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PR26435 (-ftree-loop-linear)
- From: Mark Mitchell <mark at codesourcery dot com>
- To: gcc-patches <gcc-patches at gcc dot gnu dot org>
- Date: Tue, 18 Apr 2006 17:00:04 -0700
- Subject: PR26435 (-ftree-loop-linear)
As discussed on the gcc list, -ftree-loop-linear consists of several
chunks of code. One chunk (to do with perfect loop nests) is apparently
not 100% algorithmically sound, but has the decided benefit of making
our SPEC scores substantially better.
My question is: what should we do about this, for 4.1 and for 4.2?
For 4.1, I would suggest separating the problematic chunk of code into a
separate option, and document the option as experimental, hopefully with
a note that suggests under what situations the optimization is unsafe.
That would clarify the situation for users, while not taking away
performance?
For 4.2, can we correct the code so that it doesn't do the wrong thing?
It sounds like we need some additional safety checks to avoid invalid
transformations; can we add those? And will that impact SPEC scores?
If so, what are the options we have?
--
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713