How to Prevent Compiler from Rearranging/Optimizing Inline Assembly Code

Official Hardware Mega Due
1

Hi all,

I have a piece of code that has some commands in inline assembly and I would like to be 100% sure that the compiler does not mess with the code as I need it to run in exactly that order.

So far, I have tried formatting each line as

__asm__ volatile("...code...\n\t":::"memory");

and I have tried to change the compiler optimization settings to -O0 and -Og.

However, for some reason, it seems that the compiler is still "optimizing"/rearranging the code.

Any ideas of what this might be or suggestions for how to remedy this would be greatly appreciated.

(PS. I understand that the compiler optimizations are useful for making code more efficient and faster, but that is not something I am concerned with in this case. The timing of this code is absolutely crucial and so it is important that the code remains unaltered.)

Thank you all for your help

2

The compiler can't rearrange assembly. It doesn't even know how to read assembly. It just passes that straight through to the output. It may rearrange the C code around the assembly or the storage of the variables but your code should be written to account for that.

Without seeing the code, your specific problem cannot be solved.