Re: Native compilation: the bird-eye view

[Andrea Corallo]

Eli Zaretskii <address@hidden> writes:

>> From: Andrea Corallo <address@hidden>
>> Date: Sat, 16 May 2020 12:58:11 +0000
>> Cc: address@hidden
>> 
>> > If so, they will have
>> > to be generated on the end-user machines, or perhaps by whoever
>> > prepares the Emacs binary distributions -- assuming that the binary
>> > distributions are sufficiently compatible to allow that,
>> > notwithstanding the differences between the system where the *.eln
>> > files were generated and the system where they will be installed and
>> > used.  (I don't know what is the granularity of the binary distros wrt
>> > machine architecture and OS versions -- will that allow to be sure the
>> > *.eln files are compatible with the target system?)
>> 
>> Given .eln are just shareds with (almost) no dependecies [1] their
>> degree of compatibility should be higher then the Emacs binary itself.
>
> Well, the "almost" part means we aren't actually sure about this.
> E.g., what about the dependencies related to the GCC version used to
> build libgccjit and compile the .eln files?

For 'almost' I meant what I listed in [1].  AFAIK The GCC version used
to build libgccjit and compile the eln as no dependency implication once
the eln has been produced.

>> > The next question is whether we want the *.eln files to exist up front
>> > for all the Lisp files on the end-user system, or we want them to be
>> > generated in JIT-like manner, whenever the corresponding Lisp library
>> > is loaded on demand?  The answer to this question might then influence
>> > the place where the *.eln files are kept -- the JIT alternative would
>> > suggest to have some kind of cache directory where we put the compiled
>> > files, similar to what Guile does.
>> 
>> I suspect that for the average user the best is to have the distribution
>> do all the compilation upfront for him and have deferred compilation
>> handling only additional libraries and packages.
>
> And for the "non-average" user, who builds Emacs from sources?  AFAIU,
> native compilation of all Lisp files takes many hours even on fast
> machines -- won't this be an annoyance if we don't come up with a JIT
> mechanism?

I'm not sure but I guess than the 'JIT mechanism' is already in place
and called 'deferred-compilation'.  Isn't it?

  Andrea

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