tools/gold/gold-plugin.cpp - 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 "plugin-api.h"

 #include "llvm-c/lto.h"

 #include "llvm/Support/raw_ostream.h"
 #include "llvm/System/Errno.h"
 #include "llvm/System/Path.h"
 #include "llvm/System/Program.h"

 #include <cerrno>
 #include <cstdlib>
 #include <cstring>
 #include <fstream>
 #include <list>
 #include <vector>

 using namespace llvm;

 namespace {
   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();
   }

   ld_plugin_add_symbols add_symbols = NULL;
   ld_plugin_get_symbols get_symbols = NULL;
   ld_plugin_add_input_file add_input_file = NULL;
   ld_plugin_message message = discard_message;

   int api_version = 0;
   int gold_version = 0;

   bool generate_api_file = false;
   const char *as_path = NULL;

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

   lto_codegen_model output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
   std::list<claimed_file> Modules;
   std::vector<sys::Path> Cleanup;
 }

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

 extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
 ld_plugin_status onload(ld_plugin_tv *tv) {
   // 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;
   bool registeredCleanup = false;

   for (; tv->tv_tag != LDPT_NULL; ++tv) {
     switch (tv->tv_tag) {
       case LDPT_API_VERSION:
         api_version = tv->tv_u.tv_val;
         break;
       case LDPT_GOLD_VERSION:  // major * 100 + minor
         gold_version = tv->tv_u.tv_val;
         break;
       case LDPT_LINKER_OUTPUT:
         switch (tv->tv_u.tv_val) {
           case LDPO_REL:  // .o
           case LDPO_DYN:  // .so
             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;
         }
         // TODO: add an option to disable PIC.
         //output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC;
         break;
       case LDPT_OPTION:
         if (strcmp("generate-api-file", tv->tv_u.tv_string) == 0) {
           generate_api_file = true;
         } else if (strncmp("as=", tv->tv_u.tv_string, 3) == 0) {
           if (as_path) {
             (*message)(LDPL_WARNING, "Path to as specified twice. "
                        "Discarding %s", tv->tv_u.tv_string);
           } else {
             as_path = strdup(tv->tv_u.tv_string + 3);
           }
         } else {
           (*message)(LDPL_WARNING, "Ignoring flag %s", 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;

         registeredCleanup = true;
       } break;
       case LDPT_ADD_SYMBOLS:
         add_symbols = tv->tv_u.tv_add_symbols;
         break;
       case LDPT_GET_SYMBOLS:
         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_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;
   }

   return LDPS_OK;
 }

 /// claim_file_hook - 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.
 ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
                                  int *claimed) {
   void *buf = NULL;
   if (file->offset) {
     // Gold has found what might be IR part-way inside of a file, such as
     // an .a archive.
     if (lseek(file->fd, file->offset, SEEK_SET) == -1) {
       (*message)(LDPL_ERROR,
                  "Failed to seek to archive member of %s at offset %d: %s\n",
                  file->name,
                  file->offset, sys::StrError(errno).c_str());
       return LDPS_ERR;
     }
     buf = malloc(file->filesize);
     if (!buf) {
       (*message)(LDPL_ERROR,
                  "Failed to allocate buffer for archive member of size: %d\n",
                  file->filesize);
       return LDPS_ERR;
     }
     if (read(file->fd, buf, file->filesize) != file->filesize) {
       (*message)(LDPL_ERROR,
                  "Failed to read archive member of %s at offset %d: %s\n",
                  file->name,
                  file->offset,
                  sys::StrError(errno).c_str());
       free(buf);
       return LDPS_ERR;
     }
     if (!lto_module_is_object_file_in_memory(buf, file->filesize)) {
       free(buf);
       return LDPS_OK;
     }
   } else if (!lto_module_is_object_file(file->name))
     return LDPS_OK;

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

   cf.M = buf ? lto_module_create_from_memory(buf, file->filesize) :
                lto_module_create(file->name);
   free(buf);
   if (!cf.M) {
     (*message)(LDPL_ERROR, "Failed to create LLVM module: %s",
                lto_get_error_message());
     return LDPS_ERR;
   }
   cf.handle = file->handle;
   unsigned sym_count = lto_module_get_num_symbols(cf.M);
   cf.syms.reserve(sym_count);

   for (unsigned i = 0; i != sym_count; ++i) {
     lto_symbol_attributes attrs = lto_module_get_symbol_attribute(cf.M, 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 = const_cast<char *>(lto_module_get_symbol_name(cf.M, i));
     sym.version = NULL;

     int scope = attrs & LTO_SYMBOL_SCOPE_MASK;
     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:
         sym.visibility = LDPV_DEFAULT;
         break;
       default:
         (*message)(LDPL_ERROR, "Unknown scope attribute: %d", scope);
         return LDPS_ERR;
     }

     int definition = attrs & LTO_SYMBOL_DEFINITION_MASK;
     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.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;
     }

     // LLVM never emits COMDAT.
     sym.size = 0;
     sym.comdat_key = NULL;

     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;
     }
   }

   return LDPS_OK;
 }

 /// 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.
 ld_plugin_status all_symbols_read_hook(void) {
   lto_code_gen_t cg = lto_codegen_create();

   for (std::list<claimed_file>::iterator I = Modules.begin(),
        E = Modules.end(); I != E; ++I)
     lto_codegen_add_module(cg, I->M);

   std::ofstream api_file;
   if (generate_api_file) {
     api_file.open("apifile.txt", std::ofstream::out | std::ofstream::trunc);
     if (!api_file.is_open()) {
       (*message)(LDPL_FATAL, "Unable to open apifile.txt for writing.");
       abort();
     }
   }

   // If we don't preserve any symbols, libLTO will assume that all symbols are
   // needed. Keep all symbols unless we're producing a final executable.
   if (output_type == LTO_CODEGEN_PIC_MODEL_STATIC) {
     bool anySymbolsPreserved = false;
     for (std::list<claimed_file>::iterator I = Modules.begin(),
          E = Modules.end(); I != E; ++I) {
       (*get_symbols)(I->handle, I->syms.size(), &I->syms[0]);
       for (unsigned i = 0, e = I->syms.size(); i != e; i++) {
         if (I->syms[i].resolution == LDPR_PREVAILING_DEF ||
             (I->syms[i].def == LDPK_COMMON &&
              I->syms[i].resolution == LDPR_RESOLVED_IR)) {
           lto_codegen_add_must_preserve_symbol(cg, I->syms[i].name);
           anySymbolsPreserved = true;

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

     if (generate_api_file)
       api_file.close();

     if (!anySymbolsPreserved) {
       // This entire file is unnecessary!
       lto_codegen_dispose(cg);
       return LDPS_OK;
     }
   }

   lto_codegen_set_pic_model(cg, output_type);
   lto_codegen_set_debug_model(cg, LTO_DEBUG_MODEL_DWARF);
   if (as_path) {
     sys::Path p = sys::Program::FindProgramByName(as_path);
     lto_codegen_set_assembler_path(cg, p.c_str());
   }

   size_t bufsize = 0;
   const char *buffer = static_cast<const char *>(lto_codegen_compile(cg,
                                                                      &bufsize));

   std::string ErrMsg;

   sys::Path uniqueObjPath("/tmp/llvmgold.o");
   if (uniqueObjPath.createTemporaryFileOnDisk(true, &ErrMsg)) {
     (*message)(LDPL_ERROR, "%s", ErrMsg.c_str());
     return LDPS_ERR;
   }
   raw_fd_ostream *objFile = new raw_fd_ostream(uniqueObjPath.c_str(),
                                                /*Binary=*/true,
                                                /*Force=*/true,
                                                ErrMsg);
   if (!ErrMsg.empty()) {
     delete objFile;
     (*message)(LDPL_ERROR, "%s", ErrMsg.c_str());
     return LDPS_ERR;
   }

   objFile->write(buffer, bufsize);
   objFile->close();

   lto_codegen_dispose(cg);

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

   Cleanup.push_back(uniqueObjPath);

   return LDPS_OK;
 }

 ld_plugin_status cleanup_hook(void) {
   std::string ErrMsg;

   for (int i = 0, e = Cleanup.size(); i != e; ++i)
     if (Cleanup[i].eraseFromDisk(false, &ErrMsg))
       (*message)(LDPL_ERROR, "Failed to delete '%s': %s", Cleanup[i].c_str(),
                  ErrMsg.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 "plugin-api.h"

	#include "llvm-c/lto.h"

	#include "llvm/Support/raw_ostream.h"
	#include "llvm/System/Errno.h"
	#include "llvm/System/Path.h"
	#include "llvm/System/Program.h"

	#include <cerrno>
	#include <cstdlib>
	#include <cstring>
	#include <fstream>
	#include <list>
	#include <vector>

	using namespace llvm;

	namespace {
	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();
	}

	ld_plugin_add_symbols add_symbols = NULL;
	ld_plugin_get_symbols get_symbols = NULL;
	ld_plugin_add_input_file add_input_file = NULL;
	ld_plugin_message message = discard_message;

	int api_version = 0;
	int gold_version = 0;

	bool generate_api_file = false;
	const char *as_path = NULL;

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

	lto_codegen_model output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
	std::list<claimed_file> Modules;
	std::vector<sys::Path> Cleanup;
	}

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

	extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
	ld_plugin_status onload(ld_plugin_tv *tv) {
	// 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;
	bool registeredCleanup = false;

	for (; tv->tv_tag != LDPT_NULL; ++tv) {
	switch (tv->tv_tag) {
	case LDPT_API_VERSION:
	api_version = tv->tv_u.tv_val;
	break;
	case LDPT_GOLD_VERSION: // major * 100 + minor
	gold_version = tv->tv_u.tv_val;
	break;
	case LDPT_LINKER_OUTPUT:
	switch (tv->tv_u.tv_val) {
	case LDPO_REL: // .o
	case LDPO_DYN: // .so
	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;
	}
	// TODO: add an option to disable PIC.
	//output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC;
	break;
	case LDPT_OPTION:
	if (strcmp("generate-api-file", tv->tv_u.tv_string) == 0) {
	generate_api_file = true;
	} else if (strncmp("as=", tv->tv_u.tv_string, 3) == 0) {
	if (as_path) {
	(*message)(LDPL_WARNING, "Path to as specified twice. "
	"Discarding %s", tv->tv_u.tv_string);
	} else {
	as_path = strdup(tv->tv_u.tv_string + 3);
	}
	} else {
	(*message)(LDPL_WARNING, "Ignoring flag %s", 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;

	registeredCleanup = true;
	} break;
	case LDPT_ADD_SYMBOLS:
	add_symbols = tv->tv_u.tv_add_symbols;
	break;
	case LDPT_GET_SYMBOLS:
	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_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;
	}

	return LDPS_OK;
	}

	/// claim_file_hook - 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.
	ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
	int *claimed) {
	void *buf = NULL;
	if (file->offset) {
	// Gold has found what might be IR part-way inside of a file, such as
	// an .a archive.
	if (lseek(file->fd, file->offset, SEEK_SET) == -1) {
	(*message)(LDPL_ERROR,
	"Failed to seek to archive member of %s at offset %d: %s\n",
	file->name,
	file->offset, sys::StrError(errno).c_str());
	return LDPS_ERR;
	}
	buf = malloc(file->filesize);
	if (!buf) {
	(*message)(LDPL_ERROR,
	"Failed to allocate buffer for archive member of size: %d\n",
	file->filesize);
	return LDPS_ERR;
	}
	if (read(file->fd, buf, file->filesize) != file->filesize) {
	(*message)(LDPL_ERROR,
	"Failed to read archive member of %s at offset %d: %s\n",
	file->name,
	file->offset,
	sys::StrError(errno).c_str());
	free(buf);
	return LDPS_ERR;
	}
	if (!lto_module_is_object_file_in_memory(buf, file->filesize)) {
	free(buf);
	return LDPS_OK;
	}
	} else if (!lto_module_is_object_file(file->name))
	return LDPS_OK;

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

	cf.M = buf ? lto_module_create_from_memory(buf, file->filesize) :
	lto_module_create(file->name);
	free(buf);
	if (!cf.M) {
	(*message)(LDPL_ERROR, "Failed to create LLVM module: %s",
	lto_get_error_message());
	return LDPS_ERR;
	}
	cf.handle = file->handle;
	unsigned sym_count = lto_module_get_num_symbols(cf.M);
	cf.syms.reserve(sym_count);

	for (unsigned i = 0; i != sym_count; ++i) {
	lto_symbol_attributes attrs = lto_module_get_symbol_attribute(cf.M, 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 = const_cast<char *>(lto_module_get_symbol_name(cf.M, i));
	sym.version = NULL;

	int scope = attrs & LTO_SYMBOL_SCOPE_MASK;
	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:
	sym.visibility = LDPV_DEFAULT;
	break;
	default:
	(*message)(LDPL_ERROR, "Unknown scope attribute: %d", scope);
	return LDPS_ERR;
	}

	int definition = attrs & LTO_SYMBOL_DEFINITION_MASK;
	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.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;
	}

	// LLVM never emits COMDAT.
	sym.size = 0;
	sym.comdat_key = NULL;

	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;
	}
	}

	return LDPS_OK;
	}

	/// 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.
	ld_plugin_status all_symbols_read_hook(void) {
	lto_code_gen_t cg = lto_codegen_create();

	for (std::list<claimed_file>::iterator I = Modules.begin(),
	E = Modules.end(); I != E; ++I)
	lto_codegen_add_module(cg, I->M);

	std::ofstream api_file;
	if (generate_api_file) {
	api_file.open("apifile.txt", std::ofstream::out \| std::ofstream::trunc);
	if (!api_file.is_open()) {
	(*message)(LDPL_FATAL, "Unable to open apifile.txt for writing.");
	abort();
	}
	}

	// If we don't preserve any symbols, libLTO will assume that all symbols are
	// needed. Keep all symbols unless we're producing a final executable.
	if (output_type == LTO_CODEGEN_PIC_MODEL_STATIC) {
	bool anySymbolsPreserved = false;
	for (std::list<claimed_file>::iterator I = Modules.begin(),
	E = Modules.end(); I != E; ++I) {
	(*get_symbols)(I->handle, I->syms.size(), &I->syms[0]);
	for (unsigned i = 0, e = I->syms.size(); i != e; i++) {
	if (I->syms[i].resolution == LDPR_PREVAILING_DEF \|\|
	(I->syms[i].def == LDPK_COMMON &&
	I->syms[i].resolution == LDPR_RESOLVED_IR)) {
	lto_codegen_add_must_preserve_symbol(cg, I->syms[i].name);
	anySymbolsPreserved = true;

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

	if (generate_api_file)
	api_file.close();

	if (!anySymbolsPreserved) {
	// This entire file is unnecessary!
	lto_codegen_dispose(cg);
	return LDPS_OK;
	}
	}

	lto_codegen_set_pic_model(cg, output_type);
	lto_codegen_set_debug_model(cg, LTO_DEBUG_MODEL_DWARF);
	if (as_path) {
	sys::Path p = sys::Program::FindProgramByName(as_path);
	lto_codegen_set_assembler_path(cg, p.c_str());
	}

	size_t bufsize = 0;
	const char buffer = static_cast<const char >(lto_codegen_compile(cg,
	&bufsize));

	std::string ErrMsg;

	sys::Path uniqueObjPath("/tmp/llvmgold.o");
	if (uniqueObjPath.createTemporaryFileOnDisk(true, &ErrMsg)) {
	(*message)(LDPL_ERROR, "%s", ErrMsg.c_str());
	return LDPS_ERR;
	}
	raw_fd_ostream *objFile = new raw_fd_ostream(uniqueObjPath.c_str(),
	/Binary=/true,
	/Force=/true,
	ErrMsg);
	if (!ErrMsg.empty()) {
	delete objFile;
	(*message)(LDPL_ERROR, "%s", ErrMsg.c_str());
	return LDPS_ERR;
	}

	objFile->write(buffer, bufsize);
	objFile->close();

	lto_codegen_dispose(cg);

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

	Cleanup.push_back(uniqueObjPath);

	return LDPS_OK;
	}

	ld_plugin_status cleanup_hook(void) {
	std::string ErrMsg;

	for (int i = 0, e = Cleanup.size(); i != e; ++i)
	if (Cleanup[i].eraseFromDisk(false, &ErrMsg))
	(*message)(LDPL_ERROR, "Failed to delete '%s': %s", Cleanup[i].c_str(),
	ErrMsg.c_str());

	return LDPS_OK;
	}