Danny Backx escreveu:
> On Wed, 2007-09-19 at 17:51 +0200, pgeorges wrote:
>>> Crosswords, compiled with cegcc, runs noticably slower than compiled
>>> with the m$ compiler. Eric House also reported this. I've not
>>> investigated this yet. We may have inefficiencies other than the code
>>> generated by the compiler. Something with the coredll perhaps ?
>>>
>>>     Danny
>>>   
>> Is it possible to know in which cases the slowdowns are encountered ? 
>> CPU intensive code, I/O , system calls ?
>> What is the amount of slow down ? 10 % , 50 % ?
>>
>> Pascal
> 
> I don't have an eVC4 installed (only my children have Windows PC's) so I
> have no simple way to do comparisons.
> 
> Xwords shows a noticable difference if you get it to refresh its screen.
> (It's a scrabble game application.) When compiled with cegcc, you can
> see how it draws the game board - takes one or 1.5 seconds. With the
> executable as you can download it from http://xwords.sf.net , the redraw
> is instantaneous.
> 
> So that example could lead you to the conclusion that it's either
> graphics or system (DLL?) access.
> 

I doubt it.  There shouldn't be any difference in calling system functions.
It's just a bl anyway.

Your example is about floating point arithmetic.  Is Xwords doing it a lot?

Pgeorges, is you chess engine doing a lot of fp math?

We currently generate code that assumes that the device *does not* have an fpu.

Also, we think our libgcc is not taking advantage of the:
http://msdn2.microsoft.com/en-US/library/bb330866.aspx
Which are probably pretty much optimized for the device they are running
on by the manufacturer.

If I was looking into this, I would learn which cpu I have, and which
fpu I have if any, and then have gcc output insns for it.
Something like -mfloat-abi=softfp for vfp, for example (you'll need to also
specify a cpu that supports it like -mcpu=xscale).

It may reveal interesting.

Cheers,
Pedro Alves




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