diff --git a/llvm/test/ThinLTO/X86/emit-inprocess-files.ll b/llvm/test/ThinLTO/X86/emit-inprocess-files.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/ThinLTO/X86/emit-inprocess-files.ll
@@ -0,0 +1,107 @@
+; Test InProcessThinLTO thin link output from llvm-lto2
+; Partially copied from distributed_import.ll, and added checks for {dis|en}abling imports
+
+; RUN: rm -f %t1.bc.thinlto.bc %t2.bc.thinlto.bc %t.out.1 %t.out.2 %t1.bc.imports %t2.bc.imports
+
+; Generate bitcode files with summary, as well as minimized bitcode without
+; the debug metadata for the thin link.
+; RUN: opt -thinlto-bc %s -thin-link-bitcode-file=%t1.thinlink.bc -o %t1.bc
+; RUN: opt -thinlto-bc %p/Inputs/distributed_import.ll -thin-link-bitcode-file=%t2.thinlink.bc -o %t2.bc
+; RUN: llvm-bcanalyzer -dump %t1.thinlink.bc | FileCheck --check-prefix=THINLINKBITCODE %s
+
+; First perform the thin link on the normal bitcode file using
+; -thinlto-distributed-indexes, collecting outputs to be compared with later.
+; RUN: llvm-lto2 run %t1.bc %t2.bc -o %t.o -save-temps \
+; RUN:     -thinlto-distributed-indexes \
+; RUN:     -r=%t1.bc,g, \
+; RUN:     -r=%t1.bc,analias, \
+; RUN:     -r=%t1.bc,f,px \
+; RUN:     -r=%t2.bc,g,px \
+; RUN:     -r=%t2.bc,analias,px \
+; RUN:     -r=%t2.bc,aliasee,px
+; RUN: mv %t1.bc.thinlto.bc %t1.bc.thinlto.bc.orig
+; RUN: mv %t2.bc.thinlto.bc %t2.bc.thinlto.bc.orig
+; RUN: mv %t1.bc.imports %t1.bc.imports.orig
+; RUN: mv %t2.bc.imports %t2.bc.imports.orig
+
+; Now use -thinlto-emit-indexes instead.
+; RUN: llvm-lto2 run %t1.bc %t2.bc -o %t.o -save-temps \
+; RUN:     -thinlto-emit-indexes \
+; RUN:     -r=%t1.bc,g, \
+; RUN:     -r=%t1.bc,analias, \
+; RUN:     -r=%t1.bc,f,px \
+; RUN:     -r=%t2.bc,g,px \
+; RUN:     -r=%t2.bc,analias,px \
+; RUN:     -r=%t2.bc,aliasee,px \
+; RUN:     -o=%t.out
+
+; Since InProcessThinLTO ran, there should be output
+; RUN: ls %t.out.1
+; RUN: ls %t.out.2
+
+; Ensure imports weren't generated since -thinlto-emit-imports wasn't specified
+; RUN: not ls %t1.bc.imports
+; RUN: not ls %t2.bc.imports
+
+; Compare the generated index files.
+; RUN: diff %t1.bc.thinlto.bc %t1.bc.thinlto.bc.orig
+; RUN: diff %t2.bc.thinlto.bc %t2.bc.thinlto.bc.orig
+
+; RUN: rm -f %t1.bc.thinlto.bc %t2.bc.thinlto.bc %t.out.1 %t.out.2
+
+; Do the thin link again but also emit imports files now
+; RUN: llvm-lto2 run %t1.bc %t2.bc -o %t.o -save-temps \
+; RUN:     -thinlto-emit-indexes \
+; RUN:     -thinlto-emit-imports \
+; RUN:     -r=%t1.bc,g, \
+; RUN:     -r=%t1.bc,analias, \
+; RUN:     -r=%t1.bc,f,px \
+; RUN:     -r=%t2.bc,g,px \
+; RUN:     -r=%t2.bc,analias,px \
+; RUN:     -r=%t2.bc,aliasee,px \
+; RUN:     -o=%t.out
+
+; Check the output
+; RUN: ls %t.out.1
+; RUN: ls %t.out.2
+; RUN: diff %t1.bc.thinlto.bc %t1.bc.thinlto.bc.orig
+; RUN: diff %t2.bc.thinlto.bc %t2.bc.thinlto.bc.orig
+; RUN: diff %t1.bc.imports %t1.bc.imports.orig
+; RUN: diff %t2.bc.imports %t2.bc.imports.orig
+
+target triple = "x86_64-unknown-linux-gnu"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+declare i32 @g(...)
+declare void @analias(...)
+
+define void @f() {
+entry:
+  call i32 (...) @g()
+  call void (...) @analias()
+  ret void
+}
+
+; THINLINKBITCODE-NOT: IDENTIFICATION_BLOCK_ID
+; THINLINKBITCODE-NOT: BLOCKINFO_BLOCK
+; THINLINKBITCODE-NOT: TYPE_BLOCK_ID
+; THINLINKBITCODE-NOT: VSTOFFSET
+; THINLINKBITCODE-NOT: CONSTANTS_BLOCK
+; THINLINKBITCODE-NOT: METADATA_KIND_BLOCK
+; THINLINKBITCODE-NOT: METADATA_BLOCK
+; THINLINKBITCODE-NOT: OPERAND_BUNDLE_TAGS_BLOCK
+; THINLINKBITCODE-NOT: UnknownBlock26
+; THINLINKBITCODE-NOT: FUNCTION_BLOCK
+; THINLINKBITCODE-NOT: VALUE_SYMTAB
+; THINLINKBITCODE: MODULE_BLOCK
+; THINLINKBITCODE: VERSION
+; THINLINKBITCODE: SOURCE_FILENAME
+; THINLINKBITCODE: GLOBALVAL_SUMMARY_BLOCK
+; THINLINKBITCODE: HASH
+; THINLINKBITCODE: SYMTAB_BLOCK
+; THINLINKBITCODE: STRTAB_BLOCK
+
+!llvm.dbg.cu = !{}
+
+!1 = !{i32 2, !"Debug Info Version", i32 3}
+!llvm.module.flags = !{!1}
diff --git a/llvm/tools/llvm-lto2/llvm-lto2.cpp b/llvm/tools/llvm-lto2/llvm-lto2.cpp
--- a/llvm/tools/llvm-lto2/llvm-lto2.cpp
+++ b/llvm/tools/llvm-lto2/llvm-lto2.cpp
@@ -73,6 +73,17 @@
                                        "import files for the "
                                        "distributed backend case"));
 
+static cl::opt<bool>
+    ThinLTOEmitIndexes("thinlto-emit-indexes", cl::init(false),
+                       cl::desc("Write out individual index files via "
+                                "InProcessThinLTO"));
+
+static cl::opt<bool>
+    ThinLTOEmitImports("thinlto-emit-imports", cl::init(false),
+                       cl::desc("Write out individual imports files via "
+                                "InProcessThinLTO. Must be specified together "
+                                "with -thinlto-emit-indexes"));
+
 // Default to using all available threads in the system, but using only one
 // thread per core (no SMT).
 // Use -thinlto-threads=all to use hardware_concurrency() instead, which means
@@ -306,7 +317,9 @@
                                             /* OnWrite */ {});
   else
     Backend = createInProcessThinBackend(
-        llvm::heavyweight_hardware_concurrency(Threads));
+        llvm::heavyweight_hardware_concurrency(Threads),
+        /* OnWrite */ {}, ThinLTOEmitIndexes, ThinLTOEmitImports);
+
   // Track whether we hit an error; in particular, in the multi-threaded case,
   // we can't exit() early because the rest of the threads wouldn't have had a
   // change to be join-ed, and that would result in a "terminate called without