GCC JIT vs others JIT ....

[Basile Starynkevitch <basile@starynkevitch.net>]

Hello David Malcom and all,

I am trying to understand what are the conceptual differences between
GCC JIT (when it will be mature enough) and other JIT libraries like GNU
lightning http://www.gnu.org/software/lightning/ or LLVM
http://llvm.org/ or GNU libjit http://www.gnu.org/software/libjit/ from
the point of view of the developer using the JIT library.

GNU lightning is probably much lower level than GCC JIT. It probably has
the advantage of generating quickly rather slow machine code. It mostly
gives a small set of register like variables.

LLVM probably is the equivalent competitor, since both GCC JIT and LLVM
are derived from ahead of time compilers (of course, for LLVM it was
initially not much true). So probably both GCC JIT and LLVM would
produce, a bit slowly, some good machine code. (In particular because
GCC JIT is, AFAIK, emitting assembly code).

BTW, I have no idea if GCC JIT has some option to set the optimization
level.

Libjit seems superficially similar in terms of API (to both LLVM and GCC
JIT): it offers a mini-C like intermediate representation.

I also believe that GCC JIT is probably the JIT library which runs on
much more processors than others (because GCC has a wide set of
targets).

David, do you think that a libit based JIT engine could quickly switch
to GCC JIT once it has matured? I am guessing it would be quite easy.

Cheers
-- 
Basile STARYNKEVITCH         http://starynkevitch.net/Basile/
email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359
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*** opinions {are only mine, sont seulement les miennes} ***