tools/gold/gold-plugin.cpp

   1 //===-- gold-plugin.cpp - Plugin to gold for Link Time Optimization  ------===//
   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 is a gold plugin for LLVM. It provides an LLVM implementation of the
  11 // interface described in http://gcc.gnu.org/wiki/whopr/driver .
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/Config/config.h"
  16 #include "plugin-api.h"
  17
  18 #include "llvm-c/lto.h"
  19
  20 #include "llvm/Support/ToolOutputFile.h"
  21 #include "llvm/Support/Errno.h"
  22 #include "llvm/Support/Path.h"
  23 #include "llvm/Support/Program.h"
  24
  25 #include <cerrno>
  26 #include <cstdlib>
  27 #include <cstring>
  28 #include <fstream>
  29 #include <list>
  30 #include <vector>
  31
  32 // Support Windows/MinGW crazyness.
  33 #ifdef _WIN32
  34 # include <io.h>
  35 # define lseek _lseek
  36 # define read _read
  37 #endif
  38
  39 using namespace llvm;
  40
  41 namespace {
  42   ld_plugin_status discard_message(int level, const char *format, ...) {
  43     // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
  44     // callback in the transfer vector. This should never be called.
  45     abort();
  46   }
  47
  48   ld_plugin_add_symbols add_symbols = NULL;
  49   ld_plugin_get_symbols get_symbols = NULL;
  50   ld_plugin_add_input_file add_input_file = NULL;
  51   ld_plugin_add_input_library add_input_library = NULL;
  52   ld_plugin_set_extra_library_path set_extra_library_path = NULL;
  53   ld_plugin_get_view get_view = NULL;
  54   ld_plugin_message message = discard_message;
  55
  56   int api_version = 0;
  57   int gold_version = 0;
  58
  59   struct claimed_file {
  60     void *handle;
  61     std::vector<ld_plugin_symbol> syms;
  62   };
  63
  64   lto_codegen_model output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
  65   std::string output_name = "";
  66   std::list<claimed_file> Modules;
  67   std::vector<sys::Path> Cleanup;
  68   lto_code_gen_t code_gen = NULL;
  69 }
  70
  71 namespace options {
  72   enum generate_bc { BC_NO, BC_ALSO, BC_ONLY };
  73   static bool generate_api_file = false;
  74   static generate_bc generate_bc_file = BC_NO;
  75   static std::string bc_path;
  76   static std::string obj_path;
  77   static std::string extra_library_path;
  78   static std::string triple;
  79   static std::string mcpu;
  80   // Additional options to pass into the code generator.
  81   // Note: This array will contain all plugin options which are not claimed
  82   // as plugin exclusive to pass to the code generator.
  83   // For example, "generate-api-file" and "as"options are for the plugin
  84   // use only and will not be passed.
  85   static std::vector<std::string> extra;
  86
  87   static void process_plugin_option(const char* opt_)
  88   {
  89     if (opt_ == NULL)
  90       return;
  91     llvm::StringRef opt = opt_;
  92
  93     if (opt == "generate-api-file") {
  94       generate_api_file = true;
  95     } else if (opt.startswith("mcpu=")) {
  96       mcpu = opt.substr(strlen("mcpu="));
  97     } else if (opt.startswith("extra-library-path=")) {
  98       extra_library_path = opt.substr(strlen("extra_library_path="));
  99     } else if (opt.startswith("mtriple=")) {
 100       triple = opt.substr(strlen("mtriple="));
 101     } else if (opt.startswith("obj-path=")) {
 102       obj_path = opt.substr(strlen("obj-path="));
 103     } else if (opt == "emit-llvm") {
 104       generate_bc_file = BC_ONLY;
 105     } else if (opt == "also-emit-llvm") {
 106       generate_bc_file = BC_ALSO;
 107     } else if (opt.startswith("also-emit-llvm=")) {
 108       llvm::StringRef path = opt.substr(strlen("also-emit-llvm="));
 109       generate_bc_file = BC_ALSO;
 110       if (!bc_path.empty()) {
 111         (*message)(LDPL_WARNING, "Path to the output IL file specified twice. "
 112                    "Discarding %s", opt_);
 113       } else {
 114         bc_path = path;
 115       }
 116     } else {
 117       // Save this option to pass to the code generator.
 118       extra.push_back(opt);
 119     }
 120   }
 121 }
 122
 123 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
 124                                         int *claimed);
 125 static ld_plugin_status all_symbols_read_hook(void);
 126 static ld_plugin_status cleanup_hook(void);
 127
 128 extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
 129 ld_plugin_status onload(ld_plugin_tv *tv) {
 130   // We're given a pointer to the first transfer vector. We read through them
 131   // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
 132   // contain pointers to functions that we need to call to register our own
 133   // hooks. The others are addresses of functions we can use to call into gold
 134   // for services.
 135
 136   bool registeredClaimFile = false;
 137
 138   for (; tv->tv_tag != LDPT_NULL; ++tv) {
 139     switch (tv->tv_tag) {
 140       case LDPT_API_VERSION:
 141         api_version = tv->tv_u.tv_val;
 142         break;
 143       case LDPT_GOLD_VERSION:  // major * 100 + minor
 144         gold_version = tv->tv_u.tv_val;
 145         break;
 146       case LDPT_OUTPUT_NAME:
 147         output_name = tv->tv_u.tv_string;
 148         break;
 149       case LDPT_LINKER_OUTPUT:
 150         switch (tv->tv_u.tv_val) {
 151           case LDPO_REL:  // .o
 152           case LDPO_DYN:  // .so
 153             output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC;
 154             break;
 155           case LDPO_EXEC:  // .exe
 156             output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
 157             break;
 158           default:
 159             (*message)(LDPL_ERROR, "Unknown output file type %d",
 160                        tv->tv_u.tv_val);
 161             return LDPS_ERR;
 162         }
 163         // TODO: add an option to disable PIC.
 164         //output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC;
 165         break;
 166       case LDPT_OPTION:
 167         options::process_plugin_option(tv->tv_u.tv_string);
 168         break;
 169       case LDPT_REGISTER_CLAIM_FILE_HOOK: {
 170         ld_plugin_register_claim_file callback;
 171         callback = tv->tv_u.tv_register_claim_file;
 172
 173         if ((*callback)(claim_file_hook) != LDPS_OK)
 174           return LDPS_ERR;
 175
 176         registeredClaimFile = true;
 177       } break;
 178       case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
 179         ld_plugin_register_all_symbols_read callback;
 180         callback = tv->tv_u.tv_register_all_symbols_read;
 181
 182         if ((*callback)(all_symbols_read_hook) != LDPS_OK)
 183           return LDPS_ERR;
 184
 185         code_gen = lto_codegen_create();
 186       } break;
 187       case LDPT_REGISTER_CLEANUP_HOOK: {
 188         ld_plugin_register_cleanup callback;
 189         callback = tv->tv_u.tv_register_cleanup;
 190
 191         if ((*callback)(cleanup_hook) != LDPS_OK)
 192           return LDPS_ERR;
 193       } break;
 194       case LDPT_ADD_SYMBOLS:
 195         add_symbols = tv->tv_u.tv_add_symbols;
 196         break;
 197       case LDPT_GET_SYMBOLS:
 198         get_symbols = tv->tv_u.tv_get_symbols;
 199         break;
 200       case LDPT_ADD_INPUT_FILE:
 201         add_input_file = tv->tv_u.tv_add_input_file;
 202         break;
 203       case LDPT_ADD_INPUT_LIBRARY:
 204         add_input_library = tv->tv_u.tv_add_input_file;
 205         break;
 206       case LDPT_SET_EXTRA_LIBRARY_PATH:
 207         set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
 208         break;
 209       case LDPT_GET_VIEW:
 210         get_view = tv->tv_u.tv_get_view;
 211         break;
 212       case LDPT_MESSAGE:
 213         message = tv->tv_u.tv_message;
 214         break;
 215       default:
 216         break;
 217     }
 218   }
 219
 220   if (!registeredClaimFile) {
 221     (*message)(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
 222     return LDPS_ERR;
 223   }
 224   if (!add_symbols) {
 225     (*message)(LDPL_ERROR, "add_symbols not passed to LLVMgold.");
 226     return LDPS_ERR;
 227   }
 228
 229   return LDPS_OK;
 230 }
 231
 232 /// claim_file_hook - called by gold to see whether this file is one that
 233 /// our plugin can handle. We'll try to open it and register all the symbols
 234 /// with add_symbol if possible.
 235 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
 236                                         int *claimed) {
 237   lto_module_t M;
 238
 239   if (get_view) {
 240     const void *view;
 241     if (get_view(file->handle, &view) != LDPS_OK) {
 242       (*message)(LDPL_ERROR, "Failed to get a view of %s", file->name);
 243       return LDPS_ERR;
 244     }
 245     M = lto_module_create_from_memory(view, file->filesize);
 246   } else if (file->offset) {
 247     // Gold has found what might be IR part-way inside of a file, such as
 248     // an .a archive.
 249     M = lto_module_create_from_fd_at_offset(file->fd, file->name, -1,
 250                                             file->filesize, file->offset);
 251   } else {
 252     M = lto_module_create_from_fd(file->fd, file->name, file->filesize);
 253   }
 254   if (!M)
 255     return LDPS_OK;
 256
 257   *claimed = 1;
 258   Modules.resize(Modules.size() + 1);
 259   claimed_file &cf = Modules.back();
 260
 261   if (!options::triple.empty())
 262     lto_module_set_target_triple(M, options::triple.c_str());
 263
 264   cf.handle = file->handle;
 265   unsigned sym_count = lto_module_get_num_symbols(M);
 266   cf.syms.reserve(sym_count);
 267
 268   for (unsigned i = 0; i != sym_count; ++i) {
 269     lto_symbol_attributes attrs = lto_module_get_symbol_attribute(M, i);
 270     if ((attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
 271       continue;
 272
 273     cf.syms.push_back(ld_plugin_symbol());
 274     ld_plugin_symbol &sym = cf.syms.back();
 275     sym.name = const_cast<char *>(lto_module_get_symbol_name(M, i));
 276     sym.name = strdup(sym.name);
 277     sym.version = NULL;
 278
 279     int scope = attrs & LTO_SYMBOL_SCOPE_MASK;
 280     switch (scope) {
 281       case LTO_SYMBOL_SCOPE_HIDDEN:
 282         sym.visibility = LDPV_HIDDEN;
 283         break;
 284       case LTO_SYMBOL_SCOPE_PROTECTED:
 285         sym.visibility = LDPV_PROTECTED;
 286         break;
 287       case 0: // extern
 288       case LTO_SYMBOL_SCOPE_DEFAULT:
 289         sym.visibility = LDPV_DEFAULT;
 290         break;
 291       default:
 292         (*message)(LDPL_ERROR, "Unknown scope attribute: %d", scope);
 293         return LDPS_ERR;
 294     }
 295
 296     int definition = attrs & LTO_SYMBOL_DEFINITION_MASK;
 297     sym.comdat_key = NULL;
 298     switch (definition) {
 299       case LTO_SYMBOL_DEFINITION_REGULAR:
 300         sym.def = LDPK_DEF;
 301         break;
 302       case LTO_SYMBOL_DEFINITION_UNDEFINED:
 303         sym.def = LDPK_UNDEF;
 304         break;
 305       case LTO_SYMBOL_DEFINITION_TENTATIVE:
 306         sym.def = LDPK_COMMON;
 307         break;
 308       case LTO_SYMBOL_DEFINITION_WEAK:
 309         sym.comdat_key = sym.name;
 310         sym.def = LDPK_WEAKDEF;
 311         break;
 312       case LTO_SYMBOL_DEFINITION_WEAKUNDEF:
 313         sym.def = LDPK_WEAKUNDEF;
 314         break;
 315       default:
 316         (*message)(LDPL_ERROR, "Unknown definition attribute: %d", definition);
 317         return LDPS_ERR;
 318     }
 319
 320     sym.size = 0;
 321
 322     sym.resolution = LDPR_UNKNOWN;
 323   }
 324
 325   cf.syms.reserve(cf.syms.size());
 326
 327   if (!cf.syms.empty()) {
 328     if ((*add_symbols)(cf.handle, cf.syms.size(), &cf.syms[0]) != LDPS_OK) {
 329       (*message)(LDPL_ERROR, "Unable to add symbols!");
 330       return LDPS_ERR;
 331     }
 332   }
 333
 334   if (code_gen)
 335     lto_codegen_add_module(code_gen, M);
 336
 337   lto_module_dispose(M);
 338
 339   return LDPS_OK;
 340 }
 341
 342 /// all_symbols_read_hook - gold informs us that all symbols have been read.
 343 /// At this point, we use get_symbols to see if any of our definitions have
 344 /// been overridden by a native object file. Then, perform optimization and
 345 /// codegen.
 346 static ld_plugin_status all_symbols_read_hook(void) {
 347   std::ofstream api_file;
 348   assert(code_gen);
 349
 350   if (options::generate_api_file) {
 351     api_file.open("apifile.txt", std::ofstream::out | std::ofstream::trunc);
 352     if (!api_file.is_open()) {
 353       (*message)(LDPL_FATAL, "Unable to open apifile.txt for writing.");
 354       abort();
 355     }
 356   }
 357
 358   // If we don't preserve any symbols, libLTO will assume that all symbols are
 359   // needed. Keep all symbols unless we're producing a final executable.
 360   bool anySymbolsPreserved = false;
 361   for (std::list<claimed_file>::iterator I = Modules.begin(),
 362          E = Modules.end(); I != E; ++I) {
 363     (*get_symbols)(I->handle, I->syms.size(), &I->syms[0]);
 364     for (unsigned i = 0, e = I->syms.size(); i != e; i++) {
 365       if (I->syms[i].resolution == LDPR_PREVAILING_DEF) {
 366         lto_codegen_add_must_preserve_symbol(code_gen, I->syms[i].name);
 367         anySymbolsPreserved = true;
 368
 369         if (options::generate_api_file)
 370           api_file << I->syms[i].name << "\n";
 371       }
 372     }
 373   }
 374
 375   if (options::generate_api_file)
 376     api_file.close();
 377
 378   if (!anySymbolsPreserved) {
 379     // All of the IL is unnecessary!
 380     lto_codegen_dispose(code_gen);
 381     return LDPS_OK;
 382   }
 383
 384   lto_codegen_set_pic_model(code_gen, output_type);
 385   lto_codegen_set_debug_model(code_gen, LTO_DEBUG_MODEL_DWARF);
 386   if (!options::mcpu.empty())
 387     lto_codegen_set_cpu(code_gen, options::mcpu.c_str());
 388
 389   // Pass through extra options to the code generator.
 390   if (!options::extra.empty()) {
 391     for (std::vector<std::string>::iterator it = options::extra.begin();
 392          it != options::extra.end(); ++it) {
 393       lto_codegen_debug_options(code_gen, (*it).c_str());
 394     }
 395   }
 396
 397   if (options::generate_bc_file != options::BC_NO) {
 398     std::string path;
 399     if (options::generate_bc_file == options::BC_ONLY)
 400       path = output_name;
 401     else if (!options::bc_path.empty())
 402       path = options::bc_path;
 403     else
 404       path = output_name + ".bc";
 405     bool err = lto_codegen_write_merged_modules(code_gen, path.c_str());
 406     if (err)
 407       (*message)(LDPL_FATAL, "Failed to write the output file.");
 408     if (options::generate_bc_file == options::BC_ONLY)
 409       exit(0);
 410   }
 411   size_t bufsize = 0;
 412   const char *objPath;
 413   if (lto_codegen_compile_to_file(code_gen, &objPath)) {
 414     (*message)(LDPL_ERROR, "Could not produce a combined object file\n");
 415   }
 416
 417   lto_codegen_dispose(code_gen);
 418   for (std::list<claimed_file>::iterator I = Modules.begin(),
 419          E = Modules.end(); I != E; ++I) {
 420     for (unsigned i = 0; i != I->syms.size(); ++i) {
 421       ld_plugin_symbol &sym = I->syms[i];
 422       free(sym.name);
 423     }
 424   }
 425
 426   if ((*add_input_file)(objPath) != LDPS_OK) {
 427     (*message)(LDPL_ERROR, "Unable to add .o file to the link.");
 428     (*message)(LDPL_ERROR, "File left behind in: %s", objPath);
 429     return LDPS_ERR;
 430   }
 431
 432   if (!options::extra_library_path.empty() &&
 433       set_extra_library_path(options::extra_library_path.c_str()) != LDPS_OK) {
 434     (*message)(LDPL_ERROR, "Unable to set the extra library path.");
 435     return LDPS_ERR;
 436   }
 437
 438   if (options::obj_path.empty())
 439     Cleanup.push_back(sys::Path(objPath));
 440
 441   return LDPS_OK;
 442 }
 443
 444 static ld_plugin_status cleanup_hook(void) {
 445   std::string ErrMsg;
 446
 447   for (int i = 0, e = Cleanup.size(); i != e; ++i)
 448     if (Cleanup[i].eraseFromDisk(false, &ErrMsg))
 449       (*message)(LDPL_ERROR, "Failed to delete '%s': %s", Cleanup[i].c_str(),
 450                  ErrMsg.c_str());
 451
 452   return LDPS_OK;
 453 }