Index: lld/trunk/ELF/Config.h
===================================================================
--- lld/trunk/ELF/Config.h
+++ lld/trunk/ELF/Config.h
@@ -158,6 +158,7 @@
   bool SysvHash = false;
   bool Target1Rel;
   bool Trace;
+  bool ThinLTOEmitImportsFiles;
   bool ThinLTOIndexOnly;
   bool UndefinedVersion;
   bool WarnBackrefs;
Index: lld/trunk/ELF/Driver.cpp
===================================================================
--- lld/trunk/ELF/Driver.cpp
+++ lld/trunk/ELF/Driver.cpp
@@ -801,6 +801,8 @@
     } else if (S.startswith("thinlto-index-only=")) {
       Config->ThinLTOIndexOnly = true;
       Config->ThinLTOIndexOnlyObjectsFile = S.substr(19);
+    } else if (S == "thinlto-emit-imports-files") {
+      Config->ThinLTOEmitImportsFiles = true;
     } else if (S.startswith("thinlto-prefix-replace=")) {
       std::tie(Config->ThinLTOPrefixReplace.first,
                Config->ThinLTOPrefixReplace.second) = S.substr(23).split(';');
Index: lld/trunk/ELF/LTO.cpp
===================================================================
--- lld/trunk/ELF/LTO.cpp
+++ lld/trunk/ELF/LTO.cpp
@@ -86,8 +86,7 @@
 static std::string getThinLTOOutputFile(StringRef ModulePath) {
   return lto::getThinLTOOutputFile(ModulePath,
                                    Config->ThinLTOPrefixReplace.first,
-                                   Config->ThinLTOPrefixReplace.second) +
-         ".thinlto.bc";
+                                   Config->ThinLTOPrefixReplace.second);
 }
 
 // Initializes IndexFile, Backend and LTOObj members.
@@ -134,7 +133,7 @@
     IndexFile = openFile(Config->ThinLTOIndexOnlyObjectsFile);
     Backend = lto::createWriteIndexesThinBackend(
         Config->ThinLTOPrefixReplace.first, Config->ThinLTOPrefixReplace.second,
-        true, IndexFile.get(), nullptr);
+        Config->ThinLTOEmitImportsFiles, IndexFile.get(), nullptr);
   }
 
   Conf.SampleProfile = Config->LTOSampleProfile;
@@ -167,8 +166,13 @@
   lto::InputFile &Obj = *F.Obj;
 
   // Create the empty files which, if indexed, will be overwritten later.
-  if (Config->ThinLTOIndexOnly)
-    openFile(getThinLTOOutputFile(Obj.getName()));
+  if (Config->ThinLTOIndexOnly) {
+    std::string Path = getThinLTOOutputFile(Obj.getName());
+    openFile(Path + ".thinlto.bc");
+
+    if (Config->ThinLTOEmitImportsFiles)
+      openFile(Path + ".imports");
+  }
 
   unsigned SymNum = 0;
   std::vector<Symbol *> Syms = F.getSymbols();
@@ -269,14 +273,17 @@
       if (F->AddedToLink || !isBitcode(F->MB))
         continue;
 
-      std::unique_ptr<raw_fd_ostream> OS =
-          openFile(getThinLTOOutputFile(F->getName()));
+      std::string Path = getThinLTOOutputFile(F->getName());
+      std::unique_ptr<raw_fd_ostream> OS = openFile(Path + ".thinlto.bc");
       if (!OS)
         continue;
 
       ModuleSummaryIndex M(false);
       M.setSkipModuleByDistributedBackend();
       WriteIndexToFile(M, *OS);
+
+      if (Config->ThinLTOEmitImportsFiles)
+        openFile(Path + ".imports");
     }
 
     // ThinLTO with index only option is required to generate only the index
Index: lld/trunk/test/ELF/lto/thinlto_emit_imports.ll
===================================================================
--- lld/trunk/test/ELF/lto/thinlto_emit_imports.ll
+++ lld/trunk/test/ELF/lto/thinlto_emit_imports.ll
@@ -0,0 +1,55 @@
+; REQUIRES: x86
+
+; Generate summary sections and test lld handling.
+; RUN: opt -module-summary %s -o %t.o
+; RUN: opt -module-summary %p/Inputs/thinlto.ll -o %t2.o
+
+; Include a file with an empty module summary index, to ensure that the expected
+; output files are created regardless, for a distributed build system.
+; RUN: opt -module-summary %p/Inputs/thinlto_empty.ll -o %t3.o
+
+; Ensure lld generates imports files if requested for distributed backends.
+; RUN: rm -f %t3.o.imports %t3.o.thinlto.bc
+; RUN: ld.lld --plugin-opt=thinlto-index-only --plugin-opt=thinlto-emit-imports-files -shared %t.o %t2.o %t3.o -o %t4
+
+; The imports file for this module contains the bitcode file for
+; Inputs/thinlto.ll
+; RUN: cat %t.o.imports | count 1
+; RUN: cat %t.o.imports | FileCheck %s --check-prefix=IMPORTS1
+; IMPORTS1: thinlto_emit_imports.ll.tmp2.o
+
+; The imports file for Input/thinlto.ll is empty as it does not import anything.
+; RUN: cat %t2.o.imports | count 0
+
+; The imports file for Input/thinlto_empty.ll is empty but should exist.
+; RUN: cat %t3.o.imports | count 0
+
+; The index file should be created even for the input with an empty summary.
+; RUN: ls %t3.o.thinlto.bc
+
+; Ensure lld generates error if unable to write to imports file.
+; RUN: rm -f %t3.o.imports
+; RUN: touch %t3.o.imports
+; RUN: chmod 400 %t3.o.imports
+; RUN: not ld.lld -m elf_x86_64 --plugin-opt=thinlto-index-only --plugin-opt=thinlto-emit-imports-files -shared %t.o %t2.o %t3.o -o %t4 2>&1 | FileCheck %s --check-prefix=ERR
+; ERR: cannot open {{.*}}3.o.imports: {{P|p}}ermission denied
+
+; Ensure lld doesn't generate import files when thinlto-index-only is not enabled
+; RUN: rm -f %t.o.imports
+; RUN: rm -f %t2.o.imports
+; RUN: rm -f %t3.o.imports
+; RUN: ld.lld -m elf_x86_64 --plugin-opt=thinlto-emit-imports-files -shared %t.o %t2.o %t3.o -o %t4
+; RUN: not ls %t.o.imports
+; RUN: not ls %t2.o.imports
+; RUN: not ls %t4.o.imports
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare void @g(...)
+
+define void @f() {
+entry:
+  call void (...) @g()
+  ret void
+}