Cycle Count Difference in SHARC-FX When Function Definition and Call Are in Separate Files

Hi,

We are also observing the same behavior. We will get back to you early next week.

Regards,
Santhakumari.V

Hi,

We recommend you to use XT_RSR_CCOUNT() built-in function to measure the cycle count in SHARC-FX.

Below is the sample snippet for your reference.

#include <stdio.h>
#include <xtensa/tie/xt_timer.h>

void myfunc(void);

int main() {
unsigned int cycles = XT_RSR_CCOUNT(); // start count
myfunc();
cycles = XT_RSR_CCOUNT() - cycles; // end count - start count
printf("myfunc took %u cycles\n", cycles);
return 0;
}

void myfunc(void){
int age;
int currentYear = 2025;
int birthYear = 1995;
age = currentYear - birthYear;

}

Hope this helps!

Regards,
Santhakumari.V

Hi Santhakumari,

I have three questions regarding cycle counts:

• I calculated the cycle counts using the built-in function XT_RSR_CCOUNT(), but I am still observing inconsistencies. When the function call and function definition are in the same file, I measure 23 cycles, whereas when they are in different files, the cycle count increases to 49 cycles. Could you explain why this difference occurs?

• In SHARC+, we used CYCLES_START() and CYCLES_STOP() to measure cycles, but for SHARC-FX you recommend using the XT_RSR_CCOUNT() built-in function. Could you explain the reason for preferring XT_RSR_CCOUNT() on SHARC-FX?

• I am seeing higher cycle counts on SHARC-FX for scalar-based operations compared to SHARC+. On SHARC+, the operation takes 5 cycles, whereas on SHARC-FX it takes 22 cycles. Since SHARC-FX is known for optimization, what steps should I follow to optimize these types of operations?

Please help clarify these points. I had also attached the project files for your reference.

ADSP-21834_Scalar_based_operation.zipADSP-21593_Scalar_based_operation.zipADSP-21834_Function_and_Call_same_file.zipADSP-21834_Function_and_Call_different_file.zip

Hi Santhakumari,

Could you please share an update on this? We need the information urgently. Thank you for your understanding.

Regards,

Franky45

Hi Franky,

We have simulated this issue in our end and working internally on this.

We will get back to you as soon as possible.

Regards,
Santhakumari.V