Optimization

AVR Studio4 컴파일 시 Error가 생길경우 Optimization 옵션을 바꾸면 Error가 사라지는 경우가 있다.

http://www.atmel.com/webdoc/atmelstudio/armtoolchain.section.bna_iff_lc.html

-Os

Signal that the generated code should be optimised for code size. 

The compiler will not care about the execution performance of the generated code

-O0

No optimisation.GCC will generate code that is easy to debug but slower and larger than with the incremental optimization levels outlined below.




-O1 or -O

This will optimise the code for both speed and size. Most statements will be executed in the same order as in the C/C++ code and most variables can be found in the generated code. This makes the code quite suitable for debugging.This is default.

-O2

Turn on most optimizations in GCC except for some optimisations that might drastically increase code size. This also enables instruction scheduling, which allows instructions to be shuffled around to minimize CPU stall cycles because of data hazards and dependencies, for CPU architectures that might benefit from this. Overall this option makes the code quite small and fast, but hard to debug.

-O3

Turn on some extra performance optimisations that might drastically increase code size but increase performance compared to the -O2 and -O1 optimization levels. This includes performing function inlining