tools/gold/gold-plugin.cpp - toolchain/llvm - Git at Google

 //===-- gold-plugin.cpp - Plugin to gold for Link Time Optimization  ------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This is a gold plugin for LLVM. It provides an LLVM implementation of the
 // interface described in http://gcc.gnu.org/wiki/whopr/driver .
 //
 //===----------------------------------------------------------------------===//

 #include "llvm/Config/config.h" // plugin-api.h requires HAVE_STDINT_H
 #include "llvm-c/lto.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/CodeGen/CommandFlags.h"
 #include "llvm/LTO/LTOCodeGenerator.h"
 #include "llvm/LTO/LTOModule.h"
 #include "llvm/Support/Errno.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Program.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/ToolOutputFile.h"
 #include <cerrno>
 #include <cstdlib>
 #include <cstring>
 #include <list>
 #include <plugin-api.h>
 #include <system_error>
 #include <vector>

 // Support Windows/MinGW crazyness.
 #ifdef _WIN32
 # include <io.h>
 # define lseek _lseek
 # define read _read
 #endif

 #ifndef LDPO_PIE
 // FIXME: remove this declaration when we stop maintaining Ubuntu Quantal and
 // Precise and Debian Wheezy (binutils 2.23 is required)
 # define LDPO_PIE 3
 #endif

 using namespace llvm;

 namespace {
 struct claimed_file {
   void *handle;
   std::vector<ld_plugin_symbol> syms;
 };
 }

 static ld_plugin_status discard_message(int level, const char *format, ...) {
   // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
   // callback in the transfer vector. This should never be called.
   abort();
 }

 static ld_plugin_add_symbols add_symbols = NULL;
 static ld_plugin_get_symbols get_symbols = NULL;
 static ld_plugin_add_input_file add_input_file = NULL;
 static ld_plugin_set_extra_library_path set_extra_library_path = NULL;
 static ld_plugin_get_view get_view = NULL;
 static ld_plugin_message message = discard_message;
 static lto_codegen_model output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
 static std::string output_name = "";
 static std::list<claimed_file> Modules;
 static std::vector<std::string> Cleanup;
 static LTOCodeGenerator *CodeGen = nullptr;
 static StringSet<> CannotBeHidden;
 static llvm::TargetOptions TargetOpts;

 namespace options {
   enum generate_bc { BC_NO, BC_ALSO, BC_ONLY };
   static bool generate_api_file = false;
   static generate_bc generate_bc_file = BC_NO;
   static std::string bc_path;
   static std::string obj_path;
   static std::string extra_library_path;
   static std::string triple;
   static std::string mcpu;
   // Additional options to pass into the code generator.
   // Note: This array will contain all plugin options which are not claimed
   // as plugin exclusive to pass to the code generator.
   // For example, "generate-api-file" and "as"options are for the plugin
   // use only and will not be passed.
   static std::vector<std::string> extra;

   static void process_plugin_option(const char* opt_)
   {
     if (opt_ == NULL)
       return;
     llvm::StringRef opt = opt_;

     if (opt == "generate-api-file") {
       generate_api_file = true;
     } else if (opt.startswith("mcpu=")) {
       mcpu = opt.substr(strlen("mcpu="));
     } else if (opt.startswith("extra-library-path=")) {
       extra_library_path = opt.substr(strlen("extra_library_path="));
     } else if (opt.startswith("mtriple=")) {
       triple = opt.substr(strlen("mtriple="));
     } else if (opt.startswith("obj-path=")) {
       obj_path = opt.substr(strlen("obj-path="));
     } else if (opt == "emit-llvm") {
       generate_bc_file = BC_ONLY;
     } else if (opt == "also-emit-llvm") {
       generate_bc_file = BC_ALSO;
     } else if (opt.startswith("also-emit-llvm=")) {
       llvm::StringRef path = opt.substr(strlen("also-emit-llvm="));
       generate_bc_file = BC_ALSO;
       if (!bc_path.empty()) {
         (*message)(LDPL_WARNING, "Path to the output IL file specified twice. "
                    "Discarding %s", opt_);
       } else {
         bc_path = path;
       }
     } else {
       // Save this option to pass to the code generator.
       extra.push_back(opt);
     }
   }
 }

 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
                                         int *claimed);
 static ld_plugin_status all_symbols_read_hook(void);
 static ld_plugin_status cleanup_hook(void);

 extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
 ld_plugin_status onload(ld_plugin_tv *tv) {
   InitializeAllTargetInfos();
   InitializeAllTargets();
   InitializeAllTargetMCs();
   InitializeAllAsmParsers();
   InitializeAllAsmPrinters();

   // We're given a pointer to the first transfer vector. We read through them
   // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
   // contain pointers to functions that we need to call to register our own
   // hooks. The others are addresses of functions we can use to call into gold
   // for services.

   bool registeredClaimFile = false;
   bool RegisteredAllSymbolsRead = false;

   for (; tv->tv_tag != LDPT_NULL; ++tv) {
     switch (tv->tv_tag) {
       case LDPT_OUTPUT_NAME:
         output_name = tv->tv_u.tv_string;
         break;
       case LDPT_LINKER_OUTPUT:
         switch (tv->tv_u.tv_val) {
           case LDPO_REL:  // .o
           case LDPO_DYN:  // .so
           case LDPO_PIE:  // position independent executable
             output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC;
             break;
           case LDPO_EXEC:  // .exe
             output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
             break;
           default:
             (*message)(LDPL_ERROR, "Unknown output file type %d",
                        tv->tv_u.tv_val);
             return LDPS_ERR;
         }
         break;
       case LDPT_OPTION:
         options::process_plugin_option(tv->tv_u.tv_string);
         break;
       case LDPT_REGISTER_CLAIM_FILE_HOOK: {
         ld_plugin_register_claim_file callback;
         callback = tv->tv_u.tv_register_claim_file;

         if ((*callback)(claim_file_hook) != LDPS_OK)
           return LDPS_ERR;

         registeredClaimFile = true;
       } break;
       case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
         ld_plugin_register_all_symbols_read callback;
         callback = tv->tv_u.tv_register_all_symbols_read;

         if ((*callback)(all_symbols_read_hook) != LDPS_OK)
           return LDPS_ERR;

         RegisteredAllSymbolsRead = true;
       } break;
       case LDPT_REGISTER_CLEANUP_HOOK: {
         ld_plugin_register_cleanup callback;
         callback = tv->tv_u.tv_register_cleanup;

         if ((*callback)(cleanup_hook) != LDPS_OK)
           return LDPS_ERR;
       } break;
       case LDPT_ADD_SYMBOLS:
         add_symbols = tv->tv_u.tv_add_symbols;
         break;
       case LDPT_GET_SYMBOLS_V2:
         get_symbols = tv->tv_u.tv_get_symbols;
         break;
       case LDPT_ADD_INPUT_FILE:
         add_input_file = tv->tv_u.tv_add_input_file;
         break;
       case LDPT_SET_EXTRA_LIBRARY_PATH:
         set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
         break;
       case LDPT_GET_VIEW:
         get_view = tv->tv_u.tv_get_view;
         break;
       case LDPT_MESSAGE:
         message = tv->tv_u.tv_message;
         break;
       default:
         break;
     }
   }

   if (!registeredClaimFile) {
     (*message)(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
     return LDPS_ERR;
   }
   if (!add_symbols) {
     (*message)(LDPL_ERROR, "add_symbols not passed to LLVMgold.");
     return LDPS_ERR;
   }

   if (!RegisteredAllSymbolsRead)
     return LDPS_OK;

   CodeGen = new LTOCodeGenerator();

   // Pass through extra options to the code generator.
   if (!options::extra.empty()) {
     for (std::vector<std::string>::iterator it = options::extra.begin();
          it != options::extra.end(); ++it) {
       CodeGen->setCodeGenDebugOptions((*it).c_str());
     }
   }

   CodeGen->parseCodeGenDebugOptions();
   if (MAttrs.size()) {
     std::string Attrs;
     for (unsigned I = 0; I < MAttrs.size(); ++I) {
       if (I > 0)
         Attrs.append(",");
       Attrs.append(MAttrs[I]);
     }
     CodeGen->setAttr(Attrs.c_str());
   }

   TargetOpts = InitTargetOptionsFromCodeGenFlags();
   CodeGen->setTargetOptions(TargetOpts);

   return LDPS_OK;
 }

 /// Called by gold to see whether this file is one that our plugin can handle.
 /// We'll try to open it and register all the symbols with add_symbol if
 /// possible.
 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
                                         int *claimed) {
   const void *view;
   std::unique_ptr<MemoryBuffer> buffer;
   if (get_view) {
     if (get_view(file->handle, &view) != LDPS_OK) {
       (*message)(LDPL_ERROR, "Failed to get a view of %s", file->name);
       return LDPS_ERR;
     }
   } else {
     int64_t offset = 0;
     // Gold has found what might be IR part-way inside of a file, such as
     // an .a archive.
     if (file->offset) {
       offset = file->offset;
     }
     ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
         MemoryBuffer::getOpenFileSlice(file->fd, file->name, file->filesize,
                                        offset);
     if (std::error_code EC = BufferOrErr.getError()) {
       (*message)(LDPL_ERROR, EC.message().c_str());
       return LDPS_ERR;
     }
     buffer = std::move(BufferOrErr.get());
     view = buffer->getBufferStart();
   }

   if (!LTOModule::isBitcodeFile(view, file->filesize))
     return LDPS_OK;

   std::string Error;
   LTOModule *M =
       LTOModule::createFromBuffer(view, file->filesize, TargetOpts, Error);
   if (!M) {
     (*message)(LDPL_ERROR,
                "LLVM gold plugin has failed to create LTO module: %s",
                Error.c_str());
     return LDPS_OK;
   }

   *claimed = 1;
   Modules.resize(Modules.size() + 1);
   claimed_file &cf = Modules.back();

   if (!options::triple.empty())
     M->setTargetTriple(options::triple.c_str());

   cf.handle = file->handle;
   unsigned sym_count = M->getSymbolCount();
   cf.syms.reserve(sym_count);

   for (unsigned i = 0; i != sym_count; ++i) {
     lto_symbol_attributes attrs = M->getSymbolAttributes(i);
     if ((attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
       continue;

     cf.syms.push_back(ld_plugin_symbol());
     ld_plugin_symbol &sym = cf.syms.back();
     sym.name = strdup(M->getSymbolName(i));
     sym.version = NULL;

     int scope = attrs & LTO_SYMBOL_SCOPE_MASK;
     bool CanBeHidden = scope == LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN;
     if (!CanBeHidden)
       CannotBeHidden.insert(sym.name);
     switch (scope) {
       case LTO_SYMBOL_SCOPE_HIDDEN:
         sym.visibility = LDPV_HIDDEN;
         break;
       case LTO_SYMBOL_SCOPE_PROTECTED:
         sym.visibility = LDPV_PROTECTED;
         break;
       case 0: // extern
       case LTO_SYMBOL_SCOPE_DEFAULT:
       case LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN:
         sym.visibility = LDPV_DEFAULT;
         break;
       default:
         (*message)(LDPL_ERROR, "Unknown scope attribute: %d", scope);
         return LDPS_ERR;
     }

     int definition = attrs & LTO_SYMBOL_DEFINITION_MASK;
     sym.comdat_key = NULL;
     switch (definition) {
       case LTO_SYMBOL_DEFINITION_REGULAR:
         sym.def = LDPK_DEF;
         break;
       case LTO_SYMBOL_DEFINITION_UNDEFINED:
         sym.def = LDPK_UNDEF;
         break;
       case LTO_SYMBOL_DEFINITION_TENTATIVE:
         sym.def = LDPK_COMMON;
         break;
       case LTO_SYMBOL_DEFINITION_WEAK:
         sym.comdat_key = sym.name;
         sym.def = LDPK_WEAKDEF;
         break;
       case LTO_SYMBOL_DEFINITION_WEAKUNDEF:
         sym.def = LDPK_WEAKUNDEF;
         break;
       default:
         (*message)(LDPL_ERROR, "Unknown definition attribute: %d", definition);
         return LDPS_ERR;
     }

     sym.size = 0;

     sym.resolution = LDPR_UNKNOWN;
   }

   cf.syms.reserve(cf.syms.size());

   if (!cf.syms.empty()) {
     if ((*add_symbols)(cf.handle, cf.syms.size(), &cf.syms[0]) != LDPS_OK) {
       (*message)(LDPL_ERROR, "Unable to add symbols!");
       return LDPS_ERR;
     }
   }

   if (CodeGen) {
     std::string Error;
     if (!CodeGen->addModule(M, Error)) {
       (*message)(LDPL_ERROR, "Error linking module: %s", Error.c_str());
       return LDPS_ERR;
     }
   }

   delete M;

   return LDPS_OK;
 }

 static bool mustPreserve(const claimed_file &F, int i) {
   if (F.syms[i].resolution == LDPR_PREVAILING_DEF)
     return true;
   if (F.syms[i].resolution == LDPR_PREVAILING_DEF_IRONLY_EXP)
     return CannotBeHidden.count(F.syms[i].name);
   return false;
 }

 /// all_symbols_read_hook - gold informs us that all symbols have been read.
 /// At this point, we use get_symbols to see if any of our definitions have
 /// been overridden by a native object file. Then, perform optimization and
 /// codegen.
 static ld_plugin_status all_symbols_read_hook(void) {
   // FIXME: raw_fd_ostream should be able to represent an unopened file.
   std::unique_ptr<raw_fd_ostream> api_file;

   assert(CodeGen);

   if (options::generate_api_file) {
     std::string Error;
     api_file.reset(new raw_fd_ostream("apifile.txt", Error, sys::fs::F_None));
     if (!Error.empty())
       (*message)(LDPL_FATAL, "Unable to open apifile.txt for writing: %s",
                  Error.c_str());
   }

   for (std::list<claimed_file>::iterator I = Modules.begin(),
          E = Modules.end(); I != E; ++I) {
     if (I->syms.empty())
       continue;
     (*get_symbols)(I->handle, I->syms.size(), &I->syms[0]);
     for (unsigned i = 0, e = I->syms.size(); i != e; i++) {
       if (mustPreserve(*I, i)) {
         CodeGen->addMustPreserveSymbol(I->syms[i].name);

         if (options::generate_api_file)
           (*api_file) << I->syms[i].name << "\n";
       }
     }
   }

   CodeGen->setCodePICModel(output_type);
   CodeGen->setDebugInfo(LTO_DEBUG_MODEL_DWARF);
   if (!options::mcpu.empty())
     CodeGen->setCpu(options::mcpu.c_str());

   if (options::generate_bc_file != options::BC_NO) {
     std::string path;
     if (options::generate_bc_file == options::BC_ONLY)
       path = output_name;
     else if (!options::bc_path.empty())
       path = options::bc_path;
     else
       path = output_name + ".bc";
     std::string Error;
     if (!CodeGen->writeMergedModules(path.c_str(), Error))
       (*message)(LDPL_FATAL, "Failed to write the output file.");
     if (options::generate_bc_file == options::BC_ONLY) {
       delete CodeGen;
       exit(0);
     }
   }

   std::string ObjPath;
   {
     const char *Temp;
     std::string Error;
     if (!CodeGen->compile_to_file(&Temp, /*DisableOpt*/ false, /*DisableInline*/
                                   false, /*DisableGVNLoadPRE*/ false, Error))
       (*message)(LDPL_ERROR, "Could not produce a combined object file\n");
     ObjPath = Temp;
   }

   delete CodeGen;
   for (std::list<claimed_file>::iterator I = Modules.begin(),
          E = Modules.end(); I != E; ++I) {
     for (unsigned i = 0; i != I->syms.size(); ++i) {
       ld_plugin_symbol &sym = I->syms[i];
       free(sym.name);
     }
   }

   if ((*add_input_file)(ObjPath.c_str()) != LDPS_OK) {
     (*message)(LDPL_ERROR, "Unable to add .o file to the link.");
     (*message)(LDPL_ERROR, "File left behind in: %s", ObjPath.c_str());
     return LDPS_ERR;
   }

   if (!options::extra_library_path.empty() &&
       set_extra_library_path(options::extra_library_path.c_str()) != LDPS_OK) {
     (*message)(LDPL_ERROR, "Unable to set the extra library path.");
     return LDPS_ERR;
   }

   if (options::obj_path.empty())
     Cleanup.push_back(ObjPath);

   return LDPS_OK;
 }

 static ld_plugin_status cleanup_hook(void) {
   for (int i = 0, e = Cleanup.size(); i != e; ++i) {
     std::error_code EC = sys::fs::remove(Cleanup[i]);
     if (EC)
       (*message)(LDPL_ERROR, "Failed to delete '%s': %s", Cleanup[i].c_str(),
                  EC.message().c_str());
   }

   return LDPS_OK;
 }
	//===-- gold-plugin.cpp - Plugin to gold for Link Time Optimization ------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// This is a gold plugin for LLVM. It provides an LLVM implementation of the
	// interface described in http://gcc.gnu.org/wiki/whopr/driver .
	//
	//===----------------------------------------------------------------------===//

	#include "llvm/Config/config.h" // plugin-api.h requires HAVE_STDINT_H
	#include "llvm-c/lto.h"
	#include "llvm/ADT/StringSet.h"
	#include "llvm/CodeGen/CommandFlags.h"
	#include "llvm/LTO/LTOCodeGenerator.h"
	#include "llvm/LTO/LTOModule.h"
	#include "llvm/Support/Errno.h"
	#include "llvm/Support/FileSystem.h"
	#include "llvm/Support/MemoryBuffer.h"
	#include "llvm/Support/Path.h"
	#include "llvm/Support/Program.h"
	#include "llvm/Support/TargetSelect.h"
	#include "llvm/Support/ToolOutputFile.h"
	#include <cerrno>
	#include <cstdlib>
	#include <cstring>
	#include <list>
	#include <plugin-api.h>
	#include <system_error>
	#include <vector>

	// Support Windows/MinGW crazyness.
	#ifdef _WIN32
	# include <io.h>
	# define lseek _lseek
	# define read _read
	#endif

	#ifndef LDPO_PIE
	// FIXME: remove this declaration when we stop maintaining Ubuntu Quantal and
	// Precise and Debian Wheezy (binutils 2.23 is required)
	# define LDPO_PIE 3
	#endif

	using namespace llvm;

	namespace {
	struct claimed_file {
	void *handle;
	std::vector<ld_plugin_symbol> syms;
	};
	}

	static ld_plugin_status discard_message(int level, const char *format, ...) {
	// Die loudly. Recent versions of Gold pass ld_plugin_message as the first
	// callback in the transfer vector. This should never be called.
	abort();
	}

	static ld_plugin_add_symbols add_symbols = NULL;
	static ld_plugin_get_symbols get_symbols = NULL;
	static ld_plugin_add_input_file add_input_file = NULL;
	static ld_plugin_set_extra_library_path set_extra_library_path = NULL;
	static ld_plugin_get_view get_view = NULL;
	static ld_plugin_message message = discard_message;
	static lto_codegen_model output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
	static std::string output_name = "";
	static std::list<claimed_file> Modules;
	static std::vector<std::string> Cleanup;
	static LTOCodeGenerator *CodeGen = nullptr;
	static StringSet<> CannotBeHidden;
	static llvm::TargetOptions TargetOpts;

	namespace options {
	enum generate_bc { BC_NO, BC_ALSO, BC_ONLY };
	static bool generate_api_file = false;
	static generate_bc generate_bc_file = BC_NO;
	static std::string bc_path;
	static std::string obj_path;
	static std::string extra_library_path;
	static std::string triple;
	static std::string mcpu;
	// Additional options to pass into the code generator.
	// Note: This array will contain all plugin options which are not claimed
	// as plugin exclusive to pass to the code generator.
	// For example, "generate-api-file" and "as"options are for the plugin
	// use only and will not be passed.
	static std::vector<std::string> extra;

	static void process_plugin_option(const char* opt_)
	{
	if (opt_ == NULL)
	return;
	llvm::StringRef opt = opt_;

	if (opt == "generate-api-file") {
	generate_api_file = true;
	} else if (opt.startswith("mcpu=")) {
	mcpu = opt.substr(strlen("mcpu="));
	} else if (opt.startswith("extra-library-path=")) {
	extra_library_path = opt.substr(strlen("extra_library_path="));
	} else if (opt.startswith("mtriple=")) {
	triple = opt.substr(strlen("mtriple="));
	} else if (opt.startswith("obj-path=")) {
	obj_path = opt.substr(strlen("obj-path="));
	} else if (opt == "emit-llvm") {
	generate_bc_file = BC_ONLY;
	} else if (opt == "also-emit-llvm") {
	generate_bc_file = BC_ALSO;
	} else if (opt.startswith("also-emit-llvm=")) {
	llvm::StringRef path = opt.substr(strlen("also-emit-llvm="));
	generate_bc_file = BC_ALSO;
	if (!bc_path.empty()) {
	(*message)(LDPL_WARNING, "Path to the output IL file specified twice. "
	"Discarding %s", opt_);
	} else {
	bc_path = path;
	}
	} else {
	// Save this option to pass to the code generator.
	extra.push_back(opt);
	}
	}
	}

	static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
	int *claimed);
	static ld_plugin_status all_symbols_read_hook(void);
	static ld_plugin_status cleanup_hook(void);

	extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
	ld_plugin_status onload(ld_plugin_tv *tv) {
	InitializeAllTargetInfos();
	InitializeAllTargets();
	InitializeAllTargetMCs();
	InitializeAllAsmParsers();
	InitializeAllAsmPrinters();

	// We're given a pointer to the first transfer vector. We read through them
	// until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
	// contain pointers to functions that we need to call to register our own
	// hooks. The others are addresses of functions we can use to call into gold
	// for services.

	bool registeredClaimFile = false;
	bool RegisteredAllSymbolsRead = false;

	for (; tv->tv_tag != LDPT_NULL; ++tv) {
	switch (tv->tv_tag) {
	case LDPT_OUTPUT_NAME:
	output_name = tv->tv_u.tv_string;
	break;
	case LDPT_LINKER_OUTPUT:
	switch (tv->tv_u.tv_val) {
	case LDPO_REL: // .o
	case LDPO_DYN: // .so
	case LDPO_PIE: // position independent executable
	output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC;
	break;
	case LDPO_EXEC: // .exe
	output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
	break;
	default:
	(*message)(LDPL_ERROR, "Unknown output file type %d",
	tv->tv_u.tv_val);
	return LDPS_ERR;
	}
	break;
	case LDPT_OPTION:
	options::process_plugin_option(tv->tv_u.tv_string);
	break;
	case LDPT_REGISTER_CLAIM_FILE_HOOK: {
	ld_plugin_register_claim_file callback;
	callback = tv->tv_u.tv_register_claim_file;

	if ((*callback)(claim_file_hook) != LDPS_OK)
	return LDPS_ERR;

	registeredClaimFile = true;
	} break;
	case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
	ld_plugin_register_all_symbols_read callback;
	callback = tv->tv_u.tv_register_all_symbols_read;

	if ((*callback)(all_symbols_read_hook) != LDPS_OK)
	return LDPS_ERR;

	RegisteredAllSymbolsRead = true;
	} break;
	case LDPT_REGISTER_CLEANUP_HOOK: {
	ld_plugin_register_cleanup callback;
	callback = tv->tv_u.tv_register_cleanup;

	if ((*callback)(cleanup_hook) != LDPS_OK)
	return LDPS_ERR;
	} break;
	case LDPT_ADD_SYMBOLS:
	add_symbols = tv->tv_u.tv_add_symbols;
	break;
	case LDPT_GET_SYMBOLS_V2:
	get_symbols = tv->tv_u.tv_get_symbols;
	break;
	case LDPT_ADD_INPUT_FILE:
	add_input_file = tv->tv_u.tv_add_input_file;
	break;
	case LDPT_SET_EXTRA_LIBRARY_PATH:
	set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
	break;
	case LDPT_GET_VIEW:
	get_view = tv->tv_u.tv_get_view;
	break;
	case LDPT_MESSAGE:
	message = tv->tv_u.tv_message;
	break;
	default:
	break;
	}
	}

	if (!registeredClaimFile) {
	(*message)(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
	return LDPS_ERR;
	}
	if (!add_symbols) {
	(*message)(LDPL_ERROR, "add_symbols not passed to LLVMgold.");
	return LDPS_ERR;
	}

	if (!RegisteredAllSymbolsRead)
	return LDPS_OK;

	CodeGen = new LTOCodeGenerator();

	// Pass through extra options to the code generator.
	if (!options::extra.empty()) {
	for (std::vector<std::string>::iterator it = options::extra.begin();
	it != options::extra.end(); ++it) {
	CodeGen->setCodeGenDebugOptions((*it).c_str());
	}
	}

	CodeGen->parseCodeGenDebugOptions();
	if (MAttrs.size()) {
	std::string Attrs;
	for (unsigned I = 0; I < MAttrs.size(); ++I) {
	if (I > 0)
	Attrs.append(",");
	Attrs.append(MAttrs[I]);
	}
	CodeGen->setAttr(Attrs.c_str());
	}

	TargetOpts = InitTargetOptionsFromCodeGenFlags();
	CodeGen->setTargetOptions(TargetOpts);

	return LDPS_OK;
	}

	/// Called by gold to see whether this file is one that our plugin can handle.
	/// We'll try to open it and register all the symbols with add_symbol if
	/// possible.
	static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
	int *claimed) {
	const void *view;
	std::unique_ptr<MemoryBuffer> buffer;
	if (get_view) {
	if (get_view(file->handle, &view) != LDPS_OK) {
	(*message)(LDPL_ERROR, "Failed to get a view of %s", file->name);
	return LDPS_ERR;
	}
	} else {
	int64_t offset = 0;
	// Gold has found what might be IR part-way inside of a file, such as
	// an .a archive.
	if (file->offset) {
	offset = file->offset;
	}
	ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
	MemoryBuffer::getOpenFileSlice(file->fd, file->name, file->filesize,
	offset);
	if (std::error_code EC = BufferOrErr.getError()) {
	(*message)(LDPL_ERROR, EC.message().c_str());
	return LDPS_ERR;
	}
	buffer = std::move(BufferOrErr.get());
	view = buffer->getBufferStart();
	}

	if (!LTOModule::isBitcodeFile(view, file->filesize))
	return LDPS_OK;

	std::string Error;
	LTOModule *M =
	LTOModule::createFromBuffer(view, file->filesize, TargetOpts, Error);
	if (!M) {
	(*message)(LDPL_ERROR,
	"LLVM gold plugin has failed to create LTO module: %s",
	Error.c_str());
	return LDPS_OK;
	}

	*claimed = 1;
	Modules.resize(Modules.size() + 1);
	claimed_file &cf = Modules.back();

	if (!options::triple.empty())
	M->setTargetTriple(options::triple.c_str());

	cf.handle = file->handle;
	unsigned sym_count = M->getSymbolCount();
	cf.syms.reserve(sym_count);

	for (unsigned i = 0; i != sym_count; ++i) {
	lto_symbol_attributes attrs = M->getSymbolAttributes(i);
	if ((attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
	continue;

	cf.syms.push_back(ld_plugin_symbol());
	ld_plugin_symbol &sym = cf.syms.back();
	sym.name = strdup(M->getSymbolName(i));
	sym.version = NULL;

	int scope = attrs & LTO_SYMBOL_SCOPE_MASK;
	bool CanBeHidden = scope == LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN;
	if (!CanBeHidden)
	CannotBeHidden.insert(sym.name);
	switch (scope) {
	case LTO_SYMBOL_SCOPE_HIDDEN:
	sym.visibility = LDPV_HIDDEN;
	break;
	case LTO_SYMBOL_SCOPE_PROTECTED:
	sym.visibility = LDPV_PROTECTED;
	break;
	case 0: // extern
	case LTO_SYMBOL_SCOPE_DEFAULT:
	case LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN:
	sym.visibility = LDPV_DEFAULT;
	break;
	default:
	(*message)(LDPL_ERROR, "Unknown scope attribute: %d", scope);
	return LDPS_ERR;
	}

	int definition = attrs & LTO_SYMBOL_DEFINITION_MASK;
	sym.comdat_key = NULL;
	switch (definition) {
	case LTO_SYMBOL_DEFINITION_REGULAR:
	sym.def = LDPK_DEF;
	break;
	case LTO_SYMBOL_DEFINITION_UNDEFINED:
	sym.def = LDPK_UNDEF;
	break;
	case LTO_SYMBOL_DEFINITION_TENTATIVE:
	sym.def = LDPK_COMMON;
	break;
	case LTO_SYMBOL_DEFINITION_WEAK:
	sym.comdat_key = sym.name;
	sym.def = LDPK_WEAKDEF;
	break;
	case LTO_SYMBOL_DEFINITION_WEAKUNDEF:
	sym.def = LDPK_WEAKUNDEF;
	break;
	default:
	(*message)(LDPL_ERROR, "Unknown definition attribute: %d", definition);
	return LDPS_ERR;
	}

	sym.size = 0;

	sym.resolution = LDPR_UNKNOWN;
	}

	cf.syms.reserve(cf.syms.size());

	if (!cf.syms.empty()) {
	if ((*add_symbols)(cf.handle, cf.syms.size(), &cf.syms[0]) != LDPS_OK) {
	(*message)(LDPL_ERROR, "Unable to add symbols!");
	return LDPS_ERR;
	}
	}

	if (CodeGen) {
	std::string Error;
	if (!CodeGen->addModule(M, Error)) {
	(*message)(LDPL_ERROR, "Error linking module: %s", Error.c_str());
	return LDPS_ERR;
	}
	}

	delete M;

	return LDPS_OK;
	}

	static bool mustPreserve(const claimed_file &F, int i) {
	if (F.syms[i].resolution == LDPR_PREVAILING_DEF)
	return true;
	if (F.syms[i].resolution == LDPR_PREVAILING_DEF_IRONLY_EXP)
	return CannotBeHidden.count(F.syms[i].name);
	return false;
	}

	/// all_symbols_read_hook - gold informs us that all symbols have been read.
	/// At this point, we use get_symbols to see if any of our definitions have
	/// been overridden by a native object file. Then, perform optimization and
	/// codegen.
	static ld_plugin_status all_symbols_read_hook(void) {
	// FIXME: raw_fd_ostream should be able to represent an unopened file.
	std::unique_ptr<raw_fd_ostream> api_file;

	assert(CodeGen);

	if (options::generate_api_file) {
	std::string Error;
	api_file.reset(new raw_fd_ostream("apifile.txt", Error, sys::fs::F_None));
	if (!Error.empty())
	(*message)(LDPL_FATAL, "Unable to open apifile.txt for writing: %s",
	Error.c_str());
	}

	for (std::list<claimed_file>::iterator I = Modules.begin(),
	E = Modules.end(); I != E; ++I) {
	if (I->syms.empty())
	continue;
	(*get_symbols)(I->handle, I->syms.size(), &I->syms[0]);
	for (unsigned i = 0, e = I->syms.size(); i != e; i++) {
	if (mustPreserve(*I, i)) {
	CodeGen->addMustPreserveSymbol(I->syms[i].name);

	if (options::generate_api_file)
	(*api_file) << I->syms[i].name << "\n";
	}
	}
	}

	CodeGen->setCodePICModel(output_type);
	CodeGen->setDebugInfo(LTO_DEBUG_MODEL_DWARF);
	if (!options::mcpu.empty())
	CodeGen->setCpu(options::mcpu.c_str());

	if (options::generate_bc_file != options::BC_NO) {
	std::string path;
	if (options::generate_bc_file == options::BC_ONLY)
	path = output_name;
	else if (!options::bc_path.empty())
	path = options::bc_path;
	else
	path = output_name + ".bc";
	std::string Error;
	if (!CodeGen->writeMergedModules(path.c_str(), Error))
	(*message)(LDPL_FATAL, "Failed to write the output file.");
	if (options::generate_bc_file == options::BC_ONLY) {
	delete CodeGen;
	exit(0);
	}
	}

	std::string ObjPath;
	{
	const char *Temp;
	std::string Error;
	if (!CodeGen->compile_to_file(&Temp, /DisableOpt/ false, /DisableInline/
	false, /DisableGVNLoadPRE/ false, Error))
	(*message)(LDPL_ERROR, "Could not produce a combined object file\n");
	ObjPath = Temp;
	}

	delete CodeGen;
	for (std::list<claimed_file>::iterator I = Modules.begin(),
	E = Modules.end(); I != E; ++I) {
	for (unsigned i = 0; i != I->syms.size(); ++i) {
	ld_plugin_symbol &sym = I->syms[i];
	free(sym.name);
	}
	}

	if ((*add_input_file)(ObjPath.c_str()) != LDPS_OK) {
	(*message)(LDPL_ERROR, "Unable to add .o file to the link.");
	(*message)(LDPL_ERROR, "File left behind in: %s", ObjPath.c_str());
	return LDPS_ERR;
	}

	if (!options::extra_library_path.empty() &&
	set_extra_library_path(options::extra_library_path.c_str()) != LDPS_OK) {
	(*message)(LDPL_ERROR, "Unable to set the extra library path.");
	return LDPS_ERR;
	}

	if (options::obj_path.empty())
	Cleanup.push_back(ObjPath);

	return LDPS_OK;
	}

	static ld_plugin_status cleanup_hook(void) {
	for (int i = 0, e = Cleanup.size(); i != e; ++i) {
	std::error_code EC = sys::fs::remove(Cleanup[i]);
	if (EC)
	(*message)(LDPL_ERROR, "Failed to delete '%s': %s", Cleanup[i].c_str(),
	EC.message().c_str());
	}

	return LDPS_OK;
	}