firefox with -O3+lto+pgo on clang?

[papu]

i am interesting for testing this but i don't know how to configure a /etc/portage/env for that

what I would do is: quickpkg of two diferentes compilations and i try to test both firefox: normal and with O3-pgo-lto

are there anybody with knowlege for helping me?

thanks so much

[fedeliallalinea]

I'm no expert but you can begin to read here while you wait for more answers.

[papu]

I'm no expert but you can begin to read here while you wait for more answers.

i continue reading things...
mmm gento-lto may be is only for entire system and focalized to gcc , isen't it?
i only want do for firefox and with clang to not interfere with my gcc

[fedeliallalinea]

Why not use firefox-bin that is compiled with lto+gpo since 2018?

[papu]

Why not use firefox-bin that is compiled with lto+gpo since 2018?

mmm ah , yes i see, but i prefer to have a compilation to see the diferences, the bin is not O3 sure O2 , and i am using pipewire without pulseaudio but i take a look

[papu]

i think that activanting just pgo use flag on firefox clang have to use it despite the informative message that gcc will be used

Code: Select all

 - - pgo             : Add support for profile-guided optimization using gcc-4.5, for faster binaries.
                       This option will double the compile time.

then i just need to know a /etc/portage/env/ config to force clang to use O3 instead O2

may be some like?

Code: Select all

/etc/portage/O3-clang
CC="clang"
CXX="clang++"
CFLAGS="-march=native -O3 -pipe"
CXXFLAGS="${CFLAGS}"
MAKEOPTS="-j4"

but i think that firefox just force compilations with O2 on clang.

[Josef.95]

papu,
I think the following should probably work (i have it not tested)
1) Enable in package.use www-client/firefox clang lto pgo
2) Set in /etc/portage/env/O3-clang CFLAGS="${CFLAGS} -O3"
and in /etc/portage/package.env www-client/firefox O3-clang
3) and then check it via: ebuild `equery w firefox` clean configure

[papu]

papu,
I think the following should probably work (i have it not tested)
1) Enable in package.use www-client/firefox clang lto pgo
2) Set in /etc/portage/env/O3-clang CFLAGS="${CFLAGS} -O3"
and in /etc/portage/package.env www-client/firefox O3-clang
3) and then check it via: ebuild `equery w firefox` clean configure

oh thanks i try and this are my questions:


is pgo bloking lto on clang?
sudo emerge -1 firefox
https://dpaste.com/34MEGF6E2

Code: Select all

0:04.28 WARNING: Disabling LTO because --enable-profile-generate is specified

thanks so much!

[alamahant]

cat /etc/portage/env/clanglto-O3.conf

Code: Select all

CC="clang"
CXX="clang++"

LTO="-flto=thin"

COMMON_FLAGS="-march=native -O3 -pipe"
CFLAGS="${COMMON_FLAGS} ${LTO}"
CXXFLAGS="${COMMON_FLAGS} ${LTO}"
LDFLAGS="-Wl,-O2 -Wl,--as-needed"  

AR="llvm-ar"
NM="llvm-nm"
RANLIB="llvm-ranlib"

and
cat /etc/portage/package.env

Code: Select all

www-client/firefox clanglto-O3.conf

and

Code: Select all

USE="pgo lto" emerge -av firefox

I dont think that firefox can be built with gcc nowadays.so the above flags should also be applicable to clang also.
Just try it.......

[Josef.95]

papu,
yes, (from your configure output):

Code: Select all

    --enable-linker=lld             forcing ld=lld due to USE=clang and USE=lto
    --enable-lto=cross              +lto
    MOZ_PGO=1                       +pgo
    --disable-debug                 -debug
    --disable-debug-symbols         Gentoo default
    --enable-optimize=-O3           from CFLAGS

I think it looks good :)

/edit: I think try a build, and then check in firefox adress bar: about:buildconfig

[papu]

error

[papu]

papu,
yes, (from your configure output):

Code: Select all

    --enable-linker=lld             forcing ld=lld due to USE=clang and USE=lto
    --enable-lto=cross              +lto
    MOZ_PGO=1                       +pgo
    --disable-debug                 -debug
    --disable-debug-symbols         Gentoo default
    --enable-optimize=-O3           from CFLAGS

I think it looks good

/edit: I think try a build, and then check in firefox adress bar: about:buildconfig

then why this warning?

Code: Select all

0:04.28 WARNING: Disabling LTO because --enable-profile-generate is specified

these messages and configurations confuse me too much

p.d: it's clear with pgo lto is desactivated (as the above message suggests), it not create lto code in firefox compilation , without pgo it create lto code, i don't know why...
I had understood that lto and pgo was compatible and also increase performance when both was activated.

[Ionen]

You don't need to set anything in package.env to do that on firefox

1. ebuild setup clang stuff for you with USE=clang, trying to change that yourself will likely break things (default-* on clang often mess things up too)
2. with USE="lto pgo" upstream firefox actually _forces_ -O3 even if you've set -O2 (well, for C++.. but C is only third party bundled stuff -- in my about:buildconfig I see my -O2 but there's a -O3 after it, and you'll see it all over the build.log), and of course uses lto

On a side-note, when using gcc, be wary of -O3 with firefox. It has a poor history of runtime issues and ebuild currently adds a -fno-tree-loop-vectorize to workaround #2 above that always enables it.

[papu]

You don't need to set anything in package.env to do that on firefox

1. ebuild setup clang stuff for you with USE=clang, trying to change that yourself will likely break things (default-* on clang often mess things up too)
2. with USE="lto pgo" upstream firefox actually _forces_ -O3 even if you've set -O2 (well, for C++.. but C is only third party bundled stuff -- in my about:buildconfig I see my -O2 but there's a -O3 after it, and you'll see it all over the build.log), and of course uses lto

On a side-note, when using gcc, be wary of -O3 with firefox. It has a poor history of runtime issues and ebuild currently adds a -fno-tree-loop-vectorize to workaround #2 above that always enables it.

yes , i return to default settings is nonsense losing time with this , may be when i have a ryzen 4

thanks so much to all!