Main problem here was that SHF_COMPRESSED has the same value with XCORE_SHF_CP_SECTION,
which was included as standart (common) flag.
As far I understand xCore is a family of controllers and it that means it's constant should be processed separately,
only if e_machine == EM_XCORE, otherwise llvm-readobj would ouput different constants twice for compressed section:
SHF_COMPRESSED (0x800) .... XCORE_SHF_CP_SECTION (0x800)
what probably does not make sence if you're not working with xcore file.