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Re: [rfc] subreg lowering pass / Overcoming double-set difficulties for CC re-use


On 6/12/06, Björn Haase <bjoern.m.haase@web.de> wrote:
Maybe concerning the pass sequence, there is no real "one size fits it all".
With my present working version of the AVR port, I am having so much
different RTL after splitting so that I am convinced that re-running at least
CSE would be a big advantage. This will be quite different for the targets
originally supporting 32 bit operations. Maybe one solution could be to use
target defines in order to selectively enable passes that could be expected
to be justified only for a subset of the targets.?

That would be one option, but not one many people would like.


It would be much better to just make CSE faster and less heavy (I'm
the lone Don Quixote who is still trying to make this happen).  There
are at least four unrelated quadratic bottle-necks in cse.c and
probably dozens silly "optimizations" that take up a lot of analysis
time without resulting in significantly better code.

Until then, you could add e.g. a post-combine machine specific pass
for AVR that runs CSE as often as you want ;-)

Gr.
Steven


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