How to count execution time?

[js4ngu]

Hi im jongsang who is user of DC-ROMA Gen2 Laptop.

Actually i have lots of interest in RVV.

now, i have curious of "vsetvli", "vle32.v", "vse32.v" Instruction's execution time.

I try to write test code like this.
`
#include <stdio.h>
#include <stdint.h>

#define VECTOR_SIZE 8
int main() {
uint64_t start, end, cycle;

asm volatile (
    "fence.i\n\t"         // Invalidate the instruction cache
    "rdcycle %0 \n\t"

    "vsetvli t0, %2, e32\n\t"
    "vsetvli t0, %2, e32\n\t"
    "vsetvli t0, %2, e32\n\t"
    "vsetvli t0, %2, e32\n\t"
    "vsetvli t0, %2, e32\n\t"

    "vsetvli t0, %2, e32\n\t"
    "vsetvli t0, %2, e32\n\t"
    "vsetvli t0, %2, e32\n\t"
    "vsetvli t0, %2, e32\n\t"
    "vsetvli t0, %2, e32\n\t"

    "fence.i\n\t"         // Invalidate the instruction cache
    "rdcycle %1 \n\t"

    : "=r"(start), "=r"(end)    // Output operands
    : "r"(VECTOR_SIZE)          // Input operand
    : "t0"                      // Clobbered register
);

printf("start: %ld\n", start);
printf("end: %ld\n", end);
cycle = end - start;
printf("cycle: %ld\n", cycle);
return 0;

}
`

But, result is confuse.

I cant understand about this result.

How does it take 0 cycles to perform "vsetvli" 10 times?

Is there any problem to my method?

If it has problem, please give some advice...

Thank you.

Best regard,

[DC-DeepComputing]

Could you raise the issue on Reddit? We may invite some technical guys to reply it.

[archanox]

@DC-DeepComputing do you have a link to the Reddit for support?