Index: lld/trunk/test/wasm/reproduce.ll
===================================================================
--- lld/trunk/test/wasm/reproduce.ll
+++ lld/trunk/test/wasm/reproduce.ll
@@ -0,0 +1,27 @@
+; REQUIRES: shell
+; RUN: rm -rf %t.dir
+; RUN: mkdir -p %t.dir
+; RUN: llc -filetype=obj %s -o %t.dir/foo.o
+; RUN: wasm-ld --reproduce=%t.dir/repro.tar -o out.wasm %t.dir/foo.o
+
+; RUN: cd %t.dir
+; RUN: tar tf repro.tar | FileCheck --check-prefix=TAR
+
+; TAR: repro/response.txt
+; TAR: repro/version.txt
+; TAR: repro/{{.*}}/foo.o
+
+; RUN: tar xf repro.tar
+; RUN: FileCheck --check-prefix=RSP %s < repro/response.txt
+
+; RSP: -o out.wasm
+; RSP: {{.*}}/foo.o
+
+; RUN: FileCheck %s --check-prefix=VERSION < repro/version.txt
+; VERSION: LLD
+
+target triple = "wasm32-unknown-unknown"
+
+define void @_start() {
+  ret void
+}
Index: lld/trunk/wasm/Driver.cpp
===================================================================
--- lld/trunk/wasm/Driver.cpp
+++ lld/trunk/wasm/Driver.cpp
@@ -16,6 +16,7 @@
 #include "lld/Common/Args.h"
 #include "lld/Common/ErrorHandler.h"
 #include "lld/Common/Memory.h"
+#include "lld/Common/Reproduce.h"
 #include "lld/Common/Strings.h"
 #include "lld/Common/Threads.h"
 #include "lld/Common/Version.h"
@@ -26,6 +27,7 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Process.h"
+#include "llvm/Support/TarWriter.h"
 #include "llvm/Support/TargetSelect.h"
 
 #define DEBUG_TYPE "lld"
@@ -504,6 +506,34 @@
       "__dso_handle", WASM_SYMBOL_VISIBILITY_HIDDEN);
 }
 
+// Reconstructs command line arguments so that so that you can re-run
+// the same command with the same inputs. This is for --reproduce.
+static std::string createResponseFile(const opt::InputArgList &Args) {
+  SmallString<0> Data;
+  raw_svector_ostream OS(Data);
+
+  // Copy the command line to the output while rewriting paths.
+  for (auto *Arg : Args) {
+    switch (Arg->getOption().getUnaliasedOption().getID()) {
+    case OPT_reproduce:
+      break;
+    case OPT_INPUT:
+      OS << quote(relativeToRoot(Arg->getValue())) << "\n";
+      break;
+    case OPT_o:
+      // If -o path contains directories, "lld @response.txt" will likely
+      // fail because the archive we are creating doesn't contain empty
+      // directories for the output path (-o doesn't create directories).
+      // Strip directories to prevent the issue.
+      OS << "-o " << quote(sys::path::filename(Arg->getValue())) << "\n";
+      break;
+    default:
+      OS << toString(*Arg) << "\n";
+    }
+  }
+  return Data.str();
+}
+
 void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
   WasmOptTable Parser;
   opt::InputArgList Args = Parser.parse(ArgsArr.slice(1));
@@ -522,6 +552,20 @@
     return;
   }
 
+  // Handle --reproduce
+  if (auto *Arg = Args.getLastArg(OPT_reproduce)) {
+    StringRef Path = Arg->getValue();
+    Expected<std::unique_ptr<TarWriter>> ErrOrWriter =
+        TarWriter::create(Path, path::stem(Path));
+    if (ErrOrWriter) {
+      Tar = std::move(*ErrOrWriter);
+      Tar->append("response.txt", createResponseFile(Args));
+      Tar->append("version.txt", getLLDVersion() + "\n");
+    } else {
+      error("--reproduce: " + toString(ErrOrWriter.takeError()));
+    }
+  }
+
   // Parse and evaluate -mllvm options.
   std::vector<const char *> V;
   V.push_back("wasm-ld (LLVM option parsing)");
Index: lld/trunk/wasm/InputFiles.h
===================================================================
--- lld/trunk/wasm/InputFiles.h
+++ lld/trunk/wasm/InputFiles.h
@@ -19,6 +19,10 @@
 #include "llvm/Support/MemoryBuffer.h"
 #include <vector>
 
+namespace llvm {
+class TarWriter;
+}
+
 namespace lld {
 namespace wasm {
 
@@ -29,6 +33,10 @@
 class InputEvent;
 class InputSection;
 
+// If --reproduce option is given, all input files are written
+// to this tar archive.
+extern std::unique_ptr<llvm::TarWriter> Tar;
+
 class InputFile {
 public:
   enum Kind {
Index: lld/trunk/wasm/InputFiles.cpp
===================================================================
--- lld/trunk/wasm/InputFiles.cpp
+++ lld/trunk/wasm/InputFiles.cpp
@@ -14,8 +14,10 @@
 #include "SymbolTable.h"
 #include "lld/Common/ErrorHandler.h"
 #include "lld/Common/Memory.h"
+#include "lld/Common/Reproduce.h"
 #include "llvm/Object/Binary.h"
 #include "llvm/Object/Wasm.h"
+#include "llvm/Support/TarWriter.h"
 #include "llvm/Support/raw_ostream.h"
 
 #define DEBUG_TYPE "lld"
@@ -27,6 +29,8 @@
 using namespace llvm::object;
 using namespace llvm::wasm;
 
+std::unique_ptr<llvm::TarWriter> lld::wasm::Tar;
+
 Optional<MemoryBufferRef> lld::wasm::readFile(StringRef Path) {
   log("Loading: " + Path);
 
@@ -39,6 +43,8 @@
   MemoryBufferRef MBRef = MB->getMemBufferRef();
   make<std::unique_ptr<MemoryBuffer>>(std::move(MB)); // take MB ownership
 
+  if (Tar)
+    Tar->append(relativeToRoot(Path), MBRef.getBuffer());
   return MBRef;
 }
 
Index: lld/trunk/wasm/Options.td
===================================================================
--- lld/trunk/wasm/Options.td
+++ lld/trunk/wasm/Options.td
@@ -85,6 +85,8 @@
 
 def relocatable: F<"relocatable">, HelpText<"Create relocatable object file">;
 
+defm reproduce: Eq<"reproduce", "Dump linker invocation and input files for debugging">;
+
 def shared: F<"shared">, HelpText<"Build a shared object">;
 
 def strip_all: F<"strip-all">, HelpText<"Strip all symbols">;