Optimization levels

RainerGund · Joined: 15 Oct 2003 Posts: 1 Location: Wiesenbach, Germany

Hi,

is there any further explanation about the functionality of the different optimization levels ?
Will it have any effect on code or memory size by changing it on the same source code ?

Tanks

R.Gund

Haplo · Joined: 06 Sep 2003 Posts: 659 Location: Sydney, Australia

Yes it does have big effects on the code/memory size. I've experienced size differences up to %10 between #opt 0 and #opt 9 on the same source code.

ajt · Joined: 07 Sep 2003 Posts: 110

Not clear why one would ever want to set a low optimization level unless this directive is the same as "bug threshold" (or inverse thereof). The manual says that the directive "may also be used if an optimization error is suspected"!

So how is one to know what to use so as to not incur latent bugs!?!
_________________
Al Testani

regan · Posted: Thu Apr 01, 2004 2:28 am

The optimisation levels are important to me at the moment as there is a bug in some of the RAM addressing in the most recent version of the PCH compiler. To get around it I need to set the opt level to 5 which uses 'conservative' switching of RAM banks. This has the undesirable effect of increasing my code size by over 12%. Meanwhile, I still have useable code until CCS find time to fix the bug. Normally, I would set the opt level to as high as possible.

Regan.