#### 8.23.6 Profiling Capability

It is a performance hit to use gcc's profiling approach for this tiny target. Even more – jtag hardware facility does not perform any profiling functions. However we've got gdb's built-in simulator where we can do anything.

We define new section .profiler which holds all profiling information. We define new pseudo operation .profiler which will instruct assembler to add new profile entry to the object file. Profile should take place at the present address.

Pseudo operation format:

.profiler flags,function_to_profile [, cycle_corrector, extra]

where:

    flags is a combination of the following characters:
  `s`
    function entry
  `x`
    function exit
  `i`
    function is in init section
  `f`
    function is in fini section
  `l`
    library call
  `c`
    libc standard call
  `d`
    stack value demand
  `I`
    interrupt service routine
  `P`
    prologue start
  `p`
    prologue end
  `E`
    epilogue start
  `e`
    epilogue end
  `j`
    long jump / sjlj unwind
  `a`
    an arbitrary code fragment
  `t`
    extra parameter saved (a constant value like frame size)
`function_to_profile`
  a function address
`cycle_corrector`
  a value which should be added to the cycle counter, zero if omitted.
`extra`
  any extra parameter, zero if omitted.

For example:

         .global fxx
         .type fxx,@function
         fxx:
         .LFrameOffset_fxx=0x08
         .profiler "scdP", fxx     ; function entry.
                              ; we also demand stack value to be saved
           push r11
           push r10
           push r9
           push r8
         .profiler "cdpt",fxx,0, .LFrameOffset_fxx  ; check stack value at this point
                                              ; (this is a prologue end)
                                              ; note, that spare var filled with
                                              ; the farme size
           mov r15,r8
         ...
         .profiler cdE,fxx         ; check stack
           pop r8
           pop r9
           pop r10
           pop r11
         .profiler xcde,fxx,3      ; exit adds 3 to the cycle counter
           ret                     ; cause 'ret' insn takes 3 cycles