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//===- Symbols.cpp --------------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "Error.h"
#include "InputFiles.h"
#include "Symbols.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm::object;
using llvm::sys::fs::identify_magic;
using llvm::sys::fs::file_magic;
namespace lld {
namespace coff {
// Returns 1, 0 or -1 if this symbol should take precedence
// over the Other, tie or lose, respectively.
int DefinedRegular::compare(SymbolBody *Other) {
if (Other->kind() < kind())
return -Other->compare(this);
if (auto *D = dyn_cast<DefinedRegular>(Other)) {
if (isCOMDAT() && D->isCOMDAT())
return 1;
return 0;
}
return 1;
}
int DefinedCommon::compare(SymbolBody *Other) {
if (Other->kind() < kind())
return -Other->compare(this);
if (auto *D = dyn_cast<DefinedCommon>(Other))
return getSize() > D->getSize() ? 1 : -1;
if (isa<Lazy>(Other) || isa<Undefined>(Other))
return 1;
return -1;
}
int DefinedBitcode::compare(SymbolBody *Other) {
assert(Other->kind() >= kind());
if (!isa<Defined>(Other))
return 1;
if (auto *B = dyn_cast<DefinedBitcode>(Other)) {
if (!Replaceable && !B->Replaceable)
return 0;
// Non-replaceable symbols win.
return Replaceable ? -1 : 1;
}
// As an approximation, regular symbols win over bitcode symbols,
// but we definitely have a conflict if the regular symbol is not
// replaceable and neither is the bitcode symbol. We do not
// replicate the rest of the symbol resolution logic here; symbol
// resolution will be done accurately after lowering bitcode symbols
// to regular symbols in addCombinedLTOObject().
if (auto *D = dyn_cast<DefinedRegular>(Other)) {
if (Replaceable || D->isCOMDAT())
return -1;
return 0;
}
if (isa<DefinedCommon>(Other))
return -1;
return 0;
}
int Defined::compare(SymbolBody *Other) {
if (Other->kind() < kind())
return -Other->compare(this);
if (isa<Defined>(Other))
return 0;
return 1;
}
int Lazy::compare(SymbolBody *Other) {
if (Other->kind() < kind())
return -Other->compare(this);
// Undefined symbols with weak aliases will turn into defined
// symbols if they remain undefined, so we don't need to resolve
// such symbols.
if (auto *U = dyn_cast<Undefined>(Other))
if (U->getWeakAlias())
return -1;
return 1;
}
int Undefined::compare(SymbolBody *Other) {
if (Other->kind() < kind())
return -Other->compare(this);
if (cast<Undefined>(Other)->getWeakAlias())
return -1;
return 1;
}
StringRef DefinedRegular::getName() {
// DefinedSymbol's name is read lazily for a performance reason.
// Non-external symbol names are never used by the linker
// except for logging or debugging.
// Their internal references are resolved not by name but by symbol index.
// And because they are not external, no one can refer them by name.
// Object files contain lots of non-external symbols, and creating
// StringRefs for them (which involves lots of strlen() on the string table)
// is a waste of time.
if (Name.empty())
File->getCOFFObj()->getSymbolName(Sym, Name);
return Name;
}
StringRef DefinedCommon::getName() {
if (Name.empty())
File->getCOFFObj()->getSymbolName(Sym, Name);
return Name;
}
std::string DefinedRegular::getDebugName() {
return (getName() + " " + File->getShortName()).str();
}
std::string DefinedCommon::getDebugName() {
return (getName() + " " + File->getShortName()).str();
}
ErrorOr<std::unique_ptr<InputFile>> Lazy::getMember() {
auto MBRefOrErr = File->getMember(&Sym);
if (auto EC = MBRefOrErr.getError())
return EC;
MemoryBufferRef MBRef = MBRefOrErr.get();
// getMember returns an empty buffer if the member was already
// read from the library.
if (MBRef.getBuffer().empty())
return std::unique_ptr<InputFile>(nullptr);
file_magic Magic = identify_magic(MBRef.getBuffer());
if (Magic == file_magic::bitcode)
return std::unique_ptr<InputFile>(new BitcodeFile(MBRef));
if (Magic == file_magic::coff_import_library)
return std::unique_ptr<InputFile>(new ImportFile(MBRef));
if (Magic != file_magic::coff_object) {
llvm::errs() << File->getName() << ": unknown file type\n";
return make_error_code(LLDError::InvalidFile);
}
std::unique_ptr<InputFile> Obj(new ObjectFile(MBRef));
Obj->setParentName(File->getName());
return std::move(Obj);
}
} // namespace coff
} // namespace lld
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