RtlFindMostSignificantBit

INT8 __stdcall RtlFindMostSignificantBit(UINT64 Set){
  bool v1; 
  __int64 v2; 
  INT8 result; 

  v1 = !_BitScanReverse64((unsigned __int64 *)&v2, Set);
  result = -1;
  if( !v1 )
    return v2;
  return result;
}

Referenced by:

MiStoreGraphicsProtectionInVad
MiValidateZeroBits