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" // plugin-api.h requires HAVE_STDINT_H
16 #include "plugin-api.h"
17
18 #include "llvm-c/lto.h"
19
20 #include "llvm/ADT/OwningPtr.h"
21 #include "llvm/Support/system_error.h"
22 #include "llvm/Support/MemoryBuffer.h"
23 #include "llvm/Support/ToolOutputFile.h"
24 #include "llvm/Support/Errno.h"
25 #include "llvm/Support/Path.h"
26 #include "llvm/Support/Program.h"
27
28 #include <cerrno>
29 #include <cstdlib>
30 #include <cstring>
31 #include <fstream>
32 #include <list>
33 #include <vector>
34
35 // Support Windows/MinGW crazyness.
36 #ifdef _WIN32
37 # include <io.h>
38 # define lseek _lseek
39 # define read _read
40 #endif
41
42 using namespace llvm;
43
44 namespace {
discard_message(int level,const char * format,...)45 ld_plugin_status discard_message(int level, const char *format, ...) {
46 // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
47 // callback in the transfer vector. This should never be called.
48 abort();
49 }
50
51 ld_plugin_add_symbols add_symbols = NULL;
52 ld_plugin_get_symbols get_symbols = NULL;
53 ld_plugin_add_input_file add_input_file = NULL;
54 ld_plugin_add_input_library add_input_library = NULL;
55 ld_plugin_set_extra_library_path set_extra_library_path = NULL;
56 ld_plugin_get_view get_view = NULL;
57 ld_plugin_message message = discard_message;
58
59 int api_version = 0;
60 int gold_version = 0;
61
62 struct claimed_file {
63 void *handle;
64 std::vector<ld_plugin_symbol> syms;
65 };
66
67 lto_codegen_model output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
68 std::string output_name = "";
69 std::list<claimed_file> Modules;
70 std::vector<sys::Path> Cleanup;
71 lto_code_gen_t code_gen = NULL;
72 }
73
74 namespace options {
75 enum generate_bc { BC_NO, BC_ALSO, BC_ONLY };
76 static bool generate_api_file = false;
77 static generate_bc generate_bc_file = BC_NO;
78 static std::string bc_path;
79 static std::string obj_path;
80 static std::string extra_library_path;
81 static std::string triple;
82 static std::string mcpu;
83 // Additional options to pass into the code generator.
84 // Note: This array will contain all plugin options which are not claimed
85 // as plugin exclusive to pass to the code generator.
86 // For example, "generate-api-file" and "as"options are for the plugin
87 // use only and will not be passed.
88 static std::vector<std::string> extra;
89
process_plugin_option(const char * opt_)90 static void process_plugin_option(const char* opt_)
91 {
92 if (opt_ == NULL)
93 return;
94 llvm::StringRef opt = opt_;
95
96 if (opt == "generate-api-file") {
97 generate_api_file = true;
98 } else if (opt.startswith("mcpu=")) {
99 mcpu = opt.substr(strlen("mcpu="));
100 } else if (opt.startswith("extra-library-path=")) {
101 extra_library_path = opt.substr(strlen("extra_library_path="));
102 } else if (opt.startswith("mtriple=")) {
103 triple = opt.substr(strlen("mtriple="));
104 } else if (opt.startswith("obj-path=")) {
105 obj_path = opt.substr(strlen("obj-path="));
106 } else if (opt == "emit-llvm") {
107 generate_bc_file = BC_ONLY;
108 } else if (opt == "also-emit-llvm") {
109 generate_bc_file = BC_ALSO;
110 } else if (opt.startswith("also-emit-llvm=")) {
111 llvm::StringRef path = opt.substr(strlen("also-emit-llvm="));
112 generate_bc_file = BC_ALSO;
113 if (!bc_path.empty()) {
114 (*message)(LDPL_WARNING, "Path to the output IL file specified twice. "
115 "Discarding %s", opt_);
116 } else {
117 bc_path = path;
118 }
119 } else {
120 // Save this option to pass to the code generator.
121 extra.push_back(opt);
122 }
123 }
124 }
125
126 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
127 int *claimed);
128 static ld_plugin_status all_symbols_read_hook(void);
129 static ld_plugin_status cleanup_hook(void);
130
131 extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
onload(ld_plugin_tv * tv)132 ld_plugin_status onload(ld_plugin_tv *tv) {
133 // We're given a pointer to the first transfer vector. We read through them
134 // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
135 // contain pointers to functions that we need to call to register our own
136 // hooks. The others are addresses of functions we can use to call into gold
137 // for services.
138
139 bool registeredClaimFile = false;
140
141 for (; tv->tv_tag != LDPT_NULL; ++tv) {
142 switch (tv->tv_tag) {
143 case LDPT_API_VERSION:
144 api_version = tv->tv_u.tv_val;
145 break;
146 case LDPT_GOLD_VERSION: // major * 100 + minor
147 gold_version = tv->tv_u.tv_val;
148 break;
149 case LDPT_OUTPUT_NAME:
150 output_name = tv->tv_u.tv_string;
151 break;
152 case LDPT_LINKER_OUTPUT:
153 switch (tv->tv_u.tv_val) {
154 case LDPO_REL: // .o
155 case LDPO_DYN: // .so
156 // FIXME: Replace 3 with LDPO_PIE once that is in a released binutils.
157 case 3: // position independent executable
158 output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC;
159 break;
160 case LDPO_EXEC: // .exe
161 output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
162 break;
163 default:
164 (*message)(LDPL_ERROR, "Unknown output file type %d",
165 tv->tv_u.tv_val);
166 return LDPS_ERR;
167 }
168 // TODO: add an option to disable PIC.
169 //output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC;
170 break;
171 case LDPT_OPTION:
172 options::process_plugin_option(tv->tv_u.tv_string);
173 break;
174 case LDPT_REGISTER_CLAIM_FILE_HOOK: {
175 ld_plugin_register_claim_file callback;
176 callback = tv->tv_u.tv_register_claim_file;
177
178 if ((*callback)(claim_file_hook) != LDPS_OK)
179 return LDPS_ERR;
180
181 registeredClaimFile = true;
182 } break;
183 case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
184 ld_plugin_register_all_symbols_read callback;
185 callback = tv->tv_u.tv_register_all_symbols_read;
186
187 if ((*callback)(all_symbols_read_hook) != LDPS_OK)
188 return LDPS_ERR;
189
190 code_gen = lto_codegen_create();
191 } break;
192 case LDPT_REGISTER_CLEANUP_HOOK: {
193 ld_plugin_register_cleanup callback;
194 callback = tv->tv_u.tv_register_cleanup;
195
196 if ((*callback)(cleanup_hook) != LDPS_OK)
197 return LDPS_ERR;
198 } break;
199 case LDPT_ADD_SYMBOLS:
200 add_symbols = tv->tv_u.tv_add_symbols;
201 break;
202 case LDPT_GET_SYMBOLS:
203 get_symbols = tv->tv_u.tv_get_symbols;
204 break;
205 case LDPT_ADD_INPUT_FILE:
206 add_input_file = tv->tv_u.tv_add_input_file;
207 break;
208 case LDPT_ADD_INPUT_LIBRARY:
209 add_input_library = tv->tv_u.tv_add_input_file;
210 break;
211 case LDPT_SET_EXTRA_LIBRARY_PATH:
212 set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
213 break;
214 case LDPT_GET_VIEW:
215 get_view = tv->tv_u.tv_get_view;
216 break;
217 case LDPT_MESSAGE:
218 message = tv->tv_u.tv_message;
219 break;
220 default:
221 break;
222 }
223 }
224
225 if (!registeredClaimFile) {
226 (*message)(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
227 return LDPS_ERR;
228 }
229 if (!add_symbols) {
230 (*message)(LDPL_ERROR, "add_symbols not passed to LLVMgold.");
231 return LDPS_ERR;
232 }
233
234 return LDPS_OK;
235 }
236
237 /// claim_file_hook - called by gold to see whether this file is one that
238 /// our plugin can handle. We'll try to open it and register all the symbols
239 /// with add_symbol if possible.
claim_file_hook(const ld_plugin_input_file * file,int * claimed)240 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
241 int *claimed) {
242 lto_module_t M;
243 const void *view;
244 OwningPtr<MemoryBuffer> buffer;
245 if (get_view) {
246 if (get_view(file->handle, &view) != LDPS_OK) {
247 (*message)(LDPL_ERROR, "Failed to get a view of %s", file->name);
248 return LDPS_ERR;
249 }
250 } else {
251 int64_t offset = 0;
252 // Gold has found what might be IR part-way inside of a file, such as
253 // an .a archive.
254 if (file->offset) {
255 offset = file->offset;
256 }
257 if (error_code ec =
258 MemoryBuffer::getOpenFile(file->fd, file->name, buffer, file->filesize,
259 -1, offset, false)) {
260 (*message)(LDPL_ERROR, ec.message().c_str());
261 return LDPS_ERR;
262 }
263 view = buffer->getBufferStart();
264 }
265
266 if (!lto_module_is_object_file_in_memory(view, file->filesize))
267 return LDPS_OK;
268
269 M = lto_module_create_from_memory(view, file->filesize);
270 if (!M) {
271 if (const char* msg = lto_get_error_message()) {
272 (*message)(LDPL_ERROR,
273 "LLVM gold plugin has failed to create LTO module: %s",
274 msg);
275 return LDPS_ERR;
276 }
277 return LDPS_OK;
278 }
279
280 *claimed = 1;
281 Modules.resize(Modules.size() + 1);
282 claimed_file &cf = Modules.back();
283
284 if (!options::triple.empty())
285 lto_module_set_target_triple(M, options::triple.c_str());
286
287 cf.handle = file->handle;
288 unsigned sym_count = lto_module_get_num_symbols(M);
289 cf.syms.reserve(sym_count);
290
291 for (unsigned i = 0; i != sym_count; ++i) {
292 lto_symbol_attributes attrs = lto_module_get_symbol_attribute(M, i);
293 if ((attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
294 continue;
295
296 cf.syms.push_back(ld_plugin_symbol());
297 ld_plugin_symbol &sym = cf.syms.back();
298 sym.name = const_cast<char *>(lto_module_get_symbol_name(M, i));
299 sym.name = strdup(sym.name);
300 sym.version = NULL;
301
302 int scope = attrs & LTO_SYMBOL_SCOPE_MASK;
303 switch (scope) {
304 case LTO_SYMBOL_SCOPE_HIDDEN:
305 sym.visibility = LDPV_HIDDEN;
306 break;
307 case LTO_SYMBOL_SCOPE_PROTECTED:
308 sym.visibility = LDPV_PROTECTED;
309 break;
310 case 0: // extern
311 case LTO_SYMBOL_SCOPE_DEFAULT:
312 sym.visibility = LDPV_DEFAULT;
313 break;
314 default:
315 (*message)(LDPL_ERROR, "Unknown scope attribute: %d", scope);
316 return LDPS_ERR;
317 }
318
319 int definition = attrs & LTO_SYMBOL_DEFINITION_MASK;
320 sym.comdat_key = NULL;
321 switch (definition) {
322 case LTO_SYMBOL_DEFINITION_REGULAR:
323 sym.def = LDPK_DEF;
324 break;
325 case LTO_SYMBOL_DEFINITION_UNDEFINED:
326 sym.def = LDPK_UNDEF;
327 break;
328 case LTO_SYMBOL_DEFINITION_TENTATIVE:
329 sym.def = LDPK_COMMON;
330 break;
331 case LTO_SYMBOL_DEFINITION_WEAK:
332 sym.comdat_key = sym.name;
333 sym.def = LDPK_WEAKDEF;
334 break;
335 case LTO_SYMBOL_DEFINITION_WEAKUNDEF:
336 sym.def = LDPK_WEAKUNDEF;
337 break;
338 default:
339 (*message)(LDPL_ERROR, "Unknown definition attribute: %d", definition);
340 return LDPS_ERR;
341 }
342
343 sym.size = 0;
344
345 sym.resolution = LDPR_UNKNOWN;
346 }
347
348 cf.syms.reserve(cf.syms.size());
349
350 if (!cf.syms.empty()) {
351 if ((*add_symbols)(cf.handle, cf.syms.size(), &cf.syms[0]) != LDPS_OK) {
352 (*message)(LDPL_ERROR, "Unable to add symbols!");
353 return LDPS_ERR;
354 }
355 }
356
357 if (code_gen)
358 lto_codegen_add_module(code_gen, M);
359
360 lto_module_dispose(M);
361
362 return LDPS_OK;
363 }
364
365 /// all_symbols_read_hook - gold informs us that all symbols have been read.
366 /// At this point, we use get_symbols to see if any of our definitions have
367 /// been overridden by a native object file. Then, perform optimization and
368 /// codegen.
all_symbols_read_hook(void)369 static ld_plugin_status all_symbols_read_hook(void) {
370 std::ofstream api_file;
371 assert(code_gen);
372
373 if (options::generate_api_file) {
374 api_file.open("apifile.txt", std::ofstream::out | std::ofstream::trunc);
375 if (!api_file.is_open()) {
376 (*message)(LDPL_FATAL, "Unable to open apifile.txt for writing.");
377 abort();
378 }
379 }
380
381 // If we don't preserve any symbols, libLTO will assume that all symbols are
382 // needed. Keep all symbols unless we're producing a final executable.
383 bool anySymbolsPreserved = false;
384 for (std::list<claimed_file>::iterator I = Modules.begin(),
385 E = Modules.end(); I != E; ++I) {
386 if (I->syms.empty())
387 continue;
388 (*get_symbols)(I->handle, I->syms.size(), &I->syms[0]);
389 for (unsigned i = 0, e = I->syms.size(); i != e; i++) {
390 if (I->syms[i].resolution == LDPR_PREVAILING_DEF) {
391 lto_codegen_add_must_preserve_symbol(code_gen, I->syms[i].name);
392 anySymbolsPreserved = true;
393
394 if (options::generate_api_file)
395 api_file << I->syms[i].name << "\n";
396 }
397 }
398 }
399
400 if (options::generate_api_file)
401 api_file.close();
402
403 if (!anySymbolsPreserved) {
404 // All of the IL is unnecessary!
405 lto_codegen_dispose(code_gen);
406 return LDPS_OK;
407 }
408
409 lto_codegen_set_pic_model(code_gen, output_type);
410 lto_codegen_set_debug_model(code_gen, LTO_DEBUG_MODEL_DWARF);
411 if (!options::mcpu.empty())
412 lto_codegen_set_cpu(code_gen, options::mcpu.c_str());
413
414 // Pass through extra options to the code generator.
415 if (!options::extra.empty()) {
416 for (std::vector<std::string>::iterator it = options::extra.begin();
417 it != options::extra.end(); ++it) {
418 lto_codegen_debug_options(code_gen, (*it).c_str());
419 }
420 }
421
422 if (options::generate_bc_file != options::BC_NO) {
423 std::string path;
424 if (options::generate_bc_file == options::BC_ONLY)
425 path = output_name;
426 else if (!options::bc_path.empty())
427 path = options::bc_path;
428 else
429 path = output_name + ".bc";
430 bool err = lto_codegen_write_merged_modules(code_gen, path.c_str());
431 if (err)
432 (*message)(LDPL_FATAL, "Failed to write the output file.");
433 if (options::generate_bc_file == options::BC_ONLY)
434 exit(0);
435 }
436 const char *objPath;
437 if (lto_codegen_compile_to_file(code_gen, &objPath)) {
438 (*message)(LDPL_ERROR, "Could not produce a combined object file\n");
439 }
440
441 lto_codegen_dispose(code_gen);
442 for (std::list<claimed_file>::iterator I = Modules.begin(),
443 E = Modules.end(); I != E; ++I) {
444 for (unsigned i = 0; i != I->syms.size(); ++i) {
445 ld_plugin_symbol &sym = I->syms[i];
446 free(sym.name);
447 }
448 }
449
450 if ((*add_input_file)(objPath) != LDPS_OK) {
451 (*message)(LDPL_ERROR, "Unable to add .o file to the link.");
452 (*message)(LDPL_ERROR, "File left behind in: %s", objPath);
453 return LDPS_ERR;
454 }
455
456 if (!options::extra_library_path.empty() &&
457 set_extra_library_path(options::extra_library_path.c_str()) != LDPS_OK) {
458 (*message)(LDPL_ERROR, "Unable to set the extra library path.");
459 return LDPS_ERR;
460 }
461
462 if (options::obj_path.empty())
463 Cleanup.push_back(sys::Path(objPath));
464
465 return LDPS_OK;
466 }
467
cleanup_hook(void)468 static ld_plugin_status cleanup_hook(void) {
469 std::string ErrMsg;
470
471 for (int i = 0, e = Cleanup.size(); i != e; ++i)
472 if (Cleanup[i].eraseFromDisk(false, &ErrMsg))
473 (*message)(LDPL_ERROR, "Failed to delete '%s': %s", Cleanup[i].c_str(),
474 ErrMsg.c_str());
475
476 return LDPS_OK;
477 }
478