1 //===- LTO.cpp ------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include "LTO.h" 10 #include "COFFLinkerContext.h" 11 #include "Config.h" 12 #include "InputFiles.h" 13 #include "Symbols.h" 14 #include "lld/Common/Args.h" 15 #include "lld/Common/CommonLinkerContext.h" 16 #include "lld/Common/Filesystem.h" 17 #include "lld/Common/Strings.h" 18 #include "lld/Common/TargetOptionsCommandFlags.h" 19 #include "llvm/ADT/STLExtras.h" 20 #include "llvm/ADT/SmallString.h" 21 #include "llvm/ADT/StringRef.h" 22 #include "llvm/ADT/Twine.h" 23 #include "llvm/Bitcode/BitcodeWriter.h" 24 #include "llvm/IR/DiagnosticPrinter.h" 25 #include "llvm/LTO/Config.h" 26 #include "llvm/LTO/LTO.h" 27 #include "llvm/Object/SymbolicFile.h" 28 #include "llvm/Support/Caching.h" 29 #include "llvm/Support/CodeGen.h" 30 #include "llvm/Support/Error.h" 31 #include "llvm/Support/FileSystem.h" 32 #include "llvm/Support/MemoryBuffer.h" 33 #include "llvm/Support/raw_ostream.h" 34 #include <algorithm> 35 #include <cstddef> 36 #include <memory> 37 #include <string> 38 #include <system_error> 39 #include <vector> 40 41 using namespace llvm; 42 using namespace llvm::object; 43 using namespace lld; 44 using namespace lld::coff; 45 46 std::string BitcodeCompiler::getThinLTOOutputFile(StringRef path) { 47 return lto::getThinLTOOutputFile(path, ctx.config.thinLTOPrefixReplaceOld, 48 ctx.config.thinLTOPrefixReplaceNew); 49 } 50 51 lto::Config BitcodeCompiler::createConfig() { 52 lto::Config c; 53 c.Options = initTargetOptionsFromCodeGenFlags(); 54 c.Options.EmitAddrsig = true; 55 for (StringRef C : ctx.config.mllvmOpts) 56 c.MllvmArgs.emplace_back(C.str()); 57 58 // Always emit a section per function/datum with LTO. LLVM LTO should get most 59 // of the benefit of linker GC, but there are still opportunities for ICF. 60 c.Options.FunctionSections = true; 61 c.Options.DataSections = true; 62 63 // Use static reloc model on 32-bit x86 because it usually results in more 64 // compact code, and because there are also known code generation bugs when 65 // using the PIC model (see PR34306). 66 if (ctx.config.machine == COFF::IMAGE_FILE_MACHINE_I386) 67 c.RelocModel = Reloc::Static; 68 else 69 c.RelocModel = Reloc::PIC_; 70 #ifndef NDEBUG 71 c.DisableVerify = false; 72 #else 73 c.DisableVerify = true; 74 #endif 75 c.DiagHandler = diagnosticHandler; 76 c.DwoDir = ctx.config.dwoDir.str(); 77 c.OptLevel = ctx.config.ltoo; 78 c.CPU = getCPUStr(); 79 c.MAttrs = getMAttrs(); 80 std::optional<CodeGenOptLevel> optLevelOrNone = CodeGenOpt::getLevel( 81 ctx.config.ltoCgo.value_or(args::getCGOptLevel(ctx.config.ltoo))); 82 assert(optLevelOrNone && "Invalid optimization level!"); 83 c.CGOptLevel = *optLevelOrNone; 84 c.AlwaysEmitRegularLTOObj = !ctx.config.ltoObjPath.empty(); 85 c.DebugPassManager = ctx.config.ltoDebugPassManager; 86 c.CSIRProfile = std::string(ctx.config.ltoCSProfileFile); 87 c.RunCSIRInstr = ctx.config.ltoCSProfileGenerate; 88 c.PGOWarnMismatch = ctx.config.ltoPGOWarnMismatch; 89 c.TimeTraceEnabled = ctx.config.timeTraceEnabled; 90 c.TimeTraceGranularity = ctx.config.timeTraceGranularity; 91 92 if (ctx.config.emit == EmitKind::LLVM) { 93 c.PostInternalizeModuleHook = [this](size_t task, const Module &m) { 94 if (std::unique_ptr<raw_fd_ostream> os = 95 openLTOOutputFile(ctx.config.outputFile)) 96 WriteBitcodeToFile(m, *os, false); 97 return false; 98 }; 99 } else if (ctx.config.emit == EmitKind::ASM) { 100 c.CGFileType = CodeGenFileType::AssemblyFile; 101 c.Options.MCOptions.AsmVerbose = true; 102 } 103 104 if (ctx.config.saveTemps) 105 checkError(c.addSaveTemps(std::string(ctx.config.outputFile) + ".", 106 /*UseInputModulePath*/ true)); 107 return c; 108 } 109 110 BitcodeCompiler::BitcodeCompiler(COFFLinkerContext &c) : ctx(c) { 111 // Initialize indexFile. 112 if (!ctx.config.thinLTOIndexOnlyArg.empty()) 113 indexFile = openFile(ctx.config.thinLTOIndexOnlyArg); 114 115 // Initialize ltoObj. 116 lto::ThinBackend backend; 117 if (ctx.config.thinLTOIndexOnly) { 118 auto OnIndexWrite = [&](StringRef S) { thinIndices.erase(S); }; 119 backend = lto::createWriteIndexesThinBackend( 120 std::string(ctx.config.thinLTOPrefixReplaceOld), 121 std::string(ctx.config.thinLTOPrefixReplaceNew), 122 std::string(ctx.config.thinLTOPrefixReplaceNativeObject), 123 ctx.config.thinLTOEmitImportsFiles, indexFile.get(), OnIndexWrite); 124 } else { 125 backend = lto::createInProcessThinBackend( 126 llvm::heavyweight_hardware_concurrency(ctx.config.thinLTOJobs)); 127 } 128 129 ltoObj = std::make_unique<lto::LTO>(createConfig(), backend, 130 ctx.config.ltoPartitions); 131 } 132 133 BitcodeCompiler::~BitcodeCompiler() = default; 134 135 static void undefine(Symbol *s) { replaceSymbol<Undefined>(s, s->getName()); } 136 137 void BitcodeCompiler::add(BitcodeFile &f) { 138 lto::InputFile &obj = *f.obj; 139 unsigned symNum = 0; 140 std::vector<Symbol *> symBodies = f.getSymbols(); 141 std::vector<lto::SymbolResolution> resols(symBodies.size()); 142 143 if (ctx.config.thinLTOIndexOnly) 144 thinIndices.insert(obj.getName()); 145 146 // Provide a resolution to the LTO API for each symbol. 147 for (const lto::InputFile::Symbol &objSym : obj.symbols()) { 148 Symbol *sym = symBodies[symNum]; 149 lto::SymbolResolution &r = resols[symNum]; 150 ++symNum; 151 152 // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile 153 // reports two symbols for module ASM defined. Without this check, lld 154 // flags an undefined in IR with a definition in ASM as prevailing. 155 // Once IRObjectFile is fixed to report only one symbol this hack can 156 // be removed. 157 r.Prevailing = !objSym.isUndefined() && sym->getFile() == &f; 158 r.VisibleToRegularObj = sym->isUsedInRegularObj; 159 if (r.Prevailing) 160 undefine(sym); 161 162 // We tell LTO to not apply interprocedural optimization for wrapped 163 // (with -wrap) symbols because otherwise LTO would inline them while 164 // their values are still not final. 165 r.LinkerRedefined = !sym->canInline; 166 } 167 checkError(ltoObj->add(std::move(f.obj), resols)); 168 } 169 170 // Merge all the bitcode files we have seen, codegen the result 171 // and return the resulting objects. 172 std::vector<InputFile *> BitcodeCompiler::compile() { 173 unsigned maxTasks = ltoObj->getMaxTasks(); 174 buf.resize(maxTasks); 175 files.resize(maxTasks); 176 file_names.resize(maxTasks); 177 178 // The /lldltocache option specifies the path to a directory in which to cache 179 // native object files for ThinLTO incremental builds. If a path was 180 // specified, configure LTO to use it as the cache directory. 181 FileCache cache; 182 if (!ctx.config.ltoCache.empty()) 183 cache = check(localCache("ThinLTO", "Thin", ctx.config.ltoCache, 184 [&](size_t task, const Twine &moduleName, 185 std::unique_ptr<MemoryBuffer> mb) { 186 files[task] = std::move(mb); 187 file_names[task] = moduleName.str(); 188 })); 189 190 checkError(ltoObj->run( 191 [&](size_t task, const Twine &moduleName) { 192 buf[task].first = moduleName.str(); 193 return std::make_unique<CachedFileStream>( 194 std::make_unique<raw_svector_ostream>(buf[task].second)); 195 }, 196 cache)); 197 198 // Emit empty index files for non-indexed files 199 for (StringRef s : thinIndices) { 200 std::string path = getThinLTOOutputFile(s); 201 openFile(path + ".thinlto.bc"); 202 if (ctx.config.thinLTOEmitImportsFiles) 203 openFile(path + ".imports"); 204 } 205 206 // ThinLTO with index only option is required to generate only the index 207 // files. After that, we exit from linker and ThinLTO backend runs in a 208 // distributed environment. 209 if (ctx.config.thinLTOIndexOnly) { 210 if (!ctx.config.ltoObjPath.empty()) 211 saveBuffer(buf[0].second, ctx.config.ltoObjPath); 212 if (indexFile) 213 indexFile->close(); 214 return {}; 215 } 216 217 if (!ctx.config.ltoCache.empty()) 218 pruneCache(ctx.config.ltoCache, ctx.config.ltoCachePolicy, files); 219 220 std::vector<InputFile *> ret; 221 bool emitASM = ctx.config.emit == EmitKind::ASM; 222 const char *Ext = emitASM ? ".s" : ".obj"; 223 for (unsigned i = 0; i != maxTasks; ++i) { 224 StringRef bitcodeFilePath; 225 // Get the native object contents either from the cache or from memory. Do 226 // not use the cached MemoryBuffer directly, or the PDB will not be 227 // deterministic. 228 StringRef objBuf; 229 if (files[i]) { 230 objBuf = files[i]->getBuffer(); 231 bitcodeFilePath = file_names[i]; 232 } else { 233 objBuf = buf[i].second; 234 bitcodeFilePath = buf[i].first; 235 } 236 if (objBuf.empty()) 237 continue; 238 239 // If the input bitcode file is path/to/a.obj, then the corresponding lto 240 // object file name will look something like: path/to/main.exe.lto.a.obj. 241 StringRef ltoObjName; 242 if (bitcodeFilePath == "ld-temp.o") { 243 ltoObjName = 244 saver().save(Twine(ctx.config.outputFile) + ".lto" + 245 (i == 0 ? Twine("") : Twine('.') + Twine(i)) + Ext); 246 } else { 247 StringRef directory = sys::path::parent_path(bitcodeFilePath); 248 StringRef baseName = sys::path::stem(bitcodeFilePath); 249 StringRef outputFileBaseName = sys::path::filename(ctx.config.outputFile); 250 SmallString<64> path; 251 sys::path::append(path, directory, 252 outputFileBaseName + ".lto." + baseName + Ext); 253 sys::path::remove_dots(path, true); 254 ltoObjName = saver().save(path.str()); 255 } 256 if (ctx.config.saveTemps || emitASM) 257 saveBuffer(buf[i].second, ltoObjName); 258 if (!emitASM) 259 ret.push_back(make<ObjFile>(ctx, MemoryBufferRef(objBuf, ltoObjName))); 260 } 261 262 return ret; 263 } 264