On Thu, 27 Mar 2014 16:02:49 +0000 Julian Brown <jul...@codesourcery.com> wrote:
> On Thu, 27 Mar 2014 09:41:28 -0600 > Jeff Law <l...@redhat.com> wrote: > > > On 03/27/14 07:50, Felix Yang wrote: > > > Hello, > > > > > > I find DCE in sched2 is disabled for C6X backend. Is this a > > > performance consideration? Or a GCC BUG? > > > And under what situations should we disable DCE in sched2? > > > Can anyone explain this? Many thanks. > > In general, if a port is disabling an optimization like this, then > > there's something wrong with the port. > > > > As to this specific issue, git/svn blame ought to point you at > > whomever wrote this code and you can ping them directly. > > IIRC, sched2 is run from md-reorg for C6X. The same trick is used by > the ia-64 backend -- it is to avoid late passes moving instructions > around after scheduling (breaking the arrangement of insns into > dispatch packets). The md-reorg pass is one of the last things the > compiler does before emitting assembly. Oops, I missed the "DCE" part. Ignore me! Apologies, Julian
