RtlFindMostSignificantBit

CCHAR __stdcall RtlFindMostSignificantBit(ULONGLONG Set){
  bool v1; 
  __int64 v2; 
  CCHAR result; 
  v1 = !_BitScanReverse64((unsigned __int64 *)&v2, Set);
  result = -1;
  if( !v1 )
    return v2;
  return result;
}

Referenced by:

MiStoreGraphicsProtectionInVad
MiValidateZeroBits