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   // Iterate over the the function.
96   for (MachineFunction::iterator mbbItr = mf->begin(), mbbEnd = mf->end();
97        mbbItr != mbbEnd; ++mbbItr) {
98     MachineBasicBlock *mbb = &*mbbItr;
99 
100     // Insert an index for the MBB start.
101     push_back(createEntry(0, index));
102     SlotIndex blockStartIndex(back(), SlotIndex::LOAD);
103 
104     index += SlotIndex::NUM;
105 
106     for (MachineBasicBlock::iterator miItr = mbb->begin(), miEnd = mbb->end();
107          miItr != miEnd; ++miItr) {
108       MachineInstr *mi = &*miItr;
109 
110       if (miItr == mbb->getFirstTerminator()) {
111         push_back(createEntry(0, index));
112         terminatorGaps.insert(
113           std::make_pair(mbb, SlotIndex(back(), SlotIndex::PHI_BIT)));
114         index += SlotIndex::NUM;
115       }
116 
117       // Insert a store index for the instr.
118       push_back(createEntry(mi, index));
119 
120       // Save this base index in the maps.
121       mi2iMap.insert(
122         std::make_pair(mi, SlotIndex(back(), SlotIndex::LOAD)));
123 
124       ++functionSize;
125 
126       unsigned Slots = mi->getDesc().getNumDefs();
127       if (Slots == 0)
128         Slots = 1;
129 
130       index += (Slots + 1) * SlotIndex::NUM;
131     }
132 
133     if (mbb->getFirstTerminator() == mbb->end()) {
134       push_back(createEntry(0, index));
135       terminatorGaps.insert(
136         std::make_pair(mbb, SlotIndex(back(), SlotIndex::PHI_BIT)));
137       index += SlotIndex::NUM;
138     }
139 
140     SlotIndex blockEndIndex(back(), SlotIndex::STORE);
141     mbb2IdxMap.insert(
142       std::make_pair(mbb, std::make_pair(blockStartIndex, blockEndIndex)));
143 
144     idx2MBBMap.push_back(IdxMBBPair(blockStartIndex, mbb));
145   }
146 
147   // One blank instruction at the end.
148   push_back(createEntry(0, index));
149 
150   // Sort the Idx2MBBMap
151   std::sort(idx2MBBMap.begin(), idx2MBBMap.end(), Idx2MBBCompare());
152 
153   DEBUG(dump());
154 
155   // And we're done!
156   return false;
157 }
158 
159 void SlotIndexes::renumberIndexes() {
160 
161   // Renumber updates the index of every element of the index list.
162   // If all instrs in the function have been allocated an index (which has been
163   // placed in the index list in the order of instruction iteration) then the
164   // resulting numbering will match what would have been generated by the
165   // pass during the initial numbering of the function if the new instructions
166   // had been present.
167 
168   functionSize = 0;
169   unsigned index = 0;
170 
171   for (IndexListEntry *curEntry = front(); curEntry != getTail();
172        curEntry = curEntry->getNext()) {
173 
174     curEntry->setIndex(index);
175 
176     if (curEntry->getInstr() == 0) {
177       // MBB start entry or terminator gap. Just step index by 1.
178       index += SlotIndex::NUM;
179     }
180     else {
181       ++functionSize;
182       unsigned Slots = curEntry->getInstr()->getDesc().getNumDefs();
183       if (Slots == 0)
184         Slots = 1;
185 
186       index += (Slots + 1) * SlotIndex::NUM;
187     }
188   }
189 }
190 
191 void SlotIndexes::dump() const {
192   for (const IndexListEntry *itr = front(); itr != getTail();
193        itr = itr->getNext()) {
194     errs() << itr->getIndex() << " ";
195 
196     if (itr->getInstr() != 0) {
197       errs() << *itr->getInstr();
198     } else {
199       errs() << "\n";
200     }
201   }
202 
203   for (MBB2IdxMap::const_iterator itr = mbb2IdxMap.begin();
204        itr != mbb2IdxMap.end(); ++itr) {
205     errs() << "MBB " << itr->first->getNumber() << " (" << itr->first << ") - ["
206            << itr->second.first << ", " << itr->second.second << "]\n";
207   }
208 }
209 
210 // Print a SlotIndex to a raw_ostream.
211 void SlotIndex::print(raw_ostream &os) const {
212   os << getIndex();
213   if (isPHI())
214     os << "*";
215 }
216 
217 // Dump a SlotIndex to stderr.
218 void SlotIndex::dump() const {
219   print(errs());
220   errs() << "\n";
221 }
222 
223