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 "DwarfAccelTable.h"
15 #include "DIE.h"
16 #include "DwarfDebug.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/ADT/Twine.h"
19 #include "llvm/CodeGen/AsmPrinter.h"
20 #include "llvm/MC/MCExpr.h"
21 #include "llvm/MC/MCStreamer.h"
22 #include "llvm/MC/MCSymbol.h"
23 #include "llvm/Support/Debug.h"
24
25 using namespace llvm;
26
27 // The length of the header data is always going to be 4 + 4 + 4*NumAtoms.
DwarfAccelTable(ArrayRef<DwarfAccelTable::Atom> atomList)28 DwarfAccelTable::DwarfAccelTable(ArrayRef<DwarfAccelTable::Atom> atomList)
29 : Header(8 + (atomList.size() * 4)), HeaderData(atomList),
30 Entries(Allocator) {}
31
AddName(StringRef Name,MCSymbol * StrSym,const DIE * die,char Flags)32 void DwarfAccelTable::AddName(StringRef Name, MCSymbol *StrSym, const DIE *die,
33 char Flags) {
34 assert(Data.empty() && "Already finalized!");
35 // If the string is in the list already then add this die to the list
36 // otherwise add a new one.
37 DataArray &DIEs = Entries[Name];
38 assert(!DIEs.StrSym || DIEs.StrSym == StrSym);
39 DIEs.StrSym = StrSym;
40 DIEs.Values.push_back(new (Allocator) HashDataContents(die, Flags));
41 }
42
ComputeBucketCount(void)43 void DwarfAccelTable::ComputeBucketCount(void) {
44 // First get the number of unique hashes.
45 std::vector<uint32_t> uniques(Data.size());
46 for (size_t i = 0, e = Data.size(); i < e; ++i)
47 uniques[i] = Data[i]->HashValue;
48 array_pod_sort(uniques.begin(), uniques.end());
49 std::vector<uint32_t>::iterator p =
50 std::unique(uniques.begin(), uniques.end());
51 uint32_t num = std::distance(uniques.begin(), p);
52
53 // Then compute the bucket size, minimum of 1 bucket.
54 if (num > 1024)
55 Header.bucket_count = num / 4;
56 if (num > 16)
57 Header.bucket_count = num / 2;
58 else
59 Header.bucket_count = num > 0 ? num : 1;
60
61 Header.hashes_count = num;
62 }
63
64 // compareDIEs - comparison predicate that sorts DIEs by their offset.
compareDIEs(const DwarfAccelTable::HashDataContents * A,const DwarfAccelTable::HashDataContents * B)65 static bool compareDIEs(const DwarfAccelTable::HashDataContents *A,
66 const DwarfAccelTable::HashDataContents *B) {
67 return A->Die->getOffset() < B->Die->getOffset();
68 }
69
FinalizeTable(AsmPrinter * Asm,StringRef Prefix)70 void DwarfAccelTable::FinalizeTable(AsmPrinter *Asm, StringRef Prefix) {
71 // Create the individual hash data outputs.
72 for (StringMap<DataArray>::iterator EI = Entries.begin(), EE = Entries.end();
73 EI != EE; ++EI) {
74
75 // Unique the entries.
76 std::stable_sort(EI->second.Values.begin(), EI->second.Values.end(), compareDIEs);
77 EI->second.Values.erase(
78 std::unique(EI->second.Values.begin(), EI->second.Values.end()),
79 EI->second.Values.end());
80
81 HashData *Entry = new (Allocator) HashData(EI->getKey(), EI->second);
82 Data.push_back(Entry);
83 }
84
85 // Figure out how many buckets we need, then compute the bucket
86 // contents and the final ordering. We'll emit the hashes and offsets
87 // by doing a walk during the emission phase. We add temporary
88 // symbols to the data so that we can reference them during the offset
89 // later, we'll emit them when we emit the data.
90 ComputeBucketCount();
91
92 // Compute bucket contents and final ordering.
93 Buckets.resize(Header.bucket_count);
94 for (size_t i = 0, e = Data.size(); i < e; ++i) {
95 uint32_t bucket = Data[i]->HashValue % Header.bucket_count;
96 Buckets[bucket].push_back(Data[i]);
97 Data[i]->Sym = Asm->GetTempSymbol(Prefix, i);
98 }
99 }
100
101 // Emits the header for the table via the AsmPrinter.
EmitHeader(AsmPrinter * Asm)102 void DwarfAccelTable::EmitHeader(AsmPrinter *Asm) {
103 Asm->OutStreamer.AddComment("Header Magic");
104 Asm->EmitInt32(Header.magic);
105 Asm->OutStreamer.AddComment("Header Version");
106 Asm->EmitInt16(Header.version);
107 Asm->OutStreamer.AddComment("Header Hash Function");
108 Asm->EmitInt16(Header.hash_function);
109 Asm->OutStreamer.AddComment("Header Bucket Count");
110 Asm->EmitInt32(Header.bucket_count);
111 Asm->OutStreamer.AddComment("Header Hash Count");
112 Asm->EmitInt32(Header.hashes_count);
113 Asm->OutStreamer.AddComment("Header Data Length");
114 Asm->EmitInt32(Header.header_data_len);
115 Asm->OutStreamer.AddComment("HeaderData Die Offset Base");
116 Asm->EmitInt32(HeaderData.die_offset_base);
117 Asm->OutStreamer.AddComment("HeaderData Atom Count");
118 Asm->EmitInt32(HeaderData.Atoms.size());
119 for (size_t i = 0; i < HeaderData.Atoms.size(); i++) {
120 Atom A = HeaderData.Atoms[i];
121 Asm->OutStreamer.AddComment(dwarf::AtomTypeString(A.type));
122 Asm->EmitInt16(A.type);
123 Asm->OutStreamer.AddComment(dwarf::FormEncodingString(A.form));
124 Asm->EmitInt16(A.form);
125 }
126 }
127
128 // Walk through and emit the buckets for the table. Each index is
129 // an offset into the list of hashes.
EmitBuckets(AsmPrinter * Asm)130 void DwarfAccelTable::EmitBuckets(AsmPrinter *Asm) {
131 unsigned index = 0;
132 for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
133 Asm->OutStreamer.AddComment("Bucket " + Twine(i));
134 if (Buckets[i].size() != 0)
135 Asm->EmitInt32(index);
136 else
137 Asm->EmitInt32(UINT32_MAX);
138 index += Buckets[i].size();
139 }
140 }
141
142 // Walk through the buckets and emit the individual hashes for each
143 // bucket.
EmitHashes(AsmPrinter * Asm)144 void DwarfAccelTable::EmitHashes(AsmPrinter *Asm) {
145 for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
146 for (HashList::const_iterator HI = Buckets[i].begin(),
147 HE = Buckets[i].end();
148 HI != HE; ++HI) {
149 Asm->OutStreamer.AddComment("Hash in Bucket " + Twine(i));
150 Asm->EmitInt32((*HI)->HashValue);
151 }
152 }
153 }
154
155 // Walk through the buckets and emit the individual offsets for each
156 // element in each bucket. This is done via a symbol subtraction from the
157 // beginning of the section. The non-section symbol will be output later
158 // when we emit the actual data.
EmitOffsets(AsmPrinter * Asm,MCSymbol * SecBegin)159 void DwarfAccelTable::EmitOffsets(AsmPrinter *Asm, MCSymbol *SecBegin) {
160 for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
161 for (HashList::const_iterator HI = Buckets[i].begin(),
162 HE = Buckets[i].end();
163 HI != HE; ++HI) {
164 Asm->OutStreamer.AddComment("Offset in Bucket " + Twine(i));
165 MCContext &Context = Asm->OutStreamer.getContext();
166 const MCExpr *Sub = MCBinaryExpr::CreateSub(
167 MCSymbolRefExpr::Create((*HI)->Sym, Context),
168 MCSymbolRefExpr::Create(SecBegin, Context), Context);
169 Asm->OutStreamer.EmitValue(Sub, sizeof(uint32_t));
170 }
171 }
172 }
173
174 // Walk through the buckets and emit the full data for each element in
175 // the bucket. For the string case emit the dies and the various offsets.
176 // Terminate each HashData bucket with 0.
EmitData(AsmPrinter * Asm,DwarfFile * D)177 void DwarfAccelTable::EmitData(AsmPrinter *Asm, DwarfFile *D) {
178 uint64_t PrevHash = UINT64_MAX;
179 for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
180 for (HashList::const_iterator HI = Buckets[i].begin(),
181 HE = Buckets[i].end();
182 HI != HE; ++HI) {
183 // Remember to emit the label for our offset.
184 Asm->OutStreamer.EmitLabel((*HI)->Sym);
185 Asm->OutStreamer.AddComment((*HI)->Str);
186 Asm->EmitSectionOffset((*HI)->Data.StrSym,
187 D->getStringPool().getSectionSymbol());
188 Asm->OutStreamer.AddComment("Num DIEs");
189 Asm->EmitInt32((*HI)->Data.Values.size());
190 for (HashDataContents *HD : (*HI)->Data.Values) {
191 // Emit the DIE offset
192 Asm->EmitInt32(HD->Die->getOffset());
193 // If we have multiple Atoms emit that info too.
194 // FIXME: A bit of a hack, we either emit only one atom or all info.
195 if (HeaderData.Atoms.size() > 1) {
196 Asm->EmitInt16(HD->Die->getTag());
197 Asm->EmitInt8(HD->Flags);
198 }
199 }
200 // Emit a 0 to terminate the data unless we have a hash collision.
201 if (PrevHash != (*HI)->HashValue)
202 Asm->EmitInt32(0);
203 PrevHash = (*HI)->HashValue;
204 }
205 }
206 }
207
208 // Emit the entire data structure to the output file.
Emit(AsmPrinter * Asm,MCSymbol * SecBegin,DwarfFile * D)209 void DwarfAccelTable::Emit(AsmPrinter *Asm, MCSymbol *SecBegin, DwarfFile *D) {
210 // Emit the header.
211 EmitHeader(Asm);
212
213 // Emit the buckets.
214 EmitBuckets(Asm);
215
216 // Emit the hashes.
217 EmitHashes(Asm);
218
219 // Emit the offsets.
220 EmitOffsets(Asm, SecBegin);
221
222 // Emit the hash data.
223 EmitData(Asm, D);
224 }
225
226 #ifndef NDEBUG
print(raw_ostream & O)227 void DwarfAccelTable::print(raw_ostream &O) {
228
229 Header.print(O);
230 HeaderData.print(O);
231
232 O << "Entries: \n";
233 for (StringMap<DataArray>::const_iterator EI = Entries.begin(),
234 EE = Entries.end();
235 EI != EE; ++EI) {
236 O << "Name: " << EI->getKeyData() << "\n";
237 for (HashDataContents *HD : EI->second.Values)
238 HD->print(O);
239 }
240
241 O << "Buckets and Hashes: \n";
242 for (size_t i = 0, e = Buckets.size(); i < e; ++i)
243 for (HashList::const_iterator HI = Buckets[i].begin(),
244 HE = Buckets[i].end();
245 HI != HE; ++HI)
246 (*HI)->print(O);
247
248 O << "Data: \n";
249 for (std::vector<HashData *>::const_iterator DI = Data.begin(),
250 DE = Data.end();
251 DI != DE; ++DI)
252 (*DI)->print(O);
253 }
254 #endif
255