How to get rid of "xxx not a recognized feature for this target" warning?

Hello LLVMer,

I am currently developing a backend targeting a stack-based VM,
When compiling with targeting to the VM, I got a bunch of outputs below.
Where in code do I miss to add to get rid of these warnings?

‘-sse4a’ is not a recognized feature for this target (ignoring feature)
‘-avx2’ is not a recognized feature for this target (ignoring feature)
‘-xop’ is not a recognized feature for this target (ignoring feature)
‘-fma4’ is not a recognized feature for this target (ignoring feature)
‘-bmi2’ is not a recognized feature for this target (ignoring feature)
‘-3dnow’ is not a recognized feature for this target (ignoring feature)
‘-3dnowa’ is not a recognized feature for this target (ignoring feature)
‘-pclmul’ is not a recognized feature for this target (ignoring feature)

The processor I used is generic,

def : Processor<“generic”, NoItineraries, >;

I used lldb to trace the code and didn’t find it ran into ::ToggleFeature()
or SubtargetFeatures::getFeatureBits() from where I see the warning string comes.

Any guide or suggestion is appreciated!
Thanks in advanced!
-ye