speedbar-use-imenu-flag

speedbar-use-imenu-flag is a variable defined in `speedbar.el'.
Its value is

t

Documentation:
Non-nil means use imenu for file parsing, nil to use etags.
XEmacs prior to 20.4 doesn't support imenu, therefore the default is to
use etags instead. Etags support is not as robust as imenu support.

You can customize this variable.