Index: test/tools/gold/X86/Inputs/thinlto_linkonceresolution.ll
===================================================================
--- /dev/null
+++ test/tools/gold/X86/Inputs/thinlto_linkonceresolution.ll
@@ -0,0 +1,4 @@
+target triple = "x86_64-unknown-linux-gnu"
+define linkonce_odr hidden void @f() {
+  ret void
+}
Index: test/tools/gold/X86/thinlto_linkonceresolution.ll
===================================================================
--- /dev/null
+++ test/tools/gold/X86/thinlto_linkonceresolution.ll
@@ -0,0 +1,27 @@
+; RUN: llvm-as -function-summary %s -o %t.o
+; RUN: llvm-as -function-summary %p/Inputs/thinlto_linkonceresolution.ll -o %t2.o
+
+; Ensure the plugin changes the symbol resolution for linkonce_odr
+; f() to LDPR_PREVAILING_DEF_IRONLY instead of LDPR_PREEMPTED_IR
+; for ThinLTO, since it isn't a full LTO link and the unreferenced
+; f() will be deleted in the other module. Note that gold picks the
+; first copy of f() as the prevailing one, so listing %t2.o first
+; is sufficient to ensure that this copy is preempted. Also,
+; set the import-instr-limit to 0 to prevent f() from being imported
+; from %t2.o which hides the problem.
+; RUN: %gold -plugin %llvmshlibdir/LLVMgold.so \
+; RUN:     --plugin-opt=thinlto \
+; RUN:     --plugin-opt=-import-instr-limit=0 \
+; RUN:     -o %t3.o %t2.o %t.o
+; RUN: llvm-nm %t3.o | FileCheck %s
+
+; CHECK-NOT: U f
+
+target triple = "x86_64-unknown-linux-gnu"
+define i32 @g() {
+  call void @f()
+  ret i32 0
+}
+define linkonce_odr hidden void @f() {
+  ret void
+}
Index: tools/gold/gold-plugin.cpp
===================================================================
--- tools/gold/gold-plugin.cpp
+++ tools/gold/gold-plugin.cpp
@@ -712,6 +712,14 @@
     if (Resolution == LDPR_PREVAILING_DEF_IRONLY_EXP && !Res.IsLinkonceOdr)
       Resolution = LDPR_PREVAILING_DEF;
 
+    // For ThinLTO the IR files are compiled through the backend independently,
+    // so gold's preemption decisions must be ignored for linkonce symbols.
+    // There is no guarantee that the symbol will be emitted into the object
+    // file with the prevailing copy.
+    if (options::thinlto && Res.IsLinkonceOdr &&
+        Resolution == LDPR_PREEMPTED_IR)
+      Resolution = LDPR_PREVAILING_DEF_IRONLY;
+
     GV->setUnnamedAddr(Res.UnnamedAddr);
     GV->setVisibility(Res.Visibility);