;
185 if (MBBI != Begin)
186 --MBBI;
187 else
188 pastStart = true;
189 } else if (MI && mi2iMap.find(MI) == mi2iMap.end()) {
190 if (MBBI != Begin)
191 --MBBI;
192 else
193 pastStart = true;
194 } else {
195 --ListI;
196 if (SlotMI)
197 removeMachineInstrFromMaps(*SlotMI);
198 }
199 }
200
201 // In theory this could be combined with the previous loop, but it is tricky
202 // to update the IndexList while we are iterating it.
203 for (MachineBasicBlock::iterator I = End; I != Begin;) {
204 --I;
205 MachineInstr &MI = *I;
206 if (!MI.isDebugValue() && mi2iMap.find(&MI) == mi2iMap.end())
207 insertMachineInstrInMaps(MI);
208 }
209 }
210
211 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dump() const212 LLVM_DUMP_METHOD void SlotIndexes::dump() const {
213 for (IndexList::const_iterator itr = indexList.begin();
214 itr != indexList.end(); ++itr) {
215 dbgs() << itr->getIndex() << " ";
216
217 if (itr->getInstr()) {
218 dbgs() << *itr->getInstr();
219 } else {
220 dbgs() << "\n";
221 }
222 }
223
224 for (unsigned i = 0, e = MBBRanges.size(); i != e; ++i)
225 dbgs() << "BB#" << i << "\t[" << MBBRanges[i].first << ';'
226 << MBBRanges[i].second << ")\n";
227 }
228 #endif
229
230 // Print a SlotIndex to a raw_ostream.
print(raw_ostream & os) const231 void SlotIndex::print(raw_ostream &os) const {
232 if (isValid())
233 os << listEntry()->getIndex() << "Berd"[getSlot()];
234 else
235 os << "invalid";
236 }
237
238 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
239 // Dump a SlotIndex to stderr.
dump() const240 LLVM_DUMP_METHOD void SlotIndex::dump() const {
241 print(dbgs());
242 dbgs() << "\n";
243 }
244 #endif
245
246