9aa82f76ac
This is a different implementation than r303225 (which was reverted in r303270, re-submitted in r303304 and then re-reverted in r303527). In the previous patch, I tried to add Live bit to each dllimported symbol. It turned out that it didn't work with "oldnames.lib" which contains a lot of weak aliases to dllimported symbols. The way we handle weak aliases is to check if undefined symbols can be resolved using weak aliases, and if so, memcpy the Defined symbols to weak Undefined symbols, so that any references to weak aliases automatically see defined symbols instead of undefined ones. This memcpy happens before MarkLive kicks in. That means we may have multiple copies of dllimported symbols. So turning on one instance's Live bit is not enough. This patch moves the Live bit to dllimport file. Since multiple copies of dllsymbols still point to the same file, we can use it as the central repository to keep track of liveness. Differential Revision: https://reviews.llvm.org/D33520 llvm-svn: 303814
87 lines
2.8 KiB
C++
87 lines
2.8 KiB
C++
//===- Symbols.cpp --------------------------------------------------------===//
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//
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// The LLVM Linker
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "Symbols.h"
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#include "Error.h"
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#include "InputFiles.h"
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#include "Memory.h"
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#include "Strings.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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using namespace llvm::object;
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// Returns a symbol name for an error message.
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std::string lld::toString(coff::SymbolBody &B) {
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if (Optional<std::string> S = coff::demangle(B.getName()))
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return ("\"" + *S + "\" (" + B.getName() + ")").str();
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return B.getName();
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}
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namespace lld {
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namespace coff {
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StringRef SymbolBody::getName() {
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// COFF symbol names are read lazily for a performance reason.
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// Non-external symbol names are never used by the linker except for logging
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// or debugging. Their internal references are resolved not by name but by
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// symbol index. And because they are not external, no one can refer them by
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// name. Object files contain lots of non-external symbols, and creating
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// StringRefs for them (which involves lots of strlen() on the string table)
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// is a waste of time.
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if (Name.empty()) {
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auto *D = cast<DefinedCOFF>(this);
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cast<ObjectFile>(D->File)->getCOFFObj()->getSymbolName(D->Sym, Name);
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}
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return Name;
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}
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InputFile *SymbolBody::getFile() {
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if (auto *Sym = dyn_cast<DefinedCOFF>(this))
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return Sym->File;
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if (auto *Sym = dyn_cast<Lazy>(this))
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return Sym->File;
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return nullptr;
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}
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COFFSymbolRef DefinedCOFF::getCOFFSymbol() {
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size_t SymSize =
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cast<ObjectFile>(File)->getCOFFObj()->getSymbolTableEntrySize();
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if (SymSize == sizeof(coff_symbol16))
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return COFFSymbolRef(reinterpret_cast<const coff_symbol16 *>(Sym));
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assert(SymSize == sizeof(coff_symbol32));
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return COFFSymbolRef(reinterpret_cast<const coff_symbol32 *>(Sym));
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}
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static Chunk *makeImportThunk(DefinedImportData *S, uint16_t Machine) {
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if (Machine == AMD64)
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return make<ImportThunkChunkX64>(S);
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if (Machine == I386)
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return make<ImportThunkChunkX86>(S);
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assert(Machine == ARMNT);
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return make<ImportThunkChunkARM>(S);
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}
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DefinedImportThunk::DefinedImportThunk(StringRef Name, DefinedImportData *S,
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uint16_t Machine)
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: Defined(DefinedImportThunkKind, Name), WrappedSym(S),
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Data(makeImportThunk(S, Machine)) {}
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Defined *Undefined::getWeakAlias() {
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// A weak alias may be a weak alias to another symbol, so check recursively.
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for (SymbolBody *A = WeakAlias; A; A = cast<Undefined>(A)->WeakAlias)
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if (auto *D = dyn_cast<Defined>(A))
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return D;
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return nullptr;
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}
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} // namespace coff
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} // namespace lld
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