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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