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+//===-- 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"
+#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;
+
+ 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;
+}
+
+namespace options {
+ static bool generate_api_file = false;
+ static std::string bc_path;
+ static const char *as_path = NULL;
+ // 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;
+
+ if (strcmp("generate-api-file", opt) == 0) {
+ generate_api_file = true;
+ } else if (strncmp("as=", opt, 3) == 0) {
+ if (as_path) {
+ (*message)(LDPL_WARNING, "Path to as specified twice. "
+ "Discarding %s", opt);
+ } else {
+ as_path = strdup(opt + 3);
+ }
+ } else if(llvm::StringRef(opt).startswith("also-emit-llvm=")) {
+ const char *path = opt + strlen("also-emit-llvm=");
+ if (bc_path != "") {
+ (*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(std::string(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) {
+ // 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:
+ 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;
+
+ 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.
+static 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.
+static 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 (options::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) {
+ lto_codegen_add_must_preserve_symbol(cg, I->syms[i].name);
+ anySymbolsPreserved = true;
+
+ if (options::generate_api_file)
+ api_file << I->syms[i].name << "\n";
+ }
+ }
+ }
+
+ if (options::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 (options::as_path) {
+ sys::Path p = sys::Program::FindProgramByName(options::as_path);
+ lto_codegen_set_assembler_path(cg, p.c_str());
+ }
+ // 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) {
+ lto_codegen_debug_options(cg, (*it).c_str());
+ }
+ }
+
+ if (options::bc_path != "") {
+ bool err = lto_codegen_write_merged_modules(cg, options::bc_path.c_str());
+ if (err)
+ (*message)(LDPL_FATAL, "Failed to write the output file.");
+ }
+ 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(), ErrMsg,
+ raw_fd_ostream::F_Binary);
+ 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;
+}
+
+static 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;
+}
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