[Bug libfortran/78549] Very slow formatted internal file output

[tkoenig at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78549

--- Comment #10 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
Here are some gprof timings:

Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total           
 time   seconds   seconds    calls  ms/call  ms/call  name    
 28.73      2.06     2.06                             delete_root
 15.76      3.19     1.13                             build_float_string
  5.86      3.61     0.42                            
formatted_transfer_scalar_write
  5.30      3.99     0.38                             _gfortrani_parse_format
  4.53      4.32     0.33                             get_float_string
  3.14      4.54     0.23                             data_transfer_init
  3.00      4.76     0.22                             write_float_0
  2.79      4.96     0.20                             next_format0
  2.09      5.11     0.15                             next_char
  1.95      5.25     0.14                             insert
  1.95      5.39     0.14                             parse_format_list
  1.81      5.52     0.13                            
_gfortrani_free_format_hash_table
  1.67      5.64     0.12                             get_precision
  1.67      5.76     0.12                             select_buffer
  1.53      5.87     0.11                             get_gfc_unit
  1.26      5.96     0.09                             _gfortrani_next_format
  1.19      6.04     0.09                             _gfortrani_write_block
  1.12      6.12     0.08                             write_float_string
  1.05      6.20     0.08                             _gfortrani_next_record

What is striking is the long time spent in delete_root.