[Bug lto/86654] [9 Regression] ICE in gen_member_die, at dwarf2out.c:24933

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86654

--- Comment #8 from rguenther at suse dot de <rguenther at suse dot de> ---
On Tue, 24 Jul 2018, marxin at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86654
> 
> --- Comment #7 from Martin Liška <marxin at gcc dot gnu.org> ---
> With the dwarf2out.c file patches, now the library builds. But it took my ~30
> minutes of linking, seeing perf top:
> 
>     36.96%  lto1           [.] lookup_external_ref
>     18.60%  lto1           [.] hash_table<external_ref_hasher,
> xcallocator>::find_empty_slot_for_expand
>      4.68%  as             [.] hash_lookup.isra.0
>      1.92%  as             [.] resolve_symbol_value
>      0.74%  lto1           [.] mark_used_flags
>      0.72%  as             [.] relax_segment

So you applied the first patch as well?  That was for debugging.  And
it didn't fire?  That's very good ;)

> and debug info of the shared library looks huge:
> 
> bloaty ./obj-x86_64-pc-linux-gnu/toolkit/library/libxul.so
>      VM SIZE                       FILE SIZE
>  --------------                 --------------
>    0.0%       0 .debug_info       937Mi  52.7%
>    0.0%       0 .debug_loc        339Mi  19.1%
>    0.0%       0 .debug_str        159Mi   9.0%
>    0.0%       0 .debug_ranges     110Mi   6.2%
>    0.0%       0 .debug_line      69.0Mi   3.9%
>   68.3%  65.3Mi .text            65.3Mi   3.7%
>    0.0%       0 .strtab          33.1Mi   1.9%
>    0.0%       0 .symtab          24.4Mi   1.4%
>    0.0%       0 .debug_abbrev    9.99Mi   0.6%
>    8.3%  7.91Mi .rela.dyn        7.91Mi   0.4%
>    8.0%  7.67Mi .rodata          7.67Mi   0.4%
>    6.2%  5.89Mi .eh_frame        5.89Mi   0.3%
>    4.1%  3.90Mi .data.rel.ro     3.90Mi   0.2%
>    1.7%  1.59Mi .dynstr          1.59Mi   0.1%
>    1.4%  1.35Mi .eh_frame_hdr    1.35Mi   0.1%
>    1.0%   990Ki [Other]          1003Ki   0.1%
>    0.6%   616Ki .bss                  0   0.0%
>    0.4%   398Ki .dynsym           398Ki   0.0%
>    0.0%       0 .debug_pubtypes   349Ki   0.0%
>    0.0%       0 .debug_pubnames   285Ki   0.0%
>    0.0%      23 [None]                0   0.0%
>  100.0%  95.6Mi TOTAL            1.74Gi 100.0%

Not so bad I think.  How's its size without LTO?

   0.0%       0 .debug_info     67.1Mi  52.8%
  58.2%  22.1Mi .text           22.1Mi  17.4%

but yes, PR83941 could be a reason for some bloat.  You could try
"counting" the number of DIEs that just contain a single 
DW_AT_abstract_origin attribute and no children.