2 files changed, 43 insertions, 22 deletions

diff --git a/lib/Transforms/IPO/ExtractGV.cpp b/lib/Transforms/IPO/ExtractGV.cpp
index fa3d72ddcf..07b05ee38a 100644
--- a/lib/Transforms/IPO/ExtractGV.cpp
+++ b/lib/Transforms/IPO/ExtractGV.cpp
@@ -21,6 +21,38 @@
 #include <algorithm>
 using namespace llvm;
 
+/// Make sure GV is visible from both modules. Delete is true if it is
+/// being deleted from this module.
+/// This also makes sure GV cannot be dropped so that references from
+/// the split module remain valid.
+static void makeVisible(GlobalValue &GV, bool Delete) {
+  bool Local = GV.hasLocalLinkage();
+  if (Local)
+    GV.setVisibility(GlobalValue::HiddenVisibility);
+
+  if (Local || Delete) {
+    GV.setLinkage(GlobalValue::ExternalLinkage);
+    return;
+  }
+
+  if (!GV.hasLinkOnceLinkage()) {
+    assert(!GV.isDiscardableIfUnused());
+    return;
+  }
+
+  // Map linkonce* to weak* so that llvm doesn't drop this GV.
+  switch(GV.getLinkage()) {
+  default:
+    llvm_unreachable("Unexpected linkage");
+  case GlobalValue::LinkOnceAnyLinkage:
+    GV.setLinkage(GlobalValue::WeakAnyLinkage);
+    return;
+  case GlobalValue::LinkOnceODRLinkage:
+    GV.setLinkage(GlobalValue::WeakODRLinkage);
+    return;
+  }
+}
+
 namespace {
   /// @brief A pass to extract specific functions and their dependencies.
   class GVExtractorPass : public ModulePass {
@@ -60,12 +92,7 @@ namespace {
             continue;
         }
 
-        bool Local = I->isDiscardableIfUnused();
-        if (Local)
-          I->setVisibility(GlobalValue::HiddenVisibility);
-
-        if (Local || Delete)
-          I->setLinkage(GlobalValue::ExternalLinkage);
+	makeVisible(*I, Delete);
 
         if (Delete)
           I->setInitializer(0);
@@ -80,12 +107,7 @@ namespace {
             continue;
         }
 
-        bool Local = I->isDiscardableIfUnused();
-        if (Local)
-          I->setVisibility(GlobalValue::HiddenVisibility);
-
-        if (Local || Delete)
-          I->setLinkage(GlobalValue::ExternalLinkage);
+	makeVisible(*I, Delete);
 
         if (Delete)
           I->deleteBody();
@@ -97,12 +119,10 @@ namespace {
         Module::alias_iterator CurI = I;
         ++I;
 
-        if (CurI->isDiscardableIfUnused()) {
-          CurI->setVisibility(GlobalValue::HiddenVisibility);
-          CurI->setLinkage(GlobalValue::ExternalLinkage);
-        }
+	bool Delete = deleteStuff == (bool)Named.count(CurI);
+	makeVisible(*I, Delete);
 
-        if (deleteStuff == (bool)Named.count(CurI)) {
+        if (Delete) {
           Type *Ty =  CurI->getType()->getElementType();
 
           CurI->removeFromParent();
diff --git a/test/Other/extract-linkonce.ll b/test/Other/extract-linkonce.ll
index 31fbf3ac46..4c6b6b76a4 100644
--- a/test/Other/extract-linkonce.ll
+++ b/test/Other/extract-linkonce.ll
@@ -1,15 +1,16 @@
 ; RUN: llvm-extract -func foo -S < %s | FileCheck %s
 ; RUN: llvm-extract -delete -func foo -S < %s | FileCheck --check-prefix=DELETE %s
 
-; Test that we don't convert weak_odr to external definitions.
+; Test that linkonce definitions are mapped to weak so that they are not
+; dropped.
 
-; CHECK:      @bar = external hidden global i32
-; CHECK:      define hidden i32* @foo() {
+; CHECK:      @bar = external global i32
+; CHECK:      define weak i32* @foo() {
 ; CHECK-NEXT:  ret i32* @bar
 ; CHECK-NEXT: }
 
-; DELETE: @bar = hidden global i32 42
-; DELETE: declare hidden i32* @foo()
+; DELETE: @bar = weak global i32 42
+; DELETE: declare i32* @foo()
 
 @bar = linkonce global i32 42