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 linkIfNeeded, 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:
@@ -1067,8 +1069,7 @@
 
   // We always have to add Src if it has appending linkage.
   if (Src.hasAppendingLinkage()) {
-    // Caller should have already determined that we can't link from source
-    // when importing (see comments in linkGlobalValueProto).
+    // Should have prevented importing for appending linkage in linkIfNeeded.
     assert(!isPerformingImport());
     LinkFromSrc = true;
     return false;
@@ -1396,17 +1397,12 @@
 
   // Handle the ultra special appending linkage case first.
   assert(!DGV || SGV->hasAppendingLinkage() == DGV->hasAppendingLinkage());
-  if (SGV->hasAppendingLinkage() && isPerformingImport()) {
-    // Don't want to append to global_ctors list, for example, when we
-    // are importing for ThinLTO, otherwise the global ctors and dtors
-    // get executed multiple times for local variables (the latter causing
-    // double frees).
-    DoNotLinkFromSource.insert(SGV);
-    return false;
-  }
-  if (SGV->hasAppendingLinkage())
+  if (SGV->hasAppendingLinkage()) {
+    // Should have prevented importing for appending linkage in linkIfNeeded.
+    assert(!isPerformingImport());
     return linkAppendingVarProto(cast_or_null<GlobalVariable>(DGV),
                                  cast<GlobalVariable>(SGV));
+  }
 
   bool LinkFromSrc = true;
   Comdat *C = nullptr;
@@ -1864,6 +1860,12 @@
        GV.hasAvailableExternallyLinkage())) {
     return false;
   }
+  // Don't want to append to global_ctors list, for example, when we
+  // are importing for ThinLTO, otherwise the global ctors and dtors
+  // get executed multiple times for local variables (the latter causing
+  // double frees).
+  if (GV.hasAppendingLinkage() && isPerformingImport())
+    return false;
   MapValue(&GV, ValueMap, RF_MoveDistinctMDs, &TypeMap, &ValMaterializer);
   return HasError;
 }
Index: test/Linker/Inputs/funcimport_appending_global.ll
===================================================================
--- /dev/null
+++ test/Linker/Inputs/funcimport_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/Linker/funcimport_appending_global.ll
===================================================================
--- /dev/null
+++ test/Linker/funcimport_appending_global.ll
@@ -0,0 +1,20 @@
+; RUN: llvm-as -function-summary %s -o %t.bc
+; RUN: llvm-as -function-summary %p/Inputs/funcimport_appending_global.ll -o %t2.bc
+; RUN: llvm-lto -thinlto -o %t3 %t.bc %t2.bc
+
+; Do the import now
+; RUN: llvm-link %t.bc -functionindex=%t3.thinlto.bc -import=foo:%t2.bc -S | FileCheck %s
+
+; Ensure that global constructor (appending linkage) is not imported
+; CHECK-NOT: @llvm.global_ctors = {{.*}}@foo
+
+declare void @f()
+@llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @f, i8* null}]
+
+define i32 @main() {
+entry:
+  call void @foo()
+  ret i32 0
+}
+
+declare void @foo()