Re: [PATCH 0/8] gitlab: speed up msys windows jobs with GCC

[Markus Armbruster <armbru@redhat.com>]

Daniel P. Berrangé <berrange@redhat.com> writes:

> This is an alternative and/or complementary to Thomas' proposal
> to use CLang with msys:
>
>   https://lists.gnu.org/archive/html/qemu-devel/2023-07/msg05402.html
>
> First of all, the current msys installer we're using is over 12
> months out of date. Thus after running the install, pacman then
> replaces most of what we've just installed with new downloaded
> content. Using the most update installer cuts 3+1/2 minutes off
> the msys install time - 7 minutes becomes 3+1/2.
>
> Secondly, QEMU defaults to compiling with -O2 and this is more
> computationally expensive for GCC. Switching to -O0 drops the
> build time from 60 minutes down to 45 minutes.

From the fine manual[*]: "The effectiveness of some warnings depends on
optimizations also being enabled.  For example '-Wsuggest-final-types'
is more effective with link-time optimization and some instances of
other warnings may not be issued at all unless optimization is enabled.
While optimization in general improves the efficacy of control and data
flow sensitive warnings, in some cases it may also cause false
positives."  Do we care?

[...]


[*] https://gcc.gnu.org/onlinedocs/gcc-13.2.0/gcc/Warning-Options.html