.macro saving_callee_prsv_regi used_regi_index
      .if used_regi_index >= 19
        i = 19
        .rept used_regi_index - 19
          str xi,[sp,#-8*(i-18)]    // fail here: xi
          i = i + 1
        .endr
      .endif
    .endm

.macro saving_callee_prsv_regi_2 used_regi_index
      .if used_regi_index >= 19
        i = 19
        .rept used_regi_index - 19
          .irp idx, i // fail here, "i" is expression not value?!
          str xidx,[sp,#-8*(idx-18)]
          i = i + 1
        .endr
       .endif
    .endm

str x19,[sp,#-8]

str x19,[sp,#-8]
    str x20,[sp,#-16]
    str x21,[sp,#-24]
    str x22,[sp,#-32]