Index: lib/Linker/LinkModules.cpp
===================================================================
--- lib/Linker/LinkModules.cpp
+++ lib/Linker/LinkModules.cpp
@@ -762,8 +762,10 @@
     // It would be incorrect to import an appending linkage variable,
     // since it would cause global constructors/destructors to be
     // executed multiple times. This should have already been handled
-    // by linkGlobalValueProto.
-    llvm_unreachable("Cannot import appending linkage variable");
+    // by linkGlobalValueProto, and we will assert in shouldLinkFromSource
+    // if we try to import, so we simply return AppendingLinkage here
+    // as this helper is called more widely in getLinkedToGlobal.
+    return GlobalValue::AppendingLinkage;
 
   case GlobalValue::InternalLinkage:
   case GlobalValue::PrivateLinkage:
@@ -1861,7 +1863,8 @@
 
   if (!DGV && !shouldOverrideFromSrc() &&
       (GV.hasLocalLinkage() || GV.hasLinkOnceLinkage() ||
-       GV.hasAvailableExternallyLinkage())) {
+       GV.hasAvailableExternallyLinkage() ||
+       (GV.hasAppendingLinkage() && isPerformingImport()))) {
     return false;
   }
   MapValue(&GV, ValueMap, RF_MoveDistinctMDs, &TypeMap, &ValMaterializer);
Index: test/Transforms/FunctionImport/Inputs/appending_global.ll
===================================================================
--- /dev/null
+++ test/Transforms/FunctionImport/Inputs/appending_global.ll
@@ -0,0 +1,6 @@
+@v = weak global i8 1
+@llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @foo, i8* @v}]
+
+define void @foo() {
+  ret void
+}
Index: test/Transforms/FunctionImport/import_appending_global.ll
===================================================================
--- /dev/null
+++ test/Transforms/FunctionImport/import_appending_global.ll
@@ -0,0 +1,18 @@
+; RUN: llvm-as -function-summary %s -o %t.bc
+; RUN: llvm-as -function-summary %p/Inputs/appending_global.ll -o %t2.bc
+; RUN: llvm-lto -thinlto -o %t3 %t.bc %t2.bc
+
+; Do the import now
+; RUN: opt -function-import -summary-file %t3.thinlto.bc %s -S | FileCheck %s
+
+; Ensure that global constructors (appending linkage) is not imported
+; CHECK-NOT: @llvm.global_ctors
+
+
+define i32 @main() {
+entry:
+  call void @foo()
+  ret i32 0
+}
+
+declare void @foo()