[Bug c++/67565] [concepts] Very slow compile time and high memory usage with complex concept definitions, even if unused

[tom at honermann dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67565

--- Comment #5 from Tom Honermann <tom at honermann dot net> ---
Nice, thanks!

Using gcc r238587, I get the times below for the examples in this report.  All
cases are dramatically improved.  Unless there is some other known issue not
captured in the discussion here, it looks to me like this issue can be
resolved.

For the example in comment 0:

$ time g++ -std=c++1z -fconcepts main.cpp
real    0m0.051s
user    0m0.040s
sys     0m0.008s

For the example in comment 2:

$ time g++ -c -std=c++1z -fconcepts t.cpp
real    0m0.009s
user    0m0.004s
sys     0m0.000s

$ time g++ -c -std=c++1z -fconcepts t.cpp -DGO_FAST1
real    0m0.009s
user    0m0.004s
sys     0m0.000s

$ time g++ -c -std=c++1z -fconcepts t.cpp -DGO_FAST2
real    0m0.009s
user    0m0.000s
sys     0m0.004s

$ time g++ -c -std=c++1z -fconcepts t.cpp -DGO_SLOWER1
real    0m0.009s
user    0m0.000s
sys     0m0.004s

Additionally, my builds of Text View [1] now complete in 0m26.140s improved
from 1m35.837s.

[1]: https://github.com/tahonermann/text_view