Re: WIP: Faster Expression Processing and Tuple Deforming (including JIT)

On 12/06/16 21:40, Andres Freund wrote:
> On 2016-12-06 14:35:43 -0600, Nico Williams wrote:
>> On Tue, Dec 06, 2016 at 12:27:51PM -0800, Andres Freund wrote:
>>> On 2016-12-06 14:19:21 -0600, Nico Williams wrote:
>>>>> I concur with your feeling that hand-rolled JIT is right out.  But
>>>>
>>>> Yeah, that way lies maintenance madness.
>>>
>>> I'm not quite that sure about that. I had a lot of fun doing some
>>> hand-rolled x86 JITing. Not that is a ward against me being mad.  But
>>> more seriously: Manually doing a JIT gives you a lot faster compilation
>>> times, which makes JIT applicable in a lot more situations.
>>
>> What I meant is that each time there are new ISA extensions, or
>> differences in how relevant/significant different implementations of the
>> same ISA implement certain instructions, and/or every time you want to
>> add a new architecture... someone has to do a lot of very low-level
>> work.
> 
> Yea, that's why I didn't pursue this path further. I *personally* think
> it'd be perfectly fine to only support JITing on linux x86_64 and
> aarch64 for now. And those I'd be willing to work on. But since I know
> that's not project policy...

Well, if this thread of thought about hand-crafted JIT should be taken
up again by someone at some point in time, I guess it could be possible
to reuse tools that are already out there, such as "DynASM"
( http://luajit.org/dynasm_features.html ) from the LuaJIT project
(currently offers x86-64, x86-32, ARM-32, PPC-32, and MIPS-32).
Maybe one could even recycle parts of the LuaJIT project itself
( http://luajit.org/luajit.html ,
  http://article.gmane.org/gmane.comp.lang.lua.general/58908 ).

-- 
Markus Nullmeier            http://www.g-vo.org
German Astrophysical Virtual Observatory (GAVO)