1 //===- IRSymtab.cpp - implementation of IR symbol tables ------------------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 #include "llvm/Object/IRSymtab.h"
10 #include "llvm/ADT/ArrayRef.h"
11 #include "llvm/ADT/DenseMap.h"
12 #include "llvm/ADT/SmallPtrSet.h"
13 #include "llvm/ADT/SmallString.h"
14 #include "llvm/ADT/SmallVector.h"
15 #include "llvm/ADT/StringRef.h"
16 #include "llvm/ADT/Triple.h"
17 #include "llvm/Config/llvm-config.h"
18 #include "llvm/IR/Comdat.h"
19 #include "llvm/IR/DataLayout.h"
20 #include "llvm/IR/GlobalAlias.h"
21 #include "llvm/IR/GlobalObject.h"
22 #include "llvm/IR/Mangler.h"
23 #include "llvm/IR/Metadata.h"
24 #include "llvm/IR/Module.h"
25 #include "llvm/Bitcode/BitcodeReader.h"
26 #include "llvm/MC/StringTableBuilder.h"
27 #include "llvm/Object/IRObjectFile.h"
28 #include "llvm/Object/ModuleSymbolTable.h"
29 #include "llvm/Object/SymbolicFile.h"
30 #include "llvm/Support/Allocator.h"
31 #include "llvm/Support/Casting.h"
32 #include "llvm/Support/Error.h"
33 #include "llvm/Support/StringSaver.h"
34 #include "llvm/Support/VCSRevision.h"
35 #include "llvm/Support/raw_ostream.h"
42 using namespace irsymtab;
44 static const char *LibcallRoutineNames[] = {
45 #define HANDLE_LIBCALL(code, name) name,
46 #include "llvm/IR/RuntimeLibcalls.def"
52 const char *getExpectedProducerName() {
53 static char DefaultName[] = LLVM_VERSION_STRING
58 // Allows for testing of the irsymtab writer and upgrade mechanism. This
59 // environment variable should not be set by users.
60 if (char *OverrideName = getenv("LLVM_OVERRIDE_PRODUCER"))
65 const char *kExpectedProducerName = getExpectedProducerName();
67 /// Stores the temporary state that is required to build an IR symbol table.
69 SmallVector<char, 0> &Symtab;
70 StringTableBuilder &StrtabBuilder;
73 // This ctor initializes a StringSaver using the passed in BumpPtrAllocator.
74 // The StringTableBuilder does not create a copy of any strings added to it,
75 // so this provides somewhere to store any strings that we create.
76 Builder(SmallVector<char, 0> &Symtab, StringTableBuilder &StrtabBuilder,
77 BumpPtrAllocator &Alloc)
78 : Symtab(Symtab), StrtabBuilder(StrtabBuilder), Saver(Alloc) {}
80 DenseMap<const Comdat *, int> ComdatMap;
84 std::vector<storage::Comdat> Comdats;
85 std::vector<storage::Module> Mods;
86 std::vector<storage::Symbol> Syms;
87 std::vector<storage::Uncommon> Uncommons;
89 std::string COFFLinkerOpts;
90 raw_string_ostream COFFLinkerOptsOS{COFFLinkerOpts};
92 std::vector<storage::Str> DependentLibraries;
94 void setStr(storage::Str &S, StringRef Value) {
95 S.Offset = StrtabBuilder.add(Value);
96 S.Size = Value.size();
100 void writeRange(storage::Range<T> &R, const std::vector<T> &Objs) {
101 R.Offset = Symtab.size();
102 R.Size = Objs.size();
103 Symtab.insert(Symtab.end(), reinterpret_cast<const char *>(Objs.data()),
104 reinterpret_cast<const char *>(Objs.data() + Objs.size()));
107 Expected<int> getComdatIndex(const Comdat *C, const Module *M);
109 Error addModule(Module *M);
110 Error addSymbol(const ModuleSymbolTable &Msymtab,
111 const SmallPtrSet<GlobalValue *, 8> &Used,
112 ModuleSymbolTable::Symbol Sym);
114 Error build(ArrayRef<Module *> Mods);
117 Error Builder::addModule(Module *M) {
118 if (M->getDataLayoutStr().empty())
119 return make_error<StringError>("input module has no datalayout",
120 inconvertibleErrorCode());
122 SmallPtrSet<GlobalValue *, 8> Used;
123 collectUsedGlobalVariables(*M, Used, /*CompilerUsed*/ false);
125 ModuleSymbolTable Msymtab;
126 Msymtab.addModule(M);
129 Mod.Begin = Syms.size();
130 Mod.End = Syms.size() + Msymtab.symbols().size();
131 Mod.UncBegin = Uncommons.size();
134 if (TT.isOSBinFormatCOFF()) {
135 if (auto E = M->materializeMetadata())
137 if (NamedMDNode *LinkerOptions =
138 M->getNamedMetadata("llvm.linker.options")) {
139 for (MDNode *MDOptions : LinkerOptions->operands())
140 for (const MDOperand &MDOption : cast<MDNode>(MDOptions)->operands())
141 COFFLinkerOptsOS << " " << cast<MDString>(MDOption)->getString();
145 if (TT.isOSBinFormatELF()) {
146 if (auto E = M->materializeMetadata())
148 if (NamedMDNode *N = M->getNamedMetadata("llvm.dependent-libraries")) {
149 for (MDNode *MDOptions : N->operands()) {
150 const auto OperandStr =
151 cast<MDString>(cast<MDNode>(MDOptions)->getOperand(0))->getString();
152 storage::Str Specifier;
153 setStr(Specifier, OperandStr);
154 DependentLibraries.emplace_back(Specifier);
159 for (ModuleSymbolTable::Symbol Msym : Msymtab.symbols())
160 if (Error Err = addSymbol(Msymtab, Used, Msym))
163 return Error::success();
166 Expected<int> Builder::getComdatIndex(const Comdat *C, const Module *M) {
167 auto P = ComdatMap.insert(std::make_pair(C, Comdats.size()));
170 if (TT.isOSBinFormatCOFF()) {
171 const GlobalValue *GV = M->getNamedValue(C->getName());
173 return make_error<StringError>("Could not find leader",
174 inconvertibleErrorCode());
175 // Internal leaders do not affect symbol resolution, therefore they do not
176 // appear in the symbol table.
177 if (GV->hasLocalLinkage()) {
178 P.first->second = -1;
181 llvm::raw_string_ostream OS(Name);
182 Mang.getNameWithPrefix(OS, GV, false);
184 Name = std::string(C->getName());
187 storage::Comdat Comdat;
188 setStr(Comdat.Name, Saver.save(Name));
189 Comdats.push_back(Comdat);
192 return P.first->second;
195 Error Builder::addSymbol(const ModuleSymbolTable &Msymtab,
196 const SmallPtrSet<GlobalValue *, 8> &Used,
197 ModuleSymbolTable::Symbol Msym) {
199 storage::Symbol &Sym = Syms.back();
202 storage::Uncommon *Unc = nullptr;
203 auto Uncommon = [&]() -> storage::Uncommon & {
206 Sym.Flags |= 1 << storage::Symbol::FB_has_uncommon;
207 Uncommons.emplace_back();
208 Unc = &Uncommons.back();
210 setStr(Unc->COFFWeakExternFallbackName, "");
211 setStr(Unc->SectionName, "");
215 SmallString<64> Name;
217 raw_svector_ostream OS(Name);
218 Msymtab.printSymbolName(OS, Msym);
220 setStr(Sym.Name, Saver.save(StringRef(Name)));
222 auto Flags = Msymtab.getSymbolFlags(Msym);
223 if (Flags & object::BasicSymbolRef::SF_Undefined)
224 Sym.Flags |= 1 << storage::Symbol::FB_undefined;
225 if (Flags & object::BasicSymbolRef::SF_Weak)
226 Sym.Flags |= 1 << storage::Symbol::FB_weak;
227 if (Flags & object::BasicSymbolRef::SF_Common)
228 Sym.Flags |= 1 << storage::Symbol::FB_common;
229 if (Flags & object::BasicSymbolRef::SF_Indirect)
230 Sym.Flags |= 1 << storage::Symbol::FB_indirect;
231 if (Flags & object::BasicSymbolRef::SF_Global)
232 Sym.Flags |= 1 << storage::Symbol::FB_global;
233 if (Flags & object::BasicSymbolRef::SF_FormatSpecific)
234 Sym.Flags |= 1 << storage::Symbol::FB_format_specific;
235 if (Flags & object::BasicSymbolRef::SF_Executable)
236 Sym.Flags |= 1 << storage::Symbol::FB_executable;
238 Sym.ComdatIndex = -1;
239 auto *GV = Msym.dyn_cast<GlobalValue *>();
241 // Undefined module asm symbols act as GC roots and are implicitly used.
242 if (Flags & object::BasicSymbolRef::SF_Undefined)
243 Sym.Flags |= 1 << storage::Symbol::FB_used;
244 setStr(Sym.IRName, "");
245 return Error::success();
248 setStr(Sym.IRName, GV->getName());
250 bool IsBuiltinFunc = false;
252 for (const char *LibcallName : LibcallRoutineNames)
253 if (GV->getName() == LibcallName)
254 IsBuiltinFunc = true;
256 if (Used.count(GV) || IsBuiltinFunc)
257 Sym.Flags |= 1 << storage::Symbol::FB_used;
258 if (GV->isThreadLocal())
259 Sym.Flags |= 1 << storage::Symbol::FB_tls;
260 if (GV->hasGlobalUnnamedAddr())
261 Sym.Flags |= 1 << storage::Symbol::FB_unnamed_addr;
262 if (GV->canBeOmittedFromSymbolTable())
263 Sym.Flags |= 1 << storage::Symbol::FB_may_omit;
264 Sym.Flags |= unsigned(GV->getVisibility()) << storage::Symbol::FB_visibility;
266 if (Flags & object::BasicSymbolRef::SF_Common) {
267 auto *GVar = dyn_cast<GlobalVariable>(GV);
269 return make_error<StringError>("Only variables can have common linkage!",
270 inconvertibleErrorCode());
271 Uncommon().CommonSize = GV->getParent()->getDataLayout().getTypeAllocSize(
272 GV->getType()->getElementType());
273 Uncommon().CommonAlign = GVar->getAlignment();
276 const GlobalObject *Base = GV->getBaseObject();
278 return make_error<StringError>("Unable to determine comdat of alias!",
279 inconvertibleErrorCode());
280 if (const Comdat *C = Base->getComdat()) {
281 Expected<int> ComdatIndexOrErr = getComdatIndex(C, GV->getParent());
282 if (!ComdatIndexOrErr)
283 return ComdatIndexOrErr.takeError();
284 Sym.ComdatIndex = *ComdatIndexOrErr;
287 if (TT.isOSBinFormatCOFF()) {
288 emitLinkerFlagsForGlobalCOFF(COFFLinkerOptsOS, GV, TT, Mang);
290 if ((Flags & object::BasicSymbolRef::SF_Weak) &&
291 (Flags & object::BasicSymbolRef::SF_Indirect)) {
292 auto *Fallback = dyn_cast<GlobalValue>(
293 cast<GlobalAlias>(GV)->getAliasee()->stripPointerCasts());
295 return make_error<StringError>("Invalid weak external",
296 inconvertibleErrorCode());
297 std::string FallbackName;
298 raw_string_ostream OS(FallbackName);
299 Msymtab.printSymbolName(OS, Fallback);
301 setStr(Uncommon().COFFWeakExternFallbackName, Saver.save(FallbackName));
305 if (!Base->getSection().empty())
306 setStr(Uncommon().SectionName, Saver.save(Base->getSection()));
308 return Error::success();
311 Error Builder::build(ArrayRef<Module *> IRMods) {
314 assert(!IRMods.empty());
315 Hdr.Version = storage::Header::kCurrentVersion;
316 setStr(Hdr.Producer, kExpectedProducerName);
317 setStr(Hdr.TargetTriple, IRMods[0]->getTargetTriple());
318 setStr(Hdr.SourceFileName, IRMods[0]->getSourceFileName());
319 TT = Triple(IRMods[0]->getTargetTriple());
321 for (auto *M : IRMods)
322 if (Error Err = addModule(M))
325 COFFLinkerOptsOS.flush();
326 setStr(Hdr.COFFLinkerOpts, Saver.save(COFFLinkerOpts));
328 // We are about to fill in the header's range fields, so reserve space for it
329 // and copy it in afterwards.
330 Symtab.resize(sizeof(storage::Header));
331 writeRange(Hdr.Modules, Mods);
332 writeRange(Hdr.Comdats, Comdats);
333 writeRange(Hdr.Symbols, Syms);
334 writeRange(Hdr.Uncommons, Uncommons);
335 writeRange(Hdr.DependentLibraries, DependentLibraries);
336 *reinterpret_cast<storage::Header *>(Symtab.data()) = Hdr;
337 return Error::success();
340 } // end anonymous namespace
342 Error irsymtab::build(ArrayRef<Module *> Mods, SmallVector<char, 0> &Symtab,
343 StringTableBuilder &StrtabBuilder,
344 BumpPtrAllocator &Alloc) {
345 return Builder(Symtab, StrtabBuilder, Alloc).build(Mods);
348 // Upgrade a vector of bitcode modules created by an old version of LLVM by
349 // creating an irsymtab for them in the current format.
350 static Expected<FileContents> upgrade(ArrayRef<BitcodeModule> BMs) {
354 std::vector<Module *> Mods;
355 std::vector<std::unique_ptr<Module>> OwnedMods;
356 for (auto BM : BMs) {
357 Expected<std::unique_ptr<Module>> MOrErr =
358 BM.getLazyModule(Ctx, /*ShouldLazyLoadMetadata*/ true,
359 /*IsImporting*/ false);
361 return MOrErr.takeError();
363 Mods.push_back(MOrErr->get());
364 OwnedMods.push_back(std::move(*MOrErr));
367 StringTableBuilder StrtabBuilder(StringTableBuilder::RAW);
368 BumpPtrAllocator Alloc;
369 if (Error E = build(Mods, FC.Symtab, StrtabBuilder, Alloc))
372 StrtabBuilder.finalizeInOrder();
373 FC.Strtab.resize(StrtabBuilder.getSize());
374 StrtabBuilder.write((uint8_t *)FC.Strtab.data());
376 FC.TheReader = {{FC.Symtab.data(), FC.Symtab.size()},
377 {FC.Strtab.data(), FC.Strtab.size()}};
378 return std::move(FC);
381 Expected<FileContents> irsymtab::readBitcode(const BitcodeFileContents &BFC) {
382 if (BFC.Mods.empty())
383 return make_error<StringError>("Bitcode file does not contain any modules",
384 inconvertibleErrorCode());
386 if (BFC.StrtabForSymtab.empty() ||
387 BFC.Symtab.size() < sizeof(storage::Header))
388 return upgrade(BFC.Mods);
390 // We cannot use the regular reader to read the version and producer, because
391 // it will expect the header to be in the current format. The only thing we
392 // can rely on is that the version and producer will be present as the first
394 auto *Hdr = reinterpret_cast<const storage::Header *>(BFC.Symtab.data());
395 unsigned Version = Hdr->Version;
396 StringRef Producer = Hdr->Producer.get(BFC.StrtabForSymtab);
397 if (Version != storage::Header::kCurrentVersion ||
398 Producer != kExpectedProducerName)
399 return upgrade(BFC.Mods);
402 FC.TheReader = {{BFC.Symtab.data(), BFC.Symtab.size()},
403 {BFC.StrtabForSymtab.data(), BFC.StrtabForSymtab.size()}};
405 // Finally, make sure that the number of modules in the symbol table matches
406 // the number of modules in the bitcode file. If they differ, it may mean that
407 // the bitcode file was created by binary concatenation, so we need to create
408 // a new symbol table from scratch.
409 if (FC.TheReader.getNumModules() != BFC.Mods.size())
410 return upgrade(std::move(BFC.Mods));
412 return std::move(FC);