At 00:15 7-10-2006, you wrote:
-----Original Message-----
From: Michael Van Canneyt <[EMAIL PROTECTED]>
To: FPC developers' list <fpc-devel@lists.freepascal.org>
Date: Fri, 6 Oct 2006 22:01:55 +0200 (CEST)
Subject: Re: [fpc-devel] rtti, arrays and performance
> Did you see a change in performance ? Can you give an order of magnitude ?
>
For me Shark profiler shows that 60%-70% of time spent in
fpc_finalize (this is on intel core duo, havn't measured on
powerpc). After change it shown just a few percents (I do not
remember exactly, and it's a little bit hard to measure exactly
because this block is performd in a few seconds now). But it's just
a mine specific case. I use dynamic arrays heavily there, too much,
it would be better to use getmem there and then type cast it as
pointer to array. Generally speaking I think that it's not a
significant optimization for most of applications. Just it was easer
for me to tweak rtl than to change my code :). But anyway - if I
have array of integer with a hundreds thousand items call to
finalize each item is not really good I think. What if user has
record with array inside, and that record has some dynamic variable?
as I understand fpc_finalize will try to finalize array too... And
as I understand dynamic arrays always finalizing their items.
>
> I think it may be indeed a better idea to see whether the
compiler can set a flag in the type info:
>
> If we change TTypeInfo to
>
> TTypeInfo = record
> Kind : TTypeKind;
> Finalize : Boolean;
> Name : ShortString;
> // here the type data follows as TTypeData record
> end;
>
> Then there is no need for a recursive loop (the compiler has
already done that...);
> Only the Finalize field needs to be retrieved. Putting this field
in the middle will
> make sure 99,9% of all existing code will still work.
>
I don't know is this good - perhaps to not break other's code such
attribute can be placed before type info record (at offset -1 or -4
from typeinfo pointer:)),so, if somebody relies on current typeinfo
format his code will be not broken?
If you relying on internal typeinfo your program already has a
cross-platform issue. So this is not an issue that we change the
internal structure. Adding the boolean is possible. But for the array
finalize we also need an extra function that will check if the array
needs finalization before entering the loop that calls Finalize().
Peter
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