On 09 Jun 2009, at 09:24, Graeme Geldenhuys wrote:
leledumbo wrote:
AFAIK only -CfSSE? and -Op??? that you have to worry.
-Op??? is no problem. It's -Cp that can generate code which won't run
on previous-generation cpus.
If you're not sure,
just use the lowest possible value (-CfX87 and -Op386). For
optimizations,
even using -O3 is fine.
Thanks. Do you know what exactly changes when you use various
optimization options? Is it primarily executable size or more speed
related optimizations?
Speed (and also a bit of size, sometimes), but the effects will only
be very minor in most cases. Only -Cfsse2 sometimes produces a
noticable speedup on more recent processors.
If it is speed related, how can I actually test the speed
differences so
see by how much it increases?
Just time your program using the Unix "time" command (taking into
account the fact that there will always be some amount of jitter).
Does FPC have such tests available
somewhere in the source code?
You can try Thomas Schatzl's cpu unit to time small code fragments:
http://members.yline.com/~tom_at_work/index.html
Jonas
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