/// Parse - Analyze the specified string (e.g. "=*&{eax}") and fill in the
/// fields in this structure. If the constraint string is not understood,
/// return true, otherwise return false.
/// Parse - Analyze the specified string (e.g. "=*&{eax}") and fill in the
/// fields in this structure. If the constraint string is not understood,
/// return true, otherwise return false.