Perhaps the port of JCL made by blikblum can be of help with unit jclsysinfo function cpuid ?Documentation on that function can be found here.
Some are readily available in FPC without further adoCode: Pascal [Select][+][-]beginwriteln (has_SSE_support);writeln (has_MMX_support)end. There may be more I don't know
And the unit CPU in the rtl, of course:Code: Pascal [Select][+][-] function AESSupport : boolean;inline; function AVXSupport : boolean;inline; function AVX2Support: boolean;inline; function FMASupport: boolean;inline;