DwarfAccelTable.cpp revision 7eabae3f50d43af1b76f2bcc5ac6c47700d12b8b 
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
45// The length of the header data is always going to be 4 + 4 + 4*NumAtoms.
46DwarfAccelTable::DwarfAccelTable(std::vector<DwarfAccelTable::Atom> &atomList) :
47  Header(8 + (atomList.size() * 4)),
48  HeaderData(atomList) {
49}
50
51DwarfAccelTable::~DwarfAccelTable() {
52  for (size_t i = 0, e = Data.size(); i < e; ++i)
53    delete Data[i];
54  for (StringMap<DataArray>::iterator
55         EI = Entries.begin(), EE = Entries.end(); EI != EE; ++EI)
56    for (DataArray::iterator DI = (*EI).second.begin(),
57           DE = (*EI).second.end(); DI != DE; ++DI)
58      delete (*DI);
59}
60
61void DwarfAccelTable::AddName(StringRef Name, DIE* die, char Flags) {
62  // If the string is in the list already then add this die to the list
63  // otherwise add a new one.
64  DataArray &DIEs = Entries[Name];
65  DIEs.push_back(new HashDataContents(die, Flags));
66}
67
68void DwarfAccelTable::ComputeBucketCount(void) {
69  // First get the number of unique hashes.
70  std::vector<uint32_t> uniques;
71  uniques.resize(Data.size());
72  for (size_t i = 0, e = Data.size(); i < e; ++i)
73    uniques[i] = Data[i]->HashValue;
74  std::stable_sort(uniques.begin(), uniques.end());
75  std::vector<uint32_t>::iterator p =
76    std::unique(uniques.begin(), uniques.end());
77  uint32_t num = std::distance(uniques.begin(), p);
78
79  // Then compute the bucket size, minimum of 1 bucket.
80  if (num > 1024) Header.bucket_count = num/4;
81  if (num > 16) Header.bucket_count = num/2;
82  else Header.bucket_count = num > 0 ? num : 1;
83
84  Header.hashes_count = num;
85}
86
87namespace {
88  // DIESorter - comparison predicate that sorts DIEs by their offset.
89  struct DIESorter {
90    bool operator()(const struct DwarfAccelTable::HashDataContents *A,
91                    const struct DwarfAccelTable::HashDataContents *B) const {
92      return A->Die->getOffset() < B->Die->getOffset();
93    }
94  };
95}
96
97void DwarfAccelTable::FinalizeTable(AsmPrinter *Asm, const char *Prefix) {
98  // Create the individual hash data outputs.
99  for (StringMap<DataArray>::iterator
100         EI = Entries.begin(), EE = Entries.end(); EI != EE; ++EI) {
101    struct HashData *Entry = new HashData((*EI).getKeyData());
102
103    // Unique the entries.
104    std::stable_sort((*EI).second.begin(), (*EI).second.end(), DIESorter());
105    (*EI).second.erase(std::unique((*EI).second.begin(), (*EI).second.end()),
106                       (*EI).second.end());
107
108    for (DataArray::const_iterator DI = (*EI).second.begin(),
109           DE = (*EI).second.end();
110         DI != DE; ++DI)
111      Entry->addData((*DI));
112    Data.push_back(Entry);
113  }
114
115  // Figure out how many buckets we need, then compute the bucket
116  // contents and the final ordering. We'll emit the hashes and offsets
117  // by doing a walk during the emission phase. We add temporary
118  // symbols to the data so that we can reference them during the offset
119  // later, we'll emit them when we emit the data.
120  ComputeBucketCount();
121
122  // Compute bucket contents and final ordering.
123  Buckets.resize(Header.bucket_count);
124  for (size_t i = 0, e = Data.size(); i < e; ++i) {
125    uint32_t bucket = Data[i]->HashValue % Header.bucket_count;
126    Buckets[bucket].push_back(Data[i]);
127    Data[i]->Sym = Asm->GetTempSymbol(Prefix, i);
128  }
129}
130
131// Emits the header for the table via the AsmPrinter.
132void DwarfAccelTable::EmitHeader(AsmPrinter *Asm) {
133  Asm->OutStreamer.AddComment("Header Magic");
134  Asm->EmitInt32(Header.magic);
135  Asm->OutStreamer.AddComment("Header Version");
136  Asm->EmitInt16(Header.version);
137  Asm->OutStreamer.AddComment("Header Hash Function");
138  Asm->EmitInt16(Header.hash_function);
139  Asm->OutStreamer.AddComment("Header Bucket Count");
140  Asm->EmitInt32(Header.bucket_count);
141  Asm->OutStreamer.AddComment("Header Hash Count");
142  Asm->EmitInt32(Header.hashes_count);
143  Asm->OutStreamer.AddComment("Header Data Length");
144  Asm->EmitInt32(Header.header_data_len);
145  Asm->OutStreamer.AddComment("HeaderData Die Offset Base");
146  Asm->EmitInt32(HeaderData.die_offset_base);
147  Asm->OutStreamer.AddComment("HeaderData Atom Count");
148  Asm->EmitInt32(HeaderData.Atoms.size());
149  for (size_t i = 0; i < HeaderData.Atoms.size(); i++) {
150    Atom A = HeaderData.Atoms[i];
151    Asm->OutStreamer.AddComment(Atom::AtomTypeString(A.type));
152    Asm->EmitInt16(A.type);
153    Asm->OutStreamer.AddComment(dwarf::FormEncodingString(A.form));
154    Asm->EmitInt16(A.form);
155  }
156}
157
158// Walk through and emit the buckets for the table. This will look
159// like a list of numbers of how many elements are in each bucket.
160void DwarfAccelTable::EmitBuckets(AsmPrinter *Asm) {
161  unsigned index = 0;
162  for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
163    Asm->OutStreamer.AddComment("Bucket " + Twine(i));
164    if (Buckets[i].size() != 0)
165      Asm->EmitInt32(index);
166    else
167      Asm->EmitInt32(UINT32_MAX);
168    index += Buckets[i].size();
169  }
170}
171
172// Walk through the buckets and emit the individual hashes for each
173// bucket.
174void DwarfAccelTable::EmitHashes(AsmPrinter *Asm) {
175  for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
176    for (HashList::const_iterator HI = Buckets[i].begin(),
177           HE = Buckets[i].end(); HI != HE; ++HI) {
178      Asm->OutStreamer.AddComment("Hash in Bucket " + Twine(i));
179      Asm->EmitInt32((*HI)->HashValue);
180    }
181  }
182}
183
184// Walk through the buckets and emit the individual offsets for each
185// element in each bucket. This is done via a symbol subtraction from the
186// beginning of the section. The non-section symbol will be output later
187// when we emit the actual data.
188void DwarfAccelTable::EmitOffsets(AsmPrinter *Asm, MCSymbol *SecBegin) {
189  for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
190    for (HashList::const_iterator HI = Buckets[i].begin(),
191           HE = Buckets[i].end(); HI != HE; ++HI) {
192      Asm->OutStreamer.AddComment("Offset in Bucket " + Twine(i));
193      MCContext &Context = Asm->OutStreamer.getContext();
194      const MCExpr *Sub =
195        MCBinaryExpr::CreateSub(MCSymbolRefExpr::Create((*HI)->Sym, Context),
196                                MCSymbolRefExpr::Create(SecBegin, Context),
197                                Context);
198      Asm->OutStreamer.EmitValue(Sub, sizeof(uint32_t), 0);
199    }
200  }
201}
202
203// Walk through the buckets and emit the full data for each element in
204// the bucket. For the string case emit the dies and the various offsets.
205// Terminate each HashData bucket with 0.
206void DwarfAccelTable::EmitData(AsmPrinter *Asm, DwarfDebug *D) {
207  uint64_t PrevHash = UINT64_MAX;
208  for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
209    for (HashList::const_iterator HI = Buckets[i].begin(),
210           HE = Buckets[i].end(); HI != HE; ++HI) {
211      // Remember to emit the label for our offset.
212      Asm->OutStreamer.EmitLabel((*HI)->Sym);
213      Asm->OutStreamer.AddComment((*HI)->Str);
214      Asm->EmitSectionOffset(D->getStringPoolEntry((*HI)->Str),
215                             D->getStringPool());
216      Asm->OutStreamer.AddComment("Num DIEs");
217      Asm->EmitInt32((*HI)->Data.size());
218      for (std::vector<struct HashDataContents*>::const_iterator
219             DI = (*HI)->Data.begin(), DE = (*HI)->Data.end();
220           DI != DE; ++DI) {
221        // Emit the DIE offset
222        Asm->EmitInt32((*DI)->Die->getOffset());
223        // If we have multiple Atoms emit that info too.
224        // FIXME: A bit of a hack, we either emit only one atom or all info.
225        if (HeaderData.Atoms.size() > 1) {
226          Asm->EmitInt16((*DI)->Die->getTag());
227          Asm->EmitInt8((*DI)->Flags);
228        }
229      }
230      // Emit a 0 to terminate the data unless we have a hash collision.
231      if (PrevHash != (*HI)->HashValue)
232        Asm->EmitInt32(0);
233      PrevHash = (*HI)->HashValue;
234    }
235  }
236}
237
238// Emit the entire data structure to the output file.
239void DwarfAccelTable::Emit(AsmPrinter *Asm, MCSymbol *SecBegin,
240                           DwarfDebug *D) {
241  // Emit the header.
242  EmitHeader(Asm);
243
244  // Emit the buckets.
245  EmitBuckets(Asm);
246
247  // Emit the hashes.
248  EmitHashes(Asm);
249
250  // Emit the offsets.
251  EmitOffsets(Asm, SecBegin);
252
253  // Emit the hash data.
254  EmitData(Asm, D);
255}
256
257#ifndef NDEBUG
258void DwarfAccelTable::print(raw_ostream &O) {
259
260  Header.print(O);
261  HeaderData.print(O);
262
263  O << "Entries: \n";
264  for (StringMap<DataArray>::const_iterator
265         EI = Entries.begin(), EE = Entries.end(); EI != EE; ++EI) {
266    O << "Name: " << (*EI).getKeyData() << "\n";
267    for (DataArray::const_iterator DI = (*EI).second.begin(),
268           DE = (*EI).second.end();
269         DI != DE; ++DI)
270      (*DI)->print(O);
271  }
272
273  O << "Buckets and Hashes: \n";
274  for (size_t i = 0, e = Buckets.size(); i < e; ++i)
275    for (HashList::const_iterator HI = Buckets[i].begin(),
276           HE = Buckets[i].end(); HI != HE; ++HI)
277      (*HI)->print(O);
278
279  O << "Data: \n";
280    for (std::vector<HashData*>::const_iterator
281           DI = Data.begin(), DE = Data.end(); DI != DE; ++DI)
282      (*DI)->print(O);
283
284
285}
286#endif
287