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Re: [tree-ssa] More aggressive dead code elimination
- From: Diego Novillo <dnovillo at redhat dot com>
- To: Jeff Law <law at redhat dot com>
- Cc: Steven Bosscher <s dot bosscher at student dot tudelft dot nl>, "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 07 Jan 2004 18:10:47 -0500
- Subject: Re: [tree-ssa] More aggressive dead code elimination
- Organization: Red Hat Canada
- References: <200401072252.i07Mq8O5031733@speedy.slc.redhat.com>
On Wed, 2004-01-07 at 17:52, law@redhat.com wrote:
> In message <1073515593.6424.11.camel@frodo.toronto.redhat.com>, Diego Novillo w
> rites:
> >On Wed, 2004-01-07 at 17:28, law@redhat.com wrote:
> >
> >> We decided a few months ago against using this approach to DCE due to
> >> performance issues.
> >>
> >Note that Steven's implementation can be switched between a fast and a
> >CD-driven DCE. It would be interesting to gather some data now that we
> >have the two implementations.
> We discussed that too -- it's simply not worth maintaining the code.
>
But we never actually gathered any data (not that I remember, anyway).
I do suspect that CD-DCE may bring marginal benefits. But, we have
cases where we need to re-run DCE now. Is it faster to run simple-DCE
twice? Or CD-DCE just once? The CD-specific bits in the implementation
look simple enough to maintain, too.
The results are probably a wash, but I just don't know.
Diego.