Tracing/profiling instructions

Question

I'd like to statistically profile my C code at the instruction level. I need to know how many additions, multiplications, divisions, etc I'm performing.

This is not your usual run of the mill code profiling requirement. I'm an algorithm developer and I want to estimate the cost of converting my code to hardware implementations. For this, I'm being asked the instruction call breakdown during run-time (parsing the compiled assembly isn't sufficient as it doesn't consider loops in the code).

After looking around, it seems VMware may offer a possible solution, but I still couldn't find the specific feature that will allow me to trace the instruction call stream of my process.

Are you aware of any profiling tools which enable this?

Answer 1

The valgrind tool cachegrind can be used to get execution counts of each line in the compiled assembly (the Ir value in the first column).

Answer 2

I eventually used a trivial yet effective solution.

1. Configured GDB to display the disassembly of the next instruction (every time it stops) by invoking:

   display/i $pc

2. Configured a simple gdb script that breaks in the function I need to analyze and proceeds to step instruction by instruction:

   set $i=0 break main run while ($i<100000) si set $i = $i + 1 end quit

3. Executed gdb with my script dumping output into a log file:

   gdb -x script a.out > log.txt

4. Analyzed the log to count specific instruction calls.

Crude, but it works...