Re: [Gimp-developer] help compiling babl

[Ken Moffat <zarniwhoop ntlworld com>]

On Mon, Aug 12, 2019 at 02:33:42PM -0400, Elle Stone wrote:
> On 08/12/2019 01:38 PM, Alexandre Prokoudine via gimp-developer-list wrote:
> > Hello,
> >
> > You should be using the Meson build system now.
>
> In case it helps anyone, here are the lines I've been using with meson to
> build babl:
>
>
> cd $SRC_DIR/babl
> git status
> rm -r build
> git checkout build
> cd build
> CFLAGS="-march=native -O3 -ffast-math -ftree-vectorize -pipe"
> CXXFLAGS="${CFLAGS}" meson --prefix=$PREFIX ..
> ninja install
>
> Here are some questions about meson:
>
> 1. Any suggestions to modify my lines?

Adding '-Dbuildtype=release' to a meson package will turn off debug
assertions, if any (e.g. mesa) and (usually) use -O3 (ISTR that at
least pango uses -O2 for a release build).

> 2. Do the CFLAGS lines actually do anything when using meson?

Do a verbose build using 'ninja -v' to see what flags and defines
are used.  I usually do separate steps for 'ninja' and 'ninja
install', but whatever works for you.  Verbose builds will produce a
_lot_ more output, teeing it to a log so you can read it afterwards
helps (but I'm sure you know that).

> 3. How do I tell meson to use "something" equivalent to the following "make"
> lines?
>
> ./autogen.sh --prefix=$PREFIX --enable-avx2=false --enable-mmx=no
> --enable-sse=no --enable-sse2=no --enable-sse3=no --enable-sse4_1=no
> --enable-f16c=no --enable-altivec=no --disable-docs

I very much doubt you are on ppc/powerpc, so altivec cannot be used.

In general, meson uses defines (-Dsomething=value, rather like
cmake) for things which are not covered by --prefix= --sysconfdir=.
To see the options for a particular package, look in the
meson_options.txt file.  That might have an option to disable docs,
or it might even be automatic if the deps are missing.

With -march=native I would tend to let gcc sort out sse and similar
options.  I'm assuming you are on x86_64.

The gcc manual gives some options (for X86) about what you can put
in CFLAGS|CXXFLAGS, see the  -mfpath= section.
https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html
(That is for 9.2, probably the only big change from 9.1 is adding
znver2).  And more generally, the -f options are linked from
.../gcc/Option-Index.html

Docs for the latest point release of each gcc version are at
https://gcc.gnu.org/onlinedocs/ if you are using an earlier major
version.

OTOH, if you have the (lots of) time needed to try playing with
these options, and scripts which you can run using 'time' (several
runs for each different build) then perhaps tuning out some of these
things might be worthwhile.  I spent a lot of time in the past couple
of months doing whole-system builds with different flags (mostly for
slight hardening) and ended up concluding there was just too much
variation between runs to get much meaningful data on timing.  And I
didn't have any runtime scripts for gimp-related actions.

ĸen
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