Compiler directives are special VHDL comments (synthetic comments) that affect the actions of Foundation Express. These comments are a special case of regular VHDL comments, which are ignored by other VHDL tools. Synthetic comments are used only to direct the actions of Foundation Express.
Synthetic comments begin with two hyphens (--) like a regular comment. If the word following these characters is pragma or synopsys, the remaining comment text is interpreted by Foundation Express as a directive.
Foundation Express displays a syntax error if an unrecognized directive is encountered after -- synopsys or -- pragma.