NIOS II - FW doesn't work with compiler optimization turned on

Hi,

Greetings and welcome to Intel's forum.

Please give me some time to check on this issue and will get back to you with the update.

Thank you.

Regards,

Fathulnaim

Hi,

I am checking this issue with internal teams.

In the meantime, can you provide the project file as I want to try and monitor the detail of the issue on my side.

Hi,

Since project cannot be shared, then we will suggest ways for you to debug the issue.

We recommend for you to enable a single optimization until the design fails. Once you can find the optimization that cause the issue then can remove it and proceed without using it for your design.

Since -O3 is using bunch of optimizations, we should try one by one:

-O0 (working or not)

-O1 (work with which optimization)

-O2 (work with O1 and plus which optimization)

-O3 (failing because of which optimization)

Based on the closer working/failing pair, we will have a smaller group to investigate.

For example,

If the pair is found to be O2-O3, these are the interested optimization to investigate

https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html

Thank you.

Regards,

Fathulnaim

Hi,

As the firmware started not working when enable optimization O2, you can proceed to investigate those pairs. Yes, you will need to disable one by one the optimization flag to find out which flag generates the issue.

For the turning off optimization for a block of code, I will need to get the information from the internal team first then will inform you on the feedback.

Hi,

Thanks for the feedback.

You said I can disable the optimization flags one by one, but I don't understand how I can disable only one. I read the link you shared with me but there is nothing about it.

For example, with the -O2 optimization, if I want to disable only the -finline-functions flag and enable all the others, how can I do that?

Thank you.

Regards,

naand

Hi,

I have news about what optimization flag is responsible for the problem; the flag is the -finline-small-functions.

Another test I did was to set the variable flag_status, used to check the Flash status, as volatile, but nothing changed (the flag_status is found in the flash_write_function.c file attached in the first message).

Are there any updates on how to disable optimization for a specific block of code?

Thanks.

Best Regards,

naand

Hi,

Sorry for not updating as I just got back from long holiday.

Will check with engineering team on the step if the optimization can be disable for a specific block of code.

Thank you.

Hi Sir,

So far there is no official document or guide from us on how to disable the optimization for a specific block of code.

However, I found this which you can try.

https://programfan.github.io/blog/2015/04/27/prevent-gcc-optimize-away-code/

Thank you.

Hi Sir,

Any update from your side?

Hi,

I am sorry for the delayed response. I have been out of the office for the last few days.

Thanks for the link, I tried the #pragma directive to disable GCC optimization for one or more functions and it works.

With this technique I was able to isolate the source of the problem: the function that causes it is flash_read_flag_status_register.

It is implemented in this way:

and is used to check if the write operation is finished and then checks for errors:

// check for errors
do {

flag_status = flash_read_flag_status_register(st);

} while (!(flag_status & FLASH_FSR_READY));

flash_clear_flag_status_register(st);
if (flag_status & FLASH_FSR_PROTECTION_ERR)
{

ret_flag = FLASH_SECTOR_PROTECTED;
break;

}
if ((flag_status & FLASH_FSR_ERASE_ERR) || (flag_status & FLASH_FSR_PROGRAM_ERR))
{

ret_flag = FLASH_ERROR;
break;

}

To avoid using #pragma I tried setting the flag_status variable as volatile, but it doesn't work.

Do you know why if I use volatile for flag_status it doesn't work?

Can you suggest other attentions I can have to avoid other problems with GCC optimization?

Thanks.

Best Regards,

naand