1 //===-- gold-plugin.cpp - Plugin to gold for Link Time Optimization ------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
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 .
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "llvm/Config/config.h"
16 #include "plugin-api.h"
17
18 #include "llvm-c/lto.h"
19
20 #include "llvm/Support/ToolOutputFile.h"
21 #include "llvm/Support/Errno.h"
22 #include "llvm/Support/Path.h"
23 #include "llvm/Support/Program.h"
24
25 #include <cerrno>
26 #include <cstdlib>
27 #include <cstring>
28 #include <fstream>
29 #include <list>
30 #include <vector>
31
32 // Support Windows/MinGW crazyness.
33 #ifdef _WIN32
34 # include <io.h>
35 # define lseek _lseek
36 # define read _read
37 #endif
38
39 using namespace llvm;
40
41 namespace {
discard_message(int level,const char * format,...)42 ld_plugin_status discard_message(int level, const char *format, ...) {
43 // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
44 // callback in the transfer vector. This should never be called.
45 abort();
46 }
47
48 ld_plugin_add_symbols add_symbols = NULL;
49 ld_plugin_get_symbols get_symbols = NULL;
50 ld_plugin_add_input_file add_input_file = NULL;
51 ld_plugin_add_input_library add_input_library = NULL;
52 ld_plugin_set_extra_library_path set_extra_library_path = NULL;
53 ld_plugin_get_view get_view = NULL;
54 ld_plugin_message message = discard_message;
55
56 int api_version = 0;
57 int gold_version = 0;
58
59 struct claimed_file {
60 void *handle;
61 std::vector<ld_plugin_symbol> syms;
62 };
63
64 lto_codegen_model output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
65 std::string output_name = "";
66 std::list<claimed_file> Modules;
67 std::vector<sys::Path> Cleanup;
68 lto_code_gen_t code_gen = NULL;
69 }
70
71 namespace options {
72 enum generate_bc { BC_NO, BC_ALSO, BC_ONLY };
73 static bool generate_api_file = false;
74 static generate_bc generate_bc_file = BC_NO;
75 static std::string bc_path;
76 static std::string obj_path;
77 static std::string extra_library_path;
78 static std::string triple;
79 static std::string mcpu;
80 // Additional options to pass into the code generator.
81 // Note: This array will contain all plugin options which are not claimed
82 // as plugin exclusive to pass to the code generator.
83 // For example, "generate-api-file" and "as"options are for the plugin
84 // use only and will not be passed.
85 static std::vector<std::string> extra;
86
process_plugin_option(const char * opt_)87 static void process_plugin_option(const char* opt_)
88 {
89 if (opt_ == NULL)
90 return;
91 llvm::StringRef opt = opt_;
92
93 if (opt == "generate-api-file") {
94 generate_api_file = true;
95 } else if (opt.startswith("mcpu=")) {
96 mcpu = opt.substr(strlen("mcpu="));
97 } else if (opt.startswith("extra-library-path=")) {
98 extra_library_path = opt.substr(strlen("extra_library_path="));
99 } else if (opt.startswith("mtriple=")) {
100 triple = opt.substr(strlen("mtriple="));
101 } else if (opt.startswith("obj-path=")) {
102 obj_path = opt.substr(strlen("obj-path="));
103 } else if (opt == "emit-llvm") {
104 generate_bc_file = BC_ONLY;
105 } else if (opt == "also-emit-llvm") {
106 generate_bc_file = BC_ALSO;
107 } else if (opt.startswith("also-emit-llvm=")) {
108 llvm::StringRef path = opt.substr(strlen("also-emit-llvm="));
109 generate_bc_file = BC_ALSO;
110 if (!bc_path.empty()) {
111 (*message)(LDPL_WARNING, "Path to the output IL file specified twice. "
112 "Discarding %s", opt_);
113 } else {
114 bc_path = path;
115 }
116 } else {
117 // Save this option to pass to the code generator.
118 extra.push_back(opt);
119 }
120 }
121 }
122
123 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
124 int *claimed);
125 static ld_plugin_status all_symbols_read_hook(void);
126 static ld_plugin_status cleanup_hook(void);
127
128 extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
onload(ld_plugin_tv * tv)129 ld_plugin_status onload(ld_plugin_tv *tv) {
130 // We're given a pointer to the first transfer vector. We read through them
131 // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
132 // contain pointers to functions that we need to call to register our own
133 // hooks. The others are addresses of functions we can use to call into gold
134 // for services.
135
136 bool registeredClaimFile = false;
137
138 for (; tv->tv_tag != LDPT_NULL; ++tv) {
139 switch (tv->tv_tag) {
140 case LDPT_API_VERSION:
141 api_version = tv->tv_u.tv_val;
142 break;
143 case LDPT_GOLD_VERSION: // major * 100 + minor
144 gold_version = tv->tv_u.tv_val;
145 break;
146 case LDPT_OUTPUT_NAME:
147 output_name = tv->tv_u.tv_string;
148 break;
149 case LDPT_LINKER_OUTPUT:
150 switch (tv->tv_u.tv_val) {
151 case LDPO_REL: // .o
152 case LDPO_DYN: // .so
153 output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC;
154 break;
155 case LDPO_EXEC: // .exe
156 output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
157 break;
158 default:
159 (*message)(LDPL_ERROR, "Unknown output file type %d",
160 tv->tv_u.tv_val);
161 return LDPS_ERR;
162 }
163 // TODO: add an option to disable PIC.
164 //output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC;
165 break;
166 case LDPT_OPTION:
167 options::process_plugin_option(tv->tv_u.tv_string);
168 break;
169 case LDPT_REGISTER_CLAIM_FILE_HOOK: {
170 ld_plugin_register_claim_file callback;
171 callback = tv->tv_u.tv_register_claim_file;
172
173 if ((*callback)(claim_file_hook) != LDPS_OK)
174 return LDPS_ERR;
175
176 registeredClaimFile = true;
177 } break;
178 case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
179 ld_plugin_register_all_symbols_read callback;
180 callback = tv->tv_u.tv_register_all_symbols_read;
181
182 if ((*callback)(all_symbols_read_hook) != LDPS_OK)
183 return LDPS_ERR;
184
185 code_gen = lto_codegen_create();
186 } break;
187 case LDPT_REGISTER_CLEANUP_HOOK: {
188 ld_plugin_register_cleanup callback;
189 callback = tv->tv_u.tv_register_cleanup;
190
191 if ((*callback)(cleanup_hook) != LDPS_OK)
192 return LDPS_ERR;
193 } break;
194 case LDPT_ADD_SYMBOLS:
195 add_symbols = tv->tv_u.tv_add_symbols;
196 break;
197 case LDPT_GET_SYMBOLS:
198 get_symbols = tv->tv_u.tv_get_symbols;
199 break;
200 case LDPT_ADD_INPUT_FILE:
201 add_input_file = tv->tv_u.tv_add_input_file;
202 break;
203 case LDPT_ADD_INPUT_LIBRARY:
204 add_input_library = tv->tv_u.tv_add_input_file;
205 break;
206 case LDPT_SET_EXTRA_LIBRARY_PATH:
207 set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
208 break;
209 case LDPT_GET_VIEW:
210 get_view = tv->tv_u.tv_get_view;
211 break;
212 case LDPT_MESSAGE:
213 message = tv->tv_u.tv_message;
214 break;
215 default:
216 break;
217 }
218 }
219
220 if (!registeredClaimFile) {
221 (*message)(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
222 return LDPS_ERR;
223 }
224 if (!add_symbols) {
225 (*message)(LDPL_ERROR, "add_symbols not passed to LLVMgold.");
226 return LDPS_ERR;
227 }
228
229 return LDPS_OK;
230 }
231
232 /// claim_file_hook - called by gold to see whether this file is one that
233 /// our plugin can handle. We'll try to open it and register all the symbols
234 /// with add_symbol if possible.
claim_file_hook(const ld_plugin_input_file * file,int * claimed)235 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
236 int *claimed) {
237 lto_module_t M;
238
239 if (get_view) {
240 const void *view;
241 if (get_view(file->handle, &view) != LDPS_OK) {
242 (*message)(LDPL_ERROR, "Failed to get a view of %s", file->name);
243 return LDPS_ERR;
244 }
245 M = lto_module_create_from_memory(view, file->filesize);
246 } else if (file->offset) {
247 // Gold has found what might be IR part-way inside of a file, such as
248 // an .a archive.
249 M = lto_module_create_from_fd_at_offset(file->fd, file->name, -1,
250 file->filesize, file->offset);
251 } else {
252 M = lto_module_create_from_fd(file->fd, file->name, file->filesize);
253 }
254 if (!M)
255 return LDPS_OK;
256
257 *claimed = 1;
258 Modules.resize(Modules.size() + 1);
259 claimed_file &cf = Modules.back();
260
261 if (!options::triple.empty())
262 lto_module_set_target_triple(M, options::triple.c_str());
263
264 cf.handle = file->handle;
265 unsigned sym_count = lto_module_get_num_symbols(M);
266 cf.syms.reserve(sym_count);
267
268 for (unsigned i = 0; i != sym_count; ++i) {
269 lto_symbol_attributes attrs = lto_module_get_symbol_attribute(M, i);
270 if ((attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
271 continue;
272
273 cf.syms.push_back(ld_plugin_symbol());
274 ld_plugin_symbol &sym = cf.syms.back();
275 sym.name = const_cast<char *>(lto_module_get_symbol_name(M, i));
276 sym.name = strdup(sym.name);
277 sym.version = NULL;
278
279 int scope = attrs & LTO_SYMBOL_SCOPE_MASK;
280 switch (scope) {
281 case LTO_SYMBOL_SCOPE_HIDDEN:
282 sym.visibility = LDPV_HIDDEN;
283 break;
284 case LTO_SYMBOL_SCOPE_PROTECTED:
285 sym.visibility = LDPV_PROTECTED;
286 break;
287 case 0: // extern
288 case LTO_SYMBOL_SCOPE_DEFAULT:
289 sym.visibility = LDPV_DEFAULT;
290 break;
291 default:
292 (*message)(LDPL_ERROR, "Unknown scope attribute: %d", scope);
293 return LDPS_ERR;
294 }
295
296 int definition = attrs & LTO_SYMBOL_DEFINITION_MASK;
297 sym.comdat_key = NULL;
298 switch (definition) {
299 case LTO_SYMBOL_DEFINITION_REGULAR:
300 sym.def = LDPK_DEF;
301 break;
302 case LTO_SYMBOL_DEFINITION_UNDEFINED:
303 sym.def = LDPK_UNDEF;
304 break;
305 case LTO_SYMBOL_DEFINITION_TENTATIVE:
306 sym.def = LDPK_COMMON;
307 break;
308 case LTO_SYMBOL_DEFINITION_WEAK:
309 sym.comdat_key = sym.name;
310 sym.def = LDPK_WEAKDEF;
311 break;
312 case LTO_SYMBOL_DEFINITION_WEAKUNDEF:
313 sym.def = LDPK_WEAKUNDEF;
314 break;
315 default:
316 (*message)(LDPL_ERROR, "Unknown definition attribute: %d", definition);
317 return LDPS_ERR;
318 }
319
320 sym.size = 0;
321
322 sym.resolution = LDPR_UNKNOWN;
323 }
324
325 cf.syms.reserve(cf.syms.size());
326
327 if (!cf.syms.empty()) {
328 if ((*add_symbols)(cf.handle, cf.syms.size(), &cf.syms[0]) != LDPS_OK) {
329 (*message)(LDPL_ERROR, "Unable to add symbols!");
330 return LDPS_ERR;
331 }
332 }
333
334 if (code_gen)
335 lto_codegen_add_module(code_gen, M);
336
337 lto_module_dispose(M);
338
339 return LDPS_OK;
340 }
341
342 /// all_symbols_read_hook - gold informs us that all symbols have been read.
343 /// At this point, we use get_symbols to see if any of our definitions have
344 /// been overridden by a native object file. Then, perform optimization and
345 /// codegen.
all_symbols_read_hook(void)346 static ld_plugin_status all_symbols_read_hook(void) {
347 std::ofstream api_file;
348 assert(code_gen);
349
350 if (options::generate_api_file) {
351 api_file.open("apifile.txt", std::ofstream::out | std::ofstream::trunc);
352 if (!api_file.is_open()) {
353 (*message)(LDPL_FATAL, "Unable to open apifile.txt for writing.");
354 abort();
355 }
356 }
357
358 // If we don't preserve any symbols, libLTO will assume that all symbols are
359 // needed. Keep all symbols unless we're producing a final executable.
360 bool anySymbolsPreserved = false;
361 for (std::list<claimed_file>::iterator I = Modules.begin(),
362 E = Modules.end(); I != E; ++I) {
363 (*get_symbols)(I->handle, I->syms.size(), &I->syms[0]);
364 for (unsigned i = 0, e = I->syms.size(); i != e; i++) {
365 if (I->syms[i].resolution == LDPR_PREVAILING_DEF) {
366 lto_codegen_add_must_preserve_symbol(code_gen, I->syms[i].name);
367 anySymbolsPreserved = true;
368
369 if (options::generate_api_file)
370 api_file << I->syms[i].name << "\n";
371 }
372 }
373 }
374
375 if (options::generate_api_file)
376 api_file.close();
377
378 if (!anySymbolsPreserved) {
379 // All of the IL is unnecessary!
380 lto_codegen_dispose(code_gen);
381 return LDPS_OK;
382 }
383
384 lto_codegen_set_pic_model(code_gen, output_type);
385 lto_codegen_set_debug_model(code_gen, LTO_DEBUG_MODEL_DWARF);
386 if (!options::mcpu.empty())
387 lto_codegen_set_cpu(code_gen, options::mcpu.c_str());
388
389 // Pass through extra options to the code generator.
390 if (!options::extra.empty()) {
391 for (std::vector<std::string>::iterator it = options::extra.begin();
392 it != options::extra.end(); ++it) {
393 lto_codegen_debug_options(code_gen, (*it).c_str());
394 }
395 }
396
397 if (options::generate_bc_file != options::BC_NO) {
398 std::string path;
399 if (options::generate_bc_file == options::BC_ONLY)
400 path = output_name;
401 else if (!options::bc_path.empty())
402 path = options::bc_path;
403 else
404 path = output_name + ".bc";
405 bool err = lto_codegen_write_merged_modules(code_gen, path.c_str());
406 if (err)
407 (*message)(LDPL_FATAL, "Failed to write the output file.");
408 if (options::generate_bc_file == options::BC_ONLY)
409 exit(0);
410 }
411 const char *objPath;
412 if (lto_codegen_compile_to_file(code_gen, &objPath)) {
413 (*message)(LDPL_ERROR, "Could not produce a combined object file\n");
414 }
415
416 lto_codegen_dispose(code_gen);
417 for (std::list<claimed_file>::iterator I = Modules.begin(),
418 E = Modules.end(); I != E; ++I) {
419 for (unsigned i = 0; i != I->syms.size(); ++i) {
420 ld_plugin_symbol &sym = I->syms[i];
421 free(sym.name);
422 }
423 }
424
425 if ((*add_input_file)(objPath) != LDPS_OK) {
426 (*message)(LDPL_ERROR, "Unable to add .o file to the link.");
427 (*message)(LDPL_ERROR, "File left behind in: %s", objPath);
428 return LDPS_ERR;
429 }
430
431 if (!options::extra_library_path.empty() &&
432 set_extra_library_path(options::extra_library_path.c_str()) != LDPS_OK) {
433 (*message)(LDPL_ERROR, "Unable to set the extra library path.");
434 return LDPS_ERR;
435 }
436
437 if (options::obj_path.empty())
438 Cleanup.push_back(sys::Path(objPath));
439
440 return LDPS_OK;
441 }
442
cleanup_hook(void)443 static ld_plugin_status cleanup_hook(void) {
444 std::string ErrMsg;
445
446 for (int i = 0, e = Cleanup.size(); i != e; ++i)
447 if (Cleanup[i].eraseFromDisk(false, &ErrMsg))
448 (*message)(LDPL_ERROR, "Failed to delete '%s': %s", Cleanup[i].c_str(),
449 ErrMsg.c_str());
450
451 return LDPS_OK;
452 }
453