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   terminatorGaps.clear();
65   clearList();
66 }
67 
68 bool SlotIndexes::runOnMachineFunction(MachineFunction &fn) {
69 
70   // Compute numbering as follows:
71   // Grab an iterator to the start of the index list.
72   // Iterate over all MBBs, and within each MBB all MIs, keeping the MI
73   // iterator in lock-step (though skipping it over indexes which have
74   // null pointers in the instruction field).
75   // At each iteration assert that the instruction pointed to in the index
76   // is the same one pointed to by the MI iterator. This
77 
78   // FIXME: This can be simplified. The mi2iMap_, Idx2MBBMap, etc. should
79   // only need to be set up once after the first numbering is computed.
80 
81   mf = &fn;
82   initList();
83 
84   // Check that the list contains only the sentinal.
85   assert(indexListHead->getNext() == 0 &&
86          "Index list non-empty at initial numbering?");
87   assert(idx2MBBMap.empty() &&
88          "Index -> MBB mapping non-empty at initial numbering?");
89   assert(mbb2IdxMap.empty() &&
90          "MBB -> Index mapping non-empty at initial numbering?");
91   assert(mi2iMap.empty() &&
92          "MachineInstr -> Index mapping non-empty at initial numbering?");
93 
94   functionSize = 0;
95   unsigned index = 0;
96 
97   push_back(createEntry(0, index));
98 
99   // Iterate over the function.
100   for (MachineFunction::iterator mbbItr = mf->begin(), mbbEnd = mf->end();
101        mbbItr != mbbEnd; ++mbbItr) {
102     MachineBasicBlock *mbb = &*mbbItr;
103 
104     // Insert an index for the MBB start.
105     SlotIndex blockStartIndex(back(), SlotIndex::LOAD);
106 
107     index += SlotIndex::NUM;
108 
109     for (MachineBasicBlock::iterator miItr = mbb->begin(), miEnd = mbb->end();
110          miItr != miEnd; ++miItr) {
111       MachineInstr *mi = miItr;
112       if (mi->isDebugValue())
113         continue;
114 
115       if (miItr == mbb->getFirstTerminator()) {
116         push_back(createEntry(0, index));
117         terminatorGaps.insert(
118           std::make_pair(mbb, SlotIndex(back(), SlotIndex::PHI_BIT)));
119         index += SlotIndex::NUM;
120       }
121 
122       // Insert a store index for the instr.
123       push_back(createEntry(mi, index));
124 
125       // Save this base index in the maps.
126       mi2iMap.insert(
127         std::make_pair(mi, SlotIndex(back(), SlotIndex::LOAD)));
128 
129       ++functionSize;
130 
131       unsigned Slots = mi->getDesc().getNumDefs();
132       if (Slots == 0)
133         Slots = 1;
134 
135       index += (Slots + 1) * SlotIndex::NUM;
136     }
137 
138     if (mbb->getFirstTerminator() == mbb->end()) {
139       push_back(createEntry(0, index));
140       terminatorGaps.insert(
141         std::make_pair(mbb, SlotIndex(back(), SlotIndex::PHI_BIT)));
142       index += SlotIndex::NUM;
143     }
144 
145     // One blank instruction at the end.
146     push_back(createEntry(0, index));
147 
148     SlotIndex blockEndIndex(back(), SlotIndex::LOAD);
149     mbb2IdxMap.insert(
150       std::make_pair(mbb, std::make_pair(blockStartIndex, blockEndIndex)));
151 
152     idx2MBBMap.push_back(IdxMBBPair(blockStartIndex, mbb));
153   }
154 
155   // Sort the Idx2MBBMap
156   std::sort(idx2MBBMap.begin(), idx2MBBMap.end(), Idx2MBBCompare());
157 
158   DEBUG(dump());
159 
160   // And we're done!
161   return false;
162 }
163 
164 void SlotIndexes::renumberIndexes() {
165 
166   // Renumber updates the index of every element of the index list.
167   // If all instrs in the function have been allocated an index (which has been
168   // placed in the index list in the order of instruction iteration) then the
169   // resulting numbering will match what would have been generated by the
170   // pass during the initial numbering of the function if the new instructions
171   // had been present.
172 
173   functionSize = 0;
174   unsigned index = 0;
175 
176   for (IndexListEntry *curEntry = front(); curEntry != getTail();
177        curEntry = curEntry->getNext()) {
178 
179     curEntry->setIndex(index);
180 
181     if (curEntry->getInstr() == 0) {
182       // MBB start entry or terminator gap. Just step index by 1.
183       index += SlotIndex::NUM;
184     }
185     else {
186       ++functionSize;
187       unsigned Slots = curEntry->getInstr()->getDesc().getNumDefs();
188       if (Slots == 0)
189         Slots = 1;
190 
191       index += (Slots + 1) * SlotIndex::NUM;
192     }
193   }
194 }
195 
196 void SlotIndexes::dump() const {
197   for (const IndexListEntry *itr = front(); itr != getTail();
198        itr = itr->getNext()) {
199     dbgs() << itr->getIndex() << " ";
200 
201     if (itr->getInstr() != 0) {
202       dbgs() << *itr->getInstr();
203     } else {
204       dbgs() << "\n";
205     }
206   }
207 
208   for (MBB2IdxMap::const_iterator itr = mbb2IdxMap.begin();
209        itr != mbb2IdxMap.end(); ++itr) {
210     dbgs() << "MBB " << itr->first->getNumber() << " (" << itr->first << ") - ["
211            << itr->second.first << ", " << itr->second.second << "]\n";
212   }
213 }
214 
215 // Print a SlotIndex to a raw_ostream.
216 void SlotIndex::print(raw_ostream &os) const {
217   os << entry().getIndex();
218   if (isPHI())
219     os << "*";
220   else
221     os << "LudS"[getSlot()];
222 }
223 
224 // Dump a SlotIndex to stderr.
225 void SlotIndex::dump() const {
226   print(dbgs());
227   dbgs() << "\n";
228 }
229 
230