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 68 // Always emit a section per function/datum with LTO. LLVM LTO should get most 69 // of the benefit of linker GC, but there are still opportunities for ICF. 70 Conf.Options.FunctionSections = true; 71 Conf.Options.DataSections = true; 72 73 // Use static reloc model on 32-bit x86 because it usually results in more 74 // compact code, and because there are also known code generation bugs when 75 // using the PIC model (see PR34306). 76 if (Config->Machine == COFF::IMAGE_FILE_MACHINE_I386) 77 Conf.RelocModel = Reloc::Static; 78 else 79 Conf.RelocModel = Reloc::PIC_; 80 Conf.DisableVerify = true; 81 Conf.DiagHandler = diagnosticHandler; 82 Conf.OptLevel = Config->LTOOptLevel; 83 if (Config->SaveTemps) 84 checkError(Conf.addSaveTemps(std::string(Config->OutputFile) + ".", 85 /*UseInputModulePath*/ true)); 86 lto::ThinBackend Backend; 87 if (Config->LTOJobs != 0) 88 Backend = lto::createInProcessThinBackend(Config->LTOJobs); 89 return llvm::make_unique<lto::LTO>(std::move(Conf), Backend, 90 Config->LTOPartitions); 91 } 92 93 BitcodeCompiler::BitcodeCompiler() : LTOObj(createLTO()) {} 94 95 BitcodeCompiler::~BitcodeCompiler() = default; 96 97 static void undefine(Symbol *S) { replaceSymbol<Undefined>(S, S->getName()); } 98 99 void BitcodeCompiler::add(BitcodeFile &F) { 100 lto::InputFile &Obj = *F.Obj; 101 unsigned SymNum = 0; 102 std::vector<Symbol *> SymBodies = F.getSymbols(); 103 std::vector<lto::SymbolResolution> Resols(SymBodies.size()); 104 105 // Provide a resolution to the LTO API for each symbol. 106 for (const lto::InputFile::Symbol &ObjSym : Obj.symbols()) { 107 Symbol *Sym = SymBodies[SymNum]; 108 lto::SymbolResolution &R = Resols[SymNum]; 109 ++SymNum; 110 111 // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile 112 // reports two symbols for module ASM defined. Without this check, lld 113 // flags an undefined in IR with a definition in ASM as prevailing. 114 // Once IRObjectFile is fixed to report only one symbol this hack can 115 // be removed. 116 R.Prevailing = !ObjSym.isUndefined() && Sym->getFile() == &F; 117 R.VisibleToRegularObj = Sym->IsUsedInRegularObj; 118 if (R.Prevailing) 119 undefine(Sym); 120 } 121 checkError(LTOObj->add(std::move(F.Obj), Resols)); 122 } 123 124 // Merge all the bitcode files we have seen, codegen the result 125 // and return the resulting objects. 126 std::vector<StringRef> BitcodeCompiler::compile() { 127 unsigned MaxTasks = LTOObj->getMaxTasks(); 128 Buff.resize(MaxTasks); 129 Files.resize(MaxTasks); 130 131 // The /lldltocache option specifies the path to a directory in which to cache 132 // native object files for ThinLTO incremental builds. If a path was 133 // specified, configure LTO to use it as the cache directory. 134 lto::NativeObjectCache Cache; 135 if (!Config->LTOCache.empty()) 136 Cache = check(lto::localCache( 137 Config->LTOCache, [&](size_t Task, std::unique_ptr<MemoryBuffer> MB) { 138 Files[Task] = std::move(MB); 139 })); 140 141 checkError(LTOObj->run( 142 [&](size_t Task) { 143 return llvm::make_unique<lto::NativeObjectStream>( 144 llvm::make_unique<raw_svector_ostream>(Buff[Task])); 145 }, 146 Cache)); 147 148 if (!Config->LTOCache.empty()) 149 pruneCache(Config->LTOCache, Config->LTOCachePolicy); 150 151 std::vector<StringRef> Ret; 152 for (unsigned I = 0; I != MaxTasks; ++I) { 153 if (Buff[I].empty()) 154 continue; 155 if (Config->SaveTemps) { 156 if (I == 0) 157 saveBuffer(Buff[I], Config->OutputFile + ".lto.obj"); 158 else 159 saveBuffer(Buff[I], Config->OutputFile + Twine(I) + ".lto.obj"); 160 } 161 Ret.emplace_back(Buff[I].data(), Buff[I].size()); 162 } 163 164 for (std::unique_ptr<MemoryBuffer> &File : Files) 165 if (File) 166 Ret.push_back(File->getBuffer()); 167 168 return Ret; 169 } 170