scripts/performance: Add topN_callgrind.py script

scripts/performance: Add topN_callgrind.py script

Python script that prints the top N most executed functions in QEMU
using callgrind.

Syntax:
topN_callgrind.py [-h] [-n] <number of displayed top functions>  -- \
                      <qemu executable> [<qemu executable options>] \
                      <target executable> [<target execurable options>]

[-h] - Print the script arguments help message.
[-n] - Specify the number of top functions to print.
     - If this flag is not specified, the tool defaults to 25.

Example of usage:
topN_callgrind.py -n 20 -- qemu-arm coulomb_double-arm

Example Output:
No.  Percentage Function Name         Source File
----  --------- ------------------    ------------------------------
   1    24.577% 0x00000000082db000    ???
   2    20.467% float64_mul           <qemu>/fpu/softfloat.c
   3    14.720% float64_sub           <qemu>/fpu/softfloat.c
   4    13.864% float64_add           <qemu>/fpu/softfloat.c
   5     4.876% helper_mulsd          <qemu>/target/i386/ops_sse.h
   6     3.767% helper_subsd          <qemu>/target/i386/ops_sse.h
   7     3.549% helper_addsd          <qemu>/target/i386/ops_sse.h
   8     2.185% helper_ucomisd        <qemu>/target/i386/ops_sse.h
   9     1.667% helper_lookup_tb_ptr  <qemu>/include/exec/tb-lookup.h
  10     1.662% f64_compare           <qemu>/fpu/softfloat.c
  11     1.509% helper_lookup_tb_ptr  <qemu>/accel/tcg/tcg-runtime.c
  12     0.635% helper_lookup_tb_ptr  <qemu>/include/exec/exec-all.h
  13     0.616% float64_div           <qemu>/fpu/softfloat.c
  14     0.502% helper_pand_xmm       <qemu>/target/i386/ops_sse.h
  15     0.502% float64_mul           <qemu>/include/fpu/softfloat.h
  16     0.476% helper_lookup_tb_ptr  <qemu>/target/i386/cpu.h
  17     0.437% float64_compare_quiet <qemu>/fpu/softfloat.c
  18     0.414% helper_pxor_xmm       <qemu>/target/i386/ops_sse.h
  19     0.353% round_to_int          <qemu>/fpu/softfloat.c
  20     0.347% helper_cc_compute_all <qemu>/target/i386/cc_helper.c

Signed-off-by: Ahmed Karaman <ahmedkhaledkaraman@gmail.com>
Signed-off-by: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Reviewed-by: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Message-Id: <20200626164546.22102-3-ahmedkhaledkaraman@gmail.com>