Index: lld/trunk/ELF/Driver.h
===================================================================
--- lld/trunk/ELF/Driver.h
+++ lld/trunk/ELF/Driver.h
@@ -68,9 +68,7 @@
 void printHelp(const char *Argv0);
 void printVersion();
 
-std::string concat_paths(StringRef S, StringRef T);
-void copyFile(StringRef Src, StringRef Dest);
-
+void saveLinkerInputs(const llvm::opt::InputArgList &Args);
 std::string findFromSearchPaths(StringRef Path);
 std::string searchLibrary(StringRef Path);
 std::string buildSysrootedPath(llvm::StringRef Dir, llvm::StringRef File);
Index: lld/trunk/ELF/Driver.cpp
===================================================================
--- lld/trunk/ELF/Driver.cpp
+++ lld/trunk/ELF/Driver.cpp
@@ -109,8 +109,6 @@
   using namespace llvm::sys::fs;
   if (Config->Verbose)
     llvm::outs() << Path << "\n";
-  if (!Config->Reproduce.empty())
-    copyFile(Path, concat_paths(Config->Reproduce, Path));
 
   Optional<MemoryBufferRef> Buffer = readFile(Path);
   if (!Buffer.hasValue())
@@ -238,25 +236,6 @@
   return false;
 }
 
-static void logCommandline(ArrayRef<const char *> Args) {
-  if (std::error_code EC = sys::fs::create_directories(
-        Config->Reproduce, /*IgnoreExisting=*/false)) {
-    error(EC, Config->Reproduce + ": can't create directory");
-    return;
-  }
-
-  SmallString<128> Path;
-  path::append(Path, Config->Reproduce, "invocation.txt");
-  std::error_code EC;
-  raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::F_None);
-  check(EC);
-
-  OS << Args[0];
-  for (size_t I = 1, E = Args.size(); I < E; ++I)
-    OS << " " << Args[I];
-  OS << "\n";
-}
-
 void LinkerDriver::main(ArrayRef<const char *> ArgsArr) {
   ELFOptTable Parser;
   opt::InputArgList Args = Parser.parse(ArgsArr.slice(1));
@@ -273,7 +252,7 @@
   initLLVM(Args);
 
   if (!Config->Reproduce.empty())
-    logCommandline(ArgsArr);
+    saveLinkerInputs(Args);
 
   createFiles(Args);
   checkOptions(Args);
Index: lld/trunk/ELF/DriverUtils.cpp
===================================================================
--- lld/trunk/ELF/DriverUtils.cpp
+++ lld/trunk/ELF/DriverUtils.cpp
@@ -87,31 +87,93 @@
   outs() << "\n";
 }
 
-// Concatenates S and T so that the resulting path becomes S/T.
-// There are a few exceptions:
-//
-//  1. The result will never escape from S. Therefore, all ".."
-//     are removed from T before concatenatig them.
-//  2. Windows drive letters are removed from T before concatenation.
-std::string elf::concat_paths(StringRef S, StringRef T) {
-  // Remove leading '/' or a drive letter, and then remove "..".
-  SmallString<128> T2(path::relative_path(T));
-  path::remove_dots(T2, /*remove_dot_dot=*/true);
-
+// Makes a given pathname an absolute path first, and then remove
+// beginning /. For example, "../foo.o" is converted to "home/john/foo.o",
+// assuming that the current directory is "/home/john/bar".
+static std::string relative_to_root(StringRef Path) {
+  SmallString<128> Abs = Path;
+  if (std::error_code EC = fs::make_absolute(Abs))
+    fatal("make_absolute failed: " + EC.message());
+  path::remove_dots(Abs, /*remove_dot_dot=*/true);
+
+  // This is Windows specific. root_name() returns a drive letter
+  // (e.g. "c:") or a UNC name (//net). We want to keep it as part
+  // of the result.
   SmallString<128> Res;
-  path::append(Res, S, T2);
+  StringRef Root = path::root_name(Path);
+  if (Path.endswith(":"))
+    Res = Root.drop_back();
+  else if (Path.startswith("//"))
+    Res = Root.substr(2);
+
+  path::append(Res, path::relative_path(Abs));
   return Res.str();
 }
 
-void elf::copyFile(StringRef Src, StringRef Dest) {
+// Copies file Src to {Config->Reproduce}/Src.
+// Returns the new path relative to Config->Reproduce.
+static std::string copyFile(StringRef Src) {
+  std::string Relpath = relative_to_root(Src);
+  SmallString<128> Dest;
+  path::append(Dest, Config->Reproduce, Relpath);
+
   SmallString<128> Dir(Dest);
   path::remove_filename(Dir);
-  if (std::error_code EC = sys::fs::create_directories(Dir)) {
+  if (std::error_code EC = sys::fs::create_directories(Dir))
     error(EC, Dir + ": can't create directory");
-    return;
-  }
   if (std::error_code EC = sys::fs::copy_file(Src, Dest))
     error(EC, "failed to copy file: " + Dest);
+  return Relpath;
+}
+
+// Quote a given string if it contains a space character.
+static std::string quote(StringRef S) {
+  if (S.find(' ') == StringRef::npos)
+    return S;
+  return ("\"" + S + "\"").str();
+}
+
+// Copies all input files to Config->Reproduce directory and
+// create a response file as "response.txt", so that you can re-run
+// the same command with the same inputs just by executing
+// "ld.lld @response.txt". Used by --reproduce. This feature is
+// supposed to be used by users to report an issue to LLD developers.
+void elf::saveLinkerInputs(const llvm::opt::InputArgList &Args) {
+  // Create the output directory.
+  if (std::error_code EC = sys::fs::create_directories(
+        Config->Reproduce, /*IgnoreExisting=*/false)) {
+    error(EC, Config->Reproduce + ": can't create directory");
+    return;
+  }
+
+  // Open "response.txt".
+  SmallString<128> Path;
+  path::append(Path, Config->Reproduce, "response.txt");
+  std::error_code EC;
+  raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::F_None);
+  check(EC);
+
+  // Dump the command line to response.txt while copying files
+  // and rewriting paths.
+  for (auto *Arg : Args) {
+    switch (Arg->getOption().getID()) {
+    case OPT_reproduce:
+      break;
+    case OPT_script:
+      OS << "--script ";
+      // fallthrough
+    case OPT_INPUT: {
+      StringRef Path = Arg->getValue();
+      if (fs::exists(Path))
+        OS << quote(copyFile(Path)) << "\n";
+      else
+        OS << quote(Path) << "\n";
+      break;
+    }
+    default:
+      OS << Arg->getAsString(Args) << "\n";
+    }
+  }
 }
 
 std::string elf::findFromSearchPaths(StringRef Path) {
Index: lld/trunk/test/ELF/reproduce.s
===================================================================
--- lld/trunk/test/ELF/reproduce.s
+++ lld/trunk/test/ELF/reproduce.s
@@ -5,16 +5,24 @@
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.dir/build1/foo.o
 # RUN: cd %t.dir
 # RUN: ld.lld build1/foo.o -o bar -shared --as-needed --reproduce repro
-# RUN: diff build1/foo.o repro/build1/foo.o
+# RUN: diff build1/foo.o repro/%:t.dir/build1/foo.o
 
-# RUN: FileCheck %s --check-prefix=INVOCATION < repro/invocation.txt
-# INVOCATION: lld{{[^\s]*}} build1/foo.o -o bar -shared --as-needed --reproduce repro
+# RUN: FileCheck %s --check-prefix=RSP < repro/response.txt
+# RSP:      {{.*}}foo.o
+# RSP-NEXT: -o bar
+# RSP-NEXT: -shared
+# RSP-NEXT: --as-needed
 
 # RUN: mkdir -p %t.dir/build2/a/b/c
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.dir/build2/foo.o
 # RUN: cd %t.dir/build2/a/b/c
 # RUN: ld.lld ./../../../foo.o -o bar -shared --as-needed --reproduce repro
-# RUN: diff %t.dir/build2/foo.o repro/foo.o
+# RUN: diff %t.dir/build2/foo.o repro/%:t.dir/build2/foo.o
+
+# RUN: not ld.lld build1/foo.o --reproduce repro2 'foo bar' -soname=foo
+# RUN: FileCheck %s --check-prefix=RSP2 < repro2/response.txt
+# RSP2:      "foo bar"
+# RSP2-NEXT: -soname=foo
 
 # RUN: not ld.lld build1/foo.o -o bar -shared --as-needed --reproduce . 2>&1 \
 # RUN:   | FileCheck --check-prefix=ERROR %s