increasing performance of nios 2

[Altera_Forum]

Hallo, 

 Is there any possibility to increase the performance of nios II in C4 related to the debug configuration? I know this from some µCs the there is a big increase by disabling the debug feature.   Is there any “switch” for nios II which results the same?   Thanks sim

[Altera_Forum]

The JTAG debug doesn't affect the execution time of normal code. 

For best performance: - Make sure you compile everything (including the BSP/C library) with -O2 or -O3. - Don't use floating point. - Don't use printf. - Try to use as little of the C libarary as possible. - Fit all your code and data into tightly coupled memory. - Don't use Altera's alt_main() code unless you really need the stdio setup and teardown (forces malloc() and friends into your image). - Use the 'small data' segment (%gp relative addressing) for as much data as possible. - Write C very carefully to give the compiler the best chance of optimising the code.

[Altera_Forum]

Hallo, 

 thanks for your answer. Could you explain your first point in more detail? Where is it to finde and what is the meaning?

[Altera_Forum]

I have also seen the option 

 APP_CFLAGS_OPTIMIZATION := -Os   in templates. But I could not find -Os in any document. What is that?   Greets sim

[Altera_Forum]

-Os is optimize for space. It will create a smaller binary, but maybe not the fastest one. If you are looking for performance it is better to use -O2 or -O3

[Altera_Forum]

Ok, thanks. 

Now I removed the '-g' option in BSP editor. Then I build all again. But the code size did not decrease. How could that be?