Symbols.cpp revision 327952 
1//===- Symbols.cpp --------------------------------------------------------===//
2//
3//                             The LLVM Linker
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 "Symbols.h"
11#include "InputFiles.h"
12#include "Strings.h"
13#include "lld/Common/ErrorHandler.h"
14#include "lld/Common/Memory.h"
15#include "llvm/ADT/STLExtras.h"
16#include "llvm/Support/Debug.h"
17#include "llvm/Support/raw_ostream.h"
18
19using namespace llvm;
20using namespace llvm::object;
21
22// Returns a symbol name for an error message.
23std::string lld::toString(coff::Symbol &B) {
24  if (Optional<std::string> S = coff::demangleMSVC(B.getName()))
25    return ("\"" + *S + "\" (" + B.getName() + ")").str();
26  return B.getName();
27}
28
29namespace lld {
30namespace coff {
31
32StringRef Symbol::getName() {
33  // COFF symbol names are read lazily for a performance reason.
34  // Non-external symbol names are never used by the linker except for logging
35  // or debugging. Their internal references are resolved not by name but by
36  // symbol index. And because they are not external, no one can refer them by
37  // name. Object files contain lots of non-external symbols, and creating
38  // StringRefs for them (which involves lots of strlen() on the string table)
39  // is a waste of time.
40  if (Name.empty()) {
41    auto *D = cast<DefinedCOFF>(this);
42    cast<ObjFile>(D->File)->getCOFFObj()->getSymbolName(D->Sym, Name);
43  }
44  return Name;
45}
46
47InputFile *Symbol::getFile() {
48  if (auto *Sym = dyn_cast<DefinedCOFF>(this))
49    return Sym->File;
50  if (auto *Sym = dyn_cast<Lazy>(this))
51    return Sym->File;
52  return nullptr;
53}
54
55bool Symbol::isLive() const {
56  if (auto *R = dyn_cast<DefinedRegular>(this))
57    return R->getChunk()->isLive();
58  if (auto *Imp = dyn_cast<DefinedImportData>(this))
59    return Imp->File->Live;
60  if (auto *Imp = dyn_cast<DefinedImportThunk>(this))
61    return Imp->WrappedSym->File->Live;
62  // Assume any other kind of symbol is live.
63  return true;
64}
65
66COFFSymbolRef DefinedCOFF::getCOFFSymbol() {
67  size_t SymSize = cast<ObjFile>(File)->getCOFFObj()->getSymbolTableEntrySize();
68  if (SymSize == sizeof(coff_symbol16))
69    return COFFSymbolRef(reinterpret_cast<const coff_symbol16 *>(Sym));
70  assert(SymSize == sizeof(coff_symbol32));
71  return COFFSymbolRef(reinterpret_cast<const coff_symbol32 *>(Sym));
72}
73
74uint16_t DefinedAbsolute::OutputSectionIndex = 0;
75
76static Chunk *makeImportThunk(DefinedImportData *S, uint16_t Machine) {
77  if (Machine == AMD64)
78    return make<ImportThunkChunkX64>(S);
79  if (Machine == I386)
80    return make<ImportThunkChunkX86>(S);
81  if (Machine == ARM64)
82    return make<ImportThunkChunkARM64>(S);
83  assert(Machine == ARMNT);
84  return make<ImportThunkChunkARM>(S);
85}
86
87DefinedImportThunk::DefinedImportThunk(StringRef Name, DefinedImportData *S,
88                                       uint16_t Machine)
89    : Defined(DefinedImportThunkKind, Name), WrappedSym(S),
90      Data(makeImportThunk(S, Machine)) {}
91
92Defined *Undefined::getWeakAlias() {
93  // A weak alias may be a weak alias to another symbol, so check recursively.
94  for (Symbol *A = WeakAlias; A; A = cast<Undefined>(A)->WeakAlias)
95    if (auto *D = dyn_cast<Defined>(A))
96      return D;
97  return nullptr;
98}
99} // namespace coff
100} // namespace lld
101