DwarfAccelTable.cpp revision 0ffe2b4dd6f26fa19827f85bf9e4a766539a859c 
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::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
76void DwarfAccelTable::FinalizeTable(AsmPrinter *Asm, const char *Prefix) {
77  // Create the individual hash data outputs.
78  for (StringMap<DIEArray>::iterator
79         EI = Entries.begin(), EE = Entries.end(); EI != EE; ++EI) {
80    struct HashData *Entry = new HashData((*EI).getKeyData());
81
82    // Unique the entries.
83    std::sort((*EI).second.begin(), (*EI).second.end());
84    (*EI).second.erase(std::unique((*EI).second.begin(), (*EI).second.end()),
85                       (*EI).second.end());
86
87    for (DIEArray::const_iterator DI = (*EI).second.begin(),
88           DE = (*EI).second.end();
89         DI != DE; ++DI)
90      Entry->addOffset((*DI)->getOffset());
91    Data.push_back(Entry);
92  }
93
94  // Figure out how many buckets we need, then compute the bucket
95  // contents and the final ordering. We'll emit the hashes and offsets
96  // by doing a walk during the emission phase. We add temporary
97  // symbols to the data so that we can reference them during the offset
98  // later, we'll emit them when we emit the data.
99  ComputeBucketCount();
100
101  // Compute bucket contents and final ordering.
102  Buckets.resize(Header.bucket_count);
103  for (size_t i = 0, e = Data.size(); i < e; ++i) {
104    uint32_t bucket = Data[i]->HashValue % Header.bucket_count;
105    Buckets[bucket].push_back(Data[i]);
106    Data[i]->Sym = Asm->GetTempSymbol(Prefix, i);
107  }
108}
109
110// Emits the header for the table via the AsmPrinter.
111void DwarfAccelTable::EmitHeader(AsmPrinter *Asm) {
112  Asm->OutStreamer.AddComment("Header Magic");
113  Asm->EmitInt32(Header.magic);
114  Asm->OutStreamer.AddComment("Header Version");
115  Asm->EmitInt16(Header.version);
116  Asm->OutStreamer.AddComment("Header Hash Function");
117  Asm->EmitInt16(Header.hash_function);
118  Asm->OutStreamer.AddComment("Header Bucket Count");
119  Asm->EmitInt32(Header.bucket_count);
120  Asm->OutStreamer.AddComment("Header Hash Count");
121  Asm->EmitInt32(Header.hashes_count);
122  Asm->OutStreamer.AddComment("Header Data Length");
123  Asm->EmitInt32(Header.header_data_len);
124  Asm->OutStreamer.AddComment("HeaderData Die Offset Base");
125  Asm->EmitInt32(HeaderData.die_offset_base);
126  Asm->OutStreamer.AddComment("HeaderData Atom Count");
127  Asm->EmitInt32(HeaderData.Atoms.size());
128  for (size_t i = 0; i < HeaderData.Atoms.size(); i++) {
129    Atom A = HeaderData.Atoms[i];
130    Asm->OutStreamer.AddComment(Atom::AtomTypeString(A.type));
131    Asm->EmitInt16(A.type);
132    Asm->OutStreamer.AddComment(dwarf::FormEncodingString(A.form));
133    Asm->EmitInt16(A.form);
134  }
135}
136
137// Walk through and emit the buckets for the table. This will look
138// like a list of numbers of how many elements are in each bucket.
139void DwarfAccelTable::EmitBuckets(AsmPrinter *Asm) {
140  unsigned index = 0;
141  for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
142    Asm->OutStreamer.AddComment("Bucket " + Twine(i));
143    if (Buckets[i].size() != 0)
144      Asm->EmitInt32(index);
145    else
146      Asm->EmitInt32(UINT32_MAX);
147    index += Buckets[i].size();
148  }
149}
150
151// Walk through the buckets and emit the individual hashes for each
152// bucket.
153void DwarfAccelTable::EmitHashes(AsmPrinter *Asm) {
154  for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
155    for (HashList::const_iterator HI = Buckets[i].begin(),
156           HE = Buckets[i].end(); HI != HE; ++HI) {
157      Asm->OutStreamer.AddComment("Hash in Bucket " + Twine(i));
158      Asm->EmitInt32((*HI)->HashValue);
159    }
160  }
161}
162
163// Walk through the buckets and emit the individual offsets for each
164// element in each bucket. This is done via a symbol subtraction from the
165// beginning of the section. The non-section symbol will be output later
166// when we emit the actual data.
167void DwarfAccelTable::EmitOffsets(AsmPrinter *Asm, MCSymbol *SecBegin) {
168  for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
169    for (HashList::const_iterator HI = Buckets[i].begin(),
170           HE = Buckets[i].end(); HI != HE; ++HI) {
171      Asm->OutStreamer.AddComment("Offset in Bucket " + Twine(i));
172      MCContext &Context = Asm->OutStreamer.getContext();
173      const MCExpr *Sub =
174        MCBinaryExpr::CreateSub(MCSymbolRefExpr::Create((*HI)->Sym, Context),
175                                MCSymbolRefExpr::Create(SecBegin, Context),
176                                Context);
177      Asm->OutStreamer.EmitValue(Sub, sizeof(uint32_t), 0);
178    }
179  }
180}
181
182// Walk through the buckets and emit the full data for each element in
183// the bucket. For the string case emit the dies and the various offsets.
184// Terminate each HashData bucket with 0.
185void DwarfAccelTable::EmitData(AsmPrinter *Asm, DwarfDebug *D) {
186  uint64_t PrevHash = UINT64_MAX;
187  for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
188    for (HashList::const_iterator HI = Buckets[i].begin(),
189           HE = Buckets[i].end(); HI != HE; ++HI) {
190      // Remember to emit the label for our offset.
191      Asm->OutStreamer.EmitLabel((*HI)->Sym);
192      Asm->OutStreamer.AddComment((*HI)->Str);
193      Asm->EmitSectionOffset(D->getStringPoolEntry((*HI)->Str),
194                             D->getStringPool());
195      Asm->OutStreamer.AddComment("Num DIEs");
196      Asm->EmitInt32((*HI)->DIEOffsets.size());
197      for (std::vector<uint32_t>::const_iterator
198             DI = (*HI)->DIEOffsets.begin(), DE = (*HI)->DIEOffsets.end();
199           DI != DE; ++DI) {
200        Asm->EmitInt32((*DI));
201      }
202      // Emit a 0 to terminate the data unless we have a hash collision.
203      if (PrevHash != (*HI)->HashValue)
204        Asm->EmitInt32(0);
205      PrevHash = (*HI)->HashValue;
206    }
207  }
208}
209
210// Emit the entire data structure to the output file.
211void DwarfAccelTable::Emit(AsmPrinter *Asm, MCSymbol *SecBegin,
212                           DwarfDebug *D) {
213  // Emit the header.
214  EmitHeader(Asm);
215
216  // Emit the buckets.
217  EmitBuckets(Asm);
218
219  // Emit the hashes.
220  EmitHashes(Asm);
221
222  // Emit the offsets.
223  EmitOffsets(Asm, SecBegin);
224
225  // Emit the hash data.
226  EmitData(Asm, D);
227}
228
229#ifndef NDEBUG
230void DwarfAccelTable::print(raw_ostream &O) {
231
232  Header.print(O);
233  HeaderData.print(O);
234
235  O << "Entries: \n";
236  for (StringMap<DIEArray>::const_iterator
237         EI = Entries.begin(), EE = Entries.end(); EI != EE; ++EI) {
238    O << "Name: " << (*EI).getKeyData() << "\n";
239    for (DIEArray::const_iterator DI = (*EI).second.begin(),
240           DE = (*EI).second.end();
241         DI != DE; ++DI)
242      (*DI)->print(O);
243  }
244
245  O << "Buckets and Hashes: \n";
246  for (size_t i = 0, e = Buckets.size(); i < e; ++i)
247    for (HashList::const_iterator HI = Buckets[i].begin(),
248           HE = Buckets[i].end(); HI != HE; ++HI)
249      (*HI)->print(O);
250
251  O << "Data: \n";
252    for (std::vector<HashData*>::const_iterator
253           DI = Data.begin(), DE = Data.end(); DI != DE; ++DI)
254      (*DI)->print(O);
255
256
257}
258#endif
259