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();
176 IndexList::iterator ListI = endIdx.listEntry();
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