1 //===-- gold-plugin.cpp - Plugin to gold for Link Time Optimization ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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 .
13 //===----------------------------------------------------------------------===//
15 #include "plugin-api.h"
17 #include "llvm-c/lto.h"
19 #include "llvm/Support/raw_ostream.h"
20 #include "llvm/System/Path.h"
31 ld_plugin_status discard_message(int level, const char *format, ...) {
32 // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
33 // callback in the transfer vector. This should never be called.
37 ld_plugin_add_symbols add_symbols = NULL;
38 ld_plugin_get_symbols get_symbols = NULL;
39 ld_plugin_add_input_file add_input_file = NULL;
40 ld_plugin_message message = discard_message;
49 std::vector<ld_plugin_symbol> syms;
52 lto_codegen_model output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
53 std::list<claimed_file> Modules;
54 std::vector<sys::Path> Cleanup;
57 ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
59 ld_plugin_status all_symbols_read_hook(void);
60 ld_plugin_status cleanup_hook(void);
62 extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
63 ld_plugin_status onload(ld_plugin_tv *tv) {
64 // We're given a pointer to the first transfer vector. We read through them
65 // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
66 // contain pointers to functions that we need to call to register our own
67 // hooks. The others are addresses of functions we can use to call into gold
70 bool registeredClaimFile = false;
71 bool registeredAllSymbolsRead = false;
72 bool registeredCleanup = false;
74 for (; tv->tv_tag != LDPT_NULL; ++tv) {
76 case LDPT_API_VERSION:
77 api_version = tv->tv_u.tv_val;
79 case LDPT_GOLD_VERSION: // major * 100 + minor
80 gold_version = tv->tv_u.tv_val;
82 case LDPT_LINKER_OUTPUT:
83 switch (tv->tv_u.tv_val) {
86 output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC;
88 case LDPO_EXEC: // .exe
89 output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
92 (*message)(LDPL_ERROR, "Unknown output file type %d",
96 // TODO: add an option to disable PIC.
97 //output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC;
100 (*message)(LDPL_WARNING, "Ignoring flag %s", tv->tv_u.tv_string);
102 case LDPT_REGISTER_CLAIM_FILE_HOOK: {
103 ld_plugin_register_claim_file callback;
104 callback = tv->tv_u.tv_register_claim_file;
106 if ((*callback)(claim_file_hook) != LDPS_OK)
109 registeredClaimFile = true;
111 case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
112 ld_plugin_register_all_symbols_read callback;
113 callback = tv->tv_u.tv_register_all_symbols_read;
115 if ((*callback)(all_symbols_read_hook) != LDPS_OK)
118 registeredAllSymbolsRead = true;
120 case LDPT_REGISTER_CLEANUP_HOOK: {
121 ld_plugin_register_cleanup callback;
122 callback = tv->tv_u.tv_register_cleanup;
124 if ((*callback)(cleanup_hook) != LDPS_OK)
127 registeredCleanup = true;
129 case LDPT_ADD_SYMBOLS:
130 add_symbols = tv->tv_u.tv_add_symbols;
132 case LDPT_GET_SYMBOLS:
133 get_symbols = tv->tv_u.tv_get_symbols;
135 case LDPT_ADD_INPUT_FILE:
136 add_input_file = tv->tv_u.tv_add_input_file;
139 message = tv->tv_u.tv_message;
146 if (!registeredClaimFile || !registeredAllSymbolsRead || !registeredCleanup ||
147 !add_symbols || !get_symbols || !add_input_file) {
148 (*message)(LDPL_ERROR, "Not all hooks registered for LLVMgold.");
155 /// claim_file_hook - called by gold to see whether this file is one that
156 /// our plugin can handle. We'll try to open it and register all the symbols
157 /// with add_symbol if possible.
158 ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
161 // If set, this means gold found IR in an ELF section. LLVM doesn't wrap its
162 // IR in ELF, so we know it's not us. But it can also be an .a file containing
165 if (lseek(file->fd, file->offset, SEEK_SET) == -1) {
166 (*message)(LDPL_ERROR,
167 "Failed to seek to archive member of %s at offset %d: %s\n",
169 file->offset, strerror(errno));
172 buf = malloc(file->filesize);
174 (*message)(LDPL_ERROR,
175 "Failed to allocate buffer for archive member of size: %d\n",
179 if (read(file->fd, buf, file->filesize) != file->filesize) {
180 (*message)(LDPL_ERROR,
181 "Failed to read archive member of %s at offset %d: %s\n",
188 if (!lto_module_is_object_file_in_memory(buf, file->filesize)) {
192 } else if (!lto_module_is_object_file(file->name))
196 Modules.resize(Modules.size() + 1);
197 claimed_file &cf = Modules.back();
199 cf.M = buf ? lto_module_create_from_memory(buf, file->filesize) :
200 lto_module_create(file->name);
203 (*message)(LDPL_ERROR, "Failed to create LLVM module: %s",
204 lto_get_error_message());
207 cf.handle = file->handle;
208 unsigned sym_count = lto_module_get_num_symbols(cf.M);
209 cf.syms.reserve(sym_count);
211 for (unsigned i = 0; i != sym_count; ++i) {
212 lto_symbol_attributes attrs = lto_module_get_symbol_attribute(cf.M, i);
213 if ((attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
216 cf.syms.push_back(ld_plugin_symbol());
217 ld_plugin_symbol &sym = cf.syms.back();
218 sym.name = const_cast<char *>(lto_module_get_symbol_name(cf.M, i));
221 int scope = attrs & LTO_SYMBOL_SCOPE_MASK;
223 case LTO_SYMBOL_SCOPE_HIDDEN:
224 sym.visibility = LDPV_HIDDEN;
226 case LTO_SYMBOL_SCOPE_PROTECTED:
227 sym.visibility = LDPV_PROTECTED;
230 case LTO_SYMBOL_SCOPE_DEFAULT:
231 sym.visibility = LDPV_DEFAULT;
234 (*message)(LDPL_ERROR, "Unknown scope attribute: %d", scope);
239 int definition = attrs & LTO_SYMBOL_DEFINITION_MASK;
240 switch (definition) {
241 case LTO_SYMBOL_DEFINITION_REGULAR:
244 case LTO_SYMBOL_DEFINITION_UNDEFINED:
245 sym.def = LDPK_UNDEF;
247 case LTO_SYMBOL_DEFINITION_TENTATIVE:
248 sym.def = LDPK_COMMON;
250 case LTO_SYMBOL_DEFINITION_WEAK:
251 sym.def = LDPK_WEAKDEF;
254 (*message)(LDPL_ERROR, "Unknown definition attribute: %d", definition);
259 // LLVM never emits COMDAT.
261 sym.comdat_key = NULL;
263 sym.resolution = LDPR_UNKNOWN;
266 cf.syms.reserve(cf.syms.size());
268 if (!cf.syms.empty()) {
269 if ((*add_symbols)(cf.handle, cf.syms.size(), &cf.syms[0]) != LDPS_OK) {
270 (*message)(LDPL_ERROR, "Unable to add symbols!");
279 /// all_symbols_read_hook - gold informs us that all symbols have been read.
280 /// At this point, we use get_symbols to see if any of our definitions have
281 /// been overridden by a native object file. Then, perform optimization and
283 ld_plugin_status all_symbols_read_hook(void) {
284 lto_code_gen_t cg = lto_codegen_create();
286 for (std::list<claimed_file>::iterator I = Modules.begin(),
287 E = Modules.end(); I != E; ++I)
288 lto_codegen_add_module(cg, I->M);
290 // If we don't preserve any symbols, libLTO will assume that all symbols are
291 // needed. Keep all symbols unless we're producing a final executable.
292 if (output_type == LTO_CODEGEN_PIC_MODEL_STATIC) {
293 bool anySymbolsPreserved = false;
294 for (std::list<claimed_file>::iterator I = Modules.begin(),
295 E = Modules.end(); I != E; ++I) {
296 (*get_symbols)(I->handle, I->syms.size(), &I->syms[0]);
297 for (unsigned i = 0, e = I->syms.size(); i != e; i++) {
298 (*message)(LDPL_WARNING, "def: %d visibility: %d resolution %d",
299 I->syms[i].def, I->syms[i].visibility, I->syms[i].resolution);
300 if (I->syms[i].resolution == LDPR_PREVAILING_DEF) {
301 lto_codegen_add_must_preserve_symbol(cg, I->syms[i].name);
302 anySymbolsPreserved = true;
307 if (!anySymbolsPreserved) {
308 // This entire file is unnecessary!
309 lto_codegen_dispose(cg);
314 lto_codegen_set_pic_model(cg, output_type);
315 lto_codegen_set_debug_model(cg, LTO_DEBUG_MODEL_DWARF);
318 const char *buffer = static_cast<const char *>(lto_codegen_compile(cg,
323 sys::Path uniqueObjPath("/tmp/llvmgold.o");
324 if (uniqueObjPath.createTemporaryFileOnDisk(true, &ErrMsg)) {
325 (*message)(LDPL_ERROR, "%s", ErrMsg.c_str());
328 raw_fd_ostream *objFile = new raw_fd_ostream(uniqueObjPath.c_str(), true,
330 if (!ErrMsg.empty()) {
332 (*message)(LDPL_ERROR, "%s", ErrMsg.c_str());
336 objFile->write(buffer, bufsize);
339 lto_codegen_dispose(cg);
340 for (std::list<claimed_file>::iterator I = Modules.begin(),
341 E = Modules.end(); I != E; ++I) {
345 if ((*add_input_file)(const_cast<char*>(uniqueObjPath.c_str())) != LDPS_OK) {
346 (*message)(LDPL_ERROR, "Unable to add .o file to the link.");
347 (*message)(LDPL_ERROR, "File left behind in: %s", uniqueObjPath.c_str());
351 Cleanup.push_back(uniqueObjPath);
356 ld_plugin_status cleanup_hook(void) {
359 for (int i = 0, e = Cleanup.size(); i != e; ++i)
360 if (Cleanup[i].eraseFromDisk(false, &ErrMsg))
361 (*message)(LDPL_ERROR, "Failed to delete '%s': %s", Cleanup[i].c_str(),