[avr-gcc-list] Optimizer -fnew-ra option

[Haase Bjoern (PT-BEU/MKP5) *]

Hello,

does someone already has experience with using the "-fnew-ra" optimizer option 
for avr-gcc? 

I have been playing around a little bit with the optimizer configurations and 
it turned out, that the "-fnew-ra" optimizer improved our code density by about 
7%! 
Since we do not have much program memory left in our ATMEGA169, we would be 
happy to use the additional 1k of PROGMEM.

For my tests, I have been comparing "-Os" with "-Os -fnew-ra" for 
avr-gcc.3.2.2. We presently still are using gcc.3.2.2 since I have the 
impression that the code efficiency of the older versions is kind of a bit 
better than the efficiency of the more recent releases. I, e.g. have been 
comparing gcc.3.2.2. with the current gcc.4.0-20041114.

When using gcc-3.2.2 with "-fnew-ra" our application seemingly still works 
fine. 
Since this optimizer feature, however, seems to be classified as "not ready for 
production use", I feel a bit uneasy about using it. (E.g. also my current 
gcc.4.0-20041114 crashes with a "segmentation fault", as soon as I try to use 
"-fnew-ra".)

For this reason, I would be like to know whether anybody has already had 
experience with this optimizer option and whether someone could give me an 
idea, which kind of errors one should look for when using the new register 
allocator.

Yours,

Björn