During completion for the commands describe-variable and
describe-function, Emacs will try to load files which may
contain definitions matching the prefix being completed. The variable
definition-prefixes holds a hashtable which maps a prefix to
the corresponding list of files to load for it. Entries to this
mapping are added by calls to register-definition-prefixes
which are generated by loaddefs-generate
(see Autoload). Files which don’t contain any definitions worth
loading (test files, for example), should set
autoload-compute-prefixes to nil as a file-local
variable.