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Re: vectorization, -floop-strip-mine, -floop-block and -floop-interchange
Hi,
sorry for my top-posting in last e-mail.
> hi,
>
> they should work completely independently from vectorization. It does not
> matter if vectorizaton is already run or not, they will apply
> if You enable them by flags.
>
> konrad
>
>
> Dorit,
> So it is correct to say that any loop that is vectorized is
> removed from consideration for these other loop optimizations?
> I ask because I am wondering if I should be testing these new
> loop optimizations at -O2 in order to see their full effect
> (without vectorization inhibiting their use).
> Jack
>
> On Wed, Aug 13, 2008 at 05:08:53PM +0300, Dorit Nuzman wrote:
>> > Can anyone explain the relationship between the current
> vectorization
>> > optimizations in the gcc trunk compiler and the new -floop-strip-mine,
>> > -floop-interchange and -floop-block loop optimizations? Which takes
>> > precedence and does one set block the other in any way? I would hope
>> > that the new loop optimizations simply redefine the loops that are then
>> > processed for vectorization so that both sets of optimizations can
>> > be in effect at the same time. Thanks in advance for any clarifications
>> > on how these optimizations interact with each other.
>>
By looking at passes.c I see that graphite is invoked before vectorizer.
This means that first the loop optimizations -floop-interchange etc.
will take place
and then vectorizer will try to vectorize them. There is no direct
interaction between those
optimizations.
I would be glad to see the results though.
>> There's currently no interaction between the Graphite optimizations and
>> vectorization. I don't know what considerations/cost-model Graphite uses
>> before applying its optimizations, but vectorization is not one of them.
> We
>> are now starting to look into teaching Graphite to take into account
>> factors that affect the applicability and profitability of vectorization,
>> but this work is in a very initial stage.
>>
>> dorit
>>
>> > Jack
>
>
>
>
konrad