Re: LuaJIT - Trace aborted again

[Benjamin Segovia <segovia.benjamin@...>]

Also, as you may see using  -jdump, there is no more "unroll loop"
issue when I use the function trick.
Ben

On Wed, Jul 20, 2011 at 11:20 PM, Benjamin Segovia
<segovia.benjamin@gmail.com> wrote:
> Unfortunately, no sucess. I encapsulated basic blocks into functions
> and add return statement instead of breaks. Exactly the same result.
> As I am not sure of what to do next, please find here a dump of the
> function I tried to compile. I just extracted it and made a
> stand-alone file with it. Mike, if you have an idea of what is going
> on.
>
> Cheers,
> Ben
>
> On Wed, Jul 20, 2011 at 4:49 PM, Benjamin Segovia
> <segovia.benjamin@gmail.com> wrote:
>> Also, Robert, I will try your suggestion :-)
>> I hope it will work ie replacing my hack (nested double loop) by the
>> (function() ... end)() hack. Using a function for each loop body, I
>> can replace breaks / continues by returns and remove one repeat ...
>> until crap.
>> I hope it will do the job :-)
>> Otherwise, I will try to go through if/then/else code transform hell...
>> So, also thanks for the suggestion :-)
>>
>> Ben
>>
>>
>> On Wed, Jul 20, 2011 at 4:45 PM, Benjamin Segovia
>> <segovia.benjamin@gmail.com> wrote:
>>> Hmmm.
>>> This is not really a if/then/else construct I need but really a
>>> forward jump. Basically, it is a SIMD scatter/gather machine. Some
>>> instructions inactivate lanes from the SIMD vector. In a block, if
>>> your instruction currently deactivates all lanes, then you exit the
>>> block, reset the mask you got before potentially modified by the
>>> computations in the previous block. Then you check the current mask.
>>> If it is still zero, then you exit the block ...
>>>
>>> Maybe to be more precise: the biggest issue basically is that I need
>>> to emulate "continue" and "breaks" because the machine can execute
>>> "continue" and "break" instructions natively.
>>> Actually "continue" instructions are really the big problem, since
>>> there is no continue in lua.
>>>
>>> Right now, I used a two-nested-loop hack to handle continue:
>>>
>>> repeat
>>> local a_break_was_used_for_a_continue = false
>>> repeat
>>>
>>> -- .... "CONTINUE"  instruction generates ->
>>> a_break_was_used_for_a_continue = true
>>> break
>>> -- end of continue
>>>
>>> -- .... "BREAK" instruction generates ->
>>> a_break_was_used_for_a_continue = false
>>> break
>>> -- end of break
>>>
>>> until true -- <- this is fake loop to early branch out (used for
>>> breaks and continues)
>>> if not a_break_was_used_for_a_continue then beak end
>>> until false -- <- this is a real loop. Youhou!
>>>
>>> As you can see, the technique is easy to implement since regardless
>>> where I am in the nested branches (like for example, deeply nested in
>>> IFs), I can early out.
>>> I am afraid that using only if/then/else to mask the code may be a
>>> more serious code transform. Something similar to unstructured
>>> branches to structures branches transform... ie not that easy to do
>>> :-)
>>>
>>> I will try other things today.
>>>
>>> Thank you very much for your help
>>>
>>> Ben
>>>
>>>
>>>
>>> On Wed, Jul 20, 2011 at 2:52 PM, Mike Pall <mikelu-1107@mike.de> wrote:
>>>> David Kastrup wrote:
>>>>> Mike Pall <mikelu-1107@mike.de> writes:
>>>>> > I do not see how that's different from doing it with a while loop.
>>>>> > You'd need to nest them and close them with 'end' as well.
>>>>>
>>>>> No, you need just a single loop at a time that can deal with dozens of
>>>>> "break" in there.
>>>>
>>>> Sure. But is that a realistic use case? If the VLIW code is
>>>> generated from typical code in a high-level language, I doubt
>>>> you'd see more than a handful of these. Nesting (say) 100
>>>> if/then/else is no problem.
>>>>
>>>> --Mike
>>>>
>>>>
>>>
>>
>