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 "plugin-api.h"
  16
  17 #include "llvm-c/lto.h"
  18
  19 #include "llvm/Support/raw_ostream.h"
  20 #include "llvm/System/Errno.h"
  21 #include "llvm/System/Path.h"
  22 #include "llvm/System/Program.h"
  23
  24 #include <cerrno>
  25 #include <cstdlib>
  26 #include <cstring>
  27 #include <fstream>
  28 #include <list>
  29 #include <vector>
  30
  31 using namespace llvm;
  32
  33 namespace {
  34   ld_plugin_status discard_message(int level, const char *format, ...) {
  35     // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
  36     // callback in the transfer vector. This should never be called.
  37     abort();
  38   }
  39
  40   ld_plugin_add_symbols add_symbols = NULL;
  41   ld_plugin_get_symbols get_symbols = NULL;
  42   ld_plugin_add_input_file add_input_file = NULL;
  43   ld_plugin_message message = discard_message;
  44
  45   int api_version = 0;
  46   int gold_version = 0;
  47
  48   bool generate_api_file = false;
  49   const char *as_path = NULL;
  50
  51   struct claimed_file {
  52     lto_module_t M;
  53     void *handle;
  54     std::vector<ld_plugin_symbol> syms;
  55   };
  56
  57   lto_codegen_model output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
  58   std::list<claimed_file> Modules;
  59   std::vector<sys::Path> Cleanup;
  60 }
  61
  62 ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
  63                                  int *claimed);
  64 ld_plugin_status all_symbols_read_hook(void);
  65 ld_plugin_status cleanup_hook(void);
  66
  67 extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
  68 ld_plugin_status onload(ld_plugin_tv *tv) {
  69   // We're given a pointer to the first transfer vector. We read through them
  70   // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
  71   // contain pointers to functions that we need to call to register our own
  72   // hooks. The others are addresses of functions we can use to call into gold
  73   // for services.
  74
  75   bool registeredClaimFile = false;
  76   bool registeredAllSymbolsRead = false;
  77   bool registeredCleanup = false;
  78
  79   for (; tv->tv_tag != LDPT_NULL; ++tv) {
  80     switch (tv->tv_tag) {
  81       case LDPT_API_VERSION:
  82         api_version = tv->tv_u.tv_val;
  83         break;
  84       case LDPT_GOLD_VERSION:  // major * 100 + minor
  85         gold_version = tv->tv_u.tv_val;
  86         break;
  87       case LDPT_LINKER_OUTPUT:
  88         switch (tv->tv_u.tv_val) {
  89           case LDPO_REL:  // .o
  90           case LDPO_DYN:  // .so
  91             output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC;
  92             break;
  93           case LDPO_EXEC:  // .exe
  94             output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
  95             break;
  96           default:
  97             (*message)(LDPL_ERROR, "Unknown output file type %d",
  98                        tv->tv_u.tv_val);
  99             return LDPS_ERR;
 100         }
 101         // TODO: add an option to disable PIC.
 102         //output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC;
 103         break;
 104       case LDPT_OPTION:
 105         if (strcmp("generate-api-file", tv->tv_u.tv_string) == 0) {
 106           generate_api_file = true;
 107         } else if (strncmp("as=", tv->tv_u.tv_string, 3) == 0) {
 108           if (as_path) {
 109             (*message)(LDPL_WARNING, "Path to as specified twice. "
 110                        "Discarding %s", tv->tv_u.tv_string);
 111           } else {
 112             as_path = strdup(tv->tv_u.tv_string + 3);
 113           }
 114         } else {
 115           (*message)(LDPL_WARNING, "Ignoring flag %s", tv->tv_u.tv_string);
 116         }
 117         break;
 118       case LDPT_REGISTER_CLAIM_FILE_HOOK: {
 119         ld_plugin_register_claim_file callback;
 120         callback = tv->tv_u.tv_register_claim_file;
 121
 122         if ((*callback)(claim_file_hook) != LDPS_OK)
 123           return LDPS_ERR;
 124
 125         registeredClaimFile = true;
 126       } break;
 127       case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
 128         ld_plugin_register_all_symbols_read callback;
 129         callback = tv->tv_u.tv_register_all_symbols_read;
 130
 131         if ((*callback)(all_symbols_read_hook) != LDPS_OK)
 132           return LDPS_ERR;
 133
 134         registeredAllSymbolsRead = true;
 135       } break;
 136       case LDPT_REGISTER_CLEANUP_HOOK: {
 137         ld_plugin_register_cleanup callback;
 138         callback = tv->tv_u.tv_register_cleanup;
 139
 140         if ((*callback)(cleanup_hook) != LDPS_OK)
 141           return LDPS_ERR;
 142
 143         registeredCleanup = true;
 144       } break;
 145       case LDPT_ADD_SYMBOLS:
 146         add_symbols = tv->tv_u.tv_add_symbols;
 147         break;
 148       case LDPT_GET_SYMBOLS:
 149         get_symbols = tv->tv_u.tv_get_symbols;
 150         break;
 151       case LDPT_ADD_INPUT_FILE:
 152         add_input_file = tv->tv_u.tv_add_input_file;
 153         break;
 154       case LDPT_MESSAGE:
 155         message = tv->tv_u.tv_message;
 156         break;
 157       default:
 158         break;
 159     }
 160   }
 161
 162   if (!registeredClaimFile) {
 163     (*message)(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
 164     return LDPS_ERR;
 165   }
 166   if (!add_symbols) {
 167     (*message)(LDPL_ERROR, "add_symbols not passed to LLVMgold.");
 168     return LDPS_ERR;
 169   }
 170
 171   return LDPS_OK;
 172 }
 173
 174 /// claim_file_hook - called by gold to see whether this file is one that
 175 /// our plugin can handle. We'll try to open it and register all the symbols
 176 /// with add_symbol if possible.
 177 ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
 178                                  int *claimed) {
 179   void *buf = NULL;
 180   if (file->offset) {
 181     // Gold has found what might be IR part-way inside of a file, such as
 182     // an .a archive.
 183     if (lseek(file->fd, file->offset, SEEK_SET) == -1) {
 184       (*message)(LDPL_ERROR,
 185                  "Failed to seek to archive member of %s at offset %d: %s\n",
 186                  file->name,
 187                  file->offset, sys::StrError(errno).c_str());
 188       return LDPS_ERR;
 189     }
 190     buf = malloc(file->filesize);
 191     if (!buf) {
 192       (*message)(LDPL_ERROR,
 193                  "Failed to allocate buffer for archive member of size: %d\n",
 194                  file->filesize);
 195       return LDPS_ERR;
 196     }
 197     if (read(file->fd, buf, file->filesize) != file->filesize) {
 198       (*message)(LDPL_ERROR,
 199                  "Failed to read archive member of %s at offset %d: %s\n",
 200                  file->name,
 201                  file->offset,
 202                  sys::StrError(errno).c_str());
 203       free(buf);
 204       return LDPS_ERR;
 205     }
 206     if (!lto_module_is_object_file_in_memory(buf, file->filesize)) {
 207       free(buf);
 208       return LDPS_OK;
 209     }
 210   } else if (!lto_module_is_object_file(file->name))
 211     return LDPS_OK;
 212
 213   *claimed = 1;
 214   Modules.resize(Modules.size() + 1);
 215   claimed_file &cf = Modules.back();
 216
 217   cf.M = buf ? lto_module_create_from_memory(buf, file->filesize) :
 218                lto_module_create(file->name);
 219   free(buf);
 220   if (!cf.M) {
 221     (*message)(LDPL_ERROR, "Failed to create LLVM module: %s",
 222                lto_get_error_message());
 223     return LDPS_ERR;
 224   }
 225   cf.handle = file->handle;
 226   unsigned sym_count = lto_module_get_num_symbols(cf.M);
 227   cf.syms.reserve(sym_count);
 228
 229   for (unsigned i = 0; i != sym_count; ++i) {
 230     lto_symbol_attributes attrs = lto_module_get_symbol_attribute(cf.M, i);
 231     if ((attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
 232       continue;
 233
 234     cf.syms.push_back(ld_plugin_symbol());
 235     ld_plugin_symbol &sym = cf.syms.back();
 236     sym.name = const_cast<char *>(lto_module_get_symbol_name(cf.M, i));
 237     sym.version = NULL;
 238
 239     int scope = attrs & LTO_SYMBOL_SCOPE_MASK;
 240     switch (scope) {
 241       case LTO_SYMBOL_SCOPE_HIDDEN:
 242         sym.visibility = LDPV_HIDDEN;
 243         break;
 244       case LTO_SYMBOL_SCOPE_PROTECTED:
 245         sym.visibility = LDPV_PROTECTED;
 246         break;
 247       case 0: // extern
 248       case LTO_SYMBOL_SCOPE_DEFAULT:
 249         sym.visibility = LDPV_DEFAULT;
 250         break;
 251       default:
 252         (*message)(LDPL_ERROR, "Unknown scope attribute: %d", scope);
 253         return LDPS_ERR;
 254     }
 255
 256     int definition = attrs & LTO_SYMBOL_DEFINITION_MASK;
 257     switch (definition) {
 258       case LTO_SYMBOL_DEFINITION_REGULAR:
 259         sym.def = LDPK_DEF;
 260         break;
 261       case LTO_SYMBOL_DEFINITION_UNDEFINED:
 262         sym.def = LDPK_UNDEF;
 263         break;
 264       case LTO_SYMBOL_DEFINITION_TENTATIVE:
 265         sym.def = LDPK_COMMON;
 266         break;
 267       case LTO_SYMBOL_DEFINITION_WEAK:
 268         sym.def = LDPK_WEAKDEF;
 269         break;
 270       case LTO_SYMBOL_DEFINITION_WEAKUNDEF:
 271         sym.def = LDPK_WEAKUNDEF;
 272         break;
 273       default:
 274         (*message)(LDPL_ERROR, "Unknown definition attribute: %d", definition);
 275         return LDPS_ERR;
 276     }
 277
 278     // LLVM never emits COMDAT.
 279     sym.size = 0;
 280     sym.comdat_key = NULL;
 281
 282     sym.resolution = LDPR_UNKNOWN;
 283   }
 284
 285   cf.syms.reserve(cf.syms.size());
 286
 287   if (!cf.syms.empty()) {
 288     if ((*add_symbols)(cf.handle, cf.syms.size(), &cf.syms[0]) != LDPS_OK) {
 289       (*message)(LDPL_ERROR, "Unable to add symbols!");
 290       return LDPS_ERR;
 291     }
 292   }
 293
 294   return LDPS_OK;
 295 }
 296
 297 /// all_symbols_read_hook - gold informs us that all symbols have been read.
 298 /// At this point, we use get_symbols to see if any of our definitions have
 299 /// been overridden by a native object file. Then, perform optimization and
 300 /// codegen.
 301 ld_plugin_status all_symbols_read_hook(void) {
 302   lto_code_gen_t cg = lto_codegen_create();
 303
 304   for (std::list<claimed_file>::iterator I = Modules.begin(),
 305        E = Modules.end(); I != E; ++I)
 306     lto_codegen_add_module(cg, I->M);
 307
 308   std::ofstream api_file;
 309   if (generate_api_file) {
 310     api_file.open("apifile.txt", std::ofstream::out | std::ofstream::trunc);
 311     if (!api_file.is_open()) {
 312       (*message)(LDPL_FATAL, "Unable to open apifile.txt for writing.");
 313       abort();
 314     }
 315   }
 316
 317   // If we don't preserve any symbols, libLTO will assume that all symbols are
 318   // needed. Keep all symbols unless we're producing a final executable.
 319   if (output_type == LTO_CODEGEN_PIC_MODEL_STATIC) {
 320     bool anySymbolsPreserved = false;
 321     for (std::list<claimed_file>::iterator I = Modules.begin(),
 322          E = Modules.end(); I != E; ++I) {
 323       (*get_symbols)(I->handle, I->syms.size(), &I->syms[0]);
 324       for (unsigned i = 0, e = I->syms.size(); i != e; i++) {
 325         if (I->syms[i].resolution == LDPR_PREVAILING_DEF ||
 326             (I->syms[i].def == LDPK_COMMON &&
 327              I->syms[i].resolution == LDPR_RESOLVED_IR)) {
 328           lto_codegen_add_must_preserve_symbol(cg, I->syms[i].name);
 329           anySymbolsPreserved = true;
 330
 331           if (generate_api_file)
 332             api_file << I->syms[i].name << "\n";
 333         }
 334       }
 335     }
 336
 337     if (generate_api_file)
 338       api_file.close();
 339
 340     if (!anySymbolsPreserved) {
 341       // This entire file is unnecessary!
 342       lto_codegen_dispose(cg);
 343       return LDPS_OK;
 344     }
 345   }
 346
 347   lto_codegen_set_pic_model(cg, output_type);
 348   lto_codegen_set_debug_model(cg, LTO_DEBUG_MODEL_DWARF);
 349   if (as_path) {
 350     sys::Path p = sys::Program::FindProgramByName(as_path);
 351     lto_codegen_set_assembler_path(cg, p.c_str());
 352   }
 353
 354   size_t bufsize = 0;
 355   const char *buffer = static_cast<const char *>(lto_codegen_compile(cg,
 356                                                                      &bufsize));
 357
 358   std::string ErrMsg;
 359
 360   sys::Path uniqueObjPath("/tmp/llvmgold.o");
 361   if (uniqueObjPath.createTemporaryFileOnDisk(true, &ErrMsg)) {
 362     (*message)(LDPL_ERROR, "%s", ErrMsg.c_str());
 363     return LDPS_ERR;
 364   }
 365   raw_fd_ostream *objFile = new raw_fd_ostream(uniqueObjPath.c_str(),
 366                                                /*Binary=*/true,
 367                                                /*Force=*/true,
 368                                                ErrMsg);
 369   if (!ErrMsg.empty()) {
 370     delete objFile;
 371     (*message)(LDPL_ERROR, "%s", ErrMsg.c_str());
 372     return LDPS_ERR;
 373   }
 374
 375   objFile->write(buffer, bufsize);
 376   objFile->close();
 377
 378   lto_codegen_dispose(cg);
 379
 380   if ((*add_input_file)(const_cast<char*>(uniqueObjPath.c_str())) != LDPS_OK) {
 381     (*message)(LDPL_ERROR, "Unable to add .o file to the link.");
 382     (*message)(LDPL_ERROR, "File left behind in: %s", uniqueObjPath.c_str());
 383     return LDPS_ERR;
 384   }
 385
 386   Cleanup.push_back(uniqueObjPath);
 387
 388   return LDPS_OK;
 389 }
 390
 391 ld_plugin_status cleanup_hook(void) {
 392   std::string ErrMsg;
 393
 394   for (int i = 0, e = Cleanup.size(); i != e; ++i)
 395     if (Cleanup[i].eraseFromDisk(false, &ErrMsg))
 396       (*message)(LDPL_ERROR, "Failed to delete '%s': %s", Cleanup[i].c_str(),
 397                  ErrMsg.c_str());
 398
 399   return LDPS_OK;
 400 }