lld/COFF/LTO.cpp

   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 }