CONFIG_SUPPORT_DENORMAL_ARITHMETIC is not available for thedefaultarchitecture x86.
Result is shown for architecture nds32

Denormal arithmetic support

configname: CONFIG_SUPPORT_DENORMAL_ARITHMETIC

Linux Kernel Configuration
└─>Denormal arithmetic support
In linux kernel since version 5 (release Date: 2019-03-03)  
Say Y here to enable arithmetic of denormalized number. Enabling
this feature can enhance the precision for tininess number.
However, performance loss in float pointe calculations is
possibly significant due to additional FPU exception.

If the calculated tolerance for tininess number is not critical,
say N to prevent performance loss.

depends
CONFIG_FPU