LD profiling suggests it's performance can be improved

[Yuri]

I profiled "ld" while running on medium-sized C++ project with about 60K total
symbols  (as reported by "nm <executable>").

Profiling data suggests that over 85% of time is spent in functions 
"htab_find_slot_with_hash" and "last_eq" in libiberty library.

Unfortunately for some reason gprof wasn't able to write detailed report on 
per-line basis but I suspect that the reason is that "ld" uses unmangled names 
for hash and hash's non-uniformity factor is very high.

Other hint is that we use lots of templates with numerous branched 
specializations and ratio #mangled/#non-mangled is often in the hundreds for 
names (580 for one of the names). So there's a lot of collisions in hash in 
"htab_find_slot_with_hash".

Thanx,
Yuri

PS: Reason I did all these experiments is that linking takes about 1-2 minutes 
which seems too high.

---------gprof report-------------------------------
Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total
 time   seconds   seconds    calls  ms/call  ms/call  name

 43.72     21.60    21.60    87073     0.25     0.50  htab_find_slot_with_hash
 41.46     42.08    20.48 153889424     0.00     0.00  last_eq
  3.40     43.76     1.68 10303941     0.00     0.00  last4_eq
  2.65     45.07     1.31   259059     0.01     0.01  bfd_hash_lookup
  1.75     45.94     0.86  9452526     0.00     0.00  wildcardp
  1.61     46.73     0.80   680907     0.00     0.00  sec_merge_hash_lookup
  1.21     47.33     0.60     2408     0.25     0.62  walk_wild_section
  1.09     47.87     0.54    11692     0.05     0.05  add_line_info
  0.34     48.04     0.17    34589     0.00     0.05  elf_i386_relocate_section
  0.28     48.18     0.14  5549788     0.00     0.00  bfd_getl32
  0.20     48.28     0.10    34589     0.00     0.01  elf_i386_check_relocs
  0.18     48.37     0.09       25     3.60    72.74  elf_link_input_bfd
  0.17     48.45     0.09  1239094     0.00     0.00  _bfd_relocate_contents
  0.16     48.53     0.08       31     2.58    32.29  
elf_link_add_object_symbols
  0.14     48.60     0.07   475918     0.00     0.00  _bfd_merged_section_offset
  0.10     48.66     0.05  1902353     0.00     0.00  bfd_putl32
  0.08     48.70     0.04        3    13.33 14565.49  merge_strings
  0.06     48.73     0.03   298999     0.00     0.00  bfd_hash_allocate
  0.06     48.76     0.03   109364     0.00     0.00  elf_link_output_extsym
  0.06     48.78     0.03    32142     0.00     0.00  
_bfd_strip_section_from_output
  0.05     48.81     0.03  1239094     0.00     0.00  _bfd_final_link_relocate
  0.04     48.83     0.02  1287139     0.00     0.00  bfd_elf32_swap_reloc_in