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.

HTH,

Julian

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