Index: include/llvm/LTO/Config.h
===================================================================
--- include/llvm/LTO/Config.h
+++ include/llvm/LTO/Config.h
@@ -73,6 +73,12 @@
   /// Sample PGO profile path.
   std::string SampleProfile;
 
+  /// The directory to store .dwo files.
+  std::string DwoDir;
+
+  /// The objcopy binary used to extract dwo files.
+  std::string Objcopy;
+
   /// Optimization remarks file path.
   std::string RemarksFilename = "";
 
Index: lib/LTO/LTOBackend.cpp
===================================================================
--- lib/LTO/LTOBackend.cpp
+++ lib/LTO/LTOBackend.cpp
@@ -30,6 +30,10 @@
 #include "llvm/Passes/PassBuilder.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FileSystem.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/Program.h"
+#include "llvm/Support/raw_ostream.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/ThreadPool.h"
 #include "llvm/Target/TargetMachine.h"
@@ -279,11 +283,71 @@
   return !Conf.PostOptModuleHook || Conf.PostOptModuleHook(Task, Mod);
 }
 
+void codegenWithSplitDwarf(Config &Conf, TargetMachine *TM,
+                           AddStreamFn AddStream, unsigned Task, Module &Mod) {
+  SmallString<128> TempFile;
+  int FD = -1;
+  if (auto EC =
+      sys::fs::createTemporaryFile("lto-llvm-fission", "o", FD, TempFile))
+    report_fatal_error("Could not create temporary file " +
+        TempFile.str() + ": " + EC.message());
+  llvm::raw_fd_ostream OS(FD, true);
+  SmallString<1024> DwarfFile(Conf.DwoDir);
+  std::string DwoName = sys::path::filename(Mod.getModuleIdentifier()).str() +
+       std::to_string(Task) + ".dwo";
+  sys::path::append(DwarfFile, DwoName);
+  TM->Options.MCOptions.SplitDwarfFile = DwarfFile.str().str();
+
+  legacy::PassManager CodeGenPasses;
+  if (TM->addPassesToEmitFile(CodeGenPasses, OS, Conf.CGFileType))
+    report_fatal_error("Failed to setup codegen");
+  CodeGenPasses.run(Mod);
+
+  if (auto EC = llvm::sys::fs::create_directories(Conf.DwoDir))
+    report_fatal_error("Failed to create directory " +
+		       Conf.DwoDir + ": " + EC.message());
+
+  SmallVector<const char*, 5> ExtractArgs, StripArgs;
+  ExtractArgs.push_back(Conf.Objcopy.c_str());
+  ExtractArgs.push_back("--extract-dwo");
+  ExtractArgs.push_back(TempFile.c_str());
+  ExtractArgs.push_back(TM->Options.MCOptions.SplitDwarfFile.c_str());
+  ExtractArgs.push_back(nullptr);
+  StripArgs.push_back(Conf.Objcopy.c_str());
+  StripArgs.push_back("--strip-dwo");
+  StripArgs.push_back(TempFile.c_str());
+  StripArgs.push_back(nullptr);
+
+  if (auto Ret = sys::ExecuteAndWait(Conf.Objcopy, ExtractArgs.data())) {
+    report_fatal_error("Failed to extract dwo from " + TempFile.str() +
+        ". Exit code " + std::to_string(Ret));
+  }
+  if (auto Ret = sys::ExecuteAndWait(Conf.Objcopy, StripArgs.data())) {
+    report_fatal_error("Failed to strip dwo from " + TempFile.str() +
+        ". Exit code " + std::to_string(Ret));
+  }
+
+  auto Stream = AddStream(Task);
+  auto Buffer = MemoryBuffer::getFile(TempFile);
+  if (auto EC = Buffer.getError())
+    report_fatal_error("Failed to load file " +
+                       TempFile.str() + ": " + EC.message());
+  *Stream->OS << Buffer.get()->getBuffer();
+  if (auto EC = sys::fs::remove(TempFile))
+    report_fatal_error("Failed to delete file " +
+                       TempFile.str() + ": " + EC.message());
+}
+
 void codegen(Config &Conf, TargetMachine *TM, AddStreamFn AddStream,
              unsigned Task, Module &Mod) {
   if (Conf.PreCodeGenModuleHook && !Conf.PreCodeGenModuleHook(Task, Mod))
     return;
 
+  if (!Conf.DwoDir.empty()) {
+    codegenWithSplitDwarf(Conf, TM, AddStream, Task, Mod);
+    return;
+  }
+
   auto Stream = AddStream(Task);
   legacy::PassManager CodeGenPasses;
   if (TM->addPassesToEmitFile(CodeGenPasses, *Stream->OS, Conf.CGFileType))
Index: tools/gold/gold-plugin.cpp
===================================================================
--- tools/gold/gold-plugin.cpp
+++ tools/gold/gold-plugin.cpp
@@ -185,6 +185,10 @@
   static std::string sample_profile;
   // New pass manager
   static bool new_pass_manager = false;
+  // Objcopy to debug fission.
+  static std::string objcopy;
+  // Directory to store the .dwo files.
+  static std::string dwo_dir;
 
   static void process_plugin_option(const char *opt_)
   {
@@ -243,10 +247,14 @@
     } else if (opt == "disable-verify") {
       DisableVerify = true;
     } else if (opt.startswith("sample-profile=")) {
-      sample_profile= opt.substr(strlen("sample-profile="));
+      sample_profile = opt.substr(strlen("sample-profile="));
     } else if (opt == "new-pass-manager") {
       new_pass_manager = true;
-    } else {
+    } else if (opt.startswith("objcopy=")) {
+      objcopy = opt.substr(strlen("objcopy="));
+    } else if (opt.startswith("dwo_dir=")) {
+      dwo_dir = opt.substr(strlen("dwo_dir="));
+    }else {
       // Save this option to pass to the code generator.
       // ParseCommandLineOptions() expects argv[0] to be program name. Lazily
       // add that.
@@ -803,6 +811,12 @@
   if (!options::sample_profile.empty())
     Conf.SampleProfile = options::sample_profile;
 
+  if (!options::dwo_dir.empty())
+    Conf.DwoDir = options::dwo_dir;
+
+  if (!options::objcopy.empty())
+    Conf.Objcopy = options::objcopy;
+
   // Use new pass manager if set in driver
   Conf.UseNewPM = options::new_pass_manager;