CONFIG_ISA_ARCOMPACT is not available for thedefaultarchitecture x86.
Result is shown for architecture arc

ARCompact ISA

modulename: entry-compact.ko

configname: CONFIG_ISA_ARCOMPACT

ARC Instruction Set
└─>ARCompact ISA
In linux kernel since version 3.10 (release Date: 2013-06-30)  
The original ARC ISA of ARC600/700 cores

source code: