Symbols.cpp revision 314564 
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 "Error.h"
12#include "InputFiles.h"
13#include "Memory.h"
14#include "Strings.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::SymbolBody &B) {
24  if (Optional<std::string> S = coff::demangle(B.getName()))
25    return ("\"" + *S + "\" (" + B.getName() + ")").str();
26  return B.getName();
27}
28
29namespace lld {
30namespace coff {
31
32StringRef SymbolBody::getName() {
33  // DefinedCOFF 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    D->File->getCOFFObj()->getSymbolName(D->Sym, Name);
43  }
44  return Name;
45}
46
47InputFile *SymbolBody::getFile() {
48  if (auto *Sym = dyn_cast<DefinedCOFF>(this))
49    return Sym->File;
50  if (auto *Sym = dyn_cast<DefinedBitcode>(this))
51    return Sym->File;
52  if (auto *Sym = dyn_cast<Lazy>(this))
53    return Sym->File;
54  return nullptr;
55}
56
57COFFSymbolRef DefinedCOFF::getCOFFSymbol() {
58  size_t SymSize = File->getCOFFObj()->getSymbolTableEntrySize();
59  if (SymSize == sizeof(coff_symbol16))
60    return COFFSymbolRef(reinterpret_cast<const coff_symbol16 *>(Sym));
61  assert(SymSize == sizeof(coff_symbol32));
62  return COFFSymbolRef(reinterpret_cast<const coff_symbol32 *>(Sym));
63}
64
65DefinedImportThunk::DefinedImportThunk(StringRef Name, DefinedImportData *S,
66                                       uint16_t Machine)
67    : Defined(DefinedImportThunkKind, Name) {
68  switch (Machine) {
69  case AMD64: Data = make<ImportThunkChunkX64>(S); return;
70  case I386:  Data = make<ImportThunkChunkX86>(S); return;
71  case ARMNT: Data = make<ImportThunkChunkARM>(S); return;
72  default:    llvm_unreachable("unknown machine type");
73  }
74}
75
76Defined *Undefined::getWeakAlias() {
77  // A weak alias may be a weak alias to another symbol, so check recursively.
78  for (SymbolBody *A = WeakAlias; A; A = cast<Undefined>(A)->WeakAlias)
79    if (auto *D = dyn_cast<Defined>(A))
80      return D;
81  return nullptr;
82}
83} // namespace coff
84} // namespace lld
85