Index: llvm/include/llvm/LTO/LTOBackend.h
===================================================================
--- llvm/include/llvm/LTO/LTOBackend.h
+++ llvm/include/llvm/LTO/LTOBackend.h
@@ -37,7 +37,7 @@
 /// Runs a regular LTO backend.
 Error backend(Config &C, AddStreamFn AddStream,
               unsigned ParallelCodeGenParallelismLevel,
-              std::unique_ptr<Module> M);
+              std::unique_ptr<Module> M, ModuleSummaryIndex &CombinedIndex);
 
 /// Runs a ThinLTO backend.
 Error thinBackend(Config &C, unsigned Task, AddStreamFn AddStream, Module &M,
Index: llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h
===================================================================
--- llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h
+++ llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h
@@ -21,6 +21,7 @@
 #include <vector>
 
 namespace llvm {
+class ModuleSummaryIndex;
 class Pass;
 class TargetLibraryInfoImpl;
 class TargetMachine;
@@ -123,6 +124,10 @@
   /// added to the per-module passes.
   Pass *Inliner;
 
+  /// The module summary index to use for passing information between the
+  /// regular LTO phase and the thin LTO backends.
+  ModuleSummaryIndex *Summary = nullptr;
+
   bool DisableTailCalls;
   bool DisableUnitAtATime;
   bool DisableUnrollLoops;
Index: llvm/lib/LTO/LTO.cpp
===================================================================
--- llvm/lib/LTO/LTO.cpp
+++ llvm/lib/LTO/LTO.cpp
@@ -602,7 +602,7 @@
       return Error::success();
   }
   return backend(Conf, AddStream, RegularLTO.ParallelCodeGenParallelismLevel,
-                 std::move(RegularLTO.CombinedModule));
+                 std::move(RegularLTO.CombinedModule), ThinLTO.CombinedIndex);
 }
 
 /// This class defines the interface to the ThinLTO backend.
Index: llvm/lib/LTO/LTOBackend.cpp
===================================================================
--- llvm/lib/LTO/LTOBackend.cpp
+++ llvm/lib/LTO/LTOBackend.cpp
@@ -168,13 +168,14 @@
 }
 
 static void runOldPMPasses(Config &Conf, Module &Mod, TargetMachine *TM,
-                           bool IsThinLTO) {
+                           bool IsThinLTO, ModuleSummaryIndex &CombinedIndex) {
   legacy::PassManager passes;
   passes.add(createTargetTransformInfoWrapperPass(TM->getTargetIRAnalysis()));
 
   PassManagerBuilder PMB;
   PMB.LibraryInfo = new TargetLibraryInfoImpl(Triple(TM->getTargetTriple()));
   PMB.Inliner = createFunctionInliningPass();
+  PMB.Summary = &CombinedIndex;
   // Unconditionally verify input since it is not verified before this
   // point and has unknown origin.
   PMB.VerifyInput = true;
@@ -191,9 +192,9 @@
 }
 
 bool opt(Config &Conf, TargetMachine *TM, unsigned Task, Module &Mod,
-         bool IsThinLTO) {
+         bool IsThinLTO, ModuleSummaryIndex &CombinedIndex) {
   if (Conf.OptPipeline.empty())
-    runOldPMPasses(Conf, Mod, TM, IsThinLTO);
+    runOldPMPasses(Conf, Mod, TM, IsThinLTO, CombinedIndex);
   else
     runNewPMCustomPasses(Mod, TM, Conf.OptPipeline, Conf.AAPipeline,
                          Conf.DisableVerify);
@@ -291,7 +292,8 @@
 
 Error lto::backend(Config &C, AddStreamFn AddStream,
                    unsigned ParallelCodeGenParallelismLevel,
-                   std::unique_ptr<Module> Mod) {
+                   std::unique_ptr<Module> Mod,
+                   ModuleSummaryIndex &CombinedIndex) {
   Expected<const Target *> TOrErr = initAndLookupTarget(C, *Mod);
   if (!TOrErr)
     return TOrErr.takeError();
@@ -302,7 +304,7 @@
   handleAsmUndefinedRefs(*Mod, *TM);
 
   if (!C.CodeGenOnly)
-    if (!opt(C, TM.get(), 0, *Mod, /*IsThinLTO=*/false))
+    if (!opt(C, TM.get(), 0, *Mod, /*IsThinLTO=*/false, CombinedIndex))
       return Error::success();
 
   if (ParallelCodeGenParallelismLevel == 1) {
@@ -367,7 +369,7 @@
   if (Conf.PostImportModuleHook && !Conf.PostImportModuleHook(Task, Mod))
     return Error::success();
 
-  if (!opt(Conf, TM.get(), Task, Mod, /*IsThinLTO=*/true))
+  if (!opt(Conf, TM.get(), Task, Mod, /*IsThinLTO=*/true, CombinedIndex))
     return Error::success();
 
   codegen(Conf, TM.get(), AddStream, Task, Mod);
Index: llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
===================================================================
--- llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -833,6 +833,10 @@
   if (VerifyInput)
     PM.add(createVerifierPass());
 
+  if (Summary)
+    PM.add(
+        createLowerTypeTestsPass(LowerTypeTestsSummaryAction::Import, Summary));
+
   populateModulePassManager(PM);
 
   if (VerifyOutput)
@@ -857,8 +861,9 @@
   // Lower type metadata and the type.test intrinsic. This pass supports Clang's
   // control flow integrity mechanisms (-fsanitize=cfi*) and needs to run at
   // link time if CFI is enabled. The pass does nothing if CFI is disabled.
-  PM.add(createLowerTypeTestsPass(LowerTypeTestsSummaryAction::None,
-                                  /*Summary=*/nullptr));
+  PM.add(createLowerTypeTestsPass(Summary ? LowerTypeTestsSummaryAction::Export
+                                          : LowerTypeTestsSummaryAction::None,
+                                  Summary));
 
   if (OptLevel != 0)
     addLateLTOOptimizationPasses(PM);
Index: llvm/test/LTO/Resolution/X86/lowertypetests.ll
===================================================================
--- /dev/null
+++ llvm/test/LTO/Resolution/X86/lowertypetests.ll
@@ -0,0 +1,21 @@
+; RUN: opt -thinlto-bc -o %t %s
+; RUN: llvm-lto2 -r %t,f,plx -r %t,foo,lx -r %t,foo,plx -o %t1 %t
+; RUN: llvm-nm %t1.0 | FileCheck --prefix=MERGED %s
+; RUN: llvm-nm %t1.1 | FileCheck %s
+
+; MERGED: R __typeid_foo_global_addr
+; CHECK: U __typeid_foo_global_addr
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@foo = global i32 0, !type !0
+
+define i1 @f(i8* %ptr) {
+  %p = call i1 @llvm.type.test(i8* %ptr, metadata !"foo")
+  ret i1 %p
+}
+
+declare i1 @llvm.type.test(i8* %ptr, metadata %typeid) nounwind readnone
+
+!0 = !{i32 0, !"foo"}