[Bug c++/70768] Increased compilation time

["trippels at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70768

Markus Trippelsdorf <trippels at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |trippels at gcc dot gnu.org
         Resolution|---                         |INVALID

--- Comment #1 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
(In reply to James Almer from comment #0)
> Created attachment 38332 [details]
> Preprocessed output
> 
> The attached preprocessed output (Created from the source using GCC 5, 6 and
> 7 for the purpose of this ticket) takes almost twice as long to compile
> using GCC 6.0.1 RC and especially GCC 7.0 compared to GCC 5.3 on a linux
> x86_64 machine with 2gb of RAM.
> 
> GCC 5.3 performed the best for all three preprocessed files.
> GCC 6.0.1 performed about the same as GCC 5.3 using the gcc5 preprocessed
> file. It however trashed my HDD a lot trying to compile the preprocessed
> output from both GCC 6 and GCC 7, and took longer to finish them. This may
> hint at increased RAM usage and explain the odd time values, but i didn't
> check.
> GCC 7 performed the worst across the table, even with the gcc5 preprocessed
> file.

Well, you simply need more RAM to compile this testcase, because gcc-6 uses
slightly over 2GB peak, so your machine starts swapping.
On my machine (with 8GB RAM) gcc-6 is actually slightly faster.

(For gcc-7 you need to configure it with --enable-checking=release to compare
timings.)