1// stringpool.cc -- a string pool for gold 2 3// Copyright 2006, 2007, 2008 Free Software Foundation, Inc. 4// Written by Ian Lance Taylor <iant@google.com>. 5 6// This file is part of gold. 7 8// This program is free software; you can redistribute it and/or modify 9// it under the terms of the GNU General Public License as published by 10// the Free Software Foundation; either version 3 of the License, or 11// (at your option) any later version. 12 13// This program is distributed in the hope that it will be useful, 14// but WITHOUT ANY WARRANTY; without even the implied warranty of 15// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16// GNU General Public License for more details. 17 18// You should have received a copy of the GNU General Public License 19// along with this program; if not, write to the Free Software 20// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, 21// MA 02110-1301, USA. 22 23#include "gold.h" 24 25#include <cstring> 26#include <algorithm> 27#include <vector> 28 29#include "output.h" 30#include "parameters.h" 31#include "stringpool.h" 32 33namespace gold 34{ 35 36template<typename Stringpool_char> 37Stringpool_template<Stringpool_char>::Stringpool_template() 38 : string_set_(), key_to_offset_(), strings_(), strtab_size_(0), 39 zero_null_(true), optimize_(false), offset_(sizeof(Stringpool_char)) 40{ 41 if (parameters->options_valid() && parameters->options().optimize() >= 2) 42 this->optimize_ = true; 43} 44 45template<typename Stringpool_char> 46void 47Stringpool_template<Stringpool_char>::clear() 48{ 49 for (typename std::list<Stringdata*>::iterator p = this->strings_.begin(); 50 p != this->strings_.end(); 51 ++p) 52 delete[] reinterpret_cast<char*>(*p); 53 this->strings_.clear(); 54 this->key_to_offset_.clear(); 55 this->string_set_.clear(); 56} 57 58template<typename Stringpool_char> 59Stringpool_template<Stringpool_char>::~Stringpool_template() 60{ 61 this->clear(); 62} 63 64// Resize the internal hashtable with the expectation we'll get n new 65// elements. Note that the hashtable constructor takes a "number of 66// buckets you'd like," rather than "number of elements you'd like," 67// but that's the best we can do. 68 69template<typename Stringpool_char> 70void 71Stringpool_template<Stringpool_char>::reserve(unsigned int n) 72{ 73 this->key_to_offset_.reserve(n); 74 75#if defined(HAVE_TR1_UNORDERED_MAP) 76 // rehash() implementation is broken in gcc 4.0.3's stl 77 //this->string_set_.rehash(this->string_set_.size() + n); 78 //return; 79#elif defined(HAVE_EXT_HASH_MAP) 80 this->string_set_.resize(this->string_set_.size() + n); 81 return; 82#endif 83 84 // This is the generic "reserve" code, if no #ifdef above triggers. 85 String_set_type new_string_set(this->string_set_.size() + n); 86 new_string_set.insert(this->string_set_.begin(), this->string_set_.end()); 87 this->string_set_.swap(new_string_set); 88} 89 90// Compare two strings of arbitrary character type for equality. 91 92template<typename Stringpool_char> 93bool 94Stringpool_template<Stringpool_char>::string_equal(const Stringpool_char* s1, 95 const Stringpool_char* s2) 96{ 97 while (*s1 != 0) 98 if (*s1++ != *s2++) 99 return false; 100 return *s2 == 0; 101} 102 103// Specialize string_equal for char. 104 105template<> 106inline bool 107Stringpool_template<char>::string_equal(const char* s1, const char* s2) 108{ 109 return strcmp(s1, s2) == 0; 110} 111 112// Equality comparison function for the hash table. 113 114template<typename Stringpool_char> 115inline bool 116Stringpool_template<Stringpool_char>::Stringpool_eq::operator()( 117 const Hashkey& h1, 118 const Hashkey& h2) const 119{ 120 return (h1.hash_code == h2.hash_code 121 && h1.length == h2.length 122 && (h1.string == h2.string 123 || memcmp(h1.string, h2.string, 124 h1.length * sizeof(Stringpool_char)) == 0)); 125} 126 127// Hash function. The length is in characters, not bytes. 128 129template<typename Stringpool_char> 130size_t 131Stringpool_template<Stringpool_char>::string_hash(const Stringpool_char* s, 132 size_t length) 133{ 134 return gold::string_hash<Stringpool_char>(s, length); 135} 136 137// Add the string S to the list of canonical strings. Return a 138// pointer to the canonical string. If PKEY is not NULL, set *PKEY to 139// the key. LENGTH is the length of S in characters. Note that S may 140// not be NUL terminated. 141 142template<typename Stringpool_char> 143const Stringpool_char* 144Stringpool_template<Stringpool_char>::add_string(const Stringpool_char* s, 145 size_t len) 146{ 147 // We are in trouble if we've already computed the string offsets. 148 gold_assert(this->strtab_size_ == 0); 149 150 // The size we allocate for a new Stringdata. 151 const size_t buffer_size = 1000; 152 // The amount we multiply the Stringdata index when calculating the 153 // key. 154 const size_t key_mult = 1024; 155 gold_assert(key_mult >= buffer_size); 156 157 // Convert len to the number of bytes we need to allocate, including 158 // the null character. 159 len = (len + 1) * sizeof(Stringpool_char); 160 161 size_t alc; 162 bool front = true; 163 if (len > buffer_size) 164 { 165 alc = sizeof(Stringdata) + len; 166 front = false; 167 } 168 else if (this->strings_.empty()) 169 alc = sizeof(Stringdata) + buffer_size; 170 else 171 { 172 Stringdata* psd = this->strings_.front(); 173 if (len > psd->alc - psd->len) 174 alc = sizeof(Stringdata) + buffer_size; 175 else 176 { 177 char* ret = psd->data + psd->len; 178 memcpy(ret, s, len - sizeof(Stringpool_char)); 179 memset(ret + len - sizeof(Stringpool_char), 0, 180 sizeof(Stringpool_char)); 181 182 psd->len += len; 183 184 return reinterpret_cast<const Stringpool_char*>(ret); 185 } 186 } 187 188 Stringdata* psd = reinterpret_cast<Stringdata*>(new char[alc]); 189 psd->alc = alc - sizeof(Stringdata); 190 memcpy(psd->data, s, len - sizeof(Stringpool_char)); 191 memset(psd->data + len - sizeof(Stringpool_char), 0, 192 sizeof(Stringpool_char)); 193 psd->len = len; 194 195 if (front) 196 this->strings_.push_front(psd); 197 else 198 this->strings_.push_back(psd); 199 200 return reinterpret_cast<const Stringpool_char*>(psd->data); 201} 202 203// Add a string to a string pool. 204 205template<typename Stringpool_char> 206const Stringpool_char* 207Stringpool_template<Stringpool_char>::add(const Stringpool_char* s, bool copy, 208 Key* pkey) 209{ 210 return this->add_with_length(s, string_length(s), copy, pkey); 211} 212 213// Add a new key offset entry. 214 215template<typename Stringpool_char> 216void 217Stringpool_template<Stringpool_char>::new_key_offset(size_t length) 218{ 219 section_offset_type offset; 220 if (this->zero_null_ && length == 0) 221 offset = 0; 222 else 223 { 224 offset = this->offset_; 225 this->offset_ += (length + 1) * sizeof(Stringpool_char); 226 } 227 this->key_to_offset_.push_back(offset); 228} 229 230template<typename Stringpool_char> 231const Stringpool_char* 232Stringpool_template<Stringpool_char>::add_with_length(const Stringpool_char* s, 233 size_t length, 234 bool copy, 235 Key* pkey) 236{ 237 typedef std::pair<typename String_set_type::iterator, bool> Insert_type; 238 239 // We add 1 so that 0 is always invalid. 240 const Key k = this->key_to_offset_.size() + 1; 241 242 if (!copy) 243 { 244 // When we don't need to copy the string, we can call insert 245 // directly. 246 247 std::pair<Hashkey, Hashval> element(Hashkey(s, length), k); 248 249 Insert_type ins = this->string_set_.insert(element); 250 251 typename String_set_type::const_iterator p = ins.first; 252 253 if (ins.second) 254 { 255 // We just added the string. The key value has now been 256 // used. 257 this->new_key_offset(length); 258 } 259 else 260 { 261 gold_assert(k != p->second); 262 } 263 264 if (pkey != NULL) 265 *pkey = p->second; 266 return p->first.string; 267 } 268 269 // When we have to copy the string, we look it up twice in the hash 270 // table. The problem is that we can't insert S before we 271 // canonicalize it by copying it into the canonical list. The hash 272 // code will only be computed once. 273 274 Hashkey hk(s, length); 275 typename String_set_type::const_iterator p = this->string_set_.find(hk); 276 if (p != this->string_set_.end()) 277 { 278 if (pkey != NULL) 279 *pkey = p->second; 280 return p->first.string; 281 } 282 283 this->new_key_offset(length); 284 285 hk.string = this->add_string(s, length); 286 // The contents of the string stay the same, so we don't need to 287 // adjust hk.hash_code or hk.length. 288 289 std::pair<Hashkey, Hashval> element(hk, k); 290 291 Insert_type ins = this->string_set_.insert(element); 292 gold_assert(ins.second); 293 294 if (pkey != NULL) 295 *pkey = k; 296 return hk.string; 297} 298 299template<typename Stringpool_char> 300const Stringpool_char* 301Stringpool_template<Stringpool_char>::find(const Stringpool_char* s, 302 Key* pkey) const 303{ 304 Hashkey hk(s); 305 typename String_set_type::const_iterator p = this->string_set_.find(hk); 306 if (p == this->string_set_.end()) 307 return NULL; 308 309 if (pkey != NULL) 310 *pkey = p->second; 311 312 return p->first.string; 313} 314 315// Comparison routine used when sorting into an ELF strtab. We want 316// to sort this so that when one string is a suffix of another, we 317// always see the shorter string immediately after the longer string. 318// For example, we want to see these strings in this order: 319// abcd 320// cd 321// d 322// When strings are not suffixes, we don't care what order they are 323// in, but we need to ensure that suffixes wind up next to each other. 324// So we do a reversed lexicographic sort on the reversed string. 325 326template<typename Stringpool_char> 327bool 328Stringpool_template<Stringpool_char>::Stringpool_sort_comparison::operator()( 329 const Stringpool_sort_info& sort_info1, 330 const Stringpool_sort_info& sort_info2) const 331{ 332 const Hashkey& h1(sort_info1->first); 333 const Hashkey& h2(sort_info2->first); 334 const Stringpool_char* s1 = h1.string; 335 const Stringpool_char* s2 = h2.string; 336 const size_t len1 = h1.length; 337 const size_t len2 = h2.length; 338 const size_t minlen = len1 < len2 ? len1 : len2; 339 const Stringpool_char* p1 = s1 + len1 - 1; 340 const Stringpool_char* p2 = s2 + len2 - 1; 341 for (size_t i = minlen; i > 0; --i, --p1, --p2) 342 { 343 if (*p1 != *p2) 344 return *p1 > *p2; 345 } 346 return len1 > len2; 347} 348 349// Return whether s1 is a suffix of s2. 350 351template<typename Stringpool_char> 352bool 353Stringpool_template<Stringpool_char>::is_suffix(const Stringpool_char* s1, 354 size_t len1, 355 const Stringpool_char* s2, 356 size_t len2) 357{ 358 if (len1 > len2) 359 return false; 360 return memcmp(s1, s2 + len2 - len1, len1 * sizeof(Stringpool_char)) == 0; 361} 362 363// Turn the stringpool into an ELF strtab: determine the offsets of 364// each string in the table. 365 366template<typename Stringpool_char> 367void 368Stringpool_template<Stringpool_char>::set_string_offsets() 369{ 370 if (this->strtab_size_ != 0) 371 { 372 // We've already computed the offsets. 373 return; 374 } 375 376 const size_t charsize = sizeof(Stringpool_char); 377 378 // Offset 0 may be reserved for the empty string. 379 section_offset_type offset = this->zero_null_ ? charsize : 0; 380 381 // Sorting to find suffixes can take over 25% of the total CPU time 382 // used by the linker. Since it's merely an optimization to reduce 383 // the strtab size, and gives a relatively small benefit (it's 384 // typically rare for a symbol to be a suffix of another), we only 385 // take the time to sort when the user asks for heavy optimization. 386 if (!this->optimize_) 387 { 388 // If we are not optimizing, the offsets are already assigned. 389 offset = this->offset_; 390 } 391 else 392 { 393 size_t count = this->string_set_.size(); 394 395 std::vector<Stringpool_sort_info> v; 396 v.reserve(count); 397 398 for (typename String_set_type::iterator p = this->string_set_.begin(); 399 p != this->string_set_.end(); 400 ++p) 401 v.push_back(Stringpool_sort_info(p)); 402 403 std::sort(v.begin(), v.end(), Stringpool_sort_comparison()); 404 405 section_offset_type last_offset = -1; 406 for (typename std::vector<Stringpool_sort_info>::iterator last = v.end(), 407 curr = v.begin(); 408 curr != v.end(); 409 last = curr++) 410 { 411 section_offset_type this_offset; 412 if (this->zero_null_ && (*curr)->first.string[0] == 0) 413 this_offset = 0; 414 else if (last != v.end() 415 && is_suffix((*curr)->first.string, 416 (*curr)->first.length, 417 (*last)->first.string, 418 (*last)->first.length)) 419 this_offset = (last_offset 420 + (((*last)->first.length - (*curr)->first.length) 421 * charsize)); 422 else 423 { 424 this_offset = offset; 425 offset += ((*curr)->first.length + 1) * charsize; 426 } 427 this->key_to_offset_[(*curr)->second - 1] = this_offset; 428 last_offset = this_offset; 429 } 430 } 431 432 this->strtab_size_ = offset; 433} 434 435// Get the offset of a string in the ELF strtab. The string must 436// exist. 437 438template<typename Stringpool_char> 439section_offset_type 440Stringpool_template<Stringpool_char>::get_offset(const Stringpool_char* s) 441 const 442{ 443 return this->get_offset_with_length(s, string_length(s)); 444} 445 446template<typename Stringpool_char> 447section_offset_type 448Stringpool_template<Stringpool_char>::get_offset_with_length( 449 const Stringpool_char* s, 450 size_t length) const 451{ 452 gold_assert(this->strtab_size_ != 0); 453 Hashkey hk(s, length); 454 typename String_set_type::const_iterator p = this->string_set_.find(hk); 455 if (p != this->string_set_.end()) 456 return this->key_to_offset_[p->second - 1]; 457 gold_unreachable(); 458} 459 460// Write the ELF strtab into the buffer. 461 462template<typename Stringpool_char> 463void 464Stringpool_template<Stringpool_char>::write_to_buffer( 465 unsigned char* buffer, 466 section_size_type bufsize) 467{ 468 gold_assert(this->strtab_size_ != 0); 469 gold_assert(bufsize >= this->strtab_size_); 470 if (this->zero_null_) 471 buffer[0] = '\0'; 472 for (typename String_set_type::const_iterator p = this->string_set_.begin(); 473 p != this->string_set_.end(); 474 ++p) 475 { 476 const int len = (p->first.length + 1) * sizeof(Stringpool_char); 477 const section_offset_type offset = this->key_to_offset_[p->second - 1]; 478 gold_assert(static_cast<section_size_type>(offset) + len 479 <= this->strtab_size_); 480 memcpy(buffer + offset, p->first.string, len); 481 } 482} 483 484// Write the ELF strtab into the output file at the specified offset. 485 486template<typename Stringpool_char> 487void 488Stringpool_template<Stringpool_char>::write(Output_file* of, off_t offset) 489{ 490 gold_assert(this->strtab_size_ != 0); 491 unsigned char* view = of->get_output_view(offset, this->strtab_size_); 492 this->write_to_buffer(view, this->strtab_size_); 493 of->write_output_view(offset, this->strtab_size_, view); 494} 495 496// Print statistical information to stderr. This is used for --stats. 497 498template<typename Stringpool_char> 499void 500Stringpool_template<Stringpool_char>::print_stats(const char* name) const 501{ 502#if defined(HAVE_TR1_UNORDERED_MAP) || defined(HAVE_EXT_HASH_MAP) 503 fprintf(stderr, _("%s: %s entries: %zu; buckets: %zu\n"), 504 program_name, name, this->string_set_.size(), 505 this->string_set_.bucket_count()); 506#else 507 fprintf(stderr, _("%s: %s entries: %zu\n"), 508 program_name, name, this->table_.size()); 509#endif 510 fprintf(stderr, _("%s: %s Stringdata structures: %zu\n"), 511 program_name, name, this->strings_.size()); 512} 513 514// Instantiate the templates we need. 515 516template 517class Stringpool_template<char>; 518 519template 520class Stringpool_template<uint16_t>; 521 522template 523class Stringpool_template<uint32_t>; 524 525} // End namespace gold. 526