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Re: Emacs Lisp JIT Compiler

From: Tom Tromey
Subject: Re: Emacs Lisp JIT Compiler
Date: Wed, 15 Aug 2018 18:32:35 -0600
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1.50 (gnu/linux)

>>>>> "Clément" == Clément Pit-Claudel <address@hidden> writes:

Clément> I compiled and installed libjit, and things seem to build fine here.

Thank you for trying it.

Clément> Benchmarking a simple loop yields an impressive 4x speedup (from 1
Clément> second down to 0.25s).  However, benchmarking a larger application
Clément> seems to yield a 30% slowdown (from 5.5s to 7.5s).  I haven't
Clément> investigated why yet.  Have you seen similar variations?

I have not really done that much benchmarking.
However, please send me your test case (or tell me what it is) and I
will take a look.

I'd expect the JIT to be at its best for some kinds of integer code and
things like walking lists -- it knows how to emit some simple things

One reason it could be slower is if the compiler is compiling many
functions that don't often run.  Many JITs have some heuristic about
when to compile, this could be done here as well.


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