forked from OSchip/llvm-project
396 lines
13 KiB
C++
396 lines
13 KiB
C++
//===- Core/SymbolTable.cpp - Main Symbol Table ---------------------------===//
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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 "lld/Core/SymbolTable.h"
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#include "lld/Core/AbsoluteAtom.h"
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#include "lld/Core/Atom.h"
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#include "lld/Core/DefinedAtom.h"
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#include "lld/Core/File.h"
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#include "lld/Core/LLVM.h"
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#include "lld/Core/LinkingContext.h"
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#include "lld/Core/Resolver.h"
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#include "lld/Core/SharedLibraryAtom.h"
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#include "lld/Core/UndefinedAtom.h"
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#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"
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#include "llvm/Support/raw_ostream.h"
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#include <algorithm>
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#include <cassert>
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#include <cstdlib>
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#include <vector>
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namespace lld {
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SymbolTable::SymbolTable(LinkingContext &context) : _context(context) {}
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bool SymbolTable::add(const UndefinedAtom &atom) { return addByName(atom); }
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bool SymbolTable::add(const SharedLibraryAtom &atom) { return addByName(atom); }
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bool SymbolTable::add(const AbsoluteAtom &atom) { return addByName(atom); }
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bool SymbolTable::add(const DefinedAtom &atom) {
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if (!atom.name().empty() &&
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atom.scope() != DefinedAtom::scopeTranslationUnit) {
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// Named atoms cannot be merged by content.
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assert(atom.merge() != DefinedAtom::mergeByContent);
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// Track named atoms that are not scoped to file (static).
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return addByName(atom);
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}
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if (atom.merge() == DefinedAtom::mergeByContent) {
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// Named atoms cannot be merged by content.
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assert(atom.name().empty());
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// Currently only read-only constants can be merged.
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if (atom.permissions() == DefinedAtom::permR__)
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return addByContent(atom);
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// TODO: support mergeByContent of data atoms by comparing content & fixups.
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}
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return false;
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}
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const Atom *SymbolTable::findGroup(StringRef sym) {
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NameToAtom::iterator pos = _groupTable.find(sym);
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if (pos == _groupTable.end())
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return nullptr;
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return pos->second;
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}
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bool SymbolTable::addGroup(const DefinedAtom &da) {
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StringRef name = da.name();
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assert(!name.empty());
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const Atom *existing = findGroup(name);
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if (existing == nullptr) {
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_groupTable[name] = &da;
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return true;
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}
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_replacedAtoms[&da] = existing;
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return false;
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}
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enum NameCollisionResolution {
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NCR_First,
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NCR_Second,
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NCR_DupDef,
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NCR_DupUndef,
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NCR_DupShLib,
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NCR_Error
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};
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static NameCollisionResolution cases[4][4] = {
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//regular absolute undef sharedLib
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{
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// first is regular
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NCR_DupDef, NCR_Error, NCR_First, NCR_First
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},
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{
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// first is absolute
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NCR_Error, NCR_Error, NCR_First, NCR_First
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},
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{
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// first is undef
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NCR_Second, NCR_Second, NCR_DupUndef, NCR_Second
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},
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{
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// first is sharedLib
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NCR_Second, NCR_Second, NCR_First, NCR_DupShLib
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}
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};
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static NameCollisionResolution collide(Atom::Definition first,
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Atom::Definition second) {
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return cases[first][second];
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}
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enum MergeResolution {
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MCR_First,
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MCR_Second,
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MCR_Largest,
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MCR_SameSize,
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MCR_Error
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};
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static MergeResolution mergeCases[][6] = {
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// no tentative weak weakAddress sameNameAndSize largest
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{MCR_Error, MCR_First, MCR_First, MCR_First, MCR_SameSize, MCR_Largest}, // no
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{MCR_Second, MCR_Largest, MCR_Second, MCR_Second, MCR_SameSize, MCR_Largest}, // tentative
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{MCR_Second, MCR_First, MCR_First, MCR_Second, MCR_SameSize, MCR_Largest}, // weak
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{MCR_Second, MCR_First, MCR_First, MCR_First, MCR_SameSize, MCR_Largest}, // weakAddress
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{MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize, MCR_SameSize}, // sameSize
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{MCR_Largest, MCR_Largest, MCR_Largest, MCR_Largest, MCR_SameSize, MCR_Largest}, // largest
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};
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static MergeResolution mergeSelect(DefinedAtom::Merge first,
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DefinedAtom::Merge second) {
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assert(first != DefinedAtom::mergeByContent);
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assert(second != DefinedAtom::mergeByContent);
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return mergeCases[first][second];
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}
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bool SymbolTable::addByName(const Atom &newAtom) {
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StringRef name = newAtom.name();
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assert(!name.empty());
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const Atom *existing = findByName(name);
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if (existing == nullptr) {
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// Name is not in symbol table yet, add it associate with this atom.
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_context.notifySymbolTableAdd(&newAtom);
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_nameTable[name] = &newAtom;
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return true;
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}
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// Do nothing if the same object is added more than once.
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if (existing == &newAtom)
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return false;
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// Name is already in symbol table and associated with another atom.
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bool useNew = true;
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switch (collide(existing->definition(), newAtom.definition())) {
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case NCR_First:
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useNew = false;
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break;
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case NCR_Second:
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useNew = true;
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break;
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case NCR_DupDef: {
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const auto *existingDef = cast<DefinedAtom>(existing);
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const auto *newDef = cast<DefinedAtom>(&newAtom);
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switch (mergeSelect(existingDef->merge(), newDef->merge())) {
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case MCR_First:
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useNew = false;
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break;
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case MCR_Second:
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useNew = true;
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break;
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case MCR_Largest: {
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uint64_t existingSize = existingDef->sectionSize();
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uint64_t newSize = newDef->sectionSize();
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useNew = (newSize >= existingSize);
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break;
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}
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case MCR_SameSize: {
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uint64_t existingSize = existingDef->sectionSize();
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uint64_t newSize = newDef->sectionSize();
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if (existingSize == newSize) {
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useNew = true;
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break;
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}
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llvm::errs() << "Size mismatch: "
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<< existing->name() << " (" << existingSize << ") "
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<< newAtom.name() << " (" << newSize << ")\n";
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// fallthrough
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}
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case MCR_Error:
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if (!_context.getAllowDuplicates()) {
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llvm::errs() << "Duplicate symbols: "
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<< existing->name()
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<< ":"
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<< existing->file().path()
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<< " and "
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<< newAtom.name()
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<< ":"
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<< newAtom.file().path()
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<< "\n";
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llvm::report_fatal_error("duplicate symbol error");
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}
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useNew = false;
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break;
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}
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break;
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}
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case NCR_DupUndef: {
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const UndefinedAtom* existingUndef = cast<UndefinedAtom>(existing);
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const UndefinedAtom* newUndef = cast<UndefinedAtom>(&newAtom);
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bool sameCanBeNull = (existingUndef->canBeNull() == newUndef->canBeNull());
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if (!sameCanBeNull &&
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_context.warnIfCoalesableAtomsHaveDifferentCanBeNull()) {
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llvm::errs() << "lld warning: undefined symbol "
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<< existingUndef->name()
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<< " has different weakness in "
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<< existingUndef->file().path()
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<< " and in " << newUndef->file().path() << "\n";
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}
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const UndefinedAtom *existingFallback = existingUndef->fallback();
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const UndefinedAtom *newFallback = newUndef->fallback();
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bool hasDifferentFallback =
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(existingFallback && newFallback &&
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existingFallback->name() != newFallback->name());
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if (hasDifferentFallback) {
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llvm::errs() << "lld warning: undefined symbol "
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<< existingUndef->name() << " has different fallback: "
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<< existingFallback->name() << " in "
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<< existingUndef->file().path() << " and "
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<< newFallback->name() << " in "
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<< newUndef->file().path() << "\n";
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}
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bool hasNewFallback = newUndef->fallback();
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if (sameCanBeNull)
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useNew = hasNewFallback;
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else
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useNew = (newUndef->canBeNull() < existingUndef->canBeNull());
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break;
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}
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case NCR_DupShLib: {
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const SharedLibraryAtom *curShLib = cast<SharedLibraryAtom>(existing);
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const SharedLibraryAtom *newShLib = cast<SharedLibraryAtom>(&newAtom);
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bool sameNullness =
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(curShLib->canBeNullAtRuntime() == newShLib->canBeNullAtRuntime());
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bool sameName = curShLib->loadName().equals(newShLib->loadName());
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if (sameName && !sameNullness &&
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_context.warnIfCoalesableAtomsHaveDifferentCanBeNull()) {
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// FIXME: need diagonstics interface for writing warning messages
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llvm::errs() << "lld warning: shared library symbol "
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<< curShLib->name() << " has different weakness in "
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<< curShLib->file().path() << " and in "
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<< newShLib->file().path();
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}
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if (!sameName && _context.warnIfCoalesableAtomsHaveDifferentLoadName()) {
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// FIXME: need diagonstics interface for writing warning messages
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llvm::errs() << "lld warning: shared library symbol "
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<< curShLib->name() << " has different load path in "
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<< curShLib->file().path() << " and in "
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<< newShLib->file().path();
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}
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useNew = false;
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break;
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}
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case NCR_Error:
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llvm::errs() << "SymbolTable: error while merging " << name << "\n";
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llvm::report_fatal_error("duplicate symbol error");
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break;
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}
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// Give context a chance to change which is kept.
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_context.notifySymbolTableCoalesce(existing, &newAtom, useNew);
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if (useNew) {
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// Update name table to use new atom.
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_nameTable[name] = &newAtom;
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// Add existing atom to replacement table.
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_replacedAtoms[existing] = &newAtom;
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} else {
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// New atom is not being used. Add it to replacement table.
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_replacedAtoms[&newAtom] = existing;
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}
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return false;
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}
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unsigned SymbolTable::AtomMappingInfo::getHashValue(const DefinedAtom *atom) {
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auto content = atom->rawContent();
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return llvm::hash_combine(atom->size(),
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atom->contentType(),
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llvm::hash_combine_range(content.begin(),
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content.end()));
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}
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bool SymbolTable::AtomMappingInfo::isEqual(const DefinedAtom * const l,
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const DefinedAtom * const r) {
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if (l == r)
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return true;
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if (l == getEmptyKey())
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return false;
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if (r == getEmptyKey())
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return false;
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if (l == getTombstoneKey())
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return false;
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if (r == getTombstoneKey())
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return false;
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if (l->contentType() != r->contentType())
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return false;
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if (l->size() != r->size())
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return false;
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if (l->sectionChoice() != r->sectionChoice())
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return false;
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if (l->sectionChoice() == DefinedAtom::sectionCustomRequired) {
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if (!l->customSectionName().equals(r->customSectionName()))
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return false;
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}
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ArrayRef<uint8_t> lc = l->rawContent();
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ArrayRef<uint8_t> rc = r->rawContent();
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return memcmp(lc.data(), rc.data(), lc.size()) == 0;
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}
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bool SymbolTable::addByContent(const DefinedAtom &newAtom) {
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AtomContentSet::iterator pos = _contentTable.find(&newAtom);
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if (pos == _contentTable.end()) {
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_contentTable.insert(&newAtom);
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return true;
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}
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const Atom* existing = *pos;
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// New atom is not being used. Add it to replacement table.
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_replacedAtoms[&newAtom] = existing;
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return false;
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}
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const Atom *SymbolTable::findByName(StringRef sym) {
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NameToAtom::iterator pos = _nameTable.find(sym);
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if (pos == _nameTable.end())
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return nullptr;
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return pos->second;
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}
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bool SymbolTable::isDefined(StringRef sym) {
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if (const Atom *atom = findByName(sym))
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return !isa<UndefinedAtom>(atom);
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return false;
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}
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void SymbolTable::addReplacement(const Atom *replaced,
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const Atom *replacement) {
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_replacedAtoms[replaced] = replacement;
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}
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const Atom *SymbolTable::replacement(const Atom *atom) {
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// Find the replacement for a given atom. Atoms in _replacedAtoms
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// may be chained, so find the last one.
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for (;;) {
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AtomToAtom::iterator pos = _replacedAtoms.find(atom);
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if (pos == _replacedAtoms.end())
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return atom;
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atom = pos->second;
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}
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}
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bool SymbolTable::isCoalescedAway(const Atom *atom) {
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return _replacedAtoms.count(atom) > 0;
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}
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unsigned int SymbolTable::size() {
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return _nameTable.size();
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}
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std::vector<const UndefinedAtom *> SymbolTable::undefines() {
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std::vector<const UndefinedAtom *> ret;
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for (auto it : _nameTable) {
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const Atom *atom = it.second;
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assert(atom != nullptr);
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if (const auto *undef = dyn_cast<const UndefinedAtom>(atom))
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if (_replacedAtoms.count(undef) == 0)
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ret.push_back(undef);
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}
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return ret;
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}
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std::vector<StringRef> SymbolTable::tentativeDefinitions() {
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std::vector<StringRef> ret;
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for (auto entry : _nameTable) {
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const Atom *atom = entry.second;
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StringRef name = entry.first;
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assert(atom != nullptr);
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if (const DefinedAtom *defAtom = dyn_cast<DefinedAtom>(atom))
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if (defAtom->merge() == DefinedAtom::mergeAsTentative)
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ret.push_back(name);
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}
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return ret;
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}
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} // namespace lld
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