CONFIG_AS_HAS_ARMV8_4 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm64

CONFIG_AS_HAS_ARMV8_4 (not configurable)

configname: CONFIG_AS_HAS_ARMV8_4

Linux Kernel Configuration
└─>Kernel Features
└─>ARMv8.4 architectural features
└─>AS_HAS_ARMV8_4
In linux kernel since version 5.1 (release Date: 2019-05-05)