How to calculate instruction cycles?

[Larry Flessland]

I have an algorithm which does quite a bit of number crunching. I'd like to know how many clock or instruction cycles this algorithm is using. How can I get or calculate the instruction cycles?

[Charles Manning]

With some tools and simulators it is possible to determine this theoretically.

What might be better though is to just toggle a GPIO when you go into the code, then again when you come out, and use a scope to measure the execution time.