[Bug tree-optimization/18595] [4.0 Regression] IV-OPTS is O(N^3)

[rakdver at atrey dot karlin dot mff dot cuni dot cz]

------- Additional Comments From rakdver at atrey dot karlin dot mff dot cuni dot cz  2005-01-25 01:24 -------
Subject: Re:  [4.0 Regression] IV-OPTS is O(N^3)

> > Which one? I cannot find anything relevant in changelog.
> >
> 
> 
>          * tree-data-ref.c (analyze_subscript_affine_affine): Implement a
>          solution for the FIXME concerning the symbolic affine
>          dependence testing; remove the FIXME.
>          (can_use_analyze_subscript_affine_affine): New function.
>          (analyze_siv_subscript): Use it.
> 
> and
> 
> 
> 2004-12-15  Daniel Berlin  <dberlin@dberlin.org>
> 
>          * Makefile.in (tree-chrec.o): Add cfgloop.h
> 
>          * tree-chrec.c: Add cfgloop.h, tree-flow.h.
>          (evolution_function_is_invariant_p): New function.
>          (evolution_function_is_affine_multivariate_p): Use
>          evolution_function_is_invariant_p instead of
>          evolution_function_is_constant_p.
> 
>          * tree-chrec.h: Add prototype for
>          evolution_function_is_invariant_p.
>          (evolution_function_is_affine_p): Use
>          evolution_function_is_invariant_p.
> 
>          * tree-data-ref.c (analyze_overlapping_iterations): chrecs that
>          are equal overlap on every iteration.
> 
> This stuff is just simple symbolic differencing, and checking of 
> invariantness of symbols,
> But it is indeed starting to se the symbolic scev info

Ugh... OK, if you think it is a right way...  Anyway, I am seriously
considering resurrecting the simple iv analysis for purposes of passes
that are not interested in this fancy stuff.  Overhead of scev is
probably acceptable if it is only used for this type of analysis,
but for other purposes it is clearly overkill.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18595