MCAsmLayout::MCAsmLayout(MCAssembler &Asm) : Assembler(Asm), LastValidFragment() { // Compute the section layout order. Virtual sections must go last. for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it) if (!it->getSection().isVirtualSection()) SectionOrder.push_back(&*it); for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it) if (it->getSection().isVirtualSection()) SectionOrder.push_back(&*it); }
/// ComputeSymbolTable - Compute the symbol table data /// /// \param StringTable [out] - The string table data. /// \param StringIndexMap [out] - Map from symbol names to offsets in the /// string table. void MachObjectWriter:: ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable, std::vector<MachSymbolData> &LocalSymbolData, std::vector<MachSymbolData> &ExternalSymbolData, std::vector<MachSymbolData> &UndefinedSymbolData) { // Build section lookup table. DenseMap<const MCSection*, uint8_t> SectionIndexMap; unsigned Index = 1; for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it, ++Index) SectionIndexMap[&it->getSection()] = Index; assert(Index <= 256 && "Too many sections!"); // Index 0 is always the empty string. StringMap<uint64_t> StringIndexMap; StringTable += '\x00'; // Build the symbol arrays and the string table, but only for non-local // symbols. // // The particular order that we collect the symbols and create the string // table, then sort the symbols is chosen to match 'as'. Even though it // doesn't matter for correctness, this is important for letting us diff .o // files. for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), ie = Asm.symbol_end(); it != ie; ++it) { const MCSymbol &Symbol = it->getSymbol(); // Ignore non-linker visible symbols. if (!Asm.isSymbolLinkerVisible(it->getSymbol())) continue; if (!it->isExternal() && !Symbol.isUndefined()) continue; uint64_t &Entry = StringIndexMap[Symbol.getName()]; if (!Entry) { Entry = StringTable.size(); StringTable += Symbol.getName(); StringTable += '\x00'; } MachSymbolData MSD; MSD.SymbolData = it; MSD.StringIndex = Entry; if (Symbol.isUndefined()) { MSD.SectionIndex = 0; UndefinedSymbolData.push_back(MSD); } else if (Symbol.isAbsolute()) { MSD.SectionIndex = 0; ExternalSymbolData.push_back(MSD); } else { MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection()); assert(MSD.SectionIndex && "Invalid section index!"); ExternalSymbolData.push_back(MSD); } } // Now add the data for local symbols. for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), ie = Asm.symbol_end(); it != ie; ++it) { const MCSymbol &Symbol = it->getSymbol(); // Ignore non-linker visible symbols. if (!Asm.isSymbolLinkerVisible(it->getSymbol())) continue; if (it->isExternal() || Symbol.isUndefined()) continue; uint64_t &Entry = StringIndexMap[Symbol.getName()]; if (!Entry) { Entry = StringTable.size(); StringTable += Symbol.getName(); StringTable += '\x00'; } MachSymbolData MSD; MSD.SymbolData = it; MSD.StringIndex = Entry; if (Symbol.isAbsolute()) { MSD.SectionIndex = 0; LocalSymbolData.push_back(MSD); } else { MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection()); assert(MSD.SectionIndex && "Invalid section index!"); LocalSymbolData.push_back(MSD); } } // External and undefined symbols are required to be in lexicographic order. std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end()); std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end()); // Set the symbol indices. Index = 0; for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) LocalSymbolData[i].SymbolData->setIndex(Index++); for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) ExternalSymbolData[i].SymbolData->setIndex(Index++); for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) UndefinedSymbolData[i].SymbolData->setIndex(Index++); // The string table is padded to a multiple of 4. while (StringTable.size() % 4) StringTable += '\x00'; }
/// ComputeSymbolTable - Compute the symbol table data void MachObjectWriter::ComputeSymbolTable( MCAssembler &Asm, std::vector<MachSymbolData> &LocalSymbolData, std::vector<MachSymbolData> &ExternalSymbolData, std::vector<MachSymbolData> &UndefinedSymbolData) { // Build section lookup table. DenseMap<const MCSection*, uint8_t> SectionIndexMap; unsigned Index = 1; for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it, ++Index) SectionIndexMap[&it->getSection()] = Index; assert(Index <= 256 && "Too many sections!"); // Build the string table. for (MCSymbolData &SD : Asm.symbols()) { const MCSymbol &Symbol = SD.getSymbol(); if (!Asm.isSymbolLinkerVisible(Symbol)) continue; StringTable.add(Symbol.getName()); } StringTable.finalize(StringTableBuilder::MachO); // Build the symbol arrays but only for non-local symbols. // // The particular order that we collect and then sort the symbols is chosen to // match 'as'. Even though it doesn't matter for correctness, this is // important for letting us diff .o files. for (MCSymbolData &SD : Asm.symbols()) { const MCSymbol &Symbol = SD.getSymbol(); // Ignore non-linker visible symbols. if (!Asm.isSymbolLinkerVisible(Symbol)) continue; if (!SD.isExternal() && !Symbol.isUndefined()) continue; MachSymbolData MSD; MSD.SymbolData = &SD; MSD.StringIndex = StringTable.getOffset(Symbol.getName()); if (Symbol.isUndefined()) { MSD.SectionIndex = 0; UndefinedSymbolData.push_back(MSD); } else if (Symbol.isAbsolute()) { MSD.SectionIndex = 0; ExternalSymbolData.push_back(MSD); } else { MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection()); assert(MSD.SectionIndex && "Invalid section index!"); ExternalSymbolData.push_back(MSD); } } // Now add the data for local symbols. for (MCSymbolData &SD : Asm.symbols()) { const MCSymbol &Symbol = SD.getSymbol(); // Ignore non-linker visible symbols. if (!Asm.isSymbolLinkerVisible(Symbol)) continue; if (SD.isExternal() || Symbol.isUndefined()) continue; MachSymbolData MSD; MSD.SymbolData = &SD; MSD.StringIndex = StringTable.getOffset(Symbol.getName()); if (Symbol.isAbsolute()) { MSD.SectionIndex = 0; LocalSymbolData.push_back(MSD); } else { MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection()); assert(MSD.SectionIndex && "Invalid section index!"); LocalSymbolData.push_back(MSD); } } // External and undefined symbols are required to be in lexicographic order. std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end()); std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end()); // Set the symbol indices. Index = 0; for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) LocalSymbolData[i].SymbolData->setIndex(Index++); for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) ExternalSymbolData[i].SymbolData->setIndex(Index++); for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) UndefinedSymbolData[i].SymbolData->setIndex(Index++); }