--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lld/COFF/LTO.cpp	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,212 @@
+//===- LTO.cpp ------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "LTO.h"
+#include "Config.h"
+#include "InputFiles.h"
+#include "Symbols.h"
+#include "lld/Common/Args.h"
+#include "lld/Common/ErrorHandler.h"
+#include "lld/Common/Strings.h"
+#include "lld/Common/TargetOptionsCommandFlags.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/Bitcode/BitcodeWriter.h"
+#include "llvm/IR/DiagnosticPrinter.h"
+#include "llvm/LTO/Caching.h"
+#include "llvm/LTO/Config.h"
+#include "llvm/LTO/LTO.h"
+#include "llvm/Object/SymbolicFile.h"
+#include "llvm/Support/CodeGen.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <cstddef>
+#include <memory>
+#include <string>
+#include <system_error>
+#include <vector>
+
+using namespace llvm;
+using namespace llvm::object;
+
+namespace lld {
+namespace coff {
+
+// Creates an empty file to and returns a raw_fd_ostream to write to it.
+static std::unique_ptr<raw_fd_ostream> openFile(StringRef file) {
+  std::error_code ec;
+  auto ret =
+      std::make_unique<raw_fd_ostream>(file, ec, sys::fs::OpenFlags::OF_None);
+  if (ec) {
+    error("cannot open " + file + ": " + ec.message());
+    return nullptr;
+  }
+  return ret;
+}
+
+static std::string getThinLTOOutputFile(StringRef path) {
+  return lto::getThinLTOOutputFile(
+      std::string(path), std::string(config->thinLTOPrefixReplace.first),
+      std::string(config->thinLTOPrefixReplace.second));
+}
+
+static lto::Config createConfig() {
+  lto::Config c;
+  c.Options = initTargetOptionsFromCodeGenFlags();
+
+  // Always emit a section per function/datum with LTO. LLVM LTO should get most
+  // of the benefit of linker GC, but there are still opportunities for ICF.
+  c.Options.FunctionSections = true;
+  c.Options.DataSections = true;
+
+  // Use static reloc model on 32-bit x86 because it usually results in more
+  // compact code, and because there are also known code generation bugs when
+  // using the PIC model (see PR34306).
+  if (config->machine == COFF::IMAGE_FILE_MACHINE_I386)
+    c.RelocModel = Reloc::Static;
+  else
+    c.RelocModel = Reloc::PIC_;
+  c.DisableVerify = true;
+  c.DiagHandler = diagnosticHandler;
+  c.OptLevel = config->ltoo;
+  c.CPU = getCPUStr();
+  c.MAttrs = getMAttrs();
+  c.CGOptLevel = args::getCGOptLevel(config->ltoo);
+
+  if (config->saveTemps)
+    checkError(c.addSaveTemps(std::string(config->outputFile) + ".",
+                              /*UseInputModulePath*/ true));
+  return c;
+}
+
+BitcodeCompiler::BitcodeCompiler() {
+  // Initialize indexFile.
+  if (!config->thinLTOIndexOnlyArg.empty())
+    indexFile = openFile(config->thinLTOIndexOnlyArg);
+
+  // Initialize ltoObj.
+  lto::ThinBackend backend;
+  if (config->thinLTOIndexOnly) {
+    auto OnIndexWrite = [&](StringRef S) { thinIndices.erase(S); };
+    backend = lto::createWriteIndexesThinBackend(
+        std::string(config->thinLTOPrefixReplace.first),
+        std::string(config->thinLTOPrefixReplace.second),
+        config->thinLTOEmitImportsFiles, indexFile.get(), OnIndexWrite);
+  } else if (config->thinLTOJobs != 0) {
+    backend = lto::createInProcessThinBackend(config->thinLTOJobs);
+  }
+
+  ltoObj = std::make_unique<lto::LTO>(createConfig(), backend,
+                                       config->ltoPartitions);
+}
+
+BitcodeCompiler::~BitcodeCompiler() = default;
+
+static void undefine(Symbol *s) { replaceSymbol<Undefined>(s, s->getName()); }
+
+void BitcodeCompiler::add(BitcodeFile &f) {
+  lto::InputFile &obj = *f.obj;
+  unsigned symNum = 0;
+  std::vector<Symbol *> symBodies = f.getSymbols();
+  std::vector<lto::SymbolResolution> resols(symBodies.size());
+
+  if (config->thinLTOIndexOnly)
+    thinIndices.insert(obj.getName());
+
+  // Provide a resolution to the LTO API for each symbol.
+  for (const lto::InputFile::Symbol &objSym : obj.symbols()) {
+    Symbol *sym = symBodies[symNum];
+    lto::SymbolResolution &r = resols[symNum];
+    ++symNum;
+
+    // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile
+    // reports two symbols for module ASM defined. Without this check, lld
+    // flags an undefined in IR with a definition in ASM as prevailing.
+    // Once IRObjectFile is fixed to report only one symbol this hack can
+    // be removed.
+    r.Prevailing = !objSym.isUndefined() && sym->getFile() == &f;
+    r.VisibleToRegularObj = sym->isUsedInRegularObj;
+    if (r.Prevailing)
+      undefine(sym);
+  }
+  checkError(ltoObj->add(std::move(f.obj), resols));
+}
+
+// Merge all the bitcode files we have seen, codegen the result
+// and return the resulting objects.
+std::vector<StringRef> BitcodeCompiler::compile() {
+  unsigned maxTasks = ltoObj->getMaxTasks();
+  buf.resize(maxTasks);
+  files.resize(maxTasks);
+
+  // The /lldltocache option specifies the path to a directory in which to cache
+  // native object files for ThinLTO incremental builds. If a path was
+  // specified, configure LTO to use it as the cache directory.
+  lto::NativeObjectCache cache;
+  if (!config->ltoCache.empty())
+    cache = check(lto::localCache(
+        config->ltoCache, [&](size_t task, std::unique_ptr<MemoryBuffer> mb) {
+          files[task] = std::move(mb);
+        }));
+
+  checkError(ltoObj->run(
+      [&](size_t task) {
+        return std::make_unique<lto::NativeObjectStream>(
+            std::make_unique<raw_svector_ostream>(buf[task]));
+      },
+      cache));
+
+  // Emit empty index files for non-indexed files
+  for (StringRef s : thinIndices) {
+    std::string path = getThinLTOOutputFile(s);
+    openFile(path + ".thinlto.bc");
+    if (config->thinLTOEmitImportsFiles)
+      openFile(path + ".imports");
+  }
+
+  // ThinLTO with index only option is required to generate only the index
+  // files. After that, we exit from linker and ThinLTO backend runs in a
+  // distributed environment.
+  if (config->thinLTOIndexOnly) {
+    if (!config->ltoObjPath.empty())
+      saveBuffer(buf[0], config->ltoObjPath);
+    if (indexFile)
+      indexFile->close();
+    return {};
+  }
+
+  if (!config->ltoCache.empty())
+    pruneCache(config->ltoCache, config->ltoCachePolicy);
+
+  std::vector<StringRef> ret;
+  for (unsigned i = 0; i != maxTasks; ++i) {
+    if (buf[i].empty())
+      continue;
+    if (config->saveTemps) {
+      if (i == 0)
+        saveBuffer(buf[i], config->outputFile + ".lto.obj");
+      else
+        saveBuffer(buf[i], config->outputFile + Twine(i) + ".lto.obj");
+    }
+    ret.emplace_back(buf[i].data(), buf[i].size());
+  }
+
+  for (std::unique_ptr<MemoryBuffer> &file : files)
+    if (file)
+      ret.push_back(file->getBuffer());
+
+  return ret;
+}
+
+} // namespace coff
+} // namespace lld