8241091: AArch64: "bad AD file" with VM option "-XX:-UsePopCountInstr…

…uction"

Reviewed-by: aph

src/hotspot/cpu/aarch64/vm_version_aarch64.cpp

@@ -425,6 +425,11 @@ void VM_Version::get_processor_features() {
   }
 
   if (FLAG_IS_DEFAULT(UsePopCountInstruction)) {
+    FLAG_SET_DEFAULT(UsePopCountInstruction, true);
+  }
+
+  if (!UsePopCountInstruction) {
+    warning("UsePopCountInstruction is always enabled on this CPU");
     UsePopCountInstruction = true;
   }