[Bug c++/80290] [6/7/8 Regression] g++ uses unreasonable amount of memory compiling nested string maps

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80290

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[6/7 Regression] g++ uses   |[6/7/8 Regression] g++ uses
                   |unreasonable amount of      |unreasonable amount of
                   |memory compiling nested     |memory compiling nested
                   |string maps                 |string maps

--- Comment #24 from Richard Biener <rguenth at gcc dot gnu.org> ---
While memory use improved the testcase in comment#10 still shows substantial
increase in memory and time for each added init element:

1.24user 0.04system 0:01.28elapsed 100%CPU (0avgtext+0avgdata
170772maxresident)k
1.49user 0.07system 0:01.56elapsed 99%CPU (0avgtext+0avgdata
206396maxresident)k
0inputs+0outputs (0major+50914minor)pagefaults 0swaps
1.70user 0.05system 0:01.76elapsed 100%CPU (0avgtext+0avgdata
233904maxresident)k

so we improved some constant factor but didn't really address the underlying
issue.

Numbers from before the patch (on a loaded system, sorry) were

3.87user 0.10system 0:04.33elapsed 91%CPU (0avgtext+0avgdata
235760maxresident)k
0inputs+0outputs (0major+54479minor)pagefaults 0swaps
5.23user 0.16system 0:06.06elapsed 88%CPU (0avgtext+0avgdata
283860maxresident)k
0inputs+0outputs (0major+64971minor)pagefaults 0swaps
6.17user 0.15system 0:06.90elapsed 91%CPU (0avgtext+0avgdata
323796maxresident)k
0inputs+0outputs (0major+74942minor)pagefaults 0swaps