DwarfAccelTable.h revision 4302a4965c4fffcecee23210dd1910d8d2c88259
1//==-- llvm/CodeGen/DwarfAccelTable.h - 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#ifndef CODEGEN_ASMPRINTER_DWARFACCELTABLE_H__ 15#define CODEGEN_ASMPRINTER_DWARFACCELTABLE_H__ 16 17#include "llvm/ADT/StringMap.h" 18#include "llvm/MC/MCSymbol.h" 19#include "llvm/Support/Dwarf.h" 20#include "llvm/Support/DataTypes.h" 21#include "llvm/Support/Debug.h" 22#include "llvm/Support/ErrorHandling.h" 23#include "llvm/Support/Format.h" 24#include "llvm/Support/FormattedStream.h" 25#include "DIE.h" 26#include <vector> 27#include <map> 28 29// The dwarf accelerator tables are an indirect hash table optimized 30// for null lookup rather than access to known data. They are output into 31// an on-disk format that looks like this: 32// 33// .-------------. 34// | HEADER | 35// |-------------| 36// | BUCKETS | 37// |-------------| 38// | HASHES | 39// |-------------| 40// | OFFSETS | 41// |-------------| 42// | DATA | 43// `-------------' 44// 45// where the header contains a magic number, version, type of hash function, 46// the number of buckets, total number of hashes, and room for a special 47// struct of data and the length of that struct. 48// 49// The buckets contain an index (e.g. 6) into the hashes array. The hashes 50// section contains all of the 32-bit hash values in contiguous memory, and 51// the offsets contain the offset into the data area for the particular 52// hash. 53// 54// For a lookup example, we could hash a function name and take it modulo the 55// number of buckets giving us our bucket. From there we take the bucket value 56// as an index into the hashes table and look at each successive hash as long 57// as the hash value is still the same modulo result (bucket value) as earlier. 58// If we have a match we look at that same entry in the offsets table and 59// grab the offset in the data for our final match. 60 61namespace llvm { 62 63class AsmPrinter; 64class DIE; 65class DwarfDebug; 66 67class DwarfAccelTable { 68 69 enum HashFunctionType { 70 eHashFunctionDJB = 0u 71 }; 72 73 static uint32_t HashDJB (StringRef Str) { 74 uint32_t h = 5381; 75 for (unsigned i = 0, e = Str.size(); i != e; ++i) 76 h = ((h << 5) + h) + Str[i]; 77 return h; 78 } 79 80 // Helper function to compute the number of buckets needed based on 81 // the number of unique hashes. 82 void ComputeBucketCount (void); 83 84 struct TableHeader { 85 uint32_t magic; // 'HASH' magic value to allow endian detection 86 uint16_t version; // Version number. 87 uint16_t hash_function; // The hash function enumeration that was used. 88 uint32_t bucket_count; // The number of buckets in this hash table. 89 uint32_t hashes_count; // The total number of unique hash values 90 // and hash data offsets in this table. 91 uint32_t header_data_len; // The bytes to skip to get to the hash 92 // indexes (buckets) for correct alignment. 93 // Also written to disk is the implementation specific header data. 94 95 static const uint32_t MagicHash = 0x48415348; 96 97 TableHeader (uint32_t data_len) : 98 magic (MagicHash), version (1), hash_function (eHashFunctionDJB), 99 bucket_count (0), hashes_count (0), header_data_len (data_len) 100 {} 101 102#ifndef NDEBUG 103 void print(raw_ostream &O) { 104 O << "Magic: " << format("0x%x", magic) << "\n" 105 << "Version: " << version << "\n" 106 << "Hash Function: " << hash_function << "\n" 107 << "Bucket Count: " << bucket_count << "\n" 108 << "Header Data Length: " << header_data_len << "\n"; 109 } 110 void dump() { print(dbgs()); } 111#endif 112 }; 113 114public: 115 // The HeaderData describes the form of each set of data. In general this 116 // is as a list of atoms (atom_count) where each atom contains a type 117 // (AtomType type) of data, and an encoding form (form). In the case of 118 // data that is referenced via DW_FORM_ref_* the die_offset_base is 119 // used to describe the offset for all forms in the list of atoms. 120 // This also serves as a public interface of sorts. 121 // When written to disk this will have the form: 122 // 123 // uint32_t die_offset_base 124 // uint32_t atom_count 125 // atom_count Atoms 126 enum AtomType { 127 eAtomTypeNULL = 0u, 128 eAtomTypeDIEOffset = 1u, // DIE offset, check form for encoding 129 eAtomTypeCUOffset = 2u, // DIE offset of the compiler unit header that 130 // contains the item in question 131 eAtomTypeTag = 3u, // DW_TAG_xxx value, should be encoded as 132 // DW_FORM_data1 (if no tags exceed 255) or 133 // DW_FORM_data2. 134 eAtomTypeNameFlags = 4u, // Flags from enum NameFlags 135 eAtomTypeTypeFlags = 5u // Flags from enum TypeFlags 136 }; 137 138 enum TypeFlags { 139 eTypeFlagClassMask = 0x0000000fu, 140 141 // Always set for C++, only set for ObjC if this is the 142 // @implementation for a class. 143 eTypeFlagClassIsImplementation = ( 1u << 1 ) 144 }; 145 146 // Make these public so that they can be used as a general interface to 147 // the class. 148 struct Atom { 149 AtomType type; // enum AtomType 150 uint16_t form; // DWARF DW_FORM_ defines 151 152 Atom(AtomType type, uint16_t form) : type(type), form(form) {} 153 static const char * AtomTypeString(enum AtomType); 154#ifndef NDEBUG 155 void print(raw_ostream &O) { 156 O << "Type: " << AtomTypeString(type) << "\n" 157 << "Form: " << dwarf::FormEncodingString(form) << "\n"; 158 } 159 void dump() { 160 print(dbgs()); 161 } 162#endif 163 }; 164 165 private: 166 struct TableHeaderData { 167 168 uint32_t die_offset_base; 169 std::vector<Atom> Atoms; 170 171 TableHeaderData(std::vector<DwarfAccelTable::Atom> &AtomList, 172 uint32_t offset = 0) : 173 die_offset_base(offset) { 174 for (size_t i = 0, e = AtomList.size(); i != e; ++i) 175 Atoms.push_back(AtomList[i]); 176 } 177 178 TableHeaderData(DwarfAccelTable::Atom Atom, uint32_t offset = 0) 179 : die_offset_base(offset) { 180 Atoms.push_back(Atom); 181 } 182 183#ifndef NDEBUG 184 void print (raw_ostream &O) { 185 O << "die_offset_base: " << die_offset_base << "\n"; 186 for (size_t i = 0; i < Atoms.size(); i++) 187 Atoms[i].print(O); 188 } 189 void dump() { 190 print(dbgs()); 191 } 192#endif 193 }; 194 195 // The data itself consists of a str_offset, a count of the DIEs in the 196 // hash and the offsets to the DIEs themselves. 197 // On disk each data section is ended with a 0 KeyType as the end of the 198 // hash chain. 199 // On output this looks like: 200 // uint32_t str_offset 201 // uint32_t hash_data_count 202 // HashData[hash_data_count] 203public: 204 struct HashDataContents { 205 DIE *Die; // Offsets 206 char Flags; // Specific flags to output 207 208 HashDataContents(DIE *D, char Flags) : 209 Die(D), 210 Flags(Flags) { } 211 #ifndef NDEBUG 212 void print(raw_ostream &O) const { 213 O << " Offset: " << Die->getOffset() << "\n"; 214 O << " Tag: " << dwarf::TagString(Die->getTag()) << "\n"; 215 O << " Flags: " << Flags << "\n"; 216 } 217 #endif 218 }; 219private: 220 struct HashData { 221 StringRef Str; 222 uint32_t HashValue; 223 MCSymbol *Sym; 224 std::vector<struct HashDataContents*> Data; // offsets 225 HashData(StringRef S) : Str(S) { 226 HashValue = DwarfAccelTable::HashDJB(S); 227 } 228 void addData(struct HashDataContents *Datum) { Data.push_back(Datum); } 229 #ifndef NDEBUG 230 void print(raw_ostream &O) { 231 O << "Name: " << Str << "\n"; 232 O << " Hash Value: " << format("0x%x", HashValue) << "\n"; 233 O << " Symbol: " ; 234 if (Sym) Sym->print(O); 235 else O << "<none>"; 236 O << "\n"; 237 for (size_t i = 0; i < Data.size(); i++) { 238 O << " Offset: " << Data[i]->Die->getOffset() << "\n"; 239 O << " Tag: " << dwarf::TagString(Data[i]->Die->getTag()) << "\n"; 240 O << " Flags: " << Data[i]->Flags << "\n"; 241 } 242 } 243 void dump() { 244 print(dbgs()); 245 } 246 #endif 247 }; 248 249 DwarfAccelTable(const DwarfAccelTable&); // DO NOT IMPLEMENT 250 void operator=(const DwarfAccelTable&); // DO NOT IMPLEMENT 251 252 // Internal Functions 253 void EmitHeader(AsmPrinter *); 254 void EmitBuckets(AsmPrinter *); 255 void EmitHashes(AsmPrinter *); 256 void EmitOffsets(AsmPrinter *, MCSymbol *); 257 void EmitData(AsmPrinter *, DwarfDebug *D); 258 259 // Output Variables 260 TableHeader Header; 261 TableHeaderData HeaderData; 262 std::vector<HashData*> Data; 263 264 // String Data 265 typedef std::vector<struct HashDataContents*> DataArray; 266 typedef StringMap<DataArray> StringEntries; 267 StringEntries Entries; 268 269 // Buckets/Hashes/Offsets 270 typedef std::vector<HashData*> HashList; 271 typedef std::vector<HashList> BucketList; 272 BucketList Buckets; 273 HashList Hashes; 274 275 // Public Implementation 276 public: 277 DwarfAccelTable(DwarfAccelTable::Atom); 278 DwarfAccelTable(std::vector<DwarfAccelTable::Atom> &); 279 ~DwarfAccelTable(); 280 void AddName(StringRef, DIE*, char = 0); 281 void FinalizeTable(AsmPrinter *, const char *); 282 void Emit(AsmPrinter *, MCSymbol *, DwarfDebug *); 283#ifndef NDEBUG 284 void print(raw_ostream &O); 285 void dump() { print(dbgs()); } 286#endif 287}; 288 289} 290#endif 291