[Bug c++/64500] New: push_to_top_level() shows up high during Chromium build.

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64500

            Bug ID: 64500
           Summary: push_to_top_level() shows up high during Chromium
                    build.
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: trippels at gcc dot gnu.org
                CC: jason at gcc dot gnu.org, marxin at gcc dot gnu.org

Created attachment 34378
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34378&action=edit
unreduced testcase

Running "perf top" during Chromium build shows that push_to_top_level() is in
the 8-12% range.

This is an older issue, because it already happens for 4.8.4.

Here is an example:

markus@x4 Release % perf record c++ -std=gnu++11 -O2 -c InspectorCSSAgent.ii
[ perf record: Woken up 6 times to write data ]
[ perf record: Captured and wrote 1.275 MB perf.data (~55717 samples) ]
markus@x4 Release % perf report
   8.01%  cc1plus  cc1plus          [.] push_to_top_level
   4.23%  cc1plus  cc1plus          [.] gt_ggc_mx_lang_tree_node
   2.13%  cc1plus  cc1plus          [.] ggc_set_mark
   1.98%  cc1plus  cc1plus          [.] lookup_page_table_entry
   1.75%  cc1plus  libc-2.19.90.so  [.] _int_malloc
   1.61%  cc1plus  cc1plus          [.] ggc_internal_alloc
   1.57%  cc1plus  cc1plus          [.] lookup_field_r