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;
48 std::vector<ld_plugin_symbol> syms;
51 lto_codegen_model output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
52 std::list<claimed_file> Modules;
53 std::vector<sys::Path> Cleanup;
56 ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
58 ld_plugin_status all_symbols_read_hook(void);
59 ld_plugin_status cleanup_hook(void);
61 extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
62 ld_plugin_status onload(ld_plugin_tv *tv) {
63 // We're given a pointer to the first transfer vector. We read through them
64 // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
65 // contain pointers to functions that we need to call to register our own
66 // hooks. The others are addresses of functions we can use to call into gold
69 bool registeredClaimFile = false;
70 bool registeredAllSymbolsRead = false;
71 bool registeredCleanup = false;
73 for (; tv->tv_tag != LDPT_NULL; ++tv) {
75 case LDPT_API_VERSION:
76 api_version = tv->tv_u.tv_val;
78 case LDPT_GOLD_VERSION: // major * 100 + minor
79 gold_version = tv->tv_u.tv_val;
81 case LDPT_LINKER_OUTPUT:
82 switch (tv->tv_u.tv_val) {
85 output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC;
87 case LDPO_EXEC: // .exe
88 output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
91 (*message)(LDPL_ERROR, "Unknown output file type %d",
95 // TODO: add an option to disable PIC.
96 //output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC;
99 (*message)(LDPL_WARNING, "Ignoring flag %s", tv->tv_u.tv_string);
101 case LDPT_REGISTER_CLAIM_FILE_HOOK: {
102 ld_plugin_register_claim_file callback;
103 callback = tv->tv_u.tv_register_claim_file;
105 if ((*callback)(claim_file_hook) != LDPS_OK)
108 registeredClaimFile = true;
110 case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
111 ld_plugin_register_all_symbols_read callback;
112 callback = tv->tv_u.tv_register_all_symbols_read;
114 if ((*callback)(all_symbols_read_hook) != LDPS_OK)
117 registeredAllSymbolsRead = true;
119 case LDPT_REGISTER_CLEANUP_HOOK: {
120 ld_plugin_register_cleanup callback;
121 callback = tv->tv_u.tv_register_cleanup;
123 if ((*callback)(cleanup_hook) != LDPS_OK)
126 registeredCleanup = true;
128 case LDPT_ADD_SYMBOLS:
129 add_symbols = tv->tv_u.tv_add_symbols;
131 case LDPT_GET_SYMBOLS:
132 get_symbols = tv->tv_u.tv_get_symbols;
134 case LDPT_ADD_INPUT_FILE:
135 add_input_file = tv->tv_u.tv_add_input_file;
138 message = tv->tv_u.tv_message;
145 if (!registeredClaimFile || !registeredAllSymbolsRead || !registeredCleanup ||
146 !add_symbols || !get_symbols || !add_input_file) {
147 (*message)(LDPL_ERROR, "Not all hooks registered for LLVMgold.");
154 /// claim_file_hook - called by gold to see whether this file is one that
155 /// our plugin can handle. We'll try to open it and register all the symbols
156 /// with add_symbol if possible.
157 ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
161 // Gold has found what might be IR part-way inside of a file, such as
163 if (lseek(file->fd, file->offset, SEEK_SET) == -1) {
164 (*message)(LDPL_ERROR,
165 "Failed to seek to archive member of %s at offset %d: %s\n",
167 file->offset, strerror(errno));
170 buf = malloc(file->filesize);
172 (*message)(LDPL_ERROR,
173 "Failed to allocate buffer for archive member of size: %d\n",
177 if (read(file->fd, buf, file->filesize) != file->filesize) {
178 (*message)(LDPL_ERROR,
179 "Failed to read archive member of %s at offset %d: %s\n",
186 if (!lto_module_is_object_file_in_memory(buf, file->filesize)) {
190 } else if (!lto_module_is_object_file(file->name))
194 Modules.resize(Modules.size() + 1);
195 claimed_file &cf = Modules.back();
197 cf.M = buf ? lto_module_create_from_memory(buf, file->filesize) :
198 lto_module_create(file->name);
201 (*message)(LDPL_ERROR, "Failed to create LLVM module: %s",
202 lto_get_error_message());
205 cf.handle = file->handle;
206 unsigned sym_count = lto_module_get_num_symbols(cf.M);
207 cf.syms.reserve(sym_count);
209 for (unsigned i = 0; i != sym_count; ++i) {
210 lto_symbol_attributes attrs = lto_module_get_symbol_attribute(cf.M, i);
211 if ((attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
214 cf.syms.push_back(ld_plugin_symbol());
215 ld_plugin_symbol &sym = cf.syms.back();
216 sym.name = const_cast<char *>(lto_module_get_symbol_name(cf.M, i));
219 int scope = attrs & LTO_SYMBOL_SCOPE_MASK;
221 case LTO_SYMBOL_SCOPE_HIDDEN:
222 sym.visibility = LDPV_HIDDEN;
224 case LTO_SYMBOL_SCOPE_PROTECTED:
225 sym.visibility = LDPV_PROTECTED;
228 case LTO_SYMBOL_SCOPE_DEFAULT:
229 sym.visibility = LDPV_DEFAULT;
232 (*message)(LDPL_ERROR, "Unknown scope attribute: %d", scope);
236 int definition = attrs & LTO_SYMBOL_DEFINITION_MASK;
237 switch (definition) {
238 case LTO_SYMBOL_DEFINITION_REGULAR:
241 case LTO_SYMBOL_DEFINITION_UNDEFINED:
242 sym.def = LDPK_UNDEF;
244 case LTO_SYMBOL_DEFINITION_TENTATIVE:
245 sym.def = LDPK_COMMON;
247 case LTO_SYMBOL_DEFINITION_WEAK:
248 sym.def = LDPK_WEAKDEF;
251 (*message)(LDPL_ERROR, "Unknown definition attribute: %d", definition);
255 // LLVM never emits COMDAT.
257 sym.comdat_key = NULL;
259 sym.resolution = LDPR_UNKNOWN;
262 cf.syms.reserve(cf.syms.size());
264 if (!cf.syms.empty()) {
265 if ((*add_symbols)(cf.handle, cf.syms.size(), &cf.syms[0]) != LDPS_OK) {
266 (*message)(LDPL_ERROR, "Unable to add symbols!");
274 /// all_symbols_read_hook - gold informs us that all symbols have been read.
275 /// At this point, we use get_symbols to see if any of our definitions have
276 /// been overridden by a native object file. Then, perform optimization and
278 ld_plugin_status all_symbols_read_hook(void) {
279 lto_code_gen_t cg = lto_codegen_create();
281 for (std::list<claimed_file>::iterator I = Modules.begin(),
282 E = Modules.end(); I != E; ++I)
283 lto_codegen_add_module(cg, I->M);
285 // If we don't preserve any symbols, libLTO will assume that all symbols are
286 // needed. Keep all symbols unless we're producing a final executable.
287 if (output_type == LTO_CODEGEN_PIC_MODEL_STATIC) {
288 bool anySymbolsPreserved = false;
289 for (std::list<claimed_file>::iterator I = Modules.begin(),
290 E = Modules.end(); I != E; ++I) {
291 (*get_symbols)(I->handle, I->syms.size(), &I->syms[0]);
292 for (unsigned i = 0, e = I->syms.size(); i != e; i++) {
293 if (I->syms[i].resolution == LDPR_PREVAILING_DEF ||
294 (I->syms[i].def == LDPK_COMMON &&
295 I->syms[i].resolution == LDPR_RESOLVED_IR)) {
296 lto_codegen_add_must_preserve_symbol(cg, I->syms[i].name);
297 anySymbolsPreserved = true;
302 if (!anySymbolsPreserved) {
303 // This entire file is unnecessary!
304 lto_codegen_dispose(cg);
309 lto_codegen_set_pic_model(cg, output_type);
310 lto_codegen_set_debug_model(cg, LTO_DEBUG_MODEL_DWARF);
313 const char *buffer = static_cast<const char *>(lto_codegen_compile(cg,
318 sys::Path uniqueObjPath("/tmp/llvmgold.o");
319 if (uniqueObjPath.createTemporaryFileOnDisk(true, &ErrMsg)) {
320 (*message)(LDPL_ERROR, "%s", ErrMsg.c_str());
323 raw_fd_ostream *objFile = new raw_fd_ostream(uniqueObjPath.c_str(), true,
325 if (!ErrMsg.empty()) {
327 (*message)(LDPL_ERROR, "%s", ErrMsg.c_str());
331 objFile->write(buffer, bufsize);
334 lto_codegen_dispose(cg);
336 if ((*add_input_file)(const_cast<char*>(uniqueObjPath.c_str())) != LDPS_OK) {
337 (*message)(LDPL_ERROR, "Unable to add .o file to the link.");
338 (*message)(LDPL_ERROR, "File left behind in: %s", uniqueObjPath.c_str());
342 Cleanup.push_back(uniqueObjPath);
347 ld_plugin_status cleanup_hook(void) {
350 for (int i = 0, e = Cleanup.size(); i != e; ++i)
351 if (Cleanup[i].eraseFromDisk(false, &ErrMsg))
352 (*message)(LDPL_ERROR, "Failed to delete '%s': %s", Cleanup[i].c_str(),