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 "llvm-c/lto.h"
17 #include "llvm/ADT/StringSet.h"
18 #include "llvm/CodeGen/CommandFlags.h"
19 #include "llvm/LTO/LTOCodeGenerator.h"
20 #include "llvm/LTO/LTOModule.h"
21 #include "llvm/Support/Errno.h"
22 #include "llvm/Support/FileSystem.h"
23 #include "llvm/Support/MemoryBuffer.h"
24 #include "llvm/Support/Path.h"
25 #include "llvm/Support/Program.h"
26 #include "llvm/Support/TargetSelect.h"
27 #include "llvm/Support/ToolOutputFile.h"
28 #include <cerrno>
29 #include <cstdlib>
30 #include <cstring>
31 #include <list>
32 #include <plugin-api.h>
33 #include <system_error>
34 #include <vector>
35
36 // Support Windows/MinGW crazyness.
37 #ifdef _WIN32
38 # include <io.h>
39 # define lseek _lseek
40 # define read _read
41 #endif
42
43 #ifndef LDPO_PIE
44 // FIXME: remove this declaration when we stop maintaining Ubuntu Quantal and
45 // Precise and Debian Wheezy (binutils 2.23 is required)
46 # define LDPO_PIE 3
47 #endif
48
49 using namespace llvm;
50
51 namespace {
52 struct claimed_file {
53 void *handle;
54 std::vector<ld_plugin_symbol> syms;
55 };
56 }
57
discard_message(int level,const char * format,...)58 static ld_plugin_status discard_message(int level, const char *format, ...) {
59 // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
60 // callback in the transfer vector. This should never be called.
61 abort();
62 }
63
64 static ld_plugin_add_symbols add_symbols = NULL;
65 static ld_plugin_get_symbols get_symbols = NULL;
66 static ld_plugin_add_input_file add_input_file = NULL;
67 static ld_plugin_set_extra_library_path set_extra_library_path = NULL;
68 static ld_plugin_get_view get_view = NULL;
69 static ld_plugin_message message = discard_message;
70 static lto_codegen_model output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
71 static std::string output_name = "";
72 static std::list<claimed_file> Modules;
73 static std::vector<std::string> Cleanup;
74 static LTOCodeGenerator *CodeGen = nullptr;
75 static StringSet<> CannotBeHidden;
76 static llvm::TargetOptions TargetOpts;
77
78 namespace options {
79 enum generate_bc { BC_NO, BC_ALSO, BC_ONLY };
80 static bool generate_api_file = false;
81 static generate_bc generate_bc_file = BC_NO;
82 static std::string bc_path;
83 static std::string obj_path;
84 static std::string extra_library_path;
85 static std::string triple;
86 static std::string mcpu;
87 // Additional options to pass into the code generator.
88 // Note: This array will contain all plugin options which are not claimed
89 // as plugin exclusive to pass to the code generator.
90 // For example, "generate-api-file" and "as"options are for the plugin
91 // use only and will not be passed.
92 static std::vector<std::string> extra;
93
process_plugin_option(const char * opt_)94 static void process_plugin_option(const char* opt_)
95 {
96 if (opt_ == NULL)
97 return;
98 llvm::StringRef opt = opt_;
99
100 if (opt == "generate-api-file") {
101 generate_api_file = true;
102 } else if (opt.startswith("mcpu=")) {
103 mcpu = opt.substr(strlen("mcpu="));
104 } else if (opt.startswith("extra-library-path=")) {
105 extra_library_path = opt.substr(strlen("extra_library_path="));
106 } else if (opt.startswith("mtriple=")) {
107 triple = opt.substr(strlen("mtriple="));
108 } else if (opt.startswith("obj-path=")) {
109 obj_path = opt.substr(strlen("obj-path="));
110 } else if (opt == "emit-llvm") {
111 generate_bc_file = BC_ONLY;
112 } else if (opt == "also-emit-llvm") {
113 generate_bc_file = BC_ALSO;
114 } else if (opt.startswith("also-emit-llvm=")) {
115 llvm::StringRef path = opt.substr(strlen("also-emit-llvm="));
116 generate_bc_file = BC_ALSO;
117 if (!bc_path.empty()) {
118 (*message)(LDPL_WARNING, "Path to the output IL file specified twice. "
119 "Discarding %s", opt_);
120 } else {
121 bc_path = path;
122 }
123 } else {
124 // Save this option to pass to the code generator.
125 extra.push_back(opt);
126 }
127 }
128 }
129
130 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
131 int *claimed);
132 static ld_plugin_status all_symbols_read_hook(void);
133 static ld_plugin_status cleanup_hook(void);
134
135 extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
onload(ld_plugin_tv * tv)136 ld_plugin_status onload(ld_plugin_tv *tv) {
137 InitializeAllTargetInfos();
138 InitializeAllTargets();
139 InitializeAllTargetMCs();
140 InitializeAllAsmParsers();
141 InitializeAllAsmPrinters();
142
143 // We're given a pointer to the first transfer vector. We read through them
144 // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
145 // contain pointers to functions that we need to call to register our own
146 // hooks. The others are addresses of functions we can use to call into gold
147 // for services.
148
149 bool registeredClaimFile = false;
150 bool RegisteredAllSymbolsRead = false;
151
152 for (; tv->tv_tag != LDPT_NULL; ++tv) {
153 switch (tv->tv_tag) {
154 case LDPT_OUTPUT_NAME:
155 output_name = tv->tv_u.tv_string;
156 break;
157 case LDPT_LINKER_OUTPUT:
158 switch (tv->tv_u.tv_val) {
159 case LDPO_REL: // .o
160 case LDPO_DYN: // .so
161 case LDPO_PIE: // position independent executable
162 output_type = LTO_CODEGEN_PIC_MODEL_DYNAMIC;
163 break;
164 case LDPO_EXEC: // .exe
165 output_type = LTO_CODEGEN_PIC_MODEL_STATIC;
166 break;
167 default:
168 (*message)(LDPL_ERROR, "Unknown output file type %d",
169 tv->tv_u.tv_val);
170 return LDPS_ERR;
171 }
172 break;
173 case LDPT_OPTION:
174 options::process_plugin_option(tv->tv_u.tv_string);
175 break;
176 case LDPT_REGISTER_CLAIM_FILE_HOOK: {
177 ld_plugin_register_claim_file callback;
178 callback = tv->tv_u.tv_register_claim_file;
179
180 if ((*callback)(claim_file_hook) != LDPS_OK)
181 return LDPS_ERR;
182
183 registeredClaimFile = true;
184 } break;
185 case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
186 ld_plugin_register_all_symbols_read callback;
187 callback = tv->tv_u.tv_register_all_symbols_read;
188
189 if ((*callback)(all_symbols_read_hook) != LDPS_OK)
190 return LDPS_ERR;
191
192 RegisteredAllSymbolsRead = true;
193 } break;
194 case LDPT_REGISTER_CLEANUP_HOOK: {
195 ld_plugin_register_cleanup callback;
196 callback = tv->tv_u.tv_register_cleanup;
197
198 if ((*callback)(cleanup_hook) != LDPS_OK)
199 return LDPS_ERR;
200 } break;
201 case LDPT_ADD_SYMBOLS:
202 add_symbols = tv->tv_u.tv_add_symbols;
203 break;
204 case LDPT_GET_SYMBOLS_V2:
205 get_symbols = tv->tv_u.tv_get_symbols;
206 break;
207 case LDPT_ADD_INPUT_FILE:
208 add_input_file = tv->tv_u.tv_add_input_file;
209 break;
210 case LDPT_SET_EXTRA_LIBRARY_PATH:
211 set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
212 break;
213 case LDPT_GET_VIEW:
214 get_view = tv->tv_u.tv_get_view;
215 break;
216 case LDPT_MESSAGE:
217 message = tv->tv_u.tv_message;
218 break;
219 default:
220 break;
221 }
222 }
223
224 if (!registeredClaimFile) {
225 (*message)(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
226 return LDPS_ERR;
227 }
228 if (!add_symbols) {
229 (*message)(LDPL_ERROR, "add_symbols not passed to LLVMgold.");
230 return LDPS_ERR;
231 }
232
233 if (!RegisteredAllSymbolsRead)
234 return LDPS_OK;
235
236 CodeGen = new LTOCodeGenerator();
237
238 // Pass through extra options to the code generator.
239 if (!options::extra.empty()) {
240 for (std::vector<std::string>::iterator it = options::extra.begin();
241 it != options::extra.end(); ++it) {
242 CodeGen->setCodeGenDebugOptions((*it).c_str());
243 }
244 }
245
246 CodeGen->parseCodeGenDebugOptions();
247 if (MAttrs.size()) {
248 std::string Attrs;
249 for (unsigned I = 0; I < MAttrs.size(); ++I) {
250 if (I > 0)
251 Attrs.append(",");
252 Attrs.append(MAttrs[I]);
253 }
254 CodeGen->setAttr(Attrs.c_str());
255 }
256
257 TargetOpts = InitTargetOptionsFromCodeGenFlags();
258 CodeGen->setTargetOptions(TargetOpts);
259
260 return LDPS_OK;
261 }
262
263 /// Called by gold to see whether this file is one that our plugin can handle.
264 /// We'll try to open it and register all the symbols with add_symbol if
265 /// possible.
claim_file_hook(const ld_plugin_input_file * file,int * claimed)266 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
267 int *claimed) {
268 const void *view;
269 std::unique_ptr<MemoryBuffer> buffer;
270 if (get_view) {
271 if (get_view(file->handle, &view) != LDPS_OK) {
272 (*message)(LDPL_ERROR, "Failed to get a view of %s", file->name);
273 return LDPS_ERR;
274 }
275 } else {
276 int64_t offset = 0;
277 // Gold has found what might be IR part-way inside of a file, such as
278 // an .a archive.
279 if (file->offset) {
280 offset = file->offset;
281 }
282 ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
283 MemoryBuffer::getOpenFileSlice(file->fd, file->name, file->filesize,
284 offset);
285 if (std::error_code EC = BufferOrErr.getError()) {
286 (*message)(LDPL_ERROR, EC.message().c_str());
287 return LDPS_ERR;
288 }
289 buffer = std::move(BufferOrErr.get());
290 view = buffer->getBufferStart();
291 }
292
293 if (!LTOModule::isBitcodeFile(view, file->filesize))
294 return LDPS_OK;
295
296 std::string Error;
297 LTOModule *M =
298 LTOModule::createFromBuffer(view, file->filesize, TargetOpts, Error);
299 if (!M) {
300 (*message)(LDPL_ERROR,
301 "LLVM gold plugin has failed to create LTO module: %s",
302 Error.c_str());
303 return LDPS_OK;
304 }
305
306 *claimed = 1;
307 Modules.resize(Modules.size() + 1);
308 claimed_file &cf = Modules.back();
309
310 if (!options::triple.empty())
311 M->setTargetTriple(options::triple.c_str());
312
313 cf.handle = file->handle;
314 unsigned sym_count = M->getSymbolCount();
315 cf.syms.reserve(sym_count);
316
317 for (unsigned i = 0; i != sym_count; ++i) {
318 lto_symbol_attributes attrs = M->getSymbolAttributes(i);
319 if ((attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
320 continue;
321
322 cf.syms.push_back(ld_plugin_symbol());
323 ld_plugin_symbol &sym = cf.syms.back();
324 sym.name = strdup(M->getSymbolName(i));
325 sym.version = NULL;
326
327 int scope = attrs & LTO_SYMBOL_SCOPE_MASK;
328 bool CanBeHidden = scope == LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN;
329 if (!CanBeHidden)
330 CannotBeHidden.insert(sym.name);
331 switch (scope) {
332 case LTO_SYMBOL_SCOPE_HIDDEN:
333 sym.visibility = LDPV_HIDDEN;
334 break;
335 case LTO_SYMBOL_SCOPE_PROTECTED:
336 sym.visibility = LDPV_PROTECTED;
337 break;
338 case 0: // extern
339 case LTO_SYMBOL_SCOPE_DEFAULT:
340 case LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN:
341 sym.visibility = LDPV_DEFAULT;
342 break;
343 default:
344 (*message)(LDPL_ERROR, "Unknown scope attribute: %d", scope);
345 return LDPS_ERR;
346 }
347
348 int definition = attrs & LTO_SYMBOL_DEFINITION_MASK;
349 sym.comdat_key = NULL;
350 switch (definition) {
351 case LTO_SYMBOL_DEFINITION_REGULAR:
352 sym.def = LDPK_DEF;
353 break;
354 case LTO_SYMBOL_DEFINITION_UNDEFINED:
355 sym.def = LDPK_UNDEF;
356 break;
357 case LTO_SYMBOL_DEFINITION_TENTATIVE:
358 sym.def = LDPK_COMMON;
359 break;
360 case LTO_SYMBOL_DEFINITION_WEAK:
361 sym.comdat_key = sym.name;
362 sym.def = LDPK_WEAKDEF;
363 break;
364 case LTO_SYMBOL_DEFINITION_WEAKUNDEF:
365 sym.def = LDPK_WEAKUNDEF;
366 break;
367 default:
368 (*message)(LDPL_ERROR, "Unknown definition attribute: %d", definition);
369 return LDPS_ERR;
370 }
371
372 sym.size = 0;
373
374 sym.resolution = LDPR_UNKNOWN;
375 }
376
377 cf.syms.reserve(cf.syms.size());
378
379 if (!cf.syms.empty()) {
380 if ((*add_symbols)(cf.handle, cf.syms.size(), &cf.syms[0]) != LDPS_OK) {
381 (*message)(LDPL_ERROR, "Unable to add symbols!");
382 return LDPS_ERR;
383 }
384 }
385
386 if (CodeGen) {
387 std::string Error;
388 if (!CodeGen->addModule(M, Error)) {
389 (*message)(LDPL_ERROR, "Error linking module: %s", Error.c_str());
390 return LDPS_ERR;
391 }
392 }
393
394 delete M;
395
396 return LDPS_OK;
397 }
398
mustPreserve(const claimed_file & F,int i)399 static bool mustPreserve(const claimed_file &F, int i) {
400 if (F.syms[i].resolution == LDPR_PREVAILING_DEF)
401 return true;
402 if (F.syms[i].resolution == LDPR_PREVAILING_DEF_IRONLY_EXP)
403 return CannotBeHidden.count(F.syms[i].name);
404 return false;
405 }
406
407 /// all_symbols_read_hook - gold informs us that all symbols have been read.
408 /// At this point, we use get_symbols to see if any of our definitions have
409 /// been overridden by a native object file. Then, perform optimization and
410 /// codegen.
all_symbols_read_hook(void)411 static ld_plugin_status all_symbols_read_hook(void) {
412 // FIXME: raw_fd_ostream should be able to represent an unopened file.
413 std::unique_ptr<raw_fd_ostream> api_file;
414
415 assert(CodeGen);
416
417 if (options::generate_api_file) {
418 std::string Error;
419 api_file.reset(new raw_fd_ostream("apifile.txt", Error, sys::fs::F_None));
420 if (!Error.empty())
421 (*message)(LDPL_FATAL, "Unable to open apifile.txt for writing: %s",
422 Error.c_str());
423 }
424
425 for (std::list<claimed_file>::iterator I = Modules.begin(),
426 E = Modules.end(); I != E; ++I) {
427 if (I->syms.empty())
428 continue;
429 (*get_symbols)(I->handle, I->syms.size(), &I->syms[0]);
430 for (unsigned i = 0, e = I->syms.size(); i != e; i++) {
431 if (mustPreserve(*I, i)) {
432 CodeGen->addMustPreserveSymbol(I->syms[i].name);
433
434 if (options::generate_api_file)
435 (*api_file) << I->syms[i].name << "\n";
436 }
437 }
438 }
439
440 CodeGen->setCodePICModel(output_type);
441 CodeGen->setDebugInfo(LTO_DEBUG_MODEL_DWARF);
442 if (!options::mcpu.empty())
443 CodeGen->setCpu(options::mcpu.c_str());
444
445 if (options::generate_bc_file != options::BC_NO) {
446 std::string path;
447 if (options::generate_bc_file == options::BC_ONLY)
448 path = output_name;
449 else if (!options::bc_path.empty())
450 path = options::bc_path;
451 else
452 path = output_name + ".bc";
453 std::string Error;
454 if (!CodeGen->writeMergedModules(path.c_str(), Error))
455 (*message)(LDPL_FATAL, "Failed to write the output file.");
456 if (options::generate_bc_file == options::BC_ONLY) {
457 delete CodeGen;
458 exit(0);
459 }
460 }
461
462 std::string ObjPath;
463 {
464 const char *Temp;
465 std::string Error;
466 if (!CodeGen->compile_to_file(&Temp, /*DisableOpt*/ false, /*DisableInline*/
467 false, /*DisableGVNLoadPRE*/ false, Error))
468 (*message)(LDPL_ERROR, "Could not produce a combined object file\n");
469 ObjPath = Temp;
470 }
471
472 delete CodeGen;
473 for (std::list<claimed_file>::iterator I = Modules.begin(),
474 E = Modules.end(); I != E; ++I) {
475 for (unsigned i = 0; i != I->syms.size(); ++i) {
476 ld_plugin_symbol &sym = I->syms[i];
477 free(sym.name);
478 }
479 }
480
481 if ((*add_input_file)(ObjPath.c_str()) != LDPS_OK) {
482 (*message)(LDPL_ERROR, "Unable to add .o file to the link.");
483 (*message)(LDPL_ERROR, "File left behind in: %s", ObjPath.c_str());
484 return LDPS_ERR;
485 }
486
487 if (!options::extra_library_path.empty() &&
488 set_extra_library_path(options::extra_library_path.c_str()) != LDPS_OK) {
489 (*message)(LDPL_ERROR, "Unable to set the extra library path.");
490 return LDPS_ERR;
491 }
492
493 if (options::obj_path.empty())
494 Cleanup.push_back(ObjPath);
495
496 return LDPS_OK;
497 }
498
cleanup_hook(void)499 static ld_plugin_status cleanup_hook(void) {
500 for (int i = 0, e = Cleanup.size(); i != e; ++i) {
501 std::error_code EC = sys::fs::remove(Cleanup[i]);
502 if (EC)
503 (*message)(LDPL_ERROR, "Failed to delete '%s': %s", Cleanup[i].c_str(),
504 EC.message().c_str());
505 }
506
507 return LDPS_OK;
508 }
509