Index: include/llvm/Linker/Linker.h
===================================================================
--- include/llvm/Linker/Linker.h
+++ include/llvm/Linker/Linker.h
@@ -29,7 +29,10 @@
     None = 0,
     OverrideFromSrc = (1 << 0),
     LinkOnlyNeeded = (1 << 1),
-    InternalizeLinkedSymbols = (1 << 2)
+    InternalizeLinkedSymbols = (1 << 2),
+    /// Don't force link referenced linkonce definitions, import declaration.
+    DontForceLinkLinkonceODR = (1 << 3)
+
   };
 
   Linker(Module &M);
Index: lib/Linker/LinkModules.cpp
===================================================================
--- lib/Linker/LinkModules.cpp
+++ lib/Linker/LinkModules.cpp
@@ -45,6 +45,9 @@
   /// to Add.
   void addLazyFor(GlobalValue &GV, IRMover::ValueAdder Add);
 
+  bool shouldLinkReferencedLinkOnce() {
+    return !(Flags & Linker::DontForceLinkLinkonceODR);
+  }
   bool shouldOverrideFromSrc() { return Flags & Linker::OverrideFromSrc; }
   bool shouldLinkOnlyNeeded() { return Flags & Linker::LinkOnlyNeeded; }
   bool shouldInternalizeLinkedSymbols() {
@@ -429,6 +432,12 @@
 }
 
 void ModuleLinker::addLazyFor(GlobalValue &GV, IRMover::ValueAdder Add) {
+  if (!shouldLinkReferencedLinkOnce())
+    // For ThinLTO we don't import more than what was required.
+    // The client has to guarantee that the linkonce will be availabe at link
+    // time (by promoting it to weak for instance).
+    return;
+
   // Add these to the internalize list
   if (!GV.hasLinkOnceLinkage())
     return;
Index: lib/Transforms/IPO/FunctionImport.cpp
===================================================================
--- lib/Transforms/IPO/FunctionImport.cpp
+++ lib/Transforms/IPO/FunctionImport.cpp
@@ -420,8 +420,10 @@
                << " from " << SrcModule->getSourceFileName() << "\n";
     }
 
-    if (TheLinker.linkInModule(std::move(SrcModule), Linker::Flags::None,
-                               &GlobalsToImport))
+    // Instruct the linker that the client will take care of linkonce resolution
+    unsigned Flags = Linker::Flags::DontForceLinkLinkonceODR;
+
+    if (TheLinker.linkInModule(std::move(SrcModule), Flags, &GlobalsToImport))
       report_fatal_error("Function Import: link error");
 
     ImportedCount += GlobalsToImport.size();
Index: test/Linker/funcimport2.ll
===================================================================
--- test/Linker/funcimport2.ll
+++ test/Linker/funcimport2.ll
@@ -3,7 +3,7 @@
 ; RUN: llvm-lto -thinlto -o %t3 %t1.bc %t2.bc
 ; RUN: llvm-link -import=bar:%t2.bc %t1.bc -summary-index=%t3.thinlto.bc -S | FileCheck %s
 
-; CHECK: define linkonce_odr hidden void @foo() {
+; CHECK: define available_externally hidden void @foo() {
 define available_externally hidden void @foo() {
     ret void
 }
Index: test/ThinLTO/X86/Inputs/alias_resolution.ll
===================================================================
--- /dev/null
+++ test/ThinLTO/X86/Inputs/alias_resolution.ll
@@ -0,0 +1,64 @@
+
+
+
+
+@globalfuncAlias = alias void (...), bitcast (void ()* @globalfunc to void (...)*)
+@globalfuncWeakAlias = weak alias void (...), bitcast (void ()* @globalfunc to void (...)*)
+@globalfuncLinkonceAlias = linkonce alias void (...), bitcast (void ()* @globalfunc to void (...)*)
+@globalfuncWeakODRAlias = weak_odr alias void (...), bitcast (void ()* @globalfunc to void (...)*)
+@globalfuncLinkonceODRAlias = linkonce_odr alias void (...), bitcast (void ()* @globalfunc to void (...)*)
+define void @globalfunc() {
+entry:
+  ret void
+}
+
+@internalfuncAlias = alias void (...), bitcast (void ()* @internalfunc to void (...)*)
+@internalfuncWeakAlias = weak alias void (...), bitcast (void ()* @internalfunc to void (...)*)
+@internalfuncLinkonceAlias = linkonce alias void (...), bitcast (void ()* @internalfunc to void (...)*)
+@internalfuncWeakODRAlias = weak_odr alias void (...), bitcast (void ()* @internalfunc to void (...)*)
+@internalfuncLinkonceODRAlias = linkonce_odr alias void (...), bitcast (void ()* @internalfunc to void (...)*)
+define internal void @internalfunc() {
+entry:
+  ret void
+}
+
+@linkonceODRfuncAlias = alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
+@linkonceODRfuncWeakAlias = weak alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
+@linkonceODRfuncLinkonceAlias = linkonce alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
+@linkonceODRfuncWeakODRAlias = weak_odr alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
+@linkonceODRfuncLinkonceODRAlias = linkonce_odr alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
+define linkonce_odr void @linkonceODRfunc() {
+entry:
+  ret void
+}
+
+@weakODRfuncAlias = alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
+@weakODRfuncWeakAlias = weak alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
+@weakODRfuncLinkonceAlias = linkonce alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
+@weakODRfuncWeakODRAlias = weak_odr alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
+@weakODRfuncLinkonceODRAlias = linkonce_odr alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
+define weak_odr void @weakODRfunc() {
+entry:
+  ret void
+}
+
+@linkoncefuncAlias = alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
+@linkoncefuncWeakAlias = weak alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
+@linkoncefuncLinkonceAlias = linkonce alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
+@linkoncefuncWeakODRAlias = weak_odr alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
+@linkoncefuncLinkonceODRAlias = linkonce_odr alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
+define linkonce void @linkoncefunc() {
+entry:
+  ret void
+}
+
+@weakfuncAlias = alias void (...), bitcast (void ()* @weakfunc to void (...)*)
+@weakfuncWeakAlias = weak alias void (...), bitcast (void ()* @weakfunc to void (...)*)
+@weakfuncLinkonceAlias = linkonce alias void (...), bitcast (void ()* @weakfunc to void (...)*)
+@weakfuncWeakODRAlias = weak_odr alias void (...), bitcast (void ()* @weakfunc to void (...)*)
+@weakfuncLinkonceODRAlias = linkonce_odr alias void (...), bitcast (void ()* @weakfunc to void (...)*)
+define weak void @weakfunc() {
+entry:
+  ret void
+}
+
Index: test/Transforms/FunctionImport/Inputs/funcimport.ll
===================================================================
--- test/Transforms/FunctionImport/Inputs/funcimport.ll
+++ test/Transforms/FunctionImport/Inputs/funcimport.ll
@@ -99,4 +99,46 @@
   ret void
 }
 
+define void @referencelargelinkonce() #0 {
+entry:
+  call void @linkonceodr()
+  ret void
+}
+
+; A large enough linkonce_odr function that should never be imported
+define linkonce_odr void @linkonceodr() #0 {
+entry:
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  call void @globalfunc2()
+  ret void
+}
+
 
Index: test/Transforms/FunctionImport/funcimport.ll
===================================================================
--- test/Transforms/FunctionImport/funcimport.ll
+++ test/Transforms/FunctionImport/funcimport.ll
@@ -23,6 +23,7 @@
   call void (...) @setfuncptr()
   call void (...) @callfuncptr()
   call void (...) @weakfunc()
+  call void (...) @referencelargelinkonce()
   ret i32 0
 }
 
@@ -78,6 +79,12 @@
 ; CHECK-DAG: %0 = load void ()*, void ()** @P.llvm.
 ; CHECK-DAG: store void ()* @staticfunc2.llvm.{{.*}}, void ()** @P.llvm.
 
+; Ensure that @referencelargelinkonce definition is pulled in, but later we
+; also check that the linkonceodr function is not.
+; CHECK-DAG: define available_externally void @referencelargelinkonce()
+; INSTLIM5-DAG: declare void @linkonceodr()
+declare void @referencelargelinkonce(...)
+
 ; Won't import weak func
 ; CHECK-DAG: declare void @weakfunc(...)
 declare void @weakfunc(...) #1
@@ -87,7 +94,7 @@
 ; INSTLIM5-DAG: declare hidden void @funcwithpersonality.llvm.{{.*}}()
 
 ; INSTLIMDEF-DAG: Import globalfunc2
-; INSTLIMDEF-DAG: 11 function-import - Number of functions imported
+; INSTLIMDEF-DAG: 13 function-import - Number of functions imported
 
 ; The actual GUID values will depend on path to test.
 ; GUID-DAG: GUID {{.*}} is weakalias
Index: tools/llvm-link/llvm-link.cpp
===================================================================
--- tools/llvm-link/llvm-link.cpp
+++ tools/llvm-link/llvm-link.cpp
@@ -276,8 +276,10 @@
     if (renameModuleForThinLTO(*SrcModule, *Index, &GlobalsToImport))
       return true;
 
-    if (L.linkInModule(std::move(SrcModule), Linker::Flags::None,
-                       &GlobalsToImport))
+    // Instruct the linker to not automatically import linkonce defintion.
+    unsigned Flags = Linker::Flags::DontForceLinkLinkonceODR;
+
+    if (L.linkInModule(std::move(SrcModule), Flags, &GlobalsToImport))
       return false;
   }