diff --git a/clang/test/CodeGen/attr-function-return.c b/clang/test/CodeGen/attr-function-return.c
--- a/clang/test/CodeGen/attr-function-return.c
+++ b/clang/test/CodeGen/attr-function-return.c
@@ -1,11 +1,12 @@
 // RUN: %clang_cc1 -std=gnu2x -triple x86_64-linux-gnu %s -emit-llvm -o - \
+// RUN:   -Werror=ignored-attributes \
 // RUN:   | FileCheck %s --check-prefixes=CHECK,CHECK-NOM
 // RUN: %clang_cc1 -std=gnu2x -triple x86_64-linux-gnu %s -emit-llvm -o - \
-// RUN:   -mfunction-return=keep | FileCheck %s \
-// RUN:   --check-prefixes=CHECK,CHECK-KEEP
+// RUN:   -Werror=ignored-attributes -mfunction-return=keep \
+// RUN:   | FileCheck %s --check-prefixes=CHECK,CHECK-KEEP
 // RUN: %clang_cc1 -std=gnu2x -triple x86_64-linux-gnu %s -emit-llvm -o - \
-// RUN:  -mfunction-return=thunk-extern | FileCheck %s \
-// RUN:  --check-prefixes=CHECK,CHECK-EXTERN
+// RUN:   -Werror=ignored-attributes -mfunction-return=thunk-extern \
+// RUN:   | FileCheck %s --check-prefixes=CHECK,CHECK-EXTERN
 
 #if !__has_attribute(function_return)
 #error "missing attribute support for function_return"
@@ -14,13 +15,13 @@
 // CHECK: @keep() [[KEEP:#[0-9]+]]
 __attribute__((function_return("keep"))) void keep(void) {}
 
-// CHECK: @keep2() [[KEEP:#[0-9]+]]
+// CHECK: @keep2() [[KEEP]]
 [[gnu::function_return("keep")]] void keep2(void) {}
 
 // CHECK: @thunk_extern() [[EXTERN:#[0-9]+]]
 __attribute__((function_return("thunk-extern"))) void thunk_extern(void) {}
 
-// CHECK: @thunk_extern2() [[EXTERN:#[0-9]+]]
+// CHECK: @thunk_extern2() [[EXTERN]]
 [[gnu::function_return("thunk-extern")]] void thunk_extern2(void) {}
 
 // CHECK: @double_thunk_keep() [[KEEP]]
@@ -39,7 +40,7 @@
 void double_keep_thunk(void) {}
 
 // CHECK: @double_keep_thunk2() [[EXTERN]]
-[[gnu::function_return("thunk-keep")]][[gnu::function_return("thunk-extern")]]
+[[gnu::function_return("keep")]][[gnu::function_return("thunk-extern")]]
 void double_keep_thunk2(void) {}
 
 // CHECK: @thunk_keep() [[KEEP]]
diff --git a/clang/test/CodeGen/attr-function-return.cpp b/clang/test/CodeGen/attr-function-return.cpp
--- a/clang/test/CodeGen/attr-function-return.cpp
+++ b/clang/test/CodeGen/attr-function-return.cpp
@@ -1,11 +1,12 @@
 // RUN: %clang_cc1 -triple x86_64-linux-gnu %s -emit-llvm -o - \
+// RUN:   -Werror=unknown-attributes \
 // RUN:   | FileCheck %s --check-prefixes=CHECK,CHECK-NOM
 // RUN: %clang_cc1 -triple x86_64-linux-gnu %s -emit-llvm -o - \
-// RUN:   -mfunction-return=keep | FileCheck %s \
-// RUN:   --check-prefixes=CHECK,CHECK-KEEP
+// RUN:   -Werror=unknown-attributes -mfunction-return=keep \
+// RUN:   | FileCheck %s --check-prefixes=CHECK,CHECK-KEEP
 // RUN: %clang_cc1 -triple x86_64-linux-gnu %s -emit-llvm -o - \
-// RUN:  -mfunction-return=thunk-extern | FileCheck %s \
-// RUN:  --check-prefixes=CHECK,CHECK-EXTERN
+// RUN:   -Werror=unknown-attributes -mfunction-return=thunk-extern \
+// RUN:   | FileCheck %s --check-prefixes=CHECK,CHECK-EXTERN
 
 int foo(void) {
   // CHECK: @"_ZZ3foovENK3$_0clEv"({{.*}}) [[NOATTR:#[0-9]+]]