diff --git a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
--- a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
+++ b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
@@ -158,7 +158,14 @@
     Function *NewF =
         Function::Create(EmptyFT, GlobalValue::ExternalLinkage,
                          F.getAddressSpace(), "", &M);
-    NewF->setVisibility(F.getVisibility());
+    // Only copy function attribtues.
+    NewF->copyAttributesFrom(&F);
+    auto Attrs = F.getAttributes();
+    for (unsigned i = 0; i < F.arg_size(); ++i) {
+      NewF->removeParamAttrs(i, Attrs.getParamAttributes(i));
+    }
+    NewF->removeAttributes(AttributeList::ReturnIndex,
+                           Attrs.getRetAttributes());
     NewF->takeName(&F);
     F.replaceAllUsesWith(ConstantExpr::getBitCast(NewF, F.getType()));
     F.eraseFromParent();
diff --git a/llvm/test/Transforms/ThinLTOBitcodeWriter/split-vfunc.ll b/llvm/test/Transforms/ThinLTOBitcodeWriter/split-vfunc.ll
--- a/llvm/test/Transforms/ThinLTOBitcodeWriter/split-vfunc.ll
+++ b/llvm/test/Transforms/ThinLTOBitcodeWriter/split-vfunc.ll
@@ -2,9 +2,9 @@
 ; RUN: llvm-modextract -b -n 0 -o - %t | llvm-dis | FileCheck --check-prefix=M0 %s
 ; RUN: llvm-modextract -b -n 1 -o - %t | llvm-dis | FileCheck --check-prefix=M1 %s
 
-; M0: @g = external constant [9 x i8*]{{$}}
-; M1: @g = constant [9 x i8*]
-@g = constant [9 x i8*] [
+; M0: @g = external constant [10 x i8*]{{$}}
+; M1: @g = constant [10 x i8*]
+@g = constant [10 x i8*] [
   i8* bitcast (i64 (i8*)* @ok1 to i8*),
   i8* bitcast (i64 (i8*, i64)* @ok2 to i8*),
   i8* bitcast (void (i8*)* @wrongtype1 to i8*),
@@ -13,7 +13,8 @@
   i8* bitcast (i64 (i8*, i8*)* @wrongtype4 to i8*),
   i8* bitcast (i64 (i8*, i128)* @wrongtype5 to i8*),
   i8* bitcast (i64 (i8*)* @usesthis to i8*),
-  i8* bitcast (i8 (i8*)* @reads to i8*)
+  i8* bitcast (i8 (i8*)* @reads to i8*),
+  i8* bitcast (i8* (i8*, i8)* @attributedFunc to i8*)
 ], !type !0
 
 ; M0: define i64 @ok1
@@ -76,4 +77,11 @@
   ret i8 %l
 }
 
+; Check function attributes are copied over splitted module
+; M0: declare dso_local noundef i8* @attributedFunc(i8* noalias, i8 zeroext) unnamed_addr #[[ATTR0:[0-9]+]]
+; M1: declare dso_local void @attributedFunc() unnamed_addr #[[ATTR1:[0-9]+]]
+declare dso_local noundef i8* @attributedFunc(i8* noalias, i8 zeroext) unnamed_addr alwaysinline willreturn
+; M0: attributes #[[ATTR0]] = { alwaysinline willreturn }
+; M1: attributes #[[ATTR1]] = { alwaysinline willreturn }
+
 !0 = !{i32 0, !"typeid"}