[Bug gdb/10952] Single Stepping into functions is very slow when not setting LD_BIND_NOW env variable

["dje at google dot com" <sourceware-bugzilla@sourceware.org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=10952

--- Comment #3 from dje at google dot com 2012-05-01 17:48:45 UTC ---
Some profiling data for the 30 seconds to step 1800 insns of dynsym resolving
code case.
gdb compiled with -g -pg -ftest-coverage -fprofile-arc.
This is with gdb 7.4.

gprof output:

Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total           
 time   seconds   seconds    calls  ms/call  ms/call  name    
 35.22      6.97     6.97    18756     0.37     0.37  find_pc_sect_psymtab
  8.84      8.72     1.75     1925     0.91     0.91  find_pc_sect_symtab
  7.38     10.18     1.46    29385     0.05     0.12  dwarf2_read_abbrevs
  7.33     11.63     1.45 167485647     0.00     0.00  read_unsigned_leb128
  4.40     12.50     0.87   358406     0.00     0.00  cpname_parse
  3.59     13.21     0.71  5015596     0.00     0.00  hash_continue
  2.68     13.74     0.53   762409     0.00     0.00  strcmp_iw_ordered
  2.27     14.19     0.45 15061184     0.00     0.00  dwarf2_lookup_abbrev
  2.12     14.61     0.42  5946084     0.00     0.00  cpname_lex
  1.54     14.92     0.31                             d_print_comp
  1.52     15.22     0.30 12193270     0.00     0.00  read_attribute_value
  1.41     15.50     0.28  2013893     0.00     0.00  read_partial_die
  1.16     15.73     0.23 10510160     0.00     0.00  dwarf_alloc_abbrev
  1.06     15.94     0.21    29094     0.01     0.12  load_partial_dies
  1.06     16.15     0.21   152021     0.00     0.00  msymbol_hash_iw

For find_pc_sect_psymtab, gcov shows this interesting tidbit:

 85699863:  364:  ALL_OBJFILE_PSYMTABS_REQUIRED (objfile, pst)
148591017:  365:    if (!pst->psymtabs_addrmap_supported
 62909784:  366:    && pc >= pst->textlow && pc < pst->texthigh)

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