Re: pure-fns in byte-opt.el

[Mark Oteiza <mvoteiza@udel.edu>]

On 29/07/17 at 08:22pm, Eli Zaretskii wrote:
>> From: Mark Oteiza <mvoteiza@udel.edu>
>> Date: Sat, 29 Jul 2017 12:43:51 -0400
>> Cc: emacs-devel@gnu.org
>>
>> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>>
>> >> (let ((pure-fns
>> >> -       '(concat symbol-name regexp-opt regexp-quote string-to-syntax)))
>> >> +       '(concat symbol-name regexp-opt regexp-quote string-to-syntax
>> >> +         make-vector)))
>> >
>> > Ah, now that makes a lot more sense: make-vector is much less pure than
>> > string-to-char.  The above will cause the compiler to replace
>> >
>> >    (make-vector 2 ?a)
>> >
>> > with
>> >
>> >    [?a ?a]
>> >
>> > so you end with a single immediate vector being re-used over and over,
>> > instead of having a new vector created each time.
>>
>> But reading a literal vector still generates a new vector, no?
>
>Why do you assume it will be read?

I guess because I don't understand how bytecode is executed.