This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: RFC: Inlines, LTO and GCC
- From: Jan Hubicka <hubicka at ucw dot cz>
- To: Richard Biener <richard dot guenther at gmail dot com>
- Cc: Jan Hubicka <hubicka at ucw dot cz>, David Brown <david at westcontrol dot com>, Jakub Jelinek <jakub at redhat dot com>, Jeff Law <law at redhat dot com>, Andrew MacLeod <amacleod at redhat dot com>, GCC <gcc at gcc dot gnu dot org>, Diego Novillo <dnovillo at google dot com>
- Date: Tue, 10 Sep 2013 14:30:10 +0200
- Subject: Re: RFC: Inlines, LTO and GCC
- Authentication-results: sourceware.org; auth=none
- References: <522E3374 dot 4000509 at redhat dot com> <522E87A4 dot 7060904 at redhat dot com> <522ED2EC dot 9090807 at westcontrol dot com> <20130910081111 dot GS1817 at tucnak dot redhat dot com> <522ED471 dot 9000702 at westcontrol dot com> <20130910090646 dot GA5522 at kam dot mff dot cuni dot cz> <CAFiYyc2DxWUX29NM0S4PGu=+Evv_HrOfq2s552e6ScmqCgqc8Q at mail dot gmail dot com>
>
> But then inlining / cloning is no longer cheap, no? And will be
> disabled at -O2?
If you declare it "inline" and not "static inline" it will be inlined pretty
much as before, only it will get unified if it ends up out of line in multiple
units.
Main difference in between static and non-static is in logic deciding when
inlining into all callers will lead to removing the offline copy from the
program. This is controlable by comdat-sharing-probability parameter.
We won't clone at -O2 unless we know code will shrink that may be something to
revisit. I think it would be resonable to enable clonning at -O2 for functions
declared inline.
I was also playing with idea adding a GCC decision to function mangling, so
comdat clones can be inlined. I.e. having something like
mangled_foo->mangled_foo.__gcc_cprop_clone.arg0_0.arg1_17 It would need to
invent unique textual representations of all/most our substitutions that can
get tricky.
Honza