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 #define DEBUG_TYPE "slotindexes"
11 
12 #include "llvm/CodeGen/SlotIndexes.h"
13 #include "llvm/CodeGen/MachineFunction.h"
14 #include "llvm/Support/Debug.h"
15 #include "llvm/Support/raw_ostream.h"
16 #include "llvm/Support/ManagedStatic.h"
17 #include "llvm/Target/TargetInstrInfo.h"
18 
19 using namespace llvm;
20 
21 
22 // Yep - these are thread safe. See the header for details.
23 namespace {
24 
25 
26   class EmptyIndexListEntry : public IndexListEntry {
27   public:
28     EmptyIndexListEntry() : IndexListEntry(EMPTY_KEY) {}
29   };
30 
31   class TombstoneIndexListEntry : public IndexListEntry {
32   public:
33     TombstoneIndexListEntry() : IndexListEntry(TOMBSTONE_KEY) {}
34   };
35 
36   // The following statics are thread safe. They're read only, and you
37   // can't step from them to any other list entries.
38   ManagedStatic<EmptyIndexListEntry> IndexListEntryEmptyKey;
39   ManagedStatic<TombstoneIndexListEntry> IndexListEntryTombstoneKey;
40 }
41 
42 char SlotIndexes::ID = 0;
43 INITIALIZE_PASS(SlotIndexes, "slotindexes",
44                 "Slot index numbering", false, false)
45 
46 IndexListEntry* IndexListEntry::getEmptyKeyEntry() {
47   return &*IndexListEntryEmptyKey;
48 }
49 
50 IndexListEntry* IndexListEntry::getTombstoneKeyEntry() {
51   return &*IndexListEntryTombstoneKey;
52 }
53 
54 
55 void SlotIndexes::getAnalysisUsage(AnalysisUsage &au) const {
56   au.setPreservesAll();
57   MachineFunctionPass::getAnalysisUsage(au);
58 }
59 
60 void SlotIndexes::releaseMemory() {
61   mi2iMap.clear();
62   mbb2IdxMap.clear();
63   idx2MBBMap.clear();
64   clearList();
65 }
66 
67 bool SlotIndexes::runOnMachineFunction(MachineFunction &fn) {
68 
69   // Compute numbering as follows:
70   // Grab an iterator to the start of the index list.
71   // Iterate over all MBBs, and within each MBB all MIs, keeping the MI
72   // iterator in lock-step (though skipping it over indexes which have
73   // null pointers in the instruction field).
74   // At each iteration assert that the instruction pointed to in the index
75   // is the same one pointed to by the MI iterator. This
76 
77   // FIXME: This can be simplified. The mi2iMap_, Idx2MBBMap, etc. should
78   // only need to be set up once after the first numbering is computed.
79 
80   mf = &fn;
81   initList();
82 
83   // Check that the list contains only the sentinal.
84   assert(indexListHead->getNext() == 0 &&
85          "Index list non-empty at initial numbering?");
86   assert(idx2MBBMap.empty() &&
87          "Index -> MBB mapping non-empty at initial numbering?");
88   assert(mbb2IdxMap.empty() &&
89          "MBB -> Index mapping non-empty at initial numbering?");
90   assert(mi2iMap.empty() &&
91          "MachineInstr -> Index mapping non-empty at initial numbering?");
92 
93   functionSize = 0;
94   unsigned index = 0;
95 
96   push_back(createEntry(0, index));
97 
98   // Iterate over the function.
99   for (MachineFunction::iterator mbbItr = mf->begin(), mbbEnd = mf->end();
100        mbbItr != mbbEnd; ++mbbItr) {
101     MachineBasicBlock *mbb = &*mbbItr;
102 
103     // Insert an index for the MBB start.
104     SlotIndex blockStartIndex(back(), SlotIndex::LOAD);
105 
106     index += SlotIndex::NUM;
107 
108     for (MachineBasicBlock::iterator miItr = mbb->begin(), miEnd = mbb->end();
109          miItr != miEnd; ++miItr) {
110       MachineInstr *mi = miItr;
111       if (mi->isDebugValue())
112         continue;
113 
114       // Insert a store index for the instr.
115       push_back(createEntry(mi, index));
116 
117       // Save this base index in the maps.
118       mi2iMap.insert(
119         std::make_pair(mi, SlotIndex(back(), SlotIndex::LOAD)));
120 
121       ++functionSize;
122 
123       unsigned Slots = mi->getDesc().getNumDefs();
124       if (Slots == 0)
125         Slots = 1;
126 
127       index += (Slots + 1) * SlotIndex::NUM;
128     }
129 
130     // We insert two blank instructions between basic blocks.
131     // One to represent live-out registers and one to represent live-ins.
132     push_back(createEntry(0, index));
133     index += SlotIndex::NUM;
134 
135     push_back(createEntry(0, index));
136 
137     SlotIndex blockEndIndex(back(), SlotIndex::LOAD);
138     mbb2IdxMap.insert(
139       std::make_pair(mbb, std::make_pair(blockStartIndex, blockEndIndex)));
140 
141     idx2MBBMap.push_back(IdxMBBPair(blockStartIndex, mbb));
142   }
143 
144   // Sort the Idx2MBBMap
145   std::sort(idx2MBBMap.begin(), idx2MBBMap.end(), Idx2MBBCompare());
146 
147   DEBUG(dump());
148 
149   // And we're done!
150   return false;
151 }
152 
153 void SlotIndexes::renumberIndexes() {
154 
155   // Renumber updates the index of every element of the index list.
156   // If all instrs in the function have been allocated an index (which has been
157   // placed in the index list in the order of instruction iteration) then the
158   // resulting numbering will match what would have been generated by the
159   // pass during the initial numbering of the function if the new instructions
160   // had been present.
161 
162   functionSize = 0;
163   unsigned index = 0;
164 
165   for (IndexListEntry *curEntry = front(); curEntry != getTail();
166        curEntry = curEntry->getNext()) {
167 
168     curEntry->setIndex(index);
169 
170     if (curEntry->getInstr() == 0) {
171       // MBB start entry. Just step index by 1.
172       index += SlotIndex::NUM;
173     }
174     else {
175       ++functionSize;
176       unsigned Slots = curEntry->getInstr()->getDesc().getNumDefs();
177       if (Slots == 0)
178         Slots = 1;
179 
180       index += (Slots + 1) * SlotIndex::NUM;
181     }
182   }
183 }
184 
185 void SlotIndexes::dump() const {
186   for (const IndexListEntry *itr = front(); itr != getTail();
187        itr = itr->getNext()) {
188     dbgs() << itr->getIndex() << " ";
189 
190     if (itr->getInstr() != 0) {
191       dbgs() << *itr->getInstr();
192     } else {
193       dbgs() << "\n";
194     }
195   }
196 
197   for (MBB2IdxMap::const_iterator itr = mbb2IdxMap.begin();
198        itr != mbb2IdxMap.end(); ++itr) {
199     dbgs() << "MBB " << itr->first->getNumber() << " (" << itr->first << ") - ["
200            << itr->second.first << ", " << itr->second.second << "]\n";
201   }
202 }
203 
204 // Print a SlotIndex to a raw_ostream.
205 void SlotIndex::print(raw_ostream &os) const {
206   os << entry().getIndex() << "LudS"[getSlot()];
207 }
208 
209 // Dump a SlotIndex to stderr.
210 void SlotIndex::dump() const {
211   print(dbgs());
212   dbgs() << "\n";
213 }
214 
215