[9fans] JIT (mostly off topic)

[9fans] JIT (mostly off topic)

[Steve Simon]

Years ago The Commander and Bart Locanthi used JIT
in the form of some C that write machine code into an
array of chars, cast it to a function pointer, and called it.
(I appologise if the details are not correct but this is the idea).

I have a need for such a thing again - trying to speed up
a compressed video decoder.

Anyone done such a thing this millenium? Does the x86 data execution
prevention mean you just cannot do this - my targets are desktop OSs
other than plan9 (sadly).

-Steve

Re: [9fans] JIT (mostly off topic)

[Aram Hăvărneanu]

You have to mmap an executable region of memory, but it is doable in
almost all cases (certainly for every desktop).

-- 
Aram Hăvărneanu

Re: [9fans] JIT (mostly off topic)

[Daniel Peyrolon]

[-- Attachment #1: Type: text/plain, Size: 917 bytes --]

Hello Steve,

I'm currently implementing JIT compilation on the FreeBSD firewall on
netmap, using LLVM.
(So yes, there's people doing this, maybe not as you expected it).
Maybe you can use LLVM on that OS, I'm not sure.

As for the DEP thing, Aram got before me, I was about to say that.


2014-09-09 22:45 GMT+01:00 Steve Simon <steve@quintile.net>:

> Years ago The Commander and Bart Locanthi used JIT
> in the form of some C that write machine code into an
> array of chars, cast it to a function pointer, and called it.
> (I appologise if the details are not correct but this is the idea).
>
> I have a need for such a thing again - trying to speed up
> a compressed video decoder.
>
> Anyone done such a thing this millenium? Does the x86 data execution
> prevention mean you just cannot do this - my targets are desktop OSs
> other than plan9 (sadly).
>
> -Steve
>
>


--
Daniel

[-- Attachment #2: Type: text/html, Size: 1390 bytes --]

Re: [9fans] JIT (mostly off topic)

[Skip Tavakkolian]

a version of pico (holzmann) for VAX by ken and rob used this
technique. rsc did a version of pico where the repl just "compiles"
pico into C, then compiles and runs it.


On Tue, Sep 9, 2014 at 2:45 PM, Steve Simon <steve@quintile.net> wrote:
> Years ago The Commander and Bart Locanthi used JIT
> in the form of some C that write machine code into an
> array of chars, cast it to a function pointer, and called it.
> (I appologise if the details are not correct but this is the idea).
>
> I have a need for such a thing again - trying to speed up
> a compressed video decoder.
>
> Anyone done such a thing this millenium? Does the x86 data execution
> prevention mean you just cannot do this - my targets are desktop OSs
> other than plan9 (sadly).
>
> -Steve
>

Re: [9fans] JIT (mostly off topic)

[Rob Pike]

The original Blit JIT (stupid name - if the compilation was "in time"
we wouldn't need a JIT. Our term was "on the fly") version was
actually done by John Reiser.

My favorite JIT I wrote was to fix up floating point after a trap on the SPARC.

-rob

Re: [9fans] JIT (mostly off topic)

[Bakul Shah]

On Tue, 09 Sep 2014 22:45:01 BST "Steve Simon" <steve@quintile.net> wrote:
> Years ago The Commander and Bart Locanthi used JIT
> in the form of some C that write machine code into an
> array of chars, cast it to a function pointer, and called it.
> (I appologise if the details are not correct but this is the idea).
>
> I have a need for such a thing again - trying to speed up
> a compressed video decoder.
>
> Anyone done such a thing this millenium? Does the x86 data execution
> prevention mean you just cannot do this - my targets are desktop OSs
> other than plan9 (sadly).

Have you looked at libjit or luajit? There are a bunch of
projects using JIT on the fly!  You may also want to look at
Nils Holm's subc (a 5Kloc compiler for a subset of C +
codegens for 386,arm,x86-64, each in 260..427 lines).  For an
example of generating assembly code using C functions.