DwarfAccelTable.h revision 263508
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 "DIE.h" 18#include "llvm/ADT/ArrayRef.h" 19#include "llvm/ADT/StringMap.h" 20#include "llvm/MC/MCSymbol.h" 21#include "llvm/Support/DataTypes.h" 22#include "llvm/Support/Debug.h" 23#include "llvm/Support/Dwarf.h" 24#include "llvm/Support/ErrorHandling.h" 25#include "llvm/Support/Format.h" 26#include "llvm/Support/FormattedStream.h" 27#include <map> 28#include <vector> 29 30// The dwarf accelerator tables are an indirect hash table optimized 31// for null lookup rather than access to known data. They are output into 32// an on-disk format that looks like this: 33// 34// .-------------. 35// | HEADER | 36// |-------------| 37// | BUCKETS | 38// |-------------| 39// | HASHES | 40// |-------------| 41// | OFFSETS | 42// |-------------| 43// | DATA | 44// `-------------' 45// 46// where the header contains a magic number, version, type of hash function, 47// the number of buckets, total number of hashes, and room for a special 48// struct of data and the length of that struct. 49// 50// The buckets contain an index (e.g. 6) into the hashes array. The hashes 51// section contains all of the 32-bit hash values in contiguous memory, and 52// the offsets contain the offset into the data area for the particular 53// hash. 54// 55// For a lookup example, we could hash a function name and take it modulo the 56// number of buckets giving us our bucket. From there we take the bucket value 57// as an index into the hashes table and look at each successive hash as long 58// as the hash value is still the same modulo result (bucket value) as earlier. 59// If we have a match we look at that same entry in the offsets table and 60// grab the offset in the data for our final match. 61 62namespace llvm { 63 64class AsmPrinter; 65class DIE; 66class DwarfUnits; 67 68class DwarfAccelTable { 69 70 static uint32_t HashDJB(StringRef Str) { 71 uint32_t h = 5381; 72 for (unsigned i = 0, e = Str.size(); i != e; ++i) 73 h = ((h << 5) + h) + Str[i]; 74 return h; 75 } 76 77 // Helper function to compute the number of buckets needed based on 78 // the number of unique hashes. 79 void ComputeBucketCount(void); 80 81 struct TableHeader { 82 uint32_t magic; // 'HASH' magic value to allow endian detection 83 uint16_t version; // Version number. 84 uint16_t hash_function; // The hash function enumeration that was used. 85 uint32_t bucket_count; // The number of buckets in this hash table. 86 uint32_t hashes_count; // The total number of unique hash values 87 // and hash data offsets in this table. 88 uint32_t header_data_len; // The bytes to skip to get to the hash 89 // indexes (buckets) for correct alignment. 90 // Also written to disk is the implementation specific header data. 91 92 static const uint32_t MagicHash = 0x48415348; 93 94 TableHeader(uint32_t data_len) 95 : magic(MagicHash), version(1), 96 hash_function(dwarf::DW_hash_function_djb), bucket_count(0), 97 hashes_count(0), header_data_len(data_len) {} 98 99#ifndef NDEBUG 100 void print(raw_ostream &O) { 101 O << "Magic: " << format("0x%x", magic) << "\n" 102 << "Version: " << version << "\n" 103 << "Hash Function: " << hash_function << "\n" 104 << "Bucket Count: " << bucket_count << "\n" 105 << "Header Data Length: " << header_data_len << "\n"; 106 } 107 void dump() { print(dbgs()); } 108#endif 109 }; 110 111public: 112 // The HeaderData describes the form of each set of data. In general this 113 // is as a list of atoms (atom_count) where each atom contains a type 114 // (AtomType type) of data, and an encoding form (form). In the case of 115 // data that is referenced via DW_FORM_ref_* the die_offset_base is 116 // used to describe the offset for all forms in the list of atoms. 117 // This also serves as a public interface of sorts. 118 // When written to disk this will have the form: 119 // 120 // uint32_t die_offset_base 121 // uint32_t atom_count 122 // atom_count Atoms 123 124 // Make these public so that they can be used as a general interface to 125 // the class. 126 struct Atom { 127 uint16_t type; // enum AtomType 128 uint16_t form; // DWARF DW_FORM_ defines 129 130 Atom(uint16_t type, uint16_t form) : type(type), form(form) {} 131#ifndef NDEBUG 132 void print(raw_ostream &O) { 133 O << "Type: " << dwarf::AtomTypeString(type) << "\n" 134 << "Form: " << dwarf::FormEncodingString(form) << "\n"; 135 } 136 void dump() { print(dbgs()); } 137#endif 138 }; 139 140private: 141 struct TableHeaderData { 142 uint32_t die_offset_base; 143 SmallVector<Atom, 1> Atoms; 144 145 TableHeaderData(ArrayRef<Atom> AtomList, uint32_t offset = 0) 146 : die_offset_base(offset), Atoms(AtomList.begin(), AtomList.end()) {} 147 148#ifndef NDEBUG 149 void print(raw_ostream &O) { 150 O << "die_offset_base: " << die_offset_base << "\n"; 151 for (size_t i = 0; i < Atoms.size(); i++) 152 Atoms[i].print(O); 153 } 154 void dump() { print(dbgs()); } 155#endif 156 }; 157 158 // The data itself consists of a str_offset, a count of the DIEs in the 159 // hash and the offsets to the DIEs themselves. 160 // On disk each data section is ended with a 0 KeyType as the end of the 161 // hash chain. 162 // On output this looks like: 163 // uint32_t str_offset 164 // uint32_t hash_data_count 165 // HashData[hash_data_count] 166public: 167 struct HashDataContents { 168 DIE *Die; // Offsets 169 char Flags; // Specific flags to output 170 171 HashDataContents(DIE *D, char Flags) : Die(D), Flags(Flags) {} 172#ifndef NDEBUG 173 void print(raw_ostream &O) const { 174 O << " Offset: " << Die->getOffset() << "\n"; 175 O << " Tag: " << dwarf::TagString(Die->getTag()) << "\n"; 176 O << " Flags: " << Flags << "\n"; 177 } 178#endif 179 }; 180 181private: 182 struct HashData { 183 StringRef Str; 184 uint32_t HashValue; 185 MCSymbol *Sym; 186 ArrayRef<HashDataContents *> Data; // offsets 187 HashData(StringRef S, ArrayRef<HashDataContents *> Data) 188 : Str(S), Data(Data) { 189 HashValue = DwarfAccelTable::HashDJB(S); 190 } 191#ifndef NDEBUG 192 void print(raw_ostream &O) { 193 O << "Name: " << Str << "\n"; 194 O << " Hash Value: " << format("0x%x", HashValue) << "\n"; 195 O << " Symbol: "; 196 if (Sym) 197 Sym->print(O); 198 else 199 O << "<none>"; 200 O << "\n"; 201 for (size_t i = 0; i < Data.size(); i++) { 202 O << " Offset: " << Data[i]->Die->getOffset() << "\n"; 203 O << " Tag: " << dwarf::TagString(Data[i]->Die->getTag()) << "\n"; 204 O << " Flags: " << Data[i]->Flags << "\n"; 205 } 206 } 207 void dump() { print(dbgs()); } 208#endif 209 }; 210 211 DwarfAccelTable(const DwarfAccelTable &) LLVM_DELETED_FUNCTION; 212 void operator=(const DwarfAccelTable &) LLVM_DELETED_FUNCTION; 213 214 // Internal Functions 215 void EmitHeader(AsmPrinter *); 216 void EmitBuckets(AsmPrinter *); 217 void EmitHashes(AsmPrinter *); 218 void EmitOffsets(AsmPrinter *, MCSymbol *); 219 void EmitData(AsmPrinter *, DwarfUnits *D); 220 221 // Allocator for HashData and HashDataContents. 222 BumpPtrAllocator Allocator; 223 224 // Output Variables 225 TableHeader Header; 226 TableHeaderData HeaderData; 227 std::vector<HashData *> Data; 228 229 // String Data 230 typedef std::vector<HashDataContents *> DataArray; 231 typedef StringMap<DataArray, BumpPtrAllocator &> StringEntries; 232 StringEntries Entries; 233 234 // Buckets/Hashes/Offsets 235 typedef std::vector<HashData *> HashList; 236 typedef std::vector<HashList> BucketList; 237 BucketList Buckets; 238 HashList Hashes; 239 240 // Public Implementation 241public: 242 DwarfAccelTable(ArrayRef<DwarfAccelTable::Atom>); 243 ~DwarfAccelTable(); 244 void AddName(StringRef, DIE *, char = 0); 245 void FinalizeTable(AsmPrinter *, StringRef); 246 void Emit(AsmPrinter *, MCSymbol *, DwarfUnits *); 247#ifndef NDEBUG 248 void print(raw_ostream &O); 249 void dump() { print(dbgs()); } 250#endif 251}; 252} 253#endif 254