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 "InputFiles.h" 13 #include "Symbols.h" 14 #include "lld/Common/ErrorHandler.h" 15 #include "lld/Common/TargetOptionsCommandFlags.h" 16 #include "llvm/ADT/STLExtras.h" 17 #include "llvm/ADT/SmallString.h" 18 #include "llvm/ADT/StringRef.h" 19 #include "llvm/ADT/Twine.h" 20 #include "llvm/IR/DiagnosticPrinter.h" 21 #include "llvm/LTO/Caching.h" 22 #include "llvm/LTO/Config.h" 23 #include "llvm/LTO/LTO.h" 24 #include "llvm/Object/SymbolicFile.h" 25 #include "llvm/Support/CodeGen.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 40 using namespace lld; 41 using namespace lld::coff; 42 43 static void diagnosticHandler(const DiagnosticInfo &DI) { 44 SmallString<128> ErrStorage; 45 raw_svector_ostream OS(ErrStorage); 46 DiagnosticPrinterRawOStream DP(OS); 47 DI.print(DP); 48 warn(ErrStorage); 49 } 50 51 static void checkError(Error E) { 52 handleAllErrors(std::move(E), 53 [&](ErrorInfoBase &EIB) { error(EIB.message()); }); 54 } 55 56 static void saveBuffer(StringRef Buffer, const Twine &Path) { 57 std::error_code EC; 58 raw_fd_ostream OS(Path.str(), EC, sys::fs::OpenFlags::F_None); 59 if (EC) 60 error("cannot create " + Path + ": " + EC.message()); 61 OS << Buffer; 62 } 63 64 static std::unique_ptr<lto::LTO> createLTO() { 65 lto::Config Conf; 66 Conf.Options = InitTargetOptionsFromCodeGenFlags(); 67 // Use static reloc model on 32-bit x86 because it usually results in more 68 // compact code, and because there are also known code generation bugs when 69 // using the PIC model (see PR34306). 70 if (Config->Machine == COFF::IMAGE_FILE_MACHINE_I386) 71 Conf.RelocModel = Reloc::Static; 72 else 73 Conf.RelocModel = Reloc::PIC_; 74 Conf.DisableVerify = true; 75 Conf.DiagHandler = diagnosticHandler; 76 Conf.OptLevel = Config->LTOOptLevel; 77 if (Config->SaveTemps) 78 checkError(Conf.addSaveTemps(std::string(Config->OutputFile) + ".", 79 /*UseInputModulePath*/ true)); 80 lto::ThinBackend Backend; 81 if (Config->LTOJobs != 0) 82 Backend = lto::createInProcessThinBackend(Config->LTOJobs); 83 return llvm::make_unique<lto::LTO>(std::move(Conf), Backend, 84 Config->LTOPartitions); 85 } 86 87 BitcodeCompiler::BitcodeCompiler() : LTOObj(createLTO()) {} 88 89 BitcodeCompiler::~BitcodeCompiler() = default; 90 91 static void undefine(Symbol *S) { replaceSymbol<Undefined>(S, S->getName()); } 92 93 void BitcodeCompiler::add(BitcodeFile &F) { 94 lto::InputFile &Obj = *F.Obj; 95 unsigned SymNum = 0; 96 std::vector<Symbol *> SymBodies = F.getSymbols(); 97 std::vector<lto::SymbolResolution> Resols(SymBodies.size()); 98 99 // Provide a resolution to the LTO API for each symbol. 100 for (const lto::InputFile::Symbol &ObjSym : Obj.symbols()) { 101 Symbol *Sym = SymBodies[SymNum]; 102 lto::SymbolResolution &R = Resols[SymNum]; 103 ++SymNum; 104 105 // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile 106 // reports two symbols for module ASM defined. Without this check, lld 107 // flags an undefined in IR with a definition in ASM as prevailing. 108 // Once IRObjectFile is fixed to report only one symbol this hack can 109 // be removed. 110 R.Prevailing = !ObjSym.isUndefined() && Sym->getFile() == &F; 111 R.VisibleToRegularObj = Sym->IsUsedInRegularObj; 112 if (R.Prevailing) 113 undefine(Sym); 114 } 115 checkError(LTOObj->add(std::move(F.Obj), Resols)); 116 } 117 118 // Merge all the bitcode files we have seen, codegen the result 119 // and return the resulting objects. 120 std::vector<StringRef> BitcodeCompiler::compile() { 121 unsigned MaxTasks = LTOObj->getMaxTasks(); 122 Buff.resize(MaxTasks); 123 Files.resize(MaxTasks); 124 125 // The /lldltocache option specifies the path to a directory in which to cache 126 // native object files for ThinLTO incremental builds. If a path was 127 // specified, configure LTO to use it as the cache directory. 128 lto::NativeObjectCache Cache; 129 if (!Config->LTOCache.empty()) 130 Cache = check( 131 lto::localCache(Config->LTOCache, 132 [&](size_t Task, std::unique_ptr<MemoryBuffer> MB, 133 StringRef Path) { Files[Task] = std::move(MB); })); 134 135 checkError(LTOObj->run( 136 [&](size_t Task) { 137 return llvm::make_unique<lto::NativeObjectStream>( 138 llvm::make_unique<raw_svector_ostream>(Buff[Task])); 139 }, 140 Cache)); 141 142 if (!Config->LTOCache.empty()) 143 pruneCache(Config->LTOCache, Config->LTOCachePolicy); 144 145 std::vector<StringRef> Ret; 146 for (unsigned I = 0; I != MaxTasks; ++I) { 147 if (Buff[I].empty()) 148 continue; 149 if (Config->SaveTemps) { 150 if (I == 0) 151 saveBuffer(Buff[I], Config->OutputFile + ".lto.obj"); 152 else 153 saveBuffer(Buff[I], Config->OutputFile + Twine(I) + ".lto.obj"); 154 } 155 Ret.emplace_back(Buff[I].data(), Buff[I].size()); 156 } 157 158 for (std::unique_ptr<MemoryBuffer> &File : Files) 159 if (File) 160 Ret.push_back(File->getBuffer()); 161 162 return Ret; 163 } 164