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//===- Core/SymbolTable.cpp - Main Symbol Table ---------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "lld/Core/SymbolTable.h"
#include "lld/Core/AbsoluteAtom.h"
#include "lld/Core/Atom.h"
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#include "lld/Core/DefinedAtom.h"
#include "lld/Core/File.h"
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#include "lld/Core/LLVM.h"
#include "lld/Core/Resolver.h"
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#include "lld/Core/SharedLibraryAtom.h"
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#include "lld/Core/UndefinedAtom.h"
#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/DenseMapInfo.h"
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#include "llvm/ADT/Hashing.h"
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#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
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#include <cstdlib>
#include <vector>
namespace lld {
SymbolTable::SymbolTable(const LinkingContext &context) : _context(context) {}
void SymbolTable::add(const UndefinedAtom &atom) {
this->addByName(atom);
}
void SymbolTable::add(const SharedLibraryAtom &atom) {
this->addByName(atom);
}
void SymbolTable::add(const AbsoluteAtom &atom) {
this->addByName(atom);
}
void SymbolTable::add(const DefinedAtom &atom) {
(atom.scope() != DefinedAtom::scopeTranslationUnit)) {
// Named atoms cannot be merged by content.
assert(atom.merge() != DefinedAtom::mergeByContent);
// Track named atoms that are not scoped to file (static).
this->addByName(atom);
} else if (atom.merge() == DefinedAtom::mergeByContent) {
// Named atoms cannot be merged by content.
assert(atom.name().empty());
this->addByContent(atom);
}
}
enum NameCollisionResolution {
NCR_First,
NCR_Second,
NCR_DupDef,
NCR_DupUndef,
NCR_DupShLib,
NCR_Error
};
static NameCollisionResolution cases[4][4] = {
//regular absolute undef sharedLib
{
// first is regular
NCR_DupDef, NCR_Error, NCR_First, NCR_First
},
{
// first is absolute
NCR_Error, NCR_Error, NCR_First, NCR_First
},
{
// first is undef
NCR_Second, NCR_Second, NCR_DupUndef, NCR_Second
},
{
// first is sharedLib
NCR_Second, NCR_Second, NCR_First, NCR_DupShLib
}
};
static NameCollisionResolution collide(Atom::Definition first,
Atom::Definition second) {
return cases[first][second];
}
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enum MergeResolution {
MCR_First,
MCR_Second,
MCR_Largest,
MCR_Error
};
static MergeResolution mergeCases[4][4] = {
// no tentative weak weakAddressUsed
{
// first is no
MCR_Error, MCR_First, MCR_First, MCR_First
},
{
// first is tentative
MCR_Second, MCR_Largest, MCR_Second, MCR_Second
},
{
// first is weak
MCR_Second, MCR_First, MCR_First, MCR_Second
},
{
// first is weakAddressUsed
MCR_Second, MCR_First, MCR_First, MCR_First
}
};
static MergeResolution mergeSelect(DefinedAtom::Merge first,
DefinedAtom::Merge second) {
return mergeCases[first][second];
}
void SymbolTable::addByName(const Atom & newAtom) {
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StringRef name = newAtom.name();
assert(!name.empty());
const Atom *existing = this->findByName(name);
// Name is not in symbol table yet, add it associate with this atom.
_nameTable[name] = &newAtom;
// Name is already in symbol table and associated with another atom.
bool useNew = true;
switch (collide(existing->definition(), newAtom.definition())) {
case NCR_First:
useNew = false;
break;
case NCR_Second:
useNew = true;
break;
case NCR_DupDef:
assert(existing->definition() == Atom::definitionRegular);
assert(newAtom.definition() == Atom::definitionRegular);
switch (mergeSelect(((DefinedAtom*)existing)->merge(),
((DefinedAtom*)(&newAtom))->merge())) {
case MCR_First:
useNew = false;
break;
useNew = true;
break;
break;
case MCR_Error:
llvm::errs() << "Duplicate symbols: "
<< existing->name()
<< ":"
<< existing->file().path()
<< " and "
<< newAtom.name()
<< ":"
<< newAtom.file().path()
<< "\n";
llvm::report_fatal_error("duplicate symbol error");
break;
}
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const UndefinedAtom* existingUndef = dyn_cast<UndefinedAtom>(existing);
const UndefinedAtom* newUndef = dyn_cast<UndefinedAtom>(&newAtom);
assert(existingUndef != nullptr);
assert(newUndef != nullptr);
bool sameCanBeNull = (existingUndef->canBeNull() == newUndef->canBeNull());
if (!sameCanBeNull &&
_context.warnIfCoalesableAtomsHaveDifferentCanBeNull()) {
llvm::errs() << "lld warning: undefined symbol "
<< existingUndef->name()
<< " has different weakness in "
<< existingUndef->file().path()
<< " and in " << newUndef->file().path() << "\n";
}
const UndefinedAtom *existingFallback = existingUndef->fallback();
const UndefinedAtom *newFallback = newUndef->fallback();
bool hasDifferentFallback =
(existingFallback && newFallback &&
existingFallback->name() != newFallback->name());
if (hasDifferentFallback) {
llvm::errs() << "lld warning: undefined symbol "
<< existingUndef->name() << " has different fallback: "
<< existingFallback->name() << " in "
<< existingUndef->file().path() << " and "
<< newFallback->name() << " in "
<< newUndef->file().path() << "\n";
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bool hasNewFallback = newUndef->fallback();
if (sameCanBeNull)
useNew = hasNewFallback;
else
useNew = (newUndef->canBeNull() < existingUndef->canBeNull());
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}
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case NCR_DupShLib: {
const SharedLibraryAtom* curShLib =
dyn_cast<SharedLibraryAtom>(existing);
const SharedLibraryAtom* newShLib =
dyn_cast<SharedLibraryAtom>(&newAtom);
assert(curShLib != nullptr);
assert(newShLib != nullptr);
bool sameNullness = (curShLib->canBeNullAtRuntime()
== newShLib->canBeNullAtRuntime());
bool sameName = curShLib->loadName().equals(newShLib->loadName());
if (!sameName) {
useNew = false;
if (_context.warnIfCoalesableAtomsHaveDifferentLoadName()) {
// FIXME: need diagonstics interface for writing warning messages
llvm::errs() << "lld warning: shared library symbol "
<< curShLib->name()
<< " has different load path in "
<< curShLib->file().path()
<< " and in "
<< newShLib->file().path();
}
} else if (!sameNullness) {
useNew = false;
if (_context.warnIfCoalesableAtomsHaveDifferentCanBeNull()) {
// FIXME: need diagonstics interface for writing warning messages
llvm::errs() << "lld warning: shared library symbol "
<< curShLib->name()
<< " has different weakness in "
<< curShLib->file().path()
<< " and in "
<< newShLib->file().path();
}
} else {
// Both shlib atoms are identical and can be coalesced.
useNew = false;
}
case NCR_Error:
llvm::errs() << "SymbolTable: error while merging " << name << "\n";
llvm::report_fatal_error("duplicate symbol error");
break;
if (useNew) {
// Update name table to use new atom.
_nameTable[name] = &newAtom;
// Add existing atom to replacement table.
_replacedAtoms[existing] = &newAtom;
} else {
// New atom is not being used. Add it to replacement table.
_replacedAtoms[&newAtom] = existing;
}
}
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unsigned SymbolTable::AtomMappingInfo::getHashValue(const DefinedAtom *atom) {
auto content = atom->rawContent();
return llvm::hash_combine(atom->size(),
atom->contentType(),
llvm::hash_combine_range(content.begin(),
content.end()));
}
bool SymbolTable::AtomMappingInfo::isEqual(const DefinedAtom * const l,
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const DefinedAtom * const r) {
return true;
return false;
return false;
return false;
return false;
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if (l->contentType() != r->contentType())
return false;
return false;
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ArrayRef<uint8_t> lc = l->rawContent();
ArrayRef<uint8_t> rc = r->rawContent();
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return memcmp(lc.data(), rc.data(), lc.size()) == 0;
}
void SymbolTable::addByContent(const DefinedAtom & newAtom) {
// Currently only read-only constants can be merged.
assert(newAtom.permissions() == DefinedAtom::permR__);
AtomContentSet::iterator pos = _contentTable.find(&newAtom);
_contentTable.insert(&newAtom);
return;
}
const Atom* existing = *pos;
// New atom is not being used. Add it to replacement table.
_replacedAtoms[&newAtom] = existing;
}
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const Atom *SymbolTable::findByName(StringRef sym) {
NameToAtom::iterator pos = _nameTable.find(sym);
if (pos == _nameTable.end())
return pos->second;
}
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bool SymbolTable::isDefined(StringRef sym) {
const Atom *atom = this->findByName(sym);
return false;
if (atom->definition() == Atom::definitionUndefined)
return false;
return true;
}
void SymbolTable::addReplacement(const Atom *replaced,
const Atom *replacement) {
_replacedAtoms[replaced] = replacement;
}
const Atom *SymbolTable::replacement(const Atom *atom) {
AtomToAtom::iterator pos = _replacedAtoms.find(atom);
if (pos == _replacedAtoms.end())
return atom;
// might be chain, recurse to end
return this->replacement(pos->second);
}
unsigned int SymbolTable::size() {
return _nameTable.size();
}
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void SymbolTable::undefines(std::vector<const UndefinedAtom *> &undefs) {
for (NameToAtom::iterator it = _nameTable.begin(),
end = _nameTable.end(); it != end; ++it) {
const Atom *atom = it->second;
if (const auto undef = dyn_cast<const UndefinedAtom>(atom)) {
AtomToAtom::iterator pos = _replacedAtoms.find(undef);
if (pos != _replacedAtoms.end())
continue;
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undefs.push_back(undef);
}
}
void SymbolTable::tentativeDefinitions(std::vector<StringRef> &names) {
for (auto entry : _nameTable) {
const Atom *atom = entry.second;
StringRef name = entry.first;
assert(atom != nullptr);
if (const DefinedAtom *defAtom = dyn_cast<DefinedAtom>(atom))
if (defAtom->merge() == DefinedAtom::mergeAsTentative)
names.push_back(name);
}
}
} // namespace lld