Index: include/llvm/LTO/Config.h
===================================================================
--- include/llvm/LTO/Config.h
+++ include/llvm/LTO/Config.h
@@ -17,6 +17,7 @@
 
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/Support/CodeGen.h"
+#include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
 
 #include <functional>
@@ -121,6 +122,9 @@
   /// called for ThinLTO tasks.
   typedef std::function<bool(unsigned Task, const Module &)> ModuleHookFn;
 
+  typedef std::function<bool(unsigned Task, const Module &, TargetMachine *)>
+      ModuleAsmHookFn;
+
   /// This module hook is called after linking (regular LTO) or loading
   /// (ThinLTO) the module, before modifying it.
   ModuleHookFn PreOptModuleHook;
@@ -143,6 +147,10 @@
   /// splitting the module.
   ModuleHookFn PreCodeGenModuleHook;
 
+  /// This module hook is called before code generation. It generates
+  /// assembly file by running all the codegen passes on module
+  ModuleAsmHookFn PostCodeGenModuleHook;
+
   /// A combined index hook is called after all per-module indexes have been
   /// combined (ThinLTO-specific). It can be used to implement -save-temps for
   /// the combined index.
@@ -175,6 +183,7 @@
         PostImportModuleHook(std::move(X.PostImportModuleHook)),
         PostOptModuleHook(std::move(X.PostOptModuleHook)),
         PreCodeGenModuleHook(std::move(X.PreCodeGenModuleHook)),
+        PostCodeGenModuleHook(std::move(X.PostCodeGenModuleHook)),
         CombinedIndexHook(std::move(X.CombinedIndexHook)) {}
   // FIXME: Remove once MSVC can synthesize move ops.
   Config &operator=(Config &&X) {
@@ -245,7 +254,6 @@
   }
   DiagnosticHandlerFunction DiagHandler;
 };
-
 }
 }
 
Index: lib/LTO/LTOBackend.cpp
===================================================================
--- lib/LTO/LTOBackend.cpp
+++ lib/LTO/LTOBackend.cpp
@@ -28,6 +28,7 @@
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
+#include "llvm/Transforms/Utils/Cloning.h"
 #include "llvm/Transforms/Utils/FunctionImportUtils.h"
 #include "llvm/Transforms/Utils/SplitModule.h"
 
@@ -76,12 +77,57 @@
     };
   };
 
+  auto setAsmHook = [&](std::string PathSuffix, ModuleAsmHookFn &Hook) {
+    // Keep track of the hook provided by the linker, which also needs to run.
+    ModuleAsmHookFn LinkerHook = Hook;
+    Hook = [=](unsigned Task, const Module &M, TargetMachine *TM) {
+      //// If the linker's hook returned false, we need to pass that result
+      //// through.
+      // if (LinkerHook && !LinkerHook(Task, M))
+      //  return false;
+
+      auto AsmGenModule = CloneModule(&M);
+      std::string PathPrefix;
+      // If this is the combined module (not a ThinLTO backend compile) or the
+      // user hasn't requested using the input module's path, emit to a file
+      // named from the provided OutputFileName with the Task ID appended.
+      if (M.getModuleIdentifier() == "ld-temp.o" || !UseInputModulePath) {
+        PathPrefix = OutputFileName + utostr(Task);
+      } else
+        PathPrefix = M.getModuleIdentifier();
+      std::string Path = PathPrefix + "." + PathSuffix + ".s";
+      std::error_code EC;
+      int FD;
+      EC = sys::fs::openFileForWrite(StringRef(Path), FD, sys::fs::F_None);
+      if (EC) {
+        // Because -save-temps is a debugging feature, we report the error
+        // directly and exit.
+        llvm::errs() << "failed to open " << Path << ": " << EC.message()
+                     << '\n';
+        exit(1);
+      }
+
+      std::unique_ptr<raw_pwrite_stream> OS =
+          llvm::make_unique<llvm::raw_fd_ostream>(FD, true);
+
+      legacy::PassManager CodeGenPasses;
+
+      if (TM->addPassesToEmitFile(CodeGenPasses, *OS,
+                                  TargetMachine::CGFT_AssemblyFile))
+        report_fatal_error("Failed to setup assembly gen in codegen");
+
+      CodeGenPasses.run(*AsmGenModule);
+      return true;
+    };
+  };
+
   setHook("0.preopt", PreOptModuleHook);
   setHook("1.promote", PostPromoteModuleHook);
   setHook("2.internalize", PostInternalizeModuleHook);
   setHook("3.import", PostImportModuleHook);
   setHook("4.opt", PostOptModuleHook);
   setHook("5.precodegen", PreCodeGenModuleHook);
+  setAsmHook("6.postcodegen", PostCodeGenModuleHook);
 
   CombinedIndexHook = [=](const ModuleSummaryIndex &Index) {
     std::string Path = OutputFileName + "index.bc";
@@ -164,6 +210,11 @@
   auto Output = AddOutput(Task);
   std::unique_ptr<raw_pwrite_stream> OS = Output->getStream();
   legacy::PassManager CodeGenPasses;
+
+  // Generate assembly file
+  if (C.PostCodeGenModuleHook && !C.PostCodeGenModuleHook(Task, M, TM))
+    return;
+
   if (TM->addPassesToEmitFile(CodeGenPasses, *OS,
                               TargetMachine::CGFT_ObjectFile))
     report_fatal_error("Failed to setup codegen");
@@ -227,7 +278,6 @@
     return make_error<StringError>(Msg, inconvertibleErrorCode());
   return T;
 }
-
 }
 
 Error lto::backend(Config &C, AddOutputFn AddOutput,