[Linker] PR33527 - Linker::LinkOnlyNeeded should import AppendingLinkage globals

Linker::LinkOnlyNeeded should always import globals with
AppendingLinkage.

This resolves PR33527.

Differential Revision: https://reviews.llvm.org/D34448

llvm-svn: 310522

1 files changed, 12 insertions, 2 deletions

diff --git a/llvm/lib/Linker/LinkModules.cpp b/llvm/lib/Linker/LinkModules.cpp
index c0ce4bf76b9..25f31a3401a 100644
--- a/llvm/lib/Linker/LinkModules.cpp
+++ b/llvm/lib/Linker/LinkModules.cpp
@@ -329,8 +329,18 @@ bool ModuleLinker::shouldLinkFromSource(bool &LinkFromSrc,
 bool ModuleLinker::linkIfNeeded(GlobalValue &GV) {
   GlobalValue *DGV = getLinkedToGlobal(&GV);
 
-  if (shouldLinkOnlyNeeded() && !(DGV && DGV->isDeclaration()))
-    return false;
+  if (shouldLinkOnlyNeeded()) {
+    // Always import variables with appending linkage.
+    if (!GV.hasAppendingLinkage()) {
+      // Don't import globals unless they are referenced by the destination
+      // module.
+      if (!DGV)
+        return false;
+      // Don't import globals that are already defined in the destination module
+      if (!DGV->isDeclaration())
+        return false;
+    }
+  }
 
   if (DGV && !GV.hasLocalLinkage() && !GV.hasAppendingLinkage()) {
     auto *DGVar = dyn_cast<GlobalVariable>(DGV);