Tracing/profiling instructions

You can use pin-instat which is a PIN tool. It's a bit over kill as it records more information than the instruction count. It still should be more efficient than your gdb approach through.

Disclaimer: I'm the author of pin-instat.

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...

The Linux tool perf will give you a good deal of profiling information; specifically, perf annotate will give you per-instruction relative counts.

It is possible to drill down to the instruction level with perf annotate. For that, you need to invoke perf annotate with the name of the command to annotate. All the functions with samples will be disassembled and each instruction will have its relative percentage of samples reported:

perf record ./noploop 5
perf annotate -d ./noploop

------------------------------------------------
 Percent |   Source code & Disassembly of noploop.noggdb
------------------------------------------------
         :
         :
         :
         :   Disassembly of section .text:
         :
         :   08048484 <main>:
    0.00 :    8048484:       55                      push   %ebp
    0.00 :    8048485:       89 e5                   mov    %esp,%ebp [...]
    0.00 :    8048530:       eb 0b                   jmp    804853d <main+0xb9>
   15.08 :    8048532:       8b 44 24 2c             mov    0x2c(%esp),%eax
    0.00 :    8048536:       83 c0 01                add    $0x1,%eax
   14.52 :    8048539:       89 44 24 2c             mov    %eax,0x2c(%esp)
   14.27 :    804853d:       8b 44 24 2c             mov    0x2c(%esp),%eax
   56.13 :    8048541:       3d ff e0 f5 05          cmp    $0x5f5e0ff,%eax
    0.00 :    8048546:       76 ea                   jbe    8048532 <main+0xae> [...]