1 //===- IRSymtab.cpp - implementation of IR symbol tables ------------------===// 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 #include "llvm/Object/IRSymtab.h" 11 #include "llvm/ADT/ArrayRef.h" 12 #include "llvm/ADT/DenseMap.h" 13 #include "llvm/ADT/SmallPtrSet.h" 14 #include "llvm/ADT/SmallString.h" 15 #include "llvm/ADT/SmallVector.h" 16 #include "llvm/ADT/StringRef.h" 17 #include "llvm/ADT/Triple.h" 18 #include "llvm/Config/llvm-config.h" 19 #include "llvm/IR/Comdat.h" 20 #include "llvm/IR/DataLayout.h" 21 #include "llvm/IR/GlobalAlias.h" 22 #include "llvm/IR/GlobalObject.h" 23 #include "llvm/IR/Mangler.h" 24 #include "llvm/IR/Metadata.h" 25 #include "llvm/IR/Module.h" 26 #include "llvm/Bitcode/BitcodeReader.h" 27 #include "llvm/MC/StringTableBuilder.h" 28 #include "llvm/Object/IRObjectFile.h" 29 #include "llvm/Object/ModuleSymbolTable.h" 30 #include "llvm/Object/SymbolicFile.h" 31 #include "llvm/Support/Allocator.h" 32 #include "llvm/Support/Casting.h" 33 #include "llvm/Support/Error.h" 34 #include "llvm/Support/StringSaver.h" 35 #include "llvm/Support/VCSRevision.h" 36 #include "llvm/Support/raw_ostream.h" 37 #include <cassert> 38 #include <string> 39 #include <utility> 40 #include <vector> 41 42 using namespace llvm; 43 using namespace irsymtab; 44 45 static const char *LibcallRoutineNames[] = { 46 #define HANDLE_LIBCALL(code, name) name, 47 #include "llvm/IR/RuntimeLibcalls.def" 48 #undef HANDLE_LIBCALL 49 }; 50 51 namespace { 52 53 const char *getExpectedProducerName() { 54 static char DefaultName[] = LLVM_VERSION_STRING 55 #ifdef LLVM_REVISION 56 " " LLVM_REVISION 57 #endif 58 ; 59 // Allows for testing of the irsymtab writer and upgrade mechanism. This 60 // environment variable should not be set by users. 61 if (char *OverrideName = getenv("LLVM_OVERRIDE_PRODUCER")) 62 return OverrideName; 63 return DefaultName; 64 } 65 66 const char *kExpectedProducerName = getExpectedProducerName(); 67 68 /// Stores the temporary state that is required to build an IR symbol table. 69 struct Builder { 70 SmallVector<char, 0> &Symtab; 71 StringTableBuilder &StrtabBuilder; 72 StringSaver Saver; 73 74 // This ctor initializes a StringSaver using the passed in BumpPtrAllocator. 75 // The StringTableBuilder does not create a copy of any strings added to it, 76 // so this provides somewhere to store any strings that we create. 77 Builder(SmallVector<char, 0> &Symtab, StringTableBuilder &StrtabBuilder, 78 BumpPtrAllocator &Alloc) 79 : Symtab(Symtab), StrtabBuilder(StrtabBuilder), Saver(Alloc) {} 80 81 DenseMap<const Comdat *, int> ComdatMap; 82 Mangler Mang; 83 Triple TT; 84 85 std::vector<storage::Comdat> Comdats; 86 std::vector<storage::Module> Mods; 87 std::vector<storage::Symbol> Syms; 88 std::vector<storage::Uncommon> Uncommons; 89 90 std::string COFFLinkerOpts; 91 raw_string_ostream COFFLinkerOptsOS{COFFLinkerOpts}; 92 93 void setStr(storage::Str &S, StringRef Value) { 94 S.Offset = StrtabBuilder.add(Value); 95 S.Size = Value.size(); 96 } 97 98 template <typename T> 99 void writeRange(storage::Range<T> &R, const std::vector<T> &Objs) { 100 R.Offset = Symtab.size(); 101 R.Size = Objs.size(); 102 Symtab.insert(Symtab.end(), reinterpret_cast<const char *>(Objs.data()), 103 reinterpret_cast<const char *>(Objs.data() + Objs.size())); 104 } 105 106 Expected<int> getComdatIndex(const Comdat *C, const Module *M); 107 108 Error addModule(Module *M); 109 Error addSymbol(const ModuleSymbolTable &Msymtab, 110 const SmallPtrSet<GlobalValue *, 8> &Used, 111 ModuleSymbolTable::Symbol Sym); 112 113 Error build(ArrayRef<Module *> Mods); 114 }; 115 116 Error Builder::addModule(Module *M) { 117 if (M->getDataLayoutStr().empty()) 118 return make_error<StringError>("input module has no datalayout", 119 inconvertibleErrorCode()); 120 121 SmallPtrSet<GlobalValue *, 8> Used; 122 collectUsedGlobalVariables(*M, Used, /*CompilerUsed*/ false); 123 124 ModuleSymbolTable Msymtab; 125 Msymtab.addModule(M); 126 127 storage::Module Mod; 128 Mod.Begin = Syms.size(); 129 Mod.End = Syms.size() + Msymtab.symbols().size(); 130 Mod.UncBegin = Uncommons.size(); 131 Mods.push_back(Mod); 132 133 if (TT.isOSBinFormatCOFF()) { 134 if (auto E = M->materializeMetadata()) 135 return E; 136 if (NamedMDNode *LinkerOptions = 137 M->getNamedMetadata("llvm.linker.options")) { 138 for (MDNode *MDOptions : LinkerOptions->operands()) 139 for (const MDOperand &MDOption : cast<MDNode>(MDOptions)->operands()) 140 COFFLinkerOptsOS << " " << cast<MDString>(MDOption)->getString(); 141 } 142 } 143 144 for (ModuleSymbolTable::Symbol Msym : Msymtab.symbols()) 145 if (Error Err = addSymbol(Msymtab, Used, Msym)) 146 return Err; 147 148 return Error::success(); 149 } 150 151 Expected<int> Builder::getComdatIndex(const Comdat *C, const Module *M) { 152 auto P = ComdatMap.insert(std::make_pair(C, Comdats.size())); 153 if (P.second) { 154 std::string Name; 155 if (TT.isOSBinFormatCOFF()) { 156 const GlobalValue *GV = M->getNamedValue(C->getName()); 157 if (!GV) 158 return make_error<StringError>("Could not find leader", 159 inconvertibleErrorCode()); 160 // Internal leaders do not affect symbol resolution, therefore they do not 161 // appear in the symbol table. 162 if (GV->hasLocalLinkage()) { 163 P.first->second = -1; 164 return -1; 165 } 166 llvm::raw_string_ostream OS(Name); 167 Mang.getNameWithPrefix(OS, GV, false); 168 } else { 169 Name = C->getName(); 170 } 171 172 storage::Comdat Comdat; 173 setStr(Comdat.Name, Saver.save(Name)); 174 Comdats.push_back(Comdat); 175 } 176 177 return P.first->second; 178 } 179 180 Error Builder::addSymbol(const ModuleSymbolTable &Msymtab, 181 const SmallPtrSet<GlobalValue *, 8> &Used, 182 ModuleSymbolTable::Symbol Msym) { 183 Syms.emplace_back(); 184 storage::Symbol &Sym = Syms.back(); 185 Sym = {}; 186 187 storage::Uncommon *Unc = nullptr; 188 auto Uncommon = [&]() -> storage::Uncommon & { 189 if (Unc) 190 return *Unc; 191 Sym.Flags |= 1 << storage::Symbol::FB_has_uncommon; 192 Uncommons.emplace_back(); 193 Unc = &Uncommons.back(); 194 *Unc = {}; 195 setStr(Unc->COFFWeakExternFallbackName, ""); 196 setStr(Unc->SectionName, ""); 197 return *Unc; 198 }; 199 200 SmallString<64> Name; 201 { 202 raw_svector_ostream OS(Name); 203 Msymtab.printSymbolName(OS, Msym); 204 } 205 setStr(Sym.Name, Saver.save(StringRef(Name))); 206 207 auto Flags = Msymtab.getSymbolFlags(Msym); 208 if (Flags & object::BasicSymbolRef::SF_Undefined) 209 Sym.Flags |= 1 << storage::Symbol::FB_undefined; 210 if (Flags & object::BasicSymbolRef::SF_Weak) 211 Sym.Flags |= 1 << storage::Symbol::FB_weak; 212 if (Flags & object::BasicSymbolRef::SF_Common) 213 Sym.Flags |= 1 << storage::Symbol::FB_common; 214 if (Flags & object::BasicSymbolRef::SF_Indirect) 215 Sym.Flags |= 1 << storage::Symbol::FB_indirect; 216 if (Flags & object::BasicSymbolRef::SF_Global) 217 Sym.Flags |= 1 << storage::Symbol::FB_global; 218 if (Flags & object::BasicSymbolRef::SF_FormatSpecific) 219 Sym.Flags |= 1 << storage::Symbol::FB_format_specific; 220 if (Flags & object::BasicSymbolRef::SF_Executable) 221 Sym.Flags |= 1 << storage::Symbol::FB_executable; 222 223 Sym.ComdatIndex = -1; 224 auto *GV = Msym.dyn_cast<GlobalValue *>(); 225 if (!GV) { 226 // Undefined module asm symbols act as GC roots and are implicitly used. 227 if (Flags & object::BasicSymbolRef::SF_Undefined) 228 Sym.Flags |= 1 << storage::Symbol::FB_used; 229 setStr(Sym.IRName, ""); 230 return Error::success(); 231 } 232 233 setStr(Sym.IRName, GV->getName()); 234 235 bool IsBuiltinFunc = false; 236 237 for (const char *LibcallName : LibcallRoutineNames) 238 if (GV->getName() == LibcallName) 239 IsBuiltinFunc = true; 240 241 if (Used.count(GV) || IsBuiltinFunc) 242 Sym.Flags |= 1 << storage::Symbol::FB_used; 243 if (GV->isThreadLocal()) 244 Sym.Flags |= 1 << storage::Symbol::FB_tls; 245 if (GV->hasGlobalUnnamedAddr()) 246 Sym.Flags |= 1 << storage::Symbol::FB_unnamed_addr; 247 if (GV->canBeOmittedFromSymbolTable()) 248 Sym.Flags |= 1 << storage::Symbol::FB_may_omit; 249 Sym.Flags |= unsigned(GV->getVisibility()) << storage::Symbol::FB_visibility; 250 251 if (Flags & object::BasicSymbolRef::SF_Common) { 252 Uncommon().CommonSize = GV->getParent()->getDataLayout().getTypeAllocSize( 253 GV->getType()->getElementType()); 254 Uncommon().CommonAlign = GV->getAlignment(); 255 } 256 257 const GlobalObject *Base = GV->getBaseObject(); 258 if (!Base) 259 return make_error<StringError>("Unable to determine comdat of alias!", 260 inconvertibleErrorCode()); 261 if (const Comdat *C = Base->getComdat()) { 262 Expected<int> ComdatIndexOrErr = getComdatIndex(C, GV->getParent()); 263 if (!ComdatIndexOrErr) 264 return ComdatIndexOrErr.takeError(); 265 Sym.ComdatIndex = *ComdatIndexOrErr; 266 } 267 268 if (TT.isOSBinFormatCOFF()) { 269 emitLinkerFlagsForGlobalCOFF(COFFLinkerOptsOS, GV, TT, Mang); 270 271 if ((Flags & object::BasicSymbolRef::SF_Weak) && 272 (Flags & object::BasicSymbolRef::SF_Indirect)) { 273 auto *Fallback = dyn_cast<GlobalValue>( 274 cast<GlobalAlias>(GV)->getAliasee()->stripPointerCasts()); 275 if (!Fallback) 276 return make_error<StringError>("Invalid weak external", 277 inconvertibleErrorCode()); 278 std::string FallbackName; 279 raw_string_ostream OS(FallbackName); 280 Msymtab.printSymbolName(OS, Fallback); 281 OS.flush(); 282 setStr(Uncommon().COFFWeakExternFallbackName, Saver.save(FallbackName)); 283 } 284 } 285 286 if (!Base->getSection().empty()) 287 setStr(Uncommon().SectionName, Saver.save(Base->getSection())); 288 289 return Error::success(); 290 } 291 292 Error Builder::build(ArrayRef<Module *> IRMods) { 293 storage::Header Hdr; 294 295 assert(!IRMods.empty()); 296 Hdr.Version = storage::Header::kCurrentVersion; 297 setStr(Hdr.Producer, kExpectedProducerName); 298 setStr(Hdr.TargetTriple, IRMods[0]->getTargetTriple()); 299 setStr(Hdr.SourceFileName, IRMods[0]->getSourceFileName()); 300 TT = Triple(IRMods[0]->getTargetTriple()); 301 302 for (auto *M : IRMods) 303 if (Error Err = addModule(M)) 304 return Err; 305 306 COFFLinkerOptsOS.flush(); 307 setStr(Hdr.COFFLinkerOpts, Saver.save(COFFLinkerOpts)); 308 309 // We are about to fill in the header's range fields, so reserve space for it 310 // and copy it in afterwards. 311 Symtab.resize(sizeof(storage::Header)); 312 writeRange(Hdr.Modules, Mods); 313 writeRange(Hdr.Comdats, Comdats); 314 writeRange(Hdr.Symbols, Syms); 315 writeRange(Hdr.Uncommons, Uncommons); 316 317 *reinterpret_cast<storage::Header *>(Symtab.data()) = Hdr; 318 return Error::success(); 319 } 320 321 } // end anonymous namespace 322 323 Error irsymtab::build(ArrayRef<Module *> Mods, SmallVector<char, 0> &Symtab, 324 StringTableBuilder &StrtabBuilder, 325 BumpPtrAllocator &Alloc) { 326 return Builder(Symtab, StrtabBuilder, Alloc).build(Mods); 327 } 328 329 // Upgrade a vector of bitcode modules created by an old version of LLVM by 330 // creating an irsymtab for them in the current format. 331 static Expected<FileContents> upgrade(ArrayRef<BitcodeModule> BMs) { 332 FileContents FC; 333 334 LLVMContext Ctx; 335 std::vector<Module *> Mods; 336 std::vector<std::unique_ptr<Module>> OwnedMods; 337 for (auto BM : BMs) { 338 Expected<std::unique_ptr<Module>> MOrErr = 339 BM.getLazyModule(Ctx, /*ShouldLazyLoadMetadata*/ true, 340 /*IsImporting*/ false); 341 if (!MOrErr) 342 return MOrErr.takeError(); 343 344 Mods.push_back(MOrErr->get()); 345 OwnedMods.push_back(std::move(*MOrErr)); 346 } 347 348 StringTableBuilder StrtabBuilder(StringTableBuilder::RAW); 349 BumpPtrAllocator Alloc; 350 if (Error E = build(Mods, FC.Symtab, StrtabBuilder, Alloc)) 351 return std::move(E); 352 353 StrtabBuilder.finalizeInOrder(); 354 FC.Strtab.resize(StrtabBuilder.getSize()); 355 StrtabBuilder.write((uint8_t *)FC.Strtab.data()); 356 357 FC.TheReader = {{FC.Symtab.data(), FC.Symtab.size()}, 358 {FC.Strtab.data(), FC.Strtab.size()}}; 359 return std::move(FC); 360 } 361 362 Expected<FileContents> irsymtab::readBitcode(const BitcodeFileContents &BFC) { 363 if (BFC.Mods.empty()) 364 return make_error<StringError>("Bitcode file does not contain any modules", 365 inconvertibleErrorCode()); 366 367 if (BFC.StrtabForSymtab.empty() || 368 BFC.Symtab.size() < sizeof(storage::Header)) 369 return upgrade(BFC.Mods); 370 371 // We cannot use the regular reader to read the version and producer, because 372 // it will expect the header to be in the current format. The only thing we 373 // can rely on is that the version and producer will be present as the first 374 // struct elements. 375 auto *Hdr = reinterpret_cast<const storage::Header *>(BFC.Symtab.data()); 376 unsigned Version = Hdr->Version; 377 StringRef Producer = Hdr->Producer.get(BFC.StrtabForSymtab); 378 if (Version != storage::Header::kCurrentVersion || 379 Producer != kExpectedProducerName) 380 return upgrade(BFC.Mods); 381 382 FileContents FC; 383 FC.TheReader = {{BFC.Symtab.data(), BFC.Symtab.size()}, 384 {BFC.StrtabForSymtab.data(), BFC.StrtabForSymtab.size()}}; 385 386 // Finally, make sure that the number of modules in the symbol table matches 387 // the number of modules in the bitcode file. If they differ, it may mean that 388 // the bitcode file was created by binary concatenation, so we need to create 389 // a new symbol table from scratch. 390 if (FC.TheReader.getNumModules() != BFC.Mods.size()) 391 return upgrade(std::move(BFC.Mods)); 392 393 return std::move(FC); 394 } 395
