"Documentation by paper"

[Richard Kenner]

    Which you have never read (at least a modern one), if you do not know
    what a dominator is.  My first compiler course, which used only part
    of Appel's "Modern compiler implementation" (which is nowhere near in
    depth with respect to Muchnick or Morgan) did teach dominators.

Correct.  My last compiler course was well over a decade ago.

    I'd love gcc to become a free compiler text, but it is not its purpose.

Of course not, but it's always useful to define each term used at least
to some extent.  GCC has always been pretty self-contained and I see no
reason to change that policy at this point.