1 //===- LTO.cpp ------------------------------------------------------------===// 2 // 3 // The LLVM Linker 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #include "LTO.h" 11 #include "Config.h" 12 #include "Error.h" 13 #include "InputFiles.h" 14 #include "Symbols.h" 15 #include "llvm/ADT/STLExtras.h" 16 #include "llvm/ADT/SmallString.h" 17 #include "llvm/ADT/StringRef.h" 18 #include "llvm/ADT/Twine.h" 19 #include "llvm/CodeGen/CommandFlags.h" 20 #include "llvm/IR/DiagnosticPrinter.h" 21 #include "llvm/LTO/Config.h" 22 #include "llvm/LTO/LTO.h" 23 #include "llvm/Object/SymbolicFile.h" 24 #include "llvm/Support/CodeGen.h" 25 #include "llvm/Support/ELF.h" 26 #include "llvm/Support/Error.h" 27 #include "llvm/Support/FileSystem.h" 28 #include "llvm/Support/MemoryBuffer.h" 29 #include "llvm/Support/raw_ostream.h" 30 #include <algorithm> 31 #include <cstddef> 32 #include <memory> 33 #include <string> 34 #include <system_error> 35 #include <vector> 36 37 using namespace llvm; 38 using namespace llvm::object; 39 using namespace llvm::ELF; 40 41 using namespace lld; 42 using namespace lld::elf; 43 44 // This is for use when debugging LTO. 45 static void saveBuffer(StringRef Buffer, const Twine &Path) { 46 std::error_code EC; 47 raw_fd_ostream OS(Path.str(), EC, sys::fs::OpenFlags::F_None); 48 if (EC) 49 error(EC, "cannot create " + Path); 50 OS << Buffer; 51 } 52 53 static void diagnosticHandler(const DiagnosticInfo &DI) { 54 SmallString<128> ErrStorage; 55 raw_svector_ostream OS(ErrStorage); 56 DiagnosticPrinterRawOStream DP(OS); 57 DI.print(DP); 58 warn(ErrStorage); 59 } 60 61 static void checkError(Error E) { 62 handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) -> Error { 63 error(EIB.message()); 64 return Error::success(); 65 }); 66 } 67 68 static std::unique_ptr<lto::LTO> createLTO() { 69 lto::Config Conf; 70 71 // LLD supports the new relocations. 72 Conf.Options = InitTargetOptionsFromCodeGenFlags(); 73 Conf.Options.RelaxELFRelocations = true; 74 75 Conf.RelocModel = Config->Pic ? Reloc::PIC_ : Reloc::Static; 76 Conf.DisableVerify = Config->DisableVerify; 77 Conf.DiagHandler = diagnosticHandler; 78 Conf.OptLevel = Config->LTOO; 79 80 // Set up a custom pipeline if we've been asked to. 81 Conf.OptPipeline = Config->LTONewPmPasses; 82 Conf.AAPipeline = Config->LTOAAPipeline; 83 84 if (Config->SaveTemps) 85 checkError(Conf.addSaveTemps(std::string(Config->OutputFile) + ".", 86 /*UseInputModulePath*/ true)); 87 88 lto::ThinBackend Backend; 89 if (Config->ThinLTOJobs != -1u) 90 Backend = lto::createInProcessThinBackend(Config->ThinLTOJobs); 91 return llvm::make_unique<lto::LTO>(std::move(Conf), Backend, 92 Config->LTOPartitions); 93 } 94 95 BitcodeCompiler::BitcodeCompiler() : LTOObj(createLTO()) {} 96 97 BitcodeCompiler::~BitcodeCompiler() = default; 98 99 template <class ELFT> static void undefine(Symbol *S) { 100 replaceBody<Undefined<ELFT>>(S, S->body()->getName(), /*IsLocal=*/false, 101 STV_DEFAULT, S->body()->Type, nullptr); 102 } 103 104 template <class ELFT> void BitcodeCompiler::add(BitcodeFile &F) { 105 lto::InputFile &Obj = *F.Obj; 106 unsigned SymNum = 0; 107 std::vector<Symbol *> Syms = F.getSymbols(); 108 std::vector<lto::SymbolResolution> Resols(Syms.size()); 109 110 // Provide a resolution to the LTO API for each symbol. 111 for (const lto::InputFile::Symbol &ObjSym : Obj.symbols()) { 112 Symbol *Sym = Syms[SymNum]; 113 lto::SymbolResolution &R = Resols[SymNum]; 114 ++SymNum; 115 SymbolBody *B = Sym->body(); 116 117 // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile 118 // reports two symbols for module ASM defined. Without this check, lld 119 // flags an undefined in IR with a definition in ASM as prevailing. 120 // Once IRObjectFile is fixed to report only one symbol this hack can 121 // be removed. 122 R.Prevailing = 123 !(ObjSym.getFlags() & object::BasicSymbolRef::SF_Undefined) && 124 B->File == &F; 125 126 R.VisibleToRegularObj = 127 Sym->IsUsedInRegularObj || (R.Prevailing && Sym->includeInDynsym()); 128 if (R.Prevailing) 129 undefine<ELFT>(Sym); 130 } 131 checkError(LTOObj->add(std::move(F.Obj), Resols)); 132 } 133 134 // Merge all the bitcode files we have seen, codegen the result 135 // and return the resulting ObjectFile(s). 136 std::vector<InputFile *> BitcodeCompiler::compile() { 137 std::vector<InputFile *> Ret; 138 unsigned MaxTasks = LTOObj->getMaxTasks(); 139 Buff.resize(MaxTasks); 140 141 checkError(LTOObj->run([&](size_t Task) { 142 return llvm::make_unique<lto::NativeObjectStream>( 143 llvm::make_unique<raw_svector_ostream>(Buff[Task])); 144 })); 145 146 for (unsigned I = 0; I != MaxTasks; ++I) { 147 if (Buff[I].empty()) 148 continue; 149 if (Config->SaveTemps) { 150 if (MaxTasks == 1) 151 saveBuffer(Buff[I], Config->OutputFile + ".lto.o"); 152 else 153 saveBuffer(Buff[I], Config->OutputFile + Twine(I) + ".lto.o"); 154 } 155 InputFile *Obj = createObjectFile(MemoryBufferRef(Buff[I], "lto.tmp")); 156 Ret.push_back(Obj); 157 } 158 return Ret; 159 } 160 161 template void BitcodeCompiler::template add<ELF32LE>(BitcodeFile &); 162 template void BitcodeCompiler::template add<ELF32BE>(BitcodeFile &); 163 template void BitcodeCompiler::template add<ELF64LE>(BitcodeFile &); 164 template void BitcodeCompiler::template add<ELF64BE>(BitcodeFile &); 165