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 
18 using namespace llvm;
19 
20 
21 // Yep - these are thread safe. See the header for details.
22 namespace {
23 
24 
25   class EmptyIndexListEntry : public IndexListEntry {
26   public:
27     EmptyIndexListEntry() : IndexListEntry(EMPTY_KEY) {}
28   };
29 
30   class TombstoneIndexListEntry : public IndexListEntry {
31   public:
32     TombstoneIndexListEntry() : IndexListEntry(TOMBSTONE_KEY) {}
33   };
34 
35   // The following statics are thread safe. They're read only, and you
36   // can't step from them to any other list entries.
37   ManagedStatic<EmptyIndexListEntry> IndexListEntryEmptyKey;
38   ManagedStatic<TombstoneIndexListEntry> IndexListEntryTombstoneKey;
39 }
40 
41 char SlotIndexes::ID = 0;
42 static RegisterPass<SlotIndexes> X("slotindexes", "Slot index numbering");
43 
44 IndexListEntry* IndexListEntry::getEmptyKeyEntry() {
45   return &*IndexListEntryEmptyKey;
46 }
47 
48 IndexListEntry* IndexListEntry::getTombstoneKeyEntry() {
49   return &*IndexListEntryTombstoneKey;
50 }
51 
52 
53 void SlotIndexes::getAnalysisUsage(AnalysisUsage &au) const {
54   au.setPreservesAll();
55   MachineFunctionPass::getAnalysisUsage(au);
56 }
57 
58 void SlotIndexes::releaseMemory() {
59   mi2iMap.clear();
60   mbb2IdxMap.clear();
61   idx2MBBMap.clear();
62   terminatorGaps.clear();
63   clearList();
64 }
65 
66 bool SlotIndexes::runOnMachineFunction(MachineFunction &fn) {
67 
68   // Compute numbering as follows:
69   // Grab an iterator to the start of the index list.
70   // Iterate over all MBBs, and within each MBB all MIs, keeping the MI
71   // iterator in lock-step (though skipping it over indexes which have
72   // null pointers in the instruction field).
73   // At each iteration assert that the instruction pointed to in the index
74   // is the same one pointed to by the MI iterator. This
75 
76   // FIXME: This can be simplified. The mi2iMap_, Idx2MBBMap, etc. should
77   // only need to be set up once after the first numbering is computed.
78 
79   mf = &fn;
80   initList();
81 
82   // Check that the list contains only the sentinal.
83   assert(indexListHead->getNext() == 0 &&
84          "Index list non-empty at initial numbering?");
85   assert(idx2MBBMap.empty() &&
86          "Index -> MBB mapping non-empty at initial numbering?");
87   assert(mbb2IdxMap.empty() &&
88          "MBB -> Index mapping non-empty at initial numbering?");
89   assert(mi2iMap.empty() &&
90          "MachineInstr -> Index mapping non-empty at initial numbering?");
91 
92   functionSize = 0;
93   unsigned index = 0;
94 
95   push_back(createEntry(0, index));
96 
97   // Iterate over the the function.
98   for (MachineFunction::iterator mbbItr = mf->begin(), mbbEnd = mf->end();
99        mbbItr != mbbEnd; ++mbbItr) {
100     MachineBasicBlock *mbb = &*mbbItr;
101 
102     // Insert an index for the MBB start.
103     SlotIndex blockStartIndex(back(), SlotIndex::LOAD);
104 
105     index += SlotIndex::NUM;
106 
107     for (MachineBasicBlock::iterator miItr = mbb->begin(), miEnd = mbb->end();
108          miItr != miEnd; ++miItr) {
109       MachineInstr *mi = &*miItr;
110 
111       if (miItr == mbb->getFirstTerminator()) {
112         push_back(createEntry(0, index));
113         terminatorGaps.insert(
114           std::make_pair(mbb, SlotIndex(back(), SlotIndex::PHI_BIT)));
115         index += SlotIndex::NUM;
116       }
117 
118       // Insert a store index for the instr.
119       push_back(createEntry(mi, index));
120 
121       // Save this base index in the maps.
122       mi2iMap.insert(
123         std::make_pair(mi, SlotIndex(back(), SlotIndex::LOAD)));
124 
125       ++functionSize;
126 
127       unsigned Slots = mi->getDesc().getNumDefs();
128       if (Slots == 0)
129         Slots = 1;
130 
131       index += (Slots + 1) * SlotIndex::NUM;
132     }
133 
134     if (mbb->getFirstTerminator() == mbb->end()) {
135       push_back(createEntry(0, index));
136       terminatorGaps.insert(
137         std::make_pair(mbb, SlotIndex(back(), SlotIndex::PHI_BIT)));
138       index += SlotIndex::NUM;
139     }
140 
141     // One blank instruction at the end.
142     push_back(createEntry(0, index));
143 
144     SlotIndex blockEndIndex(back(), SlotIndex::LOAD);
145     mbb2IdxMap.insert(
146       std::make_pair(mbb, std::make_pair(blockStartIndex, blockEndIndex)));
147 
148     idx2MBBMap.push_back(IdxMBBPair(blockStartIndex, mbb));
149   }
150 
151   // Sort the Idx2MBBMap
152   std::sort(idx2MBBMap.begin(), idx2MBBMap.end(), Idx2MBBCompare());
153 
154   DEBUG(dump());
155 
156   // And we're done!
157   return false;
158 }
159 
160 void SlotIndexes::renumberIndexes() {
161 
162   // Renumber updates the index of every element of the index list.
163   // If all instrs in the function have been allocated an index (which has been
164   // placed in the index list in the order of instruction iteration) then the
165   // resulting numbering will match what would have been generated by the
166   // pass during the initial numbering of the function if the new instructions
167   // had been present.
168 
169   functionSize = 0;
170   unsigned index = 0;
171 
172   for (IndexListEntry *curEntry = front(); curEntry != getTail();
173        curEntry = curEntry->getNext()) {
174 
175     curEntry->setIndex(index);
176 
177     if (curEntry->getInstr() == 0) {
178       // MBB start entry or terminator gap. Just step index by 1.
179       index += SlotIndex::NUM;
180     }
181     else {
182       ++functionSize;
183       unsigned Slots = curEntry->getInstr()->getDesc().getNumDefs();
184       if (Slots == 0)
185         Slots = 1;
186 
187       index += (Slots + 1) * SlotIndex::NUM;
188     }
189   }
190 }
191 
192 void SlotIndexes::dump() const {
193   for (const IndexListEntry *itr = front(); itr != getTail();
194        itr = itr->getNext()) {
195     errs() << itr->getIndex() << " ";
196 
197     if (itr->getInstr() != 0) {
198       errs() << *itr->getInstr();
199     } else {
200       errs() << "\n";
201     }
202   }
203 
204   for (MBB2IdxMap::const_iterator itr = mbb2IdxMap.begin();
205        itr != mbb2IdxMap.end(); ++itr) {
206     errs() << "MBB " << itr->first->getNumber() << " (" << itr->first << ") - ["
207            << itr->second.first << ", " << itr->second.second << "]\n";
208   }
209 }
210 
211 // Print a SlotIndex to a raw_ostream.
212 void SlotIndex::print(raw_ostream &os) const {
213   os << getIndex();
214   if (isPHI())
215     os << "*";
216 }
217 
218 // Dump a SlotIndex to stderr.
219 void SlotIndex::dump() const {
220   print(errs());
221   errs() << "\n";
222 }
223 
224