+@item Alias(@var{opt})
+@itemx Alias(@var{opt}, @var{arg})
+@itemx Alias(@var{opt}, @var{posarg}, @var{negarg})
+The option is an alias for @option{-@var{opt}}. In the first form,
+any argument passed to the alias is considered to be passed to
+@option{-@var{opt}}, and @option{-@var{opt}} is considered to be
+negated if the alias is used in negated form. In the second form, the
+alias may not be negated or have an argument, and @var{posarg} is
+considered to be passed as an argument to @option{-@var{opt}}. In the
+third form, the alias may not have an argument, if the alias is used
+in the positive form then @var{posarg} is considered to be passed to
+@option{-@var{opt}}, and if the alias is used in the negative form
+then @var{negarg} is considered to be passed to @option{-@var{opt}}.
+
+Aliases should not specify @code{Var} or @code{Mask} or
+@code{UInteger}. Aliases should normally specify the same languages
+as the target of the alias; the flags on the target will be used to
+determine any diagnostic for use of an option for the wrong language,
+while those on the alias will be used to identify what command-line
+text is the option and what text is any argument to that option.
+
+When an @code{Alias} definition is used for an option, driver specs do
+not need to handle it and no @samp{OPT_} enumeration value is defined
+for it; only the canonical form of the option will be seen in those
+places.
+
+@item Ignore
+This option is ignored apart from printing any warning specified using
+@code{Warn}. The option will not be seen by specs and no @samp{OPT_}
+enumeration value is defined for it.
+
+@item SeparateAlias
+For an option marked with @code{Joined}, @code{Separate} and
+@code{Alias}, the option only acts as an alias when passed a separate
+argument; with a joined argument it acts as a normal option, with an
+@samp{OPT_} enumeration value. This is for compatibility with the
+Java @option{-d} option and should not be used for new options.
+
+@item Warn(@var{message})
+If this option is used, output the warning @var{message}.
+@var{message} is a format string, either taking a single operand with
+a @samp{%qs} format which is the option name, or not taking any
+operands, which is passed to the @samp{warning} function. If an alias
+is marked @code{Warn}, the target of the alias must not also be marked
+@code{Warn}.
+