This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: is LTO aimed for large programs?
- From: Diego Novillo <dnovillo at google dot com>
- To: Basile STARYNKEVITCH <basile at starynkevitch dot net>
- Cc: GCC Mailing List <gcc at gcc dot gnu dot org>
- Date: Mon, 9 Nov 2009 07:35:06 -0500
- Subject: Re: is LTO aimed for large programs?
- References: <4AF74E2A.2030703@starynkevitch.net>
On Sun, Nov 8, 2009 at 18:03, Basile STARYNKEVITCH
<basile@starynkevitch.net> wrote:
> Perhaps the question is when not to use -flto and use -fwhopr instead?
I don't think anyone has systematically tried to determine these
limits. The original design tried to address a specific instance of a
program with about 400 million callgraph nodes. At the time, -flto
was running out of virtual addressing space to hold it (the gcc binary
was 32 bits), but it could be processed with -fwhopr.
The current implementation of -fwhopr is incomplete, however. It
needs fixes to the pass manager to properly apply all IPA passes (and
associated bug fixes). I would not use it in 4.5. Richi has made
numerous fixes to symbol/type handling, so -flto is now more memory
efficient than it was when I last tried it on a large application.
Diego.