1 files changed, 30 insertions, 1 deletions
diff --git a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
index 225b4fe95f67..37329b489555 100644
--- a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
+++ b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
@@ -158,7 +158,11 @@ void simplifyExternals(Module &M) {
     Function *NewF =
         Function::Create(EmptyFT, GlobalValue::ExternalLinkage,
                          F.getAddressSpace(), "", &M);
-    NewF->setVisibility(F.getVisibility());
+    NewF->copyAttributesFrom(&F);
+    // Only copy function attribtues.
+    NewF->setAttributes(
+        AttributeList::get(M.getContext(), AttributeList::FunctionIndex,
+                           F.getAttributes().getFnAttributes()));
     NewF->takeName(&F);
     F.replaceAllUsesWith(ConstantExpr::getBitCast(NewF, F.getType()));
     F.eraseFromParent();
@@ -195,6 +199,26 @@ void forEachVirtualFunction(Constant *C, function_ref<void(Function *)> Fn) {
     forEachVirtualFunction(cast<Constant>(Op), Fn);
 }
 
+// Clone any @llvm[.compiler].used over to the new module and append
+// values whose defs were cloned into that module.
+static void cloneUsedGlobalVariables(const Module &SrcM, Module &DestM,
+                                     bool CompilerUsed) {
+  SmallVector<GlobalValue *, 4> Used, NewUsed;
+  // First collect those in the llvm[.compiler].used set.
+  collectUsedGlobalVariables(SrcM, Used, CompilerUsed);
+  // Next build a set of the equivalent values defined in DestM.
+  for (auto *V : Used) {
+    auto *GV = DestM.getNamedValue(V->getName());
+    if (GV && !GV->isDeclaration())
+      NewUsed.push_back(GV);
+  }
+  // Finally, add them to a llvm[.compiler].used variable in DestM.
+  if (CompilerUsed)
+    appendToCompilerUsed(DestM, NewUsed);
+  else
+    appendToUsed(DestM, NewUsed);
+}
+
 // If it's possible to split M into regular and thin LTO parts, do so and write
 // a multi-module bitcode file with the two parts to OS. Otherwise, write only a
 // regular LTO bitcode file to OS.
@@ -287,6 +311,11 @@ void splitAndWriteThinLTOBitcode(
   StripDebugInfo(*MergedM);
   MergedM->setModuleInlineAsm("");
 
+  // Clone any llvm.*used globals to ensure the included values are
+  // not deleted.
+  cloneUsedGlobalVariables(M, *MergedM, /*CompilerUsed*/ false);
+  cloneUsedGlobalVariables(M, *MergedM, /*CompilerUsed*/ true);
+
   for (Function &F : *MergedM)
     if (!F.isDeclaration()) {
       // Reset the linkage of all functions eligible for virtual constant