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      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" // plugin-api.h requires HAVE_STDINT_H
     16 #include "llvm/ADT/DenseSet.h"
     17 #include "llvm/ADT/StringSet.h"
     18 #include "llvm/Analysis/TargetLibraryInfo.h"
     19 #include "llvm/Analysis/TargetTransformInfo.h"
     20 #include "llvm/Bitcode/ReaderWriter.h"
     21 #include "llvm/CodeGen/Analysis.h"
     22 #include "llvm/CodeGen/CommandFlags.h"
     23 #include "llvm/CodeGen/ParallelCG.h"
     24 #include "llvm/IR/AutoUpgrade.h"
     25 #include "llvm/IR/Constants.h"
     26 #include "llvm/IR/DiagnosticInfo.h"
     27 #include "llvm/IR/DiagnosticPrinter.h"
     28 #include "llvm/IR/LLVMContext.h"
     29 #include "llvm/IR/LegacyPassManager.h"
     30 #include "llvm/IR/Module.h"
     31 #include "llvm/IR/Verifier.h"
     32 #include "llvm/Linker/IRMover.h"
     33 #include "llvm/MC/SubtargetFeature.h"
     34 #include "llvm/Object/FunctionIndexObjectFile.h"
     35 #include "llvm/Object/IRObjectFile.h"
     36 #include "llvm/Support/Host.h"
     37 #include "llvm/Support/ManagedStatic.h"
     38 #include "llvm/Support/MemoryBuffer.h"
     39 #include "llvm/Support/TargetRegistry.h"
     40 #include "llvm/Support/TargetSelect.h"
     41 #include "llvm/Support/raw_ostream.h"
     42 #include "llvm/Transforms/IPO.h"
     43 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
     44 #include "llvm/Transforms/Utils/GlobalStatus.h"
     45 #include "llvm/Transforms/Utils/ModuleUtils.h"
     46 #include "llvm/Transforms/Utils/ValueMapper.h"
     47 #include <list>
     48 #include <plugin-api.h>
     49 #include <system_error>
     50 #include <vector>
     51 
     52 #ifndef LDPO_PIE
     53 // FIXME: remove this declaration when we stop maintaining Ubuntu Quantal and
     54 // Precise and Debian Wheezy (binutils 2.23 is required)
     55 # define LDPO_PIE 3
     56 #endif
     57 
     58 using namespace llvm;
     59 
     60 static ld_plugin_status discard_message(int level, const char *format, ...) {
     61   // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
     62   // callback in the transfer vector. This should never be called.
     63   abort();
     64 }
     65 
     66 static ld_plugin_release_input_file release_input_file = nullptr;
     67 static ld_plugin_get_input_file get_input_file = nullptr;
     68 static ld_plugin_message message = discard_message;
     69 
     70 namespace {
     71 struct claimed_file {
     72   void *handle;
     73   std::vector<ld_plugin_symbol> syms;
     74 };
     75 
     76 /// RAII wrapper to manage opening and releasing of a ld_plugin_input_file.
     77 struct PluginInputFile {
     78   void *Handle;
     79   ld_plugin_input_file File;
     80 
     81   PluginInputFile(void *Handle) : Handle(Handle) {
     82     if (get_input_file(Handle, &File) != LDPS_OK)
     83       message(LDPL_FATAL, "Failed to get file information");
     84   }
     85   ~PluginInputFile() {
     86     if (release_input_file(Handle) != LDPS_OK)
     87       message(LDPL_FATAL, "Failed to release file information");
     88   }
     89   ld_plugin_input_file &file() { return File; }
     90 };
     91 
     92 struct ResolutionInfo {
     93   bool IsLinkonceOdr = true;
     94   bool UnnamedAddr = true;
     95   GlobalValue::VisibilityTypes Visibility = GlobalValue::DefaultVisibility;
     96   bool CommonInternal = false;
     97   bool UseCommon = false;
     98   unsigned CommonSize = 0;
     99   unsigned CommonAlign = 0;
    100   claimed_file *CommonFile = nullptr;
    101 };
    102 }
    103 
    104 static ld_plugin_add_symbols add_symbols = nullptr;
    105 static ld_plugin_get_symbols get_symbols = nullptr;
    106 static ld_plugin_add_input_file add_input_file = nullptr;
    107 static ld_plugin_set_extra_library_path set_extra_library_path = nullptr;
    108 static ld_plugin_get_view get_view = nullptr;
    109 static Reloc::Model RelocationModel = Reloc::Default;
    110 static std::string output_name = "";
    111 static std::list<claimed_file> Modules;
    112 static StringMap<ResolutionInfo> ResInfo;
    113 static std::vector<std::string> Cleanup;
    114 static llvm::TargetOptions TargetOpts;
    115 
    116 namespace options {
    117   enum OutputType {
    118     OT_NORMAL,
    119     OT_DISABLE,
    120     OT_BC_ONLY,
    121     OT_SAVE_TEMPS
    122   };
    123   static bool generate_api_file = false;
    124   static OutputType TheOutputType = OT_NORMAL;
    125   static unsigned OptLevel = 2;
    126   static unsigned Parallelism = 1;
    127 #ifdef NDEBUG
    128   static bool DisableVerify = true;
    129 #else
    130   static bool DisableVerify = false;
    131 #endif
    132   static std::string obj_path;
    133   static std::string extra_library_path;
    134   static std::string triple;
    135   static std::string mcpu;
    136   // When the thinlto plugin option is specified, only read the function
    137   // the information from intermediate files and write a combined
    138   // global index for the ThinLTO backends.
    139   static bool thinlto = false;
    140   // Additional options to pass into the code generator.
    141   // Note: This array will contain all plugin options which are not claimed
    142   // as plugin exclusive to pass to the code generator.
    143   // For example, "generate-api-file" and "as"options are for the plugin
    144   // use only and will not be passed.
    145   static std::vector<const char *> extra;
    146 
    147   static void process_plugin_option(const char *opt_)
    148   {
    149     if (opt_ == nullptr)
    150       return;
    151     llvm::StringRef opt = opt_;
    152 
    153     if (opt == "generate-api-file") {
    154       generate_api_file = true;
    155     } else if (opt.startswith("mcpu=")) {
    156       mcpu = opt.substr(strlen("mcpu="));
    157     } else if (opt.startswith("extra-library-path=")) {
    158       extra_library_path = opt.substr(strlen("extra_library_path="));
    159     } else if (opt.startswith("mtriple=")) {
    160       triple = opt.substr(strlen("mtriple="));
    161     } else if (opt.startswith("obj-path=")) {
    162       obj_path = opt.substr(strlen("obj-path="));
    163     } else if (opt == "emit-llvm") {
    164       TheOutputType = OT_BC_ONLY;
    165     } else if (opt == "save-temps") {
    166       TheOutputType = OT_SAVE_TEMPS;
    167     } else if (opt == "disable-output") {
    168       TheOutputType = OT_DISABLE;
    169     } else if (opt == "thinlto") {
    170       thinlto = true;
    171     } else if (opt.size() == 2 && opt[0] == 'O') {
    172       if (opt[1] < '0' || opt[1] > '3')
    173         message(LDPL_FATAL, "Optimization level must be between 0 and 3");
    174       OptLevel = opt[1] - '0';
    175     } else if (opt.startswith("jobs=")) {
    176       if (StringRef(opt_ + 5).getAsInteger(10, Parallelism))
    177         message(LDPL_FATAL, "Invalid parallelism level: %s", opt_ + 5);
    178     } else if (opt == "disable-verify") {
    179       DisableVerify = true;
    180     } else {
    181       // Save this option to pass to the code generator.
    182       // ParseCommandLineOptions() expects argv[0] to be program name. Lazily
    183       // add that.
    184       if (extra.empty())
    185         extra.push_back("LLVMgold");
    186 
    187       extra.push_back(opt_);
    188     }
    189   }
    190 }
    191 
    192 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
    193                                         int *claimed);
    194 static ld_plugin_status all_symbols_read_hook(void);
    195 static ld_plugin_status cleanup_hook(void);
    196 
    197 extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
    198 ld_plugin_status onload(ld_plugin_tv *tv) {
    199   InitializeAllTargetInfos();
    200   InitializeAllTargets();
    201   InitializeAllTargetMCs();
    202   InitializeAllAsmParsers();
    203   InitializeAllAsmPrinters();
    204 
    205   // We're given a pointer to the first transfer vector. We read through them
    206   // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
    207   // contain pointers to functions that we need to call to register our own
    208   // hooks. The others are addresses of functions we can use to call into gold
    209   // for services.
    210 
    211   bool registeredClaimFile = false;
    212   bool RegisteredAllSymbolsRead = false;
    213 
    214   for (; tv->tv_tag != LDPT_NULL; ++tv) {
    215     switch (tv->tv_tag) {
    216       case LDPT_OUTPUT_NAME:
    217         output_name = tv->tv_u.tv_string;
    218         break;
    219       case LDPT_LINKER_OUTPUT:
    220         switch (tv->tv_u.tv_val) {
    221           case LDPO_REL:  // .o
    222           case LDPO_DYN:  // .so
    223           case LDPO_PIE:  // position independent executable
    224             RelocationModel = Reloc::PIC_;
    225             break;
    226           case LDPO_EXEC:  // .exe
    227             RelocationModel = Reloc::Static;
    228             break;
    229           default:
    230             message(LDPL_ERROR, "Unknown output file type %d", tv->tv_u.tv_val);
    231             return LDPS_ERR;
    232         }
    233         break;
    234       case LDPT_OPTION:
    235         options::process_plugin_option(tv->tv_u.tv_string);
    236         break;
    237       case LDPT_REGISTER_CLAIM_FILE_HOOK: {
    238         ld_plugin_register_claim_file callback;
    239         callback = tv->tv_u.tv_register_claim_file;
    240 
    241         if (callback(claim_file_hook) != LDPS_OK)
    242           return LDPS_ERR;
    243 
    244         registeredClaimFile = true;
    245       } break;
    246       case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
    247         ld_plugin_register_all_symbols_read callback;
    248         callback = tv->tv_u.tv_register_all_symbols_read;
    249 
    250         if (callback(all_symbols_read_hook) != LDPS_OK)
    251           return LDPS_ERR;
    252 
    253         RegisteredAllSymbolsRead = true;
    254       } break;
    255       case LDPT_REGISTER_CLEANUP_HOOK: {
    256         ld_plugin_register_cleanup callback;
    257         callback = tv->tv_u.tv_register_cleanup;
    258 
    259         if (callback(cleanup_hook) != LDPS_OK)
    260           return LDPS_ERR;
    261       } break;
    262       case LDPT_GET_INPUT_FILE:
    263         get_input_file = tv->tv_u.tv_get_input_file;
    264         break;
    265       case LDPT_RELEASE_INPUT_FILE:
    266         release_input_file = tv->tv_u.tv_release_input_file;
    267         break;
    268       case LDPT_ADD_SYMBOLS:
    269         add_symbols = tv->tv_u.tv_add_symbols;
    270         break;
    271       case LDPT_GET_SYMBOLS_V2:
    272         get_symbols = tv->tv_u.tv_get_symbols;
    273         break;
    274       case LDPT_ADD_INPUT_FILE:
    275         add_input_file = tv->tv_u.tv_add_input_file;
    276         break;
    277       case LDPT_SET_EXTRA_LIBRARY_PATH:
    278         set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
    279         break;
    280       case LDPT_GET_VIEW:
    281         get_view = tv->tv_u.tv_get_view;
    282         break;
    283       case LDPT_MESSAGE:
    284         message = tv->tv_u.tv_message;
    285         break;
    286       default:
    287         break;
    288     }
    289   }
    290 
    291   if (!registeredClaimFile) {
    292     message(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
    293     return LDPS_ERR;
    294   }
    295   if (!add_symbols) {
    296     message(LDPL_ERROR, "add_symbols not passed to LLVMgold.");
    297     return LDPS_ERR;
    298   }
    299 
    300   if (!RegisteredAllSymbolsRead)
    301     return LDPS_OK;
    302 
    303   if (!get_input_file) {
    304     message(LDPL_ERROR, "get_input_file not passed to LLVMgold.");
    305     return LDPS_ERR;
    306   }
    307   if (!release_input_file) {
    308     message(LDPL_ERROR, "relesase_input_file not passed to LLVMgold.");
    309     return LDPS_ERR;
    310   }
    311 
    312   return LDPS_OK;
    313 }
    314 
    315 static const GlobalObject *getBaseObject(const GlobalValue &GV) {
    316   if (auto *GA = dyn_cast<GlobalAlias>(&GV))
    317     return GA->getBaseObject();
    318   return cast<GlobalObject>(&GV);
    319 }
    320 
    321 static bool shouldSkip(uint32_t Symflags) {
    322   if (!(Symflags & object::BasicSymbolRef::SF_Global))
    323     return true;
    324   if (Symflags & object::BasicSymbolRef::SF_FormatSpecific)
    325     return true;
    326   return false;
    327 }
    328 
    329 static void diagnosticHandler(const DiagnosticInfo &DI) {
    330   if (const auto *BDI = dyn_cast<BitcodeDiagnosticInfo>(&DI)) {
    331     std::error_code EC = BDI->getError();
    332     if (EC == BitcodeError::InvalidBitcodeSignature)
    333       return;
    334   }
    335 
    336   std::string ErrStorage;
    337   {
    338     raw_string_ostream OS(ErrStorage);
    339     DiagnosticPrinterRawOStream DP(OS);
    340     DI.print(DP);
    341   }
    342   ld_plugin_level Level;
    343   switch (DI.getSeverity()) {
    344   case DS_Error:
    345     message(LDPL_FATAL, "LLVM gold plugin has failed to create LTO module: %s",
    346             ErrStorage.c_str());
    347     llvm_unreachable("Fatal doesn't return.");
    348   case DS_Warning:
    349     Level = LDPL_WARNING;
    350     break;
    351   case DS_Note:
    352   case DS_Remark:
    353     Level = LDPL_INFO;
    354     break;
    355   }
    356   message(Level, "LLVM gold plugin: %s",  ErrStorage.c_str());
    357 }
    358 
    359 static void diagnosticHandlerForContext(const DiagnosticInfo &DI,
    360                                         void *Context) {
    361   diagnosticHandler(DI);
    362 }
    363 
    364 static GlobalValue::VisibilityTypes
    365 getMinVisibility(GlobalValue::VisibilityTypes A,
    366                  GlobalValue::VisibilityTypes B) {
    367   if (A == GlobalValue::HiddenVisibility)
    368     return A;
    369   if (B == GlobalValue::HiddenVisibility)
    370     return B;
    371   if (A == GlobalValue::ProtectedVisibility)
    372     return A;
    373   return B;
    374 }
    375 
    376 /// Called by gold to see whether this file is one that our plugin can handle.
    377 /// We'll try to open it and register all the symbols with add_symbol if
    378 /// possible.
    379 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
    380                                         int *claimed) {
    381   LLVMContext Context;
    382   MemoryBufferRef BufferRef;
    383   std::unique_ptr<MemoryBuffer> Buffer;
    384   if (get_view) {
    385     const void *view;
    386     if (get_view(file->handle, &view) != LDPS_OK) {
    387       message(LDPL_ERROR, "Failed to get a view of %s", file->name);
    388       return LDPS_ERR;
    389     }
    390     BufferRef =
    391         MemoryBufferRef(StringRef((const char *)view, file->filesize), "");
    392   } else {
    393     int64_t offset = 0;
    394     // Gold has found what might be IR part-way inside of a file, such as
    395     // an .a archive.
    396     if (file->offset) {
    397       offset = file->offset;
    398     }
    399     ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
    400         MemoryBuffer::getOpenFileSlice(file->fd, file->name, file->filesize,
    401                                        offset);
    402     if (std::error_code EC = BufferOrErr.getError()) {
    403       message(LDPL_ERROR, EC.message().c_str());
    404       return LDPS_ERR;
    405     }
    406     Buffer = std::move(BufferOrErr.get());
    407     BufferRef = Buffer->getMemBufferRef();
    408   }
    409 
    410   Context.setDiagnosticHandler(diagnosticHandlerForContext);
    411   ErrorOr<std::unique_ptr<object::IRObjectFile>> ObjOrErr =
    412       object::IRObjectFile::create(BufferRef, Context);
    413   std::error_code EC = ObjOrErr.getError();
    414   if (EC == object::object_error::invalid_file_type ||
    415       EC == object::object_error::bitcode_section_not_found)
    416     return LDPS_OK;
    417 
    418   *claimed = 1;
    419 
    420   if (EC) {
    421     message(LDPL_ERROR, "LLVM gold plugin has failed to create LTO module: %s",
    422             EC.message().c_str());
    423     return LDPS_ERR;
    424   }
    425   std::unique_ptr<object::IRObjectFile> Obj = std::move(*ObjOrErr);
    426 
    427   Modules.resize(Modules.size() + 1);
    428   claimed_file &cf = Modules.back();
    429 
    430   cf.handle = file->handle;
    431 
    432   // If we are doing ThinLTO compilation, don't need to process the symbols.
    433   // Later we simply build a combined index file after all files are claimed.
    434   if (options::thinlto)
    435     return LDPS_OK;
    436 
    437   for (auto &Sym : Obj->symbols()) {
    438     uint32_t Symflags = Sym.getFlags();
    439     if (shouldSkip(Symflags))
    440       continue;
    441 
    442     cf.syms.push_back(ld_plugin_symbol());
    443     ld_plugin_symbol &sym = cf.syms.back();
    444     sym.version = nullptr;
    445 
    446     SmallString<64> Name;
    447     {
    448       raw_svector_ostream OS(Name);
    449       Sym.printName(OS);
    450     }
    451     sym.name = strdup(Name.c_str());
    452 
    453     const GlobalValue *GV = Obj->getSymbolGV(Sym.getRawDataRefImpl());
    454 
    455     ResolutionInfo &Res = ResInfo[sym.name];
    456 
    457     sym.visibility = LDPV_DEFAULT;
    458     if (GV) {
    459       Res.UnnamedAddr &= GV->hasUnnamedAddr();
    460       Res.IsLinkonceOdr &= GV->hasLinkOnceLinkage();
    461       if (GV->hasCommonLinkage()) {
    462         Res.CommonAlign = std::max(Res.CommonAlign, GV->getAlignment());
    463         const DataLayout &DL = GV->getParent()->getDataLayout();
    464         uint64_t Size = DL.getTypeAllocSize(GV->getType()->getElementType());
    465         if (Size >= Res.CommonSize) {
    466           Res.CommonSize = Size;
    467           Res.CommonFile = &cf;
    468         }
    469       }
    470       Res.Visibility = getMinVisibility(Res.Visibility, GV->getVisibility());
    471       switch (GV->getVisibility()) {
    472       case GlobalValue::DefaultVisibility:
    473         sym.visibility = LDPV_DEFAULT;
    474         break;
    475       case GlobalValue::HiddenVisibility:
    476         sym.visibility = LDPV_HIDDEN;
    477         break;
    478       case GlobalValue::ProtectedVisibility:
    479         sym.visibility = LDPV_PROTECTED;
    480         break;
    481       }
    482     }
    483 
    484     if (Symflags & object::BasicSymbolRef::SF_Undefined) {
    485       sym.def = LDPK_UNDEF;
    486       if (GV && GV->hasExternalWeakLinkage())
    487         sym.def = LDPK_WEAKUNDEF;
    488     } else {
    489       sym.def = LDPK_DEF;
    490       if (GV) {
    491         assert(!GV->hasExternalWeakLinkage() &&
    492                !GV->hasAvailableExternallyLinkage() && "Not a declaration!");
    493         if (GV->hasCommonLinkage())
    494           sym.def = LDPK_COMMON;
    495         else if (GV->isWeakForLinker())
    496           sym.def = LDPK_WEAKDEF;
    497       }
    498     }
    499 
    500     sym.size = 0;
    501     sym.comdat_key = nullptr;
    502     if (GV) {
    503       const GlobalObject *Base = getBaseObject(*GV);
    504       if (!Base)
    505         message(LDPL_FATAL, "Unable to determine comdat of alias!");
    506       const Comdat *C = Base->getComdat();
    507       if (C)
    508         sym.comdat_key = strdup(C->getName().str().c_str());
    509     }
    510 
    511     sym.resolution = LDPR_UNKNOWN;
    512   }
    513 
    514   if (!cf.syms.empty()) {
    515     if (add_symbols(cf.handle, cf.syms.size(), cf.syms.data()) != LDPS_OK) {
    516       message(LDPL_ERROR, "Unable to add symbols!");
    517       return LDPS_ERR;
    518     }
    519   }
    520 
    521   return LDPS_OK;
    522 }
    523 
    524 static void internalize(GlobalValue &GV) {
    525   if (GV.isDeclarationForLinker())
    526     return; // We get here if there is a matching asm definition.
    527   if (!GV.hasLocalLinkage())
    528     GV.setLinkage(GlobalValue::InternalLinkage);
    529 }
    530 
    531 static const char *getResolutionName(ld_plugin_symbol_resolution R) {
    532   switch (R) {
    533   case LDPR_UNKNOWN:
    534     return "UNKNOWN";
    535   case LDPR_UNDEF:
    536     return "UNDEF";
    537   case LDPR_PREVAILING_DEF:
    538     return "PREVAILING_DEF";
    539   case LDPR_PREVAILING_DEF_IRONLY:
    540     return "PREVAILING_DEF_IRONLY";
    541   case LDPR_PREEMPTED_REG:
    542     return "PREEMPTED_REG";
    543   case LDPR_PREEMPTED_IR:
    544     return "PREEMPTED_IR";
    545   case LDPR_RESOLVED_IR:
    546     return "RESOLVED_IR";
    547   case LDPR_RESOLVED_EXEC:
    548     return "RESOLVED_EXEC";
    549   case LDPR_RESOLVED_DYN:
    550     return "RESOLVED_DYN";
    551   case LDPR_PREVAILING_DEF_IRONLY_EXP:
    552     return "PREVAILING_DEF_IRONLY_EXP";
    553   }
    554   llvm_unreachable("Unknown resolution");
    555 }
    556 
    557 static void freeSymName(ld_plugin_symbol &Sym) {
    558   free(Sym.name);
    559   free(Sym.comdat_key);
    560   Sym.name = nullptr;
    561   Sym.comdat_key = nullptr;
    562 }
    563 
    564 static std::unique_ptr<FunctionInfoIndex>
    565 getFunctionIndexForFile(claimed_file &F, ld_plugin_input_file &Info) {
    566 
    567   if (get_symbols(F.handle, F.syms.size(), &F.syms[0]) != LDPS_OK)
    568     message(LDPL_FATAL, "Failed to get symbol information");
    569 
    570   const void *View;
    571   if (get_view(F.handle, &View) != LDPS_OK)
    572     message(LDPL_FATAL, "Failed to get a view of file");
    573 
    574   MemoryBufferRef BufferRef(StringRef((const char *)View, Info.filesize),
    575                             Info.name);
    576 
    577   // Don't bother trying to build an index if there is no summary information
    578   // in this bitcode file.
    579   if (!object::FunctionIndexObjectFile::hasFunctionSummaryInMemBuffer(
    580           BufferRef, diagnosticHandler))
    581     return std::unique_ptr<FunctionInfoIndex>(nullptr);
    582 
    583   ErrorOr<std::unique_ptr<object::FunctionIndexObjectFile>> ObjOrErr =
    584       object::FunctionIndexObjectFile::create(BufferRef, diagnosticHandler);
    585 
    586   if (std::error_code EC = ObjOrErr.getError())
    587     message(LDPL_FATAL, "Could not read function index bitcode from file : %s",
    588             EC.message().c_str());
    589 
    590   object::FunctionIndexObjectFile &Obj = **ObjOrErr;
    591 
    592   return Obj.takeIndex();
    593 }
    594 
    595 static std::unique_ptr<Module>
    596 getModuleForFile(LLVMContext &Context, claimed_file &F,
    597                  ld_plugin_input_file &Info, raw_fd_ostream *ApiFile,
    598                  StringSet<> &Internalize, StringSet<> &Maybe,
    599                  std::vector<GlobalValue *> &Keep) {
    600 
    601   if (get_symbols(F.handle, F.syms.size(), F.syms.data()) != LDPS_OK)
    602     message(LDPL_FATAL, "Failed to get symbol information");
    603 
    604   const void *View;
    605   if (get_view(F.handle, &View) != LDPS_OK)
    606     message(LDPL_FATAL, "Failed to get a view of file");
    607 
    608   MemoryBufferRef BufferRef(StringRef((const char *)View, Info.filesize),
    609                             Info.name);
    610   ErrorOr<std::unique_ptr<object::IRObjectFile>> ObjOrErr =
    611       object::IRObjectFile::create(BufferRef, Context);
    612 
    613   if (std::error_code EC = ObjOrErr.getError())
    614     message(LDPL_FATAL, "Could not read bitcode from file : %s",
    615             EC.message().c_str());
    616 
    617   object::IRObjectFile &Obj = **ObjOrErr;
    618 
    619   Module &M = Obj.getModule();
    620 
    621   M.materializeMetadata();
    622   UpgradeDebugInfo(M);
    623 
    624   SmallPtrSet<GlobalValue *, 8> Used;
    625   collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);
    626 
    627   unsigned SymNum = 0;
    628   for (auto &ObjSym : Obj.symbols()) {
    629     GlobalValue *GV = Obj.getSymbolGV(ObjSym.getRawDataRefImpl());
    630     if (GV && GV->hasAppendingLinkage())
    631       Keep.push_back(GV);
    632 
    633     if (shouldSkip(ObjSym.getFlags()))
    634       continue;
    635     ld_plugin_symbol &Sym = F.syms[SymNum];
    636     ++SymNum;
    637 
    638     ld_plugin_symbol_resolution Resolution =
    639         (ld_plugin_symbol_resolution)Sym.resolution;
    640 
    641     if (options::generate_api_file)
    642       *ApiFile << Sym.name << ' ' << getResolutionName(Resolution) << '\n';
    643 
    644     if (!GV) {
    645       freeSymName(Sym);
    646       continue; // Asm symbol.
    647     }
    648 
    649     ResolutionInfo &Res = ResInfo[Sym.name];
    650     if (Resolution == LDPR_PREVAILING_DEF_IRONLY_EXP && !Res.IsLinkonceOdr)
    651       Resolution = LDPR_PREVAILING_DEF;
    652 
    653     GV->setUnnamedAddr(Res.UnnamedAddr);
    654     GV->setVisibility(Res.Visibility);
    655 
    656     // Override gold's resolution for common symbols. We want the largest
    657     // one to win.
    658     if (GV->hasCommonLinkage()) {
    659       cast<GlobalVariable>(GV)->setAlignment(Res.CommonAlign);
    660       if (Resolution == LDPR_PREVAILING_DEF_IRONLY)
    661         Res.CommonInternal = true;
    662 
    663       if (Resolution == LDPR_PREVAILING_DEF_IRONLY ||
    664           Resolution == LDPR_PREVAILING_DEF)
    665         Res.UseCommon = true;
    666 
    667       if (Res.CommonFile == &F && Res.UseCommon) {
    668         if (Res.CommonInternal)
    669           Resolution = LDPR_PREVAILING_DEF_IRONLY;
    670         else
    671           Resolution = LDPR_PREVAILING_DEF;
    672       } else {
    673         Resolution = LDPR_PREEMPTED_IR;
    674       }
    675     }
    676 
    677     switch (Resolution) {
    678     case LDPR_UNKNOWN:
    679       llvm_unreachable("Unexpected resolution");
    680 
    681     case LDPR_RESOLVED_IR:
    682     case LDPR_RESOLVED_EXEC:
    683     case LDPR_RESOLVED_DYN:
    684     case LDPR_PREEMPTED_IR:
    685     case LDPR_PREEMPTED_REG:
    686       break;
    687 
    688     case LDPR_UNDEF:
    689       if (!GV->isDeclarationForLinker())
    690         assert(GV->hasComdat());
    691       break;
    692 
    693     case LDPR_PREVAILING_DEF_IRONLY: {
    694       Keep.push_back(GV);
    695       // The IR linker has to be able to map this value to a declaration,
    696       // so we can only internalize after linking.
    697       if (!Used.count(GV))
    698         Internalize.insert(GV->getName());
    699       break;
    700     }
    701 
    702     case LDPR_PREVAILING_DEF:
    703       Keep.push_back(GV);
    704       // There is a non IR use, so we have to force optimizations to keep this.
    705       switch (GV->getLinkage()) {
    706       default:
    707         break;
    708       case GlobalValue::LinkOnceAnyLinkage:
    709         GV->setLinkage(GlobalValue::WeakAnyLinkage);
    710         break;
    711       case GlobalValue::LinkOnceODRLinkage:
    712         GV->setLinkage(GlobalValue::WeakODRLinkage);
    713         break;
    714       }
    715       break;
    716 
    717     case LDPR_PREVAILING_DEF_IRONLY_EXP: {
    718       // We can only check for address uses after we merge the modules. The
    719       // reason is that this GV might have a copy in another module
    720       // and in that module the address might be significant, but that
    721       // copy will be LDPR_PREEMPTED_IR.
    722       Maybe.insert(GV->getName());
    723       Keep.push_back(GV);
    724       break;
    725     }
    726     }
    727 
    728     freeSymName(Sym);
    729   }
    730 
    731   return Obj.takeModule();
    732 }
    733 
    734 static void runLTOPasses(Module &M, TargetMachine &TM) {
    735   M.setDataLayout(TM.createDataLayout());
    736 
    737   legacy::PassManager passes;
    738   passes.add(createTargetTransformInfoWrapperPass(TM.getTargetIRAnalysis()));
    739 
    740   PassManagerBuilder PMB;
    741   PMB.LibraryInfo = new TargetLibraryInfoImpl(Triple(TM.getTargetTriple()));
    742   PMB.Inliner = createFunctionInliningPass();
    743   // Unconditionally verify input since it is not verified before this
    744   // point and has unknown origin.
    745   PMB.VerifyInput = true;
    746   PMB.VerifyOutput = !options::DisableVerify;
    747   PMB.LoopVectorize = true;
    748   PMB.SLPVectorize = true;
    749   PMB.OptLevel = options::OptLevel;
    750   PMB.populateLTOPassManager(passes);
    751   passes.run(M);
    752 }
    753 
    754 static void saveBCFile(StringRef Path, Module &M) {
    755   std::error_code EC;
    756   raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::F_None);
    757   if (EC)
    758     message(LDPL_FATAL, "Failed to write the output file.");
    759   WriteBitcodeToFile(&M, OS, /* ShouldPreserveUseListOrder */ true);
    760 }
    761 
    762 static void codegen(std::unique_ptr<Module> M) {
    763   const std::string &TripleStr = M->getTargetTriple();
    764   Triple TheTriple(TripleStr);
    765 
    766   std::string ErrMsg;
    767   const Target *TheTarget = TargetRegistry::lookupTarget(TripleStr, ErrMsg);
    768   if (!TheTarget)
    769     message(LDPL_FATAL, "Target not found: %s", ErrMsg.c_str());
    770 
    771   if (unsigned NumOpts = options::extra.size())
    772     cl::ParseCommandLineOptions(NumOpts, &options::extra[0]);
    773 
    774   SubtargetFeatures Features;
    775   Features.getDefaultSubtargetFeatures(TheTriple);
    776   for (const std::string &A : MAttrs)
    777     Features.AddFeature(A);
    778 
    779   TargetOptions Options = InitTargetOptionsFromCodeGenFlags();
    780   CodeGenOpt::Level CGOptLevel;
    781   switch (options::OptLevel) {
    782   case 0:
    783     CGOptLevel = CodeGenOpt::None;
    784     break;
    785   case 1:
    786     CGOptLevel = CodeGenOpt::Less;
    787     break;
    788   case 2:
    789     CGOptLevel = CodeGenOpt::Default;
    790     break;
    791   case 3:
    792     CGOptLevel = CodeGenOpt::Aggressive;
    793     break;
    794   }
    795   std::unique_ptr<TargetMachine> TM(TheTarget->createTargetMachine(
    796       TripleStr, options::mcpu, Features.getString(), Options, RelocationModel,
    797       CodeModel::Default, CGOptLevel));
    798 
    799   runLTOPasses(*M, *TM);
    800 
    801   if (options::TheOutputType == options::OT_SAVE_TEMPS)
    802     saveBCFile(output_name + ".opt.bc", *M);
    803 
    804   SmallString<128> Filename;
    805   if (!options::obj_path.empty())
    806     Filename = options::obj_path;
    807   else if (options::TheOutputType == options::OT_SAVE_TEMPS)
    808     Filename = output_name + ".o";
    809 
    810   std::vector<SmallString<128>> Filenames(options::Parallelism);
    811   bool TempOutFile = Filename.empty();
    812   {
    813     // Open a file descriptor for each backend thread. This is done in a block
    814     // so that the output file descriptors are closed before gold opens them.
    815     std::list<llvm::raw_fd_ostream> OSs;
    816     std::vector<llvm::raw_pwrite_stream *> OSPtrs(options::Parallelism);
    817     for (unsigned I = 0; I != options::Parallelism; ++I) {
    818       int FD;
    819       if (TempOutFile) {
    820         std::error_code EC =
    821             sys::fs::createTemporaryFile("lto-llvm", "o", FD, Filenames[I]);
    822         if (EC)
    823           message(LDPL_FATAL, "Could not create temporary file: %s",
    824                   EC.message().c_str());
    825       } else {
    826         Filenames[I] = Filename;
    827         if (options::Parallelism != 1)
    828           Filenames[I] += utostr(I);
    829         std::error_code EC =
    830             sys::fs::openFileForWrite(Filenames[I], FD, sys::fs::F_None);
    831         if (EC)
    832           message(LDPL_FATAL, "Could not open file: %s", EC.message().c_str());
    833       }
    834       OSs.emplace_back(FD, true);
    835       OSPtrs[I] = &OSs.back();
    836     }
    837 
    838     // Run backend threads.
    839     splitCodeGen(std::move(M), OSPtrs, options::mcpu, Features.getString(),
    840                  Options, RelocationModel, CodeModel::Default, CGOptLevel);
    841   }
    842 
    843   for (auto &Filename : Filenames) {
    844     if (add_input_file(Filename.c_str()) != LDPS_OK)
    845       message(LDPL_FATAL,
    846               "Unable to add .o file to the link. File left behind in: %s",
    847               Filename.c_str());
    848     if (TempOutFile)
    849       Cleanup.push_back(Filename.c_str());
    850   }
    851 }
    852 
    853 /// gold informs us that all symbols have been read. At this point, we use
    854 /// get_symbols to see if any of our definitions have been overridden by a
    855 /// native object file. Then, perform optimization and codegen.
    856 static ld_plugin_status allSymbolsReadHook(raw_fd_ostream *ApiFile) {
    857   if (Modules.empty())
    858     return LDPS_OK;
    859 
    860   // If we are doing ThinLTO compilation, simply build the combined
    861   // function index/summary and emit it. We don't need to parse the modules
    862   // and link them in this case.
    863   if (options::thinlto) {
    864     FunctionInfoIndex CombinedIndex;
    865     uint64_t NextModuleId = 0;
    866     for (claimed_file &F : Modules) {
    867       PluginInputFile InputFile(F.handle);
    868 
    869       std::unique_ptr<FunctionInfoIndex> Index =
    870           getFunctionIndexForFile(F, InputFile.file());
    871 
    872       // Skip files without a function summary.
    873       if (Index)
    874         CombinedIndex.mergeFrom(std::move(Index), ++NextModuleId);
    875     }
    876 
    877     std::error_code EC;
    878     raw_fd_ostream OS(output_name + ".thinlto.bc", EC,
    879                       sys::fs::OpenFlags::F_None);
    880     if (EC)
    881       message(LDPL_FATAL, "Unable to open %s.thinlto.bc for writing: %s",
    882               output_name.data(), EC.message().c_str());
    883     WriteFunctionSummaryToFile(CombinedIndex, OS);
    884     OS.close();
    885 
    886     cleanup_hook();
    887     exit(0);
    888   }
    889 
    890   LLVMContext Context;
    891   Context.setDiagnosticHandler(diagnosticHandlerForContext, nullptr, true);
    892 
    893   std::unique_ptr<Module> Combined(new Module("ld-temp.o", Context));
    894   IRMover L(*Combined);
    895 
    896   std::string DefaultTriple = sys::getDefaultTargetTriple();
    897 
    898   StringSet<> Internalize;
    899   StringSet<> Maybe;
    900   for (claimed_file &F : Modules) {
    901     PluginInputFile InputFile(F.handle);
    902     std::vector<GlobalValue *> Keep;
    903     std::unique_ptr<Module> M = getModuleForFile(
    904         Context, F, InputFile.file(), ApiFile, Internalize, Maybe, Keep);
    905     if (!options::triple.empty())
    906       M->setTargetTriple(options::triple.c_str());
    907     else if (M->getTargetTriple().empty())
    908       M->setTargetTriple(DefaultTriple);
    909 
    910     if (L.move(*M, Keep, [](GlobalValue &, IRMover::ValueAdder) {}))
    911       message(LDPL_FATAL, "Failed to link module");
    912   }
    913 
    914   for (const auto &Name : Internalize) {
    915     GlobalValue *GV = Combined->getNamedValue(Name.first());
    916     if (GV)
    917       internalize(*GV);
    918   }
    919 
    920   for (const auto &Name : Maybe) {
    921     GlobalValue *GV = Combined->getNamedValue(Name.first());
    922     if (!GV)
    923       continue;
    924     GV->setLinkage(GlobalValue::LinkOnceODRLinkage);
    925     if (canBeOmittedFromSymbolTable(GV))
    926       internalize(*GV);
    927   }
    928 
    929   if (options::TheOutputType == options::OT_DISABLE)
    930     return LDPS_OK;
    931 
    932   if (options::TheOutputType != options::OT_NORMAL) {
    933     std::string path;
    934     if (options::TheOutputType == options::OT_BC_ONLY)
    935       path = output_name;
    936     else
    937       path = output_name + ".bc";
    938     saveBCFile(path, *Combined);
    939     if (options::TheOutputType == options::OT_BC_ONLY)
    940       return LDPS_OK;
    941   }
    942 
    943   codegen(std::move(Combined));
    944 
    945   if (!options::extra_library_path.empty() &&
    946       set_extra_library_path(options::extra_library_path.c_str()) != LDPS_OK)
    947     message(LDPL_FATAL, "Unable to set the extra library path.");
    948 
    949   return LDPS_OK;
    950 }
    951 
    952 static ld_plugin_status all_symbols_read_hook(void) {
    953   ld_plugin_status Ret;
    954   if (!options::generate_api_file) {
    955     Ret = allSymbolsReadHook(nullptr);
    956   } else {
    957     std::error_code EC;
    958     raw_fd_ostream ApiFile("apifile.txt", EC, sys::fs::F_None);
    959     if (EC)
    960       message(LDPL_FATAL, "Unable to open apifile.txt for writing: %s",
    961               EC.message().c_str());
    962     Ret = allSymbolsReadHook(&ApiFile);
    963   }
    964 
    965   llvm_shutdown();
    966 
    967   if (options::TheOutputType == options::OT_BC_ONLY ||
    968       options::TheOutputType == options::OT_DISABLE) {
    969     if (options::TheOutputType == options::OT_DISABLE)
    970       // Remove the output file here since ld.bfd creates the output file
    971       // early.
    972       sys::fs::remove(output_name);
    973     exit(0);
    974   }
    975 
    976   return Ret;
    977 }
    978 
    979 static ld_plugin_status cleanup_hook(void) {
    980   for (std::string &Name : Cleanup) {
    981     std::error_code EC = sys::fs::remove(Name);
    982     if (EC)
    983       message(LDPL_ERROR, "Failed to delete '%s': %s", Name.c_str(),
    984               EC.message().c_str());
    985   }
    986 
    987   return LDPS_OK;
    988 }
    989