Profiling instructions

Question

I want to count several cpu instructions in my code. e.g. I would like to know how many additions, how many multiplications, how many float operations, how many branches my code executes. I currently use gprof under Linux for profiling my c++ code but it only gives the number of calls to my functions, and I manually estimate the number of instructions. Are there any tools that might do the trick for me? Maybe some virtual machine?

Answer 1

This is a general advice, not-Linux specific: you should be interested in CPU cycles instead. Forget about the number of instructions as a measure of performance. One instructions may cost same as other 10 together, so it won't tell you anything.

You should focus on CPU cycles, and in multithreaded environments (most if not all today) in the time the thread is put to sleep ("switched/out"), which will give you the idea of how much time is waiting for I/O, DB, etc to complete and it impacts CPU privileged time.

Answer 2

If you really need to count instructions then you are probably best off generating assembler and then passing the output to an intelligent grep equivalent. For gcc, try the -S switch.