Index: llvm/lib/LTO/LTO.cpp
===================================================================
--- llvm/lib/LTO/LTO.cpp
+++ llvm/lib/LTO/LTO.cpp
@@ -359,7 +359,10 @@
                // Ignore local and appending linkage values since the linker
                // doesn't resolve them.
                !GlobalValue::isLocalLinkage(S->linkage()) &&
-               !GlobalValue::isAppendingLinkage(S->linkage()))
+               S->linkage() != GlobalValue::AppendingLinkage &&
+               // We can't internalize available_externally globals because this
+               // can break function pointer equality.
+               S->linkage() != GlobalValue::AvailableExternallyLinkage)
       S->setLinkage(GlobalValue::InternalLinkage);
   }
 }
Index: llvm/test/LTO/Resolution/X86/available-externally.ll
===================================================================
--- /dev/null
+++ llvm/test/LTO/Resolution/X86/available-externally.ll
@@ -0,0 +1,16 @@
+; RUN: opt -module-summary -o %t.bc %s
+; RUN: llvm-lto2 run %t.bc -r %t.bc,foo,px -r %t.bc,bar, -o %t2
+; RUN: llvm-nm %t2.1 | FileCheck %s
+
+; CHECK: U bar
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void ()* @foo() {
+  ret void ()* @bar
+}
+
+define available_externally void @bar() {
+  ret void
+}