Index: lib/LTO/LTOBackend.cpp
===================================================================
--- lib/LTO/LTOBackend.cpp
+++ lib/LTO/LTOBackend.cpp
@@ -342,8 +342,7 @@
   if (Conf.PostPromoteModuleHook && !Conf.PostPromoteModuleHook(Task, Mod))
     return Error();
 
-  if (!DefinedGlobals.empty())
-    thinLTOInternalizeModule(Mod, DefinedGlobals);
+  thinLTOInternalizeModule(Mod, DefinedGlobals);
 
   if (Conf.PostInternalizeModuleHook &&
       !Conf.PostInternalizeModuleHook(Task, Mod))
Index: lib/Transforms/IPO/FunctionImport.cpp
===================================================================
--- lib/Transforms/IPO/FunctionImport.cpp
+++ lib/Transforms/IPO/FunctionImport.cpp
@@ -547,6 +547,14 @@
 /// Run internalization on \p TheModule based on symmary analysis.
 void llvm::thinLTOInternalizeModule(Module &TheModule,
                                     const GVSummaryMapTy &DefinedGlobals) {
+  // Skip this if there are no GV summaries. Either there are no
+  // defined GVs to internalize, or we had an empty summary (e.g.
+  // due to inline or module-level assembly that prevents us from
+  // being able to rename local references). If we don't bail out here
+  // then we would get an assert below in the MustPreserveGV callback.
+  if (DefinedGlobals.empty())
+    return;
+
   // Parse inline ASM and collect the list of symbols that are not defined in
   // the current module.
   StringSet<> AsmUndefinedRefs;
Index: test/Transforms/FunctionImport/Inputs/inlineasm.ll
===================================================================
--- test/Transforms/FunctionImport/Inputs/inlineasm.ll
+++ test/Transforms/FunctionImport/Inputs/inlineasm.ll
@@ -1,3 +1,6 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
 @myvar = internal constant i8 1, align 1
 @llvm.used = appending global [1 x i8*] [i8* @myvar], section "llvm.metadata"
 
Index: test/Transforms/FunctionImport/inlineasm.ll
===================================================================
--- test/Transforms/FunctionImport/inlineasm.ll
+++ test/Transforms/FunctionImport/inlineasm.ll
@@ -3,11 +3,21 @@
 ; RUN: opt -module-summary %p/Inputs/inlineasm.ll -o %t2.bc
 ; RUN: llvm-lto -thinlto -o %t3 %t.bc %t2.bc
 
+; RUN: llvm-lto -thinlto-action=internalize -thinlto-index %t3.thinlto.bc %t2.bc -o -  --exported-symbol=main | llvm-dis -o - | FileCheck %s --check-prefix=INTERNALIZE
+; INTERNALIZE: define void @foo(i64* %v)
+
+; RUN: llvm-lto2 -o %t3 %t.bc %t2.bc -r=%t.bc,main,plx -r=%t.bc,foo,l -r=%t2.bc,foo,pl
+; RUN: llvm-nm %t3.1 | FileCheck %s --check-prefix=NM
+; NM: T foo
+
 ; Attempt the import now, ensure below that file containing inline assembly
 ; is not imported from. Otherwise we would need to promote its local variable
 ; used in the inline assembly, which would not see the rename.
 ; RUN: opt -function-import -summary-file %t3.thinlto.bc %t.bc -S 2>&1 | FileCheck %s --check-prefix=CHECK
 
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
 define i32 @main() #0 {
 entry:
   %f = alloca i64, align 8