Re: byte-code optimizations

[Richard Stallman <rms@gnu.org>]

    After a `varbind' or `unwind-protect' or similar.  However, I doubt
    that those make much difference, so Stefan's optimization must be
    _nearly_ equivalent to mine.

It would be an error to move an unbind that matches an unwind-protect.

    >     +(defconst byte-compile-side-effect-free-dynamically-safe-ops
    >     +  '(;; Same as `byte-compile-side-effect-free-ops' but without
    >     +    ;; `byte-varref', `byte-symbol-value' and certain editing
    >     +    ;; primitives.
    >
    > Why exclude byte-symbol-value?

    Because value can change as the result of the binding we are
    trying to eliminate.

Yes, of course.

    > However, there is still the question of whether we should
    > change the standard defsubst to work the way defsubst* does.

    Maybe we can even use `defmacro' for `caar' and friends.  Since
    they evaluate their lone argument only once, there must not be
    any problems, right?

We don't want to replace defsubst with defmacro.
That's not what we're talking about.  The idea is to
to make defsubst work better, to make it do the good things
that defsubst* does.

    I vote for saying "you're not allowed to treat defsubst argument
    bindings as normal dynamic bindings, and if you have tons of code
    that does, well screw you, you're probably a crappy programmer
    anyway."

There is no reason to consider such an unpleasant alternative.
It is clearly not necessary for making an improvement here.

Anyway, please install your updated patch.