xref: /freebsd/contrib/llvm-project/lld/COFF/Symbols.cpp (revision 2f513db72b034fd5ef7f080b11be5c711c15186a)
1 //===- Symbols.cpp --------------------------------------------------------===//
2 //
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
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "Symbols.h"
10 #include "InputFiles.h"
11 #include "lld/Common/ErrorHandler.h"
12 #include "lld/Common/Memory.h"
13 #include "lld/Common/Strings.h"
14 #include "llvm/ADT/STLExtras.h"
15 #include "llvm/Support/Debug.h"
16 #include "llvm/Support/raw_ostream.h"
17 
18 using namespace llvm;
19 using namespace llvm::object;
20 
21 using namespace lld::coff;
22 
23 namespace lld {
24 
25 static_assert(sizeof(SymbolUnion) <= 48,
26               "symbols should be optimized for memory usage");
27 
28 // Returns a symbol name for an error message.
29 static std::string demangle(StringRef symName) {
30   if (config->demangle)
31     if (Optional<std::string> s = demangleMSVC(symName))
32       return *s;
33   return symName;
34 }
35 std::string toString(coff::Symbol &b) { return demangle(b.getName()); }
36 std::string toCOFFString(const Archive::Symbol &b) {
37   return demangle(b.getName());
38 }
39 
40 namespace coff {
41 
42 StringRef Symbol::getName() {
43   // COFF symbol names are read lazily for a performance reason.
44   // Non-external symbol names are never used by the linker except for logging
45   // or debugging. Their internal references are resolved not by name but by
46   // symbol index. And because they are not external, no one can refer them by
47   // name. Object files contain lots of non-external symbols, and creating
48   // StringRefs for them (which involves lots of strlen() on the string table)
49   // is a waste of time.
50   if (nameData == nullptr) {
51     auto *d = cast<DefinedCOFF>(this);
52     StringRef nameStr;
53     cast<ObjFile>(d->file)->getCOFFObj()->getSymbolName(d->sym, nameStr);
54     nameData = nameStr.data();
55     nameSize = nameStr.size();
56     assert(nameSize == nameStr.size() && "name length truncated");
57   }
58   return StringRef(nameData, nameSize);
59 }
60 
61 InputFile *Symbol::getFile() {
62   if (auto *sym = dyn_cast<DefinedCOFF>(this))
63     return sym->file;
64   if (auto *sym = dyn_cast<Lazy>(this))
65     return sym->file;
66   return nullptr;
67 }
68 
69 bool Symbol::isLive() const {
70   if (auto *r = dyn_cast<DefinedRegular>(this))
71     return r->getChunk()->live;
72   if (auto *imp = dyn_cast<DefinedImportData>(this))
73     return imp->file->live;
74   if (auto *imp = dyn_cast<DefinedImportThunk>(this))
75     return imp->wrappedSym->file->thunkLive;
76   // Assume any other kind of symbol is live.
77   return true;
78 }
79 
80 // MinGW specific.
81 void Symbol::replaceKeepingName(Symbol *other, size_t size) {
82   StringRef origName = getName();
83   memcpy(this, other, size);
84   nameData = origName.data();
85   nameSize = origName.size();
86 }
87 
88 COFFSymbolRef DefinedCOFF::getCOFFSymbol() {
89   size_t symSize = cast<ObjFile>(file)->getCOFFObj()->getSymbolTableEntrySize();
90   if (symSize == sizeof(coff_symbol16))
91     return COFFSymbolRef(reinterpret_cast<const coff_symbol16 *>(sym));
92   assert(symSize == sizeof(coff_symbol32));
93   return COFFSymbolRef(reinterpret_cast<const coff_symbol32 *>(sym));
94 }
95 
96 uint16_t DefinedAbsolute::numOutputSections;
97 
98 static Chunk *makeImportThunk(DefinedImportData *s, uint16_t machine) {
99   if (machine == AMD64)
100     return make<ImportThunkChunkX64>(s);
101   if (machine == I386)
102     return make<ImportThunkChunkX86>(s);
103   if (machine == ARM64)
104     return make<ImportThunkChunkARM64>(s);
105   assert(machine == ARMNT);
106   return make<ImportThunkChunkARM>(s);
107 }
108 
109 DefinedImportThunk::DefinedImportThunk(StringRef name, DefinedImportData *s,
110                                        uint16_t machine)
111     : Defined(DefinedImportThunkKind, name), wrappedSym(s),
112       data(makeImportThunk(s, machine)) {}
113 
114 Defined *Undefined::getWeakAlias() {
115   // A weak alias may be a weak alias to another symbol, so check recursively.
116   for (Symbol *a = weakAlias; a; a = cast<Undefined>(a)->weakAlias)
117     if (auto *d = dyn_cast<Defined>(a))
118       return d;
119   return nullptr;
120 }
121 
122 MemoryBufferRef Lazy::getMemberBuffer() {
123   Archive::Child c =
124     CHECK(sym.getMember(),
125           "could not get the member for symbol " + toCOFFString(sym));
126   return CHECK(c.getMemoryBufferRef(),
127       "could not get the buffer for the member defining symbol " +
128       toCOFFString(sym));
129 }
130 } // namespace coff
131 } // namespace lld
132