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 "DwarfCompileUnit.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/CodeGen/DIE.h"
21 #include "llvm/MC/MCExpr.h"
22 #include "llvm/MC/MCStreamer.h"
23 #include "llvm/MC/MCSymbol.h"
24 #include "llvm/Support/Debug.h"
25
26 using namespace llvm;
27
28 // The length of the header data is always going to be 4 + 4 + 4*NumAtoms.
DwarfAccelTable(ArrayRef<DwarfAccelTable::Atom> atomList)29 DwarfAccelTable::DwarfAccelTable(ArrayRef<DwarfAccelTable::Atom> atomList)
30 : Header(8 + (atomList.size() * 4)), HeaderData(atomList),
31 Entries(Allocator) {}
32
AddName(StringRef Name,MCSymbol * StrSym,const DIE * die,char Flags)33 void DwarfAccelTable::AddName(StringRef Name, MCSymbol *StrSym, const DIE *die,
34 char Flags) {
35 assert(Data.empty() && "Already finalized!");
36 // If the string is in the list already then add this die to the list
37 // otherwise add a new one.
38 DataArray &DIEs = Entries[Name];
39 assert(!DIEs.StrSym || DIEs.StrSym == StrSym);
40 DIEs.StrSym = StrSym;
41 DIEs.Values.push_back(new (Allocator) HashDataContents(die, Flags));
42 }
43
ComputeBucketCount(void)44 void DwarfAccelTable::ComputeBucketCount(void) {
45 // First get the number of unique hashes.
46 std::vector<uint32_t> uniques(Data.size());
47 for (size_t i = 0, e = Data.size(); i < e; ++i)
48 uniques[i] = Data[i]->HashValue;
49 array_pod_sort(uniques.begin(), uniques.end());
50 std::vector<uint32_t>::iterator p =
51 std::unique(uniques.begin(), uniques.end());
52 uint32_t num = std::distance(uniques.begin(), p);
53
54 // Then compute the bucket size, minimum of 1 bucket.
55 if (num > 1024)
56 Header.bucket_count = num / 4;
57 if (num > 16)
58 Header.bucket_count = num / 2;
59 else
60 Header.bucket_count = num > 0 ? num : 1;
61
62 Header.hashes_count = num;
63 }
64
65 // compareDIEs - comparison predicate that sorts DIEs by their offset.
compareDIEs(const DwarfAccelTable::HashDataContents * A,const DwarfAccelTable::HashDataContents * B)66 static bool compareDIEs(const DwarfAccelTable::HashDataContents *A,
67 const DwarfAccelTable::HashDataContents *B) {
68 return A->Die->getOffset() < B->Die->getOffset();
69 }
70
FinalizeTable(AsmPrinter * Asm,StringRef Prefix)71 void DwarfAccelTable::FinalizeTable(AsmPrinter *Asm, StringRef Prefix) {
72 // Create the individual hash data outputs.
73 for (StringMap<DataArray>::iterator EI = Entries.begin(), EE = Entries.end();
74 EI != EE; ++EI) {
75
76 // Unique the entries.
77 std::stable_sort(EI->second.Values.begin(), EI->second.Values.end(), compareDIEs);
78 EI->second.Values.erase(
79 std::unique(EI->second.Values.begin(), EI->second.Values.end()),
80 EI->second.Values.end());
81
82 HashData *Entry = new (Allocator) HashData(EI->getKey(), EI->second);
83 Data.push_back(Entry);
84 }
85
86 // Figure out how many buckets we need, then compute the bucket
87 // contents and the final ordering. We'll emit the hashes and offsets
88 // by doing a walk during the emission phase. We add temporary
89 // symbols to the data so that we can reference them during the offset
90 // later, we'll emit them when we emit the data.
91 ComputeBucketCount();
92
93 // Compute bucket contents and final ordering.
94 Buckets.resize(Header.bucket_count);
95 for (size_t i = 0, e = Data.size(); i < e; ++i) {
96 uint32_t bucket = Data[i]->HashValue % Header.bucket_count;
97 Buckets[bucket].push_back(Data[i]);
98 Data[i]->Sym = Asm->GetTempSymbol(Prefix, i);
99 }
100 }
101
102 // Emits the header for the table via the AsmPrinter.
EmitHeader(AsmPrinter * Asm)103 void DwarfAccelTable::EmitHeader(AsmPrinter *Asm) {
104 Asm->OutStreamer.AddComment("Header Magic");
105 Asm->EmitInt32(Header.magic);
106 Asm->OutStreamer.AddComment("Header Version");
107 Asm->EmitInt16(Header.version);
108 Asm->OutStreamer.AddComment("Header Hash Function");
109 Asm->EmitInt16(Header.hash_function);
110 Asm->OutStreamer.AddComment("Header Bucket Count");
111 Asm->EmitInt32(Header.bucket_count);
112 Asm->OutStreamer.AddComment("Header Hash Count");
113 Asm->EmitInt32(Header.hashes_count);
114 Asm->OutStreamer.AddComment("Header Data Length");
115 Asm->EmitInt32(Header.header_data_len);
116 Asm->OutStreamer.AddComment("HeaderData Die Offset Base");
117 Asm->EmitInt32(HeaderData.die_offset_base);
118 Asm->OutStreamer.AddComment("HeaderData Atom Count");
119 Asm->EmitInt32(HeaderData.Atoms.size());
120 for (size_t i = 0; i < HeaderData.Atoms.size(); i++) {
121 Atom A = HeaderData.Atoms[i];
122 Asm->OutStreamer.AddComment(dwarf::AtomTypeString(A.type));
123 Asm->EmitInt16(A.type);
124 Asm->OutStreamer.AddComment(dwarf::FormEncodingString(A.form));
125 Asm->EmitInt16(A.form);
126 }
127 }
128
129 // Walk through and emit the buckets for the table. Each index is
130 // an offset into the list of hashes.
EmitBuckets(AsmPrinter * Asm)131 void DwarfAccelTable::EmitBuckets(AsmPrinter *Asm) {
132 unsigned index = 0;
133 for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
134 Asm->OutStreamer.AddComment("Bucket " + Twine(i));
135 if (Buckets[i].size() != 0)
136 Asm->EmitInt32(index);
137 else
138 Asm->EmitInt32(UINT32_MAX);
139 index += Buckets[i].size();
140 }
141 }
142
143 // Walk through the buckets and emit the individual hashes for each
144 // bucket.
EmitHashes(AsmPrinter * Asm)145 void DwarfAccelTable::EmitHashes(AsmPrinter *Asm) {
146 for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
147 for (HashList::const_iterator HI = Buckets[i].begin(),
148 HE = Buckets[i].end();
149 HI != HE; ++HI) {
150 Asm->OutStreamer.AddComment("Hash in Bucket " + Twine(i));
151 Asm->EmitInt32((*HI)->HashValue);
152 }
153 }
154 }
155
156 // Walk through the buckets and emit the individual offsets for each
157 // element in each bucket. This is done via a symbol subtraction from the
158 // beginning of the section. The non-section symbol will be output later
159 // when we emit the actual data.
EmitOffsets(AsmPrinter * Asm,MCSymbol * SecBegin)160 void DwarfAccelTable::EmitOffsets(AsmPrinter *Asm, MCSymbol *SecBegin) {
161 for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
162 for (HashList::const_iterator HI = Buckets[i].begin(),
163 HE = Buckets[i].end();
164 HI != HE; ++HI) {
165 Asm->OutStreamer.AddComment("Offset in Bucket " + Twine(i));
166 MCContext &Context = Asm->OutStreamer.getContext();
167 const MCExpr *Sub = MCBinaryExpr::CreateSub(
168 MCSymbolRefExpr::Create((*HI)->Sym, Context),
169 MCSymbolRefExpr::Create(SecBegin, Context), Context);
170 Asm->OutStreamer.EmitValue(Sub, sizeof(uint32_t));
171 }
172 }
173 }
174
175 // Walk through the buckets and emit the full data for each element in
176 // the bucket. For the string case emit the dies and the various offsets.
177 // Terminate each HashData bucket with 0.
EmitData(AsmPrinter * Asm,DwarfDebug * D,MCSymbol * StrSym)178 void DwarfAccelTable::EmitData(AsmPrinter *Asm, DwarfDebug *D,
179 MCSymbol *StrSym) {
180 uint64_t PrevHash = UINT64_MAX;
181 for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
182 for (HashList::const_iterator HI = Buckets[i].begin(),
183 HE = Buckets[i].end();
184 HI != HE; ++HI) {
185 // Remember to emit the label for our offset.
186 Asm->OutStreamer.EmitLabel((*HI)->Sym);
187 Asm->OutStreamer.AddComment((*HI)->Str);
188 Asm->EmitSectionOffset((*HI)->Data.StrSym, StrSym);
189 Asm->OutStreamer.AddComment("Num DIEs");
190 Asm->EmitInt32((*HI)->Data.Values.size());
191 for (HashDataContents *HD : (*HI)->Data.Values) {
192 // Emit the DIE offset
193 DwarfCompileUnit *CU = D->lookupUnit(HD->Die->getUnit());
194 assert(CU && "Accelerated DIE should belong to a CU.");
195 Asm->EmitInt32(HD->Die->getOffset() + CU->getDebugInfoOffset());
196 // If we have multiple Atoms emit that info too.
197 // FIXME: A bit of a hack, we either emit only one atom or all info.
198 if (HeaderData.Atoms.size() > 1) {
199 Asm->EmitInt16(HD->Die->getTag());
200 Asm->EmitInt8(HD->Flags);
201 }
202 }
203 // Emit a 0 to terminate the data unless we have a hash collision.
204 if (PrevHash != (*HI)->HashValue)
205 Asm->EmitInt32(0);
206 PrevHash = (*HI)->HashValue;
207 }
208 }
209 }
210
211 // Emit the entire data structure to the output file.
Emit(AsmPrinter * Asm,MCSymbol * SecBegin,DwarfDebug * D,MCSymbol * StrSym)212 void DwarfAccelTable::Emit(AsmPrinter *Asm, MCSymbol *SecBegin, DwarfDebug *D,
213 MCSymbol *StrSym) {
214 // Emit the header.
215 EmitHeader(Asm);
216
217 // Emit the buckets.
218 EmitBuckets(Asm);
219
220 // Emit the hashes.
221 EmitHashes(Asm);
222
223 // Emit the offsets.
224 EmitOffsets(Asm, SecBegin);
225
226 // Emit the hash data.
227 EmitData(Asm, D, StrSym);
228 }
229
230 #ifndef NDEBUG
print(raw_ostream & O)231 void DwarfAccelTable::print(raw_ostream &O) {
232
233 Header.print(O);
234 HeaderData.print(O);
235
236 O << "Entries: \n";
237 for (StringMap<DataArray>::const_iterator EI = Entries.begin(),
238 EE = Entries.end();
239 EI != EE; ++EI) {
240 O << "Name: " << EI->getKeyData() << "\n";
241 for (HashDataContents *HD : EI->second.Values)
242 HD->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();
249 HI != HE; ++HI)
250 (*HI)->print(O);
251
252 O << "Data: \n";
253 for (std::vector<HashData *>::const_iterator DI = Data.begin(),
254 DE = Data.end();
255 DI != DE; ++DI)
256 (*DI)->print(O);
257 }
258 #endif
259