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Re: [tree-ssa] Dce & infinite loops
- From: Paolo Carlini <pcarlini at suse dot de>
- To: Richard Guenther <rguenth at tat dot physik dot uni-tuebingen dot de>
- Cc: Diego Novillo <dnovillo at redhat dot com>,Steven Bosscher <stevenb at suse dot de>,Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>, gcc at gcc dot gnu dot org
- Date: Thu, 18 Mar 2004 16:00:48 +0100
- Subject: Re: [tree-ssa] Dce & infinite loops
- References: <Pine.LNX.4.53.0403181538080.2417@bellatrix.tat.physik.uni-tuebingen.de>
Richard Guenther wrote:
For optimizing away empty (but finite) loops, this is certainly correct,
though maybe not what Joe average kernel hacker would expect ;) I.e.
issuing a warning if doing that is highly appreciated.
I find important this point about warnings because a loop may be written
as not
empty, then become empty as a result of previous optimizations: this may
become quite common thanks to the new powerful SSA machineries.
But this is a general issue, I think: some optimizations (the
"interesting" ones?)
may happen only thanks to previous optimizations and feedback to the user in
the "dangerous" (and "unexpected"!) cases is appreciated, isn't it?
Or just put everything under -ffast-math or something similar?
Something we lack, perhaps, is -fast, not just -ffast-math, which is not
really
the same thing as this kind of interesting discussion shows!
Paolo.