[Vm-dev] Integer comparition primitive failures on Cog

Nicolas Cellier nicolas.cellier.aka.nice at gmail.com
Tue May 3 15:49:34 UTC 2011


And if  genSmallIntegerComparison:orDoubleComparison: is correct, then
usage shall be quite straight forward

Nicolas

2011/5/3 Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com>:
> I always refused to learn x86 assembler, but by code imitation I can
> give my own try in attachment.
> Note that I did not use the trick to invert FP comparison operands
> since this does not seem necessary.
>
> Nicolas
>
>
> 2011/5/2 Eliot Miranda <eliot.miranda at gmail.com>:
>>
>> Hi Henrik,
>>
>> Eliot (phone)
>>
>> On May 2, 2011, at 3:12 AM, Henrik Sperre Johansen <henrik.s.johansen at veloxit.no> wrote:
>>
>>> As per my comment on the recent Morphic performance graphs,(http://blog.openinworld.com/2011/03/morphic-flavour-performance/#comment-59) on a Cog VM these primitives fail with a Float parameter, which leads to a huge performance hit when comparing Ints to Floats by doing silly things in the fallback code.
>>>
>>> Cog:
>>> [1 to: 2000000 do: [:i |
>>>    i < 2354.234.
>>>    i <= 2354.234.
>>>    i >= 2354.234.
>>>     i > 2354.234.]] timeToRun 26594
>>>
>>> Trunk:
>>> [1 to: 2000000 do: [:i |
>>>    i < 2354.234.
>>>    i <= 2354.234.
>>>    i >= 2354.234.
>>>     i > 2354.234.]] timeToRun 229
>>>
>>> Should this be changed in the VM,
>>
>> I think so.  When I first wrote the SmallInteger translated prims I hadn't yet written the JIT support for floats and so couldn't write int/float comparison.  Now all the support is there and it should be straight-forward.  Do you fancy trying to write this yourself?  Would be a fun exercise.  Let me know and I can hand-hold with using the simulator.
>>
>>
>> Best
>> Eliot (phone)
>>
>>
>>> or is the difference for pure int/int comparition large enough that we should instead change
>>> Float>>adaptToInteger: andCompare:
>>> to use the corresponding comparitions with Float as receiver, which does work?
>>> That's still slower than trunk in my image, but quite a bit better, above test takes about 1s.
>>>
>>> Cheers,
>>> Henry
>>
>
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