[Bug c++/65848] [c++-concepts] High memory usage and compilation times for subsuming concept chains; regression from r211824

[andrew.n.sutton at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65848

--- Comment #2 from Andrew Sutton <andrew.n.sutton at gmail dot com> ---
Here's the result of the latest commit (r222332) on my system. test.cpp is the
program in the bug report.

        Command being timed: "~/opt/bin/g++ -std=c++1z -c test.cpp"
        User time (seconds): 0.04
        System time (seconds): 0.01
        Percent of CPU this job got: 91%
        Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.07
        ...
        Maximum resident set size (kbytes): 49344
        ...
        Minor (reclaiming a frame) page faults: 4465