[fpc-pascal] code optimization

Adrian Veith adrian at veith-system.de
Wed Sep 22 08:08:45 CEST 2010

 Hi Stefan,

is this a benchmark program or a complex program you are talking about.
If it is a benchmark, then it would be interesting to see the code,
because from my experience I doubt that Delphi produces better code than
fpc (in general it is the other way round). If it is a complex program,
then you need to analyze carefully which part of the program consumes
the most time and why. A number of 50% is in anyway unrealistic (this is
something you get if you compare inlined code against uninlined) ,
because the differences you get from code optimization are in a range
from +/-10% normally - unless you have found a real performance
bottleneck. And sometimes (most of) it is only an unoptimized library code.


On 21.09.2010 16:39, stefan077 at web.de wrote:
> Hi all,
> I am currently trying to get the fastest possible code from fpc on a  modern CPU (Intel Xeon) under Windows XP. I use the compiler options:
> fpc -Mdelphi -O3 -OpPENTIUMM -Cfsse2 -Cr- -Co- -CO- -Ci- myprogram.dpr
> Are there any better settings I should use? Compiling exactly the same  program with Delphi7 results in 50% faster code. I understand that fpc  does not support the most recent CPUs, but neither does DELPHI 7. So  what optimizations are done by Delphi 7 that are not done by fpc and why  is this the case?
>  Stefan
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