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Re: [gfortran] Avoid induction variables in DO loops.
Daniel Berlin <firstname.lastname@example.org>:
> This may or may not be correct, it's hard to say.
> Yes it is true that our data dependence testing is
still in the process of
> being written.
> We have ZIV test, SIV test, and a partial MIV test
> As written below, it may not fall into the MIV test
portion we have
> implemented yet.
> I honestly don't remember.
> It would be good to know what your goal is.
> IE why you care whether it can do this data
dependence analysis or not.
I lead a small group trying to tuning GCC, especially
on IA64 alike platform.
Some progress has been made after nearly half an year.
For example, we can lower the execution time of SPEC
CFP2000 program 171.swim from 817 seconds to 310
seconds by extending the alias analysis for Fortran 95
and modifying the induction variables recognition and
prefetch optimization of GCC backend. But the
performance of GCC on IA64 is still far behind of
Intel compiler (it takes less than 100 seconds to run
According to our experiments, to further improve the
performance of 171.swim, loop nested optimization
(loop distribution/interchange) and software pipeling
with rotating register allocation are needed to be
Obviously, data dependence analysis is the base of
loop nested optimization, so we take much attention on
it. Very appreciate your work.
> Are you trying to perform some specific optimization?
We plan to implement scalar replacement. It is also
based on dependence analysis.
> I mean, you are welcome to implement the rest of the
miv test if you like
> (see tree-data-ref.c:analyze_miv_subscript for what
> implemented, however, it helps avoid duplicate work
if we know what your
> plans are, as there may already be people working on
what you want to do.
I have no plan to do it now, but I can contact with
members in my group to know whether there is someone
has instrest to continue this work.
Creative Compiler Research Group.
National University of Defense Technology, China.