CONFIG_OPENRISC_HAVE_INST_SEXT is not available for thedefaultarchitecture x86.
Result is shown for architecture openrisc

Have instructions l.ext* for sign extension


Linux Kernel Configuration
└─>Processor type and features
└─>Class II Instructions
└─>Have instructions l.ext* for sign extension
In linux kernel since version 5.2 (release Date: 2019-07-07)  
This config enables gcc to generate l.ext* instructions when compiling
the kernel which in general will improve performance and reduce the
binary size.

Select this if your implementation has support for the Class II
l.exths, l.extbs, l.exthz and l.extbz size extend instructions.

Say N if you are unsure.