DwarfAccelTable.cpp revision 8368f74c434db60c36a4044dfe80d4abee49ce27 
1//=-- llvm/CodeGen/DwarfAccelTable.cpp - Dwarf Accelerator Tables -*- C++ -*-=//
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// This file contains support for writing dwarf accelerator tables.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/CodeGen/AsmPrinter.h"
15#include "llvm/MC/MCExpr.h"
16#include "llvm/MC/MCStreamer.h"
17#include "llvm/MC/MCSymbol.h"
18#include "llvm/Support/Debug.h"
19#include "DwarfAccelTable.h"
20#include "DwarfDebug.h"
21#include "DIE.h"
22
23using namespace llvm;
24
25const char *DwarfAccelTable::Atom::AtomTypeString(enum AtomType AT) {
26  switch (AT) {
27  default: llvm_unreachable("invalid AtomType!");
28  case eAtomTypeNULL: return "eAtomTypeNULL";
29  case eAtomTypeDIEOffset: return "eAtomTypeDIEOffset";
30  case eAtomTypeCUOffset: return "eAtomTypeCUOffset";
31  case eAtomTypeTag: return "eAtomTypeTag";
32  case eAtomTypeNameFlags: return "eAtomTypeNameFlags";
33  case eAtomTypeTypeFlags: return "eAtomTypeTypeFlags";
34  }
35}
36
37// The general case would need to have a less hard coded size for the
38// length of the HeaderData, however, if we're constructing based on a
39// single Atom then we know it will always be: 4 + 4 + 2 + 2.
40DwarfAccelTable::DwarfAccelTable(DwarfAccelTable::Atom atom) :
41  Header(12),
42  HeaderData(atom) {
43}
44
45DwarfAccelTable::~DwarfAccelTable() {
46  for (size_t i = 0, e = Data.size() ; i < e; ++i)
47    delete Data[i];
48}
49
50void DwarfAccelTable::AddName(StringRef Name, DIE* die) {
51  // If the string is in the list already then add this die to the list
52  // otherwise add a new one.
53  DIEArray &DIEs = Entries[Name];
54  DIEs.push_back(die);
55}
56
57void DwarfAccelTable::ComputeBucketCount(void) {
58  // First get the number of unique hashes.
59  std::vector<uint32_t> uniques;
60  uniques.resize(Data.size());
61  for (size_t i = 0, e = Data.size(); i < e; ++i)
62    uniques[i] = Data[i]->HashValue;
63  std::stable_sort(uniques.begin(), uniques.end());
64  std::vector<uint32_t>::iterator p =
65    std::unique(uniques.begin(), uniques.end());
66  uint32_t num = std::distance(uniques.begin(), p);
67
68  // Then compute the bucket size, minimum of 1 bucket.
69  if (num > 1024) Header.bucket_count = num/4;
70  if (num > 16) Header.bucket_count = num/2;
71  else Header.bucket_count = num > 0 ? num : 1;
72
73  Header.hashes_count = num;
74}
75
76namespace {
77  // DIESorter - comparison predicate that sorts DIEs by their offset.
78  struct DIESorter {
79    bool operator()(DIE *A, DIE *B) const {
80      return A->getOffset() < B->getOffset();
81    }
82  };
83}
84
85void DwarfAccelTable::FinalizeTable(AsmPrinter *Asm, const char *Prefix) {
86  // Create the individual hash data outputs.
87  for (StringMap<DIEArray>::iterator
88         EI = Entries.begin(), EE = Entries.end(); EI != EE; ++EI) {
89    struct HashData *Entry = new HashData((*EI).getKeyData());
90
91    // Unique the entries.
92    std::stable_sort((*EI).second.begin(), (*EI).second.end(), DIESorter());
93    (*EI).second.erase(std::unique((*EI).second.begin(), (*EI).second.end()),
94                       (*EI).second.end());
95
96    for (DIEArray::const_iterator DI = (*EI).second.begin(),
97           DE = (*EI).second.end();
98         DI != DE; ++DI)
99      Entry->addOffset((*DI)->getOffset());
100    Data.push_back(Entry);
101  }
102
103  // Figure out how many buckets we need, then compute the bucket
104  // contents and the final ordering. We'll emit the hashes and offsets
105  // by doing a walk during the emission phase. We add temporary
106  // symbols to the data so that we can reference them during the offset
107  // later, we'll emit them when we emit the data.
108  ComputeBucketCount();
109
110  // Compute bucket contents and final ordering.
111  Buckets.resize(Header.bucket_count);
112  for (size_t i = 0, e = Data.size(); i < e; ++i) {
113    uint32_t bucket = Data[i]->HashValue % Header.bucket_count;
114    Buckets[bucket].push_back(Data[i]);
115    Data[i]->Sym = Asm->GetTempSymbol(Prefix, i);
116  }
117}
118
119// Emits the header for the table via the AsmPrinter.
120void DwarfAccelTable::EmitHeader(AsmPrinter *Asm) {
121  Asm->OutStreamer.AddComment("Header Magic");
122  Asm->EmitInt32(Header.magic);
123  Asm->OutStreamer.AddComment("Header Version");
124  Asm->EmitInt16(Header.version);
125  Asm->OutStreamer.AddComment("Header Hash Function");
126  Asm->EmitInt16(Header.hash_function);
127  Asm->OutStreamer.AddComment("Header Bucket Count");
128  Asm->EmitInt32(Header.bucket_count);
129  Asm->OutStreamer.AddComment("Header Hash Count");
130  Asm->EmitInt32(Header.hashes_count);
131  Asm->OutStreamer.AddComment("Header Data Length");
132  Asm->EmitInt32(Header.header_data_len);
133  Asm->OutStreamer.AddComment("HeaderData Die Offset Base");
134  Asm->EmitInt32(HeaderData.die_offset_base);
135  Asm->OutStreamer.AddComment("HeaderData Atom Count");
136  Asm->EmitInt32(HeaderData.Atoms.size());
137  for (size_t i = 0; i < HeaderData.Atoms.size(); i++) {
138    Atom A = HeaderData.Atoms[i];
139    Asm->OutStreamer.AddComment(Atom::AtomTypeString(A.type));
140    Asm->EmitInt16(A.type);
141    Asm->OutStreamer.AddComment(dwarf::FormEncodingString(A.form));
142    Asm->EmitInt16(A.form);
143  }
144}
145
146// Walk through and emit the buckets for the table. This will look
147// like a list of numbers of how many elements are in each bucket.
148void DwarfAccelTable::EmitBuckets(AsmPrinter *Asm) {
149  unsigned index = 0;
150  for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
151    Asm->OutStreamer.AddComment("Bucket " + Twine(i));
152    if (Buckets[i].size() != 0)
153      Asm->EmitInt32(index);
154    else
155      Asm->EmitInt32(UINT32_MAX);
156    index += Buckets[i].size();
157  }
158}
159
160// Walk through the buckets and emit the individual hashes for each
161// bucket.
162void DwarfAccelTable::EmitHashes(AsmPrinter *Asm) {
163  for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
164    for (HashList::const_iterator HI = Buckets[i].begin(),
165           HE = Buckets[i].end(); HI != HE; ++HI) {
166      Asm->OutStreamer.AddComment("Hash in Bucket " + Twine(i));
167      Asm->EmitInt32((*HI)->HashValue);
168    }
169  }
170}
171
172// Walk through the buckets and emit the individual offsets for each
173// element in each bucket. This is done via a symbol subtraction from the
174// beginning of the section. The non-section symbol will be output later
175// when we emit the actual data.
176void DwarfAccelTable::EmitOffsets(AsmPrinter *Asm, MCSymbol *SecBegin) {
177  for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
178    for (HashList::const_iterator HI = Buckets[i].begin(),
179           HE = Buckets[i].end(); HI != HE; ++HI) {
180      Asm->OutStreamer.AddComment("Offset in Bucket " + Twine(i));
181      MCContext &Context = Asm->OutStreamer.getContext();
182      const MCExpr *Sub =
183        MCBinaryExpr::CreateSub(MCSymbolRefExpr::Create((*HI)->Sym, Context),
184                                MCSymbolRefExpr::Create(SecBegin, Context),
185                                Context);
186      Asm->OutStreamer.EmitValue(Sub, sizeof(uint32_t), 0);
187    }
188  }
189}
190
191// Walk through the buckets and emit the full data for each element in
192// the bucket. For the string case emit the dies and the various offsets.
193// Terminate each HashData bucket with 0.
194void DwarfAccelTable::EmitData(AsmPrinter *Asm, DwarfDebug *D) {
195  uint64_t PrevHash = UINT64_MAX;
196  for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
197    for (HashList::const_iterator HI = Buckets[i].begin(),
198           HE = Buckets[i].end(); HI != HE; ++HI) {
199      // Remember to emit the label for our offset.
200      Asm->OutStreamer.EmitLabel((*HI)->Sym);
201      Asm->OutStreamer.AddComment((*HI)->Str);
202      Asm->EmitSectionOffset(D->getStringPoolEntry((*HI)->Str),
203                             D->getStringPool());
204      Asm->OutStreamer.AddComment("Num DIEs");
205      Asm->EmitInt32((*HI)->DIEOffsets.size());
206      for (std::vector<uint32_t>::const_iterator
207             DI = (*HI)->DIEOffsets.begin(), DE = (*HI)->DIEOffsets.end();
208           DI != DE; ++DI) {
209        Asm->EmitInt32((*DI));
210      }
211      // Emit a 0 to terminate the data unless we have a hash collision.
212      if (PrevHash != (*HI)->HashValue)
213        Asm->EmitInt32(0);
214      PrevHash = (*HI)->HashValue;
215    }
216  }
217}
218
219// Emit the entire data structure to the output file.
220void DwarfAccelTable::Emit(AsmPrinter *Asm, MCSymbol *SecBegin,
221                           DwarfDebug *D) {
222  // Emit the header.
223  EmitHeader(Asm);
224
225  // Emit the buckets.
226  EmitBuckets(Asm);
227
228  // Emit the hashes.
229  EmitHashes(Asm);
230
231  // Emit the offsets.
232  EmitOffsets(Asm, SecBegin);
233
234  // Emit the hash data.
235  EmitData(Asm, D);
236}
237
238#ifndef NDEBUG
239void DwarfAccelTable::print(raw_ostream &O) {
240
241  Header.print(O);
242  HeaderData.print(O);
243
244  O << "Entries: \n";
245  for (StringMap<DIEArray>::const_iterator
246         EI = Entries.begin(), EE = Entries.end(); EI != EE; ++EI) {
247    O << "Name: " << (*EI).getKeyData() << "\n";
248    for (DIEArray::const_iterator DI = (*EI).second.begin(),
249           DE = (*EI).second.end();
250         DI != DE; ++DI)
251      (*DI)->print(O);
252  }
253
254  O << "Buckets and Hashes: \n";
255  for (size_t i = 0, e = Buckets.size(); i < e; ++i)
256    for (HashList::const_iterator HI = Buckets[i].begin(),
257           HE = Buckets[i].end(); HI != HE; ++HI)
258      (*HI)->print(O);
259
260  O << "Data: \n";
261    for (std::vector<HashData*>::const_iterator
262           DI = Data.begin(), DE = Data.end(); DI != DE; ++DI)
263      (*DI)->print(O);
264
265
266}
267#endif
268